How to Clean Circuit Boards Using Ultrasonic Cleaners

When dirt, dust, and corrosion build up on your circuit boards, they stop working right. Ultrasonic cleaners use sound waves to blast away grime from even the tiniest spaces between components - places you could never reach with a brush or cotton swab. This guide cuts through the confusion and tells you exactly what you need to know about cleaning circuit boards with ultrasonic cleaners.

What Cleaning Solution You Can Use for Circuit Board Cleaning

The biggest risk isn't the ultrasonic cleaner itself—it's what you put in it. Your cleaning solution choice can make or break your circuit board restoration.

Recommended Solutions:

• Specialized Electronics Cleaners: Products like "Safe Wash" contain optimized blends of alcohols and other solvents specifically formulated for circuit board cleaning

• Isopropyl Alcohol (91% or higher): Works well for light cleaning and flux removal

• Deionized Water with Mild Detergent: Suitable for water-soluble contaminants on water-resistant boards

Never Use These On Your Boards:

• Acetone: Extremely aggressive and can create hazardous conditions in an ultrasonic cleaner

• Plain Water: Insufficient for degreasing and may cause corrosion if not properly dried

• Household Cleaners: May contain additives harmful to electronic components

Always check your cleaner's compatibility with the board materials and follow manufacturer recommendations for dilution ratios and rinsing procedures.

Components That Don't Survive Ultrasonic Cleaning

Remove these parts before cleaning or you'll regret it:

• Large electrolytic capacitors (especially valuable ones)

• Anything made with polystyrene (dissolves in many cleaning solutions)

• Unsealed relays (trap moisture inside, causing corrosion)

• Battery holders and batteries (obvious reasons)

• Delicate or irreplaceable components (better safe than sorry)

How to Clean Flux Residue on Circuit Board

Flux residue is deceptive—boards look clean to the naked eye, but under magnification, you'll see it lurking around solder joints. Left untreated, it attracts moisture and contaminants, eventually causing corrosion and electrical leakage.

Different types of flux require different cleaning approaches:

For rosin-based flux:

Rosin-based flux is the traditional amber-colored sticky residue you'll see around solder joints.

Isopropyl alcohol (91%+ concentration) works effectively when it comes to removing rosin-based flux. The ultrasonic cleaner helps the alcohol penetrate under components where flux often hides. A 5-10 minute cycle at 50°C usually removes even stubborn residue.

For water-soluble flux:

Water-soluble flux looks slightly more transparent and is specifically designed to be cleaned with water.

For this type of flux, deionized water with a specialized electronic detergent provides the best results. These fluxes are designed to clean with water, but tap water contains minerals that can damage circuits. Always use deionized water and dry thoroughly afterward.

For no-clean flux:

Despite the name, no-clean flux can still cause problems in high-reliability applications or in harsh environments. Clean with specialized flux removers designed for no-clean formulations. These solvents break down the sticky residue without damaging board materials.

Step-by-Step Circuit Board Cleaning Process

Prepare for Cleaning Circuit Board

1. Inspect the Circuit Board: Examine for obviously damaged components that might need removal

2. Document Connections: Photograph or diagram any connections you'll need to disconnect

3. Remove Sensitive Components:

• Large electrolytic capacitors

• Polystyrene components (incompatible with many cleaning solutions)

• Unsealed relays that might trap moisture

• Battery holders and batteries

• Any particularly valuable or delicate parts

Cleaning Phase

1. Fill the Ultrasonic Cleaner: Add your chosen solution (only fill between 1/4 and 3/4 full)

2. Set Temperature: Typically 40-60°C for most circuit board cleaning

3. Pre-heat the Solution: Allow it to reach the desired temperature

4. Position the Circuit Board: Place it in the cleaning basket, ensuring it doesn't touch the bottom of the tank

5. Run the Cleaning Cycle: Most boards clean effectively in 5-15 minutes

6. Rinse (if necessary): Some solutions require a rinse cycle with clean deionized water

Drying Process

The drying step is crucial for preventing damage and ensuring full restoration:

1. Initial Air Dry: Allow excess solution to drip off

2. Compressed Air: Gently blow out solution from under components and from connector sockets

3. Heat Drying: Use appropriate temperatures based on your board type

• Vintage Circuit Boards: Keep below 100°C (75-80°C is ideal)

• Modern SMD Boards: Can typically handle up to 120°C but verify component specifications

4. Thorough Inspection: Ensure no moisture remains, particularly under ICs and in connector slots

When It Comes to Different Circuit Board Types

Vintage Circuit Boards

Older boards present unique challenges:

• Components weren't designed for high-temperature processes

• Through-hole components may trap moisture underneath

• Plastics may be less heat-resistant than modern materials

"I've ruined quite a few vintage components by exposing them to excessive heat during drying. Keep temperatures moderate for older boards," warns one restoration specialist.

Modern PCBs with Surface-Mount Components

Contemporary boards generally withstand cleaning better:

• Components are designed to handle reflow soldering (220°C+)

• Fewer crevices where moisture can hide

• Many have conformal coatings that protect against moisture

Maintaining Your Ultrasonic Cleaner for Circuit Board Cleaning

To ensure optimal cleaning performance:

• Regularly clean your ultrasonic tank

• Replace cleaning solution when it becomes visibly contaminated

• Use the drain valve to empty old solution

• Dispose of used cleaning solutions properly at chemical disposal centers

• Keep the tank covered when not in use to prevent contamination

Troubleshooting Common Issues of Ultrasonic Cleaning PCBs

FAQs About Circuit Board Cleaning

1. Can ultrasonic cleaning damage my circuit board?

When done properly, ultrasonic cleaning is safe for most circuit boards. However, improper solution choice, excessive temperatures, or failing to remove sensitive components can cause damage.

2. Will my circuit board malfunction after being submerged in liquid? 

Not if you follow proper cleaning and drying procedures. Electronics fail when submerged because minerals in water cause short circuits or corrosion forms over time. Using appropriate cleaning solutions and thorough drying prevents these issues. Many electronics manufacturers actually submerge circuit boards during production cleaning—the key is using the right liquids and proper drying.

3. How often should I clean my circuit boards?

Preventative cleaning depends on the operating environment. Boards in dusty, humid, or corrosive environments may need cleaning every 6-12 months, while those in clean environments might only need attention when performance issues arise.

4. Can I clean populated circuit boards or should they be bare?

Most populated boards can be safely cleaned if sensitive components are removed first. However, for valuable or irreplaceable boards, consider testing your process on a similar but less valuable board first.

5. How do I know when my circuit board needs cleaning?

Signs include intermittent functionality, visible contamination, corrosion on contacts, sticky buttons or switches, or unexplained performance issues.

6. What size ultrasonic cleaner do I need for circuit boards?

If you are only cleaning circuit boards occasionally to extend your equipment’s lifespan, a 2-3L ultrasonic cleaner is sufficient for your use. 

For professionals cleaning multiple boards, 6-10L unit provides better batch processing capability.

Conclusion

The difference between success and disaster isn't the ultrasonic cleaner itself—it's knowing which solutions to use, which components to remove first, and how to dry your boards properly afterward. These simple steps decide if you'll be fixing your board or ruining it for good.

When you follow this guide—picking the right cleaning liquids, taking off parts that might get damaged, and drying everything carefully—you breathe new life into your circuit boards.

Start with a board you don't care much about to get the hang of it, then move to your important ones. There's nothing quite like bringing a dead device back to life, and it's worth taking the time to do it right.

If you are looking for the right ultrasonic cleaner for your project, check out Creworks for a range of high-quality options that won't break the bank. Creworks ultrasonic cleaners come in various sizes to fit everything from small circuit boards to full computer components.