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| Date: | Mon, 15 Dec 2003 09:11:59 -0600 |
| Content-Type: | text/plain |
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I recommend to anyone, that a lot test of resistance be done when new boards are received.
This is a simple test taking 1 or 2 boards from a lot and testing a few connection on them.
On an average board, there shouldn't be more than 5 Ohms. Normally 2-3 ohms.
If you experience problems there are several little tests to do. If you do get more than 5 Ohms
on a trace, heat the pad as it would be heated for assembly. Check for a higher resistance.
Often times, a poor connection will open when heated.
You may also request that the manufacturer (return 1 board that seem to be the best candidate)
do another electrical test. Test for a continuity test at less then 5 Ohm and a shorting test at 100V min.
I've never had another bad board come in using these test values.
Chris Robertson
Author "PCB Designer's Reference"
[log in to unmask]
ISBN: 0130674818
Search for it at www.amazon.com
----- Original Message -----
From: Eric Stellrecht
To: [log in to unmask]
Sent: Monday, December 15, 2003 8:10 AM
Subject: [TN] Problem With PCB Opens
Technet Members,
We have identified a field return trend in a line of circuit boards. The problem is occurs which a trace separates from the plated through hole
causing an open circuit. Unfortunatly, we had to destructively analyze two boards to reach this solution. The failure analysis points to a
manufacturing defect that will potentially affect an entire lot of boards. We are looking for a non-destructive way to analyze this lot of boards to
determine whether or not a particular board suffers from a partially or intermittant open condition, on its way to becoming a hard open. Any
recommendations would be greatly appreciated. Thanks in advance...
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