Adhesion of an aromatic thermosetting copolyester with copper foils

Copper foils have been widely used in microelectronic devices. Adequate adhesion between copper foils to various substrates, such as Si, SiO2, Polyimide, is crucial to high performance of these devices. The adhesion between a new high temperature adhesive, aromatic thermosetting copolyester (ATSP), and various copper foils, namely, zinc(Zn)-coated copper foil, copper foil and nickel (Ni)-coated copper foil was characterized by a 90degrees peel strength test. It was found that the peel strength of Zn-coated copper foil to ATSP was 1050 N/m, which was more than three times higher than copper foil and five times that of Ni-coated copper foil. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) studies indicated that this higher adhesion results from the stronger mechanical interlocking due to the rougher surface of Zn-coated copper foil, and from chemical reactions at the interface which occur during the curing process of ATSP on the Zn-coated copper surface. In contract to the adhesive failure at the ATSP/Cu and ATSP/Ni interfaces, the failure mechanism of ATSP/Zn is both cohesive and adhesive. Copyright (C) 2004 John Wiley Sons, Ltd.