2.2.2 Cleaning, Aqueous Batch Process

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 used during full assembly operations.

Acceptability References
IPC-A-610 7.0 Cleanliness
 
Procedure References
CTC 1.0 Foreword
CTC 2.1 Handling Electronic Assemblies

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 regarding damage to coatings and devices that may be sensitive to deionized water.

Tools and Materials
Batch Water Cleaning System
Brushes
Deionizing Water Filter System
Gloves
Oven
Wipes

Daily System Setup
  1. Check and record the meg ohm reading of the water exiting the deionizing filter tanks. Reading should always exceed 1 meg ohm. Immediately change filter tanks if 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 °F to 140 °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° 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 °F to 140 °F
    • Wash Cycle Time: 75 to 85 seconds
    • Rinse Cycle Temperature: 120 °F to 140 °F
    • Rinse Cycle Time: 10 to 30 seconds
  3. Remove the rack and visually examine circuit boards for cleanliness.
  4. Dry the circuit boards in 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.


Related Items
HEI-MP4-FR Stereo Zoom Microscope Package | 2.1 Handling Electronic Assemblies | 2.2.1 Cleaning, Local | 2.2.2 Cleaning, Aqueous Batch Process | 2.3.1 Coating Removal, Identification of Coating | 2.3.2 Coating Removal, Solvent Method | 2.3.3 Coating Removal, Peeling Method | 2.3.4 Coating Removal, Thermal Method | 2.3.5 Coating Removal, Grinding / Scraping Method | 2.3.6 Coating Removal, Micro Blasting Method | 2.4.1 Coating Replacement, Solder Mask | 2.4.2 Coating Replacement, Conformal Coating, Encapsulant | 2.4.3 Coating Replacement, Solder Mask, BGA Locations | 2.5 Baking and Preheating | 2.6.1 Legend/Marking, Stamping Method | 2.6.2 Legend Marking, Hand Lettering Method | 2.6.3 Legend Marking, Stencil Method | 2.7 Epoxy Mixing and Handling

2.2.2 Cleaning, Aqueous Batch Process