Castellated Boards vs. Standard PCBs: What's the Difference

In the world of electronics manufacturing and prototyping, printed circuit boards (PCBs) form the backbone of almost every device. Among the many types of PCBs, two often compared options are castellated boards and standard PCBs. While they may serve similar functions in connecting components and routing signals, their construction, purpose, and integration methods vary significantly.

This article explores the primary differences between castellated and standard PCBs, the use cases where each shines, and what engineers and product designers need to know before choosing one over the other.

1. What Are Castellated Boards?

Castellated PCBs, also known as castellated circuit boards, feature semi-plated holes or vias that are cut through along the edge of the board. These notched, plated holes resemble castle battlements—hence the term "castellated."

Unlike standard PCBs with complete via holes, the partial holes on castellated boards allow them to be soldered onto another PCB much like a surface-mounted device. This unique feature enables module-to-board soldering for devices such as RF modules, Bluetooth chips, and power supply modules.

2. What Are Standard PCBs?

Standard PCBs are the most commonly used circuit boards and serve as the foundation of countless electronic devices. They are typically manufactured using layers of conductive copper and insulating material (such as FR4) and contain plated through-holes (PTH), vias, and pads for mounting components.

Standard PCBs come in single-layer, double-layer, and multi-layer configurations, depending on the circuit’s complexity. Unlike castellated boards, standard PCBs are not intended to be surface-mounted onto another PCB.

3. Key Differences Between Castellated Boards and Standard PCBs

Let’s explore the main differences that set these two types of PCBs apart:

a. Edge Design

• Castellated Boards: Feature plated, half-cut holes along one or more edges.

• Standard PCBs: Typically have solid edges with no plated cutouts.

The edge structure in castellated designs enables a more integrated, modular connection, often acting as a sub-PCB.

b. Integration and Mounting

• Castellated Boards: Designed to be soldered onto a larger board—ideal for pre-assembled modules or breakout boards.

• Standard PCBs: Act as standalone circuit boards that host components directly and don’t integrate via edge soldering.

This makes castellated PCBs a preferred choice for scalable production or modular system design.

c. Use Cases

• Castellated Boards:

  • Wireless communication modules

  • Embedded microcontroller boards

  • Compact plug-in modules

• Standard PCBs:

  • Complete consumer electronics

  • Power electronics

  • Wearables and industrial controls

4. Benefits of Castellated PCBs

Despite the added complexity in manufacturing, castellated boards offer several advantages:

• Modularity: Enables designers to create plug-and-play modules.

• Space Efficiency: Saves board real estate by stacking or embedding functionality.

• Ease of Testing: Individual modules can be tested before integration.

• Cost Reduction in the Long Term: Easier to replace or upgrade modules than entire systems.

5. Design and Manufacturing Considerations

Choosing between a castellated board and a standard PCB isn’t just about functionality—it also involves assessing your project’s production requirements.

a. Tolerances

The castellated edges PCB must be precisely milled to align perfectly with the mating board. Tighter tolerances mean higher fabrication costs.

b. Plating Quality

Because castellated vias are partially cut, poor plating can lead to connectivity issues during soldering.

c. PCB Stack-Up

If the castellated board is multi-layered, care must be taken to ensure the internal copper layers align with the castellated edges. This is not usually a concern with standard PCBs unless they feature edge connectors.

Final Thoughts

Both castellated boards and standard PCBs have distinct roles in electronics manufacturing. Castellated boards are ideal for modular, space-saving designs where components are soldered directly onto another board. Standard PCBs, on the other hand, are versatile, cost-effective, and suitable for a wide range of applications from simple gadgets to complex machinery.

Understanding the structural and functional differences between these two types of boards helps developers make informed design choices. With precision fabrication and proper design practices, manufacturers like PCB Runner ensure that both castellated and standard PCBs meet the performance demands of modern electronics.