Effect of (Au,Ag)5Sn on the shear strength of Au–Sn/Ag joints
摘要
Ag is a widely used in electronic industry, Au–Sn eutectic is the common solder for electronic packaging. However, the interfacial reaction products and its effect on the shear strength of the Au–Sn/Ag joint is still unclear. Here, the Ag was soldered by using Au–Sn eutectic solder at 350 °C for 2–60 min, only the (Au,Ag)5Sn phase formed at the Au–Sn/Ag interface. With the extension of soldering time, the thickness of the (Au,Ag)5Sn phase gradually increases, increased from 8 μm at 5 min of soldering to 20 μm after 60 min of soldering. The Ag contents of (Au,Ag)5Sn phase were 20% and 26% after soldering for 5 min and 20 min, respectively. The Young’s modulus of the (Au,Ag)5Sn phase were 74 and 79 GPa, correspondingly. However, after soldering for 60 min, a significant Ag concentration gradient was observed along the direction perpendicular to the substrate, decreases from 56 at% near the substrate to 20 at% in the joint center. Similarly, the Young's modulus drops from 90 GPa near the substrate to 65 GPa in the central solder region. The joint strength reached 69 MPa after 2 min of soldering but decreased to 25 MPa when the soldering time was extended to 60 min The reduction in shear strength of the joint is mainly attributed to the increased Ag content in the (Au,Ag)5Sn phase.