Doug,

I think you misunderstood my question and got it mixed up with another
thread.

One person was asking about coating over no-clean but I was asking about
adding silicone spray conformal coating to our present processes of
polyurethane and acrylic.

We use an RMA flux and clean prior to coating.

Thanks,

Ken Bloomquist

-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, May 19, 2000 7:09 AM
To: [log in to unmask]; [log in to unmask]
Subject: Re: [TN] Silicone Confromal Coating


In a message dated 05/19/2000 8:43:09 AM US Eastern Standard Time,
[log in to unmask] writes:

>
>  My question is: Is there any problem adding Silicone to our process?

Maybe, maybe not.

>  What art the things we need to consider in adding this process?

Graham Naisbitt said it well that no-clean is not no-residue.  We have often

found that low solids flux residues can absorb fluids which contact them,
which is why it is really a bad idea to process OA fluxes after no cleans.

My biggest concern would be the compatibility between the low solids residue

and the solvents of the silicone coating.  The simplest experiment would be
to run some IPC-B-24 test coupons with and without flux and coat them.  Test

them using SIR for a week or so.  If the processed/coated boards come out
with essentially the same results control/coated boards, then the two are
compatible.  I just ran a test for a client recently who did this.  The
processed/coated boards failed almost immediately, compared to the
control/coated boards.  I used IPC-TM-650 method 2.6.3.3 (85/85 for 7 days)
for my testing.  You could also use method 2.6.3.1 (cyclical for 7 days).

Doug Pauls
CSL

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