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PCB Shielding: Basics to EMI and RFI

PCB-Shielding

Table of Contents

Think of PCB shielding as putting a protective bubble around sensitive electronic bits on a printed circuit board (PCB). It’s like giving them their own little safe space away from all the floating electromagnetic noise and radio frequency interference. 

This shielding usually involves using materials like metal to create a barrier that keeps the interference out and the electronics humming smoothly. It’s like giving your gadgets a cozy, interference-free home to do their thing without any disturbances from the outside world.

What is PCB Shielding?

PCB Shielding protects the sensitive electronic components on a printed circuit board from radio frequency interference and electromagnetic interference. It typically uses metal to cover or shield these components from external disturbances. This kind of shielding helps to ensure the functionality and reliability of electronic devices in environments with high levels of electromagnetic activity.

Why to Shield Your PCB?

PCB shielding is essential for reflection and absorption. A shield either bounces or absorbs electromagnetic waves. These steps are necessary for EMI protection of sensitive components.

Imagine you have a component on your PCB that’s quite sensitive to EMI or emits EMI itself. Now, enclosing it within a shield acts as a shield itself, safeguarding it from EMI. This shielding prevents EMI from messing with other circuits on the board, ensuring smooth operation.

Now, let’s discuss high-frequency circuits. Here, signal cables can be in a bit of a pickle due to parasitic reactance, which makes them more prone to EMI. But fear not! Shielding these cables comes to the rescue, reducing EMI and keeping your signals clean and crisp.

What Happens if You don't Shield Your PCB?

If you skip the PCB shielding, your electronic components may be damaged. It’s like leaving them unprotected in a storm. So, let’s see what could go wrong if you don’t shed your PCB.

EMI Mitigation: If you leave your PCB unshielded, it can act like an antenna, picking up and emitting electromagnetic waves. This unwanted energy created through electronic components can disturb the sensitive signals in your PCB. This results in malfunctioning components, producing more movies, glitches, and potential performance issues.

Signal Integrity: Unshiled PCBs are more prone to signal integrity issues, including cross talk, distortion, and ground bounce. This leads to unreliable and improper communication between the components, reduces performance, and leads to system errors.

Compliance with Regulatory Standards: Many industries have strict regulations regarding electromagnetic emissions to prevent interference and ensure the safety of the components. Unshielded PCBs are unlikely to meet these standards, resulting in legal issues, delaying product release, and more.

Types of PCB Shielding

PCB RF Shielding

Electromagnetic Interference shielding, which prevents radio frequencies, including other electromagnetic radiation, is known as PCB RF shielding. You can find this kind of shielding in wireless communications like smartphones, RF transmitters and receivers, Wi-Fi routers, and more. 

RF Shielding is achieved by using a magnetic and conductive enclosure to surround the electronic components, cables, and other sensitive devices and components from the environment. 

The effectiveness of RF shielding usually depends on factors like the design of shield, thickness of shield, materials used, gaps between the shields and the also the frequency of eletromagnteic waves. 

Arduino Shielding

The Arduino shield is an additional board attached to the Arduino microcontroller. It provides extra functionality and protection for the Arduino. Arduino shields are designed to fit on the Arduino, which makes it easy to expand its capabilities without wiring or soldering. 

For example, the Xbee Shield in Arduino is used to communicate with Zigbee. This shield comes with specific features like motors, sensors, and communication modules. This expands the capabilities of the Arduino board.

Terminologies of PCB Shielding

Enclosures

This involves placing sensitive components or entire PCBs within metal enclosures to protect them from electromagnetic interference (EMI). These enclosures, typically made of aluminum or steel, provide a physical barrier against external electromagnetic fields.

Shielding Cans

PCB Shielding cans or metal cans are placed over specific PCB components to block EMI. Strategic Faraday cages shield better. Shielding cans are made from materials like aluminum or copper. Thinness tolerance makes stamped tin-plated copper cans ideal for cavity shielding. Steel cans cause deburring and rust, so they are avoided. Bottom-side drainage avoids sensitive terminals. Solder tacking or conductive epoxy lid sealing shields. Small vent holes maintain internal pressure and reduce noise. Custom shield cans enhance confinement.

Cavity Shielding

It involves creating shield cavities within the PCB and isolating the sensitive components from the EMI. It uses the metal layer shielding techniques integrated into the PCB stack up to form enclosed cavities that block electromagnetic interference. 

Conductive Coating

If you applies the conductive coating on the PCB surface, it creates the shielding barrier. This coatings can block EMI and also you can selectively use the coating to the specific areas as needed. 

Grounding 

The effect of electromagnetic interference can be minimized by properly grounding the PCB and its components. Grounding can dissipate the unwanted electrical noise by proving the reference point for the signal of the circuit. It also reduces interference risk. 

Shielded Cables and Connectors

You can prevent electromagnetic interference from entering and exiting the PCB through external connections using the shielded cables and connectors. A conductive shield surrounds signal lines in shielded cables, while shielded connectors protect connecting points.

Via Shielding

Via shielding protects sensitive traces and components with unique designs. This method shields vias from electromagnetic interference by surrounding or filling them with conductive material.

Design Consideration for PCB Shielding

When designing PCB shielding, several vital considerations ensure adequate protection against electromagnetic interference (EMI) while maintaining the functionality and manufacturability of the PCB:

Frequency Range

Understanding the frequency range of the electromagnetic interference (EMI) that needs to be shielded is crucial. Different shielding materials and techniques are effective at various frequency ranges, so selecting the appropriate shielding method based on the frequency characteristics of the interference is essential.

Placement and Coverage

Identifying the specific components or areas of the PCB that are most susceptible to EMI and ensuring adequate shielding coverage for these areas is vital. Shielding should be placed as close to the source or target of the interference as possible to provide maximum protection.

Material Selection

Choosing a suitable shielding material is critical for adequate EMI protection. Common shielding materials include metals like aluminum, copper, and steel, as well as conductive coatings or paints. Factors such as conductivity, magnetic permeability, and cost should be considered when selecting the appropriate material.

Shielding Integrity

Ensuring the integrity of the shielding enclosure is essential to prevent the leakage of electromagnetic interference. This includes proper sealing of seams and openings and minimizing gaps or discontinuities in the shielding material.

Thermal Considerations

PCB shielding can impact the thermal performance of the components underneath, particularly if the shielding material has poor thermal conductivity. Designing for adequate heat dissipation and ventilation within the shielded enclosure is essential to prevent overheating.

Manufacturability

The PCB shielding should be made manufacturable, including ease of assembly, compatibility with standard fabrication processes, and any additional costs associated with the shielding materials or techniques used.

Conclusions

PCB shielding acts as a protective layer around the sensitive components on the PCB. It safeguards the electronic form electromagnetic interference and radio frequency interference. If you fail to shield your PCB, it could damage your components and could lead to signal integrity issues. 

Thus, you need to consider various design factors to mitigate the EMI and RFI in your circuit design, ensuring the devices’ reliability and performance. 

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About the Author
Rashila
I am an Electrical and Electronics Engineer, and I have 5 years of work experience with electronics and communication jobs. I'm the full time content creator of ELE company.
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