Patent Description:
This disclosure relates to the field of communications technologies, and in particular, to a heat dissipation apparatus, a circuit board, and an electronic device.

With development of microelectronic technologies, a size of a chip becomes smaller, a computing speed becomes higher, and a heat emission amount becomes larger. For example, in the prior art, power consumption of a GPU during running reaches <NUM> W. It can be predicted that in the near future, power consumption of a GPU with higher performance may exceed <NUM> W, and a heat dissipation requirement is increasingly high. In the prior art, a VC (Vapor chamber, vapor chamber) is used as a heat dissipation structure of a chip. This can effectively dissipate centralized heat. As shown in <FIG>, the VC mainly includes a metal thermally conductive housing, a capillary structure, and a working fluid. A working principle of the VC is as follows: A cavity in the thermally conductive housing is vacuumed and a working medium is placed in the cavity. When heat is conducted from a heat source to an evaporation region, the working medium in the cavity starts to be gasified from a liquid phase in an environment with a low vacuum degree. In this case, the working medium absorbs the heat and rapidly expands in volume, and the entire cavity is quickly filled with the gas-phase working medium When the gas-phase working medium moves to a relatively cold region, the gas-phase working medium condenses, so as to dissipate heat accumulated during evaporation. After the condensation, the liquid-phase working medium returns to the evaporation region for heat source due to a capillary attraction action of the capillary structure. This process is cyclically performed in the cavity, so that the heat generated by the heat source can dissipate. However, in the prior art, as a medium for transporting the working medium, a capillary wick in the VC provides a liquid return driving force, but increases liquid flow resistance. This affects a heat dissipation effect. Document <CIT> relates to a flat heat pipe capillary structure and a method for manufacturing a capillary structure of a flat-sheet heat pipe, comprising the following steps: providing a lower cover board which has a straight heat absorption part and two extension parts extending outwards from the two opposite ends of heat absorption part in a slant way; providing a quantity of metal power; providing a die, which is an inner pore chamber having the outline thereof similar to that of the lower cover board and an opening arranged downwards, and is provided with a first holding section corresponding to the heat absorption part of the lower cover board and a second holding section corresponding to the extension parts with the depth of the first holding section larger than that of the second holding section; filling the metal power into the die; sintering the lower cover board at high temperature to cause the metal power in the die to be sintered into a continuous capillary structure attached on the upper surface of the lower cover board, wherein the capillary structure comprises a first capillary section attached on the heat absorption part of the lower cover board and a second capillary section attached on the extension parts with the first capillary section being thinner than the second capillary section. Document <CIT> describes a loop heat pipe including a vessel having a flow path formed in a looped shape and a working fluid sealed in the vessel, and the vessel includes a first wick provided at least in an opposing area in an evaporation part and a second wick adjacent to the first wick from the side of a liquid return pipe. The vessel has a first wall facing a heat generating component and a second wall opposed to the first wall. The first wick has a first portion provided in the first wall and a second portion provided in the second wall with space from the first portion. The second wick is provided to cover the entire cross-section of the flow path between the first wall and the second wall. Document <CIT> relates to a heat pipe having a wick structure for efficiently returning working fluid to an evaporating portion. The heat pipe comprises a container sealed at its both ends, a working fluid encapsulated in the container, and a wick structure covering an inner face of the container. The wick structure includes a porous wick of a sintered metal powder, and a fiber wick buried in the porous wick. A capillary pressure of the fiber wick is weaker than that of the porous wick, and a pressure loss of the fiber wick is smaller than that of the porous wick. Document <CIT>describes a flat heat pipe with an evaporator section and a condenser section, wherein the flat heat pipe includes a casing, and a first wick structure and a second wick structure in the casing. The casing defines a first vapor channel within the evaporator section. The first wick structure contacts an inner surface of the casing at the condenser section. The first wick structure includes a contact portion in contact with the inner surface of the casing, and an isolated portion from the inner surface of the casing. The isolated portion and the inner surface of the casing cooperatively define therebetween a second vapor channel in communication with the first vapor channel. The second wick structure contacts the inner surface of the casing at the evaporator section. The second wick structure joins the first wick structure at a joint between the evaporator section and the condenser section.

This disclosure provides a heat dissipation apparatus, a circuit board, and an electronic device, to improve a heat dissipation effect for a chip. The present invention is set out by the set of appended claims.

According to a first aspect, a heat dissipation apparatus is provided. The heat dissipation apparatus is configured to dissipate heat for a chip. During specific disposal, the heat dissipation apparatus includes a thermally conductive housing, the thermally conductive housing may be a metal housing, the thermally conductive housing has a first surface, and a chip placement region is disposed on the first surface. When the heat dissipation apparatus is connected to the chip, the chip is located in the chip placement region and is connected to the thermally conductive housing in a thermally conductive manner. In addition, there is a vacuum cavity in the thermally conductive housing, and a capillary structure configured to accommodate and carry a working medium is disposed in the vacuum cavity. During use, the working medium is placed in the capillary structure and can flow in the capillary structure. To improve a heat dissipation effect for the chip, the capillary structure includes an evaporation-side capillary structure and a condensation-side capillary structure. The evaporation-side capillary structure is on a side close to the chip, and the condensation-side capillary structure is on the other side opposite to the evaporation-side capillary structure. The evaporation-side capillary structure is divided into two connected parts: a first capillary structure and a second capillary structure, and the first capillary structure and the second capillary structure are fixedly connected to an inner wall of the thermally conductive housing. When the working medium flows, the working medium absorbs heat and evaporates after flowing from a condensation side to an evaporation side. Then, the working medium flows back to the evaporation side after condensing on the condensation side. The first capillary structure is located on the evaporation side. In other words, the first capillary structure is located on a side close to the first surface. In addition, during disposal, a vertical projection of the first capillary structure on the first surface covers at least a part of a vertical projection of the chip placement region on the first surface. In addition, when a thickness of the first capillary structure and a thickness of the second capillary structure are set, a maximum thickness of the first capillary structure is less than a minimum thickness of the second capillary structure. For the capillary structure, a thicker capillary structure can reduce flow resistance of the working medium, and a thinner capillary structure can reduce thermal resistance during evaporation. Therefore, in the foregoing structure, the thinner first capillary structure is disposed in an evaporation region, so that an evaporation effect of the working medium after heat absorption is improved. In addition, the thicker second capillary structure is used to reduce backflow resistance of the working medium In this way, a heat transfer effect of the working medium is improved, and the heat dissipation effect for the chip is further improved.

Different structures may be used when the first capillary structure and the second capillary structure are specifically disposed. For example, in a specific implementation solution, the capillary structure is a groove structure or a pipe structure. Alternatively, the capillary structure may be a porous structure. In this case, both the first capillary structure and the second capillary structure are porous structures, and a pore of the first capillary structure is connected to a pore of the second capillary structure. In this way, the working medium is carried by using different structures.

When the porous structure is used, a diameter of the pore of the first capillary structure is less than or equal to a diameter of the pore of the second capillary structure. Therefore, the backflow resistance of the working medium can be further reduced, and the thermal resistance during evaporation can be reduced.

In a specific implementation solution, the first capillary structure and the second capillary structure are connected through sintering. A sintering manner is used for improvement.

The first capillary structure and the second capillary structure may be formed by using different structures. For example, in a specific implementation solution, both the first capillary structure and the second capillary structure are porous structures formed by sintering metal powder or a metal mesh. In other words, the capillary structure is formed by sintering the metal powder or the metal mesh. The metal may be different metals having a good thermally conductive effect, for example, different metals such as copper, aluminum, and iron. In a specific implementation solution, copper powder or a copper mesh made of copper is selected.

In a specific implementation solution, a diameter of metal powder used for the first capillary structure is less than or equal to a diameter of metal powder used for the second capillary structure. A diameter of a formed pore varies with a diameter of selected metal powder. A larger diameter of the metal powder leads to a larger diameter of the formed pore.

In a specific implementation solution, the second capillary structure is the metal mesh, and the first capillary structure is a porous structure formed by sintering the metal powder.

Alternatively, the second capillary structure is a porous structure formed by sintering the metal powder, and the first capillary structure is the metal mesh. In other words, both the first capillary structure and the second capillary structure may be formed by sintering the metal powder or the metal mesh.

In a specific implementation solution, the thermally conductive housing has a second surface opposite to the first surface, the heat dissipation apparatus further includes a heat sink, and the heat sink is fastened on the second surface and is connected to the thermally conductive housing in a thermally conductive manner. The heat sink is disposed to improve the heat dissipation effect. After evaporation, the working medium transfers the heat to the heat sink for heat dissipation. The heat sink may have different structures. For example, a fin-type heat sink is used.

When the first capillary structure is specifically disposed, to improve the heat dissipation effect, an area of the vertical projection of the first capillary structure on the first surface is <NUM>% to <NUM>% of an area of the vertical projection of the chip placement region on the first surface. For example, a percentage may be <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%.

In a specific implementation solution, an axis of the first capillary structure overlaps an axis of the chip placement region. In this way, the first capillary structure and the chip may correspond to each other rightly, so that the heat dissipation effect is improved.

In a specific implementation solution, the thickness of the first capillary structure is <NUM>% to <NUM>% of the thickness of the second capillary structure. In other words, the thickness of the first capillary structure may be different thicknesses, for example, may be <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of the thickness of the second capillary structure.

When the chip placement region is specifically disposed, the first capillary structure may correspond to the chip placement region in a plurality of manners. For example, there is at least one chip placement region, and the first capillary structure is in a one-to-one correspondence with the chip placement region. Alternatively, at least one chip placement region may correspond to one first capillary structure.

According to a second aspect, a circuit board is provided. The circuit board includes a circuit board body and a chip disposed on the circuit board body, and further includes the heat dissipation apparatus according to any one of the foregoing solutions. The chip is connected to a chip placement region of the heat dissipation apparatus in a thermally conductive manner. In the foregoing structure, a thinner first capillary structure is disposed in an evaporation region, so that an evaporation effect of a working medium after heat absorption is improved. In addition, a thicker second capillary structure is used to reduce backflow resistance of the working medium In this way, a heat transfer effect of the working medium is improved, and a heat dissipation effect for the chip is further improved.

According to a third aspect, an electronic device is provided. The electronic device includes a housing and the circuit board disposed in the housing according to any one of the foregoing solutions. In the foregoing structure, a thinner first capillary structure is disposed in an evaporation region, so that an evaporation effect of a working medium after heat absorption is improved. In addition, a thicker second capillary structure is used to reduce backflow resistance of the working medium In this way, a heat transfer effect of the working medium is improved, and a heat dissipation effect for a chip is further improved.

To make the objectives, technical solutions, and advantages of this disclosure clearer, the following further describes this disclosure in detail with reference to the accompanying drawings.

To understand a heat dissipation apparatus provided in an example of this disclosure, an application scenario of the heat dissipation apparatus is first described. As shown in <FIG>, the heat dissipation apparatus <NUM> is configured to dissipate heat for a chip <NUM>. During use, the heat dissipation apparatus <NUM> and the chip <NUM> are bonded together and connected in a thermally conductive manner, so that heat generated by the chip <NUM> is dissipated by using the heat dissipation apparatus <NUM>.

The heat dissipation apparatus <NUM> provided in this example of this disclosure dissipates heat for the chip <NUM> through a phase change of a working medium For ease of understanding, a working principle of the heat dissipation apparatus <NUM> is first described. As shown in <FIG>, the heat dissipation apparatus <NUM> mainly includes a thermally conductive housing <NUM>, a capillary structure <NUM>, and the working medium A structure shown in <FIG> is a sectional view of the heat dissipation apparatus <NUM>. However, the thermally conductive housing <NUM> has a cuboid structure, and includes two slabs disposed opposite to each other. The two slabs are connected in a sealed manner to form a cuboid vacuum cavity <NUM>. In addition, the chip <NUM> and a heat sink <NUM> are respectively disposed on the two opposite slabs of the thermally conductive housing <NUM>. During heat dissipation for the chip, heat of the chip needs to be transferred to the heat sink <NUM> for heat dissipation. Therefore, the capillary structure <NUM> is disposed in the vacuum cavity <NUM> in the heat dissipation apparatus <NUM>. The capillary structure mainly includes two parts: a condensation-side capillary structure attached to a slab close to the heat sink <NUM>, and an evaporation-side capillary structure attached to a slab close to the chip. In addition, the evaporation-side capillary structure is connected to the condensation-side capillary structure. During specific connection, as shown in <FIG>, the evaporation-side capillary structure is connected to the condensation-side capillary structure by disposing a capillary structure on a side wall connecting the two slabs. The evaporation-side capillary structure is connected to the condensation-side capillary structure further by disposing a support column <NUM> between the two slabs and disposing a capillary structure on the support column <NUM>. The working medium is placed in the foregoing capillary structure, and the heat of the chip is transferred to the heat sink <NUM> by using the working medium. A working principle thereof is as follows: When the heat is conducted from the chip <NUM> (a heat source) to the evaporation-side capillary structure <NUM> through the thermally conductive housing <NUM>, the working medium in the evaporation-side capillary structure <NUM> starts to be gasified from a liquid phase (as shown by black arrows) in an environment with a low vacuum degree. In this case, the working medium absorbs the heat and rapidly expands in volume, and the entire vacuum cavity <NUM> is quickly filled with the gas-phase working medium When the gas-phase working medium moves to a relatively cold region (the condensation-side capillary structure <NUM>), the gas-phase working medium condenses, so as to dissipate heat accumulated during evaporation. After the condensation, the liquid-phase working medium enters the condensation-side capillary structure <NUM> due to a capillary attraction action of the capillary structure, and then flows from the condensation-side capillary structure <NUM> back to the evaporation-side capillary structure <NUM> (as shown by white arrows). This process is cyclically performed in the vacuum cavity <NUM>, so that the heat generated by the chip <NUM> can dissipate. The working medium may be water, kerosene, or another medium that changes in phase after heat absorption. However, regardless of a specific working medium, during use, the working medium is affected by a specific structure of the capillary structure during evaporation and backflow. Therefore, an example of this disclosure provides a new heat dissipation apparatus <NUM>. The following describes the new heat dissipation apparatus <NUM> in detail with reference to specific accompanying drawings.

Referring to both <FIG>, a heat dissipation structure <NUM> provided in this example of this disclosure includes a thermally conductive housing <NUM>. The thermally conductive housing <NUM> is a housing made of a thermally conductive material. The thermally conductive material may be a metal material, such as copper, aluminum, or another metal material that can conduct heat. Certainly, the thermally conductive housing <NUM> may alternatively be made of another material.

When the thermally conductive housing <NUM> is specifically disposed, as shown in <FIG>, the thermally conductive housing <NUM> is a rectangular housing, and the housing has two opposite surfaces, which are defined as a first surface and a second surface for ease of description. A chip placement region is disposed on the first surface. When the heat dissipation apparatus is assembled with the chip <NUM>, the chip <NUM> is fastened in the chip placement region and is connected to the thermally conductive housing <NUM> in a thermally conductive manner. During specific connection, the chip <NUM> may be attached to the thermally conductive housing <NUM> by using a thermally conductive adhesive or directly. When the chip placement region is specifically disposed, the chip placement region is a surface in a partial region on the first surface. When the first surface is specifically disposed, the first surface may be a plane, a partially convex surface, or a partially concave surface. When the chip placement region is disposed, the chip placement region may be a concave part of the first surface or a convex part of the first surface. In addition, a quantity of chip placement regions may be set as required. When there are a plurality of (two or more) chips <NUM>, the chip placement regions may be in a one-to-one correspondence with the chips, or the plurality of chips may be disposed in one chip placement region. This may be specifically set as required.

Still referring to <FIG>, there is a vacuum cavity <NUM> in the housing, and the vacuum cavity <NUM> is an accommodation cavity for accommodating a working medium and a capillary structure <NUM> of the heat dissipation apparatus. The capillary structure <NUM> is a structure for carrying the working medium, and the working medium may be placed in the capillary structure <NUM>. During specific disposal, the capillary structure <NUM> is attached to an inner wall of the thermally conductive housing <NUM>. In addition, to improve a heat dissipation effect of the heat dissipation apparatus, when the capillary structure <NUM> is disposed, as shown in <FIG>, an evaporation-side capillary structure <NUM> in the capillary structure <NUM> is divided into two parts, which are named as a first capillary structure <NUM> and a second capillary structure <NUM> for ease of description. The first capillary structure <NUM> is connected to the second capillary structure <NUM>. In addition, the first capillary structure <NUM> and the second capillary structure <NUM> are fixedly connected to the inner wall of the thermally conductive housing <NUM>, and the second capillary structure <NUM> is divided and arranged on two sides of the first capillary structure <NUM>. When the working medium flows, the working medium absorbs heat and evaporates after flowing from a condensation-side capillary structure <NUM> to the evaporation-side capillary structure <NUM>. Then, the working medium flows back to the second capillary structure <NUM> and the first capillary structure <NUM> after condensing in the condensation-side capillary structure <NUM>. A vertical projection of the first capillary structure <NUM> on the first surface of the housing <NUM> covers at least a part of the chip placement region. In structures shown in <FIG>, <FIG>, and <FIG>, the vertical projection of the first capillary structure <NUM> on the first surface completely overlaps the chip placement region. However, it should be understood that <FIG>, <FIG>, and <FIG> show only one specific case, and the vertical projection of the first capillary structure <NUM> on the first surface may partially or completely cover the chip placement region in this example of this disclosure. "Completely cover" includes: an area of the vertical projection of the first capillary structure <NUM> on the first surface is greater than or equal to an area of the chip placement region. For example, when the first capillary structure <NUM> is specifically disposed, the area of the vertical projection of the first capillary structure <NUM> on the first surface is <NUM>% to <NUM>% of an area of a vertical projection of the chip placement region on the first surface. For example, an area percentage may be any percentage within a range from <NUM>% to <NUM>%, such as <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%. In addition, when the first capillary structure <NUM> is specifically disposed, the projection of the first capillary structure <NUM> on the first surface overlaps an axis of the chip placement region. As shown in <FIG>, an axis of the first capillary structure <NUM> is a center line in a thickness direction of the first capillary structure <NUM>, and the axis of the chip placement region is a center axis perpendicular to a plane of the chip placement region. When the center line overlaps the center axis, the first capillary structure <NUM> and the chip <NUM> may have a same center, so that a heat dissipation effect is improved.

In addition, still referring to <FIG>, when the first capillary structure <NUM> and the second capillary structure <NUM> are specifically disposed, a maximum thickness of the first capillary structure <NUM> is less than a minimum thickness of the second capillary structure <NUM>. The first capillary structure <NUM> and the second capillary structure <NUM> each may be an equal-thickness capillary structure or an unequal-thickness capillary structure. For example, the first capillary structure <NUM> is a capillary structure whose thickness gradually changes, and the second capillary structure <NUM> is an equal-thickness capillary structure. Alternatively, the first capillary structure <NUM> is an equal-thickness capillary structure, and the second capillary structure <NUM> is an unequal-thickness capillary structure. Alternatively, both the first capillary structure <NUM> and the second capillary structure <NUM> may be unequal-thickness capillary structures. When the first capillary structure <NUM> and the second capillary structure <NUM> are unequal-thickness structures, the first capillary structure <NUM> and the second capillary structure <NUM> each may have different cases, for example, a case in which a thickness gradually decreases, a case in which a thickness gradually increases, and a case in which a thickness first increases and then decreases periodically. However, regardless of a specific case, the maximum thickness of the first capillary structure <NUM> is less than the minimum thickness of the second capillary structure <NUM>. The following describes the first capillary structure <NUM> and the second capillary structure <NUM> by using the first capillary structure <NUM> and the second capillary structure <NUM> as examples.

As shown in <FIG>, both the first capillary structure <NUM> and the second capillary structure <NUM> shown in <FIG> are equal-thickness structures. In addition, a thickness of the second capillary structure <NUM> is greater than a thickness of the first capillary structure <NUM> by H (H is a positive integer) millimeters. For the capillary structure <NUM>, a thicker capillary structure <NUM> can reduce flow resistance of the working medium, and a thinner capillary structure <NUM> can reduce thermal resistance during evaporation. It can be learned from the foregoing description that a region above the chip placement region is a region in which the chip <NUM> transfers heat to the working medium Therefore, a corresponding part of the capillary structure <NUM> is thinner, so as to reduce thermal resistance during evaporation. In other words, the first capillary structure <NUM> needs to have a smaller thickness. The evaporation-side capillary structure <NUM> around the above region (which is an "above region" in terms of coordinates in the figure, and does not represent a placement direction of the chip and the heat dissipation apparatus during manufacture, transportation, and use) of the chip placement region is a region to which the liquid-phase working medium flows back. To be specific, a thickness of the capillary structure <NUM> needs to be increased in a region corresponding to the second capillary structure <NUM>, to reduce flow resistance of the working medium, so that the working medium flows back to the first capillary structure <NUM> through the thicker second capillary structure <NUM>. Then, the working medium quickly evaporates through the thinner first capillary structure <NUM> for heat dissipation, so as to improve heat conduction efficiency. Although <FIG> shows that the thickness of the second capillary structure <NUM> is greater than the thickness of the first capillary structure <NUM> by H millimeters, when the first capillary structure <NUM> and the second capillary structure <NUM> are specifically disposed, the thickness of the first capillary structure <NUM> falls within a range from <NUM>% to <NUM>% of the thickness of the second capillary structure <NUM>. For example, the thickness of the first capillary structure <NUM> may be any thickness such as <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% of the thickness of the second capillary structure <NUM>.

In addition, although <FIG> shows that a connection part between the first capillary structure <NUM> and the second capillary structure <NUM> is a vertical side wall, during actual disposal, as shown in <FIG>, there may be a transition part 312a between the first capillary structure <NUM> and the second capillary structure <NUM>. For example, the thickness of the second capillary structure <NUM> gradually decreases to the thickness of the first capillary structure <NUM>. In <FIG>, the transition part 312a between the first capillary structure <NUM> and the second capillary structure <NUM> is a wave surface. Certainly, the transition part 312a may alternatively be a different surface such as an inclined surface or a stepped surface.

When the capillary structure <NUM> is specifically disposed, different structures may be used. For example, the capillary structure <NUM> is a groove structure or a pipe structure. Alternatively, the capillary structure <NUM> is a porous structure. All parts of the capillary structure <NUM> may have a same structure or different structures. For example, a part of the capillary structure <NUM> has a groove structure, and the other part has a pipe structure. Alternatively, the first capillary structure <NUM> may be disposed as a structure different from the second capillary structure <NUM>. For ease of understanding, the following provides a description by using an example in which both the first capillary structure <NUM> and the second capillary structure <NUM> are porous structures. A pore of the first capillary structure <NUM> is connected to a pore of the second capillary structure <NUM>.

When the first capillary structure <NUM> and the second capillary structure <NUM> are porous structures, the pore of the first capillary structure <NUM> and the pore of the second capillary structure <NUM> may be pores with a same diameter, or may be pores with different diameters. For pores with different diameters, a diameter of the pore of the first capillary structure <NUM> is less than or equal to a diameter of the pore of the second capillary structure <NUM>, so that resistance generated when the liquid-phase working medium flows in the second capillary structure <NUM> can be reduced, in other words, backflow resistance of the working medium can be reduced. In addition, when the diameter of the pore of the first capillary structure <NUM> is relatively small, a capillary force of the capillary structure <NUM> increases, and a backflow driving force for the working medium increases.

When the first capillary structure <NUM> and the second capillary structure <NUM> are specifically disposed, different materials may be used to form porous structures. For example, the first capillary structure <NUM> and the second capillary structure <NUM> each are a porous structure formed by sintering metal powder or a metal mesh. For example, the first capillary structure <NUM> is obtained by sintering metal powder, to form a porous structure, and the second capillary structure <NUM> is obtained by sintering a metal mesh, to form the capillary structure <NUM>. Alternatively, the first capillary structure <NUM> is obtained by sintering a metal mesh, to form the capillary structure <NUM>, and the second capillary structure <NUM> is obtained by sintering metal powder, to form the capillary structure <NUM>. Alternatively, both the first capillary structure <NUM> and the second capillary structure <NUM> may be obtained by sintering metal powder, to form the capillary structure <NUM>. Alternatively, both the first capillary structure <NUM> and the second capillary structure <NUM> are obtained by sintering a metal mesh, to form the capillary structure. When the metal mesh is used to form the capillary structure, the metal mesh is woven by using a metal wire, and has a porous structure. A single-layer or multilayer mesh is welded to a wall, to form the capillary structure having a same internal part. However, regardless of whether the first capillary structure <NUM> and the second capillary structure <NUM> are made of the metal powder or metal mesh, the metal powder or metal mesh is a metal or an alloy having a good thermally conductive effect, or another material having high thermally conductive performance, for example, different metals such as copper, aluminum, and iron. In specific implementation, for example, copper powder or a copper mesh made of copper is selected to make the first capillary structure <NUM> and the second capillary structure <NUM>. To facilitate understanding of the capillary structure <NUM> provided in this example of this disclosure, the following separately describes the capillary structure <NUM>.

First, referring to <FIG>, the first capillary structure <NUM> and the second capillary structure <NUM> are made of a same material, for example, by sintering metal powder or a metal mesh. When the first capillary structure <NUM> and the second capillary structure <NUM> are made of the metal powder, the first capillary structure <NUM> and the second capillary structure <NUM> use a same pore diameter, to form the capillary structure <NUM>. In this case, the first capillary structure <NUM> and the second capillary structure <NUM> are made of metal powder with a same diameter. In other words, a diameter of metal powder used for the first capillary structure <NUM> is equal to a diameter of metal powder (in a spherical shape) used for the second capillary structure <NUM>. During sintering, because diameters of the used metal powder are the same, diameters of pores of the first capillary structure <NUM> and the second capillary structure <NUM> that are formed through sintering are equal. For ease of understanding, the diameter of the metal powder is defined. The metal powder is usually spherical metal powder. When the metal powder is in another shape, for example, a cuboid or a cylinder, the diameter of the metal powder is a maximum width of the metal powder.

As shown in <FIG>, the first capillary structure <NUM> and the second capillary structure <NUM> are made of a same material. For example, both the first capillary structure <NUM> and the second capillary structure <NUM> are obtained by sintering metal powder, to form the capillary structure <NUM>. Alternatively, both the first capillary structure <NUM> and the second capillary structure <NUM> are obtained by sintering a metal mesh, to form the capillary structure <NUM>. When the first capillary structure <NUM> and the second capillary structure <NUM> are made of the metal powder, diameters of pores of the first capillary structure <NUM> and the second capillary structure <NUM> are different, and a diameter of a pore of the first capillary structure <NUM> is less than a diameter of a pore of the second capillary structure <NUM>. During specific manufacture, a diameter of metal powder used for the first capillary structure <NUM> is less than a diameter of metal powder used for the second capillary structure <NUM>. Therefore, when the first capillary structure <NUM> and the second capillary structure <NUM> are formed through sintering, because the diameter of the metal powder used for the first capillary structure <NUM> is smaller, a pore of a porous structure formed through sintering is smaller, and because the diameter of the metal powder used for the corresponding second capillary structure <NUM> is larger, a diameter of a pore formed during sintering is larger. In addition, a larger pore diameter can help increase a backflow speed of the working medium, so that a heat dissipation effect of the entire heat dissipation apparatus is improved.

As shown in <FIG>, in a structure shown in <FIG>, the first capillary structure <NUM> and the second capillary structure <NUM> are made of different materials. Specifically, the first capillary structure <NUM> is a porous structure made of a metal mesh, and the second capillary structure <NUM> is a porous structure formed by sintering metal powder. In addition, when the first capillary structure <NUM> and the second capillary structure <NUM> are connected, the first capillary structure <NUM> and the second capillary structure <NUM> are directly connected through sintering. Certainly, <FIG> shows only one specific case. When the first capillary structure <NUM> and the second capillary structure <NUM> are made of different materials, the second capillary structure <NUM> may alternatively be a porous structure formed by sintering a metal mesh, and the first capillary structure <NUM> may alternatively be a porous structure formed by sintering metal powder. A principle thereof is the same as the foregoing principle.

In addition, all parts inside the first capillary structure <NUM> or the second capillary structure <NUM> may be made of a same material, or may be made of different materials. For example, a part of the first capillary structure <NUM> is formed by sintering metal powder, and the other part is formed by sintering a metal mesh. It can be learned from the foregoing descriptions that the first capillary structure <NUM> and the second capillary structure <NUM> provided in this example of this disclosure may be made of different materials, and both can implement an effect of carrying the working medium.

In addition, it should be understood that, although the foregoing description is provided by using an example in which the first capillary structure <NUM> and the second capillary structure <NUM> are porous structures, in this example of this disclosure, the first capillary structure <NUM> and the second capillary structure <NUM> may alternatively be groove structures, pipe structures, or similar structures.

Still referring to <FIG>, when the thermally conductive housing <NUM> is specifically disposed, the thermally conductive housing <NUM> has a second surface opposite to the first surface, and the second surface corresponds to the condensation-side capillary structure <NUM>. During use, a heat sink <NUM> is disposed on the second surface, and the heat sink <NUM> is connected to the thermally conductive housing <NUM> in a thermally conductive manner. In this way, the heat sink <NUM> can dissipate heat in the working medium, so that the working medium condenses and flows back to the first capillary structure <NUM> through the second capillary structure <NUM>. When the heat sink <NUM> is specifically disposed, the heat sink <NUM> may be fixedly connected to the thermally conductive housing <NUM> in a bonding or welding manner. In addition, during disposal, as shown in <FIG>, the heat sink <NUM> is a fin-type heat sink <NUM>. Certainly, another type of heat sink <NUM> may alternatively be used. This is not limited herein.

It can be learned from the foregoing description that the thinner first capillary structure <NUM> is disposed in an evaporation region, so that an evaporation effect of the working medium after heat absorption is improved. In addition, the thicker second capillary structure <NUM> is used to reduce backflow resistance of the working medium In this way, a heat transfer effect of the working medium is improved, and a heat dissipation effect for the chip <NUM> is further improved.

To facilitate understanding of an effect of a heat dissipation structure provided in the examples of this disclosure, the heat dissipation structure is compared with two heat dissipation apparatuses in the prior art. As shown in <FIG>, thermal resistance of the heat dissipation apparatus provided in the examples of this disclosure is far lower than that of the heat dissipation apparatuses in the prior art.

In addition, an example of this disclosure further provides a circuit board. As shown in <FIG>, the circuit board includes a circuit board body <NUM> and a chip <NUM> disposed on the circuit board body <NUM>, and further includes the above mentioned heat dissipation apparatus <NUM>. The chip <NUM> is disposed in a chip placement region of the heat dissipation apparatus <NUM>, and the chip <NUM> is connected to the chip placement region of the heat dissipation apparatus <NUM> in a thermally conductive manner. In the foregoing structure, a thinner first capillary structure <NUM> is disposed at a position corresponding to the chip <NUM>, so that a working medium in the first capillary structure <NUM> evaporates as soon as possible after absorbing heat. In addition, a thicker second capillary structure <NUM> is used to reduce backflow resistance of the working medium In this way, a heat transfer effect of the working medium is improved, and a heat dissipation effect for the chip <NUM> is further improved.

Claim 1:
A heat dissipation apparatus (<NUM>), comprising:
a thermally conductive housing (<NUM>), wherein there is a cuboid vacuum cavity (<NUM>) in the thermally conductive housing (<NUM>), and there is a chip placement region on a first surface of the thermally conductive housing (<NUM>);
a capillary structure (<NUM>) including an evaporation-side capillary structure (<NUM>) close to the chip placement region and a condensation-side capillary structure (<NUM>) on a side of the thermally conductive housing (<NUM>) opposite to the evaporation-side capillary structure (<NUM>), wherein the evaporation-side capillary structure (<NUM>) comprises a first capillary structure (<NUM>) and a second capillary structure (<NUM>) that are connected, wherein the first capillary structure (<NUM>) and the second capillary structure (<NUM>) are fixedly connected to an inner wall of the thermally conductive housing (<NUM>), the first capillary structure (<NUM>) is located on a side close to the first surface, a vertical projection of the first capillary structure (<NUM>) on the first surface covers at least a part of a vertical projection of the chip placement region on the first surface, and a maximum thickness of the first capillary structure (<NUM>) is less than a minimum thickness of the second capillary structure (<NUM>); and
a working medium disposed in the vacuum cavity (<NUM>), wherein the capillary structure (<NUM>) is configured to accommodate and carry the working medium,
wherein
the thermally conductive housing (<NUM>) has a cuboid structure and includes a first slab and a second slab disposed opposite to each other, the first and second slabs being connected in a sealed manner to form the cuboid vacuum cavity (<NUM>),
the evaporation-side capillary structure (<NUM>) is attached to the first slab close to the chip placement region and the condensation-side capillary structure (<NUM>) is attached to the second slab, and
the evaporation-side capillary structure (<NUM>) is connected to the condensation-side capillary structure (<NUM>)
- by further capillary structures on side walls of the thermally conductive housing (<NUM>) connecting the first and second slabs, and
- by at least one support column (<NUM>) between the first slab and the second slab, wherein at least one additional capillary structure is disposed on the support column (<NUM>).