How does vapour phase soldering work?

How does vapour phase soldering work?

Vapour phase soldering, also known as VPS or condensation soldering, is one of the most precise and gentle soldering processes in modern electronics production. By using physical processes, it enables controlled and even heating of even the most complex assemblies and ensures a high level of process reliability, especially for sensitive applications.

Basic principle of vapour phase soldering explained simply

The basic principle of vapour phase soldering is based on the use of a special heat transfer medium. A thermally stable perfluoropolyether fluid, such as Galden, is usually at the center of the process.

This medium is heated in a closed system to its defined boiling point, which is typically between around 200 °C and 260 °C. This creates a saturated vapour that is responsible for the actual heat transfer.

The assembly to be soldered is placed in the vapour zone, which starts the actual soldering process.

Heat transfer in vapour phase soldering by condensation

As soon as the hot steam hits the colder surface of the assembly, it condenses. This phase change releases so-called latent heat, which is transferred directly and very efficiently to the assembly.

This physical mechanism provides several decisive advantages:

• Very fast heat transfer
• Uniform temperature distribution over the entire assembly
• Independent of component size, geometry or thermal mass

The result is homogeneous heating of all components. This represents a significant advantage over convective processes.

Reflow phase in vapour phase soldering

As soon as the assembly has reached the required soldering temperature, the reflow phase begins. During this phase, the previously applied solder paste melts, wets the contact surfaces and forms the electrical and mechanical connections.

Thanks to the stable temperature control, this process is controlled and reproducible, which significantly improves the quality of the solder joints. The result is high-quality solder joints with high reliability, even on complex assemblies.

Temperature limitation during vapour phase soldering as a protective mechanism

A key unique selling point of vapour phase soldering is the physical temperature limitation. The maximum temperature of the assembly corresponds exactly to the boiling point of the medium used. It is physically impossible to exceed this temperature. This creates an integrated protection mechanism for sensitive electronics.

This offers clear advantages:

• Protection of sensitive components from overheating
• Prevention of thermal damage
• Constant and stable process conditions

This effect is particularly important for highly integrated or temperature-sensitive components.

Cooling phase after vapour phase soldering and process completion

After the actual soldering process, the assembly is removed from the vapour zone and cooled down in a controlled manner. This controlled cooling also contributes to the quality of the soldered joints and reduces thermal stresses within the assembly.

Typical areas of application for vapour phase soldering in industry

Due to its high process reliability and component protection, vapour phase soldering is used primarily in demanding industries.

Typical areas of application are:

• Aerospace
• Medical technology
• Automotive industry and automotive electronics
• Defense technology
• Prototype construction and small series production

In all these industries, reliable soldered connections and stable processes are crucial for the function and safety of electronic systems.