Aug. 18, 2025
Machinery
For electrical assembly, current leakage in a printed circuit board (PCB) can result in intermittent or permanent failure. Current leakage can occur due to insulation resistance reduction (due to presence of contamination) between adjacent solder-pads on a PCB.
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This hygroscopically induced moisture absorption phenomenon can for example intensify due to dissociated hydronium ions (i.e. from activators), to further result in malfunction and complete assembly failures.
Conformal coatings are layers of material that are applied on and adhere to the PCB and its components to protect from environmental hazards. There are a wide variety of materials used as conformal coatings ranging from thick layers of silicone to nano-coatings like Parylene.
The coating, when applied, will conform to the shape of everything on the surface, including any contaminants or residues leftover from the production process. Trapped contaminants can cause conformal coatings to warp, crack, or peel which re-exposes the PCB to the environmental hazards the coating layer was meant to protect against.
Spray-in-air inline cleaning machines are ideal when cleaning electronic assemblies with densely populated boards having low standoff components and when requiring high production throughputs.
The PCBs are placed on an automatic conveyor belt and run through individual process steps, where cleaning, rinsing and drying are performed in separate sections of the inline machine.
The spray-in-air batch system operates using technology very similar to the technology used in a dishwasher. All process steps are executed within the same process chamber. The cleaning medium is sprayed onto the electronic assemblies through nozzle fittings on rotating spray arms.
The cleaning effect is achieved primarily by the volume of cleaning medium passed over the substrates rather than the spray jet pressure like in inline processes.
Ultrasonic systems submerse the PCB in a cleaning medium that is then agitated with soundwaves exceeding 20 kHz. Ultrasonic cleaning can be useful in cleaning under components and complex geometries since the sound waves are capable of reaching the populated circuit board from every angle.
Many industry cleaning machines have an automatic frequency adjustment for the modulation of the ultrasound (sweep) working frequency, which prevents “hot spots” and allows material-friendly cleaning.
Sometimes individual PCBs need to be cleaned with unique geometries and materials. In this case, nothing beats good, ol’ fashioned elbow grease. Manual cleaning requires no investment in equipment and is popular in applications where the throughput is low like building prototypes or performing electronic component rework/repair. If a facility is producing medium/high throughput, running several shifts and requires reliable and repeatable cleaning results, an automated cleaning process is recommended.
Even PCBs that have been manufactured with high precision may cause short circuits, corrosion, or even product failure due to residual flux, dust, fingerprints, or moisture if they are not effectively cleaned. For this reason, PCB cleaning is necessary, to ensure the stability of electronic products and extend electronic devices’ service life. Whether you are an electronic DIY enthusiast, a product engineer, or a technician, understanding how to clean PCBs, mastering different types of circuit board cleaning methods, and choosing the appropriate PCB cleaner are all the basis for ensuring the long-term reliable operation of the equipment.
Next, we will delve into various PCB cleaning techniques. It covers a variety of solutions ranging from manual cleaning to the use of automated equipment such as ultrasonic PCB cleaners and deionized water cleaning machines.
PCB cleaning is not only about appearance, but also directly affects electrical performance and service life. After soldering, contaminants such as flux residue, dust, moisture or fingerprints usually remain on the PCB surface. These impurities may cause corrosion, short circuits or performance degradation of the circuit board. Therefore, it is necessary to clean the circuit board. Common cleaning scenarios include: post-soldering treatment, maintenance/rework process, treatment before applying protective coating, and treatment before long-term storage. The so-called PCB cleaner refers to the chemicals, tools or equipment used to remove these contaminants. Choosing the appropriate circuit board cleaner can effectively ensure the long-term stable operation of the circuit board.
Different types of PCB board cleaners are suitable for different contaminants and cleaning requirements. Choosing the right cleaning agent can not only effectively remove contaminants, but also prevent damage to circuit boards or affect the performance of electronic components. The following are several common PCB cleaners:
Solvent-based PCB Cleaner
This type of cleaner is based on highly volatile organic solvents and can quickly dissolve stubborn flux residues, grease, welding fumes and other contaminants. Common types of cleaners include isopropyl alcohol (IPA) or commercial flux cleaners. They are suitable for cleaning rosin and no-cleaning fluxes and are very commonly used in manual soldering and maintenance scenarios.
Water-based PCB Cleaning Solution
This kind of PCB cleaner focuses on environmental protection and low toxicity. It adopts deionized water or water-based chemical formulas, which are more friendly to the human body and the environment. It is usually used in conjunction with a spray cleaning system or a batch cleaning machine to remove water-soluble flux. This type of PCB cleaner is widely used in mass manufacturing and green electronic production.
Dedicated PCB Flux Cleaner
Dedicated solvents developed based on the type of flux (rosin, no-rinse, water-soluble) are more targeted. An excellent PCB flux cleaner can effectively remove the active residues around the solder joints and avoid leaving white deposits. It is suitable for military and medical PCB cleaning applications with high-reliability requirements.
PCB Cleaner Spray
PCB cleaner spray penetrates quickly and removes surface contamination by spraying. This cleaner is suitable for cleaning small areas or hard-to-reach parts. It is very convenient for on-site maintenance or repair personnel to use at will and is suitable for various scenarios of cleaning circuit boards.
Electronic Board Cleaner
This type of cleaner is specially designed for sensitive circuits and features anti-static, anti-corrosion and residue-free properties. This type of cleaner is suitable for high-precision equipment, such as communication base stations, industrial control systems, medical instruments, etc. It can safely clean the surface of the PCB without damaging the components, improving the overall system stability.
When choosing the most suitable PCB cleaner, it is not only necessary to consider the type of contaminants, but also to make a comprehensive judgment by taking into account the circuit board structure, component sensitivity, environmental protection requirements and cleaning methods. Next, we will introduce several common cleaning methods to you, mainly from the aspects of manual and machine cleaning.
In sample making, rework or small-batch DIY projects, manual cleaning of PCBs is a common and practical method. Compared with automated equipment, manual methods have lower costs and are more flexible to operate. This way is suitable for cleaning local solder joint residues, flux contamination or slightly oxidized areas. So, how to clean the PCB manually?
First of all, it is necessary to prepare the required tools and materials. The basic tools and cleaning supplies required include: lint-free cloths/wiping paper, anti-static brushes, cotton swabs, compressed air cans, isopropyl alcohol (IPA) or flux remover, anti-static gloves, etc. Sure, if what you pursue is convenience, you can also use PCB cleaner spray. This type of circuit board cleaner spray has good solubility and rapid evaporation characteristics, and is an ideal choice for removing flux and oil stains.
Then, the formal cleaning process can begin:
Step 1: Evenly spray the PCB cleaner spray or isopropyl alcohol on the solder joints, pins or contaminated surfaces that need cleaning, and wait for a few seconds to allow it to penetrate and soften the flux residue. This step is the initial treatment of the contaminated area.
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Step 2: Use an anti-static brush or cotton swab to gently scrub the contaminated area to help separate flux residues, dust or stains. This process requires patience and avoiding vigorous scratching to prevent damage to the solder pads.
Step 3: Use a lint-free cloth or wiping paper to remove the dissolved flux and dirt to prevent it from adhering to the surface of the circuit board again after drying.
Step 4: Use a compressed air tank or a hot air gun in the low-temperature setting to dry the PCB to ensure there is no liquid residue and avoid the risk of short circuits or corrosion.
Step 5: Use a magnifying glass or microscope to carefully observe the cleaning area again: checking if there is still flux residue or white powder, and whether there are problems caused by improper cleaning such as scratches, pad damage, burrs, etc.
If there are still residues, steps 1 to 4 can be repeated, or a more powerful PCB flux cleaner can be considered. Although manual cleaning is simple, only when the operation is standardized and the materials are properly selected can the goal of electrical safety and long-term stable operation be truly achieved. For complex or large-scale applications, it is still necessary to use the best PCB cleaner, such as automatic spray cleaning, ultrasonic or deionized water systems. Only in this way can higher consistency and efficiency be achieved, as well as more professional PCB cleaning.
For large quantities or complex circuit boards, equipment cleaning is required to achieve consistent and efficient results. Common cleaning equipment includes:
The PCB ultrasonic cleaner cleans by generating microbubble vibrations in the liquid through high-frequency sound waves. This machine can penetrate deep into cracks and crevices, effectively removing flux residues and particles. And it can be deeply cleaned without touching the circuit board, making it highly suitable for cleaning multi-layer boards and high-density components.
The vapour phase cleaning machine dissolves contaminants by heating solvent vapor and is suitable for removing no-cleaning fluxes. It has the advantages of high efficiency and suitability for industrial-grade dense circuits. However, good ventilation is required and attention should be paid to operational safety.
This type of system applies the cleaning solution to the PCB surface through a high-pressure nozzle and then dries it with an air knife. The Spray-in-air systems are suitable for large-scale cleaning and are widely used in SMT assembly lines.
This device is similar to an industrial dishwasher and is often used for batch PCB cleaning. It has high consistency and the cleaning, rinsing and drying process is fully automatic.
The deionized water cleaning machine can effectively remove particles, oxides and organic residues by combining surface activation and ultrapure water to rinse PCBs. This type of cleaning machine is an ideal choice for aerospace, medical and other applications that require ultra-clean surfaces. Its environmentally friendly and non-corrosive process is conducive to improving the reliability of subsequent adhesion, coating and welding. Moreover, this device has zero residue, no scale or metal ions, and is highly safe.
How can we clean circuit boards efficiently and safely in the face of various cleaning devices and methods? Here are some common scenarios and frequently used methods. Hope they can be of some help to you:
Application Scenario / Need
Recommended Cleaning Method
Small batch soldering, prototyping, or repair
Manual cleaning
Post-solder flux removal
Solvent-based localized cleaning
High-volume production
Automated cleaning systems
High-density or complex PCBs (e.g., BGA, QFN)
Ultrasonic cleaning
Water-soluble flux or ionic contamination
Deionized water cleaning (eco-friendly)
Spot cleaning or field repair
Spray-type cleaner
Eco-friendly and non-corrosive requirements
Water-based or plasma cleaning
Learning how to clean circuit boards is a basic skill that every electronics professional must master. Whether it is sample boards, repair parts or batch products on the production line, choosing the appropriate PCB cleaning methods and tools can greatly enhance the reliability of the products. Selecting the best PCB cleaner is the key to ensuring the stable operation of electronic products. After reading this article, you must have gained more understanding of PCB cleaning. Of course, if you need clean high-volume PCBs, you can also contact PCBasic!
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