Cracking in Conformal Coating

Cracking occurs when the cured conformal coating film fractures, creating fissures that can expose the PCB surface. Cracks undermine protection, allow moisture and contaminants to penetrate, and can reduce electrical insulation performance over time.

For the complete index of defect types and links to each dedicated article, use the hub overview: Conformal Coating Defects Hub. For wider process context (application methods, control windows and repeatability), see the Conformal Coating Processes Hub.

Collage of conformal coating cracking defects on PCB surfaces under UV and visible light inspection
Examples of cracking in conformal coating showing fracture networks across pads, component edges, and high-stress regions under UV and visible inspection.

What is Cracking in Conformal Coating?

  • Definition: Fractures and fissures in the cured coating film that can expose the underlying board.
  • Main issue: Cracks form moisture/leakage pathways, compromise insulation resistance, and can propagate under thermal or mechanical stress.

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Causes of Cracking in Conformal Coating

  • Excess cure temperature or fast ramp — high thermal gradients lock stress into the film.
  • Insufficient flash-off — trapped solvent embrittles the coating.
  • Excessive film build — higher shrink stress, especially at edges.
  • CTE mismatch — differential expansion between coating and assembly materials.
  • Inflexible chemistry / high Tg — coating cannot accommodate movement.
  • Geometry-driven stress concentrators — sharp edges, solder peaks, step-changes.
  • Service loads — vibration, shock, board flex, and thermal cycling.
  • Sanity check (look-alikes): Route to delamination, pinholes, de-wetting, or orange peel if morphology does not match fracture behaviour.

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How to Prevent Conformal Coating Cracking

  • Reduce cure stress — controlled ramps and profiles.
  • Allow adequate flash-off before heat cure.
  • Control thickness — stay within qualified limits.
  • Match material to duty — flexibility vs environment.
  • Validate profiles using representative testing.

Use the Inspection & Quality Hub to define verification and acceptance.

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Troubleshooting & Diagnosis

  • Microscopy & mapping — crack location and pattern.
  • Thickness verification — coupons and features.
  • Cure profile review — ramp/soak/peak.
  • Material condition — viscosity, age, storage.
  • Environmental replication — confirm mechanism.

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Training on Conformal Coating Defects

SCH offers conformal coating training that goes beyond theory—recognising and preventing cracking, delamination, de-wetting, orange peel, pinholes/bubbles/foam, and wicking. We cover process analysis, troubleshooting, materials, and application methods.

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Industry Standards We Work To

SCH Services aligns coating services, training, equipment supply and materials to relevant IPC standards, including:

  • IPC-A-610 – Acceptability of Electronic Assemblies
  • IPC-CC-830 – Qualification & Performance of Conformal Coatings
  • IPC-HDBK-830 – Conformal Coating Handbook (guidance and best practice)

For further details on IPC standards:
electronics.org/ipc-standards ↗

Explore Topic Hubs

Conformal Coating Processes Hub
Core coating processes (spray, dip, selective, brush) plus setup, control windows, and optimisation for repeatable results.

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Conformal Coating Equipment Hub
Equipment selection, setup and best-practice for spray/booths, dip systems, valves and selective robotics.

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Conformal Coating Masking Hub
Masking methods & materials (tapes, dots, boots, latex, custom shapes) and when to use barrier vs shielding.

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Conformal Coating Design Hub
Design-for-coating guidance: keep-outs, spacing, creepage/clearance, drainage, inspection aids, and DfM/DfCC.

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Conformal Coating Defects Hub
Defect mechanisms, root causes, diagnosis and prevention (pinholes, orange peel, de-wetting, delamination, cracking, corrosion, wicking).

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Inspection & Quality Hub
Inspection methods and control plans: UV checks, thickness verification, AQL/coupons/SPC, and standards-aligned acceptance.

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Removal & Rework Hub
Removal and rework methods (wet stripping, micro-abrasion, local vs full removal) plus structured rework workflow.

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Standards Hub
Key conformal coating and Parylene standards and how they map to inspection, workmanship and qualification expectations.

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Parylene Basics Hub
Parylene fundamentals: grades, deposition, masking, thickness measurement and specification basics.

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Parylene Design Hub
Design-for-Parylene: layout/spacing, vapour access, masking design, materials/adhesion, and DfM for scale-up.

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Parylene Application Hub
Application-led guidance across medical, PCB protection, aerospace/defence, automotive/EV, sensors/MEMS and harsh environments.

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Parylene Dimers Hub
Dimer chemistry, grades (N/C/D/AF-4), purity impacts, and selecting the right dimer for performance and reliability.

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Why Choose SCH Services?

You gain a complete, integrated platform for Conformal Coating, Parylene & ProShieldESD—plus equipment, materials and training—backed by decades of hands-on process support.

  • 🛠️ End-to-End Support – Selection, masking, inspection and troubleshooting.
  • ✅ Process Discipline – Recipes, control windows and repeatability.
  • 🌍 Global Reach – Support across Europe, North America and Asia.

📞 Call: +44 (0)1226 249019   | ✉ Email: sales@schservices.com |   💬 Contact Us ›

Note: This article provides general technical guidance only. Final design, safety, and compliance decisions must be verified by the product manufacturer and validated against the applicable standards.