2.4.1 Coating Replacement, Solder Mask

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

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

Solder Mask Required At
Outlined Area

Procedure References
CTC	1.0	Foreword
CTC	2.1	Handling Electronic Assemblies
CTC	2.2.1	Cleaning, Local
CTC	2.2.2	Cleaning, Aqueous Batch Process
CTC	2.3.1	Coating Removal, Identification of Coatings
CTC	2.4.2	Coating Replacement, Conformal Coatings/Encapsulants
CTC	2.5	Baking and Preheating
CTC	2.7	Epoxy Mixing and Handling
IPC 7721	2.4.1	Coating Replacement, Solder Mask see procedure below

Tools and Materials
Brushes
Cleaner
Color Agents
Epoxy
Foam Swabs
Heat Lamp
Microscope
Oven
Replacement Coating
Wipes

Procedure 2.4.1 Coating Replacement, Solder Mask

Figure 1: For large surfaces, apply
the replacement coating with a
foam swab to create a texture.

1.	Clean the area. Caution Surfaces to be coated must be thoroughly cleaned prior to coating to ensure adequate adhesion, minimized corrosion, and optimized electrical properties.

2.	If needed, apply Kapton tape to outline the area where the soldermask will be applied.
3.	Mix the epoxy or replacement coating. If desired, add color agent to the mixed epoxy to match the circuit board color.

4.	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 1).

5.	Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling. Caution Some components may be sensitive to high temperature.

Evaluation

1.	Visual examination for texture, color match, adhesion and coverage.

2.	Electrical tests to conductors around the repaired area as applicable.