Cody, I ask the PCB vendor what they use for their standard FR4xx dielectric constant, what the materials used are, etc. If that works for the application, that's what I use. Plain vanilla. I typically design all layers using the same dielectic constant because it's cheaper that way. There are exceptions, but most of the time one size fits all. What I am tight on is the final controlled impedance value. I allow little variation in the trace width on signal layers and the dielectric height is also fixed (for signal or power). Ken -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of steve weir Sent: Wednesday, December 10, 2008 7:21 AM To: codymiller@xxxxxxxxxx Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Designing PCB Stackups cody, the best practices qualify specific materials for each layer, and where possible specify more than one equivalent alternative. Specifying materials only generically can leave your process control and QA all over the map. I strongly discourage that. My $0.02. Steve codymiller@xxxxxxxxxx wrote: > All, > > I have a general question regarding PCB stackup design. I am evaluating > how we design our pcb stackups in our group now and I would like to put > a procedure together or a set of rules of thumb to properly design a > stackup. I would like the procedure to ask all the right questions up > front. > > One question that came up is do PCB designers typically design with > vendor specific materials in mind or do they design with generic prepreg > and core materials. I see some pros and cons to both. What is typical in > the industry. > > Any advice would be appreciated as well as if you know of any > papers/resources on the web that could be helpful. > > Thanks, > Cody > ------------------------------------------------------------------ > 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 > > > > -- Steve Weir Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 California office (866) 675-4630 Business (707) 780-1951 Fax Main office (401) 284-1827 Business (401) 284-1840 Fax Oregon office (503) 430-1065 Business (503) 430-1285 Fax http://www.teraspeed.com This e-mail contains proprietary and confidential intellectual property of Teraspeed Consulting Group LLC ---------------------------------------------------------------------------- -------------------------- Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ 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 ------------------------------------------------------------------ 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