A trace is a thin, conductive copper wire placed on a non-conductive material to carry signals across the circuit. This trace has a certain defined width, height, and thickness depending on the application. In high-frequency applications, PCB traces may produce EMI, which may disturb the functioning of the device. Also, incorrect decoupling may lead to EMI being produced by power and ground planes. Hence, shielding PCB traces is essential to protect against electromagnetic interference (EMI) and to ensure signal integrity, especially in high-frequency and sensitive circuits. While using PCB EMI shields helps effectively mitigate noise, this post discusses various ways to shield PCB traces effectively and prevent signal distortion and losses.
What Are Electrically Conductive Adhesives (ECAs)?
Electrically Conductive Adhesives (ECAs) are a type of adhesive containing tiny conductive particles such as carbon, silver, or nickel. These particles allow the adhesive to conduct electricity, enabling it to make electrical connections or grounding surfaces. ECAs are specifically designed to create a path for EMI or RFI to dissipate or be redirected. By forming a conductive bond between components, ECAs effectively shield against unwanted electromagnetic signals, guaranteeing smooth functioning of electrical equipment. Additionally, ECAs are flexible and lightweight, making them perfect for different applications where traditional shielding methods may not work well.
Types of ECA’s
When it comes to ECAs for EMI/RFI shielding, there are several types available on the market that offer different properties and benefits. Some common types of ECAs are:
- Silver-Filled ECAs: These adhesives contain silver particles as the conductive filler, offering high conductivity and excellent EMI/RFI shielding performance.
- Carbon-Filled ECAs: These adhesives utilize carbon-based fillers to achieve conductivity and EMI/RFI shielding properties. Although not as conductive as silver or copper-filled ECAs, these ECAs are known to provide cost-effective solutions for certain applications.
- Copper-Filled ECAs: These adhesives are filled with copper particles, offer good conductivity and EMI/RFI shielding capabilities. Compared to silver-filled ECAs, they are available at a lower cost.
- Hybrid ECAs: These types of ECAs combine different types of conductive fillers, such as a combination of silver and carbon. Certain applications use these adhesives to achieve a balance between conductivity, cost, and performance for specific shielding requirements.
Common Chemistries Used in ECAs
Epoxy-based and silicone-based are the two common chemistries for the base materials, which are infused with various conductive fillers in ECAs:
- Silicones: Known for their flexibility, temperature resistance, and environmental stability, silicone-based ECAs are generally used in applications where flexibility and thermal management are of utmost importance. .
- Epoxies: Epoxy-based ECAs are popular for their excellent adhesion properties, mechanical strength, and durability. Additionally, they possess good compatibility with various substrates.
Properties to Consider when Choosing an ECA
The type of ECA you choose can have a significant impact on the effectiveness of your shielding solution and the overall performance of your electronic devices. Hence, it is important to consider the following properties when choosing ECA for your applications.
- Conductivity: Considering the electrical conductivity of the adhesive is of utmost importance in order to achieve effective EMI/RFI shielding. Be informed that higher conductivity levels typically result in better shielding performance.
- Cure Time: The cure time of adhesive decides how fast it solidifies and attains its expected mechanical and electrical characteristics. Striking a balance between cure time and assembly needs is thus extremely imperative for maintaining production efficiency without compromising bond strength or shielding effectiveness.
- Viscosity: Keep in mind that the viscosity of the adhesive affects its ability to wet surfaces and flow characteristics. Having said this, choosing an adhesive with the appropriate viscosity is advisable. This helps to ensure proper coverage and adhesion, especially in applications with tight spaces of complex geometries.
- Temperature Resistance: : The adhesive’s temperature resistance highly influences its performance, particularly in high-temperature environments and during thermal cycling. Hence, it is important to choose an adhesive that has appropriate temperature resistance. This guarantees long-term stability and reliability in harsh operating conditions.
Applications of ECA’s
Following are a few of the several applications, wherein using ECAs is immensely beneficial.
- Sealing Gaps between Components and Enclosures: The adhesives are used to fill gaps and seams between components and enclosures. This helps create a continuous conductive shield that significantly prevents the entry and escape of electromagnetic interference (EMI) in the shielded area.
- Shielding Sensitive Components on PCBs: ECA’s are useful to shielding sensitive components, such as integrated circuits (ICs) or connectors, on printed circuit boards (PCBs). When the right type of ECA’s is applied, electromagnetic fields are redirected away from the sensitive areas of these components. This, in turn, leads to minimized risk of interference, while also ensuring proper device operation.
- Mounting Shielding Tape and Films: These adhesives are applied to mount shielding tape or films onto surfaces, offering EMI/RFI shielding for components or cables.
- Creating Conductive Paths for Grounding: ECAs are applied to create conductive paths for grounding between components or to ground the entire assembly. This contributes to dissipating electrical charges, reducing the risk of EMI/RFI interference.
Benefits
The following are some of the notable benefits of using Electrically Conducting Adhesives (ECAs) in EMI/RFI Shielding.
- Flexibility and Conformability: ECAs conform to irregular surfaces and complex geometries. Owing to this property, they allow for seamless integration into electronic assemblies, contributing to consistent shielding coverage.
- Minimized Assembly Time: ECAs simplify overall assembly processes by eliminating the need for mechanical fasteners or soldering, thereby reducing assembly time and complexity.
- Enhanced Reliability and Durability: As these adhesives offer robust bonding and sealing properties, they guarantee long-term reliability and durability, particularly when used in harsh operating environments. They are made to resist temperature extremes, moisture, and vibration.
- Lightweight Design: Compared to other shielding methods, the use of these adhesives is a lightweight alternative, which contributes to reducing overall weight and enhancing portability.
- Cost-effectiveness: Compared to traditional methods, such as metal enclosures or conductive coatings, ECA’s offer cost-effective solutions for EMI/RFI shielding.
- Compatibility with Various Substrates: They are suitable for diverse applications in the electronics industry owing to their compatibility with a wide range of substrates, including plastics, metals, and ceramics.
Challenges You Can Expect When Using ECAs
The following are some of the potential challenges when using Electrically Conductive Adhesives (ECAs) for EMI/RFI shielding.
- Mechanical Properties: Compared to traditional bonding methods, ECAs may have lower mechanical strength. This can negatively affect the structural integrity of assemblies, especially in high-stress environments or during the process of thermal cycling.
- Adhesion to Substrates: Although they are compatible with several substrates, including non-conductive materials like plastics or ceramics, ensuring proper adhesion can be sometimes challenging. The need for surface treatment or primer application arises during such instances.
- Cure Time and Process: Balancing the cure time of ECAs with assembly requirements and production schedules can often be challenging. As longer cure times may increase manufacturing cycle times and affect overall productivity.
- Temperature and Environmental Stability: The adhesives can experience significant changes in electrical and mechanical properties over time, particularly in extreme temperature or humidity conditions. This can be challenging as the change can impact long-term reliability and performance.
Comparison of ECAs with Board-Level Shields
When it comes to EMI/RFI shielding in electronic devices, the choice between ECAs and traditional board level shields is an important consideration. Both methods have their own advantages and disadvantages that need to be carefully evaluated before making a decision. Here is a small comparison between these two popular methods.
- As mentioned earlier, ECAs are a more cost-effective solution compared to board level shields. This is because ECAs can be easily applied in various shapes and sizes, eliminating the need for complex mechanical structures. Furthermore, these adhesives also provide better flexibility and can conform to irregular surfaces. This adds to their popularity when it comes to smaller and more intricate electronic devices.
- In contrast, board level shields are meticulously created to make a more robust and reliable shielding solution. Owing to this, they provide higher shielding effectiveness and better protection against EMI/RFI interference. Adding to their popularity, they are easier to remove and replace for maintenance purposes. Overall, for demanding applications, investing in board-level shields can be a wise decision due to their superior shielding capabilities, ease of maintenance, design flexibility, better thermal management, and enhanced signal integrity, among others.
If you are considering board level shields for EMI protection, then SnapShot® EMI shields by XGR Technologies is the best option. These board-level shields are revolutionary, offering multi-cavity shielding solutions, guaranteeing optimum protection against electromagnetic interference. With their dedicated approach to innovation and quality, you can trust in XGR’s expertise to deliver unparalleled shielding solutions that meet the highest standards of reliability and performance.
