Humiseal 1A33 | Urethane Conformal Coating

Harmonization Code : 3909.20.00.90 | Amino-resins, phenolic resins and polyurethanes, in primary forms : Melamine resins : Other

Humiseal 1A33 | Urethane Conformal Coating

Main features

Urethane Conformal Coating
Transparent (UV Fluorescent)
Low moisture vapor permeability

Product Description

HumiSeal® 1A33 is a single-component, polyurethane conformal coating designed for protection of printed circuit board (PCB) assemblies. It features excellent chemical resistance and moisture protection without containing any free isocyanates, making it safe and environmentally-friendly. The coating fluoresces under UV light, allowing for easy inspection and quality control during and after application.

HumiSeal® 1A33 can be applied by spraying, brushing, or dipping, and its viscosity can be adjusted with compatible thinners (503/521/521EU/600) to ensure uniform coverage, including sharp edges. Optional curing conditions to reach optimum properties is 30 days at RT or 30 hours @ 76°C or 20 hours @ 88°C.

HumiSeal® 1A33 meets rigorous industry standards, including MIL-I-46058C, IPC-CC-830B, IEC 60664-3, UL 746E, UL 94 V-0, and RoHS Directive 2015/863/EU. It is UL recognized (UL File Number E105698) and complies with IEC 61086 and IEC 60068-2-11, making it suitable for demanding applications in military, renewable energy, industrial, automotive, and consumer electronics sectors.

Target Applications

General printed circuit board applications
Automotive electronic applications, including in-cabin and exterior use.
Military equipment requiring durable performance.
Renewable energy systems needing robust electronic reliability.
Industrial controls exposed to high humidity, salt-spray, and corrosive environments.

Specifications
Additional Information

Technical Specifications

General Properties

Density (g)

0.95 g/cm3

Solids

44 %

Shelf Life Shelf Life Shelf life is the amount of time after manufacturing that a product is guaranteed to retain its properties. It differs vastly per product and it is based on temperature and storage conditions. The properties can be guaranteed for the temperature and time range indicated on the TDS since those are the ones tested to be the best for the product.
Shelf Life @ 25°C	730 days

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

180 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.

515 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

0.03

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.	92 ppm/°C
Coefficient of Thermal Expansion (CTE), α2 Coefficient of Thermal Expansion (CTE), α2 CTE α2 (alpha 2) is the slope of the Coefficient of thermal expansion in a temperature range above the Glass transition temperature (Tg). It explains the extent to which a material will expand after it passes Tg.	851 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.

54 °C

UL 94 Rating

UL 94 Rating
Flammability rating classification.
It determines how fast a material burns or extinguishes once it is ignited.

HB: slow burning on a horizontal specimen; burning rate less than 76 mm/min for thickness less than 3 mm or burning stops before 100 mm
V-2: burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.
V-1: burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
V-0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
5VB: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may develop a hole.
5VA: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may not develop a hole

V-0

Additional Information

Frequently Asked Questions About HumiSeal® 1A33

What are typical applications for HumiSeal® 1A33?

HumiSeal® 1A33 is widely used for protecting printed circuit board assemblies (PCBs) across a broad range of industries, including:

Military and aerospace electronics (e.g., avionics, control modules)
Industrial electronics (e.g., motor drives, sensors)
Automotive electronics (e.g., control units, electronic modules)
Consumer electronics (e.g., communication devices, household electronics)

Its robust chemical resistance and moisture protection make it ideal for harsh environments and mission-critical applications.

Why choose HumiSeal® 1A33 over other conformal coatings?

HumiSeal® 1A33 offers a single-component, urethane-based formulation that provides excellent chemical and environmental resistance without free isocyanates, ensuring safer handling and compliance with environmental regulations. It is compliant with MIL-I-46058C, IPC-CC-830B, RoHS Directive 2015/863/EU, and is UL recognized (UL File Number E105698). The coating fluoresces under UV light to enable easy inspection of coverage, and it can be applied by spraying, brushing, or dipping, offering flexibility for various production processes. Its fast curing with optional heat acceleration allows for efficient manufacturing cycles. You can learn how to select a conformal coating in our latest blog.

What is the shelf life of HumiSeal® 1A33?

HumiSeal® 1A33 has a shelf life of 12 to 24 months from the date of manufacture when stored sealed at room temperature (0 to 35°C). Before use, allow the product to reach room temperature for optimal application performance.

How should I clean tools after applying HumiSeal® 1A33?

Tools such as spray guns, brushes, or dipping tanks used for applying HumiSeal® 1A33 can be cleaned with recommended thinners like HumiSeal® Thinner 503 or 521. For coating removal during rework, use HumiSeal® Stripper 1063. Always ensure proper ventilation and use lint-free cloths during cleaning.

What happens to HumiSeal® 1A33 after its shelf life?

After the shelf life, viscosity and curing characteristics may degrade, potentially leading to uneven coating or reduced protective performance. Use of expired material is not recommended as it may compromise coating quality.

Why do curing times vary for HumiSeal® 1A33?

Curing times depend on ambient temperature and curing method. At room temperature (20–25°C), the coating becomes tack-free in about 15 minutes and fully cures within 20 to 30 hours. Heat curing at 85°C can accelerate full cure to approximately 4 hours, improving production throughput.

What is the recommended thickness for HumiSeal® 1A33?

The recommended coating thickness is 25 to 75 microns to ensure optimal protection without compromising flexibility or electrical performance.

What are the differences between application methods for HumiSeal® 1A33?

HumiSeal® 1A33 can be applied by spraying, brushing, or dipping. Spraying and dipping are preferred for large-scale production to achieve consistent coverage, while brushing is suitable for touch-ups or small batch applications. Viscosity adjustments with thinners 503 or 521 help achieve uniform coatings.

What is the maximum operating temperature for HumiSeal® 1A33?

HumiSeal® 1A33 withstands thermal shock from –65°C to +125°C as per MIL-I-46058C testing. Continuous operation above 125°C is not recommended as it may degrade coating integrity.

What safety precautions should I take when using HumiSeal® 1A33?

Use in well-ventilated areas and avoid open flames due to flammable solvents. Prevent skin and eye contact by wearing appropriate protective equipment. Consult the Safety Data Sheet (SDS) for detailed handling and disposal instructions.

How can I ensure proper application of HumiSeal® 1A33?

The coating fluoresces under UV light, allowing easy inspection of coverage and uniformity, which is critical for high-reliability electronics manufacturing.

How does HumiSeal® 1A33 perform in harsh environments?

HumiSeal® 1A33 provides excellent protection against moisture, chemicals, salt spray, and fungus, maintaining performance in humid, corrosive, and mechanically stressful environments, making it suitable for military, aerospace, automotive, and industrial applications.

Learn More About HumiSeal® 1A33

HumiSeal® 1A33 is a proven solution for engineers seeking long-term protection of electronic assemblies in demanding environments. This urethane 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

✔ Compatible with “no-clean” flux residues
✔ Cures at room temperature (30 days) or 88°C (20 hrs)
✔ Rated UL 94 V-0 for flame retardancy

Versatile Application Methods 🧰

Whether you’re using spraying, dipping, or brushing, 1A33 offers flexibility in manufacturing workflows. It can be diluted with HumiSeal® Thinner 503 to fine-tune application characteristics based on part geometry and production scale. The coating cures at room temperature in 30 hours, or in just 20 hours at 88°C, allowing integration into both batch and inline processes.

Application Methods:

Spray: 4:1 dilution with HumiSeal® Thinner 521 or 521EU
Dip: 5–15 cm/min withdrawal rate with HumiSeal® Thinner 503
Brush: For touch-up applications

Cure the coating at room temperature (30 days) for convenience, or accelerate with thermal curing (20 hrs at 88 °C) 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 (30 days) or 88°C (20 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 🧪

1A33 delivers a dielectric breakdown voltage of 515 volts/mil and an insulation resistance exceeding 2.0 × 10¹⁴ 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® 1A33 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® 1A33 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, 1A33 ensures consistent performance across varied environmental conditions. It’s particularly well-suited for mission-critical systems exposed to humidity, mechanical stress, or temperature cycling.