Currently the trend of electronic product development is to ward ¡§light and thin, multi-functional, high density and durability¡¨. When the microelectronic chips tend to be high power, high density and high speed, the rapid increase of heat in a reduced unit area of package size, will lead to failure of electronic products. The contents of thesis is to find out the dominant factors in heat transfer by changing the geometries and material properties of QFN and BGA packages. It also aims to achieve the beat the thermal performance by reducing the probability of failure. In industries it needs a lot of cost and time in experiment work due to the changes of size and materials. Herein, the softwares of ANSYS and ICEPAK are adopted to model the QFN and BGA packages with the statistical experimental design of Taguchi method L18 (21¡Ñ37) orthogonal array setting parameters and obtain the degree of effect for each factor. Eventually, we use the analysis of variance ANOVA to obtain the contribution of each factor and to identify the significant degree for various parameters by variance error integration. From the results the die attach thermal conductivity affects the contribution of thermal performance up to 81.46% for QFN package in comparison with other controlling factors of high significance and high impact effects. Die attach thermal conductivity between 0.5 W/m•k and 1.5 W/m•k the Tj declines much larger than that between 1.5 W/m•k and 8 W/m•k. Die /PKG area ratio affects the contribution of the thermal performance to 64.24% and increasing Die /PKG area ratio can reduce the Tj for BGA package. The significant effect is also higher than other factors. However, the contribution of substrate layers is 18.83% at 99% confidence level.

Laser based underwater triangulation ranging is sensitive to the environmental conditions and laser beam profile. Also, its ranging quality is greatly affected by the algorithm choices for peak detection and for image processing. By utilizing the merging least-squares approximation for laser image processing, it indeed succeeds in increasing quality of triangulation ranging in water; however, this result was obtained on the use of a laser beam with nearly circular cross-section. Therefore, by using an ellipse-like laser beam cross-section for range finding, we are really interested in understanding the quality of range finding with different peak detection algorithms. Besides, the ellipse orientation of the laser spot projected on the image plane would be various. We are also interested in learning about the relationship between the ellipse orientation and the quality of range finding. In this study, peak detection algorithms are investigated by considering four different laser beam cross-sections which are ircle, horizontal ellipse, oblique ellipse, and vertical ellipse. First, we employ polynomial regression for processing laser image to study the effect of polynomial degree on quality of triangulation ranging. It was found that the linear regression achieves the best ranging quality than others. Then, according to this result, the ranging quality associated with peak detection is evaluated by employing three different algorithms which are the illumination center, twice illumination center and the illumination center with principal component analysis. We found that the ranging quality by using the illumination center with principal component analysis is the best, next is twice illumination center, and last the illumination center. This result indicates that the orientation of elliptical laser beam has an influential effect on the quality of range finding. In addition, the ranging quality difference among peak detection algorithms is significantly reduced by implementing the merging least-squares approximation rlaser image processing. This result illustrates that the merging least-squares approximation does reduce the effect of peak detection algorithm on the quality of range finding.

ABSTRACT This thesis gathered the actual Burn-In (BI) data from one of the leading cooperation in the semiconductor industry, and analyzed the major factors¡¦ impact on BGA package solder ball deformation. The Taguchi Method was used for these analyses, and the commercial statistic software MiniTab14 was widely used on this thesis. The solder ball stress was analized by using the commercial FEM software Ansys 8.1. Some electrical characters (such as device power) can be only observed from Burn-In process, but not static acceleration tests. These effects were fully discussed in this thesis. The analyses got the result that the smaller solder ball pitch/solder ball diameter causes the more serious solder ball deformation under the specific socket vendor precondition. Burn-In time are also a significant factor for solder deformation. Basically the longer BI time cause the more serious solder deformation. The device power effect is not significant within the power sampling range of this thesis.

IC test socket and socket pogo pin are the major cost of consumption parts in IC testing house. Test yield is the key point to determine the profit for IC testing house. When the processing speed of CPU (Central Processing Unit) and GPU (Graphic Processing Unit) are boosting, heat generation and power dissipation became a serious problem for IC testing house. Most package type of CPU and GPU are packed by Flip-Chip BGA type. High temperature will melt the solder ball and cause test socket pogo pin to damage. The excellent cooling capability of impinging jet had been proofed by many literatures in past. In this article, impinging jet applied to IC test handler contact chuck is investigated. The contact chuck had been redesigned with thermal solution and uses a rectangle hot plate to simulate the thermal status of IC testing. A circular air jet impinged on the rectangle hot plate from the topside of contact chuck. Out flow open area, open area on the wall location and the distance between jet nozzle and hot plate are major parameters of this heat transfer problem. Parameter ¡§Z¡¨ is the distance between jet nozzle and hot plate; ¡§D¡¨ is the diameter of circular air jet. As shown in the result, ratio of Z/D and the location of out flow open area on the wall is obvious on heat transfer capability for redesigned contact chuck. Taguchi method and analysis of variance (ANOVA) method help to clarify the weighting of influence. The optimum Z/D is 0.5 and the optimum location of out flow open area is at dual side corner. Heat transfer capability can be improved approach to 70% after optimization. Width and height of out flow open area only made about 5% impact on heat transfer capability.

The purpose of this dissertation is to study the robust control for the smart flexible linkage mechanism. The control of flexible linkage induced inertia force under high-speed rotation is taken into consideration with the system parameter uncertainties such as modeling error, truncation error, and both of control spillover and observation spillover due to the residual modes of structural control problem. Based on the principles of LQ, optimal model following (OMF) and frequency shaping, this study proposes some sufficient conditions of stability criteria for the design of robust controller, respectively. These techniques guarantee that the controlled plant, under both bounded parameter perturbations and model truncation, could remain stable. Meanwhile, searching for the optimal locating positions of sensor and actuator by applying Taguchi method and genetic algorithm (GA) combined technique is further studied. The system is modeled through employing finite element method (FEM), and the limited lower frequency part modes are separated into controlled modes and residual modes. In time domain, at first we design a Luenberger-observer-based robust controller for the finite-dimensional mode plant keeping stability in a specified region. And then, a robust controller with the OMF is designed for the controlled system to achieve the performance as those of the specified optimum model. From the view of frequency domain, the robust controller could also be deigned according to the frequency shaping principle to suppress the exciting effect of higher frequency residual modes, and similarly avoid that the system might be destabilized. Finally, the combination of Taguchi method and GA technique to search the optimal locations for placing actuator and sensor to coincide with the stability and performance requirement is also done. From the computer simulation, the middle point movement of the linkage is obviously well controlled; hence, the designed robust controllers can certainly suppress the affection of parameter uncertainties and the spillover stimulation of residual modes, and can produce satisfactory results.

Automobiles have become an integral part of our daily life as more and more mopeds, motor cycles, cars, trucks, busses and trains are being used for transport. The main parts of an automotive engine are cylinder, piston assembly, connecting rod and crank shaft. The piston assembly consists of Piston, Piston rings and Piston Pin. Piston rings are important parts of a piston assembly. Any non-conformance in any quality characteristic of the piston ring leads to deterioration of engine performance. M/S Goetze (India) Limited a medium scale industry and a sister concern of engineering giant M/S Escorts Limited is manufacturing "GOETZE PISTON RINGS" and is producing about 800 varieties of piston rings ranging from 35.00 mm to 228.5 mm nominal diameter. The management was facing serious problem due to high scrap rate in certain types of their manufactured piston rings. Hence instead of trying to handle all of them at the same time, it seemed reasonable to tackle and find a suitable approach to solve the quality problem by taking the most notorious ring first, so that once the methodology is understood, documented and applied to the quality problem of this ring, the same can also be invoked for other rings to improve upon their quality, and thus reducing the scrap rate. One particular ring of 83.0 mm diameter which is delicate and costly, having an average scrap rate of 36.2% in past three years is selected for the study. No systematic effort was made in the past to identify the quality characteristics and the processes which were responsible for this high scrap rate and thus no immediate measure could be recommended. As a matter of fact at the beginning of the study it was not even clear which quality characteristics were mainly responsible for such high rejection. So in July' 1999 a pareto analysis was done for the first time to identify the culpability of each quality characteristic for the rejection of the ring. From the Pareto analysis it was observed that maximum proportion of rejection was due to nonconformity in axial thickness. The scrap rate due to nonconformity in axial thickness were collected for each month from Jul’ 999 to Jan'2000 which averaged at 8.7%. Since in every month the major malefactor for rejection was the nonconformity of axial thickness it was decided to first try to improve the quality of axial thickness, before trying to tackle other quality issues associated with this particular piston ring under study. Once the most problematic quality characteristic namely the axial thickness was identified, as a first step towards the goal of improving the quality of axial thickness, it was necessary to pay attention and isolate the manufacturing processes or operations affecting the axial thickness and study them in detail. So first, the entire manufacturing process flow diagram of the piston ring was studied. From the process flow diagram it appeared that there are 4 operations affecting axial thickness viz. Rough Grinding ,Medium Grinding, First Lapping and Finish Lapping. So each of these processes was critically observed to assess whether they were under statistical control or not. Studies were conducted at each of these 4 operations by collecting samples using the rational subgroup method and control charts were plotted. From the control charts, it was observed that the Rough Grinding and Medium Grinding operations were in statistical control with acceptable Cp, Cpk values. But First Lapping and Finish Lapping operations were not in statistical control. Thus we finally identified the two critical processes namely the First Lapping and Finish Lapping operations which were not in statistical control but were crucially affecting the quality of axial thickness. Since the First and Finish Lapping operations were identified as the major source of the quality problem, an in-depth study was undertaken to analyze these two processes. A brain storming session was conducted with all concerned personnel from production, maintenance, design, quality assurance and tool room to get all possible causes which might be affecting the axial thickness variation at these two processes. During the brain storming session the team suggested that the First Lapping process can be processed in medium grinding machine (DFS machine) instead of Lapping machine. The reasons behind this were two fold. First since the aim of the First Lapping is just to remove excess material which was deposited during chrome plating, the same operation can be performed in DFS machine. Since the required surface finish on axial surface was any way being aimed at the Finish Lapping operation, a similar precursory First Lapping'operation in a Lapping machine was really felt not necessary. Secondly since the performance of the DFS machine was found to be under control, albeit for the grinding operation, it was hoped that the Lapping operation in the same machine would also exhibit a similar performance. For this purpose a study was conducted on the First Lapping operation with the DFS machine. It was found that the process was well within the control limit with decent Cp and Cpk values. Thus this procedure of performing the First Lapping operation in a DFS machine took care of the first one of the two problematic processes affecting the quality of axial thickness. Next for tackling the problem with the other critical process, viz. the Finish Lapping operation, various causes were suggested by the team for axial thickness variation in the Finish Lapping operation. Based on these causes, an Ishikawa diagram (cause and effect diagram) was prepared. This Ishikawa diagram had thrown light into number of possible deficiencies in Man, Machine, Method and Material which were responsible for axial thickness variation at finish Lapping. The Ishikawa diagram was carefully analyzed. The causes were narrowed down to 6 factors. These are Grinding wheel rotating speed, Grinding Time, Grinding pressure, Holding plate, Holes (fixtures) within the holding plate and Positions within a ring. The 3 factors namely grinding wheel speed, time and pressure were identified as the control factors. Holding plate, Hole position within a plate and Checking position within a ring on the other hand were the noise factors whose different levels might exhibit a variability of axial thickness. Since there were only 3 control factors, it was decided to conduct a full factorial experiment with each control factor at 3 levels. Hence altogether there were 27 experiments at a fixed given combination of speed, time and pressure. There were 4 holding plates with each plate having 6 slotted holes leading to machining 24 rings at a time during the finish lapping operation. Next 3 measurements were taken for each one of these 24 rings. Thus altogether there were 72 observations for one of these experiments. Each experiment was replicated twice by taking measurements for 2 consecutive batches of rings. From the analysis of variance of the results of these experiments for both S/N ratio and mean it was observed that all the three main factors and their interactions were significant. The Normality assumption of standardized residuals for the S/N ratio and mean was validated by normal probability plot and Kolmonogorov-Smirnoff test. The homoscedasticity assumption was validated through Bartlett’s test and residual plots. It was found that the experiment no. 23 (Speed 84 RPM, Time 10 sees and Pressure 300 daN) yielded highest S/N ratio (η) with mean within the specification limit. That the mean and S/N ratio for the experiment no.23 were significantly different from others was established by means of Tukey's multiple comparison test. Next control charts for experiment no. 23 were plotted and was found to be well within control with acceptable Cp and Cpk values. Hence we concluded that the non-conformance in axial thickness can be substantially reduced by using the following optimal setting of factors i.e. grinding speed with 84 RPM, grinding pressure with 300 daN and grinding time with 10 seconds. Using this optimal setting the earlier average rejection rate of 8.7% due to non-conformance in axial thickness was reduced to 0.05%. Under this optimal setting, the process capability index (Cpk) of finish Lapping operation was estimated to be 2.5, which is well above acceptable standard. Due to this reduction in rejection rate in one quality characteristics of one particular ring out of 800 types, the net savings to the organization is approximately Rs. 10,44,000 per year.

La consommation annuelle totale moyenne en France dans le secteur tertiaire varie entre 300 et 380 kWh/m². Cette consommation se rapporte à l'ensemble des usages énergétiques du bâtiment: chauffage, climatisation, ventilation, éclairage, bureautique, auxiliaires et ECS. Ce travail a donné une méthode pour déterminer les meilleures combinaisons de solutions techniques existantes ou émergentes permettant de réduire les consommations énergétiques dans les bâtiments climatisés du secteur tertiaire. La réduction obtenue est d'un facteur 4 à 5. Une typologie représentative a été mise en place pour chaque secteur et les scénarios nécessaires pour effectuer les simulations définis. Une matrice de sélection du type de système par type de bâtiment a été fixée. Un niveau simplifié de modélisation des systèmes compatible avec les outils de prévision d'énergie a été employé. Vu le très grand nombre de variables à étudier, le nombre de simulations à effectuer et le traitement des résultats nécessite un temps énorme. Ce problème a été résolu par l'emploi de plans d'expériences fractionnaires. Cette méthode est nouvelle dans le domaine du bâtiment et répond à la question fréquente de réduction du nombre de simulation. Un modèle paramétrique de consommation a ainsi été élaboré. Il permet d'évaluer l'effet de chaque paramètre étudié sur les différentes postes consommateurs et la consommation annuelle totale. Ce modèle pourra servir à déduire la rentabilité des solutions et contribuer à une optimisation économique. La thèse traite la question d'un effet contradictoire possible de l'isolation sur la minimisation des consommations de refroidissement et de chauffage. Deux secteurs principaux du tertiaire sont étudiés: bâtiments de bureaux et bâtiments de santé. Le premier secteur est présenté dans l'intégralité de ses aspects tandis que le deuxième est traité brièvement. Le travail a permis d'élaborer une méthodologie complète pour minimiser les consommations énergétiques annuelles et pour étudier l'effet de chaque paramètre sur cette consommation.

De nos jours, le domaine des implants est un des enjeux important pour notre civilisation pour permettre d'améliorer notre quotidien. Pour ce faire, une large offre de matériaux et de technologies existe offrant de nombreuses possibilités afin de répondre aux attentes chirurgicales. Plusieurs familles de matériaux coexistent : les polymères, les céramiques et les matériaux métalliques ainsi que différents procédés de mise en forme. Parmi ceux-ci, le procédé de micro fusion laser sur lit de poudre est un procédé prometteur permettant de réaliser des pièces de géométries complexes. C'est précisément cette technologie qui a été retenue. Pour cela, afin d'approfondir la connaissance du procédé et évaluer l'impact des paramètres sur les structures métallographiques, une orientation se tournant vers des matériaux métalliques tels que le CoCrMo et le titane T40 a été envisagée.Ainsi, les objectifs de la thèse ont été de générer un matériau possédant de bonnes caractéristiques mécaniques ainsi qu'en faciliter son intégration dans un milieu biologique (implants). Pour ce faire, une structure de porosité contrôlée (pour faciliter le développement tissulaire) avec des propriétés mécaniques adaptées aux sollicitations est nécessaire. Le premier travail effectué fut donc une recherche préliminaire afin d'approfondir la connaissance du procédé, en particulier d'un point de vue énergétique et thermique. Afin d'identifier et d'évaluer l'impact des paramètres sur le taux de porosité et donc les propriétés mécaniques de la pièce, une méthode statistique de type Taguchi a été utilisée. Au travers de cette analyse, il est apparu que 3 paramètres inhérents au procédé (la distance entre tache laser, temps d'exposition et le pas de balayage) expliquent prêt de 80% des résultats. De plus, il est mis en évidence que les propriétés mécaniques d'une structure (module de Young et résistance à la rupture) peuvent être maitrisées grâce au taux de porosité de cette dernière et permettre ainsi un rapprochement des propriétés mécaniques de l'os cortical. Pour ce faire, des caractérisations mécaniques ont donc été réalisées pour évaluer le module de Young et la résistance à la rupture des pièces avec différentes structures. Une maîtrise des propriétés peut donc être envisagée et peut même être adaptée en réalisant des structures mixtes alliant partie dense et partie poreuse.

Semi-solid manufacturing is a near net shape forming process that takes advantage of an alloy's thixotropic behaviour. However, in order to obtain the desired thixotropic properties from an alloy in the semi -solid state, the microstructure of the as-cast feedstock metal needs to display a fine grained, equiaxed primary phase prior to reheating for the forming operation. Various methods are currently in use to obtain the required microstructure of which the MagnetoHydroDynamic (MHD) process is predominant. Two fundamental factors, namely shear rate and cooling rate, influence the formation of the fine grained, equiaxed primary phase during the MHD process. The aim of this research was to produce semi solid billets and in so doing, determine how the influence of the combination of the two fundamental factors contribute towards the final formation of the primary phase and to determine an optimal level ofthese factors' settings to deliver the desired microstructure. An MHD apparatus was constructed and the Taguchi method was used to design an experiment to investigate the influence ofthe fundamental factors involved in casting semi solid feedstock of aluminium A356.2. The issues ofthe formation of a fine eutectic phase and solidification shrinkage were also investigated. An experimental method was designed to investigate the significance ofthe fundamental factors' influence towards the appearance of the primary phase; the latter was evaluated using an image analysis system. The shear rate was controlled by varying the line frequency and the base frequency supplied to the electromagnetic stirrer and the cooling rate was controlled by initiation of a fixed, fast cooling rate at a certain melt temperature (TJ Results showed that a fine grained, equiaxed primary phase, with an average grain size of 55 /lm, was achieved after casting, prior to reheating for forming. The contribution of the base frequency and the line frequency were 8 % and 3.5 % respectively and the contribution ofTi was 86.5 % towards the outcome ofthe result. The cooling rate changed from approximately 0.3 QC/sec to 4.5 QC/sec at Ti. A fine textured eutectic phase was achieved with the fast cooling rate. The solidification shrinkage was accounted for by incorporating a riser on the mould. The feedstock produced in this research was compared, on a microstructural basis, to commercially available Semi Solid Metal (SSM) feedstock from Pechiney and SAG. The research feedstock had a larger, average primary grain size, however, it was more discrete and round grained than the commercial alloys which were finer and more rosette grained. Upon reheating to the semi solid state, ready for forming, the final, evolved grain sizes and shapes were almost identical between the research and commercial feedstock, despite the initial differences in grain sizes and shapes. However, the commercial alloys showed primary grains with trapped eutectic whereas in the research alloy, the primary grains were largely free of trapped eutectic. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.

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