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电流密度为3×103A/cm2和环境温度100℃的实验条件下,在Cu/共晶SnBi焊点/Cu焊点的阴极和阳极Cu基板上都发现了晶须的生长。经EDX检测可知,其成分为Sn-Bi的混合物。抛光后发现,大量的Cu6Sn5金属间化合物附着在Cu基板上。结果表明:随着通电时间的延长,SnBi钎料在电迁移的作用下发生了扩散迁移,在Cu基板上形成了薄薄的钎料层。在焦耳热和环境温度的作用下,钎料层中的Sn与Cu基板中的Cu反应生成了大量的Cu6Sn5金属间化合物。这些金属间化合物的形成导致在钎料层的内部形成了压应力。为了释放压应力,Sn-Bi钎料以晶须的形式被挤出。
The current density of 3 × 103A / cm2 and the ambient temperature of 100 ℃ under the experimental conditions, the Cu / eutectic SnBi solder joints / Cu solder cathode and anode Cu substrate were found whiskers growth. EDX test shows that the composition of Sn-Bi mixture. After polishing, it was found that a large amount of Cu6Sn5 intermetallic compound adhered to the Cu substrate. The results show that SnBi solder diffuses and migrates with electromigration, and a thin brazing filler metal layer is formed on the Cu substrate. Under the action of Joule heat and ambient temperature, Sn in the brazing filler metal reacts with Cu in the Cu substrate to produce a large amount of Cu6Sn5 intermetallic compound. The formation of these intermetallic compounds results in the formation of compressive stresses in the interior of the solder layer. In order to relieve compressive stress, Sn-Bi solder is extruded as whiskers.