Parylene Dimer Comparison (N, C, D & AF-4)
Understanding the key differences between Parylene dimers
Parylene dimers form the foundation of every Parylene coating, but each type—N, C, D, and (F) AF-4—offers distinct performance characteristics. Selecting the right dimer affects not only coating thickness and adhesion but also moisture resistance, dielectric strength, and temperature capability. This guide compares the main Parylene dimers side by side to help you choose the best match for your application.
Further reading: Wikipedia – Parylene
Overview
Although all Parylene coatings share the same deposition principle—sublimation, pyrolysis, and polymerisation—the chemical substitution on the dimer molecule defines the coating’s properties. Each variant balances dielectric, thermal, and barrier characteristics differently:
- Parylene N – The original, unmodified base polymer. Exceptional dielectric strength, deep penetration, and optical clarity.
- Parylene C – Monochloro-substituted for enhanced moisture and chemical resistance; the most widely used commercial grade.
- Parylene D – Dichloro-substituted for improved high-temperature tolerance while maintaining a good barrier profile.
- Parylene AF-4 – Fluorinated dimer offering superior chemical inertness, lowest surface energy, and highest thermal stability.
Chemical Structure Differences
The key distinction between each dimer lies in its halogen or fluorine substitution on the aromatic ring, which influences chain mobility and surface energy:
| Type | Substitution | Key Effect |
|---|---|---|
| Parylene N | None | Highest dielectric strength and uniform coverage |
| Parylene C | Monochloro (one chlorine atom) | Improved moisture and chemical barrier |
| Parylene D | Dichloro (two chlorine atoms) | Enhanced high-temperature stability |
| Parylene AF-4 | Tetrafluoro (four fluorine atoms) | Exceptional chemical resistance and low surface energy |
Fluorination in AF-4 drastically lowers surface energy, reducing adhesion but maximising chemical resistance—ideal for aerospace, medical, and high-frequency electronics.
Performance Comparison Table
The following summary highlights how each dimer performs across key parameters:
| Property | Parylene N | Parylene C | Parylene D | Parylene AF-4 |
|---|---|---|---|---|
| Dielectric Strength | ★★★★★ | ★★★★☆ | ★★★★☆ | ★★★☆☆ |
| Moisture Resistance | ★★★☆☆ | ★★★★★ | ★★★★☆ | ★★★★★ |
| Thermal Stability | ★★★☆☆ | ★★★★☆ | ★★★★★ | ★★★★★ |
| Chemical Resistance | ★★★☆☆ | ★★★★☆ | ★★★★☆ | ★★★★★ |
| Surface Energy | High (good adhesion) | Moderate | Moderate | Low (non-stick) |
For most electronics, Parylene C remains the balanced, go-to choice. However, Parylene D and AF-4 excel where temperature or chemical demands exceed standard limits.
Choosing the Right Dimer
When selecting a Parylene dimer, balance the functional and environmental requirements:
- Electrical Insulation: Choose Parylene N for best dielectric strength.
- Moisture & Chemical Barrier: Use Parylene C for broad reliability.
- High-Temperature Operation: Select Parylene D or AF-4.
- Extreme Chemical or Low-Surface-Energy Needs: Choose AF-4 for advanced, non-stick surfaces.
Our experts can help match dimer type, deposition parameters, and coating thickness to your exact design and qualification criteria.
Explore More on Parylene Dimers
Next steps:
Parylene Dimers Hub ·
What is Parylene Dimer? ·
How Dimer Purity Affects Coating Quality ·
Choosing the Right Dimer
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