2.4.2 Coating Replacement, Conformal Coating, Encapsulant

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Outline

This method is used to replace conformal coatings and encapsulants on circuit boards.

Minimum Skill Level - Intermediate

Recommended for technicians with skills in basic soldering and component rework, but may be inexperienced in general repair/rework procedures.

Conformance Level - High

This procedure most closely duplicates the physical characteristics of the original, and most probably complies with all the functional, environmental and serviceability factors.

Procedure References
1-0	1.0 Foreword
2-1	2.1 Handling Electronic Assemblies
2-2	2.2 Cleaning Procedures
2-3-1	2.3.1 Coating Removal, Identification of Coating
2-4-1	2.4.1 Coating Replacement, Solder Mask
2-5	2.5 Baking and Preheating
2-7	2.7 Epoxy Mixing and Handling

Tools and Materials

Circuit Bond Epoxy
Clear, superior strength epoxy in two-compartment plastic packages.

Cleaner
General purpose cleaner for removing contamination.

Cleaning Brushes
Disposable brushes for solvent cleaning and application of coatings.

Coatings
Replacement soldermask and conformal coatings.

Color Agents
One part, semi-paste ink used to tint the color of epoxy and for direct printing on circuit board surfaces.

Flex-Rack PCB Holder
Sturdy rack for PCBs used for rework and positioning.

Foam Swab, Small
Swabs for use with solvents and application of color agents and epoxies.

Microscope
Precision microscope with stand and lighting for work and inspection.

Oven
General purpose oven for drying, baking and curing epoxies.

Wipes
Nonabrasive, low-linting wipes for cleanup.

Procedure

Clean the area.
Caution: Surfaces to be coated must be thoroughly cleaned before coating to ensure adequate adhesion, minimized corrosion, and optimized electrical properties.
If needed, apply High-Temperature Tape to outline the area where the coating will be applied.
If required, bake the circuit board before applying the replacement coating.
Mix the replacement coating.
Apply the replacement coating to the board surface as required. A brush or foam swab may be used to apply and spread the replacement coating. (See Figure 1)
Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
Caution: Some components may be sensitive to high temperatures.

Evaluation

Visual examination for texture, color match, adhesion, and coverage.
Electrical tests to conductors around the repaired area as applicable.

Images

Coating Replacement, Conformal Coating, Encapsulant

Identify the area requiring coating replacement.

Apply the replacement coating to the board surface. A brush or foam swab may be used to apply and spread the replacement coating.

Continue until the required coating has been applied.