Which Circuit Board Cleaner is Better

In the PCBA process, solder paste and flux are two essential materials, and their liquid properties may result in residues on the surface of the PCBA board after processing. Initially, these residues may only affect the appearance of the board, but over time, water droplets may appear on the board’s surface. When powered on, these residues may undergo chemical reactions with the circuit, eventually forming corrosive substances such as metal halides. This has a serious impact on the lifespan of electronic products.

To address this issue, the PCB cleaning process has become a crucial step. There are various PCB cleaners available in the market, and these cleaning agents can be classified into three major categories: solvent-based, water-based, and semi-aqueous. Each type has further specific classifications, but which one is the optimal solution?

circuit board cleaning liquid

Solvent-Based Cleaner

For companies specializing in cleaning services, solvent-based PCB cleaners are the most commonly used. Although they are more expensive, they offer powerful cleaning capabilities, allowing for faster and more effective circuit board cleaning, making them suitable for small-scale cleaning tasks. Solvent-based PCB cleaners mainly include halogenated hydrocarbons, petroleum-based, alcohol-based, and ether-based cleaners.

Recognizing the advantages of these cleaners, it’s essential to be aware that they are prone to evaporation. Therefore, extra care is needed during storage, avoiding light exposure, heat, and vigorous shaking, while also paying attention to the product’s shelf life. With the increasing awareness of environmental and health concerns, substances like ODS and VOCs, which are toxic, are prohibited in production and usage. Other regulations and bans include:

  • Montreal Protocol: Enacted in 1987 to protect the ozone layer, this protocol has led most countries to phase out the use of ODS during production.
  • Clean Air Act: Strict limits on the concentration of VOCs (volatile organic compounds) in operating environments.
  • RoHS Directive: Restrictions on the use of hazardous substances such as lead, mercury, cadmium, hexavalent chromium in the electronics manufacturing industry.
  • REACH Regulation: Aimed at protecting human health and the environment, it outlines the procedures for the registration, evaluation, authorization, and restriction of chemicals.

These regulations imply that end-users of PCB cleaners need to pay extra attention to whether harmful substances are present in the raw materials and take necessary protective measures during use. Here are some common solvent-based cleaners:

Alcohol: Options include isopropyl alcohol, methanol, and ethanol. Ensure a concentration of not less than 90%. These PCB cleaners are suitable for dealing with grease, dirt, and other organic contaminants. Always avoid open flames during use.

Isopropyl PCB Alcohol Cleaner

Acetone: A strong solvent that can dissolve stubborn stains such as grease, resin, and paint on the circuit board surface. It has the advantage of easy volatilization with minimal residue after use. However, acetone has an irritating odor, so working in a well-ventilated environment is crucial, and excessive use should be avoided to prevent damage to the board.

Acetone PCB cleaner

Chlorinated Hydrocarbons: Organic compounds containing chlorine, excellent for degreasing, particularly effective against resin and grease contamination. However, most chlorinated hydrocarbon cleaners have slight toxicity, so careful selection and usage are necessary.

Water-Based Cleaner

As mentioned earlier, solvent-based cleaners may pose environmental hazards. As an alternative solution, water-based PCB cleaners have emerged. As the name suggests, these cleaners are water-based and incorporate environmentally friendly, biodegradable components, making them superior in terms of environmental, health, and safety aspects.

In addition to being environmentally friendly, water-based cleaners can handle most flux residues. Furthermore, these cleaners typically lack irritating properties, making them more favorable for sensitive components. Importantly, in the electronics manufacturing industry, which often involves large-scale production, water-based cleaners exhibit higher compatibility with equipment like ultrasonic and spray devices, meeting the requirements of automated production.

Some common water-based PCB cleaners include:

Deionized Water: Processed through deionization to remove ions and obtain ultra-pure water with low electrical conductivity. This cleaning agent is suitable for tasks requiring high sensitivity to components, ensuring no risk of short circuits or electrical faults. Its high purity ensures no residue on the circuit board surface, maintaining high cleanliness.

Emulsion-Type Cleaners: A type that combines organic solvents and water to form an emulsion. These cleaners typically include surfactants, effectively dispersing and removing organic contaminants such as grease and dirt. However, they come with higher costs and require more time for stubborn stains.

Vapor Phase Cleaners: A technology that utilizes aerosols to remove surface contaminants without using liquid cleaners. Gases such as hydrogen fluoride, chlorine, and nitrogen are involved. This technique can comprehensively cover the board surface, even in tiny gaps. However, it requires specialized equipment and operation, resulting in relatively higher costs.

Semi-Aqueous Cleaner

Semi-aqueous PCB cleaners represent a category between solvent-based and water-based cleaners, combining the advantages of both while ensuring environmental friendliness and providing outstanding cleaning performance.

The most significant advantage of semi-aqueous cleaners lies in their compatibility with various processes. This means there’s no need to alter existing processes to integrate a cleaning machine into the production line. Compared to solvent-based cleaners, they are less prone to volatilization and are compatible with most metals and plastics. Compared to water-based cleaners, they offer stronger cleaning capabilities, but with higher costs and the need for safety measures such as protection against toxic solvents, fire, and explosions.

Here are some common semi-aqueous PCB cleaners:

ZD-7 Series Semi-Aqueous Cleaners: These cleaners are based on an environmentally friendly formula, excluding halogens. They have lower volatility without losing solvency, suitable for cleaning PCBs and components.

HFE-7100: Belonging to the fluorinated hydrocarbon semi-aqueous cleaner category, it features rapid volatilization and high surface tension. It is suitable for cleaning precision electronic devices and effectively removes residual solder paste.

SC1000 Series: This is a semi-aqueous cleaner based on supercritical carbon dioxide, often considered an environmentally friendly choice. It leaves no residue during the cleaning process and is suitable for cleaning sensitive components.

Conclusion

Different types of circuit board cleaners have distinct advantages and efficacy. Careful selection based on specific requirements is crucial. Before use, it’s essential to assess:

  • Compatibility of the cleaner with the materials used on the PCB.
  • Whether the cleaning strength of the cleaner is adequate or too strong.
  • Whether it meets international standards and regulations for environmental protection.
  • The cleaning goals: oil stains, grease, flux residues, solder paste.
  • The presence of toxic gases and the provision of corresponding safety measures.
  • Compatibility between the cleaner and cleaning equipment.
  • Cost-effectiveness.

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