Importance

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Abstract

A bi-level test fixture for testing printed circuit boards is provided. A series of guide pins emanate downwardly from the diaphragm board through corresponding guide pin apertures present through the probe plate. Upon application of a full vacuum to the test fixture, the diaphragm board is drawn completely toward the probe plate thus extending the guide pins through their corresponding guide pin apertures. The portion of the guide pins below the probe plate engage with a pneumatically actuated fork member. Upon release of the vacuum to the test fixture, the upward travel of the diaphragm board is limited and at a distance so that only functional test probes are in contact with the unit under test. Application of a full vacuum again enables disengagement of the fork member with the guide pin to allow the diaphragm board to travel fully upward to its resting position for removal of the unit under test. In-circuit testing may be conducted at either or both times when a full vacuum is applied to the test fixture resulting in both the functional test probes and in-circuit test probes contacting the unit under test. A transition from functional testing to in-circuit testing, or vice versa, is accomplished without disengaging the functional test probes from the unit under test.

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First Claim