As human population increases, demand for water supplies will cause an increase in pumping rates from confined aquifers which may become unconfined after long-term pumping. Such an unconfined-confined conversion problem has not been fully investigated before and is the focus of this thesis. The objective of this thesis is to use both analytical and numerical modeling to investigate groundwater flow in an unconfined-confined aquifer including the no-flow lateral boundary effect and the regional flow influence. This study has used Girinskii’s Potential in combination with MATLAB to depict how changes in aquifer dimensions, hydraulic properties, regional flow rates, and pumping rates affect the size and shape of the unconfined-confined boundary. This study finds that the unconfined-confined conversion is quite sensitive to the distance between the piezometric surface and the upper confining bed when that distance is small, and the sensitivity lessens as that distance increases. The study shows that pumping rate is the dominating factor for controlling the size of the unconfined-confined boundary in comparison to the regional flow. It also shows that the presence of a no-flow boundary alters the normally elliptical shape of the unconfined-confined boundary.

As human population increases, demand for water supplies will cause an increase in pumping rates from confined aquifers which may become unconfined after long-term pumping. Such an unconfined-confined conversion problem has not been fully investigated before and is the focus of this thesis. The objective of this thesis is to use both analytical and numerical modeling to investigate groundwater flow in an unconfined-confined aquifer including the no-flow lateral boundary effect and the regional flow influence. This study has used Girinskii’s Potential in combination with MATLAB to depict how changes in aquifer dimensions, hydraulic properties, regional flow rates, and pumping rates affect the size and shape of the unconfined-confined boundary. This study finds that the unconfined-confined conversion is quite sensitive to the distance between the piezometric surface and the upper confining bed when that distance is small, and the sensitivity lessens as that distance increases. The study shows that pumping rate is the dominating factor for controlling the size of the unconfined-confined boundary in comparison to the regional flow. It also shows that the presence of a no-flow boundary alters the normally elliptical shape of the unconfined-confined boundary.

Hintergrund: Nach Schätzungen des GRC (German Resuscitation Council) erleiden jährlich allein in Deutschland 50.000 Menschen außerhalb eines Krankenhauses einen Herz-Kreislaufstillstand. In jeder Minute ohne Herzdruckmassage sinkt die Überlebenswahrscheinlichkeit um 10%. Bis zum Eintreffen professioneller Helfer müssen die Basismaßnahmen (Basic-Life-Support - BLS) der Reanimation durch nicht-medizinische Laien durchgeführt werden. Laien werden durch Basic-Life-Support-Kurse in den Basismaßnahmen geschult. Diese Basismaßnahmen sind als Qualitätsparameter messbar. Fragestellung: In der vorliegenden Arbeit wurde untersucht, ob ein standardisierter BLS-Kurs die Basismaßnahmen positiv beeinflussen kann und ob dieser Effekt auch noch nach 6 Monaten nachweisbar ist. Besonderer Wert wurde dabei auf den klinisch und prognostisch wichtigen Qualitätsparameter der No-Flow-Fraktion (NFF) gelegt. Methodik: Diese Prospektive Studie umfasste eine Kontrollgruppe aus Laien, die einmal in ihren Leben einen Erste-Hilfe-Kurs besucht hatten und nun ohne Schulung drei mal einem gleichen standardisierten Reanimationsszenario (5min Dauer) zugeführt wurden. Die Reanimationsleistungen wurden stets als Paarleistung im Rahmen der 2-Helfer-Methode erfasst. Dem gegenüber standen die Teilnehmer der Interventionsgruppe, welche ebenfalls Laien waren, jedoch im Rahmen ihrer Stellung als 'Betriebsersthelfer' alle 2 Jahre in Reanimation geschult wurden. Auch diese Teilnehmer wurden drei Mal dem Reanimationsszenario ausgesetzt: Einmal vor dem Auffrischungskurs, unmittelbar nach dem BLS-Kurs und erneut ohne vorherige Re-Schulung nach 6 Monaten. Die erfassten Reanimationsleistungen wurden statistisch aufgearbeitet und verschiedenen Analysen unterzogen. Ergebnis: Ein standardisierter BLS-Kurs kann die meisten Qualitätsparameter der Reanimation signifikant verbessern. Der Effekt ist auch noch nach 6 Monaten nachweisbar, lässt jedoch bereits wieder nach. Trotz regelmäßiger Schulung zeigten die Teilnehmer der Interventiontionsgruppe vor der Re-Schulung vergleichbar schlechte Reanimationsleistungen, wie die Teilnehmder der Kontrollgruppe. Das optimale Schulungsintervall bleibt somit weiter unklar. Der klinisch relevante Parameter NFF wird durch den BLS-Kurs drastisch verbessert, bleibt jedoch unzureichend hoch.

Flip Chip in Package (FCIP) has been developed to achieve the assembly process with area array interconnects. Particularly, a high I/O count coupled with finer pitch area array interconnects structured FCIP can be achieved using no-flow underfill assembly process. Using the assembly process, a high, stable yield assembly process recently reported with eutectic lead-tin solder interconnections, 150 µm pitch, and I/O counts in excess of 3000. The assembly process reported created a large number of voids among solder interconnects in FCIP. The voids formed among solder interconnections can propagate, grow, and produce defects such as solder joint cracking and solder bridging. Moreover, these voids can severely reduce reliability performance. Indeed, many studies were conducted to examine the void formation in FCIP. Based on the studies, flip chip geometric design, process conditions, and material formulation have been considered as the potential causes of void formation. However, the present research won't be able to identify the mechanism of void formation, causing a lot of voids in assembly process without consideration of chemical reaction in the assembly process with a fine-pitch, high I/O density FCIP. Therefore, this research will present process technology necessary to achieve high yields in FCIP assemblies using no-flow underfills and investigate the underlying problem of underfill void formation in these assemblies. The plausible causes of void formation will be investigated using experimental techniques. The techniques will identify the primary source of the void formation. Besides, theoretical models will be established to predict the number of voids and to explain the growth behavior of voids in the FCIP. The established theoretical models will be verified by experiments. These models will validate with respect to the relationship between process parameters to achieve a high yield and to minimize voids in FCIP assemblies using no-flow underfill materials regarding process as well as material stand points. Eventually, this research provides design guideline achieving a high, stable yield and void-free assembly process.

No-flow underfill materials that cure during the solder reflow process is a relatively new technology. Although there are several advantages in terms of cost, time and processing ease, there are several reliability challenges associated with no-flow underfills. When micron-sized filler particles are introduced in no-flow underfills to enhance the solder bump reliability, such filler particles could prevent the solder bumps making reliable electrical contacts with the substrate pads during solder reflow, and therefore, the assembly yield would be adversely affected. The use of nano-sized filler particles can potentially improve assembly yield while offering the advantages associated with filled underfill materials. The objective of this thesis is to study the thermo-mechanical reliability of nano-filled epoxy underfills (NFU) through experiments and theoretical modeling. In this work, the thermo-mechanical properties of NFUs with 20-nm filler particles have been measured. An innovative residual stress test method has been developed to measure the interfacial fracture toughness. Using the developed residual stress method and the single-leg bending test, the mode-mixity-dependent fracture toughness for NFU-SiN interface has been determined. In addition to such monotonic interfacial fracture characterization, the interface crack propagation under thermo-mechanical fatigue loading has been experimentally characterized, and a model for fatigue interface crack propagation has been developed. A test vehicle comprising of several flip chips was assembled using the NFU material and the reliability of the flip-chip assemblies was assessed under thermal shock cycles between -40oC and 125oC. The NFU-SiN interfacial delamination propagation and the solder bump reliability were monitored. In parallel, numerical models were developed to study the interfacial delamination propagation in the flip chip assembly using conventional interfacial fracture mechanics as well as cohesive zone modeling. Predictions for interfacial delamination propagation using the two approaches have been compared. Based on the theoretical models and the experimental data, guidelines for design of NFUs against interfacial delamination have been developed.