Castellated Holes for PCB Modules—Best Design Practices?

Robotics and electronics discussion Electronics
1

Hey everyone,

I’m working on a small motor driver module. It needs to be easily soldered onto a main PCB. I am trying to follow how Pololu’s motor driver and sensor breakout boards use castellated holes for edge mounting. While researching, I found this article: Understanding Castellated Holes in PCB Manufacturing. It explains the manufacturing process and common use cases.

I’m considering using castellated holes, but I have a few concerns:

  • Do castellated connections hold up well under repeated soldering and desoldering, or do they wear out quickly?
  • Is there a minimum recommended pad size for castellated edges to ensure reliable solder joints?
  • Would adding plated edge vias improve mechanical strength, or would they just complicate manufacturing?

If anyone has experience designing castellated PCBs for compact modules, I’d love to hear your insights!

2

Castellated holes are a solid choice for edge mounting motor driver modules, as they provide a reliable solder connection and allow easy integration onto a main PCB. However, repeated soldering and desoldering can degrade the pads over time, especially if excessive heat is applied. To ensure durability, using a slightly larger pad size typically at least 0.5mm wider than the hole diameter can help maintain strong solder joints. Plated edge vias can add mechanical strength by reinforcing the connection, but they may increase manufacturing complexity and cost. If your module needs extra robustness, you might also consider adding a few through-hole pads along with the castellated edges for additional support. Have you tested any prototypes yet to see how well the solder joints hold up?