How to Select the Best PCB Encapsulation Material for Your Project

Introduction to Potting and Encapsulation

Potting or encapsulation is a widely used method to protect circuit boards from damage, and it has proven to be effective. Different potting compounds are used in various circuit environments, based on the advantages and characteristics of materials. Common materials include:

• Ethylene-vinyl acetate (EVA)
• Polyphenylene sulfide (PPS)
• Polyphenylene oxide
• Polyamide-imide
• Acrylics
• Polyesters

In this article, Highleap Electronic will provide a detailed description of the advantages, disadvantages, and application scenarios of different materials. Integrating Design for Manufacturability (DFM) checks into the PCB manufacturing process ensures the best results for your project.

What is potting PCB?

Potting is a common protective measure used by most PCBA board manufacturers to safeguard electronic circuits against heat, environmental hazards, chemicals, and impacts. This is achieved by filling the enclosure of the PCB board with a potting compound, which acts as an encapsulation resin, thus protecting the entire board and its components. Here are some reasons why you should consider potting PCB board:

• Potting enhances electronic performance and circuit dependability by protecting PCBs from tampering, moisture, and voltage leaks. Potting also shields electronics from the effects of vibration and stress, preventing wiring disconnections and early system failure.
• Additionally, the PCB and PCB case’s vibration waves may pair, intensifying stress on the PCB and causing early failure. PCBs become stress and vibration resistant through potting.
• Also, Encapsulation protects PCBs from dirt and dust, which can cause overheating, signal interference, and decreased speed or performance.
• Lastly, PCB board potting improves the security and privacy of the electronic device. The nature of potting makes accessing your PCB and reverse engineering your device incredibly challenging, thereby enhancing the privacy and security of your PCB board.

Common materials for PCB Encapsulation

Ethylene-vinyl acetate (EVA)

Ethylene-vinyl acetate (EVA) is a widely used potting material in the electronics industry due to its multifunctional advantages. It is ideal for outdoor applications that require shock resistance because of its ability to absorb shock and vibration. Moreover, it exhibits good adhesion to a variety of materials such as metals, plastics, and other substrates. It maintains its properties even at low temperatures and provides excellent electrical insulation.

Despite its advantages, this potting compound has some drawbacks that are hard to ignore. While flexible materials make it impossible to crack when bent, they cannot provide as much mechanical protection as rigid materials and may not be suitable for some fragile components. Furthermore, it is not recommended for particularly extreme environments, such as high temperatures or acidic environments. While it is not expensive, it may not be easy to obtain for PCBA manufacturers in certain regions.

Considering its advantages and disadvantages, it is evident that EVA can be used in various scenarios and applications. It is commonly used in consumer electronics PCB, such as mobile phones, tablets, and laptops. However, it may not be suitable for industrial applications where some manufacturers’ industrial products, such as motor drivers, PLCs, and sensors, require printed circuits to have a certain degree of mechanical resistance that EVA may not meet. Additionally, it is not used in high-end applications such as medical equipment, marine electronics, aerospace and defense electronics, automotive electronics, and renewable energy applications. Despite its limitations, EVA remains a versatile and cost-effective encapsulation material for many electronic devices.

Polyphenylene sulfide (PPS)

Polyphenylene sulfide (PPS) is a highly durable and heat-resistant thermoplastic material that can withstand temperatures up to 260°C, making it ideal for high-temperature applications. This material is highly flame retardant and meets UL 94 V-0 flammability standards, ensuring its reliability and safety in harsh environments. Its high strength and rigidity, combined with good shrinkage and dimensional stability, make it an excellent choice for PCBs that require precise tolerances. Moreover, its exceptional corrosion resistance allows exposure to acids and bases.

It is important to note, however, that PPS is a relatively expensive option and requires specialized equipment for PCBA processing. Additionally, it is a rigid material and cannot meet the needs of flexible PCBs. Its properties may also be weakened in certain environments, such as softening at low temperatures and discoloration or degradation when exposed to UV radiation.

PPS is widely used in cutting-edge and high-priced applications such as aerospace communication equipment, defense electronics navigation systems and control modules, and sensors in self-driving cars. However, it is also highly valued by industrial customers who need to operate in challenging environments, including high temperatures and chemical corrosion. While industrial control boards can be expensive to replace or repair, PPS provides a reliable and cost-effective solution, making it an ideal choice for applications such as motor drives and PLCs.

Polyphenylene oxide

For users seeking a multifunctional material, polyphenylene oxide (PPO) is an excellent option, with a balanced blend of capabilities and affordability. While not as heat-resistant as polyphenylene sulfide, it can still operate in environments up to 140°C, which is sufficient for most applications. Furthermore, PPO provides adequate mechanical protection and dimensional stability, and has good resistance to both outdoor and acidic/alkaline environments. Its few shortcomings are overshadowed by its many advantages, with the only notable disadvantage being its occasional difficulty in procurement.

Thanks to its broad range of resistances, PPO can be used in many applications. For instance, it is commonly employed in household appliances such as TVs and air conditioners, as well as public facilities like solar panels, wind turbines, and energy storage systems. PPO is also well-suited for use in medical PCB, including implantable sensors and drug delivery systems, and can find a place in industries like aviation, military, and industrial manufacturing. All in all, PPO’s versatility and affordability make it an excellent choice for many applications.

Polyamide-imide

Polyamide-imide (PAI) is a commonly used compound in the industrial field because it is more tenacious in extreme environments and can provide long-lasting protection. It is compatible with high temperature resistance and low water absorption, which makes it ideal for preventing moisture-related problems in industrial applications, where high temperatures can cause water vapor atomization in the environment, leading to circuit board short.

However, like other high-temperature-resistant compounds, special equipment is required for processing, and warping may occur during the process, which can lead to product deformation. Polyamideimide is not suitable for applications that require a specific color, as it has a natural color that cannot be easily altered during processing. Additionally, it becomes fragile in low-temperature environments, and excessive external force can cause it to break.

Despite these limitations, PAI has higher compatibility with aluminum PCBs, making it a suitable potting compound for LED lighting systems and solar electronics. It is also useful in potting applications for oil and gas exploration equipment, such as drilling sensors and controllers.

Acrylics

Acrylic is an encapsulation compound that is easy to process and cures quickly, making it an attractive choice for customers seeking fast turnaround PCB assembly capabilities from a fabrication company. It is also a suitable material for PCB potting, as it helps reduce production time. While acrylic has excellent adhesion and chemical resistance, it has poor heat resistance and can become brittle over time, resulting in a short lifespan. However, it can be formulated to be optically transparent, making it ideal for electronic applications that require light transmission.

In terms of advantages, acrylic does not have many when compared to other materials. Its main advantage is that it is inexpensive, making it more suitable for consumer electronics applications with lower profit margins, as it does not significantly increase production costs.

Polyesters

Polyester has excellent electrical insulating properties, making it suitable for various electrical applications, including automotive electronics, power supply units, and HVAC systems. Although it is a less expensive potting compound, its lifespan is shorter, making it an economical choice. In medical devices, it is commonly used in monitoring equipment and diagnostic tools.

What are the Benefits of PCB Encapsulation?

As an engineer, I can attest to the numerous advantages that PCB encapsulation brings to the table. This process is critical for enhancing the reliability and longevity of electronic components. Here’s why:

• Robust Protection from Water and Shock: Encapsulation is vital for shielding PCBs against water damage and physical shocks, which are common threats in various environments.

• Chemical and Corrosion Resistance: This method offers exceptional protection against chemical exposure and corrosion, making it ideal for PCBs operating in harsh conditions.

• Enhanced Insulation and Functionality: By improving the insulation between electrical components, encapsulation helps reduce current loss, ensuring that the device maintains optimal functionality over time.

• Mechanical Vibration Protection: Encapsulation effectively prevents damage caused by mechanical vibrations, preserving the integrity of the components on the PCB.

• Reduction of RFI/EMI Interference: This process is highly effective in mitigating radio frequency interference (RFI) and electromagnetic interference (EMI), which can disrupt device performance.

• Stress Reduction on Solder Joints: Encapsulation provides a solid foundation for wire bonding, significantly reducing stress on solder joints and preventing potential failures or breakages.

• Barrier Against Contaminants: It forms a secure seal that keeps dust, dirt, and other contaminants at bay, protecting the PCB from potential damage.

• Protection Against Tin Whiskers: Encapsulation serves as an environmental barrier, preventing the formation of harmful tin whiskers that can cause short circuits and other failures.

• Difficulty in Reverse Engineering: From a security standpoint, encapsulated PCBs are much harder to reverse engineer compared to those with just conformal coatings, protecting your designs from being copied.

• Thermal Expansion Protection: This method also safeguards components from issues related to thermal expansion, ensuring that the PCB retains its ionic purity and moisture resistance properties.

• Cost-Effective and Efficient: Encapsulation tends to be faster and more cost-effective than other protective methods, requiring fewer application steps and eliminating the need for reassembly. Plus, VOC-free options are available for those concerned about environmental impact.

• Ease of Application: The process is straightforward and efficient, even in high-volume applications, making it a practical choice for manufacturers looking to streamline their operations.

In conclusion, PCB encapsulation is an indispensable process that offers comprehensive protection, enhances performance, and ensures the long-term reliability of electronic devices.

Conclusion

To promote the quality of your project, it is important to choose the appropriate material based on different applications and needs. When it comes to PCB protection, conformal coating is a viable alternative to potting. While both options provide protection, there are some significant differences between the two. Reading “Conformal Coating VS Potting” will help you determine which service is more suitable for your needs.

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