Ruggedized connectors: Not necessarily big or bulky

Ruggedized connectors are usually associated with military/aerospace, industrial, and some medical applications, but there are consumer ones as well, in special circumstances. Of course, the phrase “ruggedized connector” invokes different requirements in different circumstances.

In brief, it’s the ability of the connector to endure and consistently function to specifications despite extreme mechanical, environmental, and thermal stresses. These stresses differ depending on the operating conditions but often have overlap as well. For example:

  • Connectors in land-based military systems must handle severe vibration, dirt accumulation (dust, sand, grit), and cold and heat extremes.
  • Seaborne interconnects must withstand prolonged exposure to corrosive saltwater; deep-sea ones must also withstand crushing pressure.
  • Aerospace applications must tolerate repeated take-offs, landings, and in-flight vibrations in addition to wide temperature ranges.
  • Space applications have more extreme temperature swings, vacuum exposure and outgassing, and intense mechanical stress during launch and re-entry.
  • Industrial applications often need to function despite vibration, shock, dirt, grease, abuse, and even neglect.
  • Some consumer-facing applications such as vending machines, commercial washers/dryers, arcade games, and elevators/escalators also need ruggedized attributes; it’s a surprisingly long list here.

Meeting these requirements involves an understanding of multiple factors, including:

  • Vibration: connectors in military vehicles or fighter jets are tested to resist forces up to 20 g.
  • Shock: a high-impact force during rapid acceleration or deceleration is a distinct from vibration. It can be as high as 50 g for standard connectors and 100 g for nano and micro designs.
  • Temperature extremes: ground-based systems may see temperatures ranging from -65°C to +125°C while space systems can go as high as 200°C.
  • Sealing and ingress protection: connectors may need to be protected against exposure to moisture, dust, and contaminants to ensure long-term operation using sealing solutions such as O-rings, gaskets, and grommets.
  • Corrosion: it’s caused by exposure to moisture and salt spray, leading to oxidation.

Deciding on a ruggedized connector requires attention to two broad design issues: the body or shell, and the electrical contacts.

For the body or shell, vendors and users consider what it’s made of, how it mates, retention and locking, and more. For this reason, rugged connectors are often associated with relatively bulky form factor, locking rings, and similar; but this is not necessarily the case.

For the contacts, ruggedized connectors also have sophisticated, specially designed and fabricated contacts that use suitable base metals and are clad with advanced plating to withstand and maintain contact despite the challenges. The contact pairs are often based on a multipoint design with two or four mating surfaces for redundancy, rather than a single mating point.

Start with a classic

One widely used choice for a ruggedized connection is the classic D-subminiature connector. If you think that the classic 9-pin D-subminiature connector (often called DB-9) and the rest of the broader family of D-subminiature connectors have largely disappeared due to the fading away of the “ancient” RS-232 interface—along with the rise of various versions of USB and Ethernet connectors—that’s not the case at all.

The D-sub form factor has been in use since the 1950s and still offers many advantages. It’s fully shielded against EMI/RFI and provides a sealed or nearly sealed enclosure. And it’s mechanically rugged, and its mating halves can be locked to each other with small jackscrews or other arrangements. This class of connectors is still widely used due to their flexibility, integrity, track record, and wide variety of models and versions. It’s so good that it is widely used in mil/aero and space-related designs.

This connector is offered in six basic standard-size bodies, but that is only part of its versatility. It also offers flexibility in its electrical contact positions and types.

In addition to offering connector shells with the same contact type at all positions, “Combo-D” D-subs such as those from Amphenol Positronic provide a mix of independent signal and power contacts within the connector shell (Figure 1). A single D-sub can support multiple signal contacts, power contacts, and more in a variety of mix-and-match arrangements. There are available contacts for signal, power, shielded, high voltage, thermocouple, and even fiber-optic applications.

Figure 1 The Combo-D subminiature connector style supports many signal- and power-path combinations (upper); these combinations are available in standardized, named shell sizes and contact arrangements (lower). Source: Amphenol Positronic

Among the material options for the shell are:

  • Thermoplastic polymers offer excellent mechanical strength, thermal resistance, and chemical stability. These materials effectively absorb vibration and shock in a low-weight structure.
  • Composite materials such as fiberglass-reinforced polymers and carbon fiber composites provide excellent strength-to-weight ratios. They can be engineered to maximize specific properties such as tensile strength, impact resistance, or thermal stability.
  • Metal enclosures of stainless steel and aluminum alloys are preferred materials for connector housing in the high-shock, high-vibration, and high-EMI environments of aerospace and defense applications.

The virtues of the sub-D shell—or any ruggedized housing—are an important part of the connector story, but they are only half of the ruggedness reality as the electrical contacts and their attributes are also critical. Over the years, there have been many innovations in contact technology with respect to materials, design, and electrical and mechanical performance.

For example, Amphenol Positronic uses its patented PosiBand contact technology (U.S. Patent 7,115,002) in one of its D-sub families. This contact has a unique approach to provide enhanced performance, where its external pressure-element design fully separates the mechanical action from the electrical action of the connection (Figure 2).

Figure 2 The PosiBand uses a patented design to separate the mechanical action and the electrical action of the connection. Source: Amphenol Positronic

The pressure element performs the mechanical action by applying a force pressing the male pin against the inner female cavity, achieving electrical connection along a long line of direct contact. Among its many subtle but important attributes is the spring clip within the PosiBand; it’s a small but critical part of the assembly and a key contributor to its vibration/shock performance (Figure 3).

Figure 3 The PosiBand spring clip provides a normal force across the contact area and so maximizes the electrical mating-surface contact area. Source: Amphenol Positronic

This spring-tempered beryllium copper alloy provides a normal force on the male contact, contributing to a rugged and reliable contact pairing. At the same time, it offers a lower average insertion force while meeting or exceeding performance requirements.

Consumer connectors get a little more rugged, too

The recent European initiative mandating use of USB-C for many classes of consumer end products is a major factor driving the use of this connector. Due to the wide availability of USB-C connected functions and peripherals, it seems logical that the connector and associated standard would be worth considering for medical, industrial, and other non-consumer appliances.

But there’s a problem with USB-C connectors: they are not rugged or sealed against intrusion, yet that’s where many may be used beyond low-end consumer applications.

Addressing this concern, Same Sky has introduced the UJ family of waterproof USB receptacles with IPX5, IPX6, IPX7, IPX8, IP66, IP67, and IP68 ratings, making them well-suited for applications where moisture and environmental contaminants are a concern (Figure 4). If you are not familiar with Same Sky, it was known as CUI Devices until it changed its name in September 2024.

Figure 4 These USB Type C connectors from Same Sky (formerly CUI Devices) feature water/dust intrusion-resistant O-rings to meet multiple IP ratings. Source: Same Sky

The five models are compatible with reflow soldering due to their UV-glued O-rings. This simplifies the PCB assembly process, as there is no need for a separate wave-soldering step (as is often the case with connectors and other larger components).

The five IP-rated USB Type C receptacles conform to a variety of USB standards, from USB 2.0 up to USB 4.0 Gen 3×2, with data-transfer speeds up to 40 Gbps as well as power delivery up to 240 W at 48 V and 5 A. The family also includes power-only models that remove the data-transfer pins to create a more cost-effective solution for designs where charging or power is the sole needed function.

If you are looking for a ruggedized connector, you have these and many other options. The first challenge is defining what you mean by “ruggedized” in your application beyond number and type of contacts and then pick which available connectors meet those criteria.

Maybe AI can help make the selection?

Bill Schweber is a degreed senior EE who has written three textbooks, hundreds of technical articles, opinion columns, and product features. Prior to becoming an author and editor, he spent his entire hands-on career on the analog side by working on power supplies, sensors, signal conditioning, and wired and wireless communication links. His work experience includes many years at Analog Devices in applications and marketing.

Related Content

The post Ruggedized connectors: Not necessarily big or bulky appeared first on EDN.