研究了功率模块芯片在 ＤＣＢ基板上 ９２．５Ｐｂ５Ｓｎ２．５Ａｇ钎料焊层的热循环可靠性和裂纹扩展，应用超声波显微镜对裂纹扩展过程进行检测，得到了热循环失效的裂纹扩展数据，采用统一型粘塑性 Ａｎａｎｄ方程描述了 ９２．５Ｐｂ５Ｓｎ２．５Ａｇ的力学本构，模拟了焊层在热循环条件下的应力应变过程．基于裂纹扩展的实验数据和等效塑性应变增量△εｉｎｅｑ，提出了一种描述热循环裂纹扩展速率的经验方程 The thermal cycling reliability and crack propagation of 92.5Pb5Sn2.5Ag solder layer on DCB substrate were studied. The crack growth process was detected by ultrasonic microscope and the crack growth data of thermal cycling failure were obtained. The visco-plastic Anand equation describes the mechanical constitutive of 92.5Pb5Sn2.5Ag and simulates the stress-strain process of the weld layer under thermal cycling. Based on the experimental data of crack growth and the equivalent plastic strain increment △ εineq, an empirical equation describing the thermal cycle crack growth rate