Effects of the alkaline permanganate etching of epoxy on the peel adhesion of electrolessly plated copper on a fibre-reinforced epoxy composite

Abstract

The adhesion of electroplated copper to a fibre-reinforced epoxy composite is controlled by mechanical keying. Rough surfaces are prepared by chemical etching. Therefore mechanical properties could be degraded if the difference in reactivity of the composite components (fibres and matrix) is not taken into consideration. To eliminate this surface heterogeneity, a plating film (epoxy resin) is applied to the composite, which becomes chemically homogeneous. During the etching process, this plating film will protect the integrity of the composite. Later on, copper can be directly electroplated onto the intermediate layer (epoxy resin). This study describes the influence of the surface geometric characteristics of two composites on the adhesion strength of a copper coating. We have found that the mean peak-to-valley height (Rz) is not sufficient to explain the adhesion level. The technique of profilometric relocation is used for quantifying the etching effect on the surface micro-geometry, which is dependent on the initial composite substrate roughness.