A printed circuit board (PCB) is a flat board that holds and interconnects electronic components. It needs to be cleaned regularly to ensure smooth operation. Dirt and residues may lead to electrical shorts or degradation of the signals passing through the board. Residues left on PCBs can lead to corrosion, thereby causing malfunctioning or failure with time. Remains on PCBs also hamper the dissipation of heat and cause overheating problems. Regular inspection and cleaning are therefore necessary. This blog will discuss some of the best methods FC PCBA uses to clean your PCB.
How PCB Gets Dirty?
Over time, dust and dirt can accumulate in the end-use product of a printed circuit board. In addition to these airborne contaminants, the PCB manufacturing process may also generate pollution. They can be residues from drilling, plating, etching chemicals, and flux compounds. During soldering, residues may remain on the board, thus keeping it dirty. Similarly, assembly components may introduce conductive and non-conductive materials such as oil, grease, and other contaminants.
Hence, the PCB board must be cleaned regularly to maintain its best-performing condition. Three common types of contaminants are dirt, oils, and solder flux residue. These can bring about a run of issues, including electrical shorting, corrosion, and reduced thermal dissipation. For example, corrosion can damage the traces of copper on board.
These traces open or produce unwanted metal paths. Dust and Dirt add to the electrical resistance. Higher resistance automatically leads to localized heating and hotspots in the circuit. This again leads to poor performance or failure of components. Thus, cleaning PCB boards is necessary to ensure the optimal performance of components.
Types of Contaminations on Circuit Board
We’ve learned how PCBs can get dirty from above, now, let’s check some of the contaminations on the circuit board:
Particulate Contamination
Particulate contamination usually includes dust and fibers. This type of contamination is insoluble and cannot dissolve in water or cleaning substances. These contaminants can obstruct airflow and increase heat retention. An electrostatic polar cleaning fluid is necessary to break the bond that particles form with PCB surfaces. A dense cleaning solution with slightly conductive molecules will break the contaminant’s static link, causing the particle to float off the PCB substrate.
Organic Contamination
This includes oils and greases from machinery used in the manufacturing process. Besides, flux oil, residue left behind by organic compounds used in soldering flux, is also responsible for the contamination of PCB boards. Specialized cleaning solutions or flux removers dissolve and remove organic contaminants. A mild to medium-intensity cleaning solution or flux remover usually works best.
Chemical Contamination
The soldering process might also generate corrosive chemicals, such as residues from solder flux. Residues left behind on PCBs may compromise their conductivity and reliability. Similarly, residues from cleaning agents during manufacturing may lead to corrosion unless appropriately rinsed. Isopropyl alcohol is thus suggested as a cleaning agent. However, the same may not work for residues from flux. Therefore, specialized flux removers must be used in such a situation.
Thermal Contamination
Overheating can cause burn marks on the PCB. This not only damages the board but may also carbonate residue. These residues can form conductive paths that disturb the desired circuitry. Once loose material has been brushed away using a soft brush, cleaning the burned areas by applying isopropyl alcohol and gently washing them with a brush helps to remove the residue left behind.
PCB Cleaning Methods
Cleaning printed circuit boards is also very delicate. Choosing the wrong method for cleaning a printed circuit board can lead to several problems. It may damage connections, loosen components, and harm the materials. So when choosing a cleaning method, it is important to choose the right one.
Manual Cleaning
This cleaning process involves removing any kind of contaminant present by hand. A small brush and alcohol are generally used for cleaning. This method is very cheap and requires no equipment, but it takes time. Another drawback is that we can not clean every nook and complex spot. This is especially true for the PCBs that are very intricate and dense, where portions are not reachable by any means. Therefore, this method may not be the best bet for ultrasonic cleaning.
Ultrasonic Cleaning
Ultrasonic cleaning uses a machine specially made to clean PCBs. It is first submerged in a solution of ethyl alcohol. This may be done to help loosen dirt and debris. Then, it is placed into the ultrasonic cleaner’s cleansing solution bath. The equipment sends high-frequency sound waves through the liquid bath. The sound waves result in the creation and implosion of millions of tiny bubbles. This effect is referred to as “cavitation.” These bubbles dislodge any material on the board. It is very effective due to its ability to reach every nook and corner, which makes it perfect for cleaning intricate and closely packed boards.
Solvent Cleaning
This cleaning method involves using a special liquid to dissolve and remove dirt, flux residue, and other contaminants on top of the PCB. The application can be done by spraying or immersing the board. The solvent penetrates the contaminants, after that they dissolve and loosen or run, hence making it easier for them to be wiped or rinsed away. The two types of solvent-cleaning methods are documented in the section below.
- PCB Cleaning Isopropyl: During this process, Isopropyl alcohol is applied using a brush, wipe, or spray. It effectively dissolves flux residues, oils, and other contaminants on the PCB surface. After application, the board is gently wiped or brushed to remove the dissolved impurities. The alcohol evaporates quickly. This leaves behind a clean and dry surface.
- Distilled Water: The use process is the same as isopropyl alcohol. The water helps dissolve and rinse contaminants such as dust, dirt, and residues. Unlike some other solvents, distilled water is non-conductive and non-corrosive. This makes it safe to use on electronic components. However, it may not effectively remove certain contaminants, and thorough drying is essential to prevent water damage to the PCB.
Automated Cleaning Systems
These systems employ machines equipped with conveyors, brushes, sprayers, and drying stations. Sensors and cameras aid in pre-cleaning and post-cleaning inspection. Drying systems help remove moisture from the board. Combining mechanical agitation, solvent application, and drying effectively removes flux residues, oils, and contaminants from PCB surfaces.
PCB Cleaning Spray
The printed circuit boards are cleaned of all kinds of pollutants, oils, and flux residues using a solvent/cleaning solution known as PCB cleaning spray. Water-based cleaning solutions, special flux removers, Isopropyl alcohol, etc, can be some of the fluids used for such purposes. This shall be sprayed at a 45-degree angle to the surface of the PCB.
This way, the solution penetrates to the deepest and has good coverage of areas and components of confined space. It should then be brushed or wiped carefully to remove impurities dissolved therein. Then, it should be thoroughly rinsed with clean water or solvent and dried.
However, it should be remembered that it may not be ideal for highly contaminated or complex PCBs. Likewise, due care must be taken regarding proper ventilation and appropriate safety precautions, since some solvents can be dangerous.
PCB Cleaning Tools and Equipment
An outline of the instruments and apparatus frequently used to clean PCBs is shown below.
- Brush: Anti-static brushes, made of synthetic or natural fibers, remove loose dirt and debris. They do not generate static electricity.
- Lint-free Brush: Lint-free wipes are specialized cleaning cloths used to leave no lint, fibers, or residue on the surface they clean.
- Isopropyl Alcohol: Oils, dirt, and other contaminants are dissolved in isopropyl alcohol. These dissolved components then evaporate along with alcohol, leaving the surface clean.
- Compressed Air: The high-pressure air blast dislodges dirt and debris from the PCB surface. It must be used carefully so as not to damage the components.
- Ultrasonic Cleaner: They use high-frequency sound waves to create microscopic cavitation bubbles in a cleaning solution. When these bubbles collapse, they generate tiny but powerful shockwaves. These shockwaves are responsible for dislodging any dirt or grime present.
- Flux Removers: Isopropyl Alcohol, Acetone, specialized sprays, and water-based cleaners are some of the flux removers. These work by dissolving the flux residues left on the PCB after soldering. They penetrate the residue and break down its chemical structure. The dissolved flux can then be easily wiped away or rinsed off.
- Drying Ovens: These ovens utilize controlled heat and airflow to evaporate moisture.
When to Clean a PCB?
PCB cleaning is very crucial for maximum performance and a long lifespan. The following are scenarios in which one needs to clean the PCB.
- After Manufacture and Assembly: The PCB boards must be cleaned immediately following manufacture to remove solder flux residues, oils, and other extraneous materials picked up during the build.
- Visible Contaminants: The board should be cleaned off when you see any visible sign of dust and dirt on the board.
- Before and After Repair: The board must not have contaminants before the repair process begins. Likewise, after completion, the board must be cleaned to remove the grease/oils present.
- Performance Issues: If at any time the device is struggling with performance and running too hot, or maybe it is locking up and rebooting randomly, it could be the result of a buildup of dust. In these cases, the board should always be cleaned properly.
- Regular Maintenance: The boards should be cleaned regularly, especially in constant use and dusty or highly humid environments. This will prevent dirt, dust, and other airborne impurities from accumulating.
Why is Clean PCB Important?
When any user requires a board to run longer, the board must be preserved or cleaned over the years. To maintain optimal performance and prevent overheating, users should regularly clean the boards. This practice helps reduce power consumption and minimizes the risk of corrosion. Overheating has become a serious problem in small integrated circuits due to their increased sensitivity and vulnerability to external contaminants. The reliability of a PCB is extended when it operates in a clean environment free of dust and dirt. Here are specific reasons to clean your PCB.
Increased board reliability
If the PCB is assembled or soldered in unclean conditions, then flux residue always remains on the board even after assembly; or the finished PCB is not adequately protected from your environment when in use; all of these will result in a dirty PCB and reduced performance. Therefore, users must completely remove all flux residues from the PCB and must not leave any residue to maintain the long-term reliability and durability of the IC.
Preventing PCB component corrosion
External impurities in contact with the PCB may act as insulation for the component, thus impeding airflow. In addition, they can cause circuit alignments and solder joints corrosion when exposed to atomized fluids or liquids. Corrosive components on printed circuit boards can cause impedance problems and open circuits. PCB deterioration can be stopped by simply covering any exposed copper parts with a conformal coating.
Prevent Adhesion Problems with Conformal Coating
Whenever you leave any flux on the board before coating, the coating on the PCB comes off. Adhesion is more frequent in the evenly distributed spaces inside the junction. The layer is also semi-permeable, which makes it easy for moisture to block flux deposits and eventually cause corrosion.
Meeting safety standards
Because cleaning PCBs prevents short circuits and improves board reliability, certain industry standards or safety codes may require that PCBs be cleaned periodically to ensure that equipment meets safety requirements.
Improve productivity
The cleaned PCB circuit board surface is easier to bond with solder, which helps to improve solder quality and connection strength. So during manufacturing, PCB cleaning ensures that the soldering and assembly process runs smoothly and avoids production interruptions due to contamination.
Common Mistake While Cleaning Circuit Board
Some of the common mistakes in cleaning circuit boards include:
- Ignoring Safety Precautions: Failure to use personal protective equipment (PPE) may result in chemical exposure and injury from sharp components. Also, neglecting to work in a well-ventilated area may lead to inhalation of fumes from cleaning solvents.
- Neglecting ESD precautions: We must be careful that static electricity can accumulate and discharge, harming the components in the circuit. Thus, proper measures such as using grounded wrist straps and anti-static mats are necessary.
- Incomplete Drying: Failure to dry completely can lead to corrosion, short circuits, or other electrical issues. Thus, the PCB must be thoroughly dried before use.
- Using Excessive Force: Using too much force while cleaning can break or dislodge components from the board. Therefore, being gentle while handling the board during cleaning is recommended.
Conclusion
Printed circuit board cleanliness is paramount if electronic devices are to demonstrate good performance and last long in service. Contaminants like dust, oils, and remnants of fluxes may cause issues in the boards’ conductivity. They may also create corrosion and result in overheating. Hence, one should regularly clean them using manual, ultrasonic, and solvent techniques. If adequate cleanliness is maintained, PCBs can deliver their optimal performance. If you need any professional help with your PCB assembly, then contact FC PCBA. Feel free to ask for a quote.
