SOLDER ALLOY FOR ELECTRODE FOR JOINING ELECTRONIC COMPONENT AND SOLDERING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To prevent lead component from being contained in solder joints and thus improve repeated thermal fatigue resistance characteristics in high- temperature environment, by using solder alloy for electrodes for joining electronic components and using specific quantities of Sn, Ag and Cu as the major components of the alloy. SOLUTION: A solder alloy for electrodes for joining electronic components uses Sn, Ag and Cu as its major components with their weight ratio set to 92-97wt.% for Sn, 3.0-6.0wt.% for Ag and 0.1-2.0wt.% for Cu. Adding a small quantity of Ag to Sn-based solder obtains an alloy having microminiature alloy structure, excellent in thermal fatigue resistance characteristic and further increases its melting point. Further, adding a small quantity of Cu produces an intermetallic compound and enhances mechanical joining strength. Moreover, adding a small quantity of Bi improves wettability. Furthermore, adding a small quantity of In improves the elongation characteristic and thermal fatigue resistance characteristic of the alloy.