JP7744892B2 - Vapor chamber and method for manufacturing vapor chamber - Google Patents

Description

The present invention relates to a vapor chamber having an internal flow path for a fluid responsible for heat transport, and a method for manufacturing the same.

Heat-generating devices such as central processing units (CPUs) used in mobile devices such as handheld devices and tablet computers are cooled by heat dissipation components such as heat pipes (see, for example, Patent Document 1). In recent years, in order to make mobile devices thinner, there has been a demand for thinner heat dissipation components, and progress is being made in the development of vapor chambers, which can be made thinner than heat pipes.

A vapor chamber is a device that applies the heat transport mechanism of a heat pipe to a flat plate-shaped component (metal sheet). That is, in a vapor chamber, a fluid responsible for heat transport is sealed between two opposing, joined flat plate-shaped components. This fluid circulates while undergoing phase changes, transporting and diffusing heat from the heat source and cooling the heat source.

For example, a vapor chamber has a vapor flow path and a condensate flow path between opposing flat plate-like members, and a fluid responsible for heat transport is sealed in these paths. When the vapor chamber is placed near a heat source, the fluid responsible for heat transport near the heat source receives heat from the heat source and evaporates, becoming a gas (vapor) that travels down the vapor flow path. This allows heat from the heat source to be smoothly transported to a location away from the heat source, resulting in cooling of the heat source.
The gaseous fluid that transports heat from the heat source moves to a position away from the heat source, where it is cooled and condensed as heat is absorbed by the surroundings, changing into a liquid state. The liquid fluid that has changed into a liquid state passes through the condensate flow path, returns to the position of the heat source, and receives heat from the heat source again, evaporating and changing into a gaseous state.
By circulating the heat generated from the heat source as described above, the heat is transported to a location away from the heat source, and the heat source is cooled.

The joining of the opposing flat plate-shaped members is often achieved by diffusion bonding (see, for example, Patent Document 1), brazing (see, for example, Patent Document 2), or welding (see, for example, Patent Document 3).

Japanese Patent Application Laid-Open No. 2016-205693 Japanese Patent Application Laid-Open No. 2007-212028 JP 2012-132582 A

After joining the flat plate-shaped components, an optical identification structure that acts as an ID may be formed on the front or back of each of the flat plate-shaped vapor chambers in the process of being formed. The ID information held by the optical identification structure formed for each vapor chamber in the process of being formed is unique. This is because it is necessary to clearly distinguish each vapor chamber in the process of being formed in order to correlate it with lot management, the air pressure conditions when injecting the fluid responsible for heat transport, and the inspection results for the amount of fluid injected.

The optical identification structure is formed by inkjet printing or laser printing or engraving on the front or back of the vapor chamber during its formation, and the optical identification structure thus formed can often be read visually or by optical means such as a camera, scanner, or reader.

Figure 12(a) shows a top view of an example in which an optical identification structure 901 acting as an ID is formed as a QR code (registered trademark) on the upper surface 920b of the upper metal sheet 920. A QR code, which is the optical identification structure 901, is formed for each vapor chamber 900, and the ID information held by each optical identification structure 901 (QR code) is individually different. This makes it possible to individually identify each vapor chamber 900.

When the optical identification structure 901 is a QR code, it is generally preferable that the length of one side be 1 mm or more. This is because if each cell inside the QR code is a certain size or larger, it is less susceptible to variations in the formation of the optical identification structure 901 that forms the QR code, or the surface condition of the upper surface 920b of the upper metal sheet 920 or the lower surface 910b of the lower metal sheet 910 on which it is formed, allowing for more stable reading.

If the optical identification structure 901 can be accurately read by visual inspection or optical means such as a camera, scanner, or reader, the ID information contained in the optical identification structure 901 can be used to reliably and easily associate the air pressure conditions when injecting the heat transport fluid, the inspection results for the amount of fluid injected, or the functional inspection results after sealing with each vapor chamber 900, or to perform lot management. This prevents the outflow of defective products, enabling stable quality control and providing vapor chambers 900 of high quality. Even in electronic devices equipped with such vapor chambers 900, poor heat dissipation is suppressed, thereby preventing electronic device defects. Furthermore, the position of the optical identification structure 901 makes it easy to distinguish between the front and back, or top and bottom, of the vapor chamber 900, facilitating process management.

As mentioned above, when reading the optical identification structure 901 visually or by optical means such as a camera, scanner, or reader, the relationship between the optical identification structure 901 and the surface of the background material can make it difficult to read the optical identification structure 901. The main cause of this is that the shape of the internal sealed space on the upper surface 920b of the upper metal sheet 920 on which the optical identification structure 901 is formed, or on the lower surface 910b of the lower metal sheet 910, forms a pattern that hinders reading by the optical means.

As mentioned above, when the optical identification structure 901 is a QR code, the length of one side is typically 1 mm or more. Therefore, as shown in Figure 12(a), the optical identification structure 901 does not fit solely within the upper vapor flow path recess 922 or solely within the upper flow path wall 923 in a plan view. Rather, it straddles the boundary between the upper vapor flow path recess 922 and the upper flow path wall 923, or the boundary between the upper vapor flow path recess 922 and the upper peripheral wall 924, i.e., the contour of the upper vapor flow path recess 922, or the contour is located in close proximity to the optical identification structure 901. Figure 12(b) shows a partial cross-sectional conceptual diagram of the vapor chamber 900 (upper metal sheet 920) cut in the short direction at the portion of the upper metal sheet 920 where the optical identification structure 901 acting as an ID is formed. Figure 12(b) is a conceptual cross-sectional view, and therefore differs from the top view of Figure 12(a) in the locations of the optical identification structure 901 and upper steam flow path recess 922. As conceptually shown in Figure 12(b), the presence or absence of the upper steam flow path recess 922 affects the upper surface 920b of the upper metal sheet 920. When reading the optical identification structure 901, the outline of the upper steam flow path recess 922 exists within the reading area, and this outline interferes with reading by the optical means described above.

As described above, the vapor chamber 900 is formed by joining opposing flat plate-like members, and diffusion bonding may be used for this joining. Diffusion bonding involves bringing the flat plate-like members into close contact with each other and applying pressure and heat. However, in the vapor chamber being formed after diffusion bonding, the shape of the internal sealed space may appear as a pattern on the front and back surfaces, which may interfere with reading by the optical means described above. The flat plate-like members have grooves formed therein that serve as the sealed space, i.e., the flow path for the fluid responsible for heat transport. However, the shape (presence or absence of grooves) of the grooves formed on the inside of the flat plate-like members (the joining surface side, the side opposite the front and back surfaces of the vapor chamber being formed) may appear as a pattern on the opposite surface, i.e., the front and back surfaces of the vapor chamber being formed, which may interfere with reading by the optical means described above. The reason why the shape of the grooves (presence or absence of grooves) in flat plate-shaped components affects the opposite surface is thought to be because the thickness of the flat plate-shaped component is very thin, particularly in the areas where grooves are formed, and the degree of minute deformation of the flat plate-shaped component due to pressure applied during diffusion bonding differs slightly between the areas where grooves are formed and the areas where they are not. Brazing is also sometimes used for joining, but similar problems can occur, although the temperature and pressure are different.

In light of the above, the object of the present invention is to provide a vapor chamber of high quality, which has an optical identification structure formed on the front or back surface that acts as an ID, by improving the readability of the optical identification structure when read visually or by optical means such as a camera, scanner, or reader, thereby enabling stable quality control.

The present invention is a flat vapor chamber having an internal flow path for a fluid responsible for heat transport. In plan view, the vapor chamber has a flow path region in which the flow path is formed and a peripheral region surrounding the flow path region, and an optical identification structure that acts as an ID is formed in the peripheral region.

In the above invention, the optical identification structure acting as an ID may be formed via a base layer.

The present invention is a flat vapor chamber having an internal flow path for a fluid responsible for heat transport, in which an optical identification structure acting as an ID is formed via a base layer.

The present invention is a flat vapor chamber having an internal flow path for a fluid responsible for heat transport, in which an optical identification structure acting as an ID is formed on a smooth surface with a maximum height roughness Rz of 1 μm or less.

The present invention is a flat vapor chamber having an internal flow path for a fluid responsible for heat transport, in which an optical identification structure acting as an ID is formed on a smooth surface with a height difference of 30 μm or less between the area with internal space and the area without internal space.

The present invention is a method for manufacturing a flat vapor chamber that has an internal flow path for a fluid responsible for heat transport and is formed with an optical identification structure that acts as an ID. The method for manufacturing a vapor chamber includes, in order, a step of polishing the area where the optical identification structure that acts as an ID will be formed, and a step of forming the optical identification structure that acts as an ID in the polished area.

In the above invention, it is more preferable that the method for manufacturing a vapor chamber is one in which the step of polishing the portion forming the optical identification structure that acts as an ID is a step of polishing so that the maximum height roughness Rz is 1 μm or less.

In the above invention, it is more preferable that the method for manufacturing a vapor chamber is one in which the step of polishing the portion forming the optical identification structure that acts as an ID is a step of polishing so that the difference in height between the portion with an internal space and the portion without an internal space is 30 μm or less.

According to the present invention, in a vapor chamber having an optical identification structure formed on the front or back surface that acts as an ID, the readability of the optical identification structure when read visually or by optical means such as a camera, scanner, or reader is improved, enabling stable management and providing a high-quality vapor chamber.

1A and 1B are a top view and a partial cross-sectional conceptual diagram showing a vapor chamber according to a first embodiment of the present invention; FIG. 2 is a top view illustrating the internal structure of the vapor chamber shown in FIG. 1 . 3 is a cross-sectional view of the vapor chamber of FIG. 2 taken along line AA. FIG. 3 is a top view of the lower metal sheet of FIG. 2 . 3 is a bottom view of the upper metal sheet of FIG. 2; 10A and 10B are a top view and a partial cross-sectional conceptual diagram, respectively, showing a vapor chamber according to a second embodiment of the present invention. FIG. 10 is a top view showing a vapor chamber according to another example of the second embodiment of the present invention. 10A and 10B are a top view and a partial cross-sectional conceptual diagram, respectively, showing a vapor chamber according to a third embodiment of the present invention. 10A and 10B are a top view and a partial cross-sectional conceptual diagram, respectively, showing a vapor chamber according to a fourth embodiment of the present invention. FIG. 10 is a top view showing a vapor chamber according to another example of the fourth embodiment of the present invention. 10A and 10B are partial cross-sectional conceptual diagrams showing a method for manufacturing a vapor chamber according to a fourth embodiment of the present invention. 1A and 1B are a top view and a partial cross-sectional conceptual diagram, respectively, showing a conventional vapor chamber.

Embodiments of the present invention will now be described with reference to the drawings. Note that in the drawings, the scale and aspect ratios have been appropriately altered and exaggerated from those of the actual product for the sake of clarity and ease of understanding.

(First embodiment)
Fig. 1(a) shows a plan view (top view) of a vapor chamber 100 according to a first embodiment of the present invention, as seen from the upper side (surface). In the vapor chamber 100 of Fig. 1(a), an optical identification structure 101 acting as an ID is formed on the upper surface 120b of an upper metal sheet 120. In plan view, the vapor chamber 100 has a flow path region in which a flow path, i.e., an upper vapor flow path recess 122 (lower vapor flow path recess 112), is formed, and a peripheral region surrounding the flow path region, i.e., a region in which an upper peripheral wall 124 (lower peripheral wall 114) is present. In the first embodiment, the optical identification structure 101 is formed in the peripheral region (region in which the upper peripheral wall 124 is present).

In the first embodiment shown in Figure 1(a), when the optical identification structure 101 is formed, the entire optical identification structure 101 is contained within the area (peripheral area) where the upper peripheral wall 124 exists. Figure 1(b) shows a partial cross-sectional conceptual diagram of the vapor chamber 100 (upper metal sheet 120) cut in the short direction at the portion of the upper metal sheet 120 where the optical identification structure 101 acting as an ID is formed. Because Figure 1(b) is a conceptual cross-sectional view, the positions of the optical identification structure 101 and the upper vapor flow path recess 122 are different from the top view of Figure 1(a). Because the entire optical identification structure 101 is contained within the area where the upper peripheral wall 124 exists (peripheral area, i.e., the area where the upper steam flow path recess 122 is not formed), as conceptually shown in Figure 1(b), there is almost no effect from the influence of the upper steam flow path recess 122 extending to the upper surface 120b of the upper metal sheet 120.

In other words, the above-mentioned conventional problem of the outline shape of the upper vapor flow path recess 122 acting as a background pattern and adversely affecting the reading of the optical identification structure 101 can be significantly reduced. This improves the readability of the optical identification structure 101, making it possible to reliably identify defective vapor chambers 100. This prevents the outflow of defective products, enabling stable quality control and providing vapor chambers 100 of good quality. Therefore, even in electronic devices equipped with the vapor chamber 100 of the present invention, poor heat dissipation is suppressed, thereby preventing electronic device defects. Furthermore, the position of the optical identification structure 101 makes it easy to distinguish between the front and back, or top and bottom, of the vapor chamber 100, facilitating process management.

[Configuration of vapor chamber]
2 to 5, the internal structure of the vapor chamber shown in FIG. 1(a) and the internal structure of the metal sheet for the vapor chamber that constitutes the vapor chamber will be described. For simplicity, the optical identification structure that functions as an ID according to the present invention will be omitted from the structural description. The vapor chamber 800 has a sealed space 808 filled with a working fluid 807 as a flow path, and is an apparatus for cooling a device D (cooled device) that generates heat, such as a central processing unit (CPU) used in a mobile terminal such as a portable terminal or tablet terminal, by repeatedly changing phases of the working fluid 807 in the sealed space 808. The vapor chamber 800 has a generally thin, flat plate-like shape.

As shown in Figures 2 and 3, the vapor chamber 800 has a flat plate-like shape and includes a lower metal sheet 810 having an upper surface 810a, and an upper metal sheet 820 having a flat plate-like shape disposed on the lower metal sheet 810. The lower metal sheet 810 and the upper metal sheet 820 both correspond to metal sheets for the vapor chamber. The upper metal sheet 820 has a lower surface 820a (the surface facing the lower metal sheet 810) superimposed on the upper surface 810a (the surface facing the upper metal sheet 820) of the lower metal sheet 810. In the example shown in Figure 2, a device D, which is the object to be cooled, is attached to the lower surface 810b of the lower metal sheet 810 (particularly the lower surface of the evaporation section 811, described below).

A sealed space 808 containing a hydraulic fluid 807 is formed between the lower metal sheet 810 and the upper metal sheet 820. Examples of the hydraulic fluid 807 include pure water, ethanol, methanol, acetone, etc.

The lower metal sheet 810 and the upper metal sheet 820 are joined by diffusion bonding or brazing, as described below. In the embodiment shown in Figures 2 and 3, the lower metal sheet 810 and the upper metal sheet 820 are both formed in a rectangular shape when viewed from above, but this is not limited to this.

Here, a plan view refers to a view of the vapor chamber 800 as seen from a direction perpendicular to the surface that receives heat from the device D (the lower surface 810b of the lower metal sheet 810) and the surface that releases the received heat (the upper surface 820b of the upper metal sheet 820), and corresponds to, for example, a view of the vapor chamber 800 as seen from above (see Figure 2) or below.

When the vapor chamber 800 is installed inside a mobile terminal, the vertical relationship between the lower metal sheet 810 and the upper metal sheet 820 may be disrupted depending on the orientation of the mobile terminal. However, in this invention, the metal sheet that receives heat from device D is referred to as the lower metal sheet 810, and the metal sheet that dissipates the received heat is referred to as the upper metal sheet 820. The following description will be given assuming that the lower metal sheet 810 is positioned on the bottom and the upper metal sheet 820 is positioned on the top. Furthermore, with regard to the front and back surfaces, of the front and back surfaces of the flat-plate-shaped vapor chamber 800, either the top surface 820b of the upper metal sheet 820 or the bottom surface 810b of the lower metal sheet 810 will be referred to as the front surface, and the other will be referred to as the back surface.

As shown in Figure 4, the lower metal sheet 810 has an evaporation section 811 where the working fluid 807 evaporates to generate steam, and a lower steam flow path recess 812 that is provided on the upper surface 810a and has a rectangular shape in a plan view. Of these, the lower steam flow path recess 812 forms part of the sealed space 808 described above, and is configured primarily to allow the steam generated in the evaporation section 811 to pass through.

The evaporation section 811 is disposed within this lower steam flow path recess 812, and the steam within the lower steam flow path recess 812 diffuses away from the evaporation section 811, with most of the steam being transported to the relatively cool peripheral area. The evaporation section 811 is the section where the working fluid 807 within the sealed space 808 evaporates upon receiving heat from device D attached to the underside 810b of the lower metal sheet 810. For this reason, the term evaporation section 811 is not limited to the section overlapping device D, but also includes sections where the working fluid 807 can evaporate even if they do not overlap device D.

As shown in Figures 3 and 4, a plurality of lower flow path walls 813 are provided within the lower steam flow path recess 812 of the lower metal sheet 810, protruding upward (perpendicular to the bottom surface 812a) from the bottom surface 812a (described below) of the lower steam flow path recess 812. In this example, the lower flow path walls 813 are shown extending elongatedly along the longitudinal direction of the vapor chamber 800 (the left-right direction in Figure 4), and include upper surfaces 813a that abut against the lower surfaces 823a of the upper flow path walls 823 (described below). The lower flow path walls 813 are also arranged parallel to each other, spaced apart at equal intervals. In this manner, the vapor of the working fluid 807 flows around the periphery of each lower flow path wall 813, transporting the vapor to the periphery of the lower steam flow path recess 812, thereby preventing the flow of vapor from being obstructed. Furthermore, the lower flow path wall 813 is arranged to overlap the corresponding upper flow path wall 823 (described below) of the upper metal sheet 820 in a plan view, thereby improving the mechanical strength of the vapor chamber 800. The width of the lower flow path wall 813 is, for example, 100 μm to 1500 μm, and the spacing between adjacent lower flow path wall 813 is preferably 100 μm to 2000 μm. Here, the width of the lower flow path wall 813 refers to the dimension of the lower flow path wall 813 in a direction perpendicular to the longitudinal direction of the lower flow path wall 813, which corresponds to the vertical dimension in FIG. 4, for example. Furthermore, the height h0 of the lower flow path wall 813 (in other words, the depth of the lower steam flow path recess 812) (see FIG. 3) is preferably 100 μm to 300 μm.

As shown in Figures 3 and 4, a lower peripheral wall 814 is provided around the periphery of the lower metal sheet 810. The lower peripheral wall 814 is formed to surround the sealed space 808, particularly the lower steam flow path recess 812, and defines the sealed space 808. In addition, lower alignment holes 815 are provided at each of the four corners of the lower peripheral wall 814 in plan view, for aligning the lower metal sheet 810 with the upper metal sheet 820.

The upper metal sheet 820 has substantially the same structure as the lower metal sheet 810, except that it does not have the lower liquid flow path recess 818 described below. The structure of the upper metal sheet 820 is described in more detail below.

As shown in Figures 3 and 5, the upper metal sheet 820 has an upper steam flow path recess 822 provided on its lower surface 820a. This upper steam flow path recess 822 constitutes part of the sealed space 808 and is configured to allow steam generated in the evaporation section 811 to pass through and cool the steam. More specifically, the steam in the upper steam flow path recess 822 diffuses away from the evaporation section 811, and much of the steam is transported to the peripheral area, which has a relatively low temperature. Also, as shown in Figure 3, a housing member H, which constitutes part of the housing of a mobile terminal or the like, is disposed on the upper surface 820b of the upper metal sheet 820. As a result, the steam in the upper steam flow path recess 822 is cooled by outside air via the upper metal sheet 820 and the housing member H.

As shown in Figures 2 and 5, the upper flow path wall 823, upper peripheral wall 824, and upper alignment hole 825 of the upper metal sheet 820 are arranged to overlap the corresponding lower flow path wall 813, lower peripheral wall 814, and lower alignment hole 815 of the lower metal sheet 810 in a plan view, thereby improving the mechanical strength of the vapor chamber 800. It is preferable that the width and height of the upper flow path wall 823 be the same as the width and height h0 of the lower flow path wall 813 described above.

The lower metal sheet 810 and the upper metal sheet 820 are permanently bonded to each other, preferably by diffusion bonding. More specifically, the lower peripheral wall 814 and the upper peripheral wall 824 are bonded to each other. This forms a sealed space 808 between the lower metal sheet 810 and the upper metal sheet 820, sealing the hydraulic fluid 807. Furthermore, each lower flow path wall portion 813 and the corresponding upper flow path wall portion 823 are bonded to each other. This improves the mechanical strength of the vapor chamber 800.

As shown in FIG. 2, the vapor chamber 800 further includes an injection section 809 at one of a pair of longitudinal ends for injecting the working fluid 807 into the sealed space 808. This injection section 809 has a lower injection protrusion 816 protruding from the end face of the lower metal sheet 810 and an upper injection protrusion 826 protruding from the end face of the upper metal sheet 820. A lower injection channel recess 817 is formed on the upper surface of the lower injection protrusion 816, and an upper injection channel recess 827 is formed on the lower surface of the upper injection protrusion 826. The lower injection channel recess 817 is connected to the lower steam channel recess 812, and the upper injection channel recess 827 is connected to the upper steam channel recess 822. The lower injection flow path recess 817 and the upper injection flow path recess 827 form an injection flow path for the hydraulic fluid 807 when the lower metal sheet 810 and the upper metal sheet 820 are joined.

As shown in FIG. 4, a lower liquid flow path recess 818 through which the liquid working fluid 807 passes is provided on the upper surface 813a of each lower flow path wall 813. The lower liquid flow path recess 818 constitutes part of the sealed space 808 described above, and is connected to the lower steam flow path recess 812 and the upper steam flow path recess 822 described above. The lower liquid flow path recess 818 is primarily configured to transport the working fluid 807 condensed from the steam generated in the evaporation section 811 to the evaporation section 811. In this example, the lower liquid flow path recess 818 is shown as an elongated recess extending along the longitudinal direction of the lower flow path wall 813 (the left-right direction in FIG. 3), extending from one end to the other in the longitudinal direction of the lower flow path wall 813. In this way, the liquid working fluid 807 condensed around the periphery of the lower vapor flow path recess 812 and the periphery of the upper vapor flow path recess 822 is transported to the evaporation section 811 by capillary action. A plurality of lower liquid flow path recesses 818 are formed on the upper surface 813a of one lower flow path wall section 813, and the lower liquid flow path recesses 818 are arranged parallel to one another at equal intervals. Although not shown, each lower liquid flow path recess 818 also communicates with the lower vapor flow path recess 812 in the evaporation section 811.

The materials used for the lower metal sheet 810 and the upper metal sheet 820 are not particularly limited as long as they have good thermal conductivity. However, for example, it is preferable that the lower metal sheet 810 and the upper metal sheet 820 be made of copper or a copper alloy. This increases the thermal conductivity of the lower metal sheet 810 and the upper metal sheet 820. This therefore improves the heat transport efficiency of the vapor chamber 800. However, other materials may be used, such as clad materials (SUS/Cu rolled laminates) and plated materials (SUS/Cu plating, Ni plating/rolled copper). In these cases, the strength can be higher than when the lower metal sheet 810 and the upper metal sheet 820 are made of copper or a copper alloy. The lower metal sheet 810 and the upper metal sheet 820 may also be made of different materials. Furthermore, the thickness T0 of the vapor chamber 800 is 0.1 mm to 1.0 mm. Although the case is shown where the thickness T1 of the lower metal sheet 810 and the thickness T2 of the upper metal sheet 820 are equal, this is not limiting, and the thickness T1 of the lower metal sheet 810 and the thickness T2 of the upper metal sheet 820 do not have to be equal.

Second Embodiment
Incidentally, even in the first embodiment in which the optical identification structure 101 is formed in the peripheral region (the region where the upper peripheral wall 124 exists), it may be difficult to read the optical identification structure 101. The reason for this is thought to be that the boundaries (grain boundaries) of the crystal grains of the metal material that makes up the surface of the vapor chamber 100 (the upper surface 120b of the upper metal sheet 120 or the lower surface 110b of the lower metal sheet 110) interfere with reading the optical identification structure 101. As the crystal grains grow due to heating during diffusion bonding, the grain boundaries also become clearer, and it is thought that the fine irregularities caused by the grain boundaries on the surface interfere with reading.

The second embodiment addresses the above-mentioned problem of difficulty in reading the optical identification structure 201, which functions as an ID, due to grain boundaries. The second embodiment of the present invention will be described using Figures 6 and 7. In the second embodiment, the optical identification structure 201 is formed on the upper surface 220b of the upper metal sheet 220 (or the lower surface 210b of the lower metal sheet 210) via a base layer 204. As shown in the top view of Figure 6(a) and Figure 7, the base layer 204 is formed in the base layer formation region 203. In a planar view, the base layer formation region 203 is the region that coincides with the region where the optical identification structure 201 is present, or the region that includes the coincident region plus the surrounding area. At its minimum, the base layer formation region 203 coincides with the region where the optical identification structure 201 is present, and at its maximum, it is the entire surface of the vapor chamber 200 (the upper surface 220b of the upper metal sheet 220 or the lower surface 210b of the lower metal sheet 210), as shown in Figure 7. In other words, the base layer formation region 203 only needs to include an area that, in a plan view, coincides with the area where the optical identification structure 201 is present, and can be determined appropriately taking into account the readability of the optical identification structure 201, the load of forming the base layer 204 (process time, material costs), etc.

Figure 6(b) shows a partial cross-sectional conceptual diagram of the vapor chamber 200 (upper metal sheet 220) cut in the short direction at the portion of the upper metal sheet 220 where the optical identification structure 201 acting as an ID is formed. Because Figure 6(b) is a conceptual cross-sectional view, the positions of the optical identification structure 201 and the upper vapor flow path recess 222 are different from those in the top view of Figure 6(a). As conceptually shown in Figure 6(b), the base layer 204 is formed to cover the fine irregularities caused by the boundaries of the crystal grains (grain boundaries) of the metal material that makes up the top surface 220b of the upper metal sheet 220. Therefore, the influence of these fine irregularities is almost eliminated on the surface of the base layer 204 on which the optical identification structure 201 is formed (the top surface of the base layer 204 in Figure 6(b)).

The underlayer 204 is not particularly limited as long as it functions to mitigate the problem of grain boundaries impeding reading of the optical identification structure 201. However, a material that is significantly different from the optical identification structure 201 during reading is preferable. In other words, any material that makes grain boundaries less recognizable during reading is sufficient, and a material that is significantly different from the optical identification structure 201 is preferable. One example of the underlayer 204 is a single-color printing ink with a large contrast to the optical identification structure 201, uniformly applied to the underlayer formation region 203. In this case, the surface of the vapor chamber 200 is covered with the printing ink, making the grain boundaries difficult to read. This reduces the interference with reading caused by the grain boundaries. Furthermore, the large contrast between the printing ink and the optical identification structure 201 improves the readability of the optical identification structure 201 formed on the printing ink. Furthermore, the printing ink is uniformly applied (i.e., solidly) without any pattern, preventing the printing ink from impeding the readability of the optical identification structure 201.

The method for forming the base layer 204 using the printing ink is not particularly limited as long as it can be formed on the surface (upper surface 220b) of the upper metal sheet 220 or the surface (lower surface 210b) of the lower metal sheet 210, but an example is inkjet printing. The inkjet method allows for easy printing even after the upper metal sheet 220 or the lower metal sheet 210 has been singulated. If the upper metal sheet 220 or the lower metal sheet 210 is in a roll or sheet state before being singulated, offset printing, gravure printing, screen printing, and other methods are also possible. While the above describes the case where the base layer 204 is a printing ink, this is not a limitation. The appropriate base layer 204 largely depends on the method for reading the optical identification structure 201. The base layer 204 may be formed by sublimation transfer, vapor deposition, sputtering, or other methods.

In this embodiment, the optical identification structure 201 is formed on the surface of the vapor chamber 200 via the base layer 204. This reduces the problem of the grain boundaries interfering with reading the optical identification structure 201, improving readability. This makes it possible to more reliably identify defective vapor chambers 200. This prevents the outflow of defective products, enabling stable quality control and providing vapor chambers 200 of high quality. Therefore, even in electronic devices equipped with the vapor chamber 200 of the present invention, poor heat dissipation is suppressed, thereby preventing electronic device defects. Furthermore, the position of the optical identification structure 201 makes it easy to distinguish between the front and back, or top and bottom, of the vapor chamber 200, facilitating process management.

(Third embodiment)
Next, a third embodiment will be described. In the configuration in which the base layer 204 described in the second embodiment is formed, there are many cases in which the optical identification structure 201 does not need to be formed in the peripheral region (the region where the upper peripheral wall 224 exists). This is thought to be because the base layer 204 often also simultaneously improves the above-mentioned conventional problem in which the outline shape of the upper steam flow path recess 222 acts as a background pattern and adversely affects the reading of the optical identification structure 201.

As shown in Figures 8(a) and (b), in the third embodiment, the optical identification structure 301 acting as an ID does not have to be formed in the peripheral region as long as it is formed via the base layer 304. Figure 8(a) is a top view, and Figure 8(b) is a partial cross-sectional conceptual diagram of the vapor chamber 300 (upper metal sheet 320) cut in the short direction at the portion of the upper metal sheet 320 where the optical identification structure 301 acting as an ID is formed. Figure 8(b) is a conceptual cross-sectional view, and therefore differs from the top view of Figure 8(a) in the locations of the optical identification structure 301 and the upper vapor flow path recess 322, etc. As conceptually shown in FIG. 8( b), particularly when the thickness of the base layer 304 is thick, even if the surface of the vapor chamber 300 (the upper surface 320 b of the upper metal sheet 320 or the lower surface 310 b of the lower metal sheet 310) has an uneven contour of the upper vapor flow path recess 322 (lower vapor flow path recess 312), the uneven contour of the upper vapor flow path recess 322 (lower vapor flow path recess 312) hardly appears on the surface of the base layer 304 (the surface opposite to the surface where the base layer 304 contacts the surface of the vapor chamber 300 (the upper surface 320 b of the upper metal sheet 320)). That is, in the third embodiment, the base layer 304 also has the effect of flattening the surface on which the optical identification structure 301 is formed.

In the third embodiment, as in the second embodiment, the base layer formation region 303 only needs to include an area that, in a plan view, coincides with the area where the optical identification structure 301 is present, and may be formed over the entire surface of the vapor chamber 300 (the upper surface 320b of the upper metal sheet 320 or the lower surface 310b of the lower metal sheet 310) as shown in Figure 7. The method for forming the base layer 304 is also the same as that exemplified in the second embodiment.

The third embodiment also has the same effects as those described in the second embodiment. In addition, in the third embodiment, the optical identification structure 301 does not need to be formed in the peripheral region, which increases the degree of freedom in the formation position of the optical identification structure 301. As a result, restrictions on the installation location, etc. of the device that forms the optical identification structure 301 and the device that reads it can be reduced, which also has the effect of making it easier to select and install these devices.

(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to FIGS. 9 and 10 . In the fourth embodiment, an optical identification structure 401 acting as an ID is formed on a smooth surface of the vapor chamber 400 (the upper surface 420 b of the upper metal sheet 420 or the lower surface 410 b of the lower metal sheet 410) with a height difference of 30 μm or less between the portion with an internal space and the portion without an internal space. As shown in the top view of FIG. 9( a) and FIG. 10 , the smooth surface is formed in a smooth surface formation region 405. In a plan view, the smooth surface formation region 405 is a region that coincides with the region where the optical identification structure 401 is present, or a region that includes the coincident region and its surrounding area. In its minimum size, the smooth surface formation region 405 coincides with the region where the optical identification structure 401 is present, and in its maximum size, it is the entire surface of the vapor chamber 400 (the upper surface 420 b of the upper metal sheet 420 or the lower surface 410 b of the lower metal sheet 410) as shown in FIG. That is, the smooth surface forming region 405 only needs to include an area that coincides with the area where the optical identification structure 401 is present in a plan view, and may be determined appropriately in consideration of the readability of the optical identification structure 401, the load (process time) for forming the smooth surface, etc. In this case, it is desirable that the maximum height roughness Rz is 1 μm or less.

Figure 9(b) shows a partial cross-sectional conceptual diagram of the vapor chamber 400 (upper metal sheet 420) cut in the short direction at the portion of the upper metal sheet 420 where the optical identification structure 401 acting as an ID is formed. Because Figure 9(b) is a conceptual cross-sectional view, the positions of the optical identification structure 401 and the upper steam flow path recess 422 are different from those in the top view of Figure 9(a). As conceptually shown in Figure 9(b), the formation of a smooth surface significantly reduces the fine irregularities caused by the boundaries of the crystal grains (grain boundaries) of the metal material constituting the upper surface 420b of the upper metal sheet 420, as well as the influence of the formation of the upper steam flow path recess 422 extending to the upper surface 420b of the upper metal sheet 420. In other words, the formation of a smooth surface results in a maximum height roughness Rz of 1 μm or less, and the difference in height between areas with and without internal space is 30 μm or less.

The smooth surface formed in the smooth surface forming region 405 can be formed, for example, by polishing the surface (upper surface 420b) of the upper metal sheet 420 or the surface (lower surface 410b) of the lower metal sheet 410. Any of chemical polishing, electrolytic polishing, and mechanical polishing can be used as the polishing method. It is possible to polish only the smooth surface forming region 405 by masking the areas not to be polished with resist or the like and then applying chemical polishing or electrolytic polishing. In mechanical polishing, polishing with Emily paper can be followed by buffing with alumina abrasives or the like, varying the particle size of the abrasive. In each polishing method, the polishing conditions can be appropriately determined so that the maximum height roughness Rz is 1 μm or less and the difference in height between the areas with and without internal voids is 30 μm or less.

The height difference between the areas with and without internal space can be confirmed as follows: Using a laser microscope (Keyence Corporation, VK-X250) with an objective lens at 20x magnification, a profile is obtained and the height difference between the peripheral area without internal space and the areas with internal space is measured.

The maximum height roughness Rz of the smooth surface formation region 405 can be measured in accordance with JIS B 0601:2001. An example of a measurement when the smooth surface formation region 405 is formed on the surface (upper surface 420b) of the upper metal sheet 420 is shown below. A laser microscope (Keyence Corporation, VK-X250) is used, and the measurement direction is preferably perpendicular to the upper steam flow path recess 422 and upper flow path wall 423, which extend in an elongated shape along the longitudinal direction of the vapor chamber 400 (left-right direction in Figure 9) in a plan view (the short side direction of the vapor chamber 400 in a plan view (up-down direction in Figure 9)). The maximum height roughness Rz of the smooth surface formation region 405 can be measured using a laser wavelength of 408 nm, an objective lens of 100x or 150x magnification, and other parameters appropriately set.

In the fourth embodiment, the optical identification structure 401 is formed on a smooth surface on the surface of the vapor chamber 400 (the upper surface 420b of the upper metal sheet 420 or the lower surface 410b of the lower metal sheet 410) with a height difference of 30 μm or less between the areas with internal space and the areas without internal space. This significantly reduces the problem of the outline shape of the upper vapor flow path recess 422 acting as a background pattern and adversely affecting the reading of the optical identification structure 401. Therefore, unlike the first embodiment, there is no need to form the optical identification structure 401 in the peripheral region (the region where the upper peripheral wall 424 exists), and it can be formed in any position, as in the third embodiment.

Furthermore, when using the laser printing method and one side of the printing area is 1 mm or more and 3 mm or less, a smooth surface with a maximum height roughness Rz of 1 μm or less can be achieved. This polishing reduces the fine depressions caused by grain boundaries compared to the surface before polishing, significantly reducing the above-mentioned problem of grain boundaries acting as a background pattern and adversely affecting the reading of the optical identification structure 401.

Due to the above effects, even in the fourth embodiment, defective vapor chambers 400 can be reliably identified. This prevents the outflow of defective products, enabling stable quality control and providing vapor chambers 400 of good quality. Therefore, even in electronic devices equipped with the vapor chamber 400 of the present invention, poor heat dissipation is suppressed, thereby preventing defects in the electronic devices. Furthermore, the position of the optical identification structure 401 makes it easy to distinguish between the front and back, or top and bottom, of the vapor chamber 400, facilitating process management.

In the smooth surface of the fourth embodiment, it is preferable that the difference in height between the portion with internal space and the portion without internal space is 30 μm or less, and that the maximum height roughness Rz is 1 μm or less. However, it is also possible to satisfy only one of these conditions. In other words, if the difference in height between the portion with internal space and the portion without internal space is 30 μm or less, the above-mentioned effect of significantly suppressing the adverse effects of the contour shape of the upper steam flow path recess 422 can be achieved, and if the maximum height roughness Rz is 1 μm or less, the above-mentioned effect of significantly suppressing the adverse effects of crystal grain boundaries can be achieved.

Next, an example of a manufacturing method for the vapor chamber 400 in the fourth embodiment will be outlined. The manufacturing method for the vapor chamber 400 in the fourth embodiment includes, at least in this order, a step of polishing the portion where the optical identification structure 401 acting as an ID will be formed, and a step of forming the optical identification structure 401 acting as an ID in the polished portion. Figure 11 shows a partial cross-sectional conceptual diagram of a characteristic step in the fourth embodiment, within an example of a manufacturing method for the vapor chamber 400 in the fourth embodiment. Figure 11 is a partial cross-sectional conceptual diagram of the vapor chamber 400 (upper metal sheet 420) cut in the short direction at the portion of the upper metal sheet 420 where the optical identification structure 401 acting as an ID is formed. Although it is actually joined to the lower metal sheet 410, only the upper metal sheet 420 is shown.

As an example, first prepare a lower metal sheet 410 having a lower steam flow path recess 412 and a lower liquid flow path recess 418 formed therein, and an upper metal sheet 420 having an upper steam flow path recess 422 formed therein.

In this case, a resist film R is first formed on the upper surface of the metal material sheet M. An electrodeposited resist material that can be attached by an electric field is preferably used for the resist film R, but other materials, such as liquid resist materials, may also be used as long as they can form a resist film R on the metal material sheet M.

Next, the resist film R is patterned. In the case of the lower metal sheet 410, resist openings corresponding to the lower steam flow path recesses 412 and the lower liquid flow path recesses 418 are formed in the resist film R using photolithography techniques.

Next, in the half-etching process, the opening portions of the resist film R are half-etched to form the lower steam flow path recess 412, the lower flow path wall 413, and the lower peripheral wall 414. At this time, the lower liquid flow path recess 418 is formed on the upper surface 413a of the lower flow path wall 413. The lower injection flow path recess 417 shown in Figures 2 and 4 is also formed at the same time. Furthermore, the metal material sheet M is etched from the top and bottom surfaces to have the outer contour shape shown in Figure 2, thereby obtaining the predetermined outer contour shape. Note that half-etching refers to etching to form a recess that does not penetrate the material. Therefore, the depth of the recess formed by half-etching is not limited to half the thickness of the lower metal sheet 410. For example, an iron chloride-based etching solution such as a ferric chloride aqueous solution, or a copper chloride-based etching solution such as a copper chloride aqueous solution, can be used as the etching solution.

The resist film R is then removed, yielding a lower metal sheet 410 on which the lower steam flow path recess 412, lower flow path wall 413, lower peripheral wall 414, and lower liquid flow path recess 418 are formed.

Meanwhile, in the same manner as the lower metal sheet 410, the upper metal sheet 420 is half-etched from the lower surface 420a to form the upper steam flow path recess 422, the upper flow path wall portion 423, and the upper peripheral wall 424. In this way, the above-mentioned upper metal sheet 420 is obtained.

Next, the lower metal sheet 410 and the upper metal sheet 420 are joined together. At this time, the lower alignment holes 415 and the upper alignment holes 425 are aligned and temporarily fastened together, and then pressure and heat are applied in this state to permanently bond them together by diffusion bonding.

In this case, the lower metal sheet 410 and the upper metal sheet 420 are first aligned using the lower alignment holes 415 in the lower metal sheet 410 (see Figures 2 and 4) and the upper alignment holes 425 in the upper metal sheet 420 (see Figures 2 and 5). Next, the lower metal sheet 410 and the upper metal sheet 420 are temporarily joined together. The method of temporary joining is not particularly limited, but for example, the lower metal sheet 410 and the upper metal sheet 420 may be temporarily joined together by resistance welding them. In this way, the lower metal sheet 410 and the upper metal sheet 420 are temporarily joined in an aligned state.

After temporary joining, the lower metal sheet 410 and the upper metal sheet 420 are permanently bonded by diffusion bonding (Figure 11(a)). Diffusion bonding is a method in which the lower metal sheet 410 and the upper metal sheet 420 to be joined are brought into close contact with each other, and then, in a controlled atmosphere such as a vacuum or an inert gas, the metal sheets 410, 420 are pressed together in the direction of adhesion and heated, utilizing the atomic diffusion that occurs at the bonding surfaces. In diffusion bonding, the materials of the lower metal sheet 410 and the upper metal sheet 420 are heated to a temperature close to, but lower than, their melting points, preventing the metal sheets 410, 420 from melting and deforming.

Next, the area where the optical identification structure 401 will be formed is polished. That is, chemical polishing is performed on the entire surface of either the upper surface 420b of the upper metal sheet 420 or the lower surface 410b of the lower metal sheet 410, or both, so that the difference in height between the areas with and without internal voids is 30 μm or less and the maximum height roughness Rz is 1 μm or less. Figure 11(b) shows an example of chemical polishing on the entire surface. However, if the smooth surface formation region 405 does not cover the entire surface, chemical polishing can be performed after masking the areas that are not the smooth surface formation region 405 with resist or the like. The chemical polishing liquid can be appropriately selected from nitric acid-sulfuric acid-hydrochloric acid-based polishing liquid (commonly known as Kirinsu liquid), hydrogen peroxide-sulfuric acid-based polishing liquid, phosphoric acid-based polishing liquid, etc. The processing time and liquid temperature are also appropriately set so that the difference in height between the areas with and without internal voids is 30 μm or less and the maximum height roughness Rz is 1 μm or less.

Next, an optical identification structure 401 is formed on the polished portion. That is, the optical identification structure 401 is formed on a portion of the smooth surface formation region 405 (Figure 11(c)). The optical identification structure 401 of the present invention is formed as a structure that can optically read numbers, letters, symbols, two-dimensional codes such as QR codes, or barcodes, and is optically readable by devices such as cameras, scanners, or readers, or visually. The optical identification structure 401 is often formed by inkjet printing, laser printing, or engraving, but the formation method is not limited to these as long as it is optically readable. One example is a QR code printed with an inkjet printer. The ID information held by each of the formed optical identification structures 401 is unique. The ID information is used to clearly distinguish each vapor chamber in the process of being formed by associating it with lot management, air pressure conditions when injecting the fluid responsible for heat transport, and inspection results for the amount of fluid injected.

The sealed space 408 is then depressurized, after which the working fluid 407 is injected into the sealed space 408 through the injection channel formed by the lower injection channel recess 417 and the upper injection channel recess 427. The working fluid 407 is, for example, pure water. Then, for example, a laser is irradiated onto the injection section 409, partially melting the injection section 409 and sealing the injection channel. This completes the vapor chamber 400.

As an example of utilizing the optical identification structure 401 in the above process, during the process of injecting the working fluid 407 and sealing, the optical identification structure 401 (QR code) is read with a scanner, and the amount of working fluid 407 injected, which may vary in each vapor chamber 400, and the actual measured value of the pressure in the sealed space 408 at the time of sealing are associated with each vapor chamber 400. When reading the optical identification structure 401 (QR code) with the scanner as described above, the entire surface on which the optical identification structure 401 is formed is polished to create a smooth surface.

Furthermore, on the smooth surface, the difference in height between areas with internal space and areas without internal space is 30 μm or less. This has the effect of significantly reducing the above-mentioned problem of the outline shape of the upper steam flow path recess 422 acting as a background pattern and adversely affecting the reading of the optical identification structure 401.

Furthermore, the maximum height roughness Rz of the smooth surface is 1 μm or less. This has the effect of significantly reducing the above-mentioned problem of grain boundaries acting as background patterns and adversely affecting the reading of the optical identification structure 401.

In the above process example, the above effects make it possible to reliably identify defective vapor chambers 400. This prevents the outflow of defective products, enabling stable quality control and providing vapor chambers 400 of good quality. Therefore, even in electronic devices equipped with the vapor chamber 400 of the present invention, poor heat dissipation is suppressed, thereby preventing defects in the electronic devices. Furthermore, the position of the optical identification structure 401 makes it easy to distinguish between the front and back, or top and bottom, of the vapor chamber 400, facilitating process management.

Although the above embodiments have been described, the present invention is not limited to the above embodiments. The above embodiments are merely examples, and anything that has substantially the same configuration as the technical concept described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

100, 200, 300, 400, 800, 900 Vapor chamber 101, 201, 301, 401, 901 Optical identification structure 203, 303 Undercoat layer forming region 204, 304 Undercoat layer 405 Smooth surface forming region 407, 807 Working fluid 408, 808 Sealed space 409, 809 Injection section 110, 210, 310, 410, 810, 910 Lower metal sheet 810a Upper surface 110b, 210b, 310b, 410b, 810b, 910b Lower surface 811 Evaporation section 112, 312, 412, 812 Lower vapor flow path recess 812a Bottom surface 413, 813 Lower flow path wall section 413a, 813a Upper surface 114, 414, 814 Lower peripheral wall 415, 815 Lower alignment hole 816 Lower injection protrusion 417, 817 Lower injection channel recess 418, 818 Lower liquid channel recess 120, 220, 320, 420, 820, 920 Upper metal sheet 420a, 820a Lower surface 120b, 220b, 320b, 420b, 820b, 920b Upper surface 122, 222, 322, 422, 822, 922 Upper vapor channel recess 423, 823, 923 Upper channel wall 823a Lower surface 124, 224, 424, 824, 924 Upper peripheral wall 425, 825 Upper alignment hole 826 Upper injection protrusion 427, 827 Upper injection flow path recess D Device H Housing member M Metal material sheet R Resist film

Claims (4)

A flat vapor chamber having a flow path for a fluid responsible for heat transport therein,
an optical identification structure acting as an ID is formed on a surface of the vapor chamber;
A vapor chamber, wherein the optical identification structure is formed on a smooth surface spanning a portion of the surface of the vapor chamber where there is an internal space and a portion where there is no internal space. The vapor chamber described in claim 1, wherein the smooth surface is formed in an area that, in a plan view, coincides with the area where the optical identification structure is present, plus the surrounding area. The vapor chamber of claim 2, wherein the smooth surface is formed over the entire surface of the vapor chamber in a plan view. A method for manufacturing a flat vapor chamber having a flow path for a fluid responsible for heat transport therein,
forming a smooth surface in a region spanning a portion of the surface of the vapor chamber where there is an internal space and a portion where there is no internal space;
and forming an optical identification structure on the smooth surface that acts as an ID.