Vacuum Brazing of Copper and Stainless Steel

Vacuum brazed copper-to-stainless steel assemblies are frequently utilized in high-end water-cooled heat exchange plates for AI servers. These structures combine the superior thermal conductivity of copper with the pressure resistance and corrosion resistance of stainless steel, offering excellent hermetic sealing and robust stability under cyclic operating conditions. Well-suited to meet the heat dissipation demands of high-power computing equipment, this technique represents a standard process solution for highly reliable thermal management components.

The following are the procedural steps for brazing this material:

1. 1. Raise the temperature at a rate of 10–15°C/min to between 450°C and 500°C. Hold at this temperature for 10–15 minutes to ensure uniform heating throughout the workpiece—both internally and externally—and to allow for the complete volatilization of residual gases and impurities.
2. 2. Second-stage heating: Continue raising the temperature to a point just below the solidus line of the brazing filler metal (e.g., to approximately 700°C when using a silver-based filler). Hold at this temperature for 10 minutes to minimize temperature gradients within large workpieces.
3. 3. Traverse the melting range of the filler metal at a relatively rapid rate (15–20°C/min), raising the temperature directly to the designated brazing temperature (780–850°C for silver-based fillers; 1100–1130°C for copper-based fillers). This rapid heating phase is critical for preventing compositional segregation within the filler metal during the melting process.
4. 4. Upon reaching the target temperature, maintain a strict hold for 10–20 minutes. At this stage, the filler metal is fully molten; it fills the joint via capillary action and undergoes mutual diffusion with the copper and stainless steel base metals to form a robust metallurgical bond.
5. 5. Once the brazing process is complete, cut off the heating power supply. Allow the workpiece to cool down to below 500°C within the furnace under vacuum conditions.
6. 6. Furnace unloading: The furnace door may be opened and the workpiece removed only after its internal temperature has dropped below 60–80°C (premature removal from the furnace will expose the copper and stainless steel to atmospheric oxygen, resulting in oxidation and discoloration).

The core requirements for the vacuum brazing of copper and stainless steel are a high vacuum environment, clean surface conditions, appropriate filler metals and joint clearances, and precise temperature control; consequently, the equipment employed is of paramount importance. SIMUWU’s high-temperature vacuum brazing furnaces are capable of maintaining optimal heating rates, temperature uniformity, and operational stability under high-vacuum conditions. The specific technical parameters are as follows:

Should you have any technical questions or requests, please feel free to contact kevin.liu@vacfurnace.com at any time; we are dedicated to serving you.