A STUDY OF THE THERMAL CYCLING PERFORMANCE OF SOLDER JOINTS IN AREA ARRAY PACKAGING

For both the electronics manufacturer and consumer, reliability is an essential characteristic defining the quality of the electronic component and system. Gradual degradation of the electronic components decreases efficiency of the system, and lack of reliability can lead to a significant loss. Efforts at achieving better quality and reliability of electronic components involve the inspection of solder joints in area array packaging. It is of note that solder interconnections are the vulnerable parts of circuit board assemblies (CBA), because they are mainly subjected to various assembly process during electronic manufacturing as well as environmental exposure failures during service. Therefore, the reliability of solder joints is a major concern during the entire life of an area array packaging in order to minimize the electronic failure rate that may lead to large losses. This thesis aims to provide a solution that helps to overcome some of the challenges that can occur during the reliability inspection of solder joints in area array packaging. Firstly, by successfully developing a non-destructive monitoring methodology to study the performance of solder joints under thermal cycling test. The quality of the solder joints in this research work from growth to failure was monitored by using a type of ultrasonic inspection called acoustic micro imaging (AMI). Results indicate that provided a suitable AMI parameters is applied, one can generate a 3D reconstruction of the solder joints images to allow and assess the solder joints’ behaviour in flip chip packages. AMI inspection of solder joints show good agreement with the results obtained that was used to examine how the reliability was affected by the geometry and position of the joints. An automatic segmentation technique was developed that allow to characterize and extract distinctive features of solder joints on different area array packages; such features include mean intensity, structural similarities model and histogram intensity of the region of interest of solder joints. The validation experimental results have been statistically implemented using novel geometrical and time domain features extraction methods like area, form factor and standard deviation. The result from these methods were used to extrapolate the solder joint’s fatigue life at normal operating conditions. Moreover, the analysis of variance (ANOVA) was employed to determine the percentage contribution of solder joints parameters on the acquired images. The results indicated that the thickness of the printed circuit board can affect solder joint reliability

Reliability assessment of telecommunications equipment

This thesis studies the reliability of telecommunications equipment, its components, and the systems made using those components. Special attention is paid to creating stronger links between the reliability analyses performed at different hierarchy levels. The thesis starts with a temperature derating study. It is found out that the generic handbook based procedures may not always be very attractive, as they do not take satisfactorily into account the actual lifetime requirements. An alternative approach is proposed as a remedy to the current situation. Thermal cycling requirement handbooks are surveyed, and based on the findings some enhancements are proposed. Next, a component and product specific approach to create thermal cycling requirements is suggested. When applying the new approach several factors can be taken into account: the product's lifetime requirement, the field environment, the reliability test result, and the statistical distribution of the component population. A new method of how to predict the reliability of a component population that is addressed to several, different field environments is presented. Ceramic, leadless components are studied by testing and by utilizing Engelmaier's analytical solder fatigue model and Finite Element (FE) simulations. A new approach to interpret the solder joint height in conjunction with solder castellations is introduced. Based on this, a very good correlation between the test results and the predictions based on Engelmaier's model can be obtained. The parameter sensitivity of both the Engelmaier's model and the FE analysis are studied and compared. Error margins based on the parameter sensitivity studies are given. Time-averaged hazard rate functions are studied in order to be able to use component level test data in simplistic parts-count method type reliability predictions. Finally, the availability of a full 3rd generation telecommunications network is studied.reviewe

High-frequency characterization of embedded components in printed circuit boards

The embedding of electronic components is a three-dimensional packaging technology, where chips are placed inside of the printed circuit board instead of on top. The advantage of this technology is the reduced electronic interconnection length between components. The shorter this connection, the faster the signal transmission can occur. Different high-frequency aspects of chip embedding are investigated within this dissertation: interconnections to the embedded chip, crosstalk between signals on the chip and on the board, and interconnections running on top of or underneath embedded components. The high-frequency behavior of tracks running near embedded components is described using a broadband model for multilayer microstrip transmission lines. The proposed model can be used to predict the characteristic impedance and the loss of the lines. The model is based on two similar approximations that reduce the multilayer substrate to an equivalent single-layer structure. The per-unit-length shunt impedance parameters are derived from the complex effective dielectric constant, which is obtained using a variational method. A complex image approach results in the calculation of a frequency-dependent effective height that can be used to determine the per-unit-length resistance and inductance. A deliberate choice was made for a simple but accurate model that could easily be implemented in current high-frequency circuit simulators. Next to quasi-static electromagnetic simulations, a dedicated test vehicle that allows for the direct extraction of the propagation constant of these multilayer microstrips is manufactured and used to verify the model. The verification of the model using simulation and measurements shows that the proposed model slightly overestimates the loss of the measured multilayer microstrips, but is more accurate than the simulations in predicting the characteristic impedance

Challenges and New Trends in Power Electronic Devices Reliability

The rapid increase in new power electronic devices and converters for electric transportation and smart grid technologies requires a deepanalysis of their component performances, considering all of the different environmental scenarios, overload conditions, and high stressoperations. Therefore, evaluation of the reliability and availability of these devices becomes fundamental both from technical and economicalpoints of view. The rapid evolution of technologies and the high reliability level offered by these components have shown that estimating reliability through the traditional approaches is difficult, as historical failure data and/or past observed scenarios demonstrate. With the aim topropose new approaches for the evaluation of reliability, in this book, eleven innovative contributions are collected, all focusedon the reliability assessment of power electronic devices and related components

Applications of Crystal Plasticity in Forming Technologies

In this Special Issue, we have gathered work on simulations of polycrystalline metals and alloys at various length scales to model multiscale localization phenomena such as slip bands, cracks, and twins. The series highlights innovative techniques that combine simulation and experiments to capture material production and guide the development of forming theories. The published work helps to understand the effect of microstructure characteristics on deformation and damage behavior under multiaxial load conditions. Furthermore, these models and the studies can be used with machine learning technologies to optimize microstructure functions for materials application and process paths

Development of effective thermal management strategies for LED luminaires

The efficacy, reliability and versatility of the light emitting diode (LED) can outcompete most established light source technologies. However, they are particularly sensitive to high temperatures, which compromises their efficacy and reliability, undermining some of the technology s key benefits. Consequently, effective thermal management is essential to exploit the technology to its full potential. Thermal management is a well-established subject but its application in the relatively new LED lighting industry, with its specific constraints, is currently poorly defined. The question this thesis aims to answer is how can LED thermal management be achieved most effectively? This thesis starts with a review of the current state of the art, relevant thermal management technologies and market trends. This establishes current and future thermal management constraints in a commercial context. Methods to test and evaluate the thermal management performance of a luminaire system follow. The defined test methods, simulation benchmarks and operational constraints provide the foundation to develop effective thermal management strategies. Finally this work explores how the findings can be implemented in the development and comparison of multiple thermal management designs. These are optimised to assess the potential performance enhancement available when applied to a typical commercial system. The outcomes of this research showed that thermal management of LEDs can be expected to remain a key requirement but there are hints it is becoming less critical. The impacts of some common operating environments were studied, but appeared to have no significant effect on the thermal behaviour of a typical system. There are some active thermal management devices that warrant further attention, but passive systems are inherently well suited to LED luminaires and are readily adopted so were selected as the focus of this research. Using the techniques discussed in this thesis the performance of a commercially available component was evaluated. By optimising its geometry, a 5 % decrease in absolute thermal resistance or a 20 % increase in average heat transfer coefficient and 10 % reduction in heatsink mass can potentially be achieved . While greater lifecycle energy consumption savings were offered by minimising heatsink thermal resistance the most effective design was considered to be one optimised for maximum average heat transfer coefficient. Some more radical concepts were also considered. While these demonstrate the feasibility of passively manipulating fluid flow they had a detrimental impact on performance. Further analysis would be needed to conclusively dismiss these concepts but this work indicates there is very little potential in pursuing them further

DiBiCoo: Biogas Markets and Frameworks in Argentina, Ethiopia, Ghana, Indonesia, and South Africa

In Argentina, the biogas market has gained a solid foothold over the last five years and is massively industrial. However, its growth is slowing down. In 2015, Argentina has developed 100 biogas plants and has grown exponentially until 2020 through the RenovAr Programme. In 2015, INTA and PROBIOMASA have conducted a survey assessing 80 of the 100 plants built nationwide. INTA and PROBIOMASA have found that from the 80 plants surveyed, 76 of the 80 biogas plants developed up until 2015 were installed for environmental purposes, while 11 of the 80 biogas plants surveyed were utilised for energy development, consisting of large bio-digestion plants (1MW-2MW), consisting mostly of covered lagoon and mixed technologies utilising digesters, double membrane reactor, and a co-generation unit i.e. combined heat and power (CHP). It must be noted that at that time biogas was not widely used as a source of energy, rather, it was used for environmental purposes. The relatively slow growth of the biogas market until 2015 is also indicated by the low rate of biogas utilisation for the means of energy security. It is also worth highlighting that the dominating feedstock utilised for biogas in Argentina is industrial waste, followed by organic waste and virgin biomass. To accelerate the growth of the biogas market, Argentina has been implementing governmentled programs. The most notable program is the series of RenovAr programs i.e. round 1, round 1.5, and round 2) that was started from 2016 and continues until today with RenovAr 3 being implemented in August 2019. According to the World Bank IFC, RenovAR has succeeded in reaching 2.4 GW capacity of combined renewable energy alternatives in the end of 2016 and 4.4 GW of renewable energy projects in August 2017. The tenders foresee a minimum of 0.5 MW and a maximum of 10 MW of electricity capacity from each biogas project to achieve the overall goal. All in all, this program and national goal shows that biogas is seen as an important renewable energy alternative in Argentina. It must also be noted that each country included in this report elaborates on a minimum of four variables of the PESTLE’s framework depending on the degree of its relevancy and influence it has for the biogas sector.Instituto de Ingeniería RuralFil: Rahmatzafran, Avila. Resilience Development Initiative (RDI). Sustainable Development; IndonesiaFil: Rosslee, Dwight. Selectra Watertech; SudáfricaFil: Rianawati, Elisabeth. Resilience Development Initiative (RDI); IndonesiaFil: Hafiz Loeksmanto, Ichsan. Resilience Development Initiative (RDI); IndonesiaFil: Hilbert, Jorge Antonio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Ingeniería Rural; ArgentinaFil: Alemmu, Sinshaw. Iceaddis; EtiopíaFil: Mohammed. Institute for Sustainable Energy and Environmental Solution (ISEES); GhanaFil: Bogale, Wondwossen. Iceaddis; EtiopíaFil: Salie, Yaseen. Greencape; Sudáfric

ECOS 2012

The 8-volume set contains the Proceedings of the 25th ECOS 2012 International Conference, Perugia, Italy, June 26th to June 29th, 2012. ECOS is an acronym for Efficiency, Cost, Optimization and Simulation (of energy conversion systems and processes), summarizing the topics covered in ECOS: Thermodynamics, Heat and Mass Transfer, Exergy and Second Law Analysis, Process Integration and Heat Exchanger Networks, Fluid Dynamics and Power Plant Components, Fuel Cells, Simulation of Energy Conversion Systems, Renewable Energies, Thermo-Economic Analysis and Optimisation, Combustion, Chemical Reactors, Carbon Capture and Sequestration, Building/Urban/Complex Energy Systems, Water Desalination and Use of Water Resources, Energy Systems- Environmental and Sustainability Issues, System Operation/ Control/Diagnosis and Prognosis, Industrial Ecology