In situ observations on creep fatigue fracture behavior of Sn–4Ag/Cu solder joints
In situ observations on creep fatigue fracture behavior of Sn–4Ag/Cu solder joints
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DOI：
10.1016/j.actamat.2011.06.010
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发表时间：
2011-09
期刊：
影响因子：
9.4
通讯作者：
Qingke Zhang;Z. Zhang
中科院分区：
文献类型：
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作者：
Qingke Zhang;Z. Zhang
研究了Sn-Ag/Cu焊点的蠕变疲劳行为。在原位拉伸台上进行了低周蠕变疲劳试验，利用扫描电镜观察了变形形貌，并利用电子背散射衍射系统对钎料的微观结构进行了表征。结果表明，该合金的蠕变疲劳过程可分为三个阶段：应变硬化阶段、稳定变形阶段和加速断裂阶段。在最初的几个循环期间，应变迅速增加，因为焊料是软的。应变硬化后的焊料变得饱和，应变增加近似线性增加的循环，应变集中发生在焊料接近焊料/Cu 6Sn 5接口和初始微裂纹产生。当微裂纹演化为长裂纹时，破坏加速，试样在界面处断裂。蠕变疲劳应变是由焊料的塑性变形和蠕变共同作用的结果。当塑性应变达到阈值时，焊料中发生晶粒细分，然后在新形成的晶粒中发生晶粒旋转以适应进一步的应变。位错攀移是蠕变的主要机制，细化后也可促进晶界滑动。
The creep fatigue behavior of Sn–Ag/Cu solder joints was investigated in this study. Low-cycle creep fatigue tests were conducted on an in situ tensile stage, the deformation morphologies were observed by scanning electron microscopy and the microstructure of the solder was characterized using an electron back-scattered diffraction system. The results show that the creep fatigue process can be divided into three stages: a strain hardening stage, a steady deformation stage and an accelerating fracture stage. During the initial few cycles the strain increases rapidly because the solder is soft. After strain hardening of the solder becomes saturated, the strain increases approximately linearly with increasing cycles, strain concentration occurs in the solder close to the solder/Cu6Sn5interface and initial microcracks are generated. When the microcracks evolve into long cracks, the failure accelerates and the specimens fracture at the interface shortly thereafter. The creep fatigue strain is contributed by plastic deformation and creep of the solder. Grain subdivision occurs in the solder when the plastic strain reaches a threshold, and then grain rotation takes place in the newly formed grains to accommodate further straining. Dislocation climb is the major creep mechanism, and grain boundary sliding can also be promoted after subdivision.