When you are joining two wires together to make an electrical connection the best method is soldering, and correct soldering technique is important to make sure you get a good electrical connection as well as a strong mechanical connection. You do have to follow the right procedure to make the best connection possible, so that’s what we’re going to explain here with step-by-step instructions on how to make an effective soldered wire joint first time, and every time.
What is the correct procedure for soldering wires together with a soldering iron?
It might look like there are a lot of steps to making a good soldered connection using a gas soldering iron, but none of them are difficult or complicated. It is important to follow the sequence and take a bit of care to get each step done correctly, but once you have done it a few times it will become second nature.
- Work out how much exposed wire you will need
- Strip the insulation from the ends of the wires
- Twist each exposed wire end to keep the wires bundled together
- Cross the exposed twisted wires at the half-way point and wrap them around each other
- Make sure there are no stray wires sticking out that will puncture heatshrink or tape insulation later
- Make sure you have a chisel tip on your soldering iron
- Heat up the soldering iron to working temperature
- Apply a small amount of solder to the soldering iron tip
- Hold the flat chisel tip to the underside of the wire join
- Hold your solder to the other side of the wire join and wait for the heat to penetrate
- When the solder melts into the wires, feed it evenly into the twisted wire join and fill the gaps
- Remove the soldering iron and solder and wait for the connection to cool
- Slide your heatshrink insulation sleeve over the join
- Apply heat to the heatshrink with the soldering iron heater tip to seal the joint
How do you know how much exposed wire you will need to join your wires?
It is important to remove the right amount of insulation. You need to expose enough wire to be able to twist the exposed ends around each other to make a secure mechanical connection before soldering. This means that with lighter gauge wires commonly used for electrical and electronic work you will need to have at least ½” of exposed wire for the lightest gauges and 1” exposed for heavier gauges.
You may think you have too much wire showing, but remember that when you twist it together the result will be a bit less than the length of one side, and the standard tool for doing the twisting is your fingers, so make life easier for yourself by leaving more exposed than less.
What are the key points for soldering electrical wires together?
The important thing to remember when using a gas soldering iron to join electrical wires with solder is that you need to apply the heat to the wires, not to the solder. A common error is to melt a blob of solder on the chisel tip and then smear it onto the wire joint. This does not work because the molten solder simply freezes on contact with the wires and makes a superficial connection that has no strength.
- Heat the wires, not the solder
- Use a small amount of solder on the tip to improve heat transfer
- Apply the solder to the opposite side of the wire bundle
- Watch to see the solder flow into the wires
- Stop feeding the solder in immediately the joint is full of solder
To get the solder to properly connect the wires both mechanically and electrically, the wires need to be an extension of the soldering iron tip, with the solder melting onto the wires and flowing between them to make the connection. To do this you need to heat the wires and not the solder. It does make it easier to heat the wires if the soldering iron tip is not completely dry when you start, so you should apply a thin coat of solder to the tip before touching it to the wire bundle.
Should you use heatshrink to seal your soldered connection?
It’s a good idea to use heatshrink to seal your soldered connection, especially for household wiring, marine and vehicle connections to avoid problems with corrosion in the future. Heatshrink is quick and reliable compared to wrapping with electrical tape, which can be impossible in confined spaces with closed connection loops.
Good practice when preparing your heatshrink
It’s good practice to slide the heatshrink sleeve onto the wire to be joined before you make the soldered connection even if you will have a free end afterwards. If you make this your standard way of setting up for heatshrink you won’t be caught out when connecting wires that make a closed loop.
What type of gas soldering iron is good for soldering electrical wire?
You need enough power to heat the wire bundle rapidly and maintain the heat transfer through to melt the solder into the wire. This makes a high power gas soldering iron like the Iroda SolderPro 110K a good choice as it gives you the option of adjusting the power level up or down to match almost any scale of wire connection. The cable-free gas powered operation makes it easier to get into awkward and confined spaces than an electrical soldering iron, which is an additional advantage.
