PCB Blog - Safeguard Your Electronics: iPCB's acrylic conformal coating services

Conformal coating is designed to protect printed circuit boards (PCBs) from all sorts of extreme conditions and environmental hazards such as moisture, dust, chemicals, and temperature fluctuations. For that reason, also because of it belonging to a process near the finish of manufacturing, it is a very critical aspect in the entire process of electronic manufacturing (EMS).

Naturally, the question that ensues would be, what are the common materials for conformal coating process? Among the various coating materials available, acrylic resin stands out. There are several reasons for that: generally speaking, the ease of application, reworkability, and general-purpose protection. We will further delve into all the technical aspects of acrylic conformal coating, exploring its properties, applications, and key considerations for implementation.

As its name suggests, acrylic conformal coatings are formulated by making acrylic resin dissolved in volatile organic solvents. Upon application and evaporation of the solvent, a thin, transparent, and flexible film is formed on the PCB surface. This film provides a protective barrier, enhancing the reliability and lifespan of electronic assemblies. 

Note bene: Acrylic resins are a group of thermoplastic or thermosetting plastic substances derived from acrylic acid, methacrylic acid, or related compounds. And VOCs are organic chemicals that evaporate readily at room temperature. Because of that property, they are used to dissolve acrylic resins, creating a liquid solution that can be easily applied as a coating. A few of the common VOC materials are: Xylene; Toluene; Ketones (e.g., acetone); Esters... and so on. It is crucial for the coating process to have very volatile properties for the VOC material, as it allows the solvent to evaporate quickly, leaving behind a solid acrylic film.

Advantages of such a conformal coating process using acrylic material:

• Ease of Application: Acrylic coatings can be applied using various methods, including spraying, dipping, and brushing, making them adaptable to different production volumes and complexities.

• Fast Drying Time: The volatile solvents in acrylic formulations facilitate rapid drying at room temperature, accelerating the production process.

• Good Dielectric Strength: Acrylic coatings exhibit high dielectric strength, providing excellent insulation properties and preventing electrical shorts.

• General Environmental Protection: They offer effective protection against moisture, humidity, dust, and mild chemical exposure, safeguarding the PCB from corrosion and degradation.

• Reworkability: A significant advantage of acrylic coatings is their ease of removal. They can be readily dissolved using common solvents like xylene or toluene, simplifying repair and rework processes.

• Flexibility and Elasticity: Acrylic coatings possess good flexibility and elasticity, allowing them to withstand thermal cycling and mechanical stress without cracking or delamination.

• UV Indicator: Many acrylic coatings contain a UV indicator, enabling easy inspection of coating coverage under ultraviolet light.

However, there are several aspects to be considered when applying arcylic, or similarly, before choosing whether to place such a coating:

• Limited Chemical Resistance: While providing general protection, acrylic coatings offer limited resistance to harsh chemicals and solvents. They are not suitable for applications involving prolonged exposure to aggressive substances.

• Temperature Range: Acrylic coatings typically have a moderate operating temperature range, generally suitable for standard electronic applications. Extreme temperature variations may affect their performance.

• Thickness Control: Achieving uniform coating thickness can be challenging, especially with complex PCB geometries. In that case, process control and application techniques will be essential.

• Solvent Emissions: The use of solvent-based acrylic coatings raises environmental concerns due to volatile organic compound (VOC) emissions. For the consideration of enviromental-friendly usages, water-based acrylic coatings are available and provide an alternative with reduced VOCs.

• Outgassing: In some circumstances, outgassing may occur. This is when trapped solvents are released over time. This can cause issues in sealed environments.

Application Process and Best Practices:

• Surface Preparation: Thoroughly clean the PCB to remove contaminants like flux residues, dust, and oils.

• Application Method: Select the appropriate application method (spraying, dipping, or brushing) based on the PCB complexity and production volume.

• Coating Thickness: Apply the coating to the recommended thickness, ensuring uniform coverage.

• Drying and Curing: Allow the coating to dry completely at room temperature or follow the manufacturer's recommended curing schedule.

• Inspection: Inspect the coated PCB under UV light to verify coating coverage and identify any defects.

Reworkable Protection, Superior Performance! For your application, let's choose iPCB to make your acrylic-coated PCBs to achieve a result where your PCB product will both be protected and very easily repaired.