Cu CORE BALL, SOLDER PASTE AND SOLDER JOINT

Abstract

A Cu core ball suppresses a soft error and its alpha dose is low. Its surface roughness does not affect a mounting process. A pure degree of the Cu ball as an internal ball is equal to or larger than 99.9% and equal to or less than 95%. A total contained amount of Pb and/or Bi in impurity contained in the Cu ball is equal to or larger than 1 ppm. Its sphericity is equal to or higher than 0.95. A solder plating film coated on the Cu ball is a Sn solder plating film or a solder plating film comprising a lead free solder alloy whose primary component is Sn. In the solder plating film, a contained amount of U is equal to or less than 5 ppb and that of Th is equal to or less than 5 ppb. A total alpha dose of the Cu ball and the solder plating film is equal to or less than 0.0200 cph/cm 2 . An arithmetic average roughness of the Cu core ball is equal to or less than 0.3 μm.

1 . A Cu core ball, comprising:
 a Cu ball as an inside ball; and   a solder plating film for coating a surface of said Cu ball;   wherein in said Cu ball, its pure degree is equal to or higher than 99.9% and equal to or less than 99.995%, a contained amount of U is equal to or less than 5 ppb, a contained amount of Th is equal to or less than 5 ppb, a total contained amount of Pb and/or Bi is equal to or larger than 1 ppm, its sphericity is equal to or higher than 0.95 and its alpha dose is equal to or less than 0.0200 cph/cm 2 ;   wherein said solder plating film is a solder plating film comprising a lead free solder alloy, and its primary component is Sn or a Sn solder plating film; and   wherein an arithmetic average roughness of said Cu core ball is equal to or less than 0.3 μm.   
     
     
         2 . The Cu core ball according to  claim 1  characterized in that the contained amount of U in said solder plating film is equal to or less than 5 ppb and the contained amount of Th in said solder plating film is equal to or less than 5 ppb. 
     
     
         3 . The Cu core ball according to  claim 1  characterized in that said roughness is equal to or less than 0.22 μm. 
     
     
         4 . The Cu core ball according to  claim 2  characterized in that said roughness is equal to or less than 0.22 μm. 
     
     
         5 . The Cu core ball according to  claim 1  characterized in that said Cu ball is previously coated by a plating layer comprising at least one element selected from a group of Ni and Co before being coated by said solder plating film. 
     
     
         6 . The Cu core ball according to  claim 2  characterized in that said Cu ball is previously coated by a plating layer comprising at least one element selected from a group of Ni and Co before being coated by said solder plating film. 
     
     
         7 . The Cu core ball according to  claim 3  characterized in that said Cu ball is previously coated by a plating layer comprising at least one element selected from a group of Ni and Co before being coated by said solder plating film. 
     
     
         8 . The Cu core ball according to  claim 1  characterized in that the alpha dose is equal to or less than 0.0200 cph/cm 2 . 
     
     
         9 . The Cu core ball according to  claim 2  characterized in that the alpha dose is equal to or less than 0.0200 cph/cm 2 . 
     
     
         10 . The Cu core ball according to  claim 3  characterized in that the alpha dose is equal to or less than 0.0200 cph/cm 2 . 
     
     
         11 . The Cu core ball according to  claim 5  characterized in that the alpha dose is equal to or less than 0.0200 cph/cm 2 . 
     
     
         12 . A solder paste characterized in that the Cu core ball defined by  claim 1  is used. 
     
     
         13 . A solder paste characterized in that the Cu core ball defined by  claim 2  is used. 
     
     
         14 . A solder paste characterized in that the Cu core ball defined by  claim 3  is used. 
     
     
         15 . A solder paste characterized in that the Cu core ball defined by  claim 5  is used. 
     
     
         16 . A solder paste characterized in that the Cu core ball defined by  claim 8  is used. 
     
     
         17 . A solder joint characterized in that said solder joint is formed by using the Cu core ball defined by  claim 1 . 
     
     
         18 . A solder joint characterized in that said solder joint is formed by using the Cu core ball defined by  claim 2 . 
     
     
         19 . A solder joint characterized in that said solder joint is formed by using the Cu core ball defined by  claim 3 . 
     
     
         20 . A solder joint characterized in that said solder joint is formed by using the Cu core ball defined by  claim 5 . 
     
     
         21 . A solder joint characterized in that said solder joint is formed by using the Cu core ball defined by  claim 8 .