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
Clear, superior strength epoxy in two-compartment plastic packages. |
General purpose cleaner for removing contamination. |
Disposable brushes for solvent cleaning and application of coatings. |
Replacement soldermask and conformal coatings. |
One part, semi-paste ink used to tint the color of epoxy and for direct printing on circuit board surfaces. |
Sturdy rack for PCBs used for rework and positioning. |
Swabs for use with solvents and application of color agents and epoxies. |
Precision microscope with stand and lighting for work and inspection. |
General purpose oven for drying, baking and curing epoxies. |
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.
