U.S. patent application number 10/621882 was filed with the patent office on 2005-01-20 for peripheral card with hidden test pins.
Invention is credited to Takiar, Hem P..
Application Number | 20050013106 10/621882 |
Document ID | / |
Family ID | 34063084 |
Filed Date | 2005-01-20 |
United States Patent
Application |
20050013106 |
Kind Code |
A1 |
Takiar, Hem P. |
January 20, 2005 |
Peripheral card with hidden test pins
Abstract
A peripheral card includes a circuit board, various circuit
elements on the circuit board, a set of user terminals, a set of
test terminals, and an enclosure that covers a portion of the
circuit board and the circuit elements. The enclosure does not
cover the user terminals and test terminals. After the peripheral
card is tested, the test terminals are covered with a conformal
contact coating in order to prevent access to the test
terminals.
Inventors: |
Takiar, Hem P.; (Sunnyvale,
CA) |
Correspondence
Address: |
Burt Magen
Vierra Magen Marcus Harmon & DeNiro LLP
Suite 540
685 Market Street
San Francisco
CA
94105
US
|
Family ID: |
34063084 |
Appl. No.: |
10/621882 |
Filed: |
July 17, 2003 |
Current U.S.
Class: |
361/679.31 ;
174/250; 174/260; 29/593; 29/832; 29/854; 29/860; 361/679.01 |
Current CPC
Class: |
H01L 2224/32145
20130101; H01L 2224/48091 20130101; H01L 2924/14 20130101; Y10T
29/49004 20150115; Y10T 29/49169 20150115; G06K 19/077 20130101;
H01L 2224/48227 20130101; G06K 19/07732 20130101; H01L 2224/73265
20130101; H05K 1/0268 20130101; H01L 2924/14 20130101; H01L
2224/32225 20130101; H01L 2224/73265 20130101; H01L 2924/19041
20130101; Y10T 29/49179 20150115; H01L 2224/73265 20130101; H01L
2224/32225 20130101; H01L 2924/00014 20130101; H01L 2924/01004
20130101; H01L 24/73 20130101; Y10T 29/4913 20150115; H01L 2924/00
20130101; H01L 2924/00012 20130101; H01L 2224/48227 20130101; H01L
2224/48227 20130101; H01L 2924/00012 20130101; H01L 2224/32145
20130101; H05K 3/284 20130101; H01L 2224/48091 20130101; H01L
2924/1815 20130101 |
Class at
Publication: |
361/684 ;
029/854; 029/860; 029/593; 029/832; 174/250; 174/260 |
International
Class: |
G01R 001/00; H05K
001/00; H05K 005/00; H05K 003/30 |
Claims
I claim:
1. A method of making a memory card card, comprising the steps of:
adding circuit elements to a circuit board, said circuit board
includes a set of test terminals; testing one or more of said
circuit elements using said test terminals; and covering said test
terminals with a conformal contact coating in order to prevent
access to said test terminals.
2. A method according to claim 1, wherein: said step of covering
includes applying a liquid directly to a first surface of said
circuit board.
3. A method according to claim 2, wherein: said liquid includes a
solder mask.
4. A method according to claim 2, wherein: said liquid includes a
photoresist.
5. A method according to claim 2, wherein: said liquid includes a
thermoplastic.
6. A method according to claim 2, wherein: said liquid includes an
epoxy.
7. A method according to claim 2, wherein: said liquid includes
polyimide.
8. A method according to claim 2, wherein: said liquid is applied
using a screen printing process.
9. A method according to claim 1, wherein: said step of covering
includes applying a film directly to a first surface of said
circuit board.
10. A method according to claim 9, wherein: said film includes an
adhesive on one surface.
11. A method according to claim 9, wherein: said film includes
mylar.
12. A method according to claim 9, wherein: said film includes
polyimide.
13. A method according to claim 1, wherein: said step of adding
circuit elements includes adding a flash memory array to said
circuit board.
14. A method according to claim 1, wherein: said step of adding
circuit elements includes mounting a first die on said circuit
board and mounting a second die on said first die.
15. A method according to claim 14, wherein: said first die
includes a flash memory array and said second die includes a
controller.
16. A method according to claim 14, wherein: said first die is wire
bonded to said circuit board; and said second die is wire bonded to
said circuit board.
17. A method according to claim 1, wherein: said circuit board
includes a conductive layer and a first portion of said conductive
layer forms said test terminals.
18. A method according to claim 17, wherein: a second portion of
said conductive layer forms user terminals; said user terminals are
positioned on an outside surface of said memory card; and said user
terminals are in communication with at least a subset of said
circuit elements.
19. A method according to claim 1, wherein: said step of adding
circuit elements includes performing a transfer mold process to
encapsulate said circuit elements without covering said test
terminals.
20. A method according to claim 1, wherein: said step of covering
is performed after said circuit board is removed from a strip of
circuit boards.
21. A method according to claim 1, wherein: said step of covering
is performed before said circuit board is removed from a strip of
circuit boards.
22. A method according to claim 1, wherein: said memory card is a
flash memory card.
23. A method according to claim 22, wherein: said step of covering
includes applying a liquid directly to a first surface of said
circuit board.
24. A method according to claim 22, wherein: said step of covering
includes applying a film directly to a first surface of said
circuit board.
25. A method of making a peripheral card, comprising the steps of:
adding circuit elements to a plurality of circuit boards of a strip
of circuit boards, each of said plurality of circuit boards
includes a set of test terminals; separating said connected circuit
boards; testing said circuit elements of said circuit boards using
said test terminals; and applying a conformal contact coating on a
first surface of each of said circuit boards to cover said test
terminals and prevent access to said test terminals such that a
particular circuit board has its test terminals covered after said
particular circuit board has been tested.
26. A method according to claim 25, wherein: said step of
separating is performed after said step of applying.
27. A method according to claim 25, wherein: said step of
separating is performed prior to said step of applying.
28. A method according to claim 25, wherein: said step of applying
includes applying a liquid directly to a first surface of said
circuit boards.
29. A method according to claim 25, wherein: said step of applying
includes applying a film directly to a first surface of said
circuit boards.
30. A method according to claim 25, wherein: said step of adding
circuit elements includes mounting a first die on a first circuit
board and mounting a second die on said first die; said first die
includes a flash memory array and said second die includes a
controller; said first die is wire bonded to said first circuit
board; and said second die is wire bonded to said first circuit
board.
31. A method according to claim 25, wherein: said peripheral card
is a memory card.
32. A peripheral card manufactured according to a process
comprising the steps of: adding circuit elements to a circuit
board, said circuit board includes a set of test terminals; testing
one or more of said circuit elements using said test terminals; and
applying a conformal contact coating on a first surface of said
circuit board to cover said test terminals and prevent access to
said test terminals.
33. A peripheral card according to claim 32, wherein: said step of
applying includes applying a liquid directly to a first surface of
said circuit board.
34. A peripheral card according to claim 32, wherein: said step of
applying includes applying a film directly to a first surface of
said circuit board.
35. A peripheral card according to claim 32, wherein: said circuit
board includes a first die mounted on said circuit board and a
second die mounted on said first die; said first die includes a
flash memory array and said second die includes a controller; said
first die is wire bonded to said circuit board; and said second die
is wire bonded to said circuit board.
36. A peripheral card according to claim 32, wherein: said circuit
board includes a conductive layer; a first portion of said
conductive layer forms said test terminals; a second portion of
said conductive layer forms user terminals; said user terminals are
positioned on an outside surface of said peripheral card; and said
circuit elements are encapsulated by a transfer mold process
without covering said test terminals.
37. A peripheral card according to claim 32, wherein: said
peripheral card is a memory card.
38. A peripheral card, comprising: a circuit board; circuit
elements on said circuit board; a set of user terminals on said
circuit board, said user terminals are in communication with at
least a subset of said circuit elements; a set of test terminals on
said circuit board, said test terminals are in communication with
one or more of said circuit elements; an enclosure that covers a
portion of said circuit board and said circuit elements without
covering said set of user terminals and said set of test terminals;
and a conformal contact coating on a first surface of said circuit
board covering said test terminals and preventing access to said
test terminals.
39. A peripheral card according to claim 38, wherein: said
conformal contact coating is applied as a liquid directly to said
first surface of said circuit board.
40. A peripheral card according to claim 38, wherein: said
conformal contact coating includes a film that is applied directly
to said first surface of said circuit board.
41. A peripheral card according to claim 38, wherein: said circuit
elements board include a first die mounted on said circuit board
and a second die mounted on said first die.
42. A peripheral card according to claim 41, wherein: said first
die is wire bonded to said circuit board; and said second die is
wire bonded to said circuit board.
43. A peripheral card according to claim 42, wherein: said first
die includes a flash memory array and said second die includes a
controller.
44. A peripheral card according to claim 41, wherein: said first
die includes a flash memory array and said second die includes a
controller.
45. A peripheral card according to claim 38, wherein: said circuit
board includes a conductive layer; a first portion of said
conductive layer forms said test terminals; a second portion of
said conductive layer forms said user terminals; and said user
terminals are positioned on an outside surface of said peripheral
card.
46. A peripheral card according to claim 38, wherein: said
peripheral card is a memory card.
47. A method performed for a peripheral card, comprising the steps
of: testing one or more circuit elements of a first peripheral card
using one or more test terminals of said first peripheral card; and
covering said test terminals with a conformal contact coating in
order to prevent access to said test terminals.
48. A method according to claim 47, wherein: said step of covering
includes applying a liquid directly to said first peripheral
card.
49. A method according to claim 47, wherein: said step of covering
includes applying a film directly to said first peripheral
card.
50. A method according to claim 47, wherein: said circuit elements
include a flash memory array.
51. A method according to claim 47, wherein: said first peripheral
card is a memory card.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This Application is related to U.S. patent application Ser.
No. ______, "Method For Efficiently Producing Removable Peripheral
Cards," filed Jun. 23, 2003, Hem P. Takiar, Atty. Docket
SDK1P014/370, which is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is directed to technology for
peripheral cards.
[0004] 2. Description of the Related Art
[0005] Memory cards are relatively small removable cards that
provide data storage. In most cases, but not required in all cases,
the memory card is integrated circuit based. These memory cards
plug into or are received by ports or connectors on electronic
devices, including computing devices, cameras, mobile telephones,
PDAs and other devices. One example of a memory card uses
non-volatile memory. Electrical Erasable Programmable Read Only
Memory (EEPROM) and flash memory are among the most popular
non-volatile semiconductor memories. Some examples of memory cards
includes CompactFlash.TM., MMC.TM., Smart Media, Secure
Digital.TM., and the Memory Stick.
[0006] A flash memory card is a memory card that has one or more
arrays of flash memory cells. Some flash memory cards also include
bit line decoders, word line decoders, a state machine, a
controller and other circuitry. In many cases the controller will
be implemented in a first semiconductor die, while the array of
flash memory cells, bit line decoders, word line decoders, and
state machine are implemented in a second semiconductor die. Over
time, flash memory arrays have increased density by shrinking the
size of an individual memory cell and by implementing greater
numbers of memory cells in the array.
[0007] To maintain product reliability and customer satisfaction,
manufacturers of memory cards will test the memory cards during the
manufacturing process in order to determine if there are any
manufacturing defects. In many cases, the user I/O pins on the
memory card connect to the controller. However, a test performed
during manufacturing typically seeks to directly access the memory
array (bypassing the controller) in order to test each cell in the
memory array. Additionally, more pins will allow for more efficient
and complete testing of the relevant components of the memory card.
Thus, many memory cards will include test pins, in addition to the
user I/O pins. To protect the memory card from electrostatic
discharge relative to the test pins and to protect the data on the
card from being wrongfully accessed via the test pins, the test
pins should not be exposed to the user of the memory card after the
manufacturing process.
[0008] One example of a memory card is described in U.S. Pat. No.
6,410,355 (the '355 patent"), incorporated herein by reference in
its entirety. In the '355 patent, a memory card using flash memory
is manufactured with a set of test pins at one edge of the memory
card. After the memory card is tested, the test pins are cut off of
the memory card and the memory card is then packaged. While the
device of the '355 patent has worked well, there is a need for an
improvement. First, the test pins that are cut off use real estate
on the circuit board. There is a trend to increase density on
circuit boards; therefore, it would be advantageous to not use a
portion of the circuit board for components that will not ship to
customers. Second, if the memory card fails in the field, there are
no test pins to test the device in order to determine why the
memory card failed. Such tests following device failure allow a
manufacturer of memory cards to improve device reliability and the
manufacturing process.
[0009] Another example of a memory card using flash memory is the
recently released Mini-SD Card. In one commercial version of the
Mini-SD Card, the memory array is mounted on the top of the circuit
board and the controller is mounted on the memory array. User I/O
pins and test pins are formed on the bottom of the circuit board.
After the memory card is tested, the circuit board (with the
controller, memory array and other components) are enclosed by
attaching a top lid to a bottom lid. Both the bottom lid and the
top lid are made of a hard plastic, and are manufactured from a
mold prior to enclosing the circuit board. After the top and bottom
lids are made, the top lid is ultra- sonically welded to the bottom
lid to enclose the circuit board (with the controller, memory array
and other components). The bottom lid has an opening for the user
I/O pins. The bottom lid does not have an opening for the test
pins; therefore, the test pins are not exposed to users. There will
be a small air gap between the bottom lid and the bottom of the
circuit board While this design works well, the top and bottom lids
are relatively expensive to manufacture. Additionally, the lids are
relatively bulky which limits how small the memory cards can be
manufactured. The trend in the industry to further decrease the
size of memory cards.
[0010] Thus, there is a need to provide for test pins for a memory
card without the limitations described above. Similar issues exist
with other types of peripheral cards, such as peripheral cards that
implement wireless communication devices, GPS devices, cellular
devices, network interfaces, modems, disk storage systems, and
other devices.
SUMMARY OF THE INVENTION
[0011] The present invention, roughly described, pertains to
technology for a peripheral card with hidden test pins. One
embodiment of the present invention includes a circuit board,
circuit elements on said circuit board, a set of user terminals on
the circuit board that are in communication with at least a subset
of the circuit elements, a set of test terminals on said circuit
board that are in communication with one or more of the circuit
elements, an enclosure that covers a portion of the circuit board
without covering the set of user terminals and the set of test
terminals, and a conformal contact coating on a first surface of
the circuit board covering the test terminals and preventing access
to the test terminals.
[0012] One embodiment of manufacturing such a peripheral card
includes adding circuit elements to a circuit board, where the
circuit board (at some point in time) includes a set of test
terminals. One or more of the circuit elements are tested using the
test terminals. The test terminals are subsequently covered with a
conformal contact coating in order to prevent access to the test
terminals. In one implementation, the test terminals are covered
with a conformal contact coating by applying a liquid directly to a
first surface of the circuit board. In another implementation, the
test terminals are covered with a conformal contact coating by
applying a film directly to a first surface of said circuit
board.
[0013] Some embodiments of the present invention will include
manufacturing the peripheral cards a batch at a time, followed by
singulation of the batch into individualized memory cards. The
present invention allows for the covering of the test pins before
or after singulation. For example, one implementation includes the
steps of adding circuit elements to a plurality of circuit boards
of a strip (each of the plurality of circuit boards includes a set
of test terminals), separating the connected circuit boards,
testing the circuit elements of the circuit boards using the test
terminals, and applying a conformal contact coating on a first
surface of each of the circuit boards. The conformal contact
coating covers the test terminals and prevents access to the test
terminals such that a particular circuit board has its test
terminals covered after that particular circuit board has been
tested.
[0014] The present invention can be applied to the manufacture of
memory cards, including flash memory cards. The technology
disclosed herein can also be applied to other peripheral cards. For
example, the present invention can be used with removable
peripheral cards that include wireless communication devices, GPS
devices, cellular devices, network interfaces, modems, disk storage
systems, and other devices. The present invention is not limited to
any one type of peripheral card and is meant to be used with many
different types of peripheral cards.
[0015] These and other objects and advantages of the present
invention will appear more clearly from the following description
in which the preferred embodiment of the invention has been set
forth in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view of the bottom of a memory card
according to a first embodiment of the present invention.
[0017] FIG. 2 is a perspective view of the top of the memory card
according to the first embodiment of the present invention.
[0018] FIG. 3 is a first side view of the memory card according to
the first embodiment of the present invention.
[0019] FIG. 4 is a perspective view of the top of a memory card
according to a second embodiment of the present invention.
[0020] FIG. 5 is a perspective view of the top of a memory card
according to a third embodiment of the present invention.
[0021] FIG. 6 is a perspective view of the top of a memory card
according to a fourth embodiment of the present invention.
[0022] FIG. 7 is a perspective view of the bottom of the memory
card according to the fourth embodiment of the present
invention.
[0023] FIG. 8 is a perspective view of the top of a memory card
according to a fifth embodiment of the present invention.
[0024] FIG. 9 is a perspective view of the bottom of the memory
card according to the fifth embodiment of the present
invention.
[0025] FIG. 10 is a side view of the memory card according to the
fifth embodiment of the present invention.
[0026] FIG. 11 is a top view of a circuit board used for various
embodiments of the present invention.
[0027] FIG. 12 is a bottom view of the circuit board used for
various embodiments of the present invention.
[0028] FIG. 13 is a cross section of an exemplar circuit board.
[0029] FIG. 14 is a cross sectional view of one embodiment of a
circuit board and various components on the circuit board during
the manufacturing process.
[0030] FIG. 15 is a cross sectional view of one embodiment of a
circuit board and various components encapsulated on the circuit
board during the manufacturing process.
[0031] FIG. 16 is a cross sectional view of one embodiment of a
circuit board and various components on the circuit board, with a
conformal contact coating applied to a surface of the circuit
board.
[0032] FIG. 17 is a flow chart describing one embodiment of a
process for manufacturing a memory card according to the present
invention.
[0033] FIG. 18 is a plan view of a strip of memory cards prior to
singulation.
[0034] FIG. 19 is a perspective view of the top of the memory card
according to an additional embodiment of the present invention.
[0035] FIG. 20 is a perspective view of the bottom of the memory
card according to the embodiment of FIG. 19.
[0036] FIG. 21 is a perspective view of the top of the memory card
according to an additional embodiment of the present invention.
[0037] FIG. 22 is a perspective view of the bottom of the memory
card according to the embodiment of FIG. 21.
DETAILED DESCRIPTION
[0038] FIGS. 1-10 depict various embodiments of a memory card. For
example, FIG. 1 is a perspective view of the bottom of a memory
card according to a first embodiment of the present invention. FIG.
2 is a perspective view of the top of the memory card according to
the first embodiment of the present invention. FIG. 3 is a side
view of the memory card according to the first embodiment of the
present invention. The memory card of FIGS. 1-3 includes a top
surface 10, a bottom surface, a front surface 12, a back surface 14
and two side surfaces. One of the side surfaces has an angle
portion 16. Top surface 10 has a raised portion 18 adjacent to back
surface 14. Raised portion 18 allows the memory card to be more
easily grabbed by a human hand (or mechanical device) and also
provides additional room to store passive devices such as
capacitors and/or resistors. Note that raised portion 18 of FIG. 1
has a curved profile. The bottom surface includes a first portion
22 and a second portion 24. Second portion 24 is raised from first
portion 22. First portion 22 includes a set of user I/O pins 26 and
corresponds to a bottom surface of a circuit board, as discussed
below.
[0039] In one implementation, the memory card is 12 mm wide and 15
mm long. The angled portion is at a forty five degree angle. The
thickness of the memory card is 0.9 mm at second portion 24, 1.0 mm
at raised portion 18 and 0.8 mm at first portion 22. In another
embodiment, the thickness of the memory card is 0.8 mm at second
portion 24, 1.0 mm at raised portion 18 and 0.7 mm at first portion
22. In other embodiments, other dimensions can also be used.
[0040] In one embodiment, a label will be placed on the top
surface. This label can be a sticker or can be ink which is pad
printed.
[0041] FIG. 4 is a perspective view of the top of a memory card
according to a second embodiment of the present invention. The
second embodiment includes a raised portion 1 8a that has a
straight profile. FIG. 5 is a perspective view of the top of a
memory card according to a third embodiment of the present
invention which does not include a raised portion 18.
[0042] FIG. 6 is a perspective view of the top of a memory card
according to a fourth embodiment of the present invention. FIG. 7
is a perspective view of the bottom of the memory card according to
the fourth embodiment of the present invention. The fourth
embodiment includes notch 30. The notch is used to secure the card
in position when connected to a host device.
[0043] FIG. 8 is a perspective view of the top of the memory card
according to a fifth embodiment of the present invention. FIG. 9 is
a perspective view of the bottom of the memory card according to
the fifth embodiment of the present invention. FIG. 10 is a side
view of the memory card according to the fifth embodiment of the
present invention. The fifth embodiment of the present invention
implements a different orientation than the other embodiments
described above. For example, the top surface of the memory card in
the fifth embodiment includes a raised portion 54 adjacent back
edge 52, which runs along the length as opposed to the width of the
memory card. The memory card of the fifth embodiment includes a
front surface 50 that also runs along the length of the memory
card. The bottom surface of the memory card includes a first
portion 54 and second portion 56. First portion 54 includes a set
of user I/O pins 58 and corresponds to a bottom surface of a
circuit board, as discussed below. Second portion 56 is raised from
first portion 54.
[0044] FIG. 11 provides a top view of a circuit board used for
various embodiments of the present invention. FIG. 11 shows circuit
board 200. Mounted on circuit board 200 are first die 202 and
second die 204. In one embodiment, die 202 includes a flash memory
array with associated circuitry and die 204 includes a controller.
In some embodiments, the memory card may include more than one
memory array. In embodiments that include a peripheral card other
than a memory card, the dies can be components other than or in
addition to memory arrays and controllers. Note that die 202
includes contacts 212 (e.g. die bond pads) which are used to
connect die 202 to other components. Similarly, die 204 includes
contacts 214 (e.g. die bond pads) to connect die 204 to other
components. Circuit board 200 also includes passive components 220,
which could include capacitors and/or resistors. Circuit board 200
includes a number of conductive traces (not shown) which
interconnect the devices mounted on the circuit board. Connecting
regions (not depicted) are provided on the circuit board so that
the leads from dies can be connected to the circuit board by
conventional wire bonding. In other embodiments, other means
different than wire bonding can be used to connect the dies to the
circuit board.
[0045] FIG. 12 shows the bottom of circuit board 200. In one
embodiment, the bottom of circuit board 200 includes user I/O pins
230 and test pins 232. FIG. 12 depicts eight user I/O pins 230 and
sixteen test pins 232; however, different numbers of pins can also
be used. The test pins 232 can include data pins and/or power pins.
The test pins are used to test one or more of the components of the
memory card. For example, the test pins can be used to test each of
the cells of the memory array. The user I/O pins 230 are used by a
host device connected to the memory card in order to communicate
with the memory card. For example, the user I/O pins 230 can be
used to communicate with the controller on die 204. Note that in
order to have a small package, one embodiment of the present
invention includes mounting the integrated circuits on a first
surface of the circuit board (e.g. the top surface) and forming the
terminals (user I/O pins and test pins) on a conductive layer on
another surface of the circuit board (e.g. the bottom surface).
[0046] FIG. 13 shows a cross sectional view of circuit board 200.
FIG. 13 shows five layers 260, 262, 264, 266, and 268. Other
embodiments have less than or more than five layers. Layer 260, the
middle layer, is an insulating core layer. Layers 262 and 264 are
routing layers, which include conductive metal traces. Layers 266
and 268 include solder masks. Connections between layers (such as
layers 262 and 264) can be made by conductive vias. In one
embodiment, the circuit board is a printed circuit board. In
another embodiment, the circuit board is a lead frame. Other types
of circuit boards may also be used within the spirit of the present
invention.
[0047] FIGS. 14-16 graphically depict the manufacturing process for
creating the memory card according one embodiment of the present
invention. FIG. 14 is a side view of the memory card during the
manufacturing process, prior to encapsulation. FIG. 14 depicts
circuit board 200. Mounted on circuit board 200 is die 202. Mounted
on die 202 is die 204. FIG. 14 shows die 202 and die 204 wire
bonded to circuit board 200. FIG. 14 also shows passive devices
220, which can be capacitors and/or resistors. In one embodiment,
die 202 is mounted on circuit board 200 using an adhesive material.
The adhesive material may be an epoxy adhesive, soft solder or any
other adhesive material for mounting a die to a substrate. Die 204
is mounted on die 202 by way of an adhesive material applied to the
top surface of die 202 and the bottom surface of die 204. More
information about stacking two dies on top of each other can be
found in U.S. Pat. No. 5,502,289, incorporated herein by reference
in its entirety. In one embodiment, the passive devices are surface
mounted using solder.
[0048] FIG. 15 shows the memory card of FIG. 14 after
encapsulation. That is, using an injection mold process or a
transfer mold process, molding material 280 is used to encapsulate
the components of the memory card. Note that the encapsulation
covers the side surfaces, front surface, back surface, and top
surface of circuit board 200. The encapsulation also covers all the
components mounted on the top surface of circuit board 200. The
bottom surface of circuit board 200, which includes user I/O pins
230 and test pins 232, is not covered by the encapsulation.
[0049] Subsequent to encapsulation, a conformal contact coating 290
is applied to a portion of the bottom surface of circuit board 200
in order to cover test pins 232. The conformal contact coating does
not cover user I/O pins 230. FIG. 16 depicts the memory card after
the conformal contact coating 290 has been applied. For example,
the conformal contact coating 290 is applied to portion 24 (see
FIG. 1) of the bottom surface of the memory card, but not to
portion 22 of the memory card. The conformal contact coating
protects the test pins from electrostatic discharge and protects
the data in the memory from unwanted access via the test pins by
blocking the test pins. The coating is a conformal contact coating
because it conforms to the shape of the surface it is being applied
to and it is in direct contact to that surface. Some other memory
cards may use a lid to cover the bottom of the circuit board. That
lid is not in contact with the bottom surface of the circuit board.
Rather, an air gap will exist between the bottom lid and circuit
board. Additionally, because the lid is prefabricated it will not
conform to the shape of the bottom surface of the bottom of the
circuit board.
[0050] In one embodiment, the application of the conformal contact
coating includes applying a liquid directly to the bottom surface
of the circuit board. The coating then dries to a solid. In another
embodiment, the coating is applied as a film directly to the bottom
surface of the circuit board. Examples of coatings include
photoresist, solder mask, epoxy, thermoplastic, and polyimide. One
specific example of a suitable coating is the PSR-400 Solder Mask
from Taiyo America, Inc., www.taivo-america.com. Examples of a film
include mylar with an adhesive or polyimide with an adhesive. An
example of a suitable polyimide is Kapton, by DuPont. One example
of how to apply a liquid coating is to use a screen printing
process.
[0051] FIG. 17 is a flowchart depicting one embodiment of a process
for manufacturing a memory card according to the present invention.
In step 400, vias are drilled in the circuit board. In step 402, a
top pattern is applied to circuit board 200 to add the conductive
traces and connection regions discussed above. In step 404, a
bottom pattern is applied to the bottom surface of circuit board
200 to add the user I/O pins 230, 232 test pins and conductive
traces. In step 406, solder mask is added to the top surface of
circuit board 200. In step 408, the solder mask is added to the
bottom surface of circuit board 200. In step 410, first die 202 is
mounted to circuit board 200. In step 412, second die 204 is
mounted to circuit board 200. In step 414, passive devices 220 are
mounted to circuit board 200. In step 416, wire bonds are added to
connect dies 202 and 204 to circuit board 200. In one embodiment,
protective coatings are applied to the wire bonds and/or the dies.
In step 418, circuit board 200 and the components mounted on
circuit board 200 are subject to a transfer mold process so that
the circuit board and its components are encapsulated, as described
above. However, the encapsulation process of step 418 does not
cover the bottom surface of circuit board 200.
[0052] In one embodiment, a memory card is manufactured as a
unitary structure. In that case, step 420 is skipped and the
process of FIG. 17 proceeds to step 422. However, in other
embodiments the memory cards are produced a batch at a time. That
is, a strip of memory cards are produced at one time and then a
singulation process is performed to cut the strip into
individualized memory cards. In the case where the memory cards are
produced at a batch at a time, step 420 includes cutting the strip
to separate the various memory cards. Step 420 is referred to as
singulation.
[0053] In step 422, the memory cards are tested. In step 424, the
test pins are covered, as described above, by applying the
conformal contact coating to a portion of the bottom surface of the
circuit board 200 (e.g. bottom portion 24 of FIG. 1).
[0054] Step 422 includes testing the memory cards. During the
manufacturing process, the manufacturer may perform a bum-in test
of the memory card to verify that each of the memory cells in the
memory array are functional. The manufacturer may then program the
memory card to avoid bad memory cells. For example, the memory
array may include a portion of memory that stores addresses for bad
memory cells and pointers to replacement memory cells. In some
embodiments, the other components of the memory card may also be
tested. Note that FIG. 17 shows that the devices are tested and
receive the conformal contact coating after singulation. In another
embodiment, step 420 is performed after to step 422; therefore, the
various devices are tested and receive the conformal contact
coating prior to singulation.
[0055] FIG. 18 is a plan view of a strip of memory cards prior to
singulation. FIG. 18 shows strip 500. On top of strip 500 are
various instances of the memory cards. Each memory card is depicted
in dashed lines. In one embodiment, strip 500 includes 100 memory
cards (5 wide, 20 long). Note that other numbers of memory cards
can also be manufactured on a strip. Strip 500 is manufactured by
performing steps 400-418 simultaneously for each of the memory
cards on the strip. That is, the steps are performed on the strip
as a whole. Step 420 is performed by cutting the strip into
separate devices. According to one aspect of the present invention,
the memory cards are not fully rectangular in their shape.
Therefore, the singulation of the strip into individual memory
cards includes nonlinear (e.g. curvilinear) sawings. Such sawing
can be performed efficiently with a very thin saw with high
precision and detail, such that the sawing action is very fine.
Examples of the sawing devices include, for example, a water jet
cutting device, a laser cutting apparatus, a water guided laser, a
dry media cutting device, and a diamond coated wire. Water jet
cutting may be the preferred cutting method given its small cutting
width (e.g. 50 microns), its ability to shape small features and
its rapid cutting rate.
[0056] If the memory card fails after it is in use, then the failed
memory card can be debugged by removing the conformal contact
coating and using the test pins to test the memory card.
[0057] FIG. 19 is a perspective view of the top of the memory card
according to an additional embodiment of the present invention.
FIG. 20 is a perspective view of the bottom of the memory card
according to the embodiment of FIG. 19. Card 600 depicted in FIGS.
19 and 20 includes rounded notches 602 and 604, raised portion 606
and angled portion 608. Bottom surface 612 includes pins 620 and
portion 622. Portion 622 is raised from surface 612 and covers the
test pins as described herein.
[0058] FIG. 21 is a perspective view of the top of the memory card
according to an additional embodiment of the present invention.
FIG. 22 is a perspective view of the bottom of the memory card
according to the embodiment of FIG. 21. Card 700 depicted in FIGS.
21 and 22 includes notch 702, raised portion 706 and angled portion
708. Bottom surface 712 includes pins 720 and portion 722. Portion
722 is raised from surface 712 and covers the test pins as
described herein.
[0059] The description above specifically discusses memory cards.
One set of embodiments of the present invention specifically
pertain to flash memory cards, which include one or more memory
arrays that utilize flash memory technology. The embodiments
explained above pertaining to memory cards are for example purposes
and are not mean to limit the invention. The technology disclosed
herein can also be applied to other peripheral cards that connect
to a computing device and are controlled or operated with the
computing device. One example of a removable peripheral card is a
PCMCIA card. Examples of applications, in addition to memory
systems, that can be implemented on peripheral cards include
wireless communication devices, GPS devices, cellular devices,
network interfaces, modems, disk storage systems, etc. The present
invention is not limited to any one type of peripheral card and is
meant to be used with many different types of peripheral cards.
[0060] The foregoing detailed description of the invention has been
presented for purposes of illustration and description. It is not
intended to be exhaustive or to limit the invention to the precise
form disclosed. Many modifications and variations are possible in
light of the above teaching. The described embodiments were chosen
in order to best explain the principles of the invention and its
practical application to thereby enable others skilled in the art
to best utilize the invention in various embodiments and with
various modifications as are suited to the particular use
contemplated. It is intended that the scope of the invention be
defined by the claims appended hereto.
* * * * *
References