Forgive me for asking such a "newbie" question among so many experts, but just reading through this thread has made me curious... (I have never had to use blind vias before, but I have some experience with impedance control.) If the original problem was that routing out from the BGA has to be done on layer 2 from blind vias, where did he go wrong? Do other designs drill through a plane on 2 and route from 3? None of the responses ever said what the original mistake was in designing the stackup, so I am confused. Jack (aka "the new guy") steve weir <weirsi@xxxxxxxxxx> Sent by: si-list-bounce@xxxxxxxxxxxxx 04/20/2006 08:28 AM Please respond to weirsi@xxxxxxxxxx To To Balaji.S@xxxxxxxxxxxx si-list@xxxxxxxxxxxxx cc Subject [SI-LIST] Re: Impedance control with split ground planes Caterpillar: Confidential Green Retain Until: 05/20/2006 Retention Category: G90 - General Matters/Administration Balaji, I don't think there are any simple fixes. About the only think you have going for you is that SDR 133 is pretty tolerant. My best recommendation is to start with the basics: Propose a strategy and test feasibility. If it is feasible then work the details. If not, iterate using a different strategy. I know no other reliable way to design. From your questions, it sounds like you may have elected an implementation before determining overall feasibility. If so, it is time to back-up and see where you stand. If you are lucky then the strategy is feasible with some effort and/or changes. Good luck. Steve. At 12:52 AM 4/20/2006, Balaji S wrote: >Hi Steve, >A small correction. My high speed signals are routed on S2 ( and not on >S1. typo).. Still is the design so flawed?? > >Since due to microvias (aspect ratio 1:1) and cost constraint, we had to >go 4 that stack-up. > >Any suggestions for improvement will definitely be welcome.. > >Regards >Balaji S > ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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