kicad-developers team mailing list archive

[Jon Neal <reportingsjr@xxxxxxxxx>]

Thanks JP.

After doing some more research I think it would probably be a good idea to
allow blind/buried micro vias.

Regarding being able to see what layer a blind/buried via is on.. That
probably needs some rendering changes to make clearer. I don't think I want
to mess with that right now.

It does make things initially easier if you are only using micro vias to go
from an external layer to an adjacent inner layer, but forcing that setup
makes things a little more difficult if someone does want to use
blind/buried micro vias.

Andrew Zonenberg laid out these issues quite a while back (
https://lists.launchpad.net/kicad-developers/msg14792.html), but nothing
was done after that.

For now how about this:
If micro vias AND blind/buried vias are allowed then let people place
buried vias.
If only micro vias are allowed then only let them go from an external layer
to an inner layer.

I don't think this is the greatest solution, but I think it is better than
not allowing buried microvias.
Thoughts?

Jon

On Thu, Jun 18, 2015 at 2:40 PM, jp charras <jp.charras@xxxxxxxxxx> wrote:

> Le 18/06/2015 20:17, Jon Neal a écrit :
> > The code for placing a micro via in the push and shove router was just
> > using the regular/through via drill size. Reported in this bug:
> > https://bugs.launchpad.net/kicad/+bug/1464332
> >
> > This fixes that, but I did notice that the code does not check to make
> sure
> > that the layers are adjacent. There was a bit of back and forth on how to
> > handle layers with micro vias since they technically only go from one
> layer
> > to an adjacent, but they can also be stacked one on top of another.
> >
> > I don't know enough about micro vias to put that sort of check in the
> code
> > without other people's inputs.
> >
> > Also, are blind/buried vias just the regular via size, or should they be
> > micro vias?
> >
> > Jon
>
> Thanks. I just commit it.
>
> Blind/buried vias are just regular via size/drill.
>
> Technically, micro vias only go from one layer to an adjacent.
> Depending on your board maker, they can also be stacked one on top of
> another (i.e. they are Blind/buried vias) or not (this is a constraint
> really subject to change).
>
> Therefore, you can see micro vias as blind/buried vias.
> However, when routing a board, it is really hard to see if a
> blind/buried via is on a given layer or not.
>
> Due to the fact micro vias are mainly used to connect a hight density
> BGA to other layers, kicad (in legacy mode) accepts only micro-vias from
> an external layer to the adjacent layer (you can use a buried via to
> connect an other layer).
>
> Of course, this can be discussed, but the advantages are:
> 1 - It is more easy to know what are the layers connected by a micro via.
> 2 - It is (by far) easy to place a micro-via: you do not have to select
> the target layer when placing it.
>
>
> --
> Jean-Pierre CHARRAS
>
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