Guiling Deng

Simulation and experiment study of dispensing patterns influence on underfill filling process

Dispensing pattern is important for flip-chips underfill filling quality. This paper uses three-dimensional flow model to simulate underfill capillary flow and filling process for L and I dispensing patterns. The model reckons in influences of surface tension, contact angle and radius of curvature, especially contact angle and radius of curvature at wall of gap between chip and substrate, side wall of chip and surface of sold bump joints. In order to track the moving interface, the VOF model is applied. On the other hand, an experimental device has been constructed to research underfill filling process of the two dispensing patterns. Both simulation results and experiment results show that dispensing patterns have great influences on underfill filling velocity and flow front profile. In L filling pattern, underfill flow velocity is faster in diagonal direction. Comparing with experimental results and simulation results, it can be concluded the 3-D simulation model established can simulate underfill filling process well for the both L type and I type dispensing pattern.

Flow Channel Influence of a Collision-Based Piezoelectric Jetting Dispenser on Jet Performance

To improve the jet performance of a bi-piezoelectric jet dispenser, mathematical and simulation models were established according to the operating principle. In order to improve the accuracy and reliability of the simulation calculation, a viscosity model of the fluid was fitted to a fifth-order function with shear rate based on rheological test data, and the needle displacement model was fitted to a nine-order function with time based on real-time displacement test data. The results show that jet performance is related to the diameter of the nozzle outlet and the cone angle of the nozzle, and the impacts of the flow channel structure were confirmed. The approach of numerical simulation is confirmed by the testing results of droplet volume. It will provide a reliable simulation platform for mechanical collision-based jet dispensing and a theoretical basis for micro jet valve design and improvement.

Simulation and experiment study on the jetting dispensing process driven by mechanical collision

Dispensing technology is widely applied in semiconductor packaging surface mount technology,LED packaging , where needs accurate flow control. The work efficiency of jetting dispensing is 5~6 times higher than the contact dispensing and the jetting dispensing with the better consistency of dispensing volume is the mainstream in dispensing technology in the future. The jetting dispensing process related needle high-speed acceleration movement and mechanism of droplets generation in complex coupling environment is always the key concerns of research in this field .In this paper, a two-dimensional axisymmetric model based on Volume of fluid (VOF) method is built by computational fluid dynamics(CFD) software .Fluent dynamic grid technique is introduced in numerical simulation to analyzed the fluid-solid coupling process .The mechanism of on-demand dispensing is analyzed by simulation results and the effects on droplet diameter caused by related parameters are summarized. Then the jetting dispensing experiment device and micro-jetting system is built based on the simulation experiment results. The experimental results closely matched with the theoretical simulation results indicate the method is feasible. The jetting dispensing technique could achieve the maximum frequency up to 200Hz within the dots consistency ± 10% in stability.

Simulation analysis of jet dispenser based on piezoelectric actuators

Jet dispenser driven by piezoelectric actuators, based on diamond-shape shell structure without any hinges, was designed and their static and dynamic characters were investigated. The amplifier makes the dispenser small and compact, and operated in a wide range of frequency. In this study, a method to accumulate the amplifyer displacement will present firstly. In the following, dynamic model of a dispenser prototype is established and analyzed. Finally, performance of the dispenser with varies input voltages and frequency will be discussed.

Study on temperature field of fluid jet-dispenser based on two piezoelectric stacks

Fluid jet-dispenser based on two piezoelectric stacks can achieve high frequency, micro injection. Each sort of fluid has its own viscosity, which varies with temperature remarkably. Heating device was designed in order to reduce the viscosity of fluid, so the applicable scope of fluid and the stability of dispensing will be improved evidently. Based on the simulation software platform COMSOL, a three-dimensional transient temperature field model of jetting dispenser was built, in which a temperature feedback was set and the difference of two heating modes in channel was analyzed. The temperature was measured in real time in the experiment. The results showed that: the system can achieve the temperature equilibrium in 130s and the heating device system was feasible, which can achieve channel temperature stability.

Simulation and experimental study on temperature field of fluid jet-dispenser

Fluid jet-dispensing technology has been widely used in micro-electronic encapsulation industry. The fluid viscosity varies as temperature changes, while it affects the process remarkably. Besides basic method on temperature field solution, some thermal behaviors, including heat conduction and heat exchange, boundary conditions and some physical parameters are overall analyzed in this paper. Based on the simulation software platform ANSYS, a two-dimensional transient temperature field model of jet-dispenser was built, and simulation programs on temperature field for two sorts of fluid with obviously different thermal conductivity were performed. Then heating experiments were finished to validate the feasibility of FEA, and results show that temperature distribution is homogeneous along fluid area and it meets the conditions of jetting.

Design of the temperature control system for the fluid jet-dispenser

In the fluid jetting dispensing process, The fluid viscosity varies as temperature changes, while it affects the consistency of the dispensing process. In order to maintain a constant temperature in the dispensing process, the temperature control system was designed which based on PID control algorithm and AT89S51 single chip microcomputer. The performances of the system were tested by experiment. During the testing the operating temperature was set to 70°C, the maximum temperature fluctuation was 0.5°C. The experiment shows that the temperature control system can meet the demand of the fluid jetting dispensing process.

Research on thermal field of giant magnetostrictive jetting dispenser

In order to enhance the performance and stability of the injection valve, it is necessary to know the dynamic change of the thermal field in working process of the giant magnetostrictive injection valve. In this paper, thermal field finite element analysis (FEA) including the contact resistance and experiment were carried out. A little difference between simulation and experimental results shows that temperature field FEA including contact thermal resistance can reflect the actual situation accurately. The temperature variation of the injection valve is little after 2500 seconds working. The steady thermal field can ensure injection valve working stably.

A Simplified Analysis Method for the Piezo Jet Dispenser with a Diamond Amplifier

Diamond amplifiers have been widely applied in Nano actuators and Robots. In order to study the dynamic characteristics of the diamond amplifier system which is used in the piezo jet dispenser, it is simplified as a spring-mass-damper system. The dynamic characteristics of the jet dispenser system are analyzed with the simplified method. The characteristics are also tested. The results agree with the simulation, which proves the method is feasible. It will provide a simplified and intuitive representation of the movement of the amplifier, and also provide reliable simulation and experimental platforms for jet dispensing analysis.

Study on the process of fluid Jet dispensing based on high and low voltage drive

The Jet dispensing technology plays a decisive role in microelectronic packaging, which is an important link to ensure the quality of microelectronics packaging. With the reduction of the size of components, the high efficiency and low cost in the field of microelectronics packaging, the technical requirements for Jet dispensing are also getting higher and higher. The piezoelectric jetting dispensing as a non-contact dispensing mode, which is not high requirement about the work of the substrate flatness and height. And it has the advantages of high precision, high efficiency and good consistency, so it has an irreplaceable position in the field of microelectronic packaging. This paper is based on the high and low voltage driving method of piezoelectric spray Jet dispensing valve. At the theoretical level, FLUENT software is used to establish two-dimensional axisymmetric model of fluid dispensing, and simulate the formation process of droplets. Because the different high and low pressure will cause the needles different velocity, the effect of different velocity on the spray effect and the volume of the droplet is simulated. In the experiment, UV glue (industry commonly use, 0.9Pa · s) is used, and a perfect piezoelectric jet dispensing experiment platform is set up, including laser displacement sensor, piezoelectric jet dispensing valve, three axis motion platform and driving power. laser displacement sensor is used to measure the needles displacement and velocity and cylinder is used to measure droplet volume of different high and low voltage drive. High and low voltage is used to control the displacement, furthermore, which can be used to study the effect on spray droplet size and volume of spray droplets. Under the condition that droplets can be sprayed out, the minimum volume of droplets is 35.3nL.