Method of forming freestanding metal dendrites

• US 6,618,941 B2
• Filed: 08/13/2001
• Issued: 09/16/2003
• Est. Priority Date: 08/10/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Campbell, Jeffrey S., Wike, William T.
• Primary Examiner(s): CHANG, RICK KILTAE
• Application Number:
  US09/928,633
• Publication Number:
  US 20020027016A1
• Time in Patent Office: 764 Days
• Field of Search: 298/30, 298/32, 298/37, 298/46, 298/52, 174/149.R, 200/511, 264/174.11, 428/625, 439/66, 117/903
• US Class Current: 29/846
• CPC Class Codes: F28F 2215/10 Secondary fins, e.g. projections or recesses on main fins
• CPC Class Codes: F28F 2245/06 having particular radiating, reflecting or absorbing features, e.g. for improving heat transfer by radiation
• CPC Class Codes: H01L 2224/29499 Shape or distribution of the fillers
• CPC Class Codes: H01L 23/3733 having a heterogeneous or anisotropic structure, e.g. powder or fibres in a matrix, wire mesh, porous structures H01L23/3732, H01L23/3737 take precedence
• 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 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 13/2414 conductive elastomers
• CPC Class Codes: H05K 2201/0133 Elastomeric or compliant polymer elastomeric conductor H05K2201/0314
• CPC Class Codes: H05K 2201/10977 Encapsulated connections applying non-metallic protective coatings for encapsulating mounted components H05K3/284
• CPC Class Codes: H05K 2201/209 Auto-mechanical connection between a component and a PCB or between two PCBs
• CPC Class Codes: H05K 2203/0307 Providing micro- or nanometer scale roughness on a metal surface, e.g. by plating of nodules or dendrites
• CPC Class Codes: H05K 2203/0723 Electroplating, e.g. finish plating
• CPC Class Codes: H05K 3/325 by abutting or pinching, i.e. without alloying process; mechanical auxiliary parts therefor adaptations of leads inserted in holes for press-fit connections H05K3/308
• CPC Class Codes: H05K 3/4007 Surface contacts, e.g. bumps H05K3/4092 takes precedence; deposition of finish layers on pads H05K3/24; forming solder bumps H05K3/3457
• CPC Class Codes: Y10S 117/903 Dendrite or web or cage technique
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49156 with selective destruction of conductive paths

Abstract

A technique for making acicular, branched, conductive dendrites, and a technique for using the dendrites to form a conductive compressible pad-on-pad connector are provided. To form the dendrites, a substrate is provided on which dendrites are grown, preferably on a metal film. The dendrites are then removed from the substrate, preferably by etching metal from the substrate. The so formed dendrites are incorporated into a compressible dielectric material, which then forms a compressible pad-on-pad connector between two conducting elements, such as connector pads on electrical devices, e.g. an I/C chip mounted on a substrate, such as a chip carrier.

Claims

1. A method of forming free standing metal dendrites comprising the steps of:

providing a substrate on which said dendrites can be grown;

growing dendrites on said substrate;

removing said grown dendrites from said substrate; and

dispersing said dendrites in a compressible dielectric material.

2. The method as defined in claim 1 wherein said substrate includes a metal.

3. The method as defined in claim 2 wherein said step of removing the grown dendrites from the substrate includes etching the metal.

4. The method as defined in claim 3 wherein the metal is copper.

5. The method as defined in claim 4 wherein a second layer of metal overlies said copper.

6. The method as defined in claim 5 wherein said second metal is palladium.

7. The method as defined in claim 5 wherein said dendrites are grown on said second metal.

8. The method as defined in claim 1 wherein said dendrites are branched acicular structures.

9. The method as defined in claim 1 wherein the dendrites are formed at least in pert from palladium.

10. The method as defined in claim 1 further comprising providing a plurality of spaced sites on said substrate where said dendrites are grown.

11. The method as defined in claim 10 wherein said plurality of sites are formed using a photoresist coating and forming openings to define said sites in said photoresist by photolithography.

12. The method as defined in claim 1 wherein said compressible dielectric material is selected from the group of epoxies, acrylics, and polyimides.

13. The method as defined in claim 1 wherein said compressible material is a flouro-silicon.