Anisotropically electrically conductive article

• US 5,262,718 A
• Filed: 07/10/1990
• Issued: 11/16/1993
• Est. Priority Date: 08/05/1985
• Status: Expired due to Term

• Current Assignee: Tyco Electronics UK Limited (TE Connectivity Ltd. (United Kingdom))
• Original Assignee: Raychem Limited (TE Connectivity Limited)
• Inventors: Svendsen, Leo G., Bates, Nigel R.
• Primary Examiner(s): Baker, Stephen M.
• Application Number:
  US07/551,677
• Time in Patent Office: 1,225 Days
• Field of Search: 324/158 P, 324/158 F, 29/874, 205/125, 439/54
• US Class Current: 324/756.07
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01L 23/49827 Via connections through the substrates, e.g. pins going through the substrate, coaxial cables H01L23/49822, H01L23/49833, H01L23/4985, H01L23/49861 take precedence
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• 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 13/2414 conductive elastomers
• CPC Class Codes: Y10T 29/49204 Contact or terminal manufacturing

Abstract

Low tortuosity porous polymer sheets (25 to 2000 pores per square millimeter) with metal plated in the pores so as to project beyond sheet surfaces provide uniaxial electrical interconnects. A first "flash" layer of metal is electrolessly plated in the pores and the "flash" coating of metal is then removed from the sheet surface to isolate the pores electrically from one another. Further plating is then applied only to the already plated pore surfaces to fill the pores and/or project beyond the sheet surface. Solder may fill the plated pores. Polymer layers may be removed from the sheets to expose the metal in the pores. The articles are useful in making electrical connections to the contact pads of microcircuits during testing and assembly into electronic devices.

Claims

1. A uniaxially electrically conductive article comprising

porous electrically insulating sheet material of 8 to 800 micrometers thickness, at least a selected portion of which has

at least 25 substantially straight-through non-interconnected pores of 1 to 200 micrometers diameter, formed by ultraviolet laser ablation, per square millimeter of its surface,

at least a significant proportion of which pores individually contain a tubular formation of metal which provides an electrically conductive path between, and projects beyond at least one of, the main surface of the sheet material,

the metal being substantially only within the pores and each such conductive path being electrically separate from substantially all the other such conductive paths.

2. An article according to claim 1, wherein the tubular formations of metal project beyond both of the main surfaces of the sheet material.

3. An article according to claim 1, wherein the sheet material has 50 to 1000 pores per square millimeter in the selected portion of its surface.

4. An article according to claim 1, wherein electrically insulating material has been removed from one or both main surfaces of the sheet material to expose portions of the tubular formations of metal originally within the pores.

5. An article according to claim 1, wherein the electrically insulating sheet material includes a closed cell porous structure in addition to the said pores containing the tubular formations of metal.

6. An article according to claim 1, in which the metal in at least some of the said pores is provided in two portions, a first portion being provided in contact with the interior pore surface, and a second portion being provided on at least one of the end faces of the first portion, at least the second portion projecting beyond at least one of the surfaces of the sheet material.

7. An article according to claim 1, which the tubular formations of metal are provided in their respective pores by plating.

8. An electrical device which comprises:

(a) two electrically interconnected components, each having at least one connection site through which it is connected to the other component; and

(b) an article according to claim 1, which is positioned so that each of the connection sites on the respective components is in contact with respective opposite ends of at least one of the tubular formations of metal.

9. An electrical device according to claim 8, in which each of the connections sites is in contact with respective opposite ends of a plurality of the tubular formations of metal.

10. An article according to claim 1, in which the pores have a diameter of from 5 to 200 micrometers.

11. A method of making a uniaxially electrically conductive article, comprising:

(a) applying a metal substantially only to the interior surface of pores formed by ultraviolet laser ablation in a selected portion of an electrically insulating sheet material of 8 to 800 micrometers thickness, the said portion having at least 25 substantially non-interconnected pores having a mean diameter of 1 to 200 micrometers per square millimeter of its surface such that the metal in each pore provides a separate electrically conductive path between the main surfaces of the sheet material; and

(b) removing insulating material from at least one surface region of the sheet material so as to expose portions of the metal that were previously within the pores.

12. A method according to claim 11, which includes the step of forming the pores in the sheet material by the said laser ablation.

13. A method according to claim 11, in which the pores have a diameter of from 5 to 200 micrometers.

14. A method of making a uniaxially electrically conductive article, which comprises:

(a) providing a sheet of electrically insulating material of 8 to 800 micrometers thickness;

(b) forming in at least a portion of the sheet at least about 25 substantially straight-through non-interconnected pores of 1 to 200 micrometers diameter per square millimeter of its surface by ultraviolet laser ablation, the pores extending from one surface to the other surface of the sheet; and

(c) applying metal substantially only to at least part of the interior surface of at least some of the pores, the metal in each such pore being electrically separate from that in every other pore.

15. A method according to claim 14, in which the metal is provided on the interior surface of the pores by plating.

16. A method according to claim 14, which includes the step of removing material from at least one surface of the sheet material so as to expose portions of the metal that were previously within the pores.

17. A method according to claim 16, in which the portion of the sheet in which the pores are formed is defined by a screen, which defines a pattern of pores to be formed in the sheet.

18. A method according to claim 14, in which the pores are tapered inwardly from one surface of the sheet towards the other surface of the sheet.

19. A method as claimed in claim 14, which includes the step of removing material from both surfaces of the sheet material so as to expose portions of the metal that were previously within the pores.

20. A method as claimed in claim 14, which includes the step of providing a material within the pores which have a metal layer on their internal surface.

21. A method as claimed in claim 20, in which the said material is a solder.

22. A method as claimed in claim 20, in which the said material is applied to the metal of the layer on the internal surface of the pores by plating.

23. A method as claimed in claim 20, in which the said material substantially fills the pores in which it is provided.

24. A uniaxially electrically conductive article comprising porous electrically insulating sheet material, at least a portion of which has at least 25 substantially straight-through non-interconnected pores per square millimeter of its surface, at least some of the pores containing:

(a) a tubular first formation of metal which provides an electrically conductive path between, and projects beyond at least one of, the main surfaces of the sheet material, the metal being substantially only within the pores and, each such conductive path being electrically separate from substantially all the other such conductive paths, and

(b) a second portion of a material that is also substantially only within the pores and is in contact with the interior surface of the tube provided by the first portion.

25. An article according to claim 24 wherein the second portion of material is also tubular.

26. An article according to claim 24 wherein the material of the said second portion is different from the electrically conductive material of the said first portion.

27. An article as claimed in claim 24, in which the second material substantially fills the tube provided by the first formation.

28. An article as claimed in claim 24, in which the second material is applied to the tubular first formation by plating.

29. An article as claimed in claim 24, in which each of at least a significant proportion of the pores contains a tubular first formation of metal.

30. An article as claimed in claim 24, in which the pores have been formed by ultraviolet laser ablation.

31. An article as claimed in claim 24, in which the second material is a metal having a melting point lower than that of the metal of the first formation.

32. An article as claimed in claim 31, in which the second material is a solder.