Humiseal 1C51 | Low-Viscosity, Fast Thermal Curing Silicone Conformal Coating

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

Humiseal 1C51 | Low-Viscosity, Fast Thermal Curing Silicone Conformal Coating

Main features

VOC-free
Fast thermal curing
Fluoresces under UV light

Product Description

HumiSeal® 1C51 is a fast thermal curing, single-component, and VOC-free silicone conformal coating. Its low viscosity and long pot life make it an excellent choice for dipping and spraying applications. HumiSeal® 1C51 provides exceptional flexibility and includes an optical brightener for easy inspection under UV light.

Product Key Features

VOC-free formula
Fast thermal curing
Low-viscosity formulation that is perfect for dipping and spraying.
Provides excellent protection for components that experience movement or temperature changes.
Fluoresces under UV light for quick and easy quality checks under a black light.
Industry Approved: Meets MIL-I-46058C, IPC-CC-830, and RoHS 2011/65/EU standards and is recognized under UL File Number E105698.

Applications

PCB applications with extreme temprature cycling & low outgassing requirements.

Specifications
Additional Information

Technical Specifications

General Properties

Density (g)

0.99 g/cm3

Solids

98 %

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

630 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.

7000 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

2.4

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

0.01

Mechanical Properties

Storage (DMA) Modulus
Storage (DMA) Modulus @ 25°C	3.9 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.

296 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.

-65 °C

Operating Temperature

-65 - 200 °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

Other Properties

VOC-Free (100% solids content)

VOC-Free (100% solids content)
VOC means Volatile Organic compound. VOCs are evaporating molecules and are literally everywhere around us. Our scents are volatile organic compounds, most of the things that we smell are VOC etc. So what do we mean when we state that a product is VOC free?

A VOC free product, according to the FTC is one where:

1)VOCs have not been intentionally added to the product.

2)The presence of VOCs at that level does not cause material harm that consumers typically associate with VOCs, including but not limited to, harm to the environment or human health.

3)The presence of VOCs at that level does not result in concentrations higher than would be found at background levels in the ambient air.

Additional Information

Frequently Asked Questions About HumiSeal® 1C51

What are typical applications for HumiSeal® 1C51?

HumiSeal® 1C51 is a general-purpose, single-component, fast thermal-curing, low-viscosity silicone conformal coating 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® 1C51 over other conformal coatings?

HumiSeal® 1C51 provides excellent protection, with outstanding flexibility and a VOC-free, solvent-free formulation. It provides excellent electrical insulation, fluoresces under UV for easy inspection, and is easily repairable with HumiSeal® Stripper 1091. It is also compliant with IPC-CC-830, MIL-I-46058C, and the RoHS Directive 2011/65/EU, making it a trusted choice for demanding applications. You can learn how to select a conformal coating in our blog.

What is the shelf life of HumiSeal® 1C51?

HumiSeal® 1C51 has a shelf life of 12 months from the date of manufacture when stored at or below 27°C in tightly closed containers. Prior to use, allow the product to equilibrate for 24 hours at room temperature to ensure optimal performance. The product also has a long pot life, typically exceeding 30 days.

How should I clean tools after applying HumiSeal® 1C51?

Tools and equipment used for applying HumiSeal® 1C51 (e.g., spray guns, brushes, or dipping tanks) can be cleaned with a suitable solvent, such as a mineral spirit or acetone, before the coating cures. Thinner is not required or recommended for this product. For removing the coating from PCBs during rework, use HumiSeal® Stripper 1091. Always use a lint-free cloth and ensure proper ventilation during cleaning.

What happens to HumiSeal® 1C51 after its shelf life?

Past its 12-month shelf life, HumiSeal® 1C51 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. If the product has cured in the container, it cannot be recovered.

Why do curing times vary for HumiSeal® 1C51?

HumiSeal® 1C51 is a thermal-curing coating. Curing times vary depending on temperature and film thickness. The coating cures quickly under heat, with a tack-free time typically reached within 10–15 minutes at 105–130°C. The full cure is also achieved quickly, with optimum properties reached after just 15 minutes at this temperature range. Using a thermal oven accelerates the process, making it suitable for high-volume production lines.

What is the recommended thickness for HumiSeal® 1C51?

The recommended coating thickness for HumiSeal® 1C51 is 50 to 200 microns. This range ensures optimal protection without compromising flexibility or electrical performance. The thickness is controlled primarily by the application method and withdrawal rate, as the coating is not designed to be thinned.

What are the differences between application methods for HumiSeal® 1C51?

HumiSeal® 1C51 can be applied via spraying, dipping, or brushing. Spraying and dipping are ideal for large-scale production, while brushing is suited for small repairs. This product has a low viscosity and does not require thinning for any of these methods. Each method should be controlled to achieve a uniform coating, especially the withdrawal rate for dipping, which should be between 5–15 cm/min.

What is the maximum operating temperature for HumiSeal® 1C51?

HumiSeal® 1C51 can withstand thermal shock from -65°C to +200°C. It is also rated for continuous operation at 200°C, making it suitable for high-temperature applications where its protective properties must be maintained under constant thermal stress.

What safety precautions should I take when using HumiSeal® 1C51?

HumiSeal® 1C51 is VOC-free and solvent-free, reducing flammability risks. However, proper ventilation is still crucial to prevent inhalation of vapors or spray mist, especially during the curing process. 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® 1C51?

HumiSeal® 1C51 fluoresces under UV light, allowing for easy inspection of coating coverage. After application, use a UV light source to check for a uniform, void-free coating, which is critical for high-reliability electronics manufacturing.

How does HumiSeal® 1C51 perform in harsh environments?

HumiSeal® 1C51 is designed for harsh conditions, with excellent fungus resistance per ASTM G21 and exceptional moisture insulation resistance. It maintains performance in humid, mechanically stressful, or temperature-cycling environments, making it ideal for mission-critical systems.

Learn More About HumiSeal® 1C51

HumiSeal® 1C51 is a proven solution for engineers seeking long-term protection of electronic assemblies in demanding environments. This silicone conformal coating offers a unique combination of ease of use, excellent electrical insulation, and exceptional flexibility—making it an industry favorite for protecting PCBs in sectors such as automotive, aerospace, consumer electronics, and industrial automation.

Key Features at a Glance

✔ Fast thermal cure, with optimum properties in 15 minutes
✔ Long pot life of >30 days at room temperature
✔ Low viscosity and VOC-free for easy application

Versatile Application Methods 🧰

Application methods

Whether you’re using spraying, dipping, or brushing, 1C51 offers flexibility in manufacturing workflows. It is a 100% solids coating and should not be diluted. The coating cures quickly with heat, allowing for rapid integration into high-volume inline processes.

Application Methods:

Spray: Apply without thinning
Dip: 5–15 cm/min withdrawal rate
Brush: For touch-up applications

The quick thermal cure (10–15 min at 105–130°C) allows for high-speed production, while its long pot life ensures stability for dipping applications over extended periods.

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
✔ Fast thermal cure (10–15 min @ 105–130°C)

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 🧪

1C51 delivers a dielectric breakdown voltage of 7,000 volts and an insulation resistance exceeding 5.0 x 10¹⁴ ohms, protecting even the most sensitive circuit designs from moisture, contaminants, and voltage-induced failure. It is rated for a dielectric withstand voltage of >1,500 volts.

Fluorescent for Inspection 💡

To simplify quality assurance, HumiSeal® 1C51 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® 1C51 is easily repairable. Should rework or component replacement be required, the coating can be selectively removed using HumiSeal® Stripper 1091, making it ideal for prototyping, low-volume builds, or field serviceability.

Reliable Across Environments 🌍

With a wide thermal shock range of –65°C to +200°C and resistance to fungus (ASTM G21) and moisture, 1C51 ensures consistent performance across varied environmental conditions. It’s particularly well-suited for mission-critical systems exposed to humidity, mechanical stress, or temperature cycling.