Leland,
Another good practice is to verify the mechanics of the fixture prior to
placing product on the machine. Running an "all opens" and "all shorts"
test on the fixture to verify all pins are in the fixture and active can
be done by placing a shorting plate (copper plate) on the fixture,
compressing and running an all shorts test. This ties all pins together
during this test and any missing or bad contact pins will be reported as
"Opens" during this test. The operator then can diagnose whether pins
are missing, bent or otherwise unusable. Further the next phase would
be to place a non-conductive material on the fixture and run the "all
opens" test which isolates all pins from one another thus reporting if
you have any pins shorting to one another. Results from this test can
be troubleshot as above to finalize that the mechanics of the fixture
are stable. These cycles also give the fixture a "warm-up" or setting
time before a board is subject to test. Your idea is also beneficial
but should be supplemented with pin mark checks during the run to make
sure a pin has not gotten stuck and is now causing damage. The sampling
rate is totally up to you but on smaller runs it is likely to sample
first, middle and last. If it is a large run I would suggest every
tenth board or so.
Todd
------------------------------------
Todd L Kolmodin
Service/Quality Manager
Mania Technologie Inc
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Thursday, February 22, 2007 9:06 AM
To: [log in to unmask]
Subject: [TN] Test Fixture Verification Methods
TechNetters,
I would appreciate any suggestions you might have on how a Quality
Engineer should verify test fixtures.
We currently conduct strain testing, put white-out on press plate pins
to see the actual contact point with the board, use fully populated
product, and then examine both top and bottom sides beneath a microscope
to check for obvious component and/or board damage.
Are we missing anything?
Thanks in advance,
Leland Woodall
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