回流焊过程温度、潮湿和蒸汽压力对PBGA分层的影响

Effect of Temperature,Moisture and Vapor Pressure on Delamination in a PBGA During Reflow Soldering Process

研究SMT回流焊工艺中,温度、潮湿和蒸汽压力耦合作用对PBGA器件开裂失效的影响.对塑料封装PBGA器件从168 h、85°C/85%RH条件下预置吸潮到后面的无铅回流焊的整个过程进行了有限元仿真,得到了回流焊过程PBGA器件界面潮湿扩散和应力变化的规律.研究结果表明,潮湿和蒸汽压力对器件界面分层失效有很大的影响.

Interface delamination is one of the major failure modes in plastic IC packages. The encapsulating polymers used in electronic packaging are characteristic of high porosity,which makes the material susceptible to tile moisture absorption.During lead-free reflow soldering process,the entire package is exposed to the relative high soldering temperature.Under such temperatures,moisture absorbed by polymer materials evaporates,generating high internal vapor pressures in the voids.Interface delamination may be caused by the combined effect of the thermo-mechanical stress,hygro-mechanical stress and vapor pressure.This paper investigated the effects of temperature,moisture diffusion and vapor pressure on the delamination in PBGA package during SMT reflow soldering process.Finite element simulation on a plastic PBGA package was carried out for the entire thermal and moisture history from the moisture preconditioning(85°C/85%RH for 168 h) to subsequent exposure to a lead-free soldering process,and the rule of moisture diffusion and the change of stress was found.The result shows that the vapor pressure and moisture in the package have a quite significant effect on interfacial delamination failure.