Definition

Castellated holes (also called castellations or half-holes) are plated through-holes cut in half at the board edge, creating semi-circular pads along the edge. They're used to attach modular sub-assemblies (like wireless modules) to a host PCB by soldering the castellation to pads on the carrier board. Manufacturing requires drilling, plating, then routing through the hole center to create the half-cylinder shape. Castellation pitch is typically 1.27mm or 2.54mm. The plated surface allows visual inspection of solder joints.