Preparation And Property Research For Anisotropic Conductive Adhesive Film

With the increasing demand in higher integration, in/out (I/O) count, power andcalculating speed materials, the electronic products are developing towards furtherminiaturization and green. As a green packaging material, the application ofanisotropic conductive adhesive film (ACF) in electronic packaging is increasing. Inthis paper, the preparation technology of the anisotropic conductive adhesive films(ACF) was studied and mechanical properties of cured ACF were conductedexperimentally on a dynamic mechanical analyzer (DMA).Anisotropic conductive adhesive films were prepared with a kind of self-madecomposite conductive particles and resin adhesive, the process included thepreparation of polystyrene spheres used in ACF, the surface chemical nickel/silverplating technology research and optimization of polystyrene spheres and finally thepreparation of ACF. When preparing dispersion polymerization polystyrene spheres,the particle size minifies and the distribution narrows with an increase in the amountof polyvinyl pyrrolidone (PVP) and a decrease of alcohol/water ratio; as monomersand initiator increase and the reaction temperature rises, the particle size ofpolystyrene spheres increases. Using chemical plating method, a layer of nickel andthen a layer of silver can be coated on the surface of polystyrene microspheres, so anew kind of polymer-based conductive particle used in ACF is prepared. Using thiskind of novel conductive particles, the preparation of anisotropic conductive adhesivefilms with four different thicknesses has been done successfully.The uniaxial ratcheting behavior at elevated temperature and fatigue behavior ofcured ACF were comprehensively studied on a dynamic mechanical analyzer (DMA).The results show that ACF is a kind of nonlinear viscoelastic material, and its tensilemechanical properties show obvious dependency on temperature. With the increase oftemperature, Young’s modulus and tensile strength decrease and ultimate strainincreases. The ratcheting strain increased as the mean stress, stress amplitude andtemperature increased. The ratcheting strain decreases with increasing stress rate.Especially, when the temperature was over80℃, the ratcheting strain accumulatedrapidly. There are significant differences on the uniaxial ratcheting behavior of ACF at80℃and120℃. The ratcheting strain rate at120℃is nearly twenty times that at80℃. The loading histories also play an important role in the progress of ratcheting.Previous cycling with higher stress amplitude greatly restrains ratcheting strain ofsubsequent cycling at lower ones. The Gerber method is more reasonable for theprediction of ACF’s fatigue life under variable load history when considering theeffect of mean stress on life.