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May 1998

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Subject:
From:
Mark Gillan <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 29 May 1998 09:29:00 +0000
Content-Type:
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The following is based soley on my experience of Soldermask Processing,
please feel free to correct any inaccuracies.

We currently process Soldermask using P52 with 91h  and aqueous systems,
Taiyo,Carapace etc..

The main differance is the base chemistry, Probimer 52 is epoxy based where
Taiyo, Tamura etc. are aqueous based.

Yes, P52 is normally curtain coated, it also requires specific chemistry for
developing (4-Butyrolacetone) which is a one part solvent which can be
recliamed to reduce costs. Aqueous systems can use a sodium carbonate
solution which is much cheaper.

 P52 has a "very" long exposure time up to 60 sec on 7kW ORC units, again
aqueous systems require a lesser exposure time period on a 5kW lamp.

Holding fine webs is also harder using P52, typically you will have to start
adjusting exposure time v dev speed to achieve less than 6 thou webs. Taiyo
will process 4 thou with only an increase in exposure time.
Cure time for P52 is approx. 2 hours @ 150degC. Taiyo cures @ 150degC for 1
hour.

So why use P52?

On the plus side assembly shops  are usually happy with the finish due to
the resilient (hardness of 6+) and very matt finish (low to non existant
solderballing). The electrical  breakdown voltage is typically higher than
3kV which customers producing High volatge boards like. Aqueous systems are
about 0.5 to 2 kV in my experience.

One other point is cost, our experience shows that P52 can be more expensive
per sq foot than an aqueous system.
If you are looking to intrduce P52, then I would recommend 52CSM as the
solvent carrier is less toxic and finer webs are easier to attain.

If you require further info please email direct.

Mark Gillan
Process Engineer
Prestwick Circuits Ltd.
Scotland UK.

[log in to unmask]
 ----------
From: pacrim
To: TechNet
Subject: [TN] Properties of Probimer 52 Soldermas
Date: 29 May 1998 07:27

I am trying to determine the differences between Probimer-52 and other
soldermasks (Tamura, Taiyo, etc.).  I understand that application
techniques differ, as Probimer requires a curtain coating process, while
the others can be sprayed, etc.  Are there significant differences
between Probimer-52 and others?  If so, what are they?  Is one better
then the other?  I am trying to make an argument for the changing to a
more conventional S/M and any feedback would be greatly appreciated.

Thanks for all of your help in advance.

Best Regards

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