Member formed with coating film having tin as its main component, coating film forming method and soldering method

Abstract

A member having a coating film capable of suppressing whisker generation is provided. The coating film ( 3 ) including a plurality of crystalline grains ( 3 a ) made of tin or tin alloy is formed above the surface of the base member ( 1 ). An intermetallic compound ( 3 b ) of tin and the first metal is being formed along the crystalline grain boundaries of the coating film.

1 . A member comprising:
 a base member;   a coating film disposed over a surface of the base member, the coating film comprising a plurality of crystalline grains made of tin or tin alloy, and an intermetallic compound of tin and a first metal being formed along crystalline grain boundaries; and   an underlying layer containing the first metal and disposed between the base member and the coating film,   wherein the intermetallic compound formed along the crystalline grain boundaries of the coating film has a flake shape.   
     
     
         2 . The member according to  claim 1 , wherein the first metal is nickel. 
     
     
         3 . The member according to  claim 1 , wherein the intermetallic compound forms a solid solution containing an element forming a solid solution with tin. 
     
     
         4 . The member according to  claim 1 , wherein the element forming the solid solution with tin is at least one metal selected from a group consisting of copper, gold, bismuth, antimony, indium, zinc, paradigm, lead and aluminum. 
     
     
         5 . The member according to  claim 1 , wherein the coating film is formed at a temperature of 0.65 to 0.80 time a melting point in absolute temperature of crystalline grains constituting the coating film, and a heat treatment time of 3 to 30 minutes.