2.2.2 Cleaning, Aqueous Batch Process

Outline

Surface contaminants can significantly affect soldering, bonding, coating, and the electrical characteristics of circuit boards and assemblies. This procedure outlines a batch cleaning process for removing 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 removing contaminants that accumulate during full assembly operations.

Caution
Aqueous batch cleaning may not always be suitable for removing rosin-based fluxes or other contaminants 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 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, Materials and Supplies

Cleaning System
Batch or inline cleaning system for removing fluxes and contamination.

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

Daily System Setup

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.
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

Remove any loose items from circuit boards and place circuit boards in a suitable cleaning rack. Circuit boards should be placed within the rack at a minimum 45-degree angle to ensure proper rinse run-off.
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
Remove the rack and visually examine the circuit boards for cleanliness.
Dry the circuit boards in an oven, if desired.

Evaluation

Visually check board assemblies for any evidence of residual flux or contamination. Clean again if needed.
Check circuit board assemblies for any loose items. Reattach items removed prior to cleaning if needed.

Images and Figures

Cleaning, Aqueous Batch Process

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

Figure 1. Aqueous batch cleaning may not always be suitable for removing rosin based fluxes or other contaminants that are not readily soluble in water.

Figure 2. Aqueous cleaning will expose all areas of a circuit board assembly to penetrating water spray.

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2.2.2 Cleaning, Aqueous Batch Process

Procedure covers aqueous batch cleaning of circuit board assemblies. Minimum Skill Level: Intermediate Conformance Level: High

Procedure covers aqueous batch cleaning of circuit board assemblies.

Minimum Skill Level: Intermediate
Conformance Level: High