Analysis of thermal-moisture induced failure of Pb-free soldered IC packages in SMT reflow soldering process

In this paper, firstly, a moisture absorption and diffusion model is applied to obtain an accurate moisture diffusion field during moisture preconditioning and reflow processes. Secondly, based on the transient moisture distribution, a developed inner vapor model is used to get the vapor pressure, which depends on the position, temperature and moisture. Finally, tensile tests were performed for the package material, with temperatures up to 250/spl deg/C. A fracture mechanics method was used to study the crack propagation behavior under the combinational effect of the stresses. An evaluation was made based on the simulation results and the experimental results.