Polymeric materials have been widely applied in various fields such as thin film and coating technology, bio-engineering, composites, and electronic packaging. However, the very low surface energy of polymeric materials cause poor adhesion with metallic films, which makes it difficult to apply the polymers as composites and coating layers. In this work, we adopted the surface modification method by plasma to improve adhesion with metallic films. The surface of polycarbontes was modified by plasma treatment and the copper films were deposited on it in-situ. The dependence of adhesion property on plasma treatment conditions was quantitatively analyzed with four point bendng method.
The adhesion between polycarbonate and copper was quantitatively measured by four point bending method. The copper film deposited on plasma-treated polycarbonate surfaces was more well-adhered. The adhesion property improved by surface modification using plasma. However, the surface was damaged such that adhesion was poor when the time of plasma treatment was too long (e.g. over 60 sec. at plasma power of $0.013 W/cm^{+2})$.
The adhesion property was dependent on the kinds of discharge gas. The adhesion improved as a ratio of $O_2$ to Ar gas flow rate increased. The best adhesion property was obtained in case of 100% $O_2$ plasma.
The contact angle was much dependent on the processing time rather than the plasma power and the kind of discharge gas. The surface modified by plasma generally loses the surface property as time elapsed after plasma treatment. This aging was quantitatively analyzed by measuring contact angle. The degree of aging was smaller in case of $O_2$ plasma compared with Ar plasma.
Plasma diagnostics was also conducted using double Langmuir probe and mass spectroscopy. With increasing plasma power, both ion density ($N_i$) and electron temperature ($T_e$) obtained by double Langmuir probe increased and the density of positive ions obtained by mass spectroscopy also increased.
The surface of polycarbonates was also modified by atmospheric plasma. The contact angle of plasma treated polycarbonates was small and decreased in sequence of He/$O_2$, He/Ar, and He. The contact angle also decreased with increasing processing time.
