Miker wrote:

> 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

Hello to you too, Miker,

I've seen the "sticky" effect of the solder mask.
To eliminate the solder mask (top and/or bottom), just deselect them in the
CAM wizard before generating the Gerber files.
Or, just generate them and do not send the files .GTS (Top Solder) and .GBS
(Bottom Solder) to your boardhouse.
However, you might prefer to have a solder mask on the solder side of the
board. Then, only leave out the .GTS file.
Anyway, you must tell your boardhouse, that you don't want a (Top) solder
mask, or else they probably generate the solder mask themselves!

Another possibility is, to put a fill or polygon on the solder mask layer on
the locations, where you don't want soldermask.
Solder masks are used as negative layers by the boardhouse (in the gerbers,
they are positive), so if you put something on a solder mask layer, the
solder mask will be omitted there.
Of course, you should take care, that there is no copper under the
heatsinks, which could cause a shortcircuit.

BTW: concerning professionalism, I agree. Let's keep it that way.

Have a nice day!

Joop Reekers
Semecs bv,

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