Clean chemistry, flawless coatings

Behind every reliable Parylene coating lies the dimer — a crystalline, purified precursor that drives the entire deposition process. Parylene dimer purity is the single most critical factor in achieving flawless polymerisation, electrical performance and long-term reliability.

When sublimed and cleaved under vacuum, the dimer becomes a reactive monomer that polymerises onto every exposed surface, forming a perfectly conformal, pinhole-free film.

But that level of precision depends on one factor above all others: purity.

How impurities affect coating quality

Even trace contamination in a Parylene dimer can have major consequences. Impurities such as moisture, oxygen, halogens, metal residues or unreacted intermediates can:

• Reduce dielectric strength by interrupting polymer chain growth
• Cause discolouration or haziness in the deposited film
• Lead to pinholes, voids, and residues during sublimation and pyrolysis
• Trigger uneven coating thickness or adhesion issues

Because the Parylene process amplifies any chemical irregularity during polymerisation, even parts-per-million contaminants can result in visible or electrical defects.

Why SCH focuses on ultra-pure feedstock

SCH Services Ltd sources and supplies high-purity Parylene dimers for advanced electronics, aerospace, and medical applications. Each batch undergoes controlled crystallisation, vacuum drying and contamination screening to ensure complete chemical consistency.

Our commitment to purity extends beyond production — it’s independently verified.

Independent SGS verification

Independent SGS testing throughout 2025 confirmed that all SCH Parylene materials — including Parylene N, C, D and fluorinated F (AF-4) — contain no detectable Substances of Very High Concern (SVHCs), polycyclic aromatic hydrocarbons (PAHs), or PFOS/PFOA compounds to ppm-level detection limits.

Fluorinated grades also meet full RoHS 2.0 (2015/863) compliance.

This independent verification demonstrates ultra-high-purity feedstock (>99.9 % equivalent), ensuring stable polymerisation, high dielectric performance, and pinhole-free coatings across the entire SCH Parylene range.

Performance benefits of high-purity Parylene

• Improved dielectric strength and insulation resistance
• Cleaner surface finish with no whitening or carbonised residue
• Consistent film uniformity across complex geometries
• Reduced risk of adhesion failures and outgassing
• Enhanced long-term reliability under thermal or chemical stress

Certified materials for demanding industries

Whether you’re coating aerospace PCBs, medical implants, or automotive sensors, the purity of the dimer defines the quality of the final coating.

SCH’s independently tested materials ensure regulatory compliance, consistent film quality and traceable supply.

Frequently Asked Questions: Parylene Dimer Purity

Why does Parylene dimer purity matter?

Parylene dimer purity directly affects polymerisation, dielectric strength, film uniformity and long-term reliability. Even trace contaminants can disrupt chain growth, leading to pinholes, discolouration, adhesion loss or electrical instability.

What impurities cause problems in Parylene coatings?

Common problematic impurities include moisture, oxygen, halogens, metal residues and unreacted intermediates. These can cause voids during sublimation, hazy films, uneven thickness and reduced insulation resistance.

Can low-purity Parylene dimer still meet thickness targets?

Yes — but thickness alone does not guarantee performance. Low-purity dimers may reach nominal thickness while still producing coatings with reduced dielectric strength, pinholes or long-term reliability failures.

How does dimer purity affect dielectric performance?

High-purity Parylene dimers allow uninterrupted polymer chain formation, resulting in higher dielectric strength, stable insulation resistance and improved performance in high-voltage or high-humidity environments.

Are SCH Parylene dimers independently tested?

Yes. SCH Parylene materials have been independently tested by SGS and confirmed to contain no detectable SVHCs, PAHs or PFOS/PFOA to ppm-level detection limits. Fluorinated grades also meet full RoHS 2.0 compliance.

Does higher dimer purity reduce coating defects?

Yes. High-purity feedstock significantly reduces the risk of pinholes, hazing, carbonised residues, adhesion failures and outgassing — especially on complex geometries and sensitive electronics.

Learn more

Explore our full range of Parylene dimers or dive deeper into the chemistry behind coating performance in the Parylene Dimers Hub and find out how dimer purity affects coating quality.

All SCH Parylene materials have been independently tested by SGS to confirm no detectable SVHCs, PAHs or PFOS/PFOA, ensuring the highest levels of purity and performance.

When it comes to protecting sensitive electronics and critical components, the best solutions are often the ones you can’t see. Parylene coating is exactly that — an ultra-thin, transparent film that provides superior protection without adding weight, altering dimensions, or affecting performance.

In this article, we break down what Parylene is, how the process works, and why it delivers results you can trust but barely see.

What is Parylene?

Parylene is a family of polymer coatings applied using a unique vapour deposition process. Unlike liquid coatings, it doesn’t rely on solvents or curing. Instead, it forms a pinhole-free, conformal layer that follows every contour of the surface — even sharp edges, crevices, and internal cavities.

Key Characteristics:

• Completely transparent and ultra-thin (typically 5–50 µm)
• Solvent-free, vacuum-deposited protective film
• Uniform coating with no pooling or bridging
• Excellent barrier to moisture, chemicals, and gases
• High dielectric strength and electrical insulation

For a deeper understanding of how different Parylene grades behave in real applications, see our guide to Parylene basics: dimer grades, properties and applications.

How is Parylene Applied? The Vapour Deposition Process

Parylene coating isn’t sprayed or dipped — it’s deposited molecule by molecule in a vacuum chamber. Here’s how:

1. Vaporisation – Solid Parylene dimer is heated under vacuum, turning it into a vapour.
2. Pyrolysis – The vapour is heated again to break the dimer into monomers.
3. Deposition – These monomers enter a cool coating chamber where they polymerise and form a thin, uniform film over all exposed surfaces.
4. No Cure Required – Unlike liquid coatings, Parylene is ready immediately — no oven curing, no drying time.

This unique process ensures 360° coverage, reaching areas where sprays, brushes, and dips simply can’t.

Why Use Parylene? Visible Results from an Invisible Layer

Although invisible to the eye, Parylene’s protective performance delivers very real benefits:

Where Is Parylene Used?

Parylene’s versatility makes it suitable across many industries where reliability is critical:

• Aerospace & Defence — avionics, satellites, fuel systems, sensors
• Medical Devices — catheters, implants, hearing aids, surgical tools
• Automotive & EV — PCBs, battery systems, ADAS components
• Consumer Electronics — wearables, sensors, microcircuits
• Industrial & Energy — sensors, control systems, harsh environment electronics

Parylene vs Traditional Liquid Conformal Coatings

Is Parylene Right for Your Product?

Parylene is ideal when:

• You need high reliability in extreme environments
• Conventional coatings don’t reach complex geometries
• Devices are miniaturised or lightweight
• Biocompatibility and cleanliness are required
• Long-term product life and consistency are critical

Conclusions

Parylene may be invisible, but the results are not. With unmatched uniformity, protection and long-term performance, it delivers reliability where failure is simply not an option.

Whether you’re designing next-generation electronics, life-saving medical devices, or mission-critical aerospace systems — Parylene ensures invisible protection with visible results.

When it comes to Parylene coatings, adhesion is everything. A coating may offer exceptional barrier protection, but if it delaminates or peels from the substrate, performance and long-term reliability are immediately compromised. One of the most common technical questions in Parylene processing is whether adhesion decreases as coating thickness increases.

The short answer: thickness alone is not the root cause. Adhesion performance depends primarily on surface preparation, substrate chemistry, and process control.

Understanding Parylene Deposition

Parylene is applied using a vapour deposition process (CVD), where the coating polymerises directly onto the substrate at a molecular level. This produces a pinhole-free, highly uniform film that conforms perfectly to flat surfaces, sharp edges, and recessed geometries.

Unlike brush, spray, or dip-applied conformal coatings, Parylene does not rely on surface tension or solvent evaporation. However, like all coatings, its adhesion is still governed by surface energy, cleanliness, and interfacial bonding.

Parylene Thickness vs Adhesion Performance

In general, thinner Parylene coatings (typically 2–5 µm) exhibit excellent adhesion because internal stresses within the polymer layer remain low. As coating thickness increases—sometimes to 25–50 µm or more—internal mechanical stress within the film can increase.

If surface preparation is inadequate, this stress can contribute to adhesion loss. However, when substrates are properly prepared, even thick Parylene coatings can achieve outstanding adhesion and long-term durability.

Key influencing factors include:

• Smooth or low-energy surfaces can limit adhesion at any thickness
• Contamination (oils, flux residues, moisture) dramatically reduces bond strength
• Surface activation significantly improves adhesion across all thickness ranges

Best Practices to Maintain Adhesion at Any Thickness

To ensure reliable Parylene adhesion—whether applying thin or thick coatings—the following best practices are essential:

• Use plasma cleaning or chemical surface activation to increase surface energy
• Apply adhesion promoters where required for challenging substrates
• Select coating thickness based on functional need, not assumption
• Validate adhesion using recognised standards such as cross-hatch testing (ISO 2409)

Parylene Adhesion Expertise at SCH Services Ltd

At SCH Services Ltd, we understand how coating thickness, substrate preparation, and process control interact to determine Parylene adhesion performance. Our Parylene processes combine controlled surface preparation with optimised deposition parameters to deliver reliable adhesion across both ultra-thin and high-build coatings.

Whether your application requires thin Parylene films for medical sensors or thicker layers for aerospace and defence electronics, we ensure adhesion performance is never compromised.

Learn more about our capabilities:
Parylene Coating Solutions

Introduction: Why Parylene Stands Out

When it comes to protecting electronic assemblies, manufacturers have several conformal coating options available, including acrylics, silicones, urethanes, and epoxies. However, when performance, reliability, and long-term protection cannot be compromised, Parylene consistently stands apart as the industry benchmark.

At SCH Services Ltd, we provide a complete, end-to-end Parylene solution. Unlike providers that focus on a single element of the process, SCH supports the full lifecycle — from coating services and deposition systems to high-purity dimers, consumables, spares, consultancy, and training.

Whether you are outsourcing coating services, developing in-house capability, or strengthening your supply chain resilience, SCH delivers the expertise and infrastructure required to support electronics, aerospace, automotive, and medical applications.

Our focus is simple: dependable, scalable, and cost-effective Parylene solutions, backed by deep technical knowledge and proven industrial experience.

Learn more about SCH Services’ complete Parylene coating solutions here.

Below are five reasons why Parylene is widely regarded as the gold standard in conformal coating.

1. Superior Barrier Protection

Parylene forms an ultra-thin, pinhole-free polymer film that provides complete environmental protection against:

• Moisture and humidity
• Corrosive chemicals and solvents
• Salt spray and aggressive environments

Because Parylene is applied in vapour form, it coats all exposed surfaces evenly, including sharp edges, crevices, and areas beneath components. This level of coverage significantly improves long-term PCB reliability compared with liquid-applied coatings.

2. Uniform, Truly Conformal Coverage

Parylene is deposited molecule by molecule within a controlled vacuum chamber, resulting in a coating that is:

• Uniform across complex three-dimensional geometries
• Ultra-thin, typically between 10 and 50 microns
• Stress-free, with no pooling, bridging, or edge effects

This makes Parylene particularly well suited to miniaturised electronics and densely populated assemblies where conventional coatings struggle to perform.

3. Outstanding Chemical and Moisture Resistance

Parylene demonstrates excellent resistance to a wide range of environmental and chemical exposures, including:

• Water vapour transmission
• Fuels, oils, and industrial solvents
• Acidic and alkaline solutions

In automotive, industrial, and outdoor electronics applications, this resistance translates into stable, predictable protection throughout the product lifecycle.

4. Biocompatibility for Medical Applications

Parylene’s biocompatibility is a key differentiator in medical and healthcare applications. Certified to ISO 10993 standards, Parylene coatings are:

• Suitable for direct contact with human tissue and fluids
• Widely used in implantable devices such as pacemakers and stents
• Common in diagnostic equipment, sensors, and wearable technology

For medical device manufacturers, Parylene is not just a coating choice — it is a pathway to regulatory compliance and long-term device reliability.

5. Long-Term Reliability in Harsh Environments

Parylene remains stable across a wide temperature range, offers excellent dielectric strength, and resists UV and environmental degradation.

This makes it the coating of choice in demanding sectors such as:

• Aerospace and defence – avionics, satellites, and radar systems
• Automotive – electric vehicle systems and ADAS sensors
• Telecommunications and IoT – outdoor and remote installations

Where downtime or failure is unacceptable, Parylene delivers consistent long-term protection.

When to Choose Parylene Versus Other Coatings

While Parylene offers unmatched performance in high-reliability applications, it may not always be the most economical solution for low-cost or easily repairable products. Alternative coatings may be suitable where:

• Chemical exposure is minimal
• Miniaturisation is not critical
• Ease of repair is a priority

However, when reliability is critical and environmental exposure is unavoidable, Parylene remains the safest and most robust option.

Conclusion: The Benchmark for Reliability

From medical implants to aerospace electronics, Parylene has earned its reputation as the gold standard in conformal coating. Its unique vapour deposition process delivers uniform, durable, and biocompatible protection that liquid coatings cannot replicate.

For further information on Parylene coating services, equipment, and technical support, visit our Parylene services page.

SCH Services Ltd provides comprehensive Parylene solutions, supporting customers with coating services, equipment, materials, consultancy, and training from our UK base.