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May 2000

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Subject:
From:
Matthew Lamkin <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 11 May 2000 12:49:07 +0100
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Hi there Phil,

Rather than do it in house, and go through the cost of purchasing the
equipment & adding to the work and skills required of
your assemblers, why not get your PCB manufacturer to do it for you
before you get the boards.

I find that the additional 20p (or whatever) added to the cost of the
PCB is usually less than the cost of hand application and all the
messing about
waiting for it to dry etc (and uses less mask).

Simply create a Gerber file containing the areas that need it (or send
them a hand done sample) and they can then sort it out.
Its a standard service that they do.

If you have any boards in stock, then it should not be a problem to send
them back for the work to be done.

You might find that any holes larger than 3mm are a bit hard to screen
as the peelable resist goes down the holes & spreads about 
making a mess, it depends upon the consistency of the masking used. 

If the board is PTH, you could consider making any large holes (I.E.
mounting's etc) non PTH & with a slight clearance in the land around the
hole
and then add several Via's around the land (but not where they may be
under direct pressure) to enable any required continuity.
If you need land visible for earthing, then you could put a 1mm+ slot
into the bottom copper land so that the solder does not flow over it
all.

This way, they would not need peelable on big holes and they could go
through the wave bath OK.

Hope this helps - Matthew Lamkin.

>-----Original Message-----
>From:  Phil Nutting [SMTP:[log in to unmask]]
>Sent:  Wednesday, May 10, 2000 8:50 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 ChemaskŪ 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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