Cleaning treatment of electric vacuum device

Electronic vacuum devices require high cleanliness of parts and components and no oil pollution. The effect of oil contamination on plating, brazing and attenuation materials in the process of manufacturing vacuum electronic devices is studied. It is suggested to remove the oil contamination in the process of pipe making by means of ultrasonic and deoiling solution, and determine the cleaning process of the electric vacuum device, so as to ensure its cleanliness. It can reduce the outgassing rate of the device surface, ensure the cathode emission level and the compressive strength of the electron gun, and improve the reliability and service life of the device.

Introduction

With the development of space science and technology and the need of modern military equipment for national defense, electric vacuum devices must have the characteristics of high reliability, long life, low noise, broadband and high power, and are often used in ground, shipboard, airborne, satellite communication, radar, electronic countermeasures, precision guidance and other weapon systems, and their performance and quality. The quality of the weapon plays a vital role in the performance and quality of the weapon, and is regarded as a strategic device for national security. Electron tube is one of the key and core devices in the development of modern high technology electronic equipment.

It is necessary to study the surface cleaning of electrical vacuum parts, because the gas and steam sources caused by the pollutants can not obtain the required vacuum degree of the vacuum system. In addition, because of the existence of pollutants, it will also affect the strength and sealing performance of the electrical vacuum components, and have a great influence on the performance of the electronic vacuum devices.

1. The main source of the pollutants in the electric vacuum device

(1) the lubricating oil used in the processing of raw materials;

(2) the body and saliva of the operator's hands, because in the manufacture of electric vacuum devices, the assembly is done manually by manpower, and it is unavoidable to cause pollution to the parts.

(3) the residual of the solvent in the process of deoil. For example, salt and organic substances in tap water, metal deoiling agents used in metal parts, etc.

(4) when parts are stored, the air contains dust, steam and so on.

2. The effect of oil pollution on the manufacture of electric vacuum devices

(1) in the process of making vacuum electronic devices, in order to improve the weldability of metal parts and the anticorrosion of the parts outside the tube, electroplating is needed for parts of the inner and outer parts of the tube. In the process of electroplating, the oil pollution on the surface of the parts must be removed. Otherwise, the coating will have an influence on the coating, which can make it bubble and flower. Wait.

(2) in the use of brazing furnace, vacuum furnace, hydrogen furnace, drying furnace, the surface of the components is required to be clean and free from oil contamination. If there is oil contamination on the surface of the components, it will pollute the environment of the furnace and reduce the vacuum. Oil pollution will adsorb gas on the surface of parts. After the whole tube is completed, with the storage time of the vacuum device, the gas adsorbed by oil will release slowly, which reduces the vacuum degree in the whole tube. In ultra high vacuum system, the cleaning of material surface can reduce the deflation rate by several orders of magnitude. Stainless steel is exposed in the air, and the rate of gas is 2.7 * 10-1 Pa. L/ (s. M2), and 1.3 * 10-3 Pa L/ (s. M2) can be reduced to 1.3 * 10-3 Pa L/ (s. M2) after removal of oil. After cleaning, it bakes 15 h under 250 centigrade, and the outgassing rate falls to 1.3 * 10-6 Pa L/.

(3) electric vacuum solder has good vacuum tightness, strong heat shock resistance and high sealing strength. The brazing of the electric vacuum device can weld different kinds of metal and alloy parts, even connect the metal with the ceramics, connect the small parts into large and complex parts, and ensure the finish and precision of the parts.

The quality of solder directly affects the weld quality and internal quality of electrical vacuum devices. After welding, the leakage rate of the vacuum device is up to 5 x 10-9 Pa / m3/s below the helium mass spectrometer. The vacuum technology network (http://www.chvacuum.com/) believes that if the surface of the solder is unclean and oily, the wettability and dispersion of the surface of the welded material are not good. After the solder is melted, black pic or black spot will be formed on the weld surface, causing air holes to destroy the gas tightness of the weld and leakage. The vacuum performance of electronic vacuum devices affects the leakage of electrical vacuum devices, resulting in the eventual failure of devices.

(4) by reducing the quality factor of the resonator, coating the microwave attenuation material on the wall and bottom of the cavity is an effective way to reduce the quality factor. The microwave attenuation material of iron silicon aluminum film is a kind of high performance microwave attenuation material, which can be prepared on the wall of oxygen free copper resonator by coating and sintering, forming a attenuation coating. The substrate of oxygen free copper should be hairy before coating, and the attenuating material is coated on the surface of the resonant cavity according to the coating standard. The workpiece after coating is sintered at high temperature under the atmosphere of wet hydrogen. The oxygen free copper substrate needs to ensure that the surface is not oily and can be hairy, and after treatment, it is necessary to remove the oil from the surface of the oxygen free copper substrate. Oil pollution can make the bonding force between the attenuating material and the matrix worse. If the surface of the part has oil pollution, the attenuation material may fall off after the sintering of the substrate, and more serious is that the electrical vacuum device may fall off after a period of use, and this will result in more loss of the material on the oxygen free copper. Great loss.

3. Physical and chemical cleaning treatment on the surface of parts

There are many methods for the surface treatment of parts, but because of the particularity of the electric vacuum device, there are few practical methods. Most of them are from experience and lack of theoretical basis. So, even a typical cleaning method needs to be constantly modified and supplemented.

In a variety of cleaning methods,