How to Select Military (MIL-SPEC) ConnectorsHow to select Military (MIL-SPEC) ConnectorsHow to select Military (MIL-SPEC) Connectors

MIL - C- 26482 | MIL - C - 24308 | MIL - C - 28748

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Military (MIL-SPEC) connectors are shell-type connectors which 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.

 

Military (MIL-SPEC) Connectors

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Connectors typically consist of a mating pair, known as a plug and receptacle, and each pair is equipped with male (pin) or female (socket) contacts. Connectors used for electrical connections are typically made of beryllium copper or phosphor-bronze which is then plated with gold or some other type of non- corrosive, highly-conductive metal. Connectors used for fiber optic connections are typically plug (male) connectors with a protruding ferrule that holds the fibers and aligns two fibers for mating. An important specification for fiber optic connectors is the insertion loss, which is the amount of light lost in the connection.

 

Military Connector Specifications

Selecting military (MIL-SPEC) connectors requires an understanding of product parameters. Parameters to consider when specifying military (MIL-SPEC) connectors include:

 

 

how to select Military (MIL-SPEC) Connectors

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  • Number of contacts - The number of contacts is the number of conductive elements in a military connector which mate with a corresponding element to provide an electrical path.
  • Contact type - Contact types can be either pins or sockets.
  • Coupling type- Coupling types can be bayonet, threaded, push or pull (ball detent), breech lock, and spring rack or quick connect.
  • Contact size (American Wire Gauge - AWG) - Contact size is the designation used to differentiate one contact from another, typically denoted using AWG.

Geometry

In terms of device geometry, RF, and microwave connectors are either straight or right-angled. The geometry of the connector is based on the system in which it needs to fit.

 

Shell Specifications

  • Shell size- The most common shell sizes are available in .0625" increments starting at shell size 8 (.50) to shell size 36 (2.25). Both the connector and accessory manufacturers use the term "size" to designate the size of their respective products. Military (MIL-SPEC) connectors, which use threads to attach backshells, are usually equal to or within .062 of the connector shell size.
  • Shell style - The main connector housing is called the shell. For circular military (MIL-SPEC) connectors, the shell is cylindrical and available in incremental sizes starting around .375" in diameter. The shell style or gender can be straight plug, angled plug, wall or box mount receptacle, in line or cable receptacle, dummy receptacle, solder or weld mount receptacle, jam nut receptacle, and thru-bulkhead receptacle.
  • Shell gender- The gender is noted as male or female. Male "plugs" are also called header or free connectors. The plug is normal the movable portion and is attached to a cable of removable sub-assembly. In shell-type multiple contact connectors, the plug usually contains the socket contacts and is mounted on the "hot" (rack) side of the system. Plugs are inserted into female connectors such as receptacles, jacks, outlets, etc. to make circuit connectors.

Terminals

Terminals are devices that terminate a connection. They attach to posts, studs, or other conductors in order to establish an electrical connection. There are several options including,

  • Cage clamp- Electrical connections are made using a cage clamp.
  • Crimp- Crimp is the physical compression (deformation) of a contact wire barrel around a conductor to make an electrical and mechanical connection to the conductor.

Crimp. Image Credit: Multi-Contact

  • Insulation displacement connectors (ICD) - IDCs slice through cable insulation to make a connection. Forcing an insulated conductor into a restrictive slot in the connection part of the contact displaces the insulation so that the bare wire engages the sides of the slot. IDCs are mass termination connectors for flat cables and eliminate the need to strip insulation.
  • PCB solder- Electrical connection is made by soldering wires onto a printed circuit board (PCB).
  • Screw- Electrical connections are made using screws.
  • Lugs- Electrical connections are made using lugs.
  • Lanyard release- The lanyards can be of various lengths. Compliance with specific MIL-SPEC standards, the inclusion of backshell accessories and a lanyard, and applicability to audio or visual applications are other important considerations
  • Solder cup or solder- Solder cups are terminal ends or contacts into which conductors are inserted before soldering. A metal or metallic alloy is used to join metal surfaces together. Normally, a 60-40 rosin core (60% tin and 40% lead) is used for soldering electronic assemblies. Soldering is a wet process.
  • Tabs- Electrical connections are made through quick connect tabs.
  • Through-hole technology (THT)- THT mounts components on printed circuit boards by inserting component leads through holes in the board and then soldering. In pin termination, components are mounted on PCBs without soldering.
  • Wire wrap- Electrical connections are made by wrapping a stripped or unstripped solid wire around a terminal post that contains a series of sharp edges. This solderless process requires a special wrapping tool.

Military Specifications

Specific military specifications that can be met by military (MIL-SPEC) connectors include:

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.
 

Other
 

Other unlisted military standards.


 Other standards for Military (MIL-SPEC) connectors include RoHS compliance and ARINC.

  • RoHS Compliant- Restriction of Hazardous Substances (RoHS) is a European Union (EU) directive that requires all manufacturers of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of the following hazardous substances: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl, and polybrominated diphenyl ether.
  • ARINC - ARINC is a technical standard for the avionic industry. An ARINC connector complies with this standard and is used to interface avionic equipment.

Coupling Type

When selecting a military connector it is important to consider the type of coupling needed for the application. A coupler is a connector used to facilitate the joining of elements. It is typically associated with the transference of power or transference of electric waves, from one device or component, to another.

Coupling Type

 

Bayonet Coupling

Quick coupling devices for mating circular connectors, using projections riding in ramps and providing jacking and locking features with limited rotation. It is commonly used with coaxial connectors for network or video transmissions. Bayonet coupling provides constant impedance due to the small bayonet that inserts in a helical channel in the receptacles to align and secure the connector. Bayonet coupling may not perform under severe conditions with large diameter cable and backshell.
 

Breech Lock Coupling


 

Functions as a safety feature for locking and coupling. Breech lock coupling is comprised of a removable locking ring used to secure the components together without pre-loading; however it can also be used in a loaded system depending on the user’s needs. The coupling can be taken apart for cleaning and maintenance.

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Push/Pull (Ball Detent Coupling)
how to select Military (MIL-SPEC) Connectors 

A quick-axial coupling with self-locking feature. Unlocking is achieved by an axial pull on the connector. Ball detent coupling can be used to protect rotating machines and components from damage in case of overloading. 

Image Credit: Ringfeder Power Transmission
 

Spring Rack/Quick Connect
How to Select Military (MIL-SPEC) Connectors 

A type of coupling which permits relatively rapid uncoupling. Quick connect coupling has broad application for corrosive liquid flow applications. The coupling provides easy attachments for components and can be used in a wide variety of industries.  
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Threaded Coupling

how to select Military (MIL-SPEC) Connectors
 

A means of coupling by engaging screw threads present on the mating connectors.

Image Credit: Design World

 

Features

Military (MIL - SPEC) connectors are available with additional features that help it perform in the desired application.

  • Integrated filter/magnetics- The connector has a filter to protect it against unwanted signals or magnetics to provide filtering, signal conditioning or isolation.
  • Underwater use - The connector has the appropriate sealing so that it can be used in underwater applications.
  • Hermetically sealed - The connector is hermetically sealed, allowing no internal moisture leakage.
  • EMI or RFI filter/ ESD shield - The connector has a filter to eliminate electromagnetic interference (EMI), radio frequency interference (RFI), and/or shielding to prevent electrostatic discharge (ESD) or EMI.  
  • Environment resistant - The connectors are able to withstand various environmental challenges including chemicals, sun, dirt, etc.

Resources

Fiber Optics: Illustrated Dictionary

U.S. Military connector specifications

Additional information on connectors can be found in How to Select Power Connectors, and How to Select Electrical Connectors.

 

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