Superconducting bonds for thin film devices

• US 5,139,192 A
• Filed: 03/03/1992
• Issued: 08/18/1992
• Est. Priority Date: 08/30/1990
• Status: Expired due to Term

• Current Assignee: Quantum Design, Inc.
• Original Assignee: Quantum Magnetics, Inc. (GE Aerospace)
• Inventors: Simmonds, Michael B.
• Primary Examiner(s): Heinrich, Samuel M.
• Application Number:
  US07/845,037
• Time in Patent Office: 168 Days
• Field of Search: 228/179, 228/110, 228/111, 228/123, 228/208, 228/263.19, 228/904, 174/94 R, 505/925, 505/927
• US Class Current: 228/179.1
• CPC Class Codes: H01L 2224/05554 being square
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/43848 Thermal treatments, e.g. annealing, controlled cooling
• CPC Class Codes: H01L 2224/45014 Ribbon connectors, e.g. rectangular cross-section
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/4503 Stacked arrangements
• CPC Class Codes: H01L 2224/45033 Three-layer arrangements
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/4847 the connecting portion on the bonding area of the semiconductor or solid-state body being a wedge bond
• CPC Class Codes: H01L 2224/85205 Ultrasonic bonding
• 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 24/85 using a wire connector wire bonding in general B23K20/004
• 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 2924/00011 Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01014 Silicon [Si]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01041 : Niobium [Nb]
• CPC Class Codes: H01L 2924/01073 : Tantalum [Ta]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/206 : Length ranges
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H10N 60/80 : Constructional details
• CPC Class Codes: Y10S 505/927 : Metallurgically bonding superconductive members

Abstract

A method of bonding a superconductive ribbon lead to a superconductive bonding pad connected to superconducting circuitry. The thin ribbon is first coated with a fresh layer of the same material from which it is made and then a very thin layer of a noble metal is applied over that fresh layer. The bonding pad is also prepared with a very thin layer of the noble metal. Those coated surfaces are placed in facing contact and ultrasonically bonded.

Claims

1. A method of bonding a superconductive electrical lead to a superconductive thin film pad on a substrate, said method comprising the steps of:

forming a thin film bonding pad of superconductive material on the substrate, the pad having a contact surface;

forming a wire of similar superconductive material, the wire having a facing surface;

coating at least one of the pad contact surface and the wire facing surface with a very thin layer of a different material which readily coheres to the superconductive surface material;

placing the different-material coated surface in contact with the other superconductive material surface; and

then

bonding the wire to the bonding pad.

11. The method recited in claim 1, wherein the thin film bonding pad superconductive material is a refractory metal.

12. The method recited in claim 11, wherein the superconductive metal is niobium.

13. The method recited in claim 11, wherein the superconductive metal is tantalum.

14. The method recited in claim 1, wherein the different material is a noble metal.

15. The method recited in claim 14, wherein the noble metal is palladium.

16. The method recited in claim 14, wherein the noble metal is platinum.

17. The method recited in claim 14, wherein the noble metal is gold.

18. The method recited in claim 1, wherein the wire is about an order of magnitude thicker than the bonding pad.

19. The method recited in claim 1, wherein the bonding pad is about 30 to 60 times thicker than the different material coating.

20. The method recited in claim 1, and comprising the further step of coating the other of the pad contact surface and the wire facing surface with a very thin layer of the different material.

21. The method recited in claim 1, wherein the bonding step is accomplished ultrasonically.

22. The method recited in claim 1, and comprising the further step of coating the wire with a layer of the same superconductive material before applying the different material coating thereover.

23. The method recited in claim 1, wherein the bonding pad has a thickness ranging between 300 nm and 600 nm.

24. The method recited in claim 1, wherein the wire has a thickness ranging between 0.00003 and 0.0003 inch.

25. The method recited in claim 1, wherein the different material coating is about 10 nm thick.

26. The method recited in claim 22, wherein the superconductive material coating ranges between 1 and 500 nm thick and the different material coating is about 10 nm thick.

2. A method of bonding a superconductive electrical lead to a superconductive thin film pad on an electrically insulating substrate, said method comprising the steps of:

forming a thin film bonding pad of niobium on the substrate, the pad having a contact surface;

forming a wire of niobium, the wire having a facing surface;

coating at least one of the niobium pad contact surface and wire facing surface with a very thin layer of palladium;

placing the palladium coated surface and the niobium surface of the other element in contact; and

then

ultrasonically bonding the wire to the bonding pad.

3. The method recited in claim 2, and comprising the further step of coating the other of the contacting niobium surfaces with palladium prior to the placing step.

4. The method recited in claim 2, wherein the wire is about an order of magnitude thicker than the bonding pad.

5. The method recited in claim 2, wherein the bonding pad is about 30 to 60 times thicker than the palladium coating.

6. The method recited in claim 2, wherein the niobium film bonding pad has a thickness ranging between 300 nm and 600 nm.

7. The method recited in claim 2, wherein the niobium wire has a thickness ranging between 0.00003 and 0.0003 inch.

8. The method recited in claim 2, wherein the palladium layer is about 10 nm thick.

9. The method recited in claim 2, and comprising the further step of coating one surface of the niobium wire with a layer of niobium before applying the palladium coating thereover.

10. The method recited in claim 9, wherein the coating of niobium on the niobium wire ranges between 1 and 500 nm thick and the palladium layer is about 10 nm thick.