The Flow Analysis And Numerical Simulation Of The Fluid Dispensing Process

Time-pressure dispensing system plays a decisive role in the semiconductorpackaging industry. It is widely used in die attach, flip chip, chip coating and packagingprocesses. Dispensing is a multivariable coupled system and its quality （shape of thedispensing dot and the consistency） is affected by temperature, colloidal properties,dispensing time, pressure, shape of the needle and so on. Dispensing to achieve highaccuracy and high stability has become a major problem in packaging.Based on the time-pressure dispensing’s current application practice, starting from theinfluence factors on consistent quality, and aimed to improve dispensing quality, this paperresearches on the dispensing process by means of modeling, simulation, experiment.1） Establish fluid flow model for dispensing. Elaborate and summarize thenon-Newtonian fluid’s dynamic characteristics and related experience models, analysis theflow state in dispensing. Establish fluid dynamic characteristic equation in cylindricalcoordinates for time-pressure dispensing based on fluid motion feature. Estanlish apractical and simplified analysis model based on appropriate assumptions. Dispensing fluidis analyzed by finite element modeling based on the N-S equation.2） Establish and analysis3D simulation model. Model the dispensing syringe andneedle in ANSYS environment, use CFX module to simulate dispensing under steady andunsteady conditions, and then obtain the corresponding flow field distribution diagram.Study the change rule of the adbesive amount dispensed affected by the entrance pressure,diameter and length of the needle. Finally, compare the dispensing simulation values andspectral method for two order approximations, the reliability and applicability of the modelis proved.3） Analysis the important factors affecting dispensing. Establish the cavity gasmodelfor the problem of remaining amount in cylinder. Especially, introduce the staticmixer which is used in double liquid dispensing, and establish the pressure drop model in the mixer under the laminar flow condition, then analyze related factors. Discuss theresidue on tips, summarize the feasible and practical methods to reduce or even avoidsmearing.4） Experimental study on influence factors of consistency. Obtain2×2dot matrixsunder different conditions by a large number of repeated experiments and all these matrixsare meeting the predetermined dispensing consistency. Use charts to process theseexperimental datas in excel. Analysis the response of the dot amount by changing theentrance pressure. And get to know that the consistency of fluid A is the best when theentrance pressure is0.5Mpa. Realise that the fluid whose viscosity is smaller is moresensitive to pressure changes.Establish simplified model and3D model for the time-pressure dispensing, discussrelated influence factors, and achieve the conditions for better consistency based onexperiences. All the research results have certain reference value for improving thedispensing quality.