Electronic Connectors: Types, Terms and Termination Methods

What is Electronic Connectors?

Electronic connectors are devices used to interconnect electronic circuits. They are utilized for installation, assembly, and to supply power to electrical devices.

Electronic circuits whether in industrial machinery, consumer electronics, telecommunications, or home appliances, are dependent on these components.

Connectors are an intricate part of electronic products that usually go unnoticed, and they are essential to the efficient operation of electronic products.

There are some connectors that are intended for permanent connections, but the majority are temporary that allow disconnection easily.

An electrical connector consists of two parts, the contacts, and the housing, either plugs or receptacles. The housing contains the terminals to facilitate a stable connection while insulating terminals from making unwanted contact with circuit components and avoid shorts.

Plug and receptacles are there to protect against environmental factors and they typically made of insulating materials with molded plastic or some ceramics.

The connector may include some features depending on the application. The keyed connector can only be connected in one direction to reduce mis-connecting the key. Some connectors can be secured to reduce accidental disconnection.

There are connectors manufacturers make with sealed components that will work rather well underwater.

The thermal connection pins are the connector terminals and provide the complete conductive path through the circuits.

The connector terminals are attached together with conductive materials such as brass, phosphor bronze, beryllium copper, or high copper alloys.

Terminologies Used in Electronic Connectors

There are common terminologies that relate to the characteristics and functions of electronic connectors:

Gender

Gender is used to distinguish between the mating connectors which can be the same size, shape and number of pins. The plug or male has pins that connect to a receptacle, jack or socket (female) which has socket holes for terminals to attach to wires, cables or devices.

The pins of the male plug will fit in the holes of the female jack or socket to make the electrical connection.

Keying

Most connectors plug-in one orientation only. Keying is a special type of electronic connector when more than one connector pairs are needed.

A keyway serves as a protective mechanism for mechanical and electrical damages. It will make it physically impossible for 2 connectors to be mismated accidentally because connectors will not be able to plug when it has the incorrect alignment or wrong socket. A keyway is used for symmetrical connectors.

Locking Mechanisms

Locking Mechanisms are used to hold the connectors in place when mated. It will also prevent connectors from becoming displaced when bumped or jolted.

It will also prevent connectors from accidentally uncoupling which may cause damage to an electronic device. The different types of locking mechanisms can include push-pull connectors, bayonet couplings, and fine thread screw couplings.

Number of Contacts

The number of contacts means the number of pins that would make an electrical connection. Generally, the number of contacts can vary from 2 to over 200 depending on the model and design of the electrical connector.

Contact Pitch

Contact pitch, or simply pitch, is defined as the center-to-center distance from adjacent pins, measured in terms of millimeters. Depending on how the pins are arranged in an array, the pitch may differ in rows versus in columns. Contact pitch is also used to determine integrity of compatibility with other connectors.

Generally speaking a larger pitch means that there will be fewer terminals in a connector area thus minimizing electrical arcing, which occurs when electrical current jumps between the pins when they are too closely spaced. Contact pitch is given careful consideration when assembly an electrical connector.

Pin Numbering

Pin numbering provides a method of identifying each of the pins of an electronic connector. Pins are assigned a systematic counting from left to right or bottom to top, this is dependent on the type of connector. Pin numbering allows for accurate wiring connections for multiple pin connectors.

Pin Sequence

Pin sequence or mating sequence is the layout of the electronic or electrical connector, for example this layout shows the order in which each pin will make contact when it is mated.

In a pin sequence the order is paramount as it ensure proper functionality, safety to the damage of a device, the ground pins, for example, will make make contact first during the mating action.

The reason for specification of pin sequence is mainly to prioritise the sequence of which this happens.

Mating Cycles

Mating cycles defines the quantity of connector connections and disconnections an electronic connector can perform.

For example, USB connectors can be mated with a thousand mating cycles, whereas FFC (Flat Flexible Connector) and FPC (Flexible Printed Circuits) connectors typically have many less cycles.

The factors, which affect mating cycles are connector materials, type of plating, thickness of pins assessed to a pass/fail threshold, and the style of mating connectors.

Mounting

Mounting explains how an electronic connector is mounted onto an electrical device. Mounting types include, board mounting, through-hole, surface, edge and panel type and cable mounted. Mounting type dictates the placement of the connector onto the device.

Termination

Termination explains how a wire connects to the conductors in the electronic connector. The wire is stripped and fastened to the connectors contact point by crimping with a crimping tool, soldering with a soldering iron or attaching by screwing.

Strain Relief

Strain relief is the fitting or bushing, which will take the force applied to an electronic connector, relieve that force so as to prevent stress and damage, and facilitate a mechanically stable electronic connector.

Performance Parameters

The performance parameters of an electronic connector is a list of capabilities regarding environmental factors.

The following list contains all of the possible features, including current rating, voltage rating, range of operating temperature, contact resistance, insulation resistance, environmental sealing and mating force.

Types of Electronic Connectors

The world of electronics is continuously expanding and relies on electronic connectors to make connections between items. Electronic connectors have resulted in different sizes, types and types of electronic connectors that allow for connecting several devices together.

Board-to-Board Connectors

Board-to-board connectors are a group of connectors that connect two printed circuit boards PCB (without the use of a cable). Board-to-Board connectors typically consist of a plug and socket connection.

These connectors are integrated into PCBs by either vias, through holes, or surface mounts.

Connections for PCB can be perpendicular or parallel, and mezzanine connectors are a stacking configuration while edge connectors mate on the edges of single-sided and double-sided PCBs.

Box Header Connectors

Box header connectors or shrouded header connectors are a type of board-to-board connector that has a plastic guiding box with exposed pins.

The box style of the connector made mating easier, box header connectors can have keying to prevent mismating or have a cutout of the box to force correct mating.

Backplane Connectors

Backplane connectors perform the purpose of connecting several pieces of PCB to a central framework, all will connect in a way that a pin on one board aligns with a pin on each of the other boards.

Backplane connectors are commonly used in computers or telecommunications equipment as the framework for the data exchange between components.

The applications of used with backplane connectors became a backplane connectors from used with mainframe computers where the connectors were found on the back of the mainframe casing.

In contemporary computers, they are a component of top of rack switch applications and hybrid hard drive (HHD) clusters.

Power Connectors

Power connectors are connectors that allow electrical current to flow through them to provide power to a device. Power connectors can transmit a direct current (DC) or alternation current (AC) current.

Barrel Connectors

Barrel connectors, also called coaxial power connectors, connect electronic devices to an external power supply. The barrel connector passes low voltage DC current (typically from a wall-mounted adaptor) to the electronic device.

Barrel connectors are used extensively in consumer electronics and come in commonly accepted diameters and lengths.

The barrel plug consists of concentric cylinders of metal, with insulation around each cylinder. The inner cylinder contains the pin of the barrel jack, which mates with the pin of the barrel connector.

The barrel jack can be mounted to the PCB, panel, or as a connector on a cable. Within the jack, a cantilevered spring presses against the outer sleeve of the plug, ensuring that the inner sleeve of the connector makes contact with the pin.

Molex Connectors

Molex connectors were designed and patented by the Molex Connector Company in the late 1950’s and are used to supply electrical power to computer drives and other devices.

They consist of cylindrical spring metal pins that interconnect with matching cylindrical spring metal sockets.

Molex connectors are usually keyed for reliable insertion and can incorporate anywhere from 2 to 24 contacts, with the pins and sockets carefully assembled in plastic housings.

IEC Connectors

IEC connectors are connectors which adhere to the standards specified in IEC 60320. The content of the IEC standard of 60320 states the components necessary to connect power supply cords to electrical devices rated at 250 V and 16 A.

IEC connectors vary according to current rating, temperature rating, size, and number of terminals. The connector components have an outlet power end or male component and an inlet female component.

IEC components are referenced by the prefix “C” followed by a number where the inlet or female component’s number is one higher than that of the outlet or male component.

The C13 connector, for example, is used with the C14 inlet, both of which have three conductors; a current rating of 10 A, and a maximum temperature rating of 700 °C.

NEMA Connectors

A NEMA Connector is a kind of power plugs and female receptacles defined by the National Electrical Manufacturers Association (NEMA). Even though NEMA connectors are popular standards in North America; they are also specified by a few countries internationally.

The identifying feature of all NEMA connectors is a coding system made up of numbers and letters describing characteristics of the connector. The first part of the code describes the locking mechanism.

Any connector that starts with the letter “L” has a twist-lock mechanism and if it has no letter, it is a non-locking connector.

The second part of the code, which is the number that comes first, before the hyphen, describes the NEMA type, which denotes the number of poles or current-carrying terminals, wire connections, voltage rating and other identification features.

The numbers following the hyphen is the current rating in amperes for the connector. When you see a letter at the end of NEMA, it is a “P” for plug, or an “R” for females receptacle.

The non-locking NEMA connectors are designed with straight blades on their plugs which allow for easy connecting and disconnecting from their female receptacles.

The twist-locking NEMA connectors have curved blades that can be rotated and locked to securely fasten them into their mating female receptacles, which prevents unintentional disconnections.

The twist-locking connectors should be considered for industrial and commercial applications where tight amounts of security are required when connecting.

Radio Frequency (RF) Connectors

The RF connectors are built strictly to work with radio frequencies in the multi-megahertz range. RF connectors provide shielding for coaxial cables, which is why they are also called RF coaxial connectors.

RF connectors establish electrical connection in radio frequency transmission systems. Each RF connector consists of a center conductor, outer conductor, insulation to provide shielding for the coaxial cable.

As with many connectors, RF connectors are made from female, and male connectors, many times for uses which are not related to radio frequencies and rely on the protective shielding. RF connectors have fastening and spring mechanisms to minimize the insertion force.

Terminal Blocks

Terminal Blocks are modular, insulated devices which connect, or terminate multiple wires. There is a row of terminals in a strip, with each looking from a metal strip inside the housing.

The metal strip closes the circuit and is connected to the terminals. The wires are held in place via a clamping mechanism. Terminal blocks can be installed vertically, horizontally or at 45 degrees. It is usually with a panel or mounted on a cabinet wall or using a DIN rail.

Screw Terminal Blocks

Screw terminal blocks take the wires and press together the wire and the strip. This is most common type of terminal block and it is the best terminal block since it can accommodate very large ranges of wire sizes.

Using a ferrule, which comes from the Latin word for small bracelet is particularly useful in securing stranded wire for use with a screw terminal.

A ferrule is a small round metal tube that fits over the end of a strand of stranded wire, with the ferrule clamped on with the screw terminal.

When adding wires together we can use narrow metal breaking circular rings called ferrules so we securely bind the strands together.

Spring-Clamp Terminal Blocks

Spring-clamp terminal blocks are a particular great clamping mechanism for smaller wires, after which the wires are attached to the strip. There are three types of terminal blocks – single pass through, dual level, and three level. Spring-Clamp terminal blocks can achieve handling multiple wires and provide a very secure clamping method.

Push-In Terminal Blocks

Push-in terminal blocks, or quick disconnect terminal blocks can be male or female connections. Male push-in terminal blocks have tabs that go on female terminals. The female version has holes that take the male tabs. These kinds of terminal blocks can be adjusted many ways and can be offered as push-in terminal blocks so it is significant to choose the right push-in terminal for the application.

Barrier Terminal Blocks

Barrier terminal blocks have a plastic or metal case that makes it possible to connect multiple wires or conductors to a circuit. Barrier terminal blocks have either a pressure plate or a set of screws to clamp down on the wires. Barrier terminal blocks are appealing and popular and can be installed, disconnected and reconnected easily.

Universal Serial Bus (USB) Connectors

Universal Serial Bus (USB) is an interface used for data transfer and power supply in many devices like smartphones, computers and consumer electronics. 

USB connectors have a male part that plugs into a female part with four or more shielded contacts encased in plastic housing with molded strain relief. Besides USB-C, all other USB connectors are asymmetric to create a keying feature for alignment.

The USB versions are USB 1.0, USB 1.1, USB 2.0, USB 3.0, USB 3.1, and USB 3.2.  Newer versions allow for much faster data transfer but are backwards compatible.

USB connectors are defined as connectors based on the receptacles and sizes. USB A and USB B are standard with male/female versions while the USB Mini are designated Mini A, Mini B, Mini AB (both Mini A and Mini B). USB Micro is designated as Micro A, Micro B, and Micro AB with USB-C as its own designation.

USB-A female connectors are most common as the host ports for computers, hubs or devices to be connected to a peripheral. When attached to a device, it is also a USB-A female extension.

Although they are female extension cables, they have a female A connector on one end and a male A connector on the other end.

USB A male connectors are found inside keyboards and mice attached to built-in cables and on USB memory sticks, as well as, designed for board mounting.

USB B female connectors are larger than their A counterparts and/or on devices which size isn’t an issue.USB-B female connectors are highly reliable for detachable and removable applications, as they can be attached to PCBs with or without soldering.

USB-B male connectors that attach to USB cables are inexpensive.

USB Mini female connectors were once used on older MP3 players, cell phones, and external hard drives with surface mount connectors, but the USB Mini has now been mostly superseded by USB Micro.

USB Micro connectors are smaller than USB Min connectors and contain a fifth pin to carry low-speed signals as these connectors are used in USB-OTG (On-The-Go) applications.

Audio and Video Connectors Types

Audio and video connectors are a broad category of electronic connectors that support the transfer of audio and video signals. A connector may carry either analog or digital signals (both audio and video using male [plug] and female [jack] components).

Audio connectors support monophonic (one audio channel) or stereophonic (multiple audio channels) signals.

Some examples of audio and video connectors include:

Phone Connectors

Phone Connectors have coaxial contacts, called tips (T), rings (R), and sleeves (S). Phone connectors may have from three to five coaxial contacts and are found in telephones, headphone devices, speaker devices, and any audio devices.

DIN Connectors

DIN Connectors are standardized by the Deutsches Institut für Normung (German Institute for Standardization) (DIN) and support analog audio signals.

DIN Connectors consist of three or more metal pins in a conductive ring, with a notch, located in both male and female connectors, which lines up when the connectors are mated. Mini-DIN connectors are smaller versions of the DIN connectors.

RCA Connectors

RCA Connectors are designed for the transfer of stereo audio and video signals through an outer conductor and central pin as an inner conductor. They are color coded, yellow for composite video and red and white for stereo audio.

XLR Connectors

XLR Connectors have a circular shape with three to seven pins and a notch that acts as a keying device that guarantees a proper connection. First developed for professional audio and video, the XLR is an acronym for External Line Return. The balanced wiring allows for cancellation of the interference and allows use of XLR to run 48 V of phantom power.

High-Definition Multimedia Interface (HDMI) Connectors

High Definition Multimedia Interface (HDMI) Connectors are used with contemporary home entertainment systems, monitors, projectors and other digital audio devices.

HDMI connectors help, in the transmission of the TMDS (Transition Minimized Differential Signaling) apples to the use of massive amounts of digital data.

HDMI connectors are widely classified into standard types A connector, type B dual-link connector, type C mini connector, type D micro connector, and type E (Automotive Connection System) connectors.

DisplayPort (DP) Connectors

DisplayPort (DP) Connectors, limited to video with some models having audio capability, link audio and video source devices to display devices (monitors, TVs or projectors) and are used with stated by high definition graphic displays and the computer systems needed to make this happen.

DisplayPort connectors are made in different versions and are required for the transmission of video and audio signals via a single cable.

DisplayPort connectors have 20 or maybe more pins. DisplayPort Connectors have lengths available for the consumer all the way from small lengths to much longer.

Digital Visual Interface (DVI) Connectors

Digital Visual Interface (DVI) Connectors, previously, now becoming obsolete, allow for analog and digital video signals in one cable. DVI connectors differ from HDMI connectors as DVI connector solely transmits video signals.

They were developed to replace VGA connectors and represents one of the most used video connectors. DVI connectors are useful for computers because they are good for long distances relative to video signal transmission.

Video Graphic Array (VGA) Connectors

A Video Graphic Array (VGA) Connectors is a standard interface for connecting video generating devices (i.e. computers) to screens in projection or displays. VGA connectors have 15 pins (3 rows of 5 pins) housed in a trapezoidal connector housing.

VGA connectors transmit analog video signal, which VGA connectors were designed for, since they were developed by IBM in 1987 for displaying video from a computer.

They have been largely replaced by the latest DVI and HDMI cables; however they are still present into the older equipment and in certain special applications.

Electronic Connector Mounting and Terminations

There are numerous options for how to mount connectors, this is to say how the leads of the connector mount or are fastened to the circuit board.

Mount or mounting varies in type: surface mount (SM); through the hold; hanging; cutout; and through the board. Even though the terminology termination and mounting are frequently interchanged in meaning, there are important differences between them.

The word mounting refers to the entirety of the project, and how the connectors interface, fasten, and attach. While the word termination is describing how the connection is being made, and may give some indication detail about how the connector is fastened at either end.

Mounting Types

The word mount can be a little challenging as to what it is referring. In general, mount or mounting is a broad term that covers the ways connectors are attached and the various types of connectors are terminated using different mounting methods depending on the terminating leads and type of connector.

• Pin Through Hole – The pin through hole mounting method will be used the terminating leads are attached to a circuit board by inserting via holes in a board.
• Surface Mount – A surface mount is when terminating leads or pads are attached to the terminating device.
• Panel Mount – Panel mount is a type of surface mount where the connector is positioned inside a hole with attach variations of threading or a nut to secure the connector in place.
• Hanging – In a hanging mount the connector is installed on the cable whose leads are being terminated.
• Cutout mount – In a cutout mount the connector is placed at the edge of the board to take advantage of the use of the board edge. The cutout provides for mounting because the board has been made to provide use with a shortened connector. Cutout placing is used for lack of space.
• Through the Board mount – The through the board mount is a hybrid of a cutout mount and a panel mount. The total termination mounts through the board using holes in the board and solder on the same side as the mate of the connector or connectors and others, who mount from the side of the board and are surface mount.

Methods of Termination

There are various methods of termination, some based on individual preferences since there are different methods of certain terminations. It will really depend on the application and the project directions on what selection will be made.

Through Hole Soldering

Wires connecting a wire to the board or board-to-board solder terminations are typically created using solder on either through-hole mount or on surface mount devices.

In the areas of through-hole terminations, the types of connectors will be added inside drilled holes with the solder placed on the contact pads on the other side of the printed circuit board (PCB).

Surface Mount Termination

In surface mount terminations, the leads and mounting pads will be in the same surface side of the circuit board. The solder components are usually hand-placed, but can be soldered using either reflow or wave solder. The solder terminal will place solder on the contact pads, which are on the same side as the connector.

Crimping

Crimp connections would be compression from electrical wires is forced against a crimp termination, or splice band for a crimp connection. The crimp compression on the wire strands causes deformation; forming a low-resistant electrical connection, much like a cold weld.

Today’s crimp has become very important in a reliable connections and terminations for terminals. Poor crimping can cause electrical failure, or potentially fire as well.

The preparation of the wire, size, making every attempt to use the appropriate type of termination, and tools, and adjustments to provide a reliable, and permanent connection are all related. To begin making the crimp, the evaluation of, and measurement of the cross-sectional area of the wire begins.

In addition, the crimp tool can be either a ratchet crimper, or a manual crimper. The full jaws area for an entire crimp will cover the full connector surface area; with crimper dies matched to the wire gauge.

Many crimper dies are also color coded to ease set up as well. The insulated wire to be crimped fits snugly in the barrel of a connector (or terminal), measuring typically 0.25 inches (0.64 cm) in diameter.

With the wire positioned, the jaws of the crimper are closed, creating compressive forces on both the barrel and wire. The result is that the compression eliminates the insulation from the wire and exposes the conductors embedded in the wire.

A tight connection of the connector and wire is necessary to prevent failure in the connection and consequential damage.

One final operation in the crimping process is to twist the exposed wire tightly with pliers, making sure it fits snugly in the connector barrel.

The stripped and exposed wire enters the barrel of the connector until the insulation of the wire meets the barrel. No exposed wire should be visible at either the entrance to the barrel or extending through the barrel and into the tongue of the terminal.

As before, we lay the connector and stripped wire back into the crimper die in a horizontal position, looking down on the barrel end, or in the crimpers die, with the flat end of the terminal facing down and the barrel end facing up. The die on the crimper is color coded to fit the insulation color of the wire for the gauge of wire selected.

We need to position crimper in position opposite to the connector and stripped wire, in a way that would allow the crimper jaws to hold the connector and stripped wire firm and tight.

The jaws would be positioned close to the tongue of the connector and insulated end of the wire. Once the jaws have been placed, the crimper’s jaws are squeezed closed by applying a large amount of force such that it is not released when the wire is pulled away from the terminal.

Protecting the wire and connector of the terminal from exposure to the environment when the job is complete can be accomplished using either electrical tape or a heat shrink seal.

Electrical tape uses adhesive to form a tight seal, and heat shrink occurs when heat is applied melting plastic material causing it to deform to the shape of the terminal.

Crimping is more effective than soldering for wiring connections it avoids failure of soldered joints that become brittle and crack with age. Terminal manufacturers provide guidance on the correct tooling and materials, follow this guidance to avoid wiring failures.

The ratchet crimp tool allows users to feel that the crimp of the terminal is completely compressed and has a color coded dye for easy identification. The jaws of the ratchet crimp tool can only be opened until the crimp of the connector to wire is snug and tight.

Insulation Displacement Connectors

Insulation Displacement Connectors (IDCs) have sharp blades strips the wire insulation as the wire or cable is inserted. Properly placed the exposed area of the wire is cold-welded to the connector terminal making for a tight connection that will not fail.

The insulation displacement connector is commonly used for such wiring assemblies as ribbon cable connectors plug for telephones and network communications.

Push-In Termination

Push in terminations are reliable and rugged terminators, the connection can be temporary or permanently made. Wires are stripped and pushed into a connector or locked into place.

Technically, push-in and lock-in are the most common methods but there are many variations of push-in terminations. Push-in terminations are familiar and common to many connector types.

Because of potentially destructive vibration, push-in terminations must only be used on application that are rated for safe use based on the vibration rating for that application.