M78-3068UV Dual-Cure UV Conformal Coating for PCBs

Description

Product Overview：

M78-3068UV is a UV conformal coating designed to protect electronic assemblies against moisture, contamination, and environmental exposure. Its dual-cure system addresses a common challenge on populated circuit boards: components can block UV light from reaching all coated surfaces.

Directly exposed coating cures under suitable UV irradiation, while material in shadowed areas continues to cure through a secondary moisture reaction. This combination supports fast processing of accessible surfaces while providing a curing mechanism for areas beyond direct light exposure.

The product is supplied as a colorless to pale yellow transparent liquid with 100% non-volatile content reported in the TDS. Fluorescent tracking supports coating coverage inspection, helping operators identify missed areas and application inconsistencies.

After curing, M78-3068UV forms a hard, tough protective film. The TDS reports resistance to salt spray, high-temperature/high-humidity aging, and thermal shock, alongside electrical properties including volume resistivity of 2.6 × 10¹⁶ Ω·cm and dielectric strength of 75 kV/mm.

The stated typical operating range of the cured material is −55°C to +125°C. Application suitability should be verified on the actual assembly, including coating thickness, component compatibility, and completion of shadow-area curing.

Key Features and Benefits：

  · UV/Moisture Dual Cure: Combines UV curing of exposed surfaces with secondary moisture curing in areas shaded by components.

  · Rapid Primary Cure: Supports fast processing under a validated UV exposure. Final release criteria must also account for the slower moisture cure in shadowed areas.

  · 100% Non-Volatile Content: Reported in the TDS, supporting high film build without relying on conventional solvent evaporation as the main drying mechanism.

  · Fluorescent Inspection: Helps operators check coating coverage under suitable inspection lighting. Fluorescence indicates coverage, not proof of complete cure.

  · Electrical Insulation: The TDS reports dielectric strength of 75 kV/mm and volume resistivity of 2.6 × 10¹⁶ Ω·cm.

  · Salt Spray Resistance: After 172 hours at 35°C using 5% NaCl solution, the reported result shows no blistering, peeling, or wrinkling, and no substrate corrosion.

  · High-Temperature/High-Humidity Resistance: After 10 days at 85°C and 85% RH, the film showed no wrinkling, chalking, peeling, or reversion to a liquid state.

  · Thermal Shock Resistance: The film showed no delamination, wrinkling, blistering, peeling, or cracking after 100 cycles between −45°C and +135°C under the specified test conditions.

  · Tough, Abrasion-Resistant Film: Cures to a hard protective surface, with a reported Shore D hardness of 75–90.

  · Strong Adhesion: Achieves a reported cross-cut adhesion classification of Grade 0 under GB/T 9286-1998.

Typical Applications：

M78-3068UV conformal coating is intended for:

  · Populated Printed Circuit Boards: Protective coating of assemblies containing components that create UV shadow areas.

  · Thick-Film Circuit Systems: Environmental protection of compatible circuit substrates and assemblies.

  · Porous Substrates: Coating applications where substrate compatibility, penetration, and cure can be validated.

  · Electronic Assemblies Exposed to Humidity or Salt-Laden Environments: Applications requiring protection supported by assembly-level testing.

  · Production Lines Using UV Curing: Coating processes that benefit from rapid primary cure and fluorescent coverage inspection.

The coating does not replace an enclosure or establish an ingress-protection rating. Confirm compatibility with connectors, sensors, optics, plastics, and other sensitive components before use.

Physical Properties：

Post-Cure Properties：

Technical Notes:

  · UV dose in mJ/cm² and irradiance in mW/cm² are different parameters.

  · The viscosity is dynamic viscosity, not cup flow time.

  · The dielectric dissipation factor of 0.01 is dimensionless.

  · The short-duration thermal shock test at +135°C does not extend the stated typical use range above +125°C.

Application Guidance：

  · Surface cleaning

For the best bonding performance, the surface to be bonded must be dry and free of dust, grease and other contaminants;

  · Application

Any of spraying, dip coating or brushing may be chosen; carry out application tests before use for more convenient application.

  · Curing

The UV curing rate depends on lamp intensity, distance between light source and coating, required curing depth or coating gap, and substrate light transmittance;

Use UV or visible light with a wavelength range of 320-420 nm;

（- unsuitable   + suitable   ++ very suitable）

The above are recommended curing conditions. Actual conditions may vary with customer experience, application requirements and curing equipment.

  · Tack-free curing of exposed surfaces needs high UV intensity (min. 500 mW/cm²); a 1000 mW/cm² mercury/electrodeless lamp usually gives better surface drying.

  · Shadowed areas moisture-cure; ≥2-3 days recommended (25℃/50%RH). Higher temperature/humidity shortens curing; lower prolongs it.

UV vs. Conventional Conformal Coating Advantages and Limitations：

In this comparison, “conventional conformal coating” means non-UV systems that dry or cure through solvent evaporation, moisture, heat, or a chemical reaction. These include acrylic, polyurethane, silicone, and other formulations.

UV describes a curing mechanism, not a single resin chemistry. Protection, flexibility, and reworkability therefore depend on the individual formulation as well as the curing method.

UV-cured conformal coatings are used in high-throughput manufacturing, while dual-cure products add a secondary curing mechanism for shadowed regions. These regions must be included in the production release criteria. 

Main Advantages of UV Conformal Coating

  · Rapid primary cure on directly exposed surfaces.

  · Good fit for repeatable, automated production.

  · High-solids options that reduce reliance on solvent evaporation.

  · Formulations offering strong abrasion and chemical resistance.

  · Dual-cure options for populated boards with shadowed areas.

Main Limitations of UV Conformal Coating

  · Requires suitable UV equipment and exposure monitoring.

  · Shadowed areas cannot be assumed fully cured after UV exposure.

  · Secondary curing may add hours or days before final release.

  · Highly crosslinked films can complicate removal and repair.

  · Board geometry and coating thickness require careful validation.

Main Advantages of Conventional Conformal Coating

  · Broad choice of resin chemistries and application properties.

  · Some grades offer simple processing with limited curing equipment.

  · No dependence on direct UV access.

  · Reworkable acrylic grades can suit repair-intensive applications.

  · Often practical for prototypes, small batches, and existing coating lines.

Main Limitations of Conventional Conformal Coating

  · Drying or curing may require longer production time.

  · Solvent-based grades introduce vapor, odor, and flammability considerations.

  · Moisture-cure systems depend on environmental conditions.

  · Heat-cure systems require a compatible assembly and controlled oven cycle.

  · Reworkability and environmental resistance vary widely by chemistry.

Removal procedures must be selected for the actual coating. Manufacturer guidance for UV coatings includes specialized mechanical or thermal methods, with care needed to avoid damaging solder mask and components.

Precautions：

  · This product is UV-sensitive; avoid exposure to daylight, UV and artificial light sources during storage and handling.

  · After application, immediately tighten the cap of any unused product and store it sealed. On re-use, if slight skinning has formed at the seal, simply remove it — normal use is not affected.

Packaging, Storage/Transport & Shelf Life：

  · Packaging

1 KG/pail, 4 KG/pail

  · Storage

Store sealed in a dark, cool, dry, ventilated place; shelf life 6 months from production. Products past shelf life should be confirmed normal before use.

  · Transport

Transport as a special chemical per national laws and regulations.