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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