https://0tralala.blogspot.com/2006/04/castellations.html?showComment=1144095900000
Nothing Tra La La?: Castellations
nothingtrala
https://hackaday.com/2021/12/11/snip-your-way-to-diy-pcb-castellations/
Snip Your Way To DIY PCB Castellations | Hackaday
Dec 10, 2021 - Castellated PCB edges are kind of magical. The plated semicircular features are a way to make a solid, low-profile connection from one board to another, and...
your waysnipdiypcbhackaday