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