Netbook Passive Cooling Project

1. Netbook Passive Cooling Project • Jesse Crutchfield, Eduardo Guerrero, Ronald Payne, Gerard Stabley, and Jeremy Tucker • Academic Advisor: Dr. Raul Cal, Portland State University • Industry Advisor: JeredWikander, Intel Corp. The objective of this project was to produce a passive cooling solution for an existing netbook computer. An MSI Wind netbook with an existing fan–based cooling solution was used. Design Solution Evaluation of Design The final design concept consists of a copper heat sink which interacts with previously uncoupled heat sources. The copper heat sink is coupled to a graphite heat spreader. The thermo-physical properties of the graphite heat spreader are highly anisotropic, with thermal conductivity differing by orders of magnitude from one direction to the other. The final design concept requires no power, does not rely on a working fluid, is easy to manufacture, and does not significantly alter the netbook appearance. The performance of the active and the passive cooling solutions were measured while using specialized software to stress the components of the netbook. Temperature data were collected using Infrared Thermography, thermocouples attached to several heat producing components, and the internal temperature sensors on the CPU. LabVIEWExpress and a National Instruments Compact-DAQ were used for all TC data collection. Actively Cooled Passively Cooled Figure 4: Mesh density and temperature distribution modeled in Abaqus FEA software with components running at their maximum thermal design power. Manufacturing Process Figure 2: Solid model of graphite heat spreader SolidWorks™ CAE software was used to design the main components of the cooling solution. The netbook case bottom and motherboard were modeled, using CMM measurements, to ensure an accurate fit of all components. Figure 1: Solid model of copper heat sink. Figures 10 & 11: IR images of the top and bottom of the netbook during stress testingwith the active cooling solution. Figures 12 & 13: IR images of the top and bottom of the netbook during stress testing with the passive cooling solution. Figure 3: Solid model of netbook case bottom, graphite heat spreader, copper heat sink, and motherboard. Abaqus™ FEA software wasused to model the temperature distribution of the netbook components with the cooling solution design in place. Results of this modeling were used to optimize the dimensions of the heat sink and heat spreader. Figure 15: Comparison of the temperatures of the primary heat sources with the active and passive cooling solutions. Figure 14: Comparison of the CPU Digital Thermal Sensor and ACPI temperatures with the active and passive cooling solutions. Figure 7: Trek 2-axis CNC mill performing finishing operations on the heat sink. Conclusion • Infrared Thermographyindicates the maximum skin temperature of the netbook • increased by 7.4°C on the top, and 11.4°C on the bottom, with the passively cooled • solution. • Thermocouple data indicates that the CPU and ICH were ~2°C cooler with the passive • solution. The temperature of the GMCH and the RAM increased by 4.6°C and 11.7°C, • respectively, with the passive solution. • The on-board temperature of the processor increased by only 2°C. • Passive Cooling Solution successfully cools the netbook with no power consumption. Figure 6: Mastercam was used extensively to manufacture acrylic prototypes and check fit before the final copper version was manufactured. The above screen shot shows the virtual environment in which the user can check machining operations to ensure that material is not removed accidentally. Figure 8: Copper heat sink installed on netbook. Figure 9: Graphite heat spreader installed on netbook with thermocouples attached. Figure 5: Component temperatures for a range of heat sink thicknesses gathered using FEA software. These data were used to optimize the thickness of both the copper heat sink and the graphite heat spreader.