Girish, From your description it looks to me that you deal with a board with sequential lamination, and two sub-composite pieces, maybe layer 1-10 and layers 11-20 are built first before gluing them together. In any event, the fact that your blind vias penetrate several layers will result in a stub-notch frequency less than what you would expect just based on the time-of-flight along the length of the via in the same dielectric. If you want to squeeze the most out of your design, a 3D field solver simulations looks necessary. Regards, Istvan Novak SUN Microsystems Jory McKinley wrote: > Hello Grish, > Well lets see, the electrical length of the blind via you described is > roughly 10ps. For PCIe gen 2 the minimum rise/fall time is 30ps so these > vias could create impedance mismatches for your channel. I would try and > match as close as possible to your trace impedance with sufficient ground via > returns. If you are able try and model these vias in the channel with a 3D > simulator. > Regards, > -Jory > > > > > > ________________________________ > From: Girish Gopi <girish.gopi@xxxxxxxxxxxxxxxxxx> > To: si-list@xxxxxxxxxxxxx > Sent: Saturday, July 11, 2009 7:32:10 AM > Subject: [SI-LIST] PCIe routing > > Hi all, > I am having the 20 layer pcb with 3MM thickness , using blind vias from 1 to > 10 and 11 to 20 layers.Where 2nd layer using for PCIe(5GB/S) routing , can I > know that the via used for PCIe routing from layer 2 to 10 , will it be act > as a stub ?Is there any issues? > > Thanks in advance > Girish > **************** CAUTION - Disclaimer *****************This email may contain > confidential and privileged material for the > sole use of the intended recipient(s). Any review, use, retention, > distribution or disclosure by others is strictly prohibited. If you are not > the intended recipient (or authorized to receive for the recipient), please > contact the sender by reply email and delete all copies of this message. > Also, email is susceptible to data corruption, interception, tampering, > unauthorized amendment and viruses. We only send and receive emails on the > basis that we are not liable for any such corruption, interception, > tampering, amendment or viruses or any consequence thereof. > *********** End of Disclaimer ***********DataPatterns ITS Group********** > > > ------------------------------------------------------------------ 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