Brodnikovska I. Development of high heat-conducting substrates for multichip microassemblies working in extreme conditions

Dissertation is devoted to development of high heat-conducting substrates for large-size multichip microassemblies based on silicon nitride working in extreme conditions of high mechanical and thermal loadings; as well as the thermal conductivity coefficient estimation of small samples with various shape and surface roughness, and also electrical microstructure monitoring of silicon nitride ceramics. It was shown that hot pressed Si3N4-5vol.%Al2O3 ceramics, obtained with the time of isothermal holding 30-35 min and cooling rate 40-50 °C/min, with addition of up to 4vol.%TiO2 has the highest thermal conductivity (up to 65 W/(m·K)), high resistivity (10^12-10^13 Ohm·cm), hardness (up to 17 GPa), fracture toughness (up to 7 MN/m^3/2) and it is suitable for dielectric layers of MCM substrates. The management methods of electroconductive layer specific resistance at constant volume content of conductive phase by the change of dispersion of conductive particles and variation of isothermal soaking temperature were pointed. The methods of materials heat-conduction estimation by the set of probes were developed and theoretically substantiated. That extended the range of measuments (up to 20%). The nondestructive methods of microstructure monitoring on the base of activation energy, dielectric response and electrical models of microstructure were established.