High-Purity Tin or Tin Alloy and Process for Producing High-Purity Tin

Abstract

Provided is high purity tin or tin alloy wherein the respective contents of U and Th are 5 ppb or less, the respective contents of Pb and Bi are 1 ppm or less, and the purity is 5N or higher (provided that this excludes the gas components of O, C, N, H, S and P). This high purity tin or tin alloy is characterized in that the α ray count of high purity tin having a cast structure is 0.001 cph/cm 2 or less. Since recent semiconductor devices are densified and are of large capacity, there is considerable risk of a soft error occurring due to the influence of the α ray from materials in the vicinity of the semiconductor chip. In particular, there are strong demands for purifying the soldering material or tin to be used in the vicinity of semiconductor devices, as well as for materials with fewer α rays. Thus, the present invention aims to provide high purity tin or tin alloy and the manufacturing method of such high purity tin by reducing the α dose of tin so as to be adaptable as the foregoing material.

1 . High purity tin or tin alloy wherein the respective contents of U and Th are 5 ppb or less, the respective contents of Pb and Bi are 1 ppm or less, and the purity is 5N or higher provided that this excludes the gas components of O, C, N, H, S and P. 
     
     
         2 . The high purity tin or tin alloy according to  claim 1 , wherein the α ray count of high purity tin is 0.001 cph/cm 2  or less. 
     
     
         3 . A manufacturing method of high purity tin, comprising the steps of leaching tin as the raw material with acid, using the obtained leachate as an electrolytic solution, suspending an adsorbent of impurities in the electrolytic solution, and performing electrolytic refining using a raw material Sn anode so as to obtain high purity tin wherein the respective contents of U and Th are 5 ppb or less, the respective contents of Pb and Bi are 1 ppm or less, and the purity is 5N or higher provided that this excludes the gas components of O, C, N, H, S and P. 
     
     
         4 . The manufacturing method of high purity tin according to  claim 3 , wherein oxide, activated carbon or carbon is used as the adsorbent. 
     
     
         5 . The manufacturing method of high purity tin according to  claim 4 , wherein the high purity tin obtained via electrolytic refining is dissolved and cast at 250 to 500° C. and the α ray count of the cast ingot after the lapse of 6 months or longer is 0.001 cph/cm 2  or less. 
     
     
         6 . The manufacturing method of high purity tin according to  claim 3 , wherein the high purity tin obtained via electrolytic refining is dissolved and cast at 250 to 500° C. and the α ray count of the cast ingot after the lapse of 6 months or longer is 0.001 cph/cm 2  or less.