Development of Thermal Fatigue-Tolerant Active Metal Brazing Substrates Using Highly-Thermal Conductive Silicon Nitrides with High Toughness

Newly-developed silicon nitride ceramics with both high thermal conductivity of 140 W/(mK) and superior fracture toughness of 10.5 MPa m(exp 1/2) were employed for active metal brazing (AMB) substrate and its resistance to the thermal fatigue was investigated under severe heat cycle condition from -40 deg C to 250 deg C. No peeling off of copper layer was observed even after 1000 cycles. Acoustic scanning microscope imaging of the ceramic substrates after 1k cycles hardly detected cracks below the Cu layer. In addition, negligible degradation in the bending strength of the AMB substrates was observed. It was revealed that the newly-developed Si3N4 AMB substrate possesses not only excellent heat dissipating ability, but also superior mechanical reliability under harsh thermal environments.