Apparatus and method for improving circuit board solder

• US 6,429,383 B1
• Filed: 04/14/1999
• Issued: 08/06/2002
• Est. Priority Date: 04/14/1999
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Horine, Bryce, Sprietsma, John T., Joy, Steve
• Primary Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US09/291,724
• Time in Patent Office: 1,210 Days
• Field of Search: 174/260, 174/261, 174/262, 298/52, 298/79, 298/46, 361/760, 361/767, 361/807, 257/698, 228/180.1
• US Class Current: 174/260
• CPC Class Codes: H05K 1/113 Via provided in pad; Pad over filled via
• CPC Class Codes: H05K 2201/0959 Plated through-holes or plated blind vias filled with insulating material
• CPC Class Codes: H05K 2201/10636 Leadless chip, e.g. chip capacitor or resistor
• CPC Class Codes: H05K 2201/10689 Leaded Integrated Circuit [IC] package, e.g. dual-in-line [DIL]
• CPC Class Codes: H05K 2201/10734 Ball grid array [BGA]; Bump grid array
• CPC Class Codes: H05K 3/0094 Filling or covering plated through-holes or blind plated vias, e.g. for masking or for mechanical reinforcement
• CPC Class Codes: H05K 3/3452 Solder masks
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

A circuit board includes electrical interconnect mounting pads for mounting electronic devices thereto. Some of the electrical interconnect mounting pads include a plated through hole which traverses through the circuit board. One end of the plated through holes is closed, plugged or covered to prevent migration of solder through the plated through holes during a solder operation. The reduction in solder migration, as a result of plugging the plated through hole, increases solder joint quality over solder joint quality achieved using plated through holes which are not closed at one end.

Claims

1. A circuit board comprising:

an electrical interconnect mounting pad located on a first surface of the circuit board to receive a contact of a circuit device directly, without a separate trace thereto; and

a plated through hole traversing through the circuit board and the electrical interconnect mounting pad, the plated through hole having a first end located adjacent to the first surface of the circuit board and a second opposite end, the second end of the plated through hole being closed such that a liquid material cannot flow through the plated through hole from the first end and out the second end.

2. The circuit board of claim 1 wherein the plated through hole is closed using an epoxy material.

3. The circuit board of claim 1 wherein the plated through hole is closed using a nonconductive material.

4. The circuit board of claim 1 wherein the plated through hole is closed using a conductive material.

5. The circuit board of claim 1 wherein the second end of the plated through hole is closed using a film located on a second surface of the circuit board, the second surface of the circuit board is opposite the first surface of the circuit board.

6. The circuit board of claim 5 wherein the film is a solder mask.

7. The circuit board of claim 1 where the plated through hole is located directly under the contact of the circuit device.

8. The circuit board of claim 7 where the contact is a solder ball located on the device.

9. The circuit board of claim 1 where the contact of the circuit device is a lead extending from the device.

10. The circuit board of claim 9 where the plated through hole is sufficiently close to the lead that solder to attach the lead also flows into the first end of the hole.

11. A circuit board assembly comprising:

an electrical interconnect mounting pad located on a first surface of the circuit board;

a circuit device soldered directly to the electrical interconnect mounting pad without an intervening trace; and

a plated through hole traversing through the circuit board and the electrical interconnect mounting pad, the plated through hole having a first end located adjacent to the first surface of the circuit board and a second opposite end, the second end of the plated through hole being closed such that a liquid material cannot flow through the plated through hole from the first end and out the second end.

12. The circuit board assembly of claim 11 wherein the circuit device is an integrated circuit device soldered to the electrical interconnect mounting pad using a solder ball.

13. The circuit board assembly of claim 11 wherein the circuit device is an integrated circuit device soldered to the electrical interconnect mounting pad using an interconnect lead.

14. The circuit board assembly of claim 11 wherein the plated through hole is closed using a nonconductive material.

15. The circuit board assembly of claim 11 wherein the plated through hole is closed using a conductive material.

16. The circuit board assembly of claim 11 wherein the second end of the plated through hole is closed using a film located on a second surface of the circuit board, the second surface of the circuit board is opposite the first surface of the circuit board.

17. The circuit board assembly of claim 16 wherein the film is a solder mask.

18. The circuit board assembly of claim 11 wherein the circuit device is a microprocessor device.

19. The circuit board assembly of claim 11 where the circuit device has a contact located directly over the plated through hole.

20. The circuit board assembly of claim 19 where the contact is a solder ball.

21. The circuit board assembly of claim 11 where the circuit device has a lead extending therefrom.

22. The circuit board assembly of claim 21 where the plated through hole is sufficiently close to the lead that solder to attach the lead also flows into the first end of the hole.

23. A method of forming a circuit board, the method comprising:

fabricating a conductive mounting pad for a circuit device on a first surface of the circuit board;

fabricating a plated through hole traversing through the conductive mounting pad and the circuit board to an opposite surface of the printed circuit board; and

thereafter closing one end of the plated through hole only from the opposite surface of the printed circuit board and not from the first surface.

24. The method of claim 23 wherein the one end of the plated through hole is closed using a conductive material deposited inside the plated through hole.

25. The method of claim 23 wherein the one end of the plated through hole is closed using a nonconductive material deposited inside the plated through hole.

26. The method of claim 23 wherein the one end of the plated through hole is closed using a film located on a second surface of the circuit board which is opposite the first surface.

27. The method of claim 26 wherein the film is a solder mask film.

28. The method of claim 23 where the plated through hole is fabricated directly under a contact of the circuit device.

29. The method of claim 28 where the contact is a solder ball located on a bottom surface of the device.

30. The method of claim 23 where the contact of the circuit device is a lead extending laterally from the device.

31. The method of claim 30 where the plated through hole is sufficiently close to the lead that solder to attach the lead also flows into the first end of the hole.

32. A method of mounting an electronic device to a circuit board having first and second surfaces, the method comprising:

providing a conductive mounting pad on the first surface of the circuit board, the conductive mounting pad including a plated through hole traversing through the conductive mounting pad and the circuit board to the second surface;

capping one end of the plated through hole only from the second surface and not from the first surface; and

forming a solder joint between a contact of the electronic device and the conductive mounting pad.

33. The method of claim 32 wherein the one end of the plated through hole is closed by filling a portion of the plated through hole prior to forming the solder joint.

34. The method of claim 32 wherein the one end of the plated through hole is closed by covering the plated through hole with a film prior to forming the solder joint.

35. The method of claim 32 where the contact of the device is soldered directly over the plated through hole.

36. The method of claim 35 where the contact is a solder ball located on a bottom surface of the device.

37. The method of claim 32 where the contact of the device is a lead extending laterally from the device.

38. The method of claim 37 where the plated through hole is sufficiently close to the lead that solder from the joint lead also flows into the plated through hole.