Castellated holes: PCB modules you can solder onto another board
What castellated holes are, which limits apply at PCB-ELECTRA and what to check in the design before you order.
What castellated holes are
Castellated holes are plated holes that are cut in half at the board edge, so that the edge of the board shows a row of plated half-holes. A small circuit board built this way works as a module: it is soldered directly onto a carrier board, like a surface-mount component, with the solder flowing into the half-holes. Radio modules, sensor boards and development modules are common examples.
How they are made
The holes are drilled and plated like any plated through-hole. The board outline is then milled through the middle of the holes, which leaves the half-holes at the edge. In our calculator this is the plated routing option (see panelization).
Our limits
| Feature | Limit |
|---|---|
| Hole diameter | above 1 mm |
| Hole-to-hole spacing (pitch) | 0.5 mm |
| Depaneling | milling |
| Surface finish | lead-free HASL |
The complete list of limits is on the capabilities page and in the guide on vias and hole sizes.
Design checklist
- Draw the holes so that the board outline passes through their centre, and show them on the edge in the Gerber and drill files.
- Mention the castellated holes when you order, so that the edge is routed with plated milling.
- Keep copper pads along the edge of the module and keep the solder mask clear of the half-holes.
- Leave room on the carrier board for the solder joints: the pads on the carrier must reach beyond the module edge.
- Do not place components or traces close to the edge, where the milling takes place.
- Check the files in a viewer before sending them; the guide on checking Gerber files shows how.
Ordering
Enter the specification in the price calculator, choose plated routing and upload your archive. Our engineers check the edge design before production and contact you if something has to change.
Frequently asked questions
What is the minimum hole diameter for castellated holes?
The hole diameter must be above 1 mm, with a hole-to-hole spacing (pitch) of 0.5 mm.
Do I have to tell you that my board has castellated holes?
Yes. Mention it when you order, so that the edge is milled with the plated option instead of the standard outline routing.
Can I solder a module with castellated holes by hand?
Yes, with a soldering iron or hot air, provided the pads on the carrier board extend beyond the module edge so the solder can flow into the half-holes.
Browse the questions and answers →
See our manufacturing capabilities
Minimum trace and spacing, drill sizes, materials, tolerances and tests for every board type, on one page.
Open the capabilities →Ask an engineer
Not sure what applies to your board? Describe it in a few lines and our engineers will advise you.