Hi Yuriy, You should talk to someone from one of the bigger American PCB fabs. They are more likely to have "research" data like this. Some designers let the fab to choose any parameter, while others require official approval of all thicknesses and trace widths (like I do) and glass styles even before prototyping or layout design. So, instead of trying to get data about already built boards, you should work with the hardware designers at an early stage to get the data, so they can put the right numbers (width, spacing, thicknesses) into the design. Then the PCB fab only does etching compensation, but not a big modification on the trace widths. They can provide the post-lamination thicknesses during the early stackup negotiation between the HW engineer and the PCB Fab. Check how the Polar Speedstack software works, and how it calculates post lamination thicknesses. Some fabs have their own software. Basically you should try to tackle this at the lead-in part of the project, not at the tail-end. Then everything will be consistent. There is always a push from management/purchasing to allow the FABs to do whatever they want, and also some designers are only there to collect their pay check so they couldn't care less about negotiating the exact stackup. This way you end up with boards built with unknown parameters. I wrote about these a few years ago: http://www.buenos.extra.hu/download/accurate_impedance_control_pcdanf-magazine-2009nov-page20.pdf Specifically about post-lamination thicknesses, etching compensation... Regards, Istvan Nagy -----Original Message----- From: Yuriy Shlepnev Sent: Monday, September 08, 2014 1:48 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Board design adjustments by manufacturers Hello Everyone, After going through a multiple analysis to measurement validation projects, I realized that almost all boards are not manufactured as designed (what a surprise :-)). As a consequence the analysis to measurement validation may require investigation of the manufactured board geometry, that includes cutting the board and taking measurements on the cross-sections (usually important only above 10 GHz). Now I am trying to figure out what board design adjustments are needed and where to get those numbers without cross-sectioning for the accurate post-layout electromagnetic analysis. In particular, is there any way to get the following numbers without cutting the board? - change thickness of layers (account for plating and variations in thickness of laminates); - change trace width and shape (account for etching and plating); - change spacing between traces in diff pairs (if adjusted for the "impedance control"); How board manufacturers actually adjust trace widths or spacing for a given design in the "impedance controlled" process if they have just Gerber or ODB++ data? Is there any software that does it? A relevant question - are there board manufacturers out there who provide probability distribution data for stackup layer thicknesses, strip widths, back-drilling depth etc.? Can anybody point me to a source of information on this subject. Best regards, Yuriy Yuriy Shlepnev, Ph.D. President, Simberian Inc. 3030 S Torrey Pines Dr. Las Vegas, NV 89146, USA Office +1-702-876-2882; Fax +1-702-482-7903 Cell +1-206-409-2368; Virtual +1-408-627-7706 Skype: shlepnev www.simberian.com Simbeor – Accurate, Fast, Easy and Affordable Electromagnetic Signal Integrity Software 2010 and 2011 DesignVision Award Winner ------------------------------------------------------------------ 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 --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com ------------------------------------------------------------------ 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