Vapor chamber and method for manufacturing vapor chamber

Abstract

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 by optical means such as visual inspection, a camera, a scanner, or a reader is improved, thereby enabling stable quality control and providing a vapor chamber of good quality. [Solution] 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 spanning the area of ​​the surface of the vapor chamber where there is internal space and the area where there is no internal space.

Description

[Technical Field]

[0001] The present invention relates to a vapor chamber having a flow path therein for a fluid that transports heat, and a method for manufacturing the same. [Background technology]

[0002] Devices that generate heat, such as central processing units (CPUs) used in mobile devices such as portable terminals and tablet devices, are cooled by heat dissipation members 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 members, and progress has been made in the development of vapor chambers, which can be made thinner than heat pipes.

[0003] A vapor chamber is a device that applies the heat transport mechanism of a heat pipe to a flat metal sheet. In other words, a vapor chamber contains a fluid that transports heat between two opposing, joined flat metal sheets. This fluid circulates and undergoes phase changes, transporting and diffusing heat from the heat source and cooling it.

[0004] 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.

[0005] The joining of the opposing flat plate-like members is often carried out by diffusion bonding (see, for example, Patent Document 1), brazing (see, for example, Patent Document 2), or welding (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-205693 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-212028 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-132582 Summary of the Invention [Problem to be solved by the invention]

[0007] After joining the flat plate-shaped components, an optical identification structure acting as an ID may be formed on the front or back surface of each of the plate-shaped vapor chambers in the process of being formed. The ID information possessed by the formed optical identification structure is unique for each of the vapor chambers in the process of being formed. This is because it is necessary to clearly distinguish each of the vapor chambers 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.

[0008] The optical identification structure is formed by inkjet printing or laser printing or engraving on the front or back surface of the vapor chamber during its formation, and the optical identification structure thus formed is often read by optical means such as visual inspection, a camera, a scanner, or a reader.

[0009] 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 possessed by each optical identification structure 901 (QR code) is individually different. This makes it possible to identify each vapor chamber 900 individually.

[0010] 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 at least a certain size, it is less susceptible to variations in the formation of the optical identification structure 901 that forms the QR code and 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, thereby enabling more stable reading.

[0011] If the optical identification structure 901 can be accurately read by optical means such as visual inspection, a camera, a scanner, or a reader, the ID information possessed by the optical identification structure 901 can be used to reliably and easily associate the pressure conditions when injecting the fluid responsible for heat transport, 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.

[0012] As described above, when reading the optical identification structure 901 by optical means such as visual inspection, a camera, a scanner, or a 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.

[0013] As described 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, but 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 outline of the upper vapor flow path recess 922, or the outline is located in the immediate vicinity of 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. 12(b) is a conceptual cross-sectional view, and therefore differs from the top view of FIG. 12(a) in the positions of the optical identification structure 901 and the upper steam flow path recess 922. As conceptually shown in FIG. 12(b), whether or not the upper steam flow path recess 922 is formed 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 hinders reading by the optical means described above.

[0014] That is, as described above, the vapor chamber 900 is formed by bonding opposing flat plate-like members, and diffusion bonding may be used for this bonding. Diffusion bonding involves closely bonding the flat plate-like members together 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 of the member, which may interfere with reading the optical means described above. The flat plate-like members have grooves that serve as the sealed space, i.e., the flow path for the fluid responsible for heat transport. The shape of the grooves (presence or absence of 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 also 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 the optical means described above. The reason why the shape of the grooves (presence or absence of grooves) in the flat plate-like members extends to the opposite surface is presumably because the thickness of the flat plate-like members is very thin, especially in the grooved portions, and the degree of minute deformation of the flat plate-like members due to pressure during diffusion bonding is slightly different between the grooved and non-grooved portions. Brazing is also sometimes used for joining, but similar problems can occur, although the temperature and pressure are different.

[0015] In view of the above, the object of the present invention is to provide a vapor chamber of good quality, which enables stable quality control by improving the readability of the optical identification structure formed on the front or back surface, which acts as an ID, when read by optical means such as visual inspection, a camera, a scanner, or a reader. [Means for solving the problem]

[0016] The present invention is a flat vapor chamber having an internal flow path for a fluid responsible for heat transport, which, in a planar view, 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.

[0017] In the above invention, the optical identification structure acting as an ID may be formed via a base layer.

[0018] 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.

[0019] 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.

[0020] The present invention is a flat vapor chamber having an internal flow path for a fluid that transports heat, in which an optical identification structure that acts as an ID is formed on a smooth surface with a height difference of 30 μm or less between the part with internal space and the part without internal space.

[0021] The present invention is a method for manufacturing a flat vapor chamber that has a flow path for a fluid that transports heat inside and an optical identification structure that acts as an ID, and 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 the ID in the polished area.

[0022] In the above invention, it is more preferable that the method for manufacturing a vapor chamber is such that the step of polishing the portion forming the optical identification structure acting as an ID is a step of polishing so that the maximum height roughness Rz is 1 μm or less.

[0023] 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 that forms the optical identification structure that acts as an ID is a step of polishing so that the difference in height between the portion with internal space and the portion without internal space is 30 μm or less. [Effects of the Invention]

[0024] 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 by optical means such as visual inspection, a camera, a scanner, or a reader is improved, thereby enabling stable management and providing a vapor chamber of good quality. [Brief explanation of the drawings]

[0025] [Figure 1] 1A and 1B are a top view and a partial cross-sectional conceptual diagram, respectively, showing a vapor chamber according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a top view illustrating the internal structure of the vapor chamber shown in FIG. 1. [Figure 3] AA cross-sectional view of the vapor chamber in Figure 2. [Figure 4] Figure 2: Top view of the lower metal sheet. [Figure 5] Underside view of the upper metal sheet of Figure 2. [Figure 6] 1A and 1B 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. [Figure 7] FIG. 10 is a top view showing a vapor chamber according to another example of the second embodiment of the present invention. [Figure 8] 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. [Figure 9] 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. [Figure 10] FIG. 10 is a top view showing a vapor chamber according to another example of the fourth embodiment of the present invention. [Figure 11] 10A and 10B are conceptual cross-sectional views showing a method for manufacturing a vapor chamber according to a fourth embodiment of the present invention. [Figure 12] (a) Top view and (b) partial cross-sectional conceptual diagram showing a conventional vapor chamber. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the scale and aspect ratios of the actual objects have been appropriately changed and exaggerated for the sake of clarity and ease of understanding.

[0027] (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 a 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).

[0028] In the first embodiment shown in Fig. 1(a), the optical identification structure 101 is formed in its entirety within the region (peripheral region) where the upper peripheral wall 124 is present. Fig. 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. Fig. 1(b) is a conceptual cross-sectional view, and therefore differs from the top view of Fig. 1(a) in the positions of the optical identification structure 101 and the upper vapor flow path recess 122, etc. Since the entire optical identification structure 101 is contained within the area where the upper peripheral wall 124 exists (the 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 influence caused by the influence of the formation of the upper steam flow path recess 122 extending to the upper surface 120b of the upper metal sheet 120.

[0029] That is, the above-mentioned conventional problem of the contour 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 alleviated. As a result, the readability of the optical identification structure 101 is improved, and defective vapor chambers 100 can be reliably identified. 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 defects in the electronic devices. 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.

[0030] [Vapor chamber configuration] 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 a device for cooling a heat-generating device D (cooled device) such as a central processing unit (CPU) used in mobile devices such as portable terminals and tablet terminals 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.

[0031] As shown in FIGS. 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 provided 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 on the side of the lower metal sheet 810) superimposed on the upper surface 810a (the surface on the side of the upper metal sheet 820) of the lower metal sheet 810. In the example shown in FIG. 2, a device D, which is an 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, which will be described later).

[0032] 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, and acetone.

[0033] The lower metal sheet 810 and the upper metal sheet 820 are joined by diffusion bonding or brazing, which will be described later. 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 in a plan view, but this is not limiting.

[0034] Here, a planar view refers to a view of the vapor chamber 800 viewed 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 viewed from above (see Figure 2) or from below.

[0035] When vapor chamber 800 is installed inside a mobile terminal, the vertical relationship between lower metal sheet 810 and upper metal sheet 820 may be lost depending on the attitude of the mobile terminal. However, in the present invention, the metal sheet that receives heat from device D is referred to as lower metal sheet 810, and the metal sheet that dissipates the received heat is referred to as upper metal sheet 820, and the description will be given with lower metal sheet 810 arranged on the lower side and upper metal sheet 820 arranged on the upper side. Furthermore, with regard to the front and back sides, of the front and back sides of flat-plate-shaped vapor chamber 800, either the top surface 820b of upper metal sheet 820 or the bottom surface 810b of lower metal sheet 810 will be referred to as the front side, and the other will be referred to as the back side.

[0036] 4, lower metal sheet 810 has evaporation section 811 where working fluid 807 evaporates to generate steam, and lower steam flow path recess 812 that is provided on upper surface 810a and has a rectangular shape in plan view. Of these, lower steam flow path recess 812 constitutes part of sealed space 808 described above, and is configured mainly to allow steam generated in evaporation section 811 to pass through.

[0037] The evaporation section 811 is disposed within this lower vapor flow path recess 812, and the vapor within the lower vapor flow path recess 812 diffuses away from the evaporation section 811, with most of the vapor being transported to the peripheral portion which has a relatively low temperature. The evaporation section 811 is a portion where the working liquid 807 within the sealed space 808 evaporates upon receiving heat from the device D attached to the lower surface 810b of the lower metal sheet 810. For this reason, the term evaporation section 811 is not limited to a portion overlapping the device D, but is used as a concept that also includes a portion where the working liquid 807 can evaporate even if it does not overlap the device D.

[0038] As shown in FIGS. 3 and 4 , a plurality of lower flow path walls 813 are provided in a lower vapor flow path recess 812 of a lower metal sheet 810, protruding upward (in a direction perpendicular to the bottom surface 812a) from a bottom surface 812a (described later) of the lower vapor flow path recess 812. In this example, the lower flow path walls 813 extend in an elongated shape along the longitudinal direction of the vapor chamber 800 (the left-right direction in FIG. 4 ), and include upper surfaces 813a that abut against lower surfaces 823a of upper flow path walls 823 (described later). The lower flow path walls 813 are arranged parallel to each other and spaced apart at equal intervals. In this manner, the vapor of the working fluid 807 flows around the lower flow path walls 813 and is transported to the peripheral edge of the lower vapor flow path recess 812, thereby preventing the flow of the vapor from being obstructed. Furthermore, the lower flow path wall 813 is disposed so as to overlap the corresponding upper flow path wall 823 (described later) 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 interval 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, and corresponds to the dimension in the up-down direction in FIG. 4, for example. Furthermore, the height h0 of the lower flow path wall 813 (in other words, the depth of the lower vapor flow path recess 812) (see FIG. 3) is preferably 100 μm to 300 μm.

[0039] 3 and 4, a lower peripheral wall 814 is provided on the peripheral edge of the lower metal sheet 810. The lower peripheral wall 814 is formed so as to surround the sealed space 808, particularly the lower steam flow path recess 812, and defines the sealed space 808. Furthermore, lower alignment holes 815 for aligning the lower metal sheet 810 and the upper metal sheet 820 are provided at the four corners of the lower peripheral wall 814 in plan view.

[0040] The upper metal sheet 820 has substantially the same structure as the lower metal sheet 810, except that it does not have a lower liquid flow path recess 818, which will be described later. The configuration of the upper metal sheet 820 will be described in more detail below.

[0041] As shown in FIGS. 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 most of the steam is transported to the peripheral portion, which has a relatively low temperature. Also, as shown in FIG. 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.

[0042] 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, respectively, thereby improving the mechanical strength of the vapor chamber 800. Note that the width and height of the upper flow path wall 823 are preferably the same as the width and height h0 of the lower flow path wall 813 described above.

[0043] 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. As a result, a sealed space 808 that seals the hydraulic fluid 807 is formed between the lower metal sheet 810 and the upper metal sheet 820. In addition, 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.

[0044] 2, the vapor chamber 800 further includes an injection portion 809 at one of a pair of longitudinal ends for injecting the working fluid 807 into the sealed space 808. The injection portion 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 communicates with the lower steam channel recess 812, and the upper injection channel recess 827 communicates with the upper steam channel recess 822. The lower injection channel recess 817 and the upper injection channel recess 827 form an injection channel for the working fluid 807 when the lower metal sheet 810 and the upper metal sheet 820 are joined together.

[0045] 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 in communication with the lower vapor flow path recess 812 and the upper vapor flow path recess 822 described above. The lower liquid flow path recess 818 is configured mainly to transport the working fluid 807 condensed from the vapor generated in the evaporation section 811 to the evaporation section 811. In this example, the lower liquid flow path recess 818 extends in an elongated shape along the longitudinal direction of the lower flow path wall 813 (the left-right direction in Fig. 3), and extends from one end to the other end in the longitudinal direction of the lower flow path wall 813. In this way, liquid working fluid 807 condensed around the periphery of lower vapor channel recess 812 and the periphery of upper vapor channel recess 822 is transported by capillary action to evaporation section 811. A plurality of lower liquid channel recesses 818 are formed on the upper surface 813a of one lower channel wall section 813, and each lower liquid channel recess 818 is arranged parallel to one another at equal intervals. Although not shown, each lower liquid channel recess 818 also communicates with lower vapor channel recess 812 in evaporation section 811.

[0046] 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, the lower metal sheet 810 and the upper metal sheet 820 are preferably 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 increases the heat transport efficiency of the vapor chamber 800. However, the materials are not limited to the above, and may be metal materials in which different metals are laminated, such as clad materials (SUS / Cu rolled laminated materials) and plated materials (SUS / Cu plated, Ni plated / rolled copper). In these cases, the strength can be higher than when made of copper or a copper alloy. Furthermore, the lower metal sheet 810 and the upper metal sheet 820 may 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 where the thickness T1 of the lower metal sheet 810 and the thickness T2 of the upper metal sheet 820 are equal is shown, this is not limited thereto, 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.

[0047] (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 crystal grain boundaries also become clearer, and it is thought that the fine irregularities caused by the grain boundaries on the surface interfere with reading.

[0048] 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 with reference to FIGS. 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 FIG. 6(a) and FIG. 7, the base layer 204 is formed in a base layer formation region 203. In a plan view, the base layer formation region 203 is a region that coincides with the region where the optical identification structure 201 is present, or a region that includes the coincident region and its surrounding area. In its minimum size, the base layer formation region 203 coincides with the region where the optical identification structure 201 is present, and in its maximum size, 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 FIG. 7. In other words, the base layer formation area 203 only needs to include an area that, when viewed in a plane, 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 and the load of forming the base layer 204 (process time, material cost), etc.

[0049] 6(b) shows a partial cross-sectional conceptual diagram of the vapor chamber 200 (upper metal sheet 220) cut in the short direction at a portion of the upper metal sheet 220 where the optical identification structure 201 acting as an ID is formed. Because FIG. 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 FIG. 6(a). As shown conceptually in FIG. 6(b), the base layer 204 is formed so as to cover minute irregularities caused by the boundaries of crystal grains (grain boundaries) of the metal material that constitutes the top surface 220b of the upper metal sheet 220. Therefore, the influence of these minute 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 FIG. 6(b)).

[0050] The underlayer 204 is not particularly limited as long as it has the function of reducing the problem of the crystal grain boundaries impeding reading of the optical identification structure 201, but preferably has a large difference from the optical identification structure 201 during reading. In other words, it is sufficient if it has the function of making the crystal grain boundaries difficult to recognize during reading, and preferably has a large difference from the optical identification structure 201. One example of the underlayer 204 is one in which a single-color printing ink with a large contrast to the optical identification structure 201 is 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 crystal grain boundaries difficult to read. In other words, the obstruction to reading caused by the crystal grain boundaries is reduced. 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.

[0051] 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, and is, for example, 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 description deals with the case where the base layer 204 is a printing ink, this is not limiting. 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.

[0052] In this embodiment, the optical identification structure 201 is formed on the surface of the vapor chamber 200 via the base layer 204. Therefore, when reading the optical identification structure 201, the problem of the grain boundaries interfering with reading can be alleviated, improving readability. Therefore, defective vapor chambers 200 can be identified more reliably. 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.

[0053] (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.

[0054] 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 positions of the optical identification structure 301 and the upper vapor flow path recess 322, etc. 8(b), particularly when the thickness of the base layer 304 is thick, even if there are irregularities in the contour shape of the upper vapor channel recess 322 (lower vapor channel recess 312) on the surface of the vapor chamber 300 (upper surface 320b of the upper metal sheet 320 or lower surface 310b of the lower metal sheet 310), the irregularities in the contour shape of the upper vapor channel recess 322 (lower vapor channel recess 312) hardly appear 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 (upper surface 320b of the upper metal sheet 320)). That is, in the third embodiment, the base layer 304 also has the effect of flattening the target surface on which the optical identification structure 301 is formed.

[0055] In the third embodiment, as in the second embodiment, the base layer formation region 303 only needs to include an area that coincides with the area where the optical identification structure 301 is present in a plan view, 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 Fig. 7. The method of forming the base layer 304 is also the same as that exemplified in the second embodiment.

[0056] 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. This reduces restrictions on the installation position, etc., of the device that forms the optical identification structure 301 and the device that reads it, which also has the effect of making it easier to select and install these devices.

[0057] (Fourth embodiment) A fourth embodiment of the present invention will be described using 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 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 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 420b of the upper metal sheet 420 or the lower surface 410b 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.

[0058] FIG. 9(b) shows a partial cross-sectional view of the vapor chamber 400 (upper metal sheet 420) cut in the short direction at a portion of the upper metal sheet 420 where the optical identification structure 401 acting as an ID is formed. Because FIG. 9(b) is a conceptual cross-sectional view, the positions of the optical identification structure 401 and the upper vapor flow path recess 422 are different from those in the top view of FIG. 9(a). As shown conceptually in FIG. 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 and the influence of the formation of the upper vapor 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 reduces the maximum height roughness Rz to 1 μm or less, and the difference in height between the portion with internal space and the portion without internal space to 30 μm or less.

[0059] 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 may be followed by buffing with alumina abrasive grains or the like, varying the grain size of the abrasive grains. In each polishing method, the polishing conditions may 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.

[0060] The height difference between the area with internal space and the area without internal space can be confirmed as follows: A laser microscope (Keyence Corporation, VK-X250) is used to obtain a profile with an objective lens of 20x magnification, and the height difference between the peripheral area without internal space and the area with internal space is measured.

[0061] The maximum height roughness Rz of the smooth surface forming region 405 can be measured based on JIS B 0601:2001. An example of measurement when the smooth surface forming 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 the upper flow path wall 423, which extend in an elongated shape along the longitudinal direction of the vapor chamber 400 (left-right direction in FIG. 9 ) in a plan view (the short side direction of the vapor chamber 400 in a plan view (up-down direction in FIG. 9 )). The maximum height roughness Rz of the smooth surface forming region 405 can be measured using a laser wavelength of 408 nm, an objective lens with a magnification of 100x or 150x, and other parameters appropriately set.

[0062] In the fourth embodiment, the optical identification structure 401 is formed on a smooth surface of 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 portion with an internal space and the portion without an internal space, which significantly reduces the above-mentioned problem that the outline shape of the upper vapor flow path recess 422 acts as a background pattern and adversely affects 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.

[0063] Furthermore, when the laser printing method is used 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 obtained. This polishing makes it possible to reduce the fine depressions caused by grain boundaries compared to the surface before polishing, and significantly reduces the above-mentioned problem of the grain boundaries appearing as a background pattern and adversely affecting the reading of the optical identification structure 401.

[0064] 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.

[0065] 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. That is, 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 obtained, 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 obtained.

[0066] Next, an example of a manufacturing method for the vapor chamber 400 according to the fourth embodiment will be outlined. The manufacturing method for the vapor chamber 400 according to the fourth embodiment includes, at least in this order, a step of polishing a portion where the optical identification structure 401 acting as an ID is to be formed, and a step of forming the optical identification structure 401 acting as an ID in the polished portion. FIG. 11 shows a partial cross-sectional conceptual diagram of a characteristic step in the fourth embodiment, among the example of a manufacturing method for the vapor chamber 400 according to the fourth embodiment. FIG. 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 the upper metal sheet 420 is actually joined to the lower metal sheet 410, only the upper metal sheet 420 is shown.

[0067] As an example, first, a lower metal sheet 410 in which a lower steam flow path recess 412 and a lower liquid flow path recess 418 are formed, and an upper metal sheet 420 in which an upper steam flow path recess 422 is formed are prepared.

[0068] In this case, first, a resist film R is formed on the upper surface of the metal material sheet M. For the resist film R, an electrodeposited resist material that can be adhered by an electric field can be suitably used, but other materials such as a liquid resist material may also be used as long as the resist film R can be formed on the metal material sheet M.

[0069] Subsequently, the resist film R is patterned. In the case of the lower metal sheet 410, resist openings corresponding to the lower vapor flow path recesses 412 and lower liquid flow path recesses 418 are formed in the resist film R by photolithography.

[0070] Subsequently, in a half-etching process, the opening portions of the resist film R are half-etched to form a lower vapor channel recess 412, a lower channel wall 413, and a lower peripheral wall 414. At this time, a lower liquid channel recess 418 is formed on the upper surface 413a of the lower channel wall 413. A lower injection channel recess 417 shown in FIGS. 2 and 4 is also simultaneously formed. Furthermore, the metal material sheet M is etched from the upper and lower surfaces to have the outer contour shape shown in FIG. 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.

[0071] Thereafter, the resist film R is removed, and the lower metal sheet 410 is obtained, on which the lower vapor flow path recess 412, the lower flow path wall 413, the lower peripheral wall 414, and the lower liquid flow path recess 418 are formed.

[0072] 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 423, and the upper peripheral wall 424. In this manner, the above-described upper metal sheet 420 is obtained.

[0073] Next, the lower metal sheet 410 and the upper metal sheet 420 are bonded 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.

[0074] In this case, first, the lower metal sheet 410 and the upper metal sheet 420 are aligned using the lower alignment holes 415 (see FIGS. 2 and 4) in the lower metal sheet 410 and the upper alignment holes 425 (see FIGS. 2 and 5) in the upper metal sheet 420. Next, the lower metal sheet 410 and the upper metal sheet 420 are temporarily joined together. The method of temporarily joining is not particularly limited, and for example, the lower metal sheet 410 and the upper metal sheet 420 may be temporarily joined together by resistance welding the lower metal sheet 410 and the upper metal sheet 420. In this way, the lower metal sheet 410 and the upper metal sheet 420 are temporarily joined together in an aligned state.

[0075] After the temporary joining, the lower metal sheet 410 and the upper metal sheet 420 are permanently joined by diffusion bonding (FIG. 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, thereby utilizing the atomic diffusion that occurs at the joining 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, which prevents the metal sheets 410, 420 from melting and deforming.

[0076] Next, the area where the optical identification structure 401 will be formed is polished. Specifically, 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 is chemically polished 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. An example of chemical polishing of the entire surface is shown in FIG. 11(b). However, if the smooth surface formation region 405 does not cover the entire surface, the areas other than the smooth surface formation region 405 can be masked with resist or the like before chemical polishing. The chemical polishing solution can be appropriately selected from nitric acid-sulfuric acid-hydrochloric acid-based polishing solutions (commonly known as Kirinsu solution), hydrogen peroxide-sulfuric acid-based polishing solutions, phosphoric acid-based polishing solutions, and the like. The processing time and solution temperature are 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.

[0077] Next, an optical identification structure 401 is formed on the polished portion. That is, the optical identification structure 401 is formed in a part of the smooth surface formation region 405 (FIG. 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 printing using an inkjet method, 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 formed optical identification structure 401 has unique ID information. The ID information is used to clearly identify each vapor chamber in the process of being formed by associating it with lot management, air pressure conditions when injecting a fluid responsible for heat transport, and inspection results for the amount of fluid injected.

[0078] Next, the sealed space 408 is decompressed, and then 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. Thereafter, for example, a laser is irradiated onto the injection portion 409 to partially melt the injection portion 409 and seal the injection channel. This completes the vapor chamber 400.

[0079] As an example of utilizing the optical identification structure 401 in the above process, in the process of injecting the working liquid 407 and sealing, the optical identification structure 401 (QR code) is read with a scanner, and the amount of working liquid 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 a scanner as described above, the surface on which the optical identification structure 401 is formed is polished entirely to form a smooth surface.

[0080] On the smooth surface, the difference in height between the areas with internal spaces and the areas without internal spaces is 30 μm or less, which has the effect of significantly reducing the above-mentioned problem that the outline shape of upper vapor flow path recess 422 acts as a background pattern and adversely affects the reading of optical identification structure 401.

[0081] Furthermore, the smooth surface has a maximum height roughness Rz of 1 μm or less, which has the effect of significantly reducing the above-mentioned problem that the grain boundaries act as background patterns and adversely affect the reading of the optical identification structure 401.

[0082] In the above process example, the above effects allow for reliable identification of 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.

[0083] Although the embodiments have been described above, the present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0084] 100, 200, 300, 400, 800, 900 Vapor Chamber 101, 201, 301, 401, 901 Optical identification structure 203, 303 Base layer formation area 204, 304 Base layer 405 Smooth surface formation area 407, 807 hydraulic fluid 408, 808 Sealed space 409, 809 Injection part 110, 210, 310, 410, 810, 910 Lower metal sheet 810a top side 110b, 210b, 310b, 410b, 810b, 910b Bottom 811 Evaporation section 112, 312, 412, 812 Lower steam passage recess 812a Bottom 413, 813 Lower channel wall 413a, 813a top surface 114, 414, 814 Lower peripheral wall 415, 815 Lower alignment holes 816 Lower injection protrusion 417, 817 Lower injection channel recess 418, 818 Lower liquid flow path recess 120, 220, 320, 420, 820, 920 Upper metal sheet 420a, 820a bottom side 120b, 220b, 320b, 420b, 820b, 920b Top 122, 222, 322, 422, 822, 922 Upper steam passage recess 423, 823, 923 Upper channel wall 823a Bottom side 124, 224, 424, 824, 924 Upper peripheral wall 425, 825 Upper alignment holes 826 Upper injection protrusion 427, 827 Upper injection channel recess D Device H Housing material M Metallic material sheet R resist film

Claims

1. 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.

2. The vapor chamber according to claim 1 , wherein the smooth surface is formed in an area that corresponds to an area where the optical identification structure is present and a surrounding area thereof in a plan view.

3. The vapor chamber according to claim 2 , wherein the smooth surface is formed over the entire surface of the vapor chamber in a plan view.

4. 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.

Images