A probe test card assembly for testing of a device under test includes a printed circuit board, a substrate and a substrate support structure. The substrate support structure holds the substrate in position with respect to the printed circuit board. The substrate support structure may include one or more alignment members, one or more hard stop members and/or a support plate attached to the printed circuit board for positioning the substrate with respect to the printed circuit board. The one or more alignment members may extend through the printed circuit board and be connected to the one or more printed circuit board stiffener members. The probe test card assembly may also employ a proximity detection feature to indicate when the substrate is in a particular position with respect to the printed circuit board.