High speed tin plating process

Abstract

Methods for the electrolytic preparation of tin coated metals are disclosed. Organic polybasic acids, such as methanedisulfonic acid [CH 2 (SO 3 H) 2 ], 1,3-acetonedisulfonic acid [CO(CH 2 SO 3 H) 2 ], anhydrides, and their water soluble salts, and mixtures thereof may be used as the electrolyte in the plating process or as the flux in the reflow process. Acetone, gamma-butyrolactone, or a mixture thereof, may be applied to a tin plated surface, either before or after reflow. The methods of the invention produce plated material that is free of blue haze.

1 . A plating solution comprising:
 water;   about 10 g/l to 40 g/l of stannous ion; and   0.01 wt % to 10 wt % of either
 a) an alkyl polysulfonic acid, a salt thereof, or a mixture of the alkyl polysulfonic acid and one or more salts thereof; 
 b) a mixture of an alkyl polysulfonic acid and sulfuric acid in which in which the ratio of the sulfuric acid to the alkyl polysulfonic acid, based on the normality of the acids, is about 3/1 or less; or 
 c) a mixture of an alkyl polysulfonic acid and methane sulfonic acid, in which the ratio of the methane sulfonic acid to the alkyl polysulfonic acid, based on the normality of the acids, is about 1/1 or less. 
   
     
     
         2 . The plating solution of  claim 1  in which the alkyl polysulfonic acid is selected from the group consisting of methanedisulfonic acid, 1,3-acetonedisulfonic acid, anhydrides thereof, salts thereof, and mixtures thereof. 
     
     
         3 . The plating solution of  claim 2  in which the plating solution comprises a). 
     
     
         4 . The plating solution of  claim 3  in which the alkyl polysulfonic acid is methanedisulfonic acid. 
     
     
         5 . The plating solution of  claim 2  in which the plating solution comprises b). 
     
     
         6 . The plating solution of  claim 5  in which the alkyl polysulfonic methanedisulfonic acid. 
     
     
         7 . The plating solution of  claim 2  in which the plating solution comprises c). 
     
     
         8 . The plating solution of  claim 6  in which the alkyl polysulfonic acid is methanedisulfonic acid.