BACKGROUND 1. Technical Field

[0001] Embodiments described herein relate to system in packages (SiPs) and methods for making SiPs. More particularly, embodiments described herein relate to systems and methods for shielding SiPs from electromagnetic interference. 2. Description of Related Art

[0002] An SiP (system in package or system-in-a-package) includes one or more integrated circuits enclosed in a single module (e.g., a single package). The SiP may perform many (or all) of the functions of an electronic system. SiPs are typically used inside smaller electronic devices such as, but not limited to, mobile phones, digital music players, and tablets. An example of an SiP may include several chips (e.g., a specialized processor, DRAM, and/or flash memory) combined with passive components (e.g., resistors and capacitors) mounted on a single substrate. Mounting all the components on the single substrate provides a complete functional unit that can be built in a multi-chip package and few external components may be needed to make the device work. A drawback to SiPs is that any defective chip in the package will result in a non- functional packaged integrated circuit, even if all the remaining modules in the same package are functional.

[0003] EMI (''electromagnetic interference") is the unwanted effects in the electrical system due to electromagnetic (e.g., radio frequency (RF)) radiation and electromagnetic conduction.

Electromagnetic radiation and electromagnetic conduction are different in the way an EM field propagates. Conducted EMI is caused by the physical contact of the conductors as opposed to radiated EMI which is caused by induction. Electromagnetic disturbances in the EM field of a conductor will no longer be confined to the surface of the conductor and may radiate away from it. Mutual inductance between two radiated electromagnetic fields may result in EMI.

[0004] Due to EMI, the electromagnetic field around the conductor is no longer evenly distributed (e.g., resulting in skin effects, proximity effects, hysteresis losses, transients, voltage drops, electromagnetic disturbances, EMP/HEMP, eddy current losses, harmonic distortion, and reduction m the permeability of the material).

[0005] EMI can be conductive and/or radiative and its behavior is dependent on the frequency of operation and cannot be controlled at higher frequencies. For lower frequencies, EMI is caused by conduction (e.g., resulting in skin effects) and, for higher frequencies, by radiation (e.g., resulting in proximity effects),

[0006] A high frequency electromagnetic signal makes every conductor an antenna, in the sense that they can generate and absorb electromagnetic fields. In the case of a printed circuit board ("PCB"), consisting of capacitors and semiconductor devices soldered to the board, the capacitors and soldering function like antennas, generating and absorbing electromagnetic fields. The chips on these boards are so close to each other that the chances of conducted and radiated EMI are significant. Boards are designed in such a way that the case of the board is connected to the ground and the radiated EMI is typically diverted to ground. Technological advancements have drastically reduced the size of chipboards and electronics and locating SiPs along with other components closer and closer together. The decreasing distances between components, however, means that chips (e.g., SiPs) are also becoming more sensitive to EMI. Typically

electromagnetic shielding is used to inhibit EMI effects. However, EMI shielding for SiPs may ^¬ be difficult and process intensive to integrate into the SiP structure.

[0007] FIG. 1 depicts a side-view cross-sectional representation of an example for providing EMI shielding for an SiP. SiP 100 includes silicon die f 02 and passive devices f 04 coupled to the upper surface of substrate f 06. Substrate f 06 may be a two layer substrate (e.g., a substrate with a core and two metal layers). Silicon die f 02 and passive devices f 04 are encapsulated in encapsulant f 08. Terminals i f 0 may be coupled to the lower surface of substrate f 06. Underfill material i f 2 (e.g., solder resist) may be formed on the lower surface of substrate f 06 around terminals i f O.

[0008] Terminals 1 10 may couple SiP 100 to printed circuit board (PCB) 1 14. PCB 1 14 may be, for example, a multilayer PCB. Shield 1 16 is formed over encapsulant 108 of SiP 100. Shield 116 is a metal shield. As shown in FIG. i, to form an EMI shield for SiP 100, shield i f 6 contacts ground ring i f 8 at the lower edges of the shield (inside the dotted circles) on the ends (sides) of substrate i06. Ground ring f f 8 couples shield i f 6 to outermost terminals i f 0' on the lower surface of substrate f 06. Terminals i f 0' are coupled to routing in PCB i f 4 that connects the terminals (and shield i f 6) to ground layer f 20 at the bottom-most surface of the PCB. When shield i f 6 and ground layer f 20 are electrically coupled, as shown in FIG. f , they together form EMI shield 122 (e.g., a Faraday cage) around SiP iOO.

[0009] A problem that occurs with making the shield structure shown in FIG. i is that it is difficult to ensure electrical connection between shield i f 6 and ground ring i f 8. FIG. 2 depicts an enlarged cross-sectional representation of an end portion of substrate 106 with shield i f 6 and ground ring i f 8 not connected. Typically, SiP iOO is placed on an adhesive surface (e.g., adhesive tape) or in a fixture pocket with raised walls during sputtering (or electroplating) of material for shield 116 to inhibit metal deposition on the lower surface of substrate 106. The adhesive surface or the walls of the fixture pocket may form region 124 around the end portion of substrate 106, as shown in FIG. 2. For example, the adhesive surface may extend up along the side surface of substrate 106 or the walls of the fixture pocket may contact or be very close to the side surface of the substrate.

[0010] Region 124 may be inaccessible for metal deposition of shield material on the side surface of substrate 106. The lack of metal deposition may form gap 126 between shield 116 and ground ring 118. In some cases, gap 126 may include a region with a lower thickness of metal deposition (and thus higher electrical resistivity) as compared to other regions of the module. Gap 126 inhibits electrical contact (e.g., metal to metal contact) between shield 116 and ground ring 118. The inaccessibility for metal deposition due to region 124 is a particular problem as ground ring 118 has a small thickness (about 10-15 μιτι), which provides a small target area for shield 116 to contact. As substrates get thinner and thinner, contacting the ground ring will become even more difficult. Without contact between shield 116 and ground ring 118, as shown in FIG. 2, it is difficult for a complete EMI shield to be formed as there is no electrical contact between the shield and ground layer 120 (shown in FIG. 1). Thus, as shown in FIG. 2, EMI shield 122 is an incomplete shield.

SUMMARY

[0011] In certain embodiments, metal shield is formed over a system in package (SiP). The SiP may include one or more die (e.g., processor and/or memory die) and one or more passive devices (e.g., resistors and/or capacitors) coupled to an upper surface of a substrate. The upper surface of the substrate and the die and passive devices may be encapsulated in an encapsulant. Terminals on a lower surface of the substrate may couple the SiP to a printed circuit board (PCB).

[0012] In certain embodiments, the metal shield is electrically coupled to a ground layer in the PCB to form an EMI shield around the SiP. The EMI shield may inhibit EMI or other electrical interference on the components within the SiP. In certain embodiments, the metal shield is coupled to at least some metallization along vertical walls in the end portions of the substrate. The metallization along the vertical walls in the end portions of the substrate may be via metallization from through-metal vias formed through a common substrate that remains after singulation of the common substrate to form the SiP. The substrate of the SiP may be a portion of the common substrate remaining after singulation.

[0013] In certain embodiments, a ground ring couples outermost terminals on the lower surface of the substrate to the metallization along the vertical walls in the end portions of the substrate. The outermost terminals on the lower surface of the substrate may couple to the ground layer in the PCB when the SiP is coupled to the PCB. Thus, when the metal shield is coupled to the metallization along the vertical walls in the end portions of the substrate, the metal shield is coupled to the ground layer in the PCB. The metallization along the vertical walls in the end portions of the substrate may provide a large contact area for coupling the metal shield to the ground ring to ensure connection between the shield and the ground layer in the PCB.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Features and advantages of the methods and apparatus of the embodiments described in this disclosure will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the embodiments described in this disclosure when taken in conjunction with the accompanying drawings in which:

[0015] FIG. 1 depicts a side-view cross-sectional representationi of an example for providing EMI shielding for an SiP.

[0016] FIG. 2 depicts an enlarged cross-sectional representation of an end portion of a substrate with a shield and a ground ring not connected.

[0017] FIG. 3 depicts a side-view cross-sectional representation of an embodiment of a system in package (SiP).

[0018] FIG. 4 depicts a side view cross-sectional representation of an embodiment of an SiP after singulation.

[0019] FIG. 5 depicts a side view cross-sectional representation of an embodiment of an SiP with a shield.

[0020] FIG. 6 depicts a side view cross-sectional representation of an embodiment of an SiP on an adhesive surface.

[0021] FIG. 7 depicts a side view cross-sectional representation of an embodiment of an SiP on a metallization fixture.

[0022] FIG. 8 depicts an enlarged cross-sectional representation of an end portion of a substrate with a shield coupled to via metallization.

[0023] FIG. 9 depicts a side view cross-sectional representation of an embodiment a plurality of

SiPs on an adhesive surface during metal deposition to form a shield.

[0024] FIG. 10 depicts a side view cross-sectional representation of an embodiment a plurality of SiPs on a metallization fixture during metal deposition to form a shield.

[0025] FIG. 11 depicts a side view cross-sectional representation of an embodiment of an SiP coupled to a printed circuit board (PCB). [0026] FIG. 12 depicts a top view representation of the embodiment depicted in FIG. 1 1 showing terminals and metallization formed around the perimeter of an SiP on a PCB.

[0027] FIG. 13 depicts an enlarged top view representation of an embodiment of a section in an SiP before singulation.

[0028] FIG. 14 depicts a top view representation of an embodiment of a section of an SiP with through-hole vias in a non-linear pattern.

[0029] FIG. 15 depicts a top view representation of an embodiment of an SiP before singulation with through-hole vias in a staggered pattern.

[0030] While embodiments described in this disclosure may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the embodiments to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description. As used throughout this application, the word "may" is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words "include", "including", and "includes" mean including, but not limited to.

[0031] Various units, circuits, or other components may be described as "configured to" perform a task or tasks. In such contexts, "configured to" is a broad recitation of structure generally meaning "having circuitry that" performs the task or tasks during operation. As such, the unit/circuit/component can be configured to perform the task even when the

unit/circuit/component is not currently on. In general, the circuitry that forms the structure corresponding to "configured to" may include hardware circuits and/or memory storing program instructions executable to implement the operation. The memory can include volatile memory such as static or dynamic random access memory and/or nonvolatile memory such as optical or magnetic disk storage, flash memory, programmable read-only memories, etc. The hardware circuits may include any combination of combinatorial logic circuitry, clocked storage devices such as flops, registers, latches, etc., finite state machines, memory such as static random access memory or embedded dynamic random access memory, custom designed circuitry,

programmable logic arrays, etc. Similarly, various units/circuits/components may be described as performing a task or tasks, for convenience in the description. Such descriptions should be interpreted as including the phrase "configured to. " Reciting a unit/circuit/component that is configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112(f) interpretation for that unit/circuit/component.

[0032] The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the appended claims.

DETAILED DESCRIPTION OF EMBODIMENTS

[0033] This specification includes references to "one embodiment" or "an embodiment." The appearances of the phrases "in one embodiment" or "in an embodiment" do not necessarily refer to the same embodiment, although embodiments that include any combination of the features are generally contemplated, unless expressly disclaimed herein. Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure.

[0034] FIG. 3 depicts a side-view cross-sectional representation of an embodiment of a system in package (SiP). In certain embodiments, SiP 300 includes die 302 and passive devices 304 coupled to an upper surface of substrate 306. In some embodiments, SiP 300 includes only passive devices 304 (e.g., the SiP is a passive SiP). In some embodiments, SiP 300 includes more than one die 302. Die 302 may include, for example, silicon die or integrated circuit die such as processor die or logic die. In some embodiments, die 302 include DRAM or other memory die. Passive devices 304 may include passive components such as, but not limited to, resistors and capacitors. Die 302 may be coupled to substrate 306 with terminals 308. Terminals 310 may couple passive devices 304 to substrate 306. In certain embodiments, terminals 308 and terminals 310 include pads, solder bumps, or combinations pads and solder bumps.

[0035] Substrate 306 may be a thin substrate such as a coreless substrate or a dielectric core substrate with metal layers. In certain embodiments, substrate 306 is a two-layer substrate having a dielectric core and two metal layers. In certain embodiments, substrate 306 has a thickness of at most about 60 μιη. In some embodiments, substrate 306 has a thickness of at most about 100 μιτι, at most about 75 μιτι, or at most about 50 μιη.

[0036] In certain embodiments, terminals 312 are coupled to a lower surface of substrate 306. Terminals 312 may include pads, solder bumps, or combinations of pads and solder bumps. Underfill material 314 may substantially surround terminals 312 on the lower surface of substrate 306. Underfill material 314 may be, for example, solder resist. Terminals 312 are exposed through underfill material 314 so that the terminals can couple SiP 300 to another component or device (e.g., a printed circuit board).

[0037] In certain embodiments, encapsulant 316 is formed over at least part of the upper surface of substrate 306. Encapsulant 316 may include, but not be limited to, a polymer or a mold compound such as an overmold or exposed mold compound. Encapsulant 316 may encapsulate die 302 and passive devices 304 on the upper surface of substrate 306. Encapsulating die 302 and passive devices 304 may protect the die and passive devices.

[0038] SiP 300, as depicted in FIG. 3, is shown before singulation of the SiP. Before singulation, SiP 300 is formed on a common substrate along with a plurality of additional SiPs. The SiPs are spaced apart on the common substrate to provide spaces between the SiPs for singulation (separation) of the SiPs into individual SiPs. Dashed lines 318, shown in FIG. 3, represent an embodiment of locations for singulation of SiP 300. Common substrate 320 may extend beyond dashed lines 318 (e.g., common substrate 320 supports the plurality of SiPs including SiP 300). Common substrate 320 may be, for example, the two-layer substrate described above for substrate 306. Substrate 306 may be the portion of common substrate 320 between dashed lines 318.

[0039] In certain embodiments, as shown in FIG. 3, through-hole vias 322 are formed in common substrate 320 at or near dashed lines 318. Thus, through-hole vias 322 may be formed in the end portions of substrate 306. Through-hole vias 322 may include via metallization 324 through common substrate 320. The process to form through-hole vias 322 and via metallization 324 in common substrate 320 may be a simple modification to current processes for forming common substrates for SiPs. In some embodiments, via metallization 324 extends partially on the surface of common substrate 320 (e.g., on the surface beyond the vertical walls of the via through the substrate). In certain embodiments, at least a portion of via metallization 324 is coupled to ground ring 326. Ground ring 326 may include metallization that couples to terminals 312' (the outermost terminals on the lower surface of substrate 306). Thus, via metallization 324 is coupled to terminals 312' through ground ring 326.

[0040] After the plurality of SiPs (including SiP 300) are formed on common substrate 320 (e.g., after encapsulation of the SiPs), the SiPs and the common substrate may be singulated (e.g., diced or sawed) along dashed lines 318 to form individual SiPs. FIG. 4 depicts a side view cross- sectional representation of an embodiment of SiP 300 after singulation. As shown in FIG. 4, after singulation, substrate 306 may include at least some via metallization 324 in the end portions of the substrate. In certain embodiments, at least some via metallization 324 remains along the substantially vertical walls in the end portions of substrate 306 after singulation. Thus, the location of dashed lines 318 (e.g., the singulation "cut" shown in FIG. 3) is adjustable (or flexible) as long as some via metallization remains after singulation. The thickness of via metallization 324 may also provide tolerance for different saw (or laser) cut widths or alignment errors in the saw (or laser).

[0041] After SiP 300 is formed by singulation, shield 328 may be formed over the SiP. FIG. 5 depicts a side view cross-sectional representation of an embodiment of SiP 300 with a shield. In certain embodiments, shield 328 is formed over encapsulant 316 and along the substantially vertical walls in the end portions of substrate 306. In certain embodiments, shield 328 is formed by metal deposition such as sputtering or electroplating on SiP 300.

[0042] Shield 328 may be, for example, a copper shield. In some embodiments, a thin layer of stainless steel is formed on the copper shield to protect the copper. In some embodiments, shield 328 includes copper with a thickness between about 5 μηι and about 10 μηι with a stainless steel layer of about 1 μιη thickness over the copper. In some embodiments, shield 328 may include aluminum, ferrite, carbonyl iron, stainless steel, nickel silver, low-carbon steel, silicon-iron steel, foil, conductive resin, and other metals and composites capable of blocking or absorbing EMI, RFI (radio frequency interference), and other inter-device interference. In some embodiments, shield 328 may include a non-metal material such as carbon-black or aluminum flake to reduce the effects of EMI and RFI. For non-metal materials, shield 328 may be applied by lamination, spraying, or painting. In some embodiments, shield 328 may be formed as part of the encapsulation process such that encapsulant 316 includes materials such as noted above that reduce the effects of EMI and RFI.

[0043] As described above, SiP 300 is typically placed on an adhesive surface (e.g., adhesive tape) or in a fixture pocket with raised walls during metal deposition (e.g., sputtering or electroplating) of metal for shield 328 to inhibit metal deposition on the lower surface of substrate 306. FIG. 6 depicts a side view cross-sectional representation of an embodiment of SiP 300 on adhesive surface 600. Adhesive surface 600 may be, for example, adhesive tape.

Adhesive surface 600 may be placed on metallization fixture 602 during metal deposition to form shield 328. As shown in FIG. 6, SiP 300 may sag into adhesive surface 600 such that region 124 is formed around the end portions of substrate 306. Additionally, warpage in SiP 300 may cause the SiP to not sit correctly on adhesive surface 600. Metal deposition along the side walls of SiP

300 may be inhibited in region 124.

[0044] FIG. 7 depicts a side view cross-sectional representation of an embodiment of SiP 300 on metallization fixture 700. In certain embodiments, metallization fixture 700 includes raised walls 702 that form a pocket for SiP 300 during metal deposition to form shield 328. In some embodiments, underfill material 314 sits or rests on seat 704 in the pocket of metallization fixture 700. Seat 704 may inhibit metal deposition on the underside of SiP 300. As shown in FIG. 7, if SiP 300 is too close to wall 702 during metal deposition (e.g., the SiP is placed too close to the wall or shifts towards the wall), region 124 may be formed around the end portions of substrate 306. Additionally, warpage in SiP 300 may cause the SiP to not sit correctly pocket of metallization fixture 700. Metal deposition along the side walls of SiP 300 may be inhibited in region 124.

[0045] FIG. 8 depicts an enlarged cross-sectional representation of an end portion of substrate 306 with shield 328 coupled to via metallization 324. As described above, region 124 may be inaccessible for metal deposition of shield material on the side surface of substrate due to an adhesive surface or a fixture pocket wall. As shown in FIG. 8, via metallization 324 may couple shield 328 to ground ring 326. The target area for connecting shield 328 to ground ring 326 is increased by the presence of via metallization 324 as any contact between the shield and the via metallization couples the shield to the ground ring. Thus, a target area for connecting shield 328 to ground ring 326 during metal deposition is at least the thickness of substrate 306 because via metallization 324 extends at least the height of substrate 306. For example, the target area may be about 100 μιτι whereas the target area without via metallization 324 (as shown in FIG. 2) may be at most about 10-15 μιη. Thus, even if region 124 inhibits some metal deposition along the side walls of substrate 306, shield 328 may be in physical and electrical contact with via metallization 324 along the substantially vertical walls in the end portions of substrate 306 and the shield is electrically coupled to ground ring 126, as shown in FIGS. 5 and 8. The larger target area, therefore, increases the reliability of forming a connection between shield 328 and ground ring 326, increasing the yield of SiP 300 and reducing costs for forming SiPs.

[0046] It is to be understood that multiple SiPs may be processed simultaneously to form shields on each of the SiPs at substantially the same time. For example, a plurality of SiPs may be placed on adhesive surface 600 (shown in FIG. 6) or on metallization fixture 700 (shown in FIG. 7). FIG. 9 depicts a side view cross-sectional representation of an embodiment a plurality of SiPs 300 on adhesive surface 600 during metal deposition to form a shield. FIG. 10 depicts a side view cross-sectional representation of an embodiment a plurality of SiPs 300 on metallization fixture 700 during metal deposition to form a shield.

[0047] After shield 328 is formed on SiP 300 (as shown in FIG. 5), the SiP may be coupled to a printed circuit board. FIG. 11 depicts a side view cross-sectional representation of an

embodiment of SiP 300 coupled to printed circuit board (PCB) 350. FIG. 12 depicts a top view representation of the embodiment depicted in FIG. 11 showing terminals 312' and metallization 324 formed around the perimeter of SiP 300 on PCB 350. In certain embodiments, PCB 350 is a multilayer PCB. In certain embodiments, PCB 350 includes ground layer 352 at the bottom most surface of the PCB. Ground layer 352 may be coupled to terminals 354 on the upper surface of PCB 350.

[0048] As shown in FIG. 1 1 , terminals 354 may be coupled to one or more of the outermost terminals 312' on SiP 300. Thus, due to the interconnection between outermost terminals 312' and shield 328 through ground ring 326 and via metallization 324, ground layer 352 is coupled to shield 328. In certain embodiments, the coupling of ground layer 352 and shield 328 forms EMI shield 356 (e.g., a Faraday cage or fence) around SiP 300, as shown in FIGS. 11 and 12. EMI shield 356 may inhibit electromagnetic interference (EMI), RFI, and/or other inter-device interference on the components in SiP 300 (e.g., die 302 and passive devices 304) during operation of the SiP.

[0049] FIG. 13 depicts an enlarged top view representation of an embodiment of section 1300 in SiP 300 from FIG. 12 before singulation through metallization 324 (e.g., metallization 324 is as shown in FIG. 3). As shown in FIG. 13 (similar to the embodiments shown in FIGS. 3 and 8), metallization 324 is formed through through-hole vias 322 with some metallization on the surface of the substrate. Metallization 324 is coupled to terminals 312' with ground ring 326. Dashed line 318 represents the line for singulation that forms SiP 300, as described above. As shown in FIG. 13, through-hole vias 322 are aligned substantially in parallel along dashed line 318 (e.g., the "singulation line").

[0050] In some embodiments, through-hole vias 322 are aligned along the singulation line with other patterns. FIG. 14 depicts a top view representation of an embodiment of section 1300' in

SiP 300 with through-hole vias 322 aligned along dashed line 318 in a non-linear pattern. In certain embodiments, through-hole vias 322 are arranged in a staggered pattern along dashed line 318. In some embodiments, the staggered pattern of through-hole vias 322 is a zig-zag pattern of through-hole vias, as shown in FIG. 14.

[0051] FIG. 15 depicts a top view representation of an embodiment of SiP 300 before singulation with through-hole vias 322 aligned along dashed line 318 in the staggered pattern. The staggered pattern of through-hole vias 322 along dashed line 318, shown in FIGS. 14 and 15, may increase the tolerance for location of singulation (e.g., location of dashed line 318). For example, if singulation actually occurs above or below dashed line 318 as it is shown in FIG. 14, the staggered partem of through-hole vias 322 along the dashed line increases the likelihood that at least some metallization 324 remains along the edge of the substrate in SiP 300 after singulation.

[0052] Further modifications and alternative embodiments of various aspects of the embodiments described in this disclosure will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the embodiments. It is to be understood that the forms of the embodiments shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the embodiments may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description. Changes may be made in the elements described herein without departing from the spirit and scope of the following claims.