Method for inhibiting tin whisker growth

Abstract

A uniform copper-tin compound layer is electrochemically deposited on a surface of a copper-based base structure. A tin-based film is then formed on the copper-tin compound layer. The uniform copper-tin compound layer provides a barrier that effectively inhibits tin whisker growth.

1 . A method, comprising:
 electrochemically depositing a uniform copper-tin compound layer on a surface of a copper-based base structure; and   forming a tin-based film on the copper-tin compound layer.   
     
     
         2 . The method of  claim 1 , wherein the copper-tin compound layer comprises Cu 6 Sn 5 . 
     
     
         3 . The method of  claim 1 , wherein the copper-tin compound layer has a thickness in a range of 0.5 to 1.0 μm, and wherein the tin-based film has a thickness in a range of 0.5 to 1.0 μm. 
     
     
         4 . The method of  claim 1 , wherein a ratio of a thickness of the copper-tin compound layer and a thickness of the tin-based film is substantially 1:1. 
     
     
         5 . The method of  claim 1 , wherein the uniform copper-tin compound layer has a substantially constant thickness across said surface of the copper-based base structure. 
     
     
         6 . The method of  claim 1 , wherein the uniform copper-tin compound layer has a substantially constant stoichiometry over a lateral extent and thickness of the uniform copper-tin compound layer. 
     
     
         7 . The method of  claim 1 , wherein the uniform copper-tin compound layer has a homogenous granular structure with a smooth surface. 
     
     
         8 - 16 . (canceled) 
     
     
         17 . The method of  claim 1 , wherein electrochemically depositing comprises electroplating. 
     
     
         18 . The method of  claim 1 , wherein the tin-based film is made solely of tin. 
     
     
         19 . The method of  claim 1 , wherein no post-bake process is performed. 
     
     
         20 . The method of  claim 1 , wherein a stoichiometry of the uniform copper-tin compound layer is set at room temperature. 
     
     
         21 . The method of  claim 20 , wherein the stoichiometry forms Cu 6 Sn 5 .