Vacuum brazing: precision connection technology in the microscopic world

Vacuum brazing is a connection process performed in a vacuum environment. The basic principle is to use a filler metal (i.e., brazing material) with a lower melting point than the base material, heat it to a temperature higher than the melting point of the brazing material and lower than the melting point of the base material in a vacuum environment, and fill the joint gap through the wetting, spreading and capillary flow of the liquid brazing material on the surface of the base material, and diffuse with the base material to achieve connection.

There are many advantages to brazing in a vacuum environment. First, the vacuum can effectively prevent the base material and the brazing material from being oxidized during the heating process, because oxygen is one of the main factors leading to metal oxidation. Secondly, the vacuum environment helps the brazing material to flow and wet the base material better, thereby forming a high-quality, high-strength joint.
1. Application scenarios of vacuum brazing of tiny parts
a. Electronics industry
In semiconductor manufacturing, vacuum brazing technology is often used to connect tiny chip pins and package substrates. For example, for some high-power, high-frequency chips, it is necessary to accurately connect the pins to the heat dissipation substrate to ensure good thermal conduction and electrical connection. Vacuum brazing can achieve this precision connection without damaging the chip structure. Vacuum brazing is also used for some tiny metal parts in electronic devices such as mobile phones, such as the connection between the metal bracket and the lens holder in the camera module. This connection method can ensure the connection strength and stability between metal parts while the mobile phone is thin and light.
b. Medical device field

Some micro medical devices, such as the connection of tiny metal parts inside the pacemaker. The pacemaker needs to integrate various electronic components and metal connection structures in a very small space, and vacuum brazing can meet its requirements for connection reliability and biocompatibility. Tiny precision parts in surgical instruments, such as metal connectors in ophthalmic surgical instruments, require high-precision connection technology to ensure the performance and service life of the instrument. Vacuum brazing is an ideal choice.
c. Aerospace field

Connection of some tiny sensors and control components in aircraft engines. These components work in harsh environments and have high requirements for connection reliability and high temperature resistance. Vacuum brazing can ensure the stable connection of metal parts under high temperature and high pressure environments. Some tiny metal structures on satellites, such as micro connections in antenna feed networks, require high-precision and high-reliability connection technology, and vacuum brazing can meet these requirements.
2. Common solders used in vacuum brazing
a. Silver-based solder
Silver-based solder is a commonly used type of solder in micro-brazing. It has good wettability and fluidity, and can achieve brazing at lower temperatures. For example, BAg-1 (Ag-25Cu-2Zn) solder, which has a melting point between 700-800°C, is suitable for brazing copper, copper alloys, nickel, nickel alloys and other metals, and is widely used in the electronics and electrical industries. The advantages of silver-based solder also include its good electrical and thermal conductivity, which makes it perform well in brazing tiny parts that require electrical and thermal properties.
b. Copper-based solder
Copper-based solders such as BCu-1 (pure copper) and BCu-2 (Cu-0.8P) have the characteristics of low cost and high strength. BCu-1 has a melting point of around 1083°C and is often used for brazing metal materials such as steel. In the production of some tiny parts that are more cost-sensitive, copper-based solder is a good choice. However, the brazing temperature of copper-based solder is relatively high, and the process parameters need to be carefully controlled when brazing some temperature-sensitive micro parts.
c. Gold-based solder
Gold-based solder has excellent oxidation resistance, corrosion resistance and good wettability. For example, BAu-4 (Au-18Ni) solder, with a melting point between 950-1000°C, has important applications in the brazing of micro parts in aerospace and high-end electronic equipment.Due to the high cost of gold, gold-based solder is generally used in occasions with extremely high reliability and performance requirements.

Vacuum Brazing Furnace