Miniaturized contact spring
View Patent ↗This invention provides a solution to increase the yield strength and fatigue strength of miniaturized springs, which can be fabricated in arrays with ultra-small pitches. It also discloses a solution to minimize adhesion of the contact pad materials to the spring tips upon repeated contacts without affecting the reliability of the miniaturized springs. In addition, the invention also presents a method to fabricate the springs that allow passage of relatively higher current without significantly degrading their lifetime.
1. An interconnection apparatus for establishing electrical contact between two components, said apparatus comprising:
a plurality of elastic core members, each core member of said plurality of core members having an anchor portion attached to a substrate and a free portion, initially attached to said substrate, which, upon release, extends to a lift height away from said substrate due to an inherent stress gradient in said each core member;
said each core member having all exposed surfaces enveloped without any discontinuity with one or more electrodeposited coatings, said one or more coatings having a combined thickness greater than that of said core member and balanced internal stresses, wherein lift height variations among said plurality of core members are minimized and wherein a predetermined increase in the spring constant of said core members is provided to lower electrical contact resistance between said two components to within a predetermined range.
2. The interconnection apparatus of claim 1 , wherein said envelope comprises electroplated films.
3. The interconnection apparatus of claim 1 , wherein said free portion is substantially tapered having a width that gradually decreases towards the probe tip over a substantial length of the free portion.
4. The interconnection apparatus of claim 1 , wherein said free portion is substantially trapezoidal in shape.
5. The interconnection apparatus of claim 1 wherein said coating is an electrical conductor.
6. The interconnection apparatus of claim 1 , wherein said coating is selected from the group of materials comprising any of nickel, platinum group materials which comprise any of palladium, platinum rhodium, ruthenium, osmium, iridium, and, gold, silver, copper, cobalt, tungsten, and any of their alloys.
7. The interconnection apparatus of claim 1 , wherein the average grain size of at least one of said at least one electrodeposited coating ranges from 3 to 500 nm.
8. The interconnection apparatus of claim 1 , wherein at least one of said coating remains under compressive stress.
9. The interconnection apparatus of claim 1 , wherein grains of at least one said coating are substantially equiaxed with an average ratio of long to short dimensions of about 2 or less.
10. The interconnection apparatus of claim 1 , wherein at least one of said at least one coating has a lower elastic modulus than the said core that it surrounds.
11. The interconnection apparatus of claim 1 , wherein said substrate comprises any of ceramic, glass, silicon, quartz and organic materials.
12. The interconnection apparatus of claim 1 , wherein said each core member comprises any of Mo, Cr, Ti, W, Zr, Ti—W, and Mo—Cr.
13. The interconnection apparatus of claim 1 , wherein the thickness of the electrodepositedly enveloped free portion ranges from 1 to 45 microns.
14. The interconnection apparatus of claim 1 , wherein the thickness of each of said at least one coating ranges from 0.1 to 20 microns.
15. The interconnection apparatus of claim 1 , wherein said free portion has a size ranging from 10 μm to 1000 μm in length, 3 μm to 500 μm in width, and 0.1 μm to 40 μm in thickness.
16. The interconnection apparatus of claim 1 , wherein the outermost layer of said at least one coating is selected from the group consisting of copper, gold, nickel, and platinum group materials.
17. The interconnection apparatus of claim 1 , wherein the envelope comprises a plurality of different and sequentially electrodeposited films.
18. The interconnection apparatus of claim 17 , wherein the electrodeposited films are deposited in such a manner that the elastic modulus of the deposited films generally decrease progressively from the innermost core toward an outermost surface.
19. The interconnection apparatus of claim 17 , wherein the elastic modulus of said electrodeposited films decreases substantially discreetly from the innermost core toward an outermost surface.
20. The interconnection apparatus of claim 1 , further comprising:
a film layer selectively dispensed at a probe tip area onto said electrodepositedly enveloped core member.
21. The interconnection apparatus of claim 20 , wherein the film layer is deposited by electroplating.
22. The interconnection apparatus of claim 21 , wherein the film layer is selected from the group consisting of palladium, rhodium, platinum, iridium, osmium, ruthenium, and cobalt, nickel, gold, copper, silver, and their alloys.
23. An interconnection device comprising:
a plurality of elastic core members, each core member having an anchor portion attached to a substrate, said substrate having metallization comprising metallized through-vias, which are electrically connected to corresponding core member anchor portions, and further having a free portion, initially attached to said substrate, which, upon release, extends away from said substrate due to an inherent stress gradient in said each core member;
said each core member having all exposed surfaces enveloped without any discontinuity with one or more coatings, said one or more coatings having a combined thickness greater than that of said core member and balanced internal stresses, wherein lift height variations among said plurality of core members are minimized.
24. The device of claim 23 , wherein said substrate comprises any of ceramic, glass, quartz, silicon, and organic material.
25. The device of claim 23 , wherein said each core member comprises any of Mo, Cr, W, Ti, Zr, Mo—Cr, and Ti—W.