Transferable Micro Spring Structure

• US 20080268669A1
• Filed: 07/03/2008
• Published: 10/30/2008
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Hantschel, Thomas, Van Schuylenbergh, Koenraad F.
• Granted Patent: US 7,985,081 B2
• Time in Patent Office: Days
• US Class Current: 439/67
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81C 3/002 Aligning microparts
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 2221/68363 used in a transfer process involving transfer directly from an origin substrate to a target substrate without use of an intermediate handle substrate
• CPC Class Codes: H01L 2924/19041 being a capacitor
• CPC Class Codes: H01R 12/57 surface mounting terminals
• CPC Class Codes: H01R 12/714 with contacts abutting directly the printed circuit; Button contacts therefore provided on the printed circuit
• CPC Class Codes: H01R 13/24 resilient; resiliently-mounted
• CPC Class Codes: H05K 2203/0338 Transferring metal or conductive material other than a circuit pattern, e.g. bump, solder, printed component
• CPC Class Codes: H05K 3/341 Surface mounted components
• CPC Class Codes: H05K 3/4015 using auxiliary conductive elements, e.g. pieces of metal foil, metallic spheres
• CPC Class Codes: H05K 3/4092 Integral conductive tabs, i.e. conductive parts partly detached from the substrate

Abstract

A method for mounting the micro spring structures onto cables or contact structures includes forming a spring island having an “upside-down” stress bias on a first release material layer or directly on a substrate, forming a second release material over at least a portion of the spring island, and then forming a base structure over the second release material layer. The micro spring structure is then transferred in an unreleased state, inverted such that the base structure contacts a surface of a selected apparatus, and then secured (e.g., using solder reflow techniques) such that the micro spring structure becomes attached to the apparatus. The spring structure is then released by etching or otherwise removing the release material layer(s).

Claims

1. An apparatus for transferring micro spring structures, the apparatus comprising:

a substrate;

a spring island attached to the substrate, wherein the spring island has stress gradient including a relatively tensile region and a relatively compressive region, the relatively tensile region being located between the first release material portion and the relatively compressive region;

a second release material portion formed over a first portion of the spring island; and

a base structure formed over the second release material portion and a second portion of the spring island.

2. The apparatus of claim 1, further comprising a first release material portion formed between the spring island and the substrate.

3. The apparatus of claim 1, further comprising an adhesive layer formed between the spring island and the substrate.

4. The apparatus according to claim 1, wherein the spring island comprises molybdenum (Mo) and chromium (Cr), and wherein the first and second release material portions comprise titanium (Ti).

5. The apparatus according to claim 1, wherein the spring island comprises at least one of nickel (Ni), chromium (Cr), cobalt (Co), rhodium (Rh), gold (Au), copper (Cu) tin (Sn), zinc (Zn), and palladium (Pd).

6. The apparatus according to claim 1, wherein the base structure comprises Ni—

Au strips formed on the second release material portion of release material and a second portion of the spring island, and a solder layer formed on the Ni—

Au strips.

7. The apparatus according to claim 1, wherein the base structure comprises a conductive inner frame formed on the second release material portion and a second portion of the spring island, and an outer contact portion formed on the inner frame.

8. The apparatus according to claim 7, wherein the outer contact portion comprises solder.

9. An assembly for simultaneously forming a plurality of micro springs on a target apparatus, the target apparatus including a plurality of contact pads arranged in a predetermined pattern, the assembly including a plurality of unreleased micro spring structures disposed on a substrate, each said unreleased micro spring structure comprising:

a spring island attached to the substrate, wherein the spring island has stress gradient including a relatively tensile region and a relatively compressive region, the relatively tensile region being located between the first release material portion and the relatively compressive region;

a second release material portion formed over a first portion of the spring island; and

a base structure formed over the second release material portion and a second portion of the spring island,

wherein said plurality of unreleased micro spring structures are arranged in said predetermined pattern such that when the assembly is mounted onto the target apparatus, the base structure of said each unreleased micro spring structure contacts a corresponding contact pad of the plurality of contact pads.

10. The assembly of claim 9, wherein said each unreleased micro spring structure further comprises a first release material portion formed between the spring island and the substrate.

11. The assembly of claim 9, wherein said each unreleased micro spring structure further comprises an adhesive layer formed between the spring island and the substrate.

12. The assembly of claim 9, wherein the spring island of said each unreleased micro spring structure comprises molybdenum (Mo) and chromium (Cr), and wherein the first and second release material portions of said each unreleased micro spring structure comprise titanium (Ti).

13. The assembly of claim 9, wherein the spring island of said each unreleased micro spring structure comprises at least one of nickel (Ni), chromium (Cr), cobalt (Co), rhodium (Rh), gold (Au), copper (Cu) tin (Sn), zinc (Zn), and palladium (Pd).

14. The assembly of claim 9, wherein the base structure of said each unreleased micro spring structure comprises Ni—

Au strips formed on the second release material portion of release material and a second portion of the spring island, and a solder layer formed on the Ni—

Au strips.

15. The assembly according to claim 9, wherein the base structure of said each unreleased micro spring structure comprises a conductive inner frame formed on the second release material portion and a second portion of the spring island, and an outer contact portion formed on the inner frame.

16. The assembly according to claim 15, wherein the outer contact portion of said each unreleased micro spring structure comprises solder.

17. An apparatus comprising:

a substrate;

a plurality of contact pads arranged in a predetermined pattern on the substrate; and

a plurality of micro spring structures disposed on a substrate such that each said micro spring structure is mounted onto a corresponding contact pad of said plurality of contact pads, wherein each micro spring structure comprises;

a base structure including an outer contact portion secured to said corresponding contact pad, and an inner frame disposed inside of the outer contact portion; and

a spring finger having an anchor portion attached to a support portion of the inner frame such that the anchor portion extends parallel to the substrate, and a free portion having a curved shape and arranged such that a tip of said free portion is directed away from the substrate.

18. The apparatus of claim 17, wherein the spring finger of each said micro spring structure comprises at least one of molybdenum (Mo), chromium (Cr), nickel (Ni), cobalt (Co), rhodium (Rh), gold (Au), copper (Cu), tin (Sn), zinc (Zn), and palladium (Pd).

19. The apparatus according to claim 17, wherein the inner frame of the base structure of each said micro spring structure comprises Ni—

Au strips, and wherein the outer contact portion of the base structure comprises a solder layer.

20. The apparatus according to claim 17, wherein the base structure of each said micro spring structure is soldered to the corresponding contact pad of said plurality of contact pads.