Fabrication of metallic patterns on ordinary polymer substrates by laser direct activation and electroless plating

In recent years, the fabrication of metallic patterns on polymer substrates has been given increasing attention because of its wide and important applications in many fields. This paper reported a selective metallization technology on ordinary polymer substrates basing on laser direct activation of copper hydroxyl phosphate [Cu2(OH)PO4] and electroless deposition of copper. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were utilized to characterize the interaction mechanism between nanosecond-pulsed fiber laser (1064 nm wavelength) and Cu2(OH)PO4. It was found that after laser modification and activation by appropriate parameters, the special surface microstructure (e.g., porous sponge-like) appeared and explained the good adhesion strength (the highest grade of 5B) between the copper layer and substrate. At the same time, Cu+ was generated from the Cu2(OH)PO4, adsorbed on the microstructure, and acted as catalytic active centers to realize the selective copper deposition in the laser-activated zone. In addition, the copper layer possessed good selectivity (< 3% error of line space and width) and electrical conductivity (10−6 Ω·cm volume electrical resistivity). By comparison with laser direct structuring (LDS) technology and with palladium chloride as laser sensitive material, this was a more universal and less-cost technical pathway to fabricate planar and/or three dimensional (3D) metallic patterns on more kinds of ordinary polymer substrates.