Solder composition

Abstract

The present invention relates to a lead-free solder composition having a low coefficient of thermal expansion to reduce the likelihood of thermal shock to a glass substrate. The solder composition includes a granular material added to lead-free solder where the granular material may include fused silica, zirconium oxide, Invar®, or any wettable, lead-free alloy such as 36% weight nickel or 64% weight iron and the solder may include tin, silver and bismuth. When a component is soldered to a glass substrate by the present invention and exposed to a substantial change in climatic temperature the granular material counteracts and adsorbs the stress caused by contraction of the solder, thereby preventing thermal shock to the glass substrate.

1 . A solder composition comprising: 
 a mixture of elements comprising tin (Sn) and silver (Ag); and    a granular additive which is at least about 3% of the solder composition by weight, the granular additive comprising a nickel iron alloy comprising about 36% nickel (Ni) and about 64% iron (Fe), by weight.    
     
     
         2 . The solder composition of  claim 1  in which the granular additive is pretreated with flux.  
     
     
         3 . The solder composition of  claim 2  in which the flux comprises zinc chloride, ammonium chloride and hydrochloric acid.  
     
     
         4 . The solder composition of  claim 1  in which the mixture of elements comprises by weight about 95%-97% tin (Sn) and about 5%-3% silver (Ag).  
     
     
         5 . The solder composition of  claim 1  in which the mixture of elements further comprises bismuth (Bi).  
     
     
         6 . The solder composition of  claim 5  in which the mixture of elements comprises by weight about 61%-39% tin (Sb), about 59%-37% bismuth (Bi), and about 1%-3% silver (Ag).  
     
     
         7 . The solder composition of  claim 1  in which the granular additive is about 30% of the solder composition by weight.  
     
     
         8 . The solder composition of  claim 7 , in which the mixture of elements comprises by weight about 95% tin (Sn), and about 5% silver (Ag).  
     
     
         9 . The solder composition of  claim 7  in which the mixture of elements comprises by weight about 75% tin (Sn), about 23% bismuth (Bi) and about 2% silver (Ag).  
     
     
         10 . The solder composition of  claim 1  in which the granular additive is about 20% of the solder composition by weight.  
     
     
         11 . The solder composition of  claim 10  in which the mixture of elements comprises by weight about 62% tin (Sn), about 36% bismuth (Bi) and about 2% silver (Ag).  
     
     
         12 . The solder composition of  claim 10  in which the mixture of elements comprises by weight about 72% tin (Sn), about 26% bismuth (Bi) and about 2% silver (Ag).  
     
     
         13 . The solder composition of  claim 10  in which the mixture of elements comprises by weight about 78% tin (Sn), about 20% bismuth (Bi) and about 2% silver (Ag).  
     
     
         14 . The solder composition of  claim 10  in which the mixture of elements comprises by weight about 83% tin (Sn), about 15% bismuth (Bi) and about 2% silver (Ag).  
     
     
         15 . The solder composition of  claim 10  in which the mixture of elements comprises by weight about 88% tin (Sn), about 10% bismuth (Bi) and about 2% silver (Ag).  
     
     
         16 . A solder composition comprising: 
 a mixture of elements comprising tin and silver; and    a granular additive comprising a material having a low coefficient of thermal expansion and being at least about 3% of the solder composition by weight.    
     
     
         17 . The solder composition of  claim 16  in which the granular additive comprises iron.  
     
     
         18 . The solder composition of  claim 16  in which the granular additive comprises iron and nickel.  
     
     
         19 . The solder composition of  claim 16  in which the granular additive is pretreated with flux.  
     
     
         20 . The solder composition of  claim 19  in which the flux comprises zinc chloride, ammonium chloride and hydrochloric acid.  
     
     
         21 . A method of forming a solder composition comprising: 
 forming a molten mixture of elements comprising tin and silver; and    adding a granular additive to the molten mixture of elements, the granular additive being at least about 3% of the solder composition by weight, the granular additive comprising a nickel iron alloy comprising about 36% nickel (Ni) and about 64% iron (Fe), by weight.    
     
     
         22 . The method of  claim 21  further comprising pretreating the granular additive with flux before adding the granular additive to the molten mixture of elements.  
     
     
         23 . The method of  claim 22  further comprising pretreating the granular additive with flux comprising zinc chloride, ammonium chloride and hydrochloric acid.  
     
     
         24 . The method of  claim 21  further comprising forming the molten mixture of elements to comprise by weight about 95%-97% tin (Sn) and about 5%-3% silver (Ag).  
     
     
         25 . The method of  claim 21  further comprising including bismuth in the molten mixture of elements.  
     
     
         26 . The method of  claim 25  further comprising forming the molten mixture of elements to comprise by weight about 61%-39% tin (Sn), about 59%-37% bismuth (Bi), and about 1%-3% silver (Ag).  
     
     
         27 . The method of  claim 21  further comprising adding an amount of the granular additive to comprise about 30% of the solder composition by weight.  
     
     
         28 . The method of  claim 27  further comprising forming the molten mixture of elements to comprise by weight about 95% tin (Sn) and about 5% silver (Ag).  
     
     
         29 . The method of  claim 27  further comprising forming the molten mixture of elements to comprise by weight about 75% tin (Sn), about 23% bismuth and about 2% silver.  
     
     
         30 . The method of  claim 21  further comprising adding an amount of the granular additive to comprise about 20% of the solder composition by weight.  
     
     
         31 . The method of  claim 30  further comprising forming the molten mixture of elements to comprise by weight about 62% tin (Sn), about 36% bismuth (Bi) and about 2% silver (Ag).  
     
     
         32 . The method of  claim 30  further comprising forming the molten mixture of elements to comprise by weight about 72% tin (Sn), about 26% bismuth (Bi) and about 2% silver (Ag).  
     
     
         33 . The method of  claim 30  further comprising forming the molten mixture of elements to comprise by weight about 78% tin (Sn), about 20% bismuth (Bi) and about 2% silver (Ag).  
     
     
         34 . The method of  claim 30  further comprising forming the molten mixture of elements to comprise by weight about 83% tin (Sn), about 15% bismuth (Bi) and about 2% silver (Ag).  
     
     
         35 . The method of  claim 30  further comprising forming the molten mixture of elements to comprise by weight about 88% tin (Sn), about 10% bismuth (Bi) and about 2% silver (Ag).  
     
     
         36 . A method of forming a solder composition comprising: 
 forming a molten mixture of elements comprising tin and silver; and    adding a granular additive to the molten mixture of elements, the granular additive comprising a material with a low coefficient of thermal expansion and being at least about 3% of the solder composition by weight.    
     
     
         37 . The method of  claim 36  further comprising adding a granular additive comprising iron.  
     
     
         38 . The method of  claim 36  further comprising adding a granular additive comprising iron and nickel.  
     
     
         39 . The method of  claim 36  further comprising pretreating the granular additive with flux before adding the granular additive to the melting mixture of elements.  
     
     
         40 . The method of  claim 39  further comprising pretreating the granular additive with flux comprising zinc chloride, ammonium chloride and hydrochloric acid.