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采用104A/cm2数量级的电流密度对Sn3.0Ag0.5Cu倒装焊点中的电迁移机理作了研究.电迁移引起的原子(或空位)的迁移以及在此过程中形成的焦耳热,使Sn3.0Ag0.5Cu倒装焊点的显微形貌发生变化.电迁移作用下,由于空位的定向迁移和局部的电流聚集效应使阴极芯片端焊料与金属间化合物界面形成薄层状空洞.处于阴极的Cu焊盘的Ni(P)镀层与焊料间也产生了连续性空洞,但空洞面积明显小于处于阴极的芯片端焊料与金属间化合物界面.焊盘中的Cu原子在电迁移作用下形成与电子流方向一致的通量,最终导致焊点高电流密度区域出现连续性的金属间化合物且金属间化合物量由阴极向阳极逐渐增多.
The mechanism of electromigration in Sn3.0Ag0.5Cu flip-chip solder joints was investigated by using current density of the order of 104A / cm2.The migration of atoms (or vacancies) caused by electromigration and the formation of Joule heat in the process resulted in the formation of Sn3 .0Ag0.5Cu flip-chip solder micro-morphology changes under the action of electromigration, due to the directional migration of vacancies and the local current collector effect of the cathode chip side of the solder and intermetallic compounds form a thin layer of interlayer interface in the cathode Of the Cu pad also produced a continuous void between the Ni (P) plating and the solder, but the void area was significantly smaller than the interface between the chip-side solder and the intermetallic compound at the cathode. The Cu atoms in the pad formed under electromigration Flux in the same direction of electron flow finally leads to the continuity of intermetallic compounds in the high current density area of solder joint and the amount of intermetallic compound gradually increases from cathode to anode.