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| From: | "David Carr (junk AT dcarr DOT org) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com> |
| Date: | Tue, 17 Jan 2017 15:57:25 -0600 |
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| Subject: | Re: [geda-user] QFN packages solder mask |
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--001a114015e21bcee7054651650e Content-Type: text/plain; charset=UTF-8 John, gerbv can remove elements from gerber files. I'd add your tiny metal specks to get the mask relief you want and then use gerbv to manually remove those specks from the metal layer after generating the gerbers. David On Tue, Jan 17, 2017 at 3:47 PM, John Griessen (john AT ecosensory DOT com) [via geda-user AT delorie DOT com] <geda-user AT delorie DOT com> wrote: > I've been making footprints for QFN packages and came across guidelines by > the chip makers that say > it is beneficial to have some solder mask under the edge of the QFN > package, but not if it gets too thin > anywhere, as it can come off and cause trouble if it is. > > So I was wondering if there is any way to get zones of solder mask added. > PCB generates solder mask, > it does not define it directly, so I'm looking for a trick. > > I experimented with the thickness clearance and mask values in the pad > line of an element. > The sharp square corners of the mask layer cause problems at QFN package > corners. > > The reasons are graphically shown in these files: > > http://ecosensory.com/geda/qfn_lands_problem.png > http://ecosensory.com/geda/qfn_lands_problem_cure.png > > Is there a gerber editor to use? > > In a while, pcb-rnd will be probably able to handle solder mask directly > and go beyond > layer growing limitations of solder mask and clearance, but I need > something now. > > If fabs would let you, a speck of metal that would be gone in the etch > could have > solder mask opening and put it where I want it... > > Is > -- > John Griessen -- building field gear for biologists > Ecosensory Austin TX ecosensory.com > --001a114015e21bcee7054651650e Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr">John,<div><br></div><div>gerbv can remove elements from ge= rber files.=C2=A0 I'd add your tiny metal specks to get the mask relief= you want and then use gerbv to manually remove those specks from the metal= layer after generating the gerbers.</div><div><br></div><div>David</div></= div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Tue, Jan 1= 7, 2017 at 3:47 PM, John Griessen (<a href=3D"mailto:john AT ecosensory DOT com">j= ohn AT ecosensory DOT com</a>) [via <a href=3D"mailto:geda-user AT delorie DOT com">geda-= user AT delorie DOT com</a>] <span dir=3D"ltr"><<a href=3D"mailto:geda-user AT del= orie.com" target=3D"_blank">geda-user AT delorie DOT com</a>></span> wrote:<br>= <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex">I've been making footprints for QFN pack= ages and came across guidelines by the chip makers that say<br> it is beneficial to have some solder mask under the edge of the QFN package= , but not if it gets too thin<br> anywhere, as it can come off and cause trouble if it is.<br> <br> So I was wondering if there is any way to get zones of solder mask added.= =C2=A0 PCB generates solder mask,<br> it does not define it directly, so I'm looking for a trick.<br> <br> I experimented with the thickness clearance and mask values in the pad line= of an element.<br> The sharp square corners of the mask layer cause problems at QFN package co= rners.<br> <br> The reasons are graphically shown in these files:<br> <br> <a href=3D"http://ecosensory.com/geda/qfn_lands_problem.png" rel=3D"norefer= rer" target=3D"_blank">http://ecosensory.com/geda/qfn<wbr>_lands_problem.pn= g</a><br> <a href=3D"http://ecosensory.com/geda/qfn_lands_problem_cure.png" rel=3D"no= referrer" target=3D"_blank">http://ecosensory.com/geda/qfn<wbr>_lands_probl= em_cure.png</a><br> <br> Is there a gerber editor to use?<br> <br> In a while, pcb-rnd will be probably able to handle solder mask directly an= d go beyond<br> layer growing limitations of solder mask and clearance, but I need somethin= g now.<br> <br> If fabs would let you, a speck of metal that would be gone in the etch coul= d have<br> solder mask opening and put it where I want it...<br> <br> Is<span class=3D"HOEnZb"><font color=3D"#888888"><br> -- <br> John Griessen -- building field gear for biologists<br> Ecosensory=C2=A0 Austin TX=C2=A0 <a href=3D"http://ecosensory.com" rel=3D"n= oreferrer" target=3D"_blank">ecosensory.com</a><br> </font></span></blockquote></div><br></div> --001a114015e21bcee7054651650e--
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