Influence Factors of Sputtering of Precious Metal Solder for Electron Vacuum Devices

Influencing Factors of Sputtering of Precious Metal Solders for Electron Vacuum Devices JIANG Chuan-gui, OUYANG Yuan-liang, WANG Hai-yan, LAI Zhong (Guizhou Platinum Industry Co., Ltd., Kunming 650221, China) is a raw material containing oxygen. The back-feed material contains CuO and Cu2; the use of 2-3 times high-vacuum remelting is the fundamental method to solve the problem of spattering of noble metal solders used in electric vacuum devices.

The components of the noble metal solder used for the electric vacuum device must be in accordance with national standards. The spatterability of the solder has been listed as an important indicator of the quality of the solder. The precious metal solder used for the electric vacuum device used before the research is used. The solder melts during the brazing process. The solder joint is not dense and the airtightness is poor after soldering. The soldering parts are in poor contact with each other, resulting in short circuit of the device and causing “burning”. Tube phenomenon. Not only the low yield during brazing, but also seriously affect the reliability, stability and service life of electric vacuum devices, directly affecting the equipment of national key projects. To this end, the Defense Science and Technology Commission, the Ministry of Electronics Industry and Military Infrastructure Bureau and many electric vacuum device manufacturers are required to solve the problem of the quality of the noble metal solder spatter of electric vacuum devices. After a large number of experiments, the factors that affect the spatterability of solders were studied systematically from the aspects of raw materials, casting and processing techniques, and vacuum annealing processes. The influencing factors were explored and verified in dozens of tons of production practices. After the large-scale production of precious metal solder for electric vacuum devices, it fully meets the requirements for noble metal solders for military and civilian electric vacuum devices. The product's spatterability meets GB490685 and GB standards without spattering requirements.

The noble metal solders used in electric vacuum devices are mainly AgCu alloys, which account for over 90% of the total. The spattering of solder is a special requirement of the electric vacuum industry, especially the requirement for the spattering of solder by highly reliable military devices. Therefore, a thorough solution to the problem of spattering of AgCu solder is the key to solving the problem of spattering of noble metal solders used in electrical vacuum devices.

Reasons why 1AgCu solder is sputtered 1.1 Sputtering test Electroless vacuum devices use noble metal solders, which are generally brazed under hydrogen protection and brazed under vacuum conditions. The AgCu alloy has a melting point of 779°C and a brazing temperature of 780-830. In this temperature region, the free oxygen in the AgCu melt reacts with the hydrogen in the brazing furnace to generate H2, and at high temperatures the vapor entrains the AgCu melt. The body splashes onto the Ni plate and becomes a splash point. The higher the oxygen content in the AgCu solder, the more spattering is caused. Therefore, the key to solving the problem of spattering is to solve the problem of degassing during the melting process of the solder. Different degassing and casting processes have great influence on the test results of the alloy's spattering (see Table 1). Sources of oxygen in the 1.2AgCu solder 1.2.1 The oxy-silver-copper alloys brought by the raw materials are easy to inhale during smelting, mainly because silver can dissolve oxygen, and reaches a maximum value at the melting point, as shown in Table 2. Silver in the molten state can dissolve more than 20 times its volume of oxygen. If the silver cannot be well degassed during smelting, it will inevitably cause the solder itself to contain a large amount of gas. During the welding process, a large amount of gas will be released during the solidification process, resulting in the metal splash phenomenon. The important reason for the spattering of the AgCu alloy solder . On the other hand, as the ingredient Cu, there are two types: one is oxygen-free copper, and the other is electrolytic copper. Oxygen-free copper has a low content of Cu2 due to its low oxygen content, while electrolytic copper contains a certain amount of Cu2, which is also a cause of spattering of solder. Therefore, in the preparation of Cu-free sputtered alloy solder, it is best to use oxygen-free copper as an alloy raw material.

1: Jiang Chuan: Gui Jing iTcade male workers) Cheng Yu master 1 precious metal material processing manual M BU Metallurgical Industry Press, 1978. GB4907-85, electronic devices with gold, silver and alloy brazing solder inspection method S. GB4906-85, electronic The device uses gold, silver and alloy brazing materials. Beijing: Jiao Tong Shun, a mechanical industry publisher. Vacuum electronics. Beijing: Electronic Industry Press, 1984. Jiao Tongshun. Vacuum electronic device material. Beijing: Publishing of Electronic Industry

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