Heat Conduction Simulation on Copper-Aluminum Laser Welding

Welding of copper and aluminum is essential for the wiring of electronic devices. Laser welding is expected to be a precise and fast joining method. However, when the melting time at the interface is long during welding, many brittle intermetallic compounds are formed, and sufficient joint strength cannot be maintained. In this study, a heat conduction simulation model for overlap welding was developed in order to design laser parameters to achieve a temperature history that suppresses the formation of intermetallic compounds. The method was to estimate the laser absorption ratio, which was defined as a fitting parameter of the simulation model, by matching the constructed analytical model with the experimental results of overlap welding using the melt diameter of the interface. It was also confirmed that the intermetallic compound layer could be suppressed to a thin layer under the condition that the interface was kept at a temperature between the melting points of aluminum and copper using the analytical model constructed by this method.