Effects of surface treatment on the adhesion of copper to a hybrid polymer material

Abstract

The effects of various surface pretreatments on the adhesion of electroless and sputter-deposited copper metallizations to a hybrid polymer material were investigated. Without pretreatment, the adhesion between copper and the polymer was virtually zero. The adhesion of electroless copper to the polymer was poor regardless of the pretreatment used. However, the wet-chemical pretreatment of the polymer surface markedly increased the adhesion of sputtered copper to the polymer. It preferentially removed the inorganic part of the polymer and formed micropores on the surface. The plasma and reactive ion etching pretreatments, in turn, selectively etched away the organic part of the polymer and noticeably increased the hydrophilicity. Although this resulted in even higher increase in the surface free energy than was achieved with the chemical treatment, the granular surfaces became mechanically brittle. With the help of x-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and contact-angle measurements and with the recently developed pull test, the physicochemical changes of the wet-chemically pretreated polymer surfaces were demonstrated to have significant effects on the adhesion.