Flux for soldering aluminum with copper, how to solder copper wire

Soldering two wires is always better than simply twisting them - such a connection is tight, it never sparks, and therefore does not heat up and does not burn out. Copper is the best solder - it can be easily tinned and the solder sticks to this non-ferrous metal without any problems. That is why copper wires are used in the circuits of any equipment. But there are situations when soldering copper with aluminum is necessary - usually in situations where the house has old aluminum wiring and you need to install a new socket or lamp.

Problems with soldering aluminum

Aluminum oxide (Al2O3) in mineralogy is called corundum Source masterpaiki.ru
Most people who are friends with a soldering iron have tried to solder aluminum at least once in their lives and were convinced that it is almost impossible even after tinning with hydrochloric acid. But why is that? A film of aluminum oxide (Al2O3), which appears immediately after stripping, resists good contact with tin. This suggests that you first need to limit the possibility of the formation of an oxide film and only then start soldering - there is no other way.

Notably, aluminum oxide is a gemstone known as corundum. Depending on the impurity content, corundum can be red (with impurities of Cr), known as ruby, or blue, with impurities of iron (Fe) and titanium (Ti), known as sapphire. That is, solder cannot have adhesion to a stone, even a precious one.

Solder

Commonly used low-melting solder bases are tin (Sn), lead (Pb), cadmium (Cd), bismuth (Bi) and zinc (Zn). The problem is that aluminum is practically insoluble in these metals (with the exception of zinc), which makes the connection unreliable.

By using a flux with high activity and properly treating the joints, you can use tin-lead solder, but it is better to avoid such a solution. Moreover, a solder joint based on the Sn-Pb system has low corrosion resistance. Applying a paint coating to the soldering area allows you to get rid of this drawback.

For soldering aluminum parts, it is advisable to use solder based on silicon, copper, aluminum, silver or zinc. For example 34A, which consists of aluminum (66%), copper (28%) and silicon (6%), or the more common TsOP-40 (Sn - 60%, Zn - 40%).

Domestic solder – TsOP-40

Note that the higher the percentage of zinc in the solder, the stronger the connection and the higher its resistance to corrosion.

High-temperature solder is considered to be solder consisting of metals such as copper, silicon and aluminum. For example, like the above-mentioned domestic solder 34A, or its foreign analogue “Aluminium-13”, which contains 87% aluminum and 13% silicon, which allows soldering at temperatures from 590 to 600°C.

"Aluminum-13" produced by Chemet

When choosing a flux, it is necessary to take into account that not all of them can be active towards aluminum. We can recommend using products from a domestic manufacturer for such purposes - F-59A, F-61A, F-64, they consist of ammonium fluoroborates with the addition of triethanolamine. As a rule, the bottle is marked “for aluminum” or “for aluminum soldering.”

Video description

Soldering aluminum. Flux for soldering aluminum F-64.

Soldering with powder fluxes

The borax is intended for soldering using brass (copper) and silver solders Source expertsvarki.ru
Another opportunity to neutralize the oxide film (Al2O3) is the use of powder fluxes when soldering copper with aluminum. In such cases, a gas burner is most often used, and the powders are called powders. Perhaps someone imagines soldering as working with a soldering iron, but this is not entirely true, because for wires with a cross-section of 10 mm2 or more, a soldering iron is simply unsuitable, since it will not be able to heat them properly. Therefore, powder fluxes should not be discounted.

Here are some of the powders (powder fluxes):

Sodium salt of boric acid, better known as borax (Na₂[B₄O₅(OH)₄]·8H₂O), is a white powder whose melting point is 700°C (the substance becomes viscous). This flux has a low cost, dissolves in water and is easily washed off with a solution of citric acid.
Active flux F34-A. According to TU 48-4-229-87, it consists of 50% potassium chloride (KCl), 8% zinc chloride (ZnCl₂), 32% lithium chloride (LiCl) and 10% sodium fluoride (NaF). This substance is hygroscopic and dissolves well in water.

Soldering instructions

The process of soldering aluminum parts does not have its own distinctive features; it is carried out in the same way as with steel or copper.

The algorithm of actions is as follows:

the soldering area is degreased and cleaned;
the parts are fixed in the desired position;
the connection area heats up;
touch the solder rod (containing active flux) to the joint. If flux-free solder is used, then flux is applied to destroy the oxide film, after which a solid piece of solder is rubbed over the soldering area.

A brush with steel wire bristles is also used to break down the aluminum oxide film. This simple tool is used to rub molten solder over an aluminum surface.

Soldering aluminum - complete video instructions https://www.youtube.com/watch?v=ESFInizLE9U

What to do if you don’t have the necessary materials?

When it is not possible to prepare all the materials necessary for soldering, you can use an alternative method that uses tin or tin-lead solder. As for the flux, it is replaced by rosin. To prevent the formation of a new aluminum oxide film in place of the old one, stripping is carried out under a layer of molten rosin.

The soldering iron, in addition to its direct purpose, will be used as a tool that destroys the oxide film. To do this, a special scraper is put on its sting. You can increase the effectiveness of the process by adding metal filings to the rosin.

The process is carried out as follows:

use a heated tinned soldering iron to melt the rosin at the soldering site;
When the rosin completely covers the surface, they begin to rub it with a soldering iron tip. As a result, metal filings and stings destroy the aluminum oxide film. Since the layer of molten rosin does not allow air to penetrate to the aluminum surface, an oxide film does not form on it. As the film is destroyed, tinning of the part will occur;
When the tinning process is completed, the parts are joined and heated until the melting temperature of the solder is reached.

It must be warned that the process of soldering aluminum without special materials is a rather troublesome process with no guarantee of successful completion. Therefore, it is better not to waste your time and energy on such work, especially since the quality and reliability of such a connection will be questionable.

It is much easier to buy active flux and high-temperature solder, with which soldering aluminum even at home will not cause difficulties.

Soldering aluminum has always been a rather complex technological process, since its melting point is considered relatively low, and the properties of the connection are not at the highest level. Soldering aluminum with copper becomes an even more complex and problematic process, since copper is difficult to melt, although it can be soldered normally. Despite the complexity of the process, there is a need for it periodically in various industrial areas and even in the home environment. Under normal conditions, without any additional means and with standard materials, it will be almost impossible to obtain a high-quality connection without damaging the metal of the workpiece.

Soldering copper and aluminum requires a special approach, since even standard solder for soldering aluminum will be ineffective. It is worth noting right away that with aluminum there is a greater conflict with copper, since the soldering process with steel is better. Many craftsmen use this when creating complex connections. The need for such soldering arises both when connecting pipes or other large parts, and when connecting wires, which from the technical side is easier, simpler and faster, since there are no large loads on the final product.

Other methods for joining copper and aluminum

For connecting dissimilar wires, in this case, copper and aluminum, there are other methods that are fully justified, as confirmed by many years of practice.

Crimping method

When laying and installing electrical wiring, it becomes necessary to permanently connect copper and aluminum wires by crimping using sleeves Source samelectrik.ru
The soldering method for connecting aluminum and copper wires is not always suitable, and the reasons may be different. Firstly, you simply may not have flux, and the connection needs to be made urgently. Secondly, it may not be possible to connect to ≈220 V, and thirdly, there may be no free space to reach with a soldering iron. For example, in an electrical distribution box (dose), all twists must be well insulated, but the usual rag tape is not suitable in this case, since it allows oxygen to pass through, which will contribute to the oxidation of aluminum and, as a result, burnout of the twist. Therefore, one of the most optimal insulation options in such situations will be a sleeve - a fragment of the required length, cut from a heat-shrinkable tube.

Heat shrink is applied to the twist so that it captures the insulation on one and the other wire at least a centimeter at a time. First, the sleeve is put on one of the wires, then a tight twist is made, the thermal strip is moved so that it is in the center, but at the same time captures the insulation on both sides. After this, all that remains is to heat up the heat-shrinkable tube, and it will crimp both the insulation on both sides and the twist itself. It is usually heated with an ordinary burning match, and the sleeve cools down in 1-2 minutes. After this, the access of oxygen to the connection is stopped.

Terminal blocks

One of the most common ways to connect wires is with terminal blocks Source elektroznatok.ru
Terminal blocks or, as electricians call them, terminal blocks, are used to connect homogeneous and dissimilar conductive metal cores. For joining in a plastic block, bolted or clamp terminals are used, which ensure 100% contact and the complete absence of the influence of aluminum oxidation on copper. Between the terminals there is a shunt plate made of a neutral metal (usually tinned copper or brass), which is not affected by the oxide film. The most important thing in the terminal block is a good clamping of both wires, which guarantees a long service life. The only contraindication for such a connection is high air humidity. If this happens in such a room, then it is better to use heat shrink.

Flaws

High percentage of defects after completion of the process;
Soldering aluminum-copper requires a large number of different additional materials, many of which are highly specialized, without which it is impossible to obtain a high-quality connection;
Sometimes it is necessary to select steel couplings of the same diameter as the pipes being welded;
The soldering process turns out to be very expensive due to the use of fluxes, special solders and other additional means;
Many of the additional consumables are difficult to access, as they are not common and frequently used;
Not every existing soldering method is suitable for a particular case;
Only a master with extensive experience can cope with the work, and at home this is a difficult process.

Soldering difficulties

The main difficulty in soldering is that metal products made from these materials cannot connect normally, since even when the solder sets, the seam can crack even with a relatively small mechanical impact. The situation is complicated by the aluminum oxide film, which envelops the solder material, interfering with a normal connection, and also does not melt under the influence of temperature. Good cleaning and treatment with a solvent, followed by the application of a specialized flux, can help combat this.

Working with copper is also not easy in this case. After all, even solder for soldering copper pipes turns out to be not entirely suitable for such a process. It is refractory, which is what is required for such a metal. At the same time, aluminum may have a lower melting point, which will cause it to burn out before the solder itself melts. Thus, brazing aluminum to copper turns out to be quite problematic. Solder for melting aluminum may not be suitable for copper, as it turns out to be too fusible, but this is a more suitable option, since many craftsmen, especially when working at home, use silver solders.

Possible methods of soldering aluminum to copper

Soldering aluminum and copper at home and in production can be carried out in the following ways:

Soldering using a coupling. In this case, a steel part is inserted between the metals, so that both copper and aluminum are soldered on different sides of the steel in more convenient ways, which helps to obtain a reliable connection, since they interact with steel and other alloys much better than with each other.
When using special solders. Modern developments, for example, such as the Castolin brand filler material and specially developed fluxes for it, help solve many complex issues. The big disadvantage of this method is the high cost of consumables and low prevalence.

Surface soldering. In this case, a socket is made from aluminum so that a copper tube can fit into it. The edges of this socket are sealed with low-melting solders, covering most of the surface of the copper pipe to increase the joint area.

Materials and tools

Regardless of whether you need to solder aluminum to copper wires, pipes or sheets, you will need:

A burner (gas or gasoline) or a soldering iron, depending on the conditions under which all this is carried out;
Solder that will be suitable for the chosen method, since soldering through a steel coupling requires consumables that will be designed for soldering with steel;
Flux selected for solder to improve interaction with different metals;
Steel, or some other alloy, coupling, if this method is chosen;
Tools for fixing workpieces and cutting sockets.

Step-by-step instruction

All metal products that will take part in soldering are fully prepared. This includes cutting the edges, preparing the socket, mechanical treatment with a brush and solvents to remove all existing deposits and formed films.
The parts are then securely fixed so that there is no movement or displacement during the process.
At the next stage, the ends of the parts should be treated with flux.
Then you can begin direct soldering. If the method through the coupling is chosen, then it is first soldered to one workpiece, for example, a copper pipe. Then you need to take time to cool and check the quality so that there are no cracks or crevices. Only after this should you begin connecting with the second part, which is carried out in exactly the same way, but with the help of other consumables.
After completing the procedures, allow the seam to cool and check the completely finished product for defects before putting it into operation.

When choosing consumables, you need to pay attention to the strength of the resulting connection, which is especially important when working with pipes that are operated under pressure.”

How to Solder Copper to Aluminum

Aluminum is a material with good strength and high thermal and electrical conductivity.
These positive qualities contribute to the widespread use of metal in industry and everyday life.

Quite often there is a need to connect aluminum parts or seal a hole in an aluminum container. But not everyone knows how to solder aluminum at home.

Soldering aluminum

One of the most well-known methods of joining metals, especially in electrical work, is soldering.

It provides lower resistance of connections, and, as a result, less heating under the influence of electric current.

Since aluminum, along with copper , is the main conductive material in electrical networks and devices, the need for soldering arises quite often.

The difficulty is that the “winged metal” in air is instantly covered with a film of oxide, to which the molten solder does not stick. It is necessary to remove the oxide layer using mechanical cleaning, but it forms again almost instantly.

In order to avoid the re-formation of the oxide film, many techniques have been developed. Among them:

Cleaning small parts under a layer of liquid flux.
The use of fluxes in conjunction with abrasive materials.
Using copper sulfate to create a copper film on an aluminum product.
Application of special fluxes and solders.

Cleaning under the flux layer

Small aluminum parts, such as conductors, can be cleaned by dipping part of the part into a liquid flux, which can be a regular rosin solution or soldering acid. Liquid flux will protect the area being cleaned from contact with oxygen and the formation of a film. Regular transformer oil has the same protective effect.

Abrasive materials

Iron filings are often added to the flux (the same rosin). During the soldering process, it is necessary to rub the heated area with the tip of the soldering iron. Under the influence of friction, the sawdust peels off the oxide layer, and the rosin blocks the access of oxygen to the liberated metal. Instead of sawdust, any crumbling abrasive can be used: sandpaper or even brick.

Using copper sulfate

An interesting method using galvanostegy. Two aluminum electrodes are dipped into a solution of copper sulfate and connected to the poles of an electric battery. The electrode connected to the positive is stripped.

As a result of electrolysis, copper begins to deposit on the cleaned surface. When the aluminum is completely covered with a copper film, the part is dried.

After this, soldering is much easier, because copper is an excellent material for this type of connection.

Special solders

The highest quality connection at home can be obtained using low-melting solders based on tin and copper and special fluxes.

The most popular domestic flux is F64, which allows you to solder aluminum parts without mechanical stripping.

So, for example, soldering aluminum to copper can be done without problems, or an aluminum tube can be sealed from the inside, which cannot be cleaned by any other means.

In this case, conventional low-melting tin-lead solders with a melting point of 200−350 degrees are used. The soldering iron should be quite powerful - from 100 W and above. The reason is the high thermal conductivity of aluminum.

An insufficiently powerful soldering iron simply will not be able to heat the soldering area to the melting temperature of the solder.

Only very small parts (mainly in radio electronics) can be connected with a 60 W soldering iron.

A soldering iron is not suitable for soldering large aluminum parts. Here it is better to use any gas burner that provides heating up to 500-600 degrees, and one of the specialized solders. One of the most popular is HTS-2000 - a flux-free solder for soldering aluminum, copper, zinc and even titanium.

It has several advantages:

Low melting point (390 degrees Celsius).
Can be used without flux.
Reliability of the connection (in many cases it can replace argon welding).

True, HTS-2000 does not exclude the stripping process. Moreover, during the soldering process it is necessary to remove the oxide film with a solder rod or a wire brush to ensure a reliable connection. However, this method allows you to perform such work as sealing leaky aluminum containers, for example, cans, or even car aluminum radiators.

In addition, HTS-2000 is practically the only (with the exception of argon) way of joining two “winged” metals: aluminum and titanium.

There are other high temperature solders designed specifically for aluminum soldering. For example, 34A, which contains two-thirds aluminum, as well as copper and silicon. But the melting point of such solders is 500-600 degrees Celsius, which is close to the melting point of aluminum itself.

Therefore, using high-temperature solders at home is dangerous - an aluminum part can be irreparably damaged when heated to such high temperatures.

Soldering aluminum with a soldering iron and gas torch

There is a widespread belief that it is impossible to solder or tin aluminum (as well as alloys based on it) without special equipment for this.

Two factors are cited as an argument:

upon contact with air, a chemically resistant and refractory oxide film (AL2O3) is formed on the surface of the aluminum part, resulting in an obstacle to the tinning process;
The soldering process is significantly complicated by the fact that aluminum melts at a temperature of 660°C (for alloys this ranges from 500 to 640°C). In addition, the metal loses strength when, during the heating process, its temperature rises to 300°C (for alloys up to 250°C), which can cause a violation of the stability of aluminum structures.

Considering the above factors, it is truly impossible to solder aluminum using conventional means. The use of strong fluxes in combination with the use of special solders will help solve the problem. Let us consider these materials in detail.

Solder

Domestic solder – TsOP-40

Note that the higher the percentage of zinc in the solder, the stronger the connection and the higher its resistance to corrosion.

"Aluminum-13" produced by Chemet

Flux

Domestic flux

For high-temperature soldering, you should purchase flux produced under the brand 34A. It consists of potassium chloride (50%), lithium chloride (32%), sodium fluoride (10%) and zinc chloride (8%). This composition is most optimal if high-temperature soldering is performed.

Recommended flux for packing at high temperatures

Surface preparation

Before you begin tinning, you must complete the following steps:

degrease the surface using acetone, gasoline or any other solvent;
remove the oxide film from the place where soldering will be performed. For cleaning, use sandpaper, an abrasive wheel or a brush with steel wire bristles. As an alternative, etching can be used, but this procedure is not so common due to its specificity.

It should be taken into account that it will not be possible to completely remove the oxide film, since a new formation will immediately appear in the cleaned area. Therefore, stripping is carried out not with the goal of completely removing the film, but to reduce its thickness in order to simplify the task of the flux.

Heating the soldering area

To solder small parts, you can use a soldering iron with a power of at least 100W. Massive items will require a more powerful heating tool.

Soldering iron 300 Watt

The best option for heating is to use a gas burner or blowtorch.

Simple gas burner

When using a burner as a heating tool, the following nuances should be taken into account:

Do not overheat the base metal, as it may melt. Therefore, it is necessary to regularly monitor the temperature during the process. This can be done by touching the solder to the heated element. Melting the solder will let you know that the required temperature has been reached;
Oxygen should not be used to enrich the gas mixture, since it promotes strong oxidation of the metal surface.

Why is aluminum difficult to solder?

Many people have tried to solder aluminum at home and understand well: the solder does not want to stick to the surface of the parts. This occurs due to the formation of a stable oxide film on the metal, which has low adhesion to the solder material. Methods for soldering aluminum at home come down to fighting the protective film.

In mineralogy, aluminum oxide is called corundum. It consists of transparent crystals, which are gemstones. Corundum has different colors depending on the impurities: chromium gives a reddish tint, sapphire gives a bluish tint. The oxide film is highly durable and cannot be soldered. It must be removed from the surface and then begin to solder the parts.

How to solder aluminum with tin yourself

Soldering wire connections with solder is considered the most reliable method of connecting wires and cable cores. It’s good if you only need to solder copper wires, which are easily tinned with solder. It’s not for nothing that in electronics all terminals of elements are copper and tinned.

Soldering aluminum at home

Once solid wires and stranded cable strands are tinned, they are fairly easy to connect by soldering. How to solder aluminum with tin if the solder is rejected by aluminum oxide. As you know, aluminum is coated with a thin layer of oxide, which instantly forms on aluminum upon contact with oxygen. In order for the solder to adhere well to the aluminum wire, you need to remove the aluminum oxide and then tin it.

For this purpose, the following fluxes exist: soldering acid, special fluxes for aluminum, and a mixture of rosin and acetone. All these advantages destroy or hinder the formation of an oxide film on aluminum. After using this type of flux, the process of tinning aluminum is simplified.

The necessary tools for soldering aluminum with tin are: an electric soldering iron, a sharp knife, pliers for twisting wires, a small file for preparing the soldering iron tip. The materials you will need are: POS 61 or POS 50 solder, flux for soldering aluminum F-64 or similar, sponge.

Soldering aluminum with tin and flux F 64

Flux F 64 is intended for soldering aluminum. The soldering technique is not complicated. First of all, you need to remove 5 cm of insulation from the wires. The insulation is removed with a sharp knife at an angle to the wire so as not to cut it. Notched aluminum breaks off easily.

Tools and materials for soldering aluminum wire

Next, you need to thoroughly clean the wire with fine sandpaper or a sharp knife. Having stripped the wire, it is moistened with a brush with a plus and with a sharp knife they continue to strip the wire, but now under flux. In this way, the oxide film of the aluminum wire is removed, preventing it from oxidizing again in air. Next, using a heated soldering iron with solder, begin tinning the wire from its end.

If you start tinning the wire near the insulation, then you can burn it. In this case, the insulating properties of the wire will be lost.

The wire is tinned with a soldering iron, moving back and forth, while the oxide film is removed from the aluminum. It is not possible to tin the wire straight away.

Therefore, flux is again applied to the non-tinned sections of the wire and sections of the remaining oxide film are removed with a hot soldering iron with solder and movements back and forth and serviced.

In this way, the aluminum wire is completely covered with solder. After tinning, the aluminum wire is dipped in a soda solution (5 tablespoons per 200 grams of water) and the remaining flux is washed off with a toothbrush.

The flux contains active acids that not only corrode the film, but also the wire itself. Therefore, the remaining flux must be washed off.

It will not be possible to wash it off completely, since it partially remains under the solder and eats into the wire.

But at least partially it needs to be washed off. Copper wire is not treated with F 64 flux; it is better to use a solution of rosin and alcohol (50% to 50%). Using a brush, apply liquid rosin to the copper wire (having previously stripped it) and use a hot soldering iron to service the wire, starting from the end. The soldering iron tip should be smooth and clean. The shells at the end of the soldering iron tip are removed with a fine file.

And the remains of burnt solder (slag) are wiped off with a sponge or rag. Once the aluminum and copper wires are tinned, they are twisted with pliers, liquid rosin is applied with a brush and the connection is soldered, also starting from the end.

If you connect aluminum without tinning with solder, the connection may break down over time. The aluminum-copper connection is a galvanic couple, and when current passes through it, it heats up and destroys the connection.

Table of temperature conditions of solder brands

As a result, the twisted area becomes very hot and charred, which increases the fire hazard. Tin solder is neutral to aluminum, so aluminum wires must be tinned before connecting to copper. POS 61 and POS 50 solders with a low melting point of 190 - 210C are well suited for soldering aluminum wires.

Soldering aluminum with copper, tin and rosin

Soldering electrical wires using soldering acid is prohibited in the PUE. This is due to the fact that this acid does not burn completely during soldering.

As a result, the junction of the wires is corroded by acid over time, oxides are formed, which heat up when current passes and can cause the insulation to catch fire.

These acid-containing fluxes include special fluxes for soldering aluminum, including F 64.

So how to solder aluminum with copper so that the connection is high-quality and durable. In terms of complexity, the method of tinning aluminum with tin and rosin is even easier than tinning aluminum with F 64 flux. But the quality and reliability when tinning with rosin will be high. When tinning aluminum in rosin, you need to make or select a low bath for liquid rosin (rosin 60% and alcohol 40%).

Fluxes for aluminum soldering

Fill the bath with liquid rosin so that the wire is buried in it with 5-10 mm of insulation.

The wire, stripped of insulation, is placed in rosin and with a sharp knife (conveniently a scalpel) the oxide film is removed from the aluminum wire without removing it from the bath.

That is, under rosin they protect the wire along its entire length from all sides. Under the rosin, a film does not form on the cleaned areas of the aluminum wire, since there is no contact with oxygen.

Now take a heated soldering iron with solder with a power of at least 60 W and lower it onto the bare and free of oxide wire, right at the surface of the rosin, little by little scroll and pull out the already tinned sections of the wire. The essence of the method is that the wire is tinned at the very surface of the liquid rosin. So that the stripped sections of the wire from oxide cannot come into contact with air.

The soldering iron can be immersed 2-3 mm in rosin at times. After tinning the wire a little, lift the soldering iron so that it heats up again. Yes, at the beginning, there will be a lot of smoke, so it is better to learn to solder outdoors or in a room with good ventilation. After several attempts, you will develop your own tinning technique and gain a little experience.

You will decide on the position of the soldering iron, the speed of tinning the wire will increase, that is, skill will appear, and the amount of smoke will decrease. But the wire will be perfectly tinned. Next, as usual, twist the wires and solder them with a small amount of solder.

The remaining rosin on the soldered twisted wires is washed off with a brush and alcohol. The disadvantage of this method is the impossibility of soldering in hard-to-reach places. For such cases, it is better to use other methods for safely connecting aluminum to copper.

Can it be connected to copper?

Situations often arise when it is necessary to connect an aluminum wire to a copper wire. This is perhaps the only case where soldering cannot be used.

It's all about the aluminum itself. It cannot be soldered to other metals at all due to its physical and chemical properties. When connecting directly to copper, galvanic corrosion will occur between the two active metals and will quickly destroy the connection.

And if they are soldered using solder that is neutral to both materials, then the different coefficients of thermal expansion of the metals will quickly destroy the soldered contact. After all, when current passes through a conductor, it will certainly heat up, and after switching off, it will cool down.

Methods for soldering aluminum wires

Despite the fact that in modern construction, during electrical work, aluminum cables are increasingly being replaced by copper cables, aluminum remains an indispensable material in the manufacture of large-section wires and cables.

The reasons for this lie on the surface - the electrical resistivity of aluminum is approximately one and a half times greater than that of copper, and the volumetric weight is three times less.

With a large conductor cross-section, when weight is more important than strength, the choice in favor of aluminum is obvious. The cross-sectional area of an aluminum conductor will be one and a half times greater than that of a copper conductor, and at the same time, aluminum will still be two times lighter than copper. Soldering, among other methods, is used to connect wires.

Soldering methods

The problem with using aluminum conductors is their rapid oxidation. The oxide film significantly impedes the passage of electric current during connections. To do this, twisted aluminum wires are soldered.

You can solder aluminum wires in a junction box using a soldering iron or a gas torch. It is more difficult to use a soldering iron due to the inability to accurately heat to the required temperature. And for aluminum, overheating is just as unacceptable as underheating.

Metal has high thermal conductivity, and the insulation over a large area from the soldering point can simply melt.

It is easier to regulate the heating temperature with a gas burner, but it takes a long time to prepare the surface. However, it is the torch that will need to be used if it is necessary to solder any massive parts to each other. In any case, when soldering aluminum wires, they need to be prepared.

Preliminary processing

The difficulty with soldering is that aluminum itself is a very low-melting material (660 ℃) and if heated carelessly it can melt.

Another factor that makes soldering aluminum wires difficult is rapid oxidation in air.

The oxide film on the surface of the material reliably protects aluminum from the effects of all kinds of external factors, but it also prevents the adhesion of solder to the material and must be removed.

It is almost impossible to mechanically remove the oxide film under normal conditions. The material is instantly oxidized and covered with a new film. You can mechanically remove the oxide film under the oil layer.

But before this, the oil must be heated to 200 ℃ in order to remove any active oxygen that may be present there. This method is very inconvenient at home and labor-intensive.

Therefore, the ends of aluminum conductors must be tinned before soldering. Using rosin or most other fluxes will not work due to the high chemical resistance of the oxide film. It does not dissolve even with organic acids.

To tin the wires, you must use both a special flux and a mechanical method.

Of course, this must be done before the wires are twisted, otherwise it will not be possible to mechanically clean the entire surface of the wire. Only the tinned ends can be twisted together and soldered.

Working with a soldering iron

In order to solder aluminum with a soldering iron, there are several methods, the essence of which is to clean immediately under the flux layer in direct contact with the molten solder.

The first method is that aluminum conductors, before soldering, are cleaned with a hot tinned soldering iron using a mixture of rosin and steel filings.

Sawdust has an abrasive effect, rosin removes all impurities and immediately the cleaned areas are covered with solder, which should be on the soldering iron tip.

The second method involves stripping the aluminum wire on medium-grit sandpaper directly under the influence of a hot soldering iron with solder and flux.

Gas burner

Processing with a gas burner is carried out when the parts are in the position relative to each other in which they will be used. The processing smoothly transitions into the soldering process itself.

This happens as follows:

the burner heats the surfaces of aluminum parts;
upon reaching the temperature at which the metal is reduced from the oxide, the film is mechanically peeled off;
under the influence of a flame, the parts are coated with flux, and solder is introduced into the soldering area.

If the parts are thick, then their edges must be cut at an angle of 45°. Typically, heating occurs to the melting point of tin, when the solder spreads and fills the twist groove.

Differences in technology when using flux

Thanks to the achievements of modern science and technology, flux compositions for aluminum have been obtained that actively dissolve the oxide film and protect the material from further oxidation.

Examples of such drugs are formulations labeled F-59A and F-61A. The letter A means that these compounds are intended for soldering aluminum.

When using these fluxes, soldering aluminum wires is greatly facilitated. It is enough to simply treat the finished twist with flux, without even heating it, and then, after heating it with a soldering iron or torch, apply solder.

It will spread over the entire surface of the wires and adhere well, providing a strong and electrically conductive solder joint.

Features of soldering stranded wires

Stranded wires must be soldered only using a special flux, since their mechanical processing is almost impossible. Soldering technology differs in that each wire must first be well treated with flux.

To do this, the bundle will have to be untwisted and fluffed. After processing, each thin wire conductor is covered with solder and the bundle is twisted. After this, twist the two ends and solder it.

Can it be connected to copper?

Situations often arise when it is necessary to connect an aluminum wire to a copper wire. This is perhaps the only case where soldering cannot be used.

Safety precautions

Safety precautions when soldering aluminum wires boil down to observing general precautions when working with electric heating devices, open flames and aggressive liquids, such as fluxes.

It is unacceptable to use faulty soldering irons with damaged insulation and with more power than necessary.

Do not use burners near flammable objects. When working indoors, forced ventilation must be properly organized.

Difficulties in soldering aluminum wires

The main difficulty when soldering aluminum wires, as indicated above, is the presence of an oxide film on the surface of the metal. Fighting it greatly slows down the soldering process.

And if you consider that aluminum wires are now used mainly for laying external power wiring, it becomes obvious that a regular soldering iron and sandpaper will not be enough in this case. Welding is increasingly being used to connect such wires.

How to solder aluminum and copper

The procedure for soldering aluminum elements at home is a very problematic process, which is facilitated by the use of special materials.

The work is complicated by the immediate appearance of a thin oxide film at the stripping site, which interferes with soldering. An additional difficulty is created by the material itself, which has a low melting point (+660 °C).

Using solder for soldering aluminum, special strong fluxes and following technology, you can independently solder almost any aluminum object.

Features and principles of soldering

The low temperature value of metal melting complicates the technological process of soldering, as well as repairing products with your own hands.

Parts very quickly lose strength when heated, and structures reduce stability when the temperature reaches 300 degrees.

Low-melting solders consisting of bismuth, cadmium, indium, and tin come into difficult contact with aluminum and do not provide sufficient strength. Excellent solubility is observed in the metal in combination with zinc, which makes the soldered areas highly reliable.

Before soldering begins, aluminum elements are well cleaned of oxides and dirt. To do this, you can use mechanical force with brushes or use special fluxes made from a potent composition. Before the procedure itself, be sure to tin the areas to be treated.

The tin coating will protect the part from the formation of oxides. In order to reliably solder aluminum products, it is necessary to choose the right heating tool, taking into account the volume of metal being processed.

In addition, the reliability of the connection depends on the alloy chosen, as well as the flux for soldering aluminum.

Soldering methods

Soldering of aluminum products is carried out with an electric soldering iron, a blowtorch or a gas torch. There are three ways to solder various aluminum objects:

with rosin;
using solders;
electrochemical method.

With rosin

This option for soldering aluminum objects, wires, cables is used for small parts.

To do this, the cleaned section of the electrical wire is covered with rosin and placed on a piece of sandpaper with a medium grain size. The wire is pressed from above with the tinned tip of a heated soldering iron.

This action is carried out several times, after which the procedure of soldering the electrical wires itself is performed. You can use a rosin solution in diethyl ether.

In this case, the end of the soldering iron is not removed from the end being tinned, but rosin is added on top. An electric soldering iron with a power of about 50 W is suitable for twisting thin aluminum wires. With an aluminum thickness of about 1 mm, a 100 W soldering iron is required, and parts larger than 2 mm require preheating of the joint.

Using solders

This method is the most common and is used in electrical engineering, in the repair of automobile parts, as well as other products. Before soldering aluminum, the area to be soldered is pre-coated with an alloy and the tin-plated elements are subsequently connected. Pre-tinned parts are connected to each other, as well as to other alloys and metals.

Soldering of elements can be carried out using light alloy solders containing tin, zinc, and cadmium. In addition, refractory materials based on aluminum are actively used.

Why are light alloy compounds used? Because they allow you to solder an aluminum product at temperatures up to 400 degrees. This does not produce qualitative changes in the properties of the metal and maintains its strength.

Compositions with cadmium and tin do not create sufficient contact reliability and are susceptible to corrosive effects. Refractory materials containing zinc, copper, and aluminum-based silicon do not have these disadvantages.

Electrochemical method

This procedure requires a plating facility. With its help, copper plating is carried out on the surface of a product or wire. In its absence, independent processing of the part is used.

To do this, apply a few drops of a saturated solution of copper sulfate to the area cleaned with sandpaper.

After this, the negative pole of an independent power supply is connected to the workpiece.

They can be a battery, an accumulator, or any electrical rectifier.

A cleaned copper wire with a diameter of about 1 mm, located in an insulated stand, is connected to the positive terminal.

During the electrolysis process, copper will gradually deposit on the part, after which the area is tinning and dried using an electric soldering iron. After this, you can easily solder the tinned area.

Solders, materials, fluxes

Soldering of aluminum with tin is carried out subject to the use of highly active fluxes, as well as good cleaning of parts of the parts. Such tin compounds require additional coating with special compounds, since they have low strength and poor protection against corrosion processes.

How to solder aluminum elements? High-quality solder joints are obtained by using solders with silicon, aluminum, zinc, and copper. These materials are produced by both domestic and many foreign manufacturers.

Domestic brands of rods are represented by the most used solders TsOP40, which according to GOST contain 60% tin and 40% zinc, as well as 34A (aluminum - 66%, silicon - 6%, copper - 28%). The zinc used gives high strength to the contact area and provides good corrosion resistance.

These alloys are used to work with large-sized parts (radiators, pipes) with high heat dissipation using a heating pad or objects made of aluminum alloys that have a fairly high melting temperature. Novice repairmen can familiarize themselves with the soldering process by watching an instructional video. This will help to avoid many unpleasant nuances during the work process.

In addition to solders, aluminum soldering requires the use of special fluxes containing ammonium fluoroborate, zinc fluoroborate, as well as triethanolamine and other elements.

The most popular is the domestic F64, which has increased chemical activity. It can be used even without first removing the oxide film from products.

In addition to it, 34A is used, containing lithium, potassium and zinc chlorides, as well as sodium fluoride.

Preparation of products

Reliability, as well as excellent quality of connections, is ensured not only by using the right technology, but also by preparatory work. These include the treatment of sealed surfaces. It is necessary to remove contaminants and thin oxide films.

Mechanical processing is carried out using sandpaper, a metal brush, stainless steel wire mesh or a grinding machine. In addition, various acid solutions are used for cleaning.

Surface degreasing is carried out using solvents, as well as gasoline or acetone. On the cleaned aluminum area, an oxide film appears almost immediately, but its thickness is significantly lower than the original one, which facilitates the soldering process.

Heating tools

How to solder aluminum at home? Electric soldering irons are used to solder small-sized aluminum products at home. They are a universal tool, quite convenient for soldering wires, repairing small tubes and other elements.

They require a minimum of working space, as well as the presence of an electrical network. Repair of large-sized products and welding are performed with a gas torch that uses argon, butane, and propane.

To solder aluminum objects at home, you can use a standard blowtorch.

When using gas burners, it is necessary to constantly monitor their flame, which characterizes a balanced supply of oxygen and gases. With the correct gas mixture, the fiery tongue has a bright blue color. A dim hue, as well as a small flame, indicate an excess of oxygen.

Technological process

The technology for soldering aluminum objects is similar to the process of joining parts of other metal materials. The first step is to clean and degrease the areas of future adhesion. Then the connected elements are installed in working position for ease of processing.

Flux is applied to the prepared area, and the initially cold product begins to heat up using an electric soldering iron or a torch. As the temperature rises, the solder bar begins to melt, which must constantly touch the surface of the elements, controlling the heating process.

Soldering aluminum elements at home with an electric soldering iron is done in a well-ventilated room, as hazardous compounds are released during operation.

Using flux-free solder requires compliance with some nuances. To prevent the oxide film from interfering with the alloy getting onto the parts, the end of the rod makes scratching movements along the area where the elements are soldered. This breaks the oxide integrity and the solder comes into contact with the metal being processed.

Destruction of the oxide layer during soldering can be done using another method. To do this, the area to be treated is scratched with a metal brush or a stainless steel rod.

To ensure maximum strength of aluminum parts in the soldered area, the treated areas are pre-tinned. Compliance with the technology of soldering aluminum elements guarantees excellent quality of the connection, as well as its protection against corrosion.