Effect of peak current density on the mechanical and electrical properties of copper/polymide fabricated by a pulsed electrodeposition process

Copper (Cu) was deposited on a polyimide via pulsed electrodeposition for use as a conduction layer in flexible copper clad laminates. The influence of the peak current density on the mechanical hardness and electrical resistivity of the Cu films was investigated. In the fabrication process, electroless deposition was first employed to create a Cu seed layer on the polyimide. A Cu film was subsequently electro-deposited using a square wave pulse with different peak current densities. As the peak current density was increased from 1.5 to 4.0 A/dm², the grain size and degree of (220) preferred orientation decreased, while the hardness and electrical resistivity increased from 0.75 to 1.19 GPa and from 17.00 to 26.26 nm, respectively. Such changes were believed to be due to grain refinement. The relationship between grain size and resistivity was correlated with the Mayadas and Shatzkes's model.