Effect of reflux time and aging treatment on the interfacial reaction of SnAgCuSbBiNi/Cu solder joint

In the electronic industry, the packaging substrate is mainly made of copper, hence the interfacial reaction between solder and Cu during the soldering and the service process of solder joint always draw peoples' attention. In this study, a Sn3.8Ag0.7Cu1.5Sb3.0Bi0.15Ni (tentatively named as SACSBN) solder paste was evaluated on Cu substrate with comparison to Sn3.0Ag0.5Cu (SAC305). The effects of reflux time and aging temperature on the interfacial reactions of solder joints were investigated. Solid-state IMC growth behavior was also investigated through high temperature storage (HTS). The results show that within the as-reflowed solder joint, the primary Sn-rich phase, the Ag
3
Sn phase, Cu
6
Sn
5
, and Cu
3
Sn were observed in SAC305 solder joint, while SACSBN solder joint was composed of (Cu,Ni)
6
Sn
5
, Ag
3
(Sn,Sb), Cu
3
Sn phase, and Sn-Matrix with Sb and Bi dissolved in it. The Bi was precipitated and appears in the Sn matrix in small and isolated clusters in SACSBN solder joint. Besides, the thickness of IMC and the size of Cu
6
Sn
5
and Ag
3
Sn increased with reflux time. When stored at 150°C for 7 and 16 days respectively, IMC displayed a rapid thickening in a relatively short period. However, the average growth rate of IMC was decreased with aging time, especially for that of Cu
3
Sn. Moreover, the solder of SACSBN can significantly inhibit the growth of Cu
3
Sn.