Interfacial intermetallic growth and mechanical properties of carbon nanotubes reinforced Sn3.5Ag0.5Cu solder joint under current stressing

•MWCNTS are doped in Sn3.5Ag0.5Cu solder by mechanically dispersing.•With the higher addition of CNT, the IMCs become smoother and more uniform, and fewer voids are formed.•The growth rate of the IMCs is hindered in the doped solders.•Shear strength and hardness have been improved with MWCNTs reinforcement. In this work, multi-walled carbon nanotubes (MWCNTs) with various weight percentages of 0.01wt%, 0.05wt%, 0.1wt% were incorporated into Sn3.5Ag0.5Cu (SAC) solder matrix by mechanical blending followed by reflow process. The microstructure with interfacial intermetallics (IMCs) growth were investigated after aging at 100°C and a current density of 1.2×104A/cm2 for 336h. CNTs were found to be homogeneously dispersed into the solder matrix by EDX analysis. Experimental results revealed that microporosities existed in some areas of doped solders, which retarded the formation of Ag3Sn IMCs. The growth of IMCs for CNTs reinforced solders was less significantly than that of the plain solder, because CNTs affected the reaction mechanisms of both Cu5Sn6 and Cu3Sn at the anode side and alleviated IMCs growth and solder dissolution into Cu substrate at the cathode side. A slight decrease in melting temperature for CNT reinforced solders was found compared to that of the plain solder. The CNT doped solders demonstrated promising improved shear strength and hardness.