Troubleshooting Decision Tree for Conformal Coating Defects

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This conformal coating troubleshooting decision tree provides a structured diagnostic flow to identify defects before repair, rework, or escalation. It’s designed to stop the two most common failure patterns: (1) treating symptoms instead of mechanisms, and (2) “fixing” one board while the process keeps drifting.

If you want fast symptom routing first, use the Defect Identification Guide (Symptom-Based Routing).

For the complete index of defect types and links to each technical article, use the Conformal Coating Defects Hub.

Article Quicklinks

Topic	More
When to use this: what the decision tree does (and doesn’t)	🔗
Step 0: containment + stop-the-line checks	🔗
Step 1: classify the symptom (coverage / finish / cure / adhesion / electrical)	🔗
Step 2: location logic (edges, keep-outs, under parts, fine pitch)	🔗
Step 3: confirm mechanism with minimum tests (don’t guess)	🔗
Step 4: corrective actions (process fixes) vs repairs (board fixes)	🔗
Step 5: link to accept / touch-up / strip & recoat rules	🔗
Fast links: route to the right defect article quickly	🔗

When to Use This Conformal Coating Troubleshooting Decision Tree

• Use this page when you have a defect, reject, or field return and need to isolate the root cause with repeatable logic.
• Use the Identification Guide when you just need fast routing from appearance to the best-fit mechanism.
• Escalate immediately if the issue is electrical safety-critical, customer stop-ship, or indicates corrosion / ECM / CAF risk on biased conductors.

This decision tree is intentionally “process-first”: a perfect local touch-up is meaningless if the upstream cause remains active.

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Step 0 — Containment Before You Troubleshoot

Stop the drift

• Quarantine affected lots (don’t mix with “good” WIP).
• Freeze variables: same operator, same chemistry batch, same settings, same cure profile, same masking method.
• Capture evidence: UV + white light photos, location map, time stamps (clean → coat → cure), coating batch, viscosity, booth RH/temp.

Rapid checks (10–15 minutes)

• Masking boundary audit: look for edge damage, residue transfer, or ingress into keep-outs.
• Environment: confirm booth RH/temperature stability and compressed air quality.
• Viscosity & pot life: verify against your control window (don’t assume it’s fine).
• Cure profile: confirm time/temperature/UV dose matches the qualified recipe (and the real part temperature).

If the defect is at or near a keep-out boundary, assume masking or selective pathing until proven otherwise.

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Step 1 — Classify the Symptom Family

A) Coverage / boundary symptoms

• Missing/thin coating, UV weak zones, “holidays”, shadowing behind tall parts.
• Coating in connectors/test pads/mating faces; boundary bleed; keep-out contamination.

B) Flow / finish symptoms

• Runs/sags/curtains, pooling/puddling, rough/texture problems, orange peel.
• Cratering/fish-eyes, dust/fibres/FOD embedded, surface haze/residue films.

C) Cure / film formation symptoms

• Pinholes/bubbles/foam, bubbles appearing during/after cure (outgassing/blisters).
• Tacky/soft cure, brittle/over-cure, wrinkling/recoat distortion.

D) Adhesion / interface symptoms

• De-wetting islands, peel-back at boundaries, mask-edge lift during demask, delamination.
• Intercoat adhesion failure: flaking/edge lift/wrinkling between layers or touch-ups.

E) Electrical / electrochemical symptoms

• SIR leakage, intermittent shorts, dendrites/ECM, corrosion patterns, CAF in laminate.

If you’re unsure, route via the Defect Identification Guide and then return here to isolate root cause and process fixes.

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Step 2 — Apply Location Logic (The “Where” Tells You the “Why”)

• At keep-out boundaries (connectors/test pads/mating faces): masking or selective recipe/pathing is the prime suspect.
• Behind tall components: shadowing / approach angle / access limitations.
• Under low-standoff parts: capillary wicking, trapped solvent/moisture, ionic residues, outgassing risk.
• Fine pitch / biased conductors: SIR leakage, ECM/dendrites, contamination + moisture + bias mechanisms.
• Edges / board perimeters: film thinning, moisture pathways, handling contamination, cure gradients.
• Only on plastics/connector bodies: low surface energy, mould release/silicone transfer, incompatibility.

This step prevents the classic failure: spending hours tuning spray settings when the real issue is masking boundary damage or contamination transfer.

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Step 3 — Confirm the Mechanism (Minimum Tests, Maximum Certainty)

Visual + simple process confirmations

• UV + white-light inspection: coverage, thin edges, voids, contamination, boundary damage.
• Solvent swab / tack check (where valid): under-cure and surface films.
• Thickness verification (coupons / defined checks): confirm film build vs spec and local pooling risk.

Electrical / contamination confirmations (when symptoms point to reliability risk)

• SIR / humidity-bias where appropriate to replicate leakage / ECM risk.
• ROSE for process drift monitoring on comparable product/process.
• Ion chromatography for ionic species identification and source tracing (higher criticality).

If you suspect ECM/dendrites, SIR leakage, CAF or corrosion, do not “rework and hope” — confirm contamination/moisture/bias risk and treat it as a control-plan issue.

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Step 4 — Split Actions Into Two Tracks

Track 1: Process corrective actions (prevention)

• Masking control: method selection (shield vs sealed barrier), fit/seal, removal timing, post-demask inspection rules.
• Cleanliness control: validated wash/rinse/dry, handling discipline, compressed air quality, contamination transfer points.
• Recipe control: viscosity window, spray atomisation, distance, overlap, flash-off discipline, cure profiling.
• Environment control: booth RH/temp stability, airflow management, tack-off steps, FOD control.

Track 2: Product repair actions (containment)

• Local removal + touch-up (only if mechanism is localised and verification is possible).
• Strip + re-clean + verify + recoat (for systemic failures or hidden-risk mechanisms).

Rule of thumb: if you cannot inspect/verify the affected area (under low-standoff parts, deep interfaces, hidden conductors), assume the mechanism may remain active and escalate repair level.

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Step 5 — Apply Acceptance & Repair Rules (Don’t Invent Them on the Line)

Once you’ve confirmed the mechanism, apply the pre-defined decision rules for accept, touch-up, or strip & re-coat. This prevents “operator judgement drift” from becoming a new failure mode.

Use: Defect Acceptance & Repair Rules and the Top 10 Root Causes page to lock your upstream controls.

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Fast Links: Route to the Correct Defect Article

Use these links once you’ve classified the symptom family (Step 1) and applied location logic (Step 2).

Coverage & Boundary

• Insufficient Coverage & Shadowing
• Coating Ingress into Keep-Out Areas
• Bridging & Webbing
• Capillary / Wicking

Flow & Finish

• Runs, Sags & Curtains
• Pooling & Puddling
• Orange Peel
• Texture & Finish Defects (Router)
• Blooming / Surface Residue
• Fish-Eyes & Craters
• Dust, Fibres & FOD

Cure-State & Film Formation

• Pinholes, Bubbles & Foam
• Bubbles After Cure (Outgassing / Blisters)
• Haze, Whitening & Blushing
• Tacky / Soft-Cured (Under-Cure)
• Brittle / Over-Cured
• Wrinkling (Recoating / Distortion)

Adhesion & Interfaces

• De-wetting
• Poor Adhesion on Plastics / Connectors
• Mask-Edge Lift & Demask Damage
• Intercoat Adhesion Failure (Recoat / Touch-Up)
• Delamination

Reliability & Electrochemical

• SIR Failures & Leakage Under Coating
• Electrochemical Migration & Dendrite Growth
• CAF Under Coating / Under Solder Mask
• Corrosion & Ionic Contamination
• Solvent Attack & Substrate Damage
• Cracking

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Looking for Other Defect Types?

This page covers the Troubleshooting Decision Tree for conformal coating defects. For the complete index of defect types and links to each technical article:

Explore the Defects Hub ↗

Training on Conformal Coating Defects

SCH delivers practical, standards-driven training covering defect identification, troubleshooting workflows, cleanliness control, inspection discipline, and the wider defects framework used to prevent repeat failures.

Explore Conformal Coating Training ↗

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 ↗

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.