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To keep up with the growing energy demand, legacy aircooled data centers have begun to implement simple but effective energy efficiency strategies or best practices. Improving “air management”, optimizing the delivery of cool air and the collection of waste heat, are among these efficiency strategies. One of the most powerful tools for identifying energy wasteful practices is the application of the...
Reliability testing of thermally conductive, high-temperature, high-dielectric strength materials was conducted using newly developed high-temperature thermal conductivity and high-dielectric breakdown voltage characterization instruments based on ASTM Standards. These instruments and tests were used for optimizing thermal conductivity and dielectric breakdown of Bismaleimide Resin (BMI) - Boron Nitride...
Fluid flow in a microchannel is primarily laminar due to viscous forces dominating over body or inertia forces. Hence fluid circulation in a droplet greatly enhances heat transfer. As a result, slip at a wall-fluid interface could have a two fold affect on heat transfer in droplet based thermal systems; the first is a direct result of thermal slip at the fluid-wall interface, the second is due to...
The impact of increasing power consumption trends on a global economy with limited resources to sustain them cannot be understated. As worldwide communication requirements expand, data centers will need to be designed more efficiently to not only keep operation costs down for a business' bottom line, but also to be mindful of the world's power availability and resource supply. Therefore, the importance...
The thermal impedance of Gallium Nitride based High Electron Mobility Transistors (GaN HEMTs) has been characterized using the “3ω method”. The method was initially proposed by D.G. Cahill to measure the thermal conductivity of bulk materials or layers. We already demonstrated in a previous work that under certain conditions the voltage oscillation at the third harmonic is the real image of the thermal...
Physically larger more complex server processors are creating or exacerbating thermal and mechanical challenges in platform design. The larger processors are due, in large part, to the ever increasing core count, increasing integration, and growing I/O performance requirements which pushes pin count demand upwards on the socket thus driving higher processor loading requirements. As a direct result...
This paper discusses data center scale performance characterization of hybrid liquid-air cooling solutions for a full 42U rack of servers. Using data collected in a production data center at Lawrence Berkeley Laboratories, we interpret the results with a simple three parameter model which allows characterization of the major factors affecting heat recovery efficiency of the system. The model is shown...
This paper evaluates the impact of pressure drop in server racks on the cooling of the IT equipment. The measured impedance curves for servers internal resistance, rack doors, and Cable Management Arms (CMA) are used to estimate the reduction in the cooling airflow rate. In this study, 1 RU and 2 RU servers, and a 9 RU server simulator are used as representative IT equipment. A Computational Fluid...
On September 19, 2012 IBM announced its latest System z Enterprise Class zServer, the IBM zEnterprise EC12 (zEC12). This server uses a 96 mm glass ceramic substrate to interconnect processors and related cache chips on a multi-chip module (MCM). In rare applications, the power in these MCMs can exceed 2000W, well beyond air cooling capability. This paper describes a new cooling methodology IBM employs...
We investigated two phase heat transfer in staggered and inline micro pin fin arrays, using deionized water and HFE-7200 as working fluids with exit qualities up to 90%,. The inline and staggered arrays have equivalent pin fin width of 153µm and height of 305µm on a heated base area of 0.96cm width by 2.88cm length. Mass fluxes ranged from 200 kg/m2s to 600 kg/m2s for HFE-7200 and 400 kg/m2s to 1300...
Three-dimensional integration of multiple stacked silicon dies using Through-Silicon Vias has been recognized as a likely future direction of integrated circuit design. Yet, in contrast to previous architectures such 3D-ICs require extensive attention to thermal management from the moment of conception. Although such stacks are often associated with integrated, interlayer cooling solutions, it is...
Concerted efforts are being made by data center professionals to ensure that data centers are made more sustainable by reducing energy consumption. The combination of increasing IT workloads and packaging densities place stringent requirements on data center cooling systems. Various traditional airflow management technologies have been implemented that propose significant energy savings as well as...
Nanofluids are nanometer sized suspended particles in water or other base fluids. They are used for their increased nucleate boiling critical heat flux (CHF) values far beyond compared to pure water or base fluid. Therefore pool boiling heat transfer tests are performed to understand increase in CHF. The pool boiling characteristics and critical heat flux enhancement using nanofluids of dilute dispersions...
This paper presents the experimental investigation of pool boiling heat transfer performance of copper plain and grooved horizontal circular surfaces immersed in saturated water at atmospheric pressure. Effect of geometric parameters of the groove on boiling heat transfer coefficient was studied. Experimental results showed significant increase in boiling heat transfer coefficients at high heat flux...
Replacing Silicon Dioxide (SiO2) with low-k and ultralow-k (ULK), as a dielectric, in the Back-End-Of-Line (BEoL) has allowed the trend of miniaturization and convergence to continue. Although using low-k and ULK greatly increases the device performance, being mechanically weak these dielectric materials pose a serious challenge from the reliability standpoint. Delamination along the metal-dielectric...
In the electronic packaging industry, it is important to be able to make accurate predictions of board level solder joint reliability during thermal cycling exposures. The Anand viscoelastic constitutive model is often used to represent the material behavior of the solder in finite element simulations. This model is defined using nine material parameters, and the reliability prediction results are...
One of the most critical failure modes in a BGA package is the solder interconnect failure (2nd level). Conventionally, the solder damage is due to the mismatch of coefficient of thermal expansion (CTE) between the various package components and the PCB. It is absolutely critical to identify and minimize the BGA damage under thermal cycling to improve the package reliability. In the past, the critical...
A novel approach to embedded electronics cooling with a multi-phase microfluidic heat sink termed the Piranha Pin-Fin (PPF) is presented. Several first-generation PPF devices, as well as plain-channel and solid pin-fin heat sinks, have been fabricated and experimentally tested under single-phase adiabatic conditions. Details of the PPF device geometry and microfabrication process are provided. Plots...
Energy has been identified as one of the most important problems during the last few years. While energy generation and new energy resources are critical, energy efficiency in production, transportation and utilization are as important as well. One of those energy efficient technologies may reduce consumed energy in buildings from 20 percent to less than 5 percent. A novel lighting technology has...
We report the design, fabrication and modeling of a thin film evaporation device for cooling of high performance electronic systems. The design uses a membrane with pore diameters of ∼100 nm to pump liquid via capillarity to dissipate the high heat fluxes. Viscous losses are minimized by using a thin membrane (∼200 nm) which is supported by a ridge structure that provides liquid supply channels. As...
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