Heat dissipation substrate and vapor chamber

Abstract

Provided is a heat dissipation substrate including: a recessed section; a metal housing that has a through-hole connecting the inner side and the outer side of the recessed section; a substrate that is joined to the metal housing and that covers the recessed section; and an alloy layer that is located on the inner wall surface of the through-hole. The alloy layer includes a first layer and a second layer. The first layer is connected to the metal housing, includes, as the main component, a first component that is the main component of the metal housing, and includes a second component that is different from the first component. The second layer is located on a side facing the through-hole, includes the second component as the main component, and includes the first component. The metal housing and the substrate may be joined via an active brazing material.

Description

Heat dissipation board and vapor chamber

[0001] The present disclosure relates to a heat dissipation substrate and a vapor chamber.

[0002] A working fluid, which is a liquid-phase fluid for rapidly transporting heat, is sealed in a cavity within a heat pipe or vapor chamber used to efficiently dissipate heat from electronic devices, components, etc. International Publication No. 2008 / 012960 discloses a technique for injecting the liquid-phase fluid through an injection hole in the heat pipe and then closing the injection hole with a sealing member.

[0003] One aspect of the present disclosure is a heat dissipation substrate comprising: a metal casing having a recess and a through hole connecting the inside and outside of the recess; a substrate joined to the metal casing to cover the recess; and an alloy layer located on the inner wall surface of the through hole, wherein the alloy layer comprises: a first layer connected to the metal casing and having a first component that is a main component of the metal casing and containing a second component different from the first component; and a second layer located on the side facing the through hole and having the second component as a main component and containing the first component. Another aspect of the present disclosure is a vapor chamber comprising: the heat dissipation substrate described above; a seal joined to the alloy layer to seal the through hole; and a liquid-phase fluid located in the recess.

[0004] FIG. 1 is a plan view of a vapor chamber seen from above. FIG. 2 is a cross-sectional view taken along a cross-sectional line including the through-hole of the vapor chamber. FIG. 3 is a cross-sectional view showing an enlarged view of the vicinity of the through-hole in the heat dissipation substrate. FIG. 4 is a cross-sectional view showing an enlarged view of the vicinity of the through-hole in the heat dissipation substrate. FIG. 5 is a cross-sectional view showing an enlarged view of the vicinity of the through-hole in the heat dissipation substrate of a modified example. FIG. 6 is a diagram illustrating the distribution of copper components in an alloy layer. FIG. 7 is a diagram illustrating the distribution of silver components in an alloy layer. FIG. 8 is a diagram illustrating the crystal grain structure of an alloy layer. FIG. 9 is a cross-sectional view schematically illustrating an alloy layer.

[0005] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1A is a plan view of the vapor chamber 1 of this embodiment as seen from above. Fig. 1B is a cross-sectional view taken along the cross-sectional line AA in Fig. 1A, which includes the through-hole 11a. Note that the "upward" referred to here does not necessarily have to coincide with the orientation during actual use. Also, in the cross-sectional view of Fig. 1B, for the sake of explanation, the height in the vertical direction of the drawing relative to the width in the horizontal direction of the drawing is shown larger than it actually is.

[0006] The vapor chamber 1 may be, for example, rectangular in plan view, or flat in shape with a vertical width (height) shorter than its vertical width in plan view. The vapor chamber 1 receives heat from a heat source Sc, such as an IC chip, connected to wiring on its upper surface and transfers it to its lower surface. A heat sink Sk is joined to the lower surface of the vapor chamber 1 with an active brazing material W, such as silver solder. The heat transferred from the upper surface to the lower surface by the vapor chamber 1 is transferred to the heat sink Sk and released from the heat sink Sk into the air, etc.

[0007] The vapor chamber 1 includes a heat dissipation substrate 10, a mesh structure 20 sealed in the internal space of the heat dissipation substrate 10, and a liquid-phase fluid. The liquid-phase fluid is also called a working fluid. The mesh structure 20 is a void structure having three-dimensional mesh-like voids. The void structure used in a vapor chamber is called a wick. The mesh structure 20 is located, for example, along the inner wall surface facing the internal space of the heat dissipation substrate 10, connecting the upper and lower surfaces. A space not occupied by the mesh structure 20 may remain between the upper and lower surfaces. The mesh structure 20 may be an integral structure with the heat dissipation substrate 10. The mesh structure 20 may be made of metal or ceramic. The void structure does not have to be periodic like a mesh, and the void structure may be a three-dimensional structure having a large number of holes.

[0008] The mesh structure 20 allows the liquid-phase fluid to move quickly through its gaps by capillary force. The liquid-phase fluid in the gaps of the mesh structure 20 on the upper side receives heat from the heat source Sc and evaporates into a gas-phase fluid, which then diffuses and transfers heat to the lower side. The vaporized liquid-phase fluid condenses by releasing heat to the lower side of the heat dissipation substrate 10, then liquefies and returns to the liquid-phase fluid. The liquefied liquid-phase fluid quickly travels through the mesh structure 20 and returns to the upper side where the liquid-phase fluid is evaporating. This reflux cycle is repeated, allowing heat to be transferred from the upper side to the lower side of the vapor chamber 1 with high thermal conductivity. Therefore, the heat of the heat source Sc is dissipated from the heat dissipation plate Sk much more quickly than simple thermal conduction. The liquid-phase fluid is, for example, pure water, but is not limited thereto. The liquid-phase fluid may be, or may contain, acetone, methanol, ammonia, etc. In consideration of the volume expansion of the liquid-phase fluid when it evaporates, the internal space may be sealed so that the pressure is normally lower than atmospheric pressure, i.e., negative pressure. The amount of mesh structure 20 and liquid-phase fluid to be sealed can be determined depending on the size of the internal space, the amount of heat to be transported, etc.

[0009] The heat dissipation substrate 10 has a metal housing 11 having a through-hole 11a and a recess 11b, a ceramic plate 12 (substrate), and a sealing body 13 located in the through-hole 11a. The metal housing 11 and the sealing body 13 are made mainly of the same metal material. The main component may be copper. Alternatively, the main component of the sealing body 13 may be different from that of the metal housing 11. The ceramic plate 12 is an insulating substrate with high thermal conductivity, and the main component may be silicon nitride (Si ３ N ４ ), silicon carbide (SiC), aluminum nitride (AlN), aluminum oxide (Al ２ O ３ The term "major component" as used herein refers to a component that accounts for 80% by mass or more of the total. Even among compositions containing the same major component, the component ratio may be different, or the component ratio may be the same within the error range defined by the tolerance.

[0010] The through hole 11a connects the inner and outer surfaces of the recess 11b in a straight line and is used to inject a liquid-phase fluid into the recess 11b. After the liquid-phase fluid is injected, the through hole 11a is sealed with a sealer 13. The diameter of the through hole 11a required for injecting the liquid-phase fluid may be, for example, φ=0.5 to 2.0 mm, and the length of the through hole 11a may be, for example, 0.5 to 1.5 mm.

[0011] The metal housing 11 and the ceramic plate 12 are sealed by being joined with an active brazing material 14. The active brazing material 14 is, for example, a silver brazing material whose main component is silver. This firmly joins the metal housing 11 and the ceramic plate 12, providing airtightness, and the active brazing material 14 also improves the thermal conductivity between the metal housing 11 and the ceramic plate 12. Note that multiple metal housings 11 may be joined to a single ceramic plate 12.

[0012] The inner surface of the through hole 11a of the metal housing 11 and the sealing body 13 are joined and sealed via an alloy layer 15. The alloy layer 15 is an alloy of silver and copper, and as will be described later, the component ratio is non-uniform.

[0013] 2A to 2C are enlarged cross-sectional views showing the vicinity of the through-hole 11a in the heat dissipation substrate 10. Fig. 2A is a cross-sectional view taken along the cross-sectional line AA in Fig. 1A, and Fig. 2B is a cross-sectional view taken along the cross-sectional line HH in Fig. 2A.

[0014] As shown in Figures 2A and 2B, the inner surface of the through hole 11a of the metal casing 11 is not particularly limited, and the entire surface may be covered with the alloy layer 15. The thickness of the alloy layer 15 may increase from the outside (upper side in the drawing) of the recess of the metal casing 11 toward the inside (lower side in the drawing). That is, the thickness of the alloy layer 15 may be greater along the through hole 11a as it approaches the recess. Accordingly, the diameter of the sealing body 13 may be smaller as it approaches the recess. Note that this thickness trend is a trend that can be expressed as an approximation from a plane to a quadratic curve, and does not exclude the local presence of minute irregularities.

[0015] The alloy layer 15, which is an alloy of silver and copper, has a higher hardness than the sealing body 13, which is primarily composed of copper. Therefore, when the sealing body 13 is inserted into the through hole 11a, the alloy layer 15 compresses the sealing body 13 to a greater extent the closer it is to the recess 11b. The cross-sectional size (width) of the alloy layer 15 in this state may be, for example, 150 μm or less at its largest portion, in this case, near the end on the recess 11b side. However, the cross-sectional size of the alloy layer 15 is not limited to this. Furthermore, this size can vary depending on various factors, such as the size of the through hole 11a, the size of the metal housing 11, and the distance from the joining position of the active brazing material 14 to the through hole 11a.

[0016] 2B , alloy layer 15 may have a uniform thickness in the circumferential direction of through hole 11a, i.e., in the direction of angular variation from the central axis of through hole 11a. Here, "uniform" means, for example, that the thickness of alloy layer 15 in the circumferential direction varies by a maximum of 70% or 100 μm or less. Therefore, in this case, sealing body 13 inserted into through hole 11a is subjected to substantially uniform stress from the side.

[0017] The alloy layer 15 may have an alloy layer 15a that extends from the inner surface of the through hole 11a to the outer periphery. While FIG. 2A shows the alloy layer 15a extending only inside the recess, this is not limiting. FIG. 2C illustrates a modified cross-sectional shape of FIG. 2A. As shown in FIG. 2C, the alloy layer 15b may extend outside the recess 11b, i.e., onto the outer surface of the metal casing 11. In this case, the alloy layer 15b may have a thickness that does not significantly impair the flatness of the outer surface of the metal casing 11. This flatness may be achieved by cutting or polishing the surface during insertion and sealing of the sealing body 13. This cutting or polishing may remove part or all of the alloy layer 15b. Furthermore, the alloy layer 15b may be separated from the alloy layer 15 located along the inner wall surface of the through hole 11a. The alloy layer 15a inside the recess 11b may be connected to the active brazing material 14, and the boundary between them may be unclear.

[0018] The alloy layer 15 is divided by a boundary B into a first layer 151 connected to the metal casing 11 and a second layer 152 in contact with the sealing body 13. The first layer 151 is continuously connected to the metal casing 11. That is, the boundary between the first layer 151 and the metal casing 11 does not need to be clear. The first layer 151 is made of a first component, which is the main component of the metal casing 11, in this case, copper, and is mixed with a second component, which is different from the first component, in this case, silver. The second layer 152 is clearly separated from the sealing body 13. The second layer 152 is made of a second component, which is the main component of the active brazing material 14, in this case, silver, and is mixed with the first component, in this case, copper.

[0019] As described above, the hardness of the alloy layer 15 as a whole may be higher than that of each of silver and copper. The hardness of the first layer 151 and the second layer 152 may differ depending on the component ratios thereof. The hardness of the second layer 152, which has a high silver component, is lower than that of the first layer 151.

[0020] The presence of alloy layers 15, 15a, 15b, etc., on metal casing 11 so as to partially cover the periphery of through hole 11a reduces deformation when sealing body 13 is press-fitted into through hole 11a to seal it. In particular, alloy layers 15a, 15b reduce unevenness on the outer surface of metal casing 11, such as sinking around sealing body 13. Specifically, for example, the depth of a local depression caused by insertion of sealing body 13 may be 100 μm or less, and the range (length) of the local depression may be 200 μm or less. When signal lines or electronic components connected to the signal lines that serve as heat sources are located on the outer surface of metal casing 11, the flatness of the outer surface may be maintained.

[0021] Furthermore, localized voids V may exist at the boundary between the alloy layer 15 and the seal 13. The voids V may exist in multiple locations, but they are discrete, i.e., the inside of the recess 11b is sealed by the bonding between the seal 13 and the second layer 152. Such voids V function as a stress buffer between the seal 13 and the metal housing 11 and as a buffer when each part thermally expands.

[0022] The boundary B between the first layer 151 and the second layer 152 may have a corrugated surface rather than a flat surface. By providing an uneven boundary between the first layer 151 and the second layer 152, which have a relative difference in hardness, the stress caused by the thermal expansion of the sealing body and the increase in internal pressure is appropriately dispersed. Therefore, deformation of the sealing surface is reduced, and airtightness is effectively maintained.

[0023] In particular, the boundary B may include a protruding portion Bp where the second layer 152 locally protrudes and bites into the first layer 151 at an acute angle. The term "acute angle" here refers to a viewing angle of the second layer 152 from the apex of the protruding portion Bp in a plane including the apex of the protruding portion Bp and the central axis of the through hole 11a that is less than 90 degrees. The viewing angle represents the range within which the sealing body 13 is visible only through the second layer 152. In this manner, the second layer 152, which has a relatively low hardness within the alloy layer 15 having a high hardness overall, bites into the first layer 151. Therefore, the second layer 152 acts as a wedge and buffer at the bonding surface. Even if large or long-term stress is applied circumferentially around the through hole 11a due to factors such as the pressure difference between the inside and outside of the recess 11b or thermal expansion, the possibility of fracture or cracking due to the cumulative effects is reduced. The unevenness of the boundary B itself is not related to the thickness of the alloy layer 15. As a result, the ratio of the thicknesses of the first layer 151 and the second layer 152 may vary widely. For example, the thickness of the second layer 152 may be locally zero, i.e., the second layer 152 may be separated into multiple parts or may have holes. In this case, there may be parts where the first layer 151 is directly bonded to the sealing body 13. By discretely and reliably bonding the second layer 152 to the sealing body 13, stress is distributed at each bonded part, and airtightness can be maintained.

[0024] 3A to 3C, 4, and 5 are diagrams showing examples of the cross-sectional structure of the alloy layer 15. FIG. 3A shows the distribution of the copper component, and FIG. 3B shows the distribution of the silver component. FIG. 4 is a diagram explaining the crystal grain size. FIGS. 3A, 3B, and 4 are enlarged schematic views of a portion of the cross section shown in FIG. 2A. FIG. 5 is a diagram showing the alloy layer 15 divided into regions in a more simplified manner. Note that, for simplicity of explanation, boundary irregularities and voids V shown in FIG. 2A are omitted in FIG. 5.

[0025] As shown in FIGS. 3A and 3B , the first layer 151 of the alloy layer 15, which is located closer to the metal casing 11, is mainly composed of copper, the first component, continuing from the metal casing 11. Silver, the second component, may be mixed in finely. The proportion of the silver component may gradually decrease from the boundary with the second layer 152 toward the boundary with the metal casing 11. Accordingly, the density of the first layer 151 may also gradually decrease from the boundary with the second layer 152 toward the boundary with the metal casing 11. Specifically, the proportion of the silver component may be a maximum of 10% and an average of 5%. The crystal grain size of the copper in the first layer 151 may be smaller than the crystal grain size of the copper in the metal casing 11.

[0026] As shown in FIG. 4 , in the metal casing 11, the copper crystal grain size separated by the boundary Bc may often be equal to or larger than the thickness of the alloy layer 15, for example, approximately 200 μm on average. In contrast, as shown in FIG. 3A , silver atoms (particles) may be dispersed and mixed inside the first layer 151. The copper crystal grain size may be significantly smaller within these gaps, for example, approximately 10 μm on average. The individual crystal grain sizes may not be uniform. The component ratios and grain sizes may be determined, for example, by identifying the regions of each component from images of the copper component and silver component obtained by energy dispersive spectroscopy (EDS).

[0027] On the other hand, as shown in FIG. 3B , the second layer 152 includes a first component, copper crystals, mixed in the second component, i.e., silver, which is the main component. The copper crystal components may include those whose crystal grain size increases with increasing distance from the boundary B. That is, in the second layer 152, the maximum crystal grain size may increase with increasing distance from the boundary B. Specifically, the size of the copper crystal components may increase from approximately 0.5 μm to approximately 10 μm in the second layer 152, for example. Copper atoms that penetrate from the metal housing 11 into the layer of the active brazing material 14 are unlikely to grow large near the boundary. As a result, the second layer 152 may have a structure in which an intermediate layer 152a, in which copper crystal growth is relatively small, and a bonding layer 152b, in which copper crystal growth is relatively large, are continuously connected.

[0028] As described above, silver has a lower elastic modulus and a higher coefficient of thermal expansion than copper. That is, the layer with the lowest elastic modulus and hardness is located in the intermediate layer 152a, not in the bonding layer 152b facing the bonding surface with the sealing body 13. Therefore, the influence of copper crystals is greater in the bonding with the sealing body, making it easier to obtain bonding characteristics between the sealing body 13 and the same components. Meanwhile, the intermediate layer 152a allows deformation between the bonding surface and the metal housing 11, and can serve as a buffer. Therefore, the heat dissipation substrate 10 is less likely to deform near the bonding surface between the sealing body 13 and the second layer 152, making it easier to maintain airtightness.

[0029] In this way, crystals of a component different from the main component are distributed inside each layer, and the change is not discontinuous, so that local deformation between regions is unlikely to occur.

[0030] The above-described structure may be obtained by joining the ceramic plate 12 and the metal housing 11 with the active brazing material 14, with the active brazing material 14 running along the inner wall surface of the recess 11b to partially cover the inner wall surface of the through hole 11a. The high-temperature active brazing material 14 contacts the metal housing 11 at boundary B, and some copper atoms and silver atoms move back and forth across boundary B, which can result in an alloy layer 15 on both sides of boundary B. In particular, silver atoms move preferentially toward the copper grain boundary, so boundary B is likely to have a wavy shape. The thickness of the alloy layer 15 is likely to increase on the side of recess 11b of the through hole 11a, which is the inflow side of the active brazing material 14.

[0031] In this way, the active brazing material 14 acts only on the metal housing 11, and therefore the boundary between the sealing body 13 and the alloy layer 15 is clear as described above. Furthermore, when sealing is performed with the sealing body 13, the sealing body 13 itself is reliably pressure-bonded to the alloy layer 15.

[0032] Furthermore, the active brazing material 14 needs to flow along the inner wall surface of the through hole 11a. Therefore, the through hole 11a may be located near the joint position between the metal casing 11 and the ceramic plate 12, i.e., near the periphery of the metal casing 11 in a planar view. For example, the through hole 11a may be located near a vertex of the rectangular metal casing 11 in a planar view. Furthermore, the side wall surface forming the periphery of the recess 11b of the metal casing 11 and the bottom surface of the recess 11b opposite the open end covered by the ceramic plate 12 may be flat at least around the through hole 11a. If the side wall surface has steps or irregularities, it is likely that the active brazing material 14 will not flow properly into the through hole 11a. Note that the wall surface shape does not necessarily have to be flat as long as it does not significantly adversely affect the flow of the active brazing material 14.

[0033] As described above, the heat dissipation substrate 10 of this embodiment includes a metal housing 11 having a recess 11b and a through hole 11a connecting the inside and outside of the recess 11b, a ceramic plate 12 as a substrate joined to the metal housing 11 to cover the recess 11b, and an alloy layer 15 located on the inner wall surface of the through hole 11a. The alloy layer 15 includes a first layer 151 and a second layer 152. The first layer 151 is connected to the metal housing 11 and contains a first component, which is the main component of the metal housing 11, in this case copper, and a second component, silver, which is different from the first component. The second layer 152 is located on the side facing the through hole 11a and contains a second component, silver, as the main component, and copper as the first component. In this way, in the heat dissipation substrate 10, an alloy layer 15 made of a different material from the metal housing 11 and the sealing body 13 is located on the inner wall surface of the through hole 11a, and the metal housing 11 and the sealing body 13 are bonded together via this. Therefore, the heat dissipation substrate 10, and in turn the vapor chamber 1, can improve the bonding strength when bonding the sealing body 13, thereby achieving a stronger seal than conventional methods. In particular, sandwiching layers with different physical properties between the objects to be bonded improves durability against deformation due to stresses during manufacturing and operation, thereby improving airtightness. Furthermore, the alloy layer 15 includes a first layer 151 and a second layer 152 with different component ratios, thereby achieving both bonding stability and stress dispersion.

[0034] Furthermore, the metal housing 11 and the ceramic plate 12 (substrate) may be joined via an active brazing material 14. This allows the ceramic plate 12 to be firmly joined to the metal housing 11, thereby making the heat dissipation substrate 10 have a stronger and more durable structure.

[0035] Furthermore, silver, which is the second component, may be the main component of the active brazing material 14. That is, silver brazing may be used for bonding. When the ceramic plate 12 is bonded with the active brazing material 14, the active brazing material 14 flows from within the recess 11b along the inner surface of the through hole 11a, thereby obtaining the above-mentioned alloy layer 15. Therefore, the silver brazing not only effectively bonds the ceramic plate 12 but also effectively bonds the sealing body 13, thereby efficiently improving the robustness of the heat dissipation substrate 10.

[0036] The first layer is primarily made of copper, and the second layer is primarily made of silver. The alloy of copper and silver can increase the hardness of each layer. Therefore, a robust heat dissipation substrate 10 can be obtained using a material with high thermal conductivity.

[0037] Furthermore, the thickness of alloy layer 15 may increase along through hole 11a from the outside toward the inside of recess 11b. That is, on the inner surface of through hole 11a, alloy layer 15 may be thicker and harder near recess 11b. Therefore, heat dissipation substrate 10 can easily insert sealing body 13 when press-fitting, and can ensure airtightness while reducing deformation.

[0038] Furthermore, alloy layer 15 may have a uniform thickness in the circumferential direction of through hole 11a, which allows a substantially uniform stress to be applied to sealing body 13. Therefore, heat dissipation substrate 10 can reduce the possibility of an excessive load being applied to a specific part, causing the airtightness to be broken.

[0039] The alloy layer 15 may also be located around the outside of the through-hole 11a. That is, the hard alloy layer 15 may extend in a plane perpendicular to the direction of press-fitting of the sealing body 13 and the direction of expansion / contraction due to changes in internal pressure. This reduces deformation of the top surface of the metal casing 11 during manufacturing and use, allowing the heat source Sc to be stably held. Furthermore, deterioration of the bonding surface due to stress caused by deformation can be reduced.

[0040] Furthermore, the alloy layer 15b located on the outer surface of the metal housing 11 opposite the recess 11b, i.e., on the upper surface of the heat dissipation substrate 10, may have a portion separated from the alloy layer 15 along the through hole 11a. The upper surface of the heat dissipation substrate 10 on which the heat source Sc is placed and fixed is required to be flat. Therefore, the alloy layer 15b may be separated from the alloy layer 15 on the inner wall surface of the through hole 11a by cutting or polishing the upper surface. Even with this structure, the strength of the upper surface of the heat dissipation substrate 10 can be improved, and the durability of the heat dissipation substrate 10 is accordingly improved.

[0041] The second layer 152 may be separated into multiple parts. The second layer 152, which has a relatively low strength compared to the first layer 151, can be separated to connect the sealing body 13 and the first layer 151 at multiple locations, thereby appropriately dispersing stress associated with the second layer 152, which serves as a buffer. This allows the bonding strength of the heat dissipation substrate 10 to be maintained and the durability of the airtight state to be improved.

[0042] Furthermore, the copper crystal grain size of the first layer 151 is smaller than the copper crystal grain size in the metal housing 11, and the silver density is smaller as it approaches the metal housing 11. The small copper crystal grain size reduces the slippage of dislocations within the crystal grains, thereby reducing the occurrence of plastic deformation. Therefore, the heat dissipation substrate 10 maintains a strong bonded structure, improving its durability. Furthermore, the silver density gradually increases from the boundary with the metal housing 11 to the boundary with the sealing body 13, resulting in a continuous change in hardness. Therefore, the bond between the metal housing 11 and the sealing body 13 in the heat dissipation substrate 10 becomes flexible, dispersing stress and making it easier to maintain the sealed state over the long term.

[0043] Furthermore, the second layer 152 may contain copper with a larger crystal grain size as it moves away from the first layer 151. This reduces the decrease in hardness of the alloy layer 15 in the immediate vicinity of the bonding surface between the sealing body 13 and the alloy layer 15. Therefore, the heat dissipation substrate 10 is less likely to deform along the bonding surface, making it easier to maintain airtightness. On the other hand, in the alloy layer 15 of the heat dissipation substrate 10, as it moves away from the bonding surface in the direction of the metal housing 11, there is a region where the hardness decreases more significantly than in the immediate vicinity of the bonding surface. Therefore, stress is appropriately distributed in the heat dissipation substrate 10, and the bonded state is maintained strong.

[0044] The boundary between the first layer 151 and the second layer 152 may have an uneven surface. This prevents the bonding surface from shifting even when a shear stress is applied in the circumferential direction between the two layers having different hardness, and prevents the airtight state from being broken. This allows the heat dissipation substrate 10 to have high durability.

[0045] The boundary may also have a portion where the second layer 152 protrudes at an acute angle toward the first layer 151. Such a protruding portion of the second layer 152 acts as a wedge, making it less likely that the shear stress will cause a breakdown in the bond, i.e., a loss of airtightness. Furthermore, since the stress is appropriately dispersed, the bonded state can be maintained stably.

[0046] The heat dissipation substrate 10 may also include a sealing body 13 that is bonded to the alloy layer 15 to seal the through-hole 11a. The heat dissipation substrate 10 may have a localized void V between the sealing body 13 and the alloy layer 15. This allows the void V, which is easily deformed, to function as a buffer layer, appropriately alleviating stress during manufacturing and operation due to expansion / contraction in response to pressure changes in the sealed internal space and thermal expansion. This improves the durability of the heat dissipation substrate 10.

[0047] The vapor chamber 1 of this embodiment includes the heat dissipation substrate 10, the sealing body 13, and a liquid-phase fluid located in the recess 11 b. The vapor chamber 1 has improved flatness on the top surface of the metal housing 11, allowing for efficient heat dissipation from the heat source Sc and maintaining stable durability.

[0048] The above-described embodiment is merely an example, and various modifications are possible. For example, the alloy structure is not limited to the case where the first component, which is the main component of the metal casing 11 and the sealing body 13, is copper, and the second component, which is the main component of the active brazing material 14, is silver. It is sufficient that the main components can form the alloy layer 15 consisting of the first layer 151 and the second layer 152. Furthermore, the hardness of the alloy layer 15 may be higher than the hardness of the metal casing 11 and the sealing body 13. Furthermore, the boundary B between the first layer 151 and the second layer 152 may have an uneven shape, and further, one of the layers may have an acute-angled protrusion that penetrates into the other layer.

[0049] In the above description, the alloy layer 15 is formed by the active brazing material 14 flowing into the through hole 11a when the ceramic plate 12 is joined. However, this is not limited to this. When joining a metal substrate or a resin substrate to the metal casing 11 with the active brazing material 14, the active brazing material 14 flows into the through hole 11a to form the alloy layer 15. The alloy layer 15 may be formed independently of the joining of the ceramic plate 12 or the like. In accordance with or regardless of the above, the alloy layer 15 does not have to extend outward from the inner surface of the through hole 11a. Furthermore, the alloy layer 15b located on the outer surface of the metal casing 11 may be continuous with the alloy layer 15 along the inner wall surface of the through hole 11a. The metal casing 11 and the ceramic plate 12 may be joined by something other than the active brazing material 14. The through hole 11a does not have to be located near the periphery of the metal casing 11 in a plan view.

[0050] Furthermore, the thickness of the alloy layer 15 on the inner wall surface of the through hole 11 a does not need to vary along the penetration direction of the through hole 11 a. Furthermore, the alloy layer 15 does not need to extend over the entire inner wall surface.

[0051] Furthermore, the alloy layer 15 does not necessarily have to exhibit a change in the copper crystal grain size or a change in the silver density, i.e., a change in the copper-silver component ratio, depending on the distance from the metal casing 11 .

[0052] Furthermore, the through hole 11a and the plug 13 do not have to be cylindrical. For example, the through hole 11a and the plug 13 may be elliptical cylindrical or polygonal prism-shaped. Alternatively, the through hole 11a and the plug 13 may be polygonal prism-shaped with rounded corners, or may have a non-uniform shape such as a shape that combines curved and straight portions when viewed in a plan view or in a cross section perpendicular to the extension direction of the through hole 11a.

[0053] Also, the gap V along the surface of the sealing body 13 may be absent.

[0054] The ceramic plate 12 does not have to be a flat plate, but may have an uneven or curved surface depending on the shape and size of the heat sink Sk.

[0055] Furthermore, although only silver and copper have been described above, this does not exclude the inclusion of other components.

[0056] Furthermore, although the vapor chamber 1 has been described above as having been filled with a liquid-phase fluid and sealed with a sealant 13, the heat dissipation substrate 10 before filling and sealing may be distributed independently. Furthermore, the specific configurations, structures, materials, and manufacturing methods shown in the above embodiments may be modified as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention set forth in the claims and their equivalents.

[0057] The present disclosure can be used for heat dissipation substrates and vapor chambers.

[0058] REFERENCE SIGNS LIST 1 vapor chamber 10 heat dissipation substrate 11 metal housing 11a through hole 11b recess 12 ceramic plate 13 sealing body 15, 15a, 15b alloy layer 151 first layer 152 second layer 152a intermediate layer 152b bonding layer 20 mesh structure B, Bc boundary Bp protrusion V gap

Claims

1. a metal housing having a recess and a through hole connecting the inside and outside of the recess; a substrate joined to the metal housing to cover the recess; an alloy layer located on an inner wall surface of the through hole; Equipped with The alloy layer is a first layer connected to the metal housing, the first layer containing a first component that is a main component of the metal housing and a second component that is different from the first component; a second layer located on the side facing the through hole, the second layer containing the second component as a main component and the first component; a heat dissipation substrate including:

2. The heat dissipation board according to claim 1 , wherein the metal housing and the board are joined together via an active brazing material.

3. 3. The heat dissipation board according to claim 2, wherein the second component is a main component of the active brazing material.

4. The heat dissipation substrate of claim 1 , wherein the first component is copper and the second component is silver.

5. The heat dissipation board according to claim 1 , wherein the alloy layer has a thickness that increases along the through hole from the outside to the inside of the recess.

6. The heat dissipation board according to claim 1 , wherein the alloy layer has a uniform thickness in the circumferential direction of the through hole.

7. The heat dissipation board according to claim 1 , wherein the alloy layer is also located around the outer periphery of the through hole.

8. The heat dissipation board according to claim 7 , wherein the alloy layer located on the outer surface of the metal housing opposite to the recess has a portion separated from the alloy layer along the through hole.

9. The heat dissipation substrate according to claim 1 , wherein the second layer is separated into a plurality of portions.

10. The heat dissipation substrate of claim 1 , wherein the crystal grain size of the first component in the first layer is smaller than the crystal grain size of the first component in the metal housing, and the density of the second component is smaller as it is closer to the metal housing.

11. 2. The heat dissipation substrate according to claim 1, wherein the second layer contains the first component with a larger crystal grain size the farther it is from the first layer.

12. The heat dissipation substrate according to claim 1 , wherein the boundary between the first layer and the second layer has irregularities.

13. The heat dissipation substrate according to claim 12 , wherein the boundary has a portion where the second layer protrudes toward the first layer at an acute angle.

14. a sealing body that is bonded to the alloy layer to seal the through hole; The heat dissipation substrate according to claim 1 , wherein a local gap is formed between the sealing body and the alloy layer.

15. The heat dissipation substrate according to any one of claims 1 to 14, a sealing body that is bonded to the alloy layer to seal the through hole; a liquid-phase fluid located within the recess; A vapor chamber equipped with