Why does adhesion strength differ on copper and silver surfaces?
Although there are numerous theories of adhesion mechanisms, the absorption theory is the most widely applicable. Interatomic or intermolecular interactions, such as covalent and/or ionic bonding, donor/acceptor interactions, hydrogen bonding, and van der Waals forces, established between the adhesive and substrate surface are responsible for providing the adhesion. The type of interaction will depend on the chemistry of the adhesive and the chemical nature of the substrate. For example, a silver-plated copper surface consists of primarily silver atoms, whereas a copper substrate typically has an amine-type of antioxidant on the surface. For adhesion to surfaces such as silver, a metal/polymer (adhesive) complex must be formed at the interface. For adhesion to surfaces such as copper (with antioxidant), covalent bonds must be formed between the antioxidant and the adhesive system.
