Hermetic sealing is the process of providing a leak-tight or vacuum seal. That implies that any material in a specific container, regardless if it's liquid, solid or gas, will not escape from its vessel. Hermetic packages channel or insulate electricity and avoids the entry of any contaminants. With that, this type of sealing is typically used to contain electric mechanisms, as well as to encase functional gases.

Hermetic seals are used in a variety of applications, and it depends on the industry it is being used in. Here are three things you should know about hermetic seals.

1. There are Glass-to-Metal Hermetic Seals

These kinds of seals are utilized when connecting glass to a metal surface, thus its name glass-to-metal. It is commonly used for typical household items such as neon or halogen lights bulbs - the method locks the glass to the metal surface to encase the gas. Glass-to-metal seals can also be divided into two kinds, and the difference lies in the nature of the materials used.

Compression or Mismatched Seals

Compression seals are stronger and can endure high-pressure differentials (likely up to 3000 bars) and various kinds of physical stress such as shock. This kind of glass-to-metal seal uses the differences in the coefficient of thermal expansion between the glass, housing, and pins. Therefore, the metal is established around the glass. Housing materials, especially those with a high CTE, like titanium or stainless steels, are perfect for compression seals.

Matched Seals

While compression seals use differences, match seals are formed when the coefficient of thermal expansion of the glass, housing, and pins are paralleled the closest as possible. The seal's power originates from the connection between the formations of oxide on the metal and the glass. This kind of glass-to-metal seal serves to be weaker as it cannot endure high-pressure changes within the two materials.

2. There are Ceramic-to-Metal Hermetic Seals

Ceramic-to-Metal Seals are accomplished using a high-temperature furnace to produce a terminal connection with a permanent hermetic bond. Then, it is covered with a metallic pattern. The ceramic part is generated from ceramic and glass powers of distinct particle size and a tying agent and solvent employed to build a uniform slurry. This type of seal is typically stable at extremely low and high temperatures. They can also endure great thermal shock or recurred thermal cycling.

3. There are Glass-to-Glass Hermetic Seals

Glass-to-glass seals are the top choice when you are looking to connect, as stated, two glass pieces. Since the coefficient of thermal expansion has a wide gap that makes it hard to be compatible, as much as five (5) layers of glasses are required to create this type of seal. This type of hermetic seal is commonly used in glass tube components, glass envelopes and in sealing flat windows.


Hermetic seals are essential in a variety of applications and industries. For instance, ceramic-to-metal airtight seals are utilized in aerospace, medical applications, and automotive. Meanwhile, glass-to-metal seals are widely suited for high-pressure conditions and protect electronic elements from dust, dirt, or microbial growth. Hermetic seals, unwarily for most, plays a massive role in our daily living.

Author's Bio: 

Marina Pal is a renowned author and social media enthusiast.