PCB edge plating, also known as PCB edge plating or edge metallization, is a specialized process used in the manufacturing of printed circuit boards (PCBs). This technique involves applying a layer of metal, typically copper, to the edges of a PCB. The purpose of PCB edge plating is to enhance the conductivity, durability, and electromagnetic compatibility of the board’s edges while also providing a more robust mechanical structure.
What is PCB edge plating?
PCB edge plating, also known as edge plating, is the copper plating from the top to bottom surface of the board and along (at least) one perimeter edge. PCB edge plating provides a strong connection to the PCB and reduces the possibility of device failure, especially for small PCBs and motherboards, examples of this plating are commonly found in Wi-Fi and Bluetooth modules.
During the manufacturing process, the edges to be metallized should be milled prior to the copper plating process. Proper surface preparation of the PCB edges after copper deposition.
When to use PCB edge plating?
- Need to improve the conductivity of PCB
- Connections are required at the edge of the PCB
- PCB needs protection from lateral impact
- The secondary PCB is connected to the main board through the edge
- Welded edges are required to improve fit
PCB edge plating types
1. Surround edge plating
Surround plating routes the metal edges along the sides after drilling, and the routing process exposes the PCB sidewalls to the electroless base copper so that it can be applied simultaneously when applied to the drilled holes.
2. Edge of copper board
To avoid damaging the copper, we generally require a minimum distance between copper features and the edge of the PCB. This distance is:
- 0.25 mm outer layer with break
- 0.40 mm inner layer with break
- 0.45 mm on all layers with V-cut notches.
3. Board edge PTH
Board edge PTH is a plated hole cut on the edge of the circuit board, also known as a butterfly hole, used to solder two PCBs through direct soldering or through a connector. There must be enough free space at the edge of the PCB to secure the board in the production panel during the manufacturing process.
There must be pads on the top and bottom layers to securely hold the plating to the board. For smaller sizes, a gold finish is preferred.
4. Round-edge electroplating
Round edge plating means that most or part of the PCB or cutout is plated from top to bottom. Mainly to establish a good ground for the metal case or shielding purposes. To produce this board with this plating, the board profile is milled prior to the through-hole plating process.
Since the plating needs to be fixed within the production panel during processing, 100% edge plating is not feasible and there must be some issues with placing the routing tabs. For round-edge plating, electroless nickel gold is the ideal finish of choice.
How to design PCB edge plating?
1. PCB edge plating guidelines
Overlay copper is used in design/layout files to define copper-plated areas, this additional copper deposition can be copper pads, surfaces or traces.
To guarantee the manufacturability of the side panels, the metallization areas must be defined in the CAD layout with overlapping copper (copper surfaces, pads or tracks).
- Minimum overlap: 500 μm.
- On the connected layer, the min. A connecting copper wire of 300µm must be defined.
- On non-connected layers, copper should have a minimum clearance of 800 µm from the outer contour.
2. Metallized electroplating process
There are only four steps to be performed in the following order: Drilling -> Milling the metal slot -> Removing dirt -> Electroless copper plating
The outer contours that require metallization must be milled prior to the through-hole plating process since the metallization of the edges takes place in this manufacturing step. After the copper is deposited, the desired surface finish is finally applied to the edges.
3. Manufacturing problems
1. Copper peeling – on large substrates
Plating on the surface may cause the copper plating to peel off due to lack of adhesion. This problem first needs to be addressed by roughening the surface through a combination of chemical and other proprietary methods. Next, direct metallization with higher copper bond strength is used to plate the surface.
2. Burr-Edge Plating
In some plating processes, burrs can be created during the final machining. A modified proprietary process flow is required so that the burrs are polished to the edge of the feature.
Benefits of PCB edge plating
1. Enhanced current conduction
Increased current carrying capacity improves board reliability and quality. Additionally, the correct level of conduction is ideal for components to perform as required, and it also protects vulnerable edge connections.
2. Signal integrity
Edge plating enhances signal integrity by preventing interference from entering the internal electrical pulse transmission.
3. Heat distribution
Since the plated edges are metallic, they create an additional cooling surface area that is used to dissipate heat to the surrounding air. The metallic surface improves the reliability of the board, especially when components are heat sensitive.
4. Better EMC/EMI performance
Metalized edges allow stray currents to escape, preventing sporadic electric and magnetic fields.
5. Improve electromagnetic compatibility
Edge plating enhances the electromagnetic compatibility of multilayer PCB.
6. Prevent electrostatic damage
When handling circuit boards, static electricity can hit sensitive components, and metal surfaces help absorb static electricity.
Application of PCB edge plating
- Improves EMC performance by shielding multi-layered internal areas such as high-frequency PCB
- Cooling function of the edge as an additional cooling surface, active cooling can be used
- Shell connection
- Board-to-board connection
PCB edge plating, also known as edge plating, is the copper plating from the top to bottom surface of the board and along (at least) one perimeter edge. PCB edge plating provides a strong connection to the PCB and reduces the possibility of device failure, especially for small PCBs and motherboards, examples of this plating are commonly found in Wi-Fi and Bluetooth modules.
- Need to improve the conductivity of PCB
- Connections are required at the edge of the PCB
- PCB needs protection from lateral impact
- The secondary PCB is connected to the main board through the edge
- Welded edges are required to improve fit
1. Enhanced current conduction
2. Signal integrity
3. Heat distribution
4. Better EMC/EMI performance
5. Improve electromagnetic compatibility
6. Prevent electrostatic damage
