Sounds like a issue with one or more batches affected with humidity within
the PCB itself, or moisture ingress from assembly and subsequent cleaning
process.

Try drying assemblies for a couple of hours at 80-90oC to see if the drift
improves

Regards,

Colin McVean

Circuit Manufacture Ltd
Unit 9-12
Rowleys Green Lane
Longford
Coventry
CV6 6AG

Tel: 02476 666168
Fax: 02476 637089
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Murulidhara
Sent: 29 June 2004 09:48
To: [log in to unmask]
Subject: [TN] Frequency drift Problem


Dear Technetters,

We are facing a peculiar problem. One batch of PC assemblies are behaving in
strange way with regard to frequency drift.
The frequency drift noticed is more in the mornings and less in the
evenings.

The PCBs used are of multi layer type with critical components sheilded.

The same PCBs(from the same PCB manufacturer) assembled in our shop with
similar components are passing the test.

Kindly let us know the reasons for this type of problem.

What are the possible remedies to over come this?

Thanks in advance.

Muralidhara .S
Dy.Chief Engineer,
R&D, ITI Ltd.,
Bangalore - 560 016
INDIA






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