Thick Film Metallization Of AlN By The Reactive Bonded Method

The development of thick film technology was reviewed and pursued. The thick-film metallization of AlN was studied due to good applying potential. State-of-the-art techniques such as wet milling, screen printing and sintering were used for sample preparation. Effects of process, metal and reactive bonds on the properties of thick film were analyzed with XRD, DSC and electrical tests. The pastes having good applying potential were developed in this study.The technical control of the paste viscosity has been investigated. It was showed that the viscosity could be controlled between 100～300Pa?s when the percentage of castor oil, ethyl cellulose, beta-terpineol are 1.5%, 5%, 93.5% in the organic vehicle. The pastes were suitable for printing because both of thixotropic performance and dispersibility of the thick film pastes are good. It was confirmed that the thickness of thick film could be controlled between 10～20μm after theoretic analysis.Effects of the components and content of reactive bonds and sintering process on the thick film properties have been investigated. The best technique is successfully developed to produce the silver thick film: mix the Ag, TiB2, Co3O4 and organic vehicle together first ,the pencents of them are 72.8%, 1.5%, 0.7%, 25%;sinter the thick film in air from room temperature to 550℃, then sinter it at 850℃for 15 minutes in 95% N₂ . Under this technique, the thick film is dense and bright, and its adhesion strength is up to 12.7MPa and the resistance is 5.2 mΩ/â–¡.The thick film has good abilities to resist aging and resintering, and has good abilities to restrain the self-diffusion and oxidation of silver.The reactive bonded mechanism was discussed here: the thick film has satisfied adhesion strength (12.7MPa) when there are just a little reactive bonds (about 2%). It results from the mixed collaboration of glass and reactive bonds. The existence of Al₄B₂O₉ whiskers causes a pulling out process when the metallizaton film is peeled out from the surface of AlN; the existence of glass modified by TiO₂ enhances the mechanical interlocking between metal film and the substrate.