Peripheral card with hidden test pins
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.
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 INVENTION1. Field of the Invention
The present invention is directed to technology for peripheral cards.
2. Description of the Related Art
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™, MMC™, Smart Media, Secure Digital™, and the Memory Stick.
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.
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.
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.
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.
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 INVENTIONThe 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.
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.
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.
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.
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
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.
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.
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.
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.
In one embodiment, a memory card is manufactured as a unitary structure. In that case, step 420 is skipped and the process of
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
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
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.
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.
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.
Claims
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.
Type: Application
Filed: Jul 17, 2003
Publication Date: Jan 20, 2005
Inventor: Hem Takiar (Sunnyvale, CA)
Application Number: 10/621,882