Microwave generated plasma is used in a large number of different processes for coating surfaces with materials like polymers, metals, compounds for wear protection, decorative compounds etc. Besides being used for the coating process, in many cases the same process chamber is used to first clean the surfaces via a plasma etching process, ensuring an optimum bond between target and coating, please also refer to our webpage about plasma cleaning. Because the two processes take place in the same chamber directly after each other, there is no risk of contamination before the coating process, furthermore loading / unloading steps are reduced to a minimum, leading to an extremely safe as well as time- and cost-efficient manufacturing process. Possible applications include:
Metal coating, also known as metallisation, does not make direct use of a plasma for the coating process itself, as it is usually applied by vaporising the metal inside a vacuum chamber, where it will then condense on the parts to be metallised. However, in order to ensure a clean surface prior to coating and achieve an optimum bond between the part and the coating, the parts are usually first cleaned via the above mentioned plasma cleaning process. In many cases the metal coating also requires a polymer layer to protect it from oxidation and other forms of degradation, in these cases the protective layer is usually generated by means of plasma polymerisation, please see below.
Plasma polymerisation is the process of applying a polymer coating by means of a plasma discharge. The monomer, either a gas or liquid, is injected into a vacuum chamber, where it is exposed to the plasma discharge. While the actual gas temperature inside the plasma is near to room temperature and therefore does not cause any degradation to the monomer, the temperature (kinetic energy) of the electrons is by factor 10 to 100 higher and sufficient to activate the monomer. Due to its increased kinetic energy, the activated monomer is then ejected from the plasma discharge and forms a steadily growing layer on the targets, where it almost immediately polymerises with other monomers. Polymer coatings generated via plasma polymerisation are usually highly branched and cross-linked, with a very strong bond to the target substrate, and can have a thickness ranging from 0.1 μm to several μm, forming a very even layer without any pinholes or other surface defects. Another advantage is that the polymerisation process takes place almost immediately, especially when the polymerisation is accelerated by the generation of VUV light (VacuumUltraViolet light), therefore the parts can be handled without any special precautions after they are removed from the chamber. Polymers suitable for plasma polymerisation include polystyrene, polymethyl styrene, polycyclopentadiene, polyacrylate, polyethyl acrylate, polymethyl methacrylate, polyvinyl acetate and others.
Plasma-enhanced chemical vapour deposition, short PECVD, is the process of generating a coating via chemical reactions initiated by a plasma discharge. The reactants, either in form of a gas, liquid or both, are injected into a vacuum chamber and exposed to a plasma discharge, which, dependent on the reactants, causes either molecule dissociation or the formation of free radicals. Once activated by the plasma discharge the reactants undergo a chemical reaction and form the desired end product, which then forms the desired coating. PECVD is capable of very high deposition rates, while at the same time maintains the formation of a very even layer without any voids or defects. Typical applications include the deposition of optical coatings, wear-resistant coatings for cutting tools, decorative coatings and film deposition in the semiconductor production.
If you want to receive more information about the above applications or have any current requirements please contact us.