Improving insulation and thermal conductivity of anodic coating by plasma discharge treatment

Abstract

Improving the insulation layer’s thermal conductivity is a key technology when concerning conquering the bottleneck of electronic device development. For improving the insulation layer’s thermal conductivity on the surface of aluminum alloy substrates, anodizing and MAO technology had been combined to prepare thick compact crystalline alumina ceramic. In addition, the influence of current density on the coating performances had been studied. Then, results showed that after plasma discharge treatment, amorphous alumina with thickness reaching 143 µm had been transformed into crystalline alumina and the through holes were sealed. The influence of current density on the crystallinity, compactness, and adhesion of the coating had been studied, and results showed as the current density increased from 10 mA/cm2 to 50 mA/cm2, the crystallinity of the coating increased and the compactness of the coating decreased. Moreover, when the current density was lower than 30 mA/cm2, the coating had good adhesion to the substrate. The impedance, breakdown voltage, and thermal conductivity of the coating were observed for comparison with those of the anodic coating. Then from the results, it was found that after the coating had been treated with this method, the impedance increased from 60 kΩ/cm2 to 120 kΩ/cm2, while the breakdown voltage increased from 0.89 kV to 3.24 kV as the thermal conductivity increased from 10.2 W/m K to 23.7 W/m K.