Environmental concerns are being raised over residues of lead, a constituent of solder, ending up in landfills. Increasing attention is therefore being focused on the potential application of lead-free soldering in electronics manufacturing.We studied the effect of adding Bi to Sn-Ag lead-free solders from the viewpoint of the reliability of quad flat package (QFP) solder joints. The solder joint strength, interface microstructure, and thermal cycle reliability were investigated and thefollowing results were obtained. The strength of QFP solder joints decreased with the addition of Bi. The interface microstructure changed with variation of the Bi content. In the thermal cycle test, changes in joint strength were shown to be independentof the Bi content in the Sn-Ag solders. The rate of crack generation in the solder joints increased with the addition of Bi.
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