Informative Guide on How to Clean Solder Flux

The solder flux is common and well known in the technological world most especially in the electronic industry. Flux is a synthetic agent well used to ascertain the free flow of solder on metallic intersections. It functions uniquely to take out adulterant metals from the surface ready for soldering.

However, flux performs other functions such as blocking out air from causing oxidation. It also enhances the wetting feature. Even with these attributes, it has a major setback of leaving residues on the board.

The flux remnants are excesses left on the board after completing soldering. If the residues are not properly cleaned out, they could cause more than expected up to damaging the PCB. Flux remnants could cause low electromotive force. It could as well lead to producing a current outflow that gives unpleasant results.

Highlighting the root causes of problems faced as a result of ignoring flux residues will be of help.

  • Flux is a dripping resistant that can present a weak ion flow path between conductors under different conditions
  • Flux does not need a sufficient amount of residues to create leakage setbacks. Just a trace is good enough

Guess you are eager to know more of the problems and relative way out, read through this article.

What is PCB Flux?

Removing PCB flux

Soldering is the process of connecting metallic components on the board to set up an electrical or mechanical link. Cleaning the board’s surface helps achieve a superior metallurgical connection between various elements. Cleaning precedes soldering to enjoy the perfect bonding of components on the PCB.

The solution to getting strong solder joints is to use a synthetic cleaning agent. Flux serves as the agent needed during and after the soldering process. Its main aim is to get the surface ready for soldering by removing and cleaning all pollutants. The exposure of metals to air produces oxide formation. This might in turn hinder perfect solder joints.

Flux could also serve as protection to metal layers from deoxidizing. Deoxidizing occurs when soldering which could enhance the soldering process. This is through changing the surface pressure of the hot solder. Flux is from unprocessed materials and a reactor. They form the agent that aids wetting of the solder by taking out the adulterants from the metal.

It is crucial to point out that flux possesses chemicals and additives that hampers corrosion but aid the soldering process. Flux could be in pasty, solid, or liquid form depending on its usage.

Types of Flux

In soldering electronic elements, there are three types of fluxes used. They include:

Solder Reflow: This type of flux uses a paste made of adhesive flux and a little area of metal solder. The solder paste clutches the parts up till the hotness of the oven brings about reflow of the solder particles. The metallic surface becomes clean and the pale identity shut air from causing extra oxidation.

Selective Soldering: This type of flux is functional by spritzing or by the usage of a specific drizzling jet process.

Wave Soldering: Flux used for the wave soldering type is from chemicals in contrast to flux used in other applications. Spritzing of the chemical on the board comes before the board goes for a solder wave. The flux removes components that might hinder soldering and all oxidized layers formed.

Cleaning Flux Explained

Flux is customary to soldering electrical elements on the PCB. It strengthens the electrical bond on the PCB depending on the types of solder and elements used. However, ignoring any fractional part of flux could give rise to massive damage to the PCB. The leftover residues gradually eat up the elements on the board.

To avoid such damages, it is vital to ensure the cleaning process is skillfully completed. It is secure to avoid cleaning rather than cleaning wrongly. Compressed damaging residues from the no-clean soldering method can release resins to the board if not properly cleaned. Its effect could lead to functionality failure on the PCB.

Why Cleaning Flux is Necessary

Flux remnants most times are set up on soldered elements found on the circuit board. This could hurt the PCB. Cleaning the flux remnants, therefore, remains an important step in the fabricating process. The under-listed are points to note on the reasons why cleaning flux is vital

Corrosion Prevention on the PCB

The flux remnants left without being well taken out of the PCB are acidic. Allowing it on the board over a while would attract wetness from the air. Corrosion takes place as a result of the elements and PCB damage becomes inevitable. However, the PCB could be safe from such pollutants by keeping it from wetness or through the coating.

Avert Sticking Complications with Conformal Coating

Applying a thin coated film on the PCB serves as a protective measure against corrosion. This increases the integrity of the PCB. However, flux residues left on the board before coating could raise issues such as board lifting. Conformal coatings are semi-penetrable. This implies liquid vapors could enter and settle on those flux remnants causing corrosion in the process.

Enhances the attractive appearance of the PCB

The physical look of the PCB announces the work done by the manufacturer in fabricating the PCB. Flux remnants on the board could mean the quality control procedure is ineffective. It reduces the integrity of the PCB and such would not attract customers to the manufacturer.

Raises the integrity of the PCB

Integrity is a vital aspect of business that helps sustain competitiveness. This is systematically done by providing good values and customer satisfaction. The end product of the PCB is practically measured by its dependability test. Cleaning the PCB is vital to maintaining relevance and upholding its integrity.

Methods to take out Flux from the PCB

Taking out Flux on the PCB requires a thorough process. A standard framework to achieving the taking out process must be perfectly executed. A perfect cleaning machine added to the right cleanse fluid. Setting the process rightly and applying precise control measures complete the process. This will deliver a great cleaning experience with an influence on the outcome of the PCB.

The methods to clean away flux from the PCB are:

Cleaning through the use of Toothbrush

Cleaning through the use of Toothbrush

Cleaning the circuit board after soldering could be very easy using the toothbrush. The method uses tools like a clean toothbrush, Acetone or Isopropyl alcohol, and a rag.

  • Immerse the toothbrush in the cleaning agent i.e isopropyl alcohol or acetone. Flick the toothbrush a few times and use its wetness to remove the excessive firm solution on the PCB.
  • Sponge the flux on the PCB using the toothbrush. The cleanser applied liquefies the flux. Duty of care to avoid breaking soldered joints as a result of much pressure is very crucial.
  • After the removal of the flux, the parched rag wipes the cleaned area. Give some time for the PCB to dry up and blow away the little flux particles left by air.

Cleaning using Acidic Brush

It is doubtless the most economical PCB flux cleaner. This cleaning method uses tools such as an acid brush, liquid spray can, solvent, and a paper wipe. Isopropyl alcohol is the favorite solvent due to its cost-effectiveness and also how easy it is to get it. It also dries up on the PCB after use. The process requires a few steps that include:

  • Cut the acidic brush to angle the wire to have both small and extended sides. The smaller side is important for scrubbing the PCB. The extended side is to take out the flux from areas that are difficult to reach.
  • Dip the brush into the chemical solvent and scrub the flux remnants away from the board. The area where the flux is could be wet.
  • The cleaned area is then wiped by the paper to enable dryness of the solvent. The PCB is then clear and free from flux.

The use of Poly-Clean

Poly-Clean is a uniquely designed cleaning agent to clear flux out of the PCB. The Poly clean solvent and a bucket that can contain the soldered PCB when submerged are vital using this method. The steps involved in this process are:

  • Adding an adequate quantity of Poly-Clean solution into the bucket
  • Dipping the board into the Poly clean solution while turning gradually for a few seconds
  • Cleanse the PCB with carbonated water immediately the flux is out
  • Dry up the circuit board with a heat gun

What is No Clean Flux and is it Necessary?

No clean flux is a combination of organic resins blended with some inorganic agents. Its actions and properties differ depending on various solvent compositions. No clean flux means that the quantity of remnants is ignorable to an extent where cleaning is not needed.

The no-clean flux is majorly used by electronic manufacturers. Half of the quantities of PCB fabricated are with no-clean solder paste. This evolution was to remove the stress of cleaning the board after soldering.

Yet, most electronic manufacturers are battling to remove the no-clean flux substances. It is the most common type of flux electronic manufacturers clean. They clean only the fractional part they desire, not the entire circuit board. The remnants left, as a result, become harder to remove from the PCB.

The no-clean flux and solder remnant on the PCB leans on the type of thickening agents and solid components. The number of solids determines the number of residues on the PCB. Although, no-clean fluxes carry few solids in a bid to avoid cleaning.

With increasing developments in the industry, gadgets are smaller with added operating strength. The layout of the elements on the PCB becomes extra tiny to contain more elements. This brought an integrity test on the no-clean flux. Flux is acidic, which could cause corrosion on the elements and joints on the circuit board. This setback necessitated cleaning the no clean flux.

The no clean flux was critical of the circuit testing setback. This is due to the sticky debris which does not allow the pin to pierce the flux to enable an electrical link with test pads. Furthermore, remnants form on the pin, which generates maintenance and precision test issues.

Functions of Water Soluble Flux

Water soluble flux is also referred to as Organic acid flux. Generally produced from glycol bases. It is an extremely combative cleanser and oxidizer. It reacts more often than the No clean flux, thus known as a powerful cleanser.

Furthermore, Water soluble flux supplies an outstanding soldering outcome and clear solder joints. It also boasts fine wetting efforts and a reliable capacity to get a clean surface ready for soldering. Its combative character requires extra care while cleaning.

The remnants from water soluble flux are corrosive after soldering. Therefore, the circuit board requires thorough cleaning to avoid flux remnants. It is important to note that minimal flux residues left could cause the breakdown of the PCB over some time.

The water soluble flux is quite easy and quick to clean off the surface of the board. This is easily done by using the Alcohol enhanced flux remover. It is a soft, cost-friendly, and plastic shielded refluxer. It wipes water-based organic acid fluxes, rosin fluxes, and no cleans.

Furthermore, it dries up moderately slowly, which allows the operator ample time to thoroughly clean the remnants with a little quantity of water. It is not corrosive, water-free and a perfect fit for various types of electronics to include insulators and connectors.

The General purpose flux remover is a substitute cleanser. It is an all-round product that is non-flammable, cheap, user-friendly, and easy to store. Also, it is a perfect cleaning agent for all kinds of electronics as well as cables, through holes, and hybrids. It is very efficient at dealing with all flux remnants including the hard to remove fluxes. It also dries up quickly.


You must have gained vast knowledge concerning how to clean solder flux, no clean flux paste, no clean solder, and more. Cleaning solder flux is a tactical approach to maintaining competitiveness in the industry. Sustaining such competitive advantage however is an individual resolution. Thus, producing PCBs that meet standards requires obtaining educational information. Find out more in our next article.