Decorative Metallizing by Magnetron Sputtering - Effects of Geometry on Film Properties

The configurations of sputtering sources and the shape and orientation of parts to be coated exert a strong influence on the appearance and integrity of metallized decorative coatings. Magnetron sputtering sources, which have sufficient speed and low substrate heating for the practical metallizing of plastic automotive parts, are also characterized by extended shapes that influence the properties of the deposited films. Data are presented for the film stresses and reflectances of pure chromium and Cr-alloy coatings sputtered from planar and cylindrical sources. The cylindrical post magnetron geometry enhances the production of compressive film stresses that prevent cracking, while also maximizing the optical reflectance. Results are also presented for the effects of substrate orientation and rotation on the stresses and reflectance of pure chromium and stainless steel coatings. While oblique deposition and parts rotation cause tensile stress and loss of brightness, these effects can be mitigated by the careful design and positioning of parts, by the judicious choice of coating metal or alloy, and by the use of advantageous sputtering target geometries.