Evolution of interfacial IMCs and mechanical properties of Sn-Ag-Cu solder joints with Cu-modified carbon nanotube

Cu-modified carbon nanotube (Cu-CNT) was mechanical mixed with Sn-3.0Ag-0.5Cu (SAC305) solder powder to fabricate composite solder. Experiments were carried out on the composite solder to investigate its thermal behavior and mechanical properties. Evolution of interfacial intermetallic compounds (IMCs) and shear fracture behaviors of composite solder joints were explored as well. Differential scanning calorimetry results showed that the addition of Cu-CNT increased the melting point of SAC305. Nanoindentation indicated that the hardness and modulus of composite solder increased with the increase of Cu-CNT content, indicating that the addition of Cu-CNT could improve the mechanical properties of SAC305 solder. SAC-xCu-CNT/Cu (x = 0, 0.1 and 0.2 wt%) composite solder joints were obtained by reflow soldering, aging experiment was carried out subsequently. The results showed that Cu-CNT as the reinforcement phase of SAC305 solder could inhibit the growth of IMC. The suppression effect was enhanced when the content of Cu-CNT increased from 0.1 to 0.2 wt% in SAC305. The growth rate of the IMC layer of the composite solder joint with 0.2 wt% Cu-CNT was the lowest. Shear tests showed that adding Cu-CNT could improve the shear strength of solder joints and the fracture mode of the solder joint changed from mixed fracture to ductile fracture.