Study on adhesion failure of electrically conducting electroless Ni-P coating on polyethylene terephthalate substrate

Abstract

Demand for lightweight, flexible and low-cost electrically conductive materials are rapidly increasing in fields like medical, automobile, aerospace, textile and electronics. Plastics may accomplish these requirements, due to their lightweight, flexibility and low cost. However, plastics are electrically non-conductive in nature. This limitation may be addressed by deposition of a conductive coating on plastic substrates. However, the main challenge is to ensure good adhesion between such metallic coating and non-metallic substrate. In this work, electrically conducting nickel-phosphorus (Ni-P) coating was deposited on polyethene terephthalate (PET) substrate through electroless route at different coating durations i.e. 1, 3 and 5 min. Constituents of electroless bath were kept constant for all deposition runs. Bath temperature and pH were also fixed at 80 °C and 8 respectively. The surface morphology of Ni-P coated film was characterised by scanning electron microscope (SEM). The adhesion of Ni-P coating at different coating times i.e. 1, 3 and 5 min were assessed through optical imaging, bend test and scotch-tape test. Swelling and delamination of the films from the substrates were observed as deposition duration was increased beyond 2 min.