Patent Application
20060231237
Description of the Prior Art
Electronic components are known to dissipate heat during their active and standby operation. The heat generated may cause the ambient temperature around such components to increase to levels that deteriorate the performance of the components, at best, or permanently damage the component. Various cooling solutions including heat sinks, fans, and more exotic approaches, such as liquid or gas cooling, are known used for the purpose of keeping the temperature of the components at an ambient temperature level, which is close to optimal for the components' operation.
Nonetheless, the current art for cooling electronic assemblies at the chip, chip set, board, and rack levels, suffers from a number of limitations that are the result of: a) nano-scale heat transfer bottlenecks at transistor level; b) lack of sufficient surface area required by a heat exchanger to dissipate the large amounts of heat generated by dense packing of chips, chip sets, and/or stacked boards; c) the small form-factor of electronic boxes, which limits the volume required for a cooling solution; d) established limits on noise levels generated by a fan, pump, or other devices required by the heat exchanger; and, e) the amount of power available for cooling the assembly.
Together, the above limitations create severe limitations in providing cooling solutions having lower complexity, lower cost of extremely dense, hot micro-electronic assemblies, such as boards, racks, etc., which must fit in small boxes and enclosures. In the current art, the cost and the complexity of cooling grows very fast with ever increasing density of micro-electronic assemblies, e.g. chip, chip set, board and board assemblies. Aside from cost considerations, the reliability of the micro-electronic assemblies suffers from high, local temperatures which translate into lower mean-time-between failure (MBTF) performance.
A method and apparatus for overcoming the problems of rapidly increasing complexity and cost and degrading reliability measures in connection with the cooling of a multi-chip mounted on an electronic printed circuit board. Accordingly, there are combined a) nano-structures materials for micro or nano-scale heat transfer from a substrate; b) small dimension heat sinks or heat spreaders matched to the mico-scale heat transfer to control the spread resistance; c) nano-scale cooling channel surfaces or micro-channel heat exchangers to improve heat transfer coefficients of the hot components to the cooling agent, air or liquid; and d) sharing of the active device such as a fan, pump, compressor, etc., that are responsible for moving the cooling agent in an active cooling embodiment. By providing appropriate passage for the cooling agent an effective and efficient cooling of the hot surfaces is achieved.
Technical Field
The invention relates to integrate circuits, more particularly, the invention relates to an apparatus and method for cooling ICs using nano-rod based CNIP-level heat sinks.
In accordance with the disclosed invention, physical dimensions of the active component responsible for movement of a cooling fluid, e.g. gas or liquid is vastly reduced by deploying a set of components that also combined to improve the thermal performance, and reduce costs, of the overall cooling apparatus. This is accomplished by combining: a) a vastly improved thermal interface resistance; that is made possible by new nano-materials which have excellent thermal properties, e.g. nano rods, nano-wires, carbon nanotubes, carbon nanofibers, etc.; b) a small foot-print, micro-channel heat evaporator or heat exchanger; and c) a small dimension fan(s), pump(s) such as those known-in-the-art as MEMs or conventional micro-pumps, micro-fans, micro-compressors, etc. The advantages of the disclosed invention are achieved by matching the dimensions of chip micro-electronics, e.g. nano-scale dimension transistor heat source, micron sized hot spots, millimeter chip sizes, centimeter sized card or printed circuit boards, etc., to the smallest dimension cooling components that are still compatible to micro-electronic cards. Furthermore, the reliability measure is improved by minimizing local, high-temperature spots. This becomes possible when dimensions of relatively the same scale are applied to each and every element of the cooling hierarchy.
The following components comprise an exemplary embodiment of the novel heat removing system: a) a compressed air tank and/or an array of micro-valves and/or a micro-compressor pump and/or a liquid micro-pump; b) a chip-level heat sink or heat spreader (CLHS); c) access to a cold source, e.g. cold gas or liquid; and d) a system-level heat sink (SLHS), also known as a heat exchanger.
An exemplary and non-limiting CLHS 200, having small dimensions for use with ICs, is shown in
The current literature with regard to creating functionalized carbon nanotubes teaches various methods of creating conformal coating of nanotubes with various materials, e.g., metals, conductive polymers, etc. Usually, the carbon nanotubes need a pre-treatment, e.g. high temperature annealing, to remove amorphous carbon found on the nanotubes, nanowires, nanofibers, or nanotowers. Furthermore, the nano-rods 220 may be coated by a coating 225 for the purpose of better heat transfer between the nano-rod 220 and the cold source. The conformal coating 225 of the nano-rods 220 may be achieved using highly thermally conductive materials, e.g. metals such as Pd, Au, Ag, Cu, and the like. For optimal functionality of the CLHS it is enclosed from all sides and further equipped with an inlet and an outlet, such that the cold source can flow in a known direction from the inlet to the outlet.
Returning to
As noted above, in the small dimensions of micro-electronic enclosure, e.g. electronic boxes, heat density is high. It is therefore important to have control of fluid coolant temperature at all points of the thermal path between the heat source, for example 120-2 and the heat exchanger in the control unit 110. The invention disclosed herein provides advantages over the prior art in various aspects. Cost of electronic cooling is minimized by sharing the cold source compressor, for example an air compressor, storage tank, and micro-liquid pumps required to cool the IC set at the board level. The compressor, the tank, and liquid pumps provide the control needed to achieve the cost/performance required at the heat dissipation level by the electronic box. The air compressor and storage tank can be, in some embodiments, replaced by one or more fans that blows air to the heat exchanger's heat sink when a shared micro-pump is used to pump the liquid cooling in serial mode thru an individual hot chip's heat sink or heat spreader. The embodiments disclosed herein provide for area minimization by sharing coolant moving devices, e.g. fan, pump, or blower, to move small volumes of the cold source used in the electronic enclosure.
Further advantages of the invention include, for example, the minimization of noise generated by the coolant-moving-devices due to the sharing of such devices for a plurality of ICs. As heat density generated by each chip increases, the cooling capacity is increased by increasing the coolant, e.g. air or liquid, flow and further by increasing the pressure required to move such coolant across the thermal path, as shown with respect to
Although the invention is described herein with reference to the preferred embodiment, one skilled in the art will readily appreciate that other applications may be substituted for those set forth herein without departing from the spirit and scope of the present invention. Accordingly, the invention should only be limited by the Claims included below.
This application claims priority from U.S. provisional patent application Ser. No. 60/663,254, filed on Mar. 21, 2005, the entirety of which is incorporated by this reference thereto.
| Number | Date | Country | |
|---|---|---|---|
| 60663254 | Mar 2005 | US |
