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研究了表面封装焊在剪切应力作用下等温低周疲劳特征，得到疲劳寿命与循环应力幅的关系曲线．分析了６２Ｓｎ─３６Ｐｂ─２Ａｇ焊点的低周疲劳失效机理。结果表明：６２Ｓｎ─３６Ｐｂ─２Ａｇ表面封装焊点在剪应力控制等温低周疲劳过程中有明显的循环蠕变行为，焊点的失效是由于疲劳与蠕变的交互作用造成的。在２５℃，低应力水平下，焊点的失效主要受疲劳过程控制，而高应力水平下，焊点的失效主要受蠕变过程控制；１００℃等温低周疲劳的失效机理与室温疲劳相似，其由疲劳机理向蠕变机理转化的应力水平τ_（＋）较室温下为低，但在相对应力水平（τ_＋／τ_ｂ和τ_＋／τ_ｂ＇）相同时，１００℃与室温时疲劳裂纹的扩展速率ｄａ／ｄＮ基本一致。
The isothermal low cycle fatigue characteristics of the surface mount soldering under shear stress were studied, and the relationship between fatigue life and cyclic stress amplitude was obtained. The mechanism of low cycle fatigue failure of 62Sn-36Pb─2Ag solder joint was analyzed. The results show that the 62Sn-36Pb─2Ag surface mount solder joint has obvious cyclic creep behavior under the condition of low temperature stress and low cycle fatigue under shear stress control. The failure of the solder joint is caused by the interaction between fatigue and creep. At 25 ℃ and low stress level, the failure of the solder joint is mainly controlled by the fatigue process. At high stress level, the failure of the solder joint is mainly controlled by the creep process. The failure mechanism of 100 ℃ isothermal low cycle fatigue is similar to room temperature fatigue, The stress level τ_ (+) transformed from fatigue mechanism to creep mechanism is lower than that at room temperature. However, at the same relative stress level (τ_ + / τ_b and τ_ + / τ_b ’), the fatigue crack growth rate da / dN basically the same.