JP7630448B2 - Heat transfer member and method for manufacturing the same - Google Patents

Description

The present invention relates to a heat transfer member and a method for manufacturing a heat transfer member.

Conventionally, a heat transfer member has been known in which the surface of a metal material is irradiated with pulsed laser light to form periodic recesses and annular protrusions around the recesses, thereby increasing the surface area.

JP 2016-114304 A

For this type of heat transfer component, it would be beneficial to obtain a heat transfer component with a novel structure and a manufacturing method thereof that can further increase thermal conductivity.

Therefore, one of the objectives of the present invention is to obtain, for example, a heat transfer member having a novel configuration capable of further increasing thermal conductivity, and a method for manufacturing the heat transfer member.

The heat transfer member of the present invention is made of a metal material and has, for example, a surface layer having a porous structure that extends across a predetermined section of the first direction at an end in the first direction and intersects with the first direction.

In the heat transfer member, the surface layer may have a protrusion layer having more protrusions than closed pores, and a closed pore layer adjacent to the protrusion layer on the opposite side of the first direction and having more closed pores than the protrusions.

The heat transfer member of the present invention has, for example, a surface layer that extends across a predetermined section of a first direction at an end in the first direction, and the surface layer is made of a metal material having a protrusion layer in which there are more protrusions than closed pores, and a closed pore layer adjacent to the protrusion layer on the opposite side of the first direction and in which there are more closed pores than protrusions.

In the heat transfer member, the porosity of the surface layer may be 50% or more and 90% or less.

The heat transfer member of the present invention is made of a metal material, for example, and has a surface layer that extends across the first direction at the end of the first direction and has a porosity of 50% or more and 90% or less.

In the heat transfer member, the porosity outside the central position in the height direction of the surface layer may be 50% or more and 80% or less.

In the heat transfer member, the porosity of the surface layer outside the surface of the heat transfer member in the height direction may be 50% or more and 90% or less.

In the heat transfer member, the surface area increase rate of the surface layer per unit area when projected in the height direction of the surface layer may be 110% or more and 300% or less.

The heat transfer member may have a surface layer and a convex portion protruding in the first direction.

The heat transfer member may be a bus bar made of a conductive metal material.

The heat transfer member may be a heat exchange member that exchanges heat with a fluid.

The heat transfer member may be a boiling heat transfer member, and heat may be transferred from the heating element to the refrigerant through the surface layer.

In addition, the manufacturing method for a heat transfer member of the present invention includes, for example, a first step of preparing a heat transfer member made of a metal material and having a surface, and a second step of forming a surface layer having a porous structure by irradiating the surface with laser light to reattach particles blown off the surface.

In the method for manufacturing the heat transfer member, in the second step, the laser light may be swept relatively over the surface by moving an emission section that emits the laser light and the heat transfer member relatively.

In the method for manufacturing the heat transfer member, in the second step, a first sweep of the laser light in a first direction along the surface or in a direction opposite to the first direction is performed multiple times while being shifted by a first interval in the second direction or in a direction opposite to the second direction so as to be aligned in a second direction intersecting the first direction, and the first interval may be equal to or smaller than the beam diameter of the laser light.

In the method for manufacturing the heat transfer member, in the second step, the first sweep is performed multiple times aligned in the second direction, and then a second sweep in a third direction intersecting the first direction along the surface of the laser light or in a direction opposite to the third direction is performed multiple times aligned in a fourth direction intersecting the third direction, and a second interval of the second sweep in the fourth direction may be less than or equal to the beam diameter of the laser light.

In the method for manufacturing the heat transfer member, in the second step, the first sweep may be performed multiple times so as to be aligned in the second direction, and then a second sweep in the first direction along the surface of the laser light at a position shifted in the second direction from the first sweep by less than the first distance may be performed multiple times so as to be aligned in the second direction.

According to the present invention, for example, it is possible to obtain a heat transfer member having a novel configuration capable of further increasing thermal conductivity, and a method for manufacturing the heat transfer member.

FIG. 1 is an exemplary schematic plan view of a heat transfer member according to a first embodiment. FIG. 2 is a cross-sectional view taken along line II-II of FIG. FIG. 3 is a flowchart showing a method for manufacturing the heat transfer member of the first embodiment. FIG. 4 is an exemplary schematic diagram of the processing system according to the first embodiment. FIG. 5 is an illustrative schematic plan view showing an example of a laser light sweeping method in the method for manufacturing a heat transfer member according to the first embodiment. FIG. 6 is an illustrative schematic plan view showing another example of the laser beam sweeping method in the method for manufacturing the heat transfer member according to the first embodiment. FIG. 7 is an exemplary graph showing the relationship between the surface area increase rate and the thermal resistance in the surface layer of the heat transfer member of the first embodiment. FIG. 8 is a cross-sectional view taken along the line II-II of FIG. 1, and is an exemplary schematic view showing a region of the surface layer on the end side from the central position. FIG. 9 is a cross-sectional view taken along the line II-II in FIG. 1, and is an exemplary schematic view showing a region of the surface layer on the end side of the surface of the heat transfer member. FIG. 10 is an exemplary schematic plan view of a bus bar serving as a heat transfer member according to the second embodiment. FIG. 11 is a cross-sectional view taken along line XI-XI of FIG. FIG. 12 is an exemplary schematic plan view of a part of a heat exchange member as a heat transfer member of the third embodiment. FIG. 13 is an illustrative schematic plan view of a part of a heat exchange member as a heat transfer member of the fourth embodiment. FIG. 14 is an exemplary schematic cross-sectional view of a boiling cooling device having a boiling heat transfer member as the heat transfer member of the fifth embodiment.

Below, exemplary embodiments of the present invention are disclosed. The configurations of the embodiments shown below, and the actions and results (effects) brought about by said configurations, are merely examples. The present invention can also be realized with configurations other than those disclosed in the following embodiments. Furthermore, according to the present invention, it is possible to obtain at least one of the various effects (including derivative effects) obtained by the configurations.

The embodiments shown below have similar configurations. Therefore, according to the configuration of each embodiment, similar actions and effects based on the similar configurations can be obtained. Furthermore, in the following, the similar configurations are given the same reference numerals, and duplicate explanations may be omitted.

In this specification, ordinal numbers are used for convenience to distinguish parts, portions, etc., and do not indicate priority or order.

In each figure, the X direction is represented by an arrow X, the Y direction is represented by an arrow Y, and the Z direction is represented by an arrow Z. The X direction, Y direction, and Z direction intersect with each other and are perpendicular to each other. The X direction can also be called the extension direction or sweep direction, the Y direction can also be called the extension direction or sweep direction, and the Z direction can also be called the thickness direction or height direction.

[First embodiment]
FIG. 1 is a plan view of a heat transfer member 10 of the present embodiment, and FIG. 2 is a cross-sectional view taken along line II-II of FIG.

The heat transfer member 10 is made of a metal material with high thermal conductivity, such as copper, a copper alloy, aluminum, or an aluminum alloy.

[Surface structure]
1, the heat transfer member 10 has a planar surface 10a, and a surface layer 20 having a porous structure is provided on at least a portion of the surface 10a. The surface 10a is an example of a surface. The surface layer 20 is formed by irradiation with a laser beam. Processing of the surface layer 20 will be described later.

2, the surface layer 20 extends at the Z-direction end of the heat transfer member 10 with a substantially constant thickness (depth) in the Z direction, in other words, over a predetermined section in the Z direction, in the X direction and the Y direction, in other words, in a direction intersecting and perpendicular to the Z direction. The Z direction is an example of a first direction.

The surface layer 20 has a porous structure including a plurality of protrusions 20p and a plurality of closed holes 20h. The surface layer 20 can be defined as a layer that extends perpendicularly to and crosses the Z direction between the tip 20t that protrudes highest in the Z direction and the closed hole 20b that is the furthest from the tip 20t in the opposite direction to the Z direction, for example, in a predetermined range when viewed in the Z direction (opposite direction).

The surface layer 20 can be roughly divided into two layers. One is a first layer L1 in which there are more protrusions 20p than closed holes 20b, and the other is a second layer L2 in which there are more closed holes 20b than protrusions 20p. The first layer L1 crosses the Z direction at a predetermined height (thickness) and spreads perpendicularly, and the second layer L2 crosses the Z direction at a predetermined depth (thickness) and spreads perpendicularly. The first layer L1 and the second layer L2 are adjacent to each other in the Z direction. In addition, the first layer L1 is located outside the second layer L2. The first layer L1 is an example of a protrusion layer, and the second layer L2 is an example of a closed hole layer.

The porosity of the surface layer 20 is the ratio of the void region to the material region in the cross section of the surface layer 20 (measurement target portion). The porosity can be calculated, for example, as the area ratio of the void region to the material region by image processing of multiple cross-sectional images of the surface layer 20. For example, in the cross-sectional image shown in FIG. 2 that crosses the Y direction along the Z direction, the area ratio is calculated by dividing the area of the black void region by the area of the gray material region for a rectangular two-dimensional region having the length Lx in the X direction of the measurement target portion P and the length Lz (depth) in the Z direction of the measurement target portion P. Then, the area ratio is calculated for multiple different cross-sectional images (e.g., four locations) within the measurement target portion P, and the average value of the area ratios of the multiple locations can be calculated as the porosity. Here, the length Lz of the measurement target portion P can be, for example, the Z-direction length between the tip 20t that protrudes highest in the Z direction and the closed hole 20b that is furthest from the tip 20t in the opposite direction to the Z direction in multiple cross-sectional images of the measurement target portion P along the Z direction. The length Lx in the X direction of the measurement target portion P can be appropriately set within the range where the laser processing has been performed. The porosity of each layer, such as the first layer L1 and the second layer L2, can also be calculated in the same way by changing the range of the rectangular two-dimensional area to be subjected to image processing. The direction, position, number, etc. of the cross section can be appropriately set. The porosity may also be calculated as the average value of the area ratio of multiple cross sections whose normal directions are different from each other. The number of cross sections to be averaged may be at least two or more, but may be one if the variation in the processing state due to the position and direction is low, or may be three or more to further improve the measurement accuracy. The porosity is preferably calculated for multiple samples that have been subjected to the same laser processing. In this embodiment, the porosity is calculated two-dimensionally from the cross section, but when the number of cross sections to be averaged is large or when the variation in shape due to position is relatively small, it can be considered to be approximately the same as the ratio of the volume of the void to the volume of the material, that is, the three-dimensional porosity.

For example, the porosity of the surface layer 20 was (1) 76.7%, (2) 80.0%, (3) 73.7%, and (4) 81.4% in four samples, with an average of 77.9%. As a result of intensive research by the inventors, including these survey results, it was found that the porosity of the surface layer 20 is preferably 50% or more and 90% or less, and more preferably 60% or more and 85% or less. As is clear from Figure 2, the porosity of the first layer L1 is greater than the porosity of the second layer L2.

Furthermore, as can be seen from Figure 2, the surface layer 20 has irregular projections and recesses, and does not have periodic projections and recesses as in Patent Document 1.

[Surface processing by laser light irradiation]
Fig. 3 is a flow chart showing a method for manufacturing a heat transfer member. As shown in Fig. 3, in this embodiment, the heat transfer member 10 is first prepared by forming it by pressing, cutting, or the like (S1, first step), and then the surface 10a of the heat transfer member 10 is irradiated with laser light L to process the surface 10a to form a surface layer 20 (S2, second step). Note that the first step S1 (preparation step) may be a step of carrying in the heat transfer member 10 formed at another location.

Figure 4 is a schematic diagram of a processing system 100 for processing the surface layer 20. As shown in Figure 4, the processing system 100 includes a laser device 110, an optical head 120, an optical fiber 130 connecting the laser device 110 and the optical head 120, and a holding member 140.

The laser device 110 is configured to be able to output laser light with a power of, for example, several kW. For example, the laser device 110 may be configured to have multiple semiconductor laser elements therein and to be able to output multi-mode laser light with a power of several kW as the total output of the multiple semiconductor laser elements. The laser device 110 may also be equipped with various laser light sources such as a fiber laser, a YAG laser, a disk laser, etc. The laser device 110 emits continuous light of laser light by continuous wave oscillation. In other words, the laser device 110 is a CW (continuous wave) laser.

The optical fiber 130 guides the laser light output from the laser device 110 and inputs it to the optical head 120.

The holding member 140 holds the heat transfer member 10 as the workpiece W.

The optical head 120 is an optical device that emits the laser light L input from the laser device 110 via the optical fiber 130 toward the workpiece W. The optical head 120 is an example of an emission unit.

The optical head 120 is equipped with a collimating lens 121 and a condensing lens 122. The collimating lens 121 is an optical system for converting the input laser light into parallel light. The condensing lens 122 is an optical system for collecting the parallelized laser light and irradiating the workpiece W as laser light L. The optical head 120 emits the laser light L in the opposite direction to the Z direction. The laser light L is irradiated onto the surface of the workpiece W. The surface may also be referred to as the irradiated surface.

The optical head 120, the holding member 140, and the workpiece W are housed in a case 200, and the atmosphere inside the case 200 (in the processing chamber R), i.e., the atmosphere around the workpiece W, is controlled. For example, in this embodiment, gas is sprayed by a gas nozzle or the like toward the vicinity of the irradiation position of the surface 10a so that the particles of material separated from the surface 10a of the workpiece W by the irradiation of the laser light L are adhered and stacked again on the surface 10a. The flow rate, flow speed, direction, spray position, etc. of the gas can be adjusted as appropriate. The gas is an inert gas such as nitrogen gas.

The processing system 100 is configured to be able to change the relative position between the optical head 120 and the workpiece W, i.e., the holding member 140 that holds the workpiece W. This moves the irradiation position of the laser light L on the surface 10a of the workpiece W. This causes the laser light L to sweep across the surface 10a. In other words, the spot (irradiation position) of the laser light L on the surface 10a moves across the surface 10a.

Movement of the irradiation position of the laser light L on the surface 10a, i.e., the relative movement between the optical head 120 and the workpiece W, can be achieved by moving the optical head 120 alone, the workpiece W (holding member 140) alone, or a moving mechanism (not shown) that moves both the optical head 120 and the workpiece W.

[Sweeping method]
Fig. 5 shows an example of a method for sweeping a spot (not shown) of laser light L on the surface 10a of the workpiece W, and Fig. 6 shows another example of a method for sweeping a spot of laser light L on the surface 10a of the workpiece W. Note that Figs. 5 and 6 are enlarged views showing a part of the processing region of the surface 10a.

In the case of FIG. 5, first, as shown by the dashed arrow in the figure, alternating sweeps (s1) in the X direction and the opposite direction to the X direction along the surface 10a of the laser light L are performed multiple times so as to line up in the Y direction. The sweeps in the X direction and the opposite direction to the X direction are an example of a first sweep s1, the X direction is an example of a first direction, and the Y direction is an example of a second direction. The sweep positions of the first sweep s1 are shifted by an interval ps1 in the Y direction or the opposite direction to the Y direction, for example. In addition, the interval ps1 is set to be equal to or smaller than the spot diameter (beam diameter, not shown) of the laser light L. The interval ps1 is an example of a first interval. Note that, here, an example has been shown in which the first sweep s1 in the X direction and the first sweep s1 in the opposite direction to the X direction are executed alternately, but the present invention is not limited to this. For example, only the first sweep s1 in the X direction may be executed, or only the first sweep s1 in the opposite direction to the X direction may be executed, or the first sweep s1 in the X direction may be executed multiple times and then the first sweep s1 in the opposite direction to the X direction may be executed multiple times.

Next, as shown by the solid arrows in the figure, alternating sweeps (s2) in the Y direction and the opposite direction to the Y direction along the surface 10a of the laser light L are performed multiple times so as to line up in the X direction. The sweeps in the Y direction and the opposite direction to the Y direction are an example of a second sweep s2, the Y direction is an example of a third direction, and the X direction is an example of a fourth direction. The sweep positions of the second sweeps s2 are shifted by an interval ps2 in the X direction or the opposite direction to the X direction, for example. In addition, the interval ps2 is set so as to be equal to or smaller than the spot diameter (beam diameter, not shown) of the laser light L. The interval ps2 is an example of a second interval. The interval ps2 may be the same as the interval ps1 or may be different. Note that, although an example in which the second sweep s2 in the Y direction and the second sweep s2 in the opposite direction to the Y direction are alternately performed has been shown here, the present invention is not limited to this, and for example, only the second sweep s2 in the Y direction may be performed, only the second sweep s2 in the opposite direction to the Y direction may be performed, or the second sweep s2 in the Y direction may be performed multiple times and then the second sweep s2 in the opposite direction to the Y direction may be performed multiple times. Furthermore, the third direction is not limited to the Y direction as long as it intersects with the first direction, in other words, it may be a direction inclined with respect to the Y direction.

6, first, as shown by the dashed arrow in the figure, alternating sweeps (s1) in the X direction and the opposite direction to the X direction along the surface 10a of the laser light L are performed multiple times so as to line up in the Y direction. The sweeps in the X direction and the opposite direction to the X direction are an example of a first sweep s1, and the first sweep is the same as in the case of FIG. 5, so a description thereof will be omitted.

Next, as shown by the solid arrows in the figure, alternating sweeps (s2) in the X direction and the opposite direction of the X direction along the surface 10a of the laser light L are performed multiple times so as to line up in the Y direction. The sweeps in the X direction and the opposite direction of the X direction here are an example of the second sweep s2. The first sweep s1 and the second sweep s2 are parallel. The Y direction position of the second sweep s2 is performed at a position shifted by less than the interval ps1 with respect to the Y direction position of the first sweep s1. The sweep positions of the second sweep s2 are shifted by an interval ps2 in the Y direction or the opposite direction of the Y direction, for example. The interval ps2 is set so as to be equal to or smaller than the spot diameter (beam diameter, not shown) of the laser light L. The interval ps2 may be the same as the interval ps1 or may be different. Note that, here, an example has been shown in which the second sweep s2 in the X direction and the second sweep s2 in the opposite direction to the X direction are executed alternately, but the present invention is not limited to this. For example, only the second sweep s2 in the X direction may be executed, or only the second sweep s2 in the opposite direction to the X direction may be executed, or the second sweep s2 in the X direction may be executed multiple times and then the second sweep s2 in the opposite direction to the X direction may be executed multiple times.

The surface layer 20 of this embodiment is obtained by irradiating the surface 10a of the workpiece W with laser light L, which is a CW laser, to blow away the molten metal, forming recesses (voids), and by re-adhering the blown-away molten metal to form protrusions. As a result, in the surface layer 20 of this embodiment, adjacent recesses are connected two-dimensionally and three-dimensionally, and a complex and irregular uneven structure (porous metal layer) is obtained in which the openings on the outside (Z direction) of the recesses are relatively narrow, so that the surface area of the material portion in the surface layer 20 is significantly increased. With this configuration, it has been found that a larger surface area can be obtained, and thus the thermal resistance can be reduced, and the heat dissipation and heat exchange properties can be improved, compared to a conventional structure having a relatively simple uneven structure in which recesses and protrusions are regularly arranged on the surface of the material by irradiation with a pulsed laser, for example.

[Surface area increase rate and thermal resistance]
FIG. 7 is a graph showing the relationship between the surface area increase rate and the thermal resistance of the surface layer 20 in a number of samples. Under all conditions, the thermal resistance is lower than that of the unprocessed copper plate, which is 0.26. The surface area increase rate is the ratio of the surface area of the surface layer 20 increased by laser processing per unit area (for example, 1 [cm ² ]) of the projected area in the Z direction. If the surface area does not change before laser processing (unprocessed or unprocessed) and after laser processing, the surface area increase rate is 100%, and if the surface area increases even slightly compared to before laser processing by laser processing, the surface area increase rate becomes a value greater than 100%. The larger the surface area increase rate, the more the surface area is increased by the unevenness. The surface area of the surface layer 20 can be calculated from a three-dimensional surface shape measured by a measuring device such as KEYENCE's VR-3000. The surface area increase rate is obtained by dividing the surface area obtained from the measuring device for a specified range (e.g., a range of 20 mm x 20 mm when viewed in a plane in the opposite direction to the Z direction) by the area when the specified range is flat (e.g., 400 ^mm2 for a range of 20 mm x 20 mm).

As shown in Fig. 7, the inventors found that in the surface layer 20 of this embodiment, the correlation between the surface area increase rate and the thermal resistance changes at the boundary of the surface area increase rate value Rb. That is, in the surface layer 20 of this embodiment, in the range where the surface area increase rate is smaller than the value Rb, the thermal resistance is smaller as the surface area increase rate increases, but in the range where the surface area increase rate is larger than the value Rb, the thermal resistance is larger as the surface area increase rate increases. This is presumably because, as described above, in the surface layer 20 of this embodiment, closed holes 20h as shown in Fig. 2 are formed by particles that have separated from the surface 10a and reattached, but the larger the surface area increase rate of the surface layer 20, the larger the volume ratio of the closed holes 20h in the surface layer 20, i.e., the volume ratio of gas with a lower thermal conductivity.

Based on this knowledge, it has been found that it is preferable for the surface layer 20 to have a shape in which the surface area increase rate is within a range in which the thermal resistance is equal to or less than the threshold value Th, i.e., equal to or more than the lower limit value Rmin and equal to or less than the upper limit value Rmax, and more specifically, it is preferable for the surface area increase rate to be equal to or more than 110% and equal to or less than 300%, and it is even more preferable for the surface area increase rate to be equal to or more than 200% and equal to or less than 230%.

[Porosity (range different from Figure 2)]
Even when the range for calculating the porosity is different, the porosity can be calculated in the same manner by changing the target rectangular two-dimensional area in the image processing of the cross-sectional image described above.

Figure 8 shows a cross section of the heat transfer member 10 at the same position as in Figure 2. However, Figure 8 shows an area Lu of the surface layer 20 on the end side in the Z direction (surface side, outside) of the central position CF in the Z direction. The central position CF is the position of a plane that intersects and is perpendicular to the Z direction, located in the center in the Z direction between the tip 20t of the surface layer 20 and the deepest closed hole 20b within a specified range when viewed in the Z direction (opposite direction).

The porosity of the surface layer 20 outside the intermediate position CF (forward in the Z direction) was, for example, 67.5% (1), 66.0% (2), 65.6% (3), and 68.1% (4) in four samples, with an average of 66.8%. As a result of intensive research by the inventors, including these survey results, it was found that the porosity of the surface layer 20 is preferably 50% or more and 80% or less, and more preferably 60% or more and 70% or less.

Figure 9 also shows a cross section of the heat transfer member 10 at the same position as in Figure 2. However, Figure 9 shows an area Lp of the surface layer 20 that is closer to the end (surface side, outer side) in the Z direction than the surface 10a of the area where the surface layer 20 is not processed (or the surface 10a before processing).

The porosity of the surface layer 20 outside the surface 10a (forward in the Z direction) was, for example, 76.0% (1), 73.0% (2), 71.9% (3), and 76.8% (4) in four samples, with an average of 74.5%. As a result of intensive research by the inventors, including these survey results, it was found that the porosity of the surface layer 20 is preferably 50% or more and 90% or less, and more preferably 60% or more and 80% or less. The volumetric material ratio of the surface layer 20 outside the surface 10a (forward in the Z direction) is (1-porosity). In this case, it can be said that the volumetric material ratio is the ratio of redeposited material.

As described above, in this embodiment, the heat transfer member 10 is made of a metal material and has a surface layer 20. The surface layer 20 has a porous structure that extends across a predetermined section of the Z direction (first direction) at the end in the Z direction, intersecting the Z direction.

With such a configuration, for example, the surface area is likely to be larger than that of a heat transfer member that simply has porous irregularities on its surface, making it easier to improve thermal conductivity.

In addition, in this embodiment, for example, the surface layer 20 has a first layer L1 (projection layer) in which there are more protrusions 20p than closed holes 20h, and a second layer L2 (closed hole layer) adjacent to the first layer L1 on the opposite side in the Z direction (first direction) and in which there are more closed holes 20h than protrusions 20p.

As in the present embodiment, such a configuration is obtained when particles of material detached from surface 10a by irradiation with laser light L re-adhere and accumulate on surface 10a. With this configuration, the surface area tends to be larger than that of a heat transfer member having merely porous irregularities on its surface, and the thermal conductivity tends to be improved.

In addition, in this embodiment, for example, the porosity of the surface layer 20 is 50% or more and 90% or less.

In addition, in this embodiment, for example, the porosity outside the central position CF in the Z direction (height direction) of the surface layer 20 is 50% or more and 80% or less.

Furthermore, in this embodiment, for example, the porosity of the surface layer 20 outside the surface 10a of the heat transfer member 10 in the Z direction (height direction) is 50% or more and 90% or less.

The inventors' research has revealed that if the porosity is within this range, it is easier to increase thermal conductivity.

In addition, in this embodiment, for example, the surface area increase rate, i.e., the ratio of the surface layer 20 per unit area when projected in the Z direction (height direction) of the surface layer 20, is 110% or more and 300% or less.

The inventors' research has revealed that if the surface area increase rate is within this range, it is easier to increase thermal conductivity.

In addition, the manufacturing method of the heat transfer member 10 of this embodiment includes, for example, a step S1 (first step) of preparing the heat transfer member 10, and a step S2 (second step) of forming a surface layer 20 having a porous structure by irradiating the surface 10a of the heat transfer member 10 with laser light L to reattach particles blown off from the surface 10a.

The above-mentioned second step makes it possible to form a surface layer 20 having a porous structure and high thermal conductivity, thereby forming a surface layer 20 with higher thermal conductivity on the surface 10a of the heat transfer member 10.

In addition, in this embodiment, for example, in step S2 (second step), the optical head 120 (emitting portion) that emits the laser light L and the workpiece W (heat transfer member 10) are moved relative to each other to sweep the laser light L relatively over the surface 10a.

With this configuration, the surface layer 20 can be formed more quickly than when, for example, a pulsed laser beam is irradiated. In addition, by irradiating the continuous laser beam L, regular irregularities are less likely to be formed than when a pulsed laser beam is irradiated, and the surface area is therefore more likely to be increased, making it easier to increase thermal conductivity.

In addition, in this embodiment, for example, in step S2 (second step), a first sweep s1 in the X direction (first direction) or the opposite direction to the X direction (opposite direction to the first direction) along the surface 10a of the laser light L is performed multiple times while being shifted at an interval ps1 (first interval) in the Y direction or the opposite direction to the Y direction so as to be aligned in the Y direction (second direction) intersecting the X direction, and the interval ps1 is equal to or less than the beam diameter of the laser light L.

With this configuration, for example, a surface layer 20 that spreads out on the surface 10a without gaps in a plane can be formed. In addition, regular convex ridges are formed at relatively wide intervals at the boundary portion of the first sweep s1, which makes it possible to avoid the surface area from becoming difficult to increase.

In addition, in this embodiment, for example, in step S2 (second step), a first sweep s1 is performed multiple times so as to be aligned in the Y direction, and then a second sweep s2 in the Y direction (third direction) intersecting the X direction along the surface 10a of the laser light L or in the opposite direction to the Y direction is performed multiple times so as to be aligned in the X direction (fourth direction) intersecting the Y direction, and the spacing ps2 (second spacing) of the second sweep s2 in the X direction is less than or equal to the beam diameter of the laser light L.

With this configuration, for example, a surface layer 20 that spreads out planarly and without gaps can be formed on the surface 10a. In addition, regular convex ridges are formed at relatively wide intervals at the boundary portion of the first sweep s1 and the boundary portion of the second sweep s2, which makes it possible to prevent the surface area from becoming difficult to increase.

In addition, in this embodiment, in step S2 (second step), a first sweep s1 is performed multiple times so as to be aligned in the Y direction, and then a second sweep s2 in the X direction (first direction) along the surface 10a of the laser light L at a position shifted in the Y direction (second direction) from the first sweep s1 by less than the interval ps1 is performed multiple times so as to be aligned in the Y direction (second direction).

With this configuration, for example, a surface layer 20 that spreads out on the surface 10a without gaps in a plane can be formed. In addition, regular convex ridges are formed at relatively wide intervals at the boundary portion of the first sweep s1, which makes it possible to avoid the surface area from becoming difficult to increase.

The heat transfer member 10 of this embodiment has a surface layer with a large surface area due to the porous structure, and can obtain high heat dissipation by radiation from the surface layer even in a vacuum. For this reason, it is suitable for application to space structures used in space environments that are vacuum and have large temperature changes, such as space bases, space stations, rockets, space probes, and artificial satellites. Examples of materials for space structures include stainless steel, titanium, titanium alloys, molybdenum, and tantalum. In addition, since paints and the like that were applied to the surfaces of conventional space structures to improve heat dissipation are no longer necessary, there is also the advantage that the effort and cost of manufacturing the space structure can be reduced.

[Second embodiment]
FIG. 10 is a plan view of a bus bar 10A serving as a heat transfer member according to the second embodiment, and FIG. 11 is a cross-sectional view taken along line XI-XI of FIG.

The busbar 10A is made of a conductive metal material. Each of the longitudinal ends 10b has a through hole 10c for mechanically and electrically connecting to the terminals of other electrical components.

The busbar 10A is preferably made of a metal material with low electrical resistivity, such as copper, a copper alloy, aluminum, or an aluminum alloy. From the viewpoint of low electrical resistivity, the busbar 10A is preferably made of copper.

The busbar 10A has a flat, band-like, plate-like shape. The busbar 10A extends in the X direction with a substantially constant width in the Y direction and a substantially constant thickness (height) in the Z direction.

The busbar 10A has two faces 10a and 10d at the ends in the Z direction and the opposite direction of the Z direction. The faces 10a and 10d cross the Z direction and extend perpendicularly. In this embodiment, the faces 10a and 10d are perpendicular to the Z direction and extend in the X direction and Y direction. The faces 10a and 10d are examples of surfaces.

A surface layer 20 having the same configuration as that of the first embodiment is provided on the surface 10a of the busbar 10A near the through hole 10c. The through hole 10c is a connection portion with another conductor, and therefore generates heat due to the resistance of the conductor itself when electricity is passed through it. Furthermore, heat may be generated near the through hole 10c due to contact resistance between the through hole 10c and another conductor. That is, the vicinity of the through hole 10c may also be referred to as a heat generating portion. In this respect, according to the present embodiment, the surface layer 20 is provided at a position spaced apart from the through hole 10c in the vicinity of the through hole 10c, and therefore an excessive increase in temperature of the busbar 10A or a conductor connected to the busbar 10A due to contact resistance can be suppressed. That is, according to the present embodiment, the surface layer 20 can suppress the temperature increase of the busbar 10A as a heat transfer member.

11, the surface layer 20 is provided on a protruding portion 10e protruding from the surface 10a. The protruding portion 10e is an example of a convex portion. With this configuration, for example, it is possible to suppress an increase in electrical resistance due to a reduction in the cross-sectional area of the busbar 10A caused by a concave portion or a closed hole 20h in the surface layer 20.

[Third and Fourth Embodiments]
FIG. 12 is a plan view of a heat exchange member 10B serving as a heat transfer member of the third embodiment, and FIG. 13 is a plan view of a heat exchange member 10C serving as a heat transfer member of the fourth embodiment.

The heat exchange members 10B and 10C as heat transfer members are both members that exchange heat with a fluid F. The fluid F may be a gas, a liquid, or another fluid, such as a multiphase flow. A plurality of surface layers 20 are provided on the surface 10a located at the end of the heat exchange members 10B and 10C in the Z direction. The surface layers 20 each have a configuration similar to that of the first embodiment or the second embodiment. That is, the surface layer 20 may be provided on the surface 10a with a relatively low protruding height from the surface 10a as in the first embodiment, or may be provided in a state where it protrudes from the surface 10a in the Z direction as in the second embodiment. When the fluid F passes through the surface layer 20, it becomes a turbulent flow, and is effectively heat exchanged. In the flat parts between the surface layers 20, it becomes a laminar flow, which contributes to reducing the resistance of the flow path.

In the heat exchange member 10B, the surface layer 20 extends along the flow direction of the fluid F. In this example, the surface layer 20 has a rectangular or elliptical shape in a plan view extending along the flow direction (X direction) of the fluid F, but is not limited to this because it can be suitably designed according to the heat generation amount and flow rate, and may have other shapes such as, for example, an airfoil shape.

In addition, in the heat exchange member 10C, the surface layer 20 is arranged discretely, for example, in a lattice-point shape in a plan view, and the fluid F passes between the surface layers 20. In this example, the surface layer 20 of the heat exchange member 10C has a diamond shape with corners protruding in the flow direction of the fluid F (X direction) and in the opposite direction (opposite to the X direction) in a plan view, but is not limited to this and may have other shapes, such as a circle, since it can be suitably designed according to the heat generation amount and flow rate.

In this way, by providing the surface layer 20 in the heat exchange members 10B, 10C as heat transfer members, the heat flux in the heat exchange between the heat exchange members 10B, 10C and the fluid F is increased compared to when the surface layer 20 is not provided. As a result, the heat exchange members 10B, 10C can be used for applications such as water-cooled heat sinks to lower the temperature of heat generating bodies, and compared to the use of heat dissipation fins or heat dissipation pins, advantages can be obtained in terms of miniaturization and manufacturing costs.

[Fifth embodiment]
FIG. 14 is a cross-sectional view of a boiling cooling device 30 having a boiling heat transfer member 10D as a heat transfer member.

In FIG. 14, the boiling cooling device 30 comprises a chamber 31 having a heat receiving section 32 and a heat dissipating section 33. The chamber 31 has a hollow shape, and a refrigerant 34 in a liquid phase is contained within the chamber 31. The heat receiving section 32 is positioned vertically below the heat dissipating section 33, and the heat receiving section 32 and the heat dissipating section 33 are in communication with each other via an intermediate opening 35. The refrigerant 34 is sealed within the chamber 31, which is in a substantially vacuum state. In addition, a cooling fluid piping 36 is provided within the heat dissipating section 33.

An opening 32a is provided at the bottom of the heat receiving portion 32, and the opening 32a is sealed in an airtight and liquidtight state by a boiling heat transfer member 10D as a heat transfer member. The boiling heat transfer member 10D is thermally connected to the heating element H via a heat spreader 37.

The surface 10a of the boiling heat transfer member 10D is provided with a surface layer 20 similar to that of the first embodiment. The surface layer 20 is exposed in the chamber 31 and is in contact with the refrigerant 34.

In the above-mentioned boiling cooling device 30, heat from the heat generating body H is transferred to the refrigerant 34 through the heat spreader 37 and the surface layer 20 of the boiling heat transfer member 10D. The refrigerant 34 boils and becomes bubbles at the part in contact with the surface layer 20 of the boiling heat transfer member 10D, and is released into the liquid phase refrigerant 34. The bubbles rise in the liquid phase refrigerant 34 to the heat dissipation section 33, where they dissipate heat to the cooling fluid flowing in the cooling fluid piping 36, re-liquefy, and return to the heat receiving section 32. By repeating such an operation, the heat from the heat generating body H is transported to the heat dissipation section 33 through the refrigerant 34, and is dissipated from the heat dissipation section 33. According to this embodiment, the surface layer 20 increases the heat flux in the heat transfer from the boiling heat transfer member 10D to the refrigerant 34, thereby improving the efficiency of the boiling cooling device 30.

Although the above describes an embodiment of the present invention, the above embodiment is merely an example and is not intended to limit the scope of the invention. The above embodiment can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the specifications of each configuration, shape, etc. (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, etc.) can be modified as appropriate.

The present invention can be applied to heat transfer members and methods for manufacturing heat transfer members.

10...Heat transfer member 10A...Bus bar (heat transfer member)
10B...Heat exchange member (heat transfer member)
10C...Heat exchange member (heat transfer member)
10D...Boiling heat transfer member (heat transfer member)
10a... surface (front surface)
10b...end 10c...through hole 10d...surface 10e...projection 20...surface layer 20b...closed hole 20h...closed hole 20p...projection 20t...tip 30...boiling cooling device 31...chamber 32...heat receiving portion 32a...opening 33...heat dissipation portion 34...refrigerant 35...intermediate opening 36...cooling fluid piping 37...heat spreader 100...processing system 110...laser device 120...optical head 121...collimating lens 122...condensing lens 130...optical fiber 140...holding member 200...case L...laser light L1...first layer (projection layer)
L2...Second layer (closed pore layer)
Lx, Lz...Length P...Measurement target portion ps1...Spacing ps2...Spacing S1...Step S2...Step s1...First sweep s2...Second sweep R...Machining chamber W...Machining target X...Direction (extension direction, sweep direction, first direction, fourth direction)
Y...direction (extension direction, sweep direction, second direction, third direction)
Z...direction (thickness direction, height direction)

Claims (16)

A heat transfer member which is a busbar made of a conductive metal material and has a surface layer having a porous structure at an end in a first direction and extending across a predetermined section in the first direction, the surface layer having a porous structure crossing the first direction. a surface layer having an irregular uneven structure extending across a predetermined section in the first direction at an end portion in the first direction, the irregular uneven structure intersecting the first direction ;
a solid layer located on the opposite side of the end portion with respect to the surface layer;
Equipped with
A heat transfer member in which the surface layer and the solid layer are part of a single member made of a metallic material. The heat transfer member according to claim 1 or 2, wherein the surface layer has a protrusion layer having more protrusions than closed pores, and a closed pore layer adjacent to the protrusion layer on the opposite side of the first direction and having more closed pores than the protrusions. The heat transfer member according to any one of claims 1 to 3, wherein the porosity of the surface layer is 50% or more and 90% or less. The heat transfer member according to claim 1 , wherein the porosity of the surface layer on the outer side of a center position in a height direction is 50% or more and 80% or less. The heat transfer member according to claim 1 , wherein the porosity of the surface layer on the outer side in the height direction from the surface of the heat transfer member is 50% or more and 90% or less. 7. The heat transfer member according to claim 1 , wherein a surface area increase rate of the surface layer per unit area when projected in a height direction of the surface layer is 110% or more and 300% or less. The heat transfer member according to claim 1 , further comprising a protrusion having the surface layer and protruding in the first direction. The heat transfer member according to claim 2 , wherein the heat transfer member is a bus bar made of a conductive metal material. The heat transfer member according to claim 2 , wherein the heat transfer member is a heat exchange member that exchanges heat with a fluid. The heat transfer member is a boiling heat transfer member,
The heat transfer member according to claim 2 , wherein heat is transferred from a heating element to a refrigerant through said surface layer. A method for producing a heat transfer member according to any one of claims 1 to 11,
A first step of preparing a heat transfer member made of a metal material and having a surface;
a second step of forming the surface layer by irradiating the surface with a laser beam to reattach particles blown off the surface;
The method for manufacturing a heat transfer member comprising the steps of: The method for manufacturing a heat transfer member according to claim 12 , wherein in the second step, an emission unit that emits the laser light and the heat transfer member are moved relatively to sweep the laser light over the surface. A first step of preparing a heat transfer member made of a metal material and having a surface;
a second step of forming a surface layer having a porous structure or an irregularly uneven structure by redepositing the particles blown off from the surface by irradiating the surface with a laser beam;
Equipped with
In the second step,
a laser beam emitting unit that emits the laser beam and the heat transfer member are moved relative to each other to relatively sweep the laser beam on the surface;
a first sweep of the laser light along the surface in a first direction or a direction opposite to the first direction is performed a plurality of times while being shifted by a first interval in the second direction or a direction opposite to the second direction so as to be aligned in a second direction intersecting the first direction;
The method for manufacturing a heat transfer member, wherein the first interval is equal to or smaller than a beam diameter of the laser light. 15. The method for manufacturing a heat transfer member according to claim 14, wherein in the second step, after the first sweep is performed multiple times so as to be aligned in the second direction, a second sweep in a third direction intersecting the first direction along the surface of the laser light or in a direction opposite to the third direction is performed multiple times so as to be aligned in a fourth direction intersecting the third direction, and a second interval of the second sweep in the fourth direction is equal to or less than a beam diameter of the laser light. 15. The method for manufacturing a heat transfer member according to claim 14, wherein in the second step, after the first sweep is performed multiple times so as to be aligned in the second direction, a second sweep in the first direction along the surface of the laser light at a position shifted in the second direction from the first sweep by less than the first interval is performed multiple times so as to be aligned in the second direction.

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