Vacuum-actuated test fixture for testing printed circuit boards

A test fixture for testing circuit boards, comprising:

• a top plate, having at least one probe perforation made thereon for allowing at least one test probe to extend therethrough, said top plate comprising circuit board mounting means defining a movable board-bearing surface for receiving a circuit board thereon, said board-bearing surface destined to be movable relative to the at least one test probe;
• a lid having a lid frame defining a peripheral rim, said lid being movable between a first position where said lid frame peripheral rim sealingly engages said top plate, and a second position where said lid is moved away from said top plate, said lid further comprising a lid diaphragm connected to said lid frame and defining an inner surface to which is mounted circuit board securing means, said lid diaphragm being movable relative to said lid frame at least when said lid is in said first position between a rest position where said circuit board securing means is moved away from said board-bearing surface, and an operative position where said circuit board securing means is moved towards said board-bearing surface for engaging the circuit board;
• sealing means allowing a sealed interconnection between said lid diaphragm and said lid frame;
• diaphragm biasing means biasing said lid diaphragm towards said rest position and capable of yielding to allow said lid diaphragm to move towards said operative position;
• a test chamber, enclosed by said top plate and said lid when said lid is in said first position:
• at least one vacuum port in fluid communication with said test chamber, for connection to a vacuum pump which can be activated to create a vacuum within said test chamber;
• and
• circuit interface means for connecting said probes to data processing means;
• wherein when said lid is in said first position and a vacuum is created in said test chamber, said lid diaphragm is moved towards said operative position against the bias of said biasing means for moving said circuit board securing means towards the circuit board to secure the latter to said board-bearing surface.

A lid for use with a circuit board test fixture of the type having a top plate for mounting a circuit board thereon, said lid comprising:

• a lid frame defining a peripheral rim for releasable engagement on the top plate;
• a lid diaphragm carried by said lid frame opposite said peripheral rim, said lid diaphragm being movable relative to said lid frame between a rest position where said lid diaphragm is moved away from said peripheral rim, and an operative position where said lid diaphragm is moved towards said peripheral rim, said lid diaphragm defining an inner surface carrying at least one circuit board securing member for engaging the circuit board when said peripheral rim engages the top plate and when said lid diaphragm is in said operative position;
• a biasing member biasing said lid diaphragm towards said rest position and capable of yielding to allow said lid diaphragm to move towards said operative position;
• and
• sealing means allowing a sealed interconnection between said lid diaphragm and said lid frame;
• wherein said diaphragm defines an axis of displacement when it moves between said rest and operative positions, said text fixture farther comprising a first guiding member on said top plate and a second guiding member on said diaphragm cooperating with said first guiding member to guide said diaphragm along said axis of displacement said diaphragm being loosely carried by said frame so as to be at least slightly movable transversely relative to said axis of displacement for providing a self-aligning capacity to said diaphragm through the cooperating first and second guiding members.