What are the properties of low melting glass powder used in vacuum glass

In order to ensure that the vacuumglasshas good thermal insulation performance, it is required to maintain the air pressure inside the vacuum cavity below 0.1 Pa. As a building material, the life expectancy of the vacuum glass is generally not less than 20 years. As a sealing material for vacuum glass, it must have the following characteristics: (1) low sealing temperature, (2) sufficient sealing strength, (3) better chemical and thermal stability, (4) lower Gas permeability, (5) Long vacuum life, (6) Good air tightness.　The traditional sealing materials are various and the sealing methods are different. From the chemical composition, they can be roughly divided into organic materials, metal materials and inorganic non-metal materials.Organic materials include polymer materials such as silicone rubber, butyl rubber, and silicone resin. The organic sealing material has a simple process, does not need to be sealed at a higher temperature, and can meet the use conditions of most Low-E filmsHowever, organic materials are limited by their physical and chemical properties, especially under long-term humidity, high and low temperature, and sunlight, they will reduce device reliability due to moisture absorption, cracking or aging.Metal sealing materials mainly include silver, solder, and indium alloy solder. Although metal sealing has the advantages of low temperature, good flexibility, and high strength, but the high price of metal sealing materials limits its application in industrialized large-scale production. Inorganic non-metal materials are mainly low-melting glass powder, which has the characteristics of high sealing strength, good air tightness, good stability, moderate sealing temperature, and matching the thermal expansion coefficient of the substrate glass.At present, low melting point sealing glass has realized industrial production in China, and is widely used in the fields of vacuum glass sealing and electronic sealing.　　Low melting point glass powder is widely used as a sealing material for electronic component packaging due to its characteristics of good wetting and high sealing strength.In general, in order to obtain good sealing quality, including requirements for sealing strength, air tightness, and durability, the low melting point glass powder must meet the following conditions: (1) The thermal expansion coefficient of the low melting point glass powder and the thermal expansion of the substrate glass The coefficients are matched to reduce the thermal stress at the sealing interface. The difference in thermal expansion coefficient between the two is less than 10%. (2) The sealing temperature of low melting glass powder must be lower than the softening temperature of the substrate glass, otherwise the substrate glass will soften and deform during the sealing process. At the same time, the softening temperature of low melting glass powder determines its application range as a sealing material.(3) Low-melting glass powder has good wettability with the sealing substrate. The smaller the wetting angle, the better the low-melting glass powder is connected to the glass substrate. (4) Low melting point glass powder has good air tightness and fluidity. Air tightness can ensure the service life of vacuum glass. The quality of fluidity determines the quality of the sealing interface, such as sealing notches and edge stress. (5) The low melting glass frit after sealing should have high sealing strength and good chemical and thermal stability. Low-melting glass frit needs to withstand the corrosion of different media such as atmosphere, water, acid, alkali, etc., and the solidified low-melting glass frit does not crack or leak when the temperature changes. Low-melting glass is currently widely used, so Youhe Chemical's new environmentally friendly lead-free low-melting glass powder has attracted great attention from researchers at home and abroad.