Effects of process parameters on the soldering behavior of the eutectic Sn-Zn solder on Cu substrate

The effects of process parameters such as flux, dipping temperature and the heat-treatment on the soldering behaviors of the eutectic solder (composition: 91Sn-9Zn) hot-dipped on Cu substrates were investigated. The most suitable flux as tested was oleic acid for the eutectic Sn-Zn solder system hot-dipped on Cu substrate for the solder coverage. The adhesion strength obtained increased from 9.6 +/-0.6 MPa to 11.9 +/-0.6 MPa when the dipping temperature increased from 250 degreesC to 300 degreesC. However, it decreased from 11.9 +/-0.6 MPa to 5.2 +/-2.2 MPa as the sample was heated at 150 degreesC for 1200 h. Planar gamma- Cu5Zn8 isolate-shaped eta -Cu6Sn5 intermetallic layers were found in the bulk sample after heating at 150 degreesC for 300 h but was not found in the as-cast sample. In the plate samples, scallop-shaped gamma -Cu5Zn8/inverted trigonal-shaped eta -Cu6Sn5 intermetallic layers were found after heating at 150 degreesC for 600 h. Some pores were found at the interface between gamma -Cu5Zn8 intermetallic compound (IMC) and the solder alloy, which might come from the formation and growth of IMCs and decreased the adhesion strength. (C) 2000 Kluwer Academic Publishers.