Interconnect and Thermal System Reliability for Processor Units

Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) are thermally limited much below the electrical capability of the devices. The unique challenge of a GaN HEMT is its ultra-high heat flux at the micro-scale gate fingers, which cannot be effectively and adequately addressed by conventional packaging and thermal management systems and lead to a large junction-to-ambient thermal resistance. A novel thermal interface material (TIM) that offers unique heat spreading, CTE compliance and ultra-high thermal performance was developed. The new TIM enables attaching GaN die directly onto a copper carrier. The heat spreading feature of the TIM can effectively dissipate heat near junction and greatly reduce the maximum heat flux, which leads to smaller temperature difference across each layer underneath of the TIM. A preliminary demonstration of the technology on a GaN-on-Silicon device shows 50% higher heat dissipation capability, compared to the state-of-the-art pin fin cold plate liquid cooling, while maintaining the device junction temperature at 150°C.

Thermal properties of nanocomposites have been an area of intensive research for the past decade due to its potential application in electrical interconnection, heat transfer and electronics cooling. Considerable progress has been made in fabricating nanocomposite materials using different filler materials and polymer. Nanocomposites made from nanowires and nanotubes are the subject of recent interest due to the elongated one dimensional shape of the filler materials which shows unique properties e.g. lower percolation threshold, anisotropy, and other one dimensional properties. Most of the reported works used different forms of carbon allotropes (single wall, multiwall, fiber, etc.) or oxide and metallic nanowires as filler materials and mixing with polymer. Early work on carbon nanotube (CNT) based fillers focused on mechanical mixing of nanotubes with polymer and thereby achieving higher thermal conductivity as compared to polymer. Vertically aligned carbon nanotube and fiber is also investigated as thermal interface material [1]. However, the possibility of inadvertently incorporating contaminating impurities, the existence of voids between CNTs, and the growth conditions of CNT arrays greatly affect the effective thermal conductivity of CNTs, typically resulting in a thermal interface material (TIM) with a large performance uncertainty [2, 3]. Thermal properties of graphene-metal-polymer composite was thoroughly investigated in recent years [4]. Similarly, metallic nanowires both dispersed and vertically aligned were also proposed as filler materials in the metal-polymer nanocomposites [5, 6].Recently, we have demonstrated that the elongated metallic nanowires and nanowire based composites can act as thermal conduit between two surfaces and thereby able to transfer heat more efficiently as compared to carbon nanotube based composite materials [5]. However, it has been observed that heat transport through these one dimensional filler materials is a complex subject of intensive research, which includes different thermal transport mechanism depending on constituent material (whether it is an electrical conductor, semiconductor or insulator) as well its size, shape and the crystallinity [7]. This heat transfer mechanism was explained with a modified effective medium formulation based on Nan’s model [8]. Furthermore, it has been observed that modulus of the nanocomposite plays a vital role in the transferring heat when pressed between two surfaces and lower modulus composite conforms easily to the roughnesses of the mating surface [5].In this work we investigate the thermal properties of metal (Cu and Sn) nanowire-polymer composites. The thermal diffusivity of the composites was measured using a Xenon flash thermal constant analyzer. A thermal impedance system is employed according to the modified ASTM D5470 standard to measure the thermal impedance of the composites. A thermal impedance of 9±1 °Cmm2W-1is achieved at a pressure of 100 kPa, which is 50% lower thermal impedance compared to the commercial TIM.AcknowledgementsThis work is financially supported by Enterprise Ireland under commercialization fund technology development program.Grant No. CFTD/2008/322.

The performance characteristics of thermal interface materials (TIMs) are quickly outpacing our ability to measure them using steady-state techniques. In fact, scientists have turned to photothermal techniques like Time-domain Thermoreflectance (TDTR) to measure the impedance to heat flow across TIMs, namely due to their relatively low measurement uncertainties. However, such techniques are costly, require significant sample preparation, only measure local thermal impedances and are not yet equipped to measure thermal resistance as a function of pressure. Instead, it is desirable to maximize the resolution of traditional steady-state equipment for these types of measurements. In this work, we develop a more robust and accurate methodology to determine the temperature difference across the junction of a traditional steady-state apparatus using high accuracy measurements of in-situ TIM thickness in tandem with infrared thermography. This methodology eliminates a significant fraction of the uncertainty associated with the measurement of thermal interface resistance. Importantly, the use of this method improves the accuracy of the measurement device by an order of magnitude at interfacial thermal resistance values on the order of 1·10−6m2·K/W when compared to state-of-the-art, thermal probe-based measurement systems.

Gyroscopes are widely applied in weapon system and other high precision system. During the using course, the reliability and performance of gyroscope are influenced by environment and using condition. The performance of gyroscope degenerates periodically, and the remaining useful life (RUL) is payed close attention by engineers in order to monitor the whole systems steadily and safely during life-cycle. Traditionally, researchers used the reliability test and statistic method to estimate RUL. But it’s difficult to get enough samples in the test because the gyroscope cost much. In this paper, we mainly discussed the life prediction of gyroscopes, designed the accelerated life testing(ALT), and used Path Classification and Estimation(PACE) to predict the RUL of gyroscopes. In addition, we analyzed the theory of life prediction for gyroscopes, mainly about the relationship of gyroscope’s fault, nature element and useful life. Then the method is researched based on PACE method. At last, the prediction algorithms is illustrated by the practical accelerate life test data. The methods discussed in this paper was applied in a practical equipment maintenance support project, which can provide technical support for the product life prolong research work in the future. Keywords-component; gyroscopes; remaining useful life; accelerated life testing; path classification and estimation

Bolted flanged connections are widely used in the petroleum and chemical industries. The gasket is the core component of bolted flanged connections. Accurate prediction of the gasket life is of great significance for the efficient, continuous, safe, and long-term operation of the device. The gasket accelerated life prediction method is a method for predicting gasket life developed in recent years. However, the accuracy of gasket life predicted by this method has not been studied so far. In order to verify the accuracy of the gasket accelerated life prediction method, a verification model for the accuracy of gasket life prediction was proposed in this study. The maximum accelerated stress level of gasket was determined through tests, and the accelerated life test and long-term sealing performance test were carried out. The hypothesis check of the gasket life distribution, consistency check of the shape parameters, and model parameter estimation of the accelerated life equation were carried out based on the measured data. All parameters of the life verification model (LVM) were obtained. On this basis, the life estimation values of the gasket accelerated life prediction model (ALPM) and the life verification model were compared under multiple groups of normal stress levels. The results show that the error time between the prediction model and the verification model does not exceed 720 h, which verifies the accuracy of the gasket accelerated life prediction method.

This paper presents reliability, availability, and maintainability (RAM) analysis framework for evaluating the performance of a circulation system of water (WCS) used in a coal-fired power plant (CFPP). The performance of WCS is evaluated using a reliability block diagram (RBD), fault tree analysis (FTA), and Markov birth–death probabilistic approach. In this work, the system under study consists of five subsystems connected in series and parallel configuration namely condensate extraction pump (CEP), low-pressure feed water heater (LPH), deaerator (DR), boiler feed pump (BFP), high-pressure feed water heater (HPH). The reliability block diagram (RBD) and fault tree approach (FTA) have been employed for the performance evaluation of WCS. The Markov probabilistic approach based simulation model is developed. The transition diagram of the proposed model represented several states with full working capacity, reduced capacity, and failed state. The ranking of critical equipment is decided on the basis of criticality level of equipment. The study results revealed that the boiler feed pump affects the system availability at most, while the failure of deaerator affects it least. The availability of the system is optimized using the particle swarm optimization method. The optimized availability parameter (TBF, TTR) based modified maintenance strategy is recommended to enhance the availability of the plant system. The optimized failure rate and repair rate parameters of the subsystem are used to suggest a suitable maintenance strategy for the water circulation system of the thermal power plant. The proposed RAM framework helps the decision-makers to plan the maintenance activity as per the criticality level of subsystems and allocate the resources accordingly.

Investigations on heat flow management perspective-induced design criteria of thermal interface materials

The application of plug‐in electric vehicles (PEVs) is assumed to be wide in power system in regulating the system frequency in the near future. This paper provides an aggregate model of an interconnected multi‐area thermal system with the incorporation of PEVs for frequency control in each of the three areas. Two degree of freedom proportional–integral–derivative (2DOF‐PID) controller has been utilised for robust secondary control in all the three control areas. An optimisation technique inspired by nature named as wind‐driven optimisation (WDO) technique is employed to decide the optimal values of the controller gains. The effectiveness of WDO optimised 2DOF‐PID controller is verified by performing various comparative analysis with conventional PID controller under nominal system condition and random loading condition. An analysis has also been carried out to evaluate the system performance with variation in state of the integrated PEVs. The impact of introducing PEVs in the system in frequency regulation has been vigorously studied under different system conditions such as nominal, random loading condition, and simultaneous perturbation in two and three areas to testify their advantages. The comparisons reveal that with the integration of PEVs in the system, the system dynamics gets enhanced to a large extent.

Inference on adaptive progressive hybrid censored accelerated life test for Gompertz distribution and its evaluation for virus-containing micro droplets data

The paradigm shift towards electric mobility has catalysed a substantial surge in research endeavours aimed at augmenting both the performance, life, and durability of lithium-ion batteries deployed within the confines of small electric vehicles. At the crux of this pursuit lies the imperative development of robust battery thermal management systems, indispensable for the meticulous regulation of battery temperature, thereby ensuring seamless operation and bolstering safety protocols. This review paper undertakes a comprehensive synthesis of recent strides achieved in battery thermal management systems for small electric vehicles propelled by lithium-ion batteries. Encompassing a spectrum of methodologies, ranging from passive to active cooling techniques, alongside the incorporation of phase change materials and innovative thermal interface materials, it critically evaluates these strategies. Furthermore, the discourse navigates through the prevailing challenges and charts out prospective trajectories in this domain, poised to foster the evolution of efficient and dependable battery thermal management systems tailored specifically for small electric vehicles. Numerous investigations have focused on the thermal regulation of lithium-ion batteries. Despite the prevalent excitement surrounding small electric vehicles today, the crucial matter of implementing effective battery thermal management systems in small electric vehicles has not received adequate attention, potentially diminishing customer satisfaction with small electric vehicle performance. Thus, the current study aims to delve into the thermal optimization of lithium-ion batteries for small electric vehicles. Initially, the study investigates into discussing design parameters for battery thermal management systems, referencing research conducted on thermal stability, particularly concerning thermal runaway, and the performance of electric vehicles in subzero temperatures regarding battery thermal management systems. Furthermore, the study places emphasis on reviewing and analysing various theoretical and practical heat transfer techniques applied by researchers to lithium-ion batteries to enhance battery thermal management systems. Consequently, the paper’s novel contribution lies in bridging the gap between researchers and manufacturers regarding battery thermal management systems in small electric vehicles, thus propelling innovative battery designs for improved battery thermal management systems in small electric vehicles.

In product research and development, one might wish to select the most reliable of several highly-reliable competing products. Both type-I and type-II accelerated life tests (ALT) are well-known to estimate and compare the life of highly reliable (nonrepairable) products within a reasonable testing time. A common decision problem is to choose the better plan for achieving the above goal. This paper proposes an intuitive selection rule for each ALT plan, and then derives the respective optimal ALT sampling plan when the acceleration factor (AF) is known and unknown. Finally, some criteria of Mackay are used to compare the two plans. From a practical point of view, the type-II ALT sampling plan is more convenient, and needs smaller sample size than the type-I ALT sampling plan. Nevertheless, the latter has shorter mean duration time and life testing time than the former.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Geographic aggregation and wind power output variance in Denmark

Thermal transport is of grave importance in many high-value applications. Heat dissipation can be improved by utilizing liquid metals as thermal interface materials. Yet, liquid metals exhibit corrosivity towards many metals used for heat sinks, such as aluminum, and other electrical devices (i.e., copper). The compatibility of the liquid metal with the heat sink or device material as well as its long-term stability are important performance variables for thermal management systems. Herein, the compatibility of the liquid metal Galinstan, a eutectic alloy of gallium, indium, and tin, with diamond coatings and the stability of the liquid metal in this environment are scrutinized. The liquid metal did not penetrate the diamond coating nor corrode it. However, the liquid metal solidified with the progression of time, starting from the second year. After 4 years of aging, the liquid metal on all samples solidified, which cannot be explained by the dissolution of aluminum from the titanium alloy. In contrast, the solidification arose from oxidation by oxygen, followed by hydrolysis to GaOOH due to the humidity in the air. The hydrolysis led to dealloying, where In and Sn remained an alloy while Ga separated as GaOOH. This hydrolysis has implications for many devices based on gallium alloys and should be considered during the design phase of liquid metal-enabled products.

The extensive use of lithium-ion batteries and other energy storage systems (ESS) in recent years has resulted in a critical need for effective thermal management solutions that ensure safe and reliable operations. Carbon-based materials (C-bMs) are a promising candidate for addressing the thermal challenges in ESS due to their unique thermal, electrical, and structural properties. This article provides a concise overview of C-bM thermal management solutions for improved battery safety. The key thermal management requirements and failure modes associated with battery systems are highlighted, underscoring the importance of effective battery thermal management (BTM). Various forms of C-bMs, including graphite, graphene, carbon nanotubes, carbon foams, nanodiamonds, and graphdiyne, are examined for their potential applications in battery thermal management systems. The recent innovations and advancements in C-bM thermal management solutions, such as phase change composites, heat pipes, and thermal interface materials, are highlighted. Furthermore, the latest research trends focus mainly on the development of hybrid battery thermal management solutions, carbon-based aerogels, and complex C-bM structures with tailored thermal pathways for optimized thermal management. Most of the current innovations are still at the laboratory scale; hence, future research efforts will be focused on developing integrated multi-functional C-bMs, sustainable and scalable manufacturing techniques, self-healing C-bMs composites, intelligent C-bMs, and further explorations of uncommon C-bMs. These advancements are bound to enhance performance, sustainability, and application-specific adaptations for BTM. This article provides valuable insights for researchers, and stakeholders interested in leveraging C-bMs for BTM.

This paper documents the numerical parameter optimization techniques used to determine an optimum weight for a thermal protection system. Subject to temperature constraints imposed at various locations in the system, the most impressive optimization technique was an adaptive creep search followed by a pattern search. The thermodynamic problem was solved using an implicit method for reasons of numerical stability and computational speed. Numerical optimization techniques were shown to be beneficial in the design of a thermal protection system. Numerical results were obtained showing the effects of temperature constraints, materials, and material arrangement on the weight of a thermal protection system.