Anand, I've come across an app note from Merix that gives their explanation for even numbered only pcb's. It is mostly drive by manufacturing costs. See the app note below, page 2. www.merix.com/files/Designing%20Balanced%20PCBs.pdf I have heard the same at one of the PCB West conferences in one of their IPC training courses. Bob=20 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of SRINIVASAN ANAND-B06739 Sent: Thursday, April 05, 2007 11:01 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Basic doubt Hi All, I am a novice to board designing. =20 Could someone explain to me as to why the number of layers in any board need to be even? Can't i have a board with odd number of layers?=20 =20 Anand ------------------------------------------------------------------ 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: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ 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 or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu