What is Half-Cut/Castellated Holes

By Bester PCBA

Last Updated: 2024-01-02

What is Half-Cut/Castellated Holes

Half-Cut/Castellated Holes, also known as Plated Half-Holes, are specialized holes drilled along the edges of a PCB that are then plated and milled halfway. These holes serve as a means of connecting and soldering the PCB to another board or component, particularly in board-to-board connections where different technologies need to be integrated.

Half-Cut/Castellated Holes provide a solder mounting device (SMD) terminal pad for secure and reliable connections between PCBs. By directly soldering and connecting the boards, this technique offers a space-saving solution compared to using multi-pin connectors. It also allows for thinner overall systems, making it particularly advantageous in limited space applications.

Designing Half-Cut/Castellated Holes involves adhering to specific guidelines. The minimum feature pitch between nearby holes should be 1.15mm, with a minimum drill diameter of 0.6mm for forming the half-holes. The hole pad diameter should be at least 0.9mm, and the solder mask clearance and bridge should be 0.05mm and 0.1mm, respectively. The recommended surface finish is typically ENIG (Electroless Nickel Immersion Gold), although the choice may vary based on the specific application.

Manufacturing Half-Cut/Castellated Holes involves drilling complete vias along the board’s edge and then cutting the plated holes in half using milling tools. It is crucial to use heavy-duty milling bits to achieve a smooth finish and prevent breakage. After milling, the half-holes undergo inspection and deburring to meet quality control standards.

Half-Cut/Castellated Holes find various applications in the PCB industry, particularly as breakout boards or for modular designs. They provide flexibility in PCB layouts and allow for easy changes to the pin layout of components based on specific requirements. With their robust connections and space-saving advantages, Half-Cut/Castellated Holes offer a reliable solution for board-to-board connections in modern PCB designs.

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