Howdy,

You could just *not* submit the gerbers for the solder mask layers....
You can also play with what layers you wish to or wish not to CAM..

Yes, turning off the viewing of the solder mask layers does just exactly
that.... we have boards that are both solder masked and conformal coated
(since we deal with some high voltage now and again)....  Solder mask may be
a very good idea for manufacturing, especially soldering....

As far as playing with solder mask....
I had a similar problem a few years back....  I would tender, that there are
a few different ways to solve this....

1) I think solder mask is a negative layer (i.e., it behaves like a
photographic negative), just like power plane layers....  where ever you
draw primitives on the solder mask layer, is where the actual solder mask
*will not* be on the finished board from the fab house....

so, you could place a fill, or polygon pour, or track on the solder mask
layer and that's where the solder mask *will not* be located (i.e., bare
board exposed)....

2) since you are dealing with a heatsink, why not place a large rectangular
(I assume the heatsink is rectangular) pad with standard soldermask
tolerances around the pad.....  the pad would provide copper to "glue" the
heatsink to it and itself be a heat conductor with a minor amount of thermal
mass, which you may need to be careful of depending upon your specific
application....  this is provided that you have no other traces running
under the heatsink on that (top?)layer, which I hope you don't.... ;-)

Cheers,
-chris


-----Original Message-----
From: Robison Michael R CNIN [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, September 18, 2001 10:01 AM
To: 'Protel EDA Forum'
Subject: [PEDA] eliminating solder mask ??


hello,

well another embarrassing newbie question from someone who should
no better.

production is having trouble getting some heat sinks to stay "glued" to
the solder mask on some prototype boards.  the decision has been
made to not use a solder mask.  the boards will be conformal coated
anyway.

so how do i eliminate the solder mask?  i know that pads are tented by
using a negative value equal to the largest pad.  my guess is that i can
do a design/rules/manufacturing tab, double click the solder mask ex-
pansion and use a whole board scope with -1mil expansion on it.  is this
correct?  more so, is this the way to do it?  i played with this and looked
at the top and bottom solder layers (not the gerbers) using the single
layer mode and i don't see anything but the pads no matter what i do to
it.

i also entertained the thought of right-clicking on the pcb, selecting
options/board options/layers tab/ and then simply unclicking the top and
bottom solder, but i'm skeptical of this... i think all this does is control
the layers that are displayed.

i apologize for posting on such a basic issue, but i could not find the
answer in the book, and guessing makes me nervous when we're
talking about actually placing an order.

thank you, miker


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