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What is Exposed Copper on PCB​? PCB Exposed Copper Edge
Friday, August 1st, 2025

When looking at a printed circuit board (PCB), you may notice shiny areas of metal that aren’t covered by the usual green or colored solder mask. These are areas of exposed copper on PCB, and they serve important roles in how the board functions. Exposed copper can be found on pads, traces, or even along the edges of the board. But why is the copper left uncovered? And how do you design a PCB to safely include exposed copper?

In this article, we’ll explore the meaning, purpose, types, and design considerations for exposed copper on PCB, including how to manage its risks and where it’s commonly used.

What is Exposed Copper on PCB​? PCB Exposed Copper Edge

What Does Exposed Copper on PCB Mean?

In a PCB, exposed copper refers to areas where the copper layer is intentionally left uncovered by solder mask or surface finish. Normally, copper traces and pads are coated with a protective layer to prevent oxidation and corrosion. However, in certain parts of the board, copper is left exposed for electrical or mechanical reasons.

You’ll typically see exposed copper in places where components need to be soldered or where the board makes direct contact with another surface, such as in connectors or test points. These areas must have direct electrical contact, and that means the copper needs to remain accessible.

Where Is Copper Usually Exposed?

  • Component pads: These areas must be exposed for soldering.
  • Test points: Used for measuring signals during testing.
  • Thermal reliefs: Copper areas used to help dissipate heat.
  • Edge connectors: Known as pcb exposed copper edge, these are found on plug-in boards.
  • Copper pours: Large copper areas, sometimes left exposed to improve thermal or grounding performance.

Purpose of Designing Exposed Copper on PCB

Designing with exposed copper is a common and often necessary practice. Below are some of the most common reasons designers choose to expose copper on a PCB.

1. Electrical Contact

Soldering requires exposed copper. All component pads, whether for surface mount or through-hole components, need to be bare so solder can properly adhere and form a good electrical connection.

In addition to pads, test points are exposed copper areas used during assembly and troubleshooting. Probes can be placed on these spots to measure voltages or signals.

2. Thermal Management

Copper is an excellent conductor of heat. In high-power applications, such as LED lighting, motor drivers, or power supplies, leaving copper exposed can help manage heat by allowing it to dissipate more efficiently. Large exposed copper plates can act like heat sinks.

3. Grounding and Shielding

In many designs, especially in radio frequency (RF) or high-speed digital circuits, exposed copper design PCB layouts include areas for grounding or electromagnetic interference (EMI) shielding. A pcb exposed copper edge can also be connected to ground and used as part of the shielding structure to protect signal integrity.

4. Cost Considerations

Leaving copper exposed in non-critical areas can reduce costs. Surface finishes like ENIG or HASL add expense, so in low-cost or temporary boards, some copper may be left bare to save on manufacturing steps.

What is Exposed Copper on PCB​? PCB Exposed Copper Edge

Types of Exposed Copper PCB Designs

There are several ways exposed copper is used in PCB layouts, each serving a specific function depending on the design goals. Below are the most common types you’ll find, along with their applications and things to watch out for.

1. Exposed Copper Pads

Exposed copper pads are the most widely used type of exposed copper in any PCB. These are the metal areas where components are soldered onto the board. By design, they must remain uncovered to allow solder to create a solid electrical and mechanical connection between the component leads and the PCB’s copper layers.

In addition to component soldering, some exposed pads are used for mechanical support or to connect heat-generating parts to large copper pours for better heat dissipation. Proper surface finish on these pads—such as HASL or ENIG—helps prevent oxidation and improves solderability.

2. Exposed Copper Traces

In some designs, traces (the thin copper lines connecting different components) are intentionally left exposed. This is less common than exposed pads, but it’s done in specific cases where designers need direct access to the trace for testing or where the trace carries high current and benefits from better heat dissipation.

One common use for exposed copper traces is creating test points. By leaving a section of trace uncovered, engineers can place probes directly on the trace during testing or troubleshooting.

3. PCB Exposed Copper Edge

A pcb exposed copper edge refers to copper that runs right to the edge of the PCB and remains exposed for functional use. This is typically found in boards that need to connect to sockets or other boards via edge connectors. In these cases, the copper along the edge acts as contact points and must remain exposed for reliable electrical connection.

This type of exposed copper is also used for grounding purposes. For example, in RF circuits or high-speed digital designs, the board edge may have exposed copper connected to ground to reduce electromagnetic interference (EMI). Some designs use edge plating, where the copper is plated along the entire edge of the board to create a continuous conductive path.

What is Exposed Copper on PCB​? PCB Exposed Copper Edge

What Is the Clearance of Copper to Edge of PCB?

When designing PCBs, copper-to-edge clearance is critical. Copper should not be placed too close to the edge unless it is meant to be exposed. If copper unintentionally gets too close to the edge, it can cause manufacturing problems or failures in the field.

Industry Guidelines

Standard practice, according to IPC standards, recommends at least 0.25mm (10 mils) clearance between copper and the board edge. This clearance prevents copper from being damaged or exposed during board cutting.

Edge Copper Design

If you’re designing a pcb exposed copper edge, such as for a connector or grounding point, you can extend copper to the edge, but it must be plated and processed correctly. Special instructions are needed for the manufacturer to plate the edges and prevent delamination.

How to Design a PCB with an Exposed Copper Plate?

Designing exposed copper areas requires planning and proper use of your PCB design software.

Step 1: Define Copper Areas

Use copper pours, pads, or large planes for the areas you want exposed. Ensure they are connected to the correct net, whether ground, power, or signal.

Step 2: Disable Solder Mask

In your PCB layout tool, disable the solder mask over these areas. This is done by creating a solder mask opening in the relevant layer.

Step 3: Edge Exposure

For pcb exposed copper edge designs, extend the copper to the edge of the board. Indicate this clearly in your mechanical drawings. Some manufacturers require a note to plate the edge.

Step 4: Selective Surface Finish

Decide whether the copper will remain bare or have a finish like HASL (Hot Air Solder Leveling) or ENIG (Electroless Nickel Immersion Gold). These finishes prevent oxidation and improve durability.

What is Exposed Copper on PCB​? PCB Exposed Copper Edge

Risks and Challenges with Exposed Copper PCB

While exposed copper on PCB serves many useful purposes, it comes with challenges.

Oxidation and Corrosion

Copper oxidizes quickly in air, forming a dull brown or green layer. This can reduce conductivity and make soldering difficult. Moist environments accelerate this process.

Short Circuits

Exposed copper is more likely to cause shorts if it touches other metal objects. Extra care is needed in design and assembly to avoid accidental contact.

Handling Risks

Bare copper areas can be scratched or contaminated during handling. Fingerprints, dust, or moisture can affect performance. Protective packaging and careful assembly help reduce these risks.

Exposed Copper Design Guidelines in PCB Layout

Here are some helpful tips for designing exposed copper areas safely:

  • Maintain clearance from high-voltage areas unless insulation is provided.
  • Use protective coatings like conformal coating if the board will be exposed to harsh environments.
  • Clearly indicate exposed copper areas in your Gerber files and fabrication notes.
  • For pcb exposed copper edge, work with your manufacturer to ensure proper plating and durability.
  • Use thicker copper (e.g., 2 oz) for large exposed areas meant for heat dissipation or high current.

FAQs

1. How to remove copper from PCB board?

Copper can be removed through chemical etching using ferric chloride or similar solutions. It can also be scraped off mechanically or milled with CNC tools.

2. What happens to exposed copper?

Exposed copper oxidizes when exposed to air and moisture. This can affect electrical performance, so protective finishes or coatings are often applied.

3. Can exposed copper PCB be used outdoors?

Not directly. Outdoor use requires additional protection, like conformal coating, to prevent corrosion. Without protection, copper will degrade quickly.

4. How do I prevent oxidation on exposed copper areas?

Apply coatings such as OSP (Organic Solderability Preservative), clear lacquer, or conformal coating. Using surface finishes like ENIG or HASL also helps.

5. What surface finish is best if I want partial copper exposed?

ENIG and HASL can be applied selectively. Masking during the finishing process allows partial copper exposure where needed.

6. Is exposed copper safe for high-voltage applications?

Not unless proper spacing and insulation are used. High voltage requires strict clearance and protection to avoid arcing or shorts.

7. What’s the difference between exposed copper and plated finish?

Exposed copper has no added layer, while plated finishes like ENIG or HASL add protection and improve performance.

What is Difference: Exposed Copper on PCB, Bare Copper PCB?
Friday, August 1st, 2025

Exposed copper on PCB is often seen in circuit designs where certain copper areas are left uncovered. These areas serve specific functions, especially for soldering or electrical connections. Knowing how this differs from a bare copper PCB helps you choose better solutions for your needs.

Best Technology has been manufacturing PCBs and providing PCBA service to a very crowded market for over 19 years. We have a competitive edge in this area through precision processing and the customization capability, our all-process quality control system, as well as through delivery efficiency and the full turnkey EMS PCB service. Our engineering team has rich and valuable experience in optimizing exposed copper on PCB performance, improving the solderability, and the heat dissipation. There is no MOQ limit; you can enjoy the prototype, small quantity trial order, or large volume mass production service. We have the project managers to follow your project. If there is any engineering project, we will give feedback to you to avoid errors and repeated work.

It would be great if you could discuss the exposed copper on PCB requirement in the initial stages of the project, so that we could ensure the optimization from the DFM to the SMT PCBA process. There is 100% appearance checking before shipping, to ensure that there is no oxidation of exposed copper on PCB in your goods batch. Just let us know your exposed copper on PCB requirement, like exposed copper on PCB edge, special pad sizes, and heat dissipation copper surfaces at sales@bestpcbs.com, we will make every effort to meet your any customized exposed copper design requirements.

What is Difference: Exposed Copper on PCB, Bare Copper PCB?

What Does Exposed Copper on PCB Mean?

Exposed copper refers to any area on a printed circuit board (PCB) where the copper surface is not covered by solder mask or surface finish. These areas may include pads, trace edges, or specific zones designed for heat dissipation. Exposed copper is intentionally left uncovered to allow for soldering, electrical connection, or thermal transfer.

To maintain performance and avoid oxidation, these exposed areas are usually protected by a plating layer such as gold (ENIG) or an organic coating like OSP. Without this protection, the copper can easily oxidize, affecting the reliability and lifespan of the PCB.

What Does Exposed Copper on PCB Mean?

What is Copper Pour in PCB?

Copper pour is a design technique where a large area of a PCB is filled with copper. It can help reduce electrical noise, improve thermal management, and support grounding. Sometimes these poured areas are also exposed, depending on the design. Exposed copper pours need a surface finish to prevent oxidation and maintain performance.

What is Difference: Exposed Copper on PCB, Bare Copper PCB?

While both terms seem similar, they have key differences:

  • Exposed copper on PCB means certain parts of the board, like pads or edges, are uncovered for specific use.
  • Bare copper PCB refers to boards without any surface finish. The entire copper area is exposed, with no protection from oxidation or wear.

A board with exposed copper may still have other areas finished with ENIG, HASL, or silver coating. Bare copper PCBs, however, have no such finishes. They are cheaper but require careful handling and storage. In contrast, exposed copper is part of a planned design and used with protective finishes.

What are the PCB Surface Finish Types in Exposed Copper on PCB?

For exposed copper on PCB, surface finishes are used to protect the open copper areas. Each type has specific benefits depending on your application. The most common finishes include:

  • ENIG (Electroless Nickel Immersion Gold): Offers excellent durability and solderability. It protects exposed copper from oxidation and gives a flat surface for fine-pitch components.
  • Immersion Silver: A cost-effective option that works well for high-speed or high-frequency circuits. It provides a smooth surface and reliable performance but requires careful handling to prevent tarnish.
  • HASL (Hot Air Solder Leveling): Widely used and budget-friendly. It coats exposed copper with solder, which protects it and makes soldering easier, though it may not be ideal for very small components.
  • OSP (Organic Solderability Preservative): This eco-friendly coating is used mainly for short-term protection. It is easy to apply and affordable but not suitable for long-term storage.

Choosing the right finish helps you avoid oxidation and supports the function of exposed copper areas. Best Technology provides expert advice on which surface finish matches your product and performance goals.

How to Prevent Oxidation on Exposed Copper on PCB Edge?

The exposed copper on PCB edge is often used for grounding, shielding, or connectors. However, it’s prone to oxidation due to its location. To prevent this:

  • Use ENIG or immersion silver finish on the edge to seal the copper.
  • Store PCBs in dry, anti-static packaging to reduce moisture contact.
  • Apply conformal coating if the edge won’t be soldered, providing extra protection.

Best Technology supports custom edge protection methods to suit different applications, helping you avoid failures caused by corrosion or wear.

ENIG vs Immersion Silver PCB Finish: Which PCB Finish Is Better for Exposed Copper?

When comparing ENIG PCB finish and immersion silver PCB finish, both protect exposed copper but suit different needs:

  • ENIG offers better durability, excellent flatness, and is ideal for complex boards.
  • Immersion silver has lower cost and works well in high-frequency applications, but it needs careful storage to avoid tarnishing.

At Best Technology, we guide customers to choose the right finish for exposed copper areas, ensuring long-term performance and easy assembly.

How to Fix Exposed Copper on PCB?

Fixing exposed copper often depends on whether it’s intentional or a result of damage. If it’s unintentional, here’s what you can do:

  • Apply a solder mask or conformal coating to cover the copper.
  • For critical areas, add a surface finish like ENIG or HASL.
  • In repair cases, use solder to reflow and seal the copper trace or pad.

To avoid these issues, work with trusted manufacturers. Best Technology ensures all exposed copper areas are well-finished or protected, based on your specifications.

How to Fix Exposed Copper on PCB?

What’s the Pros and Cons of Exposed Copper on PCB?

Pros:

  • Allows easy soldering for components and connectors.
  • Supports grounding and thermal management.
  • Useful for test points and current paths.

Cons:

  • Risk of oxidation without surface finish.
  • Needs careful handling during assembly and storage.

With expert support, the benefits outweigh the risks. Best Technology applies the right surface finish to every exposed copper section, ensuring reliable results for your product.

Why Work with Best Technology for Exposed Copper Solution?

Many customers worry about exposed copper causing failures due to oxidation or poor soldering. Others face delays, low communication, or inconsistent quality from suppliers. At Best Technology, we solve these problems with:

  • A professional engineering team who understands your design and guides finish selection.
  • Strict quality control to ensure every board meets your needs.
  • Fast response times, full traceability, and clear communication throughout production.

We provide a smooth experience, reduce risks, and help you deliver high-quality products to your market quickly. Contact Best Technology at sales@bestpcbs.com for reliable PCB solutions and support for exposed copper designs.

Ultimately, exposed copper on PCB plays a vital role in modern circuit design. Whether used for soldering, grounding, or heat dissipation, these uncovered copper areas must be protected to maintain performance and prevent oxidation. Knowing the difference between exposed copper and bare copper PCBs, along with the right surface finish options like ENIG or immersion silver, helps ensure better product quality and reliability. Any technical problem or any PCB inquiry, just call us at +86-755-2909-1601 or at sales@bestpcbs.com.