A backing plate facilitates electrical probing of VLSI IC signals in an array of signal via pads on the back side of a printed circuit board and which correspond to an LGA of socket pads on the front side of the printed circuit board. The backing plate is constructed of electrically non conductive mechanically stiff material that already has drilled therein a hole for each signal via pad that might be probed. Polyamide is a suitable material for such a backing plate. Special symbols, legends and suitable grid identification axes can be silk screened onto the side of the backing plate that remains visible when installed. The drilled insulative backing plate can be equipped with captive threaded studs, if desired. Alternatively, it may simply have holes to receive fasteners, or have captive female threaded fasteners in lieu of holes.