Hermetic packaging is a requirement for all applications where electronic components must be protected from corrosive environments to ensure acceptable service life. Extremely high reliability is required for space electronics, often utilising hermetic packages. Metal packages with glass to metal seals are the common solution for low to medium power levels.
There are mainly two types of glass to metal seals , one is matched seal and other one is compression seal.
A "matched glass-to-metal seal" uses glass and metal materials with similar coefficients of thermal expansion (CTE), creating a bond through chemical reaction, while a "compression glass-to-metal seal" relies on a large difference in CTE between the glass and metal, where the metal housing shrinks onto the glass during cooling, creating a tight seal through compressive force; essentially, a matched seal bonds the materials together, while a compression seal physically squeezes the glass with the metal to seal it.
