Davis, Did you adjust for the emissivity differenences in the materials? The Infrared temperature sensor should have an emissivity adjustment. The default is 1.0, and copper will have a lower value than the FR-4 due to the more reflective nature of the copper. Since the copper with current is the heat generator, it seems unlikely that the FR-4 would be hotter. Glenn "Davis Chamblee" <[log in to unmask]> Wrote: | | I have been performing some ampacity tests on PCB traces using data from | IPC-D-275 and from posts to this forum. My question concerns the test | methodology. I'm running about 10 amps through a 150 mil, 2 oz trace. Using | a non-contact infrared temperature probe I read significantly higher just | off the side of the trace as opposed to directly on it. I'm sure this has | to do with the ability of the copper trace to dissipate heat more | efficiently than the FR-4 material, but am I safe to use the lower | measurement for purposes of calculating temperature rise? I don't want to | get problems down the road with the board delaminating or discoloring. For | example: with an ambient of 24 C, I read 38 C on the trace, but 49 C | adjacent to it. Is a 14 C rise correct, or would a more conservative 25 C | rise be appropriate? | | As a side note, does anyone have suggestions as to recommendations for | maximum allowable rise? | | Thanks for any help you can offer. | | Davis Chamblee | VP of Engineering | | ~~~~~~~~~~~~~~~~~~~~ | Vision Technologies, Inc. | 6500 Taylor Road | Wendell, NC 27591-8700 | Telephone (919) 365-5747 | Toll free (800) 418-7907 | Email [log in to unmask] | | ################################################################ | 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 ################################################################