Protective coating for an electronic device

• US 6,138,349 A
• Filed: 12/18/1997
• Issued: 10/31/2000
• Est. Priority Date: 12/18/1997
• Status: Expired due to Term

• Current Assignee: VLT Incorporated (Vicor Corporation)
• Original Assignee: VLT Incorporated (Vicor Corporation)
• Inventors: Curhan, Jeffrey A., Vinciarelli, Patrizio
• Primary Examiner(s): Martin-Wallace, Valencia
• Assistant Examiner(s): NGUYEN, BINH AN DUC
• Application Number:
  US08/993,503
• Time in Patent Office: 1,048 Days
• Field of Search: 29/841, 29/840, 29/850, 29/855, 29/832, 257/578, 257/499, 257/501, 428/76, 428/201, 428/203, 427/154, 427/155, 427/96, 216/41, 216/43, 216/45, 216/51
• US Class Current: 29/841
• CPC Class Codes: H01L 21/4846 Leads on or in insulating or insulated substrates, e.g. metallisation H01L21/4821 takes precedence; metallisation of ceramics in general C04B41/51; printed circuits H05K3/00
• CPC Class Codes: H01L 2224/05553 being rectangular
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/451 with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
• 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 23/04 characterised by the shape of the container or parts, e.g. caps, walls
• CPC Class Codes: H01L 23/24 solid or gel at the normal operating temperature of the device H01L23/3135 takes precedence
• CPC Class Codes: H01L 23/36 Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks H01L23/28, H01L23/40, H01L23/42, H01L23/44, H01L23/46 take precedence; heating H01L23/345
• CPC Class Codes: H01L 23/49833 the chip support structure consisting of a plurality of insulating substrates
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• 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 2924/12042 LASER
• CPC Class Codes: H05K 1/182 associated with components mounted in the printed circuit board, e.g. insert mounted components [IMC]
• CPC Class Codes: H05K 2201/0179 Thin film deposited insulating layer, e.g. inorganic layer for printed capacitor
• CPC Class Codes: H05K 2201/10477 Inverted
• CPC Class Codes: H05K 2201/10666 Plated through-hole for surface mounting on PCB
• CPC Class Codes: H05K 2203/0455 PTH for surface mount device [SMD], e.g. wherein solder flows through the PTH during mounting
• CPC Class Codes: H05K 3/0032 : of organic insulating material
• CPC Class Codes: H05K 3/284 : for encapsulating mounted components H05K1/185 takes precedence
• CPC Class Codes: H05K 3/3436 : having an array of bottom contacts, e.g. pad grid array or ball grid array components
• CPC Class Codes: H05K 3/3452 : Solder masks
• CPC Class Codes: H05K 3/368 : parallel to each other H05K3/361 takes precedence
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/49146 : with encapsulating, e.g., potting, etc.
• CPC Class Codes: Y10T 29/49147 : Assembling terminal to base
• CPC Class Codes: Y10T 29/49149 : by metal fusion bonding
• CPC Class Codes: Y10T 428/239 : Complete cover or casing

Abstract

A method for forming a protective coating on an exposed surface of an electronic device, including forming the protective coating on a conductive termination connected to a circuit element in the electronic device, and making a window in the protective coating to expose the termination.

Claims

1. A method for making external connections to an electronic device comprising:

forming a protective coating on an exposed surface of the electronic device, the electronic device comprising a substrate, at least one electronic component mounted on the substrate, a conductive termination on the substrate, and an internal connection between the electronic component and the conductive termination;

wherein the step of forming includes forming the protective coating on the conductive termination; and

making a window in the protective coating to expose the termination without exposing the electronic component or the internal connection, the window defining an area for making a connection to the termination, the connection passing through the window.

2. The method of claim 1 wherein the coating is uniform in thickness.

3. The method of claim 1 wherein the coating conforms to the geometric configuration of the electronic device.

4. The method of claim 1 wherein coating the electronic device comprises vapor deposition.

5. The method of claim 1 wherein the protective coating comprises a polymer.

6. The method of claim 5 wherein the polymer comprises poly-para-xylylene.

7. The method of claim 1 wherein the electronic device comprises an integrated power device (IPD).

8. The method of claim 1 wherein the electronic component comprises a semiconductor.

9. The method of claim 1 wherein the electronic component comprises a power semiconductor.

10. The method of claim 1 wherein making a window in the protective coating comprises using a laser to remove the protective coating.

11. The method of claim 10 wherein the laser comprises a stroke marking laser.

12. The method of claim 10 wherein the laser comprises a mask marking laser.

13. The method of claim 10 wherein the laser comprises a fixed-beam laser.

14. The method of claim 10 wherein making a window in the protective coating comprises using a predetermined pattern.

15. The method of claim 14 wherein the predetermined pattern comprises a pattern of parallel strokes for removing strips of the protective coating.

16. The method of claim 1 wherein making a window in the protective coating comprises making a perimeter cut with a laser to outline the area of the protective coating to be removed and removing the outlined area of the protective coating.

17. The method of claim 16 wherein removing the outlined area of protective coating comprises peeling the protective coating away from the surface of the electronic device.

18. The method of claim 17 wherein peeling the protective coating comprises passing a gas over the surface of the protective coating until the protective coating dislodges from the electronic device.

19. The method of claim 18 wherein the gas comprises compressed air.

20. The method of claim 18 wherein the gas comprises an inert gas.

21. The method of claim 1 further comprising:

applying solder to the portion of the conductive termination exposed by the window in the protective coating.

22. The method of claim 21 wherein applying solder comprises reflow soldering.

23. The method of claim 21 wherein:

the window restricts the region of the termination to which the solder can adhere, the exposed area defining the location of the solder bond.

24. The method of claim 1 further comprising:

connecting a second component to the termination through the window.

25. The method of claim 23 further comprising encapsulating the electronic device in a potting material.

26. The method of claim 1 further comprising:

establishing an alignment between the window and a respective conductive run on a circuit board, the alignment having the exposed portion of the termination adjacent the respective conductive run;

making a solder connection between the exposed portion of the termination and the conductive run through the window.

27. The method of claim 26 wherein the conductive run further comprises a through hole and the connection comprises a solder connection between the through hole and the exposed portion of the termination.

28. The method of claim 26 wherein the conductive run further comprises a scallop and the connection is made between the scallop and the exposed portion of the termination.

29. The method of claim 26 wherein the circuit board comprises a aperture for accommodating the electronic component, the alignment also having the electronic component in the aperture.

30. The method of claim 4 further comprising:

masking a surface of the electronic device with a removable mask prior to forming the protective coating.

31. The method of claim 30 wherein the masking comprises securing the electronic device to an adhesive sheet.

32. The method of claim 30 further comprising:

mounting the electronic device to a baseplate.