Diffusion soldering

The technique of soldering metals has been known for a very long time. Its essence lies in joining metals with molten solder. One type of soldering is diffusion soldering. It is used to create joints that operate at high temperatures. This type of soldering occurs through the mutual diffusion of the base metal and solder at a temperature above the solder's melting point. This is achieved using a vacuum system in which the part is held for a specified period of time. Diffusion soldering It is performed without any chemical influence and capillarity is the main characteristic of soldering.

Diffusion soldering technology

During diffusion soldering, molecular exchange occurs between the metals being joined. This requires creating suitable conditions to achieve a strong bond. Diffusion soldering technology It occurs in a vacuum chamber where the temperature is raised above the melting point of the solder. The process is performed as follows:

1. The surfaces of the parts to be joined are thoroughly cleaned to remove oxides. The slightest contamination significantly interferes with the diffusion soldering process;
2. The parts are placed in a vacuum unit. This protects the metals from oxidation during the manufacturing process;
3. Solder and a thin layer of certain metals are applied between the surfaces of the parts to form the bond. The choice of metal used as the bonding agent and solder depends on the properties of the metal being soldered. Silver, gold, and copper are commonly used. An intermediate bonding agent can be created by electrolytic deposition on the surface of the part.
4. Bonding foil, 0.01mm thick.
5. A specific pressure is created to reproduce diffusion processes. The pressure depends on the type of part and the material of the intermediate bond. Heating then occurs, allowing the diffusion process to complete the soldering process.
6. Such diffusion soldering technology Allows for high-quality connections. Solders and fluxes are key elements of diffusion soldering.

Solders

The choice of solder for a strong connection depends on the mechanical strength of the components, their chemical resistance, and their ability to wet and flow during soldering. Solder requirements include:

• Must be airtight and durable;
• Good fluidity when heated;
• The melting temperature is lower than that of the soldered workpiece;
• Have good electrical conductivity if the connected products are related to it.

Fluxes

They should not react chemically with the solder. The melting point of the flux should be lower than that of the solder. When heated, the flux promotes good wetting of the metal surface and the solder. Fluxes are classified:

• According to the soldering temperature range;
• By the nature of the solvent. There are aqueous and non-aqueous;
• By the nature of the activator. Common ones: fluoroborate, aniline, rosin, acid, etc.;
• By state of aggregation. There are pasty, liquid, and solid forms.