An electronic connector is an electro-mechanical device whose purpose is to quickly and easily disconnect or interrupt a circuit path or electrical circuits . Most electrical connectors have a gender – i.e. the male component, called a plug, connects to the female component, or socket. The connection may be removable (as for portable equipment), require a tool for assembly and removal, or serve as a permanent electrical joint between two points. An adapter can be used to join dissimilar connectors. In computing, electrical connectors are considered a physical interface and constitute part of the physical layer in the OSI model of networking.
Connectors are purely passive components – that is, they do not enhance the function of a circuit – so connectors should affect the function of a circuit as little as possible. Insecure mounting of connectors (primarily chassis-mounted) can contribute significantly to the risk of failure, especially when subjected to extreme shock or vibration. Other causes of failure are connectors inadequately rated for the applied current and voltage, connectors with inadequate ingress protection, and threaded backshells that are worn or damaged. High temperatures can also cause failure in connectors, resulting in an “avalanche” of failures – ambient temperature increases, leading to a decrease in insulation resistance and increase in conductor resistance; this increase generates more heat, and the cycle repeats.
Fretting (so-called dynamic corrosion) is a common failure mode in electrical connectors that have not been specifically designed to prevent it, especially in those that are frequently mated and de-mated. Surface corrosion is a risk for many metal parts in connectors, and can cause contacts to form a thin surface layer that increases resistance, thus contributing to heat buildup and intermittent connections. However, remating or reseating a connector can alleviate the issue of surface corrosion, since each cycle scrapes a microscopic layer off the surface of the contact(s), exposing a fresh, unoxidised surface.
Today’s connectors are becoming smaller and smaller owing to the general trend towards miniaturisation in electronic devices across all sectors, whether domestic, business, medical, military, manufacturing or other. The miniaturization of devices is leading to new thinking in how best to achieve connectivity and maintain it through any force that may be applied to it. This is where the importance of ruggedly designed and light smart connectors that remain reliable and continue to function through shocks, vibrations, or impacts.
Emerging trends, which have a direct impact on the dynamics of the connector industry, includes Increasing demand for high-speed connectors, shift towards compact and thinner connectors, development of high power connectors.
Small unmanned aerial vehicles (UAVs) for military use are getting even smaller and more powerful as trends toward miniaturization in modern military equipment extends to the skies. To provide increased surveillance and reconnaissance capabilities, military UAVs depend on payloads that include multiple sensors and cameras for multiple frequencies, such as thermal, infrared, and visible light. Payloads also usually include sophisticated embedded computing and storage devices.
As we power up our modern battlefield electronic technologies, we see the evolution of miniaturized modules from sensors, cameras, communicators, and actuators. Circuit chips now run on lower voltage and current levels while the data is routed shorter distances. This trend embraces the use of smaller, lighter electronics all around
This trend also allows highly portable power systems to be integrated into one common cable routing system and lower current carrying connectors. We are also seeing new cutting-edge connector securing options that reduce the use/need for tools to mate and de-mate connectors.
Powering and supplying signals simultaneously in one miniaturized cable has been key to increased mobility and safety of the battlefield troops involved. Cable with both power and high-speed digital signal processing requires new and additional wire system design and jacketing. To assure strength and environmental resistance while maintaining flexibility and small diameter cable materials have also changed.
All connector/cable combinations must be able to deliver power and clean data streams, undisturbed by electromagnetic interference or pulses, and continue working perfectly through USB 3.0 (5 Gigabits per second) and HDMI 2.1 (up to 48 Gigabits per second) connection speeds while being much smaller than 1cm in size. But even though they are small, they must be able to be easily connected/disconnected under battlefield conditions.
Keeping UAV weights down to increase flight time can be a challenge with these larger payloads. That’s also true for connector size and weight. Consequently, size, weight, and power (SWaP) and higher transmission speeds are becoming even more vital. The space remaining for electronics and interconnects is shrinking, so the challenge becomes maintaining or even increasing connector capabilities and performance within the same or a smaller package. “Interconnect companies continue to push the envelope of copper and utilize new contact configurations and materials to meet these requirements,” he said. This is intensifying the need for both SWaP-optimized designs with high-speed data rates. Connectors for military UAV applications must meet stringent environmental, electrical, mechanical, shock, and vibration specifications in order to maintain a durable, lasting system.
Yesterday’s connectors are less of an option to meet the demands in the highly aggressive mission-critical battlefields of today. Often, Mil-DTL-24308 and 38999’s are simply too big and heavy, as they were designed for older, larger bulkhead-type panel mounted systems used more traditionally on aerospace applications as opposed to soldier-worn.
An important market for such miniaturized connectors is in-man-portable electronics devices for military use. Soldiers nowadays are carrying more computing power than ever, and each device they carry will go through many different use cases. They used to carry just radios for communications, but now they may additionally be carrying cell phones, GPS devices, computers, night-vision goggles, as well as being a Wi-Fi hotspot for their colleagues to send and receive real-time battle data.
These, and all other portable devices, have one thing in common – all need rugged cables and connectors capable of transmitting data and power in some of the harshest environments anywhere. Cables and connectors for soldier-worn devices are demanding reduced sizes and weights, and also that they should be much more flexible as even uniform garments are becoming digitally enabled.
In general, military applications are pushing connectors to be more SWaP friendly, (Size, Weight, and Power). In other words, towards being smaller, lighter, and capable of carrying more data and power for applications such as space vehicles, smart munitions, missiles, communications, and a host of others, including combat uniforms.
Jackets carry power and data from source to destination through cables and connectors woven into the material, using round or rectangular small ruggedized Nano D-Sub miniature connectors that are manufactured to MIL-DTL-32139 to ensure they continue working in mission-critical applications.
Additional demands for military portability of powered circuits and connected/signal interconnects are emerging regularly in the form of soldier-worn power distributions hubs, that securely and safely control both power and data distribution of a tablet computer, heads-up displays, etc, as well as a number of IP68 cable system designed to connect to a number of peripheral cables and the main power unit.
Connectors come in a variety of sizes, shapes, complexities and quality levels
Thousands of configurations of connectors are manufactured for power, data, and audiovisual applications. Electrical connectors can be divided into four basic categories, differentiated by their function:
- Inline or cable connectors permanently attached to a cable, so it can be plugged into another terminal (either a stationary instrument or another cable)
- Chassis or panel connectors permanently attached to a piece of equipment so users can connect a cable to a stationary device
- PCB mount connectors soldered to a printed circuit board, providing a point for cable or wire attachment. (e.g. pin headers, screw terminals, board-to-board connectors)
- Splice or butt connectors (primarily insulation displacement connectors) that permanently join two lengths of wire or cable
Some connectors are designed such that certain pins make contact before others when inserted, and break first on disconnection. This is often used in power connectors to protect equipment, e.g. connecting safety ground first. It is also employed for digital signals, as a method to sequence connections properly in hot swapping.
Many connectors are keyed with some mechanical component (sometimes called a keyway), which prevents mating in an incorrect orientation. This can be used to prevent mechanical damage to connectors, from being jammed in at the wrong angle or into the wrong connector, or to prevent incompatible or dangerous electrical connections, such as plugging an audio cable into a power outlet. Keying also prevents otherwise symmetrical connectors from being connected in the wrong orientation or polarity. Keying is particularly important for situations where there are many similar connectors, such as in signal electronics. For instance, XLR connectors have a notch to ensure proper orientation, while Mini-DIN plugs have a plastic projection that fits into a corresponding hole in the socket (they also have a notched metal skirt to provide secondary keying).
For example, mobile phones might have any one of these sockets for data and power transfer: Micro-USB, Mini-USB, Mini-USB-A, Mini-USB-B, Mini-USB-C, Apple’s Lightning, and a further dizzying variety from mobile manufacturers with non-standard versions.
Your television and computer will have a selection of these: USB, USB-C, HDMI V 1.2, V 1.3, V1.4 and V2, Firewire, RJ45, Mini DisplayPort, DVI–I, DVI–D and DVI–D Dual Link, Mini DVI Connector, and VGA.
Connectors are characterized by their pinout, method of connection, materials, size, contact resistance, insulation, mechanical durability, ingress protection, lifetime (number of cycles), and ease of use.
It is usually desirable for a connector to be easy to identify visually, rapid to assemble, inexpensive, and require only simple tooling. In some cases an equipment manufacturer might choose a connector specifically because it is not compatible with those from other sources, allowing control of what may be connected. No single connector has all the ideal properties for every application; the proliferation of types is a result of the diverse yet specific requirements of manufacturers
Electrical connectors essentially consist of two classes of materials: conductors and insulators. Properties important to conductor materials are contact resistance, conductivity, mechanical strength, formability, and resilience. Insulators must have a high electrical resistance, withstand high temperatures, and be easy to manufacture for a precise fit.
Electrodes in connectors are usually made of copper alloys, due to their good conductivity and malleability. Alternatives include brass, phosphor bronze, and beryllium copper. The base electrode metal is often coated with another inert metal such as gold, nickel, or tin. The use of a coating material with good conductivity, mechanical robustness and corrosion resistance helps to reduce the influence of passivating oxide layers and surface adsorbates, which limit metal-to-metal contact patches and contribute to contact resistance. For example, copper alloys have favorable mechanical properties for electrodes, but are hard to solder and prone to corrosion. Thus, copper pins are usually coated with gold to alleviate these pitfalls, especially for analog signals and high reliability applications.
Contact carriers that hold the parts of a connector together are usually made of plastic, due to its insulating properties. Housings or backshells can be made of molded plastic or metal
Many connectors used for industrial and high-reliability applications are circular in cross section, with a cylindrical housing and circular contact interface geometries. This is in contrast to the rectangular design of some connectors, e.g. USB or blade connectors. They are commonly used for easier engagement and disengagement, tight environmental sealing, and rugged mechanical performance. They are widely used in military, aerospace, industrial machinery, and rail, where MIL-DTL-5015 and MIL-DTL-38999 are commonly specified. Fields such as sound engineering and radio communication also use circular connectors, such as XLR and BNC. AC power plugs are also commonly circular, for example, Schuko plugs and IEC 60309.
NMEA 2000 cabling using M12 connectors
The M12 connector, specified in IEC 61076-2-101, is a circular electrical plug/receptacle pair with 12mm OD mating threads, used in NMEA 2000, DeviceNet, IO-Link, some kinds of Industrial Ethernet, etc.
A disadvantage of the circular design is its inefficient use of panel space when used in arrays, when compared to rectangular connectors.
Circular connectors commonly use backshells, which provide physical and electromagnetic protection, whilst sometimes also providing a method for locking the connector into a receptacle. In some cases, this backshell provides a hermetic seal, or some degree of ingress protection, through the use of grommets, O-rings, or potting.
Originally, connectors that met military specifications—also known as Mil-Spec connectors—were created to ensure they met the toughest of requirements. It was quickly realized that these strict Mil-Spec standards produced products that are an ideal fit for rugged applications in areas such as automotive, mobile equipment, and oil and gas applications among many more. Connectors that meet the Mil-Spec requirements provide a robust, versatile solution for all applications, even in harsh environments.
Mil-Spec cordsets tested in accordance to meet IEC 60529 IP67 and IP68, which requires the product to remain fully functional after being submerged in 6 feet of water for 24 hours.
Harsh Environment Protection
To ensure reliability in applications involving snow, dirt, and wind, Mil-Spec products tested to NEMA 6P. These standards ensure protection against falling dirt, temporary submersion in water, incidental contact, and the external formation of ice on the cordset.
Mil-Spec cordsets also undergo straight and right angle pull testing. This ensures products exceed industry standards, resulting in a product built to thrive in the harshest of applications.
Previously known as MIL-C-38999, MIL-DTL-38999 connectors come in four series: Series I, Series II, Series III and Series IV. They are environmentally resistant connectors that use removable crimp contacts and have an operating range of -65 to +200°C.
Series I connectors are bayonet coupled and have high-vibration properties. They are scoop proof and are ideal for heavy wind and moisture environments. They are utilised when a fast disconnect coupling system is required.
Series II connectors are bayonet coupled, are non-scoop proof, and have a low profile, so are used when weight or space is limited, or in low-vibration, high moisture, and strong wind situations.
Series III connectors are coupled by a quick screw Tri start thread, are scoop proof, and are best suited for normal mating and unmating applications and can be used in high temperature, moisture, wind, or vibration environments when used with the correct accessories. Series III connectors are most commonly use in Military and Aerospace designs.
Series IV connectors are coupled by a Breech-Lok mechanism, are scoop proof, lightweight and suitable for blind mating applications, and they also have high-vibration attributes. They are well suited in high wind and moisture environments when used with the appropriate accessories.
Signal shielding and isolation
Additionally, EMI shielding and ensuring cyber isolation requires improved shielding methods, often using multiple shields and drain wire methods. Conventional HDMI cables use shielded twisted pairs for everyday household use but for the battlefields, these cables must be smaller in diameter and must include multiple strand elements, as well as the inclusion of separate, shielded wrapped pairs with assigned drains per pair.
New specifications too are being written to accommodate these designs in an effort to help achieve very high-speed digital signal quality for the applications. Nano-miniature connectors are no different and require being wired differently. Protecting the impedance coupling from set to set implies new wiring layouts within the connectors.
Power sections are also isolated as part of the connector design and match up with the cable. Finally, the process of over-molding the connector using a polyurethane material bonding to the same polyurethane cable jacket assures IP-68 moisture protection and strain relief on the cable to connector interface.
Meanwhile, deep inside the connector, the pins and sockets are designed to full military specifications and are gold plated to assure more than 2,000 mates and de-mates. This provides long-term reliability of the new power and signal cable throughout the battlefield duration.
Micro UAVs Demand Smaller, Lighter Connectors
High-reliability connectors and cabling solutions from Harwin combine a rugged, lightweight construction with compact size, enabling the power and data needed for military UAVs without adding unwanted bulk to the design. Harwin’s slimline 1.25mm-pitch Gecko Connectors are a high-performance alternative to conventional micro-D connectors. The Gecko-SL features stainless steel screw-locks to provide greater resilience to vibration. In addition, the company’s Datamate Mix-Tek family can combine power, signal, and RF contacts inside a single compact housing to reduce the weight of wire harnesses.
Amphenol’s RADSOK contact system is one example of how connector suppliers are coming up with innovative contact designs, insert materials, and pin layouts to handle the demand for higher speeds and higher power, while reducing size and weight, said Favale. This technology is based on a stamped, formed flat grid twisted into a hyperbolic geometry that provides robust, high-density contact to the mating pin contact. It increases reliability and power, reduces size, and reduces insertion and extraction forces, which makes it a highly versatile contact for applications requiring higher power in a smaller package, like military UAVs.
A method for quickly disconnecting cables in the field is also essential for tasks such as testing or uploading mission data, said Favale. Relevant coupling types include quick disconnect, bayonet, push-pull, and break-away, and the designer’s choice depends on the application and the environment.Amphenol’s RADSOK contacts employ hyperbolic contact geometries (inset above) to enable versatile, high-power connectors with increased reliability, reduced size, and reduced insertion and extraction forces and are also available at Avnet.
“For UAVs exposed to sand or the elements, and with a need to quickly connect for testing or software uploads, a break-away coupling with a contact system using pogo pins can be used,” said Favale. “Pogo pins are uniquely suited to mate with an electrical pad, allowing the pad side to be easily cleaned off. The pad replaces a typical socket contact, in which a good connection can be easily prevented by sand and other debris.” ITT Cannon’s Nemesis Series connectors are environmentally sealed and have a quick-disconnect coupling with a pogo pin on the plug side and an electrical pad on the receptacle side. This lets the operator quickly and reliably connect and disconnect in the harshest environments.
In some UAV applications, the micro-D, or M83513, is a good solution. This connector handles high vibration in a very small package, with only 0.05” contact spacing, said Favale. Some connector manufacturers, such as ITT Cannon, use a twisted-pin contact with seven points of contact to ensure high reliability under even the harshest conditions.
The choice of packages and shapes for connectors used in military UAVs depends on space constraints, as well as the specific application, said Favale. Designers should ask questions such as the following to determine what’s best for their application: What are the shielding requirements? What are the height, width, and depth specifications? How many signal and power pins are needed? How will the connector be terminated? and What are the cabling requirements? A growing selection of connectivity products are available to answer these questions and help military UAVs take to the skies, in any size.
The connector market is forecast to reach $82.5 billion by 2027 with a CAGR of 4.2% from 2021 to 2027. The major growth drivers for this market are growth in the communication and consumer electronics industries, miniaturization of electronic devices, and increasing electronic content in vehicles.
The future of the connector market looks promising with opportunities in the automotive and transportation, telecom/datacom, computer, and peripheral, industrial, and consumer electronics industries. The major growth drivers for this market are growing 3C applications (Computers, Communications, and Consumer Electronics), miniaturization of electronic devices, and demand for products with advanced features, convenience, and connectivity.
Transportation will remain the largest end use industry and witness the highest growth during the forecast due to increasing electronic content in automotive vehicles due to the proliferation of infotainment, telematics, and safety systems.
PCB connector will remain the largest product type due to growing automation in various sectors such as automotive, industrial, and the military is driving the PCB connectors. Fiber optic connector segment is expected to witness the highest growth rate due to its easy installation, fast connection, low signal loss, and high performance which are highly required in optical communications.
Within the connector market, automotive and transportation will remain the largest end-use industry and witness the highest growth during the forecast period due to increasing electronic content in vehicles, increasing the need for safety systems, and growing demand for hybrid and electric vehicles. The Asia-Pacific is expected to remain the largest market and will experience the highest growth over the forecast period. The growth is supported by growth in automotive production, growing demand in tablets and smartphones, and increasing industrial automation, and growth in demand for home appliances. The awareness regarding increasing air pollution levels has encouraged the adoption of electric vehicles that create tremendous opportunities for connectors in China, Japan, India, and other countries
By Type, Connectors market has been segmented into Power and Circuit Connectors, PCB Connectors, Bayonet Connector, Rectangular I/O Connector, Rf And Coaxial Connectors, Circular Connector, 2 Mm Connector, FPC Connector and others
RF coax connectors are increasingly important as the number of fixed communications and wireless enabled devices and the amount of data consumed grows at an almost unfathomable rate. The global forecast is for over 2.7 billion 5G connections by 2025 (per CCS Insights). The COVID-19 pandemic has slowed the standardization work needed to enable availability of 5G for enterprise implementations. Limitations occurring during today’s different work scenarios will add Io pent-up demand to assure fast growth.
Bishop & Associates forecasts that by 2025, 21% of all worldwide cellular connections will be 5G, which offers great potential for RF coax connectors, ranging from ultra-miniature board-to-board (B2B) for handheld and mobile devices to higher power and lower PIM connectors for base stations, and V- and E-band interconnects for greater bandwidth backhaul sites, plus all the associated infrastructure equipment, cables, and adapters.
The market for 5G small cells will be one of the fastest growing 5G segments, as installations in population-dense areas may be as close as 100 yards apart as well as layered within larger buildings. This will involve families of new coax connectors such as NEX10, 2.2/5, and 1.5/3.5 DIN, together with myriads of multi-port assemblies for antenna housings that can have upwards of 30 cable entries.
Design, production tolerances, test equipment, and methods all become more complex as frequency increases. Usually, specific-product (financial) margins follow frequency; for example, a 40GHz 2.92mm should be more profitable (and costly) than a 20GHz SMA. Higher production quantities favor lower frequency connectors having simpler technology and lower cost. As a result, most higher performance microwave and millimeter wave products are manufactured in the U.S. or Europe, while the majority of lower frequency RF interconnect currently are produced in Asia.
Several market areas have unique growth potentials. 5G communications will use the redefined E band for backhaul transmission, prompting the development of microwave connectors performing to 92GHz, while expanding sales for lower frequency standard and low-PIM connectors such as 4.1/9.5 “mini-DIN”, N, 7/16, and 4.3/10. Mobile 5G and IoT devices will also expand demand for the automated production and installation of microminiature RF coaxial connectors such as U.FL, X.FL, MHF/PCIe, and miniatures such as MMCX and HD-BNC, primarily for operation to 6GHz. High-speed video for the 2021 Olympics (postponed from 2020) and surveillance UAVs will require new 18GHz, 75Ω coax connectors and cables.
Coax connectors continue to keep pace with application advances. Vehicles will be served by new FAKRA-mini versions operating to 17GHz. Phase-steered antennas, progressively smaller instrumentation, and 5G New Radio (NR) will increase the use of miniature blind-mates such as SMP3. Larger commercial assemblies may incorporate new connectors per VITA 67.3, while the recently established SOSA Consortium is specifying other VITA Open-VPX connectors for military programs. Leading-edge test equipment will expand use of compression-mounted coax jacks and fly-over assemblies. RF connectors are also being designed to replace waveguides to support frequencies above the 145GHz provided by Anritsu’s 0.8 mm connectors.
Key suppliers of microminiature board-to-board and cable-to-board RF coax connectors include Hirose Electric, I-PEX Connectors, and JAE (an NEC Company), based in Japan, plus Amphenol SV Microwave, Molex, and Samtec in the U.S., along with European suppliers such as Radiall and Rosenberger. China is able to offer higher frequency connectors, but its stainless steel can have residual magnetic properties and surface corrosion, indicating alloy impurities.
Growing use of data transfer, powering electrical devices, and electrical signal transmissions is increasing the penetration of MIL circular connector which is driving the market growth. In addition to this, rising military applications across the world is anticipated to provide ample of growth opportunities to the players operating in the MIL circular connector market.
Major players are A.E. Petshce (Arrow Electronics, Inc.), AMETEK.Inc., Amphenol, Collins Aerospace (Raytheon Technologies Corporation), Eaton, Fischer Connectors SA, ITT Corporation, Promark Electronics Inc., Smiths Interconnect, Souriau, and TE Connectivity.
References and Resources also include: