THE DIFFERENCE BETWEEN HERMETIC AND ENVIRONMENTAL CONNECTORS

Any time an electrical component needs to be protected from the environment, there are two types of sealed connectors that can get the job done: environmental and hermetic connectors. And while both are designed to protect against damaging contaminants and other stressors, the degree to which they do this and the role each one plays varies greatly. In this article, we’ll break down the difference between the two.

FIRST, LET’S START WITH ENVIRONMENTAL CONNECTORS

Environmental connectors are good, but they aren’t without their limitations. On the continuum of simply-sealed vs. absolutely-positively-nothing-is-getting-in, environmental connectors tend to be on the simply-sealed side.
 
Environmental connectors use an interface seal, or some kind of fitted gasket, to prevent contaminants from entering the intersection between the connection area. This means they can protect against damaging contaminants, such as water, dust, and dirt, among others — the big and obvious things. While these connectors do keep contaminants out, they aren’t capable of withstanding extreme environments or high-demand situations. Environmental connectors are usually made from some type of rubber, with fluoropolymers and ethylene-propylene rubber being the most common. These types of connectors are typically used in mobile machinery, marine, and on-highway vehicles.

Environmental connectors are typically used to protect electrical components in mobile machinery, marine, and on-highway vehicles, where the environments are not as extreme.

OKAY, SO WHAT ABOUT HERMETIC CONNECTORS?

Hermetic sealing is the process of creating a container that is airtight. Unlike environmental connectors, hermetic connectors are specifically designed to operate in extreme environments or withstand high pressures while mated or unmated. They are made using glass to create the hermetic barrier— not rubber or epoxy. This means that any material inside or outside of the container, whether it’s a gas, liquid, or solid, will not leak into or out of the container – making them an ideal connector for use in harsh environments like space or military combat.

GLASS-TO-METAL HERMETIC CONNECTORS

Glass-to-metal connectors are used when joining glass to a metal surface, hence the name. There are two types of glass-to-metal connectors: matched and compression. The type of glass-to-metal connector depends on the type of materials being used.

Match seals, used primarily in light bulbs, are formed when the glass and the metal have the same coefficient of thermal expansion. The seal's strength is sourced from the bond between the glass and the formation of oxide from the metal and tends to be weaker and unable to effectively withstand high-pressure fluctuations or extreme environments.

While match seals are technically considered a hermetically sealed component, they are typically used on simple applications such as lightbulbs.

Compression glass-to-metal hermetic connectors have higher chemical durability, can resist higher temperatures, rapid degrees of temperature change, and higher degrees of mechanical and electrical shock, and can be more easily engineered and manufactured into complex and innovative components. This flexibility makes these types of connectors ideal for high-pressure applications such as commercial aviation, military aerospace, and space transportation.

Compression glass-to-metal hermetically sealed connectors are typically used in extreme environments that are at the mercy of temperature, pressure, and vibrational demands.

SELECTING THE TYPE OF CONNECTOR

Understanding the requirements of the application is essential when selecting a connector. Factors include (but are certainly not limited to things such as):

• Dust and direct prevention requirements
• Liquid immersion and/per moisture vapor transmission requirements
• Mechanical and electrical shock values
• Temperature requirements
• Pressure requirements

 
The right partner can guide you through the decision-making process to select the metal alloys, glass formulations and product geometry that will help achieve your vision. For nearly 80 years, Hermetic Seal has been the go-to premier designer and manufacturer of high-performance, high-precision custom hermetically sealed connectors. Our products are used in some of the most prominent sensing and actuating systems found in the aerospace, defense, oil and gas, and medical device industries worldwide.