Development Of The Conductive Particle Dispersing Method Based On Electrohydrodynamic Atomization Technology

Conductive particle is a kind of material which serves to be a crucial ingredient of the anisotropic conductive film(ACF), it is a heap of goldplated tiny particles with uniform diameter. These particles can establish a conductive connection between the IC chips and the substrate glass, while at the same time makes a reliable support for the IC chips as to prevent it from any shock and vibration. Unfortunately, due to the impedance of the manufacturing crafts, the distribution of the particle inside the ACF material suffered a lot of uniformity issues, which may cause pretty much connecting failures when the size of the IC chips continue to shirk. It’s therefore a dispersing method is needed to place those conductive particles uniformly and effectively.Electrohydrodynamic atomization(EHDA) is a phenomenon when a liquid was subjected into a strong electric field, and the coulomb repulsion force overcomes the surface tension of the liquid and consequently makes it breakup into tiny droplets. The repellent of the same charge enables the EHDA process to produce the smallest droplets with preferred monodispersity, so as to satisfy the requirement of particle distribution uniformity. This work was aimed at developing an effective dispersing procedure based on the EHDA technique.First and foremost, we introduced the governing leaky dielectric model for the dielectric liquids based on the electrohydrodynamic theory. Analyzed how the meniscus of the liquid to evolving into a conical shape, which was named after G. I. Taylor, and the formation of the thin jet out from the tip of the Taylor cone. Meanwhile we also introduced the scaling laws obeyed by the ejecting jet and the mechanisms lead to the atomization of that jet. Through this theoretical analyses, we explained the feasibility of deploying EHDA as a particle dispersing method;A scrutiny of each mode of the spray and the variations between different spray modes was launched with the help of a high-speed camera, which has helped us to fully understand how quite a few spray configurations may affect the behavior of spray morphologies. Based on those comparisons, we introduced and illustrated the stable cone-jet mode to be the ideal one to undertake the dispersing work. Then a parameter diagram for running the stable mode spray was given based on a variety of EHDA experiments;We utilized the MATLAB’s Image Processing Toolbox to establish an image counting, calibrating and segmentation software, and introduced three series of criterions to estimate the distribution quality, which has concerned the density, agglomeration and uniformity of the spreading particles. Together with a custom designed stepping scanning observation platform, it’s able to deal large batch of particle distribution images with standard and efficiency.Finally, the general patterns and microscope images of deposited particle were compared in order to find the most optimized spray parameters with a custom designed prototype spray equipment. The stage motion functions of the equipment are also introduced for its capability of promoting the deposition qualities and expanding the deposition area.Therefore, a complete set of solutions to utilize the EHDA technology for large batch conductive particles dispersing with low cost and great deposition qualities was proposed and verified.