Vacuum test fixture for testing printed circuit boards

A test fixture for testing a printed circuit board, comprising:

• a base plate for carrying bottom test probes;
• a top plate carried over said base plate, with said bottom test probes extend through said top plate, said top plate having a top board-bearing portion for receiving the printed circuit board thereon;
• a lid movable between an opened position away from said top plate for allowing access to said printed circuit board, and a closed position, said lid comprising:
• a peripheral rail that engages said base plate in direct air-tight fashion in said closed position of said lid;
• a shell plate carried by said rail;
• and
• a deformable seal member disposed between said shell plate and said rail;
• and
• an airtight test chamber defined in said closed position of said lid between said base plate, said shell plate and said seal member, with said top plate being enclosed in said test chamber, said test fixture comprising at least one vacuum port in fluid connection with said test chamber for allowing a vacuum to be generated in said test chamber by a vacuum device, said shell plate and said top plate being movable relative to said base plate when a vacuum is generated within said test chamber;
• wherein said shell plate and said top plate are both movable in said closed position of said lid between a resting position and a contacting position, for allowing said bottom test probes to come into contact with said circuit board at least in said contacting position;
• and wherein said seal member resiliently deforms to allow movement of said shell plate relative to said rail between said resting and said contacting positions while also sealing an area between said shell plate and said rail for maintaining the vacuum within said test fixture, with said peripheral rail not significantly moving relative said base plate in said closed position of said lid when vacuum is generated in said test chamber.

A method of testing a printed circuit board in a test fixture, the test fixture comprising a base plate for carrying bottom test probes, a top plate carried over said base plate, with said bottom test probes extending through said top plate, said top plate having a top board-bearing portion for receiving the printed circuit board thereon, a lid movable between an opened position away from said top plate for allowing access to said printed circuit board, and a closed position, a shell plate carried by said rail, and a deformable seal member disposed between said shell plate and said rail, said method comprising the steps of:

• closing the lid against the base plate such that an airtight test chamber is formed between said base plate, said shell plate and said seal member, with said top plate being entirely enclosed in said test chamber, said lid comprising a peripheral rail that engages said base plate in direct air-tight fashion when said lid is closed;
• generating a vacuum in said test chamber through at least one vacuum port that is in fluid connection with said test chamber with a vacuum device;
• said shell plate and said top plate both moving relative to said base plate under the action of the vacuum generated within said test chamber;
• said deformable seal member deforming to allow this movement of said shell plate and top plate;
• and
• said peripheral rail not significantly moving relative to said base plate in said closed position of said lid when vacuum is generated in said test chamber.