How To Clean Flux from PCB:An In-Depth Guideline

Cleaning the PCB from flux after soldering is probably one thing that is based more on myths than the facts. For instance, most technicians prefer using or at least advised to use IPS (Isopropyl alcohol) to clean the flux residues for the post-soldering procedure.

However, there are indications that such hygroscopic solvent such as the IPA is harmful to clean the soldered printed boards. Instead, you can use a specialized flux cleaner for the purpose.

To help you out in post-cleaning the PCBs, our professionals have chalked out guidelines on how to clean flux residues from boards. We have included all the possible solutions to clean the PCB boards without harming them.

So, get ready to dive deep into the article.

Table of Contents

What is the Flux?

Although the word flux has different meanings in the dictionary, in the printed circuit board industry such as Copper based PCB or Alu PCB is used differently.

Technicians use flux to solder electronic components correctly to the various types of PCBs. Technicians use flux to properly solidify and connect the electrical components using a different kind of soldering process.

When you apply to solder flux paste or only solder flux, it leaves residues on the boards. The tailings can eat up the components slowly and result in a damaged PCB board over time. It may cause etch or inhibition on the printed boards.

Thus, it is essential to clean the residues to prevent inhibition and etched wiring on PCBs. Also, the flux cleaning avoids obstructing other electrical components as well.

How to Clean Flux

When you solder printed circuit boards such as flexible PCB and heavy copper PCB using flux, it leaves a thick soap-like residue on the components. Thus, it is a must to remove the waste from the post-soldered elements to avoid damages and improper wiring.

It is even more important for the conventional PCBs which often carries conductive materials. The process includes the following steps:

Step one: Making the flux removal

Your success rate of cleaning the soldering residues from the electrical components will depend mostly on the type of removal you use for the purpose. While several manufacturers produce some best flux remover using isopropyl, you can actually create a residual removal at home.

You will require the following things to make the homemade flux remover-

  • 95% pure ethyl alcohol. It needs to be 850ml.
  • 95% pure and tested 100ml isopropyl alcohol.
  • Ethyl acetate solution of 50ml.

You can use a measuring bottle to measure the essential amount of the three chemical liquids correctly. It will help you achieve the desired proportion better. Since the purity of the chemical fluids is critical, always buy them from trusted shops.

Also, store them in the proper container and make sure the cap is sealed. Otherwise, air may contaminate the solutions. Furthermore, ethyl tends to evaporate if the lid is open.

Now let’s get into the mixing procedure. Thank god, it is secure.

Just take a proper mixing container, then, first, pour the ethyl alcohol on it. After that, add the isopropyl alcohol and ethyl acetate solution on it. That’s it, and your homemade flux remover is all set to go.

Since you won’t be using the entire liquid in a single go, pour some (approximately 100 ml of solution) in a spray bottle and use it. The mixture works on both resin and non-resin based flux as well as no-clean flux too.

Note: Always wear gloves before you handle the ethyl and isopropyl solutions and start mixing them. It helps you prevent unwanted happenings.

Step two: Cleaning the flux residue

Once you are ready with the flux cleaning solution, know that the rest of the procedure of how to clean PCB after soldering is only a matter of time.

  1. Take a clean brush. The brush should be flexible and soft so that it won’t damage the sophisticated electrical components.
  2. Drip the toothbrush on the newly made solution or use the sprayer to spray it on the soldered board.
  3. Then, wait for a few minutes. In the meantime, the isopropyl and ethyl solution will work on the residues to dissolve and make it softer.
  4. Then begin the cleaning process with the brush. Apply gentle pressure and, with patience, clean the entire board.
  5. The cleaning is straightforward and doesn’t ask you to be a master on it. The only dedicated thing you require is to be gentle and patient. Never rush on the process, or you will end up damaging the entire PCB.

An Alternative Way:

We have already told that isopropyl is somewhat harmful to printed circuit boards. Isopropyl is extraordinarily aggressive, and it intrudes plastics with detrimental effects. Thu, you may not want to use it for the flu cleaning.

Well, we have an alternative solution for you.

You can use ‘Poly Clens’ for the flux cleaning from the soldered PCBs. It is a simple plastic cleaning and paintbrush. It is made of mild detergent (many people call it surfactant), alcohol, and thinner material mixture.

You just need to pour some ‘Poly Clens’  on a non-plastic (necessarily metal) container or bowl. Then carefully apply it on the soldered flux boards. After waiting for a few minutes, brush off the dissolved residue from the boards.

Sounds easy, right?

The usefulness of ‘Poly Clens’ doesn’t end here.

As it emulsifies the soldered residues, the water will comes handy in removing any traces of deadly activating agents from the sophisticated resin flux. So, you get impressive final results.

How To Clean Flux Residue After Soldering Copper Pipe

Many amateur technicians worry about cleaning soldering residues from the copper pipe. Well, it is straightforward. You can use vinegar and a clean toothbrush for the purpose. If the copper pipe is too long to reach with a toothbrush, use a stick attached with the brush to reach the far corners.

Also, our previously described two solutions will also work best for the purpose.


The final appearance of the printed circuit boards is a distinguishable feature to differ between an amateur made and professional made PCBs. Hence, to achieve such impressive appearance and reduce damaging chances, always clean the flux residue after the soldering.

In such cases, our professional guideline on how to clean flux is a surefire shot for you.  It doesn’t ask you to be Picasso of the process; but, you will need the patience to deal with the cleaning method. Rejoice!

Peter Gong
Peter Gong

I am Peter Gong. I have been working in PCB and PCBA industry for 15+ years now. I have been a part of the PCB revolution with my dedication to circuit board technologies and creative ideas. I write in FX PCB to impart my knowledge on PCB and PCBA for all circuit board lovers, manufacturers, and users.