A stiffener structure, a wiring substrate, and a frame having a major surface disposed in a stack can be part of a probe card assembly. The wiring substrate can be disposed between the frame and the stiffener structure, and probe substrates can be coupled to the frame by one or more non-adjustably fixed coupling mechanisms. Each of the probe substrates can have probes that are electrically connected through the probe card assembly to an electrical interface on the wiring substrate to a test controller. The non-adjustably fixed coupling mechanisms can be simultaneously stiff in a first direction perpendicular to the major surface and flexible in a second direction generally parallel to the major surface.