Study on Aging Effect of Adhesion Strength Between Polyimide Film and Copper Layer

This paper experimentally confirmed that the adhesion strength of the copper layer formed on the surface of the polyimide film by wet plating greatly changes with the aging time. The adhesion strength of the copper layer showed a rapid increase from 4 to 10 h after aging had begun and then converged to a value without a significant change. The adhesion enhancement between polyimide film and copper layer by aging is due to the interlocking effect caused by the volume expansion of copper oxide (CuO) formed in the polyimide, the increased mobility of copper particles enlarged by the decrease of impurities in the copper layer grain boundaries, and the consequent change of the crystal structure of the copper layer leading to the internal stress reduction. Such adhesion improvement can be confirmed by the progress of the cohesive failure indicating the breakdown of the polyimide film.