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
