Effect of temperature on shear properties of Sn-3.0Ag-0.5Cu and Sn-58Bi solder joints

Microelectronic devices with advanced capabilities, such as multi-functions, high input/output densities, and high capacities, have recently found extensive application in areas such as servers, big data, data centers, IoT, and supercomputing. Owing to the diverse operating conditions of these applications, the reliability of the microelectronic packaging depends on the integrity of the soldered joints at various (high) operating temperatures. In this study, the mechanical shear properties of Sn-3.0Ag-0.5Cu (SAC305) and Sn-58Bi (in wt%) solder joints were studied using a ball shear test at various temperatures on substrates with two types of surface finish: organic solderability preservative (OSP) and electroless nickel-electroless palladium-immersion gold (ENEPIG). The joint strength, force-displacement curve, and fracture energy were measured and calculated for each joint, and the correlations between solder alloys, operating temperatures, and joint mechanical behaviors were revealed. In the case of the SAC305 solder, regardless of the substrate, with increasing temperature, the shear force decreased, fracture distance increased, and the fracture energy decreased. In addition, the fracture was predominantly ductile. In the case of the Sn-58Bi solder, with increasing temperature, the shear force decreased, and the fracture distance increased slightly and then decreased (OSP substrate) and kept constant then decreased (ENEPIG substrate), and the fracture energy decreased. Although ductile fracture occurred at low temperatures, the brittle fracture proportion gradually increased as the temperature increased. Further, the microstructure significantly affected the mechanical properties and fracture behavior of the SAC305 and Sn-58Bi solder joints. •Mechanical shear properties of solder joints at various temperatures were studied.•SAC305 solder showed ductile fracture at all test temperatures.•Fracture mode in the Sn-58Bi solder shifted from ductile to brittle with increasing temperature.•Microstructure significantly affected the mechanical properties and fracture behavior of the joints.