微焊点电致损伤与断裂的实验及数值研究

本文制作了微焊点试件,并通过施加较大的电载荷使其发生了电迁移。对微焊点在电迁移过程中的微观组织形貌及其演化进行了观察。结果发现,高温和常温条件下的电致失效模式都是阴极处的界面断裂,但是低温条件下的迁移试件会在阳极处形成凸丘,而高温下则没有。此外,本文还测试了微焊点在电迁移过程中的电阻、温度场以及塑性变形,以期找到微焊点电致损伤的表征方法。实验表明,红外方法可以快速准确地发现焊点表面和内部的缺陷,而电阻值对微焊点的电致损伤并不敏感。最后本文采用有限元方法分析了微焊点的电致应力及空位浓度,较好地解释了微焊点电致失效的机制。

Experimental and Numerical Study of Electrically Induced Damage and Fracture of Micro-soldering Spot

A specimen with micro-soldering spot was prepared and 8 Amp large electrical load was applied to the specimen to cause micro-soldering spot electromigration. The microstructure morphology and evolution of micro-soldering spot during electromigration was observed. It is found that the electrically induced failure modes of micro-soldering spot due to electromigration at high temperature and room temperature are same cathode interfacial fracture; but the failure mode at low temperature is different: anode hump is formed, which does not occur at high and room temperature. In order to find the characterization method for electrically induced failure of micro-soldering spot, the measurements of electrical resistivity, temperature field and plastic deformation of micro-soldering spot during electromigration were conducted. It is found that IR method can quickly and accurately find solder surface and internal defects, whereas electrical resistivity is not an ideal measure for damage evaluation due to its insensitivity to damage. Finally, finite lelement method was developed to evaluate the electrically induced stress, vacancy concentration of micro-soldering spot, which better explains the mechanism of micro-soldering spot electrically induced failure mode.