Anisotropic conductive film and method of producing the same

Abstract

An anisotropic conductive film has a three-layer structure in which a first connection layer is sandwiched between a second connection layer and a third connection layer that each are formed mainly of an insulating resin. The first connection layer has a structure in which conductive particles are arranged in a single layer in the plane direction of an insulating resin layer on a side of the second connection layer, and the thickness of the insulating resin layer in central regions between adjacent ones of the conductive particles is smaller than that of the insulating resin layer in regions in proximity to the conductive particles.

1 . An anisotropic conductive film having a three-layer structure in which a first connection layer is sandwiched between a second connection layer and a third connection layer that each are formed mainly of an insulating resin, wherein
 the first connection layer has a structure in which conductive particles are arranged in a single layer in a plane direction of an insulating resin layer on a side of the second connection layer, and the insulating resin layer has a thickness in central regions between adjacent ones of the conductive particles which is smaller than a thickness of the insulating resin layer in regions in proximity to the conductive particles.   
     
     
         2 . The anisotropic conductive film according to  claim 1 , wherein the first connection layer is a thermal- or photo-radical polymerizable resin layer containing an acrylate compound and a thermal- or photo-radical polymerization initiator or a layer obtained by subjecting the thermal- or photo-radical polymerizable resin layer to thermal- or photo-radical polymerization; or a thermal- or photo-cationic or anionic polymerizable resin layer containing an epoxy compound and a thermal- or photo-cationic or anionic polymerization initiator or a layer obtained by subjecting the thermal- or photo-cationic or anionic polymerizable resin layer to thermal- or photo-cationic or anionic polymerization. 
     
     
         3 . The anisotropic conductive film according to  claim 1 , wherein the conductive particles dig into the second connection layer. 
     
     
         4 . The anisotropic conductive film according to  claim 1 , wherein a degree of cure of the first connection layer in regions positioned between the conductive particles and a surface of the first connection layer that faces the third connection layer is lower than a degree of cure of the first connection layer in regions positioned between adjacent ones of the conductive particles. 
     
     
         5 . The anisotropic conductive film according to  claim 1 , wherein the first connection layer has a minimum melt viscosity higher than that of the second connection layer and that of the third connection layer. 
     
     
         6 . The anisotropic conductive film according to  claim 5 , wherein ratios of the minimum melt viscosity of the first connection layer to the minimum melt viscosity of the second connection layer and to the minimum melt viscosity of the third connection layer are each 1:4 to 400. 
     
     
         7 . The anisotropic conductive film according to  claim 1 , wherein a shortest distance in a horizontal direction between an end in a thickness direction of the conductive particle and the second connection layer is 0.5 to 1.5 times the diameter of the conductive particles. 
     
     
         8 . A method of producing the anisotropic conductive film according to  claim 1 , the method comprising the following steps (A) to (D):
 <Step (A)>
 the step of disposing conductive particles within openings of a transfer die with the openings, and placing an insulating resin layer formed on a release film so as to be opposed to a surface of the transfer die with the openings; 
   <Step (B)>
 the step of applying pressure to the insulating resin layer from a side of the release film to press an insulating resin into the openings, to transfer the conductive particles to a surface of the insulating resin layer, to form a first connection layer, wherein the first connection layer has a structure in which the conductive particles are arranged in a single layer in a plane direction of the insulating resin layer, and the thickness of the insulating resin layer in central regions between adjacent ones of the conductive particles is smaller than that of the insulating resin layer in regions in proximity to the conductive particles; 
   <Step (C)>
 the step of forming a second connection layer formed mainly of an insulating resin on a surface of the first connection layer on a side of the conductive particles; 
   <Step (D)>
 the step of forming a third connection layer formed mainly of an insulating resin on a surface of the first connection layer on a side opposite to the second connection layer. 
   
     
     
         9 . A method of producing the anisotropic conductive film according to  claim 1 , the method comprising the following steps (a) to (c):
 <Step (a)>
 the step of disposing conductive particles within openings of a transfer die with the openings, and placing an insulating resin layer that has been bonded to a third connection layer in advance so as to be opposed to a surface of the transfer die with the openings; 
   <Step (b)>
 the step of applying pressure to the insulating resin layer from a side of a release film to press an insulating resin into the openings, to transfer the conductive particles to a surface of the insulating resin layer, to form a first connection layer, wherein the first connection layer has a structure in which the conductive particles are arranged in a single layer in a plane direction of the insulating resin layer, and the insulating resin layer has a thickness in central regions between adjacent ones of the conductive particles smaller than a thickness of the insulating resin layer in regions in proximity to the conductive particles; 
   <Step (c)>
 the step of forming a second connection layer formed mainly of an insulating resin on a surface of the first connection layer on a side of the conductive particles. 
   
     
     
         10 . The production method according to  claim 8 , further comprising the step of irradiating the first connection layer with ultraviolet rays through the conductive particle side, the step being performed between the step (B) and the step (C). 
     
     
         11 . The production method according to  claim 9 , further comprising the step of irradiating the first connection layer with ultraviolet rays through the conductive particle side, the step being performed between the step (b) and the step (c). 
     
     
         12 . A connection structure in which a first electronic component is connected to a second electronic component by anisotropic conductive connection using the anisotropic conductive film according to  claim 1 . 
     
     
         13 . A method of connecting a first electronic component to a second electronic component by anisotropic conductive connection using the anisotropic conductive film according to  claim 1 , the method comprising:
 temporarily applying the anisotropic conductive film to the second electronic component through the third connection layer of the anisotropic conductive film; mounting the first electronic component on the anisotropic conductive film temporarily applied; and performing thermocompression bonding through the first electronic component.