tutorials on how to measure junction-to-ambient thermal resistance

Hi MichaelXPPower ,

I took a look around, and as far as I can tell you're correct, there's no specific page / article with that exact title. A quick search turned up:

https://www.analog.com/en/resources/technical-articles/thermal-characterization-of-ic-packages.html

which is not exhaustive - but it does have links to the JEDEC specs that define the test methodology. In general, in the absence of any other information in the datasheet, the thermal resistance specs are derived from JEDEC-compliant tests. However, certain parts, like some linear regulators, will often have additional thermal resistance measurements for specific PCB layouts. The reason is the JEDEC tests for theta-JA are typically designed to be pessimistic, or a worst-case value. If you look into the specs, you'll see that the test boards have minimal pad size, and small traces. Almost anything you can do to spread heat - larger traces to power or other pins, multiple ground layers with vias, etc. will lower the thermal resistance.

If you have a specific device that you're concerned with, you can ask in that part's support forum.

-Mark