Requirements for metal materials in glass sealing

    Glass and metal sealing parts are widely used in the manufacture of various electric vacuum devices. In order to ensure the reliability of the electric vacuum device, the glass and metal sealing parts should have:

    ①Good vacuum tightness;

    ②The necessary thermal stability;

    ③Sufficient mechanical strength;

    ④Good moisture resistance.

    In the production of electronic devices, there are many types of metals that are often sealed with glass, but not all metals can form a seal with glass. The metal that can form a seal with glass must meet the sealing requirements of glass. The basic requirements of metals and their alloys that can be sealed with glass are as follows:

    ①The purity of the chemical composition of metals and their alloys is high, and the impurity content cannot exceed the minimum limit;

    ②Under the conditions of fusion sealing, the melting point of metal and alloy must be higher than the processing temperature of glass, and the vapor pressure is low enough;

    ③When the composition of each metal is constant, it must have a constant and accurate thermal expansion coefficient;

    ④For matching sealing, the expansion curve of metal and glass must be consistent within the same temperature range;

    ⑤In the temperature range of sealing with glass, there should not be any allotrope transformation in the metal, because with this transformation, the expansion coefficient of the metal will change significantly;

    ⑥When sealing with glass, the metal surface must be oxidized first, and the oxide layer must be firmly adhered to the metal surface;

    ⑦The metal must have a certain degree of ductility, so that it can be processed into metal wire or metal strip;

    ⑧Before sealing with glass, some metals or alloys need to be treated with hydrogen burning and degassing;

    ⑨Metals and alloys need to be cleaned in advance, and there should be no defects such as longitudinal streaks, strains, etc., otherwise it will cause chronic leakage, air leakage or bursting at the seal;

    ⑩ If a large current needs to be passed during sealing, the metal must have good electrical conductivity and thermal conductivity, otherwise the temperature rise caused by the passage of large current will greatly increase the stress.

(Huiputech)