Preparation of functional properties on the substrate for electronics by environmentally friendly surface modification.

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Printed circuit boards(PCBs) have been required higher density and more integration, since many electronic devices have become downsized and multi-functionalized. For higher density, PCBs should have enough adhesion between substrate and conductive layer maintaining the smooth surface for finer patterning. Newly developed surface modification using TiO_2 powder as a photocatalyst and UV irradiation has realized excellent adhesion strength of 1.17kgf/cm without increasing roughness of substrate. This paper reported a mechanism of excellent adhesion and fabrication of fine patterns on PCBs with line and space of 10μm/10μm. Modified surface of PCBs in depth of 20-30 nm was created by the irradiation of UV light under the presence of TiO_2 as a photocatalyst. Moreover, it is confirmed that palladium(Pd) and tin(Sn) as the catalyst were penetrated into the surface modified layer and electroless copper(Cu) plating was initiated at the bottom of this layer. Therefore, it is suggested that excellent adhesion was originated from nano-level anchor effect by the formation of co-existed layer between PCBs and deposit copper. Accordingly, fine patterns with line and space of 10μm/10μm were actually fabricated by using the new surface modification in place of etching and followed by conventional pre-treatment. By introducing the new surface modification, fine line circuits was formed without roughening the surface of PCB and no extraneous deposition was observed between lines in contrast to the conventional method. It is concluded that this new method has intrinsic advantage for the formation of finer pattered PCBs.