JP2021131214A - Heat conducting member and manufacturing method therefor - Google Patents

Abstract

To provide a heat conducting member comprising a thin wick structure having high heat transport efficiency, and capable of reducing a fall of a material piece constituting the wick structure, and a manufacturing method therefor.SOLUTION: A heat conducting member according to the present invention comprises a case housing a working medium, and a porous wick structure 3 for transporting the working medium. The wick structure has a thickness of 0.02 mm or more and 0.1 mm or less, and has a porosity of 51% or more and 80% or less. The case comprises a first metal plate 4 supporting the wick structure. The wick structure includes a surface layer part 3L1 located separately from the first metal plate, and a body part 3L2 located between the surface layer part and the first metal plate. The surface layer has a structure different from that of the body part. Therefore, the wick structure having high heat transport efficiency can be realized.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heat conductive member and a method for manufacturing the same.

Conventionally, a heat pipe as a heat conductive member has been proposed. A working medium such as water and a wick structure are enclosed inside the heat pipe. When the heat pipe is arranged in contact with the heating element, the working medium inside is heated by the heating element and vaporized. The vaporized steam moves inside the heat pipe to the heat dissipation side and transports heat. On the heat dissipation side, the heat dissipation cools the steam and liquefies it. The working medium that has become a liquid moves in the wick structure toward the heating element due to the capillary phenomenon. Hereinafter, this cycle is repeated.

The above wick structure is formed, for example, by heating a metal paste and joining the metals contained in the metal paste (for example, Patent Document 1).

International release WO2017 / 056842

In recent years, as electronic devices have become thinner, there has been a demand for thinner heat conductive members applied to electronic devices. In order to reduce the thickness of the heat conductive member, it is necessary to reduce the thickness of the wick structure housed in the housing of the heat conductive member. When the wick structure is made thin, it becomes difficult to secure a flow path of the working medium for transporting heat in the wick structure. As a result, the heat transport efficiency may decrease.

Further, if a mass of material constituting the wick structure, that is, a piece of material falls off due to, for example, a decrease in joint strength due to use, the performance of the heat conductive member is deteriorated. Therefore, it is also necessary to reduce the dropout of the material piece.

In view of the above points, the present invention provides a heat conductive member having a thin wick structure having high heat transport efficiency and capable of reducing the falling off of material pieces constituting the wick structure, and a method for manufacturing the same. The purpose is to provide.

An exemplary heat conductive member of the present invention is a heat conductive member including a housing including an operating medium and a porous wick structure for transporting the operating medium, wherein the wick structure is 0. The housing has a first metal plate that supports the wick structure and has a thickness of .02 mm or more and 0.1 mm or less and a void ratio of 51% or more and 80% or less. The wick structure includes a surface layer portion located away from the first metal plate and a main body portion located between the surface layer portion and the first metal plate, and the surface layer portion includes the main body portion and the main body portion. It has a different structure.

In the method for producing an exemplary heat conductive member of the present invention, a metal paste containing metal particles and a volatile resin is applied onto a first metal plate with a thickness of 0.02 mm or more and 0.1 mm or less. By heating the metal paste by the coating step and laser irradiation from the side opposite to the first metal plate and sintering a part of the metal particles, the void ratio is 51% or more and 80% or less. The metal paste heating step of forming the porous wick structure on the first metal plate and the sealing step of sealing the wick structure on the first metal plate together with the working medium are included. The metal paste heating step includes a surface layer portion forming step of forming a surface layer portion at a position away from the first metal plate in the wick structure, the surface layer portion of the wick structure, and the first metal plate. In between, a main body portion forming step of forming a main body portion having a structure different from that of the surface layer portion is included.

According to the present invention, it is possible to realize a heat conductive member having a wick structure which is thin and has high heat transport efficiency. In addition, it is possible to reduce the dropout of the material pieces constituting the wick structure.

FIG. 1 is a cross-sectional view showing a schematic configuration of a vapor chamber as a heat conductive member according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the structure of the wick structure included in the vapor chamber. FIG. 3 is a cross-sectional view schematically showing a metal paste used for forming a wick structure. FIG. 4 is a flowchart showing the flow of the manufacturing process of the vapor chamber. FIG. 5 is a cross-sectional view showing each manufacturing process of the vapor chamber. FIG. 6 is a graph showing the relationship between the porosity and the temperature difference between the heating portion and the heat radiating portion, which is an index for evaluating the heat transport efficiency, for each of the different thicknesses of the wick structure. FIG. 7 is a graph showing the relationship between the particle size and the number of microcopper particles contained in the wick structure.

Hereinafter, the vapor chamber 1 as a heat conductive member according to an exemplary embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the XYZ coordinate system is shown as a three-dimensional Cartesian coordinate system as appropriate. In the XYZ coordinate system, the Z-axis direction indicates the vertical direction (that is, the vertical direction), the + Z direction is the upper side (opposite the gravity direction), and the −Z direction is the lower side (gravity direction). The Z-axis direction is also a direction in which the first metal plate 4 and the second metal plate 5, which will be described later, face each other. The X-axis direction refers to a direction orthogonal to the Z-axis direction, and one direction and the opposite direction thereof are the + X direction and the −X direction, respectively. The Y-axis direction refers to a direction orthogonal to both the Z-axis direction and the X-axis direction, and one direction and the opposite direction thereof are the + Y direction and the −Y direction, respectively.

As used herein, the "particle size" of a particle refers to the maximum outer diameter of the particle. For example, when the particles are spherical, the diameter of the particles, which is the maximum outer diameter of the particles, is the "particle size". On the other hand, when the particles have a shape other than a sphere, the outer diameter of the particles changes depending on the direction. In this case, the maximum outer diameter obtained in each direction is the "particle size" of the particles.

As used herein, the term "sintering" refers to a technique in which a metal powder or a paste containing the metal is heated to a temperature lower than the melting point of the metal to bake and harden the particles of the metal. The "sintered body" refers to an object obtained by sintering.

(1. Configuration of vapor chamber)
FIG. 1 is a cross-sectional view showing a schematic configuration of the vapor chamber 1 of one embodiment. The vapor chamber 1 is a heat conductive member that transports the heat of the heating element H. As the heating element H, for example, an electronic component that generates heat or a substrate on which the electronic component is mounted can be considered. The heating element H is cooled by transporting heat through the vapor chamber 1. Such a vapor chamber 1 is mounted on an electronic device having a heating element H, such as a smartphone or a notebook personal computer.

The vapor chamber 1 includes a heated portion 101 and a heat radiating portion 102. The heated portion 101 is arranged in contact with the heating element H, for example, and is heated by the heat generated by the heating element H. The heat radiating unit 102 releases the heat of the operating medium 2 described later, which is heated by the heated unit 101, to the outside.

The vapor chamber 1 includes a housing 1a. A part of the housing 1a is included in the heated portion 101. The other part of the housing 1a is included in the heat radiating unit 102.

The housing 1a has an internal space 1b. The internal space 1b is a closed space, and is maintained in a decompressed state where the atmospheric pressure is lower than the atmospheric pressure, for example. When the internal space 1b is in a decompressed state, the working medium 2 housed in the internal space 1b is likely to evaporate. The thickness of the housing 1a in the Z-axis direction is, for example, 100 μm or more and 1000 μm or less.

The working medium 2 and the wick structure 3 are housed in the internal space 1b of the housing 1a. The working medium 2 is, for example, water, but may be another liquid such as alcohol. The wick structure 3 is composed of a porous copper sintered body that transports the working medium 2.

That is, the vapor chamber 1 as a heat conductive member includes a housing 1a that houses the working medium 2 and the porous wick structure 3 that transports the working medium 2. The details of the wick structure 3 will be described later.

The housing 1a has a first metal plate 4. The first metal plate 4 supports the wick structure 3 from the −Z direction side. That is, the housing 1a has a first metal plate 4 that supports the wick structure 3. In this embodiment, the first metal plate 4 is copper. The first metal plate 4 may be formed by plating the surface of a metal other than copper with copper. As a metal other than copper, for example, stainless steel can be considered. Although the first metal plate 4 is formed in a concave shape recessed in the −Z direction in FIG. 1, it may be a simple flat plate.

The housing 1a further has a second metal plate 5. The second metal plate 5 is located so as to face the first metal plate 4 in the Z-axis direction. More specifically, the second metal plate 5 is located on the + Z direction side with respect to the first metal plate 4, and covers the wick structure 3 on the first metal plate 4 from the + Z direction side. That is, the housing 1a has a second metal plate 5 that is located opposite to the first metal plate 4 and covers the wick structure 3.

The second metal plate 5 is made of the same metal material as the first metal plate 4. Therefore, when the first metal plate 4 is copper, the second metal plate 5 is also made of copper. When the first metal plate 4 is made of a metal plate having a copper-plated surface of stainless steel, the second metal plate 5 is also made of a metal plate having a copper-plated surface of stainless steel.

The second metal plate 5 has a plurality of ribs 5a. The rib 5a extends from the surface of the second metal plate 5 on the −Z direction side to the −Z direction side and comes into contact with the wick structure 3. Such a rib 5a is composed of, for example, a circular cylinder when viewed from the + Z direction. Further, the ribs 5a are two-dimensionally and regularly arranged side by side in the XY direction. When the rib 5a comes into contact with the wick structure 3 in the Z-axis direction, the thickness of the housing 1a in the Z-axis direction is kept constant. The second metal plate 5 and the rib 5a may be integrated or separate.

The housing 1a further has a joint 6. The joint portion 6 has a joint structure in which the first metal plate 4 and the second metal plate 5 are joined by their respective outer edges. The joint portion 6 is located around the wick structure 3 when viewed from the + Z direction side, and joins the first metal plate 4 and the second metal plate 5. Therefore, the joint portion 6 is located with the wick structure 3 in between in the X-axis direction and the Y-axis direction perpendicular to the Z-axis direction. That is, the housing 1a has a joint portion 6 that connects the first metal plate 4 and the second metal plate 5. The joint portion 6 is located so as to sandwich the wick structure 3 in a direction perpendicular to the facing direction between the first metal plate 4 and the second metal plate 5.

The method of joining the first metal plate 4 and the second metal plate 5 is not particularly limited. For example, any joining method such as hot pressing, diffusion joining, or joining using a brazing material may be used.

Both hot pressing and diffusion joining are methods of joining two members by heating and pressurizing, but they are distinguished from each other in the following points. In diffusion bonding, for example, by heating and pressurizing for several hours, atoms or particles near the bonding interface of the two members are diffused to bond the two members.

On the other hand, in the hot press, only some atoms or particles near the bonding interface of the two members are diffused by heating and pressurizing at a lower temperature and in a shorter time than the diffusion bonding, and the two members are bonded. do.

In diffusion bonding, the bonding interface itself disappears due to the difference in the degree of diffusion of atoms or particles. On the other hand, in hot pressing, a part of the bonding interface disappears and the rest is maintained as it is. Therefore, the joint portion 6 formed by diffusion bonding and the joint portion 6 formed by hot pressing have different bonding structures near the bonding interface. In addition, due to the difference in heating and pressurizing times, the hot press has a shorter manufacturing tact time than the diffusion bonding.

The joint portion 6 may include a sealing portion. The sealing portion is, for example, a portion where an injection port for injecting the working medium 2 into the housing 1a is sealed by welding in the manufacturing process of the vapor chamber 1.

In the vapor chamber 1 having the above configuration, the heated portion 101 is heated by the heat generated by the heating element H. When the temperature of the heated portion 101 rises, the working medium 2 housed in the internal space 1b of the housing 1a evaporates. The vaporized steam moves inside the vapor chamber 1 to the heat radiating portion 102 side. In the heat radiating unit 102, the steam is cooled and liquefied by the heat radiating. The liquefied working medium 2 moves in the wick structure 3 toward the heated portion 101 due to the capillary phenomenon. In FIG. 1, the flow of vapor vaporized by the working medium 2 is indicated by a black arrow, and the flow of the liquid working medium 2 is indicated by a white arrow. As the operating medium 2 moves while changing its state as described above, heat is continuously transported from the heated portion 101 side to the heat radiating portion 102 side.

(2. Details of wick structure)
Next, the details of the wick structure 3 described above will be described. FIG. 2 is a cross-sectional view schematically showing the structure of the wick structure 3. Further, FIG. 3 is a cross-sectional view schematically showing the metal paste 30 used for forming the wick structure 3. The cross sections of FIGS. 2 and 3 are arbitrary cross sections, that is, cross sections at arbitrary positions in the Y-axis direction.

The wick structure 3 has a surface layer portion 3L1 and a main body portion 3L2. The surface layer portion 3L1 is located in the wick structure 3 away from the first metal plate 4 in the + Z direction. The main body portion 3L2 is located between the surface layer portion 3L1 and the first metal plate 4 in the Z-axis direction, and connects the surface layer portion 3L1 and the first metal plate 4. That is, the wick structure 3 has a surface layer portion 3L1 located away from the first metal plate 4, and a main body portion 3L2 located between the surface layer portion 3L1 and the first metal plate 4.

The main body 3L2 includes a plurality of micro copper particles 31 and a first copper body 32. The micro copper particles 31 are particles in which a plurality of copper atoms are aggregated or bonded. The particle size of the micro copper particles 31 is 1 μm or more and less than 1 mm. The microcopper particles 31 are, for example, porous and have pores 31p that are voids inside. In FIG. 2, for the purpose of clearly distinguishing the micro copper particles 31 from the first copper body 32 and the second copper body 3a described later, the micro copper particles 31 are shown without hatching for convenience.

The first copper body 32 is a copper molten body in which the sub-micro copper particles 32a shown in FIG. 3 are melted and solidified by sintering. The sub-micro copper particles 32a are particles in which a plurality of copper atoms are aggregated or bonded. The particle size of the sub-micro copper particles 32a before melting is 0.1 μm or more and less than 1 μm. The first copper body 32 is located around the plurality of micro copper particles 31.

The first copper body 32 includes a first copper particle connecting portion 321 and a second copper particle connecting portion 322. The first copper particle connecting portion 321 connects adjacent micro copper particles 31 to each other at a distance of less than 1 μm. Such a first copper particle connecting portion 321 is formed by sintering sub-micro copper particles 32a located between adjacent micro copper particles 31 and in contact with them.

That is, the particle size of the sub-micro copper particles 32a before melting is less than 1 μm as described above. Therefore, when the sub-micro copper particles 32a located between the adjacent micro-copper particles 31 are melted and hardened, the connecting distance of the adjacent micro-copper particles 31 by the first copper particle connecting portion 321 becomes less than 1 μm.

That is, the main body 3L2 of the wick structure 3 includes a plurality of micro copper particles 31 having a particle size of 1 μm or more, and a first copper body 32 located around the plurality of micro copper particles 31. The first copper body 32 includes a first copper particle connecting portion 321 that connects adjacent micro copper particles 31 to each other at a distance of less than 1 μm. In the main body 3L2, the micro copper particles 31 are connected in a mesh shape via the first copper particle connecting portion 321.

The second copper particle connecting portion 322 connects a part of the plurality of micro copper particles 31 and the first metal plate 4 at a distance of less than 1 μm. As a part of the plurality of micro copper particles 31, for example, among the plurality of micro copper particles 31, micro copper particles 31 located at a position facing the first metal plate 4 at a distance of less than 1 μm can be considered.

Such a second copper particle connecting portion 322 is formed by sintering sub-micro copper particles 32a located between the micro copper particles 31 and the first metal plate 4. That is, the particle size of the sub-micro copper particles 32a is less than 1 μm as described above. Therefore, when the sub-micro copper particles 32a located between the micro-copper particles 31 and the first metal plate 4 are melted and hardened, the micro-copper particles 31 and the first metal plate 4 are formed by the second copper particle connecting portion 322. The connection distance with and is less than 1 μm.

That is, the first copper body 32 includes a second copper particle connecting portion 322 that connects a part of the plurality of micro copper particles 31 and the first metal plate 4 at a distance of less than 1 μm.

The surface layer portion 3L1 includes a second copper body 3a. The second copper body 3a covers the plurality of micro copper particles 31 and the first copper body 32 of the main body 3L2 from the + Z direction side. That is, the surface layer portion 3L1 of the wick structure 3 includes the micro copper particles 31 of the main body portion 3L2 and the second copper body 3a that covers the first copper body 32. As will be described later, the second copper body 3a is formed by sintering and integrating a plurality of micro copper particles 31 and sub-micro copper particles 32a contained in the metal paste 30 by laser irradiation. Therefore, as shown in FIG. 2, the surface layer portion 3L1 and the main body portion 3L2 have different structures from each other. That is, the surface layer portion 3L1 has a structure different from that of the main body portion 3L2. The second copper body 3a is connected to and bonded to at least one of the micro copper particles 31 and the first copper body 32 of the main body 3L2.

The ratio of the thickness th1 of the surface layer portion 3L1 in the Z-axis direction to the thickness th2 of the main body portion 3L2 in the Z-axis direction is set in an appropriate range. For example, it is desirable that th1 / th2 be set to 1/4 or less in order to melt the micro-copper particles 31 of the surface layer portion 3L1 by laser irradiation while suppressing the melting of the micro-copper particles 31 of the main body portion 3L2.

The surface layer portion 3L1 and the main body portion 3L2 of the wick structure 3 further include a gap portion SP. The gap SP is a space that forms a flow path of the working medium 2 together with the pores 31p of the micro copper particles 31 described above. In the wick structure 3, in addition to the above-mentioned micro copper particles 31, the first copper body 32 and the second copper body 3a, the pore portion 31p and the void portion SP are present, so that the porous wick structure 3 is formed. It is composed. The thickness of the wick structure 3 in the Z-axis direction is 0.02 mm or more and 0.1 mm or less. Therefore, the wick structure 3 is thin.

Here, the ratio of the volume of the space to the total product of the wick structure 3 is called the porosity. The unit of porosity is%. The space includes the hole 31p and the void SP. The porosity is determined by the following method. For example, the porosity can be obtained by measuring the area of the space from the cross-sectional photograph of the wick structure 3 and calculating the ratio of the area of the space to the whole. When observing the cross section of the wick structure 3, it is preferable to use a scanning electron microscope having a deep depth of field. The method of observing the cross section is not particularly limited as long as it can easily distinguish between the metal part and the space. Also. The observation range of the cross section is preferably a viewing range that covers the entire cross section at least in the thickness direction of the wick structure 3 and can distinguish the metal portion from the space. Specifically, the observation range of the cross section is an angle range that covers the maximum diameter of the cross section of 200 μm or more and 1000 μm or less. Further, for the calculation of the void ratio based on the observation photograph, it is preferable to use image analysis software capable of dividing the metal part and the space by binarizing the grayscale image and calculating the area of each part.

The porosity can also be determined by the following calculation. That is, the total product of the wick structure 3 is V0 cm ³ . The volume of copper contained in the wick structure 3 is V1 cm ³ . The volume of the space included in the wick structure 3 is V2 cm ³ . In this case, V0 = V1 + V2. Further, where P is the porosity, P = V2 / V0 = (V0-V1) / V0 = 1- (V1 / V0). Here, V1 = (mass of copper) / (density of copper) = (mass of wick structure) / (density of copper). The density of copper is known and is 8.96 g / cm ³ . The unit of mass is g. The mass and total product V0 of the wick structure 3 can be determined by measurement or calculation. Therefore, the porosity P of the wick structure 3 can be obtained from P = 1- (V1 / V0).

The details of the porosity P of the wick structure 3 will be described later.

(3. Details of metal paste)
Next, the details of the metal paste 30 used for forming the wick structure 3 will be described. As shown in FIG. 3, the metal paste 30 further contains a resin 33 in addition to the above-mentioned micro copper particles 31 and sub-micro copper particles 32a.

The resin 33 is a volatile resin that volatilizes at a temperature equal to or lower than the melting point of the copper constituting the micro copper particles 31 and the first copper body 32. As such a volatile resin, for example, a cellulose resin such as methyl cellulose or ethyl cellulose, an acrylic resin, a butyral resin, an alkyd resin, an epoxy resin, a phenol resin or the like can be used. Among these, it is preferable to use an acrylic resin having high thermal decomposability.

The metal paste 30 further contains a dispersion medium that dissolves the resin 33. Examples of the dispersion medium include hydrocarbon solvents, cyclic ether solvents, ketone solvents, alcohol compounds, ester solvents for polyhydric alcohols, ether solvents for polyhydric alcohols, terpene solvents, and mixtures thereof. Etc. can be used. Among these, for example, texanol and terpineol having a boiling point of around 200 ° C. can be preferably used.

The particle size of the micro-copper particles 31 and the sub-micro-copper particles 32a, the compounding ratio or weight ratio of each component contained in the metal paste 30, and the like are appropriately set so as to obtain a desired porosity of the wick structure 3. Just do it.

(4. Manufacturing method of vapor chamber)
Next, a method for manufacturing the vapor chamber 1 of the present embodiment will be described. FIG. 4 is a flowchart showing the flow of the manufacturing process of the vapor chamber 1. FIG. 5 is a cross-sectional view showing each manufacturing process of the vapor chamber 1. In FIG. 4, S indicates a start and E indicates an end. The method for manufacturing the vapor chamber 1 includes a coating step S1, a metal paste heating step S2, a metal plate heating step S3, and a sealing step S4.

(4-1. Coating process)
In the coating step S1, the metal paste 30 is coated on the first metal plate 4 with a thickness of 0.02 mm or more and 0.1 mm or less. The metal paste 30 contains metal particles, a resin 33, and a dispersion medium. Here, the metal particles include the plurality of micro copper particles 31 described above and the plurality of sub micro copper particles 32a. That is, the method for producing the vapor chamber 1 is a coating step S1 in which a metal paste containing metal particles and a volatile resin is applied onto a first metal plate with a thickness of 0.02 mm or more and 0.1 mm or less. include. Further, the metal paste 30 includes a plurality of micro copper particles 31 having a particle size of 1 μm or more and a plurality of sub-micro copper particles 32a having a particle size of less than 1 μm as the metal particles.

(4-2. Metal paste heating process)
In the metal paste heating step S2, the metal paste 30 is heated while scanning the laser beam in the direction parallel to the first metal plate 4 using the laser light source La. That is, the metal paste 30 coated on the first metal plate 4 in the coating step S1 is irradiated with a laser beam from the + Z direction side and the laser beam is scanned in a direction perpendicular to the Z axis direction to scan the metal paste 30. To heat. As a result, the wick structure 3 having the surface layer portion 3L1 and the main body portion 3L2 is formed on the first metal plate 4. The emission wavelength of the laser light is, for example, 1060 to 1080 nm. The scanning speed of the laser beam is, for example, 2000 mm / sec.

More specifically, by irradiating the metal paste 30 with the laser beam, the metal paste 30 is heated with a temperature distribution in the Z-axis direction. For example, the irradiation side of the laser beam in the metal paste 30 is heated at 600 to 700 ° C. Therefore, the resin 33 contained in the metal paste 30 volatilizes, and both the micro copper particles 31 and the sub-micro copper particles 32a are sintered. As a result, the surface layer portion 3L1 is formed at a position away from the first metal plate 4 in the + Z direction. Therefore, the metal paste heating step S2 includes a surface layer portion forming step S21 for forming the surface layer portion 3L1 at a position away from the first metal plate 4. The surface layer portion 3L1 includes a second copper body 3a which is a sintered body of the micro copper particles 31 and the sub-micro copper particles 32a, and the void portion SP.

On the other hand, it is difficult for the laser beam from the + Z direction side to reach the first metal plate 4 side of the metal paste 30. Therefore, it is heated at a temperature lower than that of the surface layer portion 3L1, for example, 400 to 600 ° C. Therefore, the resin 33 contained in the metal paste 30 is volatilized, and only the sub-micro copper particles 32a are sintered. As a result, the main body portion 3L2 is formed between the surface layer portion 3L1 and the first metal plate 4. At this time, since the main body portion 3L2 is formed by sintering only the sub-micro copper particles 32a, the surface layer portion 3L1 formed by sintering both the micro copper particles 31 and the sub-micro copper particles 32a has a structure. Is different. Therefore, in the metal paste heating step S2, a main body portion forming step S22 for forming a main body portion 3L2 having a structure different from that of the surface layer portion 3L1 is performed between the surface layer portion 3L1 of the wick structure 3 and the first metal plate 4. include. The main body 3L2 includes the micro copper particles 31, the first copper particle connecting portion 321 and the second copper particle connecting portion 322 which are sintered bodies of the sub-micro copper particles 32a, and the void portion SP.

The microcopper particles 31 have a larger particle size than the submicrocopper particles 32a. Therefore, when the heating temperature is as low as 400 to 600 ° C., the micro-copper particles 31 are less likely to melt than the sub-micro-copper particles 32a. As a result, in the main body 3L2, only the sub-micro copper particles 32a are melted, and the micro-copper particles 31 remain in the form of particles.

That is, in the main body portion forming step S22, the main body portion including the first copper particle connecting portion 321 that connects the adjacent micro copper particles 31 to each other at a distance of less than 1 μm by sintering the sub-micro copper particles 32a by laser irradiation. Form 3L2.

Further, in the main body forming step S22, the sub-micro copper particles 32a are sintered to connect a part of the plurality of micro copper particles 31 and the first metal plate 4 at a distance of less than 1 μm. A main body portion 3L2 including a portion 321 is formed.

Further, the surface layer portion 3L1 formed in the surface layer portion forming step S21 covers the main body portion 3L2 from the + Z direction side. The second copper body 3a of the surface layer portion 3L1 formed by sintering the micro copper particles 31 and the sub-micro copper particles 32a covers the micro copper particles 31 and the first copper body 32 of the main body portion 3L2. That is, in the surface layer portion forming step S21, the micro copper particles 31 and the sub-micro copper particles 32a are sintered by laser irradiation to cover the micro copper particles 31 and the first copper body 32 of the main body 3L2, and the second copper body 3a is covered. The surface layer portion 3L1 containing the above is formed.

(4-3. Metal plate heating process)
In the metal plate heating step S3, the first metal plate 4 is heated from the −Z direction side. The heating of the first metal plate 4 at this time can be performed, for example, by bringing the heaters into contact with each other. The heating temperature by the heater is, for example, 400 to 600 ° C. That is, the method for manufacturing the vapor chamber 10 further includes a metal plate heating step S3 in which the first metal plate 4 is heated from the side opposite to the coating side of the metal paste 30. The metal plate heating step S3 may be performed as needed.

(4-4. Sealing process)
In the sealing step S4, the wick structure 3 and the working medium 2 are sealed. As a result, the vapor chamber 1 is completed. That is, the method for manufacturing the vapor chamber 1 includes a sealing step S4 for sealing the wick structure 3 on the first metal plate 4 together with the working medium 2.

Here, the sealing step S4 includes an arrangement step S41 and a joining step S42. In the arrangement step S41, the second metal plate 5 is arranged so as to face the first metal plate 4. At this time, the second metal plate 5 is arranged at a position covering the wick structure 3 on the first metal plate 4. In the joining step S42, the first metal plate 4 and the second metal plate 5 are joined together to form the joining portion 6 at a position around the wick structure 3 when viewed from the + Z direction. As a result, the joint portion 6 is located with the wick structure 3 in between in the X-axis direction and the Y-axis direction perpendicular to the Z-axis direction.

The joining in the joining step S42 is performed by, for example, hot pressing. The heating time in the hot press is, for example, 650 ° C., and the processing time for heating and pressurizing is, for example, about 30 seconds. The joining step S42 may be performed by diffusion joining or brazing. Further, in the joining step S32, after the operation medium 2 is injected, a step of sealing the injection port by welding is also performed.

That is, in the sealing step S4, the arrangement step S41 in which the second metal plate 5 covering the wick structure 3 is arranged so as to face the first metal plate 4, and the first metal plate 4 and the second metal plate 5 are arranged. It has a joining step S42 for joining. In the joining step S42, the first metal plate 4 and the second metal plate 5 are joined at a position where the wick structure 3 is sandwiched in a direction perpendicular to the opposite direction of the first metal plate 4 and the second metal plate 5. ..

(5. Setting the porosity)
Next, the porosity of the wick structure 3 will be described. As described above, the porosity of the wick structure 3 is set by adjusting the particle size of each metal particle contained in the metal paste 30, the blending ratio of each component, and the like. For example, when metal pastes A to C having each component in the following compounding ratios are used and the metal pastes A to C are heated by the above-mentioned method to form the wick structure 3, the following in each wick structure 3 Porosity P was obtained.

(Metal paste A)
Micro copper particles: Sub-micro copper particles: Resin: Dispersion medium = 71: 17: 0: 12
Porosity P = 40%
(Metal paste B)
Micro copper particles: Sub-micro copper particles: Resin: Dispersion medium = 70:15:13: 2
Porosity P = 55%
(Metal paste C)
Micro copper particles: Sub-micro copper particles: Resin: Dispersion medium = 62:13:22: 3
Porosity P = 70%

Here, the average particle size of the micro copper particles 31 contained in the metal pastes A to C was 15 μm, and the average particle size of the sub-micro copper particles 32a was 0.3 μm. Further, an acrylic resin was used as the resin 33 of the metal pastes A to C, and texanol was used as the dispersion medium. The compounding ratio is a weight% ratio.

Regarding the void ratio P, an image of a cross section of the wick structure was acquired by a method based on the above-mentioned cross-section observation, that is, a scanning electron microscope, and the void ratio P was obtained from the cross-sectional image using image analysis software.

In the above example, the highest porosity P is obtained in the metal paste C having a resin content of 22% by weight. It is also possible to set the porosity P of the wick structure 3 to 80% by increasing the content of the resin 33 in the metal paste C to more than 22% by weight.

By the way, the thickness of the housing 1a of the vapor chamber 1 is set to 100 μm or more and 1000 μm or less in the present embodiment from the viewpoint of thinning. In order to realize the lower limit of 100 μm as the thickness of the housing 1a, the thickness of the wick structure 3 housed in the housing 1a needs to be 100 μm or less, that is, 0.1 mm or less. .. However, when the thickness of the wick structure 3 is thin and the porosity P of the wick structure 3 is low, the working medium 2 does not flow smoothly in the wick structure 3, and the heat transport efficiency by the working medium 2 decreases. do. Therefore, in the present embodiment, the thickness of the wick structure 3 is 0.1 mm or less, and the high porosity P of the wick structure 3 is realized to improve the heat transport efficiency.

FIG. 6 shows the relationship between the porosity P and the temperature difference ΔT for each thickness T when the thickness T of the wick structure 3 is set to three types of 0.02 mm, 0.06 mm, and 0.1 mm. It is a graph. The porosity P was changed by adjusting the particle size of each metal particle contained in the metal paste 30, the compounding ratio of each component, and the like, as described above.

The temperature difference ΔT is an index for evaluating the heat transport efficiency in the vapor chamber 1, and is represented by ΔT = T1-T2. Here, as shown in FIG. 1, T1 is the temperature measured at the first temperature measurement point M1 of the heated portion 101 heated by the heating element H. T2 is the temperature measured at the second temperature measurement point M2 of the heat radiating unit 102. The smaller the temperature difference ΔT, the more efficiently the heat transport is performed, indicating that the performance as a heat conductive member is excellent. That is, the smaller the temperature difference ΔT, the more the flow path necessary for refluxing the working medium 2 from the heat radiating portion 102 to the heated portion 101 is sufficiently secured inside the wick structure 3, and the heat radiated from the heated portion 101. This means that efficient heat transfer to and from the unit 102 is realized. Specifically, when the temperature difference ΔT is 5 ° C. or less, the heat transport efficiency is evaluated to be high. Further, when the temperature difference ΔT is 4 ° C. or less, the heat transport efficiency is evaluated to be higher.

When the thickness T of the wick structure 3 is 0.02 mm or more and 0.1 mm or less, it can be seen from FIG. 6 that P ≧ 51% should be realized in order to realize ΔT ≦ 5 ° C. Further, in order to realize ΔT ≦ 4 ° C., it can be seen from FIG. 6 that P ≧ 61% should be realized. The upper limit of the porosity P may theoretically be set to exceed 80%, but if the porosity P can be achieved at 80%, T ≦ 4 ° C. can be sufficiently realized. ..

Therefore, in the present embodiment, when the thickness T of the wick structure 3 is 0.02 mm or more and 0.1 mm or less, the porosity P of the wick structure 3 is 51% or more and 80% or less, more preferably 61%. It is set to 80% or more and 80% or less. In such a wick structure 3, in the coating step S1 described above, the metal paste 30 containing the metal particles and the resin 33 in a predetermined blending ratio is placed on the first metal plate 5 with a thickness of 0.02 mm or more and 0.1 mm or less. It is formed by coating with a metal paste, heating the metal paste 30 by laser irradiation in the metal paste heating step S2, and sintering at least a part of the metal particles.

That is, in the method for manufacturing the vapor chamber 1 of the present embodiment, the metal paste 30 is heated by laser irradiation from the side opposite to the first metal plate 4, and a part of the metal particles is sintered to obtain 51%. The metal paste heating step S2 for forming the porous wick structure 3 having a void ratio of 80% or less on the first metal plate 4 is included.

(6. Effect)
As described above, in the vapor chamber 1 as a heat conductive member, the wick structure 3 has a thickness of 0.02 mm or more and 0.1 mm or less, and has a porosity of 51% or more and 80% or less. Have. That is, the wick structure 3 has a thin structure and a high porosity P. Therefore, it is possible to secure a flow path inside the thin wick structure 3 for refluxing the working medium 2 from the low temperature side to the high temperature side, that is, from the heat radiating portion 102 side to the heated portion 101 side. can. Therefore, even if the wick structure 3 is thin, it is possible to suppress a decrease in heat transport efficiency. As a result, it is possible to realize the vapor chamber 1 having the wick structure 3 which is thin and has high heat transport efficiency.

In particular, since the wick structure 3 has a porosity of 61% or more and 80% or less, the necessary flow path of the working medium 2 is surely secured inside the thin wick structure 3. Therefore, it is possible to realize the vapor chamber 1 having the wick structure 3 which is thin and has a higher heat transport efficiency.

Further, in the wick structure 3, the surface layer portion 3L1 has a structure different from that of the main body portion 3L2. Therefore, for example, the material piece, which is a mass of the material constituting the main body portion 3L2 of the wick structure 3, falls off due to the decrease in the bonding strength between the material pieces due to the use of the vapor chamber 1, that is, the main body portion 3L2 and the main body portion 3L2. Can be suppressed by the surface layer portion 3L1 having a different structure. As a result, deterioration of the heat conduction performance of the vapor chamber 1 can be suppressed. In particular, in the configuration in which the wick structure 3 contains the micro-copper particles 31, the above-mentioned material piece is a metal piece containing the micro-copper particles 31. In this case, the surface layer portion 3L1 can prevent the metal piece from falling off from the main body portion 3L2.

Further, in the coating step S1, the metal paste 30 containing the metal particles is coated on the first metal plate 4 with a thickness of 0.02 mm or more and 0.1 mm or less. Then, in the metal paste heating step S2, the metal paste 30 is heated by laser irradiation from the side opposite to the first metal plate 4, and a part of the metal particles is sintered to be 51% or more and 80% or less. A porous wick structure 3 having a void ratio is formed on the first metal plate 4. The wick structure 3 is formed as thin as 0.02 mm or more and 0.1 mm or less in thickness, but has a high porosity. Therefore, with the thin structure of the wick structure 3, it is possible to secure the necessary flow path of the working medium 2 inside the wick structure 3. Therefore, it is possible to manufacture the vapor chamber 1 having the wick structure 3 which is thin and has high heat transport efficiency. Further, the wick structure 3 to be formed includes a surface layer portion 3L1 and a main body portion 3L2 having different structures from each other. As a result, the material piece can be suppressed from falling off from the main body portion 3L2 by the surface layer portion 3L1, and the deterioration of the heat conduction performance of the vapor chamber 1 can be suppressed.

Further, in the main body portion 3L2 of the wick structure 3, adjacent micro copper particles 31 are connected to each other by a first copper particle connecting portion 321 at a distance of less than 1 μm. As described above, the first copper particle connecting portion 321 heats the sub-micro copper particles 32a having a particle size of less than 1 μm at a temperature much lower than the melting point of copper of about 1085 ° C. and in a short time. And obtained by melting. Therefore, the structure having the first copper particle connecting portion 321 can contribute to the formation of the porous wick structure 3 in a short time and the productivity improvement of the vapor chamber 1.

Further, as described above, the configuration in which the main body portion 3L1 has the micro copper particles 31 and the first copper body 32 and the first copper body 32 has the first copper particle connecting portion 321 is micro copper as the metal particles. It can be realized by heating the metal paste 30 containing the particles 31 and the sub-micro copper particles 32a by laser irradiation. Therefore, for example, when the total number of metal particles used and the volume of the wick structure 3 are constant, compared with the case where the wick structure 3 is formed using only metal particles having a particle size of 1 μm or more. As the total volume of the metal particles decreases, the void ratio of the wick structure 3 can be increased. Therefore, it becomes easy to realize the wick structure 3 which is thin and has a high porosity.

A part of the plurality of micro copper particles 31 and the first metal plate 4 are connected by a second copper particle connecting portion 322 at a distance of less than 1 μm. The second copper particle connecting portion 322 is obtained by heating and melting the sub-micro copper particles 32a at a low temperature and in a short time in the same manner as the first copper particle connecting portion 321. Therefore, the structure having the second copper particle connecting portion 322 can also contribute to the formation of the wick structure 3 in a short time and the improvement of the productivity of the heat conductive member. Further, since the micro copper particles 31 and the first metal plate 4 are connected by the second copper particle connecting portion 322, it is possible to reduce the situation where the wick structure 3 is peeled off from the first metal plate 4.

Further, the surface layer portion 3L1 of the wick structure 3 includes a second copper body 3a that covers the micro copper particles 31 of the main body portion 3L2 and the first copper body 32. The second copper body 3a is obtained, for example, by sintering the micro copper particles 31 and the sub-micro copper particles 32a as described above. Therefore, the wick structure 3 having a different structure between the surface layer portion 3L1 and the main body portion 3L2 can be realized, and the falling off of the material piece from the main body portion 3L2 can be suppressed by the second copper body 3a of the surface layer portion 3L1.

The first metal plate 4 is copper. In this case, the micro copper particles 31 and the second copper particle connecting portion 322 of the main body portion 3L2 of the wick structure 3 and the first metal plate 4 are all made of copper of the same material. Therefore, the micro copper particles 31 and the first metal plate 4 can be more easily connected via the second copper particle connecting portion 322 than when the metals of different materials are connected to each other. Therefore, peeling of the wick structure 3 from the first metal plate 4 can be reliably suppressed.

Similarly, when the first metal plate 4 is formed of a metal having a copper plating on its surface, peeling of the wick structure 3 from the first metal plate 4 can be reliably suppressed.

The first metal plate 4 and the second metal plate 5 are joined by a joint portion 6 at a position where the wick structure 3 is sandwiched in a direction perpendicular to the opposite direction. As described above, the above-mentioned effect can be obtained in the vapor chamber 1 having a structure in which the first metal plate 4 and the second metal plate 5 are arranged to face each other via the wick structure 3.

Further, in the main body portion forming step S21, the main body portion 3L2 including the first copper particle connecting portion 321 is formed by sintering the sub-micro copper particles 32a by laser irradiation. Then, in the main body portion 3L2, the adjacent micro copper particles 31 are connected to each other by the first copper particle connecting portion 321. Thereby, the situation where the micro copper particles 31 are scattered at the same time as the resin 33 is volatilized by the laser irradiation can be reduced by the presence of the first copper particle connecting portion 321. Therefore, even by the method of heating the metal paste 30 by laser irradiation, the porous wick structure 31 containing the micro copper particles 31 can be produced. Further, in the main body portion 3L2, the adjacent micro copper particles 31 are connected to each other by the first copper particle connecting portion 321 at a distance of less than 1 μm. The first copper particle connecting portion 321 is obtained by heating and melting submicro copper particles 32a having a particle size of less than 1 μm at a temperature much lower than the melting point of copper and in a short time. Therefore, the porous wick structure 3 can be formed in a short time, thereby improving the productivity of the vapor chamber 1.

In the main body portion forming step S22, the main body portion 3L2 having the second copper particle connecting portion 322 is formed. Since the micro copper particles 31 and the first metal plate 4 are connected by the second copper particle connecting portion 322, it is possible to reduce the situation where the wick structure 3 is peeled off from the first metal plate 4. Further, the second copper particle connecting portion 322 is obtained by heating and melting the sub-micro copper particles 32a at a low temperature and in a short time, similarly to the first copper particle connecting portion 321. Therefore, the wick structure 3 having the second copper particle connecting portion 322 can be formed in a short time, and the productivity of the vapor chamber 1 can be improved.

Further, the second copper body 3a contained in the surface layer portion 3L1 is formed by sintering the micro copper particles 31 and the sub-micro copper particles 32a by laser irradiation. As a result, it is possible to reduce the metal pieces containing the micro copper particles 31 constituting the surface layer portion 3L1 from falling off from the wick structure 3.

Further, by heating the first metal plate 4 from the side opposite to the laser beam irradiation side, the sub-micro copper particles located between a part of the micro copper particles 31 of the main body 3L2 and the first metal plate 4 are formed. 32a can be easily melted. As a result, it becomes easy to connect the micro copper particles 31 and the first metal plate 4 via the second copper particle connecting portion 322 which is a sintered body of the sub-micro copper particles 32a. As a result, the situation where the wick structure 3 is peeled off from the first metal plate can be easily reduced.

In the sealing step S4, the first metal plate 4 and the second metal plate 5 are arranged to face each other, and they are connected at a position where the wick structure 3 is sandwiched in a direction perpendicular to the facing direction. As a result, it is possible to obtain a vapor chamber 1 having a structure in which the first metal plate 4 and the second metal plate 5 are arranged and joined to face each other via the wick structure 3.

(7. Particle size distribution of micro copper particles)
FIG. 7 is a graph showing the relationship between the particle size Md of the microcopper particles 31 contained in the wick structure 3, particularly the main body 3L2, and the number of particles A. It is desirable that the plurality of micro copper particles 31 have a first copper particle group 31A and a second copper particle group 31B. The first copper particle group 31A is a set of micro copper particles 31 having a particle size Md1 as an average particle size. The second copper particle group 31B is a set of micro copper particles 31 having a particle size Md2 as an average particle size. However, Md1 <Md2. The particle size distribution shown in FIG. 7 has a peak P1 having a particle size of Md1 and a peak P2 having a particle size of Md2. Therefore, the particle size distribution of the plurality of micro copper particles 31 has a plurality of peaks having different particle sizes. The units of the particle sizes Md, Md1 and Md2 are μm, respectively. The unit of the number of particles A is "pieces".

In the above particle size distribution, for example, if only the peak P2 is shifted in the direction of increasing the average particle size while maintaining the peak P1, the number of microcopper particles 31 having a large particle size increases, so that the wick structure 3 The porosity P decreases. In addition, when the peak P1 is also shifted in the direction in which the average particle size increases, the porosity P further decreases. On the contrary, if only the peak P2 is shifted in the direction of decreasing the average particle size while maintaining the peak P1, the number of microcopper particles 31 having a large particle size decreases, so that the porosity P increases. In addition, when the peak P1 is also shifted in the direction in which the average particle size decreases, the porosity P further increases.

Therefore, as shown in FIG. 7, when the particle size distribution of the microcopper particles 31 has a plurality of peaks, the porosity P of the wick structure 3 can be easily changed by changing the peak of at least one particle size. be able to. That is, it becomes easy to finely adjust the porosity P of the wick structure 3.

Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to this, and various modifications can be made without departing from the gist of the invention. Further, the above-described embodiment and its modifications can be arbitrarily combined as appropriate.

The heat conductive member of the present invention can be used, for example, as a member for heat dissipation of a substrate or an electronic component mounted on an electronic device.

1 Vapor chamber (heat conductive member)
1a Housing 2 Operating medium 3 Wick structure 3a Second copper body 3L1 Surface layer part 3L2 Main body part 4 First metal plate 5 Second metal plate 6 Joint part 30 Metal paste 31 Micro copper particles 32 First copper body 32a Sub-micro copper Particle 33 Resin 321 First copper particle connecting part 322 Second copper particle connecting part P Void ratio

Claims (14)

A heat conductive member comprising a housing for accommodating an actuating medium and a porous wick structure for transporting the actuating medium.
The wick structure has a thickness of 0.02 mm or more and 0.1 mm or less, and has a porosity of 51% or more and 80% or less.
The housing has a first metal plate that supports the wick structure.
The wick structure is
A surface layer portion located away from the first metal plate and
Including a main body portion located between the surface layer portion and the first metal plate,
The surface layer portion is a heat conductive member having a structure different from that of the main body portion. The main body
With a plurality of microcopper particles having a particle size of 1 μm or more,
Includes a first copper body located around the plurality of microcopper particles.
The heat conductive member according to claim 1, wherein the first copper body includes a first copper particle connecting portion that connects adjacent micro copper particles to each other at a distance of less than 1 μm. The heat conduction according to claim 2, wherein the first copper body further includes a second copper particle connecting portion that connects a part of the plurality of micro copper particles and the first metal plate at a distance of less than 1 μm. Element. The heat conductive member according to claim 2 or 3, wherein the surface layer portion includes the micro copper particles of the main body portion and a second copper body covering the first copper body. The heat conductive member according to any one of claims 2 to 4, wherein the first metal plate is copper. The housing is
A second metal plate located opposite to the first metal plate and covering the wick structure,
It has a joint portion that connects the first metal plate and the second metal plate.
The heat conductive member according to any one of claims 1 to 5, wherein the joint portion is located so as to sandwich the wick structure in a direction perpendicular to the opposite direction of the first metal plate and the second metal plate. .. The heat conductive member according to any one of claims 1 to 6, wherein the wick structure has a porosity of 61% or more and 80% or less. The heat conductive member according to any one of claims 1 to 7, wherein the particle size distribution of the plurality of microcopper particles has a plurality of peaks having different particle sizes. A coating step of applying a metal paste containing metal particles and a volatile resin on a first metal plate with a thickness of 0.02 mm or more and 0.1 mm or less.
A porous wick having a void ratio of 51% or more and 80% or less by heating the metal paste by laser irradiation from the side opposite to the first metal plate and sintering a part of the metal particles. A metal paste heating step of forming the structure on the first metal plate, and
Including a sealing step of sealing the wick structure on the first metal plate together with a working medium.
The metal paste heating step is
In the wick structure, a surface layer portion forming step of forming a surface layer portion at a position away from the first metal plate, and
A method for manufacturing a heat conductive member, which comprises a main body portion forming step of forming a main body portion having a structure different from that of the surface layer portion between the surface layer portion of the wick structure and the first metal plate. The metal paste contains, as the metal particles, a plurality of microcopper particles having a particle size of 1 μm or more and a plurality of submicrocopper particles having a particle size of less than 1 μm.
In the main body forming step, the main body including the first copper particle connecting portion that connects the adjacent micro copper particles to each other at a distance of less than 1 μm by sintering the sub-micro copper particles by the laser irradiation. The method for manufacturing a heat conductive member according to claim 9, wherein the heat conductive member is formed. In the main body forming step, the sub-micro copper particles are sintered to form a second copper particle connecting portion that connects a part of the plurality of micro copper particles and the first metal plate at a distance of less than 1 μm. The method for manufacturing a heat conductive member according to claim 10, further comprising the main body portion. The surface layer forming step includes the micro copper particles in the main body and the second copper body covering the first copper body by sintering the micro copper particles and the sub micro copper particles by the laser irradiation. The method for producing a heat conductive member according to claim 10 or 11, which forms the surface layer portion. The method for producing a heat conductive member according to any one of claims 9 to 12, further comprising a metal plate heating step of heating the first metal plate from a side opposite to the coating side of the metal paste. The sealing step is
An arrangement step of arranging the second metal plate covering the wick structure so as to face the first metal plate,
It has a joining step of joining the first metal plate and the second metal plate.
In the joining step, the first metal plate and the second metal plate are joined at a position sandwiching the wick structure in a direction perpendicular to the opposite direction of the first metal plate and the second metal plate. , The method for manufacturing a heat conductive member according to any one of claims 9 to 13.

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