When carrying out soldering, acidic fluxes are often used to pretreat the surface of parts. The degree of activity of the material is selected depending on the type of metal and the degree of its contamination.
There are various products on sale, the composition of which is selected taking into account the specifics of the work to be done. You can make soldering acid at home yourself.
This will require certain knowledge, basic ability to make chemical compositions and a small amount of money to purchase components.
Alternative to soldering acid
It is necessary to solder the steel contacts. I don’t want to go for soldering acid, the store is too far away.. I have concentrated acetic acid at home. Wouldn’t that work? Or somehow use aspirin in this matter
Yes, any will do, be it sulfur or phosphorus (just not too diluted with water) - its purpose is to remove oxides. look at your mom's SOLITA for cleaning toilets, or a sanitary one (but it's much worse), or buy it, go to a hardware store
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Aspirin won't work. Acid has nothing to do with it. Steel cannot be soldered tightly without flux or “soldering acid.” In fact, it is not an acid, a solution of zinc chloride. It is made by so-called “etching”: strong hydrochloric acid is taken and zinc is placed there. At the same time, bubbles of hydrogen gas are released / ??/ - the “etching” process. Zinc is added little by little until gas evolution stops. But completely “etch” the acid. It is difficult to obtain a pure solution of zinc chloride at home. Therefore, zinc chloride always contains a small percentage of hydrochloric acid. And this acid residue can subsequently corrode the solder if the product is not thoroughly washed with water.
Experienced electronics engineers and home radio amateurs know that for a high-quality connection you will need not only a soldering iron, but also additional accessories. For soldering, flux and solder are used, the latter is made on the basis of lead and tin, often offered in the form of wire. The characteristics of the ratio of wire and flux may differ in parameters depending on the type of product.
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The second component is flux; a common form is used in the form of rosin. It helps to quickly and efficiently solder copper parts, wires and other materials. Soldering acid can be used to work with materials such as brass, nickel, stainless steel, etc.
Aspirin and battery electrolyte
Many experts consider the most affordable option to be the use of pharmacy aspirin.
Please note that it will not be possible to replace rosin with effervescent tablets. They contain fillers (sodium compounds) that are not needed for soldering. Therefore, the most common simple aspirin is used.
The tablets should be crushed to a powder and dissolved in water or regular wine-vodka alcohol. You can use cologne as a solvent.
Acetylsalicylic acid dissolves well. Its properties are often sufficient to clean the surface and remove dirt. It can replace rosin without difficulty.
The inconvenience is the need to work under a ventilation hood or in a ventilated place. Solders without rosin with aspirin release sharp-smelling, harmful gases when heated. It is not necessary and impossible to breathe them.
If aspirin is not available, it is recommended to replace rosin with electrolyte from a used salt battery. It is important that it is not alkaline.
Features of application and soldering with soldering acid
The category into which soldering acid falls differs from other reagents and has a number of positive properties. As a flux, the product is distributed only in liquid form; some compositions can be diluted to reduce the concentration when interacting with metal. Before using the element, it is worth understanding what soldering acid is needed for.
Before soldering metals, it is necessary to prepare the areas for use. With prolonged use, metals tend to oxidize, and a layer of dirt and dust forms on them. If it is possible to deal with dirt mechanically, using sandpaper or a file, then oxides can only be removed using chemical solutions. Soldering acid helps prevent the formation of a new film and remove existing deposits.
Cleaning metal with soldering acid
Basic metals that can be treated with soldering acid:
- copper alloys of any proportions;
- iron products;
- nickel;
- all kinds of non-ferrous metal alloys;
- steel.
Brass and copper alloys can be soldered using borax. Aluminum or steel products will not be connected in any way without soldering acid. Before soldering with acid, the part is treated to remove solid deposits, and after soldering it is washed off with water with a low alkaline content. Varieties of soldering products are produced according to GOST 23178-78 standards, they have fluidity and low viscosity.
Application of fat
Soldering flux can be made from fat with a fairly high melting point. Then at room temperature it will not soften on its own, which will make it easier to work with.
To obtain such a flux, the fat must be melted and mixed with crushed rosin and ammonia in a certain proportion. For three parts of fat by volume you will need the same amount of ammonia and one part of rosin.
For ease of use, the finished flux can be placed in the body of a medical disposable syringe and, if necessary, squeeze out the required amount.
If you are not sure whether a homemade flux is suitable for soldering a part, then you can do a little research. It is necessary to distribute the prepared substance over the surface of a piece of the same metal that is to be soldered.
If, when heated, the flux is evenly distributed over the surface, then it is considered suitable for soldering. If it collects in balls and flows down, then it will be able to provide satisfactory wettability of the part.
The ability to dissolve the oxide film on the metal surface is checked by washing off the applied flux. If the surface remains clean after washing, then the flux dissolves oxides well. On the contrary, if traces of an oxide film or rust remain, then soldering with this flux cannot be performed.
Types of soldering acids and application features
Soldering acid is divided into two main types, regardless of the scope of application, orthophosphoric and hydrochloric type. Regardless of the composition, the purpose is to remove oxides and contaminants from soldering areas. A high-quality, neat seam can only be made if the metal preparation conditions are met. The durability of materials is increased due to the formation of a protective film against oxidation on the joint surface.
It is important to know that using flux when working with electronic boards is strictly prohibited. Thin and fragile elements can be erased from the board structure; soldering acid produces conductive connections. All these factors can have a detrimental effect on the performance of the unit and the overall condition of the structure.
Zinc chloride flux
A solution of zinc chloride is used for soldering iron compounds. The composition is zinc dissolved in hydrochloric acid. The solution is made as follows:
- granular zinc is prepared;
- depending on the technical specifications, add a solution or concentrate;
- After the chemical reaction of zinc, it is possible to use a mixture.
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Proportional parts are taken using the example of 1 liter of saline solution per 400 grams of granulated zinc. At the end of the work, the surface should be treated to stop the reaction; a soap solution is excellent for this. Before making it yourself, you should remember that it is important to follow the sequence. The acid is diluted with zinc, and gases are formed, resulting in a rather explosive mixture. All actions are carried out in a ventilated place.
Oleic acid
Olein is excellent for soldering aluminum alloys. Not used in its pure form, available only in technical condition. A stable state is achieved by mixing olein with various fatty acids. Next, lithium iodide reacts, which completes the mixing of the aluminum soldering mass.
Soldering with oleic acid allows you to join materials from copper and aluminum alloys, without the formation of a chemical film and oxidation.
Oleic acid B-115
Flux is used to protect against corrosion processes at the joint; under mechanical stress, a new film is formed, which allows you to not worry about the reliability of the connection.
Instead of soldering acid, other fluxes do not have similar properties; it is possible to use machine oil with ground sawdust; the soldering process involves rubbing in the composition during joining. When heated, the oleic type of soldering acid evaporates, but the soldering area is tinned, so there is no point in worrying about the quality of the connection.
Orthophosphoric acid
When treating metals with an orthophosphorus solution, a protective film is built that prevents the formation of oxides and chemical reactions of the metal. The characteristics of the solution consist of a colorless substance, inorganic. The hygroscopic structure in the form of a paste structure reacts when heated and dissolves into a liquid composition. It has good flow properties and is easy to clean with water after use.
Soldering with phosphoric acid
Phosphoric acid is used for soldering carbon and alloy steels. Copper and nickel alloys are also suitable for work; the operating temperature for soldering starts at 350 degrees. The acid film is loosened and removed to the surface by dissolving the oxide layer. Reliable soldering is achieved by forming an oxide film with orthophosphoric acid.
Flux VTS
Salicylic base, common in aspirin, is used as a component of soldering flux. It is most widely used when working with precious metals, due to its weak interaction with the particles of the product.
The main advantage is protection from oxidation of the soldering area; there is no need to remove flux, unless additional requirements are imposed.
The versatility of application and low-cost manufacturing allow the use of soldering acid based on salicylic compounds. Caustic emissions require a working hood when performing soldering operations, and the negative side is poor interaction with aluminum.
It is possible to use improvised means, just grind an aspirin tablet or another drug containing salicylic acid. The powder is applied to the soldering area; when working with wires, soldering can be done directly on the tablet. A more convenient mixture is made together with Vaseline, proportions 1 to 2; the paste can be easily applied to the soldering area with a tampon and removed when the work is completed.
How to treat parts with acid
Liquid fluxes are applied to surfaces with a brush. In this case, a more accurate and uniform wetting of the elements to be soldered is ensured, so the brush should be included in any soldering kit. At the same time, as already written above, both more active fluxes and less active ones, to one degree or another, have a destructive effect on both the connected surfaces and the solder. If the flux is not removed at the end of the work, then on steel parts, for example, rusting processes will occur at a much faster pace.
To prevent this, after soldering, parts coated with flux must be treated with neutralizers. The simplest of them is water. To remove F-38 N, you don’t need to use anything other than it. Soda neutralizes well the effects of hydrochloric, orthophosphoric, and acetylsalicylic acid, as it is a base. After soldering, a soda solution should be applied to the parts, which is then washed off with water. Residues of VTS are removed with alcohol or acetone.
Benefits of acid
Each composition has certain advantages, soldering accessories are no exception.
Soldering aluminum with acid
Main positive aspects:
- The convenience of the process, soldering allows you to process a contact in a hard-to-reach place due to its fluidity properties.
- Increased aggressiveness allows you to destroy oxide films and rust deposits. Typically, oxide films are not visible to the eye, so the connection must be processed.
- There is no need to worry about the subsequent formation of an oxide film; soldering acid counteracts this, even mechanical stress.
- The variety of metals with which it is possible to perform operations allows the solution to be used for every job.
Soldering errors
Why is it easier to solder with soldering acid? During heating, the soldering area becomes covered with oxides faster, since the higher the temperature, the faster the chemical reactions proceed. Acid also begins to corrode these oxides faster. Here lies another problem. Acid also corrodes the soldering joint, in addition to oxides. This degrades the strength of the connection.
Why is soldering with rosin or any other simple flux more difficult? They do not contain active acids, but this does not interfere with excellent soldering without acid.
Poor soldering is preceded by many errors:
- Overheat. The flux evaporates and does not have time to take part in soldering. This happens when the temperature on the soldering iron is set above 300 degrees;
- Underheating Soldering may not be good at low temperatures. This occurs due to a small heating area, lack of understanding of soldering principles, or poor-quality equipment;
- Long touch of the soldering iron to the contact point. Soldering should not take more than a few seconds. Otherwise, most of the flux will evaporate, and the rest of the solder will form a lump and begin to oxidize.
- Amount of flux and solder. An excess or deficiency of components is also a critical factor. Too much flux - the solder will start to spread, too little - it will evaporate quickly and there will not be enough for the entire area.
Flaws
In addition to the positive aspects, there are also some disadvantages that can limit the use of the chemical element:
- It is strictly forbidden to use acids when working with radio circuits and small electronics. The properties of some compositions are such that the tracks are destroyed during the processing and growth of new conductive elements.
- The shelf life is underestimated due to the volatility of gases, so it will not be possible to purchase these fluxes with a reserve. There are also requirements for storage conditions, non-compliance with which can lead to damage to the material;
- The composition is harmful to humans if inhaled or in contact with skin. It is recommended to use personal protective equipment during mass work; soldering should be carried out in a well-ventilated area.
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Non-standard methods
If there is no rosin nearby for soldering, you can use material for rubbing bows.
It's better cleaned. All properties are saved. The cost of replacement will be significant. Savvy craftsmen who have solders with flux suggest soaking it in alcohol and waiting until the rosin has completely dissolved. It takes a little time.
They say that such an alcoholic extract can successfully replace rosin. The alcohol component will gradually evaporate. The solid component meets the requirements for fluxes.
When working with old equipment, you can replace rosin with residues in places of old soldering. You need to touch the wire and soldering iron there and make a connection. This method is acceptable for extreme situations with not very high requirements for seams.
Composition and physicochemical properties
Orthophosphoric acid has the formula H3PO4, which consists of phosphorus itself and diethylamide. The proportions may vary from the required concentration, in most cases a ratio of 1 to 4 is used. There is a type of acid with zinc impurities in ratios of 1 to 2 parts of the solution.
Phosphoric acid formula
The basic properties of the material imply aggressiveness. Active interaction occurs with any material; this fact requires careful handling of compounds. During work, you must adhere to special rules, because... a positive or negative scenario may occur. The liquid form allows the composition to penetrate into hard-to-reach places and achieve high soldering strength. The main types of soldering acid are solutions, since a 100% concentration will not allow working with most metals.
How to replace soldering flux
In the absence of flux and the impossibility of acquiring it, you can use some available materials, but you should remember that the quality of soldering will be very low, and the remaining material is often difficult to remove or toxic. However, there are some adequate options you should be aware of.
- Aspirin . Salicylic acid or a solution of aspirin tablets in water can be used for soldering, but its vapors are too toxic, and it is very advisable to work in non-residential areas with good ventilation, and preferably in the open air. It has all the disadvantages of active fluxes and requires mandatory cleaning of the surface after soldering.
- Ammonia , as well as citric or acetic acid, can also be used as a replacement for fluxes, and their concentration does not require additional dilution with water.
- Glycerin may be suitable for soldering radio components on a board, but it has residual resistance and good hygroscopicity, so it must be washed off the board.
It should be remembered that soldering will be of high quality when the flux is selected correctly. There are fluxes that are ideal for every metal, and others may not work as well. In addition, it is highly discouraged to solder boards with active fluxes, especially those containing acids, since if flux residues are not completely removed from the surface of the printed circuit board, the active components will destroy the conductive copper traces.
Parts should be soldered with a soldering iron with a perfectly tinned tip, and when carbon deposits appear, try to clean the tip in oxide, this will allow for very good soldering. Upon completion of work, flux residues from the surface of soldered parts and boards must be removed using a suitable method. The board tracks can be coated with special varnishes, for example, tsaponlak, this will protect them from moisture.
Features of choice
The composition of soldering acid is selected in accordance with the working surface of the material. The main criterion should be the quality of the solution, because If the concentration is incorrect, you can always lower it at home. It is not permissible to use formulations with sediment or cloudiness in the container.
It is important to remember that liquid fluxes are one of the few soldering accessories that have an expiration date, which you need to pay attention to before use.
Difficult choices always haunt you when purchasing. The compositions are different, there are a large number of manufacturers on the market. It is necessary to determine what type of work will be performed; for this purpose, the purpose of the soldering acid composition is studied. Orthophosphorus compounds are the most common, they fight oxides well and are not so aggressive. Salt is more versatile, because... applies to a variety of metals. Sulfur is the most active option, used when soldering thick products.
Alcohol, glycerin, rosin
You can get a good alcohol-rosin flux by dissolving rosin in ethyl alcohol. First you need to crush the rosin in a mortar as finely as possible.
Rosin dissolves very slowly in alcohol, and the speed of flux preparation will depend on its thorough grinding. After mixing the alcohol with rosin, it is better to leave the future flux for several hours to complete the dissolution.
You can speed up the process by placing the solution in a sealable glass container and heating it to 80 ℃ in a water bath. Alcohol rosin flux is completely neutral and does not even require rinsing after soldering.
Ethyl alcohol can be successfully replaced with glycerin. This glycerin flux will be thicker than alcohol rosin and will be more convenient to use. In this case, the dissolution of rosin will slow down.
It will be much more effective to first dissolve it in alcohol and then mix it with glycerin. In this case, the activity of the composition will significantly increase, but you will have to wash off the residue from the soldered workpieces.
It’s even possible to make rosin yourself, although it will take time. It is necessary to collect resin from pine trunks in warm, dry weather and melt it.
Can be used for soldering as a flux or its component, rosin for bowed string instruments. It is of very high quality and well cleaned. But its price is much higher than that of soldering rosin.
DIY making
With some knowledge and available materials, it is possible to make soldering acid at home. The set of ingredients is not large; they can be purchased at a hardware store:
- hydrochloric acid in its pure form;
- lump zinc, which is sold by the chemical reagents department; if it is not possible to purchase, a finger-type battery is carefully opened;
- container made of glass or ceramic material.
Soldering acid is made by hand in a certain sequence. It is necessary to fill the container with pieces of zinc, then fill it with saline solution. The actions are carried out in a well-ventilated area; if the solution gets on the skin, you must immediately rinse with running water. After production, the mass is poured into an airtight container for proper storage.
The need to use acid fluxes
Any soldering acid - hydrochloric or phosphoric acid - is designed to create an ideal environment for the interaction of solder with elements.
Their use makes it possible to remove contaminants and oxides from the working area, prevent the resumption of the oxidation process and reduce the tension of the solder, in order for it to spread more freely.
As a result, reliable soldering of parts is ensured.
Depending on the type of metal, the flux for soldering is selected. It is worth noting here that soldering acid is not used when assembling boards.
Precautionary measures
Aggressive properties require a special approach to safety precautions. Storage is carried out in original packaging, protected from direct sunlight.
It is better to carry out work with good ventilation, using the necessary protective equipment.
The skin reacts negatively to aggressive substances. If it gets on your hands, wash it immediately with water and laundry soap. Inhalation may cause oral irritation, and if it gets into the eyes, seek professional help.
Soldering at home
One of the oldest and fairly simple methods of reliably connecting metal parts is the so-called soldering, used in the manufacture of any product using surface diffusion, as well as when melting an intermediary metal.
This method is widely used, as a rule, when it is necessary to repair technical devices and household items. Electrical and radio engineering is the most common area of application of soldering. The positive aspects of soldering are their simplicity and universal availability, ease of repair, dismantling, and water resistance.
The negative aspects of soldering are the relatively low soldering strength, the inability to apply to some metals, and the relative intolerance to cold and heat (from -25 to +200 degrees).
Types of solders for soldering
For soldering, as a rule, so-called solder is used - a low-melting metal alloy. The central type of solder is a tin-lead alloy.
Taking into account the presence of a certain element, solders are divided according to different melting temperatures, and subsequently this circumstance determines the primary scope of their application. Solders with a temperature of about 200 degrees have become widespread.
As a rule, flux is used on the top of parts that are soldered, which destroys oxides. The efficiency of soldering without using flux is zero. A characteristic feature of the flux is that various modifications of it are used for soldering certain metals.
