Refining process for producing low alpha tin

Abstract

A method for purifying tin includes exposing an electrolytic solution comprising tin to an ion exchange resin and depositing electrorefined tin from the electrolytic solution. The deposited electrorefined tin has alpha particle emissions of less than about 0.01 counts/hour/cm 2 immediately after the deposition step, and an alpha emissivity of less than about 0.01 counts/hour/cm 2 at least 90 days after the deposition step.

What is claimed is: 
     
         1 . A method for purifying tin, the method comprising:
 exposing an electrolytic solution comprising tin to an ion exchange resin; and   depositing electrorefined tin from the electrolytic solution.   
     
     
         2 . The method of  claim 1 , wherein the electrorefined tin has alpha particle emissions of less than about 0.01 counts/hour/cm 2 . 
     
     
         3 . The method of  claim 1 , wherein the exposing and depositing steps occur at least partially concurrently. 
     
     
         4 . The method of  claim 1 , wherein the electrorefined tin has alpha particle emissions of less than about 0.001 counts/hour/cm 2 . 
     
     
         5 . The method of  claim 1 , wherein the ion exchange resin comprises functionalized carboxylic acid from the phosphonic acids group. 
     
     
         6 . The method of  claim 1 , wherein the ion exchange resin comprises phosphomethylated functional groups. 
     
     
         7 . The method of  claim 1 , wherein the ion exchange resin comprises amino methyl phosphonic acid functional groups. 
     
     
         8 . The method of  claim 1 , wherein the ion exchange resin comprises poly(4-vinyl-pyridine) functional groups. 
     
     
         9 . The method of  claim 1 , wherein a lead content of the electrorefined tin is reduced by less than about 1% as compared to tin prior to the exposing step. 
     
     
         10 . The method of  claim 1 , wherein at least 90 days after the deposition step, the electrorefined tin has an alpha particle emissions of less than about 0.01 counts/hour/cm 2 . 
     
     
         11 . The method of  claim 1  and further comprising:
 detecting alpha particle emissions from a sample of the deposited electrorefined tin; 
 determining a concentration of a target parent isotope in the sample of the deposited electrorefined tin from the alpha particle emissions detected in said detecting step and a time which has elapsed between said detecting step and said exposing and depositing steps; and 
 determining an alpha emission potential of a target decay isotope of the target parent isotope from the determined concentration of the target parent isotope and the half-life of the target parent isotope. 
 
     
     
         12 . The method of  claim 1 , further comprising the additional steps, prior to said detecting steps, of:
 obtaining a sample of the deposited electrorefined tin; and   heating the sample to diffuse atoms of the target decay isotope within the sample until a uniform concentration of atoms of the target decay isotope is obtained throughout the sample.   
     
     
         13 . The method of  claim 1 , wherein the electrolytic solution has a tin concentration from about 60 g/L to about 180 g/L. 
     
     
         14 . The method of  claim 1 , wherein the electrolytic solution includes at least one additive. 
     
     
         15 . The method of  claim 14 , wherein the additive includes at least one member selected from the group consisting of antioxidants and grain refiners. 
     
     
         16 . The method of  claim 14 , wherein the additive is present in an amount of at least about 0.5% by volume of the electrolytic solution. 
     
     
         17 . The method of  claim 1  wherein exposing the electrolytic solution to an ion exchange resin further comprises passing the electrolytic solution from a first container through the ion exchange resin in a second container and returning the electrolytic solution to the first container. 
     
     
         18 . The method of  claim 1 , wherein the electrolytic solution has pH of about 1 or less. 
     
     
         19 . The method of  claim 1 , wherein the electrorefined tin has a lead concentration of at least about 1 part per million (ppm). 
     
     
         20 . The method of  claim 1 , wherein at least 90 days after the step of depositing, the electrorefined tin has an alpha particle emissions that is at least 75% less than the alpha particle emissions of the tin prior to the exposing and depositing steps.