I agree with Kevin for the most part. In these cases we use one of two methods to get the same result required, but it depends on the geometries we are dealing with. We either use a AR gel, which you get from (Humiseal - not intended as a sales ploy) or we use a moisture cure RTV with a rubberized tape. The tape seals the bottom portion of the connector to the board (has a "L" shape), then the RTV seals the top (if possible) and the bottom. Once this is cured it is a very robust seal and difficult for moisture or other contaminates to break (non chemical of course).
Hope this helps.
Chris Schaefer
Suntron Corporation
Process Engineer
540 N. Rogers Road
Olathe, Kansas 66062
913.393.5878
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kevin Glidden
Sent: Thursday, April 06, 2006 7:20 AM
To: [log in to unmask]
Subject: Re: [TN] conformal coat masking
Phil,
Option #2 below is a very good option. A couple more options ...
Use peelable latex mask to fill the connector cavity prior to coat. Make
sure you leave enough material to get a hand or tweezer on it to get it out.
Test a few pieces first to make sure it is actually removable!
Mask this area from coating and then secondarily apply (brush) a thicker
coating. There are some coatings with higher viscosities that are less
prone to wicking. You can also thicken coatings with a filler like
Cab-0-Sil.
Good Luck,
Kevin
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Mikell
Sent: Wednesday, April 05, 2006 5:58 PM
To: [log in to unmask]
Subject: Re: [TN] conformal coat masking
Phil,
Assuming that you can change the design at this stage, you have three basic
choices. If you cannot change the design, go directly to the "Null Option"
1. No coat option. Mask the connector and coat the rest of the board.
Depending on environment, the conformal coatings purpose is to keep the
board clean.
If the connector area is not subject to much dirt, not coating around and
under it may be an option.
2. RTV seal. Seal the area around and under the connector with a bead of
moisture cure RTV. The coating can be done before RTV with a mask operation
as above. If performed after RTV seal, the conformal coating might be
changed to Type SR.
3. Change the connector. Many connector series designed for use in high
reliability or harsh environment systems have a version with sealed pins to
prevent wicking of conformal coat.
And there is always the "null option"..... subcontract the assembly to
somebody else to deal with the situation caused by the lack of a proper
concurrent design process.
Steve Mikell
[log in to unmask]
> ----- Original Message -----
> From: "Crepeau, Phil (Space Technology)" <[log in to unmask]>
> To: [log in to unmask]
> Subject: [TN] conformal coat masking
> Date: Wed, 5 Apr 2006 13:41:40 -0700
>
>
> hi,
>
> we are using several qss-050-01-l-d samtec surface mount connectors on
> a printed wiring assembly that is conformal coated with a choice of
> either an ar or a pur material. the connector pin/header interface is
> not sealed, so the conformal coating that must go under this connector
> has an easy path to wick up the leads and contaminate the mating
> surfaces of the connector. what to do?
>
> thanks,
>
> phil
>
--
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