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Re: gEDA-user: pads, mask and solder paste



On Mon, Feb 14, 2011 at 6:27 AM, Kai-Martin Knaak <kmk@xxxxxxxxxxxx> wrote:
> Hi.
> The solder paste pattern emitted by PCB seems to coincide exactly with
> the copper of the pads. This is a reasonable default. But there are use
> cases where a different solder paste size is better.
>
> 1) A pad completely covered with solder mask should not receive any
> solder paste. This kind of pads are useful a way to achieve tracks
> in footprints.

I've tried to do this - see the attached footprint ResCu250mOhm-fab.fp
This doesn't quite work.  In the GTK hid the solder mask is rendered
as a very thin line.  The gerbers contain the solder mask opening as a
line of width 0, iirc. When I had this PCB fabricated the fab house
got confused and changed the width of the solder mask opening to be
the same as the track width!  Next time I send out to fab, I'll hack
the gerbers in an editor to totally nuke the undesired solder mask
opening paths.

> 2) Pads partly covered by solder mask should receive a solder mask
> pillow that corresponds to the hole in the mask, rather than to the
> pads copper dimensions. Such partly covered pads are useful as a heat
> sink.

Yes, that works fine - see S005.fp.  This is for a SMD bridge and
works exactly as you've described.

> Is there a way to achieve these goals?

1.5 out of 3 is a start :-)

Attachment: ResCu250mOhm-fab.fp
Description: application/pcb-footprint

Attachment: S005.fp
Description: application/pcb-footprint


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