Molding Methods To Manufacture Single-Chip Chip-On-Board USB Device

• US 20070293088A1
• Filed: 07/05/2007
• Published: 12/20/2007
• Est. Priority Date: 01/06/2000
• Status: Active Grant

• Current Assignee: Super Talent Technology, Corporation
• Original Assignee: Super Talent Electronics, Inc.
• Inventors: Yu, I-Kang, Shen, Ming-Shiang, Lee, Charles, Ni, Jim, Hiew, Siew
• Granted Patent: US 7,872,871 B2
• Time in Patent Office: Days
• US Class Current: 439/607.41
• CPC Class Codes: G06F 1/1632 External expansion units, e.g. docking stations
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/85 using a wire connector
• CPC Class Codes: H01L 2224/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 2924/00014 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
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01074 Tungsten [W]
• CPC Class Codes: H01L 2924/01077 Iridium [Ir]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/19041 being a capacitor
• CPC Class Codes: H05K 1/117 Pads along the edge of rigid circuit boards, e.g. for pluggable connectors
• CPC Class Codes: H05K 2203/1316 Moulded encapsulation of mounted components
• CPC Class Codes: H05K 3/0052 Depaneling, i.e. dividing a panel into circuit boards; Working of the edges of circuit boards
• CPC Class Codes: H05K 3/284 : for encapsulating mounted components H05K1/185 takes precedence
• CPC Class Codes: H05K 5/0278 : of USB type details relating to connectors H01R27/00

Abstract

A low-profile Universal-Serial-Bus (USB) device includes a PCBA in which all passive components and unpackaged IC chips are attached to a single side of a PCB opposite to the metal contacts. The IC chips include, for example, a USB controller chip and a flash memory chip, or a single-chip (combined USB controller/flash memory) chip. Multiple flash IC chips are optionally stacked to increase storage capacity. The IC chip(s) are attached to the PCB by wire bonding or other chip-on-board (COB) technique. The passive components are attached by conventional surface mount technology (SMT) techniques. A molded housing is then formed over the IC chips and passive components such that the device has a uniform thickness. The low-profile USB device is optionally used as a modular insert that is mounted onto a metal case to provide a USB assembly having a plug shell similar to a standard USB male connector.

Claims

1. A low-profile Universal-Serial-Bus (USB) device comprising:

a printed circuit board assembly (PCBA) including;

a printed circuit board (PCB) including a PCB handle section and a PCB plug section, the PCB having opposing first and second surfaces,

a plurality of metal contacts disposed on the first surface of the PCB plug section,

at least one passive component mounted on the second surface of the PCB handle section,

at least one unpackaged integrated circuit (IC) die mounted on the second surface of the PCB handle section, and

a plurality of conductive traces formed on the PCB such that each conductive trace is electrically connected to at least one of an associated metal contact, said at least one IC die and said at least one passive component; and

a single-piece molded housing formed on the second surface of the PCBA such that said at least one passive component and said at least one IC die are covered by said molded housing, and such that substantially all of the first surface of the PCB is exposed.

2. The low-profile USB device of claim 1,

wherein the molded housing includes a planar surface extending parallel to the PCB and extends from the PCB handle section to the PCB plug section, and

wherein a first thickness measured between the first surface of the PCB and the planar surface adjacent to the metal contacts is substantially equal to a second thickness between the first surface of the PCB and the planar surface adjacent to the IC die.

3. The low-profile USB device of claim 2, wherein the first thickness is in the range of 1.95 mm to 2.05 mm.

4. The low-profile USB device of claim 2, wherein the molded housing includes a peripheral wall extending perpendicular to the planar surface, and wherein the peripheral wall is aligned with a peripheral edge of the PCB.

5. The low-profile USB device of claim 1, wherein the at least one integrated circuit (IC) die is electrically connected to the conductive traces by a plurality of wire bonds extending between said at least one IC die and corresponding contact pads disposed on the second surface of the PCB.

6. The low-profile USB device of claim 5, wherein the at least one passive component includes a lead that is soldered to a corresponding contact pad disposed on the second surface of the PCB.

7. The low-profile USB device of claim 6, wherein the at least one passive component comprises at least one of a resistor, a capacitor, an oscillator, and a light emitting diode.

8. The low-profile USB device of claim 5, wherein the at least one integrated circuit (IC) die includes a first IC die comprising an USB controller circuit, and a second IC die comprising a flash memory circuit.

9. The low-profile USB device of claim 8, wherein the at least one integrated circuit (IC) die comprises a plurality of flash memory dies disposed in a stacked arrangement such that a first flash memory die is mounted on the second surface of the PCB, and a second flash memory die is mounted on a surface of the first flash memory die.

10. The low-profile USB device of claim 9, wherein the first flash memory die is connected to said PCB by a first plurality of said wire bonds, and the second flash memory die is connected to one of the first flash memory die and said PCB by a second plurality of wire bonds.

11. The low-profile USB device of claim 5, wherein the at least one integrated circuit (IC) die includes a single-chip controller/flash die comprising controller circuit and one or more flash block mass storage circuits that are interconnected by a bus.

12. An Universal-Serial-Bus (USB) assembly comprising:

a low-profile device including;

a printed circuit board assembly (PCBA) including a printed circuit board (PCB) having opposing first and second surfaces, a plurality of metal contacts disposed on the first surface, at least one passive component mounted on the second surface, and at least one unpackaged integrated circuit (IC) die mounted on the second surface of the PCB handle section, and a plurality of conductive traces formed on the PCB such that each conductive trace is electrically connected to at least one of an associated metal contact, the IC die and the passive component, and

a single-piece molded housing formed on the second surface of the PCBA such that said at least one passive component and said at least one IC die are covered by said molded housing, and such that substantially all of the first surface of the PCB is exposed; and

a metal case fixedly connected to the low-profile device such that the metal contacts are accessible through a front opening defined by said metal case.

13. The USB assembly of claim 12, wherein the assembly further comprises:

a substrate carrier for supporting the low-profile device between a rear end plate and a front end plate, the substrate carrier being at least partially inserted into the metal case such that the front end plate is substantially aligned with the front opening defined by the metal case; and

an end piece inserted into a rear opening of the metal case, wherein the end piece includes a plastic plug structure that presses downward on a rear portion of the USB device, and a metal cover piece that covers rear opening of the metal case.

14. The USB assembly of claim 13, wherein the metal case extends an entire length of the low-profile device such that the entire low-profile device is disposed inside of the metal case.

15. The USB assembly of claim 13, wherein the metal case is shorter the low-profile device such that a portion of the low-profile device extends from the rear opening of the metal case.

16. The USB assembly of claim 13, wherein the metal case comprises depressions that press against at least one of the low-profile device and the end piece, thereby locking the end piece and the low-provide device inside the metal case.

17. The USB assembly of claim 12,

wherein the molded housing includes a planar surface extending parallel to the PCB and extends over an entire length of the PCB, and

wherein a first thickness measured between the first surface of the PCB and the planar surface adjacent to the metal contacts is substantially equal to a second thickness between the first surface of the PCB and the planar surface adjacent to the at least one IC die.

18. The USB assembly of claim 12, wherein the at least one integrated circuit (IC) die is electrically connected to the conductive traces by a plurality of wire bonds extending between said at least one IC die and corresponding contact pads disposed on the second surface of the PCB.

19. The USB assembly of claim 18, wherein the at least one passive component includes a lead that is soldered to a corresponding contact pad disposed on the second surface of the PCB.

20. The USB assembly of claim 19, wherein the at least one passive component comprises at least one of a resistor, a capacitor, an oscillator, and a light emitting diode.

21. The USB assembly of claim 18, wherein the at least one integrated circuit (IC) die includes a first IC die comprising an USB controller circuit, and a second IC die comprising a flash memory circuit.

22. The USB assembly of claim 21, wherein the at least one IC die comprises a plurality of flash memory dies disposed in a stacked arrangement such that a first flash memory die is mounted on the second surface of the PCB, and a second flash memory die is mounted on a surface of the first flash memory die.

23. The USB assembly of claim 22, wherein the first flash memory die is connected to said PCB by a first plurality of said wire bonds, and the second flash memory die is connected to one of the first flash memory die and said PCB by a second plurality of wire bonds.

24. The USB assembly of claim 18, wherein the at least one integrated circuit (IC) die includes a single-chip controller/flash die comprising controller circuit and one or more flash block mass storage circuits that are interconnected by a bus.

25. A method for producing a Universal-Serial-Bus (USB) device comprising:

producing a printed circuit board (PCB) including opposing first and second surfaces, a plurality of metal contacts disposed on the first surface, a plurality of first contact pads disposed on the second surface, a plurality of second contact pads disposed on the second surface, and a plurality of conductive traces formed on the PCB such that each conductive trace is electrically connected to at least one of an associated metal contact, a first contact pad and a second contact pad;

attaching at least one passive component to the first contact pads using a surface mount technique;

attaching at least one unpackaged integrated circuit (IC) die to the second contact pads using a chip-on-board technique; and

forming a single-piece molded housing on the second surface of the PCB such that said at least one passive component and said at least one IC die are covered by said molded housing, and such that substantially all of the first surface of the PCB is exposed.

26. The method of claim 25, wherein attaching said at least one passive component comprises:

printing a solder paste on said first contact pads;

mounting said at least one component on said first contact pads; and

reflowing the solder paste such that said at least one component is fixedly soldered to said first contact pads.

27. The method of claim 25, further comprising grinding a wafer including said at least one IC die such that a thickness of said wafer is reduced during said grinding, and then dicing said wafer to provide said at least one IC die.

28. The method of claim 27, wherein attaching at least one IC die comprises bonding said at least one IC die to the second surface of the PCB and wire bonding the at least one IC die to said second contact pad.

29. The method of claim 25,

wherein producing the PCB comprises forming a PCB panel including at least eighteen of said PCBs arranged in two rows, and

wherein the method further comprises singulating said PCB panel after forming said single-piece molded housing such that the molded housing includes a peripheral wall extending perpendicular to the PCB, and such that the peripheral wall is aligned with a peripheral edge of the PCB.