? (.025) in diameter.
      ?Bottom-side? means the main side on which test pads are located, It will
      be oriented toward the bottom of the fixture.
   2) Top-side test pads should be at least 0.045? (.035) in diameter. There is
      a tolerance stack-up that results from the tooling holes, tooling pins,
      the angle of the tooling pins, the angle of the probe, probe straightness,
      and perpendicularity of the holes for the probes and tooling pins that
      requires larger pads for top-side access. ?Top-side? means the side on
      which the fewest test pads are located. It will be oriented toward the top
      of the fixture and will be accessed via a mechanical clamp.
   3) There should be a clearance area of 0.018? around test pads so that larger
      probe head styles do not short out adjacent test pads.
   4) When there are components on the side of the boards being probed, keep a
      0.040? clearance from the edge of the test pad to an adjacent component so
      the probe does not come in contact with nearby components.
   5) there should be a clearance of 0.200? around test pads adjacent to
      components taller than 0.250?. This allows for milling out clearance for
      the taller component, and there must be sufficient material left for the
      insertion of the probe receptacle.
   6) Test pads should have 100-mil or 75-mil center-to-center spacing. If at
      all possible, avoid 50-mil spacing since 50-mil probes are much more
      fragile, cost more, are more expensive to install, wear out faster, and
      are less reliable than the larger 100 and 75-mil probes.
   7) Clearance from board edges should be a minimum of 0.125?  in order to
      assure good vacuum sealing.
   8) Identification:  If you intend to use a via as a test pad, the via must
      conform to the test pad requirements, and you should make that particular
      via a square shape. In future layout changes, do not move this particular
      via, and the test fixture will not be affected.


      Cyrus Ringle
      Sr. CAD Specialist
      Inter-Tel, Inc.  http://www.inter-tel.com
      7300 West Boston Street
      Chandler, AZ 85226
      Voice: (480) 961-2263
      Email: [log in to unmask]





Dave Hoover <[log in to unmask]> on 10/11/99 01:47:26 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to
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Subject:  [TN] ICT Test Pin Attributes