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Mail Archives: geda-user/2017/03/30/12:28:53

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Thu, 30 Mar 2017 09:26:58 -0700 (PDT)
Date: Thu, 30 Mar 2017 18:26:55 +0200
From: "Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] No support for solder paste in pcb file format ?
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> > > > >> John Luciani:
> > > > >> > I create stencil footprints with the same basename as
> > > > >> > the component footprint and a ".sfp" extension. I have
> > > > >> > a script that parses the pcb and identifies all components
> > > > >> > that have a stencil footprint.
> > > >
> > > > I couldn't find this script on your page.  Could you please post or
> > link?
> > > >
> > >
> > > The script isn't quite ready for prime-time.
> >
> > But you tell why these scipts are good?
> >
> >
> The current script identifies the footprints that should be changed when
> generating gerbers for a stencil. The completed script will perform the
> replacement.

To put it another way. Is it better to generate paste layer from a script than manually editing each footprint?


> > > > >> as thin line silk for checking or write the pads to the sfp file.
> > > > >>
> > > > >> Do you have any specific file format for your sfp files ?
> > > > >>
> > > > >
> > > > > I just make them as normal footprints. For example - the stencil
> > > > footprint
> > > > > below is for a Cree XP-G LED --
> > > > >
> > > > > Element[0x0 "LED" "" "" 0 0 9996 2996 0 100 0x0]
> > > > > (
> > > > >    Pad[-5511 -5511 -5511 5511 1968 2000 2968 "" "1" 0x0100]
> > > > >    Pad[5511 -5511 5511 5511 1968 2000 2968 "" "2" 0x0100]
> > > > >    Pad[-492 -3937 492 -3937 2952 2000 3952 "" "3" 0x0100]
> > > > >    Pad[-492 0 492 0 2952 2000 3952 "" "3" 0x0100]
> > > > >    Pad[-492 3937 492 3937 2952 2000 3952 "" "3" 0x0100]
> > > > >    ElementLine[7996 -2484 7996 -7996 1000]
> > > > >    ElementLine[7996 -7996 -7996 -7996 1000]
> > > > >    ElementLine[-7996 -7996 -7996 -2484 1000]
> > > > >    ElementLine[7996 2484 7996 7996 1000]
> > > > >    ElementLine[7996 7996 -7996 7996 1000]
> > > > >    ElementLine[-7996 7996 -7996 2484 1000]
> > > > >    ElementArc[-7996 -10496 500 500 0 360 1000]
> > > > > )
> >
> > The *.sfp files are used to define shapes for solder paste?
> >
> 
> The shapes define openings in a stencil.

Then the shapes end up on the "stencil" layer, I think "paste" layer is a common name for this layer.


> > > For thermal pads I always use the grid. I have seen a lot of production
> > > problems. Bridging and misalignments. On these large pads I use a grid
> > > which reduces the coverage to between 50 - 60%.
> >
> > You use a grid because there will be production problems for a solid shape?
> >
> 
> Yes. I have seen bridging and misalignments. All of the components that
> I have used (with thermal pads) have recommended stencil openings
> as well as footprints. I either follow the datasheet recommendation or
> the manufacturer application notes.

I do not perfectly understand this, do you have an example for example datasheet or application note?


Regards Nicklas Karlsson

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