The simulation and analysis of effect of vacuum eutectic welding parameters on void fraction of solder joint

Abstract

The vacuum eutectic solder joint is widely used in the advantages of large thermal conductivity, small thermal resistance and so on. But the void ratio of vacuum eutectic solder has a great influence on the thermal conductivity, and the smaller the void ratio is, the greater the thermal conductivity coefficient is. Therefore, it is very necessary to optimize the parameters of vacuum eutectic welding process and reduce the void ratio of solder joints. In this paper, the three-dimensional finite element simulation model of the welding of the GaAs chip and the heat sink is established by using ANSYS software. The peak temperature, cooling rate and pressure as the main welding parameters of vacuum eutectic solder joint were selected as the main welding parameters[1]. In the method of keeping the two parameters unchanged for another parameter of the change, such as changing the cooling rate and the other parameters remain unchanged for simulation, similar to change pressure and peak temperature simulation and analysis of process parameters on the solder joint void rate effect rule, get the smallest solder joint void rate combination of process parameters. The research shows that the cooling rate has the most significant effect on the void of vacuum eutectic solder joint. In the range of 1.5℃/s ~2℃/s, with the increase of cooling rate, the void ratio increases, the maximum is 8.148% at 1.6℃/s, and then remains stable. The peak temperature is less important. On the simulation of the void rate of parabolic law, in the peak temperature range of 300℃~310℃, with the increase of the peak temperature, the simulation after the void first increases and then decreases, at 307℃ to 8.148%. The effect of pressure is the smallest, with the increase of pressure, the void ratio remains unchanged after simulation. According to the analysis of the process parameters of the simulation, the vacuum co crystal welding solder joint void rate minimum combination of process parameters: peak temperature is 307℃, the cooling rate is 1.5℃/s, the pressure is 400~2000Pa.