Conformal Coating: Spray, Dip, or Brush?

Liquid conformal coatings-such as acrylics, epoxies, silicones and urethane resins–are applied to electronic applications by means of wet methods, primarily brush, dipping (component immersion) or automated/manual spraying. Parylene conformal coating is applied as a gas through chemical vapor deposition (CVD).

Material selection is largely dependent on the application or component being coated and its intended use. Selecting an unsuitable coating material inevitably leads to product malfunction or breakdown. Choosing the right coating method for material and end use is equally as important. The wrong application method can also cause poor performance and device failure.

Brush Application

In brush application, the selected conformal coating is manually applied onto the application with a brush. This method has the benefit of relative ease in applying the coating to the designated regions of the surface, particularly in small-batch production.

Dipping Methods

Dipping immerses an application entirely in a fluid conformal solution, subsequently, a film forms around the application while submerged. Although the dipping process can be done manually, the use of automated equipment is becoming more common. Typically, applications are attached to a mechanical arm, which is lowered into a dip tank containing the liquid coating. The immersion rate is set by the quantity of applications being coated.

Advantages of the dip method over other processes include: reliable coating penetration under components and generally fast processing.

Automated and Manual Spraying

A well-trained spray operator can provide superior coating surface quality in comparison to other liquid application methods. At the same time, robotics have become a key component of high-volume spray application jobs. Automated spray procedures generate enhanced project accuracy, resulting in better coatings produced faster. Dedicated spray booth applications offer efficient medium-level production while manual benchtop spray coating is recommended for smaller-scale rework and repair assignments.

Whether manual or automated, spray coating provides the advantages of high-level production volume, enhanced edge/tip coverage, reduced masking and better film uniformity.

Parylene Conformal Coatings Application Process

Chemically-inert Parylene uses a vapor-phase, chemical-vacuum polymerization process to convert powdered Parylene dimer into a gaseous form in a vacuum. Conversion occurs on a molecule-by-molecule basis, allowing Parylene to penetrate the surface crevices of the substrate, tightening even multi-layer elements with uniform, pinhole-free coating that resist chemicals, corrosives, moisture and solvents with outstanding dielectric properties and minimal thermal expansion through an exceptional range of operational conditions.

CVD-applied Parylene coatings are successful in the nanometer range, making them ideal for MEMS and nanotechnologies.

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Specialty Coating Systems offers customers regionally-located coating facilities to handle their engineering and production requirements. To discuss the benefits and properties of conformal coatings and your protection needs with an applications specialist, contact us or call +1.317.244.1200.