Hi folks - there is an IPC-JSTD-001 task group that is working on
"Conformal Coating State of the Industry Assessment" that will be a great
data set for folks who run into the issue that Guy posted. The task group
has completed 20 of 26 data sets and will be completing a big data
statistical review plus completing the final report over the next 12
months. I know it doesn't help anyone right now but there is some technical
data in the works for the near future on this topic.
Dave Hillman
Rockwell Collins
[log in to unmask]
On Thu, Sep 22, 2016 at 2:38 PM, Richard Kraszewski <
[log in to unmask]> wrote:
> Steve - We see the same issue when it gets really thin. We proceed as
> follows:
>
> > State that fluorescence of a coating is an aide to inspection, not a
> requirement.
> > Coating will often thin -out at sharp edges. Laws of physics related
> to surface tension & surface energy.
> > If insufficient coating is suspected with UV & their naked eye
> (spectacles are OK), operators can use up to 4X magnification and nature
> white lighting to determine if coating is present based upon gloss.
>
> Common customer reply is that if coating is indeed present, then is must
> be too thin to be in specification.
> To which we reply back that the industry (IPC) understands this
> phenomenon and a Qpanel hence can be used to monitor and control
> thickness. If perfect coating uniformity is required , parylene should
> be called out.
>
> We are successful in the above argument with customers perhaps 50% of the
> time at best. Rest of the time we touch up. ;>(
>
> Rich Kraszewski / PLX
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> Sent: Thursday, September 22, 2016 10:36 AM
> To: [log in to unmask]
> Subject: Re: [TN] Fwd: coating complaint
>
> Hi Guy,
>
> I got your photos posted, had to do a little repair with my web page
> software after the last Windows update. Here are the images:
>
> http://stevezeva.homestead.com/coating_under_no_filter.jpg
> http://stevezeva.homestead.com/customer_complaint-skips.jpg
> http://stevezeva.homestead.com/coating_under_UV2.jpg
> http://stevezeva.homestead.com/coating_under_UV2-1.jpg
>
> I see the same thing on component edges sometimes. It's like the UV tracer
> in the coating thins out or separates out and under UV light it looks like
> there's no coating. We've got stuff kicked from a customer for this
> problem. If I can find the photos I'll post mine...
>
> Steve
>
> On Thu, Sep 22, 2016 at 7:56 AM, Guy Ramsey <[log in to unmask]> wrote:
>
> > I am in over my head. I have little to no experience with conformal
> > coating. Can anyone with more experience comment?
> > thanks,
> > Guy
> > ---------- Forwarded message ----------
> > From: Guy Ramsey <[log in to unmask]>
> > Date: Thu, Sep 22, 2016 at 9:51 AM
> > Subject: Fwd: coating complaint
> > To: [log in to unmask]
> >
> >
> > I sent this message on to a friend who posts images for review by
> > members of the IPC technet.
> > We are looking for technical support and user experiences with this
> > material.
> > If we inspect at 5x-10x magnification we can observe the conditions
> > that our customer is complaining about.
> > But, our application process seems well controlled and the condition
> > does not exist when the material is first dispensed. The material
> > flows as it cures and becomes thin at the edges of the components.
> > Thin enough so that is does not glow under UV light. In some instances
> > components appear to have no coating (when viewed under UV). However
> > under normal light it is easy to see the parts are coated.
> > Is this normal behavior for the material? Can we expect normal
> > performance from the the coating?
> > Guy Ramsey
> >
> > ---------- Forwarded message ----------
> > From: Guy Ramsey <[log in to unmask]>
> > Date: Thu, Sep 22, 2016 at 9:41 AM
> > Subject: coating complaint
> > To: Steve Gregory <[log in to unmask]>
> >
> >
> > Hi Steve,
> > Can you post these images on your homestead page for the group please?
> > The images are of acrylic coating Humiseal 1B31. We are applying a
> > thinned mix using a dispenser through a fine needle (25AWG).
> >
> > Under room lighting we can see coating. Under UV light, at this
> > magnification our customer is complaining about skips. I don't have
> > enough experience with the material to know if this is normal or not.
> > Notice how the resistor appears to have no coating under UV, but in
> > normal light it is clearly coated.
> > Also notice how the coating flows off of the components at the edges,
> > leaving only a thin coating that may not glow under UV light.
> > Are these normal attributes of this type coating.
> >
> > We do not see this with Urethane spray coatings.
> >
>
> --
>
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