Studien undersöker huruvida revisionsbyråer vid revisionsbyråbyten initialt offererarrevisionsarvoden som understiger deras kostnader för att sedan höja revisionsarvodetefterföljande år, så kallad low-balling. I denna studie undersöks om low-balling förekommervid revisionsbyråbyten under år 2002-2009 i bolag noterade på Stockholm Nasdaq OMX. Förekomstav low-balling på revisionsmarknaden har studerats världen över sedan 1980-talet och har främstmotiverats av oron för en negativ korrelation med revisorers oberoende. Urholkning av revisorersoberoende i samband med förekomst av low-balling har argumenterats uppkomma på grund av deninitiala förlust som uppstår det första revisionsåret. Det finns därmed ökade incitament för enrevisionsbyrå att möta bolagets intresse på bekostnad av användarna av en revision för att erhållaframtida intäkter. Förekomst av low-balling är således intressant att undersöka då det kan påverkarevisorers oberoende och därmed minska revisionens försäkran. Tidigare studiers resultat omförekomst av low-balling varierar, fenomenet har dock aldrig undersökts på den svenskamarknaden. Studien påvisar förekomst av low-balling i en knapp majoritet av revisionsbyråbytenunder år 2002-2009 i bolag noterade på Stockholm Nasdaq OMX. Majoriteten av revisionsbyråbytendär förekomst low-balling påvisas innehar en sänkning av revisionsarvoden med över -10 procentvid revisionsbyråbyten följt av höjning med över 20 procent. Då resultatet uppvisar indikation påförekomst av low-balling vid revisionsbyråbyten påvisar denna studie vikten av framtida studier avaspekter som härrör till fenomenet. Aspekter så som low-balling i relation till revisionens funktionoch revisorers oberoende, drivkrafter bakom förekomst av low-balling samt eventuella effekter somkan uppstå i och med low-balling.

Binder jet additive manufacturing (BJ) offers unique advantages, including the ability to produce complex geometries and utilize a wide range of materials, but faces challenges related to part quality and defect formation. This thesis investigates the effects of process parameters on droplet-powder interaction, powder relocation, and line formation in BJ printing. A custom BJ test platform was developed to enable precise control over key process parameters and in-situ monitoring. High-speed synchrotron X-ray imaging revealed modes of powder relocation above and below the powder bed surface. Testing revealed that parameters that increase moisture in the powder bed, such as lower droplet spacings, printing adjacent to previously printed geometry, and pre-wetting, reduce powder disturbance. Powder ejection above the powder bed surface was found to be affected by powder material, density, pre-wetting, previously printed geometry, and droplet spacing. Powder relocation below the powder bed surface was found to be largely independent of binder infiltration behavior, suggesting that powder relocation below the powder bed surface is driven by the kinetic impact of the droplet. A novel approach for analyzing printed lines demonstrated the sensitivity of line formation to various parameters, including droplet spacing, inter-arrival time, volume, and velocity. Lines were found to ball more readily at lower droplet spacings when printing at lower droplet velocities, although other coupled droplet parameters such as droplet volume and formation of satellite droplets also play a role. In printing conditions susceptible to balling, the droplets at the beginning of printed lines were observed to agglomerate, relocating powder and introducing error to the starting position of the line. Pre-wetting the powder bed with a water/TEG mixture significantly reduced balling and increased the range of droplet spacings and inter-arrival times resulting in successful line formation. Printing with low droplet velocities on moisture treated powder beds further increased the range of inter-arrival times that successfully formed lines. Reducing the kinetic energy of droplet impact by reducing droplet velocity and reducing the impact of balling by pre-wetting presents a set of process print process parameters that show promise to reduce powder relocation during the printing process. These findings provide valuable insights into the fundamental mechanisms of droplet-powder interaction, modes of powder relocation during printing that may contribute to porosity defects seen in final parts, and print process parameters that mitigate powder relocation due to droplet-powder interaction.

Recent trends to miniaturized systems such as smartphones and wearables, as well as the rise of autonomous vehicles relying on all-electric and smart in-car systems, have brought unprecedented needs for superior performance, functionality, and cost requirements. Transistor scaling alone cannot meet these metrics unless the remaining system components such as substrates and interconnections are scaled down to bridge the gap between transistor and system scaling. In this regard, 3D glass system packages have emerged as a promising alternative due to their ultra-short system interconnection lengths, higher component densities and system reliability enabled by the tailorable coefficient of thermal expansion (CTE), high dimensional stability and surface smoothness, outstanding electrical properties and low-cost panel-level processability of glass. The research objectives are to demonstrate board-level reliability of large, thin, glass packages directly mounted on PCB with conventional BGAs at pitches of 400µm SMT and smaller. Two key innovations are introduced to accomplish the objectives: a.) Reworkable circumferential polymer collars providing strain-relief at critical high stress concentration areas in the solder joints, b.) novel Mn-doped SACMTM solder to provide superior drop test performance without degrading thermomechanical reliability. Modeling, package and board design, fabrication and reliability characterization were carried out to demonstrate reliable board-level interconnections of large, ultra-thin glass packages. Finite-element modeling (FEM) was used to investigate the effectiveness of circumferential polymer collars as a strain-relief solution on fatigue performance. Experimental results with polymer collars indicated a 2X improvement in drop performance and 30% improvement in fatigue life. Failure analysis was performed using characterization techniques such as confocal surface acoustic microscopy (C-SAM), optical microscopy, X-ray imaging, and scanning electron microscopy/energy dispersive spectrometry (SEM/EDS). Model-to-experiment correlation was performed to validate the effectiveness of polymer collars as a strain-relief mechanism. Enhancement in board-level reliability performance with advances in solder materials based on Mn-doped SACMTM is demonstrated in the last part of the thesis.The studies, thus, demonstrate material, design and process innovations for package-to-board interconnection reliability with ultra-thin, large glass packages.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21744号 / 工博第4561号 / 新制||工||1711(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 小林 潔司, 教授 川﨑 雅史, 教授 宇野 伸宏 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Modeling and simulation of granular matter has important applications in both natural science and industry. One widely used method is the discrete element method (DEM). It can be used for simulating granular matter in the gaseous, liquid as well as solid regime whereas alternative methods are in general applicable to only one. Discrete element analysis of large systems is, however, limited by long computational time. A number of solutions to radically improve the computational efficiency of DEM simulations are developed and analysed. These include treating the material as a nonsmooth dynamical system and methods for reducing the computational effort for solving the complementarity problem that arise from implicit treatment of the contact laws. This allow for large time-step integration and ultimately more and faster simulation studies or analysis of more complex systems. Acceleration methods that can reduce the computational complexity and degrees of freedom have been invented. These solutions are investigated in numerical experiments, validated using experimental data and applied for design exploration of iron ore pelletising systems. / <p>This work has been generously supported by Algoryx Simulation, LKAB (dnr 223-</p><p>2442-09), Umeå University and VINNOVA (2014-01901).</p>

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