If only management would co-operate with this approach. Too many times the customer makes a comment ( not necessarily a complaint ) and management is making promises and yanking on our shorts. I did have one customers Q.E's that once I said " no, you are mistaken " everything was good. Got an atta boy for improving quality.
Charles Caswell
-----Original Message-----
From: Dave Chapman [mailto:[log in to unmask]]
Sent: Thursday, August 15, 2002 10:49 AM
To: [log in to unmask]
Subject: Re: [TN] Conformal coating on top of plastic IC's
Our experience is that if that is what the Customer wants, the Customer
gets. Whether it is needed or not. As long as the joints are covered that
will be sufficient (technically). IPC loosely states that everything
specified to be covered needs coverage. Our method of operation here says
coat everything thus creating no questions from the customer even if you are
correct about moisture not being a factor after assembly. Our approach is,
if customer is trainable then work with them to educate them. Educate rather
than argue. You will both appreciate the experience.
Dave Chapman
CSI
-----Original Message-----
From: Graham Naisbitt [mailto:[log in to unmask]]
Sent: Thursday, August 15, 2002 8:43 AM
To: [log in to unmask]
Subject: Re: [TN] Conformal coating on top of plastic IC's
> Dear Technetters,
>
> We've just finished our first few boards with Humiseal 1B31 conformal
> coating, applied with a selective spraycoating machine, and we asked the
> customer to inspect the products.
> He commented that some areas on top of the IC's were not covered
> completely, which is required (so he says) because these are plastic
> components which may absorb moisture if left uncovered.
>
> I'm not gonne argue about this with the customer, but still I'm
> interested to hear from you wether the fact that the IC's are plastic is
> indeed a reason to require them to be completely covered with coating.
> As far as my knowledge goes the problem with plastic IC's and moisture
> is limited to the soldering process only, but I may be wrong.....
> Anyone can comment ?
>
> Daan Terstegge
> Unclassified mail
> Personal Website: http://www.smtinfo.net
Daan,
I suspect that the reason for the lack of coverage to the IC covers is due
to dewetting. The dewetting will probably be caused by the presence of some
mould release residues. Is this a problem?
Not really, although it would be a good idea to try and obtain IC's that do
not exhibit this problem, as it may be that if you clean the assembly, and
the mould release is silicone, then you might be spreading the silicone over
the surface of the assembly.
Is this a problem? Yes. Inspect under UV and check for dewetting in other
areas.
As to the issue of component reliability due to moisture ingress, this is
highly unlikely with the IC. However the customer is right to require it for
the reason I just outlined. It should not happen...
Hope this helps
Regards, Graham Naisbitt
--
[log in to unmask]
Concoat - Engineering Reliability in Electronics
Concoat Systems - Measuring Electronics Reliability
Synergie - Electro-chemically compatible process chemistries
Concoat Limited
Alasan House, Albany Park
Camberley, GU16 7PH - UK
Phone: +44 (0)1276 691100
Fax: +44 (0)1276 691227
Mobile: +44 (0)79 6858 2121
Web: www.concoat.co.uk & www.concoatsystems.com
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