Vacuum Brazed Liquid Cold Plate

Advantages of aluminum alloy for liquid cooling plate
Aluminum alloy is widely used in aerospace, construction, electrical appliances, automobiles, ships and other departments due to its light weight, good corrosion resistance, excellent thermal conductivity and electrical conductivity, and its usage is increasing. It has long been considered as a structural material for making heat exchangers, waveguides and many other complex components.
The processing technology of aluminum alloy plays a very important role in the manufacture of its products, and one of the important methods is the vacuum brazing process without any brazing flux.
Because it has many advantages: no complex cleaning work before and after welding, simplified operation, avoiding slag inclusion caused by brazing flux, no residual brazing flux in the structure to ensure its corrosion resistance and high productivity, etc., from the perspective of current and future environmental protection concepts, the application of vacuum brazing of aluminum alloy will become more and more extensive.
The principle of vacuum brazing of aluminum alloy
There is a dense and very stable oxide film Al2O3 on the surface of aluminum alloy, which is the main obstacle for the molten brazing material to wet the parent material. It is difficult to remove the oxide film simply by relying on vacuum conditions, and it must be assisted by some metal activators, such as magnesium Mg, bismuth Bi, etc. In the early days, some people believed that the purpose of film removal could be achieved through the action of Mg.
This is because, on the one hand, Mg reacts with the residual O2 and H2O in the vacuum to eliminate their harmful effects on aluminum; on the other hand, and most importantly, Mg reacts with Al2O3 on the surface of the base material to achieve the purpose of directly removing the oxide film.
However, a large number of studies have shown that the base material oxide film is not completely removed, so a new view on film removal has been proposed. In addition to eliminating O2 and H2O in the environment, Mg vapor penetrates into the surface material layer under the film and, together with the diffused Si, forms a low-melting-point Al-Si-Mg alloy on the surface layer and melts it, thereby destroying the bond between the surface oxide film and the base material, allowing the molten brazing material to wet the base material, spread on the base material under the film, and float the surface film and remove it.
Although a large number of studies and experiments have made aluminum alloy vacuum brazing widely used in industry, there is no reasonable explanation for many scrapped brazing joints that appear in actual production. Aluminum alloy vacuum brazing is very sensitive to slight changes in parameters. Brazing alloy coatings prefabricated by different manufacturers often have obvious differences in brazed joints even though their compositions are within the specified range.
So far, due to the lack of a truly accurate understanding of the vacuum brazing mechanism of aluminum alloys, the formulation of an ideal vacuum brazing process has been greatly limited and is still largely based on the accumulated practical experience.

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