Hope this is helpful,
Test Pads: ( Minimum or Maximum)
1) Bottom-side test pads should be at least 0.035
? (.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
Dave Hoover <[log in to unmask]>
To: [log in to unmask]
cc: (bcc: Cyrus Ringle/Inter-Tel)
Subject: [TN] ICT Test Pin Attributes
Curious about what designers are using now for
ICT test pin location access pad size (S/M also)
along with closest distance between two test points.
(Of course those flying probe ICT 's can bend
major rules but I'm thinking standard fixture/high
volume.)
David Hoover
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