Vapor chambers and electronic devices

Abstract

To provide a metal plate for a vapor chamber capable of ensuring mechanical strength and suppressing deterioration of heat transport performance, a metal strip for a vapor chamber, a vapor chamber, and an electronic device.SOLUTION: Metal plates (10, 20) for a vapor chamber according to the present disclosure are used to manufacture a sheet that covers a space part provided in an intermediate sheet (30) of a vapor chamber (1) in which working fluid is sealed. The metal plates (10, 20) for a vapor chamber are made of SUS316L or SUS316LTA. A ratio of an iron element present on the surface of the metal plates (10, 20) for a vapor chamber is 8.5 atomic% or less.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a metal plate for a vapor chamber, a metal strip for a vapor chamber, a vapor chamber, and an electronic device. [Background technology]

[0002] Electronic devices such as mobile terminals use electronic devices that generate heat. Examples of such electronic devices include central processing units (CPUs), light-emitting diodes (LEDs), and power semiconductors. Examples of mobile terminals include mobile terminals and tablet terminals.

[0003] Such electronic devices are cooled by heat dissipation devices such as heat pipes (see, for example, Patent Document 1). In recent years, there has been a demand for thinner heat dissipation devices in order to make electronic devices thinner. Vapor chambers, which can be made thinner than heat pipes, have been developed as heat dissipation devices. Vapor chambers efficiently cool electronic devices by absorbing the heat of the electronic device and diffusing it inside the sealed working fluid.

[0004] More specifically, the working fluid in the vapor chamber receives heat from the electronic device at a portion (evaporation portion) close to the electronic device. The working fluid that receives the heat evaporates to become working vapor. The working vapor diffuses in a direction away from the evaporation portion in a vapor flow path portion formed in the vapor chamber. The diffused working vapor is cooled and condensed to become working fluid. A liquid flow path portion having a capillary structure (wick) is provided in the vapor chamber. The working fluid flows through the liquid flow path portion and is transported toward the evaporation portion. The working fluid transported to the evaporation portion receives heat again in the evaporation portion and evaporates. In this way, the working fluid circulates through the vapor chamber while repeating phase changes, that is, evaporation and condensation, and diffuses the heat of the electronic device. As a result, the heat dissipation performance of the vapor chamber is improved.

[0005] As electronic devices equipped with vapor chambers become thinner, there is a demand for thinner vapor chambers. For this reason, there is a demand for thinner sheets constituting the vapor chamber. On the other hand, each sheet is also required to ensure mechanical strength. In order to meet these demands, stainless steel, which has relatively high mechanical strength, is sometimes used for the sheet covering the vapor flow path. However, when a sheet made of stainless steel is used, there is a problem that the heat transport performance of the vapor chamber is reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2018 / 221369 Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure aims to provide a metal plate for a vapor chamber, a metal strip for a vapor chamber, a vapor chamber, and an electronic device that can ensure mechanical strength and suppress a decrease in heat transport performance. [Means for solving the problem]

[0008] [1] This disclosure: A metal plate for a vapor chamber used for manufacturing a sheet that defines a space of a vapor chamber in which a working fluid is sealed, comprising: Constructed of SUS316L or SUS316LTA, The ratio of iron elements on the surface of the metal plate for the vapor chamber is 8.5 atomic % or less; It may be a metal plate for a vapor chamber.

[0009] [2] This disclosure: The ratio of the iron element is a ratio obtained by measuring the surface of the metal plate for the vapor chamber by X-ray photoelectron spectroscopy. The metal plate for a vapor chamber may be as described in [1].

[0010] [3] This disclosure: The thickness of the metal plate for the vapor chamber is 5 μm to 30 μm. The metal plate for a vapor chamber may be as described in [1] or [2].

[0011] [4] This disclosure: [1] to [3], The metal plate for the vapor chamber is wound into a cylindrical shape. It may also be a metal strip for a vapor chamber.

[0012] [5] This disclosure: A vapor chamber containing a working fluid, A space portion in which the working fluid is sealed; A first sheet defining the space, The first sheet is made of a metal plate, The metal plate is made of SUS316L or SUS316LTA, the first sheet includes a first exposed surface exposed to the space portion, The ratio of iron element in the first exposed surface is 8.5 atomic % or less. It may be a vapor chamber.

[0013] [6] This disclosure: The ratio of the iron element is a ratio obtained by measuring the first exposed surface by X-ray photoelectron spectroscopy. [5] The vapor chamber may be as described above.

[0014] [7] This disclosure: The thickness of the metal plate is 5 μm to 30 μm. The vapor chamber may be as described in [5] or [6].

[0015] [8] This disclosure: a second sheet defining the space from the opposite side to the first sheet; The second sheet is made of the metal plate, the second sheet includes a second exposed surface exposed to the space portion, The ratio of iron element in the second exposed surface is 8.5 atomic % or less. The vapor chamber may be any one of the vapor chambers described in [1] to [7].

[0016] [9] This disclosure: An intermediate sheet is provided between the first sheet and the second sheet to define the space. [8] The vapor chamber may be as described above.

[0017]

[10] This disclosure relates to: The intermediate sheet is made of oxygen-free copper. [9] The vapor chamber may be as described above.

[0018]

[11] This disclosure relates to: Housing and an electronic device contained within the housing; and a vapor chamber according to any one of [5] to

[10] , which is in thermal contact with the electronic device. It may be an electronic device. Effect of the Invention

[0019] According to the present disclosure, it is possible to ensure mechanical strength and suppress a decrease in heat transport performance. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic perspective view illustrating an electronic device according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a plan view showing the vapor chamber shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4 is a plan view showing the inner surface of the first sheet shown in FIG. [Diagram 5] FIG. 5 is a plan view showing the inner surface of the second sheet shown in FIG. [Figure 6] FIG. 6 is a plan view showing a first intermediate sheet surface of the wick sheet shown in FIG. [Figure 7] FIG. 7 is a plan view showing the second intermediate sheet surface of the wick sheet shown in FIG. [Figure 8] FIG. 8 is a partially enlarged cross-sectional view of FIG. [Figure 9] FIG. 9 is a partial enlarged view of the liquid flow path portion shown in FIG. [Figure 10] FIG. 10 is a schematic diagram for explaining a method for producing a first sheet and a second sheet from the metal strip for a vapor chamber according to this embodiment. [Figure 11] FIG. 11 is a cross-sectional view showing a modification of the vapor chamber shown in FIG. [Figure 12A] FIG. 12A is a cross-sectional view showing a modification of the vapor chamber shown in FIG. [Figure 12B] FIG. 12B is a plan view for explaining the internal structure of the vapor chamber shown in FIG. 12A. [Figure 13] FIG. 13 is a plan view showing temperature measurement points during operational performance check in this embodiment. [Figure 14] FIG. 14 is a side view of FIG. [Figure 15] FIG. 15 is a graph showing the relationship between the iron element ratio and the temperature difference obtained when confirming the operational performance after the reliability test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings attached to this specification, the scale and aspect ratios are appropriately changed and exaggerated from those of the actual objects for the convenience of illustration and understanding.

[0022] The geometric conditions, physical characteristics, terms specifying the degree of the geometric conditions or physical characteristics, and numerical values ​​indicating the geometric conditions or physical characteristics used in this specification may be interpreted without being bound by strict meaning. These geometric conditions, physical characteristics, terms, and numerical values ​​may be interpreted including the range of the degree to which similar functions can be expected. Examples of terms specifying geometric conditions include "length", "angle", "shape", and "arrangement". Examples of terms specifying geometric conditions include "parallel", "orthogonal", and "same". Furthermore, in order to clarify the drawings, the shapes of multiple parts that can be expected to have similar functions are regularly described. However, without being bound by strict meaning, the shapes of the parts may be different from each other within the range in which the functions can be expected. In the drawings, the boundary lines indicating the joint surfaces between members are shown as simple straight lines for convenience, but they are not limited to being strictly straight lines, and the shape of the boundary line is arbitrary within the range in which the desired joint performance can be expected.

[0023] 1 to 9, a metal plate for a vapor chamber, a metal strip for a vapor chamber, a vapor chamber, and an electronic device according to an embodiment of the present disclosure will be described. A vapor chamber 1 according to the present embodiment is accommodated in a housing H of an electronic device E together with an electronic device D that generates heat, and is a device for cooling the electronic device D. Examples of the electronic device E include mobile terminals such as portable terminals and tablet terminals. Examples of the electronic device D include a central processing unit (CPU), a light-emitting diode (LED), and a power semiconductor. The electronic device D may also be referred to as a cooled device.

[0024] Here, first, an electronic device E equipped with the vapor chamber 1 according to the present embodiment will be described by taking a tablet terminal as an example. As shown in FIG. 1, the electronic device E may include a housing H, an electronic device D housed in the housing H, and a vapor chamber 1. In the electronic device E shown in FIG. 1, a touch panel display TD is provided on the front surface of the housing H. The vapor chamber 1 is housed in the housing H and arranged so as to be in thermal contact with the electronic device D. The vapor chamber 1 receives heat generated by the electronic device D when the electronic device E is used. The heat received by the vapor chamber 1 is released to the outside of the vapor chamber 1 via the working fluids 2a and 2b described later, and the electronic device D is effectively cooled. When the electronic device E is a tablet terminal, the electronic device D corresponds to a central processing unit or the like.

[0025] Next, the vapor chamber 1 according to the present embodiment will be described.

[0026] As shown in Figures 2 and 3, the vapor chamber 1 has a sealed space 3 in which working fluids 2a and 2b (see Figure 6) are sealed. The working fluids 2a and 2b in the sealed space 3 repeatedly undergo phase changes, thereby cooling the above-mentioned electronic device D. The working fluids 2a and 2b contain water. Examples of the working fluids 2a and 2b include pure water and a mixture thereof.

[0027] The vapor chamber 1 according to the present embodiment includes a first sheet 10, a second sheet 20, a wick sheet 30, a vapor flow path section 50, and a liquid flow path section 60. The second sheet 20 is located on the opposite side of the wick sheet 30 from the first sheet 10. The wick sheet 30 is an example of an intermediate sheet, and is interposed between the first sheet 10 and the second sheet 20. In the vapor chamber 1 according to the present embodiment, the first sheet 10, the wick sheet 30, and the second sheet 20 are stacked in this order. In the present embodiment, an example in which the wick sheet 30 is composed of one sheet is shown, but the wick sheet 30 may be composed of two or more sheets, and the number of sheets in the wick sheet 30 is arbitrary.

[0028] The vapor chamber 1 shown in FIG. 2 is generally formed in a thin flat plate shape. The planar shape of the vapor chamber 1 is arbitrary, but may be a rectangular shape as shown in FIG. 2. The planar shape of the vapor chamber 1 may be, for example, a rectangle with one side being 1 cm and the other side being 3 cm, or a square with one side being 15 cm. The planar dimensions of the vapor chamber 1 are arbitrary. In this embodiment, an example in which the planar shape of the vapor chamber 1 is a rectangular shape with the X direction described later as the longitudinal direction will be described. In this case, as shown in FIGS. 4 to 7, the first sheet 10, the second sheet 20, and the wick sheet 30 may have the same planar shape as the vapor chamber 1. The planar shape of the vapor chamber 1 is not limited to a rectangular shape, and may be any shape such as a circular shape, an elliptical shape, an L-shape, or a T-shape.

[0029] 2, the vapor chamber 1 has an evaporation region SR where the working fluid 2b evaporates and a condensation region CR where the working vapor 2a condenses. The working vapor 2a is a working fluid in a gaseous state, and the working fluid 2b is a working fluid in a liquid state.

[0030] The evaporation region SR is a region that overlaps with the electronic device D in a planar view and is in contact with the electronic device D. The position of the evaporation region SR is arbitrary. In this embodiment, the evaporation region SR is formed at a position relatively close to one end (the left end in FIG. 2) of the vapor chamber 1 in the X direction. Heat from the electronic device D is transferred to the evaporation region SR, and the working liquid 2b is evaporated by this heat to generate working vapor 2a. The heat from the electronic device D can be transferred not only to the region that overlaps with the electronic device D in a planar view, but also to the periphery of the region that the electronic device D overlaps. Therefore, the evaporation region SR may include the region that overlaps with the electronic device D and the periphery thereof in a planar view.

[0031] The condensation region CR is a region that does not overlap with the electronic device D in a plan view, and is a region where the working vapor 2a mainly releases heat and condenses. The condensation region CR may be a region surrounding the evaporation region SR. In the condensation region CR, heat is released from the working vapor 2a. The working vapor 2a is cooled and condensed, and the working liquid 2b is generated.

[0032] Here, the plan view refers to a state in which the vapor chamber 1 is viewed from a direction perpendicular to the surface that receives heat from the electronic device D and the surface that releases the received heat. The surface that receives heat corresponds to a first sheet outer surface 10a of the first sheet 10, which will be described later. The surface that releases heat corresponds to a second sheet outer surface 20b of the second sheet 20, which will be described later. As shown in FIG. 2, the state in which the vapor chamber 1 is viewed from above or below corresponds to a plan view.

[0033] 3, the first sheet 10 includes a first sheet outer surface 10a located on the opposite side to the wick sheet 30, and a first sheet inner surface 10b facing the wick sheet 30. The above-mentioned electronic device D may be in contact with the first sheet outer surface 10a. A first intermediate sheet surface 30a (described later) of the wick sheet 30 is in contact with the first sheet inner surface 10b.

[0034] The first sheet 10 defines a steam flow path portion 50, which will be described later. The first sheet inner surface 10b includes a first exposed surface 10c exposed to the steam flow path portion 50. More specifically, the first exposed surface 10c is exposed to a first steam passage 51 or a second steam passage 52, which will be described later, and covers the steam passages 51, 52. The first intermediate sheet surface 30a of the wick sheet 30 does not contact the first exposed surface 10c, and the first exposed surface 10c is a portion that contacts the working fluids 2a, 2b.

[0035] As shown in FIG. 3 and FIG. 4, the first sheet 10 is composed of a metal plate for a vapor chamber (hereinafter, simply referred to as a metal plate 40). The first sheet 10 may be formed of a single layer composed of the metal plate 40, and no layer of other material may be formed on the surface of the metal plate 40. In this case, one surface of the metal plate 40 constitutes the first sheet outer surface 10a, and the other surface constitutes the first sheet inner surface 10b. The metal plate 40 will be described in detail later. The first sheet 10 may be formed substantially flat. The first sheet 10 may have a substantially constant thickness.

[0036] 3, the second sheet 20 includes a second sheet inner surface 20a facing the wick sheet 30, and a second sheet outer surface 20b located on the opposite side to the wick sheet 30. A housing member Ha may be in contact with the second sheet outer surface 20b. The housing member Ha is a member that constitutes the housing H. A second intermediate sheet surface 30b (described later) of the wick sheet 30 is in contact with the second sheet inner surface 20a.

[0037] The second sheet 20 defines a steam flow path portion 50 (described later) from the opposite side to the first sheet 10. The second sheet inner surface 20a includes an exposed surface 20c exposed to the steam flow path portion 50. More specifically, the second exposed surface 20c is exposed to the first steam passage 51 or the second steam passage 52 and covers the steam passages 51, 52. The second intermediate sheet surface 30b of the wick sheet 30 does not contact the second exposed surface 20c, and the second exposed surface 20c is the portion that contacts the working fluids 2a, 2b.

[0038] As shown in Figs. 3 and 5, the second sheet 20 is made of a metal plate 40 similar to the metal plate 40 constituting the first sheet 10. The second sheet 20 may be formed of a single layer made of the metal plate 40, and no other material layer may be formed on the surface of the metal plate 40. In this case, one surface of the metal plate 40 constitutes the second sheet inner surface 20a, and the other surface constitutes the second sheet outer surface 20b. The second sheet 20 may be formed substantially flat. The second sheet 20 may have a substantially constant thickness.

[0039] As shown in FIG. 3, the wick sheet 30 has a first intermediate sheet surface 30a and a second intermediate sheet surface 30b located on the opposite side to the first intermediate sheet surface 30a. The first sheet inner surface 10b of the first sheet 10 is in contact with the first intermediate sheet surface 30a. The second sheet inner surface 20a of the second sheet 20 is in contact with the second intermediate sheet surface 30b. The first sheet inner surface 10b of the first sheet 10 and the first intermediate sheet surface 30a of the wick sheet 30 may be diffusion bonded. The first sheet inner surface 10b and the first intermediate sheet surface 30a may be permanently bonded to each other. Similarly, the second sheet inner surface 20a of the second sheet 20 and the second intermediate sheet surface 30b of the wick sheet 30 may be diffusion bonded. The second sheet inner surface 20a and the second intermediate sheet surface 30b may be permanently bonded to each other. The term "permanently joined" is not limited to a strict meaning, but is used to mean that the connection is made to such an extent that the sealed space 3 can be maintained in a sealed state when the vapor chamber 1 is in operation.

[0040] The wick sheet 30 defines a steam flow passage portion 50, which will be described later. More specifically, as shown in FIG. 3, FIG. 6, and FIG. 7, the wick sheet 30 includes a frame body portion 32 and a plurality of land portions 33. The frame body portion 32 defines the steam flow passage portion 50, and is formed in a rectangular frame shape along the X direction and the Y direction in a plan view. The land portion 33 is located within the steam flow passage portion 50, and is located inside the frame body portion 32 in a plan view. The frame body portion 32 and the land portion 33 are portions where the material of the wick sheet 30 remains without being etched in an etching process, which will be described later. A first steam passage 51, through which the working steam 2a flows, is formed between the frame body portion 32 and the adjacent land portion 33. A second steam passage 52, through which the working steam 2a flows, is formed between the adjacent land portions 33.

[0041] The land portion 33 may extend in an elongated shape with the X direction as the longitudinal direction in a plan view. The planar shape of the land portion 33 may be an elongated rectangular shape. The land portions 33 may be positioned parallel to each other. The X direction is an example of a first direction, and corresponds to the left-right direction in Figs. 6 and 7. The Y direction is an example of a second direction, and corresponds to a direction perpendicular to the X direction in a plan view. The Y direction corresponds to the up-down direction in Figs. 6 and 7. The direction perpendicular to each of the X direction and the Y direction is the Z direction. The Z direction corresponds to the up-down direction in Fig. 3 and corresponds to the thickness direction.

[0042] As shown in Fig. 8, the width w1 of the land portion 33 may be, for example, 100 µm to 1500 µm. Here, the width w1 of the land portion 33 is the dimension of the land portion 33 in the Y direction. The width w1 is the dimension in the Y direction, and is the dimension of the land portion 33 on the first intermediate sheet surface 30a and the second intermediate sheet surface 30b. Fig. 8 shows an example in which the width of the land portion 33 on the first intermediate sheet surface 30a is equal to the width of the land portion 33 on the second intermediate sheet surface 30b. However, the width of the land portion 33 on the first intermediate sheet surface 30a and the width of the land portion 33 on the second intermediate sheet surface 30b may be different.

[0043] The frame portion 32 and each land portion 33 are diffusion bonded to the first sheet 10 and also to the second sheet 20. This improves the mechanical strength of the vapor chamber 1. The first intermediate sheet surface 30a and the second intermediate sheet surface 30b of the wick sheet 30 may be formed flat across the frame portion 32 and each land portion 33.

[0044] As shown in FIG. 3, the vapor flow path portion 50 may be provided on the first intermediate sheet surface 30a of the wick sheet 30. The vapor flow path portion 50 is an example of a space portion in which the working fluids 2a and 2b are sealed. The vapor flow path portion 50 may be a flow path through which the working steam 2a mainly passes. The working liquid 2b may also pass through the vapor flow path portion 50. In this embodiment, the vapor flow path portion 50 may extend from the first intermediate sheet surface 30a to the second intermediate sheet surface 30b, or may penetrate the wick sheet 30. The vapor flow path portion 50 may be covered by the first sheet 10 on the first intermediate sheet surface 30a, or may be covered by the second sheet 20 on the second intermediate sheet surface 30b. The second sheet 20 covers the vapor flow path portion 50 from the side opposite to the first sheet 10.

[0045] As shown in FIG. 6 and FIG. 7, the steam flow passage section 50 according to the present embodiment may include a first steam passage 51 and a plurality of second steam passages 52. The first steam passage 51 is formed between the frame body section 32 and the land section 33. The first steam passage 51 is an example of a space peripheral section. The first steam passage 51 is formed inside the frame body section 32 and continuously outside the land section 33. The planar shape of the first steam passage 51 may be a rectangular frame shape along the X direction and the Y direction. The second steam passage 52 is formed between the adjacent land sections 33. The planar shape of the second steam passage 52 may be an elongated rectangular shape. The steam flow passage section 50 is divided into the first steam passage 51 and a plurality of second steam passages 52 by the plurality of land sections 33.

[0046] 3, the first steam passage 51 and the second steam passage 52 include a first steam flow path recess 53 provided in the first intermediate sheet surface 30a and a second steam flow path recess 54 provided in the second intermediate sheet surface 30b. The first steam flow path recess 53 and the second steam flow path recess 54 are in communication with each other.

[0047] The first vapor flow path recess 53 may be formed by etching the first intermediate sheet surface 30a of the wick sheet 30 in an etching step described below. The first vapor flow path recess 53 is formed in a concave shape on the first intermediate sheet surface 30a. As shown in Fig. 8, the width w2 of the first vapor flow path recess 53 may be, for example, 100 µm to 5000 µm. The width w2 is the dimension in the Y direction, and is the dimension of the first vapor flow path recess 53 on the first intermediate sheet surface 30a.

[0048] The second vapor flow path recess 54 may be formed by etching the second intermediate sheet surface 30b of the wick sheet 30 in an etching step described below. The second vapor flow path recess 54 is formed in a concave shape on the second intermediate sheet surface 30b. As shown in Fig. 8, the width w3 of the second vapor flow path recess 54 may be, for example, 100 µm to 5000 µm, similar to the width w2 of the first vapor flow path recess 53 described above. The width w3 is the dimension in the Y direction, and is the dimension of the second vapor flow path recess 54 on the second intermediate sheet surface 30b.

[0049] As shown in Fig. 8, in this embodiment, the cross-sectional shape of the first steam passage 51 and the cross-sectional shape of the second steam passage 52 are formed to include the through-portion 34. The through-portion 34 is defined by a ridge line formed such that the wall surfaces of the steam flow passage recesses 53, 54 protrude inward. However, this is not limited to this. For example, the cross-sectional shape of the first steam passage 51 and the cross-sectional shape of the second steam passage 52 may be a trapezoid or a parallelogram, or may be a barrel shape.

[0050] The steam flow path portion 50 including the first steam passage 51 and the second steam passage 52 configured in this manner constitutes a part of the above-mentioned sealed space 3. Each of the steam passages 51, 52 has a relatively large flow path cross-sectional area so that the working steam 2a can pass through.

[0051] Here, in order to clarify the drawing, Fig. 8 shows an enlarged view of the first steam passage 51 and the second steam passage 52. The number and positions of the steam passages 51, 52 are different from those in Figs. 3, 6, and 7.

[0052] Although not shown, a plurality of support parts for supporting the land parts 33 on the frame part 32 may be provided in each of the steam passages 51, 52. Also, support parts for supporting adjacent land parts 33 may be provided. These support parts may be formed so as not to impede the flow of the working steam 2a diffusing through the steam passage part 50.

[0053] As shown in FIG. 2, the vapor chamber 1 may include an injection section 4 that injects the working fluid 2b into the sealed space 3. The injection section 4 includes an injection passage 36 that communicates with the first vapor passage 51. The position of the injection section 4 is arbitrary. As shown in FIG. 6 and FIG. 7, the injection passage 36 may be formed in a concave shape on the second intermediate sheet surface 30b. Alternatively, the injection passage 36 may be formed in a concave shape on the first intermediate sheet surface 30a. Depending on the configuration of the liquid flow passage section 60 described later, the injection passage 36 may be in communication with the liquid flow passage section 60.

[0054] As shown in FIG. 3 and FIG. 8, the liquid flow path portion 60 may be formed between the first sheet 10 and the wick sheet 30. In this embodiment, the liquid flow path portion 60 is formed on the first intermediate sheet surface 30a of the land portion 33. The liquid flow path portion 60 may be a flow path through which the working fluid 2b mainly passes. The above-mentioned working steam 2a may pass through the liquid flow path portion 60. The liquid flow path portion 60 constitutes a part of the above-mentioned sealed space 3 and communicates with the steam flow path portion 50. The liquid flow path portion 60 is configured as a capillary structure for transporting the working fluid 2b to the evaporation region SR. The liquid flow path portion 60 may also be called a wick. The liquid flow path portion 60 may be formed over the entire first intermediate sheet surface 30a of each land portion 33. Although not shown in FIG. 6 and the like, the liquid flow path portion 60 may be formed in an inner portion of the first intermediate sheet surface 30a of the frame portion 32. Although not shown, a liquid flow path portion may be formed on the second intermediate sheet surface 30b of the land portion 33, and a liquid flow path portion 60 may be formed on the second intermediate sheet surface 30b of the frame portion 32.

[0055] 9, the liquid flow path section 60 is an example of a groove assembly including a plurality of grooves. More specifically, the liquid flow path section 60 includes a plurality of mainstream grooves 61 and a plurality of communication grooves 65. The mainstream grooves 61 and the communication grooves 65 are grooves through which the working fluid 2b passes. The communication grooves 65 communicate with the mainstream grooves 61.

[0056] Each of the main grooves 61 extends in the X direction as shown in Fig. 9. The main grooves 61 have a small flow passage cross-sectional area so that the working fluid 2b flows mainly by capillary action. The flow passage cross-sectional area of ​​the main grooves 61 is smaller than the flow passage cross-sectional area of ​​the vapor passages 51, 52. The main grooves 61 are configured to transport the working fluid 2b condensed from the working steam 2a to the evaporation region SR.

[0057] The mainstream grooves 61 are formed by etching the first intermediate sheet surface 30a of the wick sheet 30 in an etching process described later. As shown in FIG. 8, the width w4 of the mainstream grooves 61 may be smaller than the width w2 of the first vapor flow path recess 53. The width w4 of the mainstream grooves 61 may be, for example, 5 μm to 400 μm. The width w4 refers to the dimension of the mainstream grooves 61 on the first intermediate sheet surface 30a. The width w4 corresponds to the Y-direction dimension of the mainstream grooves 61. The depth h1 of the mainstream grooves 61 may be, for example, 3 μm to 300 μm. The depth h1 corresponds to the Z-direction dimension of the mainstream grooves 61.

[0058] 9, each communication groove 65 extends in a direction different from the X direction. In this embodiment, each communication groove 65 extends in the Y direction and is formed perpendicular to the mainstream grooves 61. Some communication grooves 65 communicate with adjacent mainstream grooves 61. Other communication grooves 65 communicate with the first steam passage 51 or the second steam passage 52 and the mainstream groove 61.

[0059] The communication groove 65 has a small flow passage cross-sectional area so that the working fluid 2b flows mainly by capillary action. The flow passage cross-sectional area of ​​the communication groove 65 is smaller than the flow passage cross-sectional area of ​​the vapor passages 51, 52.

[0060] The communication groove 65 is formed by etching the first intermediate sheet surface 30a of the wick sheet 30 in the etching step described later, similar to the mainstream groove 61. The width w5 of the communication groove 65 may be smaller than the width w2 of the first vapor flow path recess 53. As shown in FIG. 9, the width w5 of the communication groove 65 may be equal to or different from the width w4 of the mainstream groove 61. The width w5 refers to the dimension of the communication groove 65 on the first intermediate sheet surface 30a. The width w5 corresponds to the X-direction dimension of the communication groove 65. The depth of the communication groove 65 may be equal to or different from the depth h1 of the mainstream groove 61.

[0061] The liquid flow path portion 60 includes a plurality of convex portions 64 provided on the first intermediate sheet surface 30a of the wick sheet 30. The convex portions 64 are defined by adjacent main grooves 61 and adjacent communication grooves 65. In a plan view, the convex portions 64 are formed in a rectangular shape such that the X direction is the longitudinal direction. The convex portions 64 are portions where the material of the wick sheet 30 remains without being etched in the etching process described later. The convex portions 64 may be positioned in a staggered manner. More specifically, the convex portions 64 adjacent to each other in the Y direction may be shifted from each other in the X direction. This shift amount may be half the arrangement pitch of the convex portions 64 in the X direction.

[0062] The materials constituting the first sheet 10, the second sheet 20, and the wick sheet 30 are not particularly limited as long as they have a sufficient thermal conductivity to ensure the heat dissipation performance of the vapor chamber 1. For example, each of the sheets 10, 20, and 30 may be made of a metal material.

[0063] The first sheet 10 and the second sheet 20 are made of a metal plate 40. The metal plate 40 is used to manufacture the first sheet 10 and the second sheet 20 that define a vapor flow path portion 50 of the vapor chamber 1 in which the working fluids 2a and 2b are sealed.

[0064] The metal plate 40 may be made of SUS316L or SUS316LTA, which are types of stainless steel. The metal plate 40 may be formed as a single layer made of SUS316L or SUS316LTA. SUS316L and SUS316LTA each contain carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), nickel (Ni), chromium (Cr), and molybdenum (Mo). The content of each element is shown in Table 1. Table 1 is in accordance with JIS G 4304-2012 and JIS G 4305-2012. [Table 1]

[0065] SUS316LTA is obtained by annealing a plate material made of SUS316L while applying a tensile force. TA stands for tension anneal. The material described as SUS316L above is different from SUS316LTA in that it is not tension annealed.

[0066] The ratio of iron element in the surface of the metal plate 40 may be 8.5 atomic % or less. An oxide film is formed on the surface of the metal plate 40 made of SUS316L and the surface of the metal plate 40 made of SUS316LTA. The oxide film is also called a passive film. The oxide film is a film formed by oxidation of chromium, which is a constituent element of SUS316L and SUS316LTA. If the oxide film is not formed densely, it is considered that iron oxide is exposed from a small hole in the oxide film. The ratio of iron element contained in the exposed iron oxide corresponds to the ratio of iron element in the surface of the metal plate 40. By setting the ratio of iron element to 8.5 atomic % or less, the corrosion resistance of the surface of the metal plate 40 can be increased. The ratio of iron element may be 8.0 atomic % or less, or may be 7.5 atomic % or less.

[0067] On the other hand, the ratio of iron element in the surface of the metal plate 40 may be 1.0 atomic % or more. This allows a chromium passivation film to be efficiently formed due to the ionization tendency, thereby improving the corrosion resistance of the surface. The ratio of iron element may be 1.5 atomic % or more, or may be 2.0 atomic % or more.

[0068] Similarly, the ratio of iron elements in the surface of the first sheet 10 formed of the metal plate 40 may be 8.5 atomic% or less, 8.0 atomic% or less, or 7.5 atomic% or less. This ratio of iron elements may be 1.0 atomic% or more, 1.5 atomic% or more, or 2.0 atomic% or more. When the first sheet 10 is in a single state, the ratio of iron elements in both the first sheet outer surface 10a and the first sheet inner surface 10b of the first sheet 10 may be 8.5 atomic% or less, 8.0 atomic% or less, or 7.5 atomic% or less. This ratio of iron elements may be 1.0 atomic% or more, 1.5 atomic% or more, or 2.0 atomic% or more. In the completed state of the vapor chamber 1, the iron element ratio in the first exposed surface 10c of the first sheet 10 described above may be 8.5 atomic% or less, 8.0 atomic% or less, or 7.5 atomic% or less. This iron element ratio may be 1.0 atomic% or more, 1.5 atomic% or more, or 2.0 atomic% or more.

[0069] Similarly, the ratio of the iron element on the surface of the second sheet 20 may be 8.5 atomic% or less, 8.0 atomic% or less, or 7.5 atomic% or less. This ratio of the iron element may be 1.0 atomic% or more, 1.5 atomic% or more, or 2.0 atomic% or more. When the second sheet 20 is in a single state, the ratio of the iron element on both the second sheet inner surface 20a and the second sheet outer surface 20b of the second sheet 20 may be 8.5 atomic% or less, 8.0 atomic% or less, or 7.5 atomic% or less. This ratio of the iron element may be 1.0 atomic% or more, 1.5 atomic% or more, or 2.0 atomic% or more. When the vapor chamber 1 is in a completed state, the ratio of the iron element on the second exposed surface 20c of the second sheet 20 described above may be 8.5 atomic% or less, 8.0 atomic% or less, or 7.5 atomic% or less. This ratio of the iron element may be 1.0 atomic % or more, 1.5 atomic % or more, or 2.0 atomic % or more.

[0070] As described above, the first sheet 10 according to the present embodiment may be formed of a single layer made of the metal plate 40, and a layer of another material may not be formed on the surface of the metal plate 40. On the other hand, if a layer made of another metal material is formed on the surface of the metal plate 40, the detection ratio of the iron element on the surface of the metal plate 40 can be reduced, but in a joining process or the like described below, the other metal material may diffuse into the inside of the metal plate 40. This increases the detection ratio of the iron element on the first exposed surface 10c of the first sheet 10, and the performance of the vapor chamber 1 may be reduced. In contrast, in the present embodiment, the first sheet 10 is made of the metal plate 40, and no layer of another material is formed on the surface of the metal plate 40, so that the detection ratio of the iron element on the first exposed surface 10c can be reduced, and the performance of the vapor chamber 1 can be improved. In addition, if a layer made of another metal material having a thermal expansion coefficient different from that of the metal plate 40 is formed on the surface of the metal plate 40, several problems may be considered. For example, there may be a problem that the first sheet 10 may be warped or that cracks may occur in the first sheet 10. For example, there may be a problem that the efficiency of manufacturing the first sheet 10 from the metal plate 40 may decrease, or the manufacturing cost of the first sheet 10 may increase. However, when the first sheet 10 is formed of a single layer constituted by the metal plate 40 as in this embodiment, these problems can be avoided. The same applies to the second sheet 20, so a detailed description will be omitted.

[0071] The ratio of iron element is a ratio obtained by measuring the surfaces of the first exposed surface 10c and the second exposed surface 20c by X-ray photoelectron spectroscopy. X-ray photoelectron spectroscopy is also called XPS. XPS is a method of measuring the energy distribution of photoelectrons emitted from a sample by irradiating the sample with X-rays to obtain the type and abundance of the constituent elements in a region within a range of several nm from the surface of the sample. The abundance of each constituent element is proportional to the peak area value calculated by integrating the area of ​​the peak corresponding to each constituent element in the spectrum measured by XPS. More specifically, first, the peak area value corresponding to each constituent element is calculated. Next, the total value of the peak area values ​​of each constituent element is calculated. Then, the peak area value of the target constituent element is divided by the total value to calculate the atomic% of the target constituent element. The relationship between the abundance of the constituent element and the peak area value may differ for each constituent element depending on the sensitivity to X-rays, etc. In this case, the peak area value of each constituent element is multiplied by a relative sensitivity coefficient for correcting the difference in sensitivity to calculate a corrected peak area value, and then the above-mentioned total value and atomic % are calculated.

[0072] When measuring the ratio of the iron element in the first exposed surface 10c and the second exposed surface 20c of the vapor chamber 1, the vapor chamber 1 is cut and a part of the first sheet 10 including the first exposed surface 10c is taken out as a sheet piece. Similarly, a part of the second sheet 20 including the second exposed surface 20c is taken out as a sheet piece. The ratio of the iron element is measured at any position on the exposed surfaces 10c, 20c of the taken-out sheet piece by the XPS method described above. When measuring the ratio of the iron element on the surface of the metal plate 40 constituting the first sheet 10 and the second sheet 20, the ratio of the iron element is measured at any position on the surface of the metal plate 40 by the XPS method.

[0073] The wick sheet 30 may include copper or a copper alloy. Copper and copper alloys have good thermal conductivity and corrosion resistance when pure water is used as the working fluid. For example, the wick sheet 30 may be made of oxygen-free copper (C1020). Oxygen-free copper contains 99.96% by weight or more of copper element. Other examples include pure copper, copper alloys containing tin, and copper alloys containing titanium (C1990, etc.). An example of a copper alloy containing tin is phosphor bronze (C5210, etc.). Other examples of materials for the wick sheet 30 include Corson copper alloys (C7025, etc.). Corson copper alloys are copper alloys containing nickel, silicon, and magnesium.

[0074] The thickness t1 of the vapor chamber 1 shown in FIG. 3 may be, for example, 100 μm to 500 μm. By making the thickness t1 100 μm or more, the vapor channel portion 50 can be properly secured. Therefore, the vapor chamber 1 can function properly. On the other hand, by making the thickness t1 500 μm or less, the thickness t1 can be prevented from becoming thick. Therefore, the vapor chamber 1 can be made thin.

[0075] The thickness of the first sheet 10 and the thickness of the second sheet 20 may be thinner than the thickness of the wick sheet 30. In the present embodiment, an example is shown in which the thickness of the first sheet 10 and the thickness of the second sheet 20 are equal. However, this is not limited to the above, and the thickness of the first sheet 10 and the thickness of the second sheet 20 may be different.

[0076] The thickness t2 of the first sheet 10 may be, for example, 5 μm to 100 μm. By setting the thickness t2 to 5 μm or more, the mechanical strength of the first sheet 10 and the long-term reliability of the vapor chamber 1 can be ensured. On the other hand, by setting the thickness t2 to 100 μm or less, the thickness t1 of the vapor chamber 1 can be prevented from becoming thick. The thickness t2 may be 5 μm to 30 μm. By setting the thickness t2 to 30 μm or less, the thickness t1 of the vapor chamber 1 can be made even thinner. In addition, when the vapor chamber 1 is bent due to a narrow installation space or the like, the vapor chamber 1 can be easily bent while maintaining the overall mechanical strength and performance. The thickness t3 of the second sheet 20 may be set to the same thickness t2 of the first sheet 10.

[0077] The thickness t4 of the wick sheet 30 may be, for example, 50 μm to 400 μm. By setting the thickness t4 to 50 μm or more, the vapor flow path portion 50 can be properly secured. Therefore, the vapor chamber 1 can function properly. On the other hand, by setting the thickness t4 to 400 μm or less, the thickness t1 of the vapor chamber 1 can be prevented from becoming thick. Therefore, the vapor chamber 1 can be made thin. The thickness t4 of the wick sheet 30 may be the distance between the first intermediate sheet surface 30a and the second intermediate sheet surface 30b.

[0078] Next, a method for manufacturing the vapor chamber 1 of this embodiment having such a configuration will be described.

[0079] First, in a preparation step, the first sheet 10, the second sheet 20 and the wick sheet 30 are prepared.

[0080] The first sheet 10 uses the above-mentioned metal plate 40. For example, as shown in FIG. 10, a metal strip for a vapor chamber (hereinafter, simply referred to as metal strip 41) in which a long metal plate 40 is wound into a cylindrical shape is prepared. The metal strip 41 is also called a metal coil. The metal plate 40 is pulled out from the metal strip 41 and cut into a desired size at a cutting section 70. In this manner, the first sheet 10 is obtained from the metal plate 40. Alternatively, the metal plate 40 formed in advance in a sheet shape may be cut into a desired size and used for the first sheet 10. The metal plate 40 formed in advance in a sheet shape may be formed into a desired size by etching and used for the first sheet 10. The second sheet 20 can be prepared in the same manner as the first sheet 10.

[0081] The ratio of iron elements on the surface of the metal plate 40 may be 8.5 atomic % or less. For example, the ratio of iron elements on the surface of the metal plate 40 may be measured, and a metal plate 40 having the measured ratio of 8.5 atomic % or less may be selected and used as the first sheet 10 and the second sheet 20.

[0082] The preparation step may include an etching step of the wick sheet 30. More specifically, the wick sheet 30 may be made of a copper plate such as oxygen-free copper. The copper plate may be etched to a desired shape and size. In this way, the wick sheet 30 according to the present embodiment can be obtained. In the etching step, the copper plate may be etched using a patterned resist film (not shown) formed by photolithography technology.

[0083] Next, in a bonding step, the first sheet 10, the wick sheet 30, and the second sheet 20 are permanently bonded together. The sheets 10, 20, and 30 may be bonded together by diffusion bonding.

[0084] Next, in the injection step, the sealed space 3 is evacuated and the working fluid 2b is injected into the sealed space 3 from the injection part 4 (see FIG. 2).

[0085] After the injection step, the above-mentioned injection flow path 36 is sealed as a sealing step. This blocks communication between the sealed space 3 and the outside, and seals the sealed space 3. The sealed space 3 filled with the hydraulic fluid 2b is obtained.

[0086] In this manner, the vapor chamber 1 according to the present embodiment is obtained.

[0087] Next, a method for operating the vapor chamber 1, that is, a method for cooling the electronic device D, will be described.

[0088] The vapor chamber 1 obtained as described above is installed in a housing H of a mobile terminal or the like. When the electronic device D generates heat, the working liquid 2b present in the evaporation region SR receives heat from the electronic device D. The received heat is absorbed as latent heat, the working liquid 2b evaporates, and working vapor 2a is generated. The generated working vapor 2a diffuses in the first vapor passage 51 and the second vapor passage 52 that constitute the sealed space 3 (see the solid line arrows in FIG. 6).

[0089] Then, the working steam 2a in each of the steam passages 51, 52 leaves the evaporation region SR and diffuses into the condensation region CR, which has a relatively low temperature. In the condensation region CR, the working steam 2a is cooled by dissipating heat mainly to the second sheet 20. The heat received by the second sheet 20 from the working steam 2a is transferred to the outside air via the housing member Ha (see FIG. 3).

[0090] The working vapor 2a loses the latent heat absorbed in the evaporation region SR by dissipating heat to the second sheet 20 in the condensation region CR. As a result, the working vapor 2a condenses to generate the working liquid 2b. The working liquid 2b continues to evaporate in the evaporation region SR. Therefore, the working liquid 2b in the condensation region CR of the liquid flow path section 60 is transported toward the evaporation region SR by the capillary action of each mainstream groove 61 (see the dashed arrow in FIG. 6). As a result, the working liquid 2b passes through the communication groove 65 of the liquid flow path section 60 and enters the mainstream groove 61. In this way, each mainstream groove 61 and each communication groove 65 is filled with the working liquid 2b. The filled working liquid 2b obtains a driving force toward the evaporation region SR by the capillary action of each mainstream groove 61, and is smoothly transported toward the evaporation region SR.

[0091] In the liquid flow path section 60, each mainstream groove 61 communicates with the adjacent other mainstream grooves 61 via the corresponding communication grooves 65. This allows the working fluid 2b to flow between the adjacent mainstream grooves 61, suppressing the occurrence of dryout in the mainstream grooves 61. As a result, a capillary action is imparted to the working fluid 2b in each mainstream groove 61, and the working fluid 2b is smoothly transported toward the evaporation region SR.

[0092] The working fluid 2b that has reached the evaporation region SR is again heated by the electronic device D and evaporates. The working vapor 2a that has evaporated from the working fluid 2b passes through the communication groove 65 in the evaporation region SR and moves to the first vapor flow path recess 53 and the second vapor flow path recess 54, which have a large flow path cross-sectional area. The working vapor 2a then diffuses within each of the vapor flow path recesses 53 and 54. In this way, the working fluids 2a and 2b circulate within the sealed space 3 while repeatedly undergoing phase changes, i.e., evaporation and condensation. This causes the heat of the electronic device D to be diffused and released. As a result, the electronic device D is cooled.

[0093] Thus, according to this embodiment, the metal plate 40 used to manufacture the first sheet 10 and the second sheet 20 that define the vapor flow path portion 50 of the vapor chamber 1 is made of SUS316L or SUS316LTA. This improves the mechanical strength of the first sheet 10 and the second sheet 20. This ensures the mechanical strength of the vapor chamber 1. The thickness of the first sheet 10 and the second sheet 20 can also be reduced, allowing the vapor chamber 1 to be made thinner.

[0094] Moreover, according to this embodiment, the ratio of iron elements on the surface of the metal plate 40 is 8.5 atomic % or less. This makes it possible to suppress the amount of exposed iron elements from the oxide film formed on the surface of the metal plate 40, and to increase the corrosion resistance of the surface of the metal plate 40. Therefore, even if the first sheet 10 and the second sheet 20 made using this metal plate 40 come into contact with water as the working fluids 2a and 2b sealed in the vapor chamber 1, the sheets 10 and 20 can be suppressed from corroding. In this case, it is possible to suppress the gas generated by corrosion from staying in the vapor channel portion 50, and it is possible to suppress the diffusion range of the working vapor 2a from being restricted. As a result, it is possible to ensure the mechanical strength of the vapor chamber 1 and suppress the deterioration of the heat transport performance.

[0095] Moreover, according to this embodiment, the wick sheet 30 is made of oxygen-free copper. This can increase the thermal conductivity of the wick sheet 30, improving the heat dissipation performance of the vapor chamber 1. In the etching process of the wick sheet 30, the workability of fine processing of the liquid flow path portion 60 and the like can be improved. Flexibility can be imparted to the wick sheet 30, improving the bendability when the vapor chamber 1 is bent.

[0096] According to the present embodiment, the first sheet 10 is made of a metal plate 40 made of SUS316L or SUS316LTA. This improves the mechanical strength of the first sheet 10. This ensures the mechanical strength of the vapor chamber 1. The thickness of the first sheet 10 can be reduced, and the vapor chamber 1 can be made thinner. Since the mechanical strength of the first sheet 10 is improved, the first sheet 10 can be prevented from entering the main groove 61 and the communication groove 65 of the liquid flow path section 60. This reduces the flow path resistance of the main groove 61 and the flow path resistance of the communication groove 65. The first sheet 10 includes a first exposed surface 10c exposed to the vapor flow path section 50, and the ratio of iron elements in the first exposed surface 10c of the first sheet 10 is 8.5 atomic% or less. This reduces the amount of iron elements exposed from the oxide film formed on the first exposed surface 10c, and improves the corrosion resistance of the first exposed surface 10c. Therefore, even if the first exposed surface 10c comes into contact with water as the working fluids 2a and 2b sealed in the vapor chamber 1, the first exposed surface 10c can be prevented from being corroded. In this case, the gas generated by the corrosion can be prevented from being retained in the vapor channel portion 50, and the diffusion range of the working vapor 2a can be prevented from being restricted. As a result, the mechanical strength of the vapor chamber 1 can be secured and the deterioration of the heat transport performance can be prevented.

[0097] In addition, according to this embodiment, the first sheet 10 is made of the metal plate 40 made of SUS316L or SUS316LTA, so that the corrosion resistance of the first sheet outer surface 10a can be improved. This can suppress the decrease in mechanical strength due to the first sheet 10 becoming brittle, and can improve long-term reliability. The first sheet 10 can also have an electromagnetic wave shielding effect. The electromagnetic wave shielding effect not only efficiently cools the heat source of the electronic device D such as an IC, but also reduces the influence of electromagnetic waves on the electronic device D such as an IC, and can suppress the performance deterioration of the electronic device D such as an IC. Since the density of SUS316L and the density of SUS316LTA are each smaller than the density of copper or a copper alloy, the first sheet 10 can be made lighter. This can suppress the increase in mass even when the thickness of the first sheet 10 is increased or the planar size of the vapor chamber 1 is increased, and the vapor chamber 1 can be made lighter.

[0098] Moreover, according to this embodiment, the second sheet 20 is made of the above-mentioned metal plate 40. This ensures the mechanical strength of the vapor chamber 1. The vapor chamber 1 can also be made thinner. In addition, the amount of iron exposed from the oxide film formed on the second exposed surface 20c of the second sheet 20 can be suppressed, and the corrosion resistance of the second exposed surface 20c can be improved. Therefore, even if the second exposed surface 20c comes into contact with water as the working fluids 2a and 2b sealed in the vapor chamber 1, the second exposed surface 20c can be prevented from corroding. As a result, the mechanical strength of the vapor chamber 1 can be ensured and the deterioration of the heat transport performance can be suppressed.

[0099] Furthermore, according to this embodiment, since the second sheet 20 is made of the above-mentioned metal plate 40, the corrosion resistance of the second sheet outer surface 20b can be improved. This makes it possible to suppress a decrease in mechanical strength due to the second sheet 20 becoming brittle, and improves long-term reliability. The second sheet 20 can also have an electromagnetic wave shielding effect. The weight of the second sheet 20 can also be reduced. This makes it possible to suppress an increase in mass, and reduce the weight of the vapor chamber 1, even if the thickness of the second sheet 20 is increased or the planar size of the vapor chamber 1 is increased.

[0100] In the above-described embodiment, an example in which the first sheet 10 is made of the metal plate 40 and the second sheet 20 is made of the metal plate 40 has been described. However, the embodiment is not limited to this. For example, one of the first sheet 10 and the second sheet 20 may be made of the metal plate 40, and the other may be made of another metal material. The wick sheet 30 may be made of the metal plate 40. For example, the sheet in contact with the electronic device D may be made of copper or a copper alloy, and the sheet not in contact with the electronic device D may be made of the metal plate 40. In the example shown in FIG. 3, the first sheet 10 in contact with the electronic device D may be made of copper or a copper alloy, and the second sheet 20 not in contact with the electronic device D may be made of the metal plate 40. In this case, the thermal conductivity of the first sheet 10 can be increased, and the evaporation efficiency of the working liquid 2b can be improved. Therefore, the heat dissipation performance of the vapor chamber 1 can be improved, and the mechanical strength of the vapor chamber 1 can be improved by the metal plate 40 of the second sheet 20.

[0101] In the above-described embodiment, an example has been described in which the electronic device D is in contact with the first sheet outer surface 10a of the first sheet 10, and the housing member Ha is in contact with the second sheet outer surface 20b of the second sheet 20. However, the embodiment is not limited to this. For example, the housing member Ha may be in contact with the first sheet outer surface 10a, and the electronic device D may be in contact with the second sheet outer surface 20b. In this case, both the first sheet 10 and the second sheet 20 may be made of a metal plate 40, or the first sheet 10 may be made of a metal plate 40 and the second sheet 20 may be made of copper or a copper alloy.

[0102] In the above-described embodiment, the vapor chamber 1 includes the first sheet 10, the second sheet 20, and the wick sheet 30. However, the present invention is not limited to this. For example, as shown in FIG. 11, the vapor chamber 1 may include the first sheet 10 and the second sheet 20, but may not include the wick sheet 30. The first sheet 10 and the second sheet 20 define a vapor flow path 50. The vapor flow path 50 and the liquid flow path 60 that constitute the sealed space 3 are formed between the first sheet 10 and the second sheet 20. The wick sheet 30 is not interposed between the first sheet 10 and the second sheet 20, and the first sheet 10 and the second sheet 20 are directly diffusion-bonded.

[0103] In the example shown in Fig. 11, the first sheet 10 includes a first frame portion 12 and a plurality of first lands 13. A first steam passage 51 is formed between the first frame portion 12 and the adjacent first lands 13, and a second steam passage 52 is formed between the adjacent first lands 13. The second sheet 20 includes a second frame portion 22 and a plurality of second lands 23. A first steam passage 51 is formed between the second frame portion 22 and the adjacent second lands 23, and a second steam passage 52 is formed between the adjacent second lands 23.

[0104] The first frame portion 12 and the second frame portion 22 correspond to the frame portion 32 of the wick sheet 30 shown in Fig. 3 and are diffusion bonded to each other. The first land portion 13 and the second land portion 23 correspond to the land portion 33 of the wick sheet 30 shown in Fig. 3 and are diffusion bonded to each other. The first land portion 13 and the second land portion 23 may extend in an elongated shape with the X direction as the longitudinal direction, similar to the land portion 33.

[0105] In the example shown in FIG. 11, the first vapor flow path recess 53 is formed on the first sheet inner surface 10b of the first sheet 10, and the second vapor flow path recess 54 is formed on the second sheet inner surface 20a of the second sheet 20. The liquid flow path section 60 is formed on the first sheet inner surface 10b. The first vapor flow path recess 53 and the liquid flow path section 60 may be formed by etching the first sheet inner surface 10b of the first sheet 10. The second vapor flow path recess 54 may be formed by etching the second sheet inner surface 20a of the second sheet 20. The liquid flow path section 60 may be formed on the second sheet inner surface 20a instead of the first sheet inner surface 10b.

[0106] At least one of the first sheet 10 and the second sheet 20 may be made of the metal plate 40 described above. In the example shown in FIG. 11, both the first sheet 10 and the second sheet 20 are made of the metal plate 40. However, only the first sheet 10 may be made of the metal plate 40, or only the second sheet 20 may be made of the metal plate 40. For example, the sheet in contact with the electronic device D may be made of copper or a copper alloy, and the sheet not in contact with the electronic device D may be made of the metal plate 40. More specifically, the first sheet 10 in contact with the electronic device D may be made of copper or a copper alloy, and the second sheet 20 not in contact with the electronic device D may be made of the metal plate 40. In this case, the thermal conductivity of the first sheet 10 can be increased, and the evaporation efficiency of the working liquid 2b can be improved. Therefore, the heat dissipation performance of the vapor chamber 1 can be improved, and the mechanical strength of the vapor chamber 1 can be improved by the metal plate 40 of the second sheet 20.

[0107] In the example shown in Fig. 11, the first exposed surface 10c is configured as a wall surface of the first steam flow path recess 53. The first exposed surface 10c is exposed to the steam flow path section 50, is not in contact with the second sheet 20, and is in contact with the working fluids 2a and 2b. Similarly, the second exposed surface 20c is configured as a wall surface of the second steam flow path recess 54. The second exposed surface 20c is exposed to the steam flow path section 50, is not in contact with the first sheet 10, and is in contact with the working fluids 2a and 2b.

[0108] In the example shown in FIG. 11, the liquid flow path portion 60 is formed between the first sheet 10 and the second sheet 20. However, the present invention is not limited to this. For example, as shown in FIG. 12A, the liquid flow path portion 60 does not have to be formed between the first sheet 10 and the second sheet 20. In this case, the wick member 80 may be provided in the vapor flow path portion 50. In the example shown in FIG. 12A, the wick member 80 is located in the sealed space 3. The wick member 80 is formed of a metal mesh or a porous sintered body, and is a member that exhibits capillary action. When the wick member 80 is formed of a metal mesh, the metal mesh may be formed of copper wire or stainless steel wire in a shape such as plain weave, twill weave, plain tatami weave, or twill tatami weave. The wick member 80 is configured to exert a capillary action to provide the working liquid 2b with a driving force toward the evaporation region SR.

[0109] As shown in FIG. 12A, the first land portion 13 may not be formed. The wick member 80 may be disposed in a portion of the sealed space 3 defined by the first sheet 10. The wick member 80 may be directly fixed to the first sheet 10, or may be housed in a case member (not shown) and fixed to the first sheet 10. The steam flow path portion 50 may be configured in a portion of the sealed space 3 defined by the second sheet 20. The second land portion 23 may be formed in a columnar shape or may abut against the wick member 80. The second land portion 23 may be formed in a circular shape in a plan view as shown in FIG. 12B, but the planar shape of the second land portion 23 is arbitrary.

[0110] At least one of the first sheet 10 and the second sheet 20 may be made of the metal plate 40 described above. In the example shown in FIG. 12A, both the first sheet 10 and the second sheet 20 are made of the metal plate 40. However, only the first sheet 10 may be made of the metal plate 40, or only the second sheet 20 may be made of the metal plate 40. For example, the sheet in contact with the electronic device D may be made of copper or a copper alloy, and the sheet not in contact with the electronic device D may be made of the metal plate 40. More specifically, the first sheet 10 in contact with the electronic device D may be made of copper or a copper alloy, and the second sheet 20 not in contact with the electronic device D may be made of the metal plate 40. In this case, the thermal conductivity of the first sheet 10 can be increased, and the evaporation efficiency of the working liquid 2b can be improved. Therefore, the heat dissipation performance of the vapor chamber 1 can be improved, and the mechanical strength of the vapor chamber 1 can be improved by the metal plate 40 of the second sheet 20.

[0111] An example of the vapor chamber 1 configured with the first sheet 10 and the second sheet 20 has been described with reference to Figures 11, 12A, and 12B. However, the form of the vapor chamber 1 having such a configuration is not limited to the form shown in Figures 11, 12A, and 12B, and may be any form.

[0112] The present disclosure is not limited to the above-mentioned embodiment and each modification, and the components can be modified and embodied in the implementation stage without departing from the gist of the present disclosure. In addition, various inventions can be formed by appropriate combinations of the multiple components disclosed in the above-mentioned embodiment and each modification. Some components may be deleted from all the components shown in the embodiment and each modification. EXAMPLES

[0113] Next, the embodiment described with reference to Figures 1 to 10 will be described in more detail with reference to examples with reference to Figures 13 to 15. The above-mentioned embodiment is not limited to the description of the following examples as long as it does not deviate from the gist of the embodiment.

[0114] Seven samples of the metal plate 40 were prepared as shown in Table 2. The material and thickness of each sample are shown in Table 2. [Table 2]

[0115] The ratio of iron element on the surface of each sample was measured using the XPS method described above. The measurement was performed using Quantum2000 manufactured by ULVAC-PHI, Inc. The measurement device settings were as follows: Incident X-ray: monochromated Al kα (Monochromatic X-rays, hv=1486.6eV) X-ray output: 15kV・30W Measurement area: 200μmφ X-ray incidence angle (angle between the direction of photoelectron irradiation from the irradiation part and the surface): 45 degrees Photoelectron capture angle: 90 degrees

[0116] The measurements were taken at two arbitrary points on the same surface of one metal plate 40, and the measurement depth from the surface was several nm. The measurement depth depends on the X-ray power. Measurements were taken at different positions on each sample, and the average of the two measurements was calculated for each sample to obtain the ratios in Table 2.

[0117] Next, the first sheet 10 and the second sheet 20 were made from the metal plate 40 of each sample, and were diffusion bonded to the wick sheet 30. The wick sheet 30 was made by etching a copper plate made of oxygen-free copper (C1020) to form the above-mentioned shape. After the diffusion bonding, pure water as the working fluid was injected into the sealed space 3, and the injection flow path 36 was sealed. In this way, seven samples of vapor chambers 1 with the same shape were obtained.

[0118] Next, an initial operating performance confirmation test was carried out on each sample.

[0119] The operating performance of each sample was confirmed based on the temperatures of four measurement points P1 to P4, as shown in FIG. 13 and FIG. 14. The measurement point P1 was placed at a position close to one end of the vapor chamber 1 in the X direction. The measurement point P1 was placed on the second sheet outer surface 20b of the vapor chamber 1. The heat source 71 was attached to the first sheet outer surface 10a on the opposite side to the measurement point P1. The region where the heat source 71 was attached corresponds to the evaporation region SR described above. The measurement point P4 was placed at a position close to the other end of the vapor chamber 1 in the X direction. Two measurement points P2 and P3 were placed between P1 and P4. The outer dimensions of the vapor chamber 1 were 105 mm×17 mm, as shown in FIG. 13, and the measurement points P1 to P4 were set at equal intervals. Thermocouples were attached to each of the measurement points P1 to P4.

[0120] Power was supplied to the heat source 71 to generate heat. The amount of heat supplied from the heat source 71 to each sample was 3 W. As described above, by causing the heat source 71 to generate heat, the working fluids 2a and 2b sealed in the vapor chamber 1 circulate within the sealed space 3 while repeatedly evaporating and condensing. This causes the heat received from the heat source 71 to diffuse, and the temperatures of not only the measurement point P1 but also the measurement points P2 to P4 increase.

[0121] The temperature of each of the measurement points P1 to P4 was measured while the heat source 71 was generating heat and in a state that could be considered as a steady state. The temperature difference ΔT1 between the temperature of the measurement point P1 and the temperature of the measurement point P4 was calculated. The results are shown in Table 2.

[0122] Next, a reliability test was conducted on each sample. The reliability test involves subjecting the samples to accelerated degradation and checking their operational performance. To accelerate degradation, each sample was placed in an oven and left in a 120°C environment for 100 hours. The samples were then removed from the oven and left to cool to room temperature.

[0123] The temperatures of measurement points P1 to P4 were measured in the same manner as in the initial state operational performance verification test described above. The temperature difference ΔT2 between the temperature of measurement point P1 and the temperature of measurement point P4 was calculated. The results are shown in Table 2. Table 2 also shows the temperature difference ΔT3 between the temperature of measurement point P1 and the temperature of measurement point P3, and the temperature difference ΔT4 between the temperature of measurement point P3 and the temperature of measurement point P4.

[0124] The operating performance was judged based on whether or not the vapor chamber 1 was able to transport heat. The results are shown in Table 2.

[0125] As shown in Table 2, for Sample 1, both ΔT1 obtained in the operation confirmation test in the initial state and ΔT2 obtained in the reliability test are relatively small. In this case, it can be said that heat can be transported well, so the operational performance of Sample 1 may be judged as "OK". On the other hand, for Sample 2, ΔT1 is relatively small, but ΔT2 is relatively large. In this case, it can be said that heat transport was good in the initial state, but heat transport after accelerated aging is insufficient, so the operational performance of Sample 2 may be judged as "NG". The same is true for Sample 3.

[0126] The reason why the judgment results of samples 2 and 3 are NG is that the ratio of iron elements on the surface of the metal plate 40 is relatively large. It is considered that corrosion occurred on the surface of the metal plate 40 that is in contact with water as the working fluids 2a and 2b sealed in the vapor chamber 1. The surfaces where corrosion may occur are the first exposed surface 10c of the first sheet 10 and the second exposed surface 20c of the second sheet 20. In general, an oxide film is formed on the surface, but it is considered that iron elements are exposed from this oxide film, and the surface is corroded by water and non-condensable gas is generated. The non-condensable gas continues to exist as a gas without condensing when the vapor chamber 1 is in operation. On the other hand, the working fluids 2a and 2b move within the sealed space 3 while repeatedly evaporating and condensing. For this reason, the non-condensable gas is driven to the end of the sealed space 3 far from the heat source 71 and stagnates there. The stagnation of the non-condensable gas limits the diffusion range of the working steam 2a, and the temperature of the measurement point P4 far from the heat source 71 becomes lower. As a result, as shown in Table 2, ΔT3 of Sample 2 and Sample 3 is relatively small like the other samples, but ΔT4 of Sample 2 and Sample 3 is larger than the other samples. In this way, the heat transport performance of Sample 2 and Sample 3 may be degraded.

[0127] The operational performance of the sample may be judged based on ΔT3 and ΔT4. For example, as shown in Table 2, when ΔT4 is less than twice ΔT3, the diffusion range of the working vapor 2a can be prevented from being restricted. In this case, it can be said that heat transport can be performed well, and the operational performance of the sample may be judged as "OK". On the other hand, when ΔT4 is more than twice ΔT3, the thermal transport may be insufficient, and the operational performance of the sample may be judged as "NG". As for sample 1, ΔT4 is less than twice ΔT3, and therefore the operational performance of sample 1 may be judged as "OK" in this respect as well.

[0128] In samples 4 to 7, both ΔT1 and ΔT2 were relatively small. ΔT4 was less than twice as large as ΔT3. Therefore, in Table 2, the operating performance of samples 4 to 7 may be judged as "OK."

[0129] 15 shows a graph plotting the relationship between the iron element ratio of each sample and the temperature difference ΔT2. The horizontal axis shows the iron element ratio, and the vertical axis shows the temperature difference ΔT2 after the reliability test.

[0130] As shown in Figure 15, ΔT2 is small for the group of samples with a relatively small iron element ratio, and is large for the group of samples with a relatively large iron element ratio. This shows that it is possible to set a threshold value between the two groups to determine whether the heat transport performance is good or not. As such a threshold, Figure 15 shows a reference line for an iron element ratio of 8.5 atomic %. This reference line is approximately halfway between the iron element ratio of Sample 1 and the iron element ratio of Sample 2.

[0131] In this way, by using the metal plate 40 in which the ratio of iron elements is 8.5 atomic % or less, ΔT2 can be reduced. Therefore, it is understood that the heat received from the heat source 71 can be diffused well, and the deterioration of the heat transport performance of the vapor chamber 1 can be suppressed.

Claims

1. A vapor chamber containing a working fluid, a space portion in which the working fluid is sealed; a first sheet covering the space; a second sheet covering the space from the opposite side to the first sheet; an intermediate sheet interposed between the first sheet and the second sheet and joined to the first sheet and the second sheet; the first sheet and the second sheet are made of metal plates, The metal plate is made of SUS316L or SUS316LTA, the first sheet includes a first exposed surface exposed to the space portion, the second sheet includes a second exposed surface exposed to the space portion, a ratio of iron element in the first exposed surface and the second exposed surface is 8.5 atomic% or less; Vapor chamber.

2. The intermediate sheet includes a land portion located within the space portion, the land portion is bonded to the first sheet and the second sheet; The vapor chamber of claim 1 .

3. The ratio of the iron element in the first exposed surface is a ratio obtained by measuring the first exposed surface by X-ray photoelectron spectroscopy, the ratio of the iron element in the second exposed surface is a ratio obtained by measuring the second exposed surface by X-ray photoelectron spectroscopy; 3. The vapor chamber according to claim 1 or 2.

4. The thickness of the metal plate is 5 μm to 30 μm.

3. The vapor chamber according to claim 1 or 2.

5. The intermediate sheet is made of oxygen-free copper.

3. The vapor chamber according to claim 1 or 2.

6. A vapor chamber according to claim 1 or 2, electronic equipment.

Images