How to use soldering flux correctly

Soldering acid, how to solder correctly with a soldering iron

All existing metals, as well as their alloys, can be combined with each other using two different technological processes. We are talking about welding and soldering. Welding of metals means short-term heating of two metal surfaces at the point of contact to extremely high temperatures.

At these temperatures, the surfaces to be joined undergo complete melting. As a result, a connection of two metals occurs at the level of interatomic bonds of the crystal lattice.

The consequence of this process is a monolithic welding seam, whose strength sometimes even exceeds the strength of the metal products being welded themselves.

What is soldering

Soldering is a completely different process. It does not affect the internal structure of the metal in any way. It occurs exclusively on the surface of the materials being soldered. No monolithic connections are formed at the atomic level during soldering.

To perform soldering, the presence of a third, lower-melting metal, which is called solder, is necessary. With the help of solder, the soldering process occurs directly. Pure tin or its various alloys are most often used as solder.

The task of any soldering is to melt the solder and ensure its good spreading over the surface of the metals being soldered.

As the solder hardens, it changes from its molten liquid state to a solid state and provides a reliable connection between two metal products.

In practice, everything turns out to be a little different. The fact is that all metals, without exception, have a fairly hard and chemically inert oxide film on their surface. The strength of this film varies among different metals. The most durable oxide film is formed on the surface of aluminum. This film, as well as all kinds of mechanical impurities that are always present on the surface of any metal, lead to the fact that the solder does not want to spread over the metal.

That is, in professional terms, tinning of the metal does not occur. Instead, the solder becomes a moving ball that rolls around the metal surface without connecting to it in any way. This suggests that the surface tension of the molten solder is much higher than the adhesion (sticking) of this solder to the metal surface. To enhance the adhesion of solder and ensure reliable soldering of two metals, so-called fluxes are used.

Acid fluxes

Why are fluxes used? The task of any flux is to:

• Dissolve the surface oxide film on the metal.
• Clean the surface from mechanical contamination.
• Prevent oxidation and the formation of a new oxide film.
• Reduce the surface tension of the molten solder, thereby facilitating its free flow over the metal.

Rosin

Among radio technicians, the most common flux is rosin. It is essentially pine tree resin from which the turpentine has been removed through an evaporation process.

It is widely used due to its low cost, ease of storage and chemical inertness. Rosin is used as a flux for soldering products made of copper, brass, silver, and nickel.

That is, those metals on the surface of which the oxide film is not very strong and is quite easily destroyed by the weak influence of molten rosin.

But when it comes to metals such as aluminum, cast iron, all kinds of steel alloys or iron, rosin stops working and its use in these cases turns out to be extremely ineffective. The rosin needs to be replaced and the flux made more aggressive to make the soldering process easier.

Soldering acid

chemically active acid fluxes were invented . There are several types of acid fluxes due to the fact that different metals form oxide compounds of different strengths on their surface.

The so-called soldering acid can be easily purchased at a specialized store and is inexpensive. But there is a small problem.

Most often, manufacturers do not indicate the exact composition of the chemical they sell under the name “soldering acid.” But, as you know, soldering different metals requires acid fluxes of different compositions.

Therefore, sometimes it will be much more rational to make one or another flux for a specific metal at home than to buy a pig in a poke.

Zinc chloride flux

For soldering, so-called pickling acid is used. This is one of the most common acid fluxes. This is the same soldering acid that is most often sold in specialized stores. This flux is mainly used for soldering iron. For example, pure hydrochloric acid can be used to solder roofing iron. Usually this is a solution of zinc in hydrochloric acid, in other words, zinc chloride.

All the necessary reagents for this reaction can be freely purchased at a chemical store, namely: granulated zinc and chemically pure hydrochloric acid. This is the composition of soldering acid.

The proportions are as follows:

• Concentrated HCl: 1000 ml.
• Pure zinc: 400 gr.

For mixing, you must have an appropriate glass, porcelain or ceramic container.

• The zinc is first placed in the container, and only then hydrochloric acid is slowly added to the zinc in a thin stream.
• In no case should you do the opposite and add zinc to hydrochloric acid. This can lead to very sad consequences, namely the splashing of acid in all directions.
• During the chemical reaction, hydrogen will be released. This gas, when combined with oxygen in the air, forms an extremely dangerous gas mixture called detonating gas. This gas explodes at any opportunity. Therefore, before you start dissolving zinc in hydrochloric acid, think about good ventilation. It would be ideal to carry out the reaction outside, in the fresh air.

Olein flux

The basis of this flux is oleic acid, which is found in olive oil or any fat. To prepare the flux, technical olein is used, which is mixed with lithium iodide.

It is used for soldering both pure aluminum and aluminum-based alloys. This is the only flux that can dissolve the extremely durable aluminum oxide film, while the protective flux layer remains until the end of the soldering process.

It is impossible to make oleic flux at home. Yes, this is not necessary. It is freely sold and inexpensive.

Orthophosphoric acid

The chemical formula is H3PO4. For soldering alloys based on chromium or nickel, flux is prepared in the following proportion:

• Ethyl alcohol: 62%;
• Phosphoric acid H3PO4: 32%;
• Rosin: 6%.

Sometimes the acid is mixed with zinc chloride in a 50/50 ratio to prepare a flux for soldering iron products.

The composition consisting of H3PO4 25% and diethylamine hydrochloride 75% is called active flux F-38N, which is used for soldering copper alloys, as well as medium-carbon and low-carbon steel. Solders pure copper well, as well as iron, steel and nickel-containing alloys.

Based on this acid, you can make any fluxes for soldering almost all types of metals, except aluminum, at home. The only problem is that acquiring pure acid is quite problematic.

Salicylic acid

Or the well-known aspirin. Purchased in tablet form at your nearest pharmacy. It costs a penny.

It belongs to the so-called inactive fluxes, that is, after soldering is completed, salicylic acid does not affect the contact point in any way and therefore no additional treatment is required after soldering to remove flux residues. Moreover, after hardening, salicylic flux protects the soldering area from corrosion.

You can solder with pure acid , using it in the form of a powder or a whole aspirin tablet. But it is much more effective to use aspirin as part of a multicomponent flux, which is called VTS.

VTS flux is used for soldering copper conductors, as well as products made of silver and platinum. The flux contains technical petroleum jelly as a filler, ethyl alcohol and acetylsalicylic acid.

This flux can be used to solder almost any metal, with the exception of aluminum.

The only disadvantage of aspirin: during soldering, extremely caustic smoke is released, which can damage the respiratory tract with frequent contact. Therefore, good exhaust is a prerequisite for productive work with this flux.

How to solder correctly

How to use soldering acid? The key to successful soldering is not only the correctly selected flux, but also the correct preparation for soldering. To do this you need to know the following:

• Before soldering, metal surfaces must be cleaned of rust and other contaminants using a file and sandpaper.
• All liquid fluxes are best applied to the surface using a special brush. In this case, maximum application accuracy and uniformity of distribution are achieved.
• The acid flux should cover the surfaces to be soldered with an even, uniform layer, without gaps. Otherwise, uniform distribution of solder over the metal surface will not be achieved.
• The tip of a well-heated soldering iron picks up a small amount of solder and transfers it to the metal surface pre-treated with flux. The solder is distributed in an even layer over the entire surface of the metal. This is called "tinning". The second metal surface is tinned in the same way. After this, both tinned surfaces are soldered.
• After completing the soldering process, it is necessary to remove any remaining acid solder. Otherwise, the acid will begin to destroy the metal and a corrosion center will arise, which can lead to destruction of the soldering area.
• Acid is neutralized by alkali. For the latter, it is best to use baking soda. The soldering area is sprinkled with soda and then washed with water.

Source: https://ObInstrumentah.info/payalnaya-kislota-kak-pravilno-payat-payalnikom/

What is flux solder and how to use it?

Reading time: 6 minutes

Solder and flux for soldering are indispensable tools for many home and professional craftsmen. With their help you can achieve high-quality, even seams. Manufacturers offer many types of fluxes and solders. There is even solder on the market that has flux inside! And all this variety is difficult to understand if you have never used solders and fluxes.

We decided to make your task easier and tell you about the types of solders and fluxes and their applications. You will learn how low-melting solders differ from high-melting solders, what active and passive fluxes are, and how to use these materials in your work.

Types of solders

Solder is a metal rod used to fill joints between two parts. It melts and mixes with the base metal or acts as a base metal altogether. May have different diameters. Made from tin, but with the addition of other metals. For example, lead zinc or copper. Can be low-melting or refractory.

Low-melting

Low melting point solders are most often used for small jobs. For example, when soldering radio equipment. Also, such solder is indispensable if soldering of radio-electronic elements is necessary. In the composition you can most often find a combination of tin with cadmium, bismuth, lead or zinc.

Based on the name, it is not difficult to guess that such solders melt easily. One small soldering iron is enough to melt them. If you need solder for working with radio electronics, then choose rods with a melting point of up to 140 degrees.

There are also special solders for tinning circuit boards. Their melting point does not exceed 100 degrees. Due to these properties, tinning is easier and faster. Solders have their own brands, but we will not focus on this. This is a topic for a separate article.

Let's just say that when soldering modern equipment, it is recommended to use lead-free solder and with a melting point of about 200 degrees. This is due to the peculiarities of foreign technology. It is manufactured in accordance with strict environmental regulations, according to which lead emits harmful fumes when soldering.

Refractory

Refractory solders are the antithesis of low-melting solders. Their melting point starts at 400 degrees. Such solders are used in professional industrial welding, where large parts need to be welded. Refractory solders contain a lot of copper, silver, nickel or magnesium. They are very strong and thick, so they are not used in home soldering. Such solders reveal their potential when welding refractory metals. For example, cast iron or brass.

Solder with flux

There is a separate category of solders - this is solder with flux inside. It's tubular solder. It is a hollow rod, the core of which contains flux. The rod melts during soldering, allowing flux to be released and perform a protective function. A striking example is Castolin 192 K flux solder and Brazetec Comet 3476U solder.

Such solders are very convenient to use because they perform two functions at once: practical and protective. There is no need to waste time applying flux and choosing it. But you must understand that such solders do not provide sufficient protection for the soldering area. They only slightly improve the quality of the seams. If you need a perfect result, it is better to use solder and flux separately from each other. Like two different materials.

But what flux is and why it is needed, you will find out further.

Types of fluxes

Flux is a substance applied to the soldering or welding site that protects the metal from oxidation and improves the quality of the seam. Flux can radically change the quality, including the evenness of the seam and its aesthetic characteristics. Therefore, you need to approach the choice of flux wisely.

There is a clear connection here with solder. The easier the solder melts, the better the properties of the flux are revealed. The flux should have a melting point slightly lower than the solder. Then you will achieve high-quality results.

Manufacturers offer two types of soldering fluxes: active and passive.

Chemically active

Chemically active fluxes contain acid-containing substances. They, in turn, are ways to destroy any plaque or signs of corrosion. Well-known hydrochloric acid, zinc chloride, etc. can be used as an acid-containing agent. If the soldering area is not cleaned of flux residues, the metal may deteriorate and new corrosion will appear.

The chemical activity of such fluxes is both an advantage and a disadvantage at the same time. If used improperly, such fluxes corrode metal and textolite if used in radio electronics. Do not forget that such fluxes can leave burns on the skin, so it is important to follow safety precautions. But when used correctly, active fluxes remove any plaque and corrosion, allowing you to improve the quality of work.

We do not recommend using chemically active fluxes in everyday soldering. They require attention and experience. And when soldering radio components, it is better not to use this type of flux at all. Because with a high probability it will corrode the textolite, and you will not be able to fix anything.

Chemically passive

Chemically passive fluxes are used very often. They do not have such pronounced oxidizing properties as chemically active ones, so they are easier to work with. Chemically passive fluxes remove grease and light stains, but not corrosion. These fluxes contain organic components, so they can be used when soldering radioelements.

Chemically passive fluxes protect the welding zone from oxidation and improve the quality of work. However, like chemically active ones.

Source: https://svarkaed.ru/rashodnye-materialy/flyus-i-svarochnaya-provoloka/chto-takoe-pripoj-s-flyusom-i-kak-ego-ispolzovat.html

Flux for soldering: purpose, method of application - Welding

In many industries, soldering is used to join solid materials. High-quality work depends on the availability of tools, equipment and consumables, one of which is flux. Those who attended an amateur radio club as a child or loved to solder at home know what flux is and why it is needed.

Flux is a special alloy of materials with a light structure and is used to join two different materials. In this case, it is more advisable to use a substance suitable for a specific material. That is, a certain composition for enameled metals, and a completely different one for joining copper objects.

But those who first encountered the procedure do not quite understand why rosin is needed when soldering. Amber pieces, familiar from childhood, are the most common flux. Their use results in better and faster soldering. Thanks to rosin, the solder has better contact with the surfaces of both materials.

The tasks of flux during soldering are as follows:

• prepare the surfaces of two products;
• clean the surface of various films and fats;
• Reduce surface tension in the solder.

When using an alloy, the contact area of ​​the objects being connected increases, which promotes strong contact. The substance also extends the service life of soldered elements, because it prevents the formation of new oxidation processes at the joints. This is why rosin and other types are needed. Having learned what it is, you should understand the classification of the alloy.

Types and characteristics

Joining alloys are classified by how they act on the components before, during and after soldering. The same rosin, like many compounds based on it, belongs to the group of low-active fluxes.

If such a flux is needed for anything, it is for soldering microcircuits, where the capabilities of the composition are fully realized. The alloy removes thin oxide films well from copper, brass and other surfaces.

 But it does not cause corrosion due to minimal activity. If it is necessary to improve the properties of rosin, the substance is combined with turpentine or alcohol. As a result, acid-free or neutral species are obtained.

This type is often used during the repair of radio electronics, as well as in its production. For such purposes, this particular alloy is chosen because the flux is a dielectric and does not generate current leaks.

If acid is added to rosin, a third type is obtained – activated. Most often, the alloy includes organic acids and amine compounds in small doses. With its help, it is possible to connect copper parts, as well as silver, iron and nickel.

Active fluxes, which include hydrochloric acid, are used to join iron products. But if you add zinc chloride to it, you get “soldering flux.” This composition is produced not only in industry, but also at home.

It is suitable for soldering silver, copper and iron components. But flux is strictly prohibited for use in radio electronics. Because the alloy has high electrical conductivity and chemical reactivity.

Fluxes are also anti-corrosion and protective. The first type is designed to remove corrosion from the surface of the element, and the second does not allow the formation of oxides on an already treated surface. Corrosive fluxes are recommended if the surfaces of both products are susceptible to rust. They include substances such as:

• salicylic acid;
• technical petroleum jelly;
• ethanol;
• triethanoamine

Protective fluxes are the familiar Vaseline, wax, powdered sugar and olive oil.

Differences between alloys

Solders and fluxes also differ in physical state into liquid, solid and paste. Thanks to this diversity, the methods of application are significantly expanded. For example, treat hard-to-reach areas of products with liquid glory to protect them from oxidation. But the amount of paste flux supplied is easier to control when soldering.

Another factor by which alloys are distinguished is temperature. There are substances that are active at high temperatures, and there is another group that melts at sub-zero temperatures. The refractory composition binds products more firmly. But there is one caveat: due to the high melting point, the composition can damage the part itself and render it unusable.

Fluxes that melt at temperatures from 50 to 400 degrees belong to the low-melting group. They are used in radio electronics. Fluxes contain lead, tin and other elements. Each type of alloy has its own purpose, taking into account which you need to choose a flux for a specific job.

Thus, hard flux should be used for soldering products with large diameters, and soft alloys are suitable for joining thin surfaces. If you need to repair metal utensils, it is better to give preference to “soldering flux” - a solution of zinc with hydrochloric acid.

The advantages of alloys are the protection of previously cleaned metal surfaces from oxidation, as well as the connection of solder to the prepared surface. You can check whether flux is really necessary if you try once to solder two different products without auxiliary material.

The best substitutes

Compositions used in industry or by professional craftsmen can rarely be found in an ordinary person’s apartment. But what to do if the need for soldering arises.

How to replace flux? One of the most common substances is aspirin dissolved in water. The composition is easy to prepare at home - just crush one tablet and pour the powder into a container with water.

The resulting solution is used as a regular liquid flux.

Another substitute is acetic or citric acid. The effectiveness of fluxes prepared at home is lower than the original ones, but certain indicators can be achieved with them.

Using concentrated hydrochloric acid is what will improve the performance. It is only important to handle acid carefully, as it is hazardous to health. Products soldered using this composition should not be thin.

You can prepare flux at home from phosphoric acid, which is sold in stores and has good performance. It perfectly removes oxides, fat deposits and various films.

Based on what characteristics should you choose a composition?

The fluxes used are selected in accordance with the following requirements:

• stretching abilities;
• strength;
• ability to conduct current and heat.

The substance for soldering is selected based on the type of metal being joined, the temperature of both the alloy itself and that achieved during the procedure. It is also necessary to take into account the strength and resistance of elements to corrosion. When choosing solder alloys, you should use those with a lower specific gravity. Then the solder will displace the flux onto the surface of the product when applied.

If soldering fluxes are selected for transistors, then ultra-low-melting compounds are used. The maximum temperature at which they are activated is 150 degrees.

Source: https://svarkaman.ru/metall/flyus-dlya-pajki-naznachenie-sposob-primeneniya.html

Brands of soft solders and fluxes for soldering with a soldering iron

For soldering with a soldering iron, solder is used, and in order for the solder to spread well over the surface of the parts being connected by soldering, a substance called flux is used. Depending on the metal of the parts and their size, the strength and tightness of the soldering, it is necessary to choose a specific brand of solder and flux. The information in the tables will help you select the required solder and flux for soldering.

Brands of soft solders for soldering with a soldering iron

The main component when soldering with an electric soldering iron is tin-lead solder. It is available in the form of wire or tube of different diameters. The tubular solder inside is filled with rosin. This type of solder is very convenient when working, since it does not require additional flux to the soldering iron tip.

Solder is an alloy of low-melting metals. As a rule, solder contains tin. You can solder with pure tin, but it is expensive and therefore cheap lead is added to the tin. Tin is an environmentally friendly metal and can be used as solder for soldering food utensils and medical instruments in its pure form. If you bend or squeeze a tube made of pure tin, it crunches. The more lead in the solder, the darker the surface of the solder.

Solders are marked with letters and numbers. For example, POS-61, which means P - solder, O - tin, S - lead, 61 - % tin content. POS-61 is the most common, as it is suitable for soldering in most cases. Popularly, POS-61 is often called a tertiary, since it contains a third of lead (Pb).

Solders can be soft or hard. The melting point of soft solders is below 450˚C. Hard solders melt when heated above 450˚C and are not used for soldering with an electric soldering iron.

Main technical characteristics of soft solders
for soldering with an electric soldering iron

The electrical resistivity of tin-lead solder (conductivity) is 0.1-0.2 Ohm/meter, aluminum 0.0271, and copper 0.0175. As you can see, solder conducts current ten times less than copper or aluminum.

The most common solder is POS-61, also called tertiary. It is excellent for soldering and tinning of live parts made of copper, brass and bronze with a sealed seam and is not expensive. Suitable for almost all household soldering situations.

Flux is an auxiliary substance necessary for freeing the surfaces of parts being soldered from oxides and for better spreading of solder over the metal surface during soldering. Without using flux, it is almost impossible to perform high-quality soldering with a soldering iron.

When preparing the most popular fluxes for soldering with an electric soldering iron, rosin is used. It is obtained from the wood of coniferous trees, mainly pine. At a temperature of about 50°C, rosin softens, and at 250°C it begins to boil.

Rosin is not resistant to atmospheric moisture - it hydrolyzes. It consists of 85-90% abietic acid. If you do not remove the remaining rosin after soldering, oxidation of the soldering area occurs. Many people do not know this and believe that rosin is harmless to metal. In addition, by absorbing water from the atmosphere, rosin increases its conductivity and can disrupt the operation of electronic devices, especially their high-voltage circuits.

Popular fluxes for soldering with an electric soldering iron

Flux based on alcohol and solvents must be stored in an airtight container, otherwise the liquid will quickly evaporate. A bottle of manicure polish is very convenient for this purpose. Always have a brush at hand, which is convenient for applying flux to the soldering area.

You can find such a bottle in almost any home. Another advantage is that the brush and twist are not dissolved by alcohol and solvent. Before filling with flux, be sure to thoroughly wash the bottle and varnish brush. If the varnish has hardened too much, pour in acetone and leave.

After a while the varnish will dissolve.

I prepare alcohol-rosin flux in a bottle. First, I pour rosin powder through a paper funnel and then fill it with alcohol. It is easy to pour alcohol into the narrow neck of the bottle if you touch the neck of the bottle with alcohol to a brush previously soaked in alcohol. You need to pour it very slowly and you won’t spill a single drop. Over time, the alcohol evaporates and the flux becomes thick. Then you need to dilute it with alcohol to the required consistency.

As a flux, I often use the undocumented flux of aspirin (acetyl salicylic acid), which is used as a medicine. With its help, you can tin copper and steel surfaces without prior preparation. Liquid flux for soldering with a soldering iron can easily be prepared on the basis of aspirin; just dissolve the tablet in a small amount of alcohol, acetone or water.

Solder pastes (tinol) for soldering

Solder paste (tinol) is a composition of solder and flux. The paste is irreplaceable when soldering with a soldering iron in hard-to-reach places, and when installing unframed radio components. The paste is applied with a spatula in the required amount to the soldering area and then heated with an electric soldering iron. The result is a beautiful and high-quality soldering. Its use is especially convenient if you have no experience working with a soldering iron.

You can make your own pasta. To do this, you need to select a brand of solder suitable for soldering the required metal. Next, use a file with a large notch to cut sawdust from the rod. Then add the liquid soldering flux selected from the table, mixing the sawdust until a paste-like composition is obtained. The paste should be stored in an airtight container. The shelf life of the paste is no more than six months, since solder filings oxidize over time.

Source: https://YDoma.info/tehnologii-remonta/kak-payat/kak-payat-pripoi-flyusy.html

Soldering aluminum at home: features of the process, types of flux and solders, how to solder a pipe

Aluminum and its alloys have very good characteristics, such as high thermal and electrical conductivity, ease of processing, low weight, and environmental safety. But this beautiful metal has one very big drawback: it is extremely difficult to solder. A properly selected flux for soldering aluminum helps solve this serious problem.

The problem with soldering aluminum is due to its chemical structure. This metal itself is chemically very active; it reacts with almost all chemicals.

This causes pure aluminum to instantly react with oxygen in air. As a result, a very thin and at the same time extremely strong oxide film is formed on the metal surface: Al2O3.

In terms of their properties, aluminum and its oxide represent two extreme opposites combined into a single whole. For example :

• The melting point of pure aluminum is 660 degrees. Aluminum oxide, or corundum as it is also called, melts at a temperature of 2600 degrees. Refractory corundum is used in industry as a refractory material.
• Aluminum is a very soft and ductile metal. Corundum has extremely high mechanical strength, which makes it possible to produce all kinds of abrasive materials from it.

Aluminum oxide turns ordinary soldering into a rather complex process. For its successful implementation, it is necessary to use specific methods and special aluminum solders and fluxes.

Metal soldering

The meaning of soldering any metal is that a special substance called solder is introduced into the space between the parts being soldered in a molten state. After hardening, the solder reliably binds two metal parts into a single whole.

When soldering aluminum, the oxide film on its surface prevents the molten solder from connecting to the metal. In other words, adhesion is impaired, and therefore the solder cannot spread over the surface of the metal and stick to it . This makes soldering aluminum almost impossible without the use of special means that partially remove the oxide from the metal surface and promote normal adhesion.

Removing oxide film

Removing oxide from the surface of aluminum is a complex process and never leads to a final result. That is, the oxide film is practically impossible to remove, since instead of the one just removed, a new one is instantly formed. It is possible only with the help of specific means to weaken its effect. This can be done using two different methods :

• Chemical method. With the help of special aluminum fluxes, the film is destroyed as a result of exposure to active acids.
• Mechanical method. Through the use of abrasive tools, the integrity of the film is damaged.

In practice, both of these methods are most often combined to achieve the maximum possible effect.

Fluxes for aluminum

Flux is used to remove oxide from the metal surface and subsequently prevent the formation of a new film. It must be remembered that during the soldering process, the flux should not interact with the solder and enter into chemical reactions with it. Fluxes can be in different states :

• Liquid.
• Paste.
• Powder.

For aluminum, liquid fluxes based on orthophosphoric acid are most often used . There are so-called no-clean fluxes, the use of which does not require subsequent washing of the soldered surfaces under running water.

However, most often aluminum fluxes contain highly toxic substances that are unsafe and, from an environmental point of view, can severely corrode the metal at the soldering site. Therefore, the use of fluxes requires thorough washing of the soldering area under running water.

The industry produces a larger number of aluminum fluxes, among which the following can be distinguished::

• F-64. Highly active flux for aluminum and its alloys. It is considered the best flux for this metal. High activity is determined by the high content of active fluorine in its composition, about 40%. When heated, fluorine destroys the oxide film on the surface of aluminum. The use of this flux requires thorough washing of the welded surfaces after the process is completed.
• F-34A. Special aluminum flux for refractory solders. Ingredients: potassium chloride 50%, lithium chloride 32%, sodium fluoride 10%, zinc chloride 8%.
• F-61A. It is used with conventional lead-tin solders, melting at a temperature of 150−350 degrees. Composition: zinc fluoroborate 10%, ammonium fluoroborate 8%, triethanolamine 82%. Used for soldering dissimilar metals, such as aluminum and copper. Therefore, when the question arises of how to solder aluminum to copper, this flux will be the answer.
• NITI-18 (F-380). Suitable for refractory solders with a melting point of 390 - 620 degrees. The peculiarity of this flux is that, while dissolving the oxide film well, it has virtually no effect on the base metal. After finishing soldering, flux residues must be removed immediately. To do this, the soldering area is first washed with hot running water, then with cold water. And finally, incubate for 15 minutes in an aqueous solution of phosphoric anhydride.
• A-214. Universal no-clean flux of medium activity. Application temperature 150−400 degrees. It does not contain harmful salts of aniline, phenol or carboxylic acids, therefore, thorough rinsing is not required after use. Residues can be easily removed with a paper towel soaked in alcohol.

Mechanical oxide removal

To facilitate the dissolution of the film using flux, it is first partially removed using mechanical methods. These techniques make it possible to only slightly weaken the effect of the oxide, since it was experimentally established that the newly formed film is somewhat inferior in strength characteristics to the old one. For these purposes the following devices are used :

• Sandpaper.
• Files and rasps.
• Hard metal brushes.

The process of mechanical removal of surface oxide can be optimized using brick dust. The soldering area is first sprinkled with fine brick chips . Then:

• A large amount of dry rosin is poured onto the brick crumbs.
• With a preheated soldering iron tip, the rosin is melted and distributed over the metal surface in an even layer.
• With the tinned tip of the soldering iron, they begin to vigorously rub the soldering area. In this case, the brick chips peel off the oxide film, and the molten rosin prevents the penetration of oxygen instead of soldering and therefore a new oxide film does not form.
• The result is a well-tinned aluminum surface.

As an abrasive, with the same effect, you can use sifted river sand or metal filings.

Soldering aluminum

The basis of any soldering is the so-called tinning or tinning. In this process, solder is distributed evenly over the surface of the metal. In order for tinning to go well, two important components are needed: a special flux and properly selected solder. We have already looked at fluxes, now it’s the turn for solders.

Special solders

Conventional solders used for soldering non-ferrous metals contain tin and lead. The question of how to solder aluminum with tin is not relevant, since such solders are not recommended for aluminum, because it is practically insoluble in these metals. Special solders are used that contain a fair amount of aluminum itself, as well as silicon, copper, silver and zinc.

• 34-A. Special refractory solder for aluminum. Melting point 530−550 degrees. Composition: aluminum 66%, copper 28%, silicon 6%. It is recommended to use it together with the corresponding flux F-34A.
• TsOP-40. Belongs to the category of tin-zinc solders. Composition: zinc 63%, tin 36%. Melting occurs within 300−320 degrees.
• HTS 2000. Special solder for aluminum made in the USA. Main components: zinc 97% and copper 3%. Melting point 300 degrees. Provides a very strong connection, comparable in strength to a weld seam.

The presence of a metal such as zinc in the solder provides it with high strength characteristics and good resistance to corrosion. The presence of copper and aluminum increases the melting point and makes the solder refractory.

The use of one or another solder is determined by the tasks facing the parts being soldered. Thus, for soldering large-sized and massive aluminum parts, which will subsequently be subjected to heavy loads, it is better to use refractory solders; their melting temperature is comparable to the melting temperature of aluminum itself.

When the question arises of how to solder an aluminum tube, you need to understand exactly what this tube will be used for in the future. Refractory solders are characterized by high strength, and the large mass of the part allows for good heat dissipation during the soldering process, which will prevent the destruction of the aluminum structure due to its melting.

Process Features

Soldering aluminum is no different from soldering any other non-ferrous metal.

At home, aluminum soldering can be divided into two types:

• High temperature soldering of large parts. As a rule, this is thick-walled aluminum of large mass. The heating temperature of the parts is 550−650 degrees.
• Low-temperature soldering of small household items and wires for electronic installation. Soldering temperature 250−300 degrees.

High-temperature soldering involves using a gas burner running on propane or butane as a heating element. But when the question suddenly arises of how to solder aluminum at home, you can just as easily use a blowtorch.

In the case of high-temperature soldering, it is necessary to constantly monitor the heating temperature of the surfaces being soldered . For this purpose, use a piece of refractory solder. As soon as the solder begins to melt, this indicates that the required temperature has been reached and heating of the part must be stopped, otherwise it may melt and subsequent destruction of the entire structure.

For low-temperature soldering, an electric soldering iron with a power of 100 to 200 watts is used, depending on the size of the parts being soldered. The larger the part, the more powerful the soldering iron will have to be used to heat it up. At the same time, a 50-watt soldering iron is quite suitable for soldering wires.

In both cases, both with high-temperature soldering and with low-temperature soldering, the stages of the process are approximately the same and consist of the following sequential steps:

• Mechanical processing of the future soldering area. It is carried out using all kinds of abrasive means. Purpose: to weaken the surface oxide film and make it more susceptible to flux.
• Degreasing the soldering area using organic solvents such as alcohol, acetone, gasoline.
• Fixing parts in the desired position.
• Applying flux to the surfaces to be soldered. If liquid flux is used, it is best to apply it with a brush.
• Warming up the soldering area using an electric soldering iron or gas torch.
• Applying molten solder to the soldering area and tinning metal surfaces (distributing the solder in an even layer).
• We connect the metal surfaces and fix them in the appropriate position.
• After that. Once the solder has cooled and the parts are soldered, we wash the soldering area under running water in order to wash away any remaining flux.

Source: https://220v.guru/fizicheskie-ponyatiya-i-pribory/payalniki/vidy-flyusa-dlya-payki-alyuminiya-v-domashnih-usloviyah.html

Purpose of different types of fluxes for soldering

Soldering parts and products using special reagents called fluxes is widespread in a wide variety of industrial sectors.

In this case, the main purpose of fluxes is to ensure ideal spreading of solder over the surface of the soldered joint and create conditions for its reliable adhesion to metal products. In other words, in most cases you cannot do without flux when soldering; they are needed to comply with the technology.

Types of flux compositions

When considering the question of why flux is needed when soldering materials, any additional explanation can be considered unnecessary.

To fully understand the scope of application and features of the work, it is necessary to familiarize yourself with the known types of fluxes used in practice.

In accordance with their main purpose, as well as the degree of impact on the products being joined, all flux compositions for soldering are divided into the following categories:

• inactive or neutral fluxes that do not include acids and practically do not conduct electric current;
• active or acidic flux reagents prepared on the basis of hydrochloric acid;
• protective (anti-corrosion) fluxes, which help protect the soldering contact zone of a ready-made joint from rust and destruction.

Each of these categories has its own scope of application. There are fluxes that are needed primarily for soldering electronic circuits. Fluxes are produced in the form of pastes, gels and liquids.

The well-known borax flux is used in powder form and is needed for soldering copper pipes. Solder paste - a mixture of solder and flux - is needed for surface mounting of parts on circuit boards.

Neutral substances

Neutral fluxes include rosin, which is recommended for soldering small radio components and microcircuits.

This popular reagent is needed in order to solder parts of heterogeneous structure made of copper and its alloys at relatively low heating temperatures at the joint (no more than 450 degrees). Moreover, this operation is permissible even if there are thin oxide films on the surface of the workpiece.

Due to their low activity, rosin-based fluxes ensure protection of products from corrosion and are therefore in high demand.

When preparing the working composition, alcohol, glycerin or turpentine are added to the rosin crushed to a powder state, which helps to improve the quality of the mixture.

Neutral flux gels are sold, which are needed for lead-free soldering of microcircuits. They are convenient to apply with a special dispenser syringe.

Active and anti-corrosion

Active fluxes are also often made on the basis of rosin, reduced to a powdery state. However, in this case, the prepared mixture contains organic compounds (acidic or amine) in small volumes.

Thanks to this, it can be used to solder not only copper parts, but also silver, nickel and steel products or blanks to a metal base.

In more complex soldering conditions, active fluxes based on hydrochloric acid with the addition of zinc chloride, obtained as a result of a simple substitution reaction, are needed.

This type of flux additive is well known to professionals: most often it is produced and sold under the name “soldering acid”. Acid fluxes are needed for soldering aluminum parts.

The scope of application of fluxes of this class is the sealing of copper and silver products. They are also needed for soldering steel workpieces and various alloys.

Since these reagents belong to the category of chemically active compounds, soldering with their use makes it possible to more effectively combat oxide films. This activity ensures more intense interaction with the base metal from which the fused workpieces are made.

Another feature of these reagents is their high electrical conductivity, which excludes the possibility of their use as an insulating protective coating.

There are compositions based on phosphoric and organic acids. Why are such fluxes needed at all?

They belong to the anti-corrosion category and are used to remove residues and traces of rust from metal surfaces, as well as to protect against the possibility of the appearance of oxides after soldering (during operation).

Since acidic components are used in the preparation of these mixtures, they are very reminiscent of soldering acids.

However, unlike the latter, anti-corrosion soldering flux does not remove oxide films. It is needed for protection from damage possible due to oxidation reactions.

Application procedure

Fluxes can be in either a solid (paste-like) or liquid state and are sold in packages of various shapes and volumes.

Thus, solid rosin goes on sale in flat jars equipped with a tight-fitting lid.

According to the initial state of aggregation of these compositions, the following methods of their use are distinguished:

• with solid flux, during soldering, the tip of the soldering iron must first be dipped into the body of the reagent, after which it captures a small amount of solder;
• in cases where a ready-made liquid mixture is prepared or used on the basis of rosin, it is simply applied to the joint using a regular brush with soft bristles;
• when working with a paste-like composition, small portions of flux are applied to the contact site with any suitable stick (squeezed out from a syringe pre-filled to the required dosage).

Often, stores sell rosin prepared in the form of a special gel, already placed in a syringe of a certain capacity.

Such gel-like compositions are usually classified as neutral reagents, widely used in radio electronics for soldering miniature parts.

Self-cooking

You can prepare working flux for soldering based on rosin yourself. To do this, just crush and grind it into powder, and then pour the resulting composition into a container and immediately pour in a small amount of industrial alcohol.

The ratio of the components used in preparing the flux should be three to five. After thoroughly shaking the prepared mixture, you should leave it for a couple of days and do not touch it until the rosin is completely dissolved in alcohol.

The most suitable container for liquid flux is a regular varnish bottle, the lid of which already has a built-in brush. Immediately before use, it is recommended to thoroughly wash the used bottle to remove traces of varnish.

Quite often, specialists use another type of active additive, close to fluxes, called solder fat. This reagent is usually classified as a conditionally neutral composition. They are needed to somewhat improve the conditions for soldering metal joints.

It should be recalled that before buying any brand of flux, you need to study the instructions for it and understand what exactly it is intended for.

Only in this case will it be possible to make a high-quality solder joint.

Source: https://svaring.com/soldering/flus/primenenie-dlja-pajki

How to solder correctly with a soldering iron and rosin

Knowledge of how to solder correctly is needed not only by radio amateurs and electrical installation specialists. Every home handyman has to deal with the need for soldering when repairing electrical appliances.

Preparing the soldering iron for use

Before soldering with a soldering iron, you should properly prepare it for work. In everyday life, an electric soldering iron with a copper tip is most often used, which, during storage and use, gradually becomes covered with a layer of oxide and is subject to mechanical damage. To obtain a solder joint of good quality, the soldering iron is prepared for use in the following sequence:

1. Using a finely cut file, clean the working part of the tip to a length of 1 cm from the edge. After cleaning, the tool should acquire a reddish color, characteristic of copper, and a metallic luster. During stripping, the tip is given a wedge-shaped, beveled, cone-shaped shape in order to solder what the master needs.
2. Plug in the soldering iron and heat it to operating temperature.
3. The tip must be tinned and covered with a thin layer of tin - the same solder used to solder the connected conductors. To do this, the tip of the tool is immersed in rosin, and then a piece of solder is passed along it. You should not use a solder rod with rosin inside for tinning a soldering iron. To distribute the solder evenly, rub the working edges against a metal surface.

During operation, the half-plate will burn and wear off, so the soldering iron will have to be cleaned and tinned several times during the soldering process. You can clean the tip with a piece of sandpaper.

If the master uses a tool with a nickel-plated, non-burnable rod, it will have to be cleaned with a special sponge or damp cloth. They tin such a sting in molten rosin, running a piece of solder over it.

Soldering can only be learned on the job, but before that it is advisable to become familiar with the basic operations.

Fluxing or tinning

The traditional and most affordable flux is rosin. If desired, you can solder with a solid substance or its alcohol solution (SKF, Rosin-gel, etc.), as well as TAGS flux.

The legs of radio components or chips are covered with half-milk at the factory. But to get rid of oxides, you can tin them again before installation, lubricating them with liquid flux and covering them with an even layer of molten solder.

Before processing with flux or tinning, copper wire is cleaned with fine emery cloth. This removes the oxide layer or enamel insulation. Liquid flux is applied with a brush, and then the soldering area is heated with a soldering iron and covered with a thin layer of tin. Tinning in solid rosin is done as follows:

• melt a piece of the substance on a stand and heat the conductor in it;
• feed the solder rod and distribute the molten metal evenly over the wire.

Correctly soldering massive copper, bronze or steel parts should be done using active fluxes that contain acids (F-34A, Glycerin-hydrazine, etc.). They will help create an even layer of poluda and firmly connect parts of large objects. Tin is applied to large surfaces with a soldering iron, spreading solder evenly over them. After working with active flux, acid residues should be neutralized with an alkaline solution (for example, soda).

Preheating and temperature selection

It is difficult for beginners to determine at what temperature the tool can start working. The degree of heating should be selected depending on the type of material:

• soldering microcircuits requires heating no higher than +250°C, otherwise the parts may be damaged;
• large individual radio components can withstand heating up to +300°C;
• Tinning and joining of copper wire can occur at +400°C or slightly lower;
• massive parts can be heated at the maximum power of the soldering iron (about +400°C).

Many models of instruments have a thermostat, and it is easy to determine the degree of heating. But in the absence of a sensor, it is worth keeping in mind that a household soldering iron can be heated to a maximum of +350 +400°C. You can start working with the tool if the rosin and solder melt within 1-2 seconds. Most POS grade solders have a melting point of about +250°C.

Even an experienced craftsman will not be able to solder correctly with a soldering iron that is not heated enough. With low heat, the solder structure becomes spongy or granular after solidification. Soldering does not have sufficient strength and does not ensure good contact between the parts, and such work is considered a defect.

Working with solder

When heated sufficiently, the molten solder should become flowable. For small jobs, you can take a drop of alloy on the tip of the tool and transfer it to the parts to be joined. But it is more convenient to use thin wire (rod) of different sections. Often inside the wire there is a layer of rosin, which helps to solder correctly with a soldering iron without distraction from the process.

With this method, a hot tool heats the surface of the connected conductors or parts. The end of the solder rod is brought to the tip and pushed a little (1-3 mm) under it. The metal instantly melts, after which the remainder of the rod is removed, and the solder is heated with a soldering iron until it acquires a bright shine.

When working with radio components, you need to take into account that heating is dangerous for them. All operations are performed within 1-2 seconds.

When soldering connections of single-core wires of large cross-section, you can use a thick rod. When the tool is heated sufficiently, it also melts quickly, but you can distribute it over the surfaces to be soldered more slowly, trying to fill all the grooves of the twist.

Source: https://odinelectric.ru/knowledgebase/kak-pravilno-payat-payalnikom

Soldering flux - what is it and what is it for?

Soldering flux is a substance of various origins or multicomponent mixtures used to remove a film of oxides and other compounds from the surfaces on which solder will be applied. Depending on their state of aggregation, they are solid, liquid, powder, and also in the form of a gel.

What is flux used for?

The main functions of these substances are the following:

• Removing films of foreign substances that interfere with the soldering process;
• Improved wetting of soldered parts;
• Improving the spreading of solder and its fixation with the surfaces being soldered;
• Preventing oxidation of metal heated during the soldering process.

Without the use of flux, the soldering process may be ineffective, and the reliability and quality of the work performed may be very low.

Types of fluxes

All fluxes are divided into 3 large groups:

• Acidic (active);
• Low-active;
• Neutral (inactive or protective).

What is electrical resistance

The main practical difference between active fluxes and weakly active and neutral ones is the need to remove their residues upon completion of the soldering process - the acids and aggressive salts contained in such substances, remaining on the soldered surfaces or parts, will cause accelerated corrosion.

On a note. In addition to the classification by melting point described above, all these substances are divided into two large groups: fusible and refractory.

Low-melting substances (rosin, its alcohol solutions, soldering acids) are used for soldering ferrous and non-ferrous metals with tin-lead solders at temperatures up to 5000C. Refractory substances (calcined borax, a solution of borax in boric acid, calcium and barium chlorides) are used for soldering ferrous and non-ferrous metals with copper, silver and copper-brass solders at temperatures above 5000C.

Soldering acids

This type of flux is represented by inorganic low concentrated acids: phosphoric or hydrochloric. To increase the activity of the acid and improve its dissolution of oxide films, a salt such as zinc chloride is often added to it. Due to its fluidity, it is well suited for working in hard-to-reach places.

Interesting. The disadvantage of soldering acids is the need to remove their residues after completion of soldering work.

Soldering acids are used for tinning corrosion-resistant steels, copper, zinc-coated iron, and parts made of nickel or chromium.

Alcohol solutions

The most common composition of this type is an alcohol-rosin solution, which is a 20-25% solution of rosin dissolved in ethyl alcohol. To increase the activity and range of soldering work performed, various salts are often added to such a solution: zinc chloride, diethylammonium chloride, phenylammonium chloride. Due to its liquid aggregate state, it is well applied to the surfaces to be soldered and does not require removal of residues after completion of soldering work.

Alcohol solutions containing no additives are used for conventional soldering using low-melting solders; varieties containing various active salts are used for soldering ferrous and non-ferrous metals, as well as their alloys (copper, brass, aluminum, etc.).

The main disadvantages of the alcohol-rosin solution are the volatility of the main component - ethyl alcohol, its increased evaporation during soldering and storage in a non-hermetically sealed container.

Aqueous solutions and improvised means

This list of homemade substances is often represented by a 16% aqueous solution of orthophosphoric acid with the addition of 3.7-4.0% ethyl industrial alcohol. Such solutions are used for soldering both ferrous and non-ferrous metals and their alloys.

Ready-made formulations

They are ready-made compositions (flux paste, FPP brand composition), convenient for application and often placed inside tubular solder wire. They are usually used for soldering with low-melting low-temperature solders.

Borax

Borax is a high-temperature powdered flux used for soldering steel, cast iron, bronze and copper parts using refractory copper-zinc or silver grades of solder.

Borax is often dissolved in boric acid for convenience and to increase efficiency. Due to its low price and wide range of soldering jobs performed with borax, it is universal and in demand both in radio electronics and in soldering non-ferrous and ferrous metals.

Gel fluxes

Gel fluxes are the most convenient and reliable. They are a mixture of crushed rosin powder and solvent. Available in small syringes for special dispensing guns, they are easy to apply and do not require removal from the surfaces to be soldered. Such substances are used for soldering work in radio electronics.

Storage

Store such substances in closed, sealed containers out of the reach of small children and pets. They should not be stored together with food, medicines, and agricultural seeds. It is advisable to designate a strictly defined cabinet or drawer for such substances.

Application of flux

Micro soldering iron for soldering microcircuits

The method of using these substances is determined by their state of aggregation and chemical composition:

• Solid rosin is applied to the surfaces to be soldered with the tip of a soldering iron, which already has molten solder;
• Soldering acid is applied to the parts or surfaces to be soldered with a small brush, a cotton swab or a simple match;
• Liquid alcohol-rosin flux is applied during tinning using a small dispenser spout mounted on a container with the solution.
• Gel-like substances are applied using special dispensing guns into which cartridges are inserted.

Important! Since fluxes are mostly substances unsafe for human health, maximum care should be taken when applying them. If this tinning substance comes into contact with the skin of your hand, it should be washed off immediately and, if necessary, neutralized with appropriate substances.

How to prepare flux for soldering yourself

Having understood what soldering flux is, it is worth considering the easiest way to independently produce a similar substance used in soldering radio components, for tinning printed circuit boards:

1. Several pieces of rosin are wrapped in thick cloth;
2. By hitting the resulting bag with a heavy hammer, the rosin inside is thoroughly crushed;
3. The resulting crushed rosin is poured into a container with ethyl alcohol and, stirring, dissolved in it completely.

In order to speed up the dissolution of rosin, place the container with alcohol in a small saucepan with hot water. To obtain a gel-like substance, glycerin is added to the resulting solution.

How to choose the right flux

In order to choose the right soldering flux, the following criteria must be taken into account:

• Material of soldered surfaces - if parts made of brass, ferrous metals, chromium or nickel are soldered, then borax, boric, hydrochloric or phosphoric acid are used. If you plan to solder radio components that are sensitive to overheating, use low-melting low-temperature fluxes: rosin and its alcohol solutions, gels.
• Ease of application - when soldering printed circuit boards and small radio components, liquid and gel-like substances are used,
• Health safety – gel flux brands are the safest. The leaders in the list of harmful and potentially dangerous substances of this type are acids.

How to replace soldering flux

If the necessary flux is not available for some reason, it can be replaced with the following available substances:

• Aqueous solution of aspirin;
• Lemon acid;
• Vinegar;
• Rosin with regular pork fat.

All these available means, although they do not have all the advantages of specialized compounds, if used correctly, soldering using them will be of sufficient quality and reliability.

Thus, having understood what soldering flux is and what it is needed for, we can say that its use is an integral step in soldering technology, without which the resulting connection will be unreliable and short-lived.

Source: https://amperof.ru/instrument/flyus-dlya-pajki.html

Rules for using fluxes for soldering microcircuits

instrument.guru > Electronics > Rules for using fluxes for soldering microcircuits

Soldering is the process of connecting radioelements to each other, and this requires the use of various filler materials such as solder and flux.

Solder is a metal or an alloy of various metals that has a melting point lower than that of the metals being joined. It provides a strong connection and fills gaps between the parts of the workpiece being connected.

• Requirements for fluxes
• Flux groups
• Review of various fluxes for soldering
• How to replace soldering flux

Requirements for fluxes

To improve the soldering of parts and the quality of the resulting connection, as well as to clean the surface from oxide film and grease, various fluxes are used. Any flux used in the work must meet the following requirements:

1. The melting point should be lower than the melting point of the solder. This is the main condition for high-quality connection of parts.
2. Should not react with solder.
3. It should ensure good spreading of solder over the surface and wet all workpieces.
4. Must remove and destroy all oxide and fatty films.
5. Residues should be washed off well from surfaces.

Fluxes are usually divided into active and neutral depending on the presence of acids in their composition. Acidic compounds actively interact with many soluble oxide films and fats.

However, they release toxic substances when evaporated and can damage the circuit board over time if they are not removed. This is due to the fact that the active acid included in these fluxes dissolves various metals well, for example, those that make up radio components and the board itself.

Neutral options often do not have these disadvantages, but soldering is not as good as when using acidic ones.

Flux groups

All existing drugs can be divided according to effectiveness into three groups according to GOST:

• Neutral group . Due to the almost zero activity of the components, these fluxes poorly clean surfaces, and the solders that are used with them must be low-melting. Used when working with copper materials, copper coated with cadmium, silver and tin. This category includes rosin, waxes, tree resins and stearin.
• Slightly corrosive group . It is characterized by dissolution in alcohol, water, various fats and weak acids. One of the required components of each flux in this group is rosin, which provides an anti-corrosion function. During the soldering process it evaporates well, decomposes and burns.
• Strong corrosive group . The components of these fluxes are chlorides, fluorides and strong inorganic acids. Manufactured in paste and solid form, they are capable of destroying persistent oxide films on ferrous and non-ferrous metals.

Review of various fluxes for soldering

1. Rosin. Rosin is distinguished by the amount of fatty acids in it; the darker it is, the more acids it contains. Although it is an inactive flux, given the presence of acids in the composition, it is better to remove rosin residues from soldering. It is the most popular and accessible material. The disadvantages include the release of a large amount of smoke during soldering and the rapid coating of the soldering iron tip with soot.

   Solid rosin is difficult to use when soldering, so it tins soldering irons and wires, but to connect radioelements it is better to use liquid rosin in alcohol.

2. Soldering acid. The composition of this flux includes strong acids - orthophosphoric or hydrochloric and zinc chloride, which can reach 50% in solution.

   An affordable and cheap material that corrodes all fatty films and allows you to solder almost any type of metal. But the acid is very toxic, so work should be carried out outside residential premises using personal protective equipment. In addition, it is a good conductor of electricity; even the slightest residue on the connection will corrode the board tracks, so it is better not to use it at all.

3. Borax.

   It is a salt of boric acid and is presented in powder form. To obtain liquid flux, it is mixed with boric acid and water. It works at very high temperatures, so it can be used when working with a hair dryer. Borax is an active flux, so it is necessary to thoroughly wash off any remaining residue.

4. Soldering fat. Depending on the composition, it can be either neutral or active.

   Consists of rosin, petroleum jelly, paraffin, zinc and ammonium chlorides. It works very well when cleaning heavily contaminated surfaces, since the paraffin in the composition draws out all the dirt from the soldering area. It evaporates slowly, leaves almost no soot, but the residue takes a long time to evaporate.

5. LTI 120.

   The composition is represented by rosin (20%), ethyl alcohol (95%) and auxiliary additives such as triethanolamine (2%) and diethylamine hydrochloride (3−5%). It is low cost and does not conduct electric current, which makes it possible to use this flux for soldering radio components. The kit often comes with a convenient brush, which is easy to apply material to the soldering area.

   Some disadvantages include rapid evaporation and potential toxicity.

6. SCF. Alcohol-rosin flux consists of ethyl alcohol (60−80%) and pine rosin (20−40%). An inactive material that you can make yourself by adding crushed rosin to alcohol. Low smoke, easy to apply.

   The disadvantage is that it dries quickly due to the evaporation of alcohol, so it should be stored in a tightly closed container.

7. Oxidal . Used for cleaning soldering iron tips, as well as soldering heavily oxidized and contaminated copper wires.

The above materials are the most accessible and popular. In addition to them, there are special fluxes in the form of gels, but they are very expensive and are unlikely to be needed in amateur radio production.