Tin electrodeposits having properties or characteristics that minimize tin whisker growth

Abstract

A method of reducing tin whisker formation by creating a tin deposit which is inherently less prone to tin whisker formation or growth facilitated by oxide presence or corrosion reactions on the tin deposit surface. This is obtained by one or more of: (i) the deposition of a fine-grained tin deposit having an average grain diameter in the range of 0.05 to 5 microns; (ii) a phosphorous compound in the solution that is used to electroplate the tin deposit so that that the deposit incorporates trace amounts of phosphorous which in turn reduces tin whisker formation by preventing surface oxides even when exposed to heat or humidity; or (iii) a phosphorous compound, mercaptan, or organic or organo-metallic compound in a solution that applies a protective coating to the surface of a previously electroplated tin deposit, wherein the protective coating acts to minimize or prevent oxide formation or corrosion of the tin deposit during exposure to heat or humidity. Such tin deposits containing 80% to 100% by weight of tin exhibit minimal to no tin whisker growth.

1 . A method of reducing tin whisker formation in a tin deposit on a substrate, which comprises electroplating a tin deposit on an electroplatable substrate, and modifying at least one physical property or characteristic of the tin deposit sufficiently to the render the deposit less prone to tin whisker growth over time or to prevent tin whisker formation, wherein the modifying occurs during or after deposition of the tin deposit on the substrate.  
   
   
       2 . The method of  claim 1 , wherein the physical property or characteristic is modified when the tin deposit is electroplated on the substrate to render it less prone to or to prevent tin whisker formation or growth in the deposit.  
   
   
       3 . The method of  claim 2 , wherein the physical property or characteristic that is modified is its grain structure, wherein the tin deposit is provided with a fine grain structure.  
   
   
       4 . The method of  claim 3 , wherein the tin deposit is provided with an average grain size of about 0.05 to 5 microns.  
   
   
       5 . The method of  claim 2 , wherein the physical property or characteristic that is modified is its surface oxidation, wherein the tin deposit is essentially free of surface oxides when deposited.  
   
   
       6 . The method of  claim 5 , wherein surface oxide formation on the tin deposit is reduced or prevented by depositing the tin deposit from a solution containing a phosphorous compound, thereby incorporating trace or small amounts of phosphorous in the tin deposit which resist surface oxide formation even when the deposit is exposed to heat or humidity.  
   
   
       7 . The method of  claim 6 , wherein the solution contains sufficient phosphorous compound to provide an amount of about 0.1 ppm to 30% by weight phosphorus in the tin deposit.  
   
   
       8 . The method of  claim 1 , wherein the tin deposit is treated after deposition to render it less prone to tin whisker growth.  
   
   
       9 . The method of  claim 8 , wherein the tin deposit is treated by applying a protective coating thereon.  
   
   
       10 . The method of  claim 9 , wherein the tin deposit is immersed in or contacted by a post-treatment solution containing one or more of a phosphorous compound, a mercaptan compound, or an organic or organo-metallic compound to apply the protective coating thereon.  
   
   
       11 . The method of  claim 1 , wherein the protective coating is applied at a thickness of about 0.1 angstroms to 1 micron.  
   
   
       12 . The method of  claim 1 , wherein the tin deposit includes at least 80% to 100% tin by weight and the substrate is an electrical component.  
   
   
       13 . The method of  claim 12 , wherein the substrate is an electronic component that include electroplatable portions and non-electroplatable portions and the tin deposit is provided upon the electroplatable portions.  
   
   
       14 . The method of  claim 1 , wherein the substrate comprises copper.  
   
   
       15 . In a tin plated electronic component that includes a copper surface upon which a fine grained tin deposit is present, the improvement which comprises minimizing or preventing tin whisker formation or growth by providing the tin deposit with one or more of: 
 (a) a fine grained structure so that the tin deposit is less prone to tin whisker formation or growth compared to tin deposits having larger grain structures;    (b) trace or small amounts of phosphorous so that the tin deposit is essentially free of surface oxidation and is less prone to tin whisker formation or growth compared to tin deposits having surface oxidation; or    (c) a protective layer so that it is less prone to tin whisker formation or growth compared to tin deposits having no protective layer.    
   
   
       16 . The tin plated electronic component of  claim 15 , wherein the tin deposit is provided with a fine grained structure having an average grain size of about 0.05 to 5 microns so that the tin deposit is less prone to tin whisker formation or growth compared to tin deposits having larger grain structures.  
   
   
       17 . The tin plated electronic component of  claim 15 , wherein the tin deposit is provided with trace or small amounts of phosphorous so that the tin deposit is essentially free of surface oxidation even when the deposit is exposed to heat or humidity and is less prone to tin whisker formation or growth than tin deposits having surface oxidation.  
   
   
       18 . The tin plated electrical component of  claim 17 , wherein the phosphorus is present in the tin deposit in an amount of about 0.1 ppm to 30% by weight.  
   
   
       19 . The tin plated electronic component of  claim 15 , wherein the tin deposit is provided with a protective layer so that it is less prone to tin whisker formation or growth compared to tin deposits having no protective layer, wherein the protective layer is provided by immersion in or contact by a post-treatment solution containing one or more of a phosphorous compound, a mercaptan compound, or an organic or organo-metallic compound.  
   
   
       20 . The tin plated electronic component of  claim 19 , wherein the protective coating is present at a thickness of about 0.1 angstroms to 1 micron.