Conformal Coating & Encapsulation Flashcards

What conformal coating defect is described as small circular depressions or craters that expose the underlying substrate?

Answer: Fisheye (cratering)

Fisheyes or cratering are circular depressions caused by surface tension differences, often from contamination or silicone, that pull the wet coating away from a point and expose the substrate.

An 'orange peel' texture on a cured conformal coating surface is generally considered:

Answer: Acceptable in most cases per IPC-A-610

Orange peel texture is a cosmetic irregularity that does not impair the protective function of the coating and is generally listed as an acceptable condition in IPC-A-610.

Which condition would constitute a defect in conformal coating per IPC-A-610 for Class 2 and Class 3 assemblies?

Answer: Exposed conductors or solder connections that are required to be coated

Exposed conductors, lands, or solder connections that should be coated leave the circuit unprotected, directly violating the protective requirement and constituting a defect per IPC-A-610.

When inspecting conformal coating under ultraviolet (UV) light, what does a dark or non-fluorescing area indicate?

Answer: Missing or insufficient coating coverage

Areas that do not fluoresce under UV light lack the fluorescent tracer present in the conformal coating, indicating that no coating or insufficient coating was applied in that location.

During conformal coating application, which types of features MUST typically be masked to prevent coating?

Answer: Edge connectors, test points, and adjustable components

Edge connectors must remain uncoated for electrical contact, test points must remain accessible for in-circuit testing, and adjustable components such as potentiometers must remain operable after assembly.

Applying conformal coating over an assembly with ionic contamination will most likely result in:

Answer: Delamination, loss of adhesion, or accelerated corrosion under the coating

Ionic contamination trapped beneath the coating retains moisture and promotes electrochemical corrosion, and the contamination can also prevent proper adhesion, leading to delamination.

Which conformal coating application method provides the most precise deposition and reduces masking requirements by applying coating only to specified areas?

Answer: Selective robotic coating system

Selective coating systems use programmable robotic dispensers to apply coating to defined areas only, dramatically reducing or eliminating the need for masking while improving repeatability.