Castellated holes / Edge Plating PCB / Castellations

Castellated features are vias or thru holes that are cut through to create a partial or half hole for the purpose of creating an opening into the side of the hole barrel. It basically looks like the board has smt pads on the bottom side with vias in them and it's been cut right through the middle of the vias. Castellated plated through holes located at the periphery of a substrate or circuit board are commonly used in circuit technology for various applications. For instance, castellated plated through holes may be used when coupling adjacent circuit boards, thereby providing a solder inspection joint to ensure the solder "wicks up" properly at the interface of the two boards.

The proper terminology is a “surface mountable module with castellated mounting holes”.

These partial features are used for the purpose of mounting a PCB to another PCB by means of solder, or insertion of specially design edge connectors.

There are multiple designs that constitute a feature that would fall under the castellation format.

Complexity Levels (or Class levels)
There are several factors that contribute to the complexity of a castellated hole. The main critical design attributes are:

• Hole size

• Number of holes per board

• Single hole or multiple hole designs

• Surface finish

Recommendations and comments

When castellated features are required, it is best to use the following general rules when at all possible

• Use the largest hole size possible

• Use the largest Outerlayer pad possible, both top and bottom sides

• If possible, place Innerlayer pads to anchor the hole barrel. This will also help reduce burring during the castellation process.

• If the castellation is not used for a mechanical connection (i.e. insertion of a connector device), allow additional dimensional tolerance for the castellation opening if possible.