Effects of thermal aging on growth behavior of interfacial intermetallic compound of dip soldered Sn/Cu joints

Abstract

Intermetallic compounds (IMCs) formations of Sn/Cu reaction couple prepared by dip soldering were studied with isothermal aging at four levels of temperatures (120, 150, 170 and 200 °C, respectively). It is found that an obvious scallop-type layer of Cu6Sn5 IMC formed between the liquid Sn solder and Cu substrates and a planar Cu3Sn IMC layer between Cu6Sn5 IMC layer and Cu substrates appears after solid-state aging treatment. A significant increment of IMC layer thickness is observed with increasing aging time as well as aging temperature. And it is further found that the thickness of IMC layer is linearly related to the square root of aging time during the aging process. The values of growth rate constants for the different solid state aging temperatures (120, 150, 170 and 200 °C) were calculated as 6.578 × 10−18, 1.595 × 10−17, 9.89 × 10−17 and 4.521 × 10−16 m2 s−1, respectively. The apparent activation energy calculated for the growth of the total IMC is 84.43 kJ mol−1. Moreover, The mean diameters of the Cu6Sn5 grains increased linearly with cubic root of aging time.