Investigation on dynamic behaviour of tin-lead welding spot of spacecraft circuit board

Abstract

Spacecraft shall be subjected to mechanical environments such as mechanical shocks during loading, unloading and transportation, and the shocks shall be transmitted to the circuit boards inside. There are plenty of tin-lead spots on the circuit board as there are a large number inside the spacecraft. The dynamic behaviour of tin-lead welding spot determines the anti-impact and anti-fatigue properties of the circuit board, and therefore, it is essential to investigate the dynamic behaviour of tin-lead welding spot based on sufficient experiments and accurate simulation. In this research work, the dynamic uniaxial tension at five different strain rates (0.1/s, 1/s, 10/s, 100/s and 1000/s) were performed, the morphology of the fracture surface was examined and the alloy ingredient was analyzed. Furthermore, the finite element models (FEM) of both the tensile sample and the circuit board were developed based on the modified Darveaux model and the cohesive zone method. According to the experiments and the simulation of the uniaxial tensile samples, it was the mass ratio of the tin to the lead that govern the micro mechanical properties, and the modified Darveaux model could precisely describe the stress-strain response of the welding spot. As a result, the calculated results of the impacting dynamical behaviour of the circuit board are reasonable and helpful. The modified Darveaux model and the developed simulation approach could also be applied to other welding structures experiencing impulsive loads. The investigation shall provide research support for the mechanical environment analysis of spacecraft and other mechanical impact.