Selectively coating bond pads

Abstract

Solder ball bond pads and wire bond pads may be selectively coated so that the wire bond bond pads have a thicker gold coating than the solder ball bond pads. This may reduce the embrittlement of solder ball joints while providing a sufficient thickness of gold for the wire bonding process. In general, gold coatings are desirable on electrical contact surfaces to prevent oxidation. However, the thickness of gold which is necessary on solder ball bond pads may be less and excessive gold may be disadvantageous. Thus, by masking the solder ball bond pads during the gold coating of the wire bond bond pads, a differential gold thickness may be achieved which is more advantageous for each application.

1 . A method comprising: 
 masking a first bond pad;    coating gold on a second bond pad with said first bond pad masked;    removing said mask from said first bond pad; and    simultaneously coating gold on said first bond pad and said second bond pad.    
   
   
       2 . The method of  claim 1  wherein simultaneously coating gold on said first bond pad and said second bond pad includes coating said first and second bond pads to provide a gold coating having a different thickness on said first bond pad and said second bond pad.  
   
   
       3 . The method of  claim 2  wherein coating said first and second bond pads includes coating said first and second bond pads to provide a thicker gold coating on said second bond pad than on said first bond pad.  
   
   
       4 . The method of  claim 3  wherein coating said first and second bond pads includes coating said second bond pad to provide a gold coating having a thickness of about 0.5 microns and said first bond pad to provide a gold coating having a thickness of approximately 0.1 to 0.3 microns.  
   
   
       5 . The method of  claim 1  including nickel coating said first and said second bond pads at the same time before coating said second bond pad with gold.  
   
   
       6 . The method of  claim 1  including using an electroless plating technique to coat gold on said second bond pad.  
   
   
       7 . The method of  claim 1  including forming a laminate structure having said first bond pad and said second bond pad on the same surface.  
   
   
       8 . The method of  claim 1  wherein said first bond pad is gold coated in a single step.  
   
   
       9 . The method of  claim 8  wherein said second bond pad is gold coated in at least two steps.  
   
   
       10 . The method of  claim 1  wherein said first bond pad is a solder ball bond pad and said second bond pad is a wire bond bond pad, and coating gold on said wire bond bond pad to a thickness of about 0.5 microns and coating gold on said solder ball bond pad to a thickness of about 0.1 to about 0.3 microns.  
   
   
       11 . A method comprising: 
 masking a first bond pad and coating gold on a second bond pad to a full desired thickness with said first bond pad masked;    unmasking said first bond pad and masking said gold coated second bond pad; and    while said second bond pad is masked, coating gold on said first bond pad to a full desired thickness.    
   
   
       12 . The method of  claim 11  including providing a gold coating on said second bond pad having a thickness of about 0.5 microns.  
   
   
       13 . The method of  claim 11  including providing a gold coating on said first bond pad of approximately 0.1 to 0.3 microns in thickness.  
   
   
       14 . The method of  claim 11  including coating said first bond pad to a thickness of approximately 0.25 microns.  
   
   
       15 . The method of  claim 11  including coating said second bond pad with gold to a thickness greater than the gold coating over said first bond pad.  
   
   
       16 . An intermediate structure for an integrated circuit comprising: 
 a plurality of gold coated first bond pads having a resist material formed thereon; and    a plurality of gold coated second bond pads, the gold coating on said second bond pads being thinner than the gold coating on said first bond pads.    
   
   
       17 . The intermediate structure of  claim 16  wherein the thickness of the gold on said second bond pads is sufficiently low to reduce the likelihood of solder ball joint embrittlement.  
   
   
       18 . The intermediate structure of  claim 16  wherein the gold coating on said second bond pads has a thickness of between about 0.1 and 0.3 microns.  
   
   
       19 . The intermediate structure of  claim 16  wherein said first bond pads have a gold coating thickness of approximately 0.5 microns.  
   
   
       20 . The intermediate structure of  claim 16  wherein said first bond pads and said second bond pads are all contained on the same planar surface.