Design and Fabrication of a Metallic Micro Heat Pipe Based on High-Aspect-Ratio Microchannels

2006 ◽  
Author(s):  
K. H. Oh ◽  
M. K. Lee ◽  
S. H. Jeong
Keyword(s):  
Aspect Ratio ◽  
Heat Pipe ◽  
Capillary Pressure ◽  
High Aspect Ratio ◽  
Scanning Speed ◽  
Cooling Capacity ◽  
Wet Etching ◽  
Direct Writing ◽  
Etching Technique ◽  
Micro Heat Pipe

The cooling capacity of a micro heat pipe is mainly governed by the magnitude of capillary pressure induced in the wick structure. For microchannel wicks, a higher capillary pressure is achievable for narrower and deeper channels. In this study, a metallic micro heat pipe adopting high-aspect-ratio microchannel wicks is fabricated. The micromachining of high-aspect-ratio microchannels is done using the laser-induced wet etching technique in which a focused laser beam irradiates the workpiece placed in a liquid etchant along a desired channel pattern. Because of the direct writing characteristic of the laser-induced wet etching method, no mask is necessary and the fabrication procedure is relatively simple. Deep microchannels of an aspect ratio close to 10 can be readily fabricated with little heat damage of the workpiece. The laser-induced wet etching process for the fabrication of high-aspect-ratio microchannels in 0.5mm thick stainless steel foil is presented in detail. The shape and size variations of microchannels with respect to the process variables, such as laser power, scanning speed, number of scans, and etchant concentration are closely examined. Also, the fabrication of a flat micro heat pipe based on the high-aspect-ratio microchannels is demonstrated.

High aspect-ratio SU-8 resist nano-pillar lattice by e-beam direct writing and its application for liquid trapping

2010 ◽  
Vol 87 (4) ◽  
pp. 663-667 ◽  
Author(s):  
D. López-Romero ◽  
C.A. Barrios ◽  
M. Holgado ◽  
M.F. Laguna ◽  
R. Casquel
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Direct Writing ◽  
Liquid Trapping

Rapid direct writing of high‐aspect‐ratio trenches in silicon

1987 ◽  
Vol 50 (8) ◽  
pp. 475-477 ◽  
Author(s):  
G. V. Treyz ◽  
R. Beach ◽  
R. M. Osgood
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Direct Writing

Topology Optimization of Micromachined Structures With the Manufacturing Constraints of KOH Etching of (110) Silicon

2008 ◽  
Author(s):  
Sudarshan Hegde ◽  
G. K. Ananthasuresh
Keyword(s):  
Topology Optimization ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Cost Effective ◽  
Wet Etching ◽  
Minimum Length ◽  
The Cost ◽  
Design Parameterization ◽  
Koh Etching ◽  
Si Wafer

The focus of this paper is on designing useful compliant micro-mechanisms of high-aspect-ratio which can be microfabricated by the cost-effective wet etching of (110) orientation silicon (Si) wafers. Wet etching of (110) Si imposes constraints on the geometry of the realized mechanisms because it allows only etch-through in the form of slots parallel to the wafer’s flat with a certain minimum length. In this paper, we incorporate this constraint in the topology optimization and obtain compliant designs that meet the specifications on the desired motion for given input forces. Using this design technique and wet etching, we show that we can realize high-aspect-ratio compliant micro-mechanisms. For a (110) Si wafer of 250 μm thickness, the minimum length of the etch opening to get a slot is found to be 866 μm. The minimum achievable width of the slot is limited by the resolution of the lithography process and this can be a very small value. This is studied by conducting trials with different mask layouts on a (110) Si wafer. These constraints are taken care of by using a suitable design parameterization rather than by imposing the constraints explicitly. Topology optimization, as is well known, gives designs using only the essential design specifications. In this work, we show that our technique also gives manufacturable mechanism designs along with lithography mask layouts. Some designs obtained are transferred to lithography masks and mechanisms are fabricated on (110) Si wafers.

Axially Tapered Microchannels of High Aspect Ratio for Evaporative Cooling Devices

2004 ◽  
Vol 126 (3) ◽  
pp. 453-462 ◽  
Author(s):  
R. H. Nilson ◽  
S. K. Griffiths ◽  
S. W. Tchikanda ◽  
M. J. Martinez
Keyword(s):  
Aspect Ratio ◽  
Cross Section ◽  
Analytical Solutions ◽  
High Aspect Ratio ◽  
Cooling Capacity ◽  
Channel Axis ◽  
Gravitational Forces ◽  
Triangular Cross Section ◽  
Cooling Devices ◽  
Channel Bottom

Analytical solutions are derived for evaporating flow in open rectangular microchannels having a uniform depth and a width that decreases along the channel axis. The flow generally consists of two sequential domains, an entry domain where the meniscus is attached to the top corners of the channel followed by a recession domain where the meniscus retreats along the sidewalls toward the channel bottom. Analytical solutions applicable within each domain are matched at their interface. Results demonstrate that tapered channels provide substantially better cooling capacity than straight channels of rectangular or triangular cross section, particularly under opposing gravitational forces. A multiplicity of arbitrarily tapered channels can be microfabricated in metals using LIGA, a process involving electrodeposition into a lithographically patterned mold.

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