In the world of electronics, component durability and reliability are of paramount importance. This concept is especially true in harsh environments where dust, moisture, chemicals, and temperature changes can compromise the performance and longevity of devices. That’s why conformal coating plays a crucial role in protecting printed circuit boards (PCBs) and other electronic components, providing a durable barrier against a wide range of environmental threats.
What is conformal coating?
A protective paint or conformal coating is a thin polymer film applied to a printed circuit board (PCB) for the purpose of protecting the board and its components from the environment and preventing corrosion. The film is generally applied in thicknesses of 25-250 µm and “conforms” to the shape of the board and its components. It is designed to cover and protect solder joints, electronic components, exposed traces and other metallized areas from corrosion and external agents, ultimately extending the life of the PCB.
There are several types of materials used for conformal coating, including silicone, acrylic, polyurethane and epoxy materials. The choice of material depends on the specific protection requirements, the application process and the operating environment of the device.
The application of conformal coating is particularly important in industries, such as electronics, automotive, or even aerospace, where devices are often exposed to critical and unpredictable environmental conditions. Conformal coating can be applied in various ways, through dipping, spraying or even brushing. Each method has its own advantages based on the specific application.
The advantages of conformal coating
A newly manufactured printed circuit board will perform well, but performance can quickly deteriorate due to external factors in its operating environment such as moisture, chemicals, salt environment, and temperature extremes.
A protective coating can be used in such environments to protect the circuit boards and their components and ultimately prevent corrosion and failure. The protection provided enables designers to meet miniaturization and reliability requirements.
Below are some of the main benefits of conformal coating in the protection of printed circuit boards (PCBs) and electronic components:
- Protection against moisture and condensation: creates an impermeable barrier that protects components from corrosion and short circuits caused by moisture;
- Resistance to chemicals: provides protection against solvents, salts, acids and alkalis in the operating environment, which could otherwise corrode or degrade them;
- Dust and debris protection: prevents the accumulation of dust and debris on components, which can cause electrical or thermal failure;
- Electrical isolation: improves electrical performance by isolating components from accidental short circuits due to contamination or condensation;
- Increased service life: by providing comprehensive protection against a range of environmental threats, conformal coating significantly extends the service life of electronic devices;
- Reduced maintenance and warranty costs: by improving reliability and reducing the failure rate of devices, conformal coating can lead to reduced costs associated with maintenance, repairs, and warranty replacements.
These benefits make conformal coating an important choice for improving the protection and reliability of electronic components in many industries.
Conformal coating: all types
Conformal coatings can be classified according to their basic chemistry; each option has its own beneficial properties for the different environments in which the PCB will need to operate.
The types of conformal coatings are:
- Acrylic conformal coating
- Polyurethane conformal coating
- Hybrid conformal coating
- Silicone conformal coating
- Water-based conformal coating
- UV cure conformal coating
- Conformal coating 2K
The most widely used materials have historically been solvent-based materials, the advantages of which include:
- Ease of processing and application
- Simple adjustment of viscosity
- Adaptability to a range of application methods
- Customized application and curing
Conformal acrylic coating
Acrylic coatings combine a reasonable price with good environmental protection; they maintain transparency and resist browning and hydrolysis under prolonged outdoor exposure. However, they have limited solvent resistance, making them suitable for rework but not for applications where chemical resistance is important.
- They offer excellent protection from moisture and salt spray.
- They are easy to apply and remove and dry quickly at room temperature due to simple solvent evaporation
- They have a good operating temperature range
- They have excellent adhesion to a wide variety of substrates
Conformal coating polyurethanes
Unlike acrylics, polyurethane Conformal coatings offer excellent chemical resistance and superior protection in harsh environments. They maintain flexibility even at very low temperatures. Like acrylics, they are also very versatile and cover a wide range of operating temperatures.
- Good flexibility, especially at low temperatures
- Excellent chemical resistance
- Polyurethane coatings can be removed with specific products
- Excellent abrasion resistance
Conformal hybrid coating
Hybrid coatings are those in which a mixture of base chemicals is used. These can result in a range of different coating options to meet the requirements of specific applications.
The range of conformal coatings usually consists of acrylic or polyurethane base resins modified with silicone to improve the resin’s properties at high temperatures. These coatings have a wide range of advantages over standard materials and, being solvent-based, also offer all the advantages of ease of application.
- Extremely wide operating temperature range
- Easy to apply
- High chemical resistance
- Can be reworked with specific products
- Good protection in a wide range of environments
Silicone Conformal Coatings
In general, silicones are the conformal coatings most resistant to high/low temperatures or thermal fluctuations due to their more flexible nature. These coatings offer a wide range of protection in harsh environments with rapid temperature variation. However, they are less resistant to moisture and corrosive gases than other coating technologies.
- Good all-around protection
- Flexible
- Wide operating temperature ranges
- Normally approved by many industry standards (e.g., IEC 61086, IPC-CC 830, MIL, UL)
- Ease of processing and rework
Water-based conformal coatings
Water-based conformal coatings cure by evaporation of water from the system. They are low-VOC options, as they replace most of the solvent in the system with water. This improves operator safety and dramatically reduces solvent emissions.
- Reduced solvent use; improved operator and environmental safety
- Safe products
- Can be applied with standard equipment; immersion and spray versions are available
- Can offer a good level of chemical resistance
UV-cured conformal coatings.
UV-cured conformal coatings are also another example of hybrid coatings. In this case, different chemistries are often used to produce a dual-cure system, thus avoiding problems with areas obscured by UV light during curing. UV-cured coatings offer the fastest cure times, with coatings curing in seconds under UV light. This is extremely advantageous for high-throughput applications, and shaded areas cure with the secondary curing system over time.
Due to their highly cross-linked structure, once cured, they can be difficult to remove but offer excellent chemical resistance.
- Extremely fast process times
- Secondary moisture curing system used to promote shadow curing
- Good protection in a range of environments
- Excellent chemical resistance
Two-component conformal coatings (2K)
2K two-component conformal coatings are hybrid technologies that combine the best properties of encapsulating resins with those of a conformal coating. These materials offer some of the best protection available while maintaining the processability and cost-effectiveness of a conformal coating (compared to a resin).
- High performance
- High levels of protection in a wide range of environments
- Thicker application than single-component coatings
- Excellent chemical and moisture protection
MD Poland’s solutions
MD Poland is the leading supplier of materials for the electronics assembly and protection industry. Our advanced DOWSIL solutions include a range of products such as encapsulation resins, conformal coatings for electronic board protection, electromagnetic interference (EMI) shielding coatings, thermal dissipation materials, and adhesives and sealants for component assembly and fastening, which facilitate electrical interconnection, provide structural integrity, offer protection from external agents, and transfer heat for increasingly reliable performance. We are proud to distribute products that improve today’s electronic technologies and enable tomorrow’s advances.
The MD Poland product range includes a wide variety of solutions such as.
acrylics, silicones, polyurethanes, epoxies and hybrids. These include environmentally friendly options, with or without solvent, with crosslinking at room temperature, by heat or by UV light.
