Conductive materials with electrical stability and good impact resistance for use in electronics devices
View Patent ↗A composition that comprises a) an admixing of at least one epoxy resin and aliphatic amine wherein the ratio of epoxy function group/amine is greater than 1; b) a conductive filler; c) one or more corrosion inhibitors, oxygen scavengers or both; d) imidazole as a curing agent/catalyst; and e) optionally other additives such as organic solvents, flow additives, adhesion promoters and rheology modifiers. The reaction of epoxy and aliphatic amine with excess epoxy functionality results in a flexible resin with remaining active epoxy groups. The compositions exhibit improved electrical stability and impact resistance over other conductive adhesive compositions that do not comprise the admixture.
1. A composition for use in microelectronic devices comprising
(a) a thermally curable resin system comprising an admixture of at least one epoxy resin and aliphatic amine, wherein said epoxy and the said amine have been pre-blended to form said admixture,
(b) a conductive filler,
(c) a corrosion inhibitor,
(d) a curing agent or catalyst,
(e) optionally, an organic solvent, and
(f) optionally, one or more of the group consisting of adhesion promoters, phenolic resin, flow additives and rheology modifiers, wherein the ratio of epoxide functional group in the epoxy resin to the amine functional group in the aliphatic amine is greater than 1.
2. The composition according to claim 1 in which
(a) the admixture is present in an amount of about 10 to about 90 weight percent;
(b) the conductive filler is present in an amount of about 30 to about 90 weight percent;
(c) the corrosion inhibitor is present in an amount up to about 10 weight percent (but not 0%),
(d) the curing agent or catalyst is present in an amount of a ratio of curing agent to resin of no greater than about 10 weight percent but not 0);
(e) the organic solvent is present in an amount of about 0 to about 10 weight percent, and
(f) the one or more of the group consisting of adhesion promoters, flow additives and rheology modifiers are present in an amount from about 0 to about 5 weight percent. for a total of 100 weight percent.
3. The composition according to claim 2 wherein the resin is present in an amount of from about 10 to about 60 weight percent.
4. The composition according to claim 2 , wherein the curing agent is present in an amount of from about 1 to about 5 weight percent.
5. The composition according to claim 2 , wherein the corrosion inhibitor is present in an amount of from about 0.1 to about 5 weight percent.
6. The composition according to claim 2 , wherein the conductive filler is present in an amount of about 40 to about 90 weight percent.
7. The composition according to claim 1 in which the conductive filler is selected from the group consisting of silver, copper, gold, palladium, platinum, carbon black, bismuth, tin, bismuth-tin alloy, carbon fiber, graphite, aluminum, indium tin oxide, silver coated copper, silver coated aluminum, metallic coated glass spheres, silver coated fiber, silver coated spheres, antimony doped tin oxide or mixtures thereof.
8. The composition according to claim 7 , wherein the conductive filler is silver.
9. The composition according to claim 1 , wherein the admixture comprises in the range of about 20 to about 100 weight percent epoxy resin, in the range of about 0 to about 99 weight percent of the chemically equivalent amount of the epoxide content in epoxy resin of aliphatic amine, and in the range of about 0.1 to about 10 weight percent of a cross-linking agent.
10. The composition according to claim 1 , wherein the resins are selected from the group of monofunctional and multifunctional glycidyl ethers of Bisphenol A and Bisphenol F, aliphatic and aromatic epoxies, saturated and unsaturated epoxies, or cycloaliphatic epoxy resins, or mixtures thereof.
11. The composition according to claim 1 , wherein the corrosion inhibitor is selected from the group consisting of ,10-phenathiodine, phenothiazine, benzotriazole, benzimidazole, mercaptobenzothiazole, dicyandiamide, 3-isoprolyamino-1-butyne, propargyl quinolinium bromide, 3-benzylamino-1-butyne, dipropargi ether, dipropargyl thioether, propargyl caproate, dianimoheptane, phenathroline, amine, diamine, triamine, hexamethyleneimide, decamethyleneimide, hexamethyleneiminebenzoate, hexamethyleneimine-3,5-dinitrobenzoate, hexamethylenetetramin, d-oximino-b-vinyl quinuclidine, aniline, 6-N-ethyl purine, 1-ethylamino-2-octadecylimidazoline, morpholine, ethanolamine, aminophenol, 2-hydroxyquinoline, 6-hydroxyquinoline, 8-hydroxyquinoline, pyridine and its derivatives, quinoline and its derivatives, acridine, imidazole and its derivatives, toluidine, mercaptan, thiophenol and its derivates, sulfide, sulfoxide, thiophosphate, thiourea and piperidine.
12. The composition of claim 11 , wherein the corrosion inhibitor is 8-hydroxyquinoline.
13. The composition of claim 1 , wherein the organic solvent is one or more of the group comprising glycidyl ethers, 1,4-butanediol diglycidyl ether; vinyl ethers, ethylene vinyl ether, vinyl esters, ethylene vinyl ester, acrylates, methyl methacrylate, and butyl carbitol.
14. The composition of claim 1 , wherein the catalyst or curing agent is imidazole.