SnAgCu-Bi-Ni无铅微焊点的电迁移行为

Electromigration of SnAgCu-Bi-Ni Pb-free Micro Solder Joints

以直径为400μm的SnAgCu-Bi-Ni(Ag<1%)微焊点为对象,研究了微焊点在电流时效过程中的电迁移行为.对球栅阵列(ball grid array,BGA)焊点组装电路在不同温度下进行不同时长的电流时效试验.从焊点微观组织和硬度梯度的变化两个方面分析了电迁移现象的行为规律.研究结果表明,电迁移试验后焊点阴极区域金属间化合物(intermetallic compound,IMC)分解,附近形成大量微空洞,Cu焊盘大量消耗,焊点中部和阳极形成了大量(Cu,Ni,)6Sn5化合物,附近形成大量小丘,电迁移作用导致焊点内部微硬度形成由阳极向阴极递减的梯度分布,较高的试验温度显著加快电迁移进程.

In this paper, the electromigration behavior of 400lxm sized solder interconnects （SnAgCu-Bi-Ni, Ag 〈 1% ） was investigated. Current stressing tests were conducted with assembled BGA package at different tem- peratures for different periods. The microstructure evoluation at the interface and hardness gradient distribution in- side older bulk were studied. The results indicated that after the electromigration test, the intermetallic compounds （IMC） disappeared and a large number of micro voids appeared closeto cathode area where the copper were con- sumed obviously. A large amount of （Cu,Ni）6Sn5 IMC and hillocks were observed at the anode. With current stressing, the hardness of solder joint increased from cathode to anode. High aging temperature increases electromi- gration behavior significantly.