What are Plated Half-Hole/Semi-Hole?

Plated half-holes (or Semi holes) are predominantly used for board-on-board connections, mostly where two printed circuit boards with different technologies are combined. E.g. the combination of complex microcontroler modules with common, individually designed PCBs.

Additional applications are display, HF or ceramic modules which are soldered to the base printed circuit board.

The board-on-board PCBs therefore need plated half-holes, which serve as SMD connection pads. Through directly connecting the PCBs together, the whole system is considerably thinner than a comparable connection with multi-pin connectors.

Manufacturing
Through setting back the copper shell from the conture, the plating is protected from mechanical damaging.
Therefore the  plated half-holes can be milled precisely what strongly improves the process reliability.
Internal Half-holes are also producable.

            


Drawing

How to indicate castellated holes in your design?


Castellated hole design varies from software to software, but the end result in the Gerber files should be as follows. Please refer to the documentation of your chosen design software for more information.

Add a via or plated hole directly on the outline of the boards where the plated half hole is required. Ensure that half of the via is on the board and half is on the outside of the outline.  

The following should be included:

- Copper layers (GTL and GBL): Copper pads on both top and bottom copper layers for each castellated hole.

- Solder mask layers (GTS and GBS): Solder mask openings on both sides.

- Drill layer (TXT/DRL): A drill hole for each castellated hole.

- Mechanical/Outline layer (GML/GKO): The outline should cross the drill hole.