Soldering is a traditional and often-used means of making electrical connections in circuits, but it is not always the best choice, and there are alternatives. In soldering, a metal alloy is heated to its melting point and used to join wires in a circuit. Alternatives include solderless plugs, connectors, wire nuts, screw terminals or terminal strips, spring terminals, crimp and multi-tap connectors. Knowing the alternatives will help you choose the best one for your application.
Soldered connections are two pieces of metal bonded by a third. Solder can be heated using a soldering iron or melted with a kerosene or propane torch. Soldered connections have many practical uses, within limits. The intense heat of hot solder may damage or destroy surrounding components and insulation. In addition, the time to heat up and cool down soldered components may not be practical in some circumstances, such as during mass production of electronic devices. A soldered connection can also be weakened and cracked over time when exposed to vibrations.
Connections must be secure physically and electrically. All designed connections must balance the demands of the materials of the wire and connector and electrical load. Most solderless connections require stripping wire of its insulation. The length varies with the type of connector and the cable or wire. Crimp or compression connectors are the best choice in applications where excess vibrations would damage or weaken any other type of connector. This may include spring terminal connections, where the wire is held in place by the compressive force of the spring. Some light switches and circuit breakers are also designed to connect to wiring using this type of connector.
Screw and Threaded Connectors
Where movement or vibration is not a concern, screw terminals or threaded connectors are practical. Screw terminals, typically flat-head or Phillips screws, may still be found in residential telephone wiring, doorbell circuits, FM radio antennas and some ground connectors. Similarly, nut-and-bolt or post connections work by compressing wire looped around a threaded post and using a bolt to secure it in place. Wire nuts, common to residential wiring, function by inserting the entwined ends of stripped or bare wires into a wire nut that is rotated until snug.
Specialized connectors, such as plugs or proprietary connectors, are designed for low voltages or signal work where shielding prevents electrical or radio interference. These may have screw or bayonet connectors for fastening.