Patent ID: 6919125

Claim:
A ceramic substrate for bonding to and supporting at least one electrically conductive trace for conduction of DC current and at least one electrically conductive trace for conduction of RF current in a microelectronic module, comprising: a ceramic body having first and second side surfaces, with said first side surface overlying said second side surface; said first side surface possessing a physical characteristic more favorable to adherence of a conductive trace for conduction of RF current than is said second side surface and said second side surface possessing a physical characteristic more favorable to adherence of conductive trace for conduction of DC current than is said first side surface; said ceramic body including a plurality of layers of sintered dielectric material, one of said plurality of layers comprising an outer layer to said ceramic body and defining said first side surface and another one of said layers comprising an outer layer to said ceramic body and defining said second side surface to said ceramic body; said one of said plurality of layers comprising a first vitrified composition of powdered ceramic material, binder and other dielectric material; said powdered ceramic material of said first vitrified composition comprising a first predetermined percentage by weight of said first vitrified composition and comprising aluminum oxide; said another one of said plurality of layers comprises a second vitrified composition of said powdered ceramic material, binder and other dielectric material; and said powdered ceramic material in said second vitrified composition comprising a second predetermined percentage by weight of said second vitrified composition and comprising aluminum oxide, said second predetermined percentage being less than said first predetermined percentage, and wherein said first predetermined percentage is 99.6 percent and wherein said second predetermined percentage is 96 percent.