Interaction between Alumina and Binary Glasses and Development of a Surface Treatment Method for AlN Substrates to Improve Adhesion with Thick-Film Conductors

摘要

Interaction between 96% alumina and three binary glasses used as frits in thick-film technology is studied. A possible interfacial reaction mechanism where a melt glass penetrates into the alumina through the grain boundaries dissolving SiO_2, one of the grain boundary components, is suggested. The formulation expressing the glass penetration rate into the alumina based on Poiseuille's law, assuming the driving force for the glass penetration is the capillary force, is consistent with the experimental growth rate of the reaction layer in the alumina. The formulation also clearly explains a relationship of the glass penetration degree to the viscosity and the surface tension of the melt glass. The extraordinary difference in K, designated as the coefficient of penetration, between the calculated result and the experimental result suggests that the process of dissolving SiO_2 into a melt glass at the alumina grain boundaries retards the glass penetration.rnA surface treatment method for AlN substrates to improve adhesion with thick-film conductors is developed based on the above interfacial reaction mechanism between 96% alumina and glasses. The surface-treated AlN substrates are prepared through oxidation and sol-gel processes. The oxidation atmosphere with high PO_2 and low PH_2O, which produced the densest Al_2O_3 layer on AlN is selected as the oxidation condition for the surface treatment. A SiO_2 film layer was prepared on the Al_2O_3 layer using the dipping technique with the sol-gel solution. The surface-treated AIN substrates with adequate thicknesses of Al_2O_3 and SiO_2 as the surface-treated layers show good adhesion strength with the conventional thick-film conductors. This is the same result as with the 96% alumina substrates, although the adhesion strength of bare AlN substrates with the conductors are poor. These results suggest that glasses in the conductors react with the surface-treated AlN substrates in this same way that they react with the 96% alumina substrates, and also that the surface-treated layer consisting of Al_2O_3 and SiO_2 on AlN substrates is effective because of the good adhesion between the substrates and the conventional thick-film conductors.