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PaxInstruments / t400-electronics

Electronics for the Pax Instruments T400 temperature datalogger
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QFN thermal pad #155

Closed charlespax closed 9 years ago

charlespax commented 9 years ago

The ATmega32U4 QFN thermal pad has a single via to transfer heat from the MCU to the bottom side. Should we add more vias?

screen shot 2015-02-21 at 17 34 59

Tsillen commented 9 years ago

no need

charlespax commented 9 years ago

[citation needed]

Tsillen commented 9 years ago

You could add up all the loads and calculate the temperature rise etc... but that is a lot of work. The TQFP version does not have any over heating issues as shown by arduino using that format on their products.

I see that you have a few IO and some busses etc. The current draw of the chip will be (very)low. In that case no extra "cooling" is needed.

But if you really want add a few more via's to it. It won't do you any good as it might make the reflow process work less good due to the increased thermal resistance that the big bottom pad will have vs the thermal resistance of those pin pads.

charlespax commented 9 years ago

Cool. Let's leave things as they are. Moving to ice box.

charlespax commented 9 years ago

Will not do. Closing issue.