Glass-to-metal sealing structure is commonly used in vacuum system, which requires air tightness and a certain intensity, baking resistance and certain electric insulation resistance. Glass-to-metal seal types are commonly divided into three parts: (1) matching sealing; (2) non-matching sealing; (3) transition sealing.

Matching sealing refers to the linear expansion coefficient of glass and metal sealing is similar in a certain temperature range (less than 10% difference value).While non- matching sealing, glass and metal linear expansion coefficient difference is bigger (more than 10% difference value ). When glass and metal linear expansion coefficient differs very big, one or several glass whose linear expansion coefficient is between glass and metal can be used for transition sealing.