Alumina substrate and method of manufacturing same
AssigneeFujitsu Limited
InventorsSeiichi Yamada, Kyohei Murakawa
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Abstract
An improved alumina substrate comprising alumina and magnesium oxide has a surface finish of no more than 0.05 .mu.m CLA and a density of at least 3.90 g/cm.sup.3 in an as-fired condition and is composed of alumina grains which are sufficiently grown to have straight grain boundaries and flat surfaces to form a surface of the substrate. The improved substrate is produced by firing a green sheet having a high content of raw material powder and a density of more than 2.60 g/cm.sup.3 at a temperature of 1525.degree. to 1650.degree. C. The green sheet with high density is formed by the process of aggregating an organic agent and a high purity alumina powder by dry milling and casting the resultant slip.
Claims13
A method of manufacturing an alumina substrate having a surface finish of no more than 0.05 .mu.m center line average on at least one major surface and a density of at least 3.90 g/cm.sup.3 in an as-fired condition, comprising the steps of:
- making an aggregated raw material powder by dry milling a mixture consisting of fine alumina particles, having high purity, and a grain growth inhibitor of 0.1 to 0.5 wt. %;
- producing a slip consisting of said aggregated raw material powder and an organic agent comprising a binder and a solvent;
- said solvent is provided to ensure that said raw material powder is uniformly dispersed in said slip;
- forming a solvent-free green sheet from said slip, having a high content of said raw material powder and a density of more than 2.60g/cm.sup.3, said step of forming including the step of subjecting said slip to a vacuum to eliminate bubbles and evaporate said solvent from said slip, followed by the step of shaping said solvent-free slip into a sheet and the further step of drying said sheet at room temperature;
- and firing said green sheet at a temperature in the range of 1525.degree. C to 1650.degree. C until said alumina particles in said fired sheet grow sufficiently to form straight boundaries and flat surfaces corresponding to said major surface of said alumina substrate.
Dependencies are inferred from the claim text.