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One of the most reliable ways to connect wires is soldering. This is a process in which the space between two conductors is filled with molten solder. In this case, the melting temperature of the solder must be lower than the melting temperature of the metals to be joined. At home, soldering is most often used with a soldering iron – a small device powered by electricity. For normal operation, the power of the soldering iron must be at least 80-100 watts.
What you need for soldering with a soldering iron
In addition to the soldering iron itself, solders, rosin or fluxes will be needed, it is advisable to have a stand. Even in the process of work, you may need a small file and small pliers.
Rosin and fluxes
To get a good connection of wires, it is necessary to clean them from contaminants, including oxide film. If mono-cores can still be manually cleaned, then stranded conductors cannot be cleaned normally. They are usually treated with rosin or flux – active substances that dissolve contaminants, including the oxide film.
Both rosin and fluxes work well, only fluxes are easier to use – you can dip the brush into the solution and quickly process the wires. It is necessary to put the conductor in rosin, then heat it with a soldering iron so that the molten substance envelops the entire surface of the metal. The disadvantage of using fluxes is that if they remain on the wires (and they remain), they will gradually corrode the adjacent sheath. To prevent this from happening, all soldering points must be processed – wash off the flux residue with alcohol.
Rosin is considered a universal remedy, and fluxes can be selected depending on the metal that you are going to solder. In the case of wires, this is copper or aluminum. For copper and aluminum wires, take LTI-120 flux or borax. Homemade flux from rosin and denatured alcohol (1 to 5) works very well, besides it is easy to do it yourself. Add rosin to alcohol (preferably dust or very small pieces of it) and shake until dissolved. Then this composition can process conductors and twists before soldering.
Solders for soldering copper wires with a soldering iron use POS 60, POS 50 or POS 40 – tin-lead. For aluminum, zinc-based compounds are more suitable. The most common are TsO-12 and P250A (from tin and zinc), grade A (zinc and tin with the addition of copper), TsA-15 (zinc with aluminum).
It is very convenient to use solders, which include rosin (POS 61). In this case, there is no need to pre-treat each conductor in rosin separately. But for high-quality soldering, a soldering iron must be powerful – 80-100 W, which can quickly heat up the soldering place to the required temperatures.
auxiliary materials
In order to normally solder wires with a soldering iron, you also need:
- Stand. Maybe it is made of metal completely or metal holders for a soldering iron are fixed on a wooden / plastic stand. It is also convenient if there is a small metal box for rosin.
Soldering with a soldering iron is more convenient with a home-made and factory stand – not very important - File. Before work, they sharpen the soldering iron. It should be smooth and clean without any traces of soot. Then it melts easily.
How to sharpen a soldering iron tip - Pliers. It is difficult to hold the wires with your fingers while soldering – copper and aluminum have a high thermal conductivity, which leads to rapid heating of nearby areas. Therefore, it is more convenient to solder wires with a soldering iron if they are held with pliers. Only the tool must be miniature, with thin handles and sponges. In principle, you can use tweezers, but it is advisable to put a heat shrink tube on its top (where it is held with your fingers) – steel also heats up quickly.
Pliers – to hold the wires
Alcohol may be required to flush the flux, and electrical tape or heat shrink tubing of various diameters may be required for insulation. That’s all the materials and tools without which soldering wires with a soldering iron is impossible.
Soldering process with an electric soldering iron
The whole technology of soldering wires with a soldering iron can be divided into several successive stages. All of them are repeated in a certain sequence:
- Conductor preparation. When soldering wires, they are released from insulation. After that, the oxide film is mechanically removed from them. You can use a small piece of fine grit sandpaper. The metal should shine and be light.
- Tinning. The soldering iron is heated to the melting point of rosin (when touched, it begins to actively melt). They take a conductor, bring it to a piece of rosin, heat it with a soldering iron so that the entire stripped part of the wire is immersed in rosin. Then a drop of solder is taken on the tip of the soldering iron and spread over the treated part of the conductor. The solder spreads quickly, covering the wire with a thin layer. To make it spread faster and more evenly, the wire is turned a little. After tinning, copper conductors lose their redness, becoming silvery. This is how all the wires that need to be soldered are processed.
Wire tinning - Tinned conductors are folded together, adjusting them with your fingers so that they fit snugly against each other. If the soldering should be of great length, twisting can be done. Holding the conductors, they take solder on the tip, press it to the place of soldering, applying some force. At the same time, the place of soldering warms up, the rosin begins to boil, the solder spreads. When it covers the entire area, flows between the conductors, we can assume that the soldering of the conductors with a soldering iron is completed. They are kept still for some time – until the solder cools down (to speed up the process, they blow on this place).
That’s all. In the same way, you can solder two or more wires, you can solder the wire to some contact pad (for example, when soldering headphones, you can solder the wire to the plug or to the pad on the earphone), etc.
After you have finished soldering the wires with a soldering iron and they have cooled down, the connection must be insulated. You can wind the electrical tape, you can put it on, and then heat up the heat shrink tube. When it comes to electrical wiring, it is usually advised to first screw a few turns of electrical tape, and put on a heat shrink tube on top, which is warmed up.
Differences in technology when using flux
If an active flux is used rather than rosin, the tinning process changes. The cleaned conductor is lubricated with the composition, after which it is heated with a soldering iron with a small amount of solder. Further, everything is as described.
There are differences when soldering twists with flux. In this case, you can not tin each wire, but twist it, then process it with a flux and immediately start soldering. Conductors can not even be stripped – active compounds corrode the oxide film. But instead, you will have to wipe the soldering points with alcohol to wash off the remnants of chemically aggressive substances.
Features of soldering stranded wires
The soldering technology described above is suitable for monofilaments. If the wire is stranded, there are nuances: before tinning, the wires are untwisted so that everything can be dipped in rosin. When applying solder, make sure that each wire is covered with a thin layer of solder. After cooling, the wires are again twisted into one bundle, then you can solder with a soldering iron as described above – by dipping the tip into the solder, warming up the place of soldering and applying tin.
Is it possible to solder copper wire with aluminum
The connection of aluminum with other reactive metals cannot be done directly. Since copper is a reactive material, copper and aluminum are not joined or soldered. The point is too different thermal conductivity and different current conductivity. When current is passed through, aluminum heats up more and expands more. Copper heats up and expands much less. Constant expansion / contraction to varying degrees leads to the fact that even the best contact is broken, a non-conductive film is formed, everything stops working. Because copper and aluminum do not solder.
If there is such a need to connect copper and aluminum conductors, make a bolted connection. Take a bolt with a suitable nut and three washers. At the ends of the wires to be connected, rings are formed according to the size of the bolt. They take a bolt, put on one washer, then a conductor, another washer – the next conductor, on top – a third washer and fix everything with a nut.
There are several other ways to connect aluminum and copper lines, but soldering is not one of them. You can read about other methods here, but bolted is the simplest and most reliable.