Pb-free solder composition and soldered article

Abstract

Provided is a Pb-free solder composition having an excellent heat resistance which does not damage a glass substrate and parts on the substrate when the soldering is carried out on to an electrode pattern formed on the substrate. The Pb-free solder composition contains, for example, not less than about 90% by weight of Bi, from about 0.1% to 9.9% by weight of Ag and from about 0.1% to 3.0% by weight of Sb, based on the whole solder composition.

1 . A solder composition which is Pb-free and comprises: 
 at least about 90% by weight of Bi as a first metallic element;    an amount of not more than about 9.9% by weight of a second metallic element which forms a binary eutectic with said first metallic element; and    about 0.1% to 3.0% by weight of a third metallic element which causes a solid and liquid to coexist at about the solidification temperature of said eutectic;    wherein all percents by weight are based on the whole solder composition, and    wherein said solder composition does not contain a low melting-point eutectic with a solidus temperature of less than about 200° C.    
     
     
         2 . A Pb-free solder composition according to  claim 1 , wherein said second metallic element is at least 0.1% by weight of said whole solder composition.  
     
     
         3 . A Pb-free solder composition according to  claim 2 , wherein said second metallic element is Ag, and said third metallic element is at least one member selected from the group consisting of about 0.1% to 0.5% by weight of Sn, about 0.1% to 0.3% by weight of Cu, about 0.1% to 0.5% by weight of In, about 0.1% to 3.0% by weight of Sb, and about 0.1% to 3.0% by weight of Zn.  
     
     
         4 . A Pb-free solder composition according to  claim 3 , wherein said third metallic element further comprises at least one element selected from the group consisting of Ge and P.  
     
     
         5 . A Pb-free solder composition according to  claim 4 , wherein the amount of Ge and P is about 0.01% to 0.1% by weight of said whole solder composition.  
     
     
         6 . A Pb-free solder composition according to  claim 5 , wherein said first metallic element is at least about 94.5% by weight and said second metallic element is about 0.15% to 3.0% by weight, based on said whole solder composition.  
     
     
         7 . A Pb-free solder composition according to  claim 1 , wherein said third metallic element is at least one element selected from the group consisting of Sn, Cu, In, Sb and Zn.  
     
     
         8 . A Pb-free solder composition according to  claim 1 , wherein said third metallic element further comprises at least one element selected from the group consisting of Ge and P.  
     
     
         9 . A Pb-free solder composition according to  claim 8 , wherein the amount of Ge and P is about 0.01% to 0.1% by weight of said whole solder composition.  
     
     
         10 . A Pb-free solder composition according to  claim 1 , wherein said first metallic element is at least about 94.5% by weight and said second metallic element is about 0.15% to 3.0% by weight, based on said whole solder composition.  
     
     
         11 . A Pb-free soldered article comprising: 
 a substrate having a conductive pattern on the surface; and    a Pb-free solder composition according to  claim 10  electrically and mechanically connected to said conductive pattern.    
     
     
         12 . A Pb-free soldered article according to  claim 11 , wherein 
 said substrate is a glass substrate having an electrode pattern on the surface; and a lead wire connected to said electrode via said Pb-free solder composition.    
     
     
         13 . A Pb-free soldered article comprising: 
 a substrate having a conductive pattern on the surface; and    a Pb-free solder composition according to  claim 8  electrically and mechanically connected to said conductive pattern.    
     
     
         14 . A Pb-free soldered article according to  claim 13 , wherein 
 said substrate is a glass substrate having an electrode pattern on the surface; and a lead wire connected to said electrode via said Pb-free solder composition.    
     
     
         15 . A Pb-free soldered article comprising: 
 a substrate having a conductive pattern on the surface; and    a Pb-free solder composition according to  claim 7  electrically and mechanically connected to said conductive pattern.    
     
     
         16 . A Pb-free soldered article according to  claim 16 , wherein 
 said substrate is a glass substrate having an electrode pattern on the surface; and a lead wire connected to said electrode via said Pb-free solder composition.    
     
     
         17 . A Pb-free soldered article comprising: 
 a substrate having a conductive pattern on the surface; and    a Pb-free solder composition according to  claim 2  electrically and mechanically connected to said conductive pattern.    
     
     
         18 . A Pb-free soldered article according to  claim 17 , wherein 
 said substrate is a glass substrate having an electrode pattern on the surface; and    a lead wire connected to said electrode via said Pb-free solder composition.    
     
     
         19 . A Pb-free soldered article comprising: 
 a substrate having a conductive pattern on the surface; and    a Pb-free solder composition according to  claim 1  electrically and mechanically connected to said conductive pattern.    
     
     
         20 . A Pb-free soldered article according to  claim 19 , wherein 
 said substrate is a glass substrate having an electrode pattern on the surface; and a lead wire connected to said electrode via said Pb-free solder composition.