How to clean PCB?

When troubleshooting a non-functional or poorly performing circuit, engineers can often run simulations or other analysis tools to consider the circuit at the schematic level. If these methods don’t solve the problem, even the best engineer can be stumped, frustrated or confused. In order to avoid getting into a similar dead end, FS Technology introduces a simple but very important tip: PCB cleaning!

The importance of PCB cleaning process

There is no denying the significance of cleanliness, and this should not be attributed to the fact that our moms lay such a strong focus on it. There is no doubt that a PCB may get tainted by grease, the oxidation of its exposed metal surfaces along with effects of PCB manufacturing process. All these factors can contribute to contamination. PCB cleaning may be required for some manufacturing processes, but this does not imply that it is essential for all of them. Then how to clean PCB board? And is this always required? Before we begin soldering, let’s take a closer look at the effects that contamination can have on PCBs.

Oxidized PBC Board
Figure 1: Example of a contaminated PCB before soldering process.

It might lead to complications while soldering. Fingerprints present on PCB also include salts, which might have an impact on the soldering process if the metallization is contacted for an extended period and the environment is damp. If there is contamination, it is possible that it has spread to places that have not been in touch with the flux or its solvent.  These marks have the potential to either cause future electrical reliability issues while the board is in service or to degrade the adhesion and overall efficacy of any post-soldering protective layer. Therefore, from the perspective of FS Technology, the circuit board cleaning procedure must be added to the PCB assembly process steps, and any cleanliness that does not meet the standards may lead to the risk of assembly failure.

Required PCB Cleaning Kit

Here are some kits that need to be used for circuit board cleaning, some are necessary and some are optional. Although there are currently many small workshops omitting this step in order to save costs, but if you want to gain customer approval, please prepare a variety of circuit board cleaning tools. For amateurs, please choose a more suitable cleaning tool according to the product description and circuit conditions.

PCB Cleaning Brush

Brushes for cleaning PCBs
Figure 2: Brush being used to clean PCB before soldering

If you need to clean broad areas quickly, a banister brush is a great choice, but if you need to get in close for precision work, inexpensive tin brushes from the hardware store will do the trick. Remember not to use a hard bristle brush but a fiberglass bristle PCB cleaning brush, which can do a better job of cleaning without damaging the circuit. When cleaning your PCB, you can get into the tinier spaces by angling the bristles of a tiny brush. This will make it possible to safely force the solvent into the board’s more inaccessible crevices. Small brushes work great for getting into small spaces on circuit boards. 

Lint-Free Towels or Microfiber Cloths

Towels for cleaning PCBs
Figure 3: Microfiber cloth being used to clean pre-soldering area of PCB

We need to use a lint-free towel or microfiber cloth to wipe the residual detergent solution on the surface of the circuit board at the end of the PCB washing process to avoid chemical corrosion caused by long-term use. They have to be lint-free or made of microfiber to reduce the likelihood of leaving dust or other particles left in your device.

Alcoholic Solvents

clean pcb with alcohol
Figure 4: Different alcoholic solvents used for removing moisture from PCBs

PCBs can contain moisture if not contained in a controlled environment and this can lead to the start of the corrosion process which, in many cases, is the main cause of circuit board short. To deal with this moisture, clean PCB with alcohol. The alcohol-based solvent reacts with water to form a solution, which subsequently evaporates along with the water. Because of this, it is the most effective method for removing corrosion damage caused by moisture on PCBs and preventing further damage.

Compressed Air

Compressed Air Cleans PCB Dust
Figure 5: Compressed Air Jet to remove debris from PCB

This step is part of the pre-soldering and cleaning procedure. Compressed air offers an inconspicuous approach to free up any dust that may have been sitting on the PCBs or within the PCB via holes and then blows it out. Many electronic enthusiasts use their mouths to blow the dust remaining on the surface of the board, which is not recommended. When water vapor in the air mixes with dust and clings to the boards it is not easy to remove, compressed air is used to spray the air contained inside the vents in short bursts.

Etching Resistant Chemical

best pcb cleaner: Etching Resistant Chemical
Figure 6:Blue coloured etching resistant chemical

The process of etching is a common method used to manufacture PCBs. Etching chemicals are strong Acidic or Alkaline solutions that, if not washed properly, can cause contamination of the PCBs. So, for the purpose of removing these chemicals from PCB many Anti-Etching solvents are used depending upon the chemical used in the etching process. 

Best way to clean PCB

  1. Before cleaning the assembled PCBA board, please make sure that the PCB connectors are removed, and desolder PCB components if necessary.
  2. Check the status of components and welding quality, and replace or repair in time if there is any defect.
  3. At the beginning of cleaning, you’ll need to place the PCB in a well-lit environment so that you can see the contaminants and not skip any spots on the PCB.
  4. Rinse the surface of the PCB slowly with water, if you use other cleaning fluids, a second cleaning is required.
  5. Blast the compressed air jet on the PCB to remove any macro debris that is clearly visible to the eye.
  6. You should begin cleaning with your alcoholic solution using the brush with the soft bristles. After applying it to all regions of the PCB, particularly the corroded portions, you should wait a few minutes before proceeding.
  7. After applying a cleaning solution, to remove any leftover dust or moisture, use a towel made of lint-free material or microfiber and pat it gently. Take special care not to wipe it down, since doing so might result in scratches.
  8. Finally, again, apply the compressor air jet to remove any leftovers.
  9. When all the above steps have been carried out, carefully apply an etching-resistant chemical and keeping in view the soldering pad areas and you have completed your PCB cleaning procedure.

Precautions for cleaning PCB board

  • Take extra care while using the brushes and towel or microfiber cloth, so that, you may not damage the PCB sensitive section including tiny wire tracks. 
  • When using an ultrasonic cleaner to clean the PCB, please place the circuit board in the fixture to avoid component damage due to vibration.
  • When cleaning component footprints for printed circuit boards (PCBs), it is in everyone’s best interest to always have access to the most up-to-date datasheets and information on the components that are being used so you may not use those chemicals which can harm the component placement terminals.
  • Since the flux residue gradually hardens over time and produces corrosive substances such as halogen salts, the assembled PCBA board should be cleaned immediately after soldering.
  • PCBA manufacturers should standardize cleaning procedures, such as wearing masks and electrostatic wristbands.
  • After cleaning, check the cleanliness of the board to ensure that it meets the PCB cleaning standards, and avoid impurities such as residual flux, tin beads, and tin slag.
  • After cleaning, avoid using excessively high drying temperature to cause damage to the circuit. Generally, the temperature of the oven should be controlled at 30 °C-40 °C.
  • Distinguish between cleaned and uncleaned PCBs, and avoid direct contact with the board surface with your hands.

That’s all there is to provide you with PCB cleanup methods. As a leading enterprise in turnkey PCB assembly in China, FS Technology keeps all the details of manufacturing in mind. With the FS Tech’s services, it is possible to save both time and money by cooperating with a partner who is skilled in Production, PCBA testingCircuit board assemblyand Mechanical Assembly. When working with PCBA, routine responsibilities include rewriting designs and changing components as required. This is the manner that commerce is conducted in the PCBA world. 

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