The Preparation Of Compliant Conductive Micro-spheres For ACF

This thesis was organized by the clue of preparation of anisotropic conductive film (ACF) and all the experimentations were focused on the synthesis of conductive micro-spheres for ACF. After the introduction of the basic knowledge and current development of ACF in electronic package, the key technologies of conductive micro-spheres for anisotropic conductive film (ACF) were developed, and the technologies were consisted of two parts, including the preparation of monodisperse polymer micro-spheres and the technology of nickel coating on the micro-spheres. In the part of the preparation of monodisperse polymer micro-spheres, polystyrene (PS) micro-spheres with mean particle size about 4.1μm and coefficient of variation about 1.63% were firstly prepared by dispersion polymerization using poly vinyl pyrroidone (PVP)as dispersant, AIBN as initiator and water/ethanol system as dispersing medium. And then the influence factors on particle size and size distribution such as inject means of reactant, influence of inhibitor in polystyrene and the others were studied in this thesis. Finally, the technology stability experiment and scale-up showed that the process was of stability and can successfully scaled up for 3 times. During the study, two decisive factors of the particle sizes increasing including particle density and monomer conversion, with which the increasing process of the micro-spheres was explained in detail, were advanced, and it was showed that the micro-spheres were not a process increasing from inside to outside gradually, but one with its density and volume increasing meanwhile. In the other part, nickel coating on the micro-spheres was successfully prepared by electroless plating, and a mature process was also obtained by optimization. In this study, it was showed the nickel disposition mode on micro-spheres was same to on block polymer materials. And then two controlling methods of the coating appearance were also advanced. A novel conductive micro-sphere with projections for ACF was prepared in this thesis. As projections mentioned above can be used to break through the oxide film of the electrodes, the ACF filled with the novel conductive micro-sphere can successful applied to fine pitch interconnection structure of electrodes with oxide film.