通孔元件焊点的抗热疲劳性能预测 Ⅰ.焊点抗热疲劳能力的实验研究

PREDICTION ON RESPONSE TO THE THERMAL FATIGUE OF THROUGH-HOLE SOLDER JOINT I. Experimental Research of Solder Joint Response to the Thermal Fatigue

针对通孔焊点进行了热冲击的可靠性测试,以非破坏性和破坏性的实验方法,对比分析了波峰焊点和再流焊点的抗热疲劳能力.结果表明, CTE(热膨胀系数)失配是焊点产生裂纹的主要原因,而焊点形态的差异又使得再流焊点内部断裂程度不同于波峰焊点.再流焊点裂纹产生在钎料内部;而波峰焊点由于具有饱满的圆角过渡形态,裂纹产生在镀铜孔与线路板的连接拐角处.裂纹的产生导致了两种焊点强度的降低,对其电性能的影响却甚微.

Experimental investigations on the reliability of through-hole solder joints under thermal shock were carried out in this paper. The difference responses of wave and reflow soldered joints to thermal fatigue was analysized in non-destructive and destructive testing ways. Results show that the cumulative damage to the solder metal is mostly caused by the coefficient of thermal expansion (CTE) mismatch. And the crack-propagation extents in both joints are dissimilar due to the difference of solder joint shape. Cracks are observed in the solder body to the reflowed samples, while they appear obviously at the corner of printed circuit board (PCB)-plated through hole (PTH) barrel interface in the wave soldered samples. Furthermore, the formation of cracks results in the degradation of solder joint strength, but affects mildly to the electrical properties.