What is PCB Side Plating? How to Design PCB Edge Plating?
By PCBA PrototypePublished On: 2025-07-20Categories: Technical0 Comments on What is PCB Side Plating? How to Design PCB Edge Plating?
By PCBA PrototypePublished On: 2025-07-20Categories: Technical0 Comments on What is PCB Side Plating? How to Design PCB Edge Plating?
I. What is PCB Side Plating?
PCB side plating, also known as edge plating, refers to a copper plating that runs from the top to the bottom surface of the board and along (at least) one peripheral edge. It ensures secure connections of the PCB and reduces the risk of device failure, especially for small PCBs and motherboards. Common examples of such plating can be found in Wi-Fi and Bluetooth modules.
During the manufacturing process, the edges to be metallized should be milled before the copper plating process. After copper deposition, proper surface treatment is applied to the PCB edges.
II. When to Use PCB Side Plating?
Situations where edge plating is implemented:
- Enhanced current conductivity of the PCB is required
- Connections need to be made at the edge of the PCB
- The PCB needs protection against lateral impacts
- A secondary PCB is connected to the motherboard via its edge
- Edge soldering is needed to improve assembly
III. Types of PCB Side Plating
1. Full Wrap-around Edge Plating
Full wrap-around plating routes the metalized edge along the side after drilling. This routing process exposes the PCB sidewalls to electroless base copper, allowing it to be applied simultaneously with the drilling process.
In the following case, the base layer creates a conductive surface on which a thicker, more durable copper layer can be plated (for better adhesion).
Full Wrap-around Edge Plating
2. Copper-to-Board Edge
To avoid damaging the copper, we typically require a minimum distance between copper features and the PCB edge. These distances are:
- 0.25mm for outer layers with breakouts
- 0.40mm for inner layers with breakouts
- 0.45mm for all layers with V-cut notches
The copper-to-board edge distance should only be used for planes and large-area copper regions, where any minor damage to the copper will not affect the board’s performance. Traces should not be placed within the minimum distance from the board edge to prevent damage.
If pads are found within the minimum distance from the board edge, they will be trimmed back to restore the minimum copper-free space, unless:
- The pads are part of an edge connector (usually with a beveled edge)
- The pads are marked “up to board edge” on a separate mechanical layer
- Trimming exceeds 25% of the pad surface, which is considered an anomaly.
3. Plated Through Holes (PTH) at Board Edges
Board edge PTHs are plated holes cut at the edge of the circuit board, also known as butterfly holes. They are used to connect two PCBs either by direct soldering or via a connector. The edge of the PCB must have sufficient free space to secure the board in the production panel during manufacturing.
Pads must be present on the top and bottom layers to firmly anchor the plating to the board. For smaller sizes, a gold surface finish is preferred.
Here are some key considerations:
- The PCB edge must have enough free space to allow us to secure the PCB in the production panel during manufacturing.
- Pads must be placed on the top and bottom layers (and possibly inner layers) to firmly attach the plating to the PCB.
- As a general rule, holes should be as large as possible to ensure good soldering to the parent PCB; 0.80mm or larger is recommended.
- All surface finishes are acceptable, but gold is preferred over nickel for smaller sizes.
4. Rounded Edge Plating
Rounded edge plating means that most or part of the PCB or cutout is plated from the top to the bottom surface. It is primarily used to establish a good ground connection for metal enclosures or shielding. To produce boards with this type of plating, the board outline must be milled before the through-hole plating process.
100% edge plating is not feasible because the plating needs to be secured within the production panel during processing, so routing tabs must be used. For rounded edge plating, electroless nickel gold is the ideal surface finish.
Here are some points to note:
- Each side requires a copper strip to enable plating connection.
- 100% edge plating is impossible due to the need to secure the circuit in the production panel during processing.
- Clearly mark the areas requiring rounded edge plating on the mechanical layer.
- Selective electroless nickel gold is the only suitable surface finish for rounded edge plating.
IV. How to Design PCB Edge Plating?
1. PCB Edge Plating Guidelines
Define the plated copper areas using overlapping copper in the design/layout files; this additional copper deposition can be in the form of copper pads, surfaces, or traces.
To ensure the producibility of side plating, the metallized areas must be defined using overlapping copper (copper surfaces, pads, or tracks) in the CAD layout.
- Minimum overlap: 500μm.
- On connecting layers, a minimum 300µm connecting copper line must be defined.
- On non-connecting layers, copper should have a minimum gap of 800μm from the outer contour.
PCB Edge Plating Guidelines
2. Metallization Plating Process
This process only requires four steps in the following order: Drilling -> Milling the metal slot -> Desmearing -> Electroless copper plating
The outer contours requiring metallization must be milled before the through-hole plating process, as edge metallization is performed during this manufacturing step. After copper deposition, the desired surface finish is finally applied to the edges.
3. Manufacturing Issues
1. Copper peeling
Plating on large substrate surfaces may cause copper peeling due to poor adhesion. This issue is first addressed by roughening the surface using a combination of chemical and other proprietary methods. Then, the plating surface is prepared using direct metallization with higher copper bonding strength.
2. Burrs
In some plating processes, burrs may form during final processing. A modified proprietary process flow is required to polish burrs to the edge of the feature.
4. Foundry Considerations
- Excessively large gold pad antenna positions can affect soldering or signal transmission.
- Inner edge pads connected to wires on the board may cause short circuits.
- Stamp holes designed in the edge grinding slot must be processed in the second drilling step.
- Continuous metallization of the outer edge cannot be achieved by manufacturing individual PCBs as panels in a process-related manner. Metallization cannot be applied where small panel bridges are located. Sliding plated metallization layers can be covered with solder mask.
- When purchasing edge-sealed boards, it is necessary to confirm with the PCB supplier the possibility of manufacturing the PCB using the plating process and the extent to which the manufacturer can seal the edges of the PCB. Gerber files or factory drawings should indicate on the mechanical layer where sliding plating is needed and the required surface finish.
V. Benefits of PCB Edge Plating
- Enhanced current conduction
Improved current-carrying capacity increases the reliability and quality of the board. Additionally, proper conduction levels are ideal for components to function as required, and it protects vulnerable edge connections. - Signal integrity
Edge plating enhances signal integrity by preventing interference from entering internal electrical pulse transmission. - Heat dissipation
Since plated edges are metallic, they create additional cooling surface area to dissipate heat into the surrounding air. The metal surface improves the board’s reliability, especially when components are heat-sensitive. - Better EMC/EMI performance
Metallized edges allow stray currents to escape, preventing the generation of sporadic electric and magnetic fields. - Improved electromagnetic compatibility
Edge plating enhances the electromagnetic compatibility of multilayer boards. - Protection against electrostatic damage
Static electricity can strike sensitive components when handling the board, and the metal surface helps absorb static electricity.
VI. Applications of PCB Side Plating
- Improving EMC performance by shielding internal areas of multilayer boards (e.g., high-frequency circuit boards)
- Cooling function with edges as additional cooling surfaces, which can use active heat dissipation
- Enclosure connections
- Board-to-board connections (see plated half-holes)
The above is the knowledge about PCB side copper plating.
Related Posts
PCBA Prototype
April 6, 2025
PCBA Prototype
March 25, 2025
PCBA Prototype
March 14, 2025
