Abstract
The mechanical strength properties of ceramic/metal substrates exposed to cyclic thermal loadings were studied in order to discuss the effects of the number of thermal loadings on the residual strength of the substrates. First, thermal stress analysis was performed using the finite element method for an examination of the thermal stress behaviors during the cyclic thermal loading processes. Next, test samples of Cu/AIN substrates, including brazing filler metals of AgCuTi, were prepared by brazing in a vacuum furnace. Thirdly, thermal cycling tests with cycle numbers of 25,50 and 100 were conducted on the test samples. Finally, four-point bending tests were conducted on the thermally-loaded samples to evaluate residual strength. The results showed that residual strength increased after 25 thermal cycles. In contrast, thermal cycling with 25-100 cycles resulted in a reduction of residual strength. These behaviors were discussed in terms of residual stress relaxation and a mechanism for the microscopic damage of sintered materials with polycrystalline structures.
