How to Solder Wires
The main function of a wire is to conduct electrical current. The most basic connection in electronics is wire to wire. Many times you will need to solder wires to each other or directly to an electronic component. How to solder wires depends on the size of the wire and available tools.
The wires should be soldered to assure a permanent connection. The connections should be covered to protect them against shorting and oxidation.
There are two kinds of wires:
The solid wire has only one strand while stranded wire has multiple strands twisted together.
The first step in soldering two wires together is the removal of the insulation.
Stripping the insulation
Wire stripping is a process of cutting and removing insulation from the wire. The wire underneath of insulation should stay undamaged.
We may remove insulation from the ends of the wire with wire strippers.
Using a knife to strip the insulation is an unacceptable method since the knife will certainly damage a wire.
Professional wire strippers are the best wire stripping tool. It comes with a gauge slot and draws the wire and insulation apart as it cuts.
Now you have a deep groove in the insulation jacket. Keep holding wire strippers a little less tightly and pull with stripper’s jaws towards the end of the wire. That will pull the section of insulation you want to remove away from the wire.
You should have an exposed section of wire ready for soldering.
A wire could be damaged during a wire stripping operation if an incorrect tool or technique is used.
Wire strippers usually come with a gauge index. You should run the wire through the appropriate gauge slot. Grasp the wire with the jaws of the wire strippers at the cutaway point. Clamp the jaws of the wire strippers down.
The wire should be pulled perpendicular to the wire strippers. It may be helpful to use a rotating motion to cut most of the way through the outer insulation.
Insulation from wire-wrap wire can't be removed with wire strippers since this wire is very thin (30 AWG).
A wire-wrap tool should be used to remove insulation from this wire.
Most of the damages to solid wire result in scraping the surface of the wire. During manufacturing in the factory, the surface of copper wire is plated with a thin layer of another metal (usually tin) to protect the copper from oxidation. When this plating is scraped, the copper is exposed to oxidation.
If you cut into the wire you will decrease the electrical and mechanical capabilities of the wire. It will decrease the cross-section of the wire for a current flow and therefore the wire becomes less conductive.
Preparation for Soldering Wires
You don’t need one of the fancy soldering stations for soldering two wires together. However, don’t use the cheapest soldering iron on the market because you may save a few dollars. Too many times I have seen soldering projects ruined by people‘s attempts to use cheap irons.
You can buy a decent temperature-controlled iron for around 50 dollars and use it later for other soldering projects such as soldering wires to circuit boards.
In any case, you will need a soldering iron with interchangeable tips for a variety of wire sizes and heat ranges.
You can use an iron with a small tip for soldering wires with a smaller diameter.
Use a large tip for soldering wires with large diameters since heavy soldering joints need more heat.
Keep iron in the iron stand whenever is not in use.
Solder in a well-ventilated area or use a bench-top fume absorber (also known as smoke extractor}.
Soldering wires don’t require many tools. You will need some specific items such as wire strippers, wire cutters and helping hand tool. These tools are not expensive, it is easy to find them and learn how to use them.
Heat-shrink is flexible plastic tubing that comes in various diameters. It will shrink 50% or more when heat is applied to it. Heat-shrink is used to insulate wires.
Cut a piece of heat-shrink tube that is long enough to cover the junction of two wires.
Insert the shrinking tube on the wire before soldering.
Once when two wires are soldered and connected, you will not be able to put a shrinking tube on the wire if the other end of the wire is already connected.
How to tin wire
Tinning the wires is the next step. Any wire that will be connected to another wire or circuit board should be tinned. Tinning should be done before the wire is connected.
It is recommended to use a soldering helping hand or similar tool which will hold the wires.
It would be a challenge to solder wires together by laying them directly on your workbench. You will burn your workbench and produce bad solder joints.
For wire tinning, choose a chisel tip 3/32” (2.38 mm).
Replace the iron tip before turning on the iron (while the iron is still cool).
Turn on the soldering iron and wait until is fully heated. If using temperature controlled soldering iron, set temperature in the range 660-750 °F (350-400 °C).
Add some water to the sponge in the iron stand to make it moist.
Add a small amount of rosin flux to the end of the wire. Rosin flux (also known as calophonium) is made from pine tree resin.
Touch the iron’s tip to one end of the wire close to insulation, hold for a couple of seconds. The rosin flux will melt and start smoking. That is an indication the flux is activated.
Now you can start adding the solder. The solder should be applied to the wire, not to the iron’s tip.
Slide iron’s tip towards the end of wire i.e. away from insulation. When using this tinning technique, no solder will be pushed up under the insulation. Leave a small gap between the end of the insulation and the beginning of the tinning.
Continue tinning until the wire end is fully coated. The wire should be shiny after tinning.
Repeat this step on the other wire.
How to Solder Wires Together
After tinning both wires, we will connect them and later solder them.
Connecting wires can be divided into two groups: butt splices and tap splices. Butt splices are any connections in which wires are connected end to end while tap splices are those connections in which one wire is inserted into an existing wire run.
How to solder solid wire to solid wire
The simplest way of connecting two solid wires is the pigtail splice. For this connection you should:
How to solder stranded wire to solid wire
Soldering stranded wire to solid wire is a little bit more difficult than soldering stranded wire to another stranded wire or soldering solid wire to another solid wire.
When soldering a stranded wire to solid wire you should:
How to solder stranded wire to stranded wire
Mesh splice technique
Another way of connecting two stranded wires is the mesh splice technique. For this connection you should:
How to solder two wires together
Another technique of soldering two wires together is the lap splice. This technique is good for both, stranded wires and solid wires.
When soldering wires with a big diameter, it is not easy to bend or twist them. So the following technique may be a good technique when soldering ticker wires.
Lap splice technique
Sometimes, it will be required to make several wire connections in the same area.
In this case, the recommendation is to stagger the connections. The junction of wires is thicker than the wire itself. Concentrating all connections in the same point creates a thick bulge and in some cases may lead to a short circuit.
How to solder wires to components
Many electronic components have terminals for connection. They are usually mounted on a front panel or a chassis of an electronic device as external components and should be connected with wires to the rest of the circuit on the PCB (printed circuit board).
These components are switches, potentiometers, audio sockets and other connectors, speakers, buzzers and more.
For this type of connection (wire to terminal) is better to use stranded wire than solid wire since it is more flexible and vibration-resistant. Solid wire can be used as well, but it is easier to work with stranded wire.
For successful soldering, both surfaces should be clean: the terminal and the wire. Inspect terminals of the component and ensure that they are clean. If not, use isopropyl alcohol or other approved cleaner to remove all contamination.
If an electronic component has been in storage for a long time, it may have more contamination and oxidation caused by environmental factors.
Use a glass-fibre brush, paintbrush or other plastic brush to remove stubborn contamination. (don’t use sandpaper or steel brush).
Place component to be soldered in the helping hand tool or another holder to keep the component in place while soldering.
The same techniques of soldering apply to most of the external electronic components that come with terminals. The two most popular techniques of soldering wires to terminals are explained below.
This technique is a quick and easy way of soldering wire to the terminal.
It is also easier to de-solder the connection if needed when replacing the component or repairing the device.
It provides a good and reliable connection in most of the applications in the electronics industry. Those are the reasons why this technique is used in the majority of wire-to-terminal joints in commercial electronic devices.
Technique for a stronger connection
How to solder wire to board
Wires could be connected directly to the metalized holes on the circuit board.
In the first step, you should tin the end of the wire. The metalized holes have already been pre-tinned with a thin layer of solder in the factory during manufacturing.
Tinning is the action of melting a bit of solder onto the wire end first before soldering it to the circuit board.
Tinning ensures that the end of the wire is without oxidation and it allows the solder to attach faster to finish with a far better result.
Stranded wires should be twisted with fingers prior to tinning.
After tinning the wire, insert the wire into the metalized hole on the circuit board.
Place tip of soldering iron to the solder joint.
After a couple of seconds apply a very small amount of solder to the solder joint.
Use a solder wire which contains rosin flux in its core to minimize oxidation during soldering.
The wire’s insulation may shrink back a little bit caused by the heat of soldering iron, so do not overheat the soldering joint by keeping solder iron for a longer time than is required.
Remove soldering iron and wait a few more seconds for solder to solidify.
Clean solder joint from flux residues using alcohol or flux remover pen.
Stranded vs solid wire
A wire is the most commonly used conductor type in electronics.
Wires are made of metal. Each type of metal has certain benefits and shortcomings.
The majority of wires are made of copper. Copper has very low resistance to current flow and relatively low costs.
Aluminum is also a good conductor so some wires are made of aluminum. Since aluminum has lower conductivity than copper, the aluminum wire needs a larger cross-section to compensate. The majority of aluminum wires are used in residential electrical systems.
Silver is the perfect conductor. It is a much better conductor than copper. However, silver is too expensive for wire production.
Some electronic components have their pins plated with a very thin layer of gold, however, no wires have been made of gold.
All wires are divided into solid wires and stranded wires. Each wire has advantages and deficiencies.
Which wire is better to use: stranded vs solid wire.
Solid wire is easier to manufacture than stranded wire, so it is cheaper. The disadvantage of solid wire is that it may be bent only a few times without damage.
The stranded wire is more flexible than solid wire and it could be bent several times without damage. It is a better conductor at higher frequencies than solid wire because it has many strands. As the frequency increases, the current is forced to flow on the surface of the wire. More strands in stranded wire mean more surface area for current to flow at high frequencies.
In addition, wires can be divided:
The magnet wire has a very thin layer of varnish or enamel as insulation. It is often called “bare wire” since it comes without any plastic or rubber insulation and looks like bare wire.
If we use a bare wire for coils in transformers and inductors, we would not be able to make the turns of the wire without touching each other.
The adjacent turns of wire will touch each other and as result, they will make a short circuit. If we use insulated wire instead of bare wire, we can wound many turns of wire and don’t care if they touch each other.
For a wire that will have several turns, insulation is absolutely necessary.
Wires come in a variety of types and sizes. Some electrical circuits conduct higher electrical current so they need a ticker wire. The diameter of the wire determines the size of the wire.
American Wire Gauge (AWG) is a standard used in the United States and Canada as a measure of the wire size. Solid and stranded wires both use the same AWG standard.
A bigger AWG number means a smaller diameter of the wire. The most common gauge of wire used in electronics is AWG 22.
Selecting a wire with a proper AWG size is important in all circuit designs.
The selection of a proper gauge is based on the maximum current ratings for the circuit.
If the designer selects a too small diameter of wire it may lead to circuit failure.
Most of the wires come as insulated wires. The function of insulation is:.
High voltage can break insulation and make a short circuit. That is a reason why each wire must have specified a maximum operating voltage.
PVC (polyvinyl chloride), rubber and teflon are the most common insulation used on wires in electronics.
Sini is a passionate Electrical Engineer with over 40 years of experience in the electronics industry and in 3 countries. He holds B. Sc. in Engineering and is a member (P. Eng) of the Association of Professional Engineers of Canada.
Sini Saja wrote several articles on Instructables.com and EzineArticles.com. He earned a silver medal for over 1 million views on Instructables. See profile here.
Updated: July 27, 2021