reflow profile

You can, and for small parts you probably won't see much difference between body temp. and lead temp. For QFPs or PLCCs there will be a much greater delta, though.

I'd be more concerned with the small surface area you're making contact on (spherical thermocouple end on flat component surface). Why don't you bury the thermocouples in the solder joints with high temp. solder? It's a pain with fine pitch, but gives you the best data since it's actually measuring the temperature within the joint (solder).

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You can measure temperatures any place that you would like, but the issue is the temperature of the solder. We've seen solder temperatures that vary from lead to lead on the same component.

Why don't you want to measure the temperature of your solder?

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We're used to placing the theromcouple on the solder joint and securing it with thermally-conductive UV adhesive. It's quick & easy to apply, and I've only seen a couple degrees difference from high-temp solder technique. Thoughts?

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I like to secure the thermalcouples with a small dot of chip-bonder(surface mount adhesive). The chip-bonder will cure durring the first pass through the oven. After I have developed my profile I remove thermalcouples and the chip-bonder with a soldering iron.. Works great, thermalcouples will not move during profiling.

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there is a company called EFD. my contact there is john kaminski. they have thermocouples that are spring loaded requiring no solder at all. they work great. you attach them to the edge of the board and you can move the end to make contact where you want. it is a little investment but they are very nice.

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