Furnace and laser methods of bonding metals to ceramics: phenomenological investigation

Several methods for direct bonding of metals to ceramics in air and various inert atmospheres using a furnace or lasers as a heating source are investigated. In order to investigate inter-diffusion between the copper layer and the sapphire and also to measure the percentage of diffused copper in sapphire, Rutherford backscattering spectroscopy (RBS) was performed. Based on heat transfer theory and on diffusion theory, a model was derived to explain and predict the behavior of furnace and laser beam bonding of metals to ceramics. The predictions of the model are in agreement with the experimental percentages of diffused copper in sapphire obtained in the RBS investigations. Based on experimental investigations and theoretical modeling, it has been concluded that the direct bonding phenomenon is a thermal effect, similar to transient liquid phase bonding. The major advantage of direct bonding is that no filler material is required between the metallic member and the ceramic substrate. Finally, the method of direct bonding of metals to ceramics using a laser beam is capable of directly drawing a metallic pattern on a ceramic substrate.