[SI-LIST] Re: Current Return Vias

  • From: "Mike Greim" <mike.greim@xxxxxxxxxxx>
  • To: <leeritchey@xxxxxxxxxxxxx>, "Chris Padilla \(cpad\)" <cpad@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Tue, 25 Jul 2006 11:12:43 -0500

Another=20alternative=20that=20I=20have=20used=20in=20the
past=20is=20to=20retain=20the=20same=20number=20of=20spokes
but=20reduce=20the=20width.=20The=20end=20result=20is=20the=20
same,=20reduce=20the=20total=20overall=20copper=20attach=20between
via=20and=20plane.=20=20=20

-----Original=20Message-----
From:=20si-list-bounce@xxxxxxxxxxxxx=20[mailto:si-list-bounce@xxxxxxxxxxxx=
g]
On=20Behalf=20Of=20Lee=20Ritchey
Sent:=20Tuesday,=20July=2025,=202006=2011:04=20AM
To:=20Chris=20Padilla=20(cpad);=20si-list@xxxxxxxxxxxxx
Subject:=20[SI-LIST]=20Re:=20Current=20Return=20Vias

Chris,

This=20problem=20has=20been=20around=20for=20as=20long=20as=20I=20have=20b=
een=20designing=20high
layer=20count=20PCBs.=20=20If=20you=20use=20two=20thermal=20ties=20per=20p=
late=20through=20hole,
you=20meet=20both=20objectives.=20=20If=20you=20connect=20the=20planes=20w=
ithout=20them
solderind=20and=20unsoldering=20is=20very=20difficult.=20=20IF=20you=20mak=
e=20no=20connections
soldering=20is=20great=20and=20SI=20is=20in=20the=20tank.

Almost=20all=20of=20my=20designs=20are=2026=20layers=20with=20many=20groun=
d=20planes=20and=20this
is=20the=20method=20we=20use.=20


>=20[Original=20Message]
>=20From:=20Chris=20Padilla=20\(cpad\)=20<cpad@xxxxxxxxx>
>=20To:=20<si-list@xxxxxxxxxxxxx>
>=20Date:=207/25/2006=208:53:52=20AM
>=20Subject:=20[SI-LIST]=20Re:=20Current=20Return=20Vias
>
>=20I=20get=20push=20back=20all=20the=20time=20in=20trying=20to=20connect=20=
all=20"gnd"=20planes=20in=20
>=20multi-layer=20stackups=20(say=2018=20layers=20+...and=20usually=20at=20=
our=20limit=20of=2026

>=20layers).=20=20The=20reason=20is=20provide=20by=20the=20manufacturing=20=
folks=20in=20that=20
>=20they=20cannot=20solder=20or=20get=20good=20solder=20flow=20because=20t=
he=20mulitple=20gnd=20
>=20planes=20act=20like=20heat=20sinks.=20=20Therefore,=20I=20am=20forced=20=
to=20used=20thermal=20
>=20reliefs=20and=20even=20in=20a=20lot=20of=20cases,=20I=20cannot=20even=20=
connect=20some=20gnd=20
>=20planes=20to=20the=20gnd=20vias!
>
>=20Any=20thoughts=20on=20this=20subject?
>
>=20Thanks,
>
>=20Chris=20Padilla
>=20Cisco=20Systems
>=20San=20Jose,=20CA=3D20
>
>=20-----Original=20Message-----
>=20From:=20si-list-bounce@xxxxxxxxxxxxx=20
>=20[mailto:si-list-bounce@xxxxxxxxxxxxx]
>=20On=20Behalf=20Of=20Lee=20Ritchey
>=20Sent:=20Monday,=20July=2024,=202006=203:44=20PM
>=20To:=20Joel=20Brown
>=20Cc:=20Kenny=20Frohlich;=20si-list@xxxxxxxxxxxxx
>=20Subject:=20[SI-LIST]=20Re:=20Current=20Return=20Vias
>
>=20Joel,
>
>=20First,=20you=20should=20have=20stitched=20your=20ground=20planes=20to=20=
each=20other=20every

>=20where=20there=20is=20a=20ground=20pin=20on=20a=20device,=20so=20these=20=
ground=20planes=20should

>=20be=20well=20tied=20to=20each=20other=20every=20place=20you=20have=20a=20=
component=20whether=20it

>=20be=20a=20bypass=20capacitor=20or=20an=20IC.=20=20(This=20argues=20for=20=
spreading=20your=20
>=20bypass=20capacitors=20=20evenly=20around=20the=20planes=20as=20has=20b=
een=20advocated=20by=20a

>=20number=20of=20members=20of=20this=20forum=20in=20the=20past.)=20=20Onl=
y=20where=20you=20might=20
>=20change=20layers=20in=20an=20empty=20part=20of=20the=20PCB=20is=20this=20=
not=20so.=20Second,=20when

>=20you=20engineer=20your=20PDS=20you=20need=20to=20insure=20that=20the=20=
impedance=20is=20a=20few=20
>=20milliohms=20across=20all=20of=20the=20frequencies=20in=20your=20signal=
s,=20so=20the=20Vdd=20
>=20planes=20are=20"shorted"=20to=20these=20ground=20planes=20by=20this=20=
method.=20=20(=20To=20
>=20achieve=20this=20low=20impedance=20across=20the=20broad=20range=20of=20=
frequencies=20in=20
>=20your=20signals,=20you=20will=20be=20using=20plane=20capacitance=20as=20=
well=20as=20a=20variety

>=20of=20different=20values=20of=20capacitors.=20=20When=20done=20right,=20=
all=20of=20the=20planes

>=20are=20"shorted"=20to=20each=20other=20and=20return=20currents=20have=20=
all=20the=20paths=20
>=20they=20need.=20=20If=20the=20PDS=20isn't=20properly=20designed=20you=20=
can=20wind=20up=20with=20
>=20EMI=20problems=20and=20unstable=20logic=20operation.
>
>
>=20>=20[Original=20Message]
>=20>=20From:=20Joel=20Brown=20<joel@xxxxxxxxxx>
>=20>=20To:=20<leeritchey@xxxxxxxxxxxxx>
>=20>=20Cc:=20Kenny=20Frohlich=20<kenny_frohlich@xxxxxxxxx>;=20
>=20>=20<si-list@xxxxxxxxxxxxx>
>=20>=20Date:=207/23/2006=2012:25:04=20PM
>=20>=20Subject:=20[SI-LIST]=20Re:=20Current=20Return=20Vias
>=20>
>=20>=20=20I=20am=20currently=20working=20on=20board=20that=20has=2012=20l=
ayers.
>=20>=20Ground=20planes=20are=20layers=202,=205,=208,=20and=2011.=3D20=20I=
f=20a=20high=20speed=20signal=20
>=20>=20changes=20from=20layer=203=20to=20layer=209=20then=20its=3D20=20re=
ference=20planes=20change=20
>=20>=20from=20layers=202=20&5=20to=20layers=208=20&11.
>=20>=20Since=20the=20return=20current=20flows=20under=20the=20signal=20tr=
ace=20on=20the=20
>=20>=20reference
>=20plane
>=20>=20,=20this=20return=20current=20has=20jump=20from=20from=20one=20set=
=20of=20planes=20to=20the=3D20

>=20>=20other
>=20set
>=20>=20at=20the=20point=20signal=20changes=20layers=20through=20a=20via.=20=
The=20return=20
>=20>=20current=3D20=20could=20jump=20through=20interplane=20capacitance=20=
or=20through=20a=20
>=20>=20ground=20via=3D20=20located=20next
>=20to
>=20>=20the=20signal=20via.=20So=20in=20this=20situation=20I=20don't=20see=
=20why=20having=20a=20
>=20>=20ground=3D20=20via=20nextto=20a=20signal=20would=20not=20be=20benef=
icial?=20Does=20the=20
>=20>=20interplane=3D20=20capacitance=20provide=20a=20lower=20impedance=20=
path=20than=20the=20
>=20>=20ground=20via=20for=20the
>
>=20>=20return=20current
>=20method=20to
>=20>=20jump=20planes?=20Please=20enlighten=20me.
>=20>=20Joel
>=20>
>=20>
>=20>=20Lee=20Ritchey=20wrote:=20Kenny,=20It=20is=20not=20true=20that=20yo=
u=20need=20a=20"return
>=20current"
>=20>=20vianext=20to=20each=20layer=20changing=20signal=20via.=20I=20conti=
nue=20to=20be=20
>=20>=20amazed=3D20=20that=20engineers=20who=20are=20looked=20upon=20as=20=
SI=20experts=20say=20such=20
>=20>=20things.=3D20=20Imagine=20you=20havea=204=20layer=20PCB,=20such=20a=
s=20the=20mother=20board=20
>=20>=20in=20a=20PC,=20where
>
>=20>=20there=20are=20only=20twoplanes,=20one=20Vdd=20and=20one=20ground,=20=
where=20would=20
>=20>=20such=3D20=20vias=20connect?=20There
>=20have
>=20>=20been=20billions=20of=20these=20made=20to=20date=20that=20work=20ju=
st=20fine=20and=20have=20
>=20>=20very=3D20=20fast=20signals=20on=20them.=20The=20return=20currents=20=
you=20are=20concerned=20
>=20>=20about=20find
>
>=20>=20their
>=20way
>=20>=20from=20plane=20to=20plane=20through=20the=20collection=20of=20deco=
upling=20
>=20>=20capacitors=3D20=20and=20interplane=20capacitance=20that=20you=20ha=
d=20to=20engineer=20
>=20>=20into=20the=20power=3D20=20delivery=20system=20in=20order=20to=20ma=
ke=20it=20stable.=20Focus=20
>=20>=20on=20this=20and=20the=3D20=20return=20currents=20takecare=20of=20t=
hemselves.=20EMI=20is
minimized=20he=20same=20way..
>
>=20>=20[Original=20Message]
>=20>=20From:=20Kenny=20Frohlich=20<kenny_frohlich@xxxxxxxxx>[1]=20To:
>=20>=20<si-list@xxxxxxxxxxxxx>[2]Date:=207/22/2006=206:45:56=20AM=20Subje=
ct:=3D20=20
>=20>=20[SI-LIST]=20Current=20Return=20Vias=20Dear=20Experts,=20I=20unders=
tand=20that=20I=20
>=20>=20need=3D20=20to=20provide
>=20ground
>=20>=20vias=20next=20to=20via=20explictly=20for=20the=20purpose=20of=20le=
tting=20return=20
>=20>=20currents=3D20=20jump=20between=20layers.=20I=20know=20it's=20a=20r=
equirement=20for=20high=20
>=20>=20speed=20signals,
>=20especially
>=20>=20differrential=20signals.=20Is=20this=20also=20required=20for=20low=
=20speed=3D20=20
>=20>=20single-ended=20signals=20(133Mhz=20or=20slower)?=20If=20this=20is=20=
a=20
>=20>=20requirement,=3D20=20what=20would=20be=20a=20good=20signal=20via=20=
to=20ground=20via=20ratio?

>=20>=20For=20example,=3D20=20there=20are=20five=20signal=20vias=20within=20=
a=201=20inch=20area,=20how

>=20>=20many=20ground=20vias=3D20=20do=20I=20need?=20Thank=20you=20Kenny=3D=
20=20
>=20>=20__________________________________________________=20Do=20You=20Ya=
hoo!?=3D20

>=20>=20Tired=20of=20spam?=20Yahoo!=20Mail=20has=20the=20best=20spam=20pro=
tection=20around
>=20>
>=20http://mail.yahoo.com[3]----------------------------------------------=

>=20--
>=20----
>=20>=20--------------=20To=20unsubscribe=20from=20si-list:
>=20si-list-request@xxxxxxxxxxxxx[4]
>=20>=20with=20'unsubscribe'=20in=20the=20Subject=20field=20or=20to=20admi=
nister=20your=3D20=20
>=20>=20membership=20froma=20web=20page,=20go=20to:=3D20=20
>=20>=20http://www.freelists.org/webpage/si-list[5]=20For
>=20help:
>=20>=20si-list-request@xxxxxxxxxxxxx[6]=20with=20'help'=20in=20the=20Subj=
ect=20field=20
>=20>=20List
>
>=20>=20FAQ=20wiki=20page=20is=20located=20at:=3D20
>=20>=20http://si-list.org/wiki/wiki.pl?Si-List_FAQ[7]
>=20List
>=20>=20technical=20documents=20are=20available=20at:=20http://www.si-list=
.org[8]=20
>=20>=20List=3D20=20archivesare=20viewable=20at:=20
>=20>=20http://www.freelists.org/archives/si-list[9]=3D20
>=20>=20or
>=20at
>=20>=20our=20remote=20archives:=3D20
>=20>=20http://groups.yahoo.com/group/si-list/messages[10]
>=20Old
>=20>=20(prior=20to=20June=206,=202001)=20list=20archives=20are=20viewable=
=20at:
>=20>=20http://www.qsl.net/wb6tpu[11]
>=20>=20------------------------------------------------------------------=
=20
>=20>=20To=3D20=20unsubscribe=20from=20si-list:=20si-list-request@freelist=
s.org[12]=20
>=20>=20with=3D20=20'unsubscribe'=20in=20the=20Subject=20field=20or=20to=20=
administer=20your=20
>=20>=20membership=3D20=20from=20a=20web=20page,=20go=20to:=20
>=20>=20http://www.freelists.org/webpage/si-list[13]
>=20For=20help:
>=20>=20si-list-request@xxxxxxxxxxxxx[14]=20with=20'help'=20in=20the=20Sub=
ject=20
>=20>=20field=3D20=20List
>=20FAQ
>=20>=20wiki=20page=20is=20located=20at:=3D20
>=20>=20http://si-list.org/wiki/wiki.pl?Si-List_FAQ[15]
>=20>=20Listtechnical=20documents=20are=20available=20at:=20
>=20>=20http://www.si-list.org[16]=3D20=20List=20archives=20are=20viewable=
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>=20>=20http://www.freelists.org/archives/si-list[17]=20or=20atour=20remot=
e=3D20
>=20>=20archives:=20http://groups.yahoo.com/group/si-list/messages[18]
>=20>=20Old(prior=20to=20June=206,=202001)=20list=20archives=20are=20viewa=
ble=20at:
>=20>=20http://www.qsl.net/wb6tpu[19]
>=20>
>=20>=20---=20Links=20---
>=20>=20=20=20=201=20mailto:kenny_frohlich@xxxxxxxxx
>=20>=20=20=20=202=20mailto:si-list@xxxxxxxxxxxxx
>=20>=20=20=20=203=20http://mail.yahoo.com
>=20>=20=20=20=204=20mailto:si-list-request@xxxxxxxxxxxxx
>=20>=20=20=20=205=20http://www.freelists.org/webpage/si-list
>=20>=20=20=20=206=20mailto:si-list-request@xxxxxxxxxxxxx
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>=20>=20=20=20=208=20http://www.si-list.org
>=20>=20=20=20=209=20http://www.freelists.org/archives/si-list
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>=20>=20=20=2012=20mailto:si-list-request@xxxxxxxxxxxxx
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>=20>=20=20=2015=20http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>=20>=20=20=2016=20http://www.si-list.org
>=20>=20=20=2017=20http://www.freelists.org/archives/si-list
>=20>=20=20=2018=20http://groups.yahoo.com/group/si-list/messages
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>=20>
>=20>=20--=20Binary/unsupported=20file=20stripped=20by=20Ecartis=20--
>=20>=20--=20Type:=20text/x-vcard
>=20>=20--=20File:=20joel.vcf
>=20>
>=20>
>=20>=20------------------------------------------------------------------=

>=20>=20To=20unsubscribe=20from=20si-list:
>=20>=20si-list-request@xxxxxxxxxxxxx=20with=20'unsubscribe'=20in=20the=20=
Subject=20
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>=20>
>=20>=20or=20to=20administer=20your=20membership=20from=20a=20web=20page,=20=
go=20to:
>=20>=20http://www.freelists.org/webpage/si-list
>=20>
>=20>=20For=20help:
>=20>=20si-list-request@xxxxxxxxxxxxx=20with=20'help'=20in=20the=20Subject=
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>=20>=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20http://si-list.org=
/wiki/wiki.pl?Si-List_FAQ
>=20>
>=20>=20List=20technical=20documents=20are=20available=20at:
>=20>=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20http://www.si-list=
.org
>=20>
>=20>=20List=20archives=20are=20viewable=20at:=20=20=20=20=3D20
>=20>=20=09=09http://www.freelists.org/archives/si-list
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>=20>=20=20=09=09http://www.qsl.net/wb6tpu
>=20>=20=20=3D20
>
>
>=20------------------------------------------------------------------
>=20To=20unsubscribe=20from=20si-list:
>=20si-list-request@xxxxxxxxxxxxx=20with=20'unsubscribe'=20in=20the=20Subj=
ect=20field
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>=20For=20help:
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i/wiki.pl?Si-List_FAQ
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>=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20http://www.si-list.org=

>
>=20List=20archives=20are=20viewable=20at:=20=20=20=20=3D20
>=20=09=09http://www.freelists.org/archives/si-list
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HIS=20E-MAIL=20IS=20NOT=20INTENDED=20AS=20A=20SUBSTITUTE=20FOR=20A=20WRITI=
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=20or=20the=20applicability=20of=20any=20other=20law=20of=20similar=20subs=
tance=20and=20effect,=20absent=20an=20express=20statement=20to=20the=20con=
trary=20hereinabove,=20this=20e-mail=20message=20its=20contents,=20and=20a=
ny=20attachments=20hereto=20are=20not=20intended=20to=20represent=20an=20o=
ffer=20or=20acceptance=20to=20enter=20into=20a=20contract=20and=20are=20no=
t=20otherwise=20intended=20to=20bind=20the=20sender,=20Sanmina-SCI=20Corpo=
ration=20(or=20any=20of=20its=20subsidiaries),=20or=20any=20other=20person=
=20or=20entity.
__________________________________________________________________________=
___
Scanned=20by=20Sanmina-SCI=20eShield=20=20________________________________=
_____________________________________________
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