Conductive adhesive having a palladium matrix interface between two metal surfaces

• US 6,425,772 B1
• Filed: 07/23/2001
• Issued: 07/30/2002
• Est. Priority Date: 12/28/1999
• Status: Expired due to Term

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Bundga, Edward G., Bernier, William E.
• Primary Examiner(s): Sircus, Brian
• Assistant Examiner(s): Zarroli, Michael C.
• Application Number:
  US09/911,270
• Publication Number:
  US 20020022384A1
• Time in Patent Office: 372 Days
• Field of Search: 429/91, 174/117.A, 174/257, 428/626, 252/514
• US Class Current: 439/91
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/29499 Shape or distribution of the fillers
• CPC Class Codes: H01L 2224/8319 Arrangement of the layer connectors prior to mounting
• CPC Class Codes: H01L 2224/838 Bonding techniques
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/83 using a layer connector
• 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 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01046 Palladium [Pd]
• CPC Class Codes: H01L 2924/01047 Silver [Ag]
• CPC Class Codes: H01L 2924/0105 Tin [Sn]
• CPC Class Codes: H01L 2924/0665 Epoxy resin
• CPC Class Codes: H01L 2924/0781 being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01R 12/52 connecting to other rigid printed circuits or like structures
• CPC Class Codes: H01R 4/04 using electrically conductive adhesives
• CPC Class Codes: H05K 2201/0129 Thermoplastic polymer, e.g. auto-adhesive layer; Shaping of thermoplastic polymer
• CPC Class Codes: H05K 2201/0218 : Composite particles, i.e. first metal coated with second metal
• CPC Class Codes: H05K 2201/0245 : Flakes, flat particles or lamellar particles
• CPC Class Codes: H05K 2201/10977 : Encapsulated connections applying non-metallic protective coatings for encapsulating mounted components H05K3/284
• 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 3/321 : by conductive adhesives
• CPC Class Codes: Y10T 428/12569 : Synthetic resin

Abstract

Forming an isotropic electrical connection and a mechanical bond between two articles having metal surfaces. The resulting bond is preferably between metal contact pads on a dielectric substrate and on an electronic device. The connection is provided by utilizing a conductive adhesive wherein the conduction is provided by metal particles which have exposed palladium thereon. The particles may be the metal palladium itself or it may be some other metal, such as silver, having palladium coated thereon. The particles typically are flakes with the palladium having an incipient dendritic form on the surface, i.e.; the palladium has a multi-pointed surface configuration that can grow into fully formed needle-like dendritic structures. The polymer preferably is conventional polyimide/siloxane which is a thermoplastic, i.e. upon heating softens and upon cooling sets, and upon reheating will soften and reflow.

Claims

1. A method of providing isotropic electrically conductive adhesive bonding between two metal surfaces comprising the steps of:

a. providing an adhesive with particles which have exposed palladium thereon;

b. interposing said adhesive with said particles between two metal surfaces; and

c. in situ growing said exposed palladium to form a continuous metal matrix of said particles and said metal surfaces surrounded by said adhesive with said palladium forming a dendrite structure which penetrates the metal surfaces and adjacent particles.

2. The invention as defined in claim 1 wherein said palladium is grown under application of heat or pressure or both.

3. The invention as defined in claim 1 wherein said adhesive is a thermoplastic.

4. The invention as defined in claim 1 wherein said particles having exposed palladium thereon includes palladium coated onto a different metal particle.

5. The invention as defined in claim 4 wherein said different metal is silver.

6. The invention as defined in claim 1 wherein said particles having exposed palladium thereon include particles of palladium metal.

7. The invention as defined in claim 3 wherein the adhesive is a polyimide/siloxane.

8. The invention as defined in claim 2 wherein the heat is from about 200°

C. to about 240°

C.

9. The invention as defined in claim 8 wherein the heat is about 220°

C.

10. The invention as defined in claim 2 wherein the pressure is from about 17 to about 51 Kg/in. sq.

11. The invention as defined in claim 10 wherein the pressure is from about 28 to about 40 Kg/in. sq.

12. The invention as defined in claim 1 wherein said bond is encapsulated in a dielectric material.

13. The invention as defined in claim 2 wherein the separation of said substrates after bonding is at least about 2.0 mils.

14. The invention as defined in claim 12 wherein the separation of said substrates after bonding is at least about 2.5 mils.