Multilayer ceramic substrate and production method thereof

A multilayer ceramic substrate having a cavity and comprising a plurality of ceramic layers integrally laminated and including a cavity bottom formation ceramic layer that constitutes a bottom of the cavity and cavity formation ceramic layers, each of which has a through hole conforming to an opening of the cavity, and a conductive pattern formed on the cavity bottom formation ceramic layer as straddling a periphery of the cavity bottom, wherein in a portion of the periphery of the cavity bottom at least overlapping the conductive pattern, a wall surface of the through hole of a first cavity formation ceramic layer laminated immediately on the cavity bottom formation ceramic layer is at a position outside a wall surface of the through hole of a second cavity formation ceramic layer laminated immediately on the first cavity formation ceramic layer.

A multilayer ceramic substrate produced through firing of a plurality of substrate green sheets laminated, having a cavity with an opening and comprising a plurality of ceramic layers including a cavity bottom formation ceramic layer that constitutes a bottom of the cavity and integrally laminated, a conductive pattern formed on the cavity bottom formation ceramic layer as straddling a periphery of the cavity bottom and a softening layer that gets soft at a firing temperature of the firing and is provided at least on a surface of the conductive pattern of a portion corresponding to the periphery of the bottom on the cavity bottom formation ceramic layer.

A production method of a multilayer ceramic substrate having a cavity, comprising the steps of laminating a plurality of substrate green sheets including cavity formation green sheets having through holes corresponding to the cavity to form a multilayer body, pressing the multilayer body, and firing the pressed body, the method further comprising the steps of, before the pressing step, laminating shrinkage suppression green sheets on surfaces of the substrate green sheets, respectively, which surfaces constitute an outermost layer of the multilayer body, laminating a shrinkage suppression green sheet piece on a substrate green sheet constituting a bottom of the cavity, disposing on the shrinkage suppression green sheet piece an embedded green sheet separate from the cavity formation green sheets to be filled in the cavity and, after the firing step, removing the embedded green sheet fired.