Thermal Fatigue Life Estimation for Lead - Free Solder Joints

在热疲劳强度评价方法上，主要报道了用Manson-Coffin准则评价微焊点区热疲劳强度的结果。因此，在本研究中，无铅焊料的热疲劳强度评估进行了曼森-科芬规则。作为对象的无铅焊料是Sn-3.5Ag-0.75Cu、Sn-2Ag-7.5Bi-0.5Cu、Sn-3.5Ag-5 Bi 3种类型。焊锡材料一般熔点较低（200℃左右）。由于试验温度高达125℃，因此考虑了蠕变的影响。而有限元分析结果表明，蠕变对混凝土的影响很小。并且，有限元分析结果表明材料具有应变率依赖性。接下来将选择机械疲劳试验方法作为加速试验的热循环疲劳试验方法，并进行了试验。并且，进行了有限元分析，以澄清什么样的应力应变行为已产生的焊点划分。根据这些结果，可以通过Manson-Coffin规则在无铅焊料微连接部门进行疲劳强度评估。进行了热循环试验，并与机械疲劳试验给出的疲劳寿命曲线进行了比较。结果，两人意见一致。且机械疲劳试验方法作为热循环试验方法加速试验是有效的。此外，在无铅焊料微连接和共晶焊料微连接部门的疲劳寿命强度进行了比较。通过与共晶钎料的疲劳寿命对比，结果表明，无铅钎料的疲劳寿命比共晶钎料稍有提高。从这一事实，它被证明，无铅焊料似乎是有效的替代金属，改变了共晶焊料。

On the thermal fatigue strength evaluation method, the result that thermal fatigue strength in the solder micro joining division can be evaluated by the Manson-Coffin rule is mainly reported. Therefore, thermal fatigue strength evaluation was carried out by the Manson-Coffin rule in Lead-Free solder in this study. The Lead-Free solder as an object was Sn-3.5Ag-0.75Cu, Sn-2Ag-7.5Bi-0.5Cu, Sn-3.5Ag-5Bi 3 types. Solder material generally melting point is low (around 200℃). And, the effect of the creep is considered, because the temperature rises to 125℃ in this test. However, the finite element analysis result showed that the effect of the creep was very little. And, the finite element analysis result showed that a material has the dependence of the strain rate. Next mechanical fatigue testing method would be selected as an acceleration test of the thermal cycling fatigue test method, and the test was carried out. And, the finite element analysis was carried out in order to clarify what kind of stress strain behavior has been generated in the soldered joints division. From those results, it was possible to carry out fatigue strength evaluation in the Lead-Free solder micro joining division by the Manson-Coffin rule. And, the thermal cycling test was carried out, and the result was compared with fatigue life curve given by the mechanical fatigue test. As the result, both agreed well. And that mechanical fatigue testing method is effective as an acceleration test of the thermal cycling test method. In addition, fatigue life strength in the Lead-Free solder micro joining and eutectic solder micro joining division was compared. In comparison with the eutectic solder, the result showed that fatigue life strength of the way of the Lead-Free solder might be excellent a little. From this fact, it was proven that the Lead-Free solder seemed to be effective as substitution metal that changes for the eutectic solder.