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April 2016

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Subject:
From:
Richard Kraszewski <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Richard Kraszewski <[log in to unmask]>
Date:
Thu, 7 Apr 2016 19:30:53 +0000
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Thanks for the quick reply.
UV Tracer is one I never thought of.
I do recall that Rockwell paper and am pretty sure I have a copy.
(perhaps some of this detail should be added to next rev of the Handbook).

Rich  Kraszewski
(920) 969-6075

From: Douglas Pauls [mailto:[log in to unmask]]
Sent: Thursday, April 07, 2016 2:24 PM
To: TechNet E-Mail Forum; Richard Kraszewski
Subject: Re: [TN] UV Cure process Harmful to Electronic Assemblies ???

Good afternoon Rich,

As Joyce and Steve have pointed out, components like UV PROMs or UV EPROMs are susceptible, but that is easily fixed with a black tape over the programming window.

In general, you should not get much damage as the UV tracer dye that is in most coatings will absorb some of the incoming UV energy.

Corey Peterson, Rockwell Automation, wrote an excellent paper on optimizing the UV cure process.  ULTRAVIOLET CONFORMAL COATING PROCESS DEVELOPMENT.

He found that some of the plastic sleeving on tall caps were damaged because the tops were much closer to the UV lamp.

"The damaged sleeving on this capacitor body shown in Figure 9 was not the result from thermal excess. A thermal profile was taken and indicated that the temperature at the top of the capacitor was only 86ÂșC. This temperature is lower than would be expected in normal wave soldering processes. The source of damage for this capacitor is from the UV energy itself. This damage could have two mechanisms. The tearing of the sleeving is right where component identification was stamped into the sleeving and could have produced a weak spot in the sleeving. The other possible mechanism is the component color itself. Sleeve tearing on Black, Dark Blue, and Brown parts could not be duplicated."

Lots of great info in that paper.  I can send you a copy if you wish.


Doug Pauls
Principal Materials and Process Engineer
Rockwell Collins

On Thu, Apr 7, 2016 at 1:59 PM, Richard Kraszewski <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Have a customer who is very concerned that  the cure UV light from conformal coating cure process might be harmful to their(any)  electronic assembly.

Historically  we have  UV cured  automotive and industrial  assemblies without issue. Solder mask usually is UV cured hence  normal cure processes shouldn't damage the PCB at minimum.
Contacted  several UV coating and equipment  manufacturers but nothing useful came out of that.
Nothing in IPC CC830 Handbook either.

I am looking for  reports/thoughts  that anyone may have , which supports or disputes this claim.
Any components know to be UV sensitive?

Thanks in advance

Rich  Kraszewski /Plexus

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