2.2.1 Cleaning, Local

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Outline

Surface contaminants can significantly affect soldering, bonding, coating, and the electrical characteristics of printed boards and assemblies. This procedure outlines the cleaning methods for circuit boards and assemblies.

NASCWPNS Final report for NON-ODS cleaning of electronics and avionics, report of October 1, 1995.

Limitations
Solvent-based cleaning solutions' ability to remove flux residue containing polyglycols should be assessed, since not all solvent-based cleaning solutions will remove polyglycols.

A deionized water rinse should follow IPA/DI cleaning, except that a water rinse may not be required for double-sided circuit boards with plated through holes.

Potable (drinking) water should not be used as a final rinse due to the potential of contaminating the circuit board assembly with chlorine, fluorine, and halides.

When automated cleaning is used for assemblies that have been conformally coated, it is important that the cleaning process be compatible with the type of coating used and with any unsealed components. The coating should be checked to ensure the cleaning process will not degrade the coating.

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

Tools and Materials

Cleaner
General purpose cleaner for removing contamination.

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

Gloves
Disposable, puncture-resistant gloves designed for handling mild chemicals.

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

Wipes
Nonabrasive, low-linting wipes for cleanup.

Procedure

Caution: Use clean gloves during this entire operation.

Note: To reduce solvent volumes, mixtures of IPA with water and IPA with solvent are available in pressurized containers. The propellants are HFCs. These containers may be fitted with a bristle brush spray attachment for additional cleaning action.

Clean the board in an Aqueous or Semi-Aqueous cleaner, or pour approximately 10 ml per 4 square inches of the affected area.
Scrub the board vigorously with a continually wet soft-bristle brush for 10 seconds.
Rinse the area with 10 ml per 4 square inches of clean Isopropyl Alcohol to effectively remove all potentially harmful residues.
Handle the board by the edges and blot the excess Isopropyl Alcohol with a clean, lint-free cloth.
Examine the board visually for cleanliness. The use of a black light will help detect contaminants that will fluoresce.
Dry boards in an oven, if desired.
If the boards or assemblies are to be stored before use or coating, remove them from the oven and allow them to cool until they can be handled. Then, place them into self-sealing bags with packages of desiccant.

Images

Cleaning, Local

Cleaning a circuit board with an aerosol spray.

Using an acid brush to remove heavy contaminants.