Information
-
Patent Grant
-
6624005
-
Patent Number
6,624,005
-
Date Filed
Wednesday, September 6, 200023 years ago
-
Date Issued
Tuesday, September 23, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Fourson; George
- Foong; Suk San
Agents
- Bever, Hoffman & Harms, LLP
- Parsons; James E.
-
CPC
- H01L25/50 - Multistep manufacturing processes of assemblies consisting of devices, each device being of a type provided for in group H01L27/00 or H01L29/00
- H01L21/561 - Batch processing
- H01L23/3121 - a substrate forming part of the encapsulation
- H01L23/49855 - for flat-cards
- H01L24/97 - the devices being connected to a common substrate
- H01L25/0657 - Stacked arrangements of devices
- H01L24/45 - of an individual wire connector
- H01L24/48 - of an individual wire connector
- H01L24/49 - of a plurality of wire connectors
- H01L24/73 - Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
- H01L2224/05554 - being square
- H01L2224/05599 - Material
- H01L2224/32145 - the bodies being stacked
- H01L2224/32225 - the item being non-metallic
- H01L2224/45099 - Material
- H01L2224/48091 - Arched
- H01L2224/48227 - connecting the wire to a bond pad of the item
- H01L2224/48472 - the other connecting portion not on the bonding area also being a wedge bond
- H01L2224/49175 - Parallel arrangements
- H01L2224/73265 - Layer and wire connectors
- H01L2224/85399 - Material
- H01L2224/97 - the devices being connected to a common substrate
- H01L2225/0651 - Wire or wire-like electrical connections from device to substrate
- H01L2225/06579 - TAB carriers beam leads
- H01L2924/00014 - the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
- H01L2924/01005 - Boron [B]
- H01L2924/01013 - Aluminum [Al]
- H01L2924/01015 - Phosphorus [P]
- H01L2924/01023 - Vanadium [V]
- H01L2924/01033 - Arsenic [As]
- H01L2924/01074 - Tungsten [W]
- H01L2924/181 - Encapsulation
- H01L2924/19043 - being a resistor
- H01L2924/19105 - in a side-by-side arrangement on a common die mounting substrate
-
US Classifications
Field of Search
US
- 438 106
- 438 127
- 438 126
- 438 977
- 438 113
- 438 118
- 438 FOR 374
- 257 679
- 264 27217
-
International Classifications
-
Abstract
Alternative methods for making memory cards for computers and such eliminate a need for a separate external housing and a separate chip encapsulation step and enable more memory to be packaged in a same-sized card. One of said methods includes providing a substrate having opposite first and second surfaces with a memory chip mounted on and in electrical connection with a first surface of said substrate. Said second surface of said substrate is temporarily attached to a first surface of a flat carrier sheet, e.g., an adhesive tape. In one embodiment, a mold having a cavity therein is placed on said first surface of said carrier sheet such that said chip and said first surface of said substrate are enclosed in said cavity between said mold and said carrier sheet. A fluid plastic is introduced into said cavity and cured to encapsulate said chip and at least said first surface of said substrate in a protective, monolithic body of hardened plastic. A completed card is then detached from said carrier sheet.
Description
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.
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.
DESCRIPTION OF DRAWINGS
FIG. 1
is top plan view of a prior art memory card, with separate external housing shown in dotted outline to reveal card details;
FIG. 2
is a cross-sectional side elevation view into said conventional card shown in
FIG. 1
, as revealed by a cross-section taken therein along lines II—II;
FIG. 3
is a bottom plan view of said prior art card shown in
FIGS. 1 and 2
;
FIG. 4
is a top plan view of an exemplary embodiment of a memory card made in accordance with a method of this invention;
FIG. 5
is a cross-sectional side elevation view into said card shown in
FIG. 4
, as revealed by a cross-section taken therein along lines V—V;
FIG. 6
is a bottom plan view of said card shown in
FIGS. 4 and 5
;
FIG. 7
is a top plan view of a plurality of memory card subassemblies connected together in a strip form during fabrication and before being encapsulated in accordance with a method of this invention;
FIG. 8
is a top plan view of said plurality of memory card subassemblies shown in
FIG. 7
attached to an elongated carrier sheet after being separated and during encapsulation in accordance with a method of this invention;
FIG. 9
is a top plan view of said plurality of memory cards subassemblies shown in
FIG. 8
after being encapsulated;
FIG. 10
is a top plan view of a plurality of memory card subassemblies connected together in a strip form during fabrication and before being encapsulated in accordance with another method of this invention;
FIG. 11
is a top plan view of said plurality of memory card subassemblies shown in
FIG. 10
attached to an elongated carrier sheet after being separated and during encapsulation in accordance with a method of this invention;
FIG. 12
is a top plan view of said plurality of memory cards subassemblies shown in
FIG. 11
after being encapsulated and singulated;
FIG. 13
is a cross-sectional side elevation view into a memory card having two stacked chips in accordance with one embodiment of this invention;
FIG. 14
is an enlarged partial cross-sectional elevation view into said memory card shown in
FIG. 4
, as revealed by a cross-section taken therein along lines XIV—XIV; and,
FIG. 15
is an enlarged partial cross-sectional elevation view into one of said memory cards shown in
FIG. 12
, as revealed by a cross-section taken therein along lines XV—XV.
DETAILED DESCRIPTION
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
FIGS. 4-6
, respectively. In
FIG. 1
, a “mold cap,” or hardened plastic body
132
encapsulating electronic components
114
and
120
and top surface of substrate
112
is shown in dotted outline to reveal underlying detail. Cross-sectional elevation view into card
110
of
FIG. 5
is produced by taking a section in
FIG. 4
along lines V—V. Top plan views of two alternative embodiments of memory card
110
at various stages in its production are shown in
FIGS. 7-9
, and
10
-
12
, respectively.
As may be seen by reference to
FIGS. 4-6
, memory card
110
is identical in size and contains elements similar to those of prior art memory card
10
illustrated in
FIGS. 1-3
. Similar elements in card
110
are referenced by similar reference numbers, plus
100
. Novel card
110
comprises a rectangular substrate
112
, e.g., a PCB, having respective first and second surfaces
111
and
113
and a semiconductor memory chip
114
mounted on and electrically connected on first surface
111
. Chip
114
is mounted on first surface
111
of substrate
112
with a layer
116
of adhesive and electrically connected to said first surface with conventional wire bonds
118
. Particular contents of memory card
110
and configuration of external contacts
122
may vary depending on particular application. For example, a plurality of memory chips and passive components may be used, or passive components may be omitted, or memory management chips may be included, among other possibilities. Again, certain industry standards apply in certain cases.
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 “C
4
” 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
FIGS. 4-6
with prior art card
10
shown in
FIGS. 1-3
also reveals some important differences. For example, thin metal or plastic external housing
26
, bed
28
of adhesive, and glob-top encapsulation
24
over chip
14
of prior art card
10
are replaced in novel card
110
by a single hardened plastic body
132
which more effectively encapsulates electronic components
114
and
120
, and respective first surface
111
and side walls
158
of substrate
112
. Moreover, replacement of such former elements and manufacturing processes related thereto by said single latter element and encapsualtion process frees up additional space H (see
FIG. 5
) in card
110
above chip
114
, namely, about 0.3 mm. This space can be used e.g., to mount additional components. For example, as shown in
FIG. 13
, a second memory chip
114
can be mounted on top of first-mounted memory chip
114
above and electrically connected to first surface
111
of substrate
112
using die-stacking techniques disclosed in, e.g., U.S. application Ser. No. 09/536,574, filed 03/28/2000, and assigned to an assignee hereof. This increases memory capacity of card
110
while retaining said same, standard form factor.
Said methods for making memory card
110
shown in
FIGS. 4-6
, as described below in connection with
FIGS. 7-9
, and
10
-
12
, respectively, are readily adapted to simultaneous production of a number of cards in an elongated strip form. However, such methods are easily extended to manufacture of a single memory card
110
, or alternatively, to simultaneous production of a rectangular array thereof (not illustrated), e.g., a 4×4 array of memory cards
110
.
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 FIG.
7
). A memory chip
114
and additional passive components
120
, if any, are mounted on and electrically connected to first surface
136
of strip substrate
134
in corresponding ones of mounting sites
140
, as described above. Alternatively, a plurality of memory chips and passive devices, or one or more memory devices and no passive devices, may be mounted on first surface
136
of strip substrate
134
. Numbers and types of memory chips and passive components are application specific, and not limiting of this invention.
As illustrated in
FIG. 7
, after electronic components
114
and
120
are mounted on and electrically connected to corresponding ones of mounting sites
140
on first surface
136
of strip substrate
134
, substrate
134
is cut along dotted lines
142
to divide assembled strip
134
into a plurality of individual substrate assemblies
144
, each having a corresponding individual substrate
112
. Respective second surfaces
138
of each individual substrate assembly
144
are temporarily attached to a first surface
146
of a flat carrier sheet
148
(see
FIG. 8
) such that individual assemblies
144
are attached to carrier sheet
148
in a spaced-apart relation-ship, as shown in FIG.
8
. Carrier sheet
148
may be a plastic film with an adhesive thereon, or a polyimide film with an adhesive thereon.
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 FIGS.
4
-
6
). This can be effected in a number of different ways. As shown in
FIG. 8
, a mold
150
(shown by dashed outline) having a plurality of cavities
152
therein is placed on first surface
146
of carrier sheet
148
such that each individual substrate assembly
144
is enclosed in a separate corresponding cavity
152
between mold
150
and carrier sheet
148
. Carrier sheet
148
may be provided with a plurality of tooling holes
154
for appropriate relative alignment of substrate assemblies
144
with mold cavities
152
. Cavities
152
are each filled with a fluid plastic, e.g., an epoxy resin, and said resin is cured to harden same. When encapsulation is complete, mold
150
is removed from carrier sheet
148
to leave a plurality of completed memory cards
110
attached thereto, as shown in FIG.
9
. Completed memory cards
110
are then detached from carrier sheet
148
for, e.g., post-encapsulation testing and packaging.
It may be noted in
FIGS. 4-6
that side walls
156
of plastic body
132
are spaced outside of corresponding side walls
158
of respective individual substrates
112
(see enlarged section of FIG.
14
), which results from interior side walls
160
of mold cavities
152
being positioned outside of side walls
158
of respective individual substrates
112
during encapsulation (see FIG.
8
). However, in other possible embodiments, one or more of corresponding respective side walls
156
and
158
of plastic body
132
and respective individual substrates
112
may be coplanar, as shown in FIG.
15
and described in more detail below.
In an alternative embodiment illustrated in
FIGS. 10-12
, a memory chip
114
and additional passive components
120
, if any, are mounted on and electrically connected to first surface
136
of strip substrate
134
in corresponding ones of chip-mounting sites
140
, as described above, to form a single strip assembly
162
(FIG.
10
). However, strip substrate
134
is not divided into individual assemblies, as above. Instead, second surface
138
of undivided strip assembly
162
is then attached to first surface
146
of carrier sheet
148
, and memory chips
114
, passive components
120
, and at least first surface
136
of strip assembly
162
are encapsulated in a single monolithic body
132
of hardened plastic, as follows.
As shown in
FIG. 11
, a mold
164
having a single cavity therein is placed on first surface
146
of carrier sheet
148
such that at least first surface
136
of substrate strip assembly
162
, including chips
114
and passive components
120
, are enclosed in cavity
166
between mold
164
and carrier sheet
148
. Cavity
166
is then filled with a fluid plastic, and said plastic is hardened into a single-piece plastic body
132
(see FIG.
11
).
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 FIG.
12
).
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 FIG.
15
. It may be further noted that, if a one-way keying chamfer
130
is not molded into each memory card
110
during encapsulation, as illustrated in
FIG. 9
, chamfer
130
can be precisely sawed into an appropriate corner of each card
110
after cards
110
are separated from carrier sheet
148
.
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.
Claims
- 1. A method of making a plurality of memory cards, said method comprising:providing a substrate having opposite first and second surfaces and a plurality of individual chip-mounting sites on said first surface thereof, wherein the substrate is a printed circuit board sheet with input/output terminals on the second surface of each chip mounting site thereof; mounting a memory chip on and in electrical connection with said first surface of said substrate in a corresponding one of each of said mounting sites; attaching said second surface of said substrate to a first surface of a carrier sheet; encapsulating each of said memory chips and a corresponding one of said mounting sites in a body of hardened plastic; cutting through said body and said printed circuit board sheet along a periphery of at least a portion of each of said mounting sites to define a plurality of individual memory cards on said carrier sheet, whereby the memory card so formed includes an encapsulated subportion of the printed circuit board sheet, said subportion having a substantially rectangular perimeter including at least four rectilinear side wall portions, wherein at least two of said rectilinear side wall portions are encapsulated during said encapsulation step and at least one said rectilinear side wall portion of the memory card so formed is not encapsulated and is coincident with a side of the plastic body; and, detaching said individual memory cards from said carrier sheet.
- 2. The method according claim 1, wherein said encapsulating comprises:placing a mold having a cavity therein on said first surface of said carrier sheet such that said memory chips and at least said first surface of said substrate are enclosed in said cavity between said mold and said carrier sheet; filling said cavity with a fluid plastic; and, hardening said plastic.
- 3. The method according to claim 1, wherein each of said individual memory cards has one or more corners, and wherein said cutting comprises cutting a chamfer on one of said corners.
US Referenced Citations (31)
Foreign Referenced Citations (1)
Number |
Date |
Country |
62-9639 |
Jan 1987 |
JP |