Anisotropic conductive adhesive

Abstract

An anisotropic conductive adhesive for anisotropic conductive connection of an electronic component to a wiring board under no pressure or a low pressure is prepared by dispersing conductive particles in a binder resin composition. A metal flake powder having a major axis of 10 to 40 μm, a thickness of 0.5 to 2 μm, and an aspect ratio of 5 to 50, is used as the conductive particles. The amount of the conductive particles contained in the anisotropic conductive adhesive is 5 to 35 mass %. This anisotropic conductive adhesive is supplied to a connection terminal of a wiring board, and a connection terminal of an electronic component is preliminarily connected to a connection terminal of a substrate while arranging the anisotropic conductive adhesive therebetween. Then, the electronic component is heated without applying a pressure or while applying a low pressure to the electronic component to connect the substrate with the electronic component.

The invention claimed is: 
     
       1. An anisotropic conductive connection method comprising:
 supplying an anisotropic conductive adhesive to a connection terminal of a wiring board; 
 preliminarily connecting a connection terminal of an electronic component to the connection terminal of the wiring board while arranging the anisotropic conductive adhesive therebetween; and 
 heating the electronic component while applying a pressure of 1 MPa or less to the electronic component to connect the wiring board with the electronic component and to completely or almost completely cure the adhesive; 
 wherein the adhesive comprises: 
 a binder resin composition and conductive particles that include a metal flake powder and are dispersed in the binder resin composition, wherein:
 the metal flake powder enables electrical connection between the connection terminals and the conductive particles due to surface connection; 
 the metal flake powder has a major axis of 10 to 40 μm, a thickness of 0.5 to 2 μm, and an aspect ratio of 5 to 50; and 
 an amount of the conductive particles contained in the anisotropic conductive adhesive is 5 to 35 mass %. 
 
 
     
     
       2. The anisotropic conductive connection method according to  claim 1 , wherein the metal flake powder is a nickel flake powder. 
     
     
       3. The anisotropic conductive connection method according to  claim 1 , wherein the binder resin composition comprises an epoxy resin and an imidazole curing agent. 
     
     
       4. The anisotropic conductive connection method according to  claim 1 , wherein the adhesive has a viscosity of 50 to 200 Pa·s at 25° C. 
     
     
       5. The anisotropic conductive connection method according to  claim 1 , wherein a pressure of 0.1 to 1 MPa is applied to the electronic component during the preliminary connecting. 
     
     
       6. The anisotropic conductive connection method according to  claim 1 , wherein the electronic component is heated without applying a pressure. 
     
     
       7. The anisotropic conductive connection method according to  claim 2 , wherein the binder resin composition comprises an epoxy resin and an imidazole curing agent. 
     
     
       8. The anisotropic conductive connection method according to  claim 2 , wherein the adhesive has a viscosity of 50 to 200 Pa·s at 25° C. 
     
     
       9. The anisotropic conductive connection method according to  claim 3 , wherein the adhesive has a viscosity of 50 to 200 Pa·s at 25° C. 
     
     
       10. The anisotropic conductive connection method according to  claim 7 , wherein the adhesive has a viscosity of 50 to 200 Pa·s at 25° C. 
     
     
       11. The anisotropic conductive connection method according to claim 1, wherein the metal flake powder has a major axis of 10 to 30 μm. 
     
     
       12. The anisotropic conductive connection method according to claim 1, wherein the metal flake powder has a thickness of 0.5 to 1.5 μm. 
     
     
       13. The anisotropic conductive connection method according to claim 1, wherein the metal flake powder has a minor axis of 10% to 50% of a length of the major axis. 
     
     
       14. The anisotropic conductive connection method according to claim 1, wherein the metal flake powder has an aspect ratio of 5 to 42. 
     
     
       15. The anisotropic conductive connection method according to claim 1, wherein the conductive particles are 7 to 30 mass % of the adhesive. 
     
     
       16. The anisotropic conductive connection method according to claim 1, wherein the conductive particles further include spherical conductive particles. 
     
     
       17. The anisotropic conductive connection method according to claim 1, wherein the adhesive has a viscosity of 50 to 150 Pa·s at 25° C. 
     
     
       18. The anisotropic conductive connection method according to claim 1, wherein the adhesive is supplied to the connection terminal as a film. 
     
     
       19. The anisotropic conductive connection method according to claim 18, wherein the film has a thickness of 30 to 50 μm. 
     
     
       20. The anisotropic conductive connection method according to claim 1, wherein a pressure of 0.5 MPa or less is applied to the electronic component during heating.