Another possibility to consider: the fluorescencing additive reacts (absorbs) at the same wavelength as the UV curable coating, and if the UV conformal coating is highly loaded with fluorescencing additive, then this can inhibit the light cure. So in UV curing systems the amount of fluorescence may be limited in comparison to solvented coatings so as not to compromise cure. Also, the reasonably high levels of UV light used to cure the coating can degrade the fluorescencing additive, causing it to fade. So in thin section of cured coating there just may not be much fluorescent response. You can try higher power black lights in very dark rooms to see if you can see better.
Peter
--------------------------------------------------------
Peter Swanson
Managing Director
INTERTRONICS, Oxford, England
t 01865 842842
m 07785 908556
e [log in to unmask]
w www.intertronics.co.uk
Read our news! http://www.intertronics.co.uk/blog/blog.htm
INTERTRONICS is the trading name of Cygnet Electronics Ltd,
registered in England No 1835617. Registered office:
17 Station Field Industrial Estate, KIDLINGTON, Oxfordshire, OX5 1JD, ENGLAND
INTERTRONICS is certified to ISO 9001:2008
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of lduso - Diamond-MT.com
Sent: 22 September 2016 15:19
To: [log in to unmask]
Subject: Re: [TN] Fwd: coating complaint
A very common mistake people make: if it does not glow, then there cannot be any coating there. It's hard to deny that it is present when you can plainly see the material under white light. Granted, it may not be at the minimum thickness required but it is there. I like inspecting the overall coating under white light first and use the UV light to inspect the coating-free areas that are tougher to see.
Lloyd Duso
Plant Manager
Diamond-MT
(814) 535-3505
www.Diamond-mt.com
On Thu, Sep 22, 2016 at 9:56 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.
>
|
