Best Way to Clean a Circuit Board

Clean circuit boards are essential for reliability and proper function. Contamination can cause electrical failures, corrosion, and coating adhesion problems. This guide covers proper PCB cleaning techniques.

Why Clean PCBs?

Contaminants affect PCB performance:

• Flux residue: Can cause dendritic growth and short circuits
• Dust and debris: May cause shorts or thermal issues
• Fingerprint oils: Attract moisture and contaminants
• Corrosion: Reduces conductivity and reliability

Cleaning Materials

Isopropyl Alcohol (IPA)

The most common and effective PCB cleaner.

Recommended concentration: 90% or higher (99% preferred)

Why high concentration? Lower concentrations contain more water, which takes longer to evaporate and may leave residue.

How to use: Apply with soft brush, cotton swab, or lint-free cloth. Scrub gently and allow to evaporate completely.

Specialized Flux Removers

Commercial flux removers are formulated to dissolve flux residue quickly.

Best for: Heavy flux contamination, rosin and no-clean flux removal.

Popular products: MG Chemicals, Techspray, Chemtronics.

Distilled Water

Safe for washing water-soluble flux residue.

Important: Use only distilled water (not tap water). Ensure complete drying before power-up.

Compressed Air

For removing dust and loose particles.

Tips: Use short bursts, keep can upright, avoid propellant liquid contact.

Cleaning Methods

Manual Cleaning

Suitable for light contamination and small quantities.

Process:

1. Remove power source and batteries
2. Apply cleaning solution to brush or cloth
3. Gently scrub contaminated areas
4. Wipe with clean lint-free cloth
5. Allow to dry completely
6. Inspect for remaining contamination
7. Repeat if necessary

Tools: Soft-bristle brush, cotton swabs, lint-free wipes.

Ultrasonic Cleaning

Best for thorough cleaning, especially under components.

Process:

1. Prepare cleaning solution in ultrasonic tank
2. Place PCB in tank (avoid impact with other objects)
3. Run ultrasonic cycle (5-15 minutes)
4. Rinse with clean solution
5. Dry thoroughly

Cautions: May damage some components (certain crystal oscillators, relays, some electrolytic capacitors). Check component datasheets.

Dishwasher Cleaning (Controversial)

Some technicians use dishwashers for heavily contaminated boards.

Cautions:

• Use no detergent
• Avoid heated dry cycle
• Remove batteries and sensitive components
• Ensure complete drying (24-48 hours or bake)
• Not suitable for all boards

Drying Methods

Complete drying is critical before power-up.

Air drying: Allow 24 hours minimum in dry environment.

Forced air: Use heat gun on low setting or fan.

Oven baking: 60-80°C for 2-4 hours (not suitable for all components).

What Not to Do

• Don't use tap water: Contains minerals that leave residue
• Don't use acetone on plastics: Damages many plastics and components
• Don't power on wet boards: Risk of short circuit and damage
• Don't use abrasive materials: Scratches traces and coatings
• Don't use excessive pressure: Can damage components

When to Clean

• After soldering (flux removal)
• Before conformal coating
• After contamination exposure
• During troubleshooting
• For visual inspection

Special Cases

Corrosion: Use white vinegar (mild acid) followed by IPA neutralization and thorough rinse.

Heavy contamination: May require multiple cleaning passes or professional cleaning service.

Conformal coated boards: Require specialized removers or may not be cleanable.

Conclusion

For most PCB cleaning, 99% isopropyl alcohol and a soft brush provide excellent results. Always ensure complete drying before applying power. For heavy contamination or production quantities, consider ultrasonic cleaning.