Method of forming composite solder by cold compaction and composite solder

Abstract

A reinforced solder is formed by mixing particles of a solder material capable of forming a metal matrix and a reinforcing particulate to form a particulate mixture; compressing the mixture at room temperature to form a solid compact; and sintering the compact to form a particulate composite in which the reinforcing particulate is embedded in a metal matrix formed from the solder material. The solder material can be a lead-free solder material. There is also provided a reinforced solder which includes a lead-free metal matrix and a reinforcing particulate embedded in the metal matrix. The metal matrix includes a combination of tin, copper, silver, and indium having volume ratios of about 91.4:0.5:4.1:4. The reinforcing particulate has an average diameter less than 100 nm. The reinforced solder has a melting point between 180° C. to 230° C.

1 . A method of forming reinforced solder, comprising: 
 mixing particles of a solder material capable of forming a metal matrix and a reinforcing particulate to form a particulate mixture;    compressing said mixture at room temperature to form a solid compact; and    sintering said compact to form a particulate composite in which said reinforcing particulate is embedded in a metal matrix formed from said solder material.    
   
   
       2 . The method of  claim 1 , wherein said solder material is lead free solder material.  
   
   
       3 . The method of  claim 2 , wherein said solder material is Viromet.  
   
   
       4 . The method of  claim 1 , wherein said reinforcing particulate comprises a ceramic.  
   
   
       5 . The method of  claim 4 , wherein said ceramic comprises Al 2 O 3 .  
   
   
       6 . The method of  claim 5 , wherein said reinforcing particulate has an average diameter less than 100 nm.  
   
   
       7 . The method of  claim 1 , further comprising extruding said compact.  
   
   
       8 . The method of  claim 1 , wherein said mixing comprises blending said mixture.  
   
   
       9 . The method of  claim 1 , wherein said compact has a melting temperature at a first temperature and said sintering comprises heating said compact in an inert gas at second temperature between about 70% to about 90% of said first temperature.  
   
   
       10 . The method of  claim 9  wherein said second temperature is between about 84° C. and 163° C.  
   
   
       11 . The method of  claim 9 , wherein said second temperature is about 150° C.  
   
   
       12 . The method of  claim 2 , wherein said lead free solder material is a lead-free metal alloy.  
   
   
       13 . The method of  claim 12 , wherein said lead-free metal alloy comprises an combination of tin, copper, silver, and indium.  
   
   
       14 . The method of  claim 5 , wherein the proportion of said reinforcing particulate is between 0 to about 5% by volume of said mixture.  
   
   
       15 . The method of  claim 1 , further comprising coating said compact with colloidal graphite.  
   
   
       16 . The method of  claim 1 , wherein said reinforcing particulate is made of a material having a density lower than the density of said solder material.  
   
   
       17 . A reinforced solder formed in accordance with the method of  claim 1 .  
   
   
       18 . A reinforced solder comprising a lead-free metal matrix and a reinforcing particulate embedded in said metal matrix, said metal matrix comprises a combination of tin, copper, silver, and indium having volume ratios of about 91.4:0.5:4.1:4, said reinforcing particulate having an average diameter less than 100 nm, and said reinforced solder having a melting point between 180° C. to 230° C.  
   
   
       19 . The reinforced solder of  claim 18 , wherein said reinforcing particulate is made of alumina and has an average diameter of about 50 nm.  
   
   
       20 . The reinforced solder of  claim 19 , wherein said reinforced solder has a density lower than that of a monolithic solder formed from a material having said combination.  
   
   
       21 . The reinforced solder of  claim 19 , wherein said reinforced solder has porosity up to 6.3%.  
   
   
       22 . The reinforced solder of  claim 19 , wherein said reinforced solder has a coefficient of thermal expansion lower than that of a monolithic solder formed from a material having said combination.  
   
   
       23 . The reinforced solder of  claim 19 , wherein said reinforced solder has hardness higher than that of a monolithic solder formed from a material having said combination.  
   
   
       24 . The reinforced solder of  claim 19 , wherein said reinforced solder has 0.2% yield strength higher than 56 MPa.  
   
   
       25 . The reinforced solder of  claim 19 , wherein said reinforced solder has an ultimate tensile strength higher than 60 MPa.  
   
   
       26 . The reinforced solder of  claim 19 , wherein said reinforced solder has ductility lower than 37%.