Design of Silicon Nitride and Stainless Steel joint for Airtight Seal Parts

The structure of Si3N4/SUS304 joints using a Cu-Ti type active-metal brazing material is discussed. As a Cu-Ti brazing metal makes a small fillet on Si3N4/SUS304 bonding, the edge structure of the copper interlayer is very important for reducing residual stress. Cone-shaped Si3N4 was applied in the present study, with the aim of suppressing local stress generated by the unequal distribution of brazing metals. A suitable thickness for the copper interlayer, as well as specifications for taper and slit formation at the interlayer edge, were determined based on stress analysis and bonding strength evaluation. Those findings led to a great improvement in the tensile test results for the joint, and the tested design proved effective in a Si3N4/SUS304 joint, providing decreased residual stress and increased reliability in the bonded seal parts.