Durable electronic assembly with conductive adhesive

• US 20040201112A1
• Filed: 04/10/2003
• Published: 10/14/2004
• Est. Priority Date: 04/10/2003
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Connell, Glen, Jannic, Patrice, Divigalpitiya, Ranjith, Kanno, David A., Arnold, Christophe, Sabatier, Richard
• Granted Patent: US 7,034,403 B2
• Time in Patent Office: Days
• US Class Current: 257/783
• CPC Class Codes: C08L 67/00 Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain of polyester-amides C08L77/12; of polyester-imides C08L79/08; Compositions of derivatives of such polymers
• CPC Class Codes: C08L 77/00 Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain of polyhydrazides C08L79/06; of polyamideimides or polyamide acids C08L79/08; Compositions of derivatives of such polymers
• CPC Class Codes: C09J 9/02 Electrically-conducting adhesives
• 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 2924/01009 Fluorine [F]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01023 Vanadium [V]
• CPC Class Codes: H01L 2924/01025 Manganese [Mn]
• CPC Class Codes: H01L 2924/01027 Cobalt [Co]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01039 Yttrium [Y]
• CPC Class Codes: H01L 2924/01047 Silver [Ag]
• CPC Class Codes: H01L 2924/01057 : Lanthanum [La]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/0781 : being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/07811 : Extrinsic, i.e. with electrical conductive fillers
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01R 4/04 : using electrically conductive adhesives
• CPC Class Codes: H05K 2201/0245 : Flakes, flat particles or lamellar particles
• CPC Class Codes: H05K 2201/0248 : Needles or elongated particles; Elongated cluster of chemically bonded particles microfibers H05K2201/0251; stacked conductors H05K2201/0379
• CPC Class Codes: H05K 2201/0281 : Conductive fibers
• CPC Class Codes: H05K 3/323 : by applying an anisotropic conductive adhesive layer over an array of pads

Abstract

An electronic assembly comprising a first electronic element, a second electronic element, and a durably flexible bond therebetween. The bond comprises an anisotropic conductive adhesive that includes elongated electrically conductive particles. The bond provides at least one electrical pathway between the first electronic element and the second electronic element through an elongated contact region. This bond is functionally maintained for at least about 200 flexes.

Claims

1. An electronic assembly comprising:

a first electronic element;

a second electronic element; and

a durably flexible bond therebetween, said bond comprising

an anisotropic conductive adhesive which comprises elongated electrically conductive particles, and

at least one electrical pathway between the first electronic element and the second electronic element provided by an elongated contact region, said bond being functionally maintained for at least about 200 Flexural Cycles.

2. The assembly of claim 1 wherein the elongated electrically conductive particles are selected from non-spherical particles, elliptical particles, fibers, and flakes and combinations thereof.

3. The assembly of claim 1 wherein the electrically conductive particles are selected from fibers having an electrically conductive coating.

4. The assembly of claim 1 wherein said bond is functionally maintained for a number of Flexural Cycles selected from at least about 500, at least about 1000, at least about 2000, at least about 4000, and at least about 5000.

5. The assembly of claim 1 wherein the adhesive is curable.

6. The assembly of claim 1 wherein the adhesive is a structural adhesive.

7. The assembly of claim 1 wherein the Tg of the adhesive does not change by more than 25°

C. after curing.

8. The assembly of claim 1 wherein the adhesive has a storage shear modulus selected from below about 100 MPa, below about 75 MPa, and below about 50 MPa.

9. The assembly of claim 1 wherein the adhesive is curable in less than about 10 seconds at a temperature below about 210°

C.

10. The assembly of claim 1 wherein the adhesive is thermoplastic.

11. The assembly of claim 10 wherein the adhesive is selected from polyesters, co-polyamides, polyether-co-polyamides, and combinations thereof.

12. The assembly of claim 1 wherein said bond is resistant to humidity.

13. The assembly of claim 1 wherein said bond is resistant to thermal shock and/or temperatures above about 200°

C. for at least about 100 hours.

14. The assembly of claim 1 wherein the adhesive comprises from about 30 to about 70 parts by weight of an elastomer and correspondingly from about 70 to 30 parts by weight of a curable polymer.

15. The assembly of claim 14 wherein the elastomer is selected from natural and synthetic rubbers, fluoroelastomers, and silicone elastomers, and combinations thereof.

16. The assembly of claim 14 wherein the elastomer is selected from butadiene-acrylonitrile copolymer, and optionally wherein the curable polymer is selected from an epoxy resin, a polyurethane resin, a phenolic resin, a phenolic novolac resin, and combinations thereof, wherein when a phenolic resin is involved, said resin optionally may include hexamethylenetetramine (HMTA).

17. The assembly of claim 16 wherein the phenolic resin has a melting point between about 90 and about 110°

C.

18. The assembly of claim 16 wherein the phenolic resin has an HMTA content in the range of about 5 to 15%, optionally in the range from about 6 to 10%.

19. The assembly of claim 16 wherein the phenolic resin has a free phenol level selected from below about 2%, below about 1%, and below about 0.2%.

20. The assembly of claim 1 wherein the adhesive comprises from about 30 to about 60 parts by weight of an elastomer and at least about 40 parts by weight of a curable polymer.

21. The assembly of claim 1 wherein the adhesive comprises at least about 50 parts by weight of an elastomer and at least about 30 parts by weight of a curable polymer.

22. The assembly of claim 1 wherein the adhesive comprises from about 45 to about 60 parts by weight of an elastomer and at least about 40 parts by weight of a curable polymer.

23. The assembly of claim 1 wherein the adhesive comprises an elastomer and a thermoplastic polymer.

24. The assembly of claim 1 wherein one electronic element is an integrated circuit chip contact.

25. The assembly of claim 1 wherein one electronic element is a flexible electronic circuit.

26. The assembly of claim 25 wherein one electronic element is rigid.

27. The assembly of claim 1 wherein the electronic assembly is a smart card or is included in a smart card.

28. The assembly of claim 1 wherein one electronic element is a radio frequency device or is included in a radio frequency device, which optionally is an RFID tag.

29. The assembly of claim 1 wherein one electronic element is included in an portable electronic device, optionally selected from a mobile phone, a personal digital assistant, a camera, a computer, a timer, and combinations thereof.

30. The assembly of claim 1 wherein the electronic assembly is tamper resistant.

31. The assembly of claim 1 further comprising non-elongated particles, wherein the non-elongated particles optionally comprise electrically conductive particles.

32. The assembly of claim 31 wherein the non-elongated particles have a major dimension average particle size less than a minor dimension average particle size of the elongated electrically conductive particles.

33. The assembly of claim 31 wherein the elongated particles comprise a majority of the total of elongated particles and non-elongated particles on a weight basis.

34. The assembly of claim 31 wherein the assembly has a Humidity test pass rate of at least about 10%, a Thermal Shock test pass rate of at least about 15%, and a 5000 Flexural Cycle test pass rate of at least about 60%.

35. A method of manufacturing an electronic device comprising providing the assembly of claim 1 wherein the adhesive is curable;

and curing said adhesive or wherein the adhesive is non-curing; and

bonding said adhesive to said electronic elements.