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How to Avoid EMC Problems During PCB Design ?

EMC In PCB
Electromagnetic compatibility (EMC) is a critical consideration in modern electronic design. It relates to the ability of electronic equipment to function properly in an electromagnetic environment without generating electromagnetic interference (IME) that affects other equipment.
Tecnologia FS will deal with EMC and EMI issues at the Conceção de PCB stage, which is the most effective and least costly means of bringing your system equipment up to EMC standards.

Understanding EMC

Next, we will discuss the importance of EMC in PCBs.

What is EMC in PCB?

Electromagnetic compatibility means that electronic equipment in the intended environment will not be degraded, lost, or damaged by the electromagnetic environment in the neighborhood. In addition, the electronic equipment will not generate excessive electromagnetic energy that could affect the normal operation of neighboring equipment.
PCB Design for EMC
EMC consists of two basic aspects: electromagnetic interference (EMI) and electromagnetic immunity (EMS). 
EMC&EMI&EMS
Identifying the source of electromagnetic interference can help you implement sound grounding, shielding, or PCB layout strategies and limit EMC issues in PCB. To ensure electronic devices can coexist in any setting without disturbing each other’s performance.
The following table summarizes key EMC standards relevant to specific industries:
Norma Descrição
IEC 61000-6-1
Immunity for residential equipment
IEC 61000-6-2
Immunity for industrial equipment
IEC 61000-6-3
Limits on residential emissions
IEC 61000-6-4
IEC 61000-6-2
CISPR 32
Limits for multimedia equipment
IEC 60601-1-2
Safety tests for electric medical equipment
MIL-STD-461
U.S. standard for EMC requirements in military applications
FCC Part 15
U.S. regulations for unintentional emissions from electronic devices.
FS Tech meets all IEC requirements relevant to your industry, so we help you to improve the quality of your products.

What is EMI in PCB?

EMI is the phenomenon of electromagnetic waves from one device interfering with another device by radiation or conduction in PCB design. It is the process by which destructive electromagnetic energy is transferred from one electronic device to another and usually includes radio frequency signals (RF) and other electromagnetic waves in the frequency range.
EMI is electromagnetic energy released by all man-made electronics. It interferes with critical components of the PCB and severely impacts electronic systems. This can have hazardous consequences in electromagnetic environments.
Hospital equipment like MRIs produce strong electromagnetic fields (EMFs) that can cause EMI in the PCBs of other dispositivos médicos, potentially endangering patients’ lives, such as pacemakers. Other common EMI sources include microwaves, TVs, radios, and power generators, which can disrupt signals and crash electronics.

Use electromagnetic compatibility techniques to manage EMI in PCBs. EMC in PCBs helps all equipment function properly and comply with the IEC 61000 series standards, which mandate limiting EMI emissions and enhancing equipment immunity. 

Adhering to these standards ensures regulatory approval and the creation of durable electrical products.
Norma Descrição
IEC 61000-3-2
Limits waveform distortions from the main electrical grid
IEC 61000-3-3
Limits flicker and fluctuation in low-voltage systems
IEC 61000-4-2
Tests electrostatic discharge (ESD) immunity
IEC 61000-4-3
Tests immunity against electromagnetic energy
Many industries have specific regulations based on their distinct electromagnetic environments. For a medical device PCB, EMI/EMC guidelines are relatively stricter. The IEC 60601 standard provides a framework to ensure that patients and healthcare providers remain safe from medical equipment hazards.
FS Tech has passed all the tests and demonstrated complete mastery of EMI and EMC in PCB design so you can trust your project to us.

What is EMS in PCB ?

Electromagnetic Susceptibility, referred to as EMS, refers to the ability of electronic equipment to function properly when subjected to external electromagnetic energy interference. It is an important indicator to assess the stability and reliability of the product in the electromagnetic environment. The purpose of an EMS test is to ensure the performance of the equipment when subjected to a specific electromagnetic interference, so as to protect the user’s safety and product reliability.
EMS test
The EMS test mainly evaluates the performance and stability of the equipment when subjected to external electromagnetic interference, including several kinds of the following figure.

Tips for Solving PCB EMC Problems

Here are some practical tips for managing  EMC in your PCB to achieve a modular design.

1. Signal Line Layout

A proper signal line layout of PCB separates signal paths to minimize interference. Group the same type of signals together and route them parallelly. It means analog and digital signals travel together without intersecting each other.
When dealing with high-speed systems like HDMI, USB, Ethernet, and PCI Express, use the differential signaling method. It reduces electromagnetic emissions by sending an inverted pair of signals along separate conductors.
The receiver then compares the two signals, extracts the relevant data, and cancels out the common-mode noise. This technique is particularly useful when you want to transfer data at faster rates.

2. Return Current Considerations

Make sure the electric current return paths are as short and direct as possible. Long and narrow return paths increase inductance and EMI. Use large or multiple ground planes to provide a stable reference for signals.
A continuous plane with minimum ground loops reduces the risk of bounce. It is a common issue in high-speed designs when fluctuating currents return to the ground at varying speeds. They should reach the ground at the same time.
It can be achieved by placing the ground planes close to high-speed signal layers and keeping the return paths short.

3.Reduction of Rise and Fall Times

Reduce the rise/fall time of the signal using low-capacitance components and matching impedance with transmission lines. When the impedance of the load and transmission lines differs, it creates reflections of the signals.
These reflections lead to oscillations in waveform called ringing. They cause the signal to bounce back to the source instead of moving cleanly towards the load. Series resistors can help in slowing signal edge rates, which eliminates ringing and bouncing.
Carefully calculate the width and spacing of each trace to maintain consistent impedance throughout the circuit.

4.Transmission Line Handling

Long traces on PCB act as transmission lines. Route them away from signal lines, especially analog, to reduce crosstalk. The interference from electromagnetic fields of fast signals leaking into long traces is called coupling. It happens when transmission lines (long traces) run parallel to high-speed data ones.
This is problematic for designs that require analog and digital signals to coexist. The rapid transition of digital signals causes voltage spikes in analog traces, leading to errors in analog-to-digital or digital-to-analog conversion.

5. Clock Line Length

Keep all clock lines to the same length to avoid timing errors when signals fail to reach the components simultaneously. This way, all clock signals will reach their destination at the same time, preventing time skews, and potential malfunction.
Precise timing is necessary in high-speed circuits in modern devices. If the signals jitter (arrive at the load at different times), the signal edge rates can shift dramatically. This leads to errors in time-sensitive processes like data transfer.
Excessive jittering can corrupt the data, disrupt the device’s function, or even damage it irreparably. Use PCB layout techniques like meandering or serpentine routing to keep equal clock line length.
These techniques add zig-zag or snake-like patterns to shorter traces, so they match the length of longer digital signal traces.

6. Ground Laying

Ground laying shields PCB from EMI to ensure seamless operation. Providing a common ground for all signals further lessens the chances of interferences and errors. The common strategy is to place ground planes near each signal layer, so the currents can return safely.
This ground layout protects against noise coupling and ground bounce. Noise coupling occurs when signal traces are close to each other, allowing EMI to jump from one to another. Ground bounce, on the other hand, is the penalty for a potential mistake.
It happens when ground planes are not continuous, letting voltages fluctuate due to poor return path. Ground bounce causes signal timing errors. For example, USB 3.0 transmits data at high speeds. If it doesn’t have enough ground planes, data faces interruption and even corruption in some cases.

8. Shielding and Encapsulation Design

Shielding and encapsulation enhance EMI and EMC in PCB design. Shielding means adding a conductive barrier like metal around components to block EMI. This barrier conducts rouge electromagnetic waves whenever they try to invade or escape the protected area.
Encapsulation, on the other hand, means adding a non-conductive barrier (plastic or resin mixtures) over the PCB. This barrier is not for conducting electricity but protecting from physical impact, moisture, and environmental factors that may affect PCB.

9. Cable Management

Managing cable infrastructure is critical for a successful EMC design. Proper routing and shielding of your cables leads to less EMI being conducted on the PCB. Place cables away from components and route them separately from power lines and signal traces.
Shield the cables to contain EMI and prevent it from interrupting Componentes PCB. Avoid loops while routing cables as they attract and radiate EMI. Twisted pair cables help in avoiding any external interference.

10. Pre-compliance Testing

Pre-compliance testing saves time and resources by identifying EMI and EMC issues in PCB early. You can make adjustments to your design along the way, before the final compliance test. Most PCB engineers already possess ideal tools and techniques but some pre-compliance tests require specialized equipment.
The testing involves measuring radiated emissions, radiated immunity, electrostatic discharge (ESD), and conducted emissions. Set up a minor in-house testing lab to conduct checks throughout the designing phase.

11. Simulation Tool Usage

Simulation tools also help designers catch problems even before manufacturing the PCB. You can simply simulate your design through software to check how EMC behaves so you can make adjustments if necessary.
Software like Altium Designer, KiCAD, or OrCAD are the most popular PCB simulation tools in 2024. If you are dealing with large-scale projects, you can use either Altium Designer or OrCAD. They both offer advanced simulation and huge libraries to handle complex operations efficiently.
For small businesses or individual designers, KiCAD is the favored option. It’s an open-source platform with a supportive community. You can access it for free for personal or educational purposes.

12. Iterative Design Process

A successful Conceção de PCB results from an iterative process of designing, testing, and refining. Continue to upgrade your PCB layout based on the results of tests and even new learnings. There is always room for improvement when it comes to electronics.

Use the results from your teste and simulation to ensure there’s nothing else to be done. There are usually minor adjustments like checking the placement of components, trace width, and ground layers.
Se rever um desenho, teste-o novamente para ver se as alterações introduzidas introduziram melhorias. Continue a verificar constantemente a placa de circuito impresso até que esta esteja no estado ótimo.

Testes e validação

Pre-compliance testing and ongoing monitoring are the best methods for evaluating your PCB and EMC against practical applications. The four tests; radiated emissions, radiated immunity, ESD, and conducted emissions, help with that.
Radiated emissions can be measured by a specialized equipment called a spectrum analyzer. It detects EMI by scanning all high, mid, and low frequencies. However, this device is rather expensive and designers normally use USB spectrum analyzers. They are cost-effective, compact, portable, and do the job using the computer’s processing power.
Radiated immunity evaluates how well the device with your PCB reacts to EMI. Expose the device to a cell phone to see if there are any performance issues. Conduct the test inside the electromagnetic field for accurate results.
ESD test checks if the device can resist static discharge that may come from nearby electronics or human contact. Send controlled discharges to various parts of the device to ensure it doesn’t malfunction from accidental sparks.
Finally, make sure the device’s ports and cables have no unwanted electric signals that produce noise. These are conducted emissions and they interfere with other devices connected to the grid. Measure these emissions to make sure the EMI is below your industry’s specified limit.
For consumer electronics, the average limit (dBuV) starts from 56 to 46 for 0.15 to 30.0 frequency ranges (Mhz).

Conclusão

We emphasize the role of EMC in modern PCB designs to meet stringent industry standards. However, the future looks intriguing with the integration of AI and 3D PCBs.
AI has revolutionized PCB design by helping in the assembly process. You can use it to collect data from sensors in modern devices. Machine learning algorithms in AI analyze this data to automate predictive maintenance, supply chain optimization, quality control, and process optimization.
3D-printed PCBs also represent a significant innovation in the designing process. You can create complex geometries that may not be possible otherwise. When both technologies advance in sync, it will be easier to resolve EMC issues.
If you are looking for cost-effective PCB/PCBA services, contactar-nos to get started with your project.
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