Semiconductor memory cards and method of making same

Details Semiconductor memory cards and method of making same Semiconductor memory cards and method of making same

2000-09-06

2003-09-23

Fourson, George (Department: 2823)

Semiconductor device manufacturing: process

Packaging or treatment of packaged semiconductor

Making plural separate devices

Reexamination Certificate

active

06624005

ABSTRACT:

BACKGROUND
1. Technical Field
This invention relates to packaging memory cards, such as flash or ROM memory cards.
2. 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 Multimedia-Card
10
, is illustrated in top plan, cross-sectional side elevation, and bottom plan views of
FIGS. 1-3
, respectively. Card
10
illustrated has standardized dimensions of 32 mm long X 24 mm wide X 1.4 mm thick, and typically includes a memory capacity of 2 to 32 megabits (“MB”) of memory, which is accessed through seven contacts
22
located on a bottom surface of card
10
using, e.g., a standard serial port interface (“SPI”) interface. A simple chamfer
30
on one corner of card
10
prevents incorrect insertion of card
10
into a connector in a host device.
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
FIG. 1
) of thin sheet metal or plastic is installed over substrate
12
assembly by embedding said top surface of assembly in a bed
28
of an adhesive contained in housing
26
.
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.
BRIEF SUMMARY
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 diestacking techniques. Said methods are well adapted to volume production techniques.


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