Studies on wetting behavior and interfacial reaction between Zn-25Sn-xCu-yTi high-temperature lead-free solder alloys and Cu substrate

Abstract

The Zn-Sn solder of high Zn content could be a great alternative high temperature Pb-free solder But high content of Zn may give rise to poor wettability Cu and Ti were selected in this study as alloying elements for improving the wettability of Zn-25Sn solder alloys The present study investigated the wetting behavior and intermetallic compound formation behavior between Zn-25Sn-x(0 1-0 3)Cu-(0 01-0 03)Ti solder alloys and Cu substrate The wetting behavior were investigated using wetting balance at Cu substrate with flux at a temperature ~40°C above the liquidus temperature of the Zn-25Sn solder The results indicate that a combination addition of Ti and Cu improves the performance in terms of wetting time and wetting force Higher addition of Cu in the concentration range investigated did not further enhance the wettability of solder alloy On the other hand continuous addition of Ti improves the wettability of Zn-25Sn-xCu-yTi The wetting interaction formed CuZn5 and Cu5Zn8 IMCs at the solder/Cu interface with Cu5Zn8 as the dominant IMC layer The elemental distribution analysis pointed out Ti tends to accumulate at the solder surface layer and in the interfacial layer The adsorption of Ti lowers tension between the solder alloy and the substrate The combination of Cu and Ti also increaseas the thickness of IMC layer and decreasing the activation energy of Cu5Zn8 IMC formation in the Zn-25Sn system

Date of Award	2020
Original language	English
Supervisor	Kwang-Lung Lin (Supervisor)