Abstract: A wiring substrate includes an insulating layer, and a build-up part formed on the insulating layer and including an interlayer insulating layer and a conductor layer. The build-up part has a cavity penetrating through the build-up part such that the cavity is formed to accommodate an electronic component and has an inner wall and a bottom surface having a groove and that the groove is extending entirely in an outer edge part of the bottom surface and formed continuously from the inner wall surface of the cavity.

Abstract: A wiring substrate includes an insulating layer, and a build-up part formed on the insulating layer and including an interlayer insulating layer and a conductor layer. The build-up part has a cavity penetrating through the build-up part such that the cavity is formed to accommodate an electronic component and has an inner wall and a bottom surface having a groove and that the groove is extending entirely in an outer edge part of the bottom surface and formed continuously from the inner wall surface of the cavity.

Abstract: There are provided a multilayer printed circuit board and a testing piece for the printed circuit board, including a substrate having an inner-layer conductor circuit and one or more outer-layer conductor circuits formed on the substrate with an insulating layer laid between the substrate and outer-layer conductor circuit, wherein a strain gauge having a resistive element held tight between resin films formed from polyimide or thermoplastic resin is buried in the substrate, and electrodes electrically connected to the resistive element are exposed to outside from the resin film and are electrically connected at exposed portions thereof to a viahole. Even if a crack is caused by an impact test to take place in the insulative resin layer, the resin film layers prevent the crack from spreading and thus the resistive element forming the strain gauge will not be ruptured.

Abstract: There are provided a multilayer printed circuit board and a testing piece for the printed circuit board, including a substrate having an inner-layer conductor circuit and one or more outer-layer conductor circuits formed on the substrate with an insulating layer laid between the substrate and outer-layer conductor circuit, wherein a strain gauge having a resistive element held tight between resin films formed from polyimide or thermoplastic resin is buried in the substrate, and electrodes electrically connected to the resistive element are exposed to outside from the resin film and are electrically connected at exposed portions thereof to a viahole. Even if a crack is caused by an impact test to take place in the insulative resin layer, the resin film layers prevent the crack from spreading and thus the resistive element forming the strain gauge will not be ruptured.