Metallization development and application for aluminum nitride substrates

The aluminum nitride (AlN) substrate, a promising candidate for improved heat dissipation in microcircuits, has several excellent characteristics at room temperature, such as high thermal conductivity, over 10 times that for alumina (Al/sub 2/O/sub 3/), a thermal expansion coefficient close to that of silicon, high electrical insulating capacity, low dielectric constant and loss, good mechanical properties, and nontoxicity. A thick-film conductor-resistor paste system with excellent performance consisting of ZnO-B/sub 2/O/sub 3/-SiO/sub 2/ glass frits has been developed. In addition to the thick-film-paste system, Ni metallization on AlN substrates has been developed using Ni paste that can be fired in a nitrogen atmosphere at 1300 degrees C. AlN, with its 260 W/mK thermal conductivity, is compatible with 99.5% BeO for high-power semiconductor packages.<>