Modeling and off-line control of fluid dispensing for electronics packaging
Date
2002
Authors
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Type
Degree Level
Doctoral
Abstract
Fluid dispensing is a method by which fluid materials are delivered to
substrates, boards or work-pieces in a controllable manner. This method has been
widely used in various packaging processes in the electronics manufacturing
industry. In these processes, the flow rate of fluid dispensed and the profile of fluid
formed on a board are the two most important performance variables to be
controlled consistently.
This research presents a comprehensive study on the modeling and control
of the time-pressure dispensing processes. First of all, the characterization of the
rheological behaviour of fluids for electronics packaging is addressed from both
time-independent and time-dependent perspectives. Under the assumption that the
pressure in the dispensing syringe has reached a steady-state status, a model
representative of the steady-state flow rate of fluid dispensed is developed. To
represent the profile of fluid formed on a board, the spreading of fluid on a board is
addressed and a solution to this problem is established.
To consider the influence of time-dependent fluid behaviour in fluid
dispensing, a method of applying model updating technique is developed in this
study. Based on this method, an off-line control of the dispensing process is
developed to improve the consistency in the flow rate of fluid dispensed, which is
broken by the time-dependent fluid behaviour.
Taking into account air compressibility and the fluid inertia, a model is
developed to represent the dynamics of the flow rate of fluid dispensed, which shows that the dynamics is sensitive to the air volume in the syringe. Based on the
model, the inconsistency in the fluid amount dispensed due to the variation of the air
volume in the syringe over a dispensing process is investigated, and an off-line
control is developed to alleviate the amount inconsistency.
Experiments on a typical commercial dispensing system are designed and
carried out to verify the effectiveness of the models and the off-line control
developed in this study. It is shown that the model results have an excellent
agreement with the experimental results. Also, with the introduction of the off-line
control, the consistency in both the flow rate and the amount of fluid dispensed can
be significantly improved.
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Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Mechanical Engineering
Program
Mechanical Engineering