In this paper, a numerical simulation of thermal process in the SMT laser microsoldering joint has been developed, in which, the influence on thermal process of the factors such as the thermal conductivity variation of solder with temperature, light reflection coefficient of the lead wire surface, and heat exchange on the surface of SMT materials all have been considered. In order to carry this numerical calculation practice and prove it's results, the reflexive characteristic of light wave to the SMT materials has been gauged, and the dynamic temperature process of laser microjoint has been measured by a new experimental method which was invented by the authors.

The results of numerical simulation have been borne out by the tests, and the influences of heating parameters on thermal process has been analysed in this paper. The conclusions will be advantageous to the further study of the microjoint quality control in the SMT laser microsoldering.