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 So, the kilometer thick coatings are probably out one day and superseded by such methods.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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