Hello Surita, (1) Yes normally the via will have a pad on other signal layers. (2) Normally not the same for inner/outer. (3) The Via's are usually on a diagonal between the Balls to escape. -Jory ________________________________ From: Surita Chandani <surita.chandani@xxxxxxxxx> To: si-list@xxxxxxxxxxxxx Sent: Thu, January 14, 2010 12:19:07 PM 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