An intermediate board has a board core formed by a main core body and a sub-core portion. The main core body has a plate-like shape and includes an open sub-core housing portion in which the sub-core portion is housed. A first terminal array of the board core has an area that overlaps an orthogonal projection of the sub-core portion. The latter incorporates a laminated ceramic capacitor formed by first and second conductor layers with a ceramic (dielectric) layer therebetween. The first layer is connected to first and second side terminals of a first type while the second layer is connected to first and second side terminals of a second type. The housing portion has an inner edge which, in cross section, is of a quadrate shape, and a radius portion is formed at each corner having a dimension of between 0.1 and 2 mm.