银含量对快速热冲击下Sn−xAg−0.5Cu焊点显微组织和力学性能的影响

Effect of Ag content on microstructure and mechanical properties of Sn−xAg−0.5Cu solder joints under rapid thermal shock

使用高频感应加热设备研究Ag含量对快速热冲击下Sn−xAg−0.5Cu焊点的显微组织和剪切强度的影响。结果表明,Ag含量的增加使焊点表面更致密光滑,减少焊点内部长条状Cu6Sn5金属间化合物(IMC)的产生,从而提高焊点的抗氧化性。Ag能够加快焊点界面IMC层的生长速度,Cu6Sn5层的生长速度由体扩散和晶界扩散共同决定,Cu3Sn层的生长速度由体扩散和界面反应共同决定。在快速热冲击环境下,焊点的断裂模式从韧性断裂转变为脆性断裂,而高Ag含量使得焊点的断裂模式转变时间更短,降低焊点的抗热疲劳性能。

The effects of Ag content on the microstructure and shear strength of Sn−xAg−0.5Cu solder joints under rapid thermal shock were investigated using high-frequency induction heating equipment.The results show that the increased Ag content can make the surface of the solder joint denser and smoother and reduce the generation of long strips of Cu6Sn5 intermetallic compound(IMC)inside the solder joint,thus enhancing the oxidation resistance of the solder joint.Ag accelerates the growth rate of the IMC layer at the solder joint interface,the growth rate of the Cu6Sn5 layer is determined by both bulk diffusion and grain boundary diffusion,and the growth rate of the Cu3Sn layer is determined by both bulk diffusion and interfacial reaction.In the rapid thermal shock environment,the fracture mode of the solder joint converts from ductile fracture to brittle fracture.At the same time,the high Ag content shortens the fracture mode transition time of the solder joint and reduces the thermal fatigue resistance of the solder joint.