Hello Fabio.

> > Personally I don't like lots of filled zones unless that really are
> > necessary, but that's a fairly minor point.
> Well, I read that this is good practice as this make less use of
> etchant during the etching process. Isn't that true?

Actually it IS a good practice to use filling zones. Not only for saving
etchant but also for grounding, shielding and low resistant power
supply. For electromagnetic compilance zone fill is essential.

But you have to be carefull. Some structures, as an example long
singular fingers or slots, are prone to get resonant and producing
additional RF Problems. You can also get isoliting problems, and low 
ground conection losses for power supply means also high shortcut
Sometimes you get even additional heat by eddy currents.

So you have to look for this issues. In my experience, you can look for
this long structures and try to get them small or remove them complete.
To get them smaller you can add bridges to the design. As an example, if
you have a long slot by a long shaped socket, try to shortcut this slot
by connecting it at one or severall places from one side to the other.

Try to connect each zone with more then one (better more than two)
connections to its potential. This connections should be spaced. As an
example at opposite corners of the zone. 

Often it helps, to put additional GND vias to the board for creating
additional zones of GND potential. So you get a unregulary grid of
Ground zones and interconnections of them at your board. If some ground
zones are covering the same area at opposite sides of the board, connect
them with vias (stitching). Try not to place this stitchings regulary,
because any regularity could get resonant, but try to place them
randomly. This will avoid to create some resonators.

As an example, you have a line of 100mm where the ground zone covers
both, the primary and secondary side of the board. So you want to stitch
them together by vias through the board, and the vias schould be spaced
equal acros this line, perhaps at 1/3 and 2/3 of the line. But DO NOT
place the vias at 33,3mm and 66,6mm, because you have a regular
structure of following 33,3mm parts, which can resonate together. The
better solution would to place one via at 30mm and the next at 80mm.
so you have three parts with different lengs 0f 30, 50 and 20mm, which
can only resonant individual. If you think, 50mm is too long, put an
additional via to divide it. But not ecactly at the middle. ;-)
also do not place the vias in an exact straight line. Move them randomly
out of the center of the line. 

Vias are expensive, if you designe for a great quantity of boards. Also
it consumes much time to create this fill zones carefully.
So i can understand Andys suggestion to avoid them. Especially if you
have to save room for isolating issues.

I have not tested yet, wether stitching works at KiCAD. ;-) Up to now,
the remaining vias of the ground net created enough vias for my simple

With best regards: Bernd Wiebus alias dl1eic


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