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2.2.2 Cleaning, Aqueous Batch Process

Outline
Surface contaminants can significantly effect soldering, bonding, coating and the electrical characteristics of circuit boards and assemblies. This procedure outlines a batch cleaning process for the removal of the small volumes of fluxes and other contaminants that may contact circuit boards during routine circuit board repair and rework operations. This batch cleaning procedure is not necessarily appropriate for the removal of contaminants that accumulate during full assembly operations.

Caution
Aqueous batch cleaning may not always be suitable for removing rosin based fluxes or other contaminants that are not readily soluble in water.

Caution
Aqueous cleaning will expose all areas of a circuit board assembly to penetrating water spray. Circuit boards must be assessed for possible damage to coatings and devices that may be sensitive to deionized water.

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-610 7.0 Cleanliness
Procedure References
1.0 Foreword
2.1 Handling Electronic Assemblies
Tools and Materials
CircuitMedic Part
Cleaning Brushes
Disposable brushes for use with solvents for cleaning and application of coatings.
Daily System Setup
  1. Check and record the meg ohm reading of the water exiting the deionizing filter tanks. Reading should always exceed 1 megohm. Immediately change filter tanks if the reading drops below 1 megohm.
  2. With the unit empty, run the batch cleaning system through 3 cycles at the start of each day. Check the following:
    - Water Pressure: 20 PSI +/- 5 PSI
    - Water Reservoir Temperature: 120 degrees F to 140 degrees F
Operation
  1. Remove any loose items from circuit boards and place circuit boards in suitable cleaning rack. Circuit boards should be placed within the rack at a minimum 45 degree angle to ensure proper rinse run off.
  2. Place the rack within the batch cleaning system and run through the cleaning cycle. Cycle temperature and cycle times follow:
    - Wash Cycle Temperature: 120 degrees F to 140 degrees F
    - Wash Cycle Time: 75 to 85 seconds
    - Rinse Cycle Temperature: 120 degrees F to 140 degrees F
    - Rinse Cycle Time: 10 to 30 seconds
  3. Remove the rack and visually examine the circuit boards for cleanliness.
  4. Dry the circuit boards in an oven, if desired.
Evaluation
  1. Visually check board assemblies for any evidence of residual flux or contamination. Clean again if needed.
  2. Check circuit board assemblies for any loose items. Reattach items removed prior to cleaning if needed.
Procedure for reference only.
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