Role and types of no-clean fluxes

Flux Flux is a chemical that aids and facilitates the soldering process while providing protection and preventing oxidation. Fluxes can be classified into three types: solid, liquid, and gas. It mainly has the functions of "auxiliary heat conduction", "removal of oxides", "reduction of surface tension of welded materials", "removal of oil stains on the surface of welded materials, increasing welding area", "prevention of re-oxidation", etc., among these functions, the key two are: "removing oxides" and "reducing the surface tension of welded materials".

Introduction to flux: Flux is usually a mixture with rosin as the main ingredient, which is an auxiliary material to ensure a smooth soldering process. Soldering is the main process in electronic assembly, and flux is an auxiliary material used in soldering, whose main role is to remove oxides on the surface of solder and the base metal to be welded, so that the metal surface can achieve the necessary cleanliness. It can prevent the surface from oxidizing again during soldering, reduce the surface tension of the solder, and improve the soldering performance. The performance of flux directly affects the quality of electronic products.

Flux ingredients: In recent decades, rosin resin-based fluxes composed mainly of rosin, resins, halogen-containing active agents, additives and organic solvents have been used in the soldering process of electronic product production. Although this type of flux is solderable and low-cost, it has a lot of post-soldering residue. The residue contains halogen ions, which can gradually lead to problems such as deterioration of electrical insulation performance and short circuits, and it is necessary to clean the rosin resin-based flux residue on the electronic printed board. This will not only increase the production cost, but also the cleaning agent that cleans the rosin resin-based flux residue is mainly fluorochlorocarbon. This compound depletes the ozone layer of the atmosphere and is banned and phased out. At present, many companies still use the process of using rosin finger flux solder and then cleaning with cleaning agent, which is low efficiency and high cost.

The main raw materials of no-clean flux are organic solvents, rosin resin and its derivatives, synthetic resin surfactants, organic acid activators, anti-corrosion agents, co-solvents, and film-forming agents. To put it simply, it is that various solid components are dissolved in various liquids to form a uniform and transparent mixed solution, in which each component accounts for different proportions and has different functions. 🔹 Organic solvents: one or several mixtures of ketones, alcohols and esters, commonly used are ethanol, propanol and butanol; acetone, toluene, isobutyl ketone; Ethyl acetate, butyl acetate, etc. As a liquid component, its main function is to dissolve the solid components in the flux to form a uniform solution, which is convenient for the components to be soldered to evenly coat the appropriate amount of flux components, and at the same time, it can also clean minor dirt and oil stains on the metal surface.

🔹 Natural resin and its derivatives or synthetic resin surfactants: halogen-containing surfactants have strong activity and high fluxing capacity, but halogen ions are difficult to clean, ion residue is high, and halogen elements (mainly chlorides) are strongly corrosive, so they are not suitable for use as raw materials for no-clean flux; Halogen-free surfactants are slightly less active, but have less ionic residues. The surfactant is mainly a non-ionic surfactant of fatty acid group or aromatic group, and its main function is to reduce the surface tension generated when the solder is in contact with the lead pin metal, enhance the surface wetting force, enhance the penetration of organic acid activator, and can also play the role of foaming agent.

🔹 Organic acid activator: composed of one or more of organic acid dibasic acids or aromatic acids, such as succinic acid, glutaric acid, itaconic acid, o-hydroxybenzoic acid, azebraic acid, heptanedic acid, malic acid, succinic acid, etc. Its main function is to remove oxides on the lead pins and oxides on the surface of molten solder, and is one of the key components offlux.

🔹 Anticorrosive agents: reduce the residue of solid components such as resins and activators after high-temperature decomposition.

🔹 Co-solvent: Prevent the tendency of solid components such as activators to dissolve from the solution, and avoid the undesirable non-uniform distribution of activators.

🔹 Film-forming agent: In the soldering process of the lead pin, the coated flux precipitates and crystallizes to form a uniform film, and the residue after high-temperature decomposition can be quickly cured, hardened and reduced viscosity due to the presence of film-forming agent.

Flux function Flux ingredients: The main component in the flux is rosin, which will be decomposed by tin at about 260 degrees Celsius, so the temperature of the tin bath should not be too high. Flux is a chemical that promotes soldering. In the soldering process, it is an indispensable auxiliary material, and its role is very important. (1) Dissolved welding mother oxide film In the atmosphere, the surface of the welded base metal is always covered with an oxide film, and its thickness is about 2×10 - 9 ~ 2×10 - 8m. When welding, the oxide film will inevitably hinder the wetting of the solder to the base metal, resulting in the welding can not be carried out normally, so the flux must be coated on the surface of the base metal to reduce the oxide on the surface of the base metal, so as to achieve the purpose of eliminating the oxide film. (2) Re-oxidation of the base metal to be welded The base metal needs to be heated during the welding process, and the oxidation of the metal surface will be accelerated at high temperatures, so the liquid flux covering the base metal and solder surface can prevent them from oxidizing. (3) Molten solder tension There is a certain tension on the surface of molten solder, just like rain falling on a lotus leaf, due to the surface tension of the liquid, it will immediately coalesce into bead-like water droplets. The surface tension of the molten solder prevents it from flowing to the surface of the base metal, affecting the normal wetting process. When the flux is applied to the surface of the molten solder, the surface tension of the liquid solder is reduced, resulting in a significant increase in wetting performance. (4) Protect the welding base metal The original surface protection layer of the welded material has been destroyed during the welding process. A good quality flux will quickly restore its protective effect on the solder consumables after soldering is completed. (5) It can speed up the transfer of heat from the soldering iron tip to the surface of the solder and the soldered object, and (6) The right flux can also make the solder joint beautiful.

Types of fluxes: There are many types of fluxes, which can be roughly divided into three series: organic, inorganic and resin. Resin flux is usually extracted from the secretion of trees, is a natural product, is not corrosive, rosin is the representative of this type of flux, so it is also called rosin flux. Since flux is usually used in conjunction with solder, it can be divided into soft flux and hard flux corresponding to solder. In the assembly and maintenance of electronic products, the commonly used rosin, rosin mixed flux, solder paste and hydrochloric acid and other soft fluxes should be selected according to different welding workpieces on different occasions. The types of fluxes can generally be divided into inorganic series, organic series and resin series. (1) Inorganic series flux Inorganic series flux has strong chemical action and very good fluxing performance, but it has a large corrosive effect and belongs to acid flux. Because it can be dissolved in water, it is also called water-soluble flux, which includes two categories: inorganic acids and inorganic salts. The main components of fluxes containing inorganic acids are hydrochloric acid, hydrofluoric acid, etc., and the main components of fluxes containing inorganic salts are zinc chloride, ammonium chloride, etc., which must be cleaned very strictly immediately after use, because any halide remaining on the weldment will cause serious corrosion. This flux is usually only used for soldering non-electronic products, and it is strictly forbidden to use such inorganic fluxes in the assembly of electronic equipment. (2) Organic flux The flux effect of organic flux is between inorganic flux and resin flux, and it is also acidic and water-soluble flux. Water-soluble flux containing organic acids is based on lactic acid and citric acid, and because its soldering residue can be retained on the solder for a period of time without serious corrosion, it can be used in the assembly of electronic equipment, but it is generally not used in SMT paste solderbecause it does not have the viscosity of rosin flux (which plays a role in preventing the movement of SMD components). (3) Resin flux In the soldering of electronic products, resin flux is the largest proportion used. Since it can only be dissolved in organic solvents, it is also known as organic solvent flux, and its main ingredient is rosin. Rosin is inactive in the solid state and only in the liquid state, its melting point is 127 °C, and the activity can last up to 315 °C. The optimal temperature of soldering is 240~250°C, which is just within the active temperature range of rosin, and its soldering residue does not have corrosion problems, these characteristics make rosin a non-corrosive flux, which is widely used in the welding of electronic equipment. To meet the needs of different applications, rosin fluxes are available in liquid, paste, and solid form. Solid fluxes are suitable for soldering iron soldering, and liquid and paste fluxes are suitable for wave soldering, respectively. In actual use, it is found that when rosin is a monomer, the chemical activity is weak, and the wetting of the solder is often not sufficient, so a small amount of active agent needs to be added to improve the activity. According to the presence or absence of active agents and the strength of chemical activity, rosin series fluxes are divided into four types: inactivated rosin, weakly activated rosin, activated rosin and super-activated rosin, which are called R, RMA, RA, RSA in the American MIL standard, and the Japanese JIS standard is divided into three grades according to the chlorine content of the flux: AA (below 0.1wt%), A (0.1~0.5wt%), and B (0.5~1.0wt%). (1) Inactivated rosin (R): It is composed of pure rosin dissolved in a suitable solvent (such as isopropanol, ethanol, etc.), in which there is no active agent, and the ability to eliminate the oxide film is limited, so the weldment is required to have very good weldability. It is usually used in some circuits that absolutely do not allow the presence of corrosion hazards, such as pacemakers implanted in the heart. (2) Weakly activated rosin (RMA): The active agents added to this type of flux include lactic acid, citric acid, stearic acid and other organic acids and salt-based organic compounds. After adding these weak active agents, it can promote the wetting, but the residue on the base metal is still not corrosive, except for high-reliability aviation and aerospace products or fine-pitch surface mounting products that need to be cleaned, general civilian consumer products (such as cassette recorders, televisions, etc.) do not need to set up a cleaning process. When using weakly activated rosin, there are strict requirements for the weldability of the weldment. (3) Activated rosin (RA) and super-activated rosin (RSA): In the activated rosin flux, the strong active agents added are aniline hydrochloride, hydrazine hydrochloride and other salt-based organic compounds, the activity of this flux is significantly improved, but the corrosion of chloride ions in the residue after soldering has become a problem that cannot be ignored, so it is rarely used in the assembly of electronic products. With the improvement of active agents, active agents have been developed that can decompose residues into non-corrosive substances at welding temperatures, which are mostly derivatives of organic compounds.

The melting point of a commonly used flux should be lower than that of a solder. The tension, viscosity and density of the surface are smaller than those of solder. It should not corrode the base metal, and at the soldering temperature, it should be able to increase the fluidity of the solder and remove the oxide film on the metal surface. Flux residue is easily removed. It will not produce toxic gases and odors, so as not to cause harm to the human body and pollute the environment.

How to choose a flux For the manufacturer, since the composition of the flux cannot be tested, if you want to know whether the flux solvent is volatile, you can simply measure the specific gravity, if the specific gravity is much higher, you can conclude that the solvent is volatile. When choosing a flux, give the following suggestions to the manufacturer: First, smell the smell Preliminary judgment of what kind of solvent is used, such as methanol has a small but choking taste, isopropanol has a strong taste, and ethanol has a mellow fragrance. Although suppliers may use solvent blends, they will generally provide an ingredient report if they are required to provide it; However, the price of isopropanol is about 3-4 times that of methanol, and if the price is lowered too hard with the supplier, the situation inside may not be easy to say. Second, determine the sample This is also the most fundamental method for many manufacturers to choose flux, when confirming the sample, the supplier should be required to provide the relevant parameter report, and compared with the sample, if the sample is confirmed OK, the subsequent delivery should be in accordance with the original parameter control, when there is an abnormality, the specific gravity, acidity value, etc. should be checked. Third, the current flux market is mixed, you should know exactly the qualifications of the supplier when choosing, if necessary, you can go to the manufacturer to see the factory, informal flux manufacturers are afraid of this set.

Prerequisites: No-clean technology

 01 No-clean concept

 (1) What is no-clean No-clean refers to the use of low solid content, non-corrosive flux in the production of electronic assembly, soldering in an inert gas environment, the residue on the circuit board after soldering is very small, non-corrosive, and has a very high surface insulation resistance (SIR), under normal circumstances, it does not need to be cleaned to meet the standard of ion cleanliness (the US military standard MIL - P - 228809 ion pollution level is divided into: first-class ≤ 1.5ugNaCl/cm² no pollution; The secondary ≤ 1.5~5.0ugNACl/cm² is of high quality; The third-level ≤5.0~10.0ugNaCl/cm² meets the requirements; The fourth grade >10.0ugNaCl/cm² is not clean) can directly enter the process technology of the next process. It must be pointed out that "no-clean" and "no-clean" are two completely different concepts, the so-called "no-clean" refers to the use of traditional rosin flux (RMA) or organic acid flux in the production of electronic assembly, although there is a certain residue left on the board surface after soldering, but it can also meet the quality requirements of some products without cleaning, such as household electronics, professional audio and video equipment, low-cost office equipment and other products, they are usually "not cleaned" when produced, but by no means "no-clean".

 (2) Advantages of no-clean (1) Improve economic benefits: After realizing no-cleaning, the most direct thing is that there is no need to carry out cleaning work, so it can save a lot of cleaning labor, equipment, site, materials (water, solvent) and energy consumption, and at the same time, due to the shortening of the process, the man-hours are saved and the production efficiency is improved. (2) Improve product quality: Due to the implementation of no-clean technology, it is necessary to strictly control the quality of materials, such as the corrosion performance of flux (halides are not allowed), the solderability of components and printed circuit boards, etc.; In the assembly process, some advanced technological means need to be adopted, such as spray coating flux, soldering under inert gas protection, etc. The implementation of the no-clean process can avoid damage to the welded components due to cleaning stress, so no-clean is extremely beneficial for improving product quality. (3) Conducive to environmental protection: After adopting no-clean technology, the use of ODS substances can be stopped, and the use of volatile organic compounds (VOCs) can be greatly reduced, thus having a positive effect on the protection of the ozone layer.

02 Requirements for no-clean materials

(1) No-clean flux In order to make the soldered PCB board surface can reach the specified quality level without cleaning, the choice of flux is the key, and there are usually the following requirements for no-clean flux: (1) Low solid content: less than 2% Traditional fluxes have high solid content (20~40%), medium solid content (10~15%) and low solid content (5~10%), and there will be more or less residue left on the PCB board surface after soldering with these fluxes. The solid content of no-clean flux is required to be less than 2%, and it cannot contain rosin, so there is basically no residue on the plate surface after soldering. (2) Non-corrosive: halogen-free, surface insulation resistance> 1.0×10¹¹ Due to the high solid content of traditional fluxes, some harmful substances can be "wrapped" after soldering, isolating contact with air and forming an insulating protective layer. However, no-clean flux cannot form an insulating protective layer due to its very low solid content, and if a small amount of harmful components remain on the board, it will lead to serious adverse consequences such as corrosion and leakage. Therefore, aliran tidak bersih are not allowed to contain halogens. ✔ The  corrosivity of flux is usually tested in the following ways: a. Copper mirror corrosion test: test the short-term corrosivity of flux (solder paste) b. Silver chromate test strip test: test the halide content in the flux c. Surface insulation resistance test: test the surface insulation resistance of the PCB after soldering to determine the reliability of the long-term electrical properties of the flux (solder paste) d. Corrosivity test: test the corrosiveness of the residue on the surface of the PCB after soldering e. Test the degree of reduction of conductor spacing on the surface of the PCB after soldering (3) Solderability: 80% expansion rate ≥ Solderability and corrosiveness are a pair of contradictory indicators, in order for the flux to have a certain ability to eliminate oxides, and to maintain a certain degree of activity throughout the preheating and soldering process, it must contain a certain acid. The most commonly used no-clean flux is the non-water-soluble acetic acid range, and there may also be amines, ammonia, and synthetic resins in the formulation, which can affect the activity and reliability of different formulations. Different companies have different requirements and internal control indicators, but they must meet the requirements of high welding quality and non-corrosive use. The activity of the flux is usually measured by the pH value, and the pH value of the no-clean flux should be controlled within the technical conditions specified in the product (the pH value varies slightly from manufacturer to manufacturer). (4) Meet the requirements of environmental protection: non-toxic, no strong pungent odor, basically do not pollute the environment, safe operation.

(2) No-clean printed circuit boards and components In the implementation of no-clean soldering process, the solderability and cleanliness of circuit boards and components are key aspects that need to be controlled. In order to ensure weldability, the manufacturer should store it in a constant temperature and dry environment under the premise of requiring the supplier to ensure the weldability, and strictly control the use of it within the effective storage time. In order to ensure cleanliness, the environment and operation specifications should be strictly controlled during the production process to avoid man-made pollution, such as handwriting, sweat, grease, dust, etc.

03 No-clean welding process

After the no-clean flux is adopted, although the soldering process remains unchanged, the implemented method and related process parameters must adapt to the specific requirements of the no-clean technology, and the main contents are as follows: (1) Flux application In order to obtain a good no-clean effect, the flux coating process must strictly control two parameters, namely the solid content of the flux and the amount of coating. Generally, there are three types of flux coating methods: foaming, wave and spray. In the no-clean process, the foaming method and the wave method should not be used for many reasons:

First, the flux of foaming method and wave method is placed in an open container, because the solvent content of no-clean flux is very high, it is particularly volatile and volatile, resulting in an increase in solid content, so it is difficult to use the specific gravity method to control the composition of the flux to remain unchanged in the production process, and a large amount of volatilization of the solvent also causes pollution and waste;

Second, because the solid content of no-clean flux is very low, it is not conducive to foaming;

(3) Discussion on soldering technology In view of the strict restrictions on the solid content and corrosiveness of flux, the effect of flux is bound to be restricted. In order to ensure good welding quality, the requirements for welding equipment also need to be increased, especially with inert gas protection. In addition to the above measures, the implementation of the no-clean process also requires stricter control of various process parameters in the soldering process, which mainly include soldering temperature, soldering time, PCB tin depth and PCB transfer angle. For different types of no-cleanfluxes, the process parameters of the wave soldering equipment need to be precisely adjusted to achieve satisfactory no-clean soldering results.

Strategies for dealing with flux residues: 1. Optimize flux selection: Choose the right flux to ensure that it effectively removes oxides from solder joints during the soldering process while reducing residue formation. 2. **Precise control of dosage**: According to the requirements of the soldering process, accurately control the dosage of flux to avoid residue accumulation caused by excessive use. 3. **Improve the soldering process**: Optimize soldering parameters such as soldering temperature, speed, and time to reduce flux evaporation and residue formation. 4. Use Cleaning Tools: Make sure soldering tools such as welding guns, solder, and flux containers are kept clean to reduce the introduction of contaminants. 5. **Strengthen soldering environment control**: During the soldering process, keep the environment clean and reduce the contamination of the flux by dust and moisture, thereby reducing the generation of residue. 6. **Regular cleaning of the equipment**: Regularly clean and maintain the soldering equipment to prevent flux residue from accumulating inside the equipment. 7. **Adopt high-efficiency cleaning methods**: Use high-efficiency cleaning agents and cleaning methods, such as ultrasonic cleaning, to completely remove flux residue from solder joints. 8. **Implement residue recycling treatment**: Recycle the residue generated during the welding process to reduce environmental pollution and recycle available resources. 9. **Training Operators**: Professional training for soldering operators to improve their knowledge and skills in flux use and residue handling. 10. **Regular inspection and evaluation**: Regularly inspect and evaluate the welding process and residue treatment effect, and adjust and optimize management measures in a timely manner.

▶ Flux residues cause distress:

Optimization of paste solder spraying method and coating process

There are three main coating methods: 1. Ultrasonic spraying technology: The oscillating electrical energy with a frequency higher than 20kHz is converted into mechanical energy through a piezoelectric ceramic transducer to realize the atomization of the flux, and then the atomized flux is evenly sprayed onto the PCB board through a high-pressure nozzle.

2. Screen printing method: Using a fine, high-density small-hole wire mesh, the flux is evenly sprayed out by the rotating air knife to form a spray, and then sprayed onto the PCB board.

3. Pressure nozzle spraying technology: The flux is mixed with air through high-pressure gas and sprayed out of the nozzle.

In the field of modern electronics manufacturing, the trend of flux is to be more environmentally friendly, efficient and precise.

**1. R&D and application progress of environmentally friendly flux**

With the increasing awareness of environmental protection, the restrictions on harmful substances in fluxes are becoming more and more stringent. Problems such as degraded electrical insulation performance and short circuits caused by the presence of halogen ions in the post-soldering residue of traditional rosin resin fluxes have prompted researchers to look for more environmentally friendly alternatives. No-clean flux came into being, and its main raw materials are organic solvents, rosin resin and its derivatives, synthetic resin surfactants, organic acid activators, anti-corrosion agents, co-solvents, film-forming agents, etc. For example, organic acid activators are composed of a variety of organic acids, such as succinic acid and glutaric acid, which play a key role in the removal of oxides while meeting environmental requirements.

Testing for corrosiveness is crucial in the development of environmentally friendly fluxes. For example, the copper mirror corrosion test is used to test the short-term corrosivity of flux (solder paste); The silver chromate test strip test can detect the halide content in the flux; Surface insulation resistance testing can determine the surface insulation resistance of a PCB after soldering to evaluate the reliability of the long-term electrical properties of flux (solder paste), etc. These test methods ensure that the flux meets the soldering needs without adversely affecting the environment and product quality.

From the perspective of market application, more and more electronic manufacturing enterprises have begun to use no-clean flux. This is not only due to its environmental compliance, but also due to the economic benefits and improved product quality of the no-clean technology. For example, in some large-scale electronic equipment production, after the use of no-clean flux, there is no need to carry out cleaning work, which saves a lot of cleaning labor, equipment, site, material (water, solvent) and energy consumption, and shortens the process flow and improves production efficiency.

**2. Application optimization of flux in different soldering processes**

1. **Wave Soldering**

   - In the wave soldering process, the selection and use of flux needs to be carefully considered. Traditional fluxes may have some problems in the wave soldering process, such as foaming and wave coating fluxes, due to the high solvent content of no-clean flux is volatile, resulting in an increase in solid content, and a large amount of solvent volatilization causes pollution and waste, which is not conducive to foaming. Therefore, when using no-clean flux in wave soldering, it is necessary to optimize the coating method, and the spray method has become a more suitable choice.

   - Process parameters such as soldering temperature, soldering time, PCB tin depth, and PCB transfer angle need to be precisely adjusted for different types ofaliran tidak bersih. For example, the soldering temperature needs to be determined based on the active temperature range of the flux and the properties of the material being soldered. If the temperature is too high, it may cause the components in the flux to decompose too quickly, affecting the soldering effect; If the temperature is too low, the oxide may not be removed effectively, making the weld not strong.

2. **Hand Soldering Iron Soldering**

   - In manual soldering irons, the requirements for flux are also different. Due to the flexibility of operation and the variety of solder joints, flux flow and wettability are particularly important. For the soldering of small solder joints, the flux needs to be able to spread quickly on the surface of the solder joint, reduce the surface tension, and allow the solder to fill the solder joint better. For example, in the manual soldering of some delicate electronic components, inactivated rosin (R) or weakly activated rosin (RMA) may be more suitable because they are less corrosive to the weldment while ensuring the welding effect.

   - Operators need to have extensive experience in controlling the amount of flux used during the manual soldering iron soldering process. Excessive use of flux may result in excessive post-solder residue, while insufficient use may not effectively remove oxides, affecting solder quality. This requires professional training for operators to improve their ability to accurately control the amount of flux used.

**3. Coordinated development of flux and new soldering materials and technologies**

With the continuous development of electronic technology, the application of new soldering materials such as lead-free solder is gradually popularized. Fluxes need to be matched to these new soldering materials. Physical properties such as melting point and surface tension of lead-free solders differ from those of traditional leaded solders, which requires fluxes to be able to adapt to these changes. For example, lead-free solders generally have a high melting point, and the flux needs to remain well active at higher temperatures to ensure a smooth soldering process.

When it comes to micro-soldering techniques, such as soldering in microelectromechanical systems (MEMS), the requirements for fluxes are even more demanding. Due to the small size of the solder, the flux needs to be applied precisely to the solder site without excessive residue affecting the properties of the microstructure. In this case, the way the flux is applied may require more advanced techniques, such as droplet jetting, which precisely sprays the flux into the tiny areas that need to be soldered.

At the same time, as the application of laser welding technology in electronics manufacturing increases, the mechanism of action of fluxes also needs to be re-evaluated. Laser welding is characterized by energy concentration and fast soldering speed, and the flux needs to be able to function in a very short time during the laser welding process, removing oxides and promoting solder wetting. This may require the development of fluxes that are specifically adapted for laser soldering and have different compositions and properties than conventional fluxes.

**Fourth, the importance of flux quality control and standardization**

The quality of flux directly affects the soldering quality and reliability of electronic products. Therefore, it is crucial to establish a strict quality control system. From the beginning of the procurement of raw materials, it is necessary to conduct strict quality inspections on various ingredients such as organic solvents and activators. For example, the purity of organic solvents, the activity of activators, etc., all need to meet the specified standards.

In the production process, the quality of the flux mixing and blending is also monitored. Ensure that the ratio of each component is accurate, and avoid unstable flux performance due to component imbalance. At the same time, the temperature, humidity and cleanliness of the production environment should also be controlled to prevent external factors from affecting the quality of flux.

The standardization of flux is also the key to ensure the healthy development of the electronic welding industry. If there is no unified standard for fluxes produced by different manufacturers, it may lead to compatibility problems during use. For example, in the repair of electronic products, if a different standard flux is used, it may have an impact on the subsequent performance of the product. There are already some international standards for fluxes, such as the American MIL standard and the Japanese JIS standard, but with the continuous development of technology, these standards also need to be constantly updated and improved to adapt to new soldering materials, processes and environmental protection requirements.