Hi, been away for a week and have just ploughed through x00 mails so this response is
somewhat of an echo. Have one little thought...
The guy from Concoat is right. Covering up your problem won't make it go away. If you are
getting migration then you have some (ionic) contamination on your PCB, which with a
little damp and some volts will give the problem. The cure is to make sure your pcbs are
clean. In addition some forms of contamination can actually inhibit some coating
formulations from curing, so you could end up worse off.
Halides in fluxes usually get the blame and there is no question that under test
conditions they are better migration promoters than similar activity non halide based
materials. Possibly in the real world also as the halide ion is more mobile (penetrative)
than organic ions. However on a pragmatic basis halide based materials are usually
considerably easier to wash  or react off in industrial plant so don't dismiss them
automatically. Unless FAther Christmas is due an early visit found your test regime and
material choice on what you can actually work with, ie your existing plant.

Good luck

Mike Fenner
Bonding Services & Products
T: +44 1295 722992
F: +44 1295 720937


----- Original Message -----
From: Matthew Lamkin <[log in to unmask]>
To: <[log in to unmask]>
Sent: 04 October 1999 13:00
Subject: Re: [TN] Electrical Migration


> As far as I understand, conformal coating the board will not necessarily
> prevent it happening.
>
> We had a demonstration session from a very knowledgeable guy from
> Concoat last week
> and I seem to remember that the original contamination just gets trapped
> under the coating
> and causes similar problems.
>
> The board has to be so, so clean before its coated to prevent the
> contamination....
>
> Or something like that....
>
>
>
> >-----Original Message-----
> >From:  Nancy Trumbull [SMTP:[log in to unmask]]
> >Sent:  Friday, October 01, 1999 3:11 PM
> >To:    [log in to unmask]
> >Subject:       [TN] Electrical Migration
> >
> >Hi Every One.
> >
> >I need information on Migration
> >
> >Question
> >1.  What will cause Electrical Migration
> >
> >Reason :
> >
> >We are seeing Dendritic Migration between components
> >
> >As of now we are applying conformal coating trying to stop the migration.
> >
> >Question:
> >
> >1. Is there a rework to prevent this condition.
> >
> >2.  Any study or data out there on reliability as far as using this method
> >to stop the migration.
> >
> >
> >Any information at all will be greatly appreciated.
> >If more information is needed please ask.  This is all I know as of now
> >I will do my best to get what ever is needed.
> >
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