Space transformers employing wire bonds for interconnections with fine pitch contacts

Abstract

Method and apparatus for electrical testing of a device under test (DUT) that employs a connection board with signal contacts for applying test signals and a space transformer that has low pitch contacts arranged on one or more circumferential shelves that define an enclosure in the space transformer. The apparatus has a substrate with fine pitch contacts positioned such that these are within the enclosure. A set of wire bonds is used for pitch reduction by interconnecting the fine pitch contacts with the low pitch contacts arranged on the shelves. The probes are connected to the fine pitch contacts and are used to apply the test signals to a DUT by contacting its pads. In some embodiments, the fine pitch contacts may be embodied by plugs or by blind metal vias.

I claim: 
     
       1. An apparatus for electrical testing, comprising:
 a) a connection board having signal contacts for applying test signals; 
 b) a space transformer having intermediate contacts connected to said signal contacts, said space transformer further having low pitch contacts connected to said intermediate contacts and arranged on at least one circumferential shelf, said at least one circumferential shelf defining an enclosure; 
 c) a substrate having fine pitch contacts and positioned such that said fine pitch contacts are within said enclosure; 
 d) a set of wire bonds interconnecting said fine pitch contacts with said low pitch contacts; 
 e) probes connected to said fine pitch contacts. 
 
     
     
       2. The apparatus of  claim 1 , wherein said fine pitch contacts comprise contact plugs lodged in corresponding vias in said substrate. 
     
     
       3. The apparatus of  claim 2 , wherein said vias are laser machined and said plugs are made by a micro-electro machining technique. 
     
     
       4. The apparatus of  claim 2 , wherein said substrate comprises a material selected from the group consisting of ceramics, organics and Al 2 O 3 . 
     
     
       5. The apparatus of  claim 1 , wherein said fine pitch contacts comprise blind metal vias. 
     
     
       6. The apparatus of  claim 1 , wherein said space transformer comprises a lower circumferential shelf bearing a lower set of said low pitch contacts and at least one upper circumferential shelf bearing an upper set of said low pitch contacts, said at least one upper circumferential shelf being inset from said lower circumferential shelf. 
     
     
       7. The apparatus of  claim 6 , wherein said lower set of said low pitch contacts comprises a ground contact. 
     
     
       8. The apparatus of  claim 6 , wherein said set of wire bonds comprises a short set of wire bonds interconnecting a set of said fine pitch contacts proximal said lower shelf with said lower set of said low pitch contacts. 
     
     
       9. The apparatus of  claim 6 , wherein said set of wire bonds comprises a long set of wire bonds interconnecting a set of said fine pitch contacts remote said lower shelf with said upper set of said low pitch contacts. 
     
     
       10. The apparatus of  claim 9 , wherein said long set of wire bonds comprises wire bonds of at most 5 millimeters in length. 
     
     
       11. The apparatus of  claim 1 , wherein said enclosure is filled with a dielectric material. 
     
     
       12. The apparatus of  claim 1 , wherein a pitch reduction from said intermediate contacts to said fine pitch contacts is about ten to one. 
     
     
       13. The apparatus of  claim 1 , employed in a probe card for testing a device under test by delivering said test signals to pads of said device under test by contacting said pads with said probes. 
     
     
       14. The apparatus of  claim 13 , wherein said device under test comprises an integrated circuit. 
     
     
       15. A method for electrically testing a device under test, said method comprising:
 a) providing a connection board having signal contacts; 
 b) providing a space transformer having intermediate contacts and low pitch contacts connected to said intermediate contacts, said low pitch contacts being arranged on at least one circumferential shelf, said at least one circumferential shelf defining an enclosure; 
 c) connecting said signal contacts to said intermediate contacts; 
 d) providing a substrate having fine pitch contacts and positioned such that said fine pitch contacts are within said enclosure; 
 e) interconnecting said fine pitch contacts with said low pitch contacts by a set of wire bonds; 
 f) connecting probes to said fine pitch contacts; 
 g) applying test signals to said signal contacts; and 
 h) contacting said probes with pads of said device under test for electrically testing said device under test. 
 
     
     
       16. The method of  claim 15 , wherein said fine pitch contacts are made by producing vias in said substrate and lodging contact plugs in said vias. 
     
     
       17. The method of  claim 16 , wherein said vias are laser machined and said plugs are made by a micro-electro machining technique. 
     
     
       18. The method of  claim 15 , wherein said space transformer comprises a lower circumferential shelf bearing a lower set of said low pitch contacts and at least one upper circumferential shelf bearing an upper set of said low pitch contacts, said at least one upper circumferential shelf being inset from said lower circumferential shelf, and wherein said method further comprises interconnecting a set of said fine pitch contacts proximal said lower shelf with said lower set of said low pitch contacts by a short set of wire bonds, and interconnecting a set of said fine pitch contacts remote said lower shelf with said upper set of said low pitch contacts by a long set of wire bonds. 
     
     
       19. The method of  claim 15 , further comprising filling said enclosure with a dielectric material. 
     
     
       20. An apparatus for electrical testing comprising:
 a layered space transformer;   a first layer of said layered space transformer comprising a substrate;   said substrate comprising a plurality of fine pitch contacts;   a second layer of said layered space transformer comprising a structure disposed around an outside circumference of said substrate;   said structure comprising at least one shelf, said shelf comprising a plurality of low pitch contacts;   said structure further comprising a ledge disposed above said shelf;   said ledge comprising a plurality of intermediate contacts;   said intermediate contacts electrically connected to corresponding said low pitch contacts via electrical connections embedded within said structure; and   a plurality of bonds interconnecting said fine pitch contacts with corresponding said low pitch contacts.   
     
     
       21. The apparatus of claim 20 further comprising an enclosure defined by said shelf. 
     
     
       22. The apparatus of claim 21 wherein said fine pitch contact is within said enclosure. 
     
     
       23. The apparatus of claim 21 further comprising a dielectric material filling the enclosure. 
     
     
       24. The apparatus of claim 20 comprising a pitch reduction from said intermediate contact to said fine pitch contact of about ten to one. 
     
     
       25. The apparatus of claim 20 further comprising at least one signal contact and wherein said signal contact is connected to said intermediate contact. 
     
     
       26. The apparatus of claim 25 wherein said connection between said signal contact and said intermediate contact comprises a solder reflow junction. 
     
     
       27. The apparatus of claim 25 further comprising a connection board connected to said signal contact. 
     
     
       28. The apparatus of claim 27 wherein said connection board comprises a printed circuit board. 
     
     
       29. The apparatus of claim 27 wherein said connection board comprises a primary contact connected to said signal contact. 
     
     
       30. The apparatus of claim 27 further comprising a probe connected to said fine pitch contact. 
     
     
       31. The apparatus of claim 20 wherein said shelf comprises a circumferential shelf. 
     
     
       32. The apparatus of claim 20 comprising an upper shelf and a lower shelf. 
     
     
       33. The apparatus of claim 32 comprising a lower set of low pitch contacts located on said lower shelf and an upper set of low pitch contacts located on said upper shelf. 
     
     
       34. The apparatus of claim 33 comprising a short set of wire bonds interconnecting a set of said fine pitch contacts proximal to said lower shelf with said lower set of low pitch contacts. 
     
     
       35. The apparatus of claim 33 wherein said lower set of low pitch contacts comprises a ground contact. 
     
     
       36. The apparatus of claim 33 comprising a long set of wire bonds interconnecting a set of said fine pitch contacts remote to said lower shelf with said upper set of said low pitch contacts. 
     
     
       37. The apparatus of claim 32 wherein said upper shelf is recessed from said lower shelf. 
     
     
       38. The apparatus of claim 32 wherein said shelves are made layer-by-layer. 
     
     
       39. The apparatus of claim 20 wherein said substrate is positioned below said shelf. 
     
     
       40. The apparatus of claim 39 wherein said substrate is permanently attached to said shelf. 
     
     
       41. The apparatus of claim 39 wherein said substrate is removably attached to said shelf. 
     
     
       42. The apparatus of claim 20 wherein said substrate comprises a circuit board. 
     
     
       43. The apparatus of claim 20 wherein said fine pitch contact comprises a via. 
     
     
       44. The apparatus of claim 43 wherein said via comprises a blind via. 
     
     
       45. The apparatus of claim 44 wherein said blind via comprises a blind metal via. 
     
     
       46. The apparatus of claim 20 wherein said wire bond is equal to or less than 5 millimeters. 
     
     
       47. The apparatus of claim 20 wherein said at least one fine pitch contact comprising a contact plug. 
     
     
       48. The apparatus of claim 47 further comprising a via, wherein said contact plug is secured in said substrate by said via. 
     
     
       49. The apparatus of claim 47 wherein said plug is micro-electro machined. 
     
     
       50. The apparatus of claim 20 wherein said substrate comprises aluminum oxide. 
     
     
       51. The apparatus of claim 20 wherein said substrate comprises ceramic. 
     
     
       52. The apparatus of claim 20 wherein said substrate comprises organics. 
     
     
       53. The apparatus of claim 20 wherein said wire bond comprises a short wire bond for bonding. 
     
     
       54. The apparatus of claim 20 wherein said apparatus is employed in a probe card. 
     
     
       55. The apparatus of claim 20 comprising three shelves. 
     
     
       56. The apparatus of claim 20 comprising a plurality of low pitch contacts staggered with respect to a plurality of fine pitch contacts. 
     
     
       57. The apparatus of claim 20 wherein said bond comprises a wire bond. 
     
     
       58. A method for testing a device under test comprising:
 providing a layered space transformer comprising a first layer of the layered space transformer having a substrate, a second layer of the layered space transformer having a structure disposed around an outside circumference of the substrate, the structure comprising at least one shelf, the shelf comprising a plurality of low pitch contacts, the structure further comprising a ledge disposed above the shelf, the ledge comprising a plurality of intermediate contacts;   disposing a plurality of fine pitch contacts on the substrate;   interconnecting the low pitch contacts to corresponding intermediate contacts via electrical connections embedded within the structure;   interconnecting the fine pitch contacts with corresponding low pitch contacts by at least one wire bond; and   applying a high frequency test signal to a device under test.   
     
     
       59. The method of claim 58 further comprising connecting the intermediate contact to a signal contact located on a connection board. 
     
     
       60. The method of claim 59 further comprising applying a test signal to the signal contact. 
     
     
       61. The method of claim 58 further comprising connecting at least one probe to the fine pitch contact. 
     
     
       62. The method of claim 61 further comprising contacting the probe with a pad of the device under test for electrically testing the device under test. 
     
     
       63. The method of claim 58 wherein said fine pitch contact comprises producing a via in said substrate and lodging a contact plug in the via. 
     
     
       64. The method of claim 63 further comprising laser-machining the via. 
     
     
       65. The method of claim 63 further comprising micro-electro machining the plug. 
     
     
       66. The method of claim 58 wherein the space transformer comprises a lower shelf bearing a lower set of low pitch contacts and at least one upper shelf bearing an upper set of the low pitch contacts. 
     
     
       67. The method of claim 66 further comprising interconnecting a set of fine pitch contacts proximal to the lower shelf with the lower set of low pitch contacts by a short set of wire bonds. 
     
     
       68. The method of claim 66 further comprising interconnecting a set of fine pitch contacts remote to the lower shelf with the upper set of low pitch contacts by a long set of wire bonds.