No description available.

The work described by this thesis is a comparison of pore opening geometry for true surface microfilters. True surface microfilters can be thought of as very fine sieves, with pore sizes less than 10 microns. All other types of so-called microfiltration membranes do not rely on sieving, but obtain their pore retention rating by particle collection mechanisms similar to depth filters. Particle deposition within such microfilters results in permeate flow rate dechne, for a fixed pressure filtration, or pressure drop rise, for a fixed rate filtration. The true surface microfilter pore geometnes considered were circular and slotted, and microfilters with filtering dimension of less than 10 microns were used. The slotted pore microfilters are not commercially available and had to be made in the laboratory as part of this study. The technique used was to plate nickel onto an existing substrate, thereby reducing the pore dimension until It was within the microfiltration range. The plating was by electroless nickel solution and not by galvanic means. Significant development of the electroless platmg technique led ultimately to the successful manufacture of process scale slotted surface microfilters.

In this work, all-copper connections between silicon microchips and substrates are developed. The semiconductor industry advances the transistor density on a microchip based on the roadmap set by Moore's Law. Communicating with a microprocessor which has nearly one billion transistors is a daunting challenge. Interconnects from the chip to the system (i.e. memory, graphics, drives, power supply) are rapidly growing in number and becoming a serious concern. Specifically, the solder ball connections that are formed between the chip itself and the package are challenging to make and still have acceptable electrical and mechanical performance. These connections are being required to increase in number, increase in power current density, and increase in off-chip operating frequency. Many of the challenges with using solder connections are limiting these areas. In order to advance beyond the limitations of solder for electrical and mechanical performance, a novel approach to creating all-copper connections from the chip-to-substrate has been developed. The development included characterizing the electroless plating and annealing process used to create the connections, designing these connections to be compatible with the stress requirements for fragile low-k devices, and finally by improving the plating/annealing process to become process time competitive with solder. It was found that using a commercially available electroless copper bath for the plating, followed by annealing at 180 C for 1 hour, the shear strength of the copper-copper bond was approximately 165 MPa. This work resulted in many significant conclusions about the mechanism for bonding in the all-copper process and the significance of materials and geometry on the mechanical design for these connections.

O revestimento de níquel químico é largamente utilizado na proteção contra a corrosão de equipamentos e estruturas utilizados na exploração de petróleo em águas profundas. Apesar de ser considerado um dos revestimentos mais adequados para esta finalidade, são muitos os casos em que se verificam falhas prematuras do revestimento em serviço. Isto tem sido atribuído às diferenças nas características do revestimento decorrentes das diferenças do processo de aplicação e da natureza e preparação da superfície dos substratos a serem protegidos. Estas diferenças decorrem do fato de não existirem especificações abrangentes que definam as características necessárias do revestimento para uma garantia de qualidade. Diante disto, o presente trabalho teve como objetivo estudar a influência dos principais fatores sobre o desempenho dos revestimentos de níquel químico utilizando ferramentas estatísticas como: planejamento fatorial, seleção dos melhores subconjuntos de regressão, regressão múltipla e curvas de nível. Os fatores considerados neste estudo foram: tipo e estado superficial do substrato, idade do banho, teor de fósforo no revestimento, natureza e teor de contaminantes no revestimento, espessura do revestimento e tipo de tratamento térmico. A caracterização dos revestimentos de níquel químico foi realizada conforme sugerida na norma ISO 4527 e o desempenho dos revestimentos foi verificado por meio dos ensaios de exposição à névoa salina (1 536 h), exposição ao dióxido de enxofre (10 ciclos) e imersão em água do mar sintética (120 dias). Ensaios eletroquímicos (polarização linear e espectroscopia de impedância eletroquímica) foram realizados somente com o intuito de compará-los ao ensaio de exposição à névoa salina e,assim, ter um ensaio capaz de verificar revestimentos de bom desempenho em um período de tempo menor. Dentro dos intervalos estudados, verificou-se que o desempenho do revestimento de níquel químico é influenciado pelo tipo de substrato, pela espessura da camada depositada, pelo teor de fósforo, pela idade do banho, pelo tratamento térmico e pelos teores dos seguintes contaminantes: enxofre, chumbo, magnésio, cobre, ferro e manganês. A metodologia estatística adotada permitiu verificar a interação entre os fatores influenciadores, fato não considerado na literatura consultada. Além disto, foi possível constatar que os ensaios adotados nas normas internacionais atuais são adequados para verificar a qualidade dos revestimentos. Verificou-se também que os ensaios eletroquímicos, apesar de adequados para o estudo da resistência intrínseca à corrosão do revestimento de níquel químico, não se mostraram adequados para detectar a presença de porosidade que é o principal indicativo da qualidade de proteção por barreira de revestimentos catódicos como o níquel químico. Com os resultados obtidos, será possível a elaboração de uma especificação para se obter revestimentos de níquel químico com bom desempenho. / The autocatalytic nickel-phosphorus (NiP) or electroless nickel (EN) coatings are widely used to protect equipment and structures against corrosion and erosion, used in the exploitation of petroleum in deep waters. Even though NiP is considered as the most appropriate coating for this purpose, many premature failures are verified in service. This has been attributed to the differences in the characteristics of the coating due to the differences in the application processes and in the nature and preparation of the substrate surfaces. The lack of broad specifications that define the required characteristics of the good quality coating is responsible for those differences. The present work had as its objective to identify the main factors related to the NiP performance using statistical tools as: factorial design, best subset regression, multiple regression and contour diagram. The considered factors were: substrate type, substrate surface finishing, bath age, phosphorus content, thickness, heat treatment and impurities. The NiP coatings were characterized in agreement with the ISO 4527 and their performance was verified through the salt spray test (1 536 h), the Kesternish test (10 cycles) and the synthetic sea water immersion test (120 days). Electrochemical tests (linear polarization and electrochemical impedance spectroscopy) were conducted in order to compare them to the salt spray test and thus reducing the testing time. In the studied range, it was verified that the NiP performance is influenced by the following factors: substrate type, thickness coating, phosphorus content, bath age (MTO), heat treatment and the impurities: sulfur, lead, magnesium, copper, iron and manganese. It was possible to verify that the types of accelerated corrosion tests adopted in the current international standards are appropriate to verify the quality of the coatings. It was also verified that the electrochemical tests, despite being suitable to indicate the NiP intrinsic corrosion resistance, are not appropriate to verify the NiP porosity (which is the main indication of a cathodic coating quality). With the obtained results, it will be possible to establish a better specification in order to obtain NiP with good quality.

Hard anodising on aluminium and its alloys has been widely practised for many years in order to improve the resistance of the otherwise poor wear characteristics of aluminium. In recent years there has been an increasing interest in other treatments and coatings, on both aluminium and other base metals. The aim of this investigation is to explain the tribological performance and wear mechanism(s) of an uncoated aluminium alloy, four anodic coated alloys, and also an electroless nickel alloy. All of the coatings are produced on three different aluminium alloys. The thickness of the anodic films is 30-35 micron, as this thickness falls within the range commonly used by industry. In an endeavour to explain the role of coating thickness on wear life, electroless nickel alloy has been produced in a range of thicknesses of 10, 20 and 30 micron. To evaluate abrasive and adhesive wear, the samples were rubbed against a single point diamond and steel ball, respectively, in a reciprocating movement at room temperature and 65-75% relative humidity, under a wide range of load and sliding distance. Some tests continued to run until a breakdown of the coatings occurred, whilst other tests were interrupted at intermediate stages. This enabled the initiation and propagation of failure mechanisms to be studied. Abrasive wear was performed under dry conditions, whereas, adhesive wear was evaluated under both dry and lubricated conditions. Wear of these coatings was proportional to the applied load and sliding distance, but there was no direct relationship between wear and hardness. The tribological performance of these coatings appears to be dictated by a) the composition of the substrate, b) the chemical and physical nature of the coatings and c) the test conditions. Under boundary lubricated conditions there was a considerable increase in the wear life of the coatings. A three dimensional surface texture is superior to a machined surface, in controlling contact conditions. There is an approximate linear relationship between coating thickness and wear life for electroless nickel alloys. These coatings predominantly fail by adhesion, plastic deformation and brittle fracture. A microscopic model for fracture of brittle materials, under both static and dynamic conditions for abrasive and adhesive wear correlates very well with the behaviour of these coatings. Analytical interpretation of adhesive wear was made by separately calculating the coefficient of wear "K" of the counterbodies. This information enables an improved understanding of the wear test itself to be added to the model of the wear mechanisms involved.

The subject of this diploma thesis is the preparation of conductive structures by electroless plating of an extruded precursor. The experimental part deals with the preparation of standard patterns based on the length of immersion time in a coppering bath. The precursor layers were applied with Fujifilm Dimatix to various receiver substrates. The individual substrates with the precursor layer were immersed in the copper solution within different time intervals. The structure of the layers of grown copper and their thickness was characterized by a profilometer.

No description available.

This diploma thesis is focused to nickel coatings on magnesium alloys. At the introduction of this work is briefly commented phase composition of AZ91 alloy, which is followed by detailed description of five very different theories of Ni-P coatings formation. Theoretical part is ended by review aimed to current states of development in areas of chemical nickel coating, influence of AZ91 alloy microstructure to current less deposition and possibility of surfactants influence to decrease of surface roughness. In experimental part of this thesis was the morphology and composition of Ni-P coatings including interlayers dependence on chemical composition of nickel-plating bath and magnesium alloy surface pre-treatment investigated using scanning electron microscopy and inverted optical microscopy. Average phosphorus content was obtained using energy dispersive analysis. Closing part of experimental part was dedicated for mechanical properties of coatings by micro-indentation analysis.

This work deals with the advanced methods of contact’s fabrication for monocrystalline solar cells and the appropriate methods for the analysis of their properties with a focus on the study and realization the contact’s structures with low contact and sheet resistance fabricated by galvanic and electroless processes. In the first part of the work is discussed the theory of solar cells and buried contacts and in the second part of the work is an evaluation of practical realization.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19724号 / 工博第4179号 / 新制||工||1644(附属図書館) / 32760 / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 平尾 一之, 教授 三浦 清貴, 教授 田中 勝久 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM