Steve,
We do coat some RF devices with both Parylene C and N. The dielectric
constants at 1 MHz are 2.95 and 2.65 respectively.
Since we just provide the coating service and do not manufacture the
actual products, we are not given all the details as to the operating
frequencies and the tuning requirements. We just know that it obviously
works, otherwise the customers would not use it. In these applications,
the typical film thickness for a moisture barrier is around 25 microns.
Repairing Parylenes can be challenging. But, the deposition is repeatable
and the systems are <$200K with no required license.
We do also offer a fluorinated version, Parylene HT, with a dielectric
constant around 2.2. It offers some offer advantages over convention
Parylenes in that it is stable in UV/oxygen environments and is thermally
stable, long-term, to 350C (short-term 450+C).
I just wanted to provide some additional information for you to consider.
Lamar
Steven Creswick <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/02/2009 05:37 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Steven Creswick <[log in to unmask]>
To
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cc
Subject
Re: [TN] humidity test failure
Sorry, $200K!
Steve
-----Original Message-----
From: Hernefjord Ingemar [mailto:[log in to unmask]]
Sent: Tuesday, June 02, 2009 2:47 AM
To: TechNet E-Mail Forum; Steven Creswick
Subject: RE: [TN] humidity test failure
200? You must have a very good source
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: tisdag 2 juni 2009 00:14
To: [log in to unmask]
Subject: Re: [TN] humidity test failure
Ingemar,
You mentioned what I was thinking of, the plasma deposition technique
offered by Integrated Surface Technologies - http://insurftech.com/ -
being
one.
Actually touted as a water-repellant coating - which is what I was
thinking
of for those that just HAD to go through humidity testing.
I've read white papers saying that even connector contact fingers [for
flex
cables could be coated] - no masking required - and still make reliable
contact. Not so sure that everyone could follow the 'no masking required'
route without additional testing, however. Trust but verify is my motto.
Sounded like a neat approach to the passivation of telecommunications and
commercial boards, however. Possibly even automotive...
I believe that something like $200 gets you a system. Bumped into a
factory
representative the other day, which prodded my memory.
Steve
-----Original Message-----
From: Inge [mailto:[log in to unmask]]
Sent: Monday, June 01, 2009 4:26 PM
To: TechNet E-Mail Forum; Steven Creswick
Subject: Re: [TN] humidity test failure
Steven,
we tried that coating many years ago for RF. The epsilon is not ideal,
that's true, but as that coating can be rather well controlled (repeated)
the disadvantages can as best be tuned for. However, we found also, that
repair was messy and the licence and machine was pretty expensive, so we
did not go on with Parylene C. So, it all depends, can you accept certain
RF
losses, distorted signal and take time for tuning, you may use this
coating.
(With tuning, I don't mean old time's tuning by trimming caps, inductors
and
shortening stubs with scalpel and other sorts. Today, most so called
tuning
is done by means of software).
If I was asked for giving advice today, I'd rather recommend some of the
'dielectric' sprays that are available since some years. These are sort of
very thin organic 'oils' that protect from corrosion, humidity and water
droplets. You get a 'fat' surface but the layer is so thin that the
electromagnetic fields won't be affected. I did a search a couple of years
ago, and rember there are also some plasma deposition methods today, kind
of
nanotech methods. So, the kilometer thick coatings are probably out one
day
and superseded by such methods.
Inge
----- Original Message -----
From: "Steven Creswick" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, June 01, 2009 8:33 PM
Subject: Re: [TN] humidity test failure
> Inge,
>
> Would you ever consider the application of parylene C on an RF board as
a
> moisture barrier? Up to what freq?
>
> I believe the dielectric constant for parylene C is nearly 3 at 1 MHz,
> compared to ~1+ for air?
>
> Steve Creswick
>
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