CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the priority of Chinese patent application no. 201 110389758.5 , filed on semiconductor packaging technology , the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention generally relates to the field of semiconductor assembly or packaging and, more particularly, to quad flat no-lead (QFN) packaging technologies.

BACKGROUND

[0003] There are mainly two types of conventional lead frame structures used in semiconductor packaging processes. For the first type, as shown in Figure 83, after performing chemical etching and electrical plating (or simply plating) on the metal substrate, a layer of high-temperature resistant film is affixed on the back surface of the metal substrate to form the lead frame carrier to be used in the packaging process.

[0004] For the second type, as shown in Figure 85, chemical half etching is first performed on the back surface of the metal substrate, and the chemically half etched areas are sealed with encapsulation material. Further, chemical half etching for inner leads is performed on the top surface of the metal substrate and followed by plating on the surface of inner leads of the lead frame so as to complete the lead frame.

[0005] However, both of these two types of lead frames may have certain disadvantages in the packaging process. For example, for the first type, the issues may include:

1) Because an expensive high-temperature film must be affixed on the back surface of the metal substrate, the manufacturing cost is directly increased;

2) In the die attaching process of the packaging process, also because a high-temperature resistant film must be affixed on the back surface of the metal substrate, only epoxy may be used in the die attaching process, and certain techniques such as the eutectic process or soft solder technique cannot be used, which greatly limits choices of available products;

3) In the wire bonding process of the packaging process, also because a high-temperature resistant film must be affixed on the back surface of the metal substrate and the high- temperature resistant film is a kind of soft material, the wire bonding parameters may become unstable, which seriously impacts on the quality of wire bonding and the reliability and stability of the product; and

4) In the molding process, also because a high-temperature resistant film must be affixed on the back surface of the metal substrate, the molding pressure during the molding process may cause certain mold bleeding between the lead frame and the high-temperature resistant film, which may change a conductive metal lead into an insulated lead, as shown in Figure 84 (certain metal leads on the left side of the drawing are insulated by bleeding material). [0006] For the second type conventional lead frame structure, the issues may include:

1) Because the etching process was carried out twice, manufacturing cost may be increased;

2) Because the composition of the lead frame is metal material and compound, when operated in a high and low temperature environment, the lead frame may be warping due to the different expansion and shrinkage stress of the different materials;

3) The warpage of the lead frame may impact the accuracy of die attaching process and may also affect the production yield due to the impact on the smooth transferring of the warping lead frames in the die attaching process;

4) The warpage of the lead frame may also impact the alignment accuracy of the wire bonding and may also affect the production yield due to the impact on the smooth transferring of the warping lead frames in the wire bonding process; and

5) Because the inner leads on the top surface of the lead frame are formed using etching technique, the width of the inner leads might have to be greater than lOOim and the distance between two adjacent inner leads also must have to be greater than 1 OOim. Thus, it may be difficult to achieve high density for the inner leads.

[0007] The disclosed methods and systems are directed to solve one or more problems set forth above and other problems. BRIEF SUMMARY OF THE DISCLOSURE

[0008] One aspect of the present disclosure includes a method for manufacturing a first-plating-then-etching quad flat no-lead (QFN) packaging structure. The method includes providing a metal substrate, forming a first photoresist film on a top surface of the metal substrate, and forming a plating pattern in the first photoresist film using photolithography. The method also includes forming a first metal layer containing a plurality of inner leads by a first multi-layer electrical plating process using the plating pattern in the first photoresist film as a mask such that a lead pitch of the plurality of inner leads is significantly reduced. Further, the method includes attaching at least one die in a predetermined region on the top surface of the metal substrate, connecting the die and the plurality of inner leads using metal wires by a wire bonding process, and sealing the die, the plurality of inner leads, and metal wires with a molding compound. The method also includes forming a second metal layer on a back surface of the metal substrate by a second multi-layer electrical plating process and, after forming the second metal layer, etching the metal substrate from the back surface of the metal substrate to form a plurality of I/O pads with pre-formed second metal layer corresponding to the plurality of inner leads. Further, the method includes filling sealant in etched areas at the back surface of the metal substrate.

[0009] Another aspect of the present disclosure includes a QFN packaging structure. The QFN packaging structure includes a metal substrate, a first die coupled to a top surface of the metal substrate, and a plurality of I/O pads formed based on the metal substrate, wherein the plurality of I/O pads having a preformed second metal layer on a back surface. The QFN packaging structure also includes a first metal layer containing a plurality of inner leads corresponding to the plurality of I/O pads and extending to proximity of the die. The first metal layer is formed on the metal substrate by a multi-layer electrical plating process such that a lead pitch of the plurality of inner leads is significantly reduced.

Further, the QFN packaging structure includes metal wires connecting the die and the plurality of inner leads. The die, the plurality of inner leads, and metal wires are sealed with a molding compound.

[0010] Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[001 1] Figures 1-18 illustrate an exemplary process for manufacturing an exemplary first-plating-then-etching QFN packaging structure consistent with the disclosed embodiments;

[0012] Figures 19(A)- 19(B) illustrate an exemplary first-plating-then- etching QFN packaging structure consistent with the disclosed embodiments;

[0013] Figures 20(A)-20(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0014] Figures 21 (A)-21 (B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments; [0015] Figures 22(A)-22(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0016] Figures 23(A)-23(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0017] Figures 24(A)-24(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0018] Figures 25(A)-25(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0019] Figures 26(A)-26(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0020] Figures 27(A)-27(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0021] Figures 28(A)-28(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0022] Figures 29(A)-29(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0023] Figures 30(A)-30(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0024] Figures 31 (A)-31 (B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments; [0025] Figures 32(A)-32(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0026] Figures 33(A)-33(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0027] Figures 34(A)-34(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0028] Figures 35(A)-35(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0029] Figures 36(A)-36(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0030] Figures 37(A)-37(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0031] Figures 38(A)-38(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0032] Figures 39(A)-39(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0033] Figures 40(A)-40(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0034] Figures 41 ( A)-41 (B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments; [0035] Figures 42(A)-42(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0036] Figures 43(A)-43(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0037] Figures 44(A)-44(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0038] Figures 45(A)-45(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0039] Figures 46(A)-46(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0040] Figures 47(A)-47(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0041] Figures 48(A)-48(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0042] Figures 49(A)-49(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0043] Figures 50(A)-50(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0044] Figures 51 (A)-51 (B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments; [0045] Figures 52(A)-52(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0046] Figures 53(A)-53(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0047] Figures 54(A)-54(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0048] Figures 55(A)-55(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0049] Figures 56(A)-56(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0050] Figures 57(A)-57(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0051] Figures 58(A)-58(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0052] Figures 59(A)-59(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0053] Figures 60(A)-60(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0054] Figures 61 (A)-61 (B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments; [0055] Figures 62(A)-62(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0056] Figures 63(A)-63(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0057] Figures 64(A)-64(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0058] Figures 65(A)-65(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0059] Figures 66(A)-66(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0060] Figures 67(A)-67(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0061] Figures 68(A)-68(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0062] Figures 69(A)-69(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0063] Figures 70(A)-70(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0064] Figures 71 (A)-71 (B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments; [0065] Figures 72(A)-72(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0066] Figures 73(A)-73(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0067] Figures 74(A)-74(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0068] Figures 75(A)-75(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0069] Figures 76(A)-76(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0070] Figures 77(A)-77(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0071] Figures 78(A)-78(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0072] Figures 79(A)-79(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0073] Figures 80(A)-80(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0074] Figures 81 (A)-81 (B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments; [0075] Figures 82(A)-82(B) illustrate another exemplary first-plating- then-etching QFN packaging structure consistent with the disclosed embodiments;

[0076] Figure 83 shows a high-temperature resistant film affixed on a lead frame;

[0077] Figure 84 shows mold bleeding between the lead frame and the high-temperature resistant film; and

[0078] Figure 85 shows a two-side etched lead frame.

DETAILED DESCRIPTION

[0079] Reference will now be made in detail to exemplary embodiments of the invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0080] Figure 19(A) and Figure 19(B) illustrate an exemplary first- plating-then-etching quad flat no-lead (QFN) packaging structure consistent with the disclosed embodiments. Figure 19(A) is a cross-section view of Figure 19(B). A first-plating-then-etching QFN packaging structure, as used herein, may refer to a QFN packaging structure whose I/O pads are formed by a plating process followed by an etching process.

[0081] As shown in Figure 19(A) and Figure 19(B), the first-plating-then- etching QFN packaging structure includes a plurality of input/output (I/O) pads 2, a plurality of inner leads 4, die 5, metal wire(s) 6, and encapsulation material 7, such as EMC compound. Certain components may be omitted and other components may be added.

[0082] Die 5 may include any pre-made semiconductor chip to be assembled or packaged. The I/O pads 2 may include a plurality of metal pads or traces to provide external connections to the die 5 or any other components inside the first-plating-then-etching QFN packaging structure through inner leads 4. The I/O pads 2 may be in any appropriate shape, such as a rectangle. The plurality of pads of the I/O pads 2 may be arranged in an array configuration or any other appropriate configuration. For example, in certain embodiments, as shown in Figure 19(B), the I/O pads 2 are arranged in a single ring configuration.

[0083] The die 5 may be mounted on the top surface of a substrate or other planar supporting structure through a conductive or non-conductive adhesive material 8, such as epoxy, soft solder, or other conductive or non- conductive material. Further, from the top surface of the I/O pads 2, an electrical plating (or simply plating) process such as multi-plating may be used to form the inner leads 4. More specifically, multiple layers may be formed by plating such that the distance between adjacent inner leads (i.e., inner lead pitch) may be substantially reduced. The top surface of the inner leads 4 and the top surface of die 5 may be connected by the metal wires 6. Further, the inner leads 4 may be formed significantly close to the die 5 via lead traces, such that the length of metal wires 6 connecting the die 5 to the inner leads 4 may also be substantially reduced.

[0084] All inner leads 4 may be referred as a first metal layer. That is, the first metal layer includes all leads of inner leads 4 or the inner leads 4 are formed as part of the first metal layer. The inner leads 4, the die 5, and the metal wires 6 are covered with encapsulation material 7, such as EMC compound. Further, at the backside of the substrate, sealant 10 is filled in the peripheral areas of the I/O pads 2 and the area between adjacent I/O pads 2. The back surface of the I/O pads 2 are exposed from the sealant 10 and a second metal layer 9 is formed on the back surface of the I/O pads 2. More particularly, the I/O pads 2 are formed with the second metal layer preformed on the back surface. Sealant 10 may include any appropriate type of sealant, such as a no-filler compound or a small- filler compound

[0085] The process for manufacturing the above described packaging structure may be explained below in detail with corresponding drawings 1-18. The process may be used to make a plurality of components (packaged ICs). Because each component or packaged IC may be made in a same way, only a single packaged IC or QFN packaging structure may be described for illustrative purposes.

[0086] As shown in Figure 1, at the beginning, a metal substrate 1 1 is provided for the lead frame manufacturing and packaging process. Metal substrate 11 may have a desired thickness and be made from various metal materials depending on particular types of die 5. For example, metal substrate 1 1 may be made from one of copper, aluminum, iron, copper alloy, stainless steel, or nickel-iron alloy. Other materials may also be used.

[0087] Further, as shown in Figure 2, a layer of photoresist film 12 and a layer of photoresist film 13 may be formed (pasted or coated) on the top surface and the back surface of the metal substrate 1 1 , respectively. The photoresist film 12 and/or photoresist film 13 may be formed using various ways. For example, photoresist film 12 and/or photoresist film 13 may be coated on the surface or may be plating on the surface. The photoresist films 1 1 and 12 may be used to protect the metal substrate 1 1 in subsequent plating processes, and the photoresist films 1 1 or 12 may include a dry photoresist film or a wet photoresist film. Other types of photoresist films may also be used.

[0088] Further, as shown in Figure 3, portions of the photoresist film 12 on the top surface of the metal substrate 1 1 may be removed to form a pattern by photolithography. As shown in Figure 3, photolithography equipment may be used to perform exposure, development, and etching on the photoresist film 12 using a corresponding mask to form a plating pattern in the photoresist film 12. The plating pattern may expose the predetermined areas of the metal substrate 1 1 for subsequent plating process to form the first metal layer 14, i.e., a first metal layer pattern.

[0089] After forming the plating pattern or the first metal layer pattern, as shown in Figure 4, a multi-layer plating process may be performed to form the first metal layer 14 in the areas of the metal substrate 1 1 exposed by the plating pattern in the photoresist film 12. In other words, the multi-layer plating process is performed on the top surface of the metal substrate 1 1 using the pattern in the photoresist film 12 as a mask to form inner leads 4 (the first metal layer 14). The inner leads 4 may be formed corresponding to the I/O pads 2 to be formed in subsequent processes and may also be arranged in a corresponding shape (e.g., a rectangle) and configuration (e.g., a single ring configuration). Other shapes and configurations may also be used.

[0090] Because the inner leads 4 are formed by the plating process, the lead pitch of the inner leads 4 and the distance between the inner leads 4 and the die 5 may be substantially reduced. For example, the inner leads 4 may be formed by a thin-line plating method on the top surface of the metal substrate 1 1. The width of the inner leads 4 may be approximately 25μπι, and the lead pitch of the inner leads 4 may also be approximately 25μηι. Comparing the lead pitch of about 1 ΟΟμπι in conventional lead frames, the width of the inner leads 4 and the lead pitch of the inner leads 4 may be significantly reduced, which may achieve high density for inner leads 4. Further, the inner leads 4 may extend to the proximity of the die 5 via lead traces. Using the plating process, the distance between the die and the inner leads 4 can also be significantly reduced such that the inner leads 4 can extend substantially close to the die 5, which can

substantially reduce the package size.

[0091] The first metal layer 14 (e.g., the inner leads 4) may include any appropriate number of layers of metal materials and/or metal layer structure. For example, the first metal layer 14 may include, from bottom to the top, a total of five layers of nickel, copper, nickel, palladium, and gold, respectively, or a total of three layers of nickel, copper, and silver. Other materials and number of layers and/or layer structures may also be used.

[0092] Different metal layers in the first metal layer 14 may provide different functionalities. For example, in a five-layer structure (nickel, copper, nickel, palladium, and gold), the bottom layer of nickel may be used as an erosion resistant and barrier layer, the middle layers of copper, nickel and palladium may be used to increase the thickness of the first metal layer 14, and the top layer of gold may be used for wire bonding. Other functionalities may also be provided and other metal layer structures may also be used.

[0093] Further, as shown in Figure 5, the remaining top surface photoresist film 12 is removed and inner leads 4 are formed on the metal substrate 1 1. The back surface photoresist film 13 is also removed.

[0094] After removing the photoresist films, the die 5 may be mounted on a predetermined die area of the metal substrate 11 using the conductive or non- conductive adhesive material 8, as shown in Figure 6, in a die attaching process. The predetermined die area of the metal substrate 1 1 may correspond to the area for attaching the die 5. More particularly, the die 5 may be mounted or attached to an area among the inner leads 4 or surrounded by the inner leads 4. The top surface of die 5 and the top surface of the inner leads 4 are connected with metal wires 6 in a wire bonding process, as shown in Figure 7.

[0095] The inner leads 4, the die 5, and the metal wires 6 are then encapsulated using encapsulation material 7, as shown in Figure 8. For example, molding equipment may be used to seal or encapsulate the metal substrate 1 1 completed die attaching and wire bonding by a molding compound. Post-molding curing may also be performed such that the molding compound or other encapsulation materials may also be cured before the next manufacturing process. [0096] As shown in Figure 9, after the encapsulation process(e.g., molding and post-molding curing), a layer of photoresist film 13 may be formed on the top surface of the metal substrate 1 1 and another layer of photoresist film 13 may be formed on the back surface of the metal substrate 1 1. The photoresist films may be used to protect the metal substrate 1 1 in a subsequent plating process, and the photoresist films may include a dry photoresist film or a wet photoresist film. Other types of photoresist films may also be used.

[0097] Further, portion of the photoresist film 13 on the back surface of the metal substrate 1 1 may be removed to form a pattern using photolithography. As shown in Figure 10, photolithography equipment may be used to perform exposure, development, and etching on the photoresist film 13 on the back surface of the metal substrate 1 1 using a second metal layer mask to form a second plating pattern in the photoresist film 13. The second plating pattern may expose the predetermined areas on the back surface of the metal substrate 11 for a subsequent plating process to form a second metal layer 9, i.e., the second metal layer pattern.

[0098] Further, as shown in Figure 11 , a second plating process or multilayer plating process may be performed on the back surface of the metal substrate 11 to form the second metal layer 9. That is, before forming the I/O pads 2 on the back surface of the metal substrate 1 1 , a second plating process or multi-plating process may be performed on the back surface of metal substrate 1 1 to form the second metal layer 9. The second metal layer 9 may be made from various materials depending on the particulars die and/or applications. For example, the second metal layer 9 may be a three-layer structure of gold, nickel, and gold (from top to bottom), a five-layer structure of gold, nickel, copper, nickel, and gold (from top to bottom), a three-layer structure of nickel, palladium, and gold (from top to bottom), a four-layer structure of gold, nickel, palladium, nickel, and gold (from top to bottom), a two-layer structure of nickel and gold (from top to bottom), or a single-layer of silver or tin, etc. Other structures may also be used.

[0099] Further, as shown in Figure 12, after the second plating process, the remaining photoresist film 13 on the back surface of the metal substrate 11 is removed to expose the back surface of the metal substrate 1 1 with the second metal layer 9. The photoresist film 13 on the top surface of the metal substrate 1 1 is also removed.

[00100] As shown in Figure 13, after the second plating process, a layer of photoresist film 13 may be formed on the top surface of the metal substrate 11 and another layer of photoresist film 13 may be formed on the back surface of the metal substrate 11. The photoresist films may be used to protect the metal substrate 1 1 in subsequent etching processes, and the photoresist films may include a dry photoresist film or a wet photoresist film. Other types of photoresist films may also be used.

[00101] Further, portion of the photoresist film 13 on the back surface of the metal substrate 1 1 may be removed to form a pattern using photolithography. As shown in Figure 14, photolithography equipment may be used to perform exposure, development, and etching on the photoresist film 13 on the back surface of the metal substrate 1 1 using a mask to form an etching pattern in the photoresist film 13. The mask may correspond to the second metal layer mask previously used. In certain embodiments, the second metal layer mask may be reused as the mask for forming the etching pattern. The etching pattern may expose the predetermined areas on the back surface of the metal substrate 11 for a subsequent etching process to form I/O pads 2, i.e., the I/O pad pattern.

[00102] After forming the etching pattern, as shown in Figure 15, an etching process may be performed on the areas of the metal substrate 1 1 exposed by the etching pattern in the photoresist film 13. In other words, the etching process is performed on the metal substrate 1 1 using the etching pattern in the photoresist film 13 as a mask. The etching process may be full etching or half etching. Etched areas are thus formed on the back surface of the metal substrate 1 1 , and the I/O pads 2 with pre-formed second metal layer 9 are also formed after the etching process. Because the second metal layer 9 is formed before the etching process forming the I/O pads 2, the lead pitch of the I/O pads 2 and/or pad width of the I/O pads 2 may be significantly reduced. For example, the I/O pads 2 may have a pad width of approximately 25μπι, and the lead pitch of the I/O pads 2 may also be approximately 25μηι.

[00103] Further, as shown in Figure 16, after the etching process, the remaining photoresist film 13 on the back surface of the metal substrate 11 is removed to expose the etched areas on the back surface of the metal substrate 11 including the peripheral areas of the I/O pads 2 and the areas between leads of the I/O pads 2. The photoresist film 13 on the top surface of the metal substrate 1 1 is also removed. [00104] Afterwards, as shown in Figure 17, the etched areas on the back surface of the metal substrate 1 1 are filled with sealant 10 using filling equipment. Post-molding curing may be performed on the sealant 10. The sealant 10 may include any appropriate sealant, such as a no-filler compound or a small-filler compound. The sealant 10 may also be filled at a certain height such that the back surface of the I/O pads 2 is slightly lower than the back surface of filled sealant 10. Thus, the I/O pads 2 may be supported by both the molding compound 7 and the sealant 10.

[00105] Thus, a first-plating-then-etching QFN packaging structure with single lead ring may be formed. Afterwards, as shown in Figure 18, the plurality of encapsulated components formed on the metal substrate 1 1 may be individually cut to obtain individual packaged ICs or individual first-plating-then-etching QFN packaging structures in a package sawing process. Other cutting methods may also be used.

[00106] Further, the first-plating-then-etching QFN packaging structure may also include various different structures and configurations. For example, Figure 20(A) and Figure 20(B) illustrate another exemplary first-plating-then- etching QFN packaging structure. Figure 20(A) is a cross-section view of Figure 20(B).

[00107] As shown in Figure 20(A) and Figure 20(B), the first-plating-then- etching QFN packaging structure in Figure 20(A) and Figure 20(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 19(A) and Figure 19(B). However, the first-plating-then-etching QFN packaging structure in Figure 20(A) also includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with inner die pad and single lead ring may be formed.

[00108] Figure 21 (A) and Figure 21 (B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 21(A) is a cross-section view of Figure 21(B).

[00109] As shown in Figure 21 (A) and Figure 21 (B), the first-plating-then- etching QFN packaging structure in Figure 21(A) and Figure 21(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 19(A) and Figure 19(B). However, the first-plating-then-etching QFN packaging structure in Figure 21(A) also includes one or more passive device 15 coupled between inner leads 4 using conductive or non-conductive adhesive material 8. The passive device 15 may be coupled between inner leads 4 before the die 5 is attached or during the die attaching process. Thus, a first-plating-then-etching QFN packaging structure with single lead ring coupled with passive device may be formed. 23 JI * w -tii - ^w - - ^_

[001 10] Figure 22(A) and Figure 22(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 22(A) is a cross-section view of Figure 22(B).

[001 1 1] As shown in Figure 22(A) and Figure 22(B), the first-plating-then- etching QFN packaging structure in Figure 22(A) and Figure 22(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 21(A) and Figure 21(B). However, the first-plating-then-etching QFN packaging structure in Figure 22(A) also includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with inner die pad and single lead ring coupled with passive device may be formed.

[001 12] Figure 23(A) and Figure 23(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 23(A) is a cross-section view of Figure 23(B).

[001 13] As shown in Figure 23(A) and Figure 23(B), the first-plating-then- etching QFN packaging structure in Figure 23(A) and Figure 23(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 19(A) and Figure 19(B). However, the first-plating-then-etching QFN packaging structure in Figure 23(A) and Figure 23(B) also includes an outer electrostatic discharge ring 16, and an inner electrostatic discharge ring 17 may be formed on the top surface of the outer electrostatic discharge ring 16 within the I/O pad ring. That is, the inner electrostatic discharge ring 17 may also be formed by the multi-layer plating process for forming the first metal layer 14. More particularly, the inner electrostatic discharge ring 17 may be arranged between the die 5 and inner leads 4 and in any appropriate shape, such as a rectangle or square. Further, the top surface of the die 5 is connected to the top surface of the inner electrostatic discharge ring 17 by the metal wire 6 such that the die 5 may be protected from the static by the internal and outer electrostatic discharge rings 15 and 16. Both the outer electrostatic discharge ring 16 and the inner electrostatic discharge ring 17 may be in any appropriate shape, such as a rectangle ring, etc. Thus, a first- plating-then-etching QFN packaging structure with inner die pad, single lead ring, and electrostatic discharge ring may be formed.

[001 14] Figure 24(A) and Figure 24(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 24(A) is a cross-section view of Figure 24(B).

[001 15] As shown in Figure 24(A) and Figure 24(B), the first-plating-then- etching QFN packaging structure in Figure 24(A) and Figure 24(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 23(A) and Figure 23(B). However, the first-plating-then-etching QFN packaging structure in Figure 24(A) also includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with inner die pad, single lead ring, and electrostatic discharge ring may be formed.

[00116] Figure 25(A) and Figure 25(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 25(A) is a cross-section view of Figure 25(B).

[001 17] As shown in Figure 25(A) and Figure 25(B), the first-plating-then- etching QFN packaging structure in Figure 25(A) and Figure 25(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 23(A) and Figure 23(B). However, the first-plating-then-etching QFN packaging structure in Figure 25(A) also includes one or more passive device 15 coupled between inner leads 4 using conductive or non-conductive adhesive material 8. Thus, a first- plating-then-etching QFN packaging structure with single lead ring coupled with passive device and electrostatic discharge ring may be formed.

[00118] Figure 26(A) and Figure 26(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 26(A) is a cross-section view of Figure 26(B).

[001 19] As shown in Figure 26(A) and Figure 26(B), the first-plating-then- etching QFN packaging structure in Figure 26(A) and Figure 26(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 25(A) and Figure 25(B). However, the first-plating-then-etching QFN packaging structure in Figure 26(A) also includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating- then- etching QFN packaging structure with inner die pad, single lead ring coupled with passive device, and electrostatic discharge ring may be formed.

[00120] Figure 27(A) and Figure 27(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 27(A) is a cross-section view of Figure 27(B).

[00121] As shown in Figure 27(A) and Figure 27(B), the first-plating-then- etching QFN packaging structure in Figure 27(A) and Figure 27(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 19(A) and Figure 19(B). However, the first-plating-then-etching QFN packaging structure in Figure 27(A) and 27(B) includes multiple rings of I/O pads 2. In other words, I/O pads 2 are arranged in a multiple-ring configuration, and the leads in the multiple rings may be arranged in a staggered or zigzag way such that the leads and lead traces can be closely placed to the die 5. Further, multiple rings of inner leads 4 may be formed on the top surface of the I/O pads 2. That is, multiple rings of inner leads 4 may also be formed by the multi-layer plating process for forming the first metal layer 14. Because the multiple rings of inner leads 4 are formed by the multi-layer plating process, the lead pitch of inner leads from a same ring and the lead pitch of inner leads from different rings may be significantly reduced. Thus, a first-plating-then-etching QFN packaging structure with multiple lead rings may be formed.

[00122] Figure 28(A) and Figure 28(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 28(A) is a cross-section view of Figure 28(B).

[00123] As shown in Figure 28(A) and Figure 28(B), the first-plating-then- etching QFN packaging structure in Figure 28(A) and Figure 28(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 27(A) and Figure 27(B). However, the first-plating-then-etching QFN packaging structure in Figure 28(A) and 28(B) includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with inner die pad and multiple lead rings may be formed.

[00124] Figure 29(A) and Figure 29(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 29(A) is a cross-section view of Figure 29(B).

[00125] As shown in Figure 29(A) and Figure 29(B), the first-plating-then- etching QFN packaging structure in Figure 29(A) and Figure 29(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 27(A) and Figure 27(B). However, the first-plating-then-etching QFN packaging structure in Figure 29(A) and 29(B) includes one or more passive device 15 coupled between inner leads 4 using conductive or non-conductive adhesive material 8. Thus, a first-plating-then-etching QFN packaging structure with multiple lead rings coupled with passive device may be formed.

[00126] Figure 30(A) and Figure 30(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 30(A) is a cross-section view of Figure 30(B).

[00127] As shown in Figure 30(A) and Figure 30(B), the first-plating-then- etching QFN packaging structure in Figure 30(A) and Figure 30(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 29(A) and Figure 29(B). However, the first-plating-then-etching QFN packaging structure in Figure 30(A) and 30(B) includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with inner die pad and multiple lead rings coupled with passive device may be formed. [00128] Figure 31 (A) and Figure 31 (B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 31(A) is a cross-section view of Figure 31 (B).

[00129] As shown in Figure 31 (A) and Figure 31 (B), the first-plating-then- etching QFN packaging structure in Figure 31(A) and Figure 31(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 27(A) and Figure 27(B). However, the first-plating-then-etching QFN packaging structure in Figure 31 (A) and 31 (B) includes an outer electrostatic discharge ring 16, and an inner electrostatic discharge ring 17 may be formed on the top surface of the outer electrostatic discharge ring 16 within the I/O pad ring. That is, the inner electrostatic discharge ring 17 may also be formed by the multi-layer plating process for forming the first metal layer 14. More particularly, the inner electrostatic discharge ring 17 may be arranged between the die 5 and inner leads 4. Further, the top surface of the die 5 is connected to the top surface of the inner electrostatic discharge ring 17 by the metal wire 6 such that the die 5 may be protected from the static by the internal and outer electrostatic discharge rings 16 and 17. Second metal layer 9 may also be formed on the back surface of the outer electrostatic discharge ring 16. Thus, a first-plating-then-etching QFN packaging structure with multiple lead rings and electrostatic discharge ring may be formed.

[00130] Figure 32(A) and Figure 32(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 32(A) is a cross-section view of Figure 32(B). [00131] As shown in Figure 32(A) and Figure 32(B), the first-plating-then- etching QFN packaging structure in Figure 32(A) and Figure 32(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 31(A) and Figure 31(B). However, the first-plating-then-etching QFN packaging structure in Figure 32(A) and 32(B) includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with inner die pad, multiple lead rings, and electrostatic discharge ring may be formed.

[00132] Figure 33(A) and Figure 33(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 33(A) is a cross-section view of Figure 33(B).

[00133] As shown in Figure 33(A) and Figure 33(B), the first-plating-then- etching QFN packaging structure in Figure 33(A) and Figure 33(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 31 (A) and Figure 31(B). However, the first-plating-then-etching QFN packaging structure in Figure 33(A) and 33(B) includes one or more passive device 15 coupled between inner leads 4 using conductive or non-conductive adhesive material 8. Thus, a first-plating-then-etching QFN packaging structure with multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed. [00134] Figure 34(A) and Figure 34(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 34(A) is a cross-section view of Figure 34(B).

[00135] As shown in Figure 34(A) and Figure 34(B), the first-plating-then- etching QFN packaging structure in Figure 34(A) and Figure 34(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 33(A) and Figure 33(B). However, the first-plating-then-etching QFN packaging structure in Figure 34(A) and 34(B) includes an inner die pad 3 formed on the predetermined area for attaching the die 5 or within a ring or rings of inner leads 4. The inner die pad 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the inner die pad 3 may also be included in the first metal layer 14. Further, the die 5 is attached at the top surface of the inner die pad 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with inner die pad, multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed.

[00136] Figure 35(A) and Figure 35(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 35(A) is a cross-section view of Figure 35 (B) .

[00137] As shown in Figure 35(A) and Figure 35(B), the first-plating-then- etching QFN packaging structure in Figure 35(A) and Figure 35(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 19(A) and Figure 19(B). However, the first-plating-then-etching QFN packaging structure in Figure 35(A) and 35(B) includes a plurality of dies 5. Each of the plurality of dies 5 is attached on predetermined areas on the substrate or other planar supporting structure or within the ring or rings of inner leads 4 by conductive or non-conductive adhesive material 8. For example, a second die 5 is arranged in a side-by-side configuration with respect to the first die 5, and both dies 5 are arranged within the ring or rings of inner leads 4. Further, the top surface of each die 5 may be connected by metal wires 6. Thus, a first-plating-then-etching QFN packaging structure with multiple dies and single lead ring may be formed.

[00138] Figure 36(A) and Figure 36(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 36(A) is a cross-section view of Figure 36(B).

[00139] As shown in Figure 36(A) and Figure 36(B), the first-plating- then- etching QFN packaging structure in Figure 36(A) and Figure 36(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 35(A) and Figure 35(B). However, the first-plating- then-etching QFN packaging structure in Figure 36(A) and 36(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, and single lead ring may be formed. [00140] Figure 37(A) and Figure 37(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 37(A) is a cross-section view of Figure 37(B).

[00141] As shown in Figure 37(A) and Figure 37(B), the first-plating-then- etching QFN packaging structure in Figure 37(A) and Figure 37(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 21(A) and Figure 21(B). However, the first-plating-then-etching QFN packaging structure in Figure 37(A) and 37(B) includes a plurality of dies 5. Each of the plurality of dies 5 is attached on predetermined areas on the substrate or other planar supporting structure or within the ring or rings of inner leads 4 by conductive or non-conductive adhesive material 8. For example, a second die 5 is arranged in a side-by-side configuration with respect to the first die 5, and both dies 5 are arranged within the ring or rings of inner leads 4. Further, the top surface of each die 5 may be connected by metal wires 6. Other configurations may also be used. Thus, a first-plating-then-etching QFN packaging structure with multiple dies and single lead ring coupled with passive device may be formed.

[00142] Figure 38(A) and Figure 38(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 38(A) is a cross-section view of Figure 38(B).

[00143] As shown in Figure 38(A) and Figure 38(B), the first-plating-then- etching QFN packaging structure in Figure 38(A) and Figure 38(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 37(A) and Figure 37(B). However, the first-plating-then-etching QFN packaging structure in Figure 38(A) and 38(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, and single lead ring coupled with passive device may be formed.

[00144] Figure 39(A) and Figure 39(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 39(A) is a cross-section view of Figure 39(B).

[00145] As shown in Figure 39(A) and Figure 39(B), the first-plating-then- etching QFN packaging structure in Figure 39(A) and Figure 39(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 23(A) and Figure 23(B). However, the first-plating-then-etching QFN packaging structure in Figure 39(A) and 39(B) includes a plurality of dies 5. Each of the plurality of dies 5 is attached on predetermined areas on the substrate or other planar supporting structure or within the ring or rings of inner leads 4 by conductive or non-conductive adhesive material 8. For example, a second die 5 is arranged in a side-by-side configuration with respect to the first die 5, and both dies 5 are arranged within the ring or rings of inner leads 4. Further, the top surface of each die 5 may be connected by metal wires 6. Other configurations may also be used. Thus, a first-plating-then-etching QFN packaging structure with multiple dies, single lead ring, and electrostatic discharge ring may be formed.

[00146] Figure 40(A) and Figure 40(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 40(A) is a cross-section view of Figure 40(B).

[00147] As shown in Figure 40(A) and Figure 40(B), the first-plating-then- etching QFN packaging structure in Figure 40(A) and Figure 40(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 39(A) and Figure 39(B). However, the first-plating-then-etching QFN packaging structure in Figure 40(A) and 40(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, single lead ring, and electrostatic discharge ring may be formed.

[0Q148] Figure 41(A) and Figure 41(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 41(A) is a cross-section view of Figure 41(B).

[00149] As shown in Figure 41(A) and Figure 41(B), the first-plating-then- etching QFN packaging structure in Figure 41(A) and Figure 41(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 25(A) and Figure 25(B). However, the first-plating-then-etching QFN packaging structure in Figure 41(A) and 41(B) includes a plurality of dies 5. Each of the plurality of dies 5 is attached on predetermined areas on the substrate or other planar supporting structure or within the ring or rings of inner leads 4 by conductive or non-conductive adhesive material 8. For example, a second die 5 is arranged in a side-by-side configuration with respect to the first die 5, and both dies 5 are arranged within the ring or rings of inner leads 4. Further, the top surface of each die 5 may be connected by metal wires 6. Other configurations may also be used. Thus, a first-plating-then-etching QFN packaging structure with multiple dies, single lead ring coupled with passive device, and electrostatic discharge ring may be formed.

[00150] Figure 42(A) and Figure 42(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 42(A) is a cross-section view of Figure 42(B).

[00151 ] As shown in Figure 42(A) and Figure 42(B), the first-plating-then- etching QFN packaging structure in Figure 42(A) and Figure 42(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 41(A) and Figure 41(B). However, the first-plating-then-etching QFN packaging structure in Figure 42(A) and 42(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, single lead ring coupled with passive device, and electrostatic discharge ring may be formed.

[00152] Figure 43(A) and Figure 43(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 43(A) is a cross-section view of Figure 43(B).

[00153] As shown in Figure 43(A) and Figure 43(B), the first-plating-then- etching QFN packaging structure in Figure 43(A) and Figure 43(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 35(A) and Figure 35(B). However, the first-plating-then-etching QFN packaging structure in Figure 43(A) and 43(B) includes multiple rings of I/O pads 2. In other words, I/O pads 2 are arranged in a multiple-ring configuration. Further, multiple rings of inner leads 4 may be formed on the top surface of the I/O pads 2. That is, multiple rings of inner leads 4 may also be formed by the multi-layer plating process for forming the first metal layer 14. Because the multiple rings of inner leads 4 are formed by the multi-layer plating process, the lead pitch of inner leads from a same ring and the lead pitch of inner leads from different rings may be significantly reduced. Thus, a first-plating-then-etching QFN packaging structure with multiple dies and multiple lead rings may be formed. [00154] Figure 44(A) and Figure 44(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 44(A) is a cross-section view of Figure 44(B).

[00155] As shown in Figure 44(A) and Figure 44(B), the first-plating-then- etching QFN packaging structure in Figure 44(A) and Figure 44(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 43(A) and Figure 43(B). However, the first-plating-then-etching QFN packaging structure in Figure 44(A) and 44(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, and multiple lead rings may be formed.

[00156] Figure 45(A) and Figure 45(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 45(A) is a cross-section view of Figure 45(B).

[00157] As shown in Figure 45(A) and Figure 45(B), the first-plating-then- etching QFN packaging structure in Figure 45(A) and Figure 45(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 37(A) and Figure 37(B). However, the first-plating-then-etching QFN packaging structure in Figure 45(A) and 45(B) includes multiple rings of I/O pads 2. In other words, I/O pads 2 are arranged in a multiple-ring configuration. Further, multiple rings of inner leads 4 may be formed on the top surface of the I/O pads 2. That is, multiple rings of inner leads 4 may also be formed by the multi-layer plating process for forming the first metal layer 14. Because the multiple rings of inner leads 4 are formed by the multi-layer plating process, the lead pitch of inner leads from a same ring and the lead pitch of inner leads from different rings may be significantly reduced. Thus, a first-plating-then-etching QFN packaging structure with multiple dies and multiple lead rings coupled with passive device may be formed.

[00158] Figure 46(A) and Figure 46(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 46(A) is a cross-section view of Figure 46(B).

[00159] As shown in Figure 46(A) and Figure 46(B), the first-plating-then- etching QFN packaging structure in Figure 46(A) and Figure 46(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 45(A) and Figure 45(B). However, the first-plating-then-etching QFN packaging structure in Figure 46(A) and 46(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, and multiple lead rings coupled with passive device may be formed.

[00160] Figure 47(A) and Figure 47(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 47(A) is a cross-section view of Figure 47(B).

[00161] As shown in Figure 47(A) and Figure 47(B), the first-plating-then- etching QFN packaging structure in Figure 47(A) and Figure 47(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 39(A) and Figure 39(B). However, the first-plating-then-etching QFN packaging structure in Figure 47(A) and 47(B) includes multiple rings of I/O pads 2. In other words, I/O pads 2 are arranged in a multiple-ring configuration. Further, multiple rings of inner leads 4 may be formed on the top surface of the I/O pads 2. That is, multiple rings of inner leads 4 may also be formed by the multi-layer plating process for forming the first metal layer 14. Because the multiple rings of inner leads 4 are formed by the multi-layer plating process, the lead pitch of inner leads from a same ring and the lead pitch of inner leads from different rings may be significantly reduced. Thus, a first-plating-then-etching QFN packaging structure with multiple dies, multiple lead rings, and electrostatic discharge ring may be formed.

[00162] Figure 48(A) and Figure 48(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 48(A) is a cross-section view of Figure 48(B). [00163] As shown in Figure 48(A) and Figure 48(B), the first-plating-then- etching QFN packaging structure in Figure 48(A) and Figure 48(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 47(A) and Figure 47(B). However, the first-plating-then-etching QFN packaging structure in Figure 48(A) and 48(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, multiple lead rings, and electrostatic discharge ring may be formed.

[00164] Figure 49(A) and Figure 49(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 49(A) is a cross-section view of Figure 49(B).

[00165] As shown in Figure 49(A) and Figure 49(B), the first-plating-then- etching QFN packaging structure in Figure 49(A) and Figure 49(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 41(A) and Figure 41(B). However, the first-plating-then-etching QFN packaging structure in Figure 49(A) and 49(B) includes multiple rings of I/O pads 2. In other words, I/O pads 2 are arranged in a multiple-ring configuration. Further, multiple rings of inner leads 4 may be formed on the top surface of the I/O pads 2. That is, multiple rings of inner leads 4 may also be formed by the multi-layer plating process for forming the first metal layer 14. Because the multiple rings of inner leads 4 are formed by the multi-layer plating process, the lead pitch of inner leads from a same ring and the lead pitch of inner leads from different rings may be significantly reduced. Thus, a first-plating-then-etching QFN packaging structure with multiple dies, multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed.

[00166] Figure 50(A) and Figure 50(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 50(A) is a cross-section view of Figure 50(B).

[00167] As shown in Figure 50(A) and Figure 50(B), the first-plating-then- etching QFN packaging structure in Figure 50(A) and Figure 50(B) is similar to the first-plating-then-etching QFN packaging structure in Figure 49(A) and Figure 49(B). However, the first-plating-then-etching QFN packaging structure in Figure 50(A) and 50(B) includes a plurality of inner die pads 3 formed on the predetermined areas for attaching the dies 5 or within a ring or rings of inner leads 4. The plurality of inner die pads 3 may also be formed by the multi-layer plating process for forming the inner leads 4. Thus, the plurality of inner die pads 3 may also be included in the first metal layer 14. Further, the plurality of dies 5 are attached at the top surface of the corresponding plurality of inner die pads 3 via the conductive or non-conductive adhesive material 8. Thus, a first-plating-then- etching QFN packaging structure with multiple dies, multiple inner die pads, multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed.

[00168] Figure 51 (A) and Figure 51 (B) illustrate an exemplary quad flat no-lead (QFN) packaging structure with an outer die pad or island consistent with the disclosed embodiments. Figure 51(A) is a cross-section view of Figure 51(B).

[00169] As shown in Figure 51 (A) and Figure 51 (B), the QFN packaging structure in Figure 51(A) and Figure 51(B) is similar to the first-plating-then- etching QFN packaging structure in Figure 19(A) and Figure 19(B). However, the QFN packaging structure in Figure 51(A) and 51(B) includes an outer die pad 1. That is, the QFN packaging structure in Figure 51(A) and 51(B) is not first- plating-then-etching. Outer die pad 1 may include any structure to be configured as a die pad to provide contact (e.g., thermal, electrical, etc.) to the die 5, and the outer die pad 1 may be in any appropriate shape, such as a rectangle, a square, or a circle, etc. The die 5 may be mounted on the top surface of the outer die pad 1 through the conductive or non-conductive adhesive material 8. The outer die pad 1 may be formed within the I/O pads 2 or surrounded by the I/O pads 2 in the same etching process forming the I/O pads 2 using the etching pattern.

[00170] Correspondingly, the second metal layer pattern for forming the second metal layer 9 before forming the outer die pad 1 and the I/O pads 2 may also include the portion of the second metal layer corresponding to the outer die pad 1. Further, at the backside of the substrate, sealant 10 are filled in the peripheral areas of the outer die pad 1 and I/O pads 2, in the area between the outer die pad 1 and I/O pads 2, and in the area between adjacent I/O pads 2. Thus, a QFN packaging structure with single outer die pad and single lead ring may be formed.

[00171] Figure 52(A) and Figure 52(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 52(A) is a cross-section view of Figure 52(B).

[00172] As shown in Figure 52(A) and Figure 52(B), the QFN packaging structure in Figure 52(A) and Figure 52(B) is similar to the QFN packaging structure in Figure 20(A) and Figure 20(B). However, the QFN packaging structure in Figure 52(A) and Figure 52(B) also includes an outer die pad 1, as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads and single lead ring may be formed.

[00173] Figure 53(A) and Figure 53(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 53(A) is a cross-section view of Figure 53(B).

[00174] As shown in Figure 53(A) and Figure 53(B), the QFN packaging structure in Figure 53(A) and Figure 53(B) is similar to the QFN packaging structure in Figure 21(A) and Figure 21(B). However, the QFN packaging structure in Figure 53(A) and 53(B) also includes an outer die pad 1, as previously explained. The die 5 is attached on the top surface of the outer die pad 1 via the conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with single outer die pad and single lead ring coupled with passive device may be formed. [00175] Figure 54(A) and Figure 54(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 54(A) is a cross-section view of Figure 54(B).

[00176] As shown in Figure 54(A) and Figure 54(B), the QFN packaging structure in Figure 54(A) and Figure 54(B) is similar to the QFN packaging structure in Figure 22(A) and Figure 22(B). However, the QFN packaging structure in Figure 54(A) and Figure 54(B) also includes an outer die pad 1 , as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads and single lead ring coupled with passive device may be formed.

[00177] Figure 55(A) and Figure 55(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 55(A) is a cross-section view of Figure 55 (B) .

[00178] As shown in Figure 55(A) and Figure 55(B), the QFN packaging structure in Figure 55(A) and Figure 55(B) is similar to the QFN packaging structure in Figure 23(A) and Figure 23(B). However, the QFN packaging structure in Figure 55(A) and Figure 55(B) also includes an outer die pad 1, as previously explained. The die 5 is attached on the top surface of the outer die pad 1 via the conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with single outer die pad, single lead ring, and electrostatic discharge ring may be formed. [00179] Figure 56(A) and Figure 56(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 56(A) is a cross-section view of Figure 56(B).

[00180] As shown in Figure 56(A) and Figure 56(B), the QFN packaging structure in Figure 56(A) and Figure 56(B) is similar to the QFN packaging structure in Figure 24(A) and Figure 24(B). However, the QFN packaging structure in Figure 56(A) and Figure 56(B) also includes an outer die pad 1, as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads, single lead ring, and electrostatic discharge ring may be formed.

[00181] Figure 57(A) and Figure 57(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 57(A) is a cross-section view of Figure 57(B).

[00182] As shown in Figure 57(A) and Figure 57(B), the QFN packaging structure in Figure 57(A) and Figure 57(B) is similar to the QFN packaging structure in Figure 25(A) and Figure 25(B). However, the QFN packaging structure in Figure 57(A) and Figure 57(B) also includes an outer die pad 1, as previously explained. The die 5 is attached on the top surface of the outer die pad 1 via the conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with single outer die pad, single lead ring coupled with passive device, and electrostatic discharge ring may be formed. [00183] Figure 58(A) and Figure 58(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 58(A) is a cross-section view of Figure 58(B).

[00184] As shown in Figure 58(A) and Figure 58(B), the QFN packaging structure in Figure 58(A) and Figure 58(B) is similar to the QFN packaging structure in Figure 26(A) and Figure 26(B). However, the QFN packaging structure in Figure 58(A) and Figure 58(B) also includes an outer die pad 1, as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads, single lead ring coupled with passive device, and electrostatic discharge ring may be formed.

[00185] Figure 59(A) and Figure 59(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 59(A) is a cross-section view of Figure 59(B).

[00186] As shown in Figure 59(A) and Figure 59(B), the QFN packaging structure in Figure 59(A) and Figure 59(B) is similar to the QFN packaging structure in Figure 27(A) and Figure 27(B). However, the QFN packaging structure in Figure 59(A) and 59(B) includes an outer die pad 1, as previously explained. The die 5 is attached on the top surface of the outer die pad 1 via the conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with single outer die pad and multiple lead rings may be formed. [00187] Figure 60(A) and Figure 60(B) illustrate another exemplary first- plating- then-etching QFN packaging structure. Figure 60(A) is a cross-section view of Figure 60(B).

[00188] As shown in Figure 60(A) and Figure 60(B), the QFN packaging structure in Figure 60(A) and Figure 60(B) is similar to the QFN packaging structure in Figure 28(A) and Figure 28(B). However, the QFN packaging structure in Figure 60(A) and 60(B) includes an outer die pad 1 , as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads and multiple lead rings may be formed.

[00189] Figure 61 (A) and Figure 61 (B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 61(A) is a cross-section view of Figure 61 (B) .

[00190] As shown in Figure 61(A) and Figure 61(B), the QFN packaging structure in Figure 61(A) and Figure 61(B) is similar to the QFN packaging structure in Figure 29(A) and Figure 29(B). However, the QFN packaging structure in Figure 61(A) and 61(B) includes an outer die pad 1, as previously explained. The die 5 is attached on the top surface of the outer die pad 1 via the conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with single outer die pad and multiple lead rings coupled with passive device may be formed. [00191] Figure 62(A) and Figure 62(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 62(A) is a cross-section view of Figure 62(B).

[00192] As shown in Figure 62(A) and Figure 62(B), the QFN packaging structure in Figure 62(A) and Figure 62(B) is similar to the QFN packaging structure in Figure 30(A) and Figure 30(B). However, the QFN packaging structure in Figure 62(A) and 62(B) includes an outer die pad 1, as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads and multiple lead rings coupled with passive device may be formed.

[00193] Figure 63(A) and Figure 63(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 63(A) is a cross-section view of Figure 63(B).

[00194] As shown in Figure 63(A) and Figure 63(B), the QFN packaging structure in Figure 63(A) and Figure 63(B) is similar to the QFN packaging structure in Figure 31(A) and Figure 31(B). However, the QFN packaging structure in Figure 63(A) and 63(B) includes an outer die pad 1, as previously explained. The die 5 is attached on the top surface of the outer die pad 1 via the conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with single outer die pad, multiple lead rings, and electrostatic discharge ring may be formed. [00195] Figure 64(A) and Figure 64(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 64(A) is a cross-section view of Figure 64(B).

[00196] As shown in Figure 64(A) and Figure 64(B), the QFN packaging structure in Figure 64(A) and Figure 64(B) is similar to the QFN packaging structure in Figure 32(A) and Figure 32(B). However, the QFN packaging structure in Figure 64(A) and 64(B) includes an outer die pad 1 , as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads, multiple lead rings, and electrostatic discharge ring may be formed.

[00197] Figure 65(A) and Figure 65(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 65(A) is a cross-section view of Figure 65(B).

[00198] As shown in Figure 65(A) and Figure 65(B), the QFN packaging structure in Figure 65(A) and Figure 65(B) is similar to the QFN packaging structure in Figure 33(A) and Figure 33(B). However, the QFN packaging structure in Figure 65(A) and 65(B) includes an outer die pad 1, as previously explained. The die 5 is attached on the top surface of the outer die pad 1 via the conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with single outer die pad, multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed. [00199] Figure 66(A) and Figure 66(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 66(A) is a cross-section view of Figure 66(B).

[00200] As shown in Figure 66(A) and Figure 66(B), the QFN packaging structure in Figure 66(A) and Figure 66(B) is similar to the QFN packaging structure in Figure 34(A) and Figure 34(B). However, the QFN packaging structure in Figure 66(A) and 66(B) includes an outer die pad 1 , as previously explained. The inner die pad 3 is formed on the top surface of the outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with outer and inner die pads, multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed.

[00201] Figure 67(A) and Figure 67(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 67(A) is a cross-section view of Figure 67(B).

[00202] As shown in Figure 67(A) and Figure 67(B), the QFN packaging structure in Figure 67(A) and Figure 67(B) is similar to the QFN packaging structure in Figure 35(A) and Figure 35(B). However, the QFN packaging structure in Figure 67(A) and 67(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. For example, a second outer die pad 1 is arranged in a side-by-side configuration with respect to the first or the original outer die pad 1 , and a second die is attached on the top surface of the corresponding second outer die pad 1. Thus, a QFN packaging structure with multiple outer die pads and single lead ring may be formed.

[00203] Figure 68(A) and Figure 68(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 68(A) is a cross-section view of Figure 68(B).

[00204] As shown in Figure 68(A) and Figure 68(B), the QFN packaging structure in Figure 68(A) and Figure 68(B) is similar to the QFN packaging structure in Figure 36(A) and Figure 36(B). However, the QFN packaging structure in Figure 68(A) and 68(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads and single lead ring may be formed.

[00205] Figure 69(A) and Figure 69(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 69(A) is a cross-section view of Figure 69(B).

[00206] As shown in Figure 69(A) and Figure 69(B), the QFN packaging structure in Figure 69(A) and Figure 69(B) is similar to the QFN packaging structure in Figure 37(A) and Figure 37(B). However, the QFN packaging structure in Figure 69(A) and 69(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with multiple outer die pads and single lead ring coupled with passive device may be formed.

[00207] Figure 70(A) and Figure 70(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 70(A) is a cross-section view of Figure 70(B).

[00208] As shown in Figure 70(A) and Figure 70(B), the QFN packaging structure in Figure 70(A) and Figure 70(B) is similar to the QFN packaging structure in Figure 38(A) and Figure 38(B). However, the QFN packaging structure in Figure 70(A) and 70(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads and single lead ring coupled with passive device may be formed.

[00209] Figure 71(A) and Figure 71(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 71(A) is a cross-section view of Figure 71(B).

[00210] As shown in Figure 71 (A) and Figure 71 (B), the QFN packaging structure in Figure 71(A) and Figure 71(B) is similar to the QFN packaging structure in Figure 39(A) and Figure 39(B). However, the QFN packaging structure in Figure 71(A) and 71(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with multiple outer die pads, single lead ring, and electrostatic discharge ring may be formed.

[00211] Figure 72(A) and Figure 72(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 72(A) is a cross-section view of Figure 72(B).

[00212] As shown in Figure 72(A) and Figure 72(B), the QFN packaging structure in Figure 72(A) and Figure 72(B) is similar to the QFN packaging structure in Figure 40(A) and Figure 40(B). However, the QFN packaging structure in Figure 72(A) and 72(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads, single lead ring, and electrostatic discharge ring may be formed.

[00213] Figure 73(A) and Figure 73(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 73(A) is a cross-section view of Figure 73(B).

[00214] As shown in Figure 73(A) and Figure 73(B), the QFN packaging structure in Figure 73(A) and Figure 73(B) is similar to the QFN packaging structure in Figure 41(A) and Figure 41(B). However, the QFN packaging structure in Figure 73(A) and 73(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with multiple outer die pads, single lead ring coupled with passive device, and electrostatic discharge ring may be formed.

[00215] Figure 74(A) and Figure 74(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 74(A) is a cross-section view of Figure 74(B).

[00216] As shown in Figure 74(A) and Figure 74(B), the QFN packaging structure in Figure 74(A) and Figure 74(B) is similar to the QFN packaging structure in Figure 42(A) and Figure 42(B). However, the QFN packaging structure in Figure 74(A) and 74(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads, single lead ring coupled with passive device, and electrostatic discharge ring may be formed.

[00217] Figure 75(A) and Figure 75(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 75(A) is a cross-section view of Figure 75(B).

[00218] As shown in Figure 75(A) and Figure 75(B), the QFN packaging structure in Figure 75(A) and Figure 75(B) is similar to the QFN packaging structure in Figure 43(A) and Figure 43(B). However, the QFN packaging structure in Figure 75(A) and 75(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with multiple outer die pads and multiple lead rings may be formed.

[00219] Figure 76(A) and Figure 76(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 76(A) is a cross-section view of Figure 76(B).

[00220] As shown in Figure 76(A) and Figure 76(B), the QFN packaging structure in Figure 76(A) and Figure 76(B) is similar to the QFN packaging structure in Figure 44(A) and Figure 44(B). However, the QFN packaging structure in Figure 76(A) and 76(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads and multiple lead rings may be formed.

[00221] Figure 77(A) and Figure 77(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 77(A) is a cross-section view of Figure 77(B).

[00222] As shown in Figure 77(A) and Figure 77(B), the QFN packaging structure in Figure 77(A) and Figure 77(B) is similar to the QFN packaging structure in Figure 45(A) and Figure 45(B). However, the QFN packaging structure in Figure 77(A) and 77(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with multiple outer die pads and multiple lead rings coupled with passive device may be formed.

[00223] Figure 78(A) and Figure 78(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 78(A) is a cross-section view of Figure 78(B).

[00224] As shown in Figure 78(A) and Figure 78(B), the QFN packaging structure in Figure 78(A) and Figure 78(B) is similar to the QFN packaging structure in Figure 46(A) and Figure 46(B). However, the QFN packaging structure in Figure 78(A) and 78(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads and multiple lead rings coupled with passive device may be formed.

[00225] Figure 79(A) and Figure 79(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 79(A) is a cross-section view of Figure 79(B).

[00226] As shown in Figure 79(A) and Figure 79(B), the QFN packaging structure in Figure 79(A) and Figure 79(B) is similar to the QFN packaging structure in Figure 47(A) and Figure 47(B). However, the QFN packaging structure in Figure 79(A) and 79(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with multiple outer die pads, multiple lead rings, and electrostatic discharge ring may be formed.

[00227] Figure 80(A) and Figure 80(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 80(A) is a cross-section view of Figure 80(B).

[00228] As shown in Figure 80(A) and Figure 80(B), the QFN packaging structure in Figure 80(A) and Figure 80(B) is similar to the QFN packaging structure in Figure 48(A) and Figure 48(B). However, the QFN packaging structure in Figure 80(A) and 80(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads, multiple lead rings, and electrostatic discharge ring may be formed.

[00229] Figure 81(A) and Figure 81(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 81(A) is a cross-section view of Figure 81(B).

[00230] As shown in Figure 81 (A) and Figure 81 (B), the QFN packaging structure in Figure 81(A) and Figure 81(B) is similar to the QFN packaging structure in Figure 49(A) and Figure 49(B). However, the QFN packaging structure in Figure 81(A) and 71(B) includes a plurality of outer die pads 1 and a plurality of dies 5. Each of the plurality of dies 5 is attached on the top surface of a corresponding outer die pad 1 by conductive or non-conductive adhesive material 8. Thus, a QFN packaging structure with multiple outer die pads, multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed.

[00231 ] Figure 82(A) and Figure 82(B) illustrate another exemplary first- plating-then-etching QFN packaging structure. Figure 82(A) is a cross-section view of Figure 82(B).

[00232] As shown in Figure 82(A) and Figure 82(B), the QFN packaging structure in Figure 82(A) and Figure 82(B) is similar to the QFN packaging structure in Figure 50(A) and Figure 50(B). However, the QFN packaging structure in Figure 82(A) and 82(B) includes a plurality of outer die pads 1. Each of the plurality of inner die pads 3 is formed on the top surface of a corresponding outer die pad 1 by the multi-layer plating process. Thus, a QFN packaging structure with multiple outer and inner die pads, multiple lead rings coupled with passive device, and electrostatic discharge ring may be formed.

[00233] By using the disclosed methods, processes, and devices, various advantageous applications may be implemented. For example, using the disclosed processes and devices, separate etching processes on both sides of the metal substrate can be avoided, and the process cost, time, personnel, power, and materials can be reduced. At the same time, the amount of potential environment- harmful substances generated in the etching processes can also be reduced.

Further, because of the use of the thin-line plating method on the top surface of the substrate, the minimum width of the inner leads may be approximately 25μπι, and the lead pitch of the inner leads may be as small as approximately 25μπι. Thus, the lead density in the lead frame can be significantly increased. Furthermore, because the I/O pads are etched after the second metal layer is formed by the plating process, the width and/or lead pitch of the I/O pads can also be significantly reduced. For example, the I/O pads 2 may have a pad width of approximately 25μπι, and the lead pitch of the I/O pads 2 may also be

approximately 25μπι.

[00234] By using the disclosed processes and devices, only lead frame is involved in the die attaching process and wire bonding process. Thus, the lead frame may be tolerant substantially high temperature, such as in a range of approximately 380 - 420 Celsius degrees, without warping.

[00235] It is understood that the disclosed embodiments may be applied to packaging any semiconductor devices. Various alternations, modifications, or equivalents to the technical solutions of the disclosed embodiments can be obvious to those skilled in the art.