Choosing the Right Parylene Dimer

How to select the optimal dimer for your coating application

Choosing the right Parylene dimer determines how your coating will perform under electrical, thermal, and environmental stress. Each dimer—Parylene N, C, D, and AF-4—delivers unique advantages that must be matched to your component design, operating environment, and qualification requirements. This guide helps you make an informed selection based on key performance priorities.

Further reading: Wikipedia – Parylene

Key Selection Factors

Before choosing a dimer, consider how your end-use environment interacts with coating properties. The following factors should guide your choice:

  • Operating Temperature: Will the part see continuous exposure above 100 °C? If so, Parylene D or AF-4 are better suited.
  • Electrical Insulation: Where high dielectric strength or deep penetration around fine geometries is critical, choose Parylene N.
  • Moisture & Chemical Exposure: For protection in humid or corrosive atmospheres, Parylene C offers the most balanced barrier.
  • Adhesion vs. Release: For surfaces requiring easy demoulding or low surface energy, AF-4 is the optimal non-stick option.

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Application-Driven Choices

Each dimer aligns naturally to specific application environments:

  • Parylene N – Ideal for high-frequency circuits, sensors, and optical assemblies where ultra-thin, uniform coverage is essential.
  • Parylene C – Preferred for automotive, industrial, and medical electronics requiring dependable moisture and chemical protection.
  • Parylene D – Suitable for high-power or under-hood electronics exposed to sustained heat and thermal cycling.
  • Parylene AF-4 – Best for aerospace, spaceflight, or chemically aggressive environments where extreme inertness is required.

Where component performance must be validated to IPC-CC-830, UL 746E or IEC 60664 PD1/PD2, dimer selection should also reflect compliance with the applicable test regime and film-thickness specification.

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Performance Trade-offs

While no single Parylene type is “best” for all situations, understanding the trade-offs allows optimal engineering compromise:

  • N vs C: Parylene N gives higher dielectric strength but lower moisture resistance than C.
  • C vs D: Parylene D withstands higher temperature but has slightly lower conformality.
  • C vs AF-4: AF-4 surpasses C in chemical resistance but is more difficult to bond or print onto due to low surface energy.

For design teams, the most practical route is to benchmark C as the baseline, then validate D or AF-4 only where operating limits demand extra headroom.

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Summary Table

The quick-reference table below summarises the most common pairing of dimer to requirement:

Primary Requirement Recommended Dimer Key Benefit
Highest dielectric performance Parylene N Excellent insulation and conformality
General-purpose reliability Parylene C Balanced barrier and adhesion
Sustained high temperature (≥150 °C) Parylene D Superior thermal endurance
Extreme chemical or plasma exposure Parylene AF-4 Inert fluoropolymer chemistry and low surface energy

Need help defining the correct Parylene type for your product? Our team supports prototype evaluation, coating trials, and qualification testing to identify the optimal dimer and process conditions for your design.

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Why Choose SCH Services?

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Note: This article provides general technical guidance only. Final design, safety, and compliance decisions must be verified by the product manufacturer and validated against the applicable standards.