Electrically conductive adhesives
The present invention relates to 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 adhesives comprise at least one resin component, micron-sized electrically conductive particles having an average particle size of 2 μm to 50 μm, and from 0.01 to 15 wt. % of sub-micron-sized electrically conductive particles having a average particle size of 300 nm to 900 nm.
1. An adhesive, comprising:
a) at least one resin component;
b) from 70 to 90 wt % of electrically conductive particles having an average particle size of 2 μm to 50 μm, and
c) from 0.01 to 15 wt. % of electrically conductive particles having an average particle size of 300 nm to 900 nm, wherein the wt. % is based on the total amount of the adhesive and wherein the electrically conductive particles of a), b) or a) and b) are selected from metal particles, metal plated particles or metal alloy particles and combinations thereof, and wherein the weight ratio of electrically conductive particles of b) to electrically conductive particles of c) is from 100:0.1 to 100:21.
2. The adhesive according to claim 1 , wherein the resin component is selected from thermosetting resins and/or thermoplastic resins.
3. The adhesive according to claim 1 , wherein the resin component is selected from epoxy resins, benzoxazine resins, acrylate resins, bismaleimide resins, cyanate ester resins, polyisobutylene resins and/or combinations thereof.
4. The adhesive according to claim 3 , wherein the epoxy resin is selected from monofunctional glycidyl ethers, polyfunctional glycidyl ethers, and/or combinations thereof.
5. The adhesive according to claim 1 , wherein the electrically conductive particles comprise copper, silver, platinum, palladium, gold, tin, indium, aluminum or bismuth, and combinations thereof.
6. The adhesive according to claim 1 , wherein the electrically conductive particles comprise the same metal, which is silver or copper.
7. The adhesive according to claim 1 , wherein the electrically conductive particles of b) have an average particle size of 2 μm to 20 μm.
8. The adhesive according to claim 1 , wherein the electrically conductive particles of c) have an average particle size of 400 nm to 800 nm.
9. The adhesive according to claim 1 , wherein the adhesive comprises the electrically conductive particles of c) in an amount of 0.5 to 7.5 wt. %, based on the total amount of the adhesive.
10. The adhesive according to claim 1 wherein the adhesive comprises the electrically conductive particles of c) in an amount of 0.75 to 2 wt. %, based on the total amount of the adhesive.
11. The adhesive according to claim 1 , wherein the adhesive additionally comprises at least one curing agent.
12. A cured product of the adhesive according to claim 1 .
13. 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 12 .
14. A bonded assembly according to claim 13 , wherein at least one inwardly facing surface has a surface area of less than 5000 μm 2 .