Masking for Parylene
Parylene masking prevents coating on keep-out areas during vacuum CVD and drives crisp edge definition. This guide covers mask types (reusable silicone boots, tapes & dots, custom shapes), vacuum-compatible materials, and a step-by-step process to avoid leakage, feathering, or wicking.
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Why Masking Matters in Parylene
- Parylene deposits everywhere line-of-sight and by diffusion—unmasked gaps, vents, and threads will coat.
- Sharp edges around connectors and mating surfaces protect functionality and speed reassembly.
- Proper masking reduces rework and the need for Parylene removal.
Background: Parylene basics · deposition parameters
Mask Types: Boots, Tapes & Custom Shapes
- Reusable Boots: Best edge quality and speed for connectors, switches, and headers. Choose sizes that compress slightly for a vacuum seal.
- Tapes & Dots: Flexible for odd keep-outs; burnish edges firmly. Use tabbed dots for fast demask.
- Custom Shapes: CNC/3D-printed or die-cut masks for complex geometries, threaded holes, and multi-level features.
Vacuum-Compatible Materials
- Prefer low-outgassing silicones and fluoro-elastomers for boots; avoid softeners that migrate.
- Use high-temperature, low-residue adhesives for tapes; pre-bake rolls to stabilise.
- Reject porous foams or paper liners that vent under vacuum.
Standards & guidance: NASA workmanship · IPC-CC-830
Application Workflow
- Design & DFM: Define keep-outs and pull clearances early; select mask types per feature.
- Prep: Clean board; pre-bake masks; verify fit on a golden sample.
- Apply: Fit boots fully; burnish tapes at edges; plug/vent holes as needed.
- Verify: Use inspection for edge seal before loading.
- Deposit: Load per CVD parameters; avoid mask shift during fixturing.
- Demask: Remove slowly at shallow angle; avoid tearing fillets.
- Inspect: Confirm edges/keep-outs; repair locally or, if needed, use micro-abrasion.
Need operator training? We run masking masterclasses for Parylene lines.
Edge Control & Common Defects
- Feathered edges: Improve compression or change mask type.
- Leakage under tape: Re-burnish; replace tape; consider a boot or custom mask.
- Wicking into gaps: Plug vents/through-holes; review fixturing and load orientation.
See the Defects Hub for de-wetting, capillary/wicking, and delamination guidance.
Process Controls & Inspection
- Document mask IDs, lot codes, and reuse cycles; retire worn boots.
- Thickness plans: AQL, coupons & SPC using optical meters or eddy-current gauges.
- Inspection gates: Magnification checks of coverage/edges, white-light finish, and keep-out verification against drawings.
Special Cases
- Connectors & headers: Use sized boots; verify mating face and latch areas remain clean.
- Press-fit & threaded features: Seal threads and vents with custom plugs/shapes.
- Cavities & under-components: Add temporary fillers or change orientation to limit diffusion paths.
If post-coat cleanup is required, see Parylene removal by micro-abrasion.
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 hands-on expertise.
- ✈️ 25+ Years of Expertise – Specialists in coating technologies trusted worldwide.
- 🛠️ End-to-End Support – Guidance on coating selection, Parylene grades, masking, inspection, and ProShieldESD integration.
- 📈 Scalable Solutions – From prototype batches to high-volume production, SCH grows with your needs.
- 🌍 Global Reach – Responsive support across Europe, North America, and Asia.
- ✅ Proven Reliability – Built on quality, consistency, and customer satisfaction.
📞 Call: +44 (0)1226 249019
✉ Email: sales@schservices.com
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