INTEGRATION OF A PIEZOELECTRIC ULTRASONIC MOTOR INTO A LOW TEMPERATURE COFIRED CERAMIC PACKAGE FOR ACTIVE OPTICAL FIBER ALIGNMENT
Open Access
- Author:
- Park, Seung Ho
- Graduate Program:
- Materials
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 15, 2007
- Committee Members:
- Kenji Uchino, Committee Chair/Co-Chair
Clive A Randall, Committee Chair/Co-Chair
Leslie Eric Cross, Committee Member
Michael T Lanagan, Committee Member
Heath Hofmann, Committee Member - Keywords:
- Cofiring
Ultrasonic motor
Piezoelectric
Alignment
High Power - Abstract:
- The major goal of this thesis was to integrate an ultrasonic motor into a ceramic package and demonstrate a useful function of the device. The chosen demonstration was a fiber-optic alignment package that utilized the strengths of the piezoelectric motor, such as its small size, low power consumption, fine position resolution, quick response and high power to weight ratio. In order to demonstrate this functionality a number of key research tasks had to be undertaken. Specifically, materials development of a low fire, piezoelectric ceramic with properties that would remain stable under high power drive conditions was required. The piezoelectric ceramic had to be processed at a firing temperature that made it compatible with low temperature cofired ceramics (LTCC) and silver electrodes. A piezoelectric miniaturized motor was designed using the electromechanical properties of piezoelectric ceramic. The motor was designed around two resonance modes that enabled an elliptical motion of the tip, which then permitted the possibility of 2 degrees of freedom when a bimorph structure was used. The motor was designed and optimized using ATILA finite element method (FEM) simulations. The motor design considered the key geometric factors controlling the resonance modes and vibration amplitudes. The motor was also considered with a variety of different electrical drive conditions and the properties were tested with prototyped motors. The properties included resonance behaviors, characterization of displacements, torque, efficiency, and so on. Based on these studies a cofired structure was then developed and similarly characterized. One of the important goals in this research was to cofire the ultrasonic motor with LTCC in order to create a reliable housing structure with low fabrication costs and facilitate mass production. In order to achieve this, various thermal, mechanical and structural factors were considered during a cofiring process. Finally, the ultrasonic motors were successfully cofired with commercial LTCC green tapes as well as with silver electrodes without encountering delamination or bending problems. In the final part of the thesis, a LTCC packaged structure was designed and fabricated with the integrated piezoelectric motors. These motors were then driven with a computer controlled circuit that was designed to aid a procedure aimed at optical alignment between a fiber and a laser. Once alignment was achieved, a pre-stressed structure with springs maintained the position of the fiber without any external electrical field or adhesive material. This package design provided a unique ability to adjust and realign an optical fiber in the case where misalignment occurs during installation or use. The optical package was characterized for thermal stability over a temperature ranging from room temperature to 50 oC.