Abstract: A test fixture for circuit cards comprising a probe board bearing electrical test probes in a fixed position with respect to the overlying test surface. A flexible sheet is supported by the probes and serves to stabilize their relative positions. The circuit card is held against the probes by vacuum force applied utilizing a thin plastic layer overlying the circuit card. The test probe utilized in the test fixture has a conductive shaft tapering to a cylindrical tip on which a conductive spring and a conductive contact cap are slidably mountable. The cap is tapered down to the tip, and the spring is designed to engage both the tapered portions of the cap and of the shaft. A twisting motion of the cap causes the spring to electrically and physically connect the cap and the shaft. The cap also an indentation for interlocking with the flexible sheet of the test fixture.

Abstract: Method of forming an electrode for imprinting or imaging a circuit board mold face includes covering a graphite substrate with a photoresist material. The photoresist material is appropriately exposed to develop a desired pattern. The unpolymerized photoresist is removed from the graphite substrate to leave the desired pattern of an exposed graphite surface. The graphite substrate is then impacted by a dry air blast of glass beads having a size in the range of approximately 200 to 325 mesh. The glass beads will remove a desired amount of graphite to thereby cut the desired pattern into the substrate but will not remove the photoresist or affect the substrate beneath the polymerized photoresist. The polymerized photoresist is removed with materials that will not interfere with the subsequent machining process. The resultant cut graphite substrate can be utilized as a electrode in an electrical discharge machining process to form a desired pattern in a mold face.