RU2581342C2 - Method for producing a cooling system and microelectronic equipment - Google Patents

Abstract

FIELD: microstructure technology.

SUBSTANCE: invention relates to the field of microstructure technology. Method includes applying a plurality of regions with nanostructured hydrophobic properties to surface 2 of the microchannel. Nanostructure regions operate as hydrophobic lanes 1 of width L. Apply nanostructure regions across the flow onto the smooth surface of a microchannel at a distance from each other at a ratio of L/B ≥ 1. Values of L and B are determined based on the properties of the liquid and the surface.

EFFECT: ensures effective reduction of resistance when a single-phase or two-phase flow occurs in microchannels with a smooth surface.

1 cl, 1 dwg

Description

The invention relates to the field of microstructural technologies.

In recent decades, the use of microchannels has received significant development in engineering and technology. In a number of practical applications, fairly long microchannels can be used. One such application is the cooling system of electronic and microelectronic equipment. A feature of such systems is the locality of heat release, i.e. when the fluid is first transported to the heat release through an adiabatic section or section of the system. In some cases, the fluid flow in a microchannel can cool several electronic components at once, between which are adiabatic sections. Most often, due to the design features of mini- and microsystems, the channel size should remain unchanged throughout the system.

One of the most important obstacles to the introduction and distribution of microsystems with extended microchannels is significant pressure drops along the channel. Significant pressure drops along the channel, first of all, arise due to the requirement to pump a strictly defined amount of liquid to ensure the removal of a certain amount of heat. Often, microsystems (in cooling systems) use boiling media, two-phase flows, or film flows. However, the problem of significant pressure drops along the channel remains for any microsystems involving non-dispersed liquid. Today this problem is solved by using coatings with nanostructured or microstructural regions, grooves or through holes. In all these cases, it is necessary to process the surface, which eliminates the use of these methods on smooth surfaces.

The objective of the invention is to provide an effective method of reducing resistance when moving a single-phase or two-phase flow in microchannels with a smooth surface.

A known method and device for controlling the resistance during movement of a fluid flow on nanostructured or microstructured surfaces (US Pat. No. 2005069458, 2005, B01L 3/00; B81B 1/00; B81B 7/04; B82B 1/00; B82B 3/00; F15C 1/00; F15C 1/04; (IPC1-7): B01L 3/00), in which a lot of nanostructured or microstructural regions are applied to the surface in order to reduce the resistance when the fluid flow is moving according to a predetermined pattern. Nanostructural or microstructural regions are cells. The parameters of the areas can be changed to achieve the desired level of resistance during the movement of the fluid flow.

A known method of microchannel cooling (patent EP 1662852 (A1), 2006, H01L 23/473; H05K 7/20), in which to reduce the resistance when the fluid flows on the surface of the microchannel, many nanostructured regions with a hydrophobic coating are applied. Nanostructural regions are protruding structures. The parameters of nanostructured regions, as well as the distance between them, are determined from the properties of the liquid and the surface.

The disadvantages of these technical solutions are:

1) the inability to use on smooth surfaces;

2) high energy costs for pumping coolant.

Closest to the claimed is a method of attaching a microbubble on the surface of the plate (patent US 20100166964, 2008, B05D 5/08), in which to reduce the resistance during movement of the fluid flow on the surface, many grooves are formed in which bubbles are formed, while the grooves are processed material with hydrophobic properties. In another embodiment, to reduce the resistance during movement of the fluid flow, a plurality of through holes are formed on the surface treated with a material with hydrophobic properties, where bubbles also form. The size of the grooves and holes in the range of 1-1000 microns.

The disadvantage of this method is the impossibility of its use on smooth surfaces, because when grooves or holes form, surface damage occurs.

The objective of the invention is to provide a method of manufacturing a cooling system of electronic and microelectronic equipment, which provides a decrease in resistance when moving a single-phase or two-phase flow in microchannels with a smooth surface.

The problem is solved in that in a method for manufacturing a cooling system for electronic and microelectronic equipment containing microchannels, in which nanostructured regions with hydrophobic properties are applied to the surface of the microchannel, according to the invention, nanostructured regions with hydrophobic properties are applied in the form of hydrophobic bands in the form of hydrophobic strips of width L across the flow of a single-phase or two-phase coolant flow at a distance B from each other with a ratio L / B≥1.

Hydrophobic bands alternate with the untreated surface of the microchannel, which usually has hydrophilic properties. Small gas bubbles, which are usually found in technical and technological systems, are deposited on hydrophobic strips. Bubbles coagulate and form a “bubble layer”, which is retained by contrast wettability on the surface of the microchannel. If necessary, micro or macro bubbles of gas or air can be specially added to the system. Under certain conditions, the "bubble layer" can turn into a continuous gas layer. It is known that the viscosity of gas is several orders of magnitude lower than that of liquids, which ensures a significant decrease in resistance during flow and, as a result, a decrease in pressure drop along the microchannel, which means lower energy costs for pumping the coolant.

Hydrophobic strips are applied practically without damaging the smooth surface of the microchannel.

In FIG. 1 shows a general view of the surface of a microchannel with hydrophobic bands applied.

1 - hydrophobic stripes, 2 - untreated surface of the microchannel, 3 - heat source.

The method is as follows.

Hydrophobic strips are applied across the flow onto the smooth surface of the microchannel. Hydrophobic bands alternate with the untreated surface of the microchannel, which is usually hydrophilic. Small gas bubbles, which are usually found in technical and technological systems, are deposited on hydrophobic strips. The boundary of contrast wetting holds the bubbles and prevents their propagation along the stream. This fact is confirmed experimentally for conditions of terrestrial gravity, microgravity and hypergravity up to 1.8 × g ₀ (Kabov O.A., Cheverda V., Biondi F., Zaytsev D., Chikov S., Queeckers P., Marengo M., Araneo L ., Rioboo R., de Coninck J., Glushchuk A., Bykovskaya E., Iorio C, Bourdon B., and Memoli M., Dynamics and Boiling Incipience in Microgravity, pp 61, Results of ESA Parabolic Flights Experiments, Fifth International Topical Team Workshop on Two-Phase Systems for Ground and Space Applications, Kyoto, Japan, September 26-29, Book of Abstracts, 2010). As the working fluid, water was used as a surface - a silicon substrate. Experiments show that for terrestrial gravity, the hydrophobic zone is covered with bubbles of a size not exceeding, as a rule, 1 mm. The area of the bubbles is clearly limited by the boundary of the contrast wetting.

Bubbles can coagulate and form a “bubble layer” that is retained by contrast wettability on the surface of the microchannel. If necessary, micro or macro bubbles of gas or air can be specially added to the system. Under certain conditions, the "bubble layer" can turn into a continuous gas layer. It is assumed that the bubbles have the shape of spheroids, and their height is much less than the base. Bubbles cover only an insignificant part of the cross section of the microchannel and practically do not increase resistance. The size of the base and the height of the bubble can be controlled by the static contact angle of contact provided by the nanostructured coating (hydrophobic strips), as well as the width of these strips.

To obtain hydrophobic bands, part of the surface of the microchannel is treated chemically (by applying a monolayer of molecules of another substance) so that a region with a nanoscale roughness and a higher contact angle of contact appears on the surface. Areas with nanostructures deposited on it are hydrophobic with respect to the rest of the surface. The thickness of nanostructures can be about 1 nm, depending on the type of surface, and is not a fundamental parameter, i.e. noticeable thermal resistance and a noticeable narrowing of the channel. The difference between the contact wetting angles on hydrophobic strips and strips with an untreated surface should be from 20-40 degrees or more.

It is known that the viscosity of gas is several orders of magnitude lower than that of liquids, which provides a significant decrease in resistance during flow and, as a result, a decrease in pressure drop along the channel, which means lower energy costs for pumping coolant. The reduction in friction will be proportional to the ratio of the width of the hydrophobic strips to the width of the strips of the untreated channel surface, i.e. L / B. With a value of L / B >> 1, a decrease in channel resistance by 2 or more times is expected. It is assumed that the minimum strip width of the untreated channel surface according to technological requirements cannot be less than 100-300 microns. The width of the hydrophobic bands is determined by the size of the base of the bubble, as well as the conditions of their coagulation and can be up to 5000 microns or more. Thus, the condition L / B >> 1 can actually be achieved in the proposed system.

Claims (1)

A method of manufacturing a cooling system for electronic and microelectronic equipment containing microchannels, including applying nanostructured regions with hydrophobic properties to the surface of the microchannel, characterized in that nanostructured regions with hydrophobic properties in the form of hydrophobic strips of width L across the flow of a single-phase or two-phase cooling stream are applied to the smooth surface of the microchannel liquids at a distance B from each other with a ratio L / B≥1.

Images