kicad-developers team mailing list archive

[jp charras <jp.charras@xxxxxxxxxx>]

Le 06/01/2018 à 22:58, kristoffer Ödmark a écrit :
> I am implementing it now, just a question, what should be the logic behind micro vias? Not very
> familiar with those.
> 
> Can they go between any number of layers, or only adjecent ones? I will treat them like buried vias
> currently, so that they can go between any two layers.

Micro vias and buried vias have constraints.
These constraints are highly dependent on board makers but usually these vias cannot go between any
two layers.

micro vias are in fact laser drilled vias, and the hole is not a cylinder, but a cone.
the max depth (Z dimension) depend on the hole diameter.
If we restrict laser drilled vias to 2 adjacent layers, it should work in any case (although a bit
restrictive).
This is one of reasons in Pcbnew microvias are only blind vias restricted to adjacent layers.
More than 2 adjacent layers is certainly possible, but only the board house can say that.
Of course standard blind/buried vias have also limitations, and cannot go between any layer pair.

For instance, see
https://www.eurocircuits.com/blog/blind-and-buried-vias/
and
https://www.pcbcart.com/pcb-capability/blind-and-buried-vias.html
for limitation examples.

And keep in mind limitations depends on the board house that will make your board.

Currently, Pcbnew is missing a layer stack manager (coming for V6), and a dialog via properties
cannot safely manage the layers pairs of non through hole vias.

Also keep in mind changing a via setup should be tested by the DRC (clearance test) and the ratsnest
rebuild if layers change (or if the size is smaller).

-- 
Jean-Pierre CHARRAS