I'm still iterating on my high-voltage pulse generator. Rev C looks very good. I've been pushing it up voltage and frequency (like, 1200 volts and 4 MHz) and seeing what parts fry, and working on them.
I have a dpak schottky diode in a sort of snubber place. According to Spice, it shouldn't get too hot, and it's soldered to all sorts of copper pours and thermal vias and stuff. It's an SBRD10200 and it's frying. I happened to have some smaller, lower current diodes around, UPS5100E3, which is a sawed-off sub-dpak thing. I figured I might squeeze in two of those in parallel... but just one runs cool.
Weird. I'm guessing that the big one has a p-n guard ring that makes it have reverse recovery current right after a big forward current spike. Data sheets never talk about that.
I heat sinked things too well, so it's a bear to desolder/resolder.