Hi David,
Thank you for your response. Answering your questions,
1. Yes the coating is completely cured.
2. No shadow areas.
3. Humidity was at standard indoor levels, nothing out of the ordinary.
Also, we processed boards on different days with similar results.
4. We thought of contaminated surface as well. We cleaned the boards, then
coated them again, same result. Even tried extra thick coating, same
results.
5. Yes, complete coverage over entire board. Used a UV light chamber to
check distribution of conformal coating.
6. Not sure about this one, seems the solder mask is not being effected by
the UV light.
Any other ideas?
Thanks,
Pete
----- Original Message -----
From: "David Douthit" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, September 25, 2003 1:26 AM
Subject: Re: [TN] conformal coating help needed
> Pete,
>
> 1. Are you sure the coating is completely cured??
> 2. Does this coating also have a secondary curing agent
> for "shadow" areas that UV light can not reach?
> 3. How high was the humidity during application and testing?
> 4. Are you coating over contaminated surfaces?
> 5. Is there complete coverage of edges, back sides, beneath, and points?
> 6. Is the solder mask completely cured and
> compatible with the coating and coating cure process
> (intense UV can damage certain materials)?
>
> These make good starting places for your answer.
> I am sure others will add to this list!
>
> David A. Douthit
> Manager
> LoCan LLC
>
> Peter Z wrote:
>
> > Hi Everyone,
> >
> > Having trouble with conformal coating. Currently using a UV cure
silicone
> > based spray on a PCB with gold plating.
> >
> > The problem we are experiencing is after the conformal coating is
applied
> > and curred (0.002" thick), using simple probes with very little pressure
on
> > the probes, we obtain conductivity between certain traces. In other
words,
> > the conformal coating is not preventing electrical conduction between
points.
> >
> > Specificially, we are having difficulty coating vias and SMT
> > resistor/capacitors.
> >
> > We tried increasing the thickness of the conformal coating sprayed, but
no luck.
> >
> > Does anyone have any ideas?
> >
> > Thanks,
> >
> > Pete
> >
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