论文部分内容阅读
研究了230℃,5×103A/cm2条件下液-固电迁移对Ni/Sn-9Zn/Ni线性焊点界面反应的影响.在液-固电迁移过程中,Ni/Sn-9Zn/Ni焊点表现出明显的反极性效应,即阴极界面金属间化合物(IMC)持续生长变厚,并且一直厚于阳极界面IMC.由于排除背应力的影响,Sn-9Zn液态钎料中Zn原子的反常迁移行为归因于其有效电荷数在高温下为正值,即在电子风力作用下Zn原子向阴极界面定向迁移,从而导致焊点在液-固电迁移过程中发生反极性效应.回流焊后,Ni/Sn-9Zn/Ni焊点两侧界面上均生成了较薄的Ni5Zn21层.液-固界面反应过程中(无电流)焊点两侧界面IMC均随时间延长而生长变厚,从而消耗钎料中的Zn原子并使界面处的相平衡发生变化,导致界面IMC由Ni5Zn21转变为[Ni5Zn21+(Ni,Zn)3Sn4].与之相较,液-固电迁移过程中阴阳两极界面IMC的类型一直为Ni5Zn21,并未发生IMC类型的转变.这是由于,在电子风力作用下,阴极界面附近钎料中Zn原子的含量充足,Zn与Ni反应生成Ni5Zn21型IMC;同时,电子风力也阻碍了Zn原子向阳极界面的扩散,从而抑制了阳极界面IMC的生长,导致界面IMC较薄,因此阳极界面也未发生IMC类型的转变.此外,运用反证法进一步验证了Zn的有效电荷数在高温下是正值.
The effect of liquid-solid electromigration on the Ni / Sn-9Zn / Ni interface at 230 ℃ and 5 × 103 A / cm2 was studied. During the liquid-solid electromigration, Ni / Sn-9Zn / Ni Point showed a significant reverse polarity effect, ie, the intermetallic compound (IMC) of the cathode interface continued to grow thicker and thicker than the IMC of the anode interface. Due to the elimination of back stress, the abnormality of Zn atoms in the Sn-9Zn liquid solder The migration behavior is attributed to the fact that the effective charge number is positive at high temperature, that is, the directional migration of Zn atoms to the cathode interface under the action of electronic wind force, resulting in the reverse polarity effect of solder joints during liquid-solid migration. The Ni5Zn21 layer was formed on the interface of Ni / Sn-9Zn / Ni solder joints.The IMC on both sides of the solder joint during liquid-solid interface reaction (no current flow) grew thicker with time, Resulting in depletion of Zn atoms in the solder and a change in the phase equilibrium at the interface, resulting in the transition of the interface IMC from Ni5Zn21 to [Ni5Zn21 + (Ni, Zn) 3Sn4]. In contrast, The type of IMC has been Ni5Zn21, and no change of IMC type occurs because the interface of the cathode under the influence of electronic wind In the vicinity of the filler metal, the amount of Zn atoms in the solder is sufficient, and Zn and Ni react to form Ni5Zn21-type IMC. At the same time, the electron wind impedes the diffusion of Zn atoms to the anode interface, thereby inhibiting the growth of the IMC at the anode interface and resulting in a thin IMC interface The change of IMC type did not occur at the anode interface.In addition, the negative charge method was used to further verify that the effective charge of Zn is positive at high temperature.