A method of constructing a planar array of electrical contact pads is disclosed, comprising the following steps. First, providing a set of dielectric layers each having two major surfaces and forming a set of first conductive paths on a first major surface, the paths terminating at or before an interior perimeter, to leave an interior area within the interior perimeter free of conductive paths and an exterior area outside of the interior perimeter having the first conductive paths. Second, forming a set of second conductive paths on a second major surface, the second conductive paths terminating generally inside the interior perimeter. Third, joining the sets of dielectric layers to form a depthwise stack of layers, the stack of layers having a top surface and the first major surface being interposed depthwise between the top surface and the second major surface. Forth, forming an array of first and second electrical contact pads on the top surface, each first electrical contact pad overlaying a portion of the exterior area and each second electrical contact pad overlaying a portion of the interior area. Fifth and finally, forming a set of plated vias to connect each first electrical contact pad to a first conductive path and each second electrical contact pad to a second conductive path.