Effect of adding 0.3 wt percent Ni into the Sn-0.7 wt percent Cu solder Part II. Growth of intermetallic layer with Cu during wetting and aging

摘要

The growth behavior of intermetallic layer with or without adding 0.3 wt percent Ni into the Sn-0.7Cu solder was studied during the wetting reaction on Cu-substrate and thereafter in solid-state aging condition. The Cu-solder reaction couple was prepared at 255,275 and 295 deg C for 10 s. The samples reacted at 255 deg C were then isothermally aged for 2-14 days at 150 deg C. The reaction species formed for the Sn-0.7Cu/Cu and Sn-0.7Cu-0.3Ni/Cu soldering systems were Cu_6Sn_5 and (CuNi)_6Sn_5, respectively. The thickness of the intermetallic compounds formed at the solder/Cu interfaces and also in the bulk of both solders increased with the increase of reaction temperature. It was found that Ni-containing Sn-0.7Cu solder exhibited lower growth of intermetallic layer during wetting and in the early stage of aging and eventually exceeded the intermetallic layer thickness of Sn-0.7Cu/Cu soldering system after 6 days of aging. As the aging time proceeds, a non-uniform intermetallic layer growth tendency was observed for the case of Sn-0.7Cu-0.3Ni solder. The growth behavior of intermetallic layer during aging for both solders followed the diffusion-controlled mechanism. The intermetallic layer growth rate constants for Sn-0.7Cu and Sn-0.7Cu-0.3Ni solders were calculated as 1.41 x 10~(-17) and 1.89 x 10~(-17) m~2/s, respectively which indicated that adding 0.3 wt percent Ni with Sn-0.7Cu solder contributed to the higher growth of intermetallic layer during aging.