Marlin Vogel

Substantiation of numerical analysis methodology for CPU package with non-uniform heat dissipation and heat sink with simplified fin modeling

Thermal design in electronic packaging is driven by the maximum allowable junction temperature of a CPU. An inadequate thermal design that underestimates the junction temperature may adversely impact the electrical performance of the CPU, making predicting the junction temperature a crucial step in package and system thermal design. A numerical model of a heat sink and thermal test package with a uniform and non-uniform power dissipation was created and used to predict their temperatures. The uniform power dissipation case was used to calibrate the numerical models TIM2 thermal impedance. In the non-uniform power cases, the maximum heat flux was over four times higher than the average heat flux. The numerical analysis results in the non-uniform power cases yielded junction temperatures within 2 degrees of the measured values. The heat sink used in the tests as well as numerically modeled contained a vapor chamber base and a plate heat sink. Three different heat sink modeling approaches were used, including: detailed modeling of the heat sink, effective convection coefficient heff, and effective thermal conductivity keff. Test data was used to establish the effective heat transfer coefficient and effective thermal conductivity. A simplified heat sink numerical model allows the computational grid density to be significantly reduced, resulting in fast convergence. Alternate heat sink designs were also considered.

New approach to system server air flow/thermal design development, validation and advancement in green fan performance

Increasing thermal demands of high-end servers require increased performance of air-cooling systems in order to meet industry requirements. Increased air cooling performance will be attained through efficient distribution of the air flow to multiple electronic modules and improved aerodynamic power conversion efficiency of the server air movers and incorporating inter-stage air flow directional control structure between tandem fans that are arranged in series air flow. A new approach is used to measure and validate air flow rates for the servers individual electronic modules. The new approach is intended to improve the accuracy of the air flow measurement and simplify the in-situ air flow measurement process, allowing reduced instrumentation cost and reduced time required to develop and validate the server air flow design.

Low profile heat pipe heat sink and green performance characterization for next generation CPU module thermal designs

Increasing thermal demands of high-end server CPUs require increased performance of air-cooling systems to meet industry needs. Improving the air-cooled heat sink thermal performance is one of the critical areas for increasing the overall air-cooling limit. One of the challenging aspects for improving the heat sink performance is the effective utilization of relatively large air-cooled fin surface areas when heat is being transferred from a relatively small heat source (CPU) with high heat flux. Increased electrical performance for the computer industry has created thermal design challenges due to increased power dissipation from the CPU and due to spatial envelope limitations. Local hot spot heat fluxes within the CPU are exceeding 100 W/cm2, while the maximum junction temperature requirement is 105 C, or less. The CPU power dissipation continues to increase and the number of CPUs per server continues to increase for next generation servers. This has resulted in increased data room energy costs associated with supplying additional power to the server, and also cooling the server. Typically in the past, if two heat sink technologies met the thermal performance requirements along with meeting the reliability performance requirements, the least expensive technology would be utilized. In the future, heat sink thermal performance specifications will consider including the impact of energy cost savings attained through reduced server air flow rate requirements if utilizing a superior heat sink technology warrants a potential increase in heat sink cost.

Preliminary specification for a closed loop liquid cooling system product reliability test plan

Future high performance systems may incorporate liquid cooling to the board. These systems will be assembled using commercially available components and subsystems, which include the pump, liquid coolant, tubing and connections, heat exchanger, and cold plate. Liquid cooling systems are known to be susceptible to more degradation and failure mechanisms than conventional solid metal heatsinks, heat pipe heatsinks or vapor chamber heatsinks. Component and system providers need guidelines to ensure that their products meet projected reliability requirements. A generic preliminary specification has been assembled based on industry standards and information collected from leading equipment suppliers.

Heatlane Technology for High Heat Flux Chip Cooling

This paper proposes a new solution for high heat flux chip cooling. The authors attempted to apply Heatlane technology for a heat sink of high-end server chip cooling. This unique technology, which is also called oscillating or pulsating heat pipe, showed very high thermal performance, and the experimental results were compared with conventional copper base heat sink in this paper. The experimental and analysis results showed that the Heatlane technology transferred heat very effectively and highly improved the fin efficiency. And the Heatlane heat sink also showed very small gravity effect and high reliability under vibrating conditions. Those experimental results were also shown in this paper. From this study, the authors has convinced that the Heatlane technology for a heat sink can be a strong candidate to solve a thermal issue of high heat flux chip cooling, especially for high-end server applications.Copyright