In the process of PCB design, copper coating is an important part of PCB design. Various PCB design software provide intelligent copper coating function, which is to cover the idle space on the PCB with a copper surface. The significance of copper coating is to reduce the impedance of the ground wire and improve its anti-interference ability; Reduce the voltage drop of power supply wiring and improve power efficiency; Connected to the ground wire, it can also reduce the loop area.

PCB copper coating: The area filled with copper in the PCB layer. This layer can be the top, bottom, or any interior of the PCB stack, and the PCB copper coating can be used for grounding, reference, or isolating specific components or circuits from the remaining elements of that layer. After the layout and wiring were completed, there were many free areas on the surface of our PCB. We used GND or some power networks to lay a whole piece of copper sheet.

There are a large number of peak pulse currents in digital circuits, so reducing the ground impedance is more necessary. It is generally believed that for circuits composed entirely of digital devices, a large area of ground should be laid. However, for some analog circuits, the ground loop formed by copper laying can actually cause electromagnetic coupling interference, which is not worth the cost.

Advantages and disadvantages of PCB copper coating

Advantages:

Electromagnetic compatibility (EMC): Covering a large area of ground or power with copper can provide shielding, help reduce electromagnetic interference, improve circuit anti-interference ability, and meet EMC requirements.

PCB manufacturing requirements: Copper plating can help ensure the uniformity of electroplating, reduce the deformation of the board during the lamination process, and improve the manufacturing quality of PCBs.

Signal integrity: providing a complete return path for high-frequency digital signals, reducing the wiring of DC networks, thereby improving the stability and reliability of signal transmission.

Heat dissipation: Reasonable copper laying can improve the heat dissipation performance of PCBs, reduce the operating temperature of components, and improve the reliability and lifespan of the system.

Special device installation: For some special devices, such as those that require grounding or special installation requirements, copper plating can provide additional connection points and fixed support, enhancing the stability and reliability of the devices.

Reducing deformation: Copper-clad PCBs can usually reduce deformation during use, especially for double-sided or multi-layer PCBs. The following are some influencing factors:

Stability: Copper coating can increase the overall stability of the PCB and reduce its deformation under temperature changes or mechanical stress.

Thermal expansion coefficient matching: If the copper foil of the PCB covers the entire surface (such as solid copper coating), the copper foil helps to reduce deformation caused by temperature changes.

Strength increase: Copper-clad layers usually increase the mechanical strength of PCBs and reduce their deformation during use, especially for large PCBs.

Laminated structure: In multi-layer PCBs, copper coating can increase the adhesion between the layers of the PCB, improve the stability of the overall structure, and thus reduce the possibility of deformation.

Properly designed PCB copper coating can effectively reduce the deformation of the PCB during use, increase the stability and reliability of the PCB. However, the specific effect also depends on factors such as design details, material selection, and usage environment.

Disadvantages:

Rapid heat dissipation and difficult soldering: If the pins of the components are fully covered with copper, it may lead to rapid heat dissipation, making disassembly and repair difficult. We know that copper has a high thermal conductivity, so whether it is manual welding or reflow welding, the copper surface will quickly conduct heat during welding, causing temperature loss of the soldering iron and other materials, which will have an impact on welding. Therefore, in the design, "cross shaped solder pads" are used as much as possible to reduce heat dissipation and facilitate welding.

Weak signal and interference: Placing copper in the surrounding area of the antenna may cause weak signals, interfere with the collected signal, and the impedance of copper placement may affect the performance of the amplification circuit. Therefore, copper is generally not placed in these areas.

Processing complexity: Copper laying requires consideration of the impact of each copper laying area during the design process. Improper design may increase processing complexity and cost, such as the need to use cross connections and other methods to avoid heat dissipation difficulties. In fact, this is negligible and can be ignored. Nowadays, the technology is relatively mature, and PCB factories will not increase your costs due to this.

Large area copper coating (solid copper coating) and grid copper coating

There are generally two basic methods of copper coating, which are solid copper coating and grid copper coating.

1. Large area copper coating

The dual effect of increasing current and shielding, but if wave soldering is used, it may cause the board to curl up and even bubble. At this time, several slots are usually opened to reduce the bubbles in the copper foil.

2. Grid copper coating

Mainly plays a shielding role, as the cross-sectional area of the copper sheet decreases, its current carrying capacity is relatively weakened compared to solid copper coating.

When choosing the method of PCB copper coating, both grid copper coating and solid copper coating have their advantages and disadvantages, depending on design requirements and application scenarios. Here is their comparison:

Grid copper coating:

Grid structure may increase the complexity of PCB manufacturing, especially requiring more attention in design and processing. Although that's the case, as long as we don't create too small a grid and don't add too much scrap copper, this actually has little impact.

For some high-frequency and high-speed signals, grid copper coating may increase signal transmission loss, leading to signal integrity issues. If copper plating is used as the reference plane for PCB wiring, it is definitely not advisable to use grid copper plating. Instead, we use a complete plane copper plating to achieve a complete reference plane.

It can reduce the weight of PCBs, especially in large PCBs, which helps to reduce the overall weight of PCBs. Under normal circumstances, it is negligible.

More flexible in handling thermal expansion and mechanical stress, which can reduce the impact of PCB under thermal deformation and stress.

Solid copper laying:

Compared to grid copper coating, solid copper coating increases the weight and cost of PCBs because it uses more copper materials.

Providing maximum conductivity and ground connection, it is an ideal choice for applications that require high conductivity.

In some PCB designs for high-frequency and high-speed signals, providing a complete reference plane and solid copper plating can help reduce signal transmission losses and improve signal integrity.

In some scenarios, solid copper laying can provide better shielding effect and reduce electromagnetic interference.

Shielding effect of large-area copper coating (solid copper coating) and grid copper coating

Both solid copper coating and grid copper coating have a certain effect on shielding effect, but the specific effect depends on the specific application scenario and design requirements.

Shielding effect of solid copper coating:

Solid copper coating provides more copper material, which can provide better shielding effect, especially for low-frequency and static electromagnetic interference.

Solid copper coating can form a complete conductive shielding layer, covering the entire area, blocking the entry and propagation of external electromagnetic waves, thereby reducing interference.

Solid copper coating can better seal and shield internal circuits, reducing the impact of electromagnetic radiation on the surrounding environment and other circuits.

The shielding effect of grid copper coating:

Although grid copper coating provides a certain shielding effect, its shielding effect may be slightly inferior to solid copper coating.

Grid copper coating usually leaves gaps, allowing electromagnetic waves to partially penetrate or pass through, so the shielding effect for high-frequency or high-speed signals may be relatively poor.

However, grid copper coating can provide shielding effect to a certain extent while reducing the use and weight of copper materials

The heat dissipation effect of solid copper coating and grid copper coating

Many online claims are nonsense. Firstly, we know that the heat source on a circuit board is mainly integrated circuits, which can dissipate heat through PCBs. So the PCB is connected to the solder pads to conduct the heat of the integrated circuit. The larger the area of the copper sheet, the better the natural heat dissipation.

How to utilize PCB heat dissipation

In terms of heat dissipation, solid copper coating is usually more effective than grid copper coating. Here is a comparison between the two:

The heat dissipation effect of solid copper coating:

Solid copper cladding provides more copper material, which can better conduct heat and therefore typically has better heat dissipation performance.

Solid copper coating can form a continuous heat conduction path, which helps to evenly distribute heat throughout the entire copper coating area, effectively reducing the operating temperature of the device.

The heat dissipation effect of grid copper coating:

Although grid copper coating can also play a certain role in heat dissipation, its heat dissipation effect may be slightly inferior to solid copper coating.

Grid copper coating may be affected by gaps in heat dissipation, and the heat conduction path is not as continuous as solid copper coating, so the heat dissipation effect may be relatively poor.

Overall, if heat dissipation is a key factor in design and good heat dissipation performance needs to be provided on PCBs, solid copper cladding is often a better choice. However, in some applications where heat dissipation requirements are not particularly strict, or in situations where lightweight design is required, grid copper coating may also be a feasible option, as it can provide heat dissipation to a certain extent and reduce the weight of PCBs.