Understanding the Volatile Nature of Thin Film Evaporation

Written by: Denton Vacuum, LLC

Thin film evaporation consists of a volatile exchange of heat, pressure, and contact.

The process of thin film evaporation revolves around the thermal separation of products or materials within a vacuum chamber. Through a mechanically generated process, a highly thin and turbulent liquid film is placed on the material resulting in a durable coating.

Diving In

The sputter coater, or thin film evaporator, takes the product and utilizes its rotor to uniformly spread the material out on the distribution ring. Upon first contact with the first rotor blades, the material is immediately formed into a film that can range anywhere from 0.5 mm to 3.5 mm (depending on the requested specifications). Now, in front of each rotor blade, the fluid will create a bow wave that further assisted the deposition process.

Note that the fluid within the gap between the heat transfer surface an the tip of the rotor blade is extremely turbulent which in turn leads to an intense heat and mass transfer rate. This is vital for the process as it ensures that there is enough pressure to convert the material into a thin film. Additionally, the turbulence also produces a high volume of heat transfer coefficients even with the presence of viscous products. The intense process and exchange prevents the process from over heating, which is especially important in diamond like carbon coatings, as well as fouling on the heat transfer surface. The elimination of these detrimental effects ensures the coating comes out even and smooth.