Just thinking about your situation and some of the responses, I was wondering how some of these limits have been established? In relation to environmental testing, has anyone determined the acceleration due to temperature? And, what is considered a failure? I was thinking this should include below and above the glass transition temperature, even if it's not a typical use environment. Then one more twist, what about the influence of humidity? Thanks is advance for any response. Glenn Pelkey Maxtek Components Corp. | ---------- | From: Sam Mollet[SMTP:[log in to unmask]] | Sent: Monday, 11 May, 1998 14:25 | To: [log in to unmask] | Subject: [TN] Maximum FR4 operating temperature | | | I have an application with a maximum ambient temperature of 70 | °C. I am using copper planes on FR4 to help cool some power resistor | leads. The copper planes can hit 115 °C. Is this a problem? Is there | a rule of thumb on how hot FR4 can continuously be operated at? ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################