Development of a multiple layer vacuum insulation chip

Abstract

Advent of micro thermal devices such as lab-on-a-chip and micro heat pump necessitates development of highly effective insulation chips or layers. This paper reports the development of a vacuum insulation chip (VIC) having very low effective thermal conductivity and very small thickness. Fifty nanometer thickness metal coating on both sides of an LCD glass chip and 5 mu m vacuum gap are stacked in a series to decrease the heat transfer by radiation. An array of support legs is necessary to maintain the structure under the atmospheric pressure. Design of VIC involves trade-offs between the heat conduction through the multi-layer structure and the mechanical strength. A model to determine the actual design values is proposed. The results are in reasonable agreement with the more refined results using commercial numerical codes. Based on these results, a VIC of 32 x 32 x 1.88 mm(3) is manufactured, and the effective thermal conductivity is measured by guarded hot plate method. The chip shows effective thermal conductivities of 0.0015 and 0.001 W/m K at vacuum levels of 1.33 and 0.24 Pa (N/m(2)), respectively. (C) 2008 Elsevier Ltd. All rights reserved.