{"id":1505,"date":"2025-09-06T09:42:00","date_gmt":"2025-09-06T01:42:00","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=1505"},"modified":"2026-10-02T17:32:35","modified_gmt":"2026-10-02T09:32:35","slug":"how-to-pcb-cleaning","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/how-to-pcb-cleaning\/","title":{"rendered":"How to Clean a PCB"},"content":{"rendered":"
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Basic Understanding of PCB Cleaning<\/h2>\n<\/div>\n
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1.1 Why Do PCBs Need to Be Cleaned?<\/h3>\n<\/div>\n
Residual contaminants can directly compromise PCB performance; for example, flux residue may reduce insulation between circuits, leading to short circuits, while metal debris adhering to circuit nodes can impair conductivity and cause unstable signal transmission. In the production process, cleaning is a critical step in ensuring soldering quality\u2014if a PCB surface is not thoroughly cleaned, an oxide layer will form, resulting in poor solder adhesion and shortening the product\u2019s service life. Cleaning requirements vary by application: Mass production requires efficient cleaning to match production capacity; repair and refurbishment require targeted removal of aged residues; and specialized industries such as medical and aerospace demand extremely high cleaning standards to prevent contaminants from compromising equipment safety.<\/div>\n
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1.2 Common Types of Contaminants on PCBs<\/h3>\n<\/div>\n
Welding-related residues are the most common type. Flux residues are mostly rosin-based organic compounds, while solder dross consists of metal oxides generated during the soldering process; if not removed, they can easily cause cold joints. During production, PCBs come into contact with machine tool oil and environmental dust. The drilling process also generates metal shavings, and photolithography may leave behind photoresist that has not been completely stripped. Among environmental and usage-related residues, moisture can cause PCBs to become damp and develop mold; long-term dust accumulation can impede heat dissipation; and corrosive gases in industrial environments can accelerate circuit corrosion. When inspecting for contaminants, obvious residues can be detected through visual inspection in simple scenarios, while microscopic residues in tiny pores require examination under a microscope. Professional testing can utilize a Fourier-transform infrared spectrometer (FTIR) to accurately identify the composition of contaminants.<\/div>\n
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1.3 Core Standards and Specifications for PCB Cleaning<\/h3>\n<\/div>\n
Among industry-wide standards, IPC-A-610 specifies that residues on the PCB surface must fall below the \u201cacceptable visual standard,\u201d with no visible contaminants and no adverse effect on electrical performance; IPC-J-STD-001, meanwhile, defines the process requirements for post-soldering cleaning, including cleaning agent compatibility and the degree of dryness after cleaning. Differences among industry standards are significant: automotive electronics PCBs must comply with ISO 16232, withstand high-temperature and high-humidity environments, and pass salt spray testing after cleaning; medical device PCBs follow relevant FDA standards, requiring that there be no biocompatibility risks after cleaning; aerospace PCBs adhere to MIL-STD-2000, with residue control precision reaching the microgram level. In terms of environmental protection and safety, China\u2019s \u201cControl Standard for Fugitive Emissions of Volatile Organic Compounds\u201d limits VOC emissions from solvent-based cleaning agents; during operation, chemical-resistant gloves and safety goggles must be worn to prevent skin contact with the cleaning agent or inhalation of volatile fumes.<\/div>\n
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PCB Cleaning Technologies and Methods<\/h2>\n<\/div>\n
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2.1 A Detailed Explanation of Traditional Cleaning Technologies<\/h3>\n<\/div>\n
Solvent cleaning methods commonly use solvents such as isopropyl alcohol and acetone, which are suitable for removing rosin-based residues. During the process, the PCB is immersed in the solvent for 10\u201315 minutes with ultrasonic assistance, and then dried with compressed air. However, it is important to note that solvents are flammable, so this procedure must be performed in a well-ventilated area. The water-based cleaning method uses deionized water as a base, with the addition of an alkaline detergent (such as sodium hydroxide solution). The PCB is rinsed using spray pressure (0.3\u20130.5 MPa). maintaining a water temperature of 50\u201360\u00b0C to improve cleaning efficiency. After cleaning, the PCBs must be dried with hot air (at 60\u201380\u00b0C) to prevent moisture residue. Ultrasonic cleaning technology uses ultrasonic vibrations at 20\u201340 kHz to generate microscopic bubbles; when these bubbles collapse, the resulting shock waves dislodge contaminants. This method is suitable for cleaning multilayer boards, and the frequency should be adjusted based on the PCB thickness \u2014 \u2014 30\u201340 kHz for thin PCBs and 20\u201325 kHz for thick PCBs. A common issue is water marks on the PCB surface after cleaning, which can be resolved by adding a rinsing step.<\/div>\n
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2.2 New Cleaning Technologies and Innovative Applications<\/h3>\n<\/div>\n
Vapor-phase cleaning technology uses environmentally friendly fluorinated liquids (such as HFE-7100) to perform cleaning through vapor-phase condensation in a sealed chamber, leaving no solvent residue. It is suitable for high-precision HDI PCBs and requires no drying after cleaning, with efficiency improved by 30% compared to traditional solvent-based methods. Plasma cleaning technology uses a high-frequency electric field to ionize gases (such as argon and oxygen) and generate plasma. The plasma removes organic residues from the PCB surface, improves surface roughness, and enhances adhesion for subsequent soldering. It is widely used in miniaturized PCBs (such as those for smartphone cameras). Laser cleaning technology uses a 1064 nm laser beam to irradiate contaminants, causing them to vaporize instantly. This non-contact cleaning method prevents PCB deformation, achieves a precision of up to 0.01 mm, and is suitable for removing stubborn contaminants such as solder slag. Green cleaning technology primarily uses biodegradable cleaning agents (such as plant-based surfactants) in conjunction with energy-efficient cleaning equipment. The cleaning wastewater is filtered and can be recycled, thereby reducing water consumption.<\/div>\n
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2.3 Tailored Cleaning Solutions for Different Types of PCBs<\/h3>\n<\/div>\n
Single- and double-sided boards have a simple structure and can be cleaned using a water-based immersion process, which simplifies the pre-cleaning steps. The cleaning agent concentration is controlled between 5% and 8%, thereby reducing costs; Multilayer boards require special attention to interlayer residue. A combined \u201cultrasonic cleaning + high-pressure spray rinsing\u201d process is used, with the rinsing pressure increased to 0.6 MPa to ensure no residue remains in the interlayer gaps. Flexible PCBs must be secured with specialized fixtures during cleaning to prevent folding or deformation. A neutral water-based cleaning agent (pH 7\u20138) should be used, and the drying temperature should not exceed 50\u00b0C. Residue in the micro-holes (hole diameter < 0.2 mm) of HDI PCBs is difficult to remove; plasma cleaning combined with vapor-phase rinsing must be used. The plasma treatment time should be controlled between 3 and 5 minutes to ensure the inner walls of the micro-holes are clean. When cleaning ceramic-substrate PCBs, avoid using acidic cleaning agents; instead, use a weakly alkaline cleaning agent (pH 8\u20139) with an ultrasonic frequency of 40 kHz to prevent cracking of the ceramic material; For metal-based PCBs, a corrosion inhibitor must be added (at a ratio of 0.5% to 1%) to prevent the cleaning agent from corroding the metal substrate.<\/div>\n
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PCB Cleaning Materials and Equipment<\/h2>\n<\/div>\n
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3.1 Classification and Selection Guide for Common Cleaning Agents<\/h3>\n<\/div>\n
Among solvent-based cleaners, alcohols (isopropyl alcohol) are environmentally friendly but have weak cleaning power, making them suitable for removing light rosin residues; ketones (acetone) have strong cleaning power but are highly volatile, so their usage must be controlled; Esters (ethyl acetate) offer good compatibility and are suitable for plastic-based PCBs; halogenated hydrocarbons (trichloroethylene) provide high cleaning efficiency but must comply with environmental emission requirements. Among water-based cleaners, alkaline cleaners (such as sodium carbonate solutions) are suitable for removing oil stains and solder residue, while acidic cleaners (such as citric acid solutions) can remove metal oxides, but cleaning time must be controlled (<5 minutes) to prevent corrosion of the PCB; Neutral cleaning agents (such as nonionic surfactant solutions) offer the highest compatibility and are suitable for PCBs made of sensitive materials. Among auxiliary additives, corrosion inhibitors prevent corrosion of metal substrates, with an addition ratio of 0.3%\u20130.5%; surfactants enhance the cleaning agent\u2019s penetrating power, with an addition ratio of 1%\u20132%; Defoamers reduce foam during cleaning, with an addition ratio of 0.1%\u20130.2%. When selecting a cleaning agent, the following factors should be considered comprehensively: Avoid acidic cleaning agents for ceramic PCBs; prioritize alkaline cleaning agents when the contaminants are solder residue; and select biodegradable cleaning agents for applications with high environmental requirements.<\/div>\n
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3.2 Detailed Overview of PCB Cleaning Equipment<\/h3>\n<\/div>\n
Among batch cleaning equipment, spray-type cleaners use high-pressure nozzles (0.4\u20130.6 MPa) to rinse PCBs, with a production capacity of 500\u20131,000 boards per hour, making them suitable for batch cleaning of single- and double-sided boards; Immersion-type cleaning machines can accommodate 200\u2013300 PCBs and, when combined with ultrasonic assistance, are suitable for cleaning multilayer boards; ultrasonic cleaning lines consist of pre-cleaning, main cleaning, rinsing, and drying units, feature a high degree of automation, and can achieve a production capacity of over 1,500 boards per hour. Among precision cleaning equipment, vacuum cleaners perform vapor-phase cleaning in a negative-pressure environment and are suitable for HDI PCBs; plasma cleaners can precisely control plasma density, requiring a vacuum level of 10\u201330 Pa during operation; The laser power of laser cleaning machines is adjusted based on the type of contaminant; a power of 50\u201380 W is selected for removing solder residue. Among small\/portable devices, handheld ultrasonic cleaning pens (10\u201320 W) are suitable for localized cleaning during repairs; desktop cleaning machines (5\u201310 L capacity) are suitable for cleaning small batches of PCBs (such as R&D samples), offering simple operation and a small footprint. Among supporting equipment, the hot-air drying oven features adjustable temperature (40\u2013100\u00b0C) and a drying time of 15\u201330 minutes; filtration equipment (filtration precision: 5\u201310 \u03bcm) purifies cleaning wastewater, achieving a recycling rate of up to 80%; wastewater treatment equipment uses neutralization and sedimentation processes to ensure the wastewater meets discharge standards.<\/div>\n
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3.3 Quality Control of Cleaning Materials and Equipment<\/h3>\n<\/div>\n
Quality testing of cleaning agents should focus on purity (purity of solvent-based cleaning agents \u2265 99.51 TP3T), corrosiveness (no significant corrosion after soaking a PCB for 24 hours), volatility (boiling point of solvent-based cleaning agents \u2265 60\u00b0C to prevent excessive evaporation), environmental friendliness (VOC content \u2264 100 g\/L). During performance testing of cleaning equipment, cleaning uniformity must be verified through sampling\u2014randomly select 10 PCBs, with a variation in residue content of \u226410%; temperature control accuracy error of \u00b12\u00b0C; pressure control accuracy error of \u00b10.05 MPa; the equipment failure rate must be \u22641% per month. Regarding consumable replacement, the concentration of the cleaning agent must be checked regularly and replenished promptly when the concentration drops by 10%; Equipment filters must be replaced every 200 hours, and vacuum pump oil must be replaced every 300 hours; regarding maintenance schedules, batch cleaning equipment must undergo a comprehensive overhaul every 3 months, and precision cleaning equipment must have its parameters calibrated every 2 months to ensure stable performance.<\/div>\n
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Optimization of PCB Cleaning Processes and Troubleshooting<\/h2>\n<\/div>\n
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4.1 Optimization of Cleaning Process Parameters<\/h3>\n<\/div>\n
Temperature has a significant impact on cleaning effectiveness. In water-based cleaning, raising the water temperature from 40\u00b0C to 60\u00b0C can improve cleaning efficiency by 40%; however, temperatures exceeding 70\u00b0C may cause the PCB substrate to age; Cleaning time must be adjusted based on the thickness of the contaminants: 5\u20138 minutes for light residue and 12\u201315 minutes for heavy residue; excessive cleaning time will increase costs; If the spray pressure is below 0.3 MPa, cleaning will be incomplete; if it exceeds 0.8 MPa, it may damage the PCB circuits. The optimal range is 0.4\u20130.6 MPa. Regarding cleaning agent concentration optimization, increasing the concentration of water-based cleaning agents from 5% to 8% improves cleaning power by 25%; however, concentrations exceeding 10% increase the risk of residue and raise costs; The service life of solvent-based cleaning agents can be extended through recirculation and filtration (5 \u03bcm filtration precision), reducing consumption by 30%. In a multi-step process design, low-pressure spraying (0.2\u20130.3 MPa) is used for pre-cleaning to remove surface dust; ultrasonic cleaning combined with high-pressure spraying is used for main cleaning; and deionized water (conductivity \u2264 10 \u03bcS\/cm) is used for rinsing; drying follows a \u201clow-temperature pre-drying (40\u00b0C, 10 minutes) + high-temperature drying (70\u00b0C, 20 minutes)\u201d process to prevent uneven heating of the PCB.<\/div>\n
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4.2 Common Cleaning Problems and Solutions<\/h3>\n<\/div>\n
Inadequate cleaning is often caused by improper parameters, such as insufficient spray pressure (<0.3 MPa) or too-low cleaning agent concentration. In such cases, increase the pressure to 0.5 MPa and adjust the cleaning agent concentration to the standard level; for localized contamination (such as residues in micro-pores), add a plasma cleaning step. If surface damage to the PCB is caused by corrosion, it is often due to excessive exposure time to acidic cleaning agents; the cleaning time should be reduced to within 5 minutes, or a neutral cleaning agent should be used. Discoloration is often caused by excessively high drying temperatures; the temperature should be lowered to below 60\u00b0C. warping is usually caused by the flexible PCB not being properly secured; it must be positioned using specialized fixtures. Cleaning agent residue is often caused by insufficient rinsing; increase the number of rinses (from 2 to 3) or raise the rinsing pressure to 0.6 MPa. Residue can be tested using the isopropyl alcohol wipe method; if the white cloth remains free of stains after wiping, the part is considered\u5408\u683c. If low cleaning efficiency is due to insufficient equipment capacity, upgrade to an automated cleaning line; if it is due to redundant processes, combine the pre-cleaning and main cleaning steps (using an integrated \u201clow-pressure spray + ultrasonic\u201d unit) to reduce the total duration by 20%.<\/div>\n
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4.3 Balancing Cost and Efficiency in Cleaning Processes<\/h3>\n<\/div>\n
Raw material costs can be controlled through the recycling of cleaning agents\u2014water-based cleaning agents can be reused 5\u20138 times after filtration and the addition of additives; solvent-based cleaning agents can be recovered through distillation (recovery rate \u226580%), thereby reducing procurement costs. Regarding energy consumption optimization, switching the heating method for cleaning equipment from electric to steam heating reduces energy consumption by 35%; combining the rinsing and drying steps and adopting \u201cdirect hot-air drying after rinsing\u201d reduces energy consumption associated with equipment start-up and shutdown. Labor costs can be reduced by introducing automated loading and unloading systems to replace manual operations, eliminating the need for 2\u20133 operators; simplifying operating procedures by presetting equipment parameters to modes such as \u201csingle-sided board\u201d and \u201cmulti-layer board\u201d eliminates the need for frequent adjustments by operators, thereby increasing per-capita efficiency by 50%.<\/div>\n
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