In modern electronics manufacturing, compact design, modular integration, and reliable interconnection are more important than ever. One technology that perfectly supports these requirements is half-hole PCB technology, also known as castellated holes.
From IoT modules to RF communication boards, half-hole PCBs enable seamless board-to-board soldering, making them a preferred choice for engineers designing compact and scalable systems. In this guide, we’ll explore how half-hole technology works, its manufacturing process, design rules, cost factors in 2026, and how to choose the right PCB partner like KingsunPCB.
1. What Are Half Holes in PCB?
Half holes, or castellated holes, are plated through holes that are cut in half along the edge of a PCB. This creates semi-circular pads that allow another board to be soldered directly onto them.
Key Characteristics:
- Located on the PCB edge
- Metallized (copper-plated) inner walls
- Half-circle shape after routing
- Function as both electrical and mechanical connectors
Half Holes vs Standard Vias:
| Feature | Half Holes | Standard Vias |
| Location | PCB edge | Inside board |
| Function | Board-to-board connection | Internal signal routing |
| Exposure | Open (half-cut) | Fully enclosed |
2. How Half-Hole (Castellated) PCBs Work
Half holes enable direct surface mounting of one PCB onto another, similar to SMT components.
Working Principle:
- The base PCB contains castellated holes along its edge
- The module PCB aligns with corresponding pads
- Solder paste is applied
- Reflow soldering creates both electrical and mechanical bonds
This approach is widely used in wireless modules, allowing easy integration without connectors.
3. PCB Half-Hole Manufacturing Process
Producing high-quality castellated holes requires precision and experience.
Step-by-Step Process:
- Drilling
Standard through holes are drilled at the PCB edge - Copper Plating (PTH)
Holes are plated to ensure conductivity - Pattern Imaging & Etching
Circuit patterns are formed - Solder Mask Application
Protects non-conductive areas - Profile Routing (Critical Step)
The PCB outline is milled, cutting holes into halves - Surface Finishing
ENIG, HASL, or other finishes applied
Key Challenge:
Maintaining plating integrity after routing is crucial. Poor control can lead to:
- Copper burrs
- Uneven edges
- Weak solder joints
This is where experienced manufacturers like KingsunPCB ensure tight tolerances and consistent quality.
4. Design Guidelines for Half-Hole PCB
Proper design is essential for manufacturability and reliability.
Recommended Design Rules:
- Hole diameter: ≥ 0.6 mm (typical)
- Pad ring width: ≥ 0.25 mm
- Hole-to-hole spacing: ≥ 0.5 mm
- Distance to board edge: precisely aligned for clean half-cut
Best Practices:
- Use non-tented vias for better solderability
- Ensure uniform spacing for automated assembly
- Add fiducials for alignment
- Optimize panelization to reduce cost
Common Mistakes:
- Too small holes → plating defects
- Insufficient copper ring → weak joints
- Poor edge routing tolerance → inconsistent geometry
5. Advantages of Half-Hole Technology
Half-hole PCBs provide several critical benefits:
5.1 Compact Design
Ideal for space-constrained applications like IoT modules
5.2 Easy Integration
Modules can be soldered directly without connectors
5.3 Strong Mechanical Bond
Better durability compared to pin headers
5.4 Cost Efficiency in Volume
Reduced assembly complexity lowers overall cost
6. Limitations and Challenges
Despite its advantages, half-hole technology comes with challenges:
- Higher manufacturing complexity
- Strict tolerance requirements
- Risk of edge plating damage
- Slightly higher cost than standard PCBs
However, these issues can be minimized with an experienced PCB manufacturer.
7. Applications of Half-Hole PCBs
Half-hole technology is widely used across industries:
Common Applications:
- IoT modules (WiFi, Bluetooth, Zigbee)
- RF communication boards
- Embedded systems
- Consumer electronics
- Industrial control modules
Example: Popular wireless modules often use castellated edges for easy motherboard integration.
8. Half-Hole PCB vs Other PCB Technologies
Half Holes vs Edge Plating
- Half holes: Used for interconnection
- Edge plating: Used for shielding or grounding
Half Holes vs Through-Hole Vias
- Half holes: External connection
- Vias: Internal signal routing
Half Holes vs SMT Pads
- Half holes: Provide stronger mechanical support
- SMT pads: Simpler but less robust
When to Choose Half Holes:
- Modular design required
- Frequent replacement or upgrade
- Compact layout needed
9. Cost Factors of Half-Hole PCB Manufacturing (2026)
Key Pricing Drivers:
- Layer count (2-layer, 4-layer, etc.)
- Material type (FR4, high-frequency materials)
- Hole size and tolerance
- Surface finish (ENIG is more expensive)
- Order quantity
Typical 2026 Pricing (USD):
| Type | Quantity | Price Range |
| Prototype (2-layer) | 5–10 pcs | $30 – $80 |
| Small batch | 50–100 pcs | $120 – $300 |
| Mass production | 1000+ pcs | $0.05 – $0.30 per unit |
Cost Optimization Tips:
- Standardize hole sizes
- Optimize panel layout
- Choose suitable surface finish
KingsunPCB offers competitive pricing with fast turnaround, making it ideal for both prototyping and volume production.
10. Choosing a Reliable Half-Hole PCB Manufacturer
Selecting the right partner is critical.
What to Look For:
- Experience with castellated PCB fabrication
- Advanced routing and plating capabilities
- Strict quality control processes
- Certifications (ISO, IPC standards)
- Fast lead times
Why Choose KingsunPCB:
- Proven expertise in half-hole PCB manufacturing
- High precision routing and plating technology
- Competitive 2026 pricing
- Reliable global delivery
11. Frequently Asked Questions (FAQ)
Q1: What is the minimum size for PCB half holes?
Typically 0.6 mm, but it depends on manufacturer capability.
Q2: Are castellated holes reliable?
Yes, when properly designed and manufactured, they provide strong and stable connections.
Q3: Can all PCB manufacturers produce half holes?
No. It requires specialized routing and plating expertise.
Q4: What files are needed for production?
- Gerber files
- Drill files
- PCB outline (mechanical layer)
12. Conclusion
Half-hole (castellated) PCB technology is a powerful solution for modern modular electronics design. It enables compact layouts, strong connections, and simplified assembly—making it ideal for IoT, RF, and embedded applications.
While it introduces some manufacturing complexity, working with an experienced supplier like KingsunPCB ensures high quality, competitive pricing, and reliable performance.