Lumped parameter mathematical model of the laser soldering process and comparison of different soldering technologies

The ever-increasing packaging density of components on printed circuit boards, and the subsequent reduction in size continues to pose great challenges to manufacturers. With the development of low-cost, high power diode laser, laser soldering is becoming very attractive for the production of miniaturised interconnects. In order to evaluate the solder joint quality, predict cycle time and select process parameters, it is necessary to model the thermal dynamic response of the solder joint. In this research paper, a lumped-parameter mathematical model has been developed for laser soldering process and validated experimentally by measuring the thermal response of the solder preforms. The model results in four first-order differential equations which can be solved with MATLAB. Further, a comparison has been made between laser and soft beam (focussed xenon-arc white light) soldering with respect to solder joint quality, cycle time and input optical energy requirements. In addition, scanning electron microscopic studies were done to compare the microstructure of the solder melted with laser, soft beam and a standard soldering iron.