Flux Remover PCB Repair PCBS Techspray

5 Best Practices for Cleaning High Reliability PCBs

Dec 2, 2025
Flux Remover for PCB CleaningAerosol 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. While there are some obvious pros of aerosol cleaning, questions remain as to whether this method of benchtop cleaning can consistently and reliably clean a circuit board. This paper 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.

For testing purposes, boards were built using Kester’s FL250D (Sn63Pb37), no-clean paste to attach two QFNs and one QFP. Two components (QFN B and QFP) were fluxed with Amerway #100 Type “R” Non-Activated Rosin Flux to simulate rework. QFN A was untouched to act as a control. Two drops of flux were added to QFN B and four drops to the QFP. The boards were then reflowed using a handheld heat/air gun at 400°F for two minutes.
Techspray 1631-16S G3 Flux RemoverTechspray’s G3 Flux Remover (part #1631-16S) aerosol was then used for benchtop removal of the flux. This solvent was chosen due to its cleaning effectiveness of Type “R” Non-Activated Rosin Flux. Board cleanliness was determined by visual inspection under 64X magnification.

1. Use a straw attachment for greater control and less waste

The use of the straw attachment allowed for a more controlled spray, eliminating excessive solvent waste. The straw was also useful in directing exactly where the solvent went, allowing the user to guide the solvent under the component. Without the straw attachment, much of the material was wasted on surrounding areas and very little ended up traveling under the component.

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 directly into the corners helped to break up any flux dams located there. The more open channels available, the greater the opportunity for the flux to be exposed to the solvent.

The choice to use an oscillating or stationary spray was dependent on the size of the component. For small components, a stationary spray was sufficient; for larger components, an oscillating spray across each side produced cleaner results.

3. How does the angle of spray affect efficiency?

An exact straw angle of 30°, 45°, or 60° to the board had no impact on cleanliness. General downward or upward angles were sufficient. When trying to remove residues from under a component, spray close to the board at an angle that guides the solvent under the component. When residues have been removed, spray from on top angling out along the edges to push residues away.

4. The right and wrong ways to use cleaning tools

Handheld brushes and swabs left the board looking dirtier than it started — they spread partially solvated flux around components which then dried, leaving a white residue. Foam swabs became flimsy when saturated with aggressive solvents and were easily torn. Best results were achieved when a final rinse was utilized. The key is not to let the board dry out. A slower evaporating solvent like IPA avoids the evaporation issue but should be followed by a rinse.
Brush attachments produced results a step above handheld tools due to the benefit of a constant supply of virgin solvent, but did not produce the same level of cleanliness as 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 was found to be a necessary step. This ensures that all solvated flux residues removed from under and around components flow off the board completely and are not simply relocated.
For disposable electronic devices assembled with no-clean flux, an overall rinse may be all that is needed. If higher reliability is required, greater care is needed to prevent latent failure from ionic contamination. Spending the time and effort up-front is often money well spent.
Courtesy of TechSpray
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