Method for joining an integrated circuit

• US 6,434,817 B1
• Filed: 12/03/1999
• Issued: 08/20/2002
• Est. Priority Date: 12/03/1999
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Feigenbaum, Haim, Schreiber, Chris M.
• Primary Examiner(s): Arbes, Carl J.
• Application Number:
  US09/454,789
• Time in Patent Office: 991 Days
• Field of Search: 298/40, 298/32, 298/47, 439/67, 439/68
• US Class Current: 29/840
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/10 Bump connectors bumps on insulating substrates, e.g. chip carriers, H01L23/49816; Manufacturing methods related thereto
• CPC Class Codes: H01L 24/13 of an individual bump 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 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01018 Argon [Ar]
• CPC Class Codes: H01L 2924/0102 Calcium [Ca]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01052 : Tellurium [Te]
• CPC Class Codes: H01L 2924/01068 : Erbium [Er]
• CPC Class Codes: H01L 2924/01075 : Rhenium [Re]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/19043 : being a resistor
• CPC Class Codes: H05K 1/189 : characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/0347 : Overplating, e.g. for reinforcing conductors or bumps; Plating over filled vias
• CPC Class Codes: H05K 2201/0367 : Metallic bump or raised conductor not used as solder bump
• CPC Class Codes: H05K 2201/10674 : Flip chip
• CPC Class Codes: H05K 3/4007 : Surface contacts, e.g. bumps H05K3/4092 takes precedence; deposition of finish layers on pads H05K3/24; forming solder bumps H05K3/3457
• CPC Class Codes: Y10T 29/4913 : Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49144 : by metal fusion
• CPC Class Codes: Y10T 29/49156 : with selective destruction of conductive paths

Abstract

A method for attaching an integrated circuit to a flexible circuit which includes the acts of providing an integrated circuit having a plurality of contact pads formed upon a surface thereof; providing a flexible circuit possessing a plurality of contact bumps formed integral to a surface area; and attaching the integrated circuit to the flexible circuit by fusing at least some of the contact bumps of the flexible circuit to at least some of the contact pads of the integrated circuit. The contact bumps have a shape which mitigates local stress buildup within the contact bumps after attachment of the contact bumps to the contact pads, so as to enhance the reliability of the electrical connection.

Claims

1. A method for forming a contact bump, the method comprising:

forming a conductive material to have a height of between approximately 0.001 inch and approximately 0.008 inch;

forming the conductive material to have a base width of between approximately 0.001 inch and approximately 0.010 inch;

forming the conductive material to have a slope angle of between approximately 40 degrees and approximately 80 degrees;

forming the conductive material to have a tip radius of between approximately 0.001 inch and approximately 0.030 inch; and

wherein the height, width, slope angle, and tip radius interact to produce the bump having a shape which mitigates local stress buildup.

2. The method as recited in claim 1, wherein:

the conductive material is formed to have a height of approximately 0.006 inch;

the conductive material is formed to have a base width of approximately 0.008 inch;

the conductive material is formed to have a slope angle of approximately 75 degrees; and

the conductive material is formed to have a tip radius of approximately 0.020 inch.

3. A method for attaching an integrated circuit to a flexible circuit while mitigating local stress buildup, the method comprising:

providing an integrated circuit having a plurality of contact pads formed upon a surface thereof,

providing a flexible circuit having a plurality of contact bumps formed integral to a surface thereof,

attaching the integrated circuit to the flexible circuit by fusing at least some of the contact bumps of the flexible circuit to at least some of the contact pads of the integrated circuit; and

wherein the contact bumps have a shape which mitigates local stress buildup within the contact bumps after attachment of the contact bumps to the contact pads, said shape which mitigates local stress buildup having a low aspect ratio defined by a height, base width, slope angle, and tip radius of each contact bump.

4. The method as recited in claim 3, wherein the contact pads of the integrated circuit comprise aluminum contact pads.

5. The method as recited in claim 3, wherein the contact bumps of the flexible circuit have a shape which facilitates distribution of stress throughout the contact bumps after attachment of the contact bumps to the contact pads.

6. The method as recited in claim 3, wherein the contact bumps of the flexible circuit have a shape which facilitates distribution of stress generally equally throughout the contact bumps after attachment of the contact bumps to the contact pads.

7. The method as recited in claim 3, wherein the contact bumps of the flexible circuit have a shape which enhances penetration of an oxidation layer of the contact pads of the integrated circuit by the contact bumps.

8. The method as recited in claim 3, wherein the contact bumps of the flexible circuit have a height of between approximately 0.001 inch and approximately 0.008 inch, a base width of between approximately 0.001 inch and approximately 0.010 inch, a slope angle of between approximately 40 degrees and approximately 80 degrees and a tip radius of between approximately 0.001 inch and approximately 0.030 inch.

9. The method as recited in claim 3, wherein the contact bumps of the flexible circuit have a height of approximately 0.006 inch, a base width of approximately 0.008 inch, a slope angle of approximately 75 degrees and a tip radius of approximately 0.020 inch.

10. The method as recited in claim 3, wherein the contact pads of the integrated circuit are non-lead containing contact pads.

11. The method as recited in claim 3, wherein the contact bumps of the flexible circuit are formed such that the number of contact bumps generally corresponds to the number of contact pads of the integrated circuit and such that the contact bumps of the flexible circuit are configured in a generally complimentary fashion with respect to the contact pads of the integrated circuit.

12. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, wherein the contact pads of the integrated circuit comprise generally flat pads.

13. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, wherein the contact pads of the integrated circuit comprise generally flat aluminum pads.

14. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, wherein the contact bumps of the flexible circuit comprise substantially pure gold.

15. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, wherein the contact bumps of the flexible circuit comprise a layer of substantially pure gold.

16. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, wherein the contact bumps of the flexible circuit comprise a layer of substantially pure gold formed upon a layer of copper.

17. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, wherein fusing the contact bumps of the flexible circuit to the contact pads of the integrated circuit comprises applying thermocompression to the contact bumps of the flexible circuit and the contact pads of the integrated circuit.

18. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, wherein fusing the contact bumps of the flexible circuit to the contact pads of the integrated circuit comprises applying thermosonic energy to the contact bumps of the flexible circuit and the contact pads of the integrated circuit.

19. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, further comprising applying an epoxy underfill intermediate the flexible circuit and the integrated circuit prior to attaching the integrated circuit to the flexible circuit.

20. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, further comprising applying an epoxy underfill to the flexible circuit prior to attaching the integrated circuit to the flexible circuit.

21. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, further comprising applying an epoxy underfill to the integrated circuit prior to attaching the integrated circuit to the flexible circuit.

22. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, further comprising applying an epoxy underfill intermediate the flexible circuit and the integrated circuit prior to attaching the integrated circuit to the flexible circuit and wherein heat is applied to facilitate generally simultaneous curing of the epoxy underfill and fusion of the contact bumps of the flexible circuit with the contact pads of the integrated circuit.

23. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, further comprising applying an encapsulant such that the encapsulant substantially covers the integrated circuit and also covers a portion of the flexible circuit proximate the integrated circuit.

24. The method for attaching an integrated circuit to a flexible circuit as recited in claim 3, further comprising applying Hysol FP4544 such that the Hysol FP4544 substantially covers the integrated circuit and also covers a portion of the flexible circuit proximate the integrated circuit.

25. A method for attaching an integrated circuit to a flexible circuit, the method comprising:

providing an integrated circuit having a plurality of contact pads formed upon a surface thereof;

providing a flexible circuit having a plurality of contact bumps formed upon a surface thereof;

applying an epoxy underfill intermediate the flexible circuit and the integrated circuit; and

attaching the integrated circuit to the flexible circuit by fusing at least some of the contact bumps of the flexible circuit to corresponding contact pads of the integrated circuit after the epoxy underfill has been applied.

26. The method as recited in claim 25, wherein the contact pads of the integrated circuit comprise contact pads.

27. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein applying an epoxy underfill intermediate the flexible circuit and the integrated circuit comprises applying an epoxy underfill to the flexible circuit prior to attaching the integrated circuit thereto.

28. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein applying an epoxy underfill intermediate the flexible circuit and the integrated circuit comprises applying an epoxy underfill to the integrated circuit prior to attaching the integrated circuit to the flexible circuit.

29. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein heat is applied to facilitate generally simultaneous curing of the epoxy underfill and fusion of the contact bumps of the flexible circuit with the contact pads of the integrated circuit.

30. The method as recited in claim 25, wherein the contact bumps of the flexible circuit are formed such that the number of contact bumps generally corresponds to the number of contact pads of the integrated circuit and wherein the contact bumps of the flexible circuit are configured in a generally complimentary fashion with respect to the contact pads of the integrated circuit.

31. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein the contact pads of the integrated circuit comprise generally flat pads.

32. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein the contact pads of the integrated circuit comprise generally flat aluminum pads.

33. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein the contact bumps of the flexible circuit comprise substantially pure gold.

34. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein the contact bumps of the flexible circuit comprises a layer of substantially pure gold.

35. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein the contact bumps of the flexible circuit comprise a layer of substantially pure gold formed upon a layer of copper.

36. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein fusing the contact bumps of the flexible circuit to the contact pads of the integrated circuit comprises applying thermocompression to the contact bumps of the flexible circuit and the contact pads of the integrated circuit.

37. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, wherein fusing the contact bumps of the flexible circuit to the contact pads of the integrated circuit comprises applying thermosonic energy to the contact bumps of the flexible circuit and the contact pads of the integrated circuit.

38. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, further comprising applying an encapsulant such that the encapsulant substantially covers the integrated circuit and also covers a portion of the flexible circuit proximate the integrated circuit.

39. The method for attaching an integrated circuit to a flexible circuit as recited in claim 25, further comprising applying Hysol FP4544 such that the Hysol FP4544 substantially covers the integrated circuit and also covers a portion of the flexible circuit proximate the integrated circuit.

40. A method for attaching a first electrical component to a second electrical component, the method comprising:

forming contact pads upon the first electrical component; and

forming corresponding contact bumps upon the second electrical component, the contact bumps having a shape which mitigates local stress buildup within the contact bumps after attachment of the contact bumps to the contact pads and the contact bumps also having a shape which enhances penetration of an oxide layer of the contact pads of the first electrical circuit.