Counterforce spring assembly for printed circuit board test fixtures

Claim 1

An automatic testing equipment test fixture for a printed circuit board having electronic devices, with connector leads, installed therein, comprising: a probe plate having an upper surface and a circumferential edge; said fixture probe plate defining a plurality of test probe apertures and at least one counterforce spring assembly aperture; a plurality of test probes residing in and through said test probe apertures, respectively; at least one counterforce spring assembly residing in and through said at least one counterforce spring assembly aperture, respectively; said at least one counterforce spring assembly including a support cup with an open top, a closed bottom with a floor and an inner wall; a circumferential flange, having a predetermined thickness, disposed about and flush with said open top; a spring residing in said support cup with an upper portion of said spring exposed above said open top; said support cup residing in said at least one counterforce spring assembly aperture with said circumferential flange providing a stop for downward travel of said support cup in said at least one counterforce spring assembly aperture and providing a spacer stop for limiting the downward travel of said top plate toward said probe plate by a length equal to the thickness of said circumferential flange; peripheral spring member means positioned on said upper surface and proximal to said circumferential edge; a top plate having an upper surface; said top plate being positioned on said peripheral spring member means and said at least one counterforce spring assembly; said top plate defining a plurality of test probe pass-through holes; and whereby creation of a vacuum between said top plate and said probe plate draws said top plate toward said probe plate thereby permitting said test probes to pass through said test probe apertures.