RU2806879C1 - Heat-conducting panel for liquid cooling systems of detector modules and method of its manufacturing - Google Patents

Abstract

FIELD: heat-conducting panel.

SUBSTANCE: heat-conducting panel for liquid cooling systems of detector modules and the method of its manufacture are among the structural elements of the cooling system of modern semiconductor electronics. The heat-conducting panel for liquid cooling systems of detector modules consists of a layered structure in the form of a rigid carbon composite substrate, which is a layer of carbon fiber between two layers of carbon fleece and a heat removal system in the form of polyamide tubes for pumping coolant along the heat-conducting panel. The tubes are covered with a layer of charcoal paper and a layer of charcoal fleece.

EFFECT: invention makes it possible to increase the efficiency of heat removal while maintaining strength and low weight.

2 cl, 5 dwg

Description

The invention relates to structural elements of a cooling system for modern semiconductor electronics. Currently, designs of this type are used to remove thermal power from large arrays of monolithic active pixel silicon detectors of internal tracking systems in collider experiments.

For thermal stabilization of detector modules created on the basis of monolithic active pixel sensors, it is necessary to create light-weight heat-conducting panels from materials with a low charge number (carbon-based) that meet the conditions for minimizing multiple scattering of detected charged particles and increasing the radiation transparency of the detector systems used. The requirements for minimizing the weight of heat-conducting panels while maintaining high heat removal efficiency require the use of technical solutions that use the latest advances in the field of composite materials.

There is a known technical solution for heat removal of internal track systems of previous generations (D. Beavis et al., The STAR Heavy Flavor Tracker Technical Design Report, 2011), where only air cooling is present. One of the disadvantages of this type of cooling is the limitation on the amount of thermal power removed from elements experiencing constant thermal loads. The limitation is due to the possibility of mechanical vibrations of the detector system if the air flow speed increases.

Another cooling method is described in the work - Miljenko S. on behalf of the ALICE Collaboration, The Novel ALICE Inner Tracking System (ITS3) Based on Truly Cylindrical, Wafer-Scale Monolithic Active Pixel Sensors, JPS Conf. Proc. 34, 010011 (2021).

In this design, cooling of the main area of the pixel detector arrays is realized through air cooling in combination with liquid traditional removal of increased thermal power from narrow peripheral areas of the sensors. The possibility of forced air flow between the layers of sensors is ensured through the use of foamed carbon separating gaskets. The latter are in thermal contact with the sensors and partially act as radiators. The main disadvantages of this technical solution are the lack of overall structural rigidity of the sensor system due to the low mechanical properties of carbon foam and limitations in air flow speed, depending on the porosity of the carbon foam used, which determines its thermal conductivity coefficient.

The closest to the claimed invention (prototype) are the heat-conducting panels described in the works: Zherebchevsky V.I et al, Experimental investigation of new ultra-lightweight support and cooling structures for the new Inner Tracking System of the ALICE Detector, JINST, 13 T08003, 2018 and V. Abelev, J. Adam, S.N. Igolkin, G.A. Feofilov, V.I. Zherebchevskii, et. al., Technical design report for the upgrade of the ALICE inner tracking system, Journal of Physics G: Nuclear and Particle Physics, Volume 41, Issue 8, 2014, 087002.

These thermally conductive panels are designed to cool the detector modules (consisting of monolithic active pixel sensors) that form the cylindrical layers of the new Inner Tracking System of the ALICE experiment at the Large Hadron Collider at CERN.

The thermally conductive panels of the Internal Track System of the ALICE experiment are made using low charge number materials (carbon-based) and consist of a layer of rigid carbon composite substrate, high thermal conductivity carbon fiber, coated on both sides with carbon fleece and an active heat removal system using a liquid cooling system. To pump the refrigerant along the heat-conducting panel, polyamide tubes are used, which are in thermal contact with the heat-conducting panel. On top of the polyamide tubes and heat-conducting panel, there is a layer of carbon paper with thermal conductivity λ=1500 W/m⋅°C in the longitudinal section and 5 W/m⋅°C in the transverse section and a layer of carbon fleece.

The carbon fiber in the thermal conductive panel allows heat to be transferred from the periphery of the thermal conductive panel to the polyamide tubes. For sufficient heat transfer from polyamide tubes with refrigerant to the periphery, special K13D2U carbon fiber produced by Mitsubishi with a high thermal conductivity coefficient along the carbon fiber (λ=800 W/m⋅°C) was used in the heat-conducting panel. Detecting devices that generate heat are glued to the outer surface of the heat-conducting panel.

The disadvantage of the above panel design, which we adopted as a prototype, is insufficiently efficient heat removal. In addition, thermally conductive carbon fiber K13D2U is not available for delivery in the Russian Federation.

The objective of the invention is to manufacture a heat-conducting panel from available materials, as well as to increase the efficiency of heat removal while maintaining strength and low weight.

The solution to the technical problem is achieved due to the fact that the carbon fiber layer has thermal conductivity from λ=155.6 W/m⋅°С to λ=800 W/m⋅°С, in addition, a layer of carbon paper with thermal conductivity λ is additionally introduced into the structure =1500 W/m⋅°С in the longitudinal section and 20 W/m⋅°С in the transverse direction.

A method for manufacturing a heat-conducting panel for liquid cooling systems is also proposed. First, a rigid carbon composite substrate is made: carbon fiber with thermal conductivity from λ=155.6 W/m⋅°C to λ=800 W/m⋅°C, impregnated with glue, is laid on a sheet of coal fleece, perpendicular to the longitudinal axis, and covered with a sheet of carbon fleece. The assembly is crimped until the charcoal fleece and carbon fiber are bonded. The resulting assembly is cut in the direction of the fibers into blanks; these blanks are polymerized at a temperature of 120°C for 9 hours. Then a heat-conducting panel is made on one side of the matrix: a rigid carbon composite substrate covered with a layer of cold-curing compound and a layer of carbon paper, which is also covered with a thin layer of compound, are sequentially laid on one of the parts of the matrix . On the other part of the matrix with grooves, the upper part of the heat-conducting panel is made: blanks of carbon fleece and carbon paper impregnated with the compound are sequentially laid in the form of strips; polyamide tubes of the cooling system with technological inserts inside are laid opposite the grooves; polyamide tubes are placed in grooves; then the upper and lower parts of the matrix are compressed until gluing and left until the compound is completely polymerized at room temperature. After the polymerization cycle, the technological inserts are removed from the polyamide tubes, the heat-conducting panel is removed from the matrix, cleaned of the polymerized compound flash and cut to size.

List of figures.

Fig. 1 Three-dimensional design of the model with spaced components:

1 - Carbon composite substrate, providing structural rigidity. Detector modules are mounted on the surface of the carbon composite substrate;

2 - A layer of carbon paper with high thermal conductivity. Provides heat transfer from detectors to the heat-conducting element.

3 - Polyamide tubes of the cooling system through which the refrigerant is pumped.

4 - The upper part of the heat-conducting panel, consisting of a layer of carbon paper, carbon fleece and polyamide tubes, ensuring heat transfer from the carbon composite substrate with a layer of carbon paper to the polyamide tubes of the cooling system.

Fig. 2 - Photo of a heat-conducting panel with an integrated liquid cooling system (left) and a carbon composite substrate (right).

Fig. 3 - Composition of the heat-conducting panel.

1 - Carbon composite substrate, providing structural rigidity. Detector modules are mounted on the surface of the carbon composite substrate;

2 - A layer of carbon paper with high thermal conductivity. Provides heat transfer from detectors to the heat-conducting element.

3 - Polyamide tubes of the cooling system through which the refrigerant is pumped.

4 - The upper part of the heat-conducting panel, consisting of a layer of carbon paper, carbon fleece and polyamide tubes, ensuring heat transfer from the carbon composite substrate with a layer of carbon paper to the polyamide tubes of the cooling system.

5 - Charcoal fleece.

6 - Carbon fiber, prepared for molding, impregnated with glue.

Fig. 4 - Graph of average temperatures on each of the heaters on a heat-conducting panel: manufactured at CERN (a), manufactured at JINR (b) under the same measurement conditions, where the X-axis is the number of the heater where the temperature was measured, the Y-axis is the temperature (° WITH).

Fig. 5 - Photo of an experimental installation of a heat-conducting panel with five heating elements (c), simulating 196 MAPS microcircuits, for thermal-hydraulic testing.

7 - Heating element (g)

Carrying out the invention

The heat-conducting panel is manufactured as follows.

A stiffening element for the carbon composite substrate is pre-fabricated: available M55J carbon fiber with λ=155.6 W/m⋅°C, impregnated with glue, produced by NIIKAM, is placed on a sheet of carbon fleece, perpendicular to the longitudinal axis, and covered with a sheet of carbon fleece. The assembly is crimped until the charcoal fleece and carbon fiber are bonded. Next, the sheet is cut perpendicular to the carbon fiber into blanks of the required length and width. These blanks are polymerized in a matrix in accordance with the technical recommendations of the manufacturer of M55J carbon fiber impregnated with glue at a temperature of 120°C for 9 hours.

On another matrix, a heat-conducting panel is manufactured in one cycle: on the lower (flat) part of the device, a rigid carbon composite substrate coated with a layer of cold-curing compound (consisting of epoxy resin, hardener and thixotrope) and a layer of carbon paper DSN5032 with thermal conductivity λ = 20 W/m are sequentially laid ⋅°C in the transverse direction, which is also covered with a thin layer of compound. On the other part of the matrix with grooves for tubes, blanks of carbon fleece and carbon paper impregnated with an adhesive compound are sequentially laid in the form of strips. Opposite the grooves, polyamide tubes of the cooling system with technological inserts inside are laid. Polyamide tubes are carefully pressed into the grooves. Next, the upper part of the matrix is laid on the lower one so that the carbon composite substrate element is located opposite the upper part of the heat-conducting panel. The upper and lower parts are compressed until gluing and left until the compound is completely polymerized at room temperature. After the polymerization cycle, the technological inserts are removed from the polyamide tubes, the heat-conducting panel is removed from the matrix, cleaned of the remnants of the polymerized compound and cut to size.

To regulate the temperature, water is supplied in the form of a “loop” pattern into the polyamide tubes: two channels are connected together at one end of the heat-conducting panel with a loop, and at the other end there is a refrigerant inlet and outlet.

Device operation.

An experimental stand was created to conduct thermohydraulic tests of the heat-conducting panel. The stand used five heaters simulating 196 MAPS microcircuits, in which the heating element was made of nichrome wire (Fig. 4), with a width of 3.4 ± 0.1 cm, length of 29.3 ± 0.1 cm and thickness equal to 0.8±0.1 cm. The simulators dissipated thermal power equal to 40 mW/cm ² .

Temperature measurements were made using an IR camera VarioCAM HD headsl. During the measurement process, the current parameters of the ambient temperature were set in the camera settings and the correctness of temperature measurements using thermocouples was checked.

Tests have shown that the proposed heat-conducting panel carries out heat removal more efficiently compared to the prototype under the same measurement conditions. The measurement results are shown on a graph of average temperatures on each of the heaters on a heat-conducting panel manufactured at CERN (a) and the proposed one manufactured at JINR (b) under the same measurement conditions (Fig. 4). When using carbon fiber with thermal conductivity higher than λ=155.6 W/m⋅°С with an additionally introduced layer of carbon paper with thermal conductivity λ=20 W/m⋅°С in the transverse direction, the heat removal efficiency increases.

The heat-conducting panel manufactured at JINR has a 0.9% difference in weight with the compared prototype, which is an insignificant difference for the tasks of the implemented installation. The proposed heat-conducting panels are designed for cooling detector modules (consisting of monolithic active pixel sensors) forming cylindrical layers of the new Internal Tracking System of the MPD (Multi-Purpose Detector) experiment at the NICA accelerator complex (Nuclotron based Ion Collider fAcility) of the Joint Institute for Nuclear Research (Dubna, Russia).

Also, such a heat-conducting panel can be used not only for cooling detector module assemblies, but also for cooling individual chips.

Claims (2)

1. A heat-conducting panel for liquid cooling systems of detector modules, consisting of a layered structure in the form of a rigid carbon composite substrate, which is a layer of carbon fiber between two layers of carbon fleece and a heat removal system in the form of polyamide tubes for pumping coolant along the heat-conducting panel, the tubes are covered with a layer of carbon paper and a layer of carbon fleece, characterized in that the carbon fiber layer has a thermal conductivity from λ=155.6 W/m⋅°C to λ=800 W/m⋅°C, and carbon paper has a thermal conductivity of λ=20 W/m⋅°C in in the transverse direction, in addition, a layer of carbon paper is additionally introduced into the structure. 2. A method for manufacturing a heat-conducting panel for liquid cooling systems, which consists in first making a rigid carbon composite substrate: carbon fiber with thermal conductivity from λ=155.6 W/m to λ=800 W/m⋅ is laid on a sheet of carbon fleece perpendicular to the longitudinal axis °C, soaked in glue, and covered with a sheet of charcoal fleece; the assembly is crimped until the carbon fleece and carbon fiber are glued together; the resulting assembly is cut in the direction of the fibers into blanks; these blanks are polymerized at a temperature of 120°C for 9 hours; then a heat-conducting panel is made on one side of the matrix: on one part of the matrix, a rigid carbon composite substrate coated with a layer of cold-curing compound and a layer of carbon paper, which is also covered with a thin layer of compound, are sequentially laid; on the other part of the matrix with grooves, the upper part of the heat-conducting panel is made: blanks of carbon fleece and carbon paper impregnated with the compound are sequentially laid in the form of strips; polyamide tubes of the cooling system with technological inserts inside are laid opposite the grooves; polyamide tubes are placed in grooves; then the upper and lower parts of the matrix are compressed until gluing and left for a while until the compound is completely polymerized at room temperature; after the polymerization cycle, the technological inserts are removed from the polyamide tubes, the heat-conducting panel is removed from the matrix, cleaned of the polymerized compound flash and cut to size.