Conformal Coating for Electronics Protection

Understanding Conformal Coating: The First Line of Defence for Electronic Assemblies

In the demanding environments of Atlantic Canada, where salt air, humidity, and dramatic temperature fluctuations are everyday realities, protecting electronic assemblies becomes not just advisable but essential. Conformal coating represents one of the most effective methods for safeguarding printed circuit boards (PCBs) and electronic components from environmental hazards that can lead to premature failure, costly repairs, and system downtime.

For industries across Nova Scotia and the Maritime provinces—from offshore energy operations to marine navigation systems, agricultural equipment to telecommunications infrastructure—conformal coating provides a critical protective barrier that extends the operational life of electronic systems while maintaining their reliability in challenging conditions.

What Is Conformal Coating and How Does It Work?

Conformal coating is a thin polymeric film, typically ranging from 25 to 250 micrometres (0.001 to 0.010 inches) in thickness, that conforms to the contours of a printed circuit board assembly. This protective layer creates a barrier between the electronic components and potentially damaging environmental factors while still allowing the circuit to function normally.

The term "conformal" refers to the coating's ability to follow the exact shape of the board and its components, providing uniform coverage over complex three-dimensional surfaces including component leads, solder joints, and exposed traces. Unlike potting or encapsulation, which completely encase electronics in a rigid shell, conformal coating maintains accessibility for testing, rework, and component replacement when necessary.

Key Protection Mechanisms

Conformal coatings protect electronic assemblies through several mechanisms:

• Moisture Barrier: Prevents water vapour and liquid moisture from reaching sensitive components and causing corrosion or electrical leakage

• Chemical Resistance: Shields against corrosive gases, solvents, and chemical contaminants common in industrial environments

• Dielectric Insulation: Provides additional electrical insulation, preventing arcing and current leakage between closely spaced conductors

• Mechanical Protection: Offers resistance to abrasion, vibration stress, and thermal shock

• Contamination Prevention: Blocks dust, salt spray, and other particulate matter from accumulating on circuit surfaces

Types of Conformal Coating Materials

Selecting the appropriate conformal coating material is crucial for achieving optimal protection. Each coating type offers distinct advantages and limitations that must be matched to the specific application requirements and operating environment.

Acrylic Conformal Coatings (AR)

Acrylic coatings are among the most widely used conformal coatings due to their excellent balance of protection, cost-effectiveness, and ease of application and removal. They typically cure at room temperature within 30 minutes and can be easily removed with common solvents for rework purposes.

Operating Temperature Range: -65°C to +125°C

Dielectric Strength: Approximately 1,500 to 2,000 volts per mil

Acrylic coatings offer good moisture and fungus resistance, making them suitable for many general-purpose applications in Atlantic Canada's humid coastal climate. However, they provide limited chemical resistance and may not be appropriate for applications involving exposure to harsh solvents.

Silicone Conformal Coatings (SR)

Silicone coatings excel in applications requiring extreme temperature performance and flexibility. Their exceptional thermal stability makes them ideal for electronics operating in environments with wide temperature variations—a common scenario for outdoor equipment in Nova Scotia, where temperatures can swing from -30°C in winter to +35°C in summer.

Operating Temperature Range: -65°C to +200°C

Dielectric Strength: Approximately 1,000 to 1,500 volts per mil

Silicone coatings maintain their flexibility and protective properties across this broad temperature range, preventing cracking and delamination that can compromise other coating types during thermal cycling.

Polyurethane Conformal Coatings (UR)

Polyurethane coatings provide excellent chemical and solvent resistance along with superior mechanical protection. They are particularly effective in harsh industrial environments where exposure to fuels, lubricants, and aggressive chemicals is common.

Operating Temperature Range: -65°C to +125°C

Dielectric Strength: Approximately 2,000 to 3,000 volts per mil

The trade-off for polyurethane's robust protection is more difficult removal for rework, typically requiring mechanical abrasion or specialized stripping compounds.

Epoxy Conformal Coatings (ER)

Epoxy coatings form the hardest and most chemically resistant films among conformal coating options. They provide exceptional protection in extremely harsh environments but are essentially permanent once applied, making rework extremely difficult.

Operating Temperature Range: -65°C to +150°C

Dielectric Strength: Approximately 2,000 to 2,500 volts per mil

Parylene Conformal Coatings (XY)

Parylene coatings are applied through a unique vacuum deposition process that produces an extremely thin (typically 0.5 to 25 micrometres), uniform, and pinhole-free film. This process allows coating penetration into the smallest crevices and under components, providing unmatched coverage uniformity.

Operating Temperature Range: -65°C to +150°C

Dielectric Strength: Approximately 5,000 to 7,000 volts per mil

While parylene offers superior protection, the specialized equipment required for application makes it more expensive than other coating types, typically reserving its use for high-reliability applications in aerospace, medical devices, and military electronics.

Application Methods and Best Practices

The effectiveness of conformal coating depends not only on material selection but also on proper application technique. Various application methods offer different advantages in terms of coverage quality, production efficiency, and cost.

Spray Application

Spray application, either manual or automated, is the most common method for applying conformal coatings. Manual spraying offers flexibility for small batches and prototype work, while automated selective spray systems provide consistent, repeatable coverage for production volumes.

Modern automated spray systems can achieve placement accuracy within ±0.5 millimetres, allowing precise coating application while avoiding keep-out areas such as connectors, switches, and test points. For manufacturers in Atlantic Canada serving diverse markets, selective spray systems offer the flexibility to handle varying product designs without extensive changeover time.

Dip Coating

Dip coating involves immersing the entire assembly in a tank of coating material, providing complete coverage in a single operation. This method is highly efficient for high-volume production of boards that require full coverage, though it requires careful attention to drainage and may not be suitable for assemblies with components that cannot be coated.

Typical withdrawal speeds range from 2 to 10 centimetres per second, with slower speeds producing thicker coatings. Controlling these parameters is essential for achieving consistent film thickness.

Brush Application

Brush application remains valuable for touch-up work, small production runs, and repair operations. While labour-intensive and less consistent than automated methods, brush application requires minimal equipment investment and allows precise control over coating placement.

Surface Preparation

Regardless of application method, proper surface preparation is fundamental to coating adhesion and long-term protection. Assemblies must be thoroughly cleaned to remove flux residues, fingerprints, dust, and other contaminants that can prevent proper coating adhesion or become trapped beneath the coating layer.

Recommended cleaning processes include:

• Aqueous Cleaning: Using deionised water with appropriate detergents at temperatures of 50°C to 65°C

• Solvent Cleaning: Using isopropyl alcohol or specialized electronics cleaning solvents

• Vapour Degreasing: For removal of heavy oil and grease contamination

Post-cleaning, assemblies should be thoroughly dried and coated within 24 hours to prevent recontamination.

Industry Standards and Quality Requirements

Conformal coating applications must often meet specific industry standards that define material properties, application requirements, and inspection criteria. Understanding these standards is essential for engineering teams specifying coating processes.

IPC-CC-830

The primary industry standard for conformal coatings, IPC-CC-830 "Qualification and Performance of Electrical Insulating Compound for Printed Wiring Assemblies," establishes test methods and performance requirements for coating materials. This standard defines tests for insulation resistance, dielectric withstanding voltage, moisture and fungus resistance, thermal shock, and flexibility.

IPC-A-610

IPC-A-610 "Acceptability of Electronic Assemblies" provides visual inspection criteria for conformal coating, including acceptable coverage, thickness, and appearance. The standard defines three classes of quality:

• Class 1: General electronic products where function is the primary requirement

• Class 2: Dedicated service electronic products requiring extended life and uninterrupted service

• Class 3: High-reliability electronic products where continuous performance is critical

For applications in marine, offshore, and critical infrastructure across Atlantic Canada, Class 2 or Class 3 requirements are typically specified.

MIL-I-46058

Although technically cancelled and superseded by IPC-CC-830, MIL-I-46058 remains referenced in many legacy specifications and contracts, particularly for defence and aerospace applications. Engineers working with existing designs may encounter references to this standard.

Applications in Maritime and Atlantic Canadian Industries

The unique environmental challenges of Atlantic Canada make conformal coating particularly relevant for numerous regional industries.

Marine and Offshore Operations

Electronics aboard vessels and offshore platforms face constant exposure to salt spray, high humidity, and vibration. Navigation systems, communication equipment, and control electronics all benefit from conformal coating protection. The combination of silicone coatings for temperature flexibility and polyurethane coatings for chemical resistance addresses the complex demands of marine environments.

Wind Energy Systems

With Nova Scotia's growing wind energy sector, protecting nacelle electronics and control systems from moisture ingress and wide temperature variations is essential for maintaining turbine availability. Conformal coating extends maintenance intervals and reduces the risk of unexpected failures in difficult-to-access locations.

Agricultural Technology

Modern agricultural equipment relies heavily on electronic sensors, controllers, and communication systems that must operate reliably despite exposure to dust, moisture, fertilisers, and temperature extremes. Conformal coating protects these systems throughout the growing season and during winter storage.

Telecommunications Infrastructure

Remote telecommunications equipment, including cellular base stations and network equipment cabinets, must maintain reliable operation despite environmental exposure. Conformal coating helps ensure continuous connectivity for rural and coastal communities across the Maritime provinces.

Inspection and Quality Assurance

Verifying conformal coating quality requires systematic inspection procedures. Modern inspection techniques combine visual examination with automated and semi-automated methods.

Visual Inspection

Trained inspectors examine coated assemblies under appropriate lighting (typically 500 to 1,000 lux) and magnification (4× to 10×) for defects including:

• Bubbles and voids exceeding specified limits

• Dewetting or orange peel texture indicating adhesion problems

• Incomplete coverage or pinholes

• Excessive thickness or pooling

• Contamination trapped beneath the coating

UV Fluorescence Inspection

Many conformal coatings contain fluorescent additives that glow under ultraviolet light, making inspection faster and more reliable. UV inspection at 365 nanometres wavelength reveals coverage uniformity, pinholes, and coating boundaries that may be difficult to see under normal lighting.

Thickness Measurement

Coating thickness can be measured using eddy current gauges, magnetic induction instruments, or cross-sectioning for destructive analysis. Automated optical inspection systems can also assess relative thickness based on colour intensity.

Partner with Sangster Engineering Ltd. for Your Conformal Coating Requirements

Implementing effective conformal coating protection requires careful consideration of material selection, application processes, quality requirements, and the specific environmental challenges your electronic products will face. Whether you're developing new products for maritime applications, upgrading existing systems for improved reliability, or addressing field failures related to environmental exposure, professional engineering guidance ensures optimal results.

Sangster Engineering Ltd. provides comprehensive electronics engineering services to clients throughout Nova Scotia, Atlantic Canada, and beyond. Our team brings extensive experience in electronics design, manufacturing processes, and environmental protection strategies tailored to the unique challenges of our region. From initial design consultation through production support, we help ensure your electronic systems deliver reliable performance throughout their intended service life.

Contact Sangster Engineering Ltd. today to discuss your conformal coating requirements and discover how proper environmental protection can enhance your product reliability and reduce lifecycle costs. Our Amherst, Nova Scotia location allows us to serve clients throughout the Maritime provinces with responsive, knowledgeable engineering support.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.