Recent advances in microelectronics and packaging industry are characterized by a progressive miniaturization in response to a general trend toward higher integration and package density. Corresponding to this are the challenges to traditional manufacturing processes. Some of these challenges can be satisfied by laser micromachining, because of its inherent advantages. In laser micromachining, there is no tool wear, the heat affected zone can be localized into a very small area, and the laser micromachining systems can be operated at a very wide range of speeds. Some applications of laser micromachining include pulsed Nd:YAG laser spot welding for the photonic devices and laser microdrilling in the computer printed circuit board market. Although laser micromachining has become widely used in microelectronics and packaging industry, it still produces results having a variability in properties and quality due to very complex phenomena involved in the process, including, but not limited to, heat transfer, fluid flow, plasma effects, and metallurgical problems. Therefore, in order to utilize the advantages of laser micromachining and to achieve anticipated results, it is necessary to develop a thorough understanding of the involved physical processes, especially those relating to microelectronics and packaging applications. The objective of this Dissertation was to study laser micromachining processes, especially laser drilling and welding of metals or their alloys, for the microscale applications. The investigations performed in this Dissertation were based on analytical, computational, and experimental solutions (ACES) methodology. More specifically, the studies were focused on development of a consistent set of equations representing interaction of the laser beam with materials of interest in this Dissertation, solution of these equations by finite difference method (FDM) and finite element method (FEM), experimental demonstration of laser micromachining, and correlation of the results. The contributions of this Dissertation include: 1)development of a finite difference method (FDM) program with color graphic interface, which has the capability of adjusting the laser power distributions, coefficient of energy absorption, and nonlinear material properties of the workpiece as functions of temperature, and can be extended to calculate the fluid dynamic phenomena and the profiles of laser micromachined workpieces, 2)detailed investigations of the effect of laser operating parameters on the results of the profiles and dimensions of the laser microdrilled or microwelded workpiece, which provide the guideline and advance currently existing laser micromachining processes, 3)use, for the first time, of a novel optoelectronic holography (OEH) system, which provides non-contact full-field deformation measurements with sub-micrometer accuracy, for quantitative characterization of thermal deformations of the laser micromachined parts, 4)experimental evaluations of strength of laser microwelds as the function of laser power levels and number of microwelds, which showed the lower values than the strength of the base material due to the increase of hardness at the heat affected zone (HAZ) of the microwelds, 5)measurements of temperature profiles during laser microwelding, which showed good correlations with computational results, 6)detailed considerations of absorption of laser beam energy, effect of thermal and aerodynamic conditions due to shielding gas, and the formation of plasma and its effect on laser micromachining processes. The investigations presented in this Dissertation show viability of the laser micromachining processes, account for the considerations required for a better understanding of laser micromachining processes, and provide guideline which can help explaining and advancing the currently existing laser micromachining processes. Results of this Dissertation will facilitate improvements and optimizations of the state-of-the-art laser micromachining techniques and enable the emerging technologies related to the multi-disciplinary field of microelectronics and packaging for the future.

The conventional methods for diagnosing pathological conditions of the tympanic membrane (TM) and other abnormalities require measuring its motion while responding to acoustic excitation. Current methodologies for characterizing the motion of the TM are usually limited to either average acoustic estimates (admittance or reflectance) or single-point mobility measurements, neither of which is sufficient to characterize the detailed mechanical response of the TM to sound. Furthermore, while acoustic and single-point measurements are useful for the diagnosis of some middle ear disorders, they are not useful in others. Measurements of the motion of the entire TM surface can provide more information than these other techniques and may be superior for the diagnosis of pathology. In this Thesis, the development of an optoelectronic holographic otoscope (OEHO) system for characterization of nanometer scale motions in TMs is presented. The OEHO system can provide full-field-of-view information of the sound-induced displacements of the entire surface of the TM at video rates, allowing rapid quantitative analysis of the mechanical response of normal or pathological TMs. Preliminary measurements of TM motion in cadaveric animals helped constrain the optical design parameters for the OEHO, including the following: image contrast, resolution, depth of field (DOF), laser power, working distance between the interferometer and TM, magnification, and field of view (FOV). Specialized imaging software was used in selecting and synthesizing the various components. Several prototypes were constructed and characterized. The present configuration has a resolution of 57.0 line pairs/mm, DOF of 5 mm, FOV of 10 ´ 10 mm2, and a 473 nm laser with illumination power of 15 mW. The OEHO system includes a computer controlled digital camera, a fiber optic subsystem for transmission and modulation of laser light, and an optomechanical system for illumination and observation of the TM. The OEHO system is capable of operating in two modes. A 'time-averaged' mode, processed at video rates, was used to characterize the frequency dependence of TM displacements as tone frequency was swept from 500 Hz to 25 kHz. A 'double-exposure' mode was used at selected frequencies to measure, in full-field-of-view, displacements of the TM surface with nanometer resolution. The OEHO system has been designed, fabricated, and evaluated, and is currently being evaluated in a medical-research environment to address basic science questions regarding TM function. Representative time-averaged holographic and stroboscopic interferometry results in post-mortem and live samples are herein shown, and the potential utilization discussed.