Sn-6.5Zn钎料/Cu基板焊点界面特征与金属间化合物的形成机理

对255℃时Sn-6.5Zn钎料/Cu基板界面反应及金属间化合物的形成与转化进行热力学计算与分析,并利用SEM、EDS、XRD研究分析255℃不同钎焊时间条件下钎料/Cu基板界面组织与IMC层形态特征。结果表明:Sn-6.5Zn钎料/Cu焊点界面紧靠Cu基板侧形成CuZn层;CuZn IMC有与钎料中的Zn原子继续反应生成Cu5Zn8 IMC的趋势;在相同钎焊温度条件下,不同钎焊时间对界面厚度影响不大;随钎焊时间延长,Sn-6.5Zn钎料/Cu基板焊点界面IMC层的平均厚度增大,界面粗糙度则由于不同钎焊时间IMC在液态钎料中生长与溶解的差异,呈现先增大而后降低到一个均衡值的变化趋势。

Formation mechanism of intermetallic compounds and interface characteristics of joint of Sn-6.5Zn solder/Cu substrate

The interfacial reaction of Sn-Zn solder/Cu substrate soldered at 255 ℃ and the formation and transformation of intermetallic compounds(IMC) were investigated by the thermodynamic calculation and analysis.The interface of the joint produced at 255 ℃ with various soldering times was analyzed by scanning electron microscope(SEM),X-ray energy dispersive spectrometer(EDS) and X-ray diffraction(XRD).The results show that CuZn IMC forms preferentially within the Cu substrate.The Cu5Zn8 IMC forms by the reaction of CuZn with Zn atoms diffused from the solder.The effect of the soldering time on the interface thickness at the same soldering temperature is slight.With prolonging soldering time,the interface thickness between Sn-6.5Zn solder and Cu substrate increases,and the interface roughness reaches obviously a maximum value,and then decreases to a stable value,which is due to the non-uniform growth and dissolution of dendrite in liquid solder.