Ultimate Guide in 2023: How to Clean Flux Off PCB


Almost all people with enough knowledge in the electronics industry know the importance of flux in a PCB. In essence, it is a chemical agent with a primary responsibility of eliminating the presence of oxides, impurities, and other substances from the board.

This way, the manufacturer will attain a board with exceptional solidity for the soldering joints. Hence, they are essential to incorporate before proceeding to the soldering phase. Although they are an excellent solution, they can pose headaches as well.

In line with this, there are a lot of instances wherein after they applied fluxing agent to the board, it leaves residues on the board. All of these residues can bring harm to the device; thus, it is recommended to thoroughly clean the board before submitting it to the following phase of production to achieve the board’s optimum quality and performance.

Consequently, to achieve all of these, we will tackle the definition of Solder Flux, various categories of a Flux, the importance of eliminating the residues, and ways to remove them using alcohol and without alcohol. We suggest completing the entire post to understand the concept of Flux in a PCB entirely; we guarantee that it is worth reading!

Introduction to PCB Flux

Introduction to PCB Flux

What is Solder Flux?

As the name states, Solder Flux is utilized in soldering electronic equipment into the circuit board. Furthermore, as mentioned, it is considered to be a chemical agent that can produce notable amounts of residues after use; hence, it is essential to clean them afterward.

In terms of usage, it can either be used for manual or automated soldering. It is regarded that circuit boards are prone to oxidation due to their copper traces, thus, leading to the unwanted formation of the solder joint. However, with the help of flux, these problems, oxidation, and contamination, can be prevented since they can be used to clean and remove such impurities.

As for its physical structure, it can be either solid, semi-solid, or liquid. Although the common ones are pasted in a tin, they can be acquired as a liquid in a bottle. The application of flux to hand soldering necessitates the presence of flux pens to incorporate them into the board properly. Apart from that, the flux is regarded as an adhesive-like compound that has the ability to hold its components reliably. Additionally, the flux is known to safeguard the metal surfaces against re-oxidation and can wet the board through its remarkable additive characteristics.

What is Solder Flux?

Definition of Solder Flux

Categories of Flux

In a nutshell, there are three (3) principal categories of Flux; these are Rosin and Rosin Substitutes, Water Soluble, and No-Clean. All of these vary from each other with their composition, capability, and availability of activators, based on the J-STD-004.

  • Rosin and Rosin Substitutes – It is regarded as one of the earliest and most traditional fluxes for electrical components. Its composition is primarily made of pine tree extract. As for its activator only shows itself when heated; otherwise, they are immobile, especially if placed in a controlled environment.
  • Water Soluble – As its name indicates, it can be easily washed off with the help of water. In most cases, they are the classification that is widely preferred for soldering electrical circuitry due to their quick cleaning of oxidation and electrical leads.
  • No-Clean – As its term implies, cleaning doesn’t require much effort as they are made out of resins and solid residues of different classifications.

Importance of Removing Flux Off PCB

Generally, the importance of eliminating the presence of Flux from PCB is pretty straightforward. Since Fluxes are from a chemical agent, they can be relatively acidic, and that acidity can lead the board to corrosion and ultimately damage the device.

As a result, it is highly suggested to maintain the board after applying Fluxes, including appropriate aftercare of the board, because almost all electronics technologies involved in medical and aerospace necessitate an immaculate board for efficient functionality. However, not every class of Flux requires thorough cleaning as there exists a category of Solder Flux known as No-Clean, wherein it doesn’t demand cleaning at all. Nonetheless, it still has its downsides since utilizing this particular Flux classification can minimize the conformal coatings’ adhesion. Hence, it is still recommended to clean the board efficiently.

Importance of Removing Flux Off PCB

Significance of PCB Flux Removal

Eliminating Flux From PCB with Isopropyl Alcohol

One of the frequently preferred categories of Flux for electrical soldering is the Rosin. In this particular situation, its residues can be eliminated by the Isopropyl Alcohol solution at 90% of its composition. Whenever performing it, it is highly recommended to utilize latex gloves and safety goggles to prevent contact with solid substances. In terms of the working station, ensure that the place is well-lit and ventilated.

  1. Firstly, securing a spotless, flexible, and soft bristles brush is recommended. In some instances, unused and new toothbrushes will do.
  2. Then, we suggest acquiring a sprayer since the Isopropyl Alcohol will be stored in that container for more accessible application to the brush and the board.
  3. After securing a spray container and a brush, sprinkle alcohol on the brush, then commence the cleanup. After that, we advise applying mild pressure to lessen the occurrences of solder junction shattering.
  4. Finally, to get rid of the excess solution, scrape off the board with the help of toilet paper or even cleanse the rag. Also, avoid wiping the PCB with anything that can produce particles and fuzz behind.

Eliminating Flux From PCB without Alcohol

As many people know, Isopropyl Alcohol is the ultimate approach to wipe off the flux residues left on circuit boards since it contains lesser chemicals, is cost-efficient, is accessible, and quickly evaporates; however, it is still possible to remove them even without the presence of alcohol. Although there are countless benefits in using alcohol to eliminate the presence of flux from the board, it has some drawbacks too. One of its cons is its ability to damage specific sorts of electronic components; hence, one can use specialized products as a substitute.

In some situations, manufacturers utilize a solution termed Surclean; it is among the well-known and influential cleaners of flux residues. Furthermore, compared to Isopropyl Alcohol (IPA), these compounds dry more slowly and have greater strength. Also, the consumption of such on the majority of layers seems to be harmless. In terms of residue removal, it has an allowable period due to its sluggish evaporation. As for the application, it has the same way as the one from Alcohol. It can start by spraying the solution with a brush, then continue spraying to wash away the spent material from the PCB. If the situation calls for drying, we suggest using warm air to obtain the desired outcome from it entirely.


To wrap things up, Flux Residues from PCB must be thoroughly washed off before the soldering; in that way, one can attain the desired performance from the board and the device. However, many people consider cleaning time-consuming; some even say it can be unpleasant. But it is the only way to achieve a flawlessly working device.

Nevertheless, if you don’t have the time and courage to perform the necessary cleaning required by the board, we at PCBTok are constantly available to perform such a service to your device. One can assure that your circuit board will be in good hands during its time with us since we will ensure that they are of the best quality before releasing them back to your hands.

Let’s not waste any more time; feel free to send us your concerns and specifications. We’ll be delighted to assist you and attend to all of your concerns with all our might. At PCBTok, we guarantee you’ll experience our top-tier service.

Scroll to Top