Preparation of Anodized Film on Metal Substrate

摘要

Insulated metal substrates(IMS) have been made by anodization. Oxide film anodized in some electrolyte acts as insulation layer. Anodized in different solutions, anodic films obtained on Al specimens have different properties. Its thickness and electrical performances were tested. The electrical resistivity of the films anodized in oxalic acid solution is greater than 10~(14)Ω cm with thickness of 20～30 μm. Whereas for the films anodized in NaOH solution, the electric resistivity is over 10~(11)Ω cm and thickness is less than 15 μm .Thermal cycling experiment showed the film anodized in NaOH solution has the better thermal shock resistivity than that anodized in oxalic acid. An SEM observation of the cross section of the former shows partly the characteristics of ductile fracture. Combinatorial process of anodization was carried out to obtain two-layer film. Aluminum substrates was anodized in NaOH solution first and then in oxalic acid with a different current density. Test results show that the resistivity of the film is greater than 10~(12)Ω cm when its thickness is about 20 μm. No crack was found on the film surface after thermal cycling between 0～100°C. The breakdown voltage of the film is more than 500 V, and the dielectric constant is about 7.0, which satisfy the insulation requirement for the substrate.