Interfacial reactions of Sn脙脙脙脙脙脙Cu solder with Ni/Au surface finish on Cu pad during reflow and aging in ball grid array packages
- 作者：Islam ; M.N. ; Chan ; Y.C.
- 关键词：Sn0.7Cu solders ; Ni UBM ; Extended time of reflow and aging ; Interfacial reactions ; Shear strength
- 刊名：Materials Science & Engineering B
- 出版年：2005
- 期刊代码：76_09215107
- 类别：ch
- 出版时间：March 25, 2005
- 卷：117
- 期：3
- 页码：246-253
- 文件大小：503 K
摘要
The interface between the solder and the under-bump metallization (UBM) affect the reliability of the solder joints. In this paper an investigation is reported on the interfacial reactions of Sn0.7Cu (wt.%) solder on electrolytic Ni layer for different times of reflow and solid-state aging. It is found that during reflow, the formation of Sn013;Cu013;Ni ternary intermetallic compounds (IMCs) at the interface of solder joints is much quicker, resulting in the entrapment of some Pb (which is present as impurity in the Sn013;Cu solder) rich phase in the ternary IMCs. The growth rate of IMCs during reflow is higher than that in aging. Less than 3
0;μm of the electrolytic Ni layer was consumed by the higher Sn-containing Sn0.7Cu solder with 180
0;min molten reaction at 250
0; 0;C and with 16 days aging at 175
0; 0;C. Ni and Au can diffuse into the Sn013;Cu solder in both solid and liquid state and form stable quaternary compounds in the solder. The diffusion of Au into the high Ni-containing ternary and quaternary compounds is found to be low. The shear strength of solder joint is relatively stable from 1.98 to 1.86
0;kgf during long time reflow with high Ni and negligible amount of Au in the ternary IMCs at the interface. The shear strength during aging increases up to 4 days and than decreases with the increase of aging time up to 12 days. It is due to the formation of quaternary compounds with relatively higher amount of Au.