Jack - I have used the following for calculating max temp rise allowable: (Tg-Max Ambient)/safety factor I.E. Tg = 180 deg C Max Ambient = 80 deg C Safety Factor = 2.5 Allowable Temp Rise = 40 deg C It isn't real scientific and I often fudge the safety factor to get closer to some nominal value but it gives you some place to start. Jeffrey A. McGlaughlin PCB Designer Battelle Memorial Institute Columbus Ohio [log in to unmask] -----Original Message----- From: Jack Olson [SMTP:[log in to unmask]] Sent: Friday, 21 May, 1999 12:00 To: [log in to unmask] Subject: [TN] Temperature Curves for PCB Traces Sorry for posting this here (after already trying the designer council) but if I don't get a logical scientifical semi-provable response I will be forced to use the dreaded "10 degree curve" for the rest of my designs.... ouch! I can't figure out how to select the appropriate temperature curve when calculating PCB trace widths versus current requirements. If you use the chart in IPC-D-275 or IPC-2221, you have to select a curve to get your minimum trace width. If you use a calculator, it will solve for the temperature rise, but you still must know if it is acceptable. So what is acceptable? Anything that won't make the material hit Tg? I'm trying to avoid the dreaded "Just use the worst case"... Am I missing something? ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################