Electrical Contact Resistance Theory for Anisotropic Conductive Films Considering Electron Tunneling and Particle Flattening

Abstract

This study models the electrical contact resistance (ECR) between two surfaces separated by an anisotropic conductive film. The film is made up of an epoxy with conductive spherical particles(metallic) dispersed within. In practical situations the particles are often heavily loaded and will undergo severe plastic deformation and may essentially be flattened out. In between the particles and the surfaces there may also be an ultra-thin insulating film (consisting of epoxy) which causes considerable electrical resistance between the surfaces. In the past this effect has been neglected and the predicted ECR was much lower than that measured experimentally. This added resistance is considered using electron tunneling theory. The severe plastic deformation of the spherical particles is modeled using a new expanded elasto-plastic spherical contact model. This work also investigates the effect of compression of the separating epoxy film on the electrical contact resistance. The model finds that the high experimental ECR measurements can be accounted for by including the existence of a thin insulating film through the electron tunneling model.

A Review of Elastic–Plastic Contact Mechanics

“…Many analytical, experimental, and numerical studies have been performed to simulate and predict various contact properties, such as the real radius of contact, stress distribution, and contact force. Spherical contact models are used by many researchers from different fields such as tribology, mechanical impact [31][32][33][34][35], and electrical contact [11,31,32,[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Even though the spherical geometry is often used to consider asperity contact, it can also be used to consider the flattening of particles between surfaces, such as in anisotropic conductive films [51] or in the presence of wear particles [55] and nanoparticles [50].…”

Analysis and prediction of electrical contact resistance for anisotropic conductive adhesives

“…Expression for R constr. of one body is: (4) Typical equation for bulk resistance of spherical body under elastic deformation is: (5) where ρ 1 is the particle resistivity and Δ 1 ,Δ 2 are deformations of particle. Nevertheless authors sometimes used different expressions for R b in the.…”

Analysis of tangential characteristics of the paraboloidal contact model

“…Examples can be found in the classical G-W model based on statistical analysis 29 and the M-B model based on fractal theory 30 . Although spherical contact models are often used to investigate rough surfaces, they can also be used in anisotropic conductive films 31 . Furthermore, like cylindrical contact models, spherical contact models are divided into elastic, elastoplastic, and plastic phases.…”