Printed wiring board and method for manufacturing printed wiring board

Abstract

A method for manufacturing a printed wiring board includes laminating a first core substrate and a second core substrate, forming a first upper buildup layer on a surface of the first core substrate, forming a second upper buildup layer on a surface of the second core substrate, separating the first core substrate and the second core substrate from each other, laminating the first upper buildup layer formed on the first core substrate and the second upper buildup layer formed on the second core substrate, forming a first lower buildup layer on the opposite surface of the first core substrate, forming a second lower buildup layer on the opposite surface of the second core substrate, and separating the first upper buildup layer and the second upper buildup layer.

What is claimed is: 
     
         1 . A printed wiring board, comprising:
 a core substrate having a first surface and a second surface on an opposite side of the first surface;   an upper buildup layer formed on the first surface of the core substrate and having an outermost resin insulation layer; and   a lower buildup layer formed on the second surface of the core substrate and having an outermost resin insulation layer,   wherein the outermost resin insulation layer of the upper buildup layer comprises a material which is different from a material of the outermost resin insulation layer of the lower buildup layer.   
     
     
         2 . The printed wiring board according to  claim 1 , wherein the outermost resin insulation layer of the upper buildup layer has a thermal expansion coefficient which is lower than a thermal expansion coefficient of the outermost resin insulation layer of the lower buildup layer. 
     
     
         3 . The printed wiring board according to  claim 1 , wherein the outermost resin insulation layer of the upper buildup layer has a reinforcing material, the core substrate has a reinforcing material, and the reinforcing material in the outermost resin insulation layer of the upper buildup layer has a thermal expansion coefficient which is lower than a thermal expansion coefficient of the reinforcing material in the core substrate. 
     
     
         4 . The printed wiring board according to  claim 1 , wherein the outermost resin insulation layer of the upper buildup layer has a reinforcing material, the core substrate has a reinforcing material, the reinforcing material in the outermost resin insulation layer of the upper buildup layer is made of S-glass, and the reinforcing material in the core substrate is made of E-glass. 
     
     
         5 . The printed wiring board according to  claim 3 , wherein the outermost resin insulation layer of the lower buildup layer does not have a reinforcing material. 
     
     
         6 . The printed wiring board according to  claim 3 , further comprising a solder-resist layer formed on the lower buildup layer. 
     
     
         7 . The printed wiring board according to  claim 6 , wherein a solder-resist layer is not formed on the upper buildup layer. 
     
     
         8 . A printed wiring board, comprising:
 a core substrate having a first surface and a second surface on an opposite side of the first surface;   an upper buildup layer formed on the first surface of the core substrate and comprising a plurality of resin insulation layers; and   a lower buildup layer formed on the second surface of the core substrate and comprising at least one resin insulation layer,   wherein the plurality of resin insulation layers in the upper buildup layer includes an outermost resin insulating layer, the at least one resin insulation layer in the lower buildup layer includes an outermost resin insulating layer, and the plurality of resin insulation layers in the upper buildup layer has a greater number of layers than the at least one resin insulation layer in the lower buildup layer.   
     
     
         9 . The printed wiring board according to  claim 8 , wherein the outermost resin insulation layer of the upper buildup layer has a thermal expansion coefficient which is lower than a thermal expansion coefficient of the outermost resin insulation layer of the lower buildup layer. 
     
     
         10 . The printed wiring board according to  claim 8 , wherein the outermost resin insulation layer of the upper buildup layer has a reinforcing material, the core substrate has a reinforcing material, and the thermal expansion coefficient of the reinforcing material in the outermost resin insulation layer of the upper buildup layer is lower than the thermal expansion coefficient of the reinforcing material in the core substrate. 
     
     
         11 . The printed wiring board according to  claim 8 , wherein the outermost resin insulation layer of the upper buildup layer has a reinforcing material, the core substrate has a reinforcing material, the reinforcing material in the outermost resin insulation layer of the upper buildup layer is made of S-glass, and the reinforcing material in the core substrate is made of E-glass. 
     
     
         12 . The printed wiring board according to  claim 10 , wherein the outermost resin insulation layer of the lower buildup layer does not have a reinforcing material. 
     
     
         13 . The printed wiring board according to  claim 10 , further comprising a solder-resist layer formed on the lower buildup layer. 
     
     
         14 . The printed wiring board according to  claim 13 , wherein a solder-resist layer is not formed on the upper buildup layer.