电迁移对Ni／Sn3．0Ag0．5Cu／Au／Pd／Ni—P倒装焊点界面反应的影响
- 大连理工大学,材料科学与工程学院,辽宁省先进连接技术重点实验室,大连116024
摘要: 本文研究了150℃，1．0×104A／cm2条件下电迁移对Ni／Sn3．0Ag0．5Cu／Au／Pd／Ni-P倒装焊点界面反应的影响．回流后在solder／Ni和solder／NiP的界面上均形成（Cu，Ni）6Sn5类型金属间化合物．时效过程中两端界面化合物都随时间延长而增厚，且化合物类型都由（Cu，Ni）6Sn5转变为（Ni，Cu）3Sn4．电迁移过程中电子的流动方向对Ni—P层的消耗起着决定性作用．当电子从基板端流向芯片端时，电迁移促进了Ni—P层的消耗，600h后阴极端Ni-P层全部转变为Ni2SnP层．阴极界面处由于Ni2SnP层的存在，使界面Cu-Sn—Ni三元金属间化合物发生电迁移脱落溶解，而且由于Ni2SnP层与Cu焊盘的结合力较差，在Ni2SnP／Cu界面处会形成裂纹．当电子从芯片端流向基板端时，阳极端Ni—P层并没有发生明显的消耗．电流拥挤效应导致了阴极芯片端Ni层和Cu焊盘均发生了局部快速溶解，溶解到钎料中的Cu和Ni原子沿电子运动的方向往阳极运动并在钎料中形成了大量的化合物颗粒．电迁移过程中（Au，Pd，Ni）Sn4的聚集具有方向性，即（Au，Pd，Ni）Sn4因电流作用而在阳极界面处聚集．
Effect of electromigration on interfacial reaction in Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P flip chip solder joints
- 大连理工大学,材料科学与工程学院,辽宁省先进连接技术重点实验室,大连116024
Abstract: The effect of electromigration (EM) on the interracial reaction in the Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P flip chip solder joint is investigated under a current density of 1.0 ×104 A/cm2 at 150℃. The (Cu,Ni)6Sn5 intermetallic compounds (IMCs) form at both solder/Ni and solder/Ni-P interfaces in the as-reflowed state. During aging at 150℃, the (Cu,Ni)6Sn5 interfacial IMCs grow thicker and transform into (Ni,Cu)3Sn4 type after 200 h at solder/Ni interface and 600 h at solder/Ni-P interface, respectively. During EM, the current direction plays an important role in Ni-P layer consumption. When electrons flow from Ni-P to Ni, EM enhances the consumption of Ni-P, i.e., the Ni-P s completely consumed and transforms into Ni2SnP after EM for 600 h. There is no Cu-Sn-Ni ternary IMC at the solder/Ni-P interface (cathode). Crack forms at the Ni2SnP/Cu interface due to the weak bonding force between Ni2SnP and Cu. When electrons flow from Ni to Ni-P, no obvious consumption of Ni-P is observed during EM; the current crowding effect induces a rapid and localized dissolution of Ni UBM and Cu pad at the chip side (cathode). The dissolved Ni and Cu atoms are driven along the flowing direction of electrons and form a large number of IMC particles in the solder matrix. During EM, the (Au,Pd,Ni)Sn4 phase prefers to be redistributed only at the anode interface, regardless of the direction of electron flow.
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