Basic conditions for glass sintering and sealing

    Glass is a common industrial raw material. It has many advantages such as high temperature resistance, high density, good electrical insulation, light transmission, corrosion resistance, and easy processing and molding. Sealing with glass and metal is a common technology for manufacturing high-quality light sources, high-vacuum devices and other optoelectronic devices.

    The purpose of glass sintering and sealing is to tightly combine glass and metal, so as to achieve vacuum tightness, high voltage resistance, high pressure resistance and other purposes. The success of glass sintering and sealing is determined by the material and physical properties of glass and metal, as well as the sintering process. The two most basic conditions are:

    1 The linear expansion coefficients of glass and metal should be very close. There is an empirical data for this difference, that is, no more than ±10%. This is to reduce the stress generated inside the glass and metal. When the stress exceeds the strength limit of the glass, the seal will crack and cause air leakage. Even if there is no cracking in the short term, cracks may gradually occur in the later stage, especially when subjected to vibrations and collisions.

    2 The glass must be able to wet the metal surface. The wettability reflects the binding ability of these two substances. In order to make the glass have good wetting properties, the metal should be surface treated before sintering, that is, cleaning treatment and heat treatment. The cleaning treatment is to remove oil, dust, moisture, etc. on the metal surface, and finally obtain a highly clean metal surface. The heat treatment of metal is to form a layer of oxide on the surface of the metal. Metal oxide can be closely combined with metal and glass. It is the transition layer between metal and glass. However, the degree of oxidation must be moderate, otherwise a good seal will not be formed.

(Huiputech)