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>=20//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>=20//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>=20//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= =20at:=3D20=20 >=20>=20//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=20//www.freelists.org/webpage/si-list >=20>=20=20=20=206=20mailto:si-list-request@xxxxxxxxxxxxx >=20>=20=20=20=207=20http://si-list.org/wiki/wiki.pl?Si-List_FAQ >=20>=20=20=20=208=20http://www.si-list.org >=20>=20=20=20=209=20//www.freelists.org/archives/si-list >=20>=20=20=2010=20http://groups.yahoo.com/group/si-list/messages >=20>=20=20=2011=20http://www.qsl.net/wb6tpu >=20>=20=20=2012=20mailto:si-list-request@xxxxxxxxxxxxx >=20>=20=20=2013=20//www.freelists.org/webpage/si-list >=20>=20=20=2014=20mailto:si-list-request@xxxxxxxxxxxxx >=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=20//www.freelists.org/archives/si-list >=20>=20=20=2018=20http://groups.yahoo.com/group/si-list/messages >=20>=20=20=2019=20http://www.qsl.net/wb6tpu >=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 >=20>=20field >=20> 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ABSENT=20AN=20EXPRESS=20STATEMENT=20TO=20THE=20CONTRARY=20HEREINABOVE,=20T= HIS=20E-MAIL=20IS=20NOT=20INTENDED=20AS=20A=20SUBSTITUTE=20FOR=20A=20WRITI= NG.=20=20Notwithstanding=20the=20Uniform=20Electronic=20Transactions=20Act= =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________________________________= _____________________________________________ ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu