In the world of the electrical interconnection market, engineers and such have come across many different types of connectors. One connector that many may have seen or mostly heard of is the MIL-SPEC Connector, also gone by as the MS, MIL-STD or Military Standard connector. As the name signifies, these connectors were originally created by and for the military’s tactical and aeronautical applications by the Department of Defense somewhere in the 1930s. Back then, they were called AN or Army/Navy connectors. Now, you can recognize them by the “MIL or MS” proceeding a products nomenclature.
Where and Why Use MIL-STD Connectors?
As we know, military and defense operations are run worldwide. In order to run these operations, equipment is required and oftentimes, specialized equipment. Electrical connectors are not exempt from being a contributing factor, better yet component, of the specialized equipment used to conduct these military assignments. As one would guess, the success rate of mission can come down to the reliability of the equipment involved. A reliable connector was created to be part of various applications such as military vehicles like Humvees, armored carriers, tanks and aircraft equipment like helicopters and the infamously popular drones. These connectors were designed to be a standard within the severe and demanding environments that is present in warfare. In addition to being used in other environmental applications such as oil, gas, marine, automotive, and other industrial arenas. The application’s environment plays a role in deciding if and what type of MS connector will be used. There are MS connectors that cater to environments requiring resistance to vibration, corrosion, high temperatures and much more.
MIL-STD connectors typically comprise of a mating pair, one part being a plug (male-pin configuration) and the other a receptacle (female-socket configuration). See image above. Each pair has a matching male (pin) contact with a female (socket) contact. These connectors are commonly constructed of beryllium-copper alloy or phosphor-bronze. These metals have excellent conductive properties which would be important when establishing electrical connections. These metals are also plated with another highly conductive non-corrosive metal, usually gold. When used for fiber optic connections, the plug (male) connectors have a protruding ferrule. This holds the fibers in place and aids in the alignment of two fibers so that a connection can be made. One important factor to keep in mind when dealing with a fiber optic connection is the connectors insertion loss. This is the amount of light that will be lost upon establishing a connection.
Selecting a MIL-STD Connector
There are 6 product parameters to consider when choosing a MIL-STD connector.
They are the connectors:
- Contacts
- Number
- Type
- Size
- Coupling method
- Shell
- Terminals
Contacts
The number of contacts defines the number of conductive elements present within the MIL-STD connector. These elements mate with their corresponding connector’s elements to create the electrical path for its designated application. The contact’s type is simply the connectors mating orientation. The contact will either be pins (male) or sockets (female) within the connector. The contact size, which uses the American Wire Gauge – AWG designation, is used to differentiate the contacts from each other. The final contact related parameter is the contact’s coupling method. There are multiple types of coupling methods available that include:
- Threaded coupling – screw threads onto the mating connector.
- Ball detent coupling – push-pull, self-locking coupling that can protect rotating elements from overloading damage.
- Bayonet coupling – jacking and fast locking capability but limited in rotation ability.
- Spring rack/Quick-connect coupling – used widely, especially for corrosive liquid flowing applications.
- Breech lock coupling – which has a removable locking ring that enables safe joining of the components and easy dismantling for cleaning and maintenance.
Connector Shell
The main housing of the connector is called the shell. This shell is typically made of metal that has been plated for corrosion resistance. Like the connectors contact type, the shell comes in various styles such as:
- Straight or angles plug
- Wall or box-mount receptacle
- In-line or cable receptacle
- Jam nut receptacle
- Dummy receptacle
- Through-bulkhead receptacle
- Solder or weld-mount receptacle
The most common connectors come in a variety of sizes starting at a shell size of 8 (0.50). The shell size then increases by increments of 0.0625” all the way up to a size 36 (2.25). For circular MIL-STD connectors, the shell is cylindrical and comes in incremental sizes starting around 0.375”. MIL-STD connectors use threads to attach back shells to the shell housing and are usually within or equal to 0.062” of the connector shell size. The connector’s shell is either designated male or female. The male (plug) is sometimes called a header or free connector. This plug is movable and is attached to a removable sub-assembly cable. To establish the circuit connection, the plug is inserted into the female (socket) which can either be a receptable, jack, or outlet of some kind.
Terminals
Used to terminate, in the electrical sense, a connection and can be attached to posts, studs, or other conductor types to create an electrical connection. Like some of the preceding parameters, there are several types of terminals used to terminal e connection. Some the most commonly used are:
- Crimp – the physical compression of a contact wire barrel around a conductor to make a mechanical and electrical connection. This is usually done with a specialized tool.
- Cage clamp – connections made using cage clamp
- Insulation Displacement Connectors (IDCs) – connection is made by slicing through the cable insulation with an IDC. They are mass termination connectors for flat cables and eliminate the need to strip the insulation manually.
- PCB solder – soldering wires onto a printed circuit board (PCB)
- Screw – connections made using screws
- Lugs – connections made using lugs
- Tabs – connections made using quick connect tabs
- Through-hole technology (THT) – mounts components by pushing component lead through holes in a PCB and then soldering. In pin termination, components are mounted without soldering.
- Lanyard release – in compliance with MIL-SPEC standards, backshell accessories and a lanyard are included.
In addition, MIL-SPEC connectors can come with other features that help fulfill a desired function. Some of those features are: integrated filter/magnetics, hermetically sealed, EMI or RFI filter/ESD shield, underwater use and environmental resistance.
After all things are considered, MIL-SPEC connectors are specially designed to comply with military specifications. Those standards are listed below with the most common 3 being MIL-C-5015, MIL-C-26482, and MIL-C-38999. See table below for listing of well-known military specifications.
| Military Specifications | |
| MIL-C-5015 | MIL-C-5015 is the most popular of all cylindrical connector standards for general use in electronic interconnection systems. These connectors are used in both military and commercial applications. This specification covers circular electrical connectors with solder or removable crimp contacts (both front and rear release). These connectors are rated for operation within a temperature range of -55°C (-67°F) to either 125°C (257 °F), 175°C (347 °F), or 200°C (392 °F) depending upon the class of the connector. |
| MIL-C-22992 | MIL-C-22992 refers to heavy duty, multi-contact; quick disconnect electrical plug and receptacle connectors normally used in industrial and military applications. They are designed to support very high levels of power. The connectors are rated for -55 degrees to +125 degrees Celsius. |
| MIL-C-26482 | MIL-C-26482 covers the general requirements for two series of environment-resisting, quick disconnect, miniature circular connectors (and accessories). Each series contains hermetic receptacles. The two series of connectors are intermateable when using power contacts and are not intermateable when using shielded contacts. The MIL-C-26482 Series I connector is widely used for military communication systems since it is small sized and the electrical, mechanical, and environment properties are excellent. |
| MIL-C-26500 | MIL-C-26500 covers an environment-resisting family of miniature, circular, electrical connectors (plugs and receptacles), designed to meet the requirements of advanced aircraft, rockets, missiles, and space vehicles. The physical characteristics for connectors include a series of plugs and receptacles in which the socket contact inserts have a resilient face, and the mating pin inserts may have either a resilient or a hard face. |
| MIL-C-27599 | MIL-C-27599 covers two series of miniature, high density, quick disconnect, bayonet coupling, circular, environment resistant, electrical connectors capable of continuous operation within a temperature range of -65C to +175C. These connectors are intermateable with applicable series I and series II connectors of MIL-C-38999. |
| MIL-C-38999 | MIL-C-38999 covers two series of miniature, high density, quick disconnect, bayonet coupling, circular, environment resistant, electrical connectors capable of continuous operation within a temperature range of -65C to +175C. These connectors are intermateable with applicable series I and series II connectors of MIL-C-27599. |
| MIL-C-81703 | MIL-C-81703 covers three series of environment resisting, circular, miniature electrical connectors (plugs and receptacles) with removable crimp and/or non-removable solder contacts, and accessories. |
| MIL-C-83723 | The Department of Defense has inactivated MIL-C-83723 Series I in favor of “MIL-C-26482 Series II”. Note: MIL-C-83723 Series I and MIL-C-26482 connectors are identical. |
| MIL-DTL-5015 | The MIL-DTL-5015 specification is the workhorse connector of the MIL-Aerospace industry. Taking the MIL-DTL-5015‘s best features of the old solder 5015 and combining them with the rear accessories that are common to the MIL-C-26482 Series II and the MIL-C-83723 Series I and II, the MIL-DTL-5015 answers the air frame and ground support industries’ requirements for highly reliable rear release connectors. |
| MIL-DTL-32139 | MIL-DTL-32139 is a joint services specification administered by the Defense Supply Center, Columbus, Ohio (DSCC). This MIL-SPEC covers both plastic and metal nanominiature connectors. |
| MIL-DTL-38999 | MIL-DTL-38999 covers four series of miniature, high density, bayonet, threaded, or breech coupling, circular, environment resistant, electrical connectors. They use removable crimp or fixed hermetic solder contacts, and are capable of operation within a temperature range of -65°C to +200°C. |
| MIL-DTL-83513 | MIL-DTL-83513 is a joint services specification administered by the Defense Supply Center, Columbus, Ohio (DSCC). The original specification was released in 1985. Revision D, released in 1997, changed the document from “MIL-C-83513” to “MIL-DTL-83513”. This change was made to adopt performance driven specifications and industry standards. The MIL-SPEC covers both plastic and metal shell Micro-D connectors. |
| MIL-DTL-83723 | MIL-DTL-83723 covers the general requirements for environment resisting, circular, electrical connectors and their associated contacts and accessories. These connectors shall utilize crimp or solder contacts and be capable of operation within the specified range. |
If you need MIL-SPEC connectors, MISUMI has all your military standard connectors, with in-stock options available for you. Explore the selection here.
Works Cited
GlobalSpec. (2023). GlobalSpec. Retrieved from Military (MIL-SPEC) Connectors Information: https://www.globalspec.com/learnmore/electrical_electronic_components/connectors/mil_spec_connectors
