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2.4.1 Coating Replacement, Solder Mask
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Outline
This method is used to replace solder mask 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 |
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| Tools and Materials |
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Alcohol Swab
Self-saturating Isopropyl alcohol swab. Squeeze handle to release alcohol.
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Cleaner
General purpose cleaner for removing contamination. |
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Cleaning Brushes
Disposable brushes for use with solvents for cleaning and application of coatings.
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Coatings
Replacement soldermask and conformal coatings. |
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Color Agents
Use to tint the color of epoxy used for solder mask repair or circuit base board repair. |
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Foam Swab
Ideal for absorbing cleaning solvents, and applying color agents and epoxies.
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Microscope
It is a challenge to undertake precision repair without a good microscope. |
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Oven
General purpose oven for drying, baking and curing epoxies. |
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Wipes
Nonabrasive, low-linting wipes for cleanup. |
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Images and Figures
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| Soldermask Required At Outlined Area |
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| Figure 1: For large surfaces, apply the replacement coating with a foam swab to create a texture. |
Procedure
- 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.
- If needed, apply High Temperature Tape to outline the area where the soldermask will be applied.
- Mix the epoxy or replacement coating. If desired, add 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 1)
- Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
Caution
Some components may be sensitive to high temperature.
Evaluation
- Visual examination for texture, color match, adhesion and coverage
- Electrical tests to conductors around the repaired area as applicable.
Procedure for reference only.
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