A. Technical Field:
This invention relates to packaging memory cards, such as flash or ROM memory cards.
B. Related Art
A recent global spate of portable electronic devices such as computers, electronic toys, PDAs, cameras, smart phones, digital recorders, pagers, and such has spawned a concomitant need for compact, removable data storage components. One response to this demand has been development of so-called “memory cards.” Typically, a memory card contains at least one or more semiconductor memory chips within a standardized enclosure that has connectors thereon for electrical connection to external circuitry. Examples of these include so-called “PC Cards” and “MultiMediaCards” made in accordance with standards promulgated by such trade associations as Personal Computer Memory Card International Association (“PCMCIA”) and MultiMediaCard Association (“MMCA”), respectively.
An exemplary embodiment of such a memory card, namely, a MultimediaCard 10, is illustrated in top plan, cross-sectional side elevation, and bottom plan views of
Memory card 10 comprises a rectangular substrate 12, such as a printed circuit board (“PCB”), and one or more semiconductor memory dies or “chips” 14 mounted on and electrically connected thereto using, e.g., a layer 16 of adhesive and conventional wire bonds 18, respectively. Surface mounting passive components 20, e.g., resistors, may also be mounted on and connected to substrate 12. Contacts 22 are connected through substrate 12 to memory circuits defined by foregoing components and serve as input-output terminals of card 10.
When components 14, 20 have been mounted on and connected to substrate 12, chip 14 is protectively encapsulated by a “glob-topping” process. A glob 24 of a viscous encapsulant is dispensed onto a top surface of chip 14, allowed to flow over its sides to said surface of substrate 12, and cured to form a protective envelope over chip 14. An external cover or housing 26 (shown by dotted outline in
While said foregoing method provides a useable memory product, it is always desirable in a rapidly evolving market such as this to develop new fabrication methods that simplify a product, reduce its costs, and enhance its functionality.
This invention provides methods for making a memory card, e.g., a MultiMediaCard, that eliminate a need for an external housing and a separate encapsulation step, and that enables more memory to be packaged in a same size of card.
In one of said methods, a substrate having opposite first and second surfaces is provided. A memory die, or chip, is mounted on and electrically connected to said first surface of said substrate, e.g., by wire bonding. Said second surface of said substrate is attached to a first surface of a flat carrier sheet, e.g., an adhesive tape. In one embodiment, a mold is placed on said first surface of said carrier sheet such that said chip and said first surface of said substrate are enclosed in a cavity defined by said mold and said carrier sheet. Said chip and said first surface of said substrate are encapsulated in a monolithic body of hardened plastic, e.g., by injecting a fluid plastic, such as a filled liquid epoxy resin, into said cavity and curing said resin to harden same. Completed cards are then detached from said carrier sheet for use.
Said methods eliminate a need for an external housing on said card and a separate chip encapsulation step. These enable a reduction in card height, or incorporation of more memory chips in a card with a standardized height using die-stacking techniques. Said methods are well adapted to volume production techniques.
A better understanding of above and other features and advantages of this invention may be had from a consideration of a detailed description below of some exemplary embodiments thereof, particularly if such consideration is made in conjunction with appended drawings.
A memory card 110 made in accordance with one exemplary embodiment of methods of this invention is illustrated in top plan, cross-sectional side elevation, and bottom plan views of
As may be seen by reference to
In another possible embodiment (not illustrated) chip 114 may be mounted on and electrically connected to first surface 111 of substrate 112 using well known “flip chip,” or “C4” method of die-to-substrate attachment. In such mounting, it may be desirable to underfill a narrow space between chip 114 and first surface 111 of substrate 112 with a solid insulative material, e.g., a hardened epoxy resin, in a known manner. Surface mounting passive components 120, e.g., resistors, may also be mounted on and electrically connected to first surface 111 of substrate 112. As in prior art memory card 10, input-output contacts 122 are located at an edge of bottom surface 113 of card 110, and a chamfer 130 is provided on one corner thereof for one-way-only insertion of card into a host device connector.
However, comparing novel card 110 shown in
Said methods for making memory card 110 shown in
Thus, one method includes providing a continuous substrate strip 134 having opposite first and second surfaces 136, 138 and a plurality of individual chip-mounting sites 140 on said first surface thereof (see
As illustrated in
Substrate assemblies 144 can be temporarily attached to carrier sheet 148 with a “tacky,” i.e., partially cured, adhesive. It is desirable that said adhesive form a seal between opposing second surfaces 138 of individual substrate assemblies 144 and first surface 146 of carrier sheet 148 to prevent encapsulant from entering between said opposing surfaces during an encapsulation procedure. Said adhesive may be of a known type that is initially tacky but which loses adhesion when exposed to ultraviolet (“U.V.”) light. In such an embodiment, subsequent detachment of parts from carrier sheet 148 comprises exposing said adhesive to ultraviolet light and lifting said parts away from sheet 148.
When substrate assemblies 144 are attached to carrier sheet 148, each of chips 114, corresponding wire bonds 118, and corresponding chip-mounting sites 140 are encapsulated in a monolithic body 132 of hardened plastic (see
It may be noted in
In an alternative embodiment illustrated in
As shown in
When plastic body 132 is hardened, mold 164 is removed from carrier sheet 148, and plastic body 132 and underlying strip substrate 134 are cut through with, e.g., a saw 168 along cutting lines 142, i.e., perpendicular to a long side of strip substrate assembly 162, to define a plurality of individual memory cards 110 attached to carrier sheet 148 and separated from each other by a width W of said cut (see
In yet another possible embodiment (not illustrated), strip substrate assembly 162 can be encapsulated in a single-piece body of encapsulant and then cut into individual memory cards 110 using apparatus and methods described in U.S. Pat. No. 5,981,314 to T. P. Glenn, et al., which is incorporated herein in its entirety by this reference.
It may be noted that in embodiments requiring cutting, plastic body 132 and/or strip substrate 134 can be precisely sawed through downwards from a top surface of plastic body 132 to, but not through, carrier sheet 148, with currently available semiconductor wafer sawing equipment, and that such cutting procedure simultaneously forms coplanar side walls 156 and 158 on both severed plastic body 132 and severed substrate 112 of each memory card 110 where such sawing has taken place, as shown enlarged in
As will be apparent by now to those of skill in this art, many modifications, variations, and substitutions are possible in this invention's methods and materials without departing from its spirit and scope. Accordingly, this invention's scope should not be limited by any particular embodiments illustrated and described herein, as these are merely exemplary in nature. Rather, this invention's should commensurate with that of claims appended hereafter and their substantial equivalents.
This application is a divisional of U.S. patent application Ser. No. 09/656,253, entitled “Semiconductor Memory Cards And Method Of Making Same” filed Sep. 6, 2000.
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Number | Date | Country | |
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Parent | 09656253 | Sep 2000 | US |
Child | 10634541 | US |