Hi William,

Dang it! You're forcing me to owe Doug Pauls another dollar.  But the
easiest answer to your questions are...It Depends!

What are folks using today for a conformal coating in a no-clean
manufacturing environment?

*** The selection of a proper coating depends a lot on the end-use
environment.  Many times conformal coats are used because the end-use
environment is not going to add to the longevity of the assembled PWB.
Obviously, there are a number of different coatings available.  My best
advice would be to speak with your customer and determine what the end
environment is going to be  (unless you already know that info.).  Then you
are in a better position to determine what will work best for those
conditions.  By-the-way, Doug Pauls is a great source of information on this
subject, as is Graham Naisbit.

Do I need to worry about cleanliness at all  today?

*** It depends on a number of factors.  There are a few coatings, where
adhesion may be affected by flux residues remaining on the board surface.
In my mind (there are probably significantly better opinions), controlling
the fluxing/paste processes and reflow conditions of no clean environments
will be a huge step in the right direction than if your process tends to
have a lot of fluctuation.  It will also depend on the flux.  If it is a
mainstream material such as Kester, Cookson (Alpha Metals), Indium, etc,
then I am certain those companies may be able to help you on what residues
are left from a given flux and how they might impact coatings.

With RoHS and lead-free processing/PCB finishes how are surface
contamination levels affected??

Again, it depends on the materials (fluxes, pastes and conformal coatings).
The best that anyone could probably offer is that the Pb-free stuff is still
a bit unknown.  However, the positive side is that more information is
learned everyday.

The best advice that I could give would be to 1) determine the end-use
environment, 2) research the coatings designed for that environment, 3)
obtain some "fake" assemblies that have similar components as your board
designs, 4) process with the flux materials that you use, 5) coat and 6)
test the performance.

Just my 2 cents!

Best Regards,

Joe Russeau
Process Analyst

Precision Analytical Laboratory, Inc.
4106 Cartwright Dr. Ste. A
Kokomo, IN 46902

P: 765-455-1993
F: 765-455-1996
E: [log in to unmask]

----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, September 13, 2006 7:27 PM
Subject: Re: [TN] bareboard cleanliness related to surface finish


> Hi Folks:  My company is beginning to be asked by several  customers for
> conformal coating on their PCB assemblies.  We are currently  building to
> IPC-A-610 using a combination of SMT and T/H technology in a  no-clean
manufacturing
> process flow.  From my old PCB days, I remember  problems with PCB
cleanliness
> and conformal coating peeling off the PCB  surface.
>
> What are folks using today for a conformal coating in a no-clean
> manufacturing environment?  Do I need to worry about cleanliness at all
today?  With
> RoHS and lead-free processing/PCB finishes how are surface  contamination
levels
> affected??
>
> I'm just looking for some basic information to point me in the right
> direction.....rather not have to re-invent the wheel.  Thought this would
be the
> perfect forum for this type of question!!!!
>
> Thanks in advance for any help and guidance you folks may  provide!!!!!!!
>
> Sincerely,
>
> William E. Black
> Medco
> Quality Assurance Manager
> Tel:   1 631 667 9699
> e-mail:  [log in to unmask] (mailto:[log in to unmask])
>
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Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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the BODY (NOT the subject field): SIGNOFF Technet
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Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
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