Conformal Coatings

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

Thin protective film to safeguard electronic assemblies

Epoxy Binding Resins Epoxy Coating Powders Conformal Coatings

Product	Type	Appearance	Film Thickness (μm)	Cure Type	Glass Transition Temperature Tg (℃)	Viscosity (mPa·s)	Dielectric Strength (kV/mm)	Dielectric Constant / Dissipation Factor at 100 kHz	Volume Resistivity (Ω·cm)
Loctite Stycast 40-UMF	UV-Based	–	Varies	–	–	–	420	2.75 / 0.12 at 1 MHz	3.5×10¹⁶
Loctite Stycast CC 8555	UV-Based	–	Varies	UVA Dual cure	–	60	27.5	2.51 / 0.057 at 1 MHz	1.46×10¹⁴
Loctite Stycast PC 18M	Polyurethane	–	Varies	2 hours at 60 °C in oven	–	350	1200	4.2	2×10¹³
Loctite Stycast PC 62	Acrylic	–	25 – 200	24 hours at 25 °C in oven	–	52	2000	2.29 / 0.12	1.04×10¹⁶
Loctite SI 5293	Silicone	–	Varies	–	–	–	406	4.6 / 0.005	1×10¹⁴
LINQCOAT PC-1032	Neutral polymer composite	Transparent	–	3 min at 80 °C	–	400 – 800	30	–	1.0×10¹⁴
LINQCOAT PC-3112	Fluoropolymer	Transparent	0.1 – 1	Ambient	44	0.6	–	–	–

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 common methods include:

Hand Brushing
Hand Dispensing
Spray Coating (Aerosol or Handspray)
Dip Coating
Selective Coating

How does conformal coating work?

The liquid coating “conforms” to every contour of the assembly, creating a continuous protective film that shields components from moisture, dust, chemicals, and electrical leakage.

How do I choose the right conformal coating chemistry?

Selection depends on environmental stresses, thermal range, humidity, mechanical stress, chemical exposure, and reworkability needs. For example:

Acrylics – easy to apply and rework, limited high-temp resistance
Silicones – excel in high-humidity, high-temp, vibration-heavy environments
Polyurethanes – resist solvents and abrasion
UV-curable – ideal for high-speed, inline production

Can conformal coatings be applied selectively?

Yes. Automated selective coating equipment can precisely deposit coating only on critical areas—leaving connectors, test points, or sockets exposed—reducing masking and cleanup.

What surface preparation is required?

Cleanliness is critical. Assemblies must be free of flux residues, oils, and particulates—often requiring plasma cleaning, ionized air, or aqueous washing. IPC-CC-830 recommends ionic contamination <1.56 µg/cm² NaCl equivalent.

How do coatings perform under thermal cycling and stress?

Performance varies by chemistry:

Silicones – best for –55 °C to +200 °C cycles, handle vibration without cracking
Acrylics/Epoxies – may crack or delaminate under extreme flex or rapid thermal change

Conformal Coatings

Thin polymeric films applied to electronic circuits and components to protect them from environmental conditions, such as:

Moisture and humidity
Dust and chemicals
Corrosive atmospheres (e.g., salt spray)
Temperature extremes

They “conform” to the shape of the board and its components — hence the name — forming a protective barrier without affecting the function of the electronics.

Moisture barrier for corrosion and short-circuit prevention

Electrical insulation and chemical shielding

Full coverage across complex and irregular geometries

UV-traceable for easy inspection and defect detection

Protecting Electronics Across Industries

Conformal coatings are essential in industries where electronic reliability is critical under environmental stress. From automotive to aerospace, consumer tech to medical equipment, these coatings form a thin, invisible shield that protects sensitive circuitry from moisture, dust, chemicals, and thermal extremes, enhancing performance, safety, and service life.

Consumer Electronics

Smartphones, wearables, home devices

Automotive

ECUs, sensors, lighting modules

Industrial

Control systems, IoT nodes

Aerospace & Defense

Avionics, guidance systems

Conformal Coating Product Ecosystem

The effectiveness of a conformal coating system relies not only on the coating itself but also on the complementary products that ensure precise application, consistent performance, and easy rework. A typical ecosystem includes:

Conformal Coating

Uniform, thin protective barrier
Prevents moisture, dust, corrosion

Chemistries:

Acrylics
Silicones
Urethanes
UV-curable

Thinner

Adjusts spray, dip or brush viscosity
Ensures uniform film thickness

Selection:

Match solvent blends to each chemistry
Balance thinning vs. adhesion

Stripper

Removes cured coatings safely
No damage to sensitive components

Types:

Fast-acting solvents for bulk
Gentle spot-stripping formulas

Masking Materials

Protects connectors & test points
Leaves critical areas coating-free

Options:

Liquid masks
Peelable tapes
Silicone plugs

Types of Conformal Coatings According to Chemistry of Base Resin

Conformal coatings come in several chemistries, each offering unique protective properties and application characteristics suited for different environments and industry needs. The most common types include acrylic, silicone, polyurethane, epoxy, and parylene coatings. These materials vary in terms of moisture resistance, chemical durability, flexibility, ease of application, and reworkability, making the selection dependent on the specific performance demands of the application.

Acrylic

Pros: Easy to apply and remove; dries quickly and is cost-effective for general use.

Cons: Limited chemical and temperature resistance; not ideal for harsh or high-performance environments.

Urethane

Pros: Strong resistance to moisture, chemicals, and abrasion; good for automotive or industrial use.

Cons: Rigid and harder to rework; long curing times and possible outgassing issues.

Silicone

Pros: Excellent flexibility and thermal stability; ideal for high-temperature or outdoor use.

Cons: Difficult to remove or rework; may have limited chemical resistance depending on formulation.

Rubber

Pros: Cost-effective coating with balanced performance for less demanding environments.

Cons: Limited high-temperature resistance; moderate chemical resistance.

Conformal Coating Selector Guide based on Resin Chemistry

Acrylic conformal coatings are typically based on polymers derived from acrylic acid or methacrylic acid esters. These resins are linear and thermoplastic, which means they do not crosslink during curing. This gives them high reworkability and allows for fast curing.

Acrylic-based coatings represent the largest market share of conformal coatings. The widespread choice of acrylics can be attributed to their ease of use, short cure time, and reworkability/repairability.

Polyurethane coatings are formed by crosslinking polyols with isocyanates, resulting in a flexible, tough layer with excellent abrasion and chemical resistance. Compared to acrylics, polyurethanes offer higher chemical resistance and mechanical strength, second only to epoxies. However, they remain easier to rework than epoxies and stand up well to salt spray and industrial gases. Note that polyurethane coatings typically require longer curing times.

Silicone-based conformal coatings are uniquely characterized by their exceptional high-temperature performance. The strong, thermally stable Si–O bonds in silicones outperform the carbon–carbon bonds found in acrylics, enabling these coatings to withstand temperatures above 150 °C. They excel in applications like industrial mining equipment, high-temperature electronics, and underhood automotive components.

While silicones are not as abrasion-resistant due to their rubbery flexibility, this same property allows them to absorb vibration. Removal typically requires specialized solvents, prolonged soak times, and mechanical agitation.

Synthetic rubber conformal coatings are elastomer-based films, often made from butyl rubber or styrene block copolymers. They offer moderate reworkability and good moisture resistance. Though not as chemically or thermally robust as polyurethanes or silicones, they deliver balanced performance for less demanding environments and withstand vibration and damping stresses well.

Acrylic

Reworkability
★★★★☆

Moisture Resistance
★★☆☆☆

Chemical Resistance
★★☆☆☆

Thermal Resistance
★★☆☆☆

Dielectric Strength
★★★★☆

Cost
$

Best for consumer electronics, fast repair, reworkable systems

Polyurethane

Reworkability
★★☆☆☆

Moisture Resistance
★★★★☆

Chemical Resistance
★★★★★

Thermal Resistance
★★★☆☆

Dielectric Strength
★★★★☆

Cost
$$

Best for automotive ECUs, industrial harsh zones

Silicone

Reworkability
★★☆☆☆

Moisture Resistance
★★★★★

Chemical Resistance
★★★☆☆

Thermal Resistance
★★★★★

Dielectric Strength
★★★★★

Cost
$$$

Best for high-temp circuits, LED lighting, solar inverters

Rubber

Reworkability
★★☆☆☆

Moisture Resistance
★★★★☆

Chemical Resistance
★★★☆☆

Thermal Resistance
★★★☆☆

Dielectric Strength
★★★☆☆

Cost
$

Best for vibration-prone, low-cost devices, LED drivers

UV-curable (Acrylates)

Reworkability
★★☆☆☆

Moisture Resistance
★★☆☆☆

Chemical Resistance
★★★★☆

Thermal Resistance
★★★☆☆

Dielectric Strength
★★★★☆

Cost
$$

Best for high-volume, inline production, VOC-sensitive processes

Types of Conformal Coatings According to Curing Mechanisms

Solvent Evaporation

Film cures as dissolved resin solids deposit when the solvent (or water) flashes off at room temperature or with mild heat.

Acrylics
Synthetic Rubbers

Moisture Cure

One-part formulations that crosslink when ambient moisture diffuses into the film and triggers polycondensation or addition.

Silicones
Polyurethanes

Heat Cure

Requires elevated temperature (often 80–150 °C) to drive crosslinking reactions in the absence of UV or moisture.

Two-part Epoxies
2K Polyurethanes

UV Cure

Uses photoinitiators that, upon UV absorption, generate radicals or cations to rapidly polymerize acrylate-based resins.

Multifunctional Acrylates
Epoxy-modified Acrylates

Dual Cure

Combines two mechanisms (e.g., UV + moisture, UV + thermal) to ensure cure in shaded areas or to boost final properties.

Hybrid Chemistries
(e.g., Acrylate + Silicone)

UV-curable Conformal Coatings

UV-curable conformal coatings are thin polymeric films applied to electronic assemblies that rapidly crosslinks and solidifies when exposed to ultraviolet (UV) light. This technology addresses the length cure cycles and complications on solvent handling required in early conformal coatings. UV-curable coatings are typically multifunctional acrylates or epoxy-modified acrylates that provide hardness and chemical resistance.

Another processing advantage is that this technology is environmentally friendly, as it contains no volatile organic compounds (VOCs) or solvents. Like silicone coatings, it is 100% solid. Due to the short cure time, UV-curable conformal coatings are suitable for high-volume applications.

Key Features

UV cure in seconds
Eliminates bake/flash steps
High chemical resistance; moderate moisture barrier
Tough yet flexible; abrasion-resistant
100 % solids; zero VOC/solvent
Compact UV stations (no ovens)
Optimized for high-volume inline lines
Hybrid chemistries (acrylate, PU, epoxy blends)

Best Use Cases

High-volume, fast-turnaround production
Temperature-sensitive components
Selective / mask-free coating
Complex geometries and fine-pitch boards
Flexible and wearable electronics
Optoelectronic and sensor modules
Field service and touch-up
Automotive electronics (under-hood / high-vibe)
Miniaturized and micro-assembly
Hybrid cure strategies

UV-curable Conformal Coatings Cure Mechanism

Pre-cure
Before any UV exposure, the coating exists as a uniform, liquid film composed of linear oligomer and monomer chains, photoinitiator molecules, and some additives.

→

UV Light Exposure and Absorption

Photoinitiator molecules absorb UV photons and cleave (radical cure) or generate cations (cationic cure). These reactive species are the “spark” that starts chain-growth polymerization of the acrylate/epoxy groups.

→

Crosslinking

Multifunctional acrylates link together, forming a three-dimensional network. Within seconds, viscosity spikes as the network percolates, and the film becomes tack-free.

Dual-cure Conformal Coatings

Dual-cure conformal coatings are hybrid systems engineered to combine two distinct curing mechanisms, typically a rapid primary cure (such as UV-initiated polymerization) and a secondary cure (moisture- or heat-driven crosslinking), to deliver both instant handling strength and complete, through-film cure even in shadowed or occluded regions.

Best Use Cases

Complex Assemblies: High-pin-count PCBs, connectors, and sensors where full 3D coverage is critical.
High-Reliability Electronics: Automotive ECUs, medical instruments, and aerospace modules needing both instant cure and long-term durability.
Inline Production Lines: Facilities seeking to maximize throughput without sacrificing cure completeness or film integrity.

Conformal Coatings Cheat Sheet,
Classification by Cure Mechanism, Typical Chemistries, and Solvent Content

Cure Mechanism	Typical Chemistries	Contains Solvent?
Solvent Evaporation	Organic-solvent acrylics	Yes
	Waterborne acrylics	Yes
	Synthetic rubbers	Yes
	Solvent-based polyurethanes	Yes
	Solvent-borne hybrids	Yes
Moisture Cure	1-part RTV silicones	No
Moisture Cure	1-part moisture-cure polyurethanes	No
Heat Cure	2-part epoxies	No
	2-part polyurethanes	Varies
	Cationic epoxies (thermal post-cure)	No
Photo-Initiated (UV-Cure)	Multifunctional acrylates	No
Photo-Initiated (UV-Cure)	UV-curable epoxy-acrylates	No
Dual-Cure / Hybrid	UV-acrylate + moisture-cure silicones	No
Dual-Cure / Hybrid	UV-acrylate + thermal-cure epoxies	No

Conformal Coating Application Methods

Applying a conformal coating isn’t a one-size-fits-all decision. If you’re running dozens or thousands of boards, a high-speed spray booth can blanket them in seconds. Need pinpoint accuracy? Robotic dispensers or stencil masks let you coat just the connectors and test points. Dip coating delivers an even film over every surface, while a simple brush or stencil approach is ideal for prototypes and spot repairs. And when only certain areas require protection, selective coating cuts down on waste and cleanup. Ultimately, the best choice comes down to your board’s shape, how tightly you’ve packed components, your production volumes, and how consistent that coating needs to be, so you protect your electronics without slowing down your workflow.

Hand Brush

Uniformity
★☆☆☆☆

Throughput
★☆☆☆☆

Wastage
★★★★★

Masking Req.
★★★★☆

Ideal Batch Size
1–10 pcs

Cost
$

Best for prototypes, rework/repair, small batches

Hand Dispensing

Uniformity
★★☆☆☆

Throughput
★★☆☆☆

Wastage
★★★★★

Masking Req.
★★★★☆

Ideal Batch Size
1–20 pcs

Cost
$

Best for selective spot coating, rework/touch up

Hand-held Spray

Uniformity
★★☆☆☆

Throughput
★★☆☆☆

Wastage
★☆☆☆☆

Masking Req.
★★★☆☆

Ideal Batch Size
10–100 pcs

Cost
$$

Best for small to medium batches, field servicing, maintenance

Selective Coating

Uniformity
★★★★★

Throughput
★★★★☆

Wastage
★★★★★

Masking Req.
★★★★★

Ideal Batch Size
up to 100 pcs

Cost
$$$$$

Best for coating only critical “hot spots,” stencil-style patterns

Automated Dip

Uniformity
★★★★★

Throughput
★★★☆☆

Wastage
★★★★★

Masking Req.
★★☆☆☆

Ideal Batch Size
50–500 pcs

Cost
$$$

Best for high-volume yields where overspray must be avoided

Automated Spray

Uniformity
★★★★☆

Throughput
★★★★★

Wastage
★☆☆☆☆

Masking Req.
★★★☆☆

Ideal Batch Size
100s–1,000s pcs

Cost
$$$

Best for mid- to high-volume production, multi-shift operations

Note: Throughput rating – ★☆☆☆☆ = slow, ★★★★★ = fast; Wastage rating – ★☆☆☆☆ = high waste, ★★★★★ = minimal waste; Masking Requirement rating – ★☆☆☆ = high effort, ★★★★★ = low effort.

Presentations

Introduction to Conformal Coatings

2025

This presentation provides a comprehensive overview of conformal coatings, exploring their key functions, material chemistries, and application methods.It also covers industry standards for qualification and testing, including IPC-CC-830 and relevant MIL-STD protocols, and concludes with a tailored question set to guide your coating selection based on substrate, environment, throughput, and performance requirements.

Related Blogs

How to Select the Right Conformal Coating

Kalliope Zembillas, September 2023

This blog guides you through selecting the right conformal coating by covering key chemistries, performance traits, and application methods. It includes a 30-day corrosive environment case study to illustrate real-world protection. A practical selector chart at the end helps you match coating characteristics to your specific requirements.