Effects of Mn nanoparticles on tensile properties of low-Ag Sn-0.3Ag-0.7Cu-xMn solder alloys and joints

In this study, the tensile tests of Sn-0.3Ag-0.7Cu-xMn composite solder alloys were carried out at strain rates of 1 × 10−4s−1, 1 × 10−3s−1, and 1 × 10−2s−1 over a range of test temperatures of 20 °C, 60 °C, and 120 °C. The tensile tests of Cu/Sn-0.3Ag-0.7Cu-xMn/Cu solder joints aged at 150 °C for 0, 144, 288, 576, 864, and 1152 h were conducted under a strain rate of 1 × 10−3s−1 at 20 °C. Scanning electron microscope (SEM) was used to observe the fracture surfaces of solder alloys and joints. Results show that the Mn-containing solder alloys and joints have higher ultimate tensile strength (UTS) than Mn-free due to the effect of particle hardening. The UTS of Sn-0.3Ag-0.7Cu-xMn composite solder alloys has a logarithmic relation with strain rate and decreases with an increase of test temperature. The tensile strengths of both Sn-0.3Ag-0.7Cu-xMn solder alloy and solder joints reach the highest value when 0.1 wt.% Mn nanoparticles is added. With an increase in aging time, the tensile strength of all solder joints shows a decreasing trend as the interfacial intermetallic compound (IMC) layer becomes thicker and thicker. This results in the fracture mode of the solder joint gradually changing from the initial ductile fracture in the solder joints into the mixed fracture mode of both the ductile and the brittle fracture, and finally to the brittle fracture mode along interface IMC.