PCB Potting Compound Selection Guide

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

Table of Contents

Epoxy resin

  • 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

  • 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

  • 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 MaterialEpoxy resinPolyurethaneSilicone rubber
Temperature Range-40°C to 150°C-55°C to 130°C-100°C to 200°C
Chemical PropertiesGood resistance to solvents, acids, and basesGood resistance to solvents, acids, and basesExcellent resistance to moisture, chemicals, and extreme temperatures
Electrical PropertiesHigh dielectric strength, low dissipation factorLow dielectric strength, moderate dissipation factorHigh dielectric strength, low dissipation factor
Physical PropertiesHard, rigid, high mechanical strengthSoft, flexible, moderate mechanical strengthSoft, flexible, low mechanical strength
CostModerateLowHigh
PCB Potting ProcessPotting, casting, and encapsulationPotting, casting, and encapsulationPotting, casting, and encapsulation
Application FieldsAerospace, automotive, electronics, and telecommunicationsElectronics, LED lighting, and consumer goodsAerospace, 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.

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