Multilayer printed wiring board and manufacturing method thereof

Abstract

A multilayer printed wiring board is characterized in that the interlayer connection material in the via holes has a lower coefficient of thermal expansion in the thickness direction than the electrically insulating substrate made of insulating material; the interlayer connection is formed at a temperature higher than the operating temperature; and the interlayer connection material is larger in thickness than the interlayer connection material of the same wiring layer at normal temperature. This causes a difference in the coefficient of thermal expansion between the different materials in the thickness direction of the printed wiring board in the environment in which it is used resulting in high connection reliability.

1 . A method for manufacturing a multilayer printed wiring board having a plurality of wiring layers, comprising:
 forming a via hole in an electrically insulating substrate made of insulating material;   forming interlayer connection material in the via hole, the interlayer connection material having a coefficient of thermal expansion in a thickness direction lower than the insulating material; and   forming interlayer connection at a temperature higher than an operating temperature of the multilayer printed wiring board, the interlayer connection being larger than the insulating material of a same wiring layer at the operating temperature in thickness.   
     
     
         2 . The method for manufacturing a multilayer printed wiring board of  claim 1 , wherein
 the interlayer connection is formed at a temperature of 180 to 400° C.   
     
     
         3 . The method for manufacturing a multilayer printed wiring board of  claim 1 , wherein
 the insulating material is made of at least one of a composite of glass woven cloth and thermosetting resin; a composite of glass unwoven cloth and thermosetting resin; a composite of aramid woven cloth and thermosetting resin; and a composite of aramid unwoven cloth and thermosetting resin.   
     
     
         4 . The method for manufacturing a multilayer printed wiring board of  claim 3 , wherein
 the thermosetting resin is an epoxy-based resin.   
     
     
         5 . The method for manufacturing a multilayer printed wiring board of  claim 1 , wherein
 the insulating material is made of at least one of a composite of glass woven cloth and thermoplastic resin; a composite of glass unwoven cloth and thermoplastic resin; a composite of aramid woven cloth and thermoplastic resin; and a composite of aramid unwoven cloth and thermoplastic resin.   
     
     
         6 . The method for manufacturing a multilayer printed wiring board of  claim 5 , wherein
 the thermoplastic resin has a glass transition temperature of at least 180° C.   
     
     
         7 . The method for manufacturing a multilayer printed wiring board of  claim 1 , wherein
 the insulating material is made of a film material.   
     
     
         8 . The method for manufacturing a multilayer printed wiring board of  claim 1 , wherein
 the interlayer connection material is formed by at least one of conductive pasting, filled plating, conformal plating, evaporating, and sputtering.