Electrically conductive adhesives comprising at least one metal precursor
The present invention relates to thermally curable adhesives that are suitable for use as electrically conductive materials in the fabrication of electronic devices, integrated circuits, semiconductor devices, passive components, solar cells, solar modules, and/or light emitting diodes. The thermally curable adhesives comprise at least one thermosetting resin, electrically conductive particles having an average particle size of 1 μm to 50 μm, and at least one metal precursor, wherein the metal precursor decomposes substantially to the corresponding metal during the thermal curing of the thermally curable adhesive.
1. A thermally curable adhesive comprising:
a) at least one thermosetting resin;
b) electrically conductive particles having an average particle size of 1 to 50 μm wherein the electrically conductive particles are present in the amount of 80 to 87 wt %, based on the total amount of the thermally curable adhesive; and
c) at least one silver precursor comprising reaction products of silver carboxylate and at least one primary or secondary amine-containing ligand, wherein the silver precursor has a decomposition temperature that is less than the cure temperature of the at least one thermosetting resin.
2. The thermally curable adhesive according to claim 1 , wherein the thermosetting resin is selected from epoxy resins, benzoxazine resins, acrylate resins, bismaleimide resins, cyanate ester resins, polyisobutylene resins and/or combinations thereof.
3. The thermally curable adhesive according to claim 1 , wherein the thermosetting resin is selected from epoxy resins.
4. The thermally curable adhesive according to claim 1 , wherein the total weight of all thermosetting resins in the thermally curable adhesive is in the range of 3 to 25 wt %, based on the total amount of the thermally curable adhesive.
5. The thermally curable adhesive according to claim 1 , wherein the electrically conductive particles are selected from metal particles, metal plated particles or metal alloy particles and/or combinations thereof.
6. The thermally curable adhesive according to claim 1 , wherein the electrically conductive particles are selected from copper, silver, platinum, palladium, gold, tin, indium, aluminum or bismuth, and/or combinations thereof.
7. The thermally curable adhesive according to claim 1 , wherein the electrically conductive particles have an average particle size of 2 to 20 μm.
8. The thermally curable adhesive according to claim 1 , wherein the electrically conductive particles are constructed from silver.
9. The thermally curable adhesive according to claim 1 , wherein the at least one primary or secondary amine-containing ligand is an N-donor ligand selected from
primary or secondary amine-functionalized polyethers;
primary amines of formula:
R a —[NH2] u ,
wherein u is an integer from 1 to 4, and R a is a saturated or partially unsaturated linear, branched or cyclic hydrocarbon residue, comprising 4 to 22 carbon atoms;
secondary amines of formula
wherein R b and R b1 are independently selected from saturated or partially unsaturated linear, branched or cyclic hydrocarbon residues, comprising 3 to 22 carbon atoms.
10. The thermally curable adhesive according to claim 1 , wherein the silver precursor is in the form of a pre-mix dissolved or dispersed in a liquid amine-containing ligand.
11. The thermally curable adhesive according to claim 10 , wherein the pre-dissolved or predispersed silver precursor is present in the thermally curable adhesive in an amount of 0.3 to 7 wt %, based on the total amount of the thermally curable adhesive.
12. The thermally curable adhesive according claim 1 , wherein the silver precursor has a decomposition temperature in the range of about 70° C. to about 220° C.
13. A cured product comprising the thermally curable adhesive according to claim 1 .
14. A bonded assembly comprising two substrates aligned in a spaced apart relationship, each of which having an inwardly facing surface and an outwardly facing surface, wherein between the inwardly facing surfaces of each of the two substrates an electrically conductive bond is formed by the cured product of claim 13 .
15. The bonded assembly according to claim 14 , wherein at least one inwardly facing surface has a surface area of less than 5000 μm 2 .
16. The thermally curable adhesive according to claim 9 , further comprising:
tertiary amines of formula
wherein R o , R c1 and R c11 are independently selected from saturated or partially unsaturated linear, branched or cyclic hydfocarbon residues, comprising 3 to 22 carbon atoms.