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The purpose of this paper is to study the effect of the addition of a small amount of Al (0.1 percent) on the properties of lead‐free solder type Sn‐4Ag‐0.5Cu (SAC 405).

The soldering properties of wettability and spreadability on a Cu substrate were studied, and the effect of Al on the growth of intermetallic compounds (IMCs) was observed. The shear strength of soldered joints was assessed. For comparison, soldering and strength tests were carried out on SAC 405 and SAC 405+ Al solders. Soldering was performed with an activated flux type ZnCl₂‐NH₄Cl, with non‐activated flux (rosin), and without flux in the air.

Experimental results show that Al addition slightly reduces the wettability and spreadability of SAC 405 solder. Also, the shear strength is moderately reduced, dropping by 8 MPa on average. Differential scanning calorimetry (DSC) analysis showed that the melting point of SAC 405+0.1%Al solder was increased to 221°C.

The positive effect of a small Al addition is due to the fact that it hinders the growth of IMCs formed on the contact surface with Cu substrate. The width of the transition zone of IMC was reduced by approximately 2 to 3 μm, depending on the soldering temperature.

The purpose of this paper is to study Bi‐11Ag solder for higher application temperatures. The aim of the research work was to determine the soldering, thermal and mechanical properties of Bi‐11Ag solder.

To determine the melting point interval of experimental Bi‐11Ag solder, DSC analysis was performed. The contact angles were studied on a copper, nickel and silver substrate by use of a sessile drop method. Wettability tests were realised at a temperature of 380°C in a shielding atmosphere (90% N₂+10% H₂). Based on experience achieved with wetting angle measurements, the specimens for measurement of shear strength of Cu, Ni and Ag/Bi‐11Ag joints were fabricated. EDX analysis was used for the study of the solder interaction with the surface of the three metallic substrates.

The best wettability at soldering in a shielding atmosphere was achieved with silver. The wetting angle at 30 min attained the value of 23°. The worst wettability was observed on copper, where at 30 min the wetting angle was 55°. Average shear strength varied from 31 to 45 MPa. The highest strength was obtained with the Cu substrate whereas the lowest was with the Ni substrate. The lowest strength achieved with the Ni substrate was caused by formation of brittle intermetallic phase NiBi₃. Joint formation is realised by eutectic reaction at the contact of Bi with the surface of the copper substrate. Similar joint formation by eutectic reaction occurs also at Bi interaction with the surface of the Ag substrate. At Bi interaction with the nickel substrate a new intermetallic phase (NiBi₃) is formed.

Wettability of Bi‐11Ag solder on Cu, Ag and Ni substrates was determined at application of a shielding atmosphere (90% N₂+10% H₂). Wettability was determined also at application of ZnCl₂‐NH₄Cl flux. The shear strength of Bi‐11Ag on different substrates was determined. The mechanism of joint formation was analysed.

The purpose of this paper is to investigate the wettability of an active Sn2Ti solder on an Al₂O₃ ceramic material at temperatures of 700°C and higher. Based on the results of the wettability study, soldered joints of Al₂O₃ ceramics/Sn2Ti solder/steel type AISI 321 were fabricated and the variation of shear strength with time was determined.

For determining melting points, differential scanning calorimetry analysis was performed. The wetting angle of Sn2Ti solder on Al₂O₃ ceramics was measured using specially developed equipment with a 10‐3 Pa vacuum at temperatures of 700, 800, 850 and 900°C. The wetting angle on AISI 321 steel at a temperature of 850°C was also determined. The joints of Al₂O₃ ceramics/Sn2Ti solder/steel type AISI 321 were prepared at 900°C, in a vacuum for times 5, 10, 15 and 20 min.

The best wettability of Sn2Ti solder was achieved at a temperature of 900°C. The wetting angle at the parameter of 900°C/ for 15 min was 47.5°. The joints of Al₂O₃ ceramics/Sn2Ti solder/steel type AISI 321 attained a strength of 18.3 MPa. It was found that the microstructure of Sn2Ti solder consists of a tin matrix with the presence of a αTi6Sn5 phase.

The results of the work are of significance for the further development of soldering with active solders in a vacuum, as well as with the application of power ultrasound. The possibility of soldering Al₂O₃ ceramics with SnTi‐based solders was thus demonstrated.

The work aims to study the direct bonding of silicon substrate with solders type Sn-Ag-Ti.

During the bonding process with ultrasound assistance, the active element (Ti,Ce,Mg) is distributed from the solder to interface with a silicon substrate, where it supports the bond formation.

Formation of a reaction layer, 1-2 μm in thickness, was observed. The new Si2Ti phases and Mg2Si phase were identified in the reaction layer.

The results of analysis suggest that the Si/Sn-Ag-Ti joint is of diffusion character. The highest average strength on silicon substrate (39 MPa) was achieved with Sn-Ag-Ti(Mg) solder.