Showing papers by "Quoc Hung Nguyen published in 2008"

Optimal design of magnetorheological valves via a finite element method considering control energy and a time constant

Abstract: This study presents an optimal design for magnetorheological (MR) valves for minimizing the control energy to be applied to coils to control the pressure drop of the valves The optimization problem identifies parameters such as applied current, coil wire size and geometric dimensions of the valves which satisfy the specified pressure drop and inductive time constant requirements After describing the configuration of MR valves, their pressure drops are obtained on the basis of the Bingham model of MR fluid Then, the control energy which is an objective function and the inductive time constant are derived Subsequently, an optimization procedure using a golden-section algorithm and a local quadratic fitting technique is constructed via a commercial finite element method parametric design language Using the optimization tool developed in this study, optimal MR valve configurations are identified, which are constrained to a specific cylindrical volume defined by its radius and height In addition, optimization results for MR valves with different required pressure drops and different constrained volumes are obtained and presented

A new type of piezostack-driven jetting dispenser for semiconductor electronic packaging: modeling and control

Abstract: This paper presents a new type of piezostack-driven jetting dispenser which can be applicable for semiconductor packaging processes. After describing the structural components of the dispensing mechanism and the operating principle, the dynamic modeling is undertaken by considering the behavior of the piezostack, hydraulic magnification, dispensing needle and adhesive fluid. In the modeling, fluid models for the adhesive fluid and hydraulic magnification are derived using a mechanical model which is analogous to the corresponding lumped parameter model. The governing equation of motion is then established by integrating the fluid models with the structural model. Subsequently, the dynamic behavior of the dispenser and its dispensing amount are investigated through both computer simulation and experiment by applying a sinusoidal driving voltage input. In addition, a control system is designed and experimentally realized to control the dispensing flow rate (dispensed amount) of the dispenser.

The design and control of a jetting dispenser for semiconductor electronic packaging driven by a piezostack and a flexible beam

Abstract: This paper presents the performance characteristics of a new type of jetting dispenser which can be applicable for modern semiconductor packaging processes. The proposed jetting dispenser is driven by both a piezostack actuator and a flexible beam mechanism. After describing the geometric configuration and operational principle of the dispenser, a mathematical model of the system is derived by considering the dynamic behaviors of structural parts such as the piezostack, the flexible beam, the needle structure, and the adhesive fluid dynamics. In the modeling, a lumped parameter method is employed and the governing equation of the whole dispenser is then formulated by integrating the structural model with the fluid model. Based on the proposed model, significant structural components of the dispenser such as the piezostack, the flexible beam, and the actuating spring are designed in order to achieve operational requirements (needle motion amplitude: up to 0.4 mm; operating frequency: up to 700 Hz). Subsequently, dispensing performances such as the dispensing dot size and flow rate are experimentally evaluated. In addition, a control algorithm is designed and empirically realized to demonstrate some benefits of the proposed jetting dispenser such as accurate controllability of dispensing amount.

Dynamic Characteristics of a New Jetting Dispenser Driven by Piezostack Actuator

Abstract: This paper proposes a new type of jetting dispenser driven by a piezostack actuator. After describing structural components of the dispensing mechanism and operating principle, a dynamic model of the dispenser is analytically formulated by considering dynamic behaviors of the piezostack-piston head and the ball-needle. The inelastic impact between the ball-needle and the ball-seat during dispensing process is also considered in the modeling. An analytical fluid-solid interaction model is then derived by integrating the dynamic behavior of the dispensing fluid. Dispensing performances such as dot size and flow rate are evaluated under various frequencies and amplitudes of the sinusoidal driving voltage applied to the piezostack actuator.

Modeling of Unsteady Laminar Flow Based on Steady Solution in Jetting Dispensing Process

Abstract: This paper proposes a new approach to model unsteady laminar flows of dispenser systems in the semiconductor packaging industry. The approach is based on the exact steady solution. After an overview of dispensing technology and historical modeling of the unsteady flows, a new modeling approach of the unsteady laminar flow in a circular pipe and annular duct is developed. From the proposed model, the modeling results of unsteady flow in an arbitrary circular pipe and annular duct are obtained and compared with the spectral solution. In addition, a comparative work between the proposed analytical dynamic model and the finite-element model is undertaken in order to demonstrate the effectiveness of the proposed modeling methodology.

Design of a Novel Jetting Dispenser Featuring Piezostack and Linear Pump

Abstract: This article presents a novel jetting dispenser featuring piezoelectric actuator incorporated with a linear positive displacement pump, to achieve high dispensing flow rate with small dot size. A multi-stack type of piezoelectric actuator is adopted and its output displacement is amplified via a hydraulic magnification mechanism. After describing the configuration and operating principle of the proposed dispensing system, static modeling is undertaken by analytical method to determine design parameters. The analytical result is then proven by finite element analysis. Subsequently, structural dynamic modeling and fluid dynamic modeling are analytically undertaken. In the dynamic modeling, fluid-solid interaction is considered to predict the dispensing dot size and average flow rate of the dispenser. Dispensing performances are investigated by changing the driving voltage of the piezostack actuator and velocity of the linear piston of the pump.

Design of a new mechanism for jetting dispenser featuring piezoactuator

Abstract: This work presents both the static and dynamic models for a new type of jetting dispenser featuring a piezostack actuator, which is applicable to electronic packaging assembly After describing the configuration of the dispensing mechanism and operational principle of the proposed piezostack-driven jetting dispenser, a static modelling for mechanical part is analysed by considering the piezostack behaviour, fluid compressibility, and structural deflection Both linear and non-linear behaviours of the structural plate are analysed and incorporated The dynamic modelling of the mechanical part is also performed by considering the dynamic behaviour of the piston and needle After optimizing the design parameters, such as piston radius and so on, the behaviour of the needle motion is obtained and checked for adhesive dispensing applicability In order to demonstrate the effectiveness of the proposed static and dynamic models, an experimental test is undertaken by showing needle displacement

Performance characteristics of a high frequency jetting dispenser featuring piezoelectric actuator

Abstract: This paper presents a new type of jetting dispenser driven by a ring type piezoelectric actuator. By operating at very high frequencies, the dispenser is expected to provide very small dispensing dot size of low viscous adhesives (viscosity of 50cp to 500cp) at high dispensing flow rate in semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the system is derived by considering behaviors of the piezostack, the actuating spring, the dispensing needle and the adhesive fluid dynamics. In the modeling, a lumped parameter method is applied to model the adhesive whose rheological property is approximately expressed by Bingham model. The governing equation of the whole dispenser is then derived by integrating the structural model with the fluid model. Based on the proposed model, the dispenser is designed and manufactured. Subsequently, the dispensing performances such as dot size and dispensing flow rate are investigated using the proposed model and then validated by experiment.

Performance Characteristics of High Speed Jetting Dispenser Using Piezoactuator

Abstract: This paper presents a new jetting dispenser driven by a piezoelectric actuator at high operating frequency to provide very small dispensing dot size of adhesive in modern semiconductor packaging processes. After describing the mechanism and operational principle of the dispenser, a mathematical model of the structured system is derived by considering behavior of each component such as piezostack and dispensing needle. In the fluid modeling, a lumped parameter method is applied to model the adhesive whose rheological property is expressed by Bingham model. The governing equations are then derived by integrating the structural model with the fluid model. Based on the proposed model, dispensing performances such as dispensing amount are investigated with respect to various input trajectories.

Performance Characteristics of a Jetting Dispenser Featuring Piezostack and Flexible Beam Mechanism

Abstract: This paper presents a new type of jetting dispenser driven by a piezostack. Via a flexible beam mechanism, the amplitude of a needle motion is amplified to such a value that can make a dispensing of medium and high viscosity adhesive. By designing the flexible beam with high resonant frequency, the dispenser can operate at a frequency much higher than that of conventional dispensers. Therefore, it is expected that the dispenser can provide very small dispensing dot size at high dispensing flow rate, which is imperatively required in modern semiconductor packaging processes. Furthermore, the dispensing flow rate and dot size can be effectively controlled by driving voltage applied to the piezostack. After describing the mechanism and operational principle of the dispenser, a mathematical model of the system is derived by considering dynamic behaviors of structural parts such as the piezostack, the flexible beam and the needle structure, and the adhesive fluid dynamics. In the modeling, a lumped parameter method is applied to model the adhesive dynamics and the governing equation of the whole dispenser is then derived by integrating the structural model with the fluid model. Based on the proposed model, the dispenser is designed and manufactured. Subsequently, dispensing performances such as a dot size and dispensing flow rate are experimentally evaluated.