Surface Modification Of Flake Aluminum Powder And Controlling Of Dielectric Properties Of Its Epoxy Resin Composites

In last decade, the increasing demands for miniaturization of electronic products in electronics industry have stimulated the research activity of the passive electronic devices, especially the embedded capacitor (EC). As a candidate of composite dielectric meeting this application, metal filled polymer material caught much attention from academic and industry circles. But, high dielectric loss and dielectric strength is key challenge faced with this kind of material. In this paper, flaky aluminum powder (f-AP) as a novel filler of epoxy resin (ER) for EC application were studied with respect to various surface modification strategy, intended to improve the dielectric properties built in metal/polymer composites.Firstly, solution passivation of f-AP is investigated by using respectively trace water and air as oxidant. The results show air-induced passivation thickens the self-passivation film of f-APs consisting mainly of Al2O3, which appears smooth and thin, while water-induced passivation produce a loose secondary film Al(OH)3, which is about a few nanometer and coated outside of self-passivation film. As a result, the thickened passivation film reduces the conductivity of f-APs, and the leakage current and dielectric loss of f-AP filled polymer composites. Particularly, water-passivated f-APs because of their thickness-designable passivation film show the potential to adjust the dielectric properties of the composites.Secondly, three organic molecules OA, APS and ASA were utilized to surface modify f-APs, the resulting grafting rate increases by the order of APS, OA and ASA. As the loading fraction increases, the dielectric constant as well as dielectric loss of f-AP/ER composite increases, and reach the value of50and0.05respectively at a mass loading fraction of30%. Upon surface modification, both parameters decrease, and the latter is limited much less than0.05. In the temperature range of25℃~130℃, these dielectric parameters increases with temperature, and changes by less than15%, indicating a good temperature stability.