The PICVD process: Forming layers in small steps

PICVD stands for Plasma Impulse Chemical Vapor Deposition. In this process the object to be coated is placed inside the coating chamber that is evacuated to the appropriate pressure. The chamber is then flooded with the gaseous coating material. By applying energy in the form of microwaves, a plasma is generated that decomposes the coating material into silicon dioxide or titanium oxide depending on the gas used. The oxides are deposited on the surface of the article. Up to this point, the process functions like a normal plasma-enhanced chemical vapor deposition process. The unique feature of PICVD is the "I” for Impulse, i.e. the plasma is pulsed. This adds a number of benefits to the process. The microwave on/off period can be controlled to maintain the coating temperature appropriate to the plastic. Reaction products are swept out of the chamber during the “off” period. When the plasma is ignited again, the chamber is full of the pure coating gas. This leads to faster coating time and a homogeneous coating, as depletion of the coating gas close to the surface is avoided. The gas composition can also be changed. This is critical to the formation of the adhesion layer. Thus the overall coating is built up in small steps, leading to a dense and homogeneous coating. The entire process can be monitored in a number of ways, ensuring precise control of the process and consistency in the coating quality.