**2.17. Shear strength of soldered joints**

The formation and composition of reaction layer may be well observed on the planar distribution of elements attained by EDX analysis. **Figure 30** shows the map of elements in the interface of soldered joint. In **Figure 30**, we may also see the segregation of Ti on Si/Sn-Ag-Ti interface; 28 wt. % Ti was observed in the reaction zone, while the balance consisted of silicon.

In case of solder type Sn-Ag-Ti, the main role in bond formation with Cu substrate is played

cases, which are growing in the direction from the phase interface to solder matrix. The

Sn5

phases were identified in the solder/Cu substrate interface in all

phase is in contact with Sn-Ag-Ti solder.

**2.16. Analysis of Sn-Ag-Ti/Cu-soldered joint**

Sn5

Cu3Sn phase is closer to Cu substrate and the Cu6

**Figure 29.** Reaction layer on Si/Sn-Ag-Ti solder interface.

**Figure 30.** Map of Si, Ag, Sn and Ti elements in the interface of Si/Sn-Ag-Ti joint.

by tin. The Cu3Sn, Cu<sup>6</sup>

86 Recent Progress in Soldering Materials

The research of this study was primary oriented to soldering of ceramic Al<sup>2</sup> O3 substrate, silicon substrate and copper substrate. However, the experiments performed in the study of shear strength of soldered joints were extended to other metallic materials (Al, Ni, Ti and CrNi steel type AISI 316) and SiC ceramics in order to approve wider applicability of Sn-Ag-Ti solder.

The measurement was performed on four specimens of each material. The results of average shear strength are documented in **Figure 32**. The lowest shear strength was observed with silicon, 23.0 MPa. Higher strength, attaining 33.0 MPa, was observed with Al2 O3 , whereas with copper the shear strength attained even 35.1 MPa.

The Sn-Ag-Ti solder exerted small differences in shear strength on metallic and ceramic materials. It may be generally said that the shear strength of joints in metallic materials is comparable with the shear strength attained on ceramic materials.

**Figure 31.** Analysed microstructure in interface of Cu/Sn-Ag-Ti solder joint.

**Figure 32.** The shear strength of joints fabricated with Sn-Ag-Ti solder.
