Lead-free solder alloys

Abstract

A lead-free solder alloy which has a relatively low melting temperature and which is suitable for soldering electronic devices consists essentially of from 5 to 9 mass % of Zn, from 2 to 15 mass % of Bi, optionally from 0.001 to 1 mass % of P or from 0.001 to 0.1 mass % of Ge, and a balance of Sn. The solder alloy has a liquidus temperature of at most 220° C.

What is claimed is:  
     
         1 . A lead-free solder alloy for use in soldering electronic devices to a printed circuit board, which consists essentially of: 
 from 5 to 9 mass % of Zn,    from 2 to 15 mass % of Bi, and    a balance of Sn.    
     
     
         2 . A lead-free solder alloy as set forth in  claim 1  wherein the total content of Zn and Bi is at most 18%.  
     
     
         3 . A lead-free solder alloy as set forth in  claim 1  wherein 5-8% of Zn is contained.  
     
     
         4 . A lead-free solder alloy as set forth in  claim 1  containing 5-10% of Bi.  
     
     
         5 . A lead-free solder alloy as set forth in  claim 1  having a liquidus temperature of at most 210° C.  
     
     
         6 . A lead-free solder alloy as set forth in  claim 1  having a solidus temperature of at least 160° C.  
     
     
         7 . A lead-free solder alloy for use in soldering electronic devices to a printed circuit board, which consists essentially of: 
 from 5 to 9 mass % of Zn,    from 2 to 15 mass % of Bi,    from 0.001 to 1 mass % of P and/or from 0.001 to 1 mass % of Ge, and    a balance of Sn.    
     
     
         8 . A lead-free solder alloy as set forth in  claim 7  wherein the total content of Zn and Bi is at most 18%.  
     
     
         9 . A lead-free solder alloy as set forth in  claim 7  wherein 5-8% of Zn is contained.  
     
     
         10 . A lead-free solder alloy as set forth in  claim 7  wherein 5-10% of Bi is contained.  
     
     
         11 . A lead-free solder alloy as set forth in  claim 7  having a liquidus temperature of at most 210° C.  
     
     
         12 . A lead-free solder alloy as set forth in  claim 7  having a solidus temperature of at least 160° C.