Why EMI Shielding Matters in Electronic Design

Unwanted electromagnetic energy can interfere with electronic circuits. Considering EMI early in development gives designers time to review likely interference sources, grounding connections and space for shielding. The appropriate material depends on the assembly’s electrical, mechanical and environmental requirements and should be evaluated as part of the complete design.

What is EMI Shielding?

EMI shielding is a technique used to protect electronic devices from electromagnetic interference (EMI). EMI shielding gaskets, conductive elastomers, conductive metals, and intrinsically conducting polymers provide effective shielding.

The most common type of EMI shielding material is metal shielding often using aluminum or copper alloy. These metals are effective at blocking electromagnetic radiation and also grounding. In terms of design, the electrical conductivity of other materials including foams, fabrics, films and adhesives may be suited to create an EMI shield.

Why is EMI Shielding Important?

The world is becoming far more electrified than ever before with the rise of smart home automation, electric vehicles, and portable devices. EMI shielding is necessary to protect devices from internal and external noise.

For example, a smartphone contains at least six major components in close proximity that are both sources of electromagnetic interference and need EMI shielding to function properly.

Cellular radio: The core component of a smartphone allows the device to communicate wirelessly with cellular networks. The cellular radio emits electromagnetic waves to connect with cell towers. The signal must be controlled for the device to function and other components must be shielded from the signal.
Wi-Fi and Bluetooth: Smartphones connect wirelessly to Wi-Fi networks through an electromagnetic wave. Just like cellular radios, the signal can cause interference with other electronic components. Bluetooth connections between two or more devices are now ubiquitous from headphones to cars, and smartphones communicate to other devices across electromagnetic fields. Electromagnetic interference can cause Bluetooth electronic equipment to fail. Dropped phone calls, scratchy noises through speakers, and weak Wi-Fi connections are all examples of EMI.
Display: When a smartphone screen plays video or bright images, the display is a source of interference. EMI shielding effectiveness can go unnoticed when the display shines bright. Poor design and wear or damage in the device can cause the screen to malfunction or affect other components.
Processor: A smartphone is essentially a miniaturized supercomputer. The processor that drives this high-speed device can generate significant amounts of electromagnetic waves and interference. EMI shielding prevents the processor from malfunctioning and also minimizes the effect on nearby components.
Camera: When taking photos and recording video, smartphone cameras can emit EMI.
Charging circuit: Both connected charging and wireless charging can generate interference. Electromagnetic shielding guards sensitive components from these signals.

This is just one example of the importance of EMI shielding in modern devices. There are many more sources of electromagnetic interference within and acting upon smartphones and other devices.

What to define before choosing a shielding material

Bring the electrical and mechanical requirements together before shortlisting materials.

Identify likely interference sources and the circuits that need protection.
Define the relevant frequency range and required grounding connections.
Record the available space, mating surfaces and any gaps to be filled.
Compare adhesive, assembly and environmental requirements.
Review the selected product’s technical data and evaluate it in the assembled design.

Use the P-SHIELD material range to compare available constructions. For tape-specific options, see the EMI shielding tape materials guide. Contact Polymer Science with your requirements to discuss the next selection step.

Types of EMI

EMI can come from internally generated sources or external sources, and it can manifest in primary wavelengths as well as harmonics. There are various types of electromagnetic interference (EMI) that must be considered in design.

Conducted EMI: Interference that travels through conductive mediums such as power sources, wires or cables. It can be caused by switching power supplies, motors, or other devices that generate electrical noise. Proper shielding and filtering techniques are employed to mitigate conducted EMI.
Radiated EMI: Radiated EMI occurs when electromagnetic energy is emitted through space and can be picked up by nearby devices or systems. Sources of radiated EMI include high-frequency signals, such as those generated by wireless communication devices, radio transmitters, or improperly shielded electronic components.
Crosstalk: Crosstalk is a type of EMI that occurs when signals from one electrical circuit interfere with signals in an adjacent circuit. It can lead to signal degradation, data corruption, or malfunctioning of electronic devices. Proper circuit layout, shielding, and signal isolation techniques are used to minimize crosstalk.
Grounding Issues: Improper grounding or grounding loops can introduce unwanted electrical noise into a system, leading to EMI. Grounding techniques, such as star grounding or using balanced lines, are employed to minimize grounding-related EMI.

Understanding the types of interference a device will be exposed to is the first consideration. Consulting with experienced suppliers and experts in EMI shielding at Polymer Science provides valuable insights.

Sensitivity of the Device

Within individual industries, there are unique concerns about the sensitivity and risks associated with the interference. In certain applications, EMI shielding effectiveness simply improves performance. In other industries including medical devices and vehicles, safety demands the highest quality EMI shield.

Medical devices: electrosurgical devices, infusion pumps, cardiac monitors and other devices can be sources and are susceptible to interference from other devices.
Electric vehicles: electric motors, battery management systems, charging systems, controls, charging systems, and other components must all work together.

Choosing the Best Shielding and Grounding Materials

The primary choice of the ideal shielding and ground material boils down to wavelength and mechanical performance. Selecting the ideal material can increase effectiveness, enhance design, and improve the manufacturing process. All of these are key to a successful design. Polymer Science provides a wide range of solutions including conductive adhesives, tapes, and coatings. There are unique benefits to using silicones, fabric, film, foils or foams.

What are Examples of EMI materials?

EMI shielding applications must be effective and suitable for the design. Polymer Science helps with both of these challenges. A wide range of materials including tapes, adhesives, fabrics and foams provide EMI shielding. When you work with a trusted supplier during your design, you gain insight into the most effective and functional EMI shielding solution for your specific application.

Conductive Silicone

For many years, Polymer Science has worked in consumer health care, consumer electronics, medical trauma, automotive and other industries. Advances in conductive silicone offer a versatile material that has been modified to make it conductive. Conductive silicone adhesive is a flexible and durable material that can be easily applied to numerous substrates. It is also resistant to a variety of chemicals and solvents, which makes it ideal for use in harsh environments. Conductive silicone can also be easily applied to electronic devices, making it an ideal material for compact applications or if the device needs to move easily.

Versatility of Design Materials

Many materials like electrically conductive adhesives serve multiple purposes, both in shielding interference and securing components. Conductive foams conform to housings. Conductive fabrics, films and foils can protect sensitive components from light, dirt, water, chemicals and other debris. Some of the examples of P-SHIELD® Shielding & Grounding Materials include:

Conductive Fabric: Without an adhesive, conductive fabrics are often used as air loops and EMI shielding gaskets. Laminated on either conductive acrylic pressure sensitive adhesives (PSA) or heat activated adhesives, fabric tapes are durable, flexible and offer a lightweight profile. Black fabric can block light. Electrical conductivity can be enhanced when the woven fabric is combined with metals.
Conductive Tapes: Fabric tapes offer distinct advantages but there are many applications where film, foil and foam most effectively shield and protect EMI applications.
- Film Tape: Anisotropic Polyimide film with a conductive acrylic PSA adheres to many substrates.
- Foil Tape: The electrical conductivity of foil tape is exceptional. Conductive copper and aluminum foil are effective, economical, and provide a good wet out on many surfaces.
- Foam Tape: Copper and nickel plating mesh core provides shielding in all directions and foam conforms to fill gaps.
Conductive Adhesives: Pressure sensitive electrically conductive adhesive and heat activated adhesive provide excellent X, Y, Z axis conductivity. Polymer Science can customize formulations and adhesion levels of adhesives.
Conductive Foams: Foams manage electromagnetic interference and supply a path for electrical current grounding. Conformable and compressible, conductive foam without adhesive is a great solution for EMI shielding gaskets in housings.

Finding the ideal EMI shielding material to suit your design and application can be challenging. Working with a trusted partner early in the process is vital to successfully bring products to the market.

If you have questions about EMI sources and EMI shielding solutions, contact our team. We are also eager to share our ideas, experiences and learn from other industry leaders.