Finite Element Method Optimization And Preperation Of Copper/Zirconium Tungstate Functionally Graded Films

Zirconium tungstate is a kind of isotropic negative thermal expansion material, the properties and the composite materials of Zirconium tungstate are new frontiers of material science. Zirconium tungstate powders were synthesized by solid state reaction; co-precipitation method; Sol-Gel method. Zirconium tungstate films were synthesized by the magnetic sputtering and laser sputtering. Cu/Zirconium tungstate functionally graded films prepared by magnetic sputtering would be used to decrease the heat stress on the surfaces of electronic equipments.Optimization on parametres of Cu/Zirconium tungstate functionally graded films by finite element method could accelerate the research progress:to establish mathmetical model with the parametres gotten from the previous experiments; to prepare functionally films according with the pre-optimized parametres; to measure the properties of film, then to modify the optimized parametres.A mathematical model of the Cu/ZrW₂O₈ functionally graded films was built using finite element method.The effects of the parameters, such as the quantity of layers (N), distribution of components (P), thickness of graded films (Hf), thickness of S substrate (Hm), thickness of pure Cu layer (Hc) and temperature (Τ), on the thermal stress fields of Cu/ZrW₂O₈ functionally graded films were discussed. The results of thermodynamic calculation show that the more layers of the functionally graded films, the more the thermal stress can reduce. When P= 1 and N≥5, the maximum value of heat stress between the silicon and the functionally graded films decreased. When N= 5 and 3≥P≥2, the maximum value of heat stress appeared inside the functionally graded films. The increased values of H_f and Hm can favor the reduction of the maximum value of heat stress. This functionally graded film can protect the pure Cu layer from room temperature to the a-ZrW₂O₈ phase transformation temperature (120℃).Several characterization methods were applied to analyse the phases constitute, the surface morphology, and the thermal stress of the film using the XRD, SEM, X-ray stress tester, respectively. The result show that the thermal stress distribution is similar to that from the numerical calculation. The maximum value of thermal stress decreases to 72%of the original coating without the functionally graded films, and it do appear in the middle of the functionally graded film.