振动载荷下特种设备中电路板级焊点疲劳寿命预测

Fatigue life prediction of board level solder joints for special equipment under vibration loads

基于内聚力模型,提出一种用于振动载荷下特种设备中电路板级焊点疲劳寿命预测的介观尺度模型。将单调载荷与振动周期载荷相结合,建立焊点累积损伤参数来表征焊点的剩余疲劳寿命,利用焊点损伤累积率来表征焊点损伤演化规律。以Sn3.0Ag0.5Cu(SAC305)细间距无铅焊点为例分析了模型参数确定方法,并通过振幅为5 mm与10 mm的定频振动试验对模型的预测精度进行了验证,寿命预测结果误差小于10%。由于模型参数为焊点钎料累积塑性应变的固有函数,与焊点尺寸与几何形态无关,通过小样本试验,数据一经确定即可应用于同种钎料不同尺寸焊点在不同振动等级下的疲劳寿命预测,节约了时间与试验成本,该模型能为特种设备中的电子组件提供一种评估板级焊点疲劳寿命的简洁、实用方法。

A fatigue life prediction meso-scale model of board level solder joint was proposed for special equipmentunder vibration load based on cohesive zone model （CZM）. Incorporating with monotonic and cyclic loadings, anaccumulated damage parameter was constructed as an internal representation of solder joints’ residual fatigue life. So thedamage accumulation law can be identified by a damage accumulation rate. Sn3.0Ag0.5Cu （SAC305） solder joints of finepitch devices were taken as an example to determine the parameters of the model. The predictive capability of the modelwas verified by conducting constant frequency vibration tests whose amplitudes were 5 mm and 10 mm. The resultsindicate that the prediction error is less than 10%. The parameters are intrinsic functions of solder’s accumulated plasticstrain and have nothing with the geometries of solder joints. Once the parameters of the CZM are calibrated by simple testconfiguration, the model can be used to predict the fatigue life of solder joints which is made of the same solder but withdifferent geometries and loading conditions. So a great quantity of time and costs of experiments can be avoided. Thismethod can be regarded as an analytical tool to evaluate the fatigue life of solder joints in practice.