Development and reliability of a direct access sensor using flip chip on flex technology with anisotropic conductive adhesive

Technological developments in biomedical microsystems are opening up new opportunities to improve healthcare procedures. Swallowable diagnostic sensing capsules are an example of these. In none of the diagnostic sensing capsules, is the sensor’s first level packaging achieved via Flip Chip Over Hole (FCOH) method using Anisotropic Conductive Adhesive (ACA). In a capsule application with direct access sensor (DAS), ACA not only provides the electrical interconnection but simultaneously seals the interconnect area and the underlying electronics. The development showed that the ACA FCOH was a viable option for the DAS interconnection. Adequate adhesive formed a strong joint that withstood a shear stress of 120N/mm2 and a compressive stress of 6N required to secure the final sensor assembly in place before encapsulation. Electrical characterization of the ACA joint in a fluid environment showed that the ACA was saturated with moisture and that the ions in the solution actively contributed to the leakage current, characterized by the varying rate of change of conductance. Long term hygrothermal aging of the ACA joint showed that a thermal strain of 0.004 and a hygroscopic strain of 0.0052 were present and resulted in a fatigue like process. In-vitro tests showed that high temperature and acidity had a deleterious effect of the ACA and its joint. It also showed that the ACA contact joints positioned at around or over 1mm would survive the gastrointestinal (GI) fluids and would be able to provide a reliable contact during the entire 72hr of the GI transit time. A final capsule demonstrator was achieved by successfully integrating the DAS, the battery and the final foldable circuitry into a glycerine capsule. Final capsule soak tests suggested that the silicone encapsulated system could survive the 72hr gut transition

Development and Evaluation of Accelerated Environmental Test Methods for Products with High Reliability Requirements

Reliability testing of electronics is performed to ensure that products function as planned in specific conditions for a specified amount of time. This is usually both time-consuming and expensive and therefore test time acceleration is often required. The acceleration may be realized by using more severe stress levels or higher use cycle frequencies, but at the same time the risk increases of inducing failure mechanisms not relevant to the use conditions. As a consequence, the accelerated reliability testing of products with markedly long lifetimes and high reliability is frequently challenging. In this thesis different methods for test time acceleration for products with high reliability requirements and long service lives were studied. Both standard tests and modifications of these were used. The effect of the accelerated tests used on the failure modes and mechanisms observed was examined and the limitations of the test methods discussed. The research in this work was conducted at both interconnection level and at device level. The interconnection level testing focused on anisotropically conductive adhesive (ACA) flex-on-board (FOB) attachments. In addition to the effect of the curing process on the mechanical strength of ACA FOB attachments, their applicability and long-term performance in industrial applications was studied. According to the real-time resistance measurement the assembly tested was observed to be extremely resilient in thermal cycling and hygrothermal aging. However, a significant decrease in the mechanical strength of the FOB attachment was also seen. Hydrolysis and embrittlement of the flex material was also observed to limit the applicability of harsher hygrothermal aging conditions. Clear ACA joint failures were only observed with moisture condensation testing, but this may not be a suitable test method for applications that are not susceptible to such a stressor. The device level testing comprised reliability analysis of two frequency converter models. The older generation device and its field failure data were used as the starting point in the development of a test method that could be used to minimize testing time and to induce comparable failure modes to those occurring in the use conditions of the devices. The tests showed that only with the simultaneous use of stresses could a significant reduction in the testing time be achieved. However, the application of the same test method to the newer generation device proved challenging because of differences in materials, components and layouts. Although similar failure modes were observed in both devices, the combined effect of the stresses used on the failure mechanisms requires further study. In addition, knowledge of the service conditions, the environmental stresses and their severity is critical. The main disadvantage of simultaneous stress testing was observed to be the interpretation of the test results, especially due to the complexity of the devices tested. Moreover, the results obtained may be highly application specific. However, regardless of the difficulties in the lifetime estimation, the use of combined stresses was observed to be a practical method to study the weaknesses in a product

Performance and Reliability of Polymer-based Sensor Packages at High Temperatures

Electronics is increasingly used in many applications. In addition to new consumer electronics, there is a trend to implement electronics and sensors in many industrial applications, which often requires improved reliability in very demanding conditions. This thesis concerns the effect of high temperature on electronics packages. High temperature tends to accelerate chemical reactions, aging of materials and thereby also failures. Properties of polymer materials, which are often used in electronic packaging, are heavily temperature-dependent. They are, however, very versatile and compatible materials which are readily available and easy to manufacture compared to expensive high-temperature speciality materials such as ceramics. Therefore, using polymers at high temperatures would be highly beneficial. However, it is crucial to understand the effects of high temperature on polymer materials before they are used.This work concentrates on the reliability of polymer-based sensor packages at high temperatures and the changes occurring in their materials at different temperatures. The structures were aged using several high temperature tests including thermal cycling, step stress and thermal storage tests at several temperatures around 200°C. The effects of high temperature on several commercial polymer-based printed circuit boards (PCB) and electrically conductive adhesives (ECA) were analysed from an electrical and mechanical perspective. Moreover, changes in material parameters due to aging were studied to achieve a more profound understanding of the effects of high temperatures.The temperature of 180°C seemed to be low enough not to cause reliability problems in the polymer-based packages studied. Additionally, a good performance in thermal cycling testing up to 180°C was achieved. At 200°C degradation was seen on the surfaces of the polymer materials and their mechanical properties gradually declined. Good electrical performance was nevertheless achieved with suitable material choices. A temperature of 240°C was shown to be too high for extended exposure of the materials studied. With careful material choices relatively good electrical performance was achieved, but FTIR showed dramatic and rapid degradation with most of the polymerbased materials at this temperature. The degradation was much more severe than at 200°C, and the mechanical properties also showed drastic impairment at 240°C.Material selection was shown to be absolutely critical for the reliability of the whole polymer-based package. With poor PCB material interconnections failed much earlier than with more stable PCB materials. Additionally, ECA selection was also important. This thesis showed that polymer-based electronic packages can withstand high temperatures, especially for limited exposure times. However, it is crucial that all materials present are able to withstand the selected temperatures.<br/

Mechanical characterization of composites based on a novel vacuum-infused thermoplastic matrix

Este estudo está focado na avaliação do desempenho mecânico e dos mecanismos de falha de compósitos à base de uma resina termoplástica líquida sob várias condições de carregamento em comparação com compósitos à base de epóxi. Os laminados compostos reforçados por fibras de carbono foram fabricados pela VARTM (Moldagem por transferência de resina assistida a vácuo). Os compósitos foram submetidos às condições de carregamento do modo II, a fim de verificar sua tolerância a danos. Nesse caso, os compósitos termoplásticos apresentaram 40% mais resistência à fratura interlaminar em comparação aos compósitos epóxi. Esses materiais obtiveram desempenho superior na resistência à propagação de trincas, pois tendem a absorver a energia associada à propagação de trincas na forma de deformação plástica em comparação aos compósitos epóxi. Também foram realizados testes de resistência à tração e cisalhamento no plano para avaliar a resposta de ambos os materiais em amostras não condicionadas e condicionadas. Os compósitos termoplásticos apresentaram 30% mais resistência à tração em comparação aos compósitos epóxi. Para amostras condicionadas, essa diferença foi de 14%. Esses resultados foram relacionados à plastificação, que tende a favorecer o amolecimento do polímero, proporcionando maior deformação plástica da matriz, promovendo uma fratura dúctil do compósito. Por outro lado, as propriedades de cisalhamento no plano foram 30% maiores para os laminados termoendurecíveis em ambas as condições. Nesse caso, a umidade pode ter favorecido a formação de rachaduras na superfície e enfraquecido a adesão interfacial fibra / matriz. Análises adicionais baseadas no projeto de experimentos mostraram que a resina Elium® 150 afeta significativamente todas as respostas e apresentou, de fato, um melhor comportamento em comparação à resina epóxi. Embora os efeitos do condicionamento tenham apresentado uma contribuição estatisticamente perceptível à resistência à tração, a presença da umidade não proporcionou um aprimoramento significativo da resistência ao cisalhamento no plano. A análise baseada na metodologia de teste acelerado de compósitos Carbon Fiber / Elium® 150 mostra que as altas frequências aumentam a transição vítrea (Tg) para valores mais altos, provavelmente favorecidos pelo movimento das cadeias poliméricas. A rede neural artificial evidenciou uma excelente concordância entre os valores treinados e experimentais. A previsão de vida útil em longo prazo usando curvas mestres confirma que este novo material pode ser considerado para fins de amortecimento acústico ou vibracional, considerando seu uso em temperaturas abaixo de Tg

Mechanical characterization of composites based on a novel vacuum-infused thermoplastic matrix

Este estudo está focado na avaliação do desempenho mecânico e dos mecanismos de falha de compósitos à base de uma resina termoplástica líquida sob várias condições de carregamento em comparação com compósitos à base de epóxi. Os laminados compostos reforçados por fibras de carbono foram fabricados pela VARTM (Moldagem por transferência de resina assistida a vácuo). Os compósitos foram submetidos às condições de carregamento do modo II, a fim de verificar sua tolerância a danos. Nesse caso, os compósitos termoplásticos apresentaram 40% mais resistência à fratura interlaminar em comparação aos compósitos epóxi. Esses materiais obtiveram desempenho superior na resistência à propagação de trincas, pois tendem a absorver a energia associada à propagação de trincas na forma de deformação plástica em comparação aos compósitos epóxi. Também foram realizados testes de resistência à tração e cisalhamento no plano para avaliar a resposta de ambos os materiais em amostras não condicionadas e condicionadas. Os compósitos termoplásticos apresentaram 30% mais resistência à tração em comparação aos compósitos epóxi. Para amostras condicionadas, essa diferença foi de 14%. Esses resultados foram relacionados à plastificação, que tende a favorecer o amolecimento do polímero, proporcionando maior deformação plástica da matriz, promovendo uma fratura dúctil do compósito. Por outro lado, as propriedades de cisalhamento no plano foram 30% maiores para os laminados termoendurecíveis em ambas as condições. Nesse caso, a umidade pode ter favorecido a formação de rachaduras na superfície e enfraquecido a adesão interfacial fibra / matriz. Análises adicionais baseadas no projeto de experimentos mostraram que a resina Elium® 150 afeta significativamente todas as respostas e apresentou, de fato, um melhor comportamento em comparação à resina epóxi. Embora os efeitos do condicionamento tenham apresentado uma contribuição estatisticamente perceptível à resistência à tração, a presença da umidade não proporcionou um aprimoramento significativo da resistência ao cisalhamento no plano. A análise baseada na metodologia de teste acelerado de compósitos Carbon Fiber / Elium® 150 mostra que as altas frequências aumentam a transição vítrea (Tg) para valores mais altos, provavelmente favorecidos pelo movimento das cadeias poliméricas. A rede neural artificial evidenciou uma excelente concordância entre os valores treinados e experimentais. A previsão de vida útil em longo prazo usando curvas mestres confirma que este novo material pode ser considerado para fins de amortecimento acústico ou vibracional, considerando seu uso em temperaturas abaixo de Tg

Assessment, Diagnosis and Service Life Prediction

Service life prediction is crucial for the adoption of more sustainable solutions, allowing developers to optimize the costs and environmental impact of buildings during their life cycle. An accurate assessment of the service life of buildings requires a thorough understanding of the degradation mechanisms and behaviour of the construction materials. Building pathology assessment methods characterize the deterioration state of buildings, using specific measurable properties as indicators. Based on this information, different service life prediction methodologies can be defined to provide reliable data concerning the most probable failure time of whole buildings and individual components according to their characteristics and their age. This Special Issue provides new perspectives on the existing knowledge related with various aspects of the Assessment, Diagnosis and Service Life Prediction of buildings and their components. The ten original research studies published in this Special Issue result from research centres and university departments of Civil and Construction Engineering, Safety Management, Environmental Engineering, Geotechnical Engineering, and Architecture and the Built Environment, with relevant contributions from experts from Australia, Brazil, the Czech Republic, Hong Kong, Iran, Israel, Norway, Portugal, and Taiwan. The studies included in this Special Issue address topics related to: Building pathology assessment methods; Diagnosis of defects in buildings and components; Appropriate intervention and repair techniques; Deterministic and stochastic service life prediction models

Nanowires for 3d silicon interconnection – low temperature compliant nanowire-polymer film for z-axis interconnect

Semiconductor chip packaging has evolved from single chip packaging to 3D heterogeneous system integration using multichip stacking in a single module. One of the key challenges in 3D integration is the high density interconnects that need to be formed between the chips with through-silicon-vias (TSVs) and inter-chip interconnects. Anisotropic Conductive Film (ACF) technology is one of the low-temperature, fine-pitch interconnect method, which has been considered as a potential replacement for solder interconnects in line with continuous scaling of the interconnects in the IC industry. However, the conventional ACF materials are facing challenges to accommodate the reduced pad and pitch size due to the micro-size particles and the particle agglomeration issue. A new interconnect material - Nanowire Anisotropic Conductive Film (NW-ACF), composed of high density copper nanowires of ~ 200 nm diameter and 10-30 µm length that are vertically distributed in a polymeric template, is developed in this work to tackle the constrains of the conventional ACFs and serves as an inter-chip interconnect solution for potential three-dimensional (3D) applications

Proceedings of the COST Action TU1403 : Adaptive Facades Network Final Conference

info:eu-repo/semantics/publishedVersio