A printed wiring board (PWB) and assembly are described which are suitable for high density mounting of an electronic component and which can provide a thin and light assembly. A recess is formed in one part of a PWB and components are received in this recess. The components are lower than the surface of the PWB. A conductive pad is provided to the bottom of the recess and a connecting terminal and the conductive pad are electrically connected by using a solder ball or a conductive adhesive material. The recess is formed by partially removing one or more layers of plural conductive layers and insulating layers which make up the multilayer PWB.