Hi, Yu-yuan You may refer to the following patents. Let me know how you think: 1. Via structure for improving signal integrity. US8084695 2. Interconnection structure for improving signal integeiry. US 8153906 Hope this help.. Best regards, Robert Hsu CC: weirsi@xxxxxxxxxx; leeritchey@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx From: lee.home.61@xxxxxxxxx Subject: [SI-LIST] Re: One stitching via or more vias is better for 25Gbps application??? Date: Tue, 9 Sep 2014 07:08:30 +0800 To: bertsimonovich@xxxxxxxxxx; bipinpd@xxxxxxxxx Bert, Thank you so much After studying document you indicated, 1. It seems only one vias (-90dB) with symmetric configuration is better than multi vias (-55dB) with symmetric configuration under 10Ghz frequency. How about above 10Ghz frequency range? Is it the same trend? 2. The lowest coupling with two GND layer means that it had better to remove pad at other GND planes. Is it true or not? Do anyone do this kind of simulation? Lee Bipin Dhavale <bipinpd@xxxxxxxxx> 於 2014/9/8 下午11:56 寫道: In addition to paper you sent, below is one study with asymmetric differential pairs. ( most large bga breakouts wont have symmetric diff pairs) http://www.univ-brest.fr/SPI/pages/Slides/SPI_2009_S7_1.pdf Its not the exact same case of transition via's but still. ------------------------------------------------------------------ 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list 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