Multi-phase coatings for inhibiting tin whisker growth and methods of making and using the same

Abstract

An electrical component includes a conductive substrate, a tin layer formed on the substrate, and a multi-phase coating formed on the tin layer to impede tin whisker growth. The multi-phase coating comprises a polymer matrix having pores dispersed therethrough, with the pores constituting at least 30% by volume of the coating. To form the multi-phase coating, the tin plating or finish is covered with a coating comprising a polymer matrix having a second material mixed therein. The second material is subsequently removed from the polymer matrix to produce a coating having pores in the matrix where the second material was disposed before being removed.

1 . An electrical component, comprising:
 a conductive substrate;   a tin layer formed on the substrate; and   a multi-phase coating formed on the tin layer to impede tin whisker growth, the multi-phase coating comprising a polymer matrix having pores dispersed therethrough, wherein the pores constitute at least 30% by volume of the coating.   
   
   
       2 . The electrical component according to  claim 1 , wherein the pores have an average width of at least 30 microns. 
   
   
       3 . The electrical component according to  claim 1 , wherein the pores have an average width of at least 50 microns. 
   
   
       4 . The electrical component according to  claim 1 , wherein the polymer matrix comprises a polymer selected from the group consisting of urethane, silicone, acrylic, paralenes, and polymers having an epoxy group in the molecule thereof. 
   
   
       5 . The electrical component according to  claim 1 , wherein the pores are dispersed in a manner whereby at least one pore is present in any cross-sectional slice of the porous coating. 
   
   
       6 . The electrical component according to  claim 1 , wherein the pores are at least partially filled with a material that is different than the polymer matrix. 
   
   
       7 . The electrical component according to clam  1 , wherein the material filling the pores is substantially softer than the polymer matrix. 
   
   
       8 . A method for impeding tin whisker growth from a tin plating or finish formed over an electrical component, the method comprising:
 covering the tin plating or finish with a coating comprising a polymer matrix having a second material mixed therein; and   removing the second material from the polymer matrix to produce a porous coating having pores in the matrix where the second material was disposed before being removed.   
   
   
       9 . The method according to  claim 8 , wherein the step of removing the second material from the polymer matrix produces pores that constitute at least 30% by volume of the coating. 
   
   
       10 . The method according to  claim 8 , wherein the step of removing the second material from the polymer matrix comprises contacting the coating with a solvent in which the second material is more soluble than the polymer matrix. 
   
   
       11 . The method according to  claim 10 , wherein the solvent is water. 
   
   
       12 . The method according to  claim 8 , wherein the step of removing the second material from the polymer matrix comprises heating the coating to a temperature below the melting temperature of the polymer matrix but at least as high as the second material melting temperature. 
   
   
       13 . The method according to  claim 8 , wherein the step of removing the second material from the polymer matrix comprises exposing the coating to radiation to thereby melt or decompose the second material. 
   
   
       14 . The method according to  claim 8 , further comprising the step of:
 at least partially filling the pores with a material that is different than the polymer matrix.   
   
   
       15 . The method according to  claim 14 , wherein the step of at least partially filling the pores comprises at least partially filling the pores with a material that is substantially softer than the polymer matrix. 
   
   
       20 . The method according to  claim 8 , wherein the polymer matrix in the porous coating comprises a polymer selected from the group consisting of urethane, silicone, acrylic, paralenes, and polymers having an epoxy group in the molecule thereof. 
   
   
       17 . The method according to  claim 20 , wherein the polymer matrix in the porous coating comprises urethane. 
   
   
       18 . The method according to  claim 8 , wherein the step of removing the second material from the polymer matrix produces pores having an average width of at least 30 microns. 
   
   
       19 . The method according to  claim 8 , wherein the step of removing the second material from the polymer matrix produces pores having an average width of at least 50 microns.