Electrical connectors are devices that join electrical circuits together. Most connectors are removable or temporary, but some can be permanent. Connectors make electronic products easier to assemble and manufacture. They also ease circuit repairs and allow flexibility in design and modification. They are used extensively on circuits for communications, computers, industrial machinery, and consumer electronics.
Most connectors are composed of two main parts: housing and terminals.
Housing is the case or structure used to hold the terminals, stabilize the connection, and protect the contacts from shorting and/or from various environmental hazards. Housing is normally made up of some type of molded plastic, but can be made out of any type of insulator material (e.g. ceramics).
Terminal pins in a connector provide the electrical conduction that makes the connection. They are nearly always made up of some type of metal, but any material that conducts electricity can be used (e.g. carbon or silicon).
Types of Electrical Connectors
There are a vast amount of individual electrical connector types that can be differentiated in a number of ways, namely by level, function, and termination.
Each connector type can fit into one (or more) of five categories, referred to as levels in industry. These were defined by various companies under the support of the National Electrical Distributors Association (NEDA).
• Wire-to-board or subassembly-to-subassembly level
• Box-to-box or input/output level
• IC chip or chip-to-package level
• IC package or package-to-board level
• PC board-to-board level
Audio connectors are used to affix cables to other audio equipment, providing electronic signal transference and grounding protection. Applications for audio connectors can be general purpose, telephone, or microphone. Most audio connectors are for commercial purposes, but some may conform to military specifications.
Automotive electrical connectors are designed to be used specifically in vehicles.
Board Mounted Connectors, or Circuit Board Connectors, are connectors that can be used as components embedded on a computer board.
Board mount connectors or circuit board connectors are connectors that can be used as components embedded on a computer board. The boards can be customized to meet the user application.
Centronics connectors are standard parallel interface devices for connecting printers and other peripherals such as portable disc drives, tape backup drives, and CD-ROM players to computers. Centronics connectors are named after the printer that first used them and include two rows of flat contacts.
Circular connectors are multi-pin connectors primarily used for external interfacing. They can be used for data transfer, electrical signal transmissions, or for powering electrical devices. In some cases, circular connectors have been designed to carry what may be referred to as a mixed signal and may be described as a power and control connector. These types of multi-pin connectors are used for both power and signal transmissions.
Coaxial connectors are composed of an insulated central conducting wire wrapped in another cylindrical conductor (the shield). The cable is usually wrapped in another insulating layer and an outer protective layer. Coaxial cables and connectors have the capacity to carry vast quantities of information. They are typically used in high-speed data and CATV applications.
DIN connectors are high frequency, multi-pin, electrical connectors that meet standards established by Deutsches Institut für Normung (DIN), a German national organization for standardization. The ends of DIN connectors are round, notched, and protected by a metal skirt to ensure that pins line up correctly.
D-subminiature or D-sub connectors are sturdy electrical connectors with a mating face shaped like the letter D. They provide polarization because male and female connectors can fit together in only one way.
Card edge connectors (also called edge card connectors) are embedded devices that mate with the edges of single-sided or double-sided printed circuit boards (PCBs) in order to provide an external electrical connection. Industry standards define power specifications such as voltage levels, power pin placements, and power requirements. For example, PICMG 1.0/1.2 standards define the power specifications for peripheral component interconnect (PCI) and industry standard architecture (ISA) buses.
Fiber Channel connectors are high-speed connectors used in Fiber Channel systems.
IEEE 1394 connectors are used to connect FireWire® devices such as host controllers, adapters, hard drives, hubs, repeaters, and card readers. FireWire, a registered trademark of Apple Computer, is a communications protocol for the transmission of data, video, and audio over a single cable at very high bit rates.
Gender changers are devices that change the end of a cable into another type, allowing two cable assemblies with the same or different genders to mate.
Heavy duty rectangular connectors are designed to accommodate large electrical loads and direct signals under a multitude of operating conditions. They are normally used in industrial applications where the delivery of high power is required. For this reason special terminations such as solder cup, wire wrap, and other heavy duty terminals, are used to secure the safe delivery of power.
IC interconnect interface or connect microelectronic semiconductor chips to printed circuit boards (PCB) or larger-scale devices. An electronic interconnect device bridges a gap between two conductors and allows the flow of current or light waves from one to the other. Electronic packaging consists of a plastic, ceramic, or metal enclosure that houses an integrated circuit (IC) on a silicon or metal die.
Instrument power connectors and computer (disk drive) power connectors are used to connect a computer’s power supply to a hard disk, floppy disk, compact disk (CD), digital video disk (DVD), or other type of disk drive. They are also used with removable media drives such as Zip disks, and computer cooling devices such as fans and electro-thermal coolers.
Medical electronics connectors are used with medical devices and medical equipment in hospitals, clinics, doctors' offices, and other health-care facilities.
Micro connectors and nano connectors exhibit contact pitches of 0.05” (micro) and 0.025” (nano), respectively. They have one or more rows of plated contacts and are either straight or right-angled. Some micro connectors and nano connectors are circular or cylindrical. Others are designed for coaxial cables or RF and microwave applications. Both male and female devices are available. Micro connectors and nano connectors are used in a variety of industries and applications.
Military (MIL-SPEC) connectors are shell-type connectors that are built in accordance with military specifications. Their design takes into account the need to protect the connection from environmental factors, allowing them to be used in military and aerospace applications. The type AN (Army-Navy) connector set the standard for modern day connectors. They are often referred to as Military Standard, "MIL-STD", or "MIL-SPEC" connectors.
Modular connectors and RJ connectors include two similar, yet distinct styles of connectors. Modular connectors are made of "plug-in units" that can be added together to make the system larger, improve the capabilities, or expand its size. Registered Jack (RJ) is a telephone and data jack application specific connector registered with the FCC.
Panel interface connectors (PICs) are devices installed in the outside of a panel that houses a PLC, a computer, or other devices. The PIC allows the user to interface the PLC or the computer without opening the panel door avoiding potential safety hazards. Power receptacles and communication ports can be placed in a number of combinations to produce various customizable products.
PC card connectors are used to connect PC cards, CompactFlash cards, and other devices to computers. The PC card form factor is defined and maintained by the Personal Computer Memory Card International Association (PCMCIA), a U.S. computer industry trade organization. Known originally as PCMCIA, or PCMCIA cards, PC cards were designed for computer storage expansion. They are now used as network cards, modems, and even hard disks.
Phone jacks and plugs are connectors used with telephones. They are also known as modular jacks (female) and modular plugs (male).
Radio frequency (RF) and microwave connectors are used to connect the ends of cables in systems that operate in the radio frequency or microwave spectrum. Microwave refers to electromagnetic energy with a frequency higher than 1 gigahertz and a wavelength shorter than 30 centimeters. Radio frequency refers to alternating current that generates an electromagnetic field suitable for wireless broadcasting and/or communications if the current is input to an antenna. An RF connector can be found in transmission systems and allows for the coupling or uncoupling of system components. A mated pair consists of a plug and a jack.
Solar connectors facilitate electrical connectivity in solar energy systems. Numerous versions of connectors or standard non-connector junction boxes are employed in the solar industry and are the primary characteristic elements of solar modules.
Solenoid valve connectors are used to connect solenoid valves and pressure switches. Solenoid valve connectors are often used as environmentally resistant junction boxes. These protective enclosures can be used with either hydraulic or pneumatic solenoid valves or pressure switches. Specific devices are capable of working with either AC or DC voltages, although some types can handle both.
Terminal blocks are modular, insulated blocks that secure two or more wires together. Terminal blocks are used to secure and/or terminate wires and, in their simplest form, consist of several individual terminals arranged in a long strip. Terminals are useful for connecting wiring to a ground or, in the case of electrical power, for connecting electrical switches and outlets to the mains.
Thermocouple connectors are used to transmit temperature readings from a thermocouple (T/C). These specialized connectors are designed to extend the thermocouple wire and must be rated for a particular T/C. Lettered choices for thermocouple types include B, C, E, J, K, N, R, S, T, and W.
USB connectors are used with universal serial bus (USB) ports. They can be used to connect USB products together, or to connect USB wires and peripherals to other standard port types.
Wire terminals are passive conductors used to facilitate a connection that is not soldered. They are two-piece assemblies that consist of a receptor (female) and blade (male), which help to provide repeated connection and disconnection. There are many types of products. Examples include spade terminals, ring terminals, blade terminals, and heat-sinkable terminals.
Wire-to-board connectors are used to interconnect printed circuit boards (PCBs) by using connectors attached to wires.
Wire-to-wire connectors are used to connect two wire-terminated connectors. They are used as electrical connectors, electronic connectors, and computer connectors. General specifications for a wire-to-wire connector include mating combination or gender, number of circuits or positions, and wire size. Male wire-to-wire connectors are designed to plug into female wire to wire connectors.
Some connectors may be further characterized based on how the wire is terminated or fastened to the connector.
Crimping is used to create a separable connection between wires and connectors. It involves inserting a stripped wire into a metal section (barrel or terminal) and using a crimping tool to apply pressure and compress the section tightly around the wire. They are often used for terminating stranded wire. Ring, spade, and blade connectors use crimping to join a wire to the connector.
Crimped wire connection. Image Credit: Eastern Beaver Company
Crimped connections are often preferred for a number of reasons:
• Easy, fast, and cheap to make/reproduce connections in large-scale production.
• No dangerous processes involved in making the connection.
• Little mechanical strain in the connection.
Types of crimped connections include barrel and open-barrel.
Barrel connections involve the crimping of cylindrical sections that (depending on the tool) usually result in an oval-like shape. These are widely used in common consumer applications.
Open-barrel connections involve the crimping of a pre-crimp section into a U or V shape. These connections are easier to automate and are generally stronger than barrel crimped connections, making them more common in industrial applications.
Insulation displacement connectors (IDCs) are used to connect insulated wire or cable to a device without pre-stripping the cable or wire. By incorporating a sharp blade or multiple blades in the connector, the insulation is cut as it is inserted.
Image Credit: Belit Elktronik
IDC connectors are great for manufacturers because it eliminates the stripping step, providing a simpler connecting process. However, over time, the blade that cuts the insulation can cut wires within the connector, lowering current handling (which can cause connector burnout). Also, the strength of the connection is much lower than a crimped connection. Tools for non-production insulation displacement tend to cost more than effective crimping tools.
Solder connections involve melting a filler metal (solder) onto an electrical joint. The solder then solidifies, creating a fused connection between two metal items. Solder can provide a very smooth, robust, and reliable connection if done well and with the right type of solder (solder components should match the metals of the electronic components being joined). These connections are generally slower and more involved than crimped connections.
In PCB solder or solder pin termination, electrical connection is made by soldering wires or pins onto a printed circuit board. With solder cup terminations, soldering the connector onto the mounting location creates an electrical connection. Through hole technology (THT) mounts components on PCBs by inserting component leads in the board and then soldering the pins on the other side.
When selecting electrical connectors, there are a number of factors that may be important to consider, depending on the type of connector and its application.
Performance parameters describe the conditions at which an electrical connector is designed to operate.
• Current describes the current (rate of flow of electricity) a connector is designed to carry, measured in amperes or amps (A). Current ratings on connectors usually range from 1 A to 50 A.
• Voltage describes the voltage rating of the connector, measured in volts (V). Typical ratings are 50 V, 125 V, 250 V, and 600 V.
• Operating temperature describes the recommended, range, or minimum/maximum operating temperature(s) of the electrical connector.
Physical parameters describe how an electrical connector is physically designed.
Contact pitch—the distance (from center to center) between adjacent pins or terminals in a connector, typically measured in millimeters (mm). A larger contact pitch describes a lower connection density (less pins or connections per area). Pitch affects arcing, which occurs when two conductors are close (pitch is low), causing interference.
Number of contacts—the number of conductive elements that mate with a corresponding element to provide an electrical path.
Materials—the materials used to construct the connector. Connectors are typically made of metal and plastic, but can be constructed using just about any conductor and insulating material. Properties of conducting materials that are important for electrical contacts include conductivity, mechanical strength, formability, and resilience. Some common terminal metals are described in the table below:
Zinc content varies from 5-40%; cheapest metal by weight; good spring, strength, and electrical properties
Good strength, toughness, and conductibility; excellent fatigue resistance; superior elasticity
Electrical contact springs
Finest copper alloy for spring terminals; priced significantly less than phosphor bronze
Applications demanding optimum performance
High copper alloy
High strength modified copper; good thermal and electrical properties; resists softening at high temperatures
Mainly automotive applications
Table Credit: Molex
Some applications may require electrical connectors to possess certain features.
Keyed connectors are designed to only connect at a specific orientation. This prevents the user from damaging pins or inserting them into the wrong sockets. Pins and casing are oriented so that the plug cannot be inserted incorrectly.
Image Credit: wikipedia | Dimensions Guide
Locked connectors provide a means to lock the connection in place, preventing the connection from being undone accidentally.
Hermetically sealed connectors are fully functional underwater and can withstand water pressure up to a certain depth.
Water resistant connectors are designed to protect connections from water damage.
Moisture/oil resistant connectors are designed to protect connections from oil or moisture damage.
EMI or RFI filtering on connectors provides protection against electromagnetic interference (EMI) and/or radio frequency interference (RFI).
ESD shielded connectors provide protection against electrostatic damage (ESD) to an electrical connection