Selecting the right potting compound is crucial for protecting printed circuit boards, but it can be a daunting task for even the most experienced engineers. With so many factors to consider, including physical and chemical properties, application environment, and mechanical strength requirements, it’s important to have a deep understanding of different PCB potting materials to make informed choices. In this TechSparks article, we will discuss these materials in detail to help you make a more informed decision when choosing.
Advanced Reading: PCB Potting: The Ultimate Guide to Protecting Your Circuit Boards
- Epoxy resin is a thermosetting polymer that undergoes curing to form a strong, durable, and rigid material.
- It exhibits excellent thermal conductivity and can withstand high temperature environments of up to 155°C.
- It offers excellent resistance to acid and chemical corrosion, making it well-suited for industrial applications.
- PCB encapsulation epoxy has excellent mechanical properties, providing physical protection for electronic applications that require it.
- The material maintains stability before and after the process flow, ensuring consistency in performance.
- Its exceptional adhesion properties make it ideal for sealing holes and voids in PCBs.
- For applications with high stamping strength, it is recommended to include a toughening agent in the formula.
- Flexible circuits, such as FPCs, are not suitable for use with epoxy resin due to its hard shell after curing, which can lead to adhesive cracking when bent.
- SMT components are also not recommended for use with epoxy resin.
- Polyurethane coating, or “PU,” is a popular compound used to protect circuit boards in extreme environments.
- Unlike epoxy resin, polyurethane has a softer nature and can be used for flexible PCBs, making it suitable for protecting components from physical stress.
- Although it is a more expensive material, its versatility makes it worth the investment.
- The longer curing time is a disadvantage of using polyurethane.
- It can absorb physical shock and vibration without cracking or breaking.
- Circuit boards that require potting often involve a variety of substrates, including metal compounds, ceramics, plastics, and glass, so it is important to choose a potting compound that can protect the unique properties of different substrates.
- This circuit board potting compound emphasizes adaptability, stretch, and scratch resistance rather than moisture, heat, and corrosion resistance.
- The temperature range can be increased by modifying the formula, but it usually ranges from -40°C to 125°C.
- It is the preferred choice for SMT assembly and is suitable for both small and large batch production.
- It is not recommended for use with LSE plastic as it may not sufficiently wet the plastic.
- Silicone rubber is an ideal circuit board potting compound known for its excellent elongation properties.
- The specially formulated silicone rubber compound can function in temperatures ranging from -55°C to 200°C.
- Its lightweight properties make it an excellent option for products that require a lightweight design.
- TechSparks thinks that if your electronics are used in wet environments, silicone rubber is the right thing to do because of its excellent water resistance.
- Can cure quickly under UV light. However, it has the longest curing time compared to other materials.
- Silicone rubber also offers excellent electrical insulation properties and can withstand high voltages and electrical stresses.
- This material is easy to process and can be applied using a variety of potting techniques, including injection molding and casting.
- It is not recommended for applications that require high thermal conductivity because it has relatively low thermal conductivity compared to other materials.
- Insufficient primer adhesion can sometimes be a problem.
Comparison of encapsulation materials
|Encapsulation Material||Epoxy resin||Polyurethane||Silicone rubber|
|Temperature Range||-40°C to 150°C||-55°C to 130°C||-100°C to 200°C|
|Chemical Properties||Good resistance to solvents, acids, and bases||Good resistance to solvents, acids, and bases||Excellent resistance to moisture, chemicals, and extreme temperatures|
|Electrical Properties||High dielectric strength, low dissipation factor||Low dielectric strength, moderate dissipation factor||High dielectric strength, low dissipation factor|
|Physical Properties||Hard, rigid, high mechanical strength||Soft, flexible, moderate mechanical strength||Soft, flexible, low mechanical strength|
|PCB Potting Process||Potting, casting, and encapsulation||Potting, casting, and encapsulation||Potting, casting, and encapsulation|
|Application Fields||Aerospace, automotive, electronics, and telecommunications||Electronics, LED lighting, and consumer goods||Aerospace, automotive, electronics, and medical devices|
Note: The information provided in this table is general and may vary depending on the specific formulation and application of the encapsulation materials.