Best solvent for PCB cleaning
Printed Circuit Board Cleaning – Solvents vs. Water-Based Cleaners
Removing flux is a very important step in PCB´s manufacturing process because flux residues can cause electric short and damage the PCB and whole electronic device.
For flux removal DCT produces two categories of cleaners. Water and solvent based.
Generally speaking, solvent-based liquids are not recommended for automated PCBA cleaning anymore.
The most appropriate cleaning fluids for the automated circuit board cleaning are water-based ones. Decotrons®.
We can recommend use of solvent-based chemistries for PCBA cleaning only in case of MANUAL cleaning.
In the SMT industry, PCBs are manually cleaned in small productions or after soldering repair.
For these purposes, our company developed manual cleaning spray Flux Remover 4 which provides easy and effective removal of flux residues from PCB after soldering,
Best DCT solvent for MANUAL PCB cleaning - Flux Remover 4
Flux Removal 4 is an aerosol spray – the blend of solvents in aerosol form is sprayed onto the PCB and a special brush is used to clean flux residues. Our brush is with higher hardness fibers and excellent chemical and mechanical resistance, which prevents deformation and fraying of the brush.
After cleaning, use of ESD wiper to swab/wipe all dissolve impurities is recommended.
No additional final rinse of PCBA is needed. The remaining cleaning agent evaporates quickly without leaving any traces on the cleaned surface.
Apart from flux removal, PCBs can be cleaned from other different PCB contaminants, such as dust, grime, rust, oil, fingerprints, etc.
Use of IPA for PCBA Cleaning – not recommended
Isopropyl alcohol (IPA) has been used to remove flux residues after soldering for many years as it is internationally approved to standards required by major electronics manufactures. It is a good solvent for natural resins which are main parts of flux. However, with the development of no-clean solder pastes and fluxes, IPA for dissolving flux residues is not sufficient anymore. Generally, after using IPA, an undissolved white flux residue is left at solder joint, which can contain ionic contaminants.
The use of IPA in the automatic cleaners (or other solvent-based cleaners) has many disadvantages such as flammability and the risk of fire. All equipment using IPA must be specially treated to prevent the generation of static electricity that can cause sparks. IPA’s flammability also makes it difficult and expensive to ship. IPA is a VOC (volatile organic compound) and this means that the use of alcohols and other organic substances can be restricted by strict regulations.
Please note IPA should not be used in any DCT automatic cleaning machine for its flash point – 12 °C, which can cause a fire of the machine in case of any small spark.
Water-based agents for PCBA cleaning - recommended
Water-based cleaning fluids are therefore preferable cleaning solution for several reasons in combination with the automatic cleaning systems. Not only they are non-flammable, low VOC, making them environmental-friendly, they even have better cleaning efficiency than IPA alone, speaking about removal of no-clean solder paste. DCT offers many water-based types of cleaning agents, so called Decotrons®, which are designed for PCB defluxing process. DCT water-based cleaning agents are usually alkaline (with pH higher than 7) for better cleaning efficiency.
Automated water-based cleaning of PCBs after soldering:
Batch system for PCB cleaning: cleaning system when cleaning fluid (water-based – Decotrons) is sprayed over the PCBs. Cleaning, rinsing, and drying take place in one chamber. Specific example is DCT cleaning machine InJet® 388 CRD with vertical high-pressure spay-in-air technology or InJet® 888 CRD with horizontal high-pressure spray-in-air technology. Recommended cleaning fluids for these machines are Decotron® 351S and Decotron® 409A.
Inline system for PCB cleaning: inline cleaning system has more chambers, where every step (cleaning, rinsing, and drying) takes place in a separate one. Alternatively, the cleaning system can have three chambers where the first one is used for cleaning, the second one for rinsing and the third one for final rinsing and drying (specific example of InJet® 388 TRIPLE CRRD with vertical high-pressure spray-in-air technology). Example of two chamber cleaning system for PCB cleaning is InJet® 388 TWIN CRD where cleaning takes place in the first chamber and rinsing and drying in the second separate chamber. Separation of the rinsing from the cleaning chamber ensures cleaning fluid saving and less cross-contamination. Recommended cleaning agent for these cleaning systems is Decotron® CP381.
Ultrasonic cleaning system: Ultrasonic cleaning is a physical process using ultrasound to clean polluted components such as circuit boards. The process takes place at the interface between the surface of the PCB and the liquid cleaning medium. Flux residues are agitated by ultrasound waves and then washed off the surface by mechanical energy. In the past, machines with ultrasonic technology were often used for PCBA cleaning, which is no longer recommended due to component sensitivity, miniaturization, or higher rinsing quality requirements, because ultrasound waves can damage sensitive PCB components.