STUDY OF THE ADHESION OF FRIT-BONDED THICK FILM CONDUCTORS (METALIZATION, SINTERING, WETTING, MICROSTRUCTURE)
Abstract
Many science and engineering areas are involved in the adhesion of metalization films. The emphases in this work are mostly related to the development of microstructure, in particular, the distribution of the glassy phase. The frit-bonded conductors are the simplest systems. Oxide free Cu conductors and Ag conductors were chosen for study. The epoxy tensile test was chosen as the technique used for the adhesion measurements. The materials system of an oxide free copper conductor on a cordierite substrate, which was used in this study, is different from a common copper conductor in the following ways: (i) it is fired in a much lower oxygen partial pressure; (ii) the cordierite has a coefficient of thermal expansion as low as 2.7 ppm/(DEGREES)C. Thermodynamics and kinetics of the Cu-O and C-O systems were studied to establish the firing window and to determine the CO/CO(,2) and H(,2)/H(,2)O/inert gas atmospheres. Lead oxide and bismuth oxide are prohibited. Oxide scavengers were developed to remove the native oxide. Glass systems were developed with the considerations of: (i) the conductors should be fired at 900 to 950(DEGREES)C; and (ii) the glass should function well to develop adhesion on the cordierite substrate. The spreading behaviors of the glasses were investigated in a video hot stage. The densification of the metalization films on the rigid substrates was studied. The results indicated that solid state sintering plays an important role in the development of microstructure, and that liquid phase sintering in the conductor films is different from a classic meniscus liquid sintering. The results also indicated that the wetting-spreading may be the major process in the glass spreading. The tolerance of the mismatch of the thermal expansions between the glass frit and the substrate was studied. A new organic vehicle was studied for an easier burn-off. The effects of the metal particle size in the adhesion strength was investigated. A model of adhesion development of the frit-bonded conductors and the dependence of the adhesion on particle size was proposed. Experimental results were in good agreement with the theoretical model.
Degree
Ph.D.
Subject Area
Materials science
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