Research On Manufacture Process And Quality Of Inkjet Printing Of Electronic Products

The key of studying the inkjet technique is the formed droplets. Higher productivity and printed quality require small adjustable droplets ejected at high repetition rates. That involves formation and fall of droplets and impact of droplets on the substrate. The two courses involve complex changes of fluid shapes, which is always a difficult problem. To improve the theoretical understanding of piezoelectric ink-jet printing and know the details in the course of droplet changes and the effect of various factors on practical production and scientific research, the thesis adopts the numerical simulation method to simulate the formation of liquid droplets from the nozzle exit and the course of droplets impact on the substrate.Firstly, the course of water droplet's formation and fall is simulated in the thesis. Then four kinds of other liquids (liquid A, B, C, D) with different surface tension and viscosity are also chosen as research objects to study the effect of the actual physical quantities such as surface tension and viscosity on the droplet ejection process. A, B and water have different surface tension and uniform other properties (e.g. density and viscosity), while the same viscosity and different other properties for water, C and D. The breakup time, the droplet length and changes of the tail droplet are also compared in the paper.Secondly, the course of droplets impact on the substrate is simulated and the diffusion mechanism of droplets is analyzed from aspects of the droplet shape and the pressure change in the thesis. It is a very complex process that droplets impact on the solid substrate, which involves three-phase changes (air-phase, liquid-phase and solid phase). The entire impact course may be divided into four phases based on the droplet's spreading area. Droplets spread out on the substrate, which is influenced by various factors such as droplet viscosity, surface tension, impact velocity, contact angle, liquid quality, surface conditions of substrate and so on. We mainly analyze the effect of various factors on the maximum spreading radius, the balance radius and the needed time in the entire spreading course.The result indicates that numerical simulation is suitable for simulating the formation and fall of droplets and the contact and impact problems. Analyzing the courses of droplet's formation and deposition by the numerical simulation method has a very important meaning for practical applications. Through simulating the droplet formation, we can further understand the formation mechanism of droplets and get some experiences to improve the droplet ejection system. Through simulating the contact and impact of droplets, we can predict the deposition effect and estimate various defects in the course of droplet deposition. Based on that above, we can control the related parameters to achieve the ideal deposition effect.