Abstract
In the paper the conditions of joining of copper matrix-carbon fibre composite with thin gold layer coated alumina by In50Pb50 and Sn60Pb36.5Ag3.5 (Soldamol 170) solders and their influence on the joint strength are presented. Joining was done in vacuum of the order of 10^-3 Pa at the temperatures 483-523 (553) K during 600-1800 s. Joint strength (shear strength) was measured by push-off method in Instron testing machine. Maximum shear strength with Soldamol 170 solder, 23.4 MPa, was reached for joining temperature 523 K and time 600 s, maximum shear strength with In-Pb solder, 17.2 MPa, was reached for joining temperature 523 K and time 1800 s. Joint strength increases with time and temperature of joining for both solders until defect in joint integrity originates due to the difference in thermal expansion of ceramic, solder and composite. The joint structure study reveals that joint strength is controlled by the mutual diffusion of gold and indium into InPb solder, and gold and tin in Soldamol 170 solder, and by the development of the
phases corresponding to AuIn₂ and AuSn₄, respectively.

Key words
composite material, copper matrix, aluminium oxide, joining, joint strength

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