Chapter 25 – Process Variables

There are a number of other factors that can affect the vacuum deposition process that can vary with time and from system to system. These differences can account for why systems that appear identical may produce different coatings or to achieve the same coating may require different system settings. Described are items such as the surface roughness of the deposition drum and substrate back surface. These two surfaces are brought into contact with each other and the heat transfer coefficient will depend on the number and size of the points of contact. The moisture content of the substrate and the rate at which the moisture is released from the back surface may also affect the heat transfer coefficient which means the consistency of the incoming material becomes an important factor. The deposition source is another variable as the boat temperature can be varied along with the winding speed and wire feed which will all impact on the heat load seen by the substrate.