EMI Shielding in PCB Design
- TapRen Team
- Jul 29
- 5 min read
Updated: 3 days ago
Abstract
Electromagnetic interference (EMI) can disrupt PCB design by degrading signal integrity and corrupting data, potentially causing the entire PCB system to fail. EMI shielding in PCB design helps control unwanted electromagnetic energy generated by internal circuits. Proper grounding and good layout can minimize electromagnetic interference on PCBs. This article provides an overview of EMI shielding, its applications, and techniques for EMI shielding in PCBs.
What is EMI Shielding?
EMI shielding is the process of using magnetic barriers to block or redirect electromagnetic interference generated by the PCB due to high current flow and an unmanaged circuit layout. On most PCBs, several EMI shielding levels can be applied, including component, board, and enclosure levels. The basic aim of EMI shielding is to create a low-impedance path that confines high-frequency energy and protects sensitive circuits.
Why is EMI Shielding Important in PCB Design?
Electromagnetic interference shielding is not just a shield against magnetic interference. This shielding helps streamline the certification process for the component(s) and reduces PCB redesign costs. It provides safety in medical electronic systems, where radiation can cause health issues. Modern electronics systems, such as high-speed digital logic and RF in tight spaces, require shielding to keep everything operating for longer durations with maximum safety.
Application of EMI Shielding
EMI shielding is used in a range of applications, from industrial equipment to tiny consumer products. The major areas where EMI shielding is applicable are shown below:
Automotive electronics: The ECUs and ADAS systems operate near the noisy alternator, high-current areas, and ignition wiring. The EMI shielding and filtering must be applied to protect the system from interference.
Wireless and RF devices: Tiny consumer products, such as smartphones, Wi-Fi routers, and IoT modules, can be shielded to reduce noise.
Medical equipment: Patient monitors and diagnostic equipment must be shielded to resist external interference. It must avoid emitting system noise, which is harmful to other devices and humans.
Industrial and power electronics: Voltage converters, motor drivers, and high-power inverters generate significant noise from switching and high-current operation, which must be shielded to protect nearby devices. This EMI shielding also provides better control over the devices.
High-speed computing and networks: Network servers and high-speed serial links primarily rely on EMI shielding to protect the systems. Proper use of enclosures and careful stacking of network cables keeps noise inside and maintains signal integrity, allowing the overall system to run smoothly.
EMI Shielding Materials
The selection of EMI shielding materials is crucial to the shielding process. The materials must be conductive and magnetic, and have good mechanical properties for better shielding. Here are the major materials that are suitable for use in EMI shielding in PCBs, as follows:
Copper, Aluminum, and steel are all conductive materials: Copper is used to make planes and is produced as foil and tape. Aluminum is commonly used in housing and covers due to its lightweight, inexpensive nature. Steel is a good conductor and has very high strength, making it well-suited for enclosures and housing.
Plated plastics: The plastic housing, coated internally with conductive paint layers, is also used for EMI shielding in PCB designs. It provides the flexibility to use lightweight materials instead of steel and other heavy metals.
Conductive Gaskets and elastomers: These are used between housings or enclosures to maintain electrical continuity. These also protect the PCB units from dust and moisture.
6. PCB Layout vs Shielding
Improper PCB layout is a major cause of EMI problems. Secondly, shielding also causes EMI problems. The bad layout and partitioning in the PCBs play a significant role in EMI problems. The good stack-up between the ground planes and high-speed signal layers reduces the noise and radiation. However, the poor return-path design on the PCBs increases EMI in the system. The placement of switching regulators, coils, or digital noise away from the analog or RF region helps reduce direct coupling. The improved PCB layout increases system shielding. So that the proper layout must be done for each component that is on the PCBs.
How to Reduce EMI and Increase EMC in PCB Design
The main step to reduce EMI in PCB design is proper layout. Some of the most common steps to reduce EMI and increase EMC in PCB design are listed below.
Minimize loop areas and place a decoupling capacitor close to the IC power pins, with the shortest distance to the ground planes, to reduce supply noise in the PCB system.
Use the appropriate termination tool for the high-frequency signal to reduce ringing and overshoot in the system.
Use a different pin of controlled impedance to limit the emissions and increase the shielding
Add ferrite beads and LC filters to the connectors and cables to stop noise from entering and leaving the PCB.
Physically and electrically separate noisy circuits, such as switching power and digital logic, from the precision RF and analog signals.
PCB Designing Method For Reducing EMI Shielding
PCB design and layout can reduce EMI and improve shielding. There are several design methods that could help to reduce the EMI in PCB, as given below:
Define the EMC and environmental targets: Identify the basic standards, parameters, and interference sources to help set goals for noise emission and shielding.
Partition the boards into zones: Partitioning the boards into RF, analog, digital, and power sections helps identify shielding selection.
Add shielding structures: Placing fences around the RF blocks and edges helps reduce EMI.
Route with EMI constraint: Controlling routes and maintaining impedance helps avoid plane crossings, which also reduces EMI.
Review and refine: Design checks, such as signal-integrity and component tests via simulation, help identify problems that can be mitigated before fabrication. These simulations reduce noisy areas and refine shielding and filtering.
Conclusions
Electromagnetic interference shielding is a protection system that combines proper use of materials, PCB layout, grounding, and enclosure design. EMI shielding helps minimize electromagnetic energy within PCBs. Understanding EMI generation, using a shield can, and proper PCB layout help limit EMI and improve EMC in PCBs. EMI shielding protects critical components on PCBs from both internal and external sources. Design considerations for routing and partitioning reduce EMI in PCBs. This EMI shielding has wider applicability across industries, from tiny consumer electronics to heavy power control and industrial equipment.
10. FAQs
1. How does PCB layout affect shielding?
An improper PCB layout can cause circuit overlap and poor return paths that increase noise or radiation. Improperly grounded lines can also cause short circuits, affecting critical components. So, a proper PCB layout is necessary before the shielding.
2. What types of materials can I use for the EMI shielding?
The selection of the materials is very critical for shielding. Conductive, magnetic, and high-strength materials are recommended for EMI shielding in PCB design. Aluminum and copper can be used for the enclosure. Steel can be used in strength requirements sections, such as housing, to protect the system from dust and moisture.
3. Is it always necessary to split analog and digital grounds?
It is not necessary to split the analog and digital grounds. A single solid ground plane with proper routing can work better than split planes. However, proper partitioning is required to avoid current loops, which can increase EMI.
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