I'm curious to see how many of you engage in thermal testing. For a long time thermal testing was something I couldn't do, since I work remote and don't have access to a local Avnet facility that may have that capability. After several years of lobbying however, I was finally able to get approval for a "bench top" thermal chamber to put in my garage. Even though it took some convincing up front, all it took was one end of life component replacement that needed validation to more than pay for the investment in the chamber.
I was able to outfit my garage with a basic thermal test environment for about $9k. Not a trivial amount to spend on equipment, however if you compare that to the hiring of an external resource to do testing more than likely you will quickly see that the equipment cost pays for itself quickly and then becomes a valuable resource moving forward. All in all I had to put in a dedicated 20A circuit to my main breaker box, pick up an external thermocouple reader and outfit a low end laptop with some basic communication capability to communicate with units under test in the chamber.
With this basic setup I can do quite a bit. I can use the laptop to run test scripts, repetitive startup testing at temperature extremes, log component temperatures while under test at temperature extremes, etc. As needs grow I have the ability to possibly add a data logger or automated test software.
The external thermocouple is nice as when you set the chamber temperature, without it you are basically relying on the readout to be accurate. In my experiences so far, I find the chamber to be about 2C "low" at the extremes. Meaning if I set it to -40C the thermocouple reads -38C and at 85C it reads about 83C. Setting the temperature 2 degrees more extreme than my desired temp consistently measures what I expect. The other nice thing about the thermocouple reader is that it is a 4 channel device. Meaning I can crazy glue probes down to heatsinks or critical parts and read their temperatures as well from the meter. Yes I could use a multimeter with multiple probes and just plug them in one by one to read them, but that's no fun. Besides these readers are pretty inexpensive and help demonstrate how in an automated setup a datalogger that could read and store these measurements over different test criteria could be valuable.
I'm pushing very hard right now on promoting thermal relief solutions at Avnet. We are working towards offering more products and support in this growing area of need. As I work with partners to design new heatsinks and applications it will be very valuable for me to be able to use my chamber to do validation closer to the product limits than a simple open air, ambient bench top setup. I've already used this setup to aid in the prototype testing of a couple of different heatsink solutions around our products. It definitely helps me feel more confident in the solutions we provide and promote. You will see me leverage this equipment in my future blogs about various products and technologies.
If anyone else out there has some cool thermal test environments set up I'd love to hear about them. Any tricks or best practices you'd like to share? I'd love to hear feedback in the comments. One thing I remember learning was how quickly the temperature would rise on my product when you turned off the chamber power at 85C. The airflow inside the chamber effectively equalized the temperature, which eliminated hotspots. When you turned off the chamber there were parts of the board that would instantly start climbing. That led me to using cardboard boxes to enclose units under test to eliminate "unintentional" airflow from affecting the test.
