UL makes it's money twice with this one - It first approves the laminate at the laminate manufacturer, with MOT's (maximum operating temperature) then further approves the MOT at the PCB fabricator. The two values do not necessarily match up dependant on how the fabricator builds his boards. I have seen some instances of 130oC laminate approved at fabricators to only 105oC. Best to check in the first instance with the PCB supplier to check what they have in terms of approvals. UL also tests minimum board thickness, maximum un-pierced ground plane, minimum track width, maximum copper thickness, bond strength as well as flammability. Rgds Colin W.T. McVean M.Inst.C.T Production Manager Artetch Circuits Ltd (www.artetch.co.uk) Direct Dial 01903 712926 Switch Board 01903 725365 Skype: colin.artetch 40th Anniversary 1967 - 2007 P Before printing , please think about the Environment -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ian Hanna Sent: 25 June 2007 18:45 To: [log in to unmask] Subject: Re: [TN] UL specification on temp rating for bare board material UL lists a 'maximum operating temperature' for listed circuit boards -- in the old days this was usually 105C -- now its usually 130C for FR-4-- again, this has to do with the safety of the materials more than the electrical performance of a finished board... how many layers is your design? Spec'ing tg170 on an 8-layer shouldn't impact price very much but the same call-out could add substantial cost to a double-sided build... ian -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Brooks,Bill Sent: Monday, June 25, 2007 1:32 PM To: [log in to unmask] Subject: Re: [TN] UL specification on temp rating for bare board material Here's a good description of the 94V spec.. http://www.boedeker.com/bpi-ul94.htm Cheers, Bill -----Original Message----- From: Ted Tontis [mailto:[log in to unmask]] Sent: Monday, June 25, 2007 9:31 AM To: [log in to unmask] Subject: Re: [TN] UL specification on temp rating for bare board material My employer is telling me that UL specifies the opperating tempature of the PCB material. From what I understand UL only specifies the flame rating and voltage rating. Proper opperating tempature is provided by the manufacture of the lamanate? Thats my question does UL specifiy the opperating tempature of the PCB lamanet? Here is what is stated on the old drawings. 1. CIRCUIT BOARDS MUST CONFORM TO UL 94 VERTICAL FLAME TEST AND UL796 2. MATERIAL: 0.062 +/- .006 THICK FR-4 LAMINATE - 2 LAYERS Here is what I have 2. Fabercate PCB in accordance to IPC-6012A Class 2; per IPC-6011 using the customer supplied data files. 3. Materials: A) Laminate and prepeg (B-stage) to be in accordance with IPC-4101/23 or IPC 4101/24. Material must meet UL 94V-0 Flammability rating with a Tg rating of 170 or greater is recommended. Finished thickness shall be .062 +/- .006 B) Copper foil to be in accordance with IPC-MF-150. Unless other wise specified, all copper weight for inner signal layers to be 35um (1 oz). For outer layers 71um (2 oz). Copper weight is to be considered "finished copper weight" I do not have a copy of UL 796 nor does my employer. I have no idea what that is or if thats where the temp rating comes from. I am pretty sure the guy is just cutting cost where ever he can and this is just one more place to cut them. I have just never heard of UL making recomendations for opperating tempatures of PCB lamate material. Thank you, Ted --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/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 -----------------------------------------------------