What Are Connectors?

Connectors are electromechanical devices that create separable electrical or optical junctions between cables, printed circuit boards, chassis, and other components in an electronic system. By providing a defined and repeatable mating interface, connectors enable the assembly, maintenance, testing, and reconfiguration of complex electrical systems without the need for permanent joints. They are a foundational component class in virtually every segment of electrical engineering, from consumer electronics to space-qualified avionics.

Every connector pair consists of two complementary halves: a plug and a receptacle. Standards bodies, including the IEEE and the IEC, have established naming conventions to distinguish these halves and to define the performance requirements that govern their interoperability. The IEC connector standards define a broad range of interface geometries, insulation materials, contact ratings, and environmental classifications used across international markets.

Connector Families and Interface Types

Connectors are organized into families defined by the geometry of the mating interface, the signal type, and the application environment. Coaxial connectors, such as the BNC, SMA, N-type, and TNC series, carry single-ended RF and microwave signals by maintaining a controlled characteristic impedance through the connector body. Precision coaxial connectors used in metrology and high-frequency measurement are standardized by IEEE 287.1-2021, which covers connectors from DC to 110 GHz. Rectangular multi-pin connectors, such as D-subminiature and DIN 41612, carry multiple signals or mixed signal-and-power lines in a single housing. Circular mil-spec connectors such as MIL-DTL-38999 serve harsh-environment applications in aviation and defense. Fiber optic connectors including LC, SC, and MPO types align optical fibers with ferrules polished to minimize insertion and return loss.

Electrical and Environmental Performance

Connector performance is specified in terms of contact resistance, insulation resistance, current-carrying capacity, rated voltage, and mating cycle life. Contact resistance is governed by the normal force between mating surfaces, contact geometry, and plating material. Gold is preferred for low-level signal contacts because of its resistance to tarnishing; tin and silver serve higher-current power contacts at lower cost. Environmental performance is rated using the IEC 60529 ingress protection (IP) code, which classifies resistance to dust and water. Connectors for outdoor telecom, marine, and automotive applications typically require IP67 or IP68 ratings. High-temperature grades, often using polyetherimide or liquid crystal polymer insulators, are required in under-hood automotive and industrial furnace contexts. A comparative survey of connector types, materials, and application environments is available through the GlobalSpec electrical connector selection guide.

Board and Cable Termination Styles

Connectors are also classified by how they terminate to conductors. Wire-to-board connectors are crimped or insulation-displacement-terminated to individual wires and then mated to a header soldered on a PCB. Board-to-board connectors link two PCBs directly, with mated-height tolerances in the sub-millimeter range for compact handheld devices. Zero-insertion-force (ZIF) connectors, common in SIM card and flat flexible cable applications, use a locking actuator to grip the contact with no insertion force applied, protecting fragile cables. Cable-assembly connectors for high-speed serial data interfaces, including USB, HDMI, and SFP transceivers, integrate impedance-controlled contact geometries to support multi-gigabit signaling.

Applications

Connectors have applications in a range of fields, including:

• Telecommunications and data center networking infrastructure
• Aerospace and defense electronics and avionics
• Automotive and electric vehicle power and data buses
• Medical devices, patient monitoring, and diagnostic equipment
• Consumer electronics, computing, and mobile devices