| Summary: | 碩士 === 國立交通大學 === 工學院碩士在職專班半導體材料與製程設備組 === 99 === Flip-chip technology has become a mainstream trend in advanced electronic packaging because of its capability of higher I/O density and smaller package size. With higher current and smaller size trends, electromigration in flip-chip solder has become an critical of reliability concern.
The effect of pre-aging on electromigration is investigated in this study using flip-chip SnPb solder joints. The solder joints were pre-aged at 170°C for 25 h, 50 h, and 100 h, and then they were subjected to electromigration tests of 1.0 A at 150°C. It was found that the average failure time increased when the joints were pre-aged for no pre-aged, 25 h, 50 h and 100 h. It is proposed that the major contributor to the prolonged failure time may be the densification of the nickel and copper under-bump metallization (UBM) and the solder due to the aging treatment. The pre-aging treatment at 170°C may stabilize the microstructure of the solder. The vacancies in the solder might be annihilated during the heat treatment, causing a slower diffusion rate. In addition, the IMC structure became thicker after the pre-aging process. Thus, the thicker IMC structure may lead to smaller current crowding effect and slower consumption rates of the nickel and copper layers, resulting in the enhancement of electromigration resistance.
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