Hi, I have some thoughts about the limits to high speed links. Since I currently don't have industrial experience in this field, could someone comments on them with his/her industrial insights? Thanks! From the SI books and papers, I understand that dielectric loss dominates the transmission line loss over skin effect loss at high frequencies. If we define FC as the frequency where the two loss mechanisms equal, then for conventional FR4 board, FC should be around 1G, which means for high speed link >10Gb/s, dielectric loss is dominant on FR4 boards. But if more expensive materials such as Rogers are used, this FC will be tens of GHz. Does this mean that for <50Gb/s links, if high performance materials are used, the optimization should be to minimize the skin effect loss? And once the loss tangent is below for example 0.002, it doesn't help much to reduce it even further. Is that true? Or for links <50G, neither skin effect loss nor dielectric loss is dominant. Instead, the vias, connectors and packages will be the major bottlenecks. So the emphasis should rather be put on 3D optimization of those transitions. ------------------------------------------------------------------ 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