Hi Chris, I would think that you either specify the material per the IPC spec or you specify the characteristics you want and let the board shop pick the material. I'm sure they would prefer the IPC spec to matching the characteristics, it would make their job easier and less confusing. So if he says the board will not experience more than a 5 degree rise then there must not be any hot components on the board or any appreciable current in the traces... According to the spec IPC4101/21 is good up to 110 deg C, any higher and all bets are off. The mix of ratio of glass to resin will give the board different Tg characteristics, so they give a large range from 110degC to 150degC based upon the material combinations that can fall into this specs category. A good design will make sure that the board never sees more than the 110degC... If there are heat generating parts on the surface of the board then you have to reduce the ambient accordingly so that the surface of the board never exceeds the minimum Tg of the material. Or you move to a material with a higher Tg to accommodate the higher temps. Also a good designer never designs against the minimums or maximums but gives themselves some margin for tolerances... as I'm sure you already know... :) Bill Brooks - KG6VVP PCB Design Engineer, C.I.D.+, C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 _______________________________________ Member of the San Diego Chapter of the IPC Designers Council Communications Officer, Web Manager http://dcchapters.ipc.org/SanDiego/ http://pcbwizards.com -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Friday, April 22, 2005 5:23 AM To: (Designers Council Forum); Brooks,Bill Subject: Re: [DC] High Temperature Environment In this case, Don says he doesn't anticipate even a 5 degree rise above ambient anywhere... Is it bad form then to specify IPC-4101/21 with a min Tg of 135C, for example? I always get hung up on interpreting these spec's. Is any IPC-4101/21 OK down to 110C, or can you specify where in the range you want your IPC-4101/21 to fall? Happy Friday, -Chris --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------