PCB Edge Plating

You might have heard this concept called “edge plating” or “castellation,” or” sideplating” , which all means: the copper plating that runs from the top to the bottom surfaces of a PCB, and runs along at least one of the perimeter edges. So portions of the printed circuit`s contour but also partial areas within the circuit board are metallized.

PCB Edge plating process is a standard common process, but it requires specialized equipment and well trained workers. If workers do not follow the right working instructions, edge plating circuit board (circuit board castellation) would cause the internal power planes to come to the edge of the board, it can short the edge plating.

PCB Edge Plating

The (outer) edges to be metallized, must be milled before the through-hole plating process, as the metallization of the edges take place during this production step.

After the deposition of copper, the intended surface finish is finally applied to the circuit board edges. For PCB edge plating we recommend the surface ENIG (chemical gold).

Several industries require edge-plated printed circuit boards, especially in applications that require better support function. You’ll find PCB edge castellation (PCB edge plating) applied in many applications, such as:

  • Improving current-carrying capabilities for better EMC performance such as High Frequency (HF) PCBs
  • Edge connections and protection (Being metallized to provide cooling function)
  • Edge soldering to improve fabrication
  • Better support for connections such as boards that slide into housing connection

PCB Edge plating requires precision handling of the printed circuit boards, chiefly around preparing the edges for plating and creating a lifetime adhesion for the plated material. This requires a controlled process during circuit board fabrication to limit any potential hazard for PTH and edge plating.

The most significant concern is the creation of burrs, which leads to discontinuities in PTH walls and limits the life of adhesion of the edge plating.

Venture have state-of-the-art printed circuit board edge plating lines, and has experienced many PCB designs that have required PCB edge plating. This allows us to overcome many problems in the industry.

We are able to keep quality to tight tolerances for PCB edge plating during proper execution of PCB edge castellation process, even after profiling. For technical details on the PCB edge plating process and specifications, please feel free to contact our sales team and we will be happy to answer all you questions.

PCB Edge Plating: The Ultimate FAQ Guide

With PCB edge plating, you can improve the performance of printed circuit boards.

So, if you’re wondering how to metallize your PCBs, this guide offers a perfect solution for you.

Keep reading to learn more.

What is PCB Edge Plating?

PCB edge plating refers to the metallization of the sides of a printed circuit board across its height.

You can carry out edge plating on just one of the board edges or all round.

Through edge plating, you equip the board with a reliable connection and rigidity.

Consequently, you find edge plated boards do not easily succumb to the failure of various board aspects.

 PCB Edge Plating

PCB Edge Plating

How is the Edge Plating Process Handled?

The edge plating process is one that requires fastidiousness to overcome the challenges with laying the plating.

For you to properly execute an edge plating process, you require special equipment and decent skills.

Before a PCB edge is plated, it requires decent handling and preparation for cohesion with the plating.

The plating is to remain attached to the edge for as long as the board is in operation.

Furthermore, the soldering process for the edge plating has to be controlled to avoid damage to the interlayer through-hole connections.

The utmost concern is afforded to the process to prevent the formation of burrs.

Burrs can cause catastrophic board failure.

Where is Edge Plating Used?

Plating PCB edges has been practiced across various industries for various usages.

Some of the common areas where you will find edge plating are:

  • Where there is a need to enhance the conductivity capabilities of a PCB.
  • Where connection is to be established along the edge of the board.
  • Where the printed circuit board requires protection from lateral shocks.
  • Where soldering of the edge is sought to improve the PCB construction.
  • Where secondary boards are used and connected to the mainboard through edge connections.

Are the Internal Power Planes Connected to the Edge Plating?

When plating the edge of a circuit board, it is paramount for no contact to exist with the buried power layers.

Since both the power planes and edge plate are conductive, their interaction can result in an electrical short.

As a result, board failure can follow such an occurrence.

You find it important to provide a space allowance when attaching an edge plating.

The gap serves to prevent the interaction of the board’s internal conductive layers with the plating.

Why does the Edge Plating Peel Off?

A PCB edge plating can peel off, mainly when applied over an extended area.

The leading cause of peeling is attributable to inadequate adhesion forces.

You can increase the strength of your adhesion by coarsening the edges before the plating process.

Roughing the edges can be facilitated by the use of chemicals or abrasion.

Moreover, when plating the edge, direct metallization is preferable.

Using this method ensures the formation of a stronger bond between the copper plating and the surface.

Printed-circuit-board-edge

Printed circuit board edge plating

What are some of the Benefits of PCB Edge Plating?

PCB edge plating is associated with numerous advantages that allow you to derive your board’s maximum use.

You find edge plating of PCBs particularly useful with high-frequency boards where signal quality is of concern.

When you employ PCB edge plating, you increase a circuit board’s electromagnetic compatibility for multilayer constructions.

The metallization of the edges acts as a shield to the inner planes of the circuit board.

The interference of signals emanating from external sources is thereby minimized.

Furthermore, printed circuit boards with edge plating are protected from electrostatic damage that can occur during handling.

With the edges plated, the potential levels that the board is subjected to will be similar to the handler’s.

How does Electroplating in PCB Construction Affect PCB Edge Plating?

Electroplating is a method of depositing a metal layer on a surface.

In multilayer printed circuit board constructions, the conductive layers are connected through drilled holes made conductive via electroplating.

The walls to the through-holes are layered with copper by a cathode and anode based plating process.

A continuous conductive path for electrical signals is thus created.

You find these through-holes connecting multiple layers can be slotted or milled to suit different performance needs.

Furthermore, in such a structure, plating the edge will involve tinkering with the production flow.

For instance, the surface has to be prepped before the electroplating of the interlayer connection path.

Additionally, the contours can be scored or nicked to increase adhesion strength.

Through these processes, the contours can be made to feature across the PCB height or to a certain thickness.

Furthermore, a complete edge plating will require non-plated groves for panel securing.

Thus, you find the procedures used for electroplating the through-holes can be employed for the edge plating.

The resulting costs are, therefore, minimized since there are no new processes or equipment involved.

Does PCB Edge Plating Impact Thermal Performance?

Edge plating was primarily developed for the regulation of the electromagnetic characteristics of PCBs.

However, using edge plating was seen to improve the thermal performance of the circuit board.

Thermal issues are a concern, especially where board performance is increased while the size is reduced.

Channeling the dissipated heat safely away becomes an important consideration.

When heat is allowed to build-up, it poses a significant threat to the circuit board’s functionality.

It can result in thermal-induced strains that could damage the board.

Several contingencies are put in place to combat the thermal situation on a circuit board.

You find the conductive traces packed with wider spacing while the use of heat sinks is also regarded.

However, these strategies are nonetheless costly in terms of diminishing performance and acquiring equipment, respectively.

Using edge plating on PCBs, however, kills two birds with one stone, literally.

While it manages the board’s EMC levels, its connection to the conductive layers allows it to conduct away surface heat.

The heat is efficiently dissipated to the environment from the edge.

 PCB edge plating

PCB Edge plating

How is Signal Integrity Upheld with PCB Edge Plating?

PCB edge plating was put forward as a measure to control the circuit board’s electromagnetic properties.

Notably, the quality of signals is maintained from the generation point and its transfer to the reception point.

Typically, the signal quality is vulnerable to interference on its path.

When cabling is used for signal transfer from the circuit board, the signals are no longer shielded by the inner planes.

Consequently, at this point, the signals may be hampered, affecting their quality.

However, plugs can be employed alongside the cables and PCB plating to safeguard the signals’ quality.

In this case, the PCB edge plating is furnished with plugs to provide a transmission path for the differentiated signals.

The plug is constructed with a plane of reference on a metal plate.

The reverse of this metal plate facade is joined with the edge plating.

Can you Apply a Surface Finish to PCB Edge Plating?

Yes, you can.

Copper is commonly employed as the metal for PCB edge plating.

Preferment of copper is because of its good conductivity and low resistance.

However, copper is prone to corrosion induced by oxygen presence.

Consequently, the copper plating has to be protected to prevent its deterioration that could hamper its functionality.

Surface finishes are employed to offer the copper metal used in edge plating protection from corrosion.

A PCB surface finish prevents the interaction of the underlying copper with oxygen, thus maintaining its structural integrity and functionality.

Furthermore, it offers a long service life to the edge plating.

What are some of the Surface Finishes you can Employ on PCB Edge Plating?

There are several surface finishes available in PCB fabrication.

Many factors affect the choice of surface finish, such as availability, cost, ease of application, and even environmental concern.

Standard surface finish types include the Electroless-Nickel Immersion Gold (ENIG), Immersion Silver, Immersion Tin, and Hot Air Solder Leveling.

Immersion finishes are applied by chemically depositing the preferred metal ions over the copper plating.

On the other hand, hot air solder leveling is employed by bathing the plating in solder.

The solder contains lead and tin elements and is thereafter leveled by a hot air stream to produce a uniform surface.

Why is ENIG Preferred Over other Surface Finishes for PCB Edge Plating?

Electroless Nickel Immersion Gold is a two-part finish encompassing nickel and gold elements. In this process, the edge plating is electrolessly deposited with a nickel layer.

Afterward, a gold layer is chemically deposited via the immersion method to protect the nickel layer from corrosion.

You find the use of this finish type is favored for reasons such as its durability.

As such, you can obtain a long service life from an ENIG finish without having to perform a rework.

Additionally, the resulting surface achieved is even and smooth, providing high aesthetic value.

Even so, using an ENIG finish adequately protects the copper plating from corrosion.

Why is it Difficult to Carry Out All-round PCB Edge Plating for large productions?

An all-round edge plating process of the PCB involves the metallization of the edge of a PCB across its perimeter.

Such an endeavor is possible for a prototype or a single board.

However, it poses a challenge in large volume PCB fabrication.

The difficulty in achieving an all-round edge metallization is compounded by the fabrication of large PCB volumes on panels.

In this case, a panel typically consists of multiple boards furnished on a single piece to simplify the fabrication process.

Separation is only done at later stages when the fabrication process and assembly is completed.

Therefore, edge plating the board sides sharing boundaries with other boards on the panel is virtually impossible.

What is Wraparound Edge Plating?

Wraparound edge plating is a form of edge plating where the board edge is metalized all-round to offer conductive services particularly.

A wraparound plating is employed instead of a via system.

To conveniently execute the wrapping process, you need to route the PCB along the edge following the drilling process.

Routing allows you to bare the PCB edge for copper deposition during the electroless metallization process for the interlayer through-holes.

Consequently, you can simultaneously carry out the plating process for both.

Thereafter, you can deposit another copper layer through electroplating, which will achieve better adhesion to the electroless film.

How Different is Castellated Edge Plating?

With castellated edge plating, the plating does not entirely cover the edge of the circuit board.

Instead, castellated edge plating involves the connection by plating of successive drilled holes.

The holes are plated, extending to the PCB boundary from where they are routed.

Castellated edge plating is particularly useful when peripheral board connections are to be used.

Such peripheral devices can be modules or slaves that are employed to augment a device’s performance.

The castellations are organized such that they are in alignment with the landing pads of the mainboard.

What are the Common Problems with Castellated Edge Plating?

Applying castellated edge plating is a process guided with close tolerance values that are difficult to adhere to.

The situation is exacerbated by the hole sizes that are small and, therefore, sensitive to tolerance deviations.

Common problems observed include the following.

In such a system with close tolerances and small design aspects, misalignment occurs at the slightest shift.

Such shifts can be expressed when the PCB is taken through different fabrication processes.

Consequently, the work area for edge plating installation is vastly reduced.

Furthermore, you note that the drilled holes are perpendicular to the board edge and unsecured.

As a result, when carrying out the final routing procedure, they can slide out.

This can hinder the overall process by encroaching into the split holes that could damage the interlayer structure when removed.

How do you Achieve EMC Stability in PCB Edge Plating?

Electromagnetic compatibility (EMC) is an agglomeration of various aspects such as emission and immission.

You find a system is said to have EMC stability if it lacks the inherent generation of interferences.

Also, when a system is not prone to externally generated interferences, it is stable.

An electromagnetic system is built up in a PCB from the various planes used in signal transfer.

These planes provide a path for electrical signal transfer constituting the power and ground planes.

Furthermore, the employment of specific board peripherals such as memory drives will also impact the EMC standards.

The ground plane provides a path for a return signal through the power plane.

Thus, an electromagnetic field is created not just in the x and y dimension but also in the z-axis. The generated field needs to be contained to prevent its signals from causing interference, hence the need for a shielding system.

An adequate shield has to cover all three axes of influence.

Shielding in the x and y-axis is achieved by positioning the signal planes as a PCB’s internal layers.

Edge plating the PCB provides a metal barricade across the board’s height, effectively providing shielding in the z-axis.

Consequently, higher EMC stability is achieved this way.

Depending on your specific needs, Venture Electronics offers the perfect solution in PCB edge plating.

Contact us now for the best solutions in your PCB fabrication needs.

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