kicad-developers team mailing list archive

[Nick Østergaard <oe.nick@xxxxxxxxx>]

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

Nick

2014-11-26 18:03 GMT+01:00 jp charras <jp.charras@xxxxxxxxxx>:
> 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
>
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