We're Class 3, mostly military aircraft electronics.
Historically, we've used Type UR, but we've recently
brought in some work from another plant that has
been using acrylic.  We're in the process of switching
everything over to our UV-curable urethane for the
following reasons:

1. UV-curing saves a whole lot of cycle time.  The
acrylic must be air-dried or baked.

2. In order to perform any rework at all, you must be
very careful when removing coating in particular spots,
and things can look pretty ugly after recoating.  More
often than not, we end up stripping and re-coating the
whole thing.  More lost time.

3. Some of our designs require solvent-resistant coating.
If we're going to settle on one type of coating, it might
as well be urethane.

For the record, we haven't noticed any compatibility
issues with the fluxes and solder masks that we've been
using.

Of course, YMMV.  If you're doing occasional touchup on
a solder joint or two, Type UR may be preferred.  If you
need to replace a lot of components, it's probably easier
to strip the coating and start over.

-Joe

-----Original Message-----
From: - Bogert [mailto:[log in to unmask]]
Sent: Monday, March 08, 2004 4:55 PM
To: [log in to unmask]
Subject: [TN] Pros and Cons on Type UR vice Type AR Conformal Coating


As a Class 3 customer we are considering mandating transition from Type UR
to Type AR conformal coating, to make it easier to replace failed
components.  Are there any Class 3 users of Type AR coating?  What is track
record for using Type AR?  Are there any compatibility issues with certain
types of solder masks?  Any input you have would help.  Another advantage
with AR would be for returned equipment.  The OEM could remove all the
coating from an assembly using alcohol, then perform
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bed-of-nails testing to quickly identify failed components.

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