ELECTRO-THERMO-MECHANICAL RESPONSES OF CONDUCTIVE ADHESIVE MATERIALS

Micromechanics models which aim to provide an understanding of conduct ive adhesive materials from the level of micro-particles (less than 30 mm) are presented in this paper, The pressure-induced conducting mech anisms are investigated, A deformation analysis reveals a logarithmic pressure-resistance relationship and is capable of addressing the cond ucting phenomena for both rigid and deformable particle systems within a contact mechanics framework. This logarithmic relationship also pro vides analytical support for findings reported in the literature of co nductive adhesive research. It is observed that electrical contacts ar e made by squashing conducting particles for a deformable particle sys tem while the particle penetration creates a crater in metallization t o make contacts for a rigid particle system, The current analysis prov ides simple closed-form solutions for the elastic deformation of singl e-particle contacts and based on the assumption that the contact force s are evenly distributed in a conductive him, the pressure-resistance responses are correlated to the particle volume fraction, The high vol ume fraction, while ensuring that there are a sufficient number of par ticles to make contacts, may limit the particle deformation due to ove rall increased stiffness, resulting in the increased resistance on a p er particle basis, The current analysis also offers insight into desig n considerations whereby limited amount of deformation (low processing temperature) and sufficiently low electrical resistance are to be sim ultaneously satisfied, For the mechanical performance, the uniaxial no nlinear stress-strain relationship is obtained for conductive adhesive systems in terms of polymer and particle material properties, The Mor i-Tanaka's method is utilized to account for particle-particle and par ticle-matrix interactions, The behavior in thermal expansion within th e elastoplastic deformation range is also obtained in a similar fashio n, In all these calculations, only a very simplified finite element an alysis for the problem of a particle embedded into an infinitely exten ded matrix material needs to be carried out.