Hermetic Sealing 101: What You Need to Know About The Process and Applications

Hermetic sealing is the process of creating a container of some sort that is airtight. That means that any material in the container, whether it's a gas, liquid, or solid, will not leak from the container. Hermetic sealing is commonly used to encase electrical mechanisms, as well as to contain functional gases. 

 
Types of Hermetic Sealing

1. Glass-to-Metal
   These types of seals are used when joining glass to a metal surface, hence the name glass-to-metal. Often used for common household items such as halogen or neon light bulbs, the process seals the glass to a metal surface to contain the gas. There are two types of glass-to-metal seals; which process is used depends on the type of materials being used.
   
   
   • Matched Seals: Used in light bulbs mainly, matched seals 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 formations of oxide on the metal. This type of seal tends to be weaker since it cannot withstand high-pressure fluctuations between the two materials.
    
   • Compression Seals: These seals are the stronger of the two and can withstand high-pressure differentials and types of physical stress such as shock. Alternatively to matched seals, compression seals take place when the coefficients of thermal expansion are different and therefore the metal forms around the glass.
 
2. Ceramic-to-Glass
   This seal is a high-pressure alternative to glass seals and is often used in applications that put large amounts of stress on the seal itself.
 
3. Epoxy Seals
   Epoxy resins are often used in vacuum seals and are commonly used to seal copper, brass, and other materials. They allow for more design flexibility but have a much smaller window of temperature variation and therefore epoxy seals are only feasible in certain applications.