Adhesion and Tribological Properties of Sputtered Polymer Thin Films with Thermally Stable Polymer Targets

Polymer thin films were sputtered with thermally stable polymer targets onto a copper and glass slide substrate with a conventional RF sputtering apparatus. Polymer structures and adhesion and tribological properties of these polymer thin films were evaluated. The pull strength between evaporated metal films and sputtered poly(tetrafluoroethylene) (PTFE) thin film was higher than that between evaporated metal thin films and the bulk PTFE. This difference was apparently due to differences in chemical bonding states between the sputtered PTFE thin film and the bulk PTFE. The PTFE thin films were sputtered at various conditions. Surface free energy of the PTFE thin films decreased with increase of fluorine content of the PTFE thin films. Although dispersion force component of the surface free energy slightly decreased, dipole force component dramatically decreased with increase of temperature of the substrate. Polymer thin films were sputtered onto copper substrate with two polyimide (Kapton-VTM and Upilex-STM) targets. Argon and nitrogen were introduced into the sputtering chamber for the sputtering gases. Sputtering rate of the polymer thin film with argon gas showed highest value at a pressure of 0.67 Pa. However, the sputtering rate with nitrogen gas showed highest value at a pressure of 8 Pa. Nitrogen content in the thin film sputtered with the nitrogen gas (N2 sputtered thin film) increased compared to that sputtered with argon gas (Ar sputtered thin film) and target material. Friction coefficient and wear durability of the N2 sputtered thin film were higher than those of the thin film sputtered with the Ar sputtered thin film. The pull strength between the N2 sputtered thin film and copper substrate was higher than that between the Ar sputtered thin film and copper substrate. In addition, the N2 sputtered thin film was introduced between the copper substrate and Ar sputtered thin film (Ar/N2/Cu laminate). The pull strength of this laminate showed higher value than that between the Ar sputtered thin film and copper substrate.