CQFN封装结构的热疲劳寿命研究

Study on Thermal Fatigue Life of CQFN Package Structure

基于陶瓷四边无引线(CQFN)封装结构,采用有限元仿真方法,针对实际外壳建立了三维有限元模型,对焊点在温度循环试验中的应力应变分布开展了研究,重点分析了印刷电路板(PCB)厚度、外壳尺寸大小、引出端形式和温度变动范围等对焊点的影响规律。采用Anand本构模型对铅锡焊点的粘塑性进行了表征,同时利用Coffin-Manson方程对CQFN封装结构在温度循环载荷作用下的热循环疲劳寿命进行了计算。研究表明,适当地增加PCB板厚度、合理地选取外壳外形尺寸及引出端的形式和尽量地降低温度变动范围,可以有效地提高焊点的热疲劳寿命。

Based on the CQFN package structure, a three-dimensional finite element model is established for the actual package by using finite element simulation method, and the stress and strain distribution of solder joints in the temperature cycle test is studied, and the influence rule of PCB thickness, shell size, outlet form and temperature variation range on solder joints are analyzed. Anand constitutive model is used to characterize the viscoplasticity of lead tin solder joints, and Coffin-Manson equation is used to calculate the thermal cycle fatigue life of CQFN packaging structure under temperature cycle load. The researchs show that the thermal fatigue life of solder joints can be effectively improved by properly increasing the thickness of PCB board, reasonably selecting the package dimension and the form of the outlet, and minimizing the temperature variation range.