Parylene Coating for PCB Protection

Parylene coating for PCB protection provides an ultra-thin, pinhole-free barrier that protects complex assemblies from moisture, chemicals, ionic contamination and corrosion. Unlike conventional liquid conformal coatings, Parylene is deposited from the vapour phase, delivering perfectly conformal coverage even under components, inside tight gaps and around sharp edges.

SCH Services offers turnkey Parylene solutions for PCB protection – from subcontract coating services and
design-for-Parylene support through to Parylene equipment, dimers and training for in-house lines.

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Parylene is chosen for PCB protection where long-term reliability and miniaturised, high-density designs make traditional brush, dip or spray coatings less effective.

• True 3D conformity – vapour deposition allows Parylene to coat all exposed surfaces, including under components, inside vias and tight gaps.
• Excellent moisture and corrosion barrier – extremely low water vapour transmission rate (WVTR) to protect copper, solder joints and component terminations.
• High dielectric strength at low thickness – enables tight creepage and clearance distances on dense PCBs while maintaining insulation performance.
• No pinholes, puddling or meniscus – uniform thin film without the edge build, bubbles or voids often seen with liquid conformal coatings.
• Low thermal and mechanical stress – room-temperature deposition; ideal for sensitive components, sensors and mixed-technology assemblies.
• Chemical resistance – protects PCBs exposed to fuels, oils, cleaning agents and process chemicals in harsh environments.
• Long-term stability – Parylene films are chemically inert and non-migrating, maintaining protection over the full life of the assembly.

These properties make Parylene particularly attractive where PCB failure carries a high cost, safety impact or inaccessibility for field repair.

Parylene PCB protection is widely adopted in sectors where downtime, recall or field failures are unacceptable:

• Aerospace & defence – flight control units, guidance electronics, mission-critical PCBs.
• Automotive & EV – under-bonnet ECUs, battery management systems, sensor modules.
• Industrial & process control – PCBs exposed to condensation, chemicals, dust and corrosive atmospheres.
• Medical & life sciences – diagnostic instruments, patient monitoring, sterilisation-exposed electronics.
• Energy & renewables – power conversion, inverters, outdoor and offshore electronics.
• Consumer & wearable devices – sweat, humidity and splash-prone assemblies where thin, invisible protection is required.

SCH can help identify which PCB families truly benefit from Parylene and where traditional conformal coatings remain the best fit. This ensures the coating strategy is technically sound and commercially balanced.

Getting the best from Parylene starts with design-for-coating (DfC). SCH works with design, PCB layout and manufacturing teams to optimise assemblies for Parylene, typically focusing on:

• Masking & keep-out areas – defining coating-free zones for connectors, test points, switch contacts, RF shields and high-current terminations.
• Vent holes and access – ensuring vapour can enter and exit housings, cavities and under-component areas to achieve full coverage.
• Sharp edges and standoffs – managing features that may concentrate stress or challenge uniform thickness.
• Thickness selection – balancing dielectric performance, environmental resistance and cost (typical Parylene thicknesses for PCBs are in the 5–25 µm range).
• Substrate and finish compatibility – tin-lead, ENIG, OSP and other finishes, plus plastics, elastomers and over-moulds present on the assembly.
• Cleanliness and pre-treatment – defining cleaning, bake and surface activation requirements for good adhesion and long-term performance.

Early engagement allows many of these points to be built into the PCB and assembly design, reducing rework and masking complexity once production starts.

SCH follows a controlled, documented process for PCB Parylene coating, tailored to the application and customer standards:

1. Assessment & specification – agree Parylene type, target thickness, critical areas and inspection criteria.
2. Cleaning & pre-bake – removal of flux residues and contaminants; controlled bake to drive off absorbed moisture.
3. Masking – application of high-reliability masking to connectors, keep-outs and functional surfaces.
4. Parylene deposition – vacuum deposition in qualified Parylene systems with monitored process parameters.
5. Demasking & finishing – careful removal of masks, visual checks around edges and interfaces.
6. Inspection & testing – thickness measurement, visual inspection, adhesion checks and functional test as required.
7. Documentation & traceability – batch records, process logs and test data retained to support quality and regulatory needs.

For PCB applications, consistent Parylene coverage and thickness are critical to long-term reliability. SCH provides:

• Coating thickness measurement – on witness coupons and representative PCB locations.
• Adhesion and cross-hatch checks – where appropriate to verify bond to solder mask and component materials.
• Visual inspection under magnification – confirmation of coverage in critical areas, edges and under components.
• Environmental and functional testing – in conjunction with customers for high-reliability programmes.

This approach supports repeatable production and quick root-cause analysis if issues arise anywhere in the supply chain.

SCH can support PCB manufacturers, OEMs and EMS providers at any stage of their Parylene journey:

• Subcontract PCB Parylene coating – from prototypes and qualification builds to volume production.
• Application development & trials – defining coating windows, test plans and qualification documentation.
• In-house Parylene capability – supply of Parylene systems, dimers and training to bring the process on-site.
• Design & troubleshooting support – help with design-for-Parylene, defect analysis and process optimisation.

Next step: share a sample PCB or design and we can advise on the most appropriate Parylene approach, costs and qualification route.

Arrange a PCB review with SCH ›

Related Parylene Resources

• Parylene Coating Services
• Parylene Deposition Equipment
• Parylene Dimer Supply
• Design for Parylene – Masking & DfC Guidelines

Explore More Parylene Applications

• Medical Devices
• Aerospace & Defence Electronics (coming soon)
• Automotive & EV Electronics (coming soon)
• Sensors, MEMS & High-Density Electronics (coming soon)

External Technical Reference

• IPC Standards for PCB Design & Protection