ULTIMATE SHEAR STRENGTHS OF COPPER SILICA AND NICKEL SILICA INTERFACES

A technique developed recently at Cornell University to measure the ultimate shear strength of metal-ceramic interfaces is used to measure the relative strength of the copper-silica and nickel-silica interfaces. The shear strength of the copper-silica interface is found to be 0.9 GPa in comparison with 1.4 GPa for the nickel-silica interface. The difference is significantly greater than the margin of error in the technique, which is estimated to be less than 20%. The technique consists of depositing a thin film of the ceramic on a thick metal substrate. When the metal is deformed plastically in tension, the ceramic film develops nearly equispaced cracks that are aligned normal to the loading axis. The spacing between the cracks is inversely proportional to the shear strength of the interface. For a given interfacial strength, the spacing varies linearly with the thickness of the film; data which confirm this relationship are also presented. The possible effect of film thickness on delamination vs. shear yielding at the interface is discussed. © 1990.