Research On Deformation And Stress Testing Methods Of Thin Film Substrate Structure

With the development of science and technology,thin film/substrate structure has been widely used in various fields of high-tech industry because of its special structure and performance.The film coated on the substrate will inevitably generate residual stress in the manufacturing and processing process,and thermal stress will be generated due to the thermodynamic coupling in service.The film stress has an adverse effect on the performance and service life,and it is the key factor leading to film failure.Therefore,it is of great scientific significance to develop theoretical formula derivation and experimental measurement to detect the film stress.The main research contents of this paper are as follows:1.A non-contact high temperature full-field deformation measurement system was established,and a simple high temperature speckle fabrication method was proposed,which can be used for high precision measurement of film curvature.The results show that the accuracy of deformation measurement and curvature measurement is 0.45μm and 1.5×10-6mm^-1 for the specimen with a radius of 25mm.2.Based on the linear thermoelastic constitutive model,the stress formula of multilayer films with non-uniform deformation was derived,and the direct relationship between the stress of each layer of films and the temperature field and the curvature of the sample was established.The results show that the local stress is not only related to the local curvature of the point,but also to the global curvature of the system.3.Through finite element simulation,the error of the film stress calculation method based on curvature is analyzed.The results show that the larger the thickness ratio is,the smaller the calculation error is.When the thickness ratio is greater than 25,the calculation error of the film stress is less than 5%.The ratio of elastic modulus and the thermal expansion coefficient of thin film substrate have little influence on the calculation of thin film stress.4.The machining and thermal curvature changes of single film brass base nickel plating sample and double film thermal barrier coating sample were measured successfully,and the residual stress and thermal stress of the film were calculated,which provided a reliable method for measuring the full-field stress of the film with multi-layer film substrate.