[SI-LIST] Re: Stackups with Microvias
- From: "Peterson, James F (FL51)" <james.f.peterson@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 17 Feb 2005 05:21:41 -0700
Chris -
I agree with Bob, layers 2 and 11 have to be signal layers for reasons he
describes below. Remember that a micro via, because of aspect ratio
limitations, can't penetrate more than 1, maybe 2, layers.
here's a quick thought on a 12 layer stackup (no allowance for any core
power here).
1 - breakout/gnd
2 - uvia layer (you can route signals on this layer also)
3 - G
4 - Sig
5 - Sig
6 - IO power
7 - Ground
8 - Sig
9 - Sig
10 - Ground
11 - uvia layer (you can route signals on this layer also)
12 - Breakout/Ground
regards,
Jim Peterson
Honeywell
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of rsefton@xxxxxxxxxxxxx
Sent: Wednesday, February 16, 2005 6:42 PM
To: si-list@xxxxxxxxxxxxx; 'Chris McGrath'
Subject: [SI-LIST] Re: Stackups with Microvias
=0D =0D
Chris -
Layer 2 would typically be a signal layer for this. You microvia down to la=
yer 2 and break out from there where you don't have to contend with the BGA=
pads. On layer layer 2 you just have to route around the microvia (si= gnal)
pads and through-hole via (power & ground) anti-pads.=0D
Bob S.
On Wed Feb 16 15:05 , "Chris McGrath" sent:
=0D
When designing a microvia breakout (microvia from surface to layer
immediately below it), is it still preferable to have a ground layer on
layer 2 or can it be a power layer? Can anybody offer some advice about
microvia breakout as it relates to stackup assuming that the surface layer
is flooded with ground except for thru-holes and component pads?
My thinking was (for an example twelve layer stackup):
1 - Breakout/Ground
2 - Power1
3 - Ground
4 - Sig
5 - Sig
6 - Ground
7 - Ground
8 - Sig
9 - Sig
10 - Ground
11 - Power2
12 - Breakout/Ground
I'm wide open to suggestions. Our board will probably be 20-24 layers, but
this is just an example that mainly pertains to the question of microvia
breakout.
Thanks,
Chris
------------------------------------------
Chris McGrath
Sr. Hardware Engineer
ADIC
ph: (607) 241-4858
eM: chris.mcgrath@xxxxxxxx[1]
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