Electrical connector

An electrical connector is an electromechanical device used to join parts of an electrical circuit.

By connecting these parts, the device creates a path for electric current to flow. This allows separate components or even entirely different circuits to function together as one larger system. Some connectors are designed to be removable, which is helpful for portable equipment. Others are permanent joints that may require specific tools for assembly and removal.

In the world of computing, these connectors serve as a physical interface. They are considered part of the physical layer within the OSI model of networking.

Most electrical connectors follow a gendered system to ensure they fit correctly. The male component is known as a plug, while the female component is called a socket.

Engineers categorize these devices into four main functional groups. Inline or cable connectors are permanently attached to a cable for use with other terminals. Chassis or panel connectors are fixed to a piece of equipment so users can attach cables to stationary devices. PCB mount connectors are soldered directly to a printed circuit board to provide attachment points for wires. Finally, splice or butt connectors, such as insulation displacement connectors, are used to join two lengths of wire permanently.

To function correctly, a connector must be built from two specific classes of materials: conductors and insulators. Conductors are the parts that carry the electricity. They are typically made from copper alloys, such as brass, phosphor bronze, or beryllium copper, because these metals are conductive and malleable.

Because copper alloys can be difficult to solder or prone to corrosion, the base metal is often coated with an inert metal like gold, nickel, or tin. For example, gold coatings help reduce contact resistance in high-reliability applications. Insulators serve to stop the flow of electricity. These are usually made of plastic to act as contact carriers. In extremely high-temperature environments, such as near large incandescent lamps, connector bodies may be made of fired ceramic.

Connectors come in many different shapes and mechanical designs. Circular connectors are often used in industrial, military, and aerospace applications.

These feature a cylindrical housing and circular contact geometries, which allow for easy engagement and rugged performance. They are often used in rail or aircraft where environmental sealing is vital. In contrast, some connectors use a rectangular design, such as USB or blade connectors. Hybrid connectors offer a modular approach by allowing different types of interfaces to exist in one housing. These can mix electrical, pneumatic, or even optical fiber connections to simplify assembly and repair.

Mechanical features are often added to improve safety and reliability. Many connectors use "keying," which involves a mechanical component called a keyway. This prevents a user from plugging a connector in the wrong orientation or into the wrong device. This is critical for preventing dangerous mistakes, like plugging an audio cable into a power outlet. Some connectors also feature specific pin sequences. This ensures that certain pins, such as a safety ground, make contact before others during insertion. To prevent accidental disconnection, many housings include locking mechanisms like levers, jackscrews, or bayonet systems.

Despite their design, connectors can fail due to various factors. According to data compiled from sources like the NASA Parts Application Handbook, the most common failure is an open circuit, which occurs about 61% of the time. Poor contact accounts for 23% of failures, and short circuits make up 16%.

High temperatures can cause an "avalanche" of failures. This occurs when rising temperatures decrease insulation resistance and increase conductor resistance, which in turn generates even more heat. Surface corrosion can also increase resistance and cause intermittent connections. However, reseating a connector can sometimes fix this by scraping off the oxide layer to expose a fresh metal surface.

Advanced engineering provides solutions for even the most extreme environments. For instance, hyperboloid contacts are used when standard pin and socket designs are not enough. These contacts use longitudinal wires twisted into a hyperbolic shape that act like linear springs. This design can withstand extreme vibration and shock while requiring approximately 40% less insertion force. Additionally, many industrial connectors use backshells. These accessories protect the connector from electromagnetic interference or mechanical stress. They can also provide a hermetic seal using components like O-rings or grommets to protect against dust and water.