How to Solder: Castellated Mounting Holes

Contributors: Shawn Hymel
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A popular trend among manufacturers is board-to-board soldering. This technique allows companies to produce integrated modules (often containing dozens of parts) on a single board that can be built into another assembly during production. One easy way to produce a PCB that is destined to be mounted to another PCB is to create castellated mounting holes. These are also known as "castellated vias" or "castellations."

Castellated mounting holes

In this tutorial, we show you how to hand solder a board with castellated mounting holes to another PCB with the appropriate footprint.

Mounted module

We will be using a SparkFun RF Transceiver Breakout - RFM22B as our example throughout this tutorial.


If you are a visual learner, we made a video showing how to solder a module with castellated mounting holes. It covers most of what is written in this tutorial.

Suggested Reading

If you have never soldered before, we definitely recommend that you read our through-hole soldering tutorial and try soldering some plated through-hole (PTH) parts first. Check out any other tutorials below that you are unfamiliar with, before proceeding.