HIGH DENSITY MEMORY CARD SYSTEM AND METHOD

Related Applications

[001] This application is a continuation-in-part of U.S. Pat. App. No. 11/330,307, filed

January 11, 2006, pending.

Technical Field

[002] This invention relates to high density memory cards that employ leaded package integrated circuits.

Background

[003] A variety of systems and techniques are known for stacking packaged integrated circuits. Some techniques are devised for stacking chip-scale packaged devices (CSPs) while other systems and methods are better directed to leaded packages such as those that exhibit a set of leads extending from at least one lateral side of a typically rectangular package. [004] Memory devices are packaged in both chip-scale (CSP) and leaded packages.

However, techniques for stacking CSP devices are typically not optimum for stacking leaded devices. Although CSP devices are gaining market share, in many areas, integrated circuits continue to be packaged in high volumes in leaded packages. For example, the well-known flash memory integrated circuit is typically packaged in a leaded package with fine-pitched leads emergent from one or both sides of the package. A common package for flash memory is the thin small outline package commonly known as the TSOP typified by leads emergent from one or more (typically a pair of opposite sides) lateral sides of the package.

[005] The on-going demand for miniaturized and modular data storage has spawned a variety of memory module configurations, and many such designs employ leaded flash memory devices. Consumer electronics such as digital cameras and portable computers employ a variety of memory modules and cards to allow storage mobility and cross-platform flexibility. As with many developments in electronics, a variety of formats and configurations for storage have recently been developed such as the Multi Media Card (MMC) and the Memory Stick from

i

Sony. One of the more successful recent portable memory storage configurations is the "Secure Digital" or "SD" format for memory cards first developed by Matsushita, SanDisk and Toshiba in the late 1990's. The "secure" part of the name for this card comes the encryption capability typically incorporated into the cards to reduced music piracy concerns. This capability is seldom employed, however.

[006] The circuitry employed in a typical memory card is often a flash memory die or flash circuit in a specialized package integrated into a plastic casing configured to comply with the relevant dimensional requirements. Use of flash memory die or specialized packaging fails, however, to leverage testing and reliability and cost advantages implicit in TSOP packaged flash memory resulting from testing and volume production of memory circuitry fabricated and packaged in that format. What is needed, therefore, is a memory card configured to employ TSOP packaged memory.

[007] Although the art has many techniques for stacking leaded devices, a new system and method for stacking leaded package TSOP devices in a memory card format is a welcome development. Accordingly, the present application discloses improved systems and methods for electrically and thermally coupling adjacent integrated circuit devices in stacked modules configured as memory cards.

Summary of the Invention

[008] The present invention provides a system and method for employing leaded packaged memory devices in memory cards. Leaded packaged ICs are disposed on one or both sides of a flex circuitry structure to create an IC-populated structure. In a preferred embodiment, leads of constituent leaded IC packages are configured to allow the lower surface of the leaded IC packages to contact respective surfaces of the flex circuitry structure. Contacts for typical embodiments are supported by a rigid portion of the flex circuitry structure and the IC-populated structure is disposed in a casing to provide card structure for the module.

Brief Description of the Drawings

[009] Fig. 1 is an exploded view of a stacked module devised in accordance with a preferred embodiment of the present invention.

[0010] Fig. 2 is a side view of a stacked module devised in accordance with a preferred embodiment of the present invention.

[0011] Fig. 3 is a plan view of one side of a flex circuit in accordance with an embodiment of the present invention.

[0012] Fig. 4 is a plan view of another side of a flex circuit in accordance with an embodiment of the present invention.

[0013] Fig. 5 depicts the area marked "A" in Fig. 2.

[0014] Fig. 6 is a side view of a stacked module in accordance with an alternative preferred embodiment of the present invention.

[0015] Fig. 7 is a plan view of a stacked module in accordance with an alternative preferred embodiment of the present invention.

[0016] Fig. 8 is a plan view of a stacked module in accordance with another alternative preferred embodiment of the present invention.

[0017] Fig. 9 is a plan view of a stacked module in accordance with another alternative preferred embodiment of the present invention.

[0018] Fig. 10 is a plan view of another side of a stacked module in accordance with another alternative preferred embodiment of the present invention.

[0019] Fig. 11 is a perspective depiction of an exemplar memory card devised in accordance with a preferred embodiment of the present invention.

[0020] Fig. 12 depicts a reverse side of an exemplar memory card devised in accordance with a preferred embodiment of the present invention.

[0021] Fig. 13 is an exploded depiction of an exemplar memory card devised in accordance with a preferred embodiment of the present invention.

[0022] Fig. 14 depicts a flex circuitry structure populated with ICs packaged in leaded packages.

[0023] Fig. 15 is a depiction of a reserve side of a flex circuitry structure populated with ICs in leaded packages.

[0024] Fig. 16 is a cross-sectional depiction of a portion of an IC-populated flex circuitry structure of an exemplar memory card in accordance with a preferred embodiment of the present invention.

Detailed Description

[0025] Fig. 1 is an exploded view of an exemplar stacked module 10 devised in accordance with a preferred embodiment of the present invention. Exemplar module 10 is comprised of leaded ICs 20 and 22 each having upper and lower sides or surfaces 23 and 25, respectively, and lateral sides S 1 and S2 which, as those of skill will recognize, may be in the character of edges or sides and need not be perpendicular in aspect to the upper and lower surfaces 23 and 25. Leads 24 are emergent from sides Sl and S2. In a preferred embodiment, leads 24 are deflected to remain within the space defined by planes PL and PU defined by lower surfaces 25 and 23 respectively of the respective ICs to allow the lower surfaces 25 of each of the respective leaded packaged ICs to be in contact with the respective surfaces 15 and 17 of flex circuit 12 when the ICs are connected to the flex. In this disclosure, contact between the lower surface 25 of a leaded IC and the surfaces of flex circuit 12 includes not only direct contact between surface or side 25 and flex but shall include those instances where intermediate materials such as adhesive is used between the respective leaded IC and flex.

[0026] The present invention may also be employed with circuitry other than or in addition to memory such as the flash memory depicted in a number of the present Figs. Other exemplar types of circuitry that may be aggregated in stacks in accordance with embodiments of the invention include, just as non-limiting examples, DRAMs, FPGAs, and system stacks that include logic and memory as well as communications or graphics devices. It should be noted, therefore, that the depicted profile for ICs 20 and 22 is not a limitation and that upper and lower leaded ICs 20 and 22 respectively need not be TSOPs or TSOP-like and the packages employed may have more than one die or leads emergent from one, two, three or all sides of the respective package body. For example, a module 10 in accordance with embodiments of the present invention may employ leaded ICs 20 and 22 that have more than one die within each package and may exhibit leads emergent from only one side of the package. In such cases, adhesives will

typically be employed between the IC and flex circuit. Further, a module 10 in accord with the present invention need not have two ICs as the invention may be employed to devise a stacked module 10 with two or more ICs as those of skill will understand after appreciating this disclosure. Further, techniques disclosed herein may be employed to stack a leaded IC in a leaded-CSP combination stack.

[0027] In the depicted preferred embodiment, flex circuit 12 (e.g., "flex", "flex circuitry", "flexible circuit" etc.) is disposed between leaded ICs 20 and 22 and exhibits a first side 15 having two pluralities of connective sites 34 and 36 adapted for connection to a leaded IC and, in this embodiment, another optional plurality of connective sites 32. Flex circuit 12 also exhibits a second side 17 having two pluralities of connective sites 44 and 46. Those of skill will recognize that flex circuit 12 may be comprised from traditional flexible circuitry or, in some of the alternative embodiments, what is sometimes called rigid-flex may be employed. Such rigid flex exhibits rigid areas and flexible areas to provide an interconnection function required of flex circuit 12 in the present invention.

[0028] Pluralities 34 and 36 and 44 and 46 of connective sites are adapted for connection to the leads of leaded packages IC 20 and IC 22, respectively, each of which has a plurality of peripheral sides, individual ones of which sides are identified as Sl and S2. Optional third plurality of connective sites 32 is adapted for connection of module 10 to an external circuit or environment.

[0029] Plural leads 24 are emergent from at least one of the plural sides of the ICs and typically, a plurality of leads 24 is emergent from one of the plural sides of each of the ICs 20 and 22 and a second plurality of leads 24 is emergent from another one of the plural sides of each of ICs 20 and 22. Leaded ICs 20 and 22 are connected to flex circuit 12 through the leads 24 of leaded ICs 20 and 22. As those of skill will recognize, many techniques exist for connecting the leads of leaded ICs 20 and 22 to the connective sites. Such techniques include, as a non-limiting example, use of solder or other conductive attachment. Other forms of bonding other than solder between the connecting sites and leads 24 may also be employed (such as brazing or

welding for example) but soldering techniques are well understood and adapted for use in large scale manufacturing.

[0030] Fig. 2 depicts a side perspective view of a stacked module 10 devised in accordance with a preferred embodiment of the present invention. As depicted, lower side 25 of each of leaded ICs 20 and 22 are adjacent to sides 15 and 17 respectively, of flex circuit 12. To realize the adjacent and, preferably, contact (touching) relationship between the lower side 25 of a selected leaded IC and the respective flex circuit side, leads 24 typically require modification or reconfiguration which is preferably performed before mounting of the leaded IC to flex circuit 12. Those of skill will note that a preferred method for reconfiguration of leads 24 comprises use of a jig to fix the position of body 29 of the respective leaded IC and, preferably, support the lead at the point of emergence from the body at sides S 1 and S2 of leaded ICs 20 and 22 before deflection of the respective leads toward the upper plane PU to confine leads 24 to the space between planes PL and PU of the respective leaded IC as earlier shown in Fig. 1. This is because typically, leaded ICs such as TSOPs are configured with leads that extend beyond the lower plane PL. In order for the lower surface 25 of the respective leaded packaged ICs to contact (either directly or through an adhesive or thermal intermediary) the respective surfaces of the flex circuit, the leads 24 must be typically reconfigured.

[0031] Fig. 3 depicts a plan view of side 15 of the flex circuit. As depicted, side 15 exhibits three pluralities of connective sites, 32, 34, and 36, each comprised of individual connective sites 32C, 34C, and 36C, respectively. First and second pluralities 34 and 36 are adapted for connection to leaded IC 20 through leads 24, with optional plurality of connective sites 32 being adapted for connecting module 10 to an external circuit or environment.

[0032] Fig. 4 depicts a plan view of side 17 of flex circuit 12. As depicted, side 17 exhibits two pluralities of connective sites 44 and 46 respectively, each comprised of multiple connective sites 44C and 46C, respectively, these sites being adapted for connection to leaded IC 22 through leads 24.

[0033] Fig. 5 depicts the area identified by "A" in earlier Fig. 2. As depicted, the standard lead shape is modified or reconfigured to reduce the profile X of module 10 as lower surfaces 25 of

leaded ICs 20 and 22 are adjacent to and, preferably, in contact with surfaces 15 and 17, respectively, of flex circuit 12. Profile X is the distance between respective upper planes PU20 and PU22. Leads 24 of leaded ICs 20 and 22 are preferably configured to allow leaded ICs 20 and 24 to be in either direct or indirect (through intermediary adhesive for example) contact with flex 12.

[0034] Leads 24 of leaded ICs 20 and 22 employed in an exemplar module 10 are shown in contact with connective sites 34C and 44C, for example, while lower surface 25 of the leaded

ICs 20 and 22 are in contact with the respective sides 15 and 17 of flex circuit 12.

[0035] Fig. 6 depicts an exemplar module 10 having connective sites 32 for connection to an external circuit or environment. Those of skill will recognize that when a third plurality of connective sites such as the depicted reference 32 are employed, they may be disposed on either side 15 or 17 of flex circuit 12. In this depiction, adhesive 33 is shown between lower surfaces

25 and respective sides of flex circuit 12.

[0036] Fig. 7 illustrates that, in devising a module in accordance with the present invention, some embodiments may be constructed where connective sites 32 take the form of edge connector pads for connection with an edge connector such as, for example, those typically found in computer applications for memory expansion.

[0037] Fig. 8 illustrates a plan view of an exemplar module 10 in accordance with an alternative preferred embodiment of the present invention. Fig. 8 employs a socket connector as the third plurality of connective sites 32 for connecting stacked module 10 to an external circuit or environment.

[0038] Fig. 9 illustrates a module 10 in accordance with an alternative preferred embodiment of the present invention, showing alternative arrangements of the pluralities of connection sites on side 15 of the flex circuit. In the depiction of Fig. 9, the first and second pluralities of connective sites are oriented in a first direction while the third plurality of connective sites for connection of the circuit module to an application environment are oriented in a direction perpendicular to the orientation of the first and second pluralities of connective sites.

[0039] Figure 10 is a plan view of another side of the stacked module depicted in Figure 9, sharing alternative arrangements of the pluralities of connective sites on side 17 of the flex circuit.

[0040] Fig. 11 is a perspective depiction of an exemplar memory card 100 devised in accordance with a preferred embodiment of the present invention. Although a variety of combinations of leaded devices may be aggregated according to the principles of the present invention to create a variety of memory cards, in this exemplar embodiment, memory card 100 is comprised from leaded ICs 2OA and 2OB visible in the depiction of Fig. 11 and another two leaded ICs 22A and 22B which are visible in later Figs. In preferred SD memory card configurations, ICs 2OA and 2OB as well as 22A and 22B will typically be flash memory circuits in TSOP packages. As those of skill will recognize, card 100 can be dimensioned to comply with SD or other card or module requirements.

[0041] Memory card 100 exhibit card contacts 102 _l5 102 ₂ * * * 102 _n and may exhibit write lock 108 familiar to those of skill in the art. Plastic case 104 provides structure for card 100 and when the two typical parts of case 104 are assembled, case 104 will present obverse and reverse sides 104A and 104B, respectively. Because of typically tight tolerances in fitting ICs 2OA, 2OB, 22A and 22B with case 104, package molding flash often found along seams of leaded IC bodies are preferably removed before assembly of card 100.

[0042] Fig. 12 depicts a reverse side of an exemplar memory card devised in accordance with a preferred embodiment of the present invention. Lower ICs 22A and 22B are shown as is case 104 and reverse surface 104B of case 104.

[0043] Fig. 13 is an exploded depiction of an exemplar memory card devised in accordance with a preferred embodiment of the present invention. As shown, exemplar casing 104 has two parts 104i and 104 ₂ that exhibit windows Wl and W2 to provide space for bodies 29 of the leaded ICs populated on flexible circuitry 120. Parts 104i and 104 ₂ fit together to frame flexible circuitry structure 106 as shown. Flexible circuitry structure 106 is preferably an IC-populated flex circuit 120 which, as will be shown, preferably has areas that are rigid and areas that are flexible. Populated along a first side of flexible circuit 120 are ICs 2OA and 2OB, while ICs 22A and 22B

are populated along a second side of flexible circuit 120. Each of the depicted leaded ICs exhibits a plurality of leads 24 emergent from at least one of the plural peripheral sides Sl or Sl of the respective bodies 29 of the respective leaded ICs as shown in greater detail in earlier Figs. As those of skill will recognize, the number and orientation of leaded packaged ICs employed in card 100 can vary with the particular dimensional and electrical requirements imposed. [0044] Fig. 14 depicts an obverse side of an exemplar flexible circuitry structure 106 populated with leaded ICs. As shown, flexible circuitry 120 is comprised of rigid portions 120R that provide support for card contacts 102i-102 _n and flexible portions 120F upon which are populated the respective leaded ICs 2OA and 2OB. Card contacts 102i-102 _n shown along the first major side 15 of flexible circuitry 120 may, as those of skill will recognize, be along one or both major sides of flexible circuitry 120. Further, those of skill will recognize that flexible circuitry 120 need not have both rigid and flexible portions, but that employment of such dual natured flex circuitry provides construction advantages in building card 100 that are of value in creating a card 100 that tolerates the rough usage requirements of consumer electronics, for example.

[0045] Fig. 15 is a depiction of a reserve side of a flexible circuitry structure 106 populated with ICs in leaded packages and shows ICs 22A and 22B populated along a second side of flexible portion 120F of flex circuitry 120. A controller 110 is shown disposed in a rigid portion 120R of flexible circuitry 120 of IC-populated flex circuitry structure 106. Although typically devised from multiple leaded ICs populated along a flexible circuit 120 comprised of both rigid and flexible portions 120R and 120F, flexible circuitry structure 106 may also employ for example a separate rigid material adhered to a portion of flexible flex circuitry as shown in Fig. 16 to create a rigid portion 120R preferred for support of card contacts 102i - 102 _n which are located in an insertion area of card 100. Card contacts 102i - 102 _n are configured to fit into an SD slot when card 100 is configured for SD use. As those in field will know, an SD card is typically configured or dimensioned to have the dimensions of 32 mm x 24 mm x 2.1 mm, but can be as thin as 1.4 mm.

[0046] Fig. 16 is a cross-sectional depiction of a portion of an IC-populated flexible circuitry structure 106 of an exemplar memory card 100 in accordance with a preferred embodiment of the present invention. As earlier shown in Figs. 1 and 5, leads 24 of the respective leaded ICs are deflected to remain within the space defined by planes PL and PU defined by lower and upper surfaces 25 and 23, respectively, to allow the lower surfaces 25 of each of the respective leaded packaged ICs to be in contact with the respective surfaces 15 and 17 of flexible circuitry 120 along which the ICs are disposed. The leaded ICs are typically connected to flexible circuitry 120 by connective sites such as the individual ones shown and identified in Fig. 16 with references 34 and 44 although a variety of techniques may be employed to populate flexible circuitry 120 with exemplar leaded ICs 2OA, 2OB, 22A and 22B. In this disclosure, contact between the lower surface 25 of a leaded IC and the respective major surface of flexible circuit 120 includes not only immediate and direct contact between lower surface 25 and flexible circuitry 120 but shall include those instances where intermediate materials such as adhesive 33 shown in Fig. 16 are between the lower surface 25 of the respective leaded IC and the respective major surface of the flexible circuitry.

[0047] It will be seen by those skilled in the art that many embodiments taking a variety of specific forms and reflecting changes, substitutions, and alternations can be made without departing from the spirit and scope of the invention. Therefore, the described embodiments illustrate but do not restrict the scope of the claims.