Parylene vs Liquid Coatings: Selection Guide
Parylene vs liquid coatings is a common decision in electronics protection. This guide compares performance, geometry coverage, cost, process, and validation so you can select the right coating with confidence.
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What to Use When (Quick Summary)
- Choose Parylene for complex 3D assemblies, fine pitch, crevices, or harsh environments demanding ultra-conformal, pinhole-free barrier and high dielectric strength.
- Choose Liquid (acrylic, urethane, silicone, epoxy) for fast cycle time, easier rework, large volumes, or when localised masking/edge control is straightforward.
- Unsure? Start with a small design-of-experiments: coat witness coupons and a pilot build with both, then compare thickness verification and defect rates.
Performance Comparison
- Barrier to moisture/ionics: Parylene (C/F) excellent; liquids vary by chemistry and build. See defects risks: corrosion & ionic contamination.
- Dielectric strength at thin builds: Parylene N/C high; liquids require thicker films to match.
- High-temperature/chemicals: Parylene D/F strong; silicone/epoxy liquids good at temperature; check solvent resistance per datasheet.
- UV & outdoor exposure: Liquids can be formulated for UV; Parylene may need over-coat depending on application.
- Biocompatibility/medical: Parylene grades widely used; verify per device standard.
Background: Parylene basics · How to select a conformal coating
Geometry & Coverage
- Parylene: True 3D conformality via CVD—coats edges, under leads, and narrow gaps; ideal for dense/miniaturised PCBs.
- Liquid: Good planar coverage; risk of capillary wicking, de-wetting, or shadowing if process control is weak.
- Inspection: Verify edges using UV coverage for conformal coatings & a microscope for edge definition.
Process, Throughput & Equipment
- Parylene: Room-temp CVD; slower cycle times; requires vacuum chamber and fixturing. See deposition parameters.
- Liquid: Spray/selective/dip with rapid cure options (heat/UV/moisture). Easier to scale high volume.
- Masking: Parylene prefers reusable boots and custom shapes; liquids rely on tapes & dots plus process sealants.
- Inspection & thickness: Use optical meters (Parylene) and eddy-current gauges; manage plans via AQL, coupons & SPC.
Cost & Lifecycle
- Material & cycle cost: Liquids generally lower; Parylene has higher material/equipment time cost.
- Yield & field reliability: Parylene’s conformality can reduce latent failures; liquids excel where designs are simple and protection needs are moderate.
- Rework/repair: Liquids are easier to strip and spot-repair; Parylene requires precision micro-abrasion (see Parylene removal).
Standards, Inspection & Verification
- Align acceptance with IPC-A-610 (Class 1–3) and material qualification per IPC-CC-830 .
- Use inspection standards & methods and UV inspection for edges and keep-outs.
- Reference best-practice workmanship.
Selection Checklist
- Environment: humidity, salt, chemicals, temperature, UV exposure.
- Geometry: crevices, under-components, fine pitch, connectors.
- Electrical: dielectric margin vs thickness budget.
- Throughput: takt time, batch size, cure requirements.
- Rework: accessibility and removal method.
- Verification: coverage, edge quality, and thickness plan.
Hybrid Strategies
- Parylene + Local Liquid Over-coat: Parylene for 3D protection; add liquid dams or edge sealing where needed.
- Mixed Bill of Process: Critical assemblies in Parylene; cost-sensitive boards in liquid—with shared inspection and thickness control.
Need help deciding? Explore Parylene services or liquid coating services, plus training & consultancy.
Why Choose SCH Services?
Partnering with SCH Services means more than just outsourcing — you gain a complete, integrated platform for Conformal Coating, Parylene & ProShieldESD Solutions, alongside equipment, materials, and training, all backed by decades of expertise.
- ✈️ 25+ Years of Expertise – Trusted worldwide across aerospace, defence, medical, automotive, and electronics
- 🛠️ End-to-End Support – Coating selection, Parylene grades, masking strategies, application methods, inspection, and ProShieldESD integration
- 📈 Scalable Solutions – From prototypes to full-scale production
- 🌍 Global Reach – Technical support across Europe, North America, and Asia
- ✅ Proven Reliability – Consistent results, quality, and customer satisfaction
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