Cu6Sn5 precipitation during Sn-based solder/Cu joint solidification and its effects on the growth of interfacial intermetallic compounds

A study was performed on the precipitation behavior of Cu6Sn5 during the solidification of Sn-based solders/Cu joints and its effect on the growth of interfacial intermetallic compounds (IMCs). During cooling, Cu in molten solder precipitates in the form of Cu6Sn5 both within the solder matrix and at the interface. The precipitation at the interface can greatly affect the interfacial IMC morphology and thickness but cannot change the interfacial IMC orientation. In general, additional Cu6Sn5 will precipitate at the solder/Cu interface when the Cu content is increased in the molten solder during soldering and when the cooling rate decreases during solder solidification. If the Cu content in the molten solder is sufficiently high, during cooling, the precipitated Cu6Sn5 will develop a prismatic morphology with the exposed surface indexed as (10-10) along the [0 0 0 1] direction of the existing Cu6Sn5 grains at the interface. (c) 2013 Elsevier B.V. All rights reserved.