Epoxy, epoxy system, and method of forming a conductive adhesive connection

• US 6,902,689 B2
• Filed: 04/26/2001
• Issued: 06/07/2005
• Est. Priority Date: 02/27/1998
• Status: Expired due to Fees

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Kumar, Krishna, Lake, Rickie C.
• Primary Examiner(s): Gupta, Yogendra N.
• Assistant Examiner(s): Hamlin, Derrick G.
• Application Number:
  US09/844,824
• Publication Number:
  US 20010025947A1
• Time in Patent Office: 1,503 Days
• Field of Search: 252/500, 252/509, 252/510, 252/519.2, 252/519.33, 523/427, 523/437, 523/457
• US Class Current: 252/519.33
• CPC Class Codes: C08L 2666/28 Non-macromolecular organic substances
• CPC Class Codes: C08L 2666/54 Inorganic substances
• CPC Class Codes: C08L 63/00 Compositions of epoxy resins; Compositions of derivatives of epoxy resins
• CPC Class Codes: C09J 163/00 Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins
• CPC Class Codes: C09J 2463/00 Presence of epoxy resin
• CPC Class Codes: C09J 5/06 involving heating of the applied adhesive
• CPC Class Codes: H01B 1/20 Conductive material dispersed in non-conductive organic material organic macromolecular compounds or compositions C08

Abstract

The invention encompasses epoxies, epoxy systems, and methods of forming conductive adhesive connections between electrical nodes. An epoxy contains: a) a liquid mixture of a hardener and a base epoxy; and b) a concentration of an ionic salt within the liquid mixture, the concentration of the ionic salt being high enough that a 15 mil length sample of the liquid mixture having cross-sectional dimensions of 50 mil by 2 mil would have a resistance of less than about 100 ohms along its length.

Claims

1. An epoxy comprising:

a liquid mixture of a hardener and a base epoxy resin; and

a concentration of a lithium salt within the liquid mixture, the concentration of lithium salt being high enough that a 15 mil length sample of the liquid mixture having cross-sectional dimensions of 50 mil by 2 mil exhibits a resistance of less than about 100 ohms along its length while exhibiting a viscosity of less than 100,000 cps.

2. The epoxy of claim 1 wherein the lithium salt is LiN(CF₃SO₂)₂.

3. The epoxy of claim 1 wherein the lithium salt is LiAsF₆.

4. The epoxy of claim 1 further comprising silver particles.

5. An epoxy comprising:

a liquid mixture of a hardener and a base epoxy resin;

silver particles; and

LiN(CF₃SO₂)₂ as an ionic salt, a concentration of the ionic salt within the liquid mixture being high enough that a 15 mil length sample of the liquid mixture having cross-sectional dimensions of 50 mil by 2 mil exhibits a resistance of less than about 100 ohms along its length while exhibiting a viscosity of less than 100,000 cps.

6. A method of forming a conductive adhesive connection comprising:

forming a liquid epoxy mixture of a first liquid comprising a hardener and a second liquid comprising a base epoxy resin, the liquid epoxy mixture having a concentration of a lithium salt high enough that a 15 mil length sample of the liquid epoxy mixture having cross-sectional dimensions of 50 mil by 2 mil exhibits a resistance of less than about 100 ohms along its length while exhibiting a viscosity of less than 100,000 cps;

while exhibiting the resistance of less than about 100 ohms and the viscosity of less than 100,000 cps, providing the liquid epoxy mixture between first and second electrical nodes to form a conductive connection therebetween; and

curing the liquid epoxy mixture.

7. The method of claim 6 wherein the lithium salt is LiN(CF₃SO₂)₂.

8. The method of claim 6 wherein the lithium salt is LiAsF₆.

9. The method of claim 6 wherein the liquid epoxy mixture further comprises silver particles.

10. The method of claim 6 wherein the first and second electrical nodes are comprised respectively by an integrated circuit chip and a battery.

11. A method of forming a conductive adhesive connection comprising:

forming a liquid epoxy mixture of a first liquid comprising a hardener, a second liquid comprising a base epoxy resin, and silver particles, the liquid epoxy mixture having a concentration of LiN(CF₃SO₂)₂ as an ionic salt high enough that a 15 mil length sample of the liquid epoxy mixture having cross-sectional dimensions of 50 mil by 2 mil exhibits a resistance of less than about 100 ohms along its length while exhibiting a viscosity of less than 100,000 cps;

while exhibiting the resistance of less than about 100 ohms and the viscosity of less than 100,000 cps, providing the liquid epoxy mixture between first and second electrical nodes to form a conductive connection therebetween; and

curing the liquid epoxy mixture.

12. A method of forming a conductive adhesive connection comprising:

mixing a first liquid with a second liquid to form a liquid conductive epoxy mixture, the first liquid comprising a hardener and the second liquid comprising a base epoxy resin;

the liquid conductive epoxy mixture comprising a lithium salt and having sufficient conductivity that a 15 mil length sample of the liquid conductive epoxy having cross-sectional dimensions of 50 mil by 2 mil has a resistance of less than about 100 ohms along its length while having a viscosity of less than about 100,000 cps;

providing the liquid conductive epoxy mixture between first and second electrical nodes to form a conductive connection between an integrated circuit chip and a battery; and

curing the liquid conductive epoxy mixture.

13. The method of claim 12 wherein the conductive epoxy mixture further comprises silver particles.

14. The method of claim 12 wherein the lithium salt comprises a lithium imide salt.

15. The method of claim 12 wherein the lithium salt comprises one or more salts selected from the group consisting of LiAsF₆ and LiN(CF₃SO₂)₂.

16. The method of claim 12 wherein the lithium salt is LiN(CF₃SO₂)₂.

17. The method of claim 12 wherein the lithium salt is LiAsF₆.

18. The method of claim 12 wherein the 15 mil length sample exhibits the resistance within at most about 30 minutes after the first and second liquids are mixed and while having a viscosity of less than about 100,000 cps.

19. The method of claim 18 wherein the 15 mil length sample exhibits the resistance within at most 10 minutes.

20. The method of claim 12 wherein the liquid conductive epoxy mixture viscosity remains less than about 100,000 cps for longer than 10 minutes after the first and second liquids are mixed.

21. The method of claim 12 wherein the liquid conductive epoxy mixture remains a liquid for longer than 10 minutes after the first and second liquids are mixed.

22. The method of claim 12 wherein the liquid epoxy mixture is formed by combining the first and second liquids with a third liquid, the third liquid comprising the lithium salt.

23. The method of claim 22 wherein the lithium salt is completely dissolved in the third liquid prior to combining the third liquid with the first and second liquids.

24. The method of claim 12 wherein the liquid epoxy mixture is formed by combining the first and second liquids with a third liquid, the third liquid comprising a thinner selected from the group consisting of aliphatic glycidyl ethers and aromatic glycidyl ethers, the ionic salt being a lithium salt present in the third liquid to a concentration of from about 0.5 molar to about 1.2 molar prior to combining the third liquid with the first and second liquids.