Lead-Free Solder with Improved Properties at Temperatures >150°C
Lead-free solders based on an Sn—In—Ag solder alloy contain 88 to 98.5 wt. % Sn, 1 to 10 wt. % In, 0.5 to 3.5 wt. % Ag, 0 to 1 wt. % Cu, and a doping with a crystallization modifier, the crystallization modifier preferably being a maximum of 100 ppm neodymium.
1 .- 11 . (canceled)
12 . A lead-free solder based on an Sn—In—Ag solder alloy containing:
88 to 98.5 wt. % Sn,
1 to 10 wt. % In,
0.5 to 3.5 wt. % Ag,
0 to 1 wt. % Cu, and
a doping with a crystallization modifier, which inhibits growth of intermetallic phases in the solder, when solidified.
13 . The lead-free solder according to claim 1 , wherein the alloy contains:
88 to 98.5 wt. % Sn,
1 to 8 wt. % In,
0.5 to 3.5 wt. % Ag,
0 to 1 wt. % Cu,
0 to 3 wt. % Ga, Sb, Bi in total,
up to 1 wt. % additives or impurities, and
a doping with a crystallization modifier.
14 . The lead-free solder according to claim 12 , wherein the crystallization modifier is neodymium and has a concentration of 100 ppm maximum.
15 . The lead-free solder according to claim 12 , wherein the alloy comprises between 1.5 and 5 wt. % indium.
16 . The lead-free solder according to claim 12 , wherein the alloy comprises between 1 and 3 wt. % silver.
17 . The lead-free solder according to claim 12 , wherein the alloy has a melting temperature above 210° C.
18 . The lead-free solder according to claim 12 , wherein formation of Ag 3 Sn phases in the solder results with a star shape under a temperature load.
19 . The lead-free solder according to claim 12 , wherein the crystallization modifier is dissolved in the alloy matrix.
20 . A method for production of a solder according to claim 14 , comprising steps of producing a master alloy of Nd with one component of the Sn—In—Ag alloy, and diluting the master alloy in remaining components of the Sn—In—Ag alloy.
21 . The lead-free solder according to claim 12 , wherein the solder is present in a device in wafer bumping technology.
22 . A solder point made from the lead-free solder according to claim 12 , wherein the solder point is present in a device used at temperatures between 140 and 200° C.
23 . The solder point according to claim 22 , wherein the solder point is present in a device used at temperatures between 150 and 190° C.