Le 27/11/2014 12:22, "Torsten Hüter" a écrit : > Hi Jean-Pierre, > > I agree that a the trapezoidal pad is seldom used for most circuits > and this feature isn't important. However, commercial tools like > Altium Designer or Mentor Expedition support custom pad shapes, there > is a lot of freedom for the pad geometry (any polygonal shape). Have > a look here, how Altium does this: > > http://techdocs.altium.com/display/ADOH/Creating+a+Custom+Pad+Shape > > For custom shapes, you have to define there polygon connection points > - see the section "Thermal Connections for Custom Pads".
Generally speaking, using polygons on copper layers (such as polygonal shapes attached to pads, which is roughly what Altium is doing, and also the microwave tools in Pcbnew) need to take in account polygons in DRC code. Currently this in not the case in Pcbnew. This is acceptable for microwave applications, which are very specific (even DRC is specific in microwave applications, because traces are not equipot) But for usual applications DRC must take in account polygons. Currently I do not know a way to do that with a calculation time compatible with the on line DRC (calculating min dist between polygons is not as fast as calculating a min dist between basic shapes. Having said that, I am not opposed to add thermal reliefs to trapezoidal pads. I just said until now, it was not needed. Obviously, if these pads are now used in usual boards ( I mean not microwave applications) thermal reliefs are needed. > > -- > > About the discontinuities: I've used a few years ago the RF package > of Mentor Expedition, there you can create tapered striplines for > these purposes. And of course the copper fill follows these shapes. > > You can find on youtube a good video about a typical RF design > process; have a look here (RF Design with Expedition PCB): > > https://www.youtube.com/watch?v=qaeOii1rLN0 > > Bye, Torsten > I am thinking you are not really talking about discontinuities, but about using specific shapes: stubs, gaps, polygons and other geometric shapes to create inductors, capacitors, filters, impedance adapters, isolators and other microwave components (which are therefore "virtual" components, because created by specific shapes on copper layers and are not soldered components). I am not a microwave specialist, but I worked with specialists (who where widely using ADS from Agilent to calculate/simulate microwave designs), when I wrote the pcb calculator and microwave tools in Pcbnew. Because geometric shapes are used to create inductors, capacitors ... non specialists can understand why discontinuities (and/or 90 deg track segments) are bad: they add parasitic components to the path of a signal. -- 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
