Soldering strands of aluminum and copper wire

So, let's talk about how to solder aluminum. Those who have faced this task know that aluminum is difficult to solder. This is due to a thin oxide film that quickly forms on the surface of this metal in the open air. Therefore, special fluxes are used for soldering aluminum. I will demonstrate the aluminum soldering process using the example of tinning and soldering strands of wire.
When installing electrical wiring, I always prefer solder connections. I believe that this method provides better electrical contact compared to conventional twisting of wires without soldering or crimping them into a sleeve or tip.
Soldering strands of aluminum and copper wire

Required tools and materials


We will need:
  • a regular soldering iron with a power of 40 watts;
  • knife for stripping and stripping wires;
  • flux for soldering aluminum (F-61A, F-59A, F-64, etc.);
  • a solution of rosin in acetone or alcohol;
  • lead-tin solder;
  • trimming aluminum and copper wires with a cross-section of 2.5 - 4 square meters. mm.

Soldering strands of aluminum and copper wire

Let's start soldering


Soldering twisted aluminum wires


Let's start by soldering twisted aluminum wires.Before twisting the wires, you need to make sure that the surface of the aluminum conductors is clean. Otherwise, you need to strip the wire with a knife. The surface of the wire should be light silver, not dark gray.
Soldering strands of aluminum and copper wire

We twist with pliers.
Soldering strands of aluminum and copper wire

For soldering aluminum we use a special flux. It may have a specific brand F-61A, F-59A, F-64, etc., or simply be called “flux for soldering aluminum.” A 25 ml bottle costs approximately 45 rubles and will last a long time.
Soldering strands of aluminum and copper wire

Using a brush, apply a thin layer of flux to the twist on all sides.
Soldering strands of aluminum and copper wire

Wet the soldering iron tip, heated to operating temperature, with solder by lightly touching it. Stroking the twist with the working surface of the tip, apply solder to it.
Soldering strands of aluminum and copper wire

Solder and aluminum are similar in color, but this does not prevent you from observing how the solder spreads over the surface of the wires, filling the gaps between them. You should not overdo it with the amount of solder; a thin layer on the surface of the aluminum is sufficient; frozen drops should be avoided.

Soldering copper twist


Soldering strands of aluminum and copper wire

I solder copper strands in the same way, only the flux in this case is a solution of rosin in acetone. I prepare it as follows. I pour about 30 ml of acetone into the bottle and gradually add rosin, previously crushed into powder, into it. By stirring I achieve complete dissolution of the rosin. As a result, the solution should acquire the color of weak tea. I also apply flux with a brush; the consumption of rosin is negligible, and thanks to the fluidity of acetone, the solution penetrates into the smallest crevices. If you use undissolved rosin, it doesn’t work out so neatly; the excess then has to be removed.
Soldering strands of aluminum and copper wire

Twisted copper and aluminum wire


Soldering strands of aluminum and copper wire

When installing electrical wiring, it is prohibited to directly connect wires with current-carrying conductors made of copper and aluminum. As a result of electrochemical processes, an oxide film is formed at the interface between these metals, which increases the contact resistance. The presence of moisture activates the reaction. As a result, the junction begins to heat up, which further accelerates the corrosion process. Copper and aluminum are connected through a third metal. Typically, a bolted connection is used with a steel washer installed between the wires, or special clamps that prevent direct contact of the wires.
Soldering strands of aluminum and copper wire

Soldering strands of aluminum and copper wire

If it is necessary to connect wires with copper and aluminum conductors, I proceed as follows.
Soldering strands of aluminum and copper wire

I pre-tin the copper and aluminum wires that need to be connected, that is, I cover them with a thin layer of solder.
Soldering strands of aluminum and copper wire

Soldering strands of aluminum and copper wire

At the same time, I use a different flux for each metal, but I use the same solder. After that, I twist the wires and solder the twist on the outside. As a result, the copper and aluminum wires are connected through a layer of solder separating them. Tin and lead included in the solder are chemically neutral to copper and aluminum, which eliminates the occurrence of electrochemical corrosion. The outer layer of solder applied to the twist seals the contact and protects it from external influences.
Soldering strands of aluminum and copper wire

Sometimes you can hear the opinion that soldering twists carries a potential danger. It is believed that when the twist is overheated, the solder melts and, as it drips, damages the insulation of other wires. Let's figure this out.
Soldering strands of aluminum and copper wire

The twist itself, especially when soldered, provides an area of ​​electrical contact that is several times larger than the cross-section of the main wire.This means that when the electrical wiring is overloaded, the heating of the twist will be minimal. In this case, the wire will overheat along its entire length, which can lead to melting of the insulation much earlier than melting of the solder. The reason for this situation is not the presence of twisting or soldering, but the absence of a circuit breaker or its incorrect choice.
As for the “destructive” effect of molten solder, during the soldering process you can make sure that drops of it that accidentally fall from the soldering iron tip do not even burn through the newspaper on the table.

Conclusion


When performing soldering, follow basic safety rules. Working with an electric soldering iron involves the following dangers:
  • electric shock if it malfunctions (phase breakdown on the body and soldering iron tip);
  • the possibility of getting a burn (the melting point of lead-tin solders is about 200°C).

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Comments (22)
  1. Akril
    #1 Akril Guests 8 April 2019 14:33
    5
    In life everything is much more prosaic and simpler than on the screen.I haven’t seen a single electrician soldering strands of wiring, it’s pure nonsense and may only be useful for a bet on whether I can solder it or not. Judge for yourself, the twisting is done within 5-10 seconds, and how long will the hoop warm up, how many preparations must be made to solder it, and if there are hundreds of them, where will you stock up on so much solder and flux?
    1. Evgeniy Danilov
      #2 Evgeniy Danilov Guests 8 April 2019 16:46
      1
      And if you also take into account how much fluorine is inhaled by acetone...
    2. Konstantin Sokolov
      #3 Konstantin Sokolov Guests 8 April 2019 20:28
      4
      As far as I understand, there is twisting of aluminum with copper... Such twisting without soldering will not last long, it will spark and burn out.
      1. Vita
        #4 Vita Guests April 9, 2019 09:39
        4
        Konstantin, carefully study the essence: that’s what soldering is for. But in this case, I would not recommend using acid. Moreover, the result may be the same without it (chemistry). Well, you need to be able to twist it correctly.
    3. Vita
      #5 Vita Guests April 9, 2019 09:58
      7
      In vain, you are. Twisting can be good or bad, but the contact should always be good, especially at high currents. With soldering it is more reliable, and even better is welding the end of the twist.
  2. Guest Vitaly
    #6 Guest Vitaly Guests 8 April 2019 16:57
    10
    An electrician, of course, will not bother with soldering, because he has a flow and does not have time to lick every wire.
    The advice given here is not for electricians, but for ordinary people who need to do it efficiently, reliably, for themselves. And not yet, there are 1-2-10 twists, which can easily take 10-20 minutes.
  3. Guest Sergey
    #7 Guest Sergey Guests April 10, 2019 08:12
    4
    I have been working with electrical and electronics almost all my life. Soldered twist, as practice shows, is an extremely reliable connection.Crimping and bolted connections cannot be compared in any way. But in the case of copper and aluminum, I would refrain from such a decision (possibly only in case of emergency).
  4. Konstantin
    #8 Konstantin Guests 10 April 2019 14:38
    1
    On an industrial scale, for example, when constructing electrical wiring for multi-storey buildings, installation companies twist wires in junction boxes and duplicate these same connections by welding conductors with special equipment, this gives a more reliable connection for almost the entire service life.
    1. Dmitry Spitsyn
      #9 Dmitry Spitsyn Guests 11 April 2019 14:50
      0
      It is unlikely that copper and aluminum will be welded. The author's idea is good. But most likely you won’t find flux for aluminum on hand, and without it you can’t tin the aluminum.
  5. Guest Yuri
    #10 Guest Yuri Guests 11 April 2019 08:45
    0
    IMHO. Copper twisting under PPE will cope with any task if the cable cross-section is chosen correctly. Probably up to 90% of the wiring connections in apartments have been done this way, and everything works.
    1. Vita
      #11 Vita Guests 11 April 2019 20:43
      3
      Yuri, you know that at first you abandoned aluminum, and now, due to the copper shortage, you have decided to return to it again. Aluminum and copper are not compatible: electrocorrosion, especially in humid environments. Soldering is basically a mechanical and chemical protection of the twist.
      1. Akril
        #12 Akril Guests April 12, 2019 11:19
        2
        It’s not all so critical that it’s directly incompatible, under normal conditions of indoor lighting, for example, why not? I installed old aluminum wiring, updated it with new copper, and in 10 years nothing has happened. Even with a load of 2 kW of appliances such as a kettle or a vacuum cleaner, the only boiler on a separate power unit works without any rations. And so, in life no one bothers with this.
        1. Alexey 163
          #13 Alexey 163 Guests 7 July 2019 22:36
          4
          Well, wait! HE usually comes unexpectedly! )
          But in real life, NOBODY does that!

          PS: electrician, 20 years of experience, installation + maintenance...
  6. Ruslan
    #14 Ruslan Guests 12 September 2019 16:06
    2
    Electrocorrosion occurs only in a wet state and when there is an electrolyte in the external circuit, for example alkali or water, if the room is dry, then the twist between aluminum and copper will live forever, if the walls are damp, then only copper wiring is better. As a last resort, you can protect the twist with Vaseline oil, as electricians often do, but in my opinion this is limited to one place.
  7. Energetik
    #15 Energetik Guests 2 November 2019 20:49
    0
    copper and aluminum... the material must be homogeneous!
  8. Guest Alexey
    #16 Guest Alexey Guests 11 January 2020 02:35
    0
    I wonder what kind of education the author of this article has, and whether he has any idea about documents such as PUE?
    Does he have any idea about such a thing as a galvanic couple? It is precisely because of the formation of a galvanic couple that a direct connection of a copper/aluminum pair cannot be made.
    Does anyone have any idea that the electrical resistance of a tin-soldered connection is tens of times greater than the resistance of a crimped or welded connection of conductors?

    So, for the installation of 220V household wiring with a single-core wire, connection methods by crimping, as well as twisting with welding of the end of the twist, are acceptable.
    You can, of course, get confused by soldering twisted copper with high-temperature copper solder, but this is a rather complicated and fire-hazardous process, and it is unlikely that anyone will do it.
    But connection by soldering with tin is clearly prohibited. Due to its electrical and mechanical unreliability.

    So for those who do not want to experience rather unpleasant consequences, even a fire, 10-20 years after soldering the wiring, I offer two simple and very technologically advanced ways to connect conductors:
    1) The fastest and most technologically advanced for a small amount of work is crimping a connection using a GML-type sleeve and special pliers (mechanical or hydraulic). The method is 100% reliable, has no contraindications, and does not require special skills. All you need is to purchase press pliers and sleeves for crimping.
    2) A less technologically advanced, but equally reliable method is twisting with welding of the end of the twist. First, the conductors are twisted, and then the end of the twist is welded using a special welding machine with a carbon electrode. The disadvantages of this method are the need to purchase (or manufacture) a special resistance welding machine and the need to learn how to set up and use it. But, we must pay tribute, this method will be faster for mass installation.

    The reliability of both methods is 100% and the service life of such connections is limited only by the service life of the connected wires.
    1. Guest Andrey
      #17 Guest Andrey Guests 24 May 2023 13:24
      0
      I was surprised, maybe I don’t remember something.
      I wasn’t too lazy, climbed in and found the PEU-7.
      2.1.21. Connection, branching and termination of wires and cables must be made using crimping, welding, rations or squeezes (screw, bolt, etc.) in accordance with current instructions approved in the prescribed manner.
  9. Engineer
    #18 Engineer Guests 15 January 2020 15:00
    0
    Not bad idea. To spite the critics, this is a real-life situation. Al is coming from my post.wire, and copper to the meter (done by a certified electrician from RES, yeah, twisted it and everything is ready, pay a little money). Every six months, all this shit burns off for me. I tried both on terminal blocks and on bolts, up to one place, only the wires were shortened. If it burns out next time, I’ll try to solder it using the suggested method.
  10. Sergey
    #19 Sergey Guests 9 April 2020 02:18
    2
    All this is soldered with ordinary rosin - no need to reinvent the wheel
    1. Gogivan
      #20 Gogivan Guests March 16, 2021 01:37
      2
      Daragoy, I’ll tell you one hell of a smart idea, yes, just don’t be offended. This rosin is a FLUX, they don’t solder with it at all :)