How to Solder Wires to Terminals
How to solder wires to terminals depends on the type of wire and type of terminals.
Updated: April 08, 2021
There are two kinds of insulated wires: solid wires and stranded wires. In any case, the wire must be stripped of its insulation before soldering to the terminal.
The stripping of wire can be performed using various tools. The best way to strip insulation of the wire is with professional wire strippers (shown in the picture).
The wire stripper tool is properly calibrated to control the depth of the cut. Wire strippers provide a clean strip without any damage to the wire. Most of the wire strippers can remove insulation from wires which gauges are in the range 10 AWG – 22 AWG. The gauge of wire is usually printed on the wire.
You do not buy professional wire strippers if you use them occasionally for your hobby. Decent commercial wire strippers (shown in this image) are an inexpensive tool and could be good enough for most of your hobby projects.
You must use the correct stripper notches on the wire strippers for the wire gauge being stripped. If you use a wire notch that is smaller than the wire gauge you may damage the wire - you may cut and remove a few strands of stranded wire.
However, never use an executive knife to strip the insulation from the wire. This tool will cause damage to the wire.
Don’t use wire cutters with V-shaped notches. to remove the insulation from the wire. The wire has a round cross-section and a V-shaped notch doesn’t fit the round wire. As result, wire cutters with V-notch will scratch the surface of the wire.
Tin wires before soldering to terminals. This will prevent strand separation in the stranded wire while wrapping the wire to fit the terminal.
Twist stranded wire with fingers before tinning.
After tinning, we have to wrap the wire around the terminal. Use round nose pliers to form a loop at the tinned end of the wire. This end of the wire will be wrapped around the terminal lead.
The loop may be a one–half turn, one full turn or anything in between half and full turn. A one-half loop is easier to desolder and remove if needed.
If you soldering only one wire on a terminal, it should be placed flush with the surface of a circuit board. This will better distribute mechanical stress to the circuit board.
If you are soldering two or three wires on a terminal they should come from the same direction, and wrap in the same direction. Wires should be positioned one on top of the other.
To make a better connection between wires and the terminal, you may apply a small amount of solder flux to the solder junction. Read more about how to use solder flux here.
Before soldering wires to terminals we should choose the correct iron tip. In this guide, we will use a 3/32 inch (2.38mm) chisel style tip. This tip is a little bit bigger than tips used when soldering circuit boards.
Soldering wires to the terminal is not a sensitive process as soldering small components on a circuit board. A technique used for soldering wires to terminals is similar to a technique used for soldering wires to connectors. Therefore you can solder wires to the terminal and connector with a simple soldering pencil.
However, better results will be achieved if you use a temperature-controlled soldering iron. In this "how to solder wires to terminals" guide we will use WE1010 Weller temperature-controlled soldering iron.
So finally after all preparations in the previous steps, we are ready for soldering. Now is time to turn on the soldering iron. Set the temperature to 750 °F (400 °C) if you are using a temperature-controlled soldering iron.
Place the iron near the mid-point of wire wrap and hold it for a couple of seconds. Keep holding iron and apply solder to the point opposite to the point where iron is placed. The solder will melt and stick to the metal terminal. After a few more seconds remove the solder first and then soldering iron. When removing soldering iron make a quick circle around the solder joint.
Wait a minute while the solder cools down and solidifies. Clean the solder joint and remove flux.
Visually inspect the connection between wire and terminal.
You may use a digital multimeter and inspect the electrical connection between the wire and the terminal.
Switch your digital multimeter to ohmmeter and measure resistance between the other end of the wire and the terminal. If wire and terminal form a good connection then the resistance should be less than one ohm.
After soldering you may use a heat shrink to electrically insulate exposed terminals.
There are different types of terminals and wiring in electrical devices. Terminals found on a speaker or a PCB are different than ones used in the automotive industry.
Some types of terminals such as ring or fork terminals could be crimped to wire with a crimping tool. Crimp connections are not as good as soldered ones.