Nick, I have used trapezoidal pads to connect between PCB antennas and traces. There are precise rules on trace thickness for antennas, and this let me have one thing I could modify in the footprint to handle multiple different feedline widths.
Adam Wolf Cofounder and Engineer W&L On Wed, Nov 26, 2014 at 1:16 PM, Nick Østergaard <[email protected]> wrote: > 2014-11-26 20:00 GMT+01:00 jp charras <[email protected]>: > > Le 26/11/2014 18:43, Nick Østergaard a écrit : > >> This is indeed an annoyting bug, it has existed since 2009 at least. > >> There is already a bug report about it. See: > >> > >> https://bugs.launchpad.net/kicad/+bug/1035621 > > > > Sorry, but I already said why a trapezoidal pad is designed. > > > > The fact an user is thinking something is not expected is not a proof of > > a bug. > > I do follow you, but I still thought it was worth linking this thread > with the bug report. > > > Trapezoidal pads have a very specific purpose. > > I am pretty sure a copper zone around tracks in a microwave design > > breaks the design. > > Indeed, IIRC this special behaivour of the trapez pad is not described > in the manual, so one could only assume it was a bug. > > On top of my head I can not come up with a design that requires a > trapez pad instead of an oval, rectangular or circular pad. Maybe > wayse could fill in, since he has them in his design. > > > So : > > First, define the purpose of trapezoidal pads. > > After, and depending on this purpose, decide if thermal reliefs are good > > or not. > > > >> > >> Nick > >> > >> 2014-11-26 18:03 GMT+01:00 jp charras <[email protected]>: > >>> Le 26/11/2014 17:18, Wayne Stambaugh a écrit : > >>>> I just discovered something I never noticed before. Trapezoidal SMD > >>>> pads are not connected to zone files (see attached screen shot). The > >>>> zone fill also does not follow the contour of the pad outline. Is > this > >>>> by design or should I file a bug report? > >>>> > >>> > >>> Currently, this is by design. > >>> > >>> The primary goal of these trapezoidal pads is microwave applications. > >>> > >>> For these microwave applications, they are used to connect a large > track > >>> to a narrow pin ( transistor or IC) ( or a narrow track to a large pin) > >>> *without discontinuity* of the copper width. > >>> (A discontinuity between a track and a copper pad area can create > signal > >>> integrity issues. In fact any discontinuity on the signal path creates > >>> issues, at very high frequencies ) > >>> A trapezoidal shape with an edge having the same size as the track, and > >>> the opposite edge having the size of the transistor or IC pin does not > >>> create discontinuity. > >>> One could use also rectangular pads, and trapezoidal track segments to > >>> avoid discontinuity, but Pcbnew does not know trapezoidal track > >>> segments, mainly because they are not easy to handle in DRC. > >>> > >>> When you are using trapezoidal shapes for pads, you are expected > connect > >>> a track to these pads using the right edge, and the right track width > >>> (or the right pad size) > >>> If this is not the case, a rectangular pad or an oval pad is better > >>> (more easy to use). > >>> > >>> Adding thermal relief to a trapezoidal shape creates discontinuity, and > >>> the shape is no more a trapezoid. > >>> In fact, using a trapezoidal shape for a pad in a copper zone has no > >>> interest. > >>> > >>> For these reasons, I did not spent time to code thermal reliefs for > >>> trapezoidal shapes. > >>> > >>> Of course, trapezoidal shapes can have now applications outside the > >>> microwave applications, but I don't know these applications. > >>> > >>> -- > >>> Jean-Pierre CHARRAS > >>> > >>> _______________________________________________ > >>> Mailing list: https://launchpad.net/~kicad-developers > >>> Post to : [email protected] > >>> Unsubscribe : https://launchpad.net/~kicad-developers > >>> More help : https://help.launchpad.net/ListHelp > >> > > > > > > -- > > Jean-Pierre CHARRAS > > > > _______________________________________________ > > Mailing list: https://launchpad.net/~kicad-developers > > Post to : [email protected] > > Unsubscribe : https://launchpad.net/~kicad-developers > > More help : https://help.launchpad.net/ListHelp > > _______________________________________________ > Mailing list: https://launchpad.net/~kicad-developers > Post to : [email protected] > Unsubscribe : https://launchpad.net/~kicad-developers > More help : https://help.launchpad.net/ListHelp >
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