无铅焊料Sn-3.8Ag-0.7Cu的低周疲劳行为

Low cycle fatigue behavior of Sn-3.8Ag-0.7Cu lead-free solder

测量了Sn-3.8Ag-0.7Cu无铅焊料试样的循环滞后回线、循环应力响应曲线、循环应力-应变和应变-寿命关系,研究了焊料在总应变幅控制下的低周疲劳行为.结果表明:该焊料合金在总应变幅较高(1％)时发生连续的循环软化,而在总应变幅较低(≤0.4％)时则表现为循环稳定.线性回归分析表明,该焊料的低周疲劳寿命满足Coffin-Manson经验关系式,由此给出了焊料在室温下的低周疲劳参数.采用扫描电镜观测和分析了焊料在疲劳前后的组织特征.

Low cycle fatigue tests of Sn-3.8Ag-0.7Cu lead-free solder alloy were carried out under total strain amplitude control at room temperature. The fatigue behavior of the solder alloy was characterized by the cyclic stress-strain hysteresis loops, cyclic stress responses, cyclic stress-strain curves, and the relationship between strain and fatigue life. At higher strain amplitudes (1%), the solder alloy exhibited cycle-dependent softening. At lower strain amplitudes (≤0.4%), stable cyclic response was observed over a significant portion of the fatigue life. The fatigue life of the solder alloy followed the Coffin-Manson equation, from which relevant fatigue parameters were determined. The fatigue behavior of the solder alloy was related to the fatigue-induced microstructural variations and the fracture mechanism.