Fabrication and Reliability Evaluation of Silicon Nitride-Copper Ceramic Substrates

Abstract：The high reliability of silicon nitride-copper ceramic substrates makes it one of the most promising materials for the power electronics in the field of high-speed train，electric cars，and etc. The import from Japan is expensive and time consuming which is an obstacle for the development of related industries. High performance silicon nitride ceramic was fabricated by gas pressure sintering. And the silicon nitride-copper ceramic substrate was obtained by active metal brazing method. The bending strength of silicon nitride ceramics is 800 MPa. The fracture toughness is 8. 0 MPa·m^½. The thermal conductivity is 90 W/（m·K）. The breakdown strength under alternate current is 40 kV/mm. The volume resistivity is 3. 7 × 10¹⁴ Ω·cm. The peeling strength of the silicon nitride-copper ceramic substrates by active metal brazing is 130 N/cm. The thermal shock test was carried out under - 45-150 ℃ . As a result，the cycles of silicon nitride-AMB-copper ceramic substrates are 10 times and 100 times than the aluminum nitride-AMB-copper and alumina-DBC-copper ceramic substrates， respectively. As the thickness of copper is 0. 32 mm/0. 25 mm，the cycles reach 5 000 times；and the thickness of copper is 0. 5 mm/0. 5 mm，the cycles reach 1 000 times；both the silicon nitride-AMB-copper ceramic substrates are in good condition without microcracks. As the thickness of copper is 0. 8 mm/0. 8 mm，the cycles reach 500 times without microcracks，which is similar to the cycles of the aluminum nitride-AMB-copper ceramic substrates with the copper thickness of 0. 32 mm/0. 25 mm. The reliability of silicon nitride copper-ceramic substrates is obviously better than aluminum nitride products.

Key words：Si3N4 ceramic；copper clad substrate；active metal brazing；reliability；power device