Modification of solder alloy compositions to suppress interfacial void formation in solder joints

Abstract

A solder joint comprising a solder capture pad on a substrate having a circuit; and a lead containing or a lead free solder selected from the group comprising Sn—Ag—Cu solder, Sn—Cu solder and Sn—Ag solder adhered to the solder capture pad; the solder selected from the group comprising between 0.1 and 6.0 percent by weight Zn. A solder joint, comprising a solder capture pad on a substrate having a circuit; and a Sn—Cu lead free solder adhered to the solder capture pad, the solder comprising between 0.1 and 6.0% by weight Zn. Formation of voids at an interface between the solder and the solder capture pad is suppressed. A method for forming solder joints using the solders.

1 . A method for forming a solder joint on a solder capture pad of a substrate having a circuit, comprising:
 applying to said capture pad a lead solder, and   adhering said solder to said solder capture pad by melting and cooling said solder;   said solder comprising between 0.1 and 6.0 percent by weight Zn, so that formation of voids at an interface between said solder and said solder capture pad is suppressed.   
     
     
         2 . The method of  claim 1 , wherein the solder further comprises 0.5% by weight Bi. 
     
     
         3 . The method of  claim 1 , wherein said solder is heated to a temperature of less than 280° C. to melt said solder. 
     
     
         4 . The method of  claim 1 , wherein said solder is heated to a temperature of between 217 and 280 degrees C. to melt said solder. 
     
     
         5 . The method of  claim 1 , wherein said solder capture pad is comprised of copper. 
     
     
         6 . The method of  claim 5 , wherein said solder capture pad is annealed prior to adhering said solder to said solder capture pad. 
     
     
         7 . The method of  claim 5 , wherein said solder capture pad is annealed at a temperature of approximately 550° C. prior to adhering said solder to said solder capture pad. 
     
     
         8 . The method of  claim 1 , further comprising placing an organic solderability preservative on said solder capture pad prior to applying said solder to said pad. 
     
     
         9 . The method of  claim 1 , wherein the solder is a SnPb solder. 
     
     
         10 . The method of  claim 9 , wherein the SnPb solder contains substantially 37% by weight Pb.