Phil: There are a variety of screenable temporary solder
resists(TSR)available. The basic equipment requirements are:
1. Screen table w/pins or base plate
2. Squeegee 60 durometer
3. Drying/baking oven   
4. Screen mesh 60-70 polyester
5. Screen chase @ 30-50% larger than the board 
6. Image data or film
Items 4-6 can usually be provided by a screen making supply service.

The type of TSR material you use depends on your post solder cleaning
process. 
If you use a wash it is usually better to go with a material that is soluble
in your wash system to eliminate the labor of hand removal of the mask as in
the peelable version you are currently using. When using a wash soluble mask
it is preferable to use a prewash section on your cleaner for the majority
of removal to prevent carry over into the wash sump. Also try to use a non
filled system to prevent filler build up in the wash, sprays and pumps.

If you are not washing and want to stay with a peelable mask there are two
basic types acrylic and latex, although I've seen some silicone and
urethanes but at higher costs. I prefer the acrylics, if you go with latex
use the non-ammoniated
One of the problems with the screened peelables is you have to build up a
fairly thick and wide deposit to prevent it from tearing at removal, this
may require multiple screen applications. The peelables do not release and
remove well from small isolated features.
	
Regards
	
Michael Barmuta
	
Staff Engineer
	
Fluke Corp.
	
Everett Wa
	
425-356-6076                                    	
	


-----Original Message-----
From: Phil Nutting [mailto:[log in to unmask]]
Sent: Wednesday, May 10, 2000 12:50 PM
To: [log in to unmask]
Subject: [TN] Through Hole Wave Solder Mask Application


To all,

We are trying to cost reduce part of our through hole assembly.  We build
high voltage power supplies and they don't lend themselves to SMT.  The
boards have the standard LPI solder mask, but we need to mask some component
holes for components that are installed after wave solder.  Currently we
apply Chemask® Peelable solder mask by hand from an 8 fluid ounce bottle.  I
know there are ways of applying a solder mask using a silkscreen.

What equipment is needed?

What mask material should I use?

What support equipment do I need?

Did I leave anything out?

Thanks in advance for your input.

Phil Nutting
Manufacturing Engineer
Kaiser Systems, Inc.
126 Sohier Road
Beverly, MA 01915
ph: 978-922-9300
fx: 978-922-8374
[log in to unmask]

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