Mail Archives: geda-user/2022/08/19/05:51:23
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Almost missed this one:
Op 17-08-2022 om 14:59 schreef Erich Heinzle (a1039181 AT gmail DOT com) [via
geda-user AT delorie DOT com]:
> Two thoughts
>
> 1) I have heard of many people doing reflow at home who use locating
> pins on a precisely drilled support block that positively locates the
> pcb itself and the overlying stencil with matching holes when applying
> the paste
>
> 2) It could be that your apertures in the stencil are not optimal.
> Smaller apertures may allow more precise results. IIRC gEDA PCB solder
> mask aperture shrinkage relative to the pad shape can only be defined,
> if at all, on a whole board basis.
>
> pcb-rnd treats each pad as a padstack, where layer apertures on each
> layer can be defined individually, or autogenerated, in the
> :padstackedit action.
>
> Identical pads, i. e. in a QFN, can use the same padstack prototype
> for all the pads, once defined. This gives you very granular
> control, down to the individual padstack if required. Slots and
> arbitrary simple polygonal pad shapes are also supported in padstacks.
>
> How are you generating your gerbers for the stencil?
I use pcb's export function in a shell script I wrote: pcb -x gerber
$projname.pcb
(This script also collates the gerbers and xy files into a zip file, and
sorts and converts the bom into a format that I can import in a
LibreOffice spreadsheet.)
A switch to pcb-rnd is tempting, as it offers more control and richer
features, and I have tried it out in the past -- however, there are
several reasons for me to stick with pcb, including familiarity and
compatibility with some colleagues of mine (who also use pcb).
I'll take another look at pcb-rnd, and see what I can do with regard to
stencil apertures (I noticed that many PCB houses automatically split up
large single holes into multiple smaller ones) -- but first, I'll focus
on the mechanical set-up and workflow here, because I think that is the
biggest cause of my problems.
Regards,
Richard
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<p>Almost missed this one:<br>
</p>
<div class="moz-cite-prefix">Op 17-08-2022 om 14:59 schreef Erich
Heinzle (<a class="moz-txt-link-abbreviated" href="mailto:a1039181 AT gmail DOT com">a1039181 AT gmail DOT com</a>) [via <a class="moz-txt-link-abbreviated" href="mailto:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>]:<br>
</div>
<blockquote type="cite"
cite="mid:CAHUm0tOM07EoJjh0UC5_e8mKp_XZcM+Mh0ixHHzdp35emvX9yA AT mail DOT gmail DOT com">
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<div dir="auto">
<div>Two thoughts</div>
<div dir="auto"><br>
</div>
<div dir="auto">1) I have heard of many people doing reflow at
home who use locating pins on a precisely drilled support
block that positively locates the pcb itself and the overlying
stencil with matching holes when applying the paste</div>
<div dir="auto"><br>
</div>
<div dir="auto">2) It could be that your apertures in the
stencil are not optimal. Smaller apertures may allow more
precise results. IIRC gEDA PCB solder mask aperture shrinkage
relative to the pad shape can only be defined, if at all, on
a whole board basis. </div>
<div dir="auto"><br>
</div>
<div dir="auto">pcb-rnd treats each pad as a padstack, where
layer apertures on each layer can be defined individually, or
autogenerated, in the :padstackedit action.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Identical pads, i. e. in a QFN, can use the
same padstack prototype for all the pads, once defined. This
gives you very granular control, down to the individual
padstack if required. Slots and arbitrary simple polygonal pad
shapes are also supported in padstacks.</div>
<div dir="auto"><br>
</div>
<div dir="auto">How are you generating your gerbers for the
stencil?</div>
</div>
</blockquote>
<p>I use pcb's export function in a shell script I wrote: <span
style="font-family:monospace"><span
style="color:#000000;background-color:#ffffff;">pcb -x gerber
$projname.pcb</span><br>
</span></p>
<p>(This script also collates the gerbers and xy files into a zip
file, and sorts and converts the bom into a format that I can
import in a LibreOffice spreadsheet.)</p>
<p>A switch to pcb-rnd is tempting, as it offers more control and
richer features, and I have tried it out in the past -- however,
there are several reasons for me to stick with pcb, including
familiarity and compatibility with some colleagues of mine (who
also use pcb).</p>
<p>I'll take another look at pcb-rnd, and see what I can do with
regard to stencil apertures (I noticed that many PCB houses
automatically split up large single holes into multiple smaller
ones) -- but first, I'll focus on the mechanical set-up and
workflow here, because I think that is the biggest cause of my
problems.</p>
<p>Regards,</p>
<p>Richard<br>
</p>
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