5 Best Practices for Cleaning High Reliability PCBs

Aerosol cleaning introduces a continuous supply of clean, unused solvent throughout the entire bench cleaning process of printed circuit boards (PCBs). Aerosol cleaning prevents the introduction of new contaminants. This article examines the role that different variables play in aerosol cleaning and offers guidelines to improve an aerosol cleaning process.

For a full overview of electronics cleaning chemicals and solvents at MTE Solutions, visit our Electronics Cleaning Chemicals & Solvents resource hub.

Techspray’s G3 Flux Remover (part #1631-16S) aerosol was used for benchtop removal of the flux. Board cleanliness was determined by visual inspection under 64X magnification.

1. Use a Straw Attachment for Greater Control and Less Waste

The straw attachment is the single most impactful technique improvement for aerosol PCB cleaning. It allows controlled spray delivery directly under components, eliminating excessive solvent waste on surrounding areas. Without the straw, much of the solvent is wasted on surrounding areas and very little travels under the component where flux residues accumulate.

2. Spray Techniques for Effective Cleaning Under Components

Best results were obtained when both corners and sides of each contaminated component were addressed. Directing solvent into the corners first is critical — flux dams form in corners and block solvent from reaching the center of the component. The more open channels available, the greater the opportunity for flux to be exposed to solvent.

The choice to use an oscillating or stationary spray depends on component size. For small components, a stationary spray is sufficient; for larger components, an oscillating spray across each side produces cleaner results.

3. How Spray Angle Affects Cleaning Efficiency

An exact straw angle of 30°, 45°, or 60° to the board had no measurable impact on cleanliness. Direction matters more than angle — spray close to the board at an angle that guides the solvent under the component to remove residues, then spray from above angling outward along the edges to push residues away from the board.

4. The Right and Wrong Ways to Use Cleaning Tools

Handheld brushes and foam swabs left boards looking dirtier than before cleaning — they spread partially solvated flux around components which then dried, leaving white residues. Foam swabs became flimsy when saturated with aggressive solvents and were easily torn. Brush attachments produced better results than handheld tools due to the constant supply of virgin solvent, but did not match aerosol-only cleaning. Without the force of an aerosol spray, residues under components are unlikely to be fully pushed out.

5. A Final Rinse Is Required

The final rinse is a necessary step — without it, solvated flux residues are relocated rather than removed. This ensures that all solvated flux residues removed from under and around components flow off the board completely. For disposable electronic devices assembled with no-clean flux, an overall rinse may be sufficient. For high-reliability applications, skipping the final rinse is the most common cause of post-cleaning ionic contamination failures that pass functional test but cause field failures.

Frequently Asked Questions About PCB Cleaning

Purchase Techspray’s G3 Flux Remover (part #1631-16S)

Courtesy of TechSpray

Related Resources:

• Electronics Cleaning Chemicals & Solvents Hub
• PCB Rework & Precision Tools Hub
• Mastering Modern PCB Rework: Techniques That Reduce Scrap & Improve Yield