Liquid Cooling Plate Vacuum Brazing Process

There are two main materials for liquid cooling plates: copper and aluminum.

Copper is expensive and weighs much more than aluminum of the same volume. Therefore, in many places, aluminum is used where aluminum can be used, and copper is the last resort.

Aluminum alloy liquid cooling plates also come in various sizes and shapes and corresponding different manufacturing processes depending on the usage scenarios. Such as friction stir welding, brazing, laser welding, argon arc welding, etc.

Welding is a very important process in the processing of water-cooled plates. Today, the welding processing technology of water-cooled plates is mainly divided into three categories: galvanic diffusion bonding, vacuum brazing and friction stir welding. Because vacuum brazed liquid-cooled plates have the characteristics of flexible design structure and high welding efficiency, they are widely used in some aluminum alloy products. Processing.

Welding principle of vacuum brazing

1. It refers to the heating and welding of workpieces in a vacuum chamber, which is mainly used for the welding of products requiring high quality and easily oxidized materials;

2. Brazing is a solid-phase connection. The base metal does not melt during brazing. Since a filler metal with a lower melting temperature than the base metal is used, the heating temperature is lower than the solidus line of the base metal and higher than the liquidus line of the filler metal. connection method;

3. The connected parts and the solder are heated until the solder melts, and the liquid solder is used to wet the surface of the base material, spread and dissolve and diffuse with the base metal, and wet, capillaryly flow, and fill the gaps between the base metal and the base metal. The materials dissolve and diffuse with each other to realize the connection between parts;

4. Vacuum brazing uses a vacuum environment and different action mechanisms to remove oxide films. Since no flux is used, the corrosion resistance of the product is significantly improved;

5. The solder has good wettability and fluidity, and can be used to weld more complex and narrow channel parts, with a high yield and good safe production conditions.

Advantages of vacuum brazing process

1. Multiple adjacent welds can be brazed at one time to cover the entire surface. The furnace can be stacked during welding. According to the capacity of the furnace, multiple components can be brazed in the same furnace to improve the welding efficiency.

2. The welded products can withstand high pressure without deformation.

3. The tooling and fixtures are universal and require a one-time investment. Usually there is no need to invest in special product design.

4. The entire workpiece is heated evenly and the thermal stress is small. The deformation can be controlled to a minimum, and the workpiece can be flat and easy to process with a small margin.

5. When the workpiece is under vacuum conditions, there will be no oxidation, carburization, decarburization, contamination or deterioration. The brazing seam will be beautiful in shape and difficult to corrode.

6. Corresponding to the cold plate flow channel structure, complex flow channels can be designed arbitrarily according to parameters, which can achieve superior and more stable product performance and heat dissipation characteristics.

Disadvantages of vacuum brazing process

1. The hardness of the material decreases after high-temperature welding, and the characteristics of the cold plate require re-heat treatment to increase the hardness, which increases the cost.

2. The welding operation requires high process requirements, high technical difficulty, high energy consumption and long time.

3. Cleaning and environmental protection costs before welding are high.

The principle of aluminum alloy vacuum brazing

There is a dense and very stable oxide film Al2O3 on the surface of the aluminum alloy, which is the main obstacle for the molten solder to wet the base metal. It is difficult to remove the oxide film simply by relying on vacuum conditions, and some metal activators must be used at the same time, 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 remaining 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 directly remove the oxide film. Purpose.

However, a large number of studies since then have shown that the oxide film of the base material has not been completely removed, so a new perspective has been put forward on film removal. In addition to the role of Mg in eliminating O2 and H2O in the environment, Mg vapor penetrates into the surface material layer under the film and diffuses Together with Si, the surface layer forms a low melting point Al-Si-Mg alloy and melts, thereby destroying the combination of the surface oxide film and the base material, allowing the molten solder to wet the base material, spread on the base material under the film, and Lift the surface film and remove it.