At 10:24 AM 3/27/2002 +0100, Waldemar Kulajew wrote:
>Abdulrahman
>
>         You are right when it comes to Blind vias. But a microvia is not 
> only a blind
>via.

I wrote about a blind via, but, unless there is a bug which I have not 
seen, exactly the same would be true of buried vias. The layer pair should 
be set up under the Stack Manager (Under "Drill Pairs.")

>  Because it is "driiled" by a laser or a similar process there are nearly
>complete other requirements. One can chose the hole for a micro via 
>between 0.05
>and 0.1mm (2-4mil). The anular ring for the second layer can, 
>theortically,  be
>0 (yes zero!), because it is an Optical process using the second Layer as
>reference. Because of all this reasons I need to design other vias but the
>tradional mechanical drilled ones. And that is what causes the problems.

Laser drilled vias are no different from regular drilled vias as far as 
Protel would be concerned.

>         I add some comments below.
>
> > There are better ways. I just set a Top/Mid1 layer pair in the Stack
> > Manager. I was routing on the Top layer, pressed the * or + key so that Mid
> > 1 became the current routing layer, and the via which was floating was a
> > blind via.
> >
> > It is also possible, of course, to edit globally a set of selected vias (or
> > otherwise chosen vias) to a particular layer pair.
>
>         Yes these may be one way. But when I use microvias mostly that 
> will be a
>problem of place. When I place "standard" vias and edit them afterwards I will
>find I give away place on my PCB. Opposite, when I place Microvias and 
>edit them
>I will find a lot of DRC-errors on the other layers.

First of all, blind and buried vias are subject to a display bug. Vias live 
on Multilayer for display purposes, and thus they display on all layers 
even though they only exist on a subset of the layers. Secondly, error 
markers do not necessarily disappear even when error conditions are 
removed, sometimes it is necessary to clear them out. I think rerunning DRC 
will do it.

I think my comments about how to interactively route with blind and buried 
vias have not been understood. The layer pairs should be set up in the 
Stackup Manager under the "Drill Pairs" setup button. I just verified that 
the vias are properly created according to drill pair settings, and that a 
buried via does not create a drc error with a bottom pad at the same XY 
location.

>         I guess you know what I wanted to say. Different via types should 
> have
>different rules possible for anular rings and hole sizes. And for me it is not
>only a "nice to have" feature. But I have to say I have not found DRC mighty
>enough to check this in other EDA-tools. So protel is still on the top. But...

Blind and buried vias are new for Protel. However, one can set a design 
rule (in 99SE) filtered on "via Specification." Among the specifications 
are start and end layers. This would appear to fully support blind and 
buried vias, I haven't tested it. Normally one is only adding one size of 
blind and buried via to a board, so it is quite easy to make sure that all 
of them are the right size!

Abdulrahman Lomax
Easthampton, Massachusetts USA

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