I etched a few boards while in college, including one while I was in Australia preparing for a solar car race. Eventually the solar car team found a local PCB m

I etched a few boards while in college, including one while I was in Australia preparing for a solar car race. Eventually the solar car team found a local PCB manufacturer excited to sponsor us, though. It was pretty great getting 1-2 day turn around on boards as a college student. I tried to keep everything standard 2 layer to make it easy to manufacture. The sponsor kept saying, "Come on, give us a challenge. We specialize in heavy copper!" So... I designed a 40-pole 4-turn brushless motor stator meant to do 7KW+, with each phase consisting of 3 parallel traces to minimize eddy current losses. 32 layers of 8oz copper, 90%+ copper fill. We also pushed it to the physical limits of chemical etching in terms of trace spacing. They tried their darnedest to manufacture it. They had to program their mills to peck drill for the first time. The plate was so heavy that it damaged several conveyor belts on the line. They managed to get me a 16 layer prototype, and we actually drove the car for a couple hours on it (but with an appropriately reduced torque limit due to the increased resistance). They couldn't get all the kinks out of the full stackup before our race deadline, but they eventually produced a 6oz 28 layer stackup that was pretty much perfect. I still have it as a momento. I think it weighs maybe 15lb.