Intercoat Adhesion Failure in Conformal Coating

Intercoat adhesion failure is a conformal coating defect where a second coat (or local touch-up) does not bond to the first, causing peel-back, flaking, edge lift, wrinkling, or delamination between layers. It is usually driven by recoat timing, partial cure state, surface contamination, or chemical incompatibility between coats.

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

Quick Links

Sanity check (look-alikes):

• If the defect is mainly surface distortion after recoating, see Wrinkling / Recoat Defects.
• If coating lifts from the PCB substrate (not between coats), route to Delamination.
• If the surface shows craters/pull-back rings, check Fish-Eyes & Craters.
• If you suspect under-cure, see Tacky / Soft-Cured (Under-Cure).

What Intercoat Adhesion Failure Looks Like

• Peel-back or flaking of the second coat, often at touch-up edges or overlap zones.
• Layer separation where the top film can be lifted without disturbing the base coat.
• Edge lift after de-masking where a touch-up coat bridges onto a previously cured film.
• Wrinkling/rippling that appears only after recoating (often indicates recoat window or solvent interaction).
• “Two-tone” adhesion: one pass bonds, another pass fails (frequently contamination or cure drift).

Intercoat failures are high-risk because the coating may look “covered” but can create hidden moisture pathways at the interface and can fail during handling, vibration, or thermal cycling.

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Root Causes (Most Common Mechanisms)

1) Recoat window violated (too soon or too late)

Recoating too soon can trap solvent or disturb a soft film; recoating too late can mean the surface is fully cured and no longer receptive to bonding without activation.

2) Partial cure / skinning (surface feels “dry” but isn’t cured)

A skinned surface can look acceptable but still contains solvent or reactive species underneath. Recoating can cause intercoat shear, waviness, or weak adhesion. Cross-check Under-cure.

3) Contamination between coats

Common sources include masking residue, handling oils, airborne dust, silicone transfer, cleaning residue, or “tack cloth” contamination. If you see circular pull-back, also check Fish-Eyes & Craters.

4) Chemical incompatibility or solvent attack of the base coat

Some solvents can re-soften a cured coating, creating a weak boundary layer. This overlaps with Wrinkling / Recoat Defects and, on sensitive substrates, Solvent Attack.

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Fast Checks (Diagnose in Minutes)

1. Where does it occur? If it’s only at overlap/touch-up edges, suspect recoat window or contamination between coats.
2. Lift test at the interface: Can the top layer be peeled while the base layer stays attached? That’s classic intercoat failure.
3. Process history check: Was there a delay, shift change, bake/cure interruption, or masking removed/reapplied before touch-up?
4. Contamination check: Identify “last touch” between coats (gloves, fixtures, compressed air, dust exposure, masking residue).
5. Cure state check: If the base coat is soft/tacky, route to Under-cure first.

If the second coat shows wrinkling/rippling rather than peel-back, treat it as a recoat film-formation problem and cross-check Wrinkling / Recoat Defects.

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Prevention (What Actually Works in Production)

Lock the recoat rules

• Define the recoat window (minimum and maximum) and treat it as a controlled process requirement.
• Standardise touch-up timing after de-masking (don’t allow “whenever it’s convenient”).
• Control film build: heavy recoats raise solvent dwell and increase interface risk.

Control what happens between coats

• No-silicone rules, glove discipline, and clean fixtures for all handling after first coat.
• Protect WIP from dust/FOD (covered storage, defined dwell times).
• Masking residue control: if de-masking leaves adhesive residue, fix the masking method (don’t “clean and hope”).

Validate cure stability

• Keep time/temperature/UV dose stable within a validated window (drift creates intercoat variability).
• Where required, qualify surface activation/scuff/solvent wipe steps as a controlled process (not operator preference).

Tie prevention back to upstream control: Processes Hub, Masking Hub, and Inspection & Quality Hub.

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Rework & Repair Rules (When You Find It)

• Do not “coat over a failed interface”: recoating on top of intercoat failure usually peels again.
• Remove back to a sound edge: strip until the remaining film is firmly bonded and stable.
• Restore the surface condition: clean/activate per your approved method before recoating.
• Escalate if repeatable: if multiple boards show the same interface failure, treat it as a process-window or contamination event.

For structured removal and rework methods, use the Removal & Rework Hub.

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Training on Recoat Windows & Adhesion Failures

SCH delivers conformal coating training focused on real production failure modes—recoating windows, cure-state control, contamination transfer, masking discipline, and repair rules aligned to IPC expectations and customer requirements.

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.

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