Barbara: Parylene(paraxylylenes)coatings are certainly very good possibly
the best. It uses a dimer applied by vapor condensation as opposed to a
liquid polymer for the other types of conformal coatings. However it is
quite expensive when compared to some of the other common conformal coating
materials such as acrylic and polyurethane's.
Instead of plunging into ten pages of the pluses and minuses of each coating
lets step back and define what the requirement is for your product.
1. What are the environmental conditions that it will be exposed to,
temperature, chemicals, corrosive atmosphere, humidity?
2. What are the electrical requirements, voltage, insulation resistance,
dielectric strength, dissipation factor, dielectric constant?
3.Do you require a uniform coating of a given thickness over the entire
assembly?
4.What is the maintainable cleanliness level of the assembly prior to
coating?
5.How will you do rework and recoat?
6. Do you have any $ cost constraints?
7. How do you know you need a conformal coating?
This list can go on and on but I think you see the idea. I have no doubt the
parylene coating would probably work great for you but it may be overkill.
The better you can define your design requirements the wiser choice you can
make if a coating is needed.
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Barbara Burcham
Sent: Monday, May 16, 2005 2:56 PM
To: [log in to unmask]
Subject: [TN] Conformal Coating of Assembled Boards
Well, my company now has an application requiring conformal coating on
some small assembled boards. We need to mask off 3 connectors and coat
everything else.
I have some information on a product called Parylene applied by Parylene
Coating Services, Inc. in Katy, Texas.
We did a small lot with a simple spray-on process, but that is not the
way to do production runs, of course.
What would you recommend?
Thanks,
Barbara
Barbara J. Burcham, C.I.D.
Fairfield Industries, Inc
281-275-7687
[log in to unmask]
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