Process for forming open-centered multilayer ceramic substrates

Abstract

A multilayer ceramic substrate with an internal cavity extending from the top to the bottom surface of the substrate is produced using an insert material which fits within a cavity defined by aligned openings of individual ceramic sheets in a multilayer stack. The multilayer stack of ceramic sheets, together with the insert, is press-molded together with the insert serving as an internal mold that maintains the internal dimensions of the cavity. The insert is slightly larger in its top to bottom dimension than the multilayer stack and is driven into a compressible material underlying the multilayer stack during the pressing operation. The insert prevents the ceramic from flowing upwards into the center of the cavity during the pressing operation. In addition, the insert embeds electrically conductive pads located at various levels inside the cavity on individual ceramic sheets in the multilayer stack into the top surfaces of the ceramic sheets. After molding, the insert and the compressible material are removed from the multilayer structure. The invention has a particular application for forming multilayer ceramic structures that are connected to an integrated circuit chip and heat sink combination that will be positioned inside the cavity of the ceramic structure.