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April 2006

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Thu, 6 Apr 2006 07:09:30 -0500
Content-Type:
text/plain
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text/plain (93 lines)
The primary purpose of conformal coating is not to keep the board clean,
although that is 
a secondary benefit. Its purpose is to seal the assembly from moisture.
Before arbitrarily deciding not to conformal coat a portion of the
board, especially a connector, one should consider the ramifications.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Mikell
Sent: Wednesday, April 05, 2006 4:58 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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