Experimental Techniques for Static and Dynamic Analysis of Thick Bonding Wires

Thick bonding wires are used in modern power modules as connectors between integrated circuits, carrying current from one circuit to another. They experience high values of current, which generates heat through Joule heating and can lead to various failure mechanisms. Typically used wire materials in industry are aluminum (Al), copper (Cu), and intermetallic compounds of Cu-Al. They are broadly used because of their strength, high thermal conductivity, and low resistivity. This study reports on the influence of thermal loading on the mechanical behaviour of bonding wires. Experimental techniques are developed and introduced in this thesis to analyze quasi-static and dynamic response of bonding wires 300 µm in diameter. First, an experimental technique is developed to measure the quasi-static displacement of bonding wires carrying DC currents. It is then deployed to measure the displacement, as well as peak temperature, of three types of bonding wires, Al, Cu and Aluminum coated Copper (CuCorAl) to study the response under DC current. Secondly, an experimental technique is established and deployed for modal analysis of bonding wires under thermal loading. Experimental results demonstrate a drop in the natural frequency of bonding wires with increased thermal loads. Moreover, a harmonic analysis technique using thermal excitation is developed and applied to analyze the mode shapes and frequency response of bonding wires. Furthermore, an analytical model and a finite element model are used to analyze static and dynamic responses of bonding wires. Numerical and experimental results are compared in this thesis

Design and simulation of a direct and indirect drive electrostatically actuated resonant micro-mirrors for scanner applications

Laser scanners have been an integral part of MEMS research for more than three decades. The demand for electrostatically actuated scanning micro-mirrors have been growing in the last decade, mainly for pico-projection and medical applications. These type of actuation wins over others, because it provides long-term stability, size advantages and fabrication schemes which are easier to render CMOS compatibility. The growing field in softwares capable of design and simulate MEMS devices, have been a crucial help for engineers, which are limited to a few of them and still cost huge amount of time. MEMS+® is a software platform that provides simulation results up to 100 times faster than conventional finite element analysis tools and allows to integrate designs in MathWorks®. In this work two types of electrostatically actuated scanning micro-mirrors were designed and simulated using both MEMS+® and MathWorks®, one is a direct drive micro-mirror and the other an indirect drive micro-mirror. In the first the torque is imparted directly from the actuation mechanism to the frame containing the mirror, and in the second the resonance mode amplifies a small motion in a larger mass to a considerably larger motion in the smaller mirror. Regarding the direct-drive micro-mirror, the presented work mainly shows the reliability of MEMS+® compared to other softwares. The indirect drive one, is a state-of-art solution for high frequency electrostatically actuated micro-mirrors, and all the simulations taken on it were aimed to verify it´s behaviour, and then proceed with the microfabrication step. The target microfabrication technology is SOIMUMPs

Integrated Ultra-High Q Bulk Acoustic Wave Resonators in Thick Monocrystalline Silicon Carbide

Monocrystalline 4H-silicon carbide has emerged as an intriguiging substrate for wafer level fabrication of ultra-high Q electrostatic acoustic resonators. As a wide band-gap semiconductor, it's already under heavy investigation in the field of power electronics for its exemplary electrical and thermal robustness; further, its stoichiometric properties find it germane to a diverse array of applications from biomedical sensors to quantum photonics. Acoustically, it possesses sublime structural properties and mechanical dissipation characteristics, with theoretical mechanical quality factors prescribed by phonon scattering limits surpassing silicon by an order of magnitude. High Q is almost universally desirable: improved motional resistance and insertion loss, greater displacements, longer decay times, along with reduced phase and Brownian noise translate to more sensitive, stable, efficient and precise instruments. This thesis expounds upon a platform for thick, single crystal silicon carbide resonant MEMS, explores the roots of dissipation and the structural properties most pertinent to thick single crystal silicon carbide bulk acoustic wave resonators and their applications in inertial sensors. Record-high measured mechanical quality factors demonstrate proof of concept resonators ready to make the leap toward high performance sensors and instruments. Strong emphasis is placed on developments in fabrication techniques and processes to enable the implementation of silicon carbide in sensors across the gamut of environments and applications.Ph.D

Measuring the Quality Factor in MEMS Devices

This paper demonstrates and compares different experimental techniques utilized to estimate the quality factor (Q) and natural frequency from non-contact measurements of Microelectromechanical Systems (MEMS) motions. The relative merits of those techniques are contrasted in Q factor estimation for a cantilever beam MEMS actuator, operated in three configurations: free standing, arc-shaped, and s-shaped. It is found that damping estimation techniques that seek to minimize the deviation between the response of an “assumed” linear oscillator and the measured time-history of the motions are superior to those traditional techniques, such as logarithmic decrement and half-power bandwidth. Further, it is found that Q increases three-fold as the actuator contact with the substrate evolves from a line to an area