Humiseal 1A27LU | Urethane Conformal Coating

Harmonization Code : 3208.20.90 | Paints and varnishes that are dispersed or dissolved in a non aqueous medium

Humiseal 1A27LU | Urethane Conformal Coating

Main features

Isocyanate-free
Single-component
UV fluorescent

Product Description

HumiSeal® 1A27LU is a single-component, polyurethane conformal coating designed for general-purpose printed circuit board applications. 1A27LU contains no free isocyanates, making it a safer option. This coating also fluoresces under UV light, which allows for easy inspection.

Product Key Features

Isocyanate-free
Single-component — Easy to apply without needing to mix multiple parts.
UV fluorescent — Glows under UV light, simplifying the inspection process.
Adheres to the RoHS Directive 2002/95/EC.
Recognized under UL File Number E105698.

Applications

Provides a protective layer for general-purpose PCB applications.

Specifications
Additional Information

Technical Specifications

General Properties

Density (g)

0.96 g/cm3

Solids

50 %

Physical Properties

Viscosity

Viscosity
Viscosity is a measurement of a fluid’s resistance to flow.

Viscosity is commonly measured in centiPoise (cP). One cP is defined as
the viscosity of water and all other viscosities are derived from this base. MPa is another common unit with a 1:1 conversion to cP.

A product like honey would have a much higher viscosity -around 10,000 cPs-
compared to water. As a result, honey would flow much slower out of a tipped glass than
water would.

The viscosity of a material can be decreased with an increase in temperature in
order to better suit an application

1700 mPa.s

Electrical Properties

Breakdown Voltage

Breakdown Voltage
Breakdown voltage is the minimum voltage necessary to force an insulator to conduct some amount of electricity.
It is the point at which a material ceases to be an insulator and becomes a resistor that conducts electricity at some proportion of the total current.

After dielectric breakdown, the material may or may not behave as an insulator any more because of the molecular structure alteration. The current flow tend to create a localised puncture that totally alters the dielectric properties of the material.

This electrical property is thickness dependent and is the maximum amount of voltage that a dielectric material can withstand before breaking down. The breakdown voltage is calculated by multiplying the dielectric strength of the material times the thickness of the film.

7500 V

Dielectric Constant

Dielectric Constant
Dielectric Constant (k), commonly known as relative permittivity, is a number relating the ability of a material to carry alternating current to the ability of vacuum to carry alternating current.

It determines the ability of an insulator to store electrical energy and is the ratio of electric permeability in vacuum against the electric permeability of a material.

The lower the dielectric constant (κ) and dissipation factor, the less energy is absorbed from an electric field, making it a much better insulator.

It is a dimensionless property that can be affected by various factors such as the thickness uniformity of a material, insufficient contact between the sample and electrodes, water adsorption and contact resistance.

Dielectric Constant @ 1000 kHz

3.6

Dissipation Factor

Dissipation Factor
Dissipation factor is commonly known as loss tangent or tan delta.

It is a ratio of the loss index and the relative permittivity and it measures the inefficiency of an insulating material to maintain energy (that otherwise dissipates in the form of heat). The lower the factor, the better the insulation.

It is the reciprocal of the quality factor and always refers to a specific temperature and frequency.

Dissipation Factor @ 25°C /1000 kHz

0.02

Mechanical Properties

Storage (DMA) Modulus
Storage (DMA) Modulus @ 25°C	18.1 N/mm2

Thermal Properties

Coefficient of Thermal Expansion (CTE)

Coefficient of Thermal Expansion (CTE)
CTE (Coefficient of thermal expansion) is a material property that is indicative of the extent to which a material expands with a change in temperature. This can be a change in length, area or volume, depending on the material.

Knowing the CTE of the layers is helpful in analyzing stresses that might occur when a
system consists of an adhesive plus some other solid component.

Coefficient of Thermal Expansion (CTE) , α1

Coefficient of Thermal Expansion (CTE) , α1
CTE α1 (alpha 1) is the slope of the Coefficient of thermal expansion in a temperature range below the Glass transition temperature (Tg).

It explains how much a material will expand until it reaches Tg.

170 ppm/°C

Glass Transition Temperature (Tg)

Glass Transition Temperature (Tg)
The glass transition temperature for organic adhesives is a temperature region where the polymers change from glassy and brittle to soft and rubbery. Increasing the temperature further continues the softening process as the viscosity drops too. Temperatures between the glass transition temperature and below the decomposition point of the adhesive are the best region for bonding.

The glass-transition temperature Tg of a material characterizes the range of temperatures over which this glass transition occurs.

28 °C

Operating Temperature

-65 - 125 °C

Curing Conditions

Curing Schedule Curing Schedule Curing schedule is the time and temperature required for a mixed material to fully cure. While this applies to materials that cure with heat, there are also other materials that can be cured with UV. Even though some materials can cure on ambient temperatures, others will require elevated temperature conditions to properly cure. There are various curing schedules depending on the material type and application. For heat curing, the most common ones are Snap cure, Low temperature cure, Step cure and Staged cure. Recommended cure type, schedule, time and temperature can always be found on the Technical data sheets.
Cure Time	25 minutes
Full Cure Time	30 hours

Additional Information

Frequently Asked Questions About HumiSeal® 1A27LU

What are typical applications for HumiSeal® 1A27LU?

HumiSeal® 1A27LU is a general-purpose, single-component, fast air drying acrylic conformal coating that is used for protecting printed circuit board assemblies (PCBs) in various industries, including:

Aerospace systems (e.g., avionics, control modules)
Automotive electronics (e.g., engine control units, sensors)
Industrial automation (e.g., motor drives, PLCs)
Consumer electronics (e.g., smartphones, gaming devices)

Why choose HumiSeal® 1A27LU over other conformal coatings?

HumiSeal® 1A27LU is easy to use and provides excellent protection. It provides excellent electrical insulation, fluoresces under UV for easy inspection, and is easily repairable with HumiSeal® Stripper 1063. It is also compliant with MIL-I-46058C and RoHS 2002/95/EC, making it a trusted choice for demanding applications. You can learn how to select a conformal coating in our latest blog.

What is the shelf life of HumiSeal® 1A27LU?

HumiSeal® 1A27LU has a shelf life of 24 months from the date of manufacture when stored at room temperature (0 to 35°C) in tightly closed containers. Prior to use, allow the product to equilibrate for 24 hours at 18 to 32°C to ensure optimal performance.

How should I clean tools after applying HumiSeal® 1A27LU?

Tools and equipment used for applying HumiSeal® 1A27LU (e.g., spray guns, brushes, or dipping tanks) can be cleaned using HumiSeal® Thinner 521 for spraying. For removing the coating from PCBs during rework, use HumiSeal® Stripper 1063. Always use a lint-free cloth and ensure proper ventilation during cleaning.

What happens to HumiSeal® 1A27LU after its shelf life?

Past its 24-month shelf life, HumiSeal® 1A27LU may experience changes in viscosity, which could affect application consistency and coating uniformity. Using expired product may lead to suboptimal performance, and the manufacturer will not be liable for quality or performance issues if expired material is used.

Why do curing times vary for HumiSeal® 1A27LU?

HumiSeal® 1A27LU is a fast air drying coating. Drying times vary depending on temperature, humidity, and film thickness. Typically, the coating will be tack-free in approximately 15 minutes, dry to handle in one hour, and fully cured in 24 hours.

What is the recommended thickness for HumiSeal® 1A27LU?

The recommended coating thickness for HumiSeal® 1A27LU is 25 to 75 microns. This range ensures optimal protection without compromising flexibility or electrical performance. The thickness can be adjusted by controlling viscosity with HumiSeal® Thinner 521 during application.

What are the differences between application methods for HumiSeal® 1A27LU?

HumiSeal® 1A27LU can be applied via spraying, dipping, or brushing. Spraying and dipping are ideal for large-scale production, while brushing is suited for small repairs. Each method requires adjusting viscosity with Thinner 521 for a uniform coating.

What is the maximum operating temperature for HumiSeal® 1A27LU?

HumiSeal® 1A27LU can withstand thermal shock from –65°C to +125°C. It is not recommended for continuous operation above 130°C, as prolonged exposure to higher temperatures may degrade its protective properties.

What safety precautions should I take when using HumiSeal® 1A27LU?

The solvents in HumiSeal® 1A27LU are flammable, so avoid open flames or sparks during application. Use in a well-ventilated area to prevent inhalation of vapors or spray mist, and avoid skin and eye contact. Always consult the Safety Data Sheet (SDS) prior to use for detailed safety guidelines.

How can I ensure proper application of HumiSeal® 1A27LU?

HumiSeal® 1A27LU fluoresces under UV light, allowing for easy inspection of coating coverage. After application, use a UV light source to check for uniform coating and ensure there are no missed areas, which is critical for high-reliability electronics manufacturing.

How does HumiSeal® 1A27LU perform in harsh environments?

HumiSeal® 1A27LU is designed for harsh conditions, with a moisture insulation resistance of 1.2 × 10¹⁰ ohms (12GΩ) and fungus resistance per ASTM G21. It maintains performance in humid, mechanically stressful, or temperature-cycling environments, making it ideal for mission-critical systems.

Learn More About HumiSeal® 1A27LU

HumiSeal® 1A27LU is a proven solution for engineers seeking long-term protection of electronic assemblies in demanding environments. This acrylic conformal coating offers a unique combination of ease of use, excellent electrical insulation, and mechanical resilience—making it an industry favorite for protecting PCBs in sectors such as automotive, aerospace, consumer electronics, and industrial automation.

Key Features at a Glance

✔ Tack-free in 15 minutes at room temperature
✔ Compatible with “no-clean” flux residues
✔ Rated UL 94 V-0 for flame retardancy

Versatile Application Methods 🧰

Application methods

Whether you’re using spraying, dipping, or brushing, 1A27LU offers flexibility in manufacturing workflows. It can be diluted with HumiSeal® Thinner 521 to fine-tune application characteristics based on part geometry and production scale. The coating cures at room temperature in 24 hours, allowing integration into both batch and inline processes.

Application Methods:

Spray: Dilute 1:1 with HumiSeal® Thinner 521
Dip: 5–15 cm/min withdrawal rate
Brush: For touch-up applications

Cure the coating at room temperature (24 hrs) for convenience, or accelerate with thermal curing to match fast-paced production cycles.

Application Compatibility

It integrates well with lead-free processes, supports standard cleaning practices, and offers strong performance even on flux-contaminated surfaces.

Compatible With:

✔ Compatible with “no-clean” flux residues
✔ Common PCB finishes including ENIG, HASL, and OSP
✔ High-reliability applications requiring low ionic content
✔ Lead-free and RoHS-compliant manufacturing environments
✔ Cures at room temperature (24 hrs)

Additionally, its UV fluorescence ensures easy inspection, and the coating is reworkable using standard HumiSeal strippers—ideal for repairable designs and serviceable assemblies.

High-Performance Electrical Protection 🧪

1A27LU delivers a dielectric breakdown voltage of 1,500 volts and an insulation resistance exceeding 5.0 × 10¹² ohms, protecting even the most sensitive circuit designs from moisture, contaminants, and voltage-induced failure. It’s also rated UL 94 V-0, ensuring flame retardancy in critical applications.

Fluorescent for Inspection 💡

To simplify quality assurance, HumiSeal® 1A27LU fluoresces under UV light, making it easy to confirm proper coating coverage during post-application inspection—an essential feature for high-reliability electronics manufacturers.

Repairable and Reworkable 🔁

Unlike many conformal coatings, HumiSeal® 1A27LU is easily repairable. Should rework or component replacement be required, the coating can be selectively removed using HumiSeal® Stripper 1063, making it ideal for prototyping, low-volume builds, or field serviceability.

Reliable Across Environments 🌍

With a wide thermal shock range of –65°C to +125°C and resistance to fungus (ASTM G21) and moisture, 1A27LU ensures consistent performance across varied environmental conditions. It’s particularly well-suited for mission-critical systems exposed to humidity, mechanical stress, or temperature cycling.