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This panel will discuss the inherent conflict between the application of (Discrete-Event) Simulation and Scheduling techniques to manage and optimise capacity and material flow in Semiconductor Frontend Manufacturing (wafer fabrication). Representatives from both industry and academia will describe advantages and shortcomings of the respective techniques, with a specific focus on challenges arising from the recent and anticipated future evolution of the nature of such manufacturing environments, and suggest solution approaches as well as research issues that need to be addressed.

Small form factor (1” HDD) and 2.5” hard disk drives are widely used in mobile consumer electronics. Due to their mobile applications, mobile HDDs are susceptible to an environmental shock/ vibration. The shock/ vibration can be very severe that can damage the HDDs and the data stored in it. In this thesis, we propose several different shock/ vibration isolation techniques to reduce the risk of head slap which can happen if the HDD is subjected to a very severe shock. These techniques are compared and documented in this thesis. The core of this thesis is divided into two parts. The first part discusses the techniques to mitigate the shock in 1” HDD, in which we use Seagate ST1 as our case study. The first technique is to use a cantilever beam as an external shock isolator. The technique covers the study of the cantilever beam natural frequency, the cantilever beam damping ratio, and the mechanical properties of the HDD’s mountings; which can reduce the shock input significantly. A Simulink model is first created to help develop the shock isolator. The model is created using mode superposition and reduced mode method. The final design which is created in Simulink – MATLAB® is then compared with a finite element model in ANSYS. Simulation results show that the cantilever beam shock isolator is able to protect the micro HDD from operational shock up to 1000 G’s 0.5 ms and has increased the ST1 shock tolerance by 77%. As a comparison, we have designed another type of external shock isolator for the ST1 using elastomeric materials. The elastomer layers are added beneath the base plate of the ST1 and outside of the ST1 case. The analysis of the elastomeric shock isolator system is done in ANSYS. The results show that the cantilever beam performs better than the elastomeric system to reduce the shock to the HDD. MASTER OF ENGINEERING (MAE)

The hard disk drives have been increasingly used in consumer electronics and mobile computing, in which they may experience severe shock and vibration. Additionally, there is a fierce competition from the solid state drives. Hence, there is a need for rapid innovation, especially in the ever shorter drives design cycle. This in turn requires faster and accurate simulation method. This dissertation focuses on the formulation of an efficient theoretical model for design parametric studies and optimization in modern hard disk drives. It integrates both drive structural model and air bearing model. The structural models are developed using flexible multi body dynamics formulation and state-space mode superposition theory. The air bearing model is developed using finite volume formulation and modified quasi-static concept. The coupled structural and air bearing models can simulate the shock response at drive level and also predict the operational shock tolerance effectively. Hertz elastic contact theory is incorporated to deal with structural discontinuities. A modified state-space formulation is also included to simulate the dynamic air bearing location due to disk rotation. In the analysis of the quasi-static air bearing, it is found that air bearing equilibrium condition does not occur almost-immediately due to the squeeze term effect. Addition of optimized damping elements to quasi-static air bearing model can increase its accuracy and enable it to predict the same air bearing force as the finite volume model. From parametric studies, it is found that lower contact stiffness between suspension (dimple) and slider (flexure) yield higher shock tolerance. A more rigid cover is also found to increase the shock tolerance. Shock response analysis shows that the first-three most dominant actuator modes that affect the read/write head shock response are induced by the flexibility of suspension and flexure. It is also discovered that updating the position on the disk, at which the air bearing forces act, at every simulation time-step does not have significant effect on the shock response. Hence, it is not necessary to update the air bearing force location on the disk. From HDD vibration isolation studies, it can be observed that to survive a harsh shock and random vibration defined in MIL-STD-810E, the natural frequencies of the external vibration isolation system should be between 10 to 20 Hz. The damping ratio required is relatively high (> 10%). To reduce the peak-to-peak displacement during shock event, combination of soft and stiff isolators can be used. DOCTOR OF PHILOSOPHY (MAE)

International audience; The room temperature optical constants n and k of MBE grown FeF 2 films are reported. Because of poor chemical stability, FeF 2 had to be coated with a protective Au layer. Reflection spectral ellipsometry in the photon energy range between 1.3 and 5.2 eV was performed on structures with a typical profile Au(0.5 nm)/FeF 2 (120 nm)/Au(30 nm) /Ag(20 nm) /Fe(0.6 nm) grown on GaAs(001) substrate. The spectra of n and k in FeF 2 were subsequently employed in the design of FeF 2 /Fe/FeF 2 sandwiches considered as magneto-optic (MO) sensors for weak microwave currents. Their MO response was evaluated using reflection MO (Kerr) spectroscopy at polar magnetization. The present results may be of interest in MO studies of magnetic nanostructures with Fe/FeF 2 /Fe, including MO magnetometry and MO magnetic domain imaging.