Reliability analysis and optimization of LGA solder joints under thermal shock conditions
In order to improve the reliability of solder joints of land grid array(LGA),the ANAND constitu-tive model is used to describe the mechanical behavior of SAC305 lead-free solder joints.The stress-strain distri-bution,the viscoplastic strain energy density and the fatigue life of LGA solder joints under the thermal shock load(-55℃～125℃)are analyzed by using finite element analysis method and the energy-based Darveaux fatigue life prediction model.Finally,Taguchi test is employed to evaluate the effects of the four factors of solder joint height,thermal expansion coefficient(TEC)of plastic sealing material,BT substrate TEC,and pad TEC on fatigue life of solder joints,and the optimal design scheme is also proposed.The experimental results are shown as follows:Un-der the thermal shock load,the stress value of the LGA solder joint farthest from the geometric center is the high-est and varies periodically.The main factors affecting the fatigue life of solder joints are the TEC of plastic sealing material and the height of solder joints.After optimization,the increment of equivalent plastic strain energy densi-ty of solder joints is reduced by 57%;the thermal fatigue life is 2.32 times of that before optimization.Obviously,the thermal reliability of LGA solder joint structure is improved.
solder joints of land grid array(LGA)finite element analysisthermal shockfatigue life
万方数据
维普
