How about using a mating connector to mask off the contact surfaces that you want to keep the coating from contaminating?
In my experience, it is not the 1B31 wicking properties that causes the contamination but rather it is the lack of proper masking that allows the overspray to get up inside the connector body and onto the contacts. Take away the free air surrounding the contacts by using a mating connector (or molded tool) and the contacts will remain clean.
I still don't understand why anything that is gold plated has to be conformal coated with 1B31.....
Phil B
ps: I still remember the nightmare days when we had to inject UR beneath the cruise missile board connectors and then tilt it so that it could run in all four directions without allowing it to wick up inside the connector.......
"Douglas O. Pauls" <[log in to unmask]> wrote:
Ramon,
I can tell you that it is more a function of the surface tension of the
coating, which is dependent on solvent system and viscosity. We use
Humiseal 1B31 and even when the Zahn #2 reading is around 60 seconds
(straight from the can), the material will still wick into connectors. You
either need the reeeeeealy thick stuff that does not wick, or seal with
another material.
As a possible alternative, you might consider a water based coating.
There, the surface tension of water works for you, rather than against you.
Doug Pauls
"Dehoyos, Ramon"
C.COM> To
Sent by: TechNet [log in to unmask]
cc
Subject
04/06/2006 08:40 Re: [TN] conformal coat masking
AM
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"Dehoyos, Ramon"
C.COM>
Phil:
The reason the wicking up is the low viscosity of the
coating. Mask the connector when the board is being spray coated. Remove
the mask and brush coat the connectors with coating straight from the
can. Better choice, make sure the coating is at least 30 seconds plus on
the # 2 Zhan cup. Do some testing first to confirm your specific
product. 30 seconds or more will make the coating too thick to wick up
the pins of the connectors
Regards,
Ramon
> ----- Original Message -----
> From: "Crepeau, Phil (Space Technology)"
> 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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