In grad school we built a lot of logic boards from scratch. They were used for submersible robots, and we had a 350,000 gallon water tank that we kept heated to

In grad school we built a lot of logic boards from scratch. They were used for submersible robots, and we had a 350,000 gallon water tank that we kept heated to 88 degrees. This was three stories above the ground in a metal building. You can't really air condition that, so in the summer it got quite hot. It was not uncommon to return from lunch to find than an embedded computer board that had been working when you left wasn't any more. One way to debug them was to put them in the refrigerator for a while. If they then worked, you knew you had a bad solder joint or an IC that was on the verge of failing.