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研究电流密度为1.5×104A/cm2时,共晶SnBi焊点的微观组织的演变。试验过程中应用MicroviewMVC2000图像采集卡对焊点形态的变化进行实时监控。通电仅110s,焊点的局部区域开始熔化;130s后达到完全熔融的状态。结果表明:通电10min后,焊点的阳极附近形成了大量的块状Bi相,而在阴极则以细条形的Bi相为主。然而抛光后发现,阴极和阳极的微观组织保持一致,钎料基体内出现了大量的Bi的小颗粒形成的聚集,阴极界面出现了空洞。通电30min后,共晶组织的均匀分布已经被打乱。阳极附近出现了Bi的聚集,而且阳极界面的IMC层比阴极界面的IMC层厚。
The evolution of the microstructure of eutectic SnBi solder joints at a current density of 1.5 × 10 4 A / cm 2 was studied. During the test, the application of MicroviewMVC2000 image acquisition card to monitor the change of spot shape in real time. Power only 110s, the local area of the weld began to melt; after 130s to completely melt state. The results show that a large number of bulk Bi phases are formed near the anode of the solder joint, while the thin bar Bi phase is the main cathode in the cathode after 10min. However, after polishing, it was found that the microstructure of the cathode and the anode remained the same. A large amount of small particles of Bi formed in the solder matrix and the cathode interface was hollow. After 30min, the uniform distribution of eutectic structure has been disrupted. Bi accumulation occurred near the anode, and the IMC layer at the anode interface was thicker than the IMC layer at the cathode interface.