Role of Equivalent Modeling In Other Design Issues |
The process of plasma surface modificationcan be divided into four distinct mechanisms: ablation, cross linking,activation and polymerization: Ablation is the process of breaking down weakcovalent bonds in a polymer through bombardment with high energy particles..Processing with inert gases can be used to cross-link polymers and produce aharder surface with improved wear or chemical resistance. Activation is theprocess of replacement of surface polymer groups with chemical groups from theplasma. The plasma breaks down weak bonds in the polymer and replaces them withhighly reactive carbonyl, carboxyl, hydroxyl, peroxyl, amino or otherfunctional groups. Active groups on the surface can change the surfacecharacteristics, such as its wetting properties, adhesivity etc. Polymerizationis the process of forming very large molecules by joining many small linkablemolecules called monomers. The process involves reaction utilizing a widevariety of gases, organic or organo-metallic vapors which deposit non-volatilepolymer films. When the process gas mixture contains hydrocarbons, thehydrocarbon molecules are fractured into free radical fragments. These freeradicals initiate polymerization. Plasma can also polymerize materials, whichdo not form polymers under conventional chemical methods. The properties of thepolymer film can be controlled during deposition and combine different featuressuch as good adhesion of the film at the substrate surface and high hardness atthe upper film surface.