Thermal Behavior of Nominally Flat Silicon-Based Heat Spreaders

2005 ◽  
Vol 128 (4) ◽  
pp. 370-379
Author(s):  
Ta-Wei Lin ◽  
Ming-Chang Wu ◽  
Cheng-Hsien Peng ◽  
Po-Li Chen ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Thermal Resistance ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Spreader ◽  
Heat Spreaders ◽  
Silicon Based ◽  
Maximum Thermal Resistance ◽  
Effect Of Surface

Thermal characteristics for a horizontal heated chip mounted with three types of nominally flat silicon-based heat spreaders have been systematically investigated. They include the natural convective and radiative heat transfer from the top surface of the heat spreaders to the external ambient, external thermal resistance, and maximum overall thermal resistance. In the aspect of natural convection, an axisymmetric bowl-shaped profile of local Nusselt number is achieved, and the highest convective heat transfer performance occurs at the location near the rim of the heat spreader. The effect of surface roughness on both local and average natural convective heat transfer behaviors from nominally flat silicon-based spreader surfaces to the external ambient is not significant. Two new generalized correlations of local and average Nusselt numbers for various heat spreader surfaces are presented. The contributions of convection and radiation on the total heat dissipated from the top surface of the heat spreader to the ambient are about 72% and 28%, respectively. The effect of surface roughness on external thermal resistance for nominally flat silicon-based surfaces is not significant. The influence of the conductive thermal resistance within the silicon-based heat spreader on the maximum thermal resistance is not significant. The maximum thermal resistance is mainly dominated by external thermal resistance for flat nominally silicon-based heat spreaders.

Microchannel Optimization for Heat Dissipation From a Solid Substrate

2008 ◽  
Author(s):  
C. B. Sobhan ◽  
P. S. Anoop ◽  
Kuriyan Arimboor ◽  
Thomas Abraham ◽  
G. P. Peterson
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Thermal Resistance ◽  
Computational Model ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Solid Substrate ◽  
Nusselt Numbers

A computational model was developed to analyze and optimize the convective heat transfer for water flowing through rectangular microchannels fabricated in a silicon substrate. A baseline case was analyzed by solving the nondimensional governing equations. Using a quasi three-dimensional computational model, the velocity and temperature distributions were obtained and the numerical results were then used to determine the overall dimensionless thermal resistance for the convective heat transfer from the substrate to the fluid. To validate the numerical model, the average Nusselt numbers as determined by the numerical model were compared with experimental results available in the literature, for channels with comparable hydraulic diameters. The procedure for arriving at an optimum geometric configuration and arrangement of microchannels on the substrate, subject to given design constraints, so that the thermal resistance is at a minimum, is described and demonstrated using the computational model.

Flat Polymer Heat Spreader With High Aspect Ratio Micro Hybrid Wick Operating Under Adverse Gravity

2011 ◽  
Author(s):  
Christopher Oshman ◽  
Qian Li ◽  
Li-Anne Liew ◽  
Ronggui Yang ◽  
Y. C. Lee ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Thermal Resistance ◽  
High Aspect Ratio ◽  
Circuit Board ◽  
Gravitational Acceleration ◽  
Heat Spreader ◽  
Flexible Polymer ◽  
Heat Spreaders

We report the successful fabrication and application of a micro-scale hybrid liquid wicking structure in flat polymer-based heat spreaders to improve the heat transfer performance under gravitational acceleration. The hybrid wick consists of 100 μm high, 200 μm wide square electroformed high aspect ratio copper micro-pillars with 31 μm spacing for liquid flow. A woven copper mesh with 51 μm diameter and 76 μm spacing was bonded to the top surface of the pillars to enhance evaporation and condensation heat transfer. The exterior device geometry is 40 mm × 40 mm × 1.0 mm. The 100 μm thick liquid crystal polymer (LCP) casing contains a two-dimensional array of copper filled vias to reduce the overall thermal resistance. The device was tested with heat flux input of up to 63 W/cm2 at horizontal and vertical orientations. The difference in temperature between the evaporator and condenser was measured and compared to a copper reference block of identical exterior dimensions. The experimentally determined thermal resistance of the copper block remained nearly constant at 1.2 K/W. The thermal resistance of the flat polymer heat spreader at horizontal orientation was 0.55 K/W. The same device at −90° adverse orientation resulted in a thermal resistance of 0.60 K/W. These measurements indicate that this hybrid wicking structure is capable of providing a capillary pumping pressure that is effective at transferring at least 63 W/cm2 heat flux regardless of orientation. This work illustrates an important step to developing more effective thermal management strategies for the next generation of heat generating components and the possibility of developing flexible, polymer-based heat spreaders fabricated with standardized printed circuit board technologies.

A Study on the Convective Heat Transfer Coefficient and Thermal Resistance of Clothing under Cross Ventilation

2011 ◽  
Vol 10 (2) ◽  
pp. 155-162
Author(s):  
Keiko Sato ◽  
Takashi Kurabuchi ◽  
Takeshi Ogasawara ◽  
Masaaki Ohba ◽  
Shizuo Iwamoto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient
Sign in / Sign up

Export Citation Format

Share Document