Basic and applied studies of electrically conductive adhesives.

摘要

The electrical properties of isotropically electrical conductive adhesives were studied in this dissertation from the bulk materials to the actual adhesive joints for the surface mount applications. The material properties including thermal analysis, rheology, and microstructure were investigated. Electrical reliability in 85;Cure studies show that inadequate cure schedules are suggested by the manufacturers. Cure models were developed which established the cure kinetics of these materials for choosing optimum cure schedules. Cure temperature is the main parameter to ensure full cure. Computer simulations were performed to predict the percolation thresholds and resistivities of the composites with filler sizes, distributions, and contact effects, in addition to the silver flake alignment effects.;The variations of electrical properties with process parameters of anisotropic Z-axis adhesive films were studied. Computer programs based on the microstructural investigations were developed to predict the limiting pitch application for commercial films, and for the inverse selection process.;High frequency impedance tests demonstrate the metallic behavior of these composites, and no capacitive effects between the silver flakes are seen. DC electrical measurement does not show any non-ohmic behavior. Metallic conduction is the dominant conduction mechanism in the completely cured materials. The contact resistances between the silver flakes are the controlling factors for the electrical conduction development during cure. They change from the insulating to tunneling, and finally to metallic conduction associated with the decomposition of the acid layer on the flakes and breakage of tarnish films. The temperature coefficient of the resistivity (TCR) is closely related to the silver flake sizes and distributions. The adhesives filled with smaller particles have more contacts and lower TCRs.