Electroless Copper Plating on Liquid Crystal Polymer Films Using Dimethylamine Borane as Reducing Agent

Abstract Dimethylamine borane (DMAB) was used in electroless copper plating on liquid crystal polymer (LCP) films. An orthogonal test was applied to optimize the plating condition. With Cu film resistivity as the evaluation index, the optimum plating condition is: 10 g/L of CuSO4 ⋅ 5H2O, 14 g/L of EDTA‐2Na, 6 g/L of DMAB, 9.5 of pH value and 50 °C. As pH value increases, the Cu film resistivity decreases and the depo‐ sition rate increases. As temperature increases, the Cu film resistivity decreases first and then increases with a minimum at 50 °C while the deposition rate increases first and then decreases with a maximum at 50 °C. The decreased Cu film resistivity can be attributed to the occurrence of CuO. The adhesive strength of copper layer to LCP film is constant at pH values lower than 8.5 and decreases slightly with the increase in pH value. As temperature increases, the adhesive strength decreases slightly. The decreased adhesive strength with both pH and temperature may be a result of an increased corrosion attack from the bath to the surface of LCP films. Low Cu film resistivity and high deposition rate as well as high adhesive strength can be obtained using DMAB reducing agent.