焊点热疲劳多模式失效寿命分析

Research on Thermal Fatigue Life under Multi-failure Modes

采用概率分析方法研究表面贴装器件无铅焊点的可靠性。以片式元件0603为例,基于非弹性切应变的疲劳寿命模型Coffin-Manson关系式,建立无铅焊点简化几何模型和热疲劳寿命预测的概率求解方法,对该方法的精确度进行验证。将生产制造过程所导致的焊点几何参数随机性和产品在实际服役过程中环境温度的不确定性对热疲劳寿命的影响进行量化分析,为产品初期设计、质量控制标准的制定及售后质量的预测提供依据。研究结果表明,随着随机变量的增多,焊点热疲劳寿命明显降低。将焊点几何参数H、L及温度循环范围?θ等影响低周热疲劳寿命的关键因素视为相互独立并服从正态分布的随机变量,利用已测得的焊点几何参数的均值及方差和小样本试验数据,可以预测同批次所有样本的焊点热疲劳寿命。

A probabilistic method is utilized to predict solder joint reliability of surface mounting devices.Chip component 0603 is taken as an example.Based on the simplified joint geometry model and Coffin-Manson relation,equations and solutions of thermal fatigue life are established and validated to determine the probability of failure for lead-free solder joints.Uncertainties in the solder＇s geometry are often related to manufacturing processes,and the ambient temperature varies due to the diversity of end-users.Using the approach,the influence of each uncertainty on the thermal fatigue life is quantified.This information can be used to optimize the product design,establish acceptance criteria for quality control,and predict after-sales product quality.The result shows that the thermal fatigue life of the solder joints decreases significantly with the increase of random variables.The key aspects of the normally distributed random variables,solder joint geometry,H,L and thermal range Δθ are involved to predict the low cycle thermal fatigue life according to the experimental data of small sample with measured standard deviation and mean value.