Tin electroplating solution and tin electroplating method

Abstract

To provide a tin electroplating solution devoid of harmful lead and having excellent solder wettability, and a method for depositing a tin film on electronic parts using such a tin electroplating solution. The tin electroplating solution includes organic acids, a naphtholsulfonic acid and, as needed, an antioxidant and a surfactant is disclosed.

1 - 8 . (canceled) 
   
   
       9 . A tin electroplating solution comprising one or more compounds for supplying stannous ions selected from the group consisting of stannous salts of sulfuric acid, alkane sulfonic acids, and alkanol sulfonic acids, one or more organic acids selected from the group consisting of alkane sulfonic acids and alkanol sulfonic acids and one or more of 2-naphthol-7-sulfonic acid and alkali metal salts thereof in amounts of 0.3 g/L to 5 g/L. 
   
   
       10 . The tin electroplating solution of  claim 9 , wherein the alkali metal salt of 2-naphthol-7-sulfonic acid is sodium 2-naphthol-7-sulfonate. 
   
   
       11 . The tin electroplating solution of  claim 9 , further comprising one or more antioxidants. 
   
   
       12 . The tin electroplating solution of  claim 11 , wherein the one or more antioxidants is chosen from substituted and unsubstituted dihydroxybenzene compounds. 
   
   
       13 . The tin electroplating solution of  claim 9 , further comprising one or more surfactants. 
   
   
       14 . A method for electroplating a tin film on a substrate comprising:
 a) providing a tin electroplating solution comprising one or more compounds for supplying stannous ions selected from the group consisting of stannous salts of sulfuric acid, alkane sulfonic acids and alkanol sulfonic acids, one or more organic acids selected from the group consisting of alkane sulfonic acids and alkanol sulfonic acids and one or more of 2-naphthol-7-sulfonic acid or alkali metal salts thereof in amounts of 0.3 g/L to 5 g/L;   b) contacting the substrate with the tin electroplating solution; and   c) electroplating the tin film on the substrate.   
   
   
       15 . The method of  claim 14 , further comprising a step of subjecting the substrate to an activation step prior to contacting the substrate with the tin electroplating solution. 
   
   
       16 . The method of  claim 14 , wherein the alkali metal salt of 2-naphthol-7-sulfonic acid is sodium 2-naphthol-7-sulfonate.