Solder joints can experience fatigue cracking at the interface between the solder and substrate during thermal cycling due to the difference in thermal expansion between joined components. In order to strengthen the interfacial region and prevent cracking, two Cu pad surface treatments were studied on Sn-3Ag-0.5Cu solder, and on matte Sn plate and Ni plate coatings. The resulting intermetallic microstructures were characterized using scanning electron microscopy and energy-dispersive spectroscopy. Mechanical testing was performed using nano-indentation on the solder joints. The matte Sn plate on Cu sample formed an uneven distribution of Ag₃Sn particles and a planar Cu₆Sn₅ interfacial intermetallic. The Ni-plated sample formed a needle-like Ni-rich interfacial intermetallic and uniform dispersion of Ag₃Sn particles. The rough intermetallic compound (IMC)/solder interface and even IMC particle distribution cause the Ni-plated sample to experience reduced damage under board-level thermomechanical cycling because the interfacial structure reduces the Sn matrix recrystallization that contributes to fatigue cracking. In contrast, the matte Sn-plated sample exhibited an Ag₃Sn particle-free zone adjacent to a planar Cu₆Sn₅ IMC layer which allows for rapid Sn recrystallization and fatigue crack propagation.

由于连接的组件之间的热膨胀差异，在热循环过程中，焊点可能会在焊料和基板之间的界面处产生疲劳裂纹。为了增强界面区域并防止开裂，研究了在Sn-3Ag-0.5Cu焊料以及亚光Sn板和Ni板涂层上的两种Cu垫表面处理。使用扫描电子显微镜和能量色散光谱对所得的金属间显微组织进行表征。机械测试是在焊点上使用纳米压痕进行的。Cu样品上的无光泽Sn板形成了Ag ₃ Sn颗粒和平面Cu ₆ Sn ₅的不均匀分布金属间界面。镀镍的样品形成了针状的富Ni界面金属间化合物，并均匀分散了Ag ₃ Sn颗粒。粗糙的金属间化合物（IMC）/焊料界面，甚至IMC颗粒分布，都使镀镍样品在板级热机械循环下受到的损伤减少，因为界面结构减少了有助于疲劳裂纹的Sn基体再结晶。相反，无光泽的镀锡样品在与平面Cu ₆ Sn ₅ IMC层相邻的位置显示出无Ag ₃ Sn颗粒的区域，从而可以快速进行Sn再结晶和疲劳裂纹扩展。