Research of joining the SiC and Cu combination by use of SnTi solder filled with SiC nanoparticles and with active ultrasound assistance

The aim of this study was to characterize a Sn-Ti solder alloy containing 6 wt.% SiC nanoparticles and evaluate its use for direct soldering of SiC ceramics to a copper (Cu) substrate. Soldering was performed with direct ultrasound activation. The average tensile strength of the solder alloy was 17.1 MPa. Differential Thermal Analysis (DTA) analysis revealed an apparent transition at 234 ℃, corresponding to a eutectic reaction within the Sn-Ti binary system, indicating structural changes in the solder. The solder matrix consisted primarily of pure tin, while titanium combined with SiC nanoparticles to form a TiC phase. The existence of this phase was confirmed by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis of the solder. The bond at the interface between the SiC ceramic substrate and the solder was formed through diffusion and chemical reactions. The XRD analysis of the fractured surface from the SiC side confirmed the formation of phases such as TiC, Ti₂Sn, CTi₂, CuSn, SiC, and Cu₆Sn₅; the TiC and CTi₂ phases resulted from the interaction of active Ti in the solder with the SiC ceramic surface. The bond at the Cu substrate interface formed due to the high solubility of tin in the solder and the formation of probable CuSnTi and CuSnTi3₅ phases, along with a mixture of Sn + η Cu₆Sn₅ solid solution. The average shear strength of the SiC/Cu joint, fabricated using SnTi3 solder with 6 wt.% SiC nanoparticles, was 21.5 MPa.