Study on thermal simulation technology for SMA in lead-free reflow soldering

The thermal mathematical model under intensive convection in lead-free reflow soldering process is constructed for surface mounted assemblies, and the heat conduction governing equation, initial condition and boundary condition are made. A thermal mathematical model of SMA is transformed into solid model which can be analyzed by the thermal analysis software FLOTHERM. Then by defining the reasonable boundary condition and model simulating analysis, the thermograph contour map and profile for the SMA are obtained. Using the data relevant to simulation reflow profile and orthogonal experiment design to set up the factor effect table, the degree of the critical parameters of lead-free reflow soldering process affecting the key index of thermal profile would be obtained. The results show that the heating rate is mainly affected by the conveyer belt speed, temperature of heating zone No.6 and No.2; the maximum temperature is mainly affected by the conveyer belt speed, temperature of heating zone No.6 and No.7; and the soldering time of extension melting point temperature is mostly affected by conveyer belt speed.