温度与振动耦合条件下的电路板级焊点失效模式与疲劳寿命分析

Analysis of Failure Modes and Life of Solder Joints Under Coupling of Vibration and Thermal Loads

基于正交试验法研究不同温度与振动耦合条件下的板级焊点失效行为与模式,采用L9(34)混合水平正交表设计了不同温度(T)、加速度功率谱密度(PSD)与频率(V)条件下的加速寿命试验,结果表明三者对焊点可靠性影响程度为T>PSD>V,且温度是影响焊点失效模式的主要因素,随温度的升高,焊点裂纹逐渐从近封装侧的界面金属化合物(IMC)层向钎体内部扩展,焊点失效模式从脆性断裂向韧性断裂演化.基于焊点失效数据分析,发现焊点疲劳寿命对数值与PCB板背侧最大应变范围存在关联关系,并采用多项式拟合的方法建立了焊点疲劳寿命模型,拟合结果显示,该模型能较好的评估温度与振动耦合条件下的焊点寿命,预测精度较高.

The failure behavior and modes of board level solder joints under coupling of vibration and thermal loads were studied based on the orthogonal experiment design method. The accelerated life tests with different temperature（ T）,power spectral density（ PSD） and frequency（ V） were conducted by using a L9（ 34） mixed-level orthogonal array. The results showthat the degree of influence that the three factors have on the reliability of solder joints is T 〉 PSD 〉 V. The temperature is the main factor that can affect the failure modes of solder joints significantly. The crack initiates in the intermetalic compound（ IMC） and propagates into the bulk solder gradually as the temperature rises. The failure mode evolves from the brittle fracture to ductile fracture. Based on the analysis of the failure data,a fatigue life model of solder joint was developed by using the polynomial fitting method,according to the relationship between the logarithmic fatigue life value and the strain range of the back side of the printed circuit board. The fitting results indicate that the model can evaluate the fatigue life of solder joints under the coupling of the vibration and thermal loads accurately.