Conformal Coatings

Acrylic, Polyurethane, Silicone, UV and Rubber-Based Conformal Coatings

thin protective film to safeguard electronic assemblies

Conformal Coatings

A conformal coating is a thin protective film designed to safeguard electronic assemblies from corrosion and environmental hazards in harsh operating conditions. The term "conformal" refers to its ability to conform precisely to the complex contours of the surface it covers. This coating offers several advantages, including protection from debris and dust infiltration, enhancing corrosion resistance, extending product warranties, and increasing overall reliability and safety. In essence, applying a conformal coating effectively prolongs the longevity and durability of electronic assemblies.

One of the main advantages of conformal coatings is their dielectric properties. These coatings exhibit excellent insulation resistance, effectively protecting electronic components and assemblies from electrical failures. Another significant advantage is moisture resistance, which serves as a crucial defense against moisture ingress, preventing potential damage and electrical failures in humid or damp environments. Additionally, the breakdown voltage characteristic plays a pivotal role in protecting the component from high voltages and electrical stresses. Finally, the flexibility of the coating endows the substrate with enhanced mechanical resilience, enabling it to better withstand external stresses and environmental fluctuations without deforming, cracking, or delaminating.

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Product Selector Guide

 Henkel Conformal Coatings

 

Loctite Stycast PC 62

Loctite Stycast PC 18M

Loctite SI 5293

Loctite Stycast 40-UMF

Film Thickness (µm)

25-200 Varies Varies Varies

Insulation Resistance, ohms:
(50µm film, 25ºC / 50% RH) 

>2.3×1014  >1×1015 N/A N/A

Volume Resistivity, (ohms-cm)

1.04×1016  2×1013 1×1014 3.5×1016

Dielectric Strength, (volts/mil)

2,000 1200 406 420

Dielectric Constant / Dissipation Factor @ 100 KHz

2.29 / 0.12 4.2 4.6 / 0.005 2.75 / 0.12 @ 1 mHz

TYPICAL ENVIRONMENTAL RESISTANCE

Fungus Resistance per ASTM G21- Non nutrient Fungus Resistance per ASTM G21-Non nutrient N/A  NASA Outgassing:
TML, % 0.87
CVCM, % <0.01
WVR, % 0.36

TYPE OF COATING

Acrylic Polyurethane Silicone UV-Based

 


Frequently Asked Questions

Frequently Asked Questions about Conformal coatings

How is a conformal coating applied?


There are multiple ways to apply a conformal coating, all based on the specifics of the application. Some methods include:

  • Hand Brushing
  • Hand Dispensing
  • Spray Coating - Aerosol/Handspray
  • Dip Coating
  • Selective Coating

How does conformal coating work?


The liquid coating "conforms" to any varied profile of an electronic component, completely covering all parts of the assembly to protect it from environmental factors. 


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Different types of conformal coatings

Acrylic - Acrylic-based coatings represent the largest market share of conformal coatings. These coatings are formulated from single components and provide superior moisture resistance properties, making them highly suitable for protecting electronic assemblies in challenging environments. The widespread choice of acrylic-based coatings can be attributed to their ease of use, short cure time, and reworkability/repairability. Acrylic-based coatings are most often used in Engine Control Units (ECUs), Avionics, and communication equipment.

Polyurethane - Polyurethane-based coatings have excellent chemical resistance, rendering them highly effective in countering the effects of compounds such as salt spray and noxious gas. Available in both one-part and two-part systems, these coatings are easy to apply. Compared to other conformal coatings, polyurethane-based coatings do have a lengthier curing time. Reworkability is a notable advantage of these coatings, and they are commonly used in demanding environments with applications that include industrial controls, marine electronics, and chemical processes.

Silicone - Silicone-based conformal coatings are uniquely characterized by their exceptional high-temperature performance. Due to this characteristic, they are suitable for industrial mining equipment, electronics with temperatures greater than 150°C, and underhood components in the automotive industry. Silicone-based conformal coatings offer reasonable moisture protection while remaining reworkable and repairable. They are solvent-free, yielding a 100% solid content and good solvent resistance. Moreover, these coatings incorporate flexible elastomers, enhancing their flexibility. This adaptability allows the coating to accommodate mechanical stresses and temperature fluctuations without compromising its integrity.

UV-Based - UV-Based conformal coatings are primarily selected for their short cure time, which occurs within a matter of seconds. This expedited curing process reduces the cycle time while providing increased temperature performance to the coated components. UV Based coatings exhibit excellent resistance to moisture and chemicals while also having high flexibility and abrasion resistance. One of the main advantages of this type of coating is that it is environmentally friendly, as it contains no Volatile Organic Compounds (VOCs) or solvents. Like Silicone Coatings, it is 100% solid content. Due to the short cure time, UV Based conformal coatings are suitable for high-volume applications.

Rubber-Based - Ruber-based conformal coatings represent a class of single-component coatings with excellent moisture resistance and low Moisture Vapor Permeability (MVP). Like other conformal coatings, they are easy to repair/rework, have a short cure time, and have excellent adhesion to various substrates. The characteristic that distinguishes rubber-based coatings is their superb flexibility and thermal-mechanical properties. Specifically, their low Coefficient of Thermal Expansion (CTE) and Glass Transition Temperature (Tg) enables the components to effectively withstand thermal shock, enhancing overall performance and reliability. This quality makes rubber-based coatings particularly well-suited for applications where temperature fluctuations pose a challenge, preserving functionality and integrity even in demanding environments.

 

 

How to select the right coating for your application
 

ACRYLIC

URETHANE

UV

SILICONE

RUBBER

TOUGHNESS ABRASION RESISTANCE

Low

Medium

Medium

Low

Low

HIGH TEMP RESISTANCE 

Low

Medium

Best

Best

Medium

FLEXIBILITY

Best

Medium

Best

Best

Best

THERMAL SHOCK RESISTANCE

Low

Medium

Best

Best

Best

MOISTURE RESISTANCE (MVP)

Medium

Medium

Best

Low

Best

SIR/MIR

Medium

Medium

Best

Medium

Medium

ENVIRONMENT

Med/Low

Med/Low

Best

Best

Low

MAIN FEATURES

General Purpose

Chemical Resistance

Environment, High Temp, Chemical Resistance, Volume Production

High Temp

Thermal Shock