Impact of underfill and other physical dimensions on Silicon Lateral IGBT package reliability using computer model with discrete and continuous design variables

An effort to design and build a prototype LED driver system which is energy efficient, highly compact and with few component count was initiated by a consortium UK universities. The prototype system will be based on Silicon Lateral IGBT (LIGBT) device combined with chip on board technology. Part of this effort, finite element modelling and analysis were undertaken in order to mitigate the underfill dielectric breakdown failure and solder interconnect fatigue failure of the LIGBT package structure. Electro-static analysis was undertaken to predict the extreme electric field distribution in the underfill. Based on electro-static analysis, five commercial underfill were selected for thermo-mechanical finite element analysis on solder joint fatigue failure prediction under cyclic loading. A design optimisation analysis was endeavoured to maximise the solder interconnect reliability by utilising a computer model with continuous variable (physical dimensions) and discrete variables underfill type) and a stochastic optimiser such as multi-objective mixed discrete particle swarm optimisation. From the optimisation analysis best trade off solution are obtained

High Efficiency Polymer based Direct Multi-jet Impingement Cooling Solution for High Power Devices

Liquid jet impingement cooling is an efficient cooling technique where the liquid coolant is directly ejected from nozzles on the chip backside resulting in a high cooling efficiency due to the absence of the TIM and the lateral temperature gradient. In literature, several Si-fabrication based impingement coolers with nozzle diameters of a few distributed returns or combination of micro-channels and impingement nozzles. The drawback of this Si processing of the cooler is the high fabrication cost. Other fabrication methods for nozzle diameters for ceramic and metal. Low cost fabrication methods, including injection molding and 3D printing have been introduced for much larger nozzle diameters (mm range) with larger cooler dimensions. These dimensions and processes are however not compatible with the chip packaging process flow. This PhD focuses on the modeling, design, fabrication and characterization of a micro-scale liquid impingement cooler using advanced, yet cost efficient, fabrication techniques. The main objectives are: (a) development of a modeling methodology to optimize the cooler geometry; (b) exploring low cost fabrication methods for the package level impingement jet cooler; (c) experimental thermal and hydraulic characterization and analysis of the fabricated coolers; (d) applying the direct impingement jet cooling solutions to different applications

Thermal management of solid state power switches

The transient temperature of solid state power switches is investigated using thermal resistance network modelling and experimental testing. The ability of a heat sink mounted to the top of the device to reduce the transient temperature is assessed. Transient temperatures for heat pulses of up to 100ms are of most interest. The transient temperature distribution inside a typical stack-up of a solid state power switch is characterised. The thermal effects of adding a heat sink to the top of the device are then assessed. A variety of heat sink thicknesses and materials are evaluated. Components of the device stack-up are varied in order to assess their affect on the effectiveness of the heat sink in reducing the device temperature. Thermal networks are successfully applied to model the transient heat conduction inside the stack-ups. This modelling technique allowed a good understanding of the thermal behaviour inside the stack-up and heat sink during the transient period. The concept of using a heat sink to suppress the transient temperature was validated experimentally on two types of solid state power switch

Thermal management of solid state power switches

The transient temperature of solid state power switches is investigated using thermal resistance network modelling and experimental testing. The ability of a heat sink mounted to the top of the device to reduce the transient temperature is assessed. Transient temperatures for heat pulses of up to 100ms are of most interest. The transient temperature distribution inside a typical stack-up of a solid state power switch is characterised. The thermal effects of adding a heat sink to the top of the device are then assessed. A variety of heat sink thicknesses and materials are evaluated. Components of the device stack-up are varied in order to assess their affect on the effectiveness of the heat sink in reducing the device temperature. Thermal networks are successfully applied to model the transient heat conduction inside the stack-ups. This modelling technique allowed a good understanding of the thermal behaviour inside the stack-up and heat sink during the transient period. The concept of using a heat sink to suppress the transient temperature was validated experimentally on two types of solid state power switch

Evaporador de jatos bifásicos incidentes integrado a um sistema de refrigeração compacto para resfriamento de componentes eletrônicos

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2016.Abstract: The proper functioning and reliability of electronic components depend upon adequate thermal management since high temperature isthe principal vector of failure in these devices. The growing complexityof current electronic component design associated with the everincreasingpower consumption and the continuous scale reduction placethermal management of electronics as one of the most strategic challengesfor technological innovation in heat transfer. Therefore, new conceptsfor high heat ux removal are required, such as mechanical vapor compression refrigeration, which is among the most promising activecooling technologies. This thesis presents a novel heat sink for thermalmanagement of electronic devices. The cooler was designed to operateintegrated with a compact vapor compression refrigeration system andcombines the expansion device and the evaporator in a single coolingunit, thus producing a highly eective two-phase jet impingement cooling of the heated surface. An experimental apparatus was designedand built which operates with a small-scale oil-free linear compressor using R-134a as the working uid. A purpose-built calorimeter wasdeveloped to measure the heat dissipation rate through the compressorshell, thus providing closure for the overall system energy balance. Thethermal performance of both the jet impingement cooling module andthe vapor compression refrigeration system were evaluated for a varietyof operating conditions. In addition, a comprehensive thermodynamicanalysis was performed using dierent performance metrics. Experimentshave been carried out with single and multiple orice congurationsof the jet heat sink. The inuence of the following parameters wasquantied: (i) applied thermal load, (ii) orice diameter, (iii) oriceto-heater distance, (iv) hot reservoir temperature and (v) compressorpiston displacement. At operating conditions for which the system pressure ratio ranged from 1.4 to 2.2, the two-phase jet heat sink wascapable of dissipating cooling capacities of up to 160 W and 200 Wfrom a 6.4-cm2 surface for single and multiple orice congurations,respectively, maintaining the temperature of the impingement surfacelower than 40°C with heat transfer coecients ranging from around 14,000 to 16,000 W/(m2K).O funcionamento e a confiabilidade de componentes eletrônicos dependem do seu gerenciamento térmico visto que temperatura e o principal vetor de falha operacional nestes sistemas. A crescente complexidade no projeto de componentes eletrônicos associada ao aumento do consumo de potencia e a contínua redução de escala colocam o gerenciamento térmico de dispositivos eletrônicos como um dos maiores desafio para inovação tecnológica em transferência de calor. Assim, novos conceitos são necessários tais como o emprego de sistemas de refrigeração por compressão mecânica de vapor, que estão entre as mais promissoras tecnologias de resfriamento ativo. A presente tese introduz um novo aparato para o resfriamento de componentes eletrônicos que opera integrado a um sistema de refrigeração compacto e combina o dispositivo de expansão e o evaporador em uma mesma unidade de resfriamento. A técnica de resfriamento e baseada em jatos bifásicos incidentes sobre uma superfície aquecida. Uma bancada experimental que opera comum compressor linear compacto e utiliza R-134a puro como fluido refrigerante foi projetada e construída. Um calorímetro foi desenvolvido para verificação indireta do fechamento dos balancos de energia do sistema, quantificando o calor dissipado na carcaça do compressor. Os desempenhos térmicos do evaporador de jatos bifásicos e do sistema de refrigeração foram avaliados para varias condições operacionais. Uma análise termodinâmica foi conduzida envolvendo diferentes métricas de desempenho. Experimentos foram realizados com um único bocal e com múltiplos bocais de atomização. A influência dos seguintes parâmetros foi quantificada: (i) carga térmica aplicada, (ii) diâmetro do orifício do bocal, (iii) distancia do bocal a superfície de incidência, (iv) temperatura do reservatório quente e (v) deslocamento linear do pistão do compressor.Em condições de operação para as quais a razão de pressão do sistema variou de 1,4 a 2,2, o evaporador de jatos bifásicos foi capaz de remover cargas térmicas de ate 160 W e 200 W em uma superfície com 6,4 cm2 de área utilizando configurações de jatos único e múltiplos, respectivamente. Para estes casos, a temperatura da superfície foi mantida abaixo de 40°C e coeficientes de transferência de calor de 14.000 a 16.000 W/(m2K) foram atingidos