AIN properties of various producers

AlN has many advantageous properties. These concern a high thermal conductivity, a non-toxic nature, a temperature coefficient of expansion (TCE) that closely matches the TCE`s of both silicon and gallium arsenide making AlN useful for direct mounting of large VLSI dies. A constant quality of this ceramic is decisive for a reproducible packaging. Different substrate qualities (as-fired, lapped, polished) of 5 producers were investigated. The substrates distinguish in following: I. the middle size of grains in the AlN-polycrystal (1...11 mu m); II. the substrate roughness (0,2...0,9 mu m); III. the amount of additional phases (Al2Y4O9, AlYO3, Al5Y3O12); IV. the thermal conductivity (100...200 W/mK); V. the bending strength (300...430 MPa).