Yeah, it was the QB324 boards. They didn't come with nylon washers but they did come with button-head screws which, once secured, overlapped the copper trace underneath the solder mask. A few cycles of heating up and cooling down meant the aluminium board pressed up hard against the screw heads and ate through the solder mask into the copper, which shorted the board after about two weeks of use.
So there were really two issues: the board shouldn't have been designed with copper that close to the mounting holes to begin with, and if you're going to sell a board that is at risk of shorting out because the supplied screws overlap the copper layer, then you should be supplying nylon washers. But even nylon washers are not infallible, as if you over-tighten them you can split them.
The QB324s are high voltage boards, too – 108V if I recall correctly – so with two in series, that's 216V, and you don't want to get hit with that. So you'll understand why I wasn't too happy at the time. And why, when it came to designing our own boards, we mad esure there was plenty of clearance around the mounting holes. We even drew circles and lines on the boards to delineate the safe areas.
Other than that, I really liked the QB324s. And if they have been in stock at the time we wanted to buy more, we never would have designed our own boards to replace them. Funny the way things turn out.
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