2.4.1 Coating Replacement, Solder Mask

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Outline

This method is used to replace solder masks or coatings on circuit boards. Most replacement coatings can be applied by dipping, brushing, or spraying.

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.

Acceptability References
IPC-A-600 2.0	Externally Observable Characteristics
IPC-A-610 10.0	Laminate Conditions


Procedure References
1.0	Foreword
2.1	Handling Electronic Assemblies
2.2	Cleaning
2.3.1	Coating Removal, Identification Of Coatings
2.4.2	Coating Replacement, Conformal Coatings/Encapsulants
2.5	Baking and Preheating
2.7	Epoxy Mixing and Handling
IPC7721 2.4.1	Coating Replacement, Solder Resist

Tools, Materials and Supplies

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

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

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

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

Cleaner
General purpose cleaner for removing contamination.

Coatings
Replacement soldermask and conformal coatings.

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.

Precision Tool Set
Nine precision-crafted tools for detailed circuit board work.

Repair Skills Practice Kit
Training kit to practice circuit board repair skills prior to testing for certification.

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 solder mask will be applied.
Mix the epoxy or replacement coating. If desired, add a color agent to the mixed epoxy to match the circuit board color.
Apply the replacement coating to the board surface as required. A brush or foam swab may be used to apply and spread the epoxy or replacement coating. (See Figure 2)
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 and Figures

Coating Replacement, Solder Mask

Figure 1. Identify the area requiring solder mask replacement

Figure 2. If needed, apply tape to outline the area where the solder mask will be applied.

Figure 3. Apply the replacement solder mask to the board surface as required. A brush or foam swab may be used to apply and spread the coating.

2.4.1 Coating Replacement, Solder Mask

Restore solder mask to protect circuitry and maintain electrical isolation. Covers surface preparation, mask application, curing and inspection practices for durable, professional repair results. Minimum Skill Level: Intermediate Conformance Level: High

Restore solder mask to protect circuitry and maintain electrical isolation. Covers surface preparation, mask application, curing and inspection practices for durable, professional repair results.

Minimum Skill Level: Intermediate
Conformance Level: High