Molybdenum foil for lamps
Some electric light source devices adopt the sealing process of quartz glass and molybdenum foil, such as halogen incandescent lamp and gas discharge lamp. However, in the sealing process, molybdenum foil is often fractured, crushed and other problems, which affects the electrifying performance of the lamp and further affects the production pass rate. To track and analyze this phenomenon, and find out some related reasons.
Why do halogen incandescent lamps and gas discharge lamps adopt the sealing process of quartz glass and molybdenum foil? This is because halogen incandescent lamp and gas discharge lamp are small in size, and the operating temperature at the ignition point is very high. The inside of the lamp chamber can be more than 800C, while the melting point of ordinary glass is around 800°C, so it is difficult to withstand such a high temperature. In addition, due to the rapid expansion of gas in the lamp, the expansion pressure can be several atmospheres, ordinary glass is difficult to bear. Therefore, only by choosing quartz glass, can we overcome the problem of high temperature and pressure resistance.
The melting point temperature of quartz glass is about 1700°C, which is the best high temperature resistance among all glass materials. However, its expansion coefficient is too small, and the expansion coefficient of metal for matching sealing with it must be similar to this value. Therefore, almost all metal materials used for vacuum sealing cannot be matched with it. And the melting point temperature of this metal is at least above 1700°C (because when sealing, at least let the quartz glass melt), in addition to some excellent characteristics of vacuum, such as high temperature discharge rate is small, not easy to oxidation. Currently, the only refractory metal that comes close is molybdenum.
The expansion coefficient of molybdenum metal differs greatly from that of quartz glass, which exceeds 10% of the limit requirement and cannot reach the matching seal
Answer the request. In order to seal molybdenum metal and quartz glass, and there is no chronic leakage, the only feasible way is to use non-matching sealing: molybdenum metal processing into "foil belt" shape, taking into account the requirements of air tightness, the two edges of the foil belt made of "blade" shape, which is often said molybdenum foil.
