Waveguide Slot Antennas Vacuum Brazing

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Waveguide slot antennas have been greatly developed since the middle of last century, and are widely used in various fields such as ground, shipboard, airborne, and navigation. Because the slot array antenna is easy to control the amplitude distribution in the antenna aperture plane, the aperture surface utilization rate is high, the volume is small, and it is easy to achieve low or extremely low sidelobes, etc., so it is widely used. In the research of waveguide slot antenna, many scholars have done a lot of basic research work on the theory and experiment of slot antenna, so the theory of waveguide slot antenna is more and more mature.

Process of vacuum brazing waveguide slot antenna:

1 part forming

2 cleaning before welding, vacuum brazing

3 Machining and forming. The process of the flat-panel slot antenna is: 1) digital punch array panel forming, waveguide and other parts milling or wire cutting forming; 2) workpiece and solder surface treatment before welding, especially the treatment of wire cutting and cutting surface; 3) assembly and brazing forming , including fixture design; 4) Shape correction; 5) Electrical performance test.

In order to ensure the necessary welding speed and dimensional accuracy, the design of vacuum brazing tooling is very important. This kind of vacuum brazing uses elastic tools with precise structure to ensure that the assembly gap occupied by the solder is effectively closed after the solder is melted. A compression mechanism can follow to compensate for the amount of collapse of the structure after the solder melts and maintain some degree of compression. This can also effectively correct the original unevenness of the antenna parts, control the size of the pressure, and avoid excessive pressure. Large and deformed, it not only ensures the quality of vacuum brazing, but also ensures the dimensional accuracy.

The vacuum brazed waveguide slot antenna adopts a sandwich structure in which a composite solder plate is clamped in the base material. This structure utilizes the good brazing performance of the composite solder plate. As long as the process is well controlled, the vacuum brazing quality is easy to guarantee, but the above The structure of the waveguide slot antenna should take into account the flow and strength of the solder. If the temperature is too high, the solder will flow seriously, and if the temperature is too low, the strength will not be easy to protect. The vacuum brazed waveguide slot antenna adopts a structure of twisted tenon and brazing material foil in the middle. Compared with the commonly used expansion riveting tenon structure, this joint reduces riveting stress and is more convenient to process.

Heating under the protection of a vacuum atmosphere can reduce the oxidation of the base metal and the solder, decompose, remove or destroy the oxide film on the surface of the base metal and the solder, and wet the base metal after the solder melts. Caulk and form joints after cooling. Vacuum brazing generally does not require flux, and does not need to clean the flux after brazing, the workpiece is protected from oxidation, and the brazing seam is beautifully formed. It is a high-quality vacuum brazing process. The removal mechanism of the oxide film in a vacuum atmosphere is that the high degree of vacuum reduces the oxidation of the metal during heating, and the following reactions occur: decomposition of the oxide film under vacuum; volatilization of the oxide; reduction of the oxide film by H or CO; The reduction of C on the oxide film; the diffusion or dissolution of oxygen on the surface to the interior of the material; the rupture of the dense oxide film, etc. The combined effect of the above reactions removes or destroys the oxide film and promotes the wetting of the solder to the base metal. From the thermodynamic conditions of the vacuum film removal mechanism, the oxide film removal is not only related to the vacuum degree, but also requires a certain brazing temperature. A welding method that uses a metal material with a lower melting point than the base metal as the solder, wets the base metal with liquid solder and fills the gap between the workpiece and interdiffusion with the base metal. Vacuum brazing has small deformation and smooth and beautiful joints, which is suitable for welding precision, complex and components composed of different materials, such as waveguide slot antennas, etc.

Vacuum brazing equipment selection：SIMUWU aluminum vacuum brazing furnace adopts multi-temperature zone temperature control, temperature uniformity ± 3 ℃, working vacuum degree ≤ 1.3*10^-3Pa, most suitable for vacuum brazing of composite plate (with solder) structural workpieces, in For heat exchangers in air separation equipment, radiators for bicycles and electronic equipment, etc., special processes are required for vacuum brazing of workpieces with special structures, such as waveguide slot antennas.

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