Film casting technology for aluminium oxide ceramic substrates

Abstract

The paper presents the technology of aluminum oxide ceramic substrates formation by film casting using "KEKO" line (Slovenia). Components of binder (dispersion phase) including polymeric bonding agent, plasticizer, dispersant, solvent are presented. The following binder components were used: polymeric binder - polyvinyl butyral, plasticizer - dibutyl phthalate, dispersant - fish oil and solvent - mixture of toluene and ethanol. The preparation regimes for the slurry, casting and lamination of the ceramic strip are given. According to the thermal analysis (DSC and TG) of raw corundum substrate the main mass of the removed binder occurs in the temperature range 240-450oC, the observed exo-effects in this temperature range are caused by successive processes of decomposition and removal of binder components. Based on the results of thermal analysis the regime of organic component removal from the "raw blanks-substrates" which provides for heating to a temperature of 500oC with a given rate of heating and cooling is determined. The technology of film-casting provides obtaining raw billet-substrate with a given density and the necessary technological strength. We experimentally set the firing mode of corundum substrates in vacuum (0.1-1.0 Pa) at a speed of temperature 100оС/h to 1450оС with an exposure time of 2 hours, then at a speed of 60оС/h to a maximum temperature of 1620-1660оС with an exposure time of 4 hours. The substrates were cooled at a rate of 100oC/h. The structure of the annealed substrates is represented by corundum crystals with sizes predominantly not more than 10 microns, intergrain porosity not more than 0.5%. Sintered products have high density and minimum number of defects.