Mirka Halas wrote:

> Dave,
>      this topic is of great interest to me.
> I am using Cadence Allegro and recently I started
> to look into HDI.
> We do not have demand for via in pad yet,but
> I tried my design with blind via in pad.
> The Specctra autorouter would not put microvia
> in fine pitch pads 20 mils.
> I am not sure why, there is enough space.
> I am waiting for Cadence to help me with this problem.
>
> So what I am saying is I did not find Cadence to be great
> for HDI.
> I would like to hear from other Cadence and other designers as well.
>
> Happy Friday
>
> Mirka
>
> Requesting some feedback from end users -
>
> Which toolset is the best for HDI/Microvia design?
>
> Thanks,
>
> Dave Schaefer                          Voice: (204)478-8059
> Senior PCB Designer                 FAX:  (204)942-3001
> Symbol Technologies                Email: [log in to unmask]
> 1000 Waverley Street
> Winnipeg, MB  R3T 0P3
>
> --
> | Mirka Halas                            TSI TelSys Incorporated   |
> | Senior PCB Designer                    7100 Columbia Gateway Dr. |
> | [log in to unmask]                  Columbia, Maryland 21046  |
> | http://www.tsi-telsys.com              (410) 872-3900: Main      |
> | (410) 872-3922: Direct                 (410) 872-3901: FAX       |
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Try looking at your via-to-pin clearances.  The pin next door to the via-in-pad is usally the
problem.
We set our via-to-pin clearances to 6 mils because we use tented vias (soldermask over via).
Also, try a 0 via grid because some pin pads are on a very fine grid.

We have used microvias with this router very successfully.  It does microvias and via-in-pad
very well.  Don't protect the fanout vias in pad though.  Let the autorouter decide if that
via
is best left there or should be pulled out.  This tends to let the router route a lot on the
outside
layers which some do not like.

John Bradley
Alcatel USA
Plano, TX

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