Surface contaminants can significantly effect 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.
The ability of solvent based cleaning solutions 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 for double sided circuit boards with plated through holes may not be required.
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 that the coating will not be degraded by the cleaning process.
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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.
General purpose cleaner for removing contamination.
Disposable brushes for use with solvents for cleaning and application of coatings.
Disposable, puncture-resistant gloves designed for handling mild chemicals.
General purpose oven for drying, baking and curing epoxies.
Use clean gloves during this entire operation.
To reduce solvent volumes, mixtures of IPA with water and IPA with solvent are available in pressurized containers. The propellants are HFC's. 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 effected 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 to cool until they can be handled. Place the boards or assemblies into self sealing bags with packages of desiccant.