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December 2001

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Subject:
From:
Peter Swanson <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 10 Dec 2001 17:13:02 -0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (188 lines)
Graham,

UV or light curing coatings:
- Solvent free
- Full cure in seconds, on-line
- Single part
- Non flammable
- Can meet MIL I-46058C and UL
- Good to excellent environmental resistance
- Can be "rigid" or "flexible" (Shore D80 to Shore D40)
- Can be used on flex
- Can have strong fluorescence for inspection, or even be black

They are not suitable for all applications - are better sprayed, not so good
for dipping. If sprayed (say, using PVA or Nordson type selective spray
equipment), then full cure can often be achieved just with light. Otherwise,
secondary cures for shadowed areas may be achieved with heat, anaerobic,
moisture or other mechanisms.

To answer Mike Fenner's question, most pcb coatings are acrylic based, which
is a free radical cure. Expose to the correct wavelength/intensity of light
for required time and full cure is achieved. In fact, if the light is taken
away, curing stops. All the coating must be exposed to the light.

There are some coatings (a few) based on epoxy chemistry and a cationic
cure. Some cross linking will continue after the light is removed, but only
for thin sections (i.e. it doesn't propagate far), and just like the free
radical cure, all the coating must be exposed to the light.

So, an interesting technology which certainly has its place in the panoply
of coatings available for circuit protection. Whilst not a universal
panacea, they can often offer processing speed and simplicity, including
perhaps some environmental and health & safety advantages.

IMHO, they should not be dismissed totally out of hand by competitors to the
technology in an open forum; for one thing, this might insult the many
companies who are successfully using them!

Regards,
Peter
--
=========================================================
Peter Swanson            [log in to unmask]
INTERTRONICS                http://www.intertronics.co.uk

INTERTRONICS is dedicated to providing quality material,
  consumable and equipment solutions to the electronics
manufacturing and other technology based industries, with
   the highest levels of technical support and customer
                         service.


-----Original Message-----
From: Graham Naisbitt [mailto:[log in to unmask]]
Sent: 09 December 2001 19:01
To: [log in to unmask]
Subject: Re: [TN] 2 Conformal Coating ?'s


Peter,

I am semi-comatose now, so please, tell us what exactly are the advantages
of UV curable coatings?

Regards, Graham Naisbitt

[log in to unmask]
www.concoat.co.uk <http://www.concoat.co.uk>

For instant access to Product Data Sheets register on the Tech-Shot area of
http:// www.concoat.co.uk <http://www.concoat.co.uk>

Concoat Limited
Alasan House, Albany Park
CAMBERLEY GU16 7PH UK
Phone: +44 (0)1276 691100
Fax: +44 (0)1276 691227
Mobile: +44 (0)79 6858 2121


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Peter Swanson
Sent: Friday, December 07, 2001 05:51
To: [log in to unmask]
Subject: Re: [TN] 2 Conformal Coating ?'s


Graham,

You really must see someone about your delusions over UV cured coatings,
which are successfully used to coat many thousands of pcb's each year. I
know someone who has a nice sofa you can stretch out on whilst you tell him
all about it.... <g>

Suitability for UV has nothing to do with 3D v. 2D, more to do with the
complexity of the assembly geometry and the application methodology. These
will determine if a secondary cure mechanism is needed for the application.
In many instances (and with some of our customers), full cure is achieved
just with light.

Regards,
Peter
--
--------------------------------------------------------
Peter Swanson        [log in to unmask]
INTERTRONICS            http://www.intertronics.co.uk

   INTERTRONICS is dedicated to providing quality
  material, consumable and equipment solutions to the
 electronics manufacturing and other technology based
  industries, with the highest levels of technical
           support and customer service.


-----Original Message-----
From: Graham Naisbitt [mailto:[log in to unmask]]
Sent: 06 December 2001 16:52
To: [log in to unmask]
Subject: Re: [TN] 2 Conformal Coating ?'s


Mike

You would be better to go with a conventional coating. UV is not ideal for
3D objects - works great in 2D, cos you don't have to bend light! :-)

I cannot remember what the operating environment was for your circuit - if
you would care to repeat, I can recommend something - however, I am sure
that a one part AR or UR coating from a reliable supplier will give you the
best overall results - process and operating environment.

Regards, Graham Naisbitt

[log in to unmask]
www.concoat.co.uk <http://www.concoat.co.uk>

For instant access to Product Data Sheets register on the Tech-Shot area of
http:// www.concoat.co.uk <http://www.concoat.co.uk>

Concoat Limited
Alasan House, Albany Park
CAMBERLEY GU16 7PH UK
Phone: +44 (0)1276 691100
Fax: +44 (0)1276 691227
Mobile: +44 (0)79 6858 2121





-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Mike Manwell
Sent: Thursday, December 06, 2001 02:41
To: [log in to unmask]
Subject: [TN] 2 Conformal Coating ?'s


Hello,
Thanks in advance if you have taken the time to read this!

#1- Im trying different materials in a spray application. Both are cured
using UV. One material does a "secondary cure" w/ moisture. This is cool
because after 100 hours after UV cure, all material is fully cured.
The other material Im trying uses HEAT for a secondary cure, or, if
shodowed during UV cure, the material wont cure and never will. Obviously I
dont want the stuff dripping or running anywhere, but being new to this
wonderful process, just dont feel good about leaving uncured material on a
product for it's entire life. Iv been told that you can "test" the product
to see if the uncured material is causing a problem but Im not sure what
type of test that would consist of. Any insight?

#2- Has anyone out there ever installed refelctive metal plates in their UV
oven to limit shadowing?

Thanks so much,

Mike Manwell

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