Bonding metals and non-metals using inductive heating

• US 20070105341A1
• Filed: 11/09/2006
• Published: 05/10/2007
• Est. Priority Date: 11/09/2005
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Pisano, Albert, Lin, Liwei, Sosnowchik, Brian
• Granted Patent: US 7,452,800 B2
• Time in Patent Office: Days
• US Class Current: 438/455
• CPC Class Codes: B23K 1/0016 Brazing of electronic components
• CPC Class Codes: B23K 1/002 Soldering by means of induction heating
• CPC Class Codes: B23K 1/203 Fluxing, i.e. applying flux onto surfaces
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/08 Non-ferrous metals or alloys
• CPC Class Codes: B23K 2103/10 Aluminium or alloys thereof
• CPC Class Codes: B23K 2103/12 Copper or alloys thereof
• CPC Class Codes: B23K 2103/18 Dissimilar materials
• CPC Class Codes: B23K 2103/26 Alloys of Nickel and Cobalt and Chromium
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 2103/54 Glass
• CPC Class Codes: B23K 2103/56 semiconducting
• CPC Class Codes: B81C 3/001 Bonding of two components
• CPC Class Codes: G01L 1/2293 of the semi-conductor type semi-conductor devices controllable by variations of applied mechanical force H01L29/84
• CPC Class Codes: H01L 2224/29111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/83222 Induction heating, i.e. eddy currents
• CPC Class Codes: H01L 2224/83801 Soldering or alloying
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/83 using a layer 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 2924/00012 : 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 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01024 : Chromium [Cr]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/0103 : Zinc [Zn]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01075 : Rhenium [Re]
• 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 2924/0132 : Binary Alloys
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/01327 : Intermediate phases, i.e. intermetallics compounds
• CPC Class Codes: H01L 2924/0133 : Ternary Alloys
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/30105 : Capacitance
• CPC Class Codes: H01L 2924/3512 : Cracking
• CPC Class Codes: H05B 3/845 : specially adapted for reflecting surfaces, e.g. bathroom - or rearview mirrors

Abstract

A bonding technique suitable for bonding a non-metal body, such as a silicon MEMS sensor, to a metal surface, such a steel mechanical component is rapid enough to be compatible with typical manufacturing processes, and avoids any detrimental change in material properties of the metal surface arising from the bonding process. The bonding technique has many possible applications, including bonding of MEMS strain sensors to metal mechanical components. The inventive bonding technique uses inductive heating of a heat-activated bonding agent disposed between metal and non-metal objects to quickly and effectively bond the two without changing their material properties. Representative tests of silicon to steel bonding using this technique have demonstrated excellent bond strength without changing the steel'"'"'s material properties. Thus, with this induction bonding approach, silicon MEMS devices can be manufacturably bonded to mechanical steel components for real time monitoring of the conditions/environment of a steel component.

Claims

1. A method of bonding a non-metal body to a metal surface comprising the steps of:

a) contacting the non-metal body with the metal surface with a heat activated bonding agent therebetween; and

b) heating the solder with an inductive heater to bond the non-metal body to the metal surface.

2. The method of claim 1, wherein the heat activated bonding agent is selected from the group consisting of solder, brazing material, and heat-setting adhesive.

3. The method of claim 2, wherein the heat activated bonding agent comprises solder.

4. The method of claim 3, wherein the solder is applied to the metal surface prior to contacting the non-metal body and the metal surface.

5. The method of claim 3, wherein the solder is applied to the non-metal body prior to contacting the non-metal body and the metal surface.

6. The method of claim 5, wherein a pressure is applied during heating to promote contact of the non-metal body, bonding agent and metal surface.

7. The method of claim 1, wherein the non-metal body comprises a material selected from the group consisting of silicon, ceramic and glass.

8. The method of claim 3, wherein the non-metal body comprises silicon.

9. The method of claim 1, wherein the metal surface is ferromagnetic.

10. The method of claim 9, wherein the metal surface is selected from the group consisting of steel, iron and Ni.

11. The method of claim 8, wherein the metal surface is steel.

12. The method of claim 1, wherein the metal surface is non-ferromagnetic.

13. The method of claim 12, wherein the metal surface is selected from the group consisting of Al and Cu.

14. The method of claim 8, wherein the metal surface is Al.

15. The method of claim 3, further comprising an adhesion layer between the non-metal body and metal surface.

16. The method of claim 15, wherein the adhesion layer comprises a metal.

17. The method of claim 16, wherein the adhesion layer metal is selected from the group consisting of Ni, Au, Ag and Cu.

18. The method of claim 17, wherein the adhesion layer metal is Ni.

19. The method of claim 15, wherein step a) is preceded by the step of forming a seed layer on the surface of the non-metal body for adherence of the adhesion layer.

20. The method of claim 19, wherein the seed layer is selected from chromium-copper, chromium-nickel, chromium-gold, titanium-copper, titanium-nickel, titanium-gold, chromium and titanium.

21. The method of claim 3, wherein the solder comprises Pb.

22. The method of claim 3, wherein the solder is Pb-free.

23. The method of claim 3, wherein the solder comprises flux.

24. The method of claim 22, wherein the metal is ferromagnetic and the solder is a tin-silver-copper solder.

25. The method of claim 22, wherein the metal is non-ferromagnetic and the solder is a tin-zinc solder.

26. The method of claim 3, wherein the inductive heating has a duration of less than 10 seconds.

27. The method of claim 3, wherein the inductive heating has a duration of less than 5 seconds.

28. The method of claim 3, wherein the material properties of the metal are substantially unaffected by the soldering operation.

29. The method of claim 3, wherein, prior to application of the solder, the metal surface is prepared for bonding by removing native oxide.

30. The method of claim 29, wherein the surface preparation comprises cleaning and roughening.

31. The method of claim 18, wherein a thin layer of a solder is applied to the adhesion layer to prevent oxidation prior to bonding.

32. The method of claim 8, wherein the silicon body is a silicon chip.

33. The method of claim 32, wherein the silicon chip includes a MEMS device.

34. A method of bonding a silicon body to a steel surface comprising the steps of:

a) forming an adhesion layer of nickel on a surface of the silicon body;

b) applying solder to the steel surface;

c) placing the silicon body on the steel surface with the layer of nickel adjacent to the solder; and

d) heating the solder with an inductive heater for less than 5 seconds to solder the nickel layer to the steel surface.