**2.13. Active solder with titanium content**

**Figure 23.** Planar EDX analysis of soldered interface of Sn2La/Al2

82 Recent Progress in Soldering Materials

**Figure 24.** Mechanism of bond formation at UT activation of SnLa2 solder.

O3 . The aim of research [28] was to study the solderability of Al<sup>2</sup> O3 ceramics, silicon and copper at the application of solder type Sn-Ag-Ti activated by ultrasound. The interactions between solder, ceramic and silicon substrates were analysed. The shear strength of fabricated soldered joints was measured.

**Figure 25.** Results of measurements of shear strength in joints fabricated with Sn2La solder.

The Sn3.5Ag4Ti (Ce, Ga) solder was used for soldering. Soldered joints were fabricated with the application of mechanical activation by power ultrasound. Heating was realized by a hot-plate method. The soldering temperature was 280°C. The dwell time at soldering temperature was 30 s and the time of ultrasound acting was 5 s. The test specimens were prepared of Al<sup>2</sup> O3 ceramics, silicon as non-metallic material and Cu as metallic material.

The microstructure of solder type Sn-Ag-Ti is documented in **Figure 26**. It consists of tin matrix. The tin matrix contains unevenly distributed constituents of intermetallic Ti-Sn phases and fine needles of silver phase, Ag<sup>3</sup> Sn, uniformly distributed along the tin grains. The presence of Ag3 Sn phase was proved by X-ray diffractometer (XRD) analysis.

XRD analysis revealed also the Ti-Sn phases. Actually identified were the Ti<sup>6</sup> Sn5 and Ti<sup>2</sup> Sn3 phases, where Ti<sup>6</sup> Sn5 phase was mostly represented. The formation of individual titanium phases depends on manufacturing the temperature of the solder, the amount of titanium added to solder and also the way of Ti addition to solder during its manufacture.

#### **2.14. Analysis of soldered joint of Sn-Ag-Ti/Al<sup>2</sup> O3**

The microstructure of Sn-Ag-Ti solder/Al2 O3 ceramics is documented in **Figure 27**. A pronounced transition zone, reaction layer with an average thickness of 2.6 μm, is formed in the interface.

The energy-dispersive X-ray spectroscopy (EDX) analysis of chemical composition has revealed that the reaction layer (**Figure 28**) contains 5.35 wt.% Al; 37.33 wt.% Ti; 2.84 wt.% Ag and 54.48 wt.% Sn. The linear course of concentration of individual elements is documented in **Figure 26**.

During soldering process, the titanium from solder is distributed to the interface with ceramic material, where a reaction layer is formed, which ensures the wettability of Al2 O3 ceramics. An oxidation-reduction reaction takes place between the active solder and ceramic material at the formation of reaction products, which allow the wetting of ceramics by an active solder (**Figure 28**).

**Figure 26.** Microstructure of Sn-Ag-Ti solder (a) in polished condition, (b) after etching of tin matrix.

Recent Advances in Solderability of Ceramic and Metallic Materials with Application of Active... http://dx.doi.org/10.5772/intechopen.69552 85

**Figure 27.** A detailed view of reaction layer in Al<sup>2</sup> O3 /Sn-Ag-Ti interface.
