[SI-LIST] Re: BGA Breakout.

  • From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
  • To: "alex@xxxxxxxx" <alex@xxxxxxxx>, si-list@xxxxxxxxxxxxx
  • Date: Wed, 20 Jan 2010 13:14:14 -0800

I will have it posted on my web site www.speedingedge.com by tomorrow along
with several other pertinent papers by tomorrow.  It will be under "Related
Articles".
We will have a booth at DesignCon.  Stop by and see us.  That's Speeding
Edge.

Meantime, here is a copy for you.

Lee


> [Original Message]
> From: <alex@xxxxxxxx>
> To: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> Date: 1/20/2010 1:00:13 PM
> Subject: [SI-LIST] Re: BGA Breakout.
>
> Hi Lee,
>
> Could you please put the "attached" file on a server somewhere so
> everybody on the SI-LIST can check it?  The server is not distributing
> attachments....
>
> Thank you very much, and I hope to see you at DesignCon!
>
>
> Alexandre Desnoyers
>
>
> > Sol,
> > I have attached an analysis I did of clearances, tolerances and
> > reliability
> > requirements when routing PCBs.  Hope this makes it clear what the risks
> > are when routing 2 between on 1 mm pitch BGAs.
> >
> > Lee
> >
> >
> >> [Original Message]
> >> From: Sol Tatlow <Sol.Tatlow@xxxxxxxxxxxxxxxxxxxx>
> >> To: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
> >> Cc: Surita Chandani <surita.chandani@xxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
> >> Date: 1/18/2010 1:39:42 PM
> >> Subject: [SI-LIST] Re: BGA Breakout.
> >>
> >> With all respect, Lee, I beg to differ (at least a little bit ;)!): I
> >> personally have routed many boards with 1mm BGAs of over 1700 balls
> >> (with 1200+ signals, ALL 1700+ balls connected), and, depending upon
how
> >> these signals are to be routed (which is, admittedly, a fairly big
> >> 'depending'), 18 layers can be (and usually is) enough already.
> >> Since roughly 2001/2002, I have had such BGAs on boards where I
> >> generally have around 18-20 layers in <2,0mm (78 mil) together with
> >> 0,5mm (20mil) via pads (the drill doesn't really interest me, in
> >> general, just the reliability of the results!) - this leaves 0,1mm (4
> >> mil) track and gap (roughly speaking) for 2 tracks between vias... and
> >> the '2 traces between the vias' is the key to holding down board
> >> thickness and layer count. This has worked for me even up to 26 layers
> >> and ~2,5mm board thickness.
> >>
> >> With (in the meantime) 30,000-60,000 component pins/balls per board,
and
> >> a resulting via count of only somewhat less than the pin count, it is
> >> still possible to have these boards manufactured in series quantities
at
> >> affordable prices from a comfortable number of manufacturers around the
> >> world; the results, in some cases, have been in operation since 2002
and
> >> we have very good reliability results across the board (I sweated back
> >> then a little, but in the meantime, it's 100% normal... I sleep easily
> >> at night now :D!!).
> >>
> >> One typical problem occurs, of course, in the planning phase: if you
> >> assume too many power/gnd _pairs_ (as opposed to _individual_ gnd or
pwr
> >> layers), you are automatically forced to have a thicker board, where it
> >> may no longer be possible to have small enough vias to route 2 tracks
> >> between the vias; this is a downward spiral, of course, forcing the
> >> number of signal layers up, and then again, the pwr/gnd count.
> >>
> >> I have, up until now, avoided having exclusively pwr/gnd power
> >> sandwiches (however nice an idea these are) for exactly this reason;
> >> instead, alternating (in general) GND-SIG-SIG-PWR-SIG-SIG- etc. coupled
> >> with good routing strategies has given me very good results - there are
> >> many proponents for always using pwr/gnd 'sandwich' pairs, but this is,
> >> quite simply, not always necessary).
> >>
> >> Not that I want to start a fight, Lee, just wanted to voice my
> >> experience/opinion :D!!
> >>
> >> Regards,
> >> Sol
> >>
> >> P.S. What 'affordable' means, depends, of course, on the end product
;),
> >> but usually, the 0,1mm track and gap means reduced costs in comparison
> >> to thicker boards with more coarse structures and higher layer count...
> >> in some cases, you might even go to slightly bigger via pads and LESS
> >> than 0,1mm track and gap, to reduce costs... this depends upon the
> >> manufacturer, thickness of the board, availability of specific
> >> materials, etc.
> >>
> >> Lee Ritchey schrieb:
> >> > Surita,
> >> >
> >> > I believe this kind of routing is possible with very thin PCBs with
> >> very
> >> > small holes such as in laptop motherboards.  However, with very large
> > BGAs
> >> > such as yours, it is unlikely that it w ill route on a thin PCB.  My
> >> > experience with BGAs of your size is that a 22-26 layer PCB will be
> > needed
> >> > and that will likely be 100+ mils thick resulting in the need for 12
> >> mil
> >> > drills.
> >> >
> >> > Lee
> >> >
> >> >
> >> >
> >> >> [Original Message]
> >> >> From: Surita Chandani <surita.chandani@xxxxxxxxx>
> >> >> To: <si-list@xxxxxxxxxxxxx>
> >> >> Date: 1/15/2010 11:43:41 AM
> >> >> Subject: [SI-LIST] Re: BGA Breakout.
> >> >>
> >> >> Thanks Lee for your comments.
> >> >> The suggestions for two traces between Vias comes directly from
Intel
> >> >>
> >> > document, also this document is from 2002. Their pitch is 1.067 mm.
> >> The
> >> > document itself is available at:
> >> >
> >> >>
> >> >> http://download.intel.com/support/processors/xeon/sb/25039702.pdf
> >> >> ; Page 43.
> >> >>
> >> >>
> >> >>
> >> >> --- On Fri, 1/15/10, Lee Ritchey <leeritchey@xxxxxxxxxxxxx> wrote:
> >> >> Surita,
> >> >>
> >> >> You are right, you cannot successfully route two traces between pins
> > on a
> >> >>
> >> > 1
> >> >
> >> >> mm pitch BGA without significant risk of shorts.
> >> >>
> >> >> If you drill a 12 mil hole, your antipad does not have to be larger
> > than
> >> >>
> >> > 32
> >> >
> >> >> mils.  This leaves you with a 7.37 mil web, which works nicely for a
> >> >>
> >> > single
> >> >
> >> >> trace, but not two traces..  Your surface or signal layer pads can
be
> > 24
> >> >> mils for 1 mil annular ring and 26 mils for 2 mil annular ring.
> >> >>
> >> >> There will only be pads on inner layers where traces connect.
> >> >>
> >> >> By the way, what vendor told you to route 2 traces between pins?
> >> >>
> >> >> Lee Ritchey
> >> >>
> >> >>
> >> >>
> >> >>
> >> >>> [Original Message]
> >> >>> From: Surita Chandani <surita.chandani@xxxxxxxxx>
> >> >>> To: <si-list@xxxxxxxxxxxxx>
> >> >>> Date: 1/14/2010 9:19:08 AM
> >> >>> Subject: [SI-LIST] BGA Breakout.
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>> Hello Gurus;
> >> >>>
> >> >>>
> >> >>>
> >> >>> I am doing some preliminary calculations on the breakout of
> >> >>> a 1,400+  Ball  , BGA. Roughly one half of them are signal
> >> >>> connections which would need traces running up to them. The vendor
> >> >>>
> >> > claims
> >> >
> >> >> you
> >> >>
> >> >>> can run two traces between Vias, my calculations are not adding up,
> >> I
> >> >>>
> >> >> have a
> >> >>
> >> >>> few questions.
> >> >>>
> >> >>>
> >> >>>
> >> >>> 1. Generally, do the Vias have a pad even on the signal
> >> >>> layer it is not connecting to?.
> >> >>>
> >> >>>
> >> >>>
> >> >>> 2. Do the Vias have a larger pad on the inner layers?
> >> >>>
> >> >>>
> >> >>>
> >> >>> 3.  With a Ball pitch
> >> >>> of 1 mm (39 mils.) and an Antipad of 35 mils, there is hardly any
> >> room
> >> >>>
> >> >> for one
> >> >>
> >> >>> trace between Vias, what am I doing wrong?
> >> >>>
> >> >>>
> >> >>>
> >> >>> Thanks,
> >> >>>
> >> >>>
> >> >>>
> >> >>> Surita Chandani
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>> ------------------------------------------------------------------
> >> >>> 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 technical documents are available at:
> >> >>>                  http://www.si-list.net
> >> >>>
> >> >>> List archives are viewable at:
> >> >>>         //www.freelists.org/archives/si-list
> >> >>>
> >> >>> Old (prior to June 6, 2001) list archives are viewable at:
> >> >>>           http://www.qsl.net/wb6tpu
> >> >>>
> >> >>>
> >> >>
> >> >>
> >> >>
> >> >>
> >> >> ------------------------------------------------------------------
> >> >> 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 technical documents are available at:
> >> >>                 http://www.si-list.net
> >> >>
> >> >> List archives are viewable at:
> >> >>                 //www.freelists.org/archives/si-list
> >> >>
> >> >> Old (prior to June 6, 2001) list archives are viewable at:
> >> >>                 http://www.qsl.net/wb6tpu
> >> >>
> >> >>
> >> >
> >> >
> >> > ------------------------------------------------------------------
> >> > 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 technical documents are available at:
> >> >                 http://www.si-list.net
> >> >
> >> > List archives are viewable at:
> >> >          //www.freelists.org/archives/si-list
> >> >
> >> > Old (prior to June 6, 2001) list archives are viewable at:
> >> >                  http://www.qsl.net/wb6tpu
> >> >
> >> >
> >> >
> >>
> >> --
> >> ________________________________________
> >>
> >> Sol Tatlow, M. Eng. (Oxon)
> >> Product Developer
> >>
> >> Pro Design Electronic GmbH
> >> Albert-Mayer-Str. 16
> >> D-83052 Bruckmuehl
> >> Phone: +49 (0) 8062/808-302
> >> PCFax: +49 (0) 8062/808-2302
> >> sol.tatlow@xxxxxxxxxxxxxxxxxxxx
> >> www.prodesign-europe.com
> >> ________________________________________
> >>
> >> Vertretungsberechtigte Geschaeftsfuehrer:
> >> Helmut Mahr, Ulrike Angersbach, Stephan Roeslmair, Dieter Lessenich
> >>
> >> Registergericht: Amtsgericht Traunstein  Registernummer: HRB 13 002
> >>
> >>
> >>
> >> ------------------------------------------------------------------
> >> 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 technical documents are available at:
> >>                 http://www.si-list.net
> >>
> >> List archives are viewable at:
> >>            //www.freelists.org/archives/si-list
> >>
> >> Old (prior to June 6, 2001) list archives are viewable at:
> >>            http://www.qsl.net/wb6tpu
> >>
> >
> >
> >
> > ------------------------------------------------------------------
> > 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 technical documents are available at:
> >                 http://www.si-list.net
> >
> > List archives are viewable at:
> >             //www.freelists.org/archives/si-list
> >
> > Old (prior to June 6, 2001) list archives are viewable at:
> >             http://www.qsl.net/wb6tpu
> >
> >
> >
>
>
> ------------------------------------------------------------------
> 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 technical documents are available at:
>                 http://www.si-list.net
>
> List archives are viewable at:     
>               //www.freelists.org/archives/si-list
>  
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>   



------------------------------------------------------------------
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 technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                //www.freelists.org/archives/si-list
 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: