Very smooth and flat polycrystalline alumina substrates from direct firing
AssigneeNorton Company
InventorsAnil K. Agarwal, Robert A. Hay
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Abstract
This invention provides thin, flat, water-impervious polycrystalline ceramic bodies composed of at least 99.5% by weight alumina, predominantly in the alpha crystal form. These bodies have a density of at least 3.9 Mg/m.sup.3, an average surface roughness of 44 nm or less, typically 40 nm or less. The properties of the finished ceramic bodies make them ideal substrates for highly reliable electronic components, especially for high temperature environments. Processes for obtaining such bodies by direct firing of slip cast tapes are also described.
Claims10
An as-fired thin, flat, water-impermeable sintered polycrystalline ceramic body consisting essentially of at least 99.5% by weight alpha-alumina said ceramic body having a density of at least 3.9 Mg/m.sup.3, and an average surface roughness on both major surfaces not greater than 44 nm said alumina being made from generally uniformly sized particles such that 98% have a size of less than 1. micron and more than 90% are within a size range of about 0.3 microns or less.
In a process for the production of thin, flat, water-impermeable sintered polycrystalline ceramic substrates by tape casting a slurry of ceramic powder, drying to give a greenwave substrate, and firing to give a coherent ceramic substrate, the improvement wherein the ceramic powder used to prepare said slurry is processed to obtain a narrow particle size dispersion such that the ceramic powder in such slurry has at least 90% of its particles within a size range not broader than 0.3 microns and also 98% of its particles are less than 1 micron in size.
A thin, flat, water-impermeable non-fused polycrystalline ceramic body consisting essentially of at least 99.5% by weight of alpha-alumina said ceramic body having a density of at least 3.9 Mg/m.sup.3 and being capable of being ground or polished to a ceramic body which is substantially free of surface defects having an average surface roughness not greater than 44 nm wherein said ceramic body is prepared from an alumina slurry having at least 90% of its alumina particles within a size range of no broader than 0.3 micron, and with 98% of its particles less than 1 micron in size.
Dependencies are inferred from the claim text.