Effect of the ultrasonic-assisted soldering on the interfacial reaction and IMC growth behavior of SAC305 solder with Cu alloy substrates

This paper aims to study the effect of soldering time and ultrasonic-assisted time to microstructures, chemical compositions and thickness of intermetallic compounds (IMCs) of three types solder joints after soldering at 290 °C. The Sn3.0Ag0.5Cu (SAC305) solder and three types substrate (pure Cu, Cu–50Co and Cu–50Fe) were selected. The results showed that the compounds formed at the SAC305/Cu solder joint were Cu 3 Sn and spherical Cu 6 Sn 5 , the stick-like (Co,Cu)Sn 3 and finely needle-like (Cu,Co) 6 Sn 5 were generated in SAC305/Cu–50Co, while the prismatic (Cu,Fe) 6 Sn 5 and finely granular FeSn 2 were produced in SAC305/Cu–50Fe. With the soldering time increased, the IMC overall thickness of all three types solder joints gradually increased. While ultrasound was used, the morphology of Cu 6 Sn 5 , (Co,Cu)Sn 3 and (Cu,Fe) 6 Sn 5 transformed into prismatic shapes, blocky and slender stick due to cavitation and acoustic flow effects. Moreover, with the application of ultrasound, the IMC thickness of SAC305/Cu and SAC305/Cu–50Co solder joints decreased first then started to up, while that of SAC305/Cu–50Fe solder joints decreased and then remained unchanged.