Hi Inge and Everyone! I have your diagrams posted, they're here: http://stevezeva.homestead.com/files/Inge_s_diagrams.doc Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar Sent: Wednesday, September 19, 2007 1:52 AM To: [log in to unmask] Subject: Re: [TN] Trace Peel on FR4 Robert, this design area is very complex. Don't you have a guidance book? Anyway, you need sit down and make a analysis of the situation. There are numerous factors to count upon. E.g. copper resistivity is not linear, it increases with temperature. Via resistivity and losses are often forgotten, maybe they get hotter than the traces. And the cooling of the traces is dependent of many things, like air velocity, heat radiation, lateral heat transportation, number of layers, copper thickness, board thickness etc. My reaction is, that something is very wrong when the temp diff between the board (approx room) and the traces is (105-25)= 80 Centigrades. Copper traces should not be used as 'heater elements' for making a cup of coffee (we took small pieces of PWB, etched a meander loop, dipped the board in a cup with water, ran a lot of current through, and got hot water!). So, my opinion is, that current losses of copper traces should be kept to as low as possible level. Yes, conservative. I'll send two diagrams to Steve for his famous wall. These diagrams will show you trace cross section vs. current vs. temperature vs copper oz etc....may give you a helping hand. And somewhere I have a very good paper from TI that describes every step and all maths you need. If I find it, I'll send it to you. Inge -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Croslin, Robert Sent: den 18 september 2007 19:59 To: [log in to unmask] Subject: [TN] Trace Peel on FR4 Dear 'Netters, We have a product used to measure on/off status on flat screen TV's that was designed a few years ago. Over time, with the newer, bigger TV's, there is a much higher current draw than we'd envisioned way back when. So, as the devices cycle back through our repair depot, we're making mods to upgrade them to handle these new TV's. A problem we've seen in testing is that the traces that handle the AC pass-through are now getting quite warm. We've measured the traces at 105*C at room temperature. The base is plain old FR4. We haven't been able to get any to fail in testing, but are concerned about the differential under load possibly causing the trace to peel away from the FR4. Our concern is thermal cycling over time; could it cause the trace to lift? If the trace is hot but the board cool in a steady state condition, is there any risk there? Does anyone know of any specifications that would address this situation? Bob Croslin Nielsen Media Research --------------------------------------------------- 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 -----------------------------------------------------