Just checked. The article on up on the web site. it is titled "Why not two traces between pins on 1 mm pitch BGAs?" > [Original Message] > From: Lee Ritchey <leeritchey@xxxxxxxxxxxxx> > To: alex@xxxxxxxx <alex@xxxxxxxx>; <si-list@xxxxxxxxxxxxx> > Date: 1/20/2010 1:19:37 PM > Subject: [SI-LIST] Re: BGA Breakout. > > 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 > ------------------------------------------------------------------ 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