Formation and growth of intermetallic phases at the interface in the Cu/ Sn-Zn-Ag-Cu /Cu joints

This work presents the effect of soldering time and temperature on the microstructure and electrical properties of Cu/solder/Cu joints, where solder are Sn14.7Zn0.5Ag1.0Cu and Sn14.7Zn1.0Ag1.0Cu0.1Al (at.%) alloys. Soldering of Cu/solder/Cu joints was performed for 3, 8, 15, 30 and 60 min at 250 degrees C, and at 230 and 280 degrees C for 8 min, with the use of flux. Aging of Cu/solder/Cu joints was carried out at 170 degrees C for 1, 10 and 30 days. After soldering, it was found that Cu5Zn8 and AgZn3 are formed at the solder/Cu interface. The thickness of Cu5Zn8 increases with time, while layer of AgZn3 grows up to 15 min and later diminishes. Precipitates of AgZn3 are found in the central part of joints, with their number increasing with soldering temperature. Higher content of Ag and addition of Al hinder growth of Cu5Zn8. During aging Cu6Sn5 starts to appear at the interface on the expense of Cu5Zn8. The electrical resistivity of joints decreases with time and temperature of soldering but increases after aging. (C) 2015 Elsevier B.V. All rights reserved.