3 Key Properties of Acrylic Conformal Coating

Acrylic resin (AR) conformal coatings are widely used because of their distinctive beneficial properties, including protecting printed circuit boards (PCBs) and similar electronics from corrosion, dirt, dust, fungus, moisture and thermal shocks. User-friendly liquid AR can be applied by brush, dip or manual/robotic spray, generally providing a fast turnaround-time. The coating’s ease of application and rework results in lower cost for both manufacturer and client. AR’s moisture protection is also very highly rated, adding to its utility for a wide range of coating uses.

Ease of Application/Rework

Acrylic conformal coatings are applied very easily by standard wet methods. In accordance with IPC-610, film thickness varies between .002 in and .005 in. As one‐part systems, there are similarly few obstacles to their rework or removal. Liquid application methods for acrylic conformal coatings include brush, dip, spray or robotic techniques. The following factors should be considered when selecting which application method to use:

• Product requiring coating
• Surface complexity of the substrate
• Difficulty of masking requirements
• Quantity of items being coated
• Performance requirements of the AR-coating during operation
• Throughput requirements
• Operators’ skill level

Acrylic Application Methods Overview:

• The brush coating process is suitable for low-volume application, finishing and repair. Larger-volume brushing often results in coating defects like film bubbles. Using skilled coating specialists for film application helps to assure quality results at the appropriate thickness.
• Dipping offers a very repeatable process that can generate the high-volume production. Due to the submersion of components, it requires expert masking to ensure quality and complete AR penetration while immersed. The potential of leakage limits dipping application for many applications.
• Suitable for low and medium volume processing, dedicated spray booth coating uses a spray aerosol or gun for application. If the PCB is cleaned adequately, and the coating has no adhesion issues, a skilled operator can provide results superior to all other methods.
• Fast and accurate robotic-atomized spraying is the best method for high-volume applications, providing components excellent coating coverage. Applicator technologies program material flow rates and viscosity, moving above PCBs, dispensing AR to precise, selected substrate regions.

AR curing rarely exceeds 30 minutes, making it an excellent option when a short turnaround time is necessary to meet production scheduling. AR coatings are easily repaired by applying solvent to the region requiring attention. They can also be soldered through if solvent application is unsuccessful. Because acrylic coatings can be removed with weak solvents like isopropyl alcohol or xylene, AR is unsuitable for many coating purposes.

Low Cost

AR’s lower costs are directly connected to its straightforward application and/or rework procedures. AR application requires less time to complete than coating with other conformal film materials like liquid epoxy, silicone or urethane or vapor-deposited Parylene. The manufacturing costs of liquid conformal coating application are invariably driven by labor and the complexity of the process. In this case, AR’s ease of application lowers production expenses considerably; also, by limiting the amount of touch time involved, costs similarly decline.

Moisture Protection

AR offers superior moisture protection to PCBs that may be subject to harsh operating conditions. It provides dependable, long-term defense from environmental developments that present obstacles to appropriate functioning, including:

• Rain and saltwater
• Moisture condensation
• Water spray
• Other liquidized threats to component performance

Because of its ability to withstand humidity during component operation, quick drying AR is recommended for the resistance of moisture development within the assembly.

Conclusion

Acrylic resin is one of the most commonly used compounds in the conformal coating industry for coating PCBs and similar electronics. Despite lower abrasive/chemical and solvent resistance, AR coatings provide good acid and base protection. Acrylic conformal films are easily applied, cleaned, reworked and removed. These factors combined with its low production costs and superior moisture protection make it a good choice for less complex conformal coating processes.