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采用Sn3.0Ag0.5Cu倒装芯片研究由电迁移导致的互连焊点显微结构的变化对倒装焊点热冲击性能及失效位置和形态的影响,分析导致电迁移前后焊点热冲击失效界面变化的微观机制。单纯热冲击应力作用下倒装焊点的开裂失效位于Al互连与凸点下金属化层之间,电迁移作用下,倒装焊点的热冲击失效界面发生变化,电子风力作用下空位的定向迁移是导致焊点热冲击失效界面变化的根本机制。空位在阴极附近聚集,达到过饱和后形成连续性空洞,导致焊点在阴极空洞位置发生开裂失效。宏观上焊点回路中电子流方向的交替变化导致整个串联回路中出现芯片一侧和焊盘一侧交替开裂的有规律的失效现象。
Sn3.0Ag0.5Cu flip chip was used to study the influence of the change of the microstructure of interconnection solder joints caused by electromigration on the thermal shock performance and the location and morphology of the flip-chip solder joints. The thermal shock failure of the solder joints before and after electromigration was analyzed Micro-mechanism of interface change. Cracking failure of the flip-chip solder joints under the effect of pure thermal shock stress is located between the Al interconnect and the bump metallization layer. Under the effect of electromigration, the thermal shock failure interface of flip-chip solder joints changes. Directional migration is the fundamental mechanism leading to the change of thermal shock failure interface of solder joints. Gaps accumulate near the cathode to form a continuous void after saturation, resulting in cracking of the solder joint at the cathode void. Macroscopically, the alternating change of the direction of the electron flow in the solder joint circuit leads to the regular failure of alternately cracking the chip side and the pad side in the entire series circuit.