Microstructure and electromagnetic interference shielding effectiveness of electroless Ni-P alloy coating on PVC plastic

Electroless Ni-P alloy coating with an amorphous nickel phase were fabricated on polyvinyl chloride (PVC) plastic substrate using sodium hypophosphite as reducing agent. The present work aims to study influence of bath pH value on the deposition rate, phosphorus content, morphology, microstructure and the corresponding shielding property of the Ni-P alloy coatings on PVC plastic. The morphology, composition and microstructure of the Ni-P alloy coatings were also characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The results show that the deposition rate of the Ni-P alloy coatings increase, accompanying with the decrease of phosphorus content in the deposits with increasing bath pH value. Moreover, the morphology of the Ni-P alloy coatings strongly depend on the bath pH value, and the nodule size of the Ni-P alloy coatings increase with the increase of bath pH value. The measurements of electromagnetic interference shielding effectiveness (EMI SE) for the Ni-P alloy coatings indicate that the EMI SE of the Ni-P alloy coatings also increase with the increase of bath pH value because the low phosphorus content in the coating decrease the sheet electrical resistance of the Ni-P alloy coating.