Lead-free and antimony-free tin solder reliable at high temperatures

Abstract

A lead-free, antimony-free tin solder which is reliable at high temperatures and comprises from 3.5 to 4.5 wt.% of silver, 2.5 to 4 wt.% of bismuth, 0.3 to 0.8 wt.% of copper, 0.03 to 1 wt.% nickel, 0.005 to 1 wt.% germanium, and a balance of tin, together with any unavoidable impurities.

1 . A lead-free, antimony-free solder alloy comprising:
 (a) 3 to 5 wt% of silver   (b) 2.5 to 5 wt% of bismuth   (c) 0.3 to 2 wt% of copper   (d) at least one of the following elements
 up to 1 wt.% of nickel 
 up to 1 wt.% of titanium 
 up to 1 wt.% of cobalt 
 up to 3.5 wt.% of indium 
 up to 1 wt.% of zinc 
 up to 1 wt.% of arsenic 
   (e) optionally one or more of the following elements
 0 to 1 wt.% of manganese 
 0 to 1 wt. % of chromium 
 0 to 1 wt.% of germanium 
 0 to 1 wt.% of iron 
 0 to 1 wt.% of aluminum 
 0 to 1 wt.% of phosphorus 
 0 to 1 wt.% of gold 
 0 to 1 wt.% of gallium 
 0 to 1 wt.% of tellurium 
 0 to 1 wt.% of selenium 
 0 to 1 wt.% of calcium 
 0 to 1 wt.% of vanadium 
 0 to 1 wt.% of molybdenum 
 0 to 1 wt.% of platinum 
 0 to 1 wt.% of magnesium 
 0 to 1 wt.% of rare earths 
   (f) the balance tin, together with any unavoidable impurities;   wherein the alloy affirmatively contains said Ni in a concentration of 0.01 to 1 wt%; and   wherein the alloy affirmatively contains said Ge in a concentration of 0.005 to 1 wt%.   
     
     
         2 . The solder alloy according to  claim 1 , wherein the alloy comprises:
 from 3.5 to 4.5 wt.% of silver;   from 2.5 to 4 wt.% of bismuth;   from 0.3 to 0.8 wt.% of copper;   from 0.03 to 1 wt.% nickel;   from 0.005 to 1 wt.% germanium,   the balance tin, together with any unavoidable impurities.   
     
     
         3 . The solder alloy according to  claim 2 , wherein the alloy comprises from 2.8 to 4 wt% bismuth. 
     
     
         4 . The solder alloy according to  claim 2 , wherein the alloy comprises from 0.6 to 0.8 wt% copper. 
     
     
         5 . The solder alloy according to  claim 2 , wherein the alloy comprises from 0.03 to 0.6 wt.% nickel. 
     
     
         6 . The solder alloy according to  claim 2 , wherein the solder alloy consists essentially of:
 from 3.5 to 4.5 wt.% of silver;   from 2.8 to 4 wt.% bismuth;   from 0.4 to 0.7 wt.% copper:   from 0.1 to 0.3 wt.% nickel: and   from 0.005 to 0.01 wt.% germanium,   the balance tin, together with any unavoidable impurities.   
     
     
         7 . The solder alloy as claimed in  claim 2 , wherein the alloy has melting point of from 195 to 222° C. 
     
     
         8 . The solder alloy as claimed in  claim 2  in the form of a bar, a stick, a solid or flux cored wire, a foil or strip, or a powder or paste (powder plus flux blend), or solder spheres for use in ball grid array joints or chip scale packages, or other pre-formed solder pieces, with or without a flux core or a flux coating. 
     
     
         9 . A soldered joint comprising an alloy as defined in  claim 2 . 
     
     
         10 . A method of forming a solder joint comprising:
 (i) providing two or more work pieces to be joined;   (ii) providing a solder alloy as defined in  claim 2 ; and   (iii) heating the solder alloy in the vicinity of the work pieces to be joined.   
     
     
         11 . The solder alloy as claimed in  claim 2 , wherein the solder alloy comprises from 0.005 to 1 wt% of a rare earth metal. 
     
     
         12 . The solder alloy as claimed in  claims 11 , wherein the rare earth metal is cerium. 
     
     
         13 . A lead-free, antimony-free solder alloy comprising:
 (a) 3 to 5 wt% of silver;   (b) 2.5 to 5 wt% of bismuth;   (c) 0.3 to 2 wt% of copper;   (d) 0.03 to 1 wt.% nickel; and   (e) 0.005 to 1 wt% of a rare earth metal;   the balance tin, together with any unavoidable impurities.   
     
     
         14 . The solder alloy as claimed in  claim 13 , where the rare earth metal is cerium. 
     
     
         15 . The solder alloy as claimed in  claim 13 , wherein the alloy contains germanium in a concentration of 0.005 to 1 wt%. 
     
     
         16 . A lead-free, antimony-free solder alloy comprising:
 (a) 3.5 to 5 wt% of silver;   (b) 2 to 5 wt% of bismuth;   (c) 0.3 to 2 wt% of copper;   (d) 0.03 to 1 wt.% nickel; and   (e) at least one of 0.01 to 0.2 wt% cerium, 0.01 to 0.08 wt% lanthanum, or 0.01 to 0.08 wt% neodymium;   the balance tin, together with any unavoidable impurities.   
     
     
         17 . The solder alloy as claimed in  claim 16 , wherein the alloy contains germanium in a concentration of 0.005 to 1 wt%. 
     
     
         18 . A lead-free, antimony-free solder alloy comprising:
 (a) 3.5 to 5 wt% of silver;   (b) 2 to 5 wt% of bismuth;   (c) 0.3 to 2 wt% of copper; and   (d) 0.01 to 3.5 wt.% indium; and   the balance tin, together with any unavoidable impurities.   
     
     
         19 . The solder alloy as claimed in  claim 18 , wherein the alloy contains nickel in a concentration of 0.03 to 1 wt.%. 
     
     
         20 . The solder alloy as claimed in  claim 19 , wherein the alloy contains germanium in a concentration of 0.005 to 1 wt%.