I'd like to expand upon what Doug said because I know his company has done
studies related to this... I'm not sure if that data is available
publically or not.

I manufacture UV and Thermal cure ovens as well as SMT Reflow ovens.

It is common practice to attach thermocouples to PCB Assemblies and record
thermal profiles for use in verifying the reflow process. Data such as rise
rate and peak temperature are recorded.

How many of you have conducted thermal profiling in your UV curing process?
You would be amazed to see the rise rates, which far exceed the limits of
SMT reflow soldering.

YMMV,

Brian


On Thu, Apr 7, 2016 at 12:23 PM, Douglas Pauls <
[log in to unmask]> wrote:

> 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 86ºC. 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]> 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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-- 
Brian Stumm
ETS, Inc.
+1-509-276-2015

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