Abstract
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.
