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January 2006

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Wed, 11 Jan 2006 10:28:28 -0600
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"Douglas O. Pauls" <[log in to unmask]>
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I agree with all of Graham's comments as well as all of the other "gotchas
mentioned by other people.  You can figure on devices like QFPs and BGAs
having lots of coating sucked underneath them, and allllllllll that solvent
is NOT going to come out quickly.  You are going to see coating defects
like you have never seen before.  Second, are the assemblies DESIGNED to be
dip coated?  Most are not.  Third, if you are going to do dip coating
right, I mean really right, then you dip at a controlled rate, withdraw at
a controlled rate, then reverse the orientation of the board for a set
time, then let come to tack free in a dead flat condition.  You can't just
hang it up like wash on a line.  You get thin coating on one end and thick
the other.

I don't like dip coating, if you have not guessed.

Doug Pauls




             Graham Naisbitt
             <Graham.Naisbitt@
             CONCOAT.CO.UK>                                             To
             Sent by: TechNet          [log in to unmask]
             <[log in to unmask]>                                          cc

                                                                   Subject
             01/11/2006 08:13          Re: [TN] Manual conformal coat
             AM                        dipping process


             Please respond to
              TechNet E-Mail
                   Forum
             <[log in to unmask]>
             ; Please respond
                    to
              Graham Naisbitt
             <Graham.Naisbitt@
              CONCOAT.CO.UK>






Andrew

Following Mike comments, I think you should be aware that manual dipping
may
lead to other issues: the coating will be too thick and the runs that will
develop might take you outside IPC A-610 acceptance criteria.

Furthermore, the solvents in the coating may well be flammable, so using
electric drives etc., must be avoided - otherwise you might flambee the
assembly, and yourself!

The advantage, and probable reason for requiring the dip process is
coverage
under, as well as over, the components. Of course both sides are coated at
the same time and, as Mike said, you can simultaneously coat many
assemblies
at the same time - we can do 30 to 40 per 3 minute cycles.

Hope this helps,

Graham Naisbitt


On 10/1/06 21:40, "Joseph H. Smith" <[log in to unmask]> wrote:

> Fellow technetters.
>
> Anyone out there have experience with 'manually' dip coating conformal
coat.
> I have never done the dipping coating process.  Machine spray and hand
spray I
> have done.  The concept sounds simple enough but I was looking for advice
on
> process got ya's or issues to watch for when doing the dipping.  Our
customer
> is requiring the dipping process and currently doesn't wish to spend the
money
> on more automated equipment.
>
> Andrew Kettlewell
> Sr Process Engineer
> Sypris Electronics
> Tampa, Fl
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