Parylene Conformal Coatings

Parylene is the name for a series of polymers from paraxylene and is considered by many to be the ultimate conformal coating. Parylene coatings are applied at room temperature through vapor deposition polymerization (VPD), a type of chemical vapor deposition (CVD), ensuring they uniformly conform to complex surfaces and penetrate small gaps and crevices.

What Are the Benefits of Parylene Coatings?

Parylene coatings have unique properties that offer several benefits, including:

• Ultra-thin and lightweight: Applied in thicknesses measured in microns, Parylene adds little to no weight to delicate or weight-sensitive components.
• Pinhole-free: The CVD process produces a pinhole-free, uniform coating.
• Chemical and thermal stability: Parylene maintains its integrity even in extreme temperatures or when exposed to chemical contaminants.
• Moisture and chemical barrier: Parylene protects sensitive components against moisture, chemicals, gases or any other environmental contaminants.
• Dielectric qualities: Parylene provides exceptional electrical insulation and has a low dielectric constant, minimizing interference with electrical signals.
• Biocompatibility: Parylene is frequently chosen to coat medical devices, elastomers and mandrels because it is biocompatible and biostable. 
• Dry-film lubricity: Parylene’s low coefficient of friction makes it an effective lubricious coating.
• Halogen-free variants: Halogen-free Parylene options are available for applications with specific environmental requirements.

What Are the Main Types of Parylene?

Parylene is available in several variants, each with distinct characteristics that make it ideal for different application requirements.

Parylene N

Parylene N is a primary dielectric, exhibiting a very low dissipation factor, high dielectric strength and a low dielectric constant invariant with frequency.

Parylene C

Parylene C has a useful combination of electrical and physical properties, plus a very low permeability to moisture and corrosive gases.

Parylene D

Parylene D is similar in properties to Parylene C with the added ability to withstand slightly higher operating temperatures.

Parylene HT^®

Parylene HT^® is useful in high-temperature applications (short-term up to 450°C) and those in which long-term UV stability is required.

ParyFree^®

ParyFree^® is a halogen-free Parylene variant that offers the advanced barrier properties of Parylene C and provides improved mechanical and electrical properties compared to other commercially available Parylenes.

What Are the Industries That Use Parylene Coatings?

Electronics

Electronic components like PCBs, LEDs, sensors, MEMS and semiconductors often employ Parylene for moisture resistance, corrosion protection and dielectric properties.

Medical Devices

Biocompatible and biostable Parylene protects critical medical devices and components, including elastomers, stents, medical electronics and surgical tools, against moisture, chemicals and harsh operating environments.

Automotive

The automotive and transportation industry relies heavily on Parylene to protect electrical systems, gaskets and seals, sensors and other critical components from hostile vehicular environments.

Aerospace and Defense

The aerospace and defense industries were among the first to use Parylene.  It provides weight-sensitive aircraft and defense components with lightweight protection against moisture, fumes, dust and other environmental hazards.

Frequently Asked Questions About Parylene Coatings

Is Parylene waterproof?

Yes. Electronics coated with SCS Parylenes N, C, Parylene HT and ParyFree have passed third-party testing to the IPX7 and IPX8 requirements of IEC 60529, demonstrating protection against water ingress.  Learn more about the waterproof protection provided by SCS Parylenes.

How thick is Parylene coating?

Parylene thickness can range from 0.1–50 µm, depending on the substrate, application and performance requirements. If you’re unsure what thickness your application requires, contact an SCS expert.

How is Parylene applied?

Parylene is applied through a chemical vapor deposition (CVD) process. Parylene’s raw material, known as dimer, is heated under vacuum conditions until it is vaporized. The dimeric gas is then broken down into its monomeric form. In a room-temperature deposition chamber, the monomer deposits on all surfaces, creating a continuous, solid film. Learn more about the CVD process.

What are the key considerations for Parylene deposition?

Optimal Parylene coating performance depends on several factors during deposition:

• Substrate material: Parylene can be applied to most surfaces, but some materials require pre-treatment to ensure proper adhesion. Read more about SCS adhesion technologies.
• Substrate cleanliness: Particulates, oils and other contaminants can prevent proper Parylene adhesion. SCS follows pre-treatment procedures to prevent contamination that could interfere with the coating process.
• Substrate preparation: Because Parylene conformally coats exposed surfaces and penetrates crevices and multilayer components, substrates require appropriate fixturing and masking procedures to ensure only the intended areas are coated.

What are the limitations of Parylene coatings?

Parylene is not ideal for every application. Potential limitations include its higher costs compared with some liquid conformal coatings, extensive substrate preparation, batch processing and greater difficulty with removal and rework. Read more about the limitations of Parylene. 

Are there safety precautions or concerns about using Parylene?

Parylene dimer must be handled and processed according to the manufacturer’s safety guidelines, including ventilation and PPE requirements. Outsourcing Parylene application eliminates the need to handle or process coating materials in-house. Consult with an SCS expert to discuss Parylene coating services.

What is the service life of Parylene?

Under normal operating conditions, Parylene is considered a lifetime conformal coating. Exposure to UV radiation, high temperatures, abrasion or other extreme conditions can reduce its service life. Learn more about Parylene’s service life, or speak to an SCS expert to discuss your application requirements.

Can Parylene coatings be removed?

Yes, but because they are chemically resistant, Parylene coatings cannot be removed with standard solvent stripping. Removal methods include micro-abrasion, laser ablation, mechanical removal, plasma removal and thermal removal. Specialized solvent methods may be suitable for certain applications. Learn more about Parylene coating removal options.

What are the industry standards for Parylene?

IPC-CC-830C is the primary material qualification standard for Parylene coatings. It establishes qualification requirements for materials and evaluates key characteristics such as application, performance, shelf life and material properties.  Learn more about Parylene coating standards, or see s are not as easy as other coatings to rework.  There are a few mechanical means of removing Parylene; using an excimer laser and various abrasion techniques are a place to start.  Once the coating is removed and the board has been reworked, Parylene coatings can be reapplied to the entire assembly or, depending on customer preference and requirements, alternate coatings may be used for touch-up.