Determination of local thermal conductivity of soldered joints of InGaP/Ga(In)As/Ge heterostructure with heat-dissipating AlN ceramics based on Sn$_{42}$Bi$_{58}$ alloy by laser photodeflection microscopy

The method of laser scanning photodeflection microscopy was used to study heat flows through soldered joints in the kilohertz modulation range. Local thermal conductivities inside the solders made using flux and fluxless solders based on the eutectic alloy Sn$_{42}$Bi$_{58}$ were estimated. It was shown that the thermal conductivity of the solder differs from the tabular thermal conductivity of the alloy and depends on the type of solder and soldering technology. Increasing the pressure on the elements being joined during sol-dering allows reducing the thermal resistance of the solder.