Castellated Holes on PCBs — How Half-Holes Really Work
WHAT THIS VIDEO COVERS
This video explains castellated holes (also known as castellations or half-holes) - semi-circular plated pads along the edge of a PCB that allow one board to be soldered directly onto another, creating strong, space-saving module connections.
The manufacturing process starts with standard plated through-holes. After copper plating the barrel, the board edge is precisely milled to expose the characteristic half-moon shape. This technique is widely used in Wi-Fi, Bluetooth, and compact expansion modules where quick, reliable vertical or horizontal board stacking is needed.
Key design considerations include finished hole diameter (recommended ≥0.5 mm), pad spacing (≥0.5 mm), and exact centering on the cut line. Misalignment or poor plating can lead to weak joints, especially under thermal stress or mechanical vibration.
Properly designed castellated holes improve assembly efficiency and reliability in IoT devices, industrial control systems, and consumer electronics.
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KEY HIGHLIGHTS
- Castellated holes are created by drilling and plating through-holes, then milling the board edge to form half-moon pads for direct board-to-board soldering.
- Minimum recommended specifications: finished hole diameter ≥0.5 mm and pad spacing ≥0.5 mm with precise alignment on the cut line.
- Ideal for Wi-Fi, Bluetooth, and modular IoT designs, but require tight fabrication tolerances to ensure strong, reliable solder joints under thermal and mechanical stress.
FAQ
Q1: What are the minimum design rules for castellated holes?
A1: Maintain finished hole diameter of at least 0.5 mm, pad spacing of 0.5 mm or more, and ensure the hole is perfectly centered on the board edge cut line for strong solder joints.
Q2: How are castellated holes manufactured on PCBs?
A2: The process involves drilling plated through-holes, copper plating the barrels, then precision milling the board edge to create the half-hole castellations.
Q3: When should you use castellated holes instead of connectors?
A3: Use castellated holes for compact, low-profile module connections (such as Wi-Fi or sensor boards) where space is limited and direct soldering provides better reliability and lower cost than traditional connectors.
Ever noticed tiny half-circles along a PCB's edge, like neat castle battlements?
Those are castellated holes — they let one board solder directly to another, almost snapping two modules together.
You'll often find them on Wi-Fi, Bluetooth, or compact expansion boards where quick edge-to-board connections matter.
The process seems easy, but accuracy is key. First, a plated through-hole is made, then copper coats the barrel, finally the edge is milled to turn the via into a half-moon pad. Misalignment or uneven plating weakens joints, especially after repeated heating or stress.
For stronger soldering,keep finished hole diameter≥0.5 mm，adjacent pad spacing ≥0.5 mm and center the hole exactly on the cut-line.
Small tweaks make half-hole boards better — what tips worked best for you?
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