High dielectric AlN/Al2O3 composite powder using a plasma spray approach for microelectronics application

Increasing demand for higher performance dielectric material for multi-laye r ceramics packaging has led to the use of the AlN system due to its very h igh thermal conductivity and coefficient of expansion compatibility with si licon. This paper reports on a novel process method used to produce an AlN/ Al2O3 composite powder system which can be subsequently tape cast as a diel ectric substrate. The mixture of both Al2O3 and AlN was first mechanically alloyed and then spray-dried to obtain a suitable agglomerated powder that was subsequently plasma-sprayed, resulting in a fine micrometer level integ rated composite powder. The two main criteria used to ascertain the optimal process parameters during plasma spraying were a high gamma/alpha Al2O3 ph ase ratio, which ensured that all the Al2O3 phase had melted during plasma spraying, and a minimal reduction in the AlN/Al2O3 ratio to ensure minimal change in the AlN during processing. For the plasma-sprayed composite powde rs, fully sintered ceramic tapes were produced attaining > 99.0% of the the oretical density after sintering at 1650 degrees C for 6 h, which yielded a thermal conductivity value of 32.0 W m(-1) K-1.