1995 Volume 13 Issue 2 Pages 309-314
In this report, the problems are investigated for improving the performance of substrates, such as a large current capacity, a high dielectric breakdown voltage, a low thermal conductivity and a high reliability.
The large current capacity and the high dielectric breakdown voltage are determined respectively by the size of conductor and insulator. It was clarified by theoretical consideration that increase of conductor thickness lower the reliability and increase of insulator thickness lower thermal conductivity. The design acceptable region of performance of the substrates has been generally bounded by a dielectric breakdown voltage, a current capacity, a thermal conductivity and a thermal stress. The design acceptable region become more narrow as the performance of the substrates improved. As the reslult, a layered structure of copper and molybdenum has been suggested as the conductor and it was shown by computer simulation that molybdenum had good properties to reduce the stress of ceramics, for molybdenum properties of a low thermal expansion and a high young's modulus are suitable to restrict a expansion of copper. Furthermore, the layered conductor is effective to improve current capacity and thermal conductivity of the substrates system.
