Lead-free solder compositions

Abstract

Disclosed is a high temperature, high performance lead-free solder alloy comprising effective amounts of tin, copper, silver, bismuth, and antimony and having a liquidus temperature above 215° C. More particularly, several lead-free solder alloys are disclosed that comprise about (i) at least about 90% Sn, 0.2 to 5.0% Cu, 0.05 to 5.0% Bi; or (ii) at least about 75% Sn, 0.5 to 7.0% Cu, 0.05 to 18% Sb; or (iii) at least about 67% Sn, 3 to 15% Ag, 0.01 to 18% Sb; (iv) at least about 78% Sn, 0.8 to 7.0% Cu, 4 to 15% Ag; (v) at least about 96% Sn, and at least one of 0.01 to 2.0% Ni, and 0.01 to 2.0% Co; (vi) at least about 90% Sn, 0.05 to 5.0% Bi, and 0 to 5.0% Sb; and (vii) at least about 90% Sn, 0.2 to 0.9% Cu, and 0.1 to 5.0% Bi.

I claim:  
     
         1 . A lead-free solder alloy selected from the group consisting of: 
 (i) an alloy including at least about 90% Sn, 0.2 to 5.0% Cu, and 0.05 to 5.0% Bi;    (ii) an alloy including at least about 75% Sn, 0.5 to 7.0% Cu, 0.05 to 18% Sb;    (iii) an alloy including at least about 67% Sn, 3 to 15% Ag, and 0.01 to 18% Sb;    (iv) an alloy including at least about 78% Sn, 0.8 to 7.0% Cu, and 4 to 15% Ag;    (v) an alloy including at least about 96% Sn, and at least one of 0.01 to 2.0% Ni, and 0.01 to 2.0% Co;    (vi) an alloy including at least about 90% Sn, 0.05 to 5.0% Bi, and 0 to 5.0% Sb; and    (vii) an alloy including at least about 90% Sn, 0.2 to 0.9% Cu, and 0.1 to 5.0% Bi.    
     
     
         2 . The lead-free solder alloy of  claim 1  having a liquidus melting temperature greater than 215° C.  
     
     
         3 . The lead-free solder alloy of  claim 1 , wherein the alloy is alloy (i) and includes about 90 to 99% Sn, 0.2 to 5.0% Cu, and 0.05 to 5.0% Bi.  
     
     
         4 . The lead-free solder alloy of  claim 3 , wherein the solder alloy composition comprises about 96.0% Sn, 3.0% Cu, and 1.0% Bi.  
     
     
         5 . The lead-free solder alloy of  claim 1 , wherein the alloy is alloy (ii) and includes about 75 to 99% Sn, 0.5 to 7.0% Cu, and 0.05 to 18% Sb.  
     
     
         6 . The lead-free solder alloy of  claim 5 , wherein the solder alloy composition comprises about 82% Sn, 3% Cu, and 15% Sb.  
     
     
         7 . The lead-free solder alloy of  claim 1 , wherein the alloy is alloy (iii) and includes about 67 to 97% Sn, 3 to 15% Ag, and 0.01 to 18% Sb.  
     
     
         8 . The lead-free solder alloy of  claim 7 , wherein the solder alloy composition comprises about 75% Sn, 10% Ag, and 15% Sb.  
     
     
         9 . The lead-free solder alloy of  claim 7 , wherein the solder alloy composition comprises about 93.5% Sn, 5% Ag, and 1.5% Sb.  
     
     
         10 . The lead-free solder alloy of  claim 1 , wherein the alloy is alloy (iv) and includes about 78 to 96% Sn, 0.8 to 7.0% Cu, and 4 to 15% Ag.  
     
     
         11 . The lead-free solder alloy of  claim 10 , wherein the solder alloy composition comprises about 87% Sn, 3% Cu, and 10% Ag.  
     
     
         12 . The lead-free solder alloy of  claim 1 , wherein the alloy is alloy (v) and includes about 96 to 99% Sn, and at least one of 0.01 to 2.0% Ni, and 0.01 to 2% Co.  
     
     
         13 . The lead-free solder alloy of  claim 12 , wherein the solder alloy composition comprises about 99.3% Sn, 0.2% Ni, and 0.5% Co.  
     
     
         14 . The lead-free solder alloy of  claim 1 , wherein the alloy is alloy (vi) and includes about 90 to 99% Sn, 0.05 to 5.0% Bi, and 0 to 5.0% Sb.  
     
     
         15 . The lead-free solder alloy of  claim 14 , wherein the solder alloy composition comprises about 98.5% Sn, 1% Bi, and 0.5% Sb.  
     
     
         16 . The lead-free solder alloy of  claim 1 , wherein the alloy is alloy (vii) and includes about 90 to 99% Sn, 0.2 to 0.9% Cu, and 0.1 to 5.0% Bi.  
     
     
         17 . The lead-free solder alloy of  claim 16 , wherein the solder alloy composition comprises about 98.3% Sn, 0.7% Cu, and 1% Bi.  
     
     
         18 . The lead-free solder alloy of  claim 16 , wherein the solder alloy exhibits a tensile strength and fatigue life at 0.2% strain greater than a Sn/Cu eutectic composition of 99.3Sn/0.7Cu.