Given the vital rule of data center availability and since the inlet temperature of the IT equipment increase rapidly until reaching a certain threshold value after which IT starts throttling or shut down because of overheat during cooling system failure. Hence, it is especially important to understand failures and their effects. This study presented experimental investigation and analysis of a facility-level cooling system failure scenario in which chilled water interruption introduced to the data center. Quantitative instrumentation tools including wireless technology such as wireless temperature and pressure sensors were used to measure the discrete air inlet temperature and pressure differential though cold aisle enclosure, respectively. In addition, Intelligent Platform Management Interface (IPMI) and cooling system data during failure/recovery were reported. Furthermore, the IT equipment performance and response for opened and contained environments were simulated and compared. Finally, an experiment based analysis of the Ride Through Time (RTT) of servers during chilled water interruption of the cooling infrastructure presented as well. The results showed that for all three classes of servers tested during the cooling failure, CAC helped keep the server’s cooler for longer. The containment provided a barrier between the hot and cold air streams and caused slight negative pressure to build up, which allowed the servers to pull cold air from the underfloor plenum. In addition, the results show that the effect of CAC in containment solutions on the IT equipment performance and response could vary and depend on the server’s airflow, generation and hence types of servers deployed in cold aisle enclosure. Moreover, it was shown that when compared to the discrete sensors, the IPMI inlet temperature sensors underestimate the Ride Through Time (RTT) by 42% and 12% for the CAC and opened cases, respectively.

Gravity-driven two-phase liquid cooling systems using flow boiling within micro-scale evaporators are becoming a game-changing solution for electronics cooling. The optimization of the system’s filling ratio can however become a challenging problem for a system operating over a wide range of cooling capacities and temperature ranges. The benefits of a liquid accumulator to overcome this difficulty are evaluated in the present paper. An experimental thermosyphon cooling system was built to cool multiple electronic components up to a power dissipation of 1800 W. A double-ended cylinder with a volume of 150 cm 3 is evaluated as the liquid accumulator for two different system volumes (associated to two different condensers). Results demonstrated that the liquid accumulator provided robust thermal performance as a function of filling ratio for the entire range of heat loads tested. In addition, the present liquid accumulator was more effective for a small volume system, 599 cm 3 , than for a large volume system, 1169 cm 3 , in which the relative size of the liquid accumulator increased from 12.8 % to 25% of the total system’s volume.

During ultrasonic ball bonding of copper wire to aluminum pad, the two alloys are joined over an immensely short period of time (<100ms), at a relatively low temperature (< 200°C). Bond formation in such condition is related to accelerated diffusional processes and formation of intermetallic compounds (IMC). Despite the industrial importance of the phenomenon, the micro-mechanism of IMC formation is not clearly understood, nor deeply studied. One of the main barriers toward understanding the phenomena is the limited capability of experimental analysis for analyzing processes occurring over short period of time. In this research, a combination of theoretical analysis and finite element simulation is used to investigate the mechanisms that lead to diffusion enhancement and, as a result, IMCs formation.

Heat pipes are recognized as an excellent heat transport devices and extensively investigated for applications in electronic cooling. Different types of heat pipes have been developed such as micro/miniature heat pipes, loop heat pipes and so on, and these heat pipes have been widely applied in the field of electronics cooling such as notebook, desktop, data center; as well as aerospace, industrial cooling field. However, in recent years the application of heat pipe is widening to the filed of hand held mobile electronic devices such as smart phone, tablet pc, digital camera etc. With the development in technology these devices have different user friendly functions and capabilities, which requires the highest processor clock speed. In general, high clock speed of processor generates lot of heat which need to be spread or removed to eliminate the hot spot. It becomes a challenging task to cool such electronic devices as mentioned above with a very confined space and concentrated heat sources. Regarding to this challenge, ultra thin flat heat pipe is developed; this newly developed heat pipe consists of a special fiber wick structure which can ensure vapor spaces on the two sides of the wick structure. In this paper a novel thin spreader is proposed to eliminate the hot spot; generally the proposed heat spreader consists of 0.20mm thick metal plate and ultra thin heat pipe of 0.40mm thickness soldered in its body. Maximum thickness of this spreader is 0.63mm. Metal plate is 60mm × 110mm in size; and the ultra thin heat pipe can be fabricated from different original diameter ranges from 2.0mm to 3.0mm Cu tube. Theoretical and experimental analysis have been done to evaluate this thin spreader. In addition, some real application of this spreader will be introduced in this paper.

As the energy footprint of data centers continues to increase, models that allow for “what-if” simulations of different data center design and management paradigms will be important. Prior work by the authors has described a multi-scale energy efficiency model that allows for evaluating the coefficient of performance of the data center ensemble ( COP Grand ), and demonstrated the utility of such a model for purposes of choosing operational set-points and evaluating design trade-offs. However, experimental validation of these models poses a challenge because of the complexity involved with tailoring such a model for implementation to legacy data centers, with shared infrastructure and limited control over IT workload. Further, test facilities with dummy heat loads or artificial racks in lieu of IT equipment generally have limited utility in validating end-to-end models owing to the inability of such loads to mimic phenomena such as fan scalability, etc. In this work, we describe the experimental analysis conducted in a special test chamber and data center facility. The chamber, focusing on system level effects, is loaded with an actual IT rack, and a compressor delivers chilled air to the chamber at a preset temperature. By varying the load in the IT rack as well as the air delivery parameters — such as flow rate, supply temperature, etc. — a setup which simulates the system level of a data center is created. Experimental tests within a live data center facility are also conducted where the operating conditions of the cooling infrastructure are monitored — such as fluid temperatures, flow rates, etc. — and can be analyzed to determine effects such as air flow recirculation, heat exchanger performance, etc. Using the experimental data a multi-scale model configuration emulating the data center can be defined. We compare the results from such experimental analysis to a multi-scale energy efficiency model of the data center, and discuss the accuracies as well as inaccuracies within such a model. Difficulties encountered in the experimental work are discussed. The paper concludes by discussing areas for improvement in such modeling and experimental evaluation. Further validation of the complete multi-scale data center energy model is planned.

The shift of the DC characteristics of nMOSFETs during a resin-molding process was investigated experimentally. A silicon chip including the nMOSFETs was encapsulated in a quad flat package, and the drain current and transconductance shifts were measured. The drain current decreased during the resin-molding process, while no significant shift in threshold voltage was observed. The experimental results were estimated adequately from the residual stress predicted by numerical and experimental analysis, and from the stress sensitivity of the nMOSFETs measured by the four-point bending method. Also, we verified the validity of an electron mobility model that includes the effect of stress, used for drift-diffusion device simulation, by comparison with experimental results, and several improvements to the electron mobility model were found out.

In liquid-cooled large drives, controlling air temperature and maintaining air circulation is very important to the lifetime and functions of electrical and electronic components in power cell cabinet. In application, air/water heat exchangers and associated fans are employed to cool the air and force it through the cells. A computational fluid dynamics (CFD) analysis is performed to predict the air circulation in cell cabinet. The results are applied in air baffle arrangement to obtain an ideal air flow distribution. A fundamental analysis is conducted for heat exchanger and its thermal performance defined. It is found that the air supply temperature from heat exchanger is almost independent of air flow rate and altitude within application range. A thermal model is developed to simulate air temperatures into and out of cell cabinet heat exchanger for evaluating its cooling capacity. Flow and heat-run tests are performed for a cell cabinet. The testing results prove that the simulation models are accurate, and the developed air-cooling system can satisfy cooling requirement. A parametric study is complemented with the simulation models to guide cooling management regarding variations in operational and environmental conditions.

This paper presents the mechanical contribution of shrinkage stress in a bonding process to electrical conduction establishment and reliability of ACF joint. The conduction establishment and reliability of ACF joint strongly depend on joint clamping force related with the thermal and mechanical properties of ACF. Therefore, it is important to understand the effect of ACF shrinkage stresses on the conduction establishment and reliability. In this study, thermal and mechanical properties of ACF materials were investigated during and after thermal reaction. The important mechanical mechanism of ACF conduction for good bonding quality and reliability is the joint clamping force developed during curing and cooling-down process of ACFs. Based on thermo-mechanical properties involved in ACF thermal reaction, the build-up behavior of thermally induced shrinkage stress during curing and cooling-down processes of ACF materials was experimentally investigated. It was experimentally shown that the shrinkage stresses of ACF materials are strongly dependent on material properties such as modulus, CTE and T g . Moreover, it was evident that in temperature aging test, ACF joint reliability was affected by compressive stress. These results indicate that shrinkage stress, developed by the thermal reaction of ACFs, is the important parameter to the electrical conduction establishment and reliability of interconnects using ACF material.