The Ultimate Guide on How to Clean Circuit Board

Clean circuit boards, especially those used in personal gadgets, such as smartphones and laptops, are often exposed to dust and other dirty contaminants. Apart from accumulating dust and dirt that enters through the open spaces in casings, electronics are also susceptible to liquids that may accidentally pour from users' hands. Consequently, there has been an increasing need for PCB cleaning and repair services from electronic product users.

Cleaning circuit boards to restore electronics' efficiency is a delicate process that you should handle with a lot of care. You may tamper with your connections, loosen some parts, and even misplace some components. To avoid making these mistakes, you must proceed with caution when choosing cleaning detergents like making the PCB.

Welcome to the ultimate guide on how to clean circuit boards.

1. How do Circuit Boards Get Dirty?

Manufacturers fix PCBs within electronic gadgets, but they are not wholly safe from dust and other contaminants. Ports and ventilation spaces on casings easily allow dirt to enter and accumulate on circuit boards. Besides, fans' spinning effects, especially in big machines, can also blow contaminated air on the board.

1.1 Residues Resulting from Manufacturing

Historically, manufacturers applied activated rosin-based fluxes to produce circuit boards. But, since these materials contained chlorine and other halogens, the residue remaining after soldering resulted in corrosion. Consequently, manufacturers invented different cleaning methods to replace the halides.

Most circuit board manufacturers utilize no-clean fluxes, comprising organic acids such as adipic and citric acids. The soldering heat quickly decomposes these organic acids, sticking to the solder firmly and leaving little corrosive.

It is practically not rare for the applied solder to cover some flux, blocking the heat needed for decomposition. After manufacturing, the partially decomposed change remains on the soldered parts as residue. It would be best if you cleared the rubble to ensure the optimal functioning of the PCB throughout its lifespan.

1.2 Impact of the Working Environment

Flux residues are mostly caused by negligence after assembly. Nevertheless, even after clearing the rubble from your PCB, you should still consider environmental contaminants. For example, if you are working in a dusty environment, it is highly likely that dust particles may enter your products and accumulate on PCBs.

Electronics used in the humid and dusty environments seem to depreciate faster than those in non-dusty and hot climates. Even if you trust your electronics' IP rating, check the PCBs regularly to clear dirty before it accumulates.

1.3 Improper Use

Circuit boards are delicate products and need a lot of care during operation. Although you may not fully regulate your equipment's surroundings, overlooking basic fabrication and handling precautions can place your board at risk of pollution.

For example, a PCB with active parts should be housed in a well-ventilated casing to allow heat dissipation. It would help if you lined the container's airways with fins to block express routes for the dust to the PCB. A board enclosed in an openly ventilated casing accumulates contaminants faster than the one in a finned-type container.

2. Why Clean a Circuit Board?

Since cleaning a circuit board is not always in most companies' maintenance routine and adds time and expenses to the manufacturing and repair processes, it is essential to understand why you should regularly clean these devices.

2.1 Enhance Aesthetic Appearance of PCB

If you are a PCB engineer, designer, or manufacturer, your products' visual presentation tells the world much about your work. A greasy-appearance residue on solder joints may spark questions from the quality assurance officers.

2.2 Improve the Reliability of Circuit Boards

The nature of the end products mostly influences reliability demands. For example, pacesetter devices' requirements- where PCB malfunctioning can directly cause loss of life- are more strict. Cleaning is needed post assembly, and you should exhaustively test the process for efficiency.

2.3 Prevent PCB Component Corrosion

Flux remains on PCBs are acidic. If you fail to remove them, they can absorb moisture from the air and cause corrosion.

2.4 Prevent Adhesion Issues with Conformal Coating

When you leave flux on a board before coating, the coating will lift from your PCB's surface. Adhesion is more common in well-spaced pockets within the solder joints. Furthermore, layers are semi-permeable and can easily let moisture clog the flux deposits, and eventually cause corrosion.

2.5 Avoid Dendritic Growth from Ionic Residues

Ionic particles resulting from flux deposits, when they come in contact with moisture and when current is flowing, can form a dendritic chain. Since these chains are conductive, they can cause accidental traces that leak current.

3. Types of Contaminants

There are various types of contaminating agents that can clog your circuit board. Understanding the different PCB contaminants will help you choose the most suitable and effective method and prevent any severe side effects.

4. Tools for Cleaning Circuit Boards

Apart from a PCB cleaner, it would help if you had these tools to clear dry contaminants and dry all wet impurities.

4.1 Baking Soda

You can use baking soda to clear corrosions from your PCB. These corrosions result from exposure to salty water and acidic leakages. The mildly abrasive nature of the soda removes the corrosions without causing any side effects.

4.2 Isopropyl Alcohol

Isopropyl alcohol is an excellent circuit cleaner tool because it is cheap and evaporates quickly. Besides, the drink contains fewer chemicals, unlike other PCB cleaners. Highly concentrated isopropyl alcohol (above 90%) can damage your skin; hence, always wear gloves when handling it.

4.3 Distilled or Deionized Water

Many people prefer distilled/deionized water to hard water because it lacks ions that conduct electric current; therefore, it will not degrade your circuit board. Ensure that your water bottle is closed when not used to avoid contaminating dirt and dust particles in the air.

4.4 Compressed Air

Compressed air is a non-disruptive method of clearing dust accumulated on surfaces and within electronics—leverage short bursts to blow air inside your gadget through the open spaces of your device. If the openings are small, you can open your equipment and carefully clean your board with the compressed air.

4.5 PCB Ultrasonic Cleaners

Ultrasonic cleaning is the safest method of cleaning contaminants from components that are too fragile to displace. Small precision components have unreachable surfaces that prove difficult to the other PCB cleaning methods.

4.6 PCB Cleaning Brushes

PCB cleaning brushes are suitable for cleaning tiny assemblies in PCBs and texturing soft surfaces. Using a brush with soft bristles and slim enough to reach hidden parts is the best decision you can make. If you lack special PCB cleaning brushes, you can still use a toothbrush to clean your circuit board.

4.7 Household Cleaners

You can also use a phosphate-free cleaner to clean your circuit board neatly. Although phosphates are good agents of preventing corrosion and contain useful cleansing properties, phosphorous pollution in water bodies has emerged as a primary concern worldwide, and manufacturers exclude them from cleaning reagents. Manufacturers are now producing phosphate-free cleaners that equally do a good job.

4.8 Lintel-Free Towels/Microfiber Cloths

If you need a simple PCB cleaning tool, consider using towels. They should be lint-free to avoid leaving debris on the circuit board.

4.9 An Oven or Blow Dryer

Although the cleaning tools highlighted above can eliminate debris, some of them fail to dry liquid contaminants. It would be best if you had a cleaning tool that generates heat to dry all liquid pollutants.

4.10 Gas-Phase Cleaners

Gas or vapor phase cleaning involves boiling a chemical solvent to produce steam for dissolving contaminants accumulated on PCBs. The method is efficient and eco-friendly since most solvents can be recycled after filtering the impurities.

You should select the solvent-based on the impurities you want to remove, whether it is flammable, and whether they are eco-friendly. The method is more effective for dense circuit boards as the vapor can reach the board's inaccessible parts.

5. A Step-by-Step Guide on How to Clean a Circuit Board

Step 1: Disassemble your equipment- The first thing you need to do is disassembling your gadget with a screwdriver to access the PCB. You may also need to detach cables from the PCB. If you are not well familiar with the device's assembly, take pictures to assist you in the reassembling process.

Step 2: Make a cleaning solution by mixing baking soda and distilled water- You need a quarter cup of distilled water and two tablespoons of baking soda. Mix them until you get a thick paste.

Step 3: With the help of a PCB cleaning brush, start cleaning your board with the solution you made in step 2. Gently apply the mixture to each corroded part and give it 30 minutes to dry.

Step 4: After your cleaning reagent has dried, rinse it well with distilled water.

Step 5: Apply a phosphate-free household cleaner on your PCB and allow it to be still for about 15 minutes. With the help of the cleaner and a PCB brush, remove all remaining corrosions.

Step 6: Use a lint-free towel to clean off all remaining debris and water droplets/moisture. Do not wipe it down to avoid creating scratches.

Step 7: Preheat your oven to 1700, switch it off, and place the PCB inside for almost three hours to dry any remaining moisture.

Step 8: Reassemble your PCB and test whether it is properly functioning.

6. How to Clean a Wet Circuit Board

6.1 Tools needed

Liquids, like water, drinking juice, and oil, may spill over electronics' surfaces and get their way inside. When your board gets in contact with these liquids, it does not always call for a total replacement if you adhere to the right cleaning procedure.

To prevent corrosion of your circuit board, clean it quickly after it wets using a container, 90% isopropyl alcohol, distilled or deionized water, a soft-bristled brush, and a blow dryer.

6.2  Steps of cleaning a Wet Circuit Board

The first step of cleaning a wet PCB entails primary safety and simple removal of moisture methods from gadgets.

First, unplug your equipment from the power source before handling it. When liquids mix with electricity, they cause shocks.

Secondly, switch it off.

Thirdly, rotate and shake it well to drain the liquid.

Then, remove the battery.

Disassemble any possible connection to create more space for the liquid to flow out of the device.

Soak up all visible liquids using a lint-free cloth. Do not rub the circuit board with material because it could scratch the surface. Put the lint-free cloth on the PCB and drag it gently to soak any remaining liquid.

Drain any remaining liquid, including all drops of dry liquids, by brushing with a bristled brush. Clear both wet and dry contaminants by blowing compressed air over the board. Blow in a single direction in rapid gusts because the canister can be too cold when applied for prolonged sprays.

Rinse the PCB with deionized water to clear any sticky contaminant. Wrap it gently with a lint-free cloth to dry the rinsing liquid.

Reassemble your equipment and try whether it is working correctly. Most electronics can withstand brief spills if you follow these steps well.

7. How to Clean Solder Flux from a Circuit Board

Soldering takes place when you join two connections with a hot metal that binds them together. It would be best if you had flux in soldering to prevent joints from oxidation by transforming the oxides into salt and water, sealed in the change after hardening.

Solder flux may mount up with stained yellow layers on-chip pins where soldering has taken place. The issue is prevalent when a manufacturer handles a PCB inappropriately, but the problem can be solved. You require a soft-bristled PCB brush, 90% isopropyl alcohol, and a lint-free towel.

Apply some isopropyl alcohol on your bristled brush and gently scrub your PCB until the solder flux vanishes. Once you are satisfied with the appearance of your PCB, dab it with a lint-free towel. If you have anhydrous alcohol or a specialized flux cleaner, you will fast perform the flux removal process. But, substituting these tools and reagents with highly concentrated scrubbing alcohol is the most cost-effective method.

Alternatively, you can watch this video to gain a visual understanding of how to clean solder flux from a circuit board.

https://www.youtube.com/watch?v=HSB1wM1sgBY

7.1 Factors that make it Difficulty to Clean Flux Residues

Process engineers agree that the key to creating a repeatable method is controlling the variables. When cleaning flux residues from PCBs, several variables might considerably affect the cleaning tools and techniques' cleaning effectiveness.

R, RA, and RMA fluxes are easier to clean with regular flux cleaners and 90% isopropyl alcohol. Since manufacturers design no-clean fluxes to remain on the circuit board, you cannot easily remove them. You require a more abrasive flux cleaner, extra agitation such as brushing, or a steamed solvent.

It would be best if you cleaned aqueous fluxes in a batch. Alternatively, you can remove them by an inline cleaning method with distilled water. Besides, highly concentrated alcohol-based solvents can be applied to clear aqueous flux residues.

Higher solids flux- Cleaning a circuit board manufactured with a blend of different methods can also be a challenging task. Tacky flux residues with high solids concentrations can be challenging to clean; hence, call for more agitation and cleaning time.

Quantity of flux- Thicker flux residues are more challenging to clear and can cause flux dams in low stand-off parts. The barriers make it harder to access those sections fully.

Soldering temperature is common knowledge that higher temperatures are more likely to bake-on flux remains, proving more challenging to remove. Fusing under high temperatures requires extra cleaning and soak time.

Lead-free solder- You need higher temperatures and highly activated fluxes when dealing with lead-free solders. Fluxes left after lead-free soldering need extra cleaning time and agitation.

8. Circuit Board Corrosion

Unprotected PCBs are highly susceptible to corrosion, making it a significant source of circuit board failure. The process raises the inefficiency of copper on a circuit board, and if extensively corroded, minimizes the efficiency of the PCB. Luckily, there are known significant causes of corrosion, and addressing them can enable circuit boards to function well for the rest of their lifespans.

8.1 Causes of Circuit Board Corrosion

When oxygen bonds with metal, it oxidizes it altering its chemical and electrical factors. Generally, most people call the oxidized parts rust, which peels off, minimizing the metal's size gradually. However, the whole process is called corrosion.

Metals exhibit different corrosion rates. Some are more resistant to corrosion, but there are still some that quickly corrode. For example, copper alloys are more resistant to corrosion, while lead is more vulnerable to decay.

PCBs majorly comprise films and traces of copper, and though there is a coating of surface polish, boards are more likely to corrode.

There are several forms of corrosion based on the root of the rusting of the parts:

• The first one is general attack corrosion.
• The second one is localized corrosion.
• The third is galvanic corrosion.
• The fourth is electrolytic dendrite corrosion.
• The fifth is inter-granular corrosion.
• The sixth is fretting corrosion.
• The seventh is environmental cracking corrosion.
• The eighth is flow-accelerated corrosion.
• The night is de-alloying corrosion.
• The last one is the high-temperature corrosion.

General attack corrosion is a significant form of corruption. It results from a chemical process between oxygen, moisture/water, and copper metal, forming the copper oxide. This oxide is a poor conductor of electric current, reducing the efficiency of circuit boards. Nevertheless, it is not hard to foresee, handle, and prevent this type of corrosion.

Contrary to the general attack, which erodes a bigger surface, localized corrosion affects a small portion. On the other hand, galvanic corrosion occurs when two different metals begin to corrode because of corrosive electrolytes.

 8.2 How to Prevent Corrosion in Circuit Boards

As discussed above, corrosion mainly results from moisture and electrolytic particles on circuit boards. Severe environmental conditions, like acidic and humid conditions, make circuits more vulnerable to decay. You can prevent your PCB from corroding by:

• Clearing flux remains.
• You are keeping your circuit board dry as much as possible.
• You are blocking electrolytes from dampening your board.
• I am coating the board with a regular layer.

Ancient flux components were known to generate chlorine and other harmful gases, which lead to pitting corrosion. Fortunately, organic detergents in modern fluxes are non-halogen emitters, and they only crumble at high temperatures. When doing wave soldering, your PCB may not pass the disintegrating climate. It would help if you manually cleared the remaining residues to avoid crevice corrosion.

Corrosion can be a thing of the past if you prevent liquids and moisture from entering your device. You can realize this through numerous methods, like putting your circuit board in a casing with an appropriate IP score.

In impossible instances where you cannot hem in the board, you can perform a conformal coating. Various forms of conformal coverings, like solder mask, are reasonable preventions of corrosion. But, for circuit boards containing parts that generate a lot of heat, you should do conformal coating cautiously to avoid hindering heat management.

9. Safety and Prevention Practices When Handling Circuit Boards

When cleaning a PCB, you should carefully handle it to avoid causing unintended damages that may add up the maintenance expenses.

Detach your equipment from the power source.

Do not stand on or near any liquid.

Put on dry clothes and protective gear, like masks.

Final Thoughts on the Ultimate Guide on How to Clean a Circuit Board

Cleaning a circuit board is not an overwhelming activity, as some think. This article has exhausted all the tips and guidelines for cleaning a PCB. Observing these guidelines and tips will ensure you adhere to the right PCB cleaning procedure.

Carrying out regular maintenance practices on your board increases the efficiency and lifespan of your electronic products. Generally, though dirty PCBs can reduce your electronics' efficiency and speed, they are fortunately easy to clean and restore normal conditions.