Morphologies and evolution of intermetallic compounds formed between Sn1.0Ag0.7Cu composite solder and Cu substrate

Abstract

This study investigated the morphologies of the intermetallic compounds (IMC) formed during soldering reaction between Sn1.0Ag0.7Cu–1.0SnO2 composite solder and Cu substrate at various temperatures. The prism-type Cu6Sn5 forms when the soldering temperature is 260 or 280 °C, while those grains transform from prism type to scallop type at the temperatures of 300 and 320 °C. It can be found that the morphologies of Cu6Sn5 grains affect adsorption of Ag3Sn nanoparticles during soldering reaction. The scallop-type grains with a higher growth rate need to adsorb large amounts of Ag3Sn particles. In terms of mechanical behavior, the shear strength of solder joint is improved from 40 to 46 MPa at soldering temperature of 300 °C. In addition, the thickness of IMC increases with the extension of aging time. During aging, the morphology of Cu6Sn5 grains remains scallop type, but the number of Ag3Sn nanoparticles is reduced largely. The scallop-type Cu6Sn5 can increase in size and flatten in morphology with the aging time increasing. When the soldering temperature changes from 260 to 360 °C, the morphologies of Cu6Sn5 grains transformed from prism-type to scallop-type. The shear strength of solder joint is improved from 40 to 46 Mpa at 300 °C soldering temperature