Composite microelectronic spring structure and method for making same

• US 7,063,541 B2
• Filed: 12/22/2000
• Issued: 06/20/2006
• Est. Priority Date: 03/17/1997
• Status: Expired due to Fees

• Current Assignee: FormFactor Incorporated
• Original Assignee: FormFactor Incorporated
• Inventors: Mathieu, Gaetan L., Grube, Gary W., Khandros, Igor Y.
• Primary Examiner(s): Abrams, Neil
• Application Number:
  US09/746,716
• Publication Number:
  US 20010012739A1
• Time in Patent Office: 2,006 Days
• Field of Search: 439/66, 439/81, 324/754, 324/762
• US Class Current: 439/66
• CPC Class Codes: G01R 1/06727 Cantilever beams
• CPC Class Codes: G01R 1/06744 Microprobes, i.e. having dimensions as IC details
• CPC Class Codes: G01R 1/07342 the body of the probe being at an angle other than perpendicular to test object, e.g. probe card
• CPC Class Codes: G01R 3/00 Apparatus or processes specially adapted for the manufacture or maintenance of measuring instruments , e.g. of probe tips
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/04042 Bonding areas specifically adapted for wire connectors, e.g. wirebond pads
• CPC Class Codes: H01L 2224/06136 Covering only the central area of the surface to be connected, i.e. central arrangements
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/29099 Material
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 23/49811 Additional leads joined to the metallisation on the insulating substrate, e.g. pins, bumps, wires, flat leads H01L23/49827 takes precedence
• CPC Class Codes: H01L 24/06 of a plurality of bonding areas
• 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 24/72 Detachable connecting means consisting of mechanical auxiliary parts connecting the device, e.g. pressure contacts using springs or clips
• 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 2924/00013 Fully indexed content
• 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 2924/01012 : Magnesium [Mg]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 : Silicon [Si]
• CPC Class Codes: H01L 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/01022 : Titanium [Ti]
• CPC Class Codes: H01L 2924/01027 : Cobalt [Co]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01042 : Molybdenum [Mo]
• CPC Class Codes: H01L 2924/01045 : Rhodium [Rh]
• CPC Class Codes: H01L 2924/01046 : Palladium [Pd]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01051 : Antimony [Sb]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• 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 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/30105 : Capacitance
• CPC Class Codes: H05K 3/20 : by affixing prefabricated conductor pattern H05K1/187, H05K3/046, H05K3/4658, H05K3/4682 takes precedence
• CPC Class Codes: H05K 3/3421 : Leaded components

Abstract

An improved microelectronic spring structure, and method of making the same, are disclosed. The improvement comprises, in a spring contact of the type comprising a beam attached to a post, of replacing the post with a plurality of column elements. The beam component is thus provided with one or more column elements which both structurally support and electrically connect one end of the beam to an electronic component. The column elements are preferably comprised of relatively straight segments of wire elements that are ball-bonded to a substrate and are over-coated with suitable structural and/or conducting materials. In the alternative, the improvement comprises a single column element comprised of a relatively straight segment of wire that is ball-bonded to a substrate and over-coated with suitable structural and conducting materials, wherein the column element is essentially rigid. The improved spring structures are especially useful for use as spring contacts on substrates such as probe cards, interposers, semiconductor devices, and other electronic components.

Claims

1. A microelectronic contact structure, comprising:

a plurality of substantially rigid column elements, each of said plurality of column elements comprising;

a core element comprising a segment of wire attached at a first end to a terminal of an electronic component, and

an over coat covering at least a portion of said core element, wherein said core element comprises a first material and said over coat comprises a second material, and said first material is one of softer, less rigid, or has a lower modulus of elasticity than said second material; and

a contact element that is joined to a second end of each of said plurality of column elements.

2. The microelectronic contact structure of claim 1, wherein said contact element further comprises a beam formed of a resilient material.

3. The microelectronic contact structure of claim 1, wherein said contact element further comprises a contact pad joined to each of said column elements.

4. The microelectronic contact structure of claim 1, wherein said column elements are substantially straight and parallel to one another.

5. The microelectronic contact structure of claim 2, wherein said beam is positioned transverse to each of said plurality of column elements and joined to each of said column elements.

6. The microelectronic contact structure of claim 1, wherein said column elements are inclined to said contact element at an angle between 70°

and 110°

excluding 90°

.

7. The microelectronic contact structure of claim 1, wherein said column elements are perpendicular to said contact element.

8. The microelectronic contact structure of claim 1, wherein each of said column elements is substantially cylindrical.

9. The microelectronic contact structure of claim 2, wherein said beam is sloped away from said column elements.

10. The microelectronic contact structure of claim 2, further comprising a sacrificial substrate joined to said beam.

11. The microelectronic contact structure of claim 2, wherein said beam is contoured.

12. The microelectronic contact structure of claim 2, wherein said beam is fabricated by a lithographic process that includes depositing said resilient material on a sacrificial substrate.

13. The microelectronic contact structure of claim 2, further comprising a tip structure positioned on a surface of said beam opposite to said plurality of column elements.

14. The microelectronic contact structure of claim 2, wherein said beam has a free end cantilevered from said plurality of column elements.

15. The microelectronic contact structure of claim 14, further comprising a tip structure positioned on said beam between said free end of said beam and said plurality of column elements.

16. The microelectronic contact structure of claim 15, wherein said tip structure is positioned on a surface of said beam opposite to said column elements.

17. The microelectronic contact structure of claim 15, wherein said tip structure is positioned adjacent to said free end of said beam.

18. The microelectronic contact structure of claim 15, wherein said tip structure comprises a stand-off mounted to said beam, and a contact tip mounted to said stand-off.

19. The microelectronic contact structure of claim 1, further comprising said substrate joined to each of said column elements at said base thereof.

20. The microelectronic contact structure of claim 2, further comprising said substrate joined to each of said column elements at said base thereof, and wherein said beam has a free end cantilevered from said column elements.

21. The microelectronic contact structure of claim 20, wherein said microelectronic spring structure is configured such that said top of each of said column elements is substantially fixed while said free end of said beam will deflect under a force applied to said beam at said free end in a direction transverse to said substrate.

22. The microelectronic contact structure of claim 1, wherein said first material is softer than said second material.

23. The microelectronic contact structure of claim 1, wherein said first material is less rigid than said second material.

24. The microelectronic contact structure of claim 1, wherein said first material has a lower modulus of elasticity than said second material.

25. The microelectronic contact structure of claim 1, wherein said over coat anchors said core element to said terminal of said electronic component.

26. A microelectronic contact structure, comprising:

a column element comprising a top and a base, and wherein said base is positioned for attachment to a substrate; and

a cantilevered, elongate beam, a first portion of said beam joined to said top of said column element, and a second portion of said beam disposed away from said column element and free to deflect independent of said first portion,

wherein said column element comprises a wire.

27. The microelectronic contact structure of claim 26 further comprising a plurality of column elements each comprising a top and a base, wherein each said base is positioned for attachment to said substrate, and said beam is joined to said tops of each of said plurality of column elements.

28. A microelectronic contact structure, comprising:

a plurality of substantially rigid column elements, each of said plurality of column elements comprising;

a core element attached at a first end to a terminal of an electronic component, and

an over coat covering at least a portion of said core element, wherein said core element comprises a first material and said over coat comprises a second material, and said first material is one of softer, less rigid, or has a lower modulus of elasticity than said second material; and

a contact element joined to a second end of said plurality of column elements,

further comprising a substrate joined to each of said column elements at said base thereof, and wherein said contact element comprises a beam and said beam has a free end cantilevered from said column elements,

wherein said microelectronic spring structure is configured such that said top of each of said column elements is substantially fixed while said free end of said beam will deflect under a force applied to said beam at said free end in a direction transverse to said substrate, and

each of said column elements is connected at said base thereof to a terminal of said substrate, and further comprising a connector comprising a wire core joined to said terminal of said substrate, and connected to a second terminal of said substrate.

29. A substrate having a plurality of microelectronic spring structures mounted thereto, wherein each of said microelectronic spring structures comprises:

at least two substantially rigid column elements, wherein each column element has a top and a base, and is joined to said substrate at said base; and

a beam comprising a column connection region and a contact tip region and joined to each of said column elements at said column connection region, wherein said beam is positioned transverse to each of said colunm elements and said column elements are positioned such that the top of one of said column elements is positioned between the top of said other column element and the contact tip region of said beam.

30. The substrate of claim 29, wherein said substrate comprises a probe card.

31. The substrate of claim 29, wherein said substrate comprises a semiconductor material containing an integrated circuit.

32. The substrate of claim 29, wherein said substrate comprises an interposer.

33. The substrate of claim 29, wherein said substrate comprises a space transformer.

34. The substrate of claim 29, wherein said substrate comprises an electrical connector.

35. A substrate-mounted microelectronic spring structure, comprising:

a substrate;

a substantially rigid column element having a top and a base, and joined at said base to said substrate, wherein said column element comprises a substantially straight segment of wire; and

a resilient cantilevered beam having a free end, and joined to said top of said column element at a joint a distance away from said free end;

wherein said microelectronic spring structure is configured such that said top of said column element is substantially fixed while said cantilever beam permits elastic deflection of said free end thereof under a force applied to said beam at said free end towards said substrate.

36. The microelectronic spring structure of claim 35, wherein said column element is inclined to said beam at an angle between 70°

and 110°

excluding 90°

.

37. The microelectronic spring structure of claim 35, wherein said resilient cantilevered beam is sloped away from said substrate.

38. The microelectronic spring structure of claim 35, wherein said resilient cantilevered beam is contoured in a direction perpendicular to said substrate.

39. The microelectronic spring structure of claim 35, wherein said resilient cantilevered beam is fabricated by a lithographic process that includes depositing said resilient material on a sacrificial substrate.

40. The microelectronic spring structure of claim 35, further comprising a tip structure positioned on a surface of said beam opposite to said column element.

41. The microelectronic spring structure of claim 35, wherein said tip structure is positioned adjacent to said free end of said beam.

42. The microelectronic spring structure of claim 41, wherein said tip structure comprises a stand-off mounted to said beam, and a contact tip mounted to said stand-off.

43. The microelectronic spring structure of claim 35, wherein said column element comprises a wire core enclosed in a shell comprising at least one shell material.

44. The microelectronic spring structure of claim 43, wherein said shell is formed by plating said shell material onto said wire cores.

45. The microelectronic spring structure of claim 43, wherein said wire core is ball-bonded to said substrate.

46. The substrate-mounted microelectronic spring structure of claim 35 further comprising a plurality of said colunm elements.

47. The substrate-mounted microelectronic spring structure of claim 35, wherein said substrate-mounted microelectronic spring structure includes only one column element.

48. A microelectronic spring structure, comprising:

substrate means for supporting a structure;

support means for supporting a beam, for securing a beam to said substrate means, and for elevating a beam above said substrate means, wherein said support means comprises at least one substantially rigid column element having an at least partially over coated core element, wherein said core element comprises a first material and said over coat comprises a second material, and said first material is one of softer, less rigid, or has a lower modulus of elasticity than said second material; and

resilient beam means for contacting an electronic component, said resilient beam means supported by said support means,

wherein said core element of said at least one column element comprises a segment of wire.

49. The microelectronic spring structure of claim 48, wherein said support means comprises a group of said substantially rigid column elements.

50. The microelectronic spring structure of claim 48, wherein said resilient beam means comprises a substantially straight beam of resilient material.

51. The microelectronic spring structure of claim 48, wherein said resilient beam means comprises a beam of resilient material contoured in a direction perpendicular to said substrate.

52. The microelectronic spring structure of claim 48, further comprising contact tip means for contacting a terminal of an electronic component, said contact tip means supported by and secured to said resilient beam means.

53. The microelectronic spring structure of claim 52, wherein said contact tip means comprises a stand-off, and a contact tip mounted to said stand-off.

54. The microelectronic spring structure of claim 48, wherein said first material is softer than said second material.

55. The microelectronic spring structure of claim 48, wherein said first material is less rigid than said second material.

56. The microelectronic spring structure of claim 48, wherein said first material has a lower modulus of elasticity than said second material.

57. The microelectronic spring structure of claim 48, wherein said over coat anchors said core element to said terminal of said substrate means.