Suresh, the ASCII picture shows (I hope) the idea of via pattern giving some extra routing space: 1 2 1 trace traces trace .-. | .-. | | .-. | .-. [....] '-' | '-' | | '-' | '-' 1 trace ---- | | | .-. .-. .-. .-. '-' '-' '-' '-' --------- 2 traces --------- .-. .-. .-. .-. '-' '-' '-' '-' 1 trace --------- .-. .-. .-. .-. '-' '-' '-' '-' --------- 2 traces --------- .-. .-. .-. .-. '-' '-' '-' '-' 1 trace -------- .-. .-. .-. .-. '-' '-' '-' '-' [...] Robert Suresh Kumar - ERS, HCL Tech wrote: > Hi Robert, > > That's very interesting! > > I am find my imagination not working to visualize the " two traces between > every second routing channel " > > so, Could you pl. send me some snap shot to understand better ? > > > thanks in advance > > regards, > Suresh > > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On > Behalf Of Robert Szumowicz > Sent: Thursday, January 21, 2010 3:01 PM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: BGA Breakout. > > I have designed boards where 2 traces are routed between 1mm BGA vias > without going for very thin traces/clearances or small drills (for me it > meant 0.125mm trace/clearance and 0.25mm/0.5mm vias). I used a trick > with a non regular via pattern what allowed routing two traces between > every second routing channel (not two traces in-between all vias). As a > result ~30% more traces can escape a BGA per an internal signal layer. > > Non regular via patter which I invented meant that vias were not centred > between four BGA pads but rather placed with an varying offset to build > an extra horizontal and vertical routing channels. > > Robert > > > Lee Ritchey wrote: > >> 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 > > > > > DISCLAIMER: > ----------------------------------------------------------------------------------------------------------------------- > > The contents of this e-mail and any attachment(s) are confidential and > intended for the named recipient(s) only. > It shall not attach any liability on the originator or HCL or its affiliates. > Any views or opinions presented in > this email are solely those of the author and may not necessarily reflect the > opinions of HCL or its affiliates. > Any form of reproduction, dissemination, copying, disclosure, modification, > distribution and / or publication of > this message without the prior written consent of the author of this e-mail > is strictly prohibited. If you have > received this email in error please delete it and notify the sender > immediately. Before opening any mail and > attachments please check them for viruses and defect. > > ----------------------------------------------------------------------------------------------------------------------- > ------------------------------------------------------------------ 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