Tensile fracture of tin–lead solder joints in copper

Tensile testing was carried out at constant cross-head speed of 0.5 mm/min on specimens of two Cu blocks of length 45 mm with rectangular area of cross-section (10 mm×3 mm) soldered using Sn–Pb solder alloys with 200–300 μm thick. Four compositions of Sn–Pb alloys were used. The testing specimens were aged at 175 °C in an oven with a temperature measuring accuracy of ±1 °C for different times of up to 16 days to study the effect of isothermal ageing on the strength of the joints. The fracture surface was analysed both in the plan and cross-sectional views to identify the fracture location in the solder joint. It was identified that the morphology of the intermetallic compound (IMC) layer plays a role on the strength of the joint, especially when it fails through the solder/IMC interface. Also, the Pb-content in the solder alloy has a profound effect on the fracture path.