| Summary: | The aim of this study was to characterize a Zn-Mg type soldering alloy and direct soldering of SiC ceramics with a copper substrate. The Zn1.5Mg solder exerts a wider melting interval. The temperature of the eutectic reaction was 365 °C, and the liquidus temperature was 405 °C. The microstructure of the soldering alloy is comprised of a zinc matrix. Segregation of binary eutectics in the form of (Zn) + Mg<sub>2</sub>Zn<sub>11</sub> lamellas occurred on the boundaries of Zn grains. Additionally, the presence of a MgZn<sub>2</sub> magnesium phase was observed in the solder matrix. The SiC/solder bond was formed due to magnesium distribution from solder to the boundary with SiC ceramics, where magnesium reacts with silicon, which is infiltered in SiC ceramics. By a mutual interaction, a new Mg<sub>2</sub>Si phase is formed. An interaction between the molten zinc solder and Cu substrate occurred on the boundary of the Cu/substrate joint at the formation of a transition zone composed of two new phases, namely the γCu (Cu<sub>5</sub>Zn<sub>8</sub>) non-wettable phase type, approximately 30 µm wide, and a wettable (CuZn<sub>4</sub>) phase type ε, approximately 12 µm wide. The average shear strength of a combined SiC/Cu joint fabricated using Zn1.5Mg solder was 44 MPa.
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