Sn3.0Ag0.5Cu/Cu回流焊点界面化合物尺寸分布特征及生长机制

Size distribution and growth mechanism of interfacial intermetallic compounds in Sn3.0Ag0.5Cu/Cu reflow solder joints

在电子封装过程中,钎料与基体之间形成金属间化合物层,其主要成分为Cu_(6)Sn_(5),Cu_(6)Sn_(5)晶粒的尺寸和形貌特征能够显著影响焊点的服役性能.采用回流焊的方法制备了一系列Sn3.0Ag0.5Cu/Cu焊点,使用Image-Pro Plus软件对焊接界面化合物Cu_(6)Sn_(5)晶粒的尺寸分布和化合物层的厚度进行了统计分析.结果表明,Cu_(6)Sn_(5)的平均粒径正比于t^(0.38)(t为回流时间),界面化合物层的平均厚度正比于t^(0.32).随着回流时间的增加,界面化合物生长速度变慢,Cu_(6)Sn_(5)晶粒的尺寸分布更加均匀.回流时间较长的样品中Cu_(6)Sn_(5)的粒径尺寸分布与FRD模型的理论曲线基本相符,而对于回流时间短的样品,晶粒尺寸分布与FRD理论偏离较大.统计结果显示,出现频次最高的晶粒尺寸小于平均值.最后讨论了界面Cu_(6)Sn_(5)晶粒的生长机制,分析了回流时间对界面Cu_(6)Sn_(5)晶粒生长方式的影响.

In the process of electronic packaging,an intermetallic compounds layer is formed at the interface between solder and Cu substrate.The intermetallic compounds layer is mainly composed of Cu_(6)Sn_(5)compounds.The size and morphology of the Cu_(6)Sn_(5)intermetallic compounds have a notable influence on the reliability of solder joints.A series of Sn3.0 Ag0.5 Cu/Cu solder joints were prepared by reflow soldering method.Image-Pro Plus software was used to statistically analyze the size distribution and the thickness of the Cu_(6)Sn_(5)grains.The results show that the average diameter of Cu_(6)Sn_(5)grains is proportional to t^(0.38),where t is the reflow time.The mean thickness of the interfacial compounds layer is proportional to t^(0.32).With the increase of reflow time,the growth rate of interfacial compound slows down,and Cu_(6)Sn_(5)grain size distribution becomes more uniform.The size distribution of Cu_(6)Sn_(5)in samples with long reflow time is basically consistent with the theoretical curve of FRD model,while for samples with short reflow time,the grain size distribution deviates from the FRD theory.The statistical results show that the grain size with the highest frequency is less than the average value.The growth mechanism of interfacial Cu_(6)Sn_(5)grains was discussed,and the effect of reflow time on the growth way of Cu_(6)Sn_(5)grains was analyzed.