Bill, Our rigid boards are 2, 4 and 6 layer boards where Dk, Tg, and other arcana are not important enough to warrant any material beyond IPC 4101/21 "normal" FR-4. We allow the fabricator to choose the prepreg. The standard 2-layer core is mostly 0.059 inch these days. We're fortunate we can be flexible, so there's no reason to pay more for what you don't really need, right? Valerie St. Cyr had a comment on this topic also which was interesting and I will go reply to hers next. Thanks, Gary -----Original Message----- From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Brooks,Bill Sent: Wednesday, March 09, 2005 12:04 PM To: [log in to unmask] Subject: Re: [DC] Finished thickness tolerance Hi Gary, You'd be surprised how often this sort of question pops up. The 'standard' thickness for PCB's here in the US I believe was derived from the single and double sided board days back in the 1960's era... Material was offered clad with copper in various thicknesses and in 1/32 inch increments. It is still the 'defacto' standard. That's why you see so many people specifying .031 (.03125) .063 (.0625) .094 (.09375) .125 thickness materials. In fact the industry has become so flexible now that we could specify just about any thickness we need in .002 in. increments because that's the standard thickness of the prepreg material used to build up the final thickness of any multilayer board. I think they still sell the single and double side clad materials though... If you check with your chosen board manufacturer I'm sure they can tell you what materials they normally stock and use and will give you a broad range of options for finished board thickness... even if you are designing in metric. :) Best regards, Bill Brooks - KG6VVP PCB Design Engineer , C.I.D.+, C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 e-mail:[log in to unmask] http://www.dtwc.com http://pcbwizards.com -----Original Message----- From: Gary M. Koven [mailto:[log in to unmask]] Sent: Wednesday, March 09, 2005 8:05 AM To: [log in to unmask] Subject: [DC] Finished thickness tolerance We design Class 2 boards and have been specifying on drawing finished thickness 0.031 in +/- 0.004 in or 0.062 in +/- 0.008 in. I'm looking for the finished thickness tolerance tables by class. I could not find these details of what I need in IPC-2221, 2222, 6011, or 6012, just vague general references. Are these in IPC-4101? If anyone can verify or correct what we have been specifying and reference whatever updated standard to use, I'd appreciate it. TIA and Best Regards, ====================== Gary M. Koven Engineering Services Manager Dynazign, Inc. 806 Tyvola Road, Suite 100 Charlotte, NC 28217 P: 704.405.1234 x210 F: 704.405.1402 http://www.dynazign.com/ ---------------------------------------------------------------------------- ----- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ---------------------------------------------------------------------------------