Chemical Modification of Buildup Epoxy Surfaces for Altering the Adhesion of Electrochemically Deposited Copper

Abstract

The adhesion of electrochemically deposited copper on top of chemically surface modified epoxy layers for buildup purposes is examined. Using a wet-chemical surface synthesis reaction iminodiacetic acid, imidazole, and mercaptopyrimidine groups were chemically imprinted on the surface of buildup epoxy layers based on nucleofilic substitutions. The synthesis was followed by an identical electroless Cu deposition and peel strength measurement sequence. The identity of certain groups at the surface has pronounced influence on the adhesion strength of electrochemically deposited metals and is compared with traditional swell/oxidation treatments of the surface of the polymer. By varying the identity of the chemical groups at the surface, the chemical part of the adhesion can be altered. The changes in roughness of the polymer surface were minimized by choosing solvents that exhibit minimum diffusion into the polymer and by limiting the reaction temperature. In this way the changes in the physical part of adhesion could be kept to a minimum. The chemical composition of the surface is examined by attenuated total reflection-infrared and X-ray photoelectron spectroscopy measurements. Weight changes were recorded after each separate wet-chemical treatment. Surface synthesis influences the peel strength negatively or positively and modifies the deposition rate and etching speed of electrochemically deposited copper.