Lead-free solder alloy and a manufacturing process of electric and electronic apparatuses using such a lead-free solder alloy

Abstract

A lead-free solder alloy composition containing Sn, Ag and Bi, with respective concentrations set such that the lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.

What is claimed is:  
     
         1 . A lead-free solder ally composition containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.  
     
     
         2 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said solder alloy composition contains Sn with an amount of 96.5×(100−X)/100 in wt % and Ag with an amount of 3.5×(100−X)/100 in wt %, wherein X represents the amount of Bi represented in wt %.  
     
     
         3 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said solder alloy composition contains Ag with an amount not exceeding 4.0 wt %, Bi with an amount equal to or larger than 1.0 wt %, and Sn with an amount not exceeding 95.0 wt %.  
     
     
         4 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said lead-free solder alloy composition contains Ag with an amount between 1.0 wt % and 4.0 wt %, Bi with an amount between 1.0 wt % and 40.0 wt %, and Sn with an amount between 55.0 wt % and 95.0 wt %.  
     
     
         5 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said lead-free solder alloy composition contains Ag with an amount of approximately 3.3 wt %, Bi with an amount of approximately 5.0 wt %, and Sn with an amount of approximately 91.7 wt %.  
     
     
         6 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said lead-free solder alloy composition contains Ag with an amount of approximately 3.1 wt %, Bi with an amount of approximately 10.0 wt %, and Sn with an amount of approximately 86.9 wt %.  
     
     
         7 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said lead-free solder alloy composition contains Ag with an amount of 3.0 wt %, Bi with an amount of 15.0 wt %, and Sn with an amount of 82.0 wt %.  
     
     
         8 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said lead-free solder alloy composition contains Ag with an amount of 2.8 wt %, Bi with an amount of 20.0 wt %, and Sn with an amount of 77.2 wt %.  
     
     
         9 . A lead-free solder composition as claimed in  claim 1 , wherein said leadfree solder alloy composition contains Ag with an amount of 2.4 wt %, Bi with an amount of 30.0 wt %, and Sn with an amount of 67.6 wt %.  
     
     
         10 . A lead-free solder alloy composition as claimed in  claim 1 , wherein said lead-free solder alloy composition contains Ag with an amount of 2.1 wt %, Bi with an amount of 40.0 wt %, and Sn with an amount of 57.9 wt %.  
     
     
         11 . A lead-free solder powder comprising: 
 a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 μm;    each of said lead-free solder particles containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.    
     
     
         12 . A lead-free solder paste, comprising: 
 a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 μm; each of said lead-free solder particles containing Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said solder alloy; said lead-free solder powder being contained with a proportion of 80.0-95.0 wt %; and    a mixture of an amine halide, a polyhydric alcohol; and a polymer, with a proportion of 20.0-5.0 wt %.    
     
     
         13 . A lead-free solder paste, comprising: 
 a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 μm; each of said lead-free solder particles containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder particle has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered; and    a mixture of an amine halide, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.    
     
     
         14 . A lead-free solder paste, comprising: 
 a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 μm; each of said lead-free solder particles containing Sn, Bi and In, with respective concentrations set such that said lead-free solder powder has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered, said lead-free solder powder being contained with a proportion of 80.0-95.0 wt %; and    a mixture of an organic acid, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.    
     
     
         15 . A lead-free solder paste, comprising: 
 a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 μm; each of said lead-free solder particles containing Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said solder alloy; said lead-free solder powder being contained with a proportion of 80.0-95.0 wt %; and    a mixture of an organic acid, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.    
     
     
         16 . A lead-free solder paste, comprising: 
 a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 μm; each of said lead-free solder particles containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered; and    a mixture of an organic acid, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.    
     
     
         17 . A printed circuit board, comprising: 
 a substrate;    a conductor pattern provided on said substrate; and    a lead-free solder alloy covering said conductor pattern, said lead-free solder alloy containing: Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a component to be soldered upon said substrate.    
     
     
         18 . An electronic component, comprising: 
 an electronic component body;    an electrode projecting from said electronic component body; and    a lead-free solder alloy covering said conductor pattern, said lead-free solder alloy containing: Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a component to be soldered upon said substrate.    
     
     
         19 . An electronic apparatus, comprising: 
 a substrate;    a conductor pattern provided on said substrate;    an electronic component mounted upon said substrate in electrical connection with said conductor pattern, said electronic component having an electrode projecting therefrom; and    a lead-free solder alloy connecting said electrode to said conductor pattern, said lead-free solder alloy containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of said electronic component.