Translucent A1N Ceramic Substrate

A translucent aluminum nitride (AlN) substrate has recently come into the market which has a thermal conductivity of 140 W/mK at room temperature and 130 W/mK at 100°C, eight times that of alumina (Al
2
O
3
) and one-half to two-thirds that of beryllia (BeO). Its excellent electrical and mechanical properties as well as inherent light transmitting property ensure that the new AlN material can be used as high-performance ceramic substrates for high-power and high-speed semiconductor modules. Metallization of the ceramic has been done by three methods: 1) tungsten metallization by a co-firing process, which is a fundamental technology for the coming multilayer AlN packages; 2) metallization with silver-palladium (Ag/Pd) conductor and ruthenium-oxide (RuO
2
) resistor, which was developed for the translucent AlN substrate; and 3) molten metal metallization, which gives very high adhesive strength. Development of an improved AlN ceramic with a thermal conductivity exceeding that of BeO is also described.