Connectors for harsh environments
From the battlefield to the factory floor, connectors provide the power and communications for a wide range of demanding applications in the most challenging environments. Electrical and electronic connectors face significant challenges in these harsh environments where factors such as water exposure, extreme temperatures, vibration, and corrosive substances can lead to performance degradation or systems failure. Waterproof, vibration-resistant, and corrosion-resistant connectors are designed to mitigate these risks, but the conditions in which connectors work vary enormously from one application and market to another. This makes it essential for engineers to specify components with a full understanding of the conditions present during everyday operations as well as potential irregular events.
The right connectivity solution for harsh environment applications depends on a thorough understanding of the disruptive environmental factors and how they affect sensitive equipment. From robust mechanical designs and advanced materials to optimized electrical properties and sophisticated plating techniques, the industry has developed a comprehensive range of connectors that deliver reliability. By understanding the environment, engineers can select robust connectors capable of withstanding the most extreme operational environments.
Protecting connectors from water, moisture and contaminants
Electricity and water do not go together. Water has the power to dissolve, to corrode, and to conduct. It can damage metal components, it can affect plastics and other non-metallic parts, and it can create short circuits. Designers go to considerable lengths to protect electronics from the damage that can be caused by water and moisture. Manufacturers use the IP rating system to describe the level of protection that their equipment can deliver. IP ratings have now become common, even on consumer devices. The simple system uses a two-digit number to denote the level of protection. When using the IP rating to choose a connector, be sure to consider the environment. For instance, the IP68 and IP69K ratings are commonly applied to connectors but the difference between the two is subtle but important. The IP68 rating is intended for components that are expected to be immersed in water. While we might assume that the IP69K rating is superior for that condition, it is not; IP69K is specifically intended to protect against high-pressure water jets, not against being left in static water. This is an instance where engineers need to carefully match a component’s performance to the application requirements.
Table 1: Common IP-Rated Connectors for Harsh Environments
| IP Rating | Meaning | Common Applications |
|---|---|---|
| IP20 | Unsealed | Equipment in safe environments |
| IP44 | Basic splash and dust protection | Household appliances |
| IP54 | Dust-protected, water splashes from any direction | Indoor environments |
| IP65 | Dust-tight, low-pressure water jets | Outdoor enclosures, architectural lighting, CCTV equipment |
| IP67 | Dust-tight, submersible up to 1m for 30 min | Rugged electronics |
| IP68 | Fully waterproof beyond 1m depth | Marine, industrial, military |
| IP69K | High-pressure, high-temperature water jets | Food processing, automotive, agricultural equipment |
Engineers must be aware of another limitation of sealed or waterproof connectors. Most waterproof connectors only provide environmental protection when mated and must use other methods to remain sealed if left unconnected. However, there may be situations in which a connector is left unmated when in use. One example of this application would be the input/output (I/O) connector of a remote sensor. This connector may be left unmated for months and only used when staff return to download stored data. While it remains in the field, it is vital to protect the unmated connector with a cap to prevent water from damaging the sensor.
The right connector materials for maximum durability
Water also has the potential to create damaging corrosion. Most of us are familiar with corrosion in the form of iron oxide, otherwise known as rust. Rust occurs in the presence of water and oxygen. For this reason, few connectors use iron or steel as part of their construction. However, oxidization is not limited to ferrous materials.
Aluminum is a popular material for connector shells, especially in the defense and aerospace sectors. It is strong, lightweight, and electrically conductive. Aluminum bonds readily with oxygen, forming a layer of aluminum oxide on the surface. However, if the aluminum oxide is subjected to corrosive chemicals such as those found in rain or seawater, the protective layer of aluminum oxide will be destroyed, exposing the aluminum underneath and causing long-term damage to the connector body.
Aluminum can be protected from corrosion with electroplating. However, connector bodies often need to be conductive to provide shielding for the electrical signals within, and designers need to select the correct plating for their application to provide both environmental protection and shielding.
Other materials are more resistant to corrosion. Stainless steel and marine bronze (usually an alloy of nickel, aluminum, and bronze) are often used in applications that are exposed to seawater, but both choices are heavy and expensive. Plastic materials provide more affordable – and lightweight – solutions but bring other challenges.
Electronic equipment must work in environments that are filled with electromagnetic radiation. Many sources, from radio communications to the unwanted emissions from long cables, generate radiation, including electromagnetic interference (EMI) or radio frequency interference (RFI). To protect against EMI, electronic equipment is provided with conductive shielding. Plastics do not provide the electrical conductivity that is needed to protect against EMI, so designers must consider this limitation.
Extremes of temperature impact electronics materials. Equipment may be exposed to winter conditions in the Canadian north or the heat of equatorial Africa. Some rubber and plastic materials are brittle at low temperatures, while others become soft in high heat. This is also further complicated as some plastics become unstable when exposed to ultraviolet radiation in sunlight for long periods. Connectors intended for outdoors, therefore, use materials such as polyamide to provide the best combination of strength, operating temperature, and resistance to UV radiation.
Circular vs. rectangular connectors
Even the shape of the connector can play a role in its suitability for use in tough conditions. The broad range of available sealed or robust connectors are often circular or cylindrical in design. This is not a coincidence.
While many rectangular connectors are satisfactory for harsh or industrial applications, circular connectors have certain advantages. The cylindrical design is physically strong and resistant to the shock and vibration commonly found in tough environments. It is relatively easy to make a circular connector waterproof using O-ring seals. If the shell is made of metal, it will provide a 360° shield to help prevent EMI, and its circular shape accommodates cable-mounting, as most cables are also round.
As a result, many military connector specifications are circular and are seen by users as the ultimate harsh environment solution. These types deliver high performance in some of the toughest environments on earth, but there is a penalty to be paid for selecting military-grade connectors: Military circulars tend to be bulky, and their performance requires that they be manufactured from the highest-quality — and more expensive — materials.
Table 2: Commonly Used Materials for Connectors in Harsh Environments
| Material | Corrosion Resistance | Strength | Temperature Range | Common Applications |
|---|---|---|---|---|
| Stainless steel (316L, 304) | Excellent | High | -200˚C to 800˚C | Marine, food processing, medical, aerospace, industrial |
| Brass (plated or unplated) | Moderate (better with plating) | Medium | -100˚C to 200˚C | Industrial automation, general-purpose connectors |
| Aluminum (anodized or electroplated) | Good (with plating) | High | -200˚C to 600˚C | Aerospace, military, automotive, lightweight connectors |
| Titanium | Excellent | Very High | -250˚C to 600˚C | Aerospace, deep-sea, medical, extreme environments |
| Marine bronze (nickel, aluminum bronze - NAB) | Outstanding (especially in seawater) | High | -200˚C to 300˚C | Marine, offshore, shipbuilding, oil & gas |
| Plastic (PEEK, PPS, nylon, PVC, polyamide) | Varies (from moderate to very good) | Medium | -50˚C to 250˚C (depending on material) | Chemical plants, medical, consumer electronics, lightweight applications |
| Nickel alloys (inconel, monel) | Outstanding | Very High | -250˚C to 1000˚C (depending on material) | Extreme heat, offshore, chemical processing |
The industrial world boasts many affordable alternatives to high-performance military connectors. Some of them share a common heritage with military connectors, but are more cost-effective due to the use of plastic shells, compact designs, and ease-of-use features that commercial or industrial connectors can offer.
Not every application requires the full protection of military-grade components; many high-quality alternatives deliver the reliability and performance needed. With careful evaluation of environmental factors, designers can choose the best connector for the job.
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