*Active Solders and Active Soldering DOI: http://dx.doi.org/10.5772/intechopen.82382*

*Fillers - Synthesis, Characterization and Industrial Application*

reaction with the substrate. Smith [41] has reported that mechanical agitation such as edge abrasion, brushing, vibration, and ultrasonic pressure can disrupt the molten active solder's surface oxide, thus permitting metallurgical interaction between the active elements, Ti and rare earth elements, and substrate. **Figure 6** illustrates mechanical agitation to disrupt the oxide layer to activate the molten active solder [41].

*Schematic of the wetting process of low melting point filler metal with high-temperature activation [44].*

**56**

**Figure 6.**

**Figure 5.**

*Schematic of mechanical activation and soldering process [41].*

Chang et al. [26, 29, 30] have investigated ITO/Cu, ZnS–SiO2/Cu, and Al2O3/ Cu joints using Sn3.5Ag4Ti(Ce, Ga) and mechanical agitation at 250°C. They have indicated that the affinity of rare earth elements to oxygen gives rise to the reaction of Ti with ITO, ZnS-SiO2, and Al2O3 at a low temperature of 250°C. Their results have also shown a strong tendency of Ti to segregate at the ITO/solder, ZnS-SiO2/ solder, and Al2O3/solder interfaces. Cheng et al. [45, 46] investigated the influences of the active element Ti on interfacial reaction and soldering strength between Sn3.5Ag4Ti(Ce, Ga) alloy filler and Si substrate as well as SiO2/SiO2 joints. They also found that Ti played a critical role in obtaining reliable bonds for active soldering. The chemical adsorption of Ti on the substrate and the interfacial reaction between Ti and substrate were the active mechanisms. Similar to the cases in previous studies [24, 27], the joining process of ceramics can be performed using Sn56Bi4Ti(Ce, Ga) filler at temperatures lower than 180°C. The schematic in **Figure 7** illustrates the wetting process of low melting point filler metal with mechanical activation [47].
