Graham,
I have had a couple of job estimates where the requirement needed the use of
the Parylene Conformal Coat. This is what I know about it.
1) My only contact has been through SCS, Hans Bok, out of North Dartmouth,
MA 800-356-8260.
2) There are 3 different grades of parylene, Parylene C, D, and N. Class C
is for electronic boards. Company literature elaborates very well on the
physical properties of each. This is a vacuum deposition process. Place
items in a vacuum chamber. Pump the system down, 3 sections, The coating
material , a dimer, goes through Vaporization, Pyrolysis, and Deposition.
Totally automatic process. Again, company literature explains the process
nicely.
3) Two machines available, a lab type machine costs $25K includes chiller.
It has a 21 liter chamber. This is a batch type process, fit everything you
can into the chamber, without touching. Takes about 6 - 8 hours to apply a
0.5 -1.0 mil coating. Holds a quarter pound of material. Material is about
$440.00 /lb.
4) Production level machine costs $65K without chiller. (Note: the chiller
is needed to keep the parylene from depositing itself into the vacuum
system.) It has a 63 liter chamber. Production time is dependent upon vacuum
pump down time. At equilibrium, deposition occurs at 5 microns/hr.
5) If you have a small volume. I suggest you send out and have this done.
6) Masking of the item to be coated sounds to me like the biggest challenge.
Do not plan on being able to remove this coating unless the use of a band
saw is in your arsenal of printed circuit board rework tools. (We don't
allow our operators to use a band saw for rework, [TIC]) Seriously, what I'm
saying is that, if you have masked off a round circle dot, you have to cut
through the coating to lift the dot off. I don't know what you might do if
you have to mask off areas with traces. Trace damage is almost a certainty.
7) This is the thinnest and the hardest coating I've ever seen. Do not plan
on being able to rework.
Good Luck, call me if you have questions. I hope that I've been of some
help.
Bill Kasprzak
Moog Inc.
716-652-2000 ext 2507
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