On W= ed, Mar 29, 2017 at 12:29 PM, Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com] <= geda-user AT delori= e.com> wrote:

> > >> John Luciani:
> > >> > I create stencil footprints with the same basename = as
> > >> > the component footprint and a ".sfp" exte= nsion. I have
> > >> > a script that parses the pcb and identifies all com= ponents
> > >> > that have a stencil footprint.
> >
> > I couldn't find this script on your page.=C2=A0 Could you ple= ase post or link?
> >
>
> The script isn't quite ready for prime-time.

But you tell why these scipts are good?

The curr= ent script identifies the footprints that should be changed when

<= div>generating gerbers for a stencil. The completed script will perform the=

replacement.

=C2=A0

> > >> Then I could have a flag in the fp generator to either m= ake paste pads
> > >> 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 ste= ncil
> > footprint
> > > below is for a Cree XP-G LED --
> > >
> > > Element[0x0 "LED" "" "" 0 0 99= 96 2996 0 100 0x0]
> > > (
> > >=C2=A0 =C2=A0 Pad[-5511 -5511 -5511 5511 1968 2000 2968 "= ;" "1" 0x0100]
> > >=C2=A0 =C2=A0 Pad[5511 -5511 5511 5511 1968 2000 2968 "&= quot; "2" 0x0100]
> > >=C2=A0 =C2=A0 Pad[-492 -3937 492 -3937 2952 2000 3952 "&= quot; "3" 0x0100]
> > >=C2=A0 =C2=A0 Pad[-492 0 492 0 2952 2000 3952 "" &q= uot;3" 0x0100]
> > >=C2=A0 =C2=A0 Pad[-492 3937 492 3937 2952 2000 3952 "&qu= ot; "3" 0x0100]
> > >=C2=A0 =C2=A0 ElementLine[7996 -2484 7996 -7996 1000]
> > >=C2=A0 =C2=A0 ElementLine[7996 -7996 -7996 -7996 1000]
> > >=C2=A0 =C2=A0 ElementLine[-7996 -7996 -7996 -2484 1000]
> > >=C2=A0 =C2=A0 ElementLine[7996 2484 7996 7996 1000]
> > >=C2=A0 =C2=A0 ElementLine[7996 7996 -7996 7996 1000]
> > >=C2=A0 =C2=A0 ElementLine[-7996 7996 -7996 2484 1000]
> > >=C2=A0 =C2=A0 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.

=C2=A0

> For thermal pads I always use the grid. I have seen a lot of productio= n
> 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 m= isalignments. All of the components that
I have used (with th= ermal pads) have recommended stencil openings
as well as foo= tprints. I either follow the datasheet recommendation or
the = manufacturer application notes.

John L

=

=C2=A0

--
http://www.wiblocks.com =C2=A0