Abstract: A multi-layer blank for an electrical circuit board has at least one internal layer, which may constitute a common power supply or ground plane. The inner layer consists of an electrically conductive network extending throughout the area of the inner layer and formed by the repetition of an elementary predetermined pattern in two orthogonal directions. The elementary pattern has such a shape that adjacent patterns are in electrical contact so that the network is equipotential. The pattern is also of such a shape that there is formed a first regular grid of predetermined pitch p whose nodes constitute insulated sites and a second grid off-set by p/2 from the first grid in at least one of the orthogonal directions. The second grid has the same pitch p as the first one and has nodes one at least of which per elementary pattern is insulated while the other ones belong to the conducting network.