Investigation of PCM-assisted heat pipe for electronic cooling

This paper presents an experimental investigation on a copper miniature loop heat pipe (mLHP) with a flat disk shaped evaporator, 30mm in diameter and 10-mm thick, designed for thermal control of computer microprocessors. Tests were conducted with water as the heat transfer fluid. The device was capable of transferring a heat load of 70W through a distance up to 150mm using 2-mm diameter transport lines. For a range of power applied to the evaporator, the system demonstrated very reliable startup and was able to achieve steady state without any symptoms of wick dry-out. Unlike cylindrical evaporators, flat evaporators are easy to attach to the heat source without need of any cylinder-to-plane reducer material at the interface and thus offer very low thermal resistance to the heat acquisition process. In the horizontal configuration, under air cooling, the minimum value for the mLHP thermal resistance is 0.17degC/W with the corresponding evaporator thermal resistance of 0.06degC/W. It is concluded from the outcomes of the current study that a mLHP with flat evaporator geometry can be effectively used for the thermal control of electronic equipment including notebooks with limited space and high heat flux chipsets. The results also confirm the superior heat transfer characteristics of the copper-water configuration in mLHPs

/pdf/miniature-loop-heat-pipe-with-flat-evaporator-for-cooling-4bytmmeo3r.pdf

Miniature Loop Heat Pipe With Flat Evaporator for Cooling Computer CPU

In this paper, polymer-based flat heat pipes (PFHPs) with a thickness on the order of 1 mm have been successfully developed and tested. Liquid-crystal polymer (LCP) films with copper-filled thermal vias are employed as the case material. A copper micropillar/woven mesh hybrid wicking structure was designed and fabricated to promote evaporation/condensation heat transfer and the liquid supply to the evaporator of the PFHP. Water was selected as the working fluid because of its superior thermophysical properties. An experimental study was conducted to examine the PFHP performance. The test data demonstrated that the PFHP can operate with a heat flux of 11.94 W/cm2 and results in effective thermal conductivity ranging from 650 to 830 W/m · K, with the value varying with the input heat flux and the tilt angle. With the employment of flexible LCP as casing material, the PFHP could potentially be directly integrated into a printed circuit board or flexible circuits for thermal management of heat-generating components.

/pdf/the-development-of-polymer-based-flat-heat-pipes-2ik0u91bqw.pdf

The Development of Polymer-Based Flat Heat Pipes

Self-assembling materials, such as block copolymers, are used as mandrels for pitch multiplication. The copolymers are deposited over a substrate and directed to self-assemble into a desired pattern. One of the blocks forming the block copolymers is selectively removed. The remaining blocks are used as mandrels for pitch multiplication. Spacer material is blanket deposited over the blocks. The spacer material is subjected to a spacer etch to form spacers on sidewalls of the mandrels. The mandrels are selectively removed to leave free-standing spacers. The spacers may be used as pitch-multiplied mask features to define a pattern in an underlying substrate.

Pitch multiplication using self-assembling materials

Investigation on the CPU nanofluid cooling

Improving thermal performance of miniature heat pipe for notebook PC cooling

Provided are a chip, a chip stack, and a method of manufacturing the Same A plurality of chips which each include: at least one pad formed on a wafer; and a metal layer which protrudes up to a predetermined thickness from the bottom of the wafer and is formed in a via hole exposing the bottom of the pad are stacked such that the pad and the metal layer of adjacent chips are bonded This leads to a simplified manufacturing process, high chip performance and a small footprint for a chip stack

Method of manufacturing a chip and a chip stack

Provided are a chip, a chip stack, and a method of manufacturing the same. A plurality of chips which each include: at least one pad formed on a wafer; and a metal layer which protrudes up to a predetermined thickness from the bottom of the wafer and is formed in a via hole exposing the bottom of the pad are stacked such that the pad and the metal layer of adjacent chips are bonded. This leads to a simplified manufacturing process, high chip performance and a small footprint for a chip stack.

Method of manufacturing a chip

Microgratings whose diffracted field at a fixed angle generate IR spectra of SF6 or NH3 were fabricated by MEMS techniques for the purpose of IR correlation spectroscopy. Each micrograting was composed of 1441 reflecting lines in the area of 19.2 × 19.2 mm. The depth profile of the line elements was determined with a gradient searching method that was described in our previous publication (J. Mod. Opt. 2013, 60, 324-330), and was discretized into 16 levels between 0 and 6.90 μm. The diffraction field from a given depth profile was calculated with Fraunhofer equation. The fabricated microgratings showed errors in the depth and the width within acceptable ranges. As the result, the diffracted IR spectrum of each micrograting matched well with its target reference spectrum within spectral resolution of our optical setup.

http://koreascience.or.kr:80/article/JAKO201409864555515.pdf

Fabrication of Microgratings and their IR Diffraction Spectra

We studied how the passive intermodulation (PIM) power arising in air cavity filters could be calculated and how the design of the filter could be optimized in order to reduce the amplitude of the PIM signal. To do this, using simulated results, we optimized the various parameters of a filter. PIM in an air cavity filter depends on the power dissipated in its cavities. A reduction of this power loss therefore decreases the PIM power in the air cavity filter. Our experimental results confirm that it is possible to design and produce air cavity filters that generate low PIM signals.

Young Il Kang

Papers

Improving thermal performance of miniature heat pipe for notebook PC cooling

Method of manufacturing a chip and a chip stack

Method of manufacturing a chip

Fabrication of Microgratings and their IR Diffraction Spectra

Analysis and optimization of passive intermodulation in microwave coaxial cavity filters