If you're a PCB designer, you've probably heard senior engineers talking about "isolated copper" or "dead copper." These two terms refer to the same thing – copper traces on the PCB that are "unconnected." They may seem insignificant, but if not handled properly, they can cause the entire board's performance to collapse, or even lead to product failure! Today, we'll explain the dangers of isolated copper and how to solve the problem in simple terms, so even beginners can understand it easily!

First, let's understand: What is "isolated copper"? Why does it occur?

Simply put, isolated copper is copper trace on the PCB that is "isolated"—it doesn't have a defined electrical property and isn't connected to any circuit network (such as GND or VCC), like an "orphan" on the circuit board.

This isolated copper isn't intentionally designed; it's mostly an "accident" that occurs after copper pouring: either the components on the PCB are too densely packed, or the routing is too complex, preventing the copper from completely covering the area, leaving a small piece of "scrap" that isn't connected to any network. Don't think this is a minor problem; its destructive power is far more serious than you imagine!

Beware! The 6 Major Hazards of Isolated Copper, Directly Affecting Product Reliability

Many beginners think, "It's just a small piece of copper, no need to worry," but in actual projects, untreated isolated copper can cause a series of problems, even rendering all previous efforts useless:

• Antenna Effect

Isolated copper acts like a hidden antenna, actively receiving and radiating electromagnetic waves. Especially in high-frequency circuits, it severely enhances electromagnetic interference, leading to signal crosstalk and increased noise, making signal transmission a chaotic mess;

• Noise Propagation

It becomes a "propagation channel" for high-frequency noise. Nearby sensitive signals (such as PWM signals and clock lines) are easily interfered with, resulting in signal jitter and distortion, ultimately affecting product functionality;

• Distributed Capacitance Coupling

Isolated copper and adjacent wires form "invisible capacitors," which not only couple noise but also change the impedance characteristics of the signal, a "fatal blow" to high-speed signal transmission;

• Thermal Management Risks

When large currents pass through, the isolated copper area experiences uneven heat dissipation, and increased local resistance easily leads to overheating, accelerating circuit aging and shortening product lifespan;

• PCB Deformation Risk

During soldering (such as wave soldering), large areas of isolated copper expand unevenly due to heat, leading to PCB warping and delamination, rendering the board unusable;

• Reduced Process Reliability

During etching and plating processes, isolated copper areas are prone to copper foil detachment due to stress concentration, affecting the long-term stability of the product.

Practical Tips: 2 Methods for Handling Isolated Copper, Easy for Beginners

Since isolated copper poses such significant hazards, how should it be handled? Here are two of the most commonly used and reliable methods, choose according to your needs:

Method 1: Giving Isolated Copper a "Support System" – Assigning GND Attribute
This is the most common method. The core idea is to make the isolated copper "part of the group." Generally, the isolated copper is assigned to the GND (ground) network. The operation is simple: add GND vias to the isolated copper, connecting it to the underlying GND copper layer.

Note: The prerequisite is that the underlying copper layer must have the GND attribute; otherwise, it will lead to new electrical problems!

Method 2: Preventing from the Source – Adding a Copper Pour Exclusion Area
If you want to avoid isolated copper altogether, you can "set up defenses" in advance. Taking Altium Designer (AD) software as an example (the logic is similar in other software), before copper pouring, first draw the areas where copper pouring is prohibited. This prevents copper from being generated in these areas, thus avoiding isolated copper from the source.

Operation steps: Open Altium Designer software → Click "Place" at the top → Select "Keepout" → Draw the area where copper pouring needs to be prohibited → Then perform the copper pouring operation to obtain a complete copper pour without isolated copper.

Finally, a reminder:

Isolated copper treatment may seem like a "minor detail" in PCB design, but it directly relates to the product's electrical performance, stability, and lifespan. Whether you are a novice or a senior engineer, you must develop the habit of checking for and addressing isolated copper when designing PCBs to avoid costly mistakes.