I didn't know that castellated holes on a PCB were to facilitate SMT.

Sure makes it look like a stamp though… ;-)

Castellations also enable use in a "burning fixture" like the below. The fixture has bent pins that hold the PCB physically and connect electrically to the PCB's leads.

https://www.amazon.com/DIYmall-ESP32-WROOM-32-Programming-Fi...

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geerlingguy 3 days ago | parent [-]

Would love to see someone design a PLCC or IC Socket that would let you slide one of these in (like those old sockets they had in Macs for optional FPU chips).

	▲	adolph 3 days ago \| parent [-]
		I just looked that up and it seems like a nice system (although physically complex/costly to manufacture) [0]. The only FPU-optional Mac I had was a IIsi which had an optional FPU that used the Nubus slot. 0. https://www.worthpoint.com/worthopedia/macintosh-color-class...