Making the Connection: Solder vs. Solderless Terminals

Making the Connection: Solder vs. Solderless Terminals

The debate as to whether to solder or not to solder an electrical connection is akin to the debate between Gulliver's Lilliputians and Blefuscuans over whether to open an egg at the big end or at the little end. The argument may never be settled, and, ultimately, there may be no right or wrong answer. In the case of vehicle electrical connections, so long as the engine starts, the lights shine, and the meters and gauges function, either choice will be correct. Yet each side has its steadfast proponents.

A properly soldered electrical connection has its virtues. Solder reinforces the mechanical connection of joined wires and helps to prevent their inadvertent separation. Solder is an excellent conductor, and causes minimal voltage drop. Solder allows for visual inspection of the exterior of the connection. Solder has an almost universal application, regardless of differences in wire gauge, component location, available space, and component function. Solder is always in stock somewhere, and is available seven days per week. And soldering is a time honored tradition. But soldering is not perfect.

Solder is hot! Even with a heat sink, solder may seep into areas beyond the intended joint or may cause damage to adjacent wires and components. Solder may trap moisture that eventually may corrode a connection from within. Too much solder may reduce the electrical conductivity of the stranded wires. Too little solder may cause the joint to fail. Solder does not permit visual inspection of the interior of the joint. Solder may raise health or environmental issues. A soldered connection will be less flexible than the original stranded wire, and may weaken over time due to vibration. A soldered connection must be insulated by heat shrink, by electrical tape or by other insulator. A soldered connection is permanent and cannot conveniently be disconnected. And many of us lack the knowledge or skill to solder properly. Enter the solderless terminal.

Solderless terminals fall into two categories: those that require crimping and those that do not. Crimp terminals are by far the more common in vehicle electrical circuits.

Crimp terminals are familiar to all of us, and include blade terminals, snap (bullet) terminals, ring terminals, spade terminals, taps, and butt (splice) connectors. Some crimp terminals (e.g., blade and snap terminals) allow for the “quick disconnect” of joined wires and generally require a pair of terminals, one male and one female. Other crimp terminals (e.g., butt connectors) allow for a permanent connection of joined wires, and do not require a mating terminal. Ring and blade terminals enable a wire to be connected to an electrical component. Crimp terminals may be insulated or uninsulated. Some may come with integral heat shrink and adhesive. Some may be part of a composite assembly that includes one or more terminals, connector housings and weatherproof seals. The latter may require a special tool to unseat the terminals from the connectors. And some so-called crimp connectors actually may contain solder to enhance the connection.

Though the average person intuitively might suspect that most electrical connections are soldered, that suspicion is far from accurate. In reality, most modern vehicle electrical circuits rely upon crimp terminals rather than solder to make the wire-to-wire and wire-to-component electrical connections. And with good reason. Crimp terminals are inexpensive, make a secure mechanical connection, retain the flexibility and electrical conductivity of the wires to which they are affixed, are resistant to vibration, allow for visual inspection, do not damage adjacent wires or circuits, are light weight, and lend themselves to assembly line applications. A proper crimp “cold welds” the wires to the connector. A weld is stronger than solder.

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