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From: "John Luciani (jluciani AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Date: Wed, 29 Mar 2017 17:44:21 -0400
Message-ID: <CA+qhd=_y_waDfNMpmROtd7X6E1Rn-BYcYiD7SHkePNwhCKTXZg@mail.gmail.com>
Subject: Re: [geda-user] No support for solder paste in pcb file format ?
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On Wed, 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 delorie DOT com> wrote:

> > > >> 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.



>
> > > >> Then I could have a flag in the fp generator to either make 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 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.



>
>
> > 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.

John L







-- 
http://www.wiblocks.com

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Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote">On W=
ed, Mar 29, 2017 at 12:29 PM, Nicklas Karlsson (<a href=3D"mailto:nicklas.k=
arlsson17 AT gmail DOT com">nicklas DOT karlsson17 AT gmail DOT com</a>) [via <a href=3D"mail=
to:geda-user AT delorie DOT com">geda-user AT delorie DOT com</a>] <span dir=3D"ltr">&lt;=
<a href=3D"mailto:geda-user AT delorie DOT com" target=3D"_blank">geda-user AT delori=
e.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"m=
argin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left=
:1ex"><span class=3D"gmail-">&gt; &gt; &gt;&gt; John Luciani:<br>
&gt; &gt; &gt;&gt; &gt; I create stencil footprints with the same basename =
as<br>
&gt; &gt; &gt;&gt; &gt; the component footprint and a &quot;.sfp&quot; exte=
nsion. I have<br>
&gt; &gt; &gt;&gt; &gt; a script that parses the pcb and identifies all com=
ponents<br>
&gt; &gt; &gt;&gt; &gt; that have a stencil footprint.<br>
&gt; &gt;<br>
&gt; &gt; I couldn&#39;t find this script on your page.=C2=A0 Could you ple=
ase post or link?<br>
&gt; &gt;<br>
&gt;<br>
&gt; The script isn&#39;t quite ready for prime-time.<br>
<br>
</span>But you tell why these scipts are good?<br>
<span class=3D"gmail-"><br></span></blockquote><div><br></div><div>The curr=
ent script identifies the footprints that should be changed when<br></div><=
div>generating gerbers for a stencil. The completed script will perform the=
<br></div><div>replacement.<br></div><div><br>=C2=A0</div><blockquote class=
=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rg=
b(204,204,204);padding-left:1ex"><span class=3D"gmail-">
<br>
&gt; &gt; &gt;&gt; Then I could have a flag in the fp generator to either m=
ake paste pads<br>
&gt; &gt; &gt;&gt; as thin line silk for checking or write the pads to the =
sfp file.<br>
&gt; &gt; &gt;&gt;<br>
&gt; &gt; &gt;&gt; Do you have any specific file format for your sfp files =
?<br>
&gt; &gt; &gt;&gt;<br>
&gt; &gt; &gt;<br>
&gt; &gt; &gt; I just make them as normal footprints. For example - the ste=
ncil<br>
&gt; &gt; footprint<br>
&gt; &gt; &gt; below is for a Cree XP-G LED --<br>
&gt; &gt; &gt;<br>
&gt; &gt; &gt; Element[0x0 &quot;LED&quot; &quot;&quot; &quot;&quot; 0 0 99=
96 2996 0 100 0x0]<br>
&gt; &gt; &gt; (<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 Pad[-5511 -5511 -5511 5511 1968 2000 2968 &quot=
;&quot; &quot;1&quot; 0x0100]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 Pad[5511 -5511 5511 5511 1968 2000 2968 &quot;&=
quot; &quot;2&quot; 0x0100]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 Pad[-492 -3937 492 -3937 2952 2000 3952 &quot;&=
quot; &quot;3&quot; 0x0100]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 Pad[-492 0 492 0 2952 2000 3952 &quot;&quot; &q=
uot;3&quot; 0x0100]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 Pad[-492 3937 492 3937 2952 2000 3952 &quot;&qu=
ot; &quot;3&quot; 0x0100]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 ElementLine[7996 -2484 7996 -7996 1000]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 ElementLine[7996 -7996 -7996 -7996 1000]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 ElementLine[-7996 -7996 -7996 -2484 1000]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 ElementLine[7996 2484 7996 7996 1000]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 ElementLine[7996 7996 -7996 7996 1000]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 ElementLine[-7996 7996 -7996 2484 1000]<br>
&gt; &gt; &gt;=C2=A0 =C2=A0 ElementArc[-7996 -10496 500 500 0 360 1000]<br>
&gt; &gt; &gt; )<br>
<br>
</span>The *.sfp files are used to define shapes for solder paste?<br></blo=
ckquote><div><br></div><div>The shapes define openings in a stencil.<br></d=
iv><div><br>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0=
px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<span class=3D"gmail-"><br>
<br>
&gt; For thermal pads I always use the grid. I have seen a lot of productio=
n<br>
&gt; problems. Bridging and misalignments. On these large pads I use a grid=
<br>
&gt; which reduces the coverage to between 50 - 60%.<br>
<br>
</span>You use a grid because there will be production problems for a solid=
 shape?<br></blockquote><div><br></div><div>Yes. I have seen bridging and m=
isalignments. All of the components that<br></div><div>I have used (with th=
ermal pads)  have recommended stencil openings<br></div><div>as well as foo=
tprints. I either follow the datasheet recommendation or<br></div><div>the =
manufacturer application notes.<br><br></div><div>John L<br></div><div><br>=
</div><div><br><br>=C2=A0</div></div><br><br clear=3D"all"><br>-- <br><div =
class=3D"gmail_signature"><a href=3D"http://www.wiblocks.com" target=3D"_bl=
ank">http://www.wiblocks.com</a> =C2=A0</div>
</div></div>

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