Vacuum Aluminum Brazing of Radar Transceiver Box

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The transceiver unit box is an important part of a radar system. Its function is to install and fasten all the electronic functional components in it, and provide it with a good ventilation, heat dissipation, electromagnetic compatibility and sealed three-proof working environment to ensure In its normal work, it has the characteristics of high thermal conductivity, light weight, small size, high strength and strong adaptability. The receiving and dispatching box is mainly welded by the following parts: (front panel; rear panel; left and right panels; partitions; guide rails; fins, etc.), as shown in Figure 1, the process uses vacuum aluminum brazing to complete the assembly at one time Clip welding not only ensures the strength and tightness of the box, but also meets the requirements of its shape and size accuracy.

Figure 1 Structure diagram of a radar transceiver box

1. Analysis of the processing technology of the receiving and sending box

The assembly and welding process of the box:

Cleaning-Clamping solder-Assembly-Vacuum aluminum brazing-Post-weld verification treatment

A. Cleaning Before brazing, it is necessary to carefully clean the weldment, the purpose is to remove the oil stains and thick oxide film on the surface of the weldment. Specifically, all welded parts are first boiled and washed in hot alkali (NaOH solution) at 80°C, then washed with water, neutralized with acid, and dried.

B. Clamping before assembly welding is mainly:

Connect and position the parts and solder according to the requirements of the drawings; adjust the reasonable gap of each welding seam to promote the occurrence of capillary action; prevent and reduce the deformation during the welding process. Therefore, the rationality of welding fixture design directly affects the dimensional accuracy of parts and the quality of welding.

2. Analysis of vacuum aluminum brazing welding process

The principle of vacuum aluminum brazing

When the brazing filler metal is put into the vacuum furnace, the mechanical pump and the diffusion pump work at the same time to pump the brazing furnace to the required vacuum (below 10-0.3Pa), and then start electric heating. When the temperature reaches When it is lower than the melting point of the base material and higher than the melting point of the solder, the molten solder is immersed and held in the gap between the parent metal by wetting and capillary action, and the liquid solder fills the gap between the parent metal.

And mutually diffuse to form a bond. It is then cooled in the furnace to below 150°C and taken out of the furnace. There is a dense and very stable oxide film (AL203) on the surface of aluminum alloy. This is the main obstacle for the molten solder to wet the base material. It is difficult to remove the oxide film by relying solely on high vacuum conditions. A metal activator, such as MgBi, must be used at the same time. Eliminate the harmful components remaining in the vacuum, so that the molten solder can fully wet the base material, and improve the welding strength of the weldment.

The reaction mechanism is as follows:

Mg+1/2 02→MgO

Mg+1/3 AL2O3→ MgO+2/3 AL

3. Determination of box brazing process parameters

The main technological parameters of the brazing process are heating temperature and holding time, which directly affect the process of filler filling and the interaction between the filler metal and the base metal, and therefore have a decisive effect on the quality of the joint. Generally, the heating temperature is selected to be 25 ~ 60°C higher than the liquidus temperature of the solder, and the holding time is specifically considered according to the box shape and wall thickness. Under the condition of ensuring the penetration, the brazing holding time should be as short as possible . By consulting the data, trial welding and analysis, the specific thermal cycle curve of the box body brazing is shown in Figure 2 below.

Figure 2 Thermal cycle curve of vacuum aluminum brazing process

Through the implementation of the process of the chassis, the box of the transceiver unit has been successfully processed, and the product has entered the stage of small batch production. Through the analysis of the design of the elastic clamping fixture during the vacuum aluminum brazing process of the box, the welding process parameters, etc. , It has opened up a new situation for the processing and assembly of aluminum alloy frame parts. Its main advantage is high brazing quality, especially those parts with large size and complex structure. It has great reference value for the design and processing of similar parts.

Learn more:

High Temperature Vacuum Brazing Furnace

Aluminum Vacuum Brazing Furnace

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