Understanding MIL-Spec Connectors for Rugged Environments

In the high-stakes arena of military and aerospace applications, the reliability and durability of equipment is non-negotiable. Military Specification connectors, also known as MIL-Spec connectors, have become the go-to solution for engineers working in harsh and no-fail environments. That’s because these connectors boast a remarkable track record for longevity and reliability. However, understanding why they are the backbone of connectivity can be a daunting task for those less versed in technical details.

Most Common MIL-Spec Connectors

At the core of MIL-Spec connectivity are circular connectors, and understanding their construction is fundamental when selecting the right connectors. The most common MIL-Spec connectors in use are MIL-DTL-5015, MIL-DTL-26482, and MIL-DTL-38999.

MIL-DTL-5015

• Traditional, heavy-duty, larger series of circular connectors.
• Commonly found on military equipment and commercial applications and rated for minimum temperatures of -55°C up to maximum temperatures of 200°C
• Primarily handles heavy current loads.

MIL-DTL-26482

• Widely used small connectors that meet general requirements for two series of environment-resisting, quick disconnect, and miniature circular connectors.
• Extensively used in military equipment, including aircraft, and commercial applications.
• Available with either crimp or solder-type contacts.
• 3-point bayonet coupling.

MIL-DTL-38999

• Covers two series of miniature, high-density, quick disconnect, bayonet coupling, circular, environment-resistant electrical connectors that are capable of continuous operation within a temperature range of -65°C to +175C. These connectors are preferred for new military designs.
• Smallest of all MIL-Spec connector types.
• Witnessing significant growth, especially in automotive and autosport products.
• Features rear release, crimp removable contacts.

Rules of thumb to remember MIL-Spec Connectors:

• MIL-DTL-5015: traditional and largest connectors.
• MIL-DTL-26482: most common and widely adopted.
• MIL-DTL-38999: smallest and rapidly becoming the connector of choice for new designs.

Other MIL-Spec Standards

• MIL-C-22992, MIL-C-26500, MIL-C-27599, MIL-C-81703, MIL-C-83723, MIL-DTL-32139, MIL-DTL-83513: these cover various connector types and applications.

Beyond considering the core specifications when selecting a connector, a few additional compliance considerations can be crucial. RoHS Compliance ensures adherence to European Union directives that restrict hazardous substances in electronic and electrical equipment, while ARINC is a technical standard for the aviation industry that ensures compatibility with avionic equipment.

What are the most widely used MIL-Spec connectors?

The top three MIL-spec connectors include MIL-DTL-5015 for robust, threaded power and signal connections. MIL-DTL-38999 for high-density, environmentally resistant circular connections. And MIL-DTL-24308 for compact D-subminiature connectors optimal for space-limited applications. Each type offers various contact arrangements and is engineered to withstand the demanding conditions of military and aerospace operations.

Quick MIL-Spec Connectors Overview

MIL-Spec connectors consist of mating pairs – plugs and receptacles – equipped with male (pin) or female (socket) contacts.

Connectors for electrical applications are typically made of materials like beryllium copper or phosphor-bronze, plated with gold or other non-corrosive, highly-conductive metals.

Fiber optic connectors, on the other hand, feature plug connectors with protruding ferrules for aligning and holding fibers during mating.

Key Specifications for Selection

• Number of Contacts: The number of conductive elements in a military connector.
• Contact Type: Pins or sockets
• Coupling Type: Bayonet, threaded, push/pull (ball detent), breech lock, and spring rack or quick connect.
• Contact Size (AWG): Differentiated using American Wire Gauge (AWG)

Shell Specifications

The shell is the connector’s housing, made of anodized or plated aluminum, and comes in various styles such as circular, rectangular, and D-shaped. The shell’s style depends on the connector’s use and application requirements.

• Size:
  • Common sizes are available in 0.0625″ increments.
  • Threads used to attach backshells are usually equal to or within 0.062″ of the connector shell size.
•  Style:
  • Straight plug
  • Angled plug
  • Wall or box mount receptacle
  • In-line or cable receptacle
  • Dummy receptacle
  • Solder or weld mount receptacle
  • Jam nut receptacle
  • Thru-bulkhead receptacle
• Gender:

What Are Terminals? Here’s What You Need to Know:

Terminals are devices used to connect electrical conductors that attach to posts, studs, or other conductors to establish an electrical connection.

• Cage Clamp: electrical connections are made using a cage clamp.
• Crimp: physical compression of a contact wire barrel around a conductor.
• Insulation Displacement Connectors (IDC): slice through cable insulation for connection.
• PCB Solder: electrical connection made by soldering wires onto a printed circuit board.
• Screw, Lugs, Lanyard Release: connections made using screws, lugs, or lanyard release mechanisms.
• Solder Cup or Solder: terminal ends or contacts for soldering.
• Tabs, Through-Hole Technology (THT), Wire Wrap: Connections through quick connect tabs, THT mounts, or wire wrap.

How to Choose the Right Connection Mechanisms

Selecting the appropriate coupling type is pivotal for optimal connector performance in specific applications. The coupling types include bayonet, breech lock, push/pull (ball detent), spring rack/quick connect, and threaded coupling. Each type has different advantages.

Bayonet Coupling

Quick coupling comes with projections that ride in ramps for jacking and locking features. This type of coupling is commonly found in coaxial connectors that are widely used for network or video transmissions. The coupling provides a constant impedance as it comes equipped with a small bayonet that not only aligns but also secures the connector in place. This feature ensures that the connection is maintained and the signal quality is consistent, making it an ideal choice for applications where reliable transmission is crucial.

Breech Lock Coupling

This component functions as a locking and coupling safety feature. It has a removable locking ring that secures components without pre-loading. It can be disassembled for cleaning and maintenance purposes.

Push/Pull (Ball Detent Coupling)

The mechanism features a quick-axial coupling with a self-locking design, which ensures secure attachment between connected components. To unlock the connector, an axial pull suffices. The mechanism also includes an overload protection system that limits energy transfer to prevent damage to rotating parts.

Spring Rack/Quick Connect

This coupling type is designed to allow for relatively rapid and easy uncoupling, making it a convenient option for applications involving the flow of corrosive liquids. It is widely applicable across various industries, providing easy attachments for components in a range of settings. With its fast uncoupling feature, this coupling type can save users time and effort during maintenance and repairs while also offering a reliable and durable solution for corrosive liquid flow applications.

Threaded Coupling

Threaded coupling is achieved by screw threads on mating connectors, commonly used in military and industrial settings. It’s a simple and effective means of joining two components together, allowing for quick and easy assembly and disassembly.

MIL-Spec Connector Features for Demanding Environments

MIL-Spec connectors are equipped with features that enhance their performance in demanding environments:

• Integrated Filter/Magnetics: protection against unwanted signals or magnetics for filtering, signal conditioning, or isolation.
• Underwater Use: sealing for underwater applications without internal moisture leakage.
• Hermetically Sealed: ensures no internal moisture leakage.
• EMI or RFI Filter/ESD Shield: includes a filter to eliminate electromagnetic interference (EMI) or radio frequency interference (RFI), and/or shielding to prevent electrostatic discharge (ESD).
• Environment Resistant: capable of withstanding various environmental challenges, including exposure to chemicals, sunlight, dirt, etc.

How to Choose the Right MIL-Spec Connector

Now that you understand the qualities of MIL-Spec connectors. There are specific factors to consider when making your selection. Aside from considering the above-mentioned things like shell specifications, coupling mechanisms, contact configuration, etc… The next thing to consider is your application requirements. Ask the questions: what are the environmental conditions where the connector will operate? Will it be exposed to extreme temperatures or moisture? Are there chemicals present? Does the application involve vibration or shock? What are the size and weight limitations, if any? Does the connector need to have additional features? By asking these questions, you can use the information in this article and a process of elimination to find the right connector.

Key Takeaways:

• At the core of MIL-Spec connectivity are circular connectors, and understanding their construction is fundamental when selecting the right connectors.
• The most common MIL-Spec connectors in use are MIL-DTL-5015, MIL-DTL-26482, and MIL-DTL-38999
• MIL-DTL-5015: oldest and largest connectors.
• MIL-DTL-26482: most common and widely adopted.
• MIL-DTL-38999: smallest and rapidly becoming the connector of choice for new designs.
• Selecting the right coupling type is pivotal for optimal connector performance in specific applications.
• Beyond considering the core specifications when selecting a connector, a few additional compliance considerations can be crucial.

The Air Electro Connection

The unforgiving landscapes of military and aerospace operations require an understanding of MIL-Spec connectors that is not just an exercise in technical knowledge but a strategic imperative. The robust design and adherence to stringent standards of these connectors stand as the linchpin of reliable communication in the face of extreme conditions.

Air Electro offers a diverse range of interconnect products, including MIL-DTL-38999 Series I, II, & III in Aluminum, Steel, and Composite Shells, MIL-DTL-26500 qualified to BACC Connector Specifications, EPX General Purpose Rectangular Connectors, and ARINC 404 & 600 Series.We proudly hold the title of the world’s largest distributor for Tri-Star Mil-DTL-39029 contacts, in addition to their BACC47 and EN3155 Series.

Choose Air Electro for a seamless and reliable connection that stands the test of time.Start today.