How to Solder Wires

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Types of Electronics Wire

The two most common types of wires found in electronics are solid and stranded. Solid wire has a single conductor whereas stranded has many smaller conductors that make up the wire. There is also what's called braided wire which is tightly laced strands used primarily for shielding in long runs of cable like coax. 

Wire Gauges

The size of the wire is known as the wire gauge which refers to its diameter including insulation. The American Wire Gauge system works in reverse so the higher the number the smaller the wire and vice versa. Also, the larger the wire gauge, the more current it can handle.    

Wire Stripping

One of the most crucial skills to master for soldering wires is cleanly stripping the insulation. There are a few different methods you can use depending on what tools you have on hand. 

Utility Knife

This is the simplest and most crude tools available for wire stripping but effective nonetheless. The blade should be decently sharp for this to work well. Simply hold the knife and score around the wire jacket making sure not to cut too deep. Once finished pull the wire jacket off. 

Manual Wire Stripper

The manual wire stripper is our favorite tool for several reasons. It's cheap, it gives you a lot of control and flexibility, and it works great! There are basically two versions you will come across. Some have just open jaws with no markings and others have several indents for specific wire gauges. If you know the wire gauge, the marked ones are great because you know it won't cut too deep. However the basic type can handle most gauges as long as you're careful. Just bite down on the insulation and twist the around the wire. With the insulation still in the jaws pull up to remove. 

Pro Tip: Wire strippers work a bit better for you when they have dulled a bit. The sharpness of a new pair can cut through the insulation too easily leaving you with broken conductors. 

Automatic Wire Stripper

The last option is the most sophisticated and possibly the easiest. If you have to make a ton of wires and repeatability is a factor these could be your best choice. The automatic strippers just clamp right down and do all the work for you in one quick motion. It is also less fatigue on your hands and joints. 

Pre-Tinning

Pre-tinning wires before soldering them can help speed up the soldering process by cutting down dwell time. In the case of stranded wires, it also keeps them together if you need to insert it into a hole.

Heat Shrink Tubing

When making a wire repair 
If using a lighter, keep the tip of the flame away from the tubing, use the blue base and you will not get any discoloration, or burn marks. 
The tip of the flame will instantly burn a hole it in the heat shrink.

Mechanical Connection Methods

J Hooks

When working with solid core wire, one of the easiest ways to connect two wires together is interlocking J hooks. 

Strip the wire insulation equally on both wires

Using a pair of needle-nose pliers, come down a quarter of the way on the exposed wire and bend the wire around to form a "J" shape. Repeat this step on the second wire. 

Cut a piece of heat shrink tubing that will cover the exposed wires and a bit of insulation on each side. Slide the tubing down one of the wires for later. 

Bring the two wires together by hooking the ends on each other. 

Press the ends of the wire down with your fingers to pliers to form a solid mechanical connection.

Solder the connection

Slide the heat shrink over the newly soldered connection so it is completely covered. 

Using a lighter or heat gun, shrink the tubing down on the connection.  

Rat-Tail / Twist Splice 

The rat-tail splice, also called a twist splice or pig-tail splice is done by simply twisting two or more bare wires together. It is used frequently in home electrical but much less common in electronics because it is not very reliable. It is best used for short term connections that may have to be changed in the near future. Electricians will twist the wires in a receptacle up 

Lineman's Knot / Western Union Splice 

The Lineman’s Knot is a special wire repair that creates such a robust mechanical connection that it cannot be pulled apart. The story goes that in the early days of telegraph, people needed a way of repairing transmission lines that were laying on the ground. In these locations where there is nothing around and no way to solder. They needed a way of actually getting phone wire connected and back into the air in a way that would not fall apart. The lineman’s knot has been integrated into all kinds of electronic repair for its strength. Which is made even greater by soldering the wires and protecting them with heat shrink tubing. 

How to do a lineman's knot

  1. Strip about an inch of wire insulation on both wires to be connected.

  2. Dry fit your heat shrink tubing and cut the appropriate length to cover the entire repair.

  3. Slide heat shrink tubing onto one end of the wire for later. Keep away from heat until ready to shrink.

  4. Twist the strands of the wires up with your fingers

  5. Come up from insulation about a 1/3 of the way and put bend in it

  6. Put the wires together and bend them back on themselves

  7. Wind the wires up you should get a couple of wraps by wrapping them both in opposite directions

  8. Apply some rosin flux paste and solder the wires.

  9. Slide the heat shrink over repaired area and make sure it covers completely.

  10. Using a heat gun or lighter, shrink the tubing.
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