When forming a seed layer on polyimide (PI) film using electroless nickel plating, the adhesion strength between the layer and the film was improved by a hydrofluoric acid dip at any stage of the plating process prior to the electroless nickel plating. No increase in the roughness nor change in the chemical composition of the PI surface was observed after the treatment. Furthermore, no change appeared at the boundary of the PI film and the seed layer. However, peeling of the plated film exposed a large amount of PI adhering on the seed layer indicating a change in the boundary by the treatment. In addition, Dynamic Mechanical Analysis of the PI film before and after the treatment indicated an increase in the storage elastic modulus of the film. The color tone of the film was also changed by hydrofluoric acid treatment. Based on a theory of elasticity, a change in the mechanical properties of the resin made to adhere to metal has an influence on peel strength. The authors concluded that the change in the mechanical properties of the PI film due to the hydrofluoric acid treatment improved the peel strength.

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The influence of crystallographic structure on the etching rate of copper was studied in 1 mol/dm³ ammonium peroxodisulfate solution using a scanning probe microscope (SPM), electron back scatter diffraction patterns (EBSD), and corrosion potential measurements. The (001), (101), and (111) faces etched at slower rates than the (327) and (425) faces, which have higher Miller indices. The etching rate of the (001) or (101) oriented polycrystalline copper was approximately half that for the oriented polycrystalline copper with higher indices. The polycrystalline copper etched at highly rate showed a relatively noble corrosion potential. It was suggested that the etching rate of polycrystalline copper was controlled by the mean value of the reduction kinetics of the peroxodisulfate ion on each of the grain surfaces.

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