JP7494726B2 - Heat conducting structure and method for manufacturing the same - Google Patents

Description

The present invention relates to a heat conducting structure and a method for manufacturing a heat conducting structure.

Patent document 1 discloses a light source device that includes a light source that emits blue light and a wavelength conversion optical system that absorbs the blue light and converts it into fluorescence. The wavelength conversion optical system includes a lens that collects light, a phosphor, a substrate that is in thermal contact with the phosphor, and a heat sink that is bonded to the substrate.

Since the phosphor is irradiated with blue light from the light source, it may become hot and its characteristics may deteriorate. For this reason, it is necessary to dissipate heat from the phosphor through a substrate or heat sink. Patent Document 1 discloses that Al or Cu, which have low thermal resistance, can be used as the substrate material.

JP 2014-165058 A

The Al and Cu substrate materials disclosed in Patent Document 1 have high thermal conductivity among metal materials, but their thermal resistance is still too high to dissipate the heat of the phosphor sufficiently. For this reason, depending on the intensity of the blue light irradiated on the phosphor, the phosphor may become hot, reducing the efficiency of excitation of the fluorescence.

In addition, carbon materials such as graphite and graphene are known as materials for heat dissipation substrates. While these materials have sufficiently high thermal conductivity, they are anisotropic in thermal conduction. This anisotropy is one of the factors that reduces the efficiency of heat transfer between the phosphor and the heat sink.

The thermal conduction structure according to the application example of the present invention includes:
a mounting substrate having a plurality of diamond substrates bonded together and connected to a heat source;
a thermally conductive substrate bonded to the mounting substrate on an opposite side to the heat source, the thermally conductive substrate being thicker than the diamond substrate;
The present invention is characterized by comprising:

A method for manufacturing a heat conduction structure according to an embodiment of the present invention includes the steps of:
forming a surface modification film containing a metal material on a surface of an individual piece mainly made of diamond to obtain a diamond substrate;
bonding the diamond substrates together to obtain a mount substrate;
bonding the mounting substrate to a thermally conductive substrate that is thicker than the diamond substrate;
connecting a heat source to the mounting substrate opposite the thermally conductive substrate;
bonding a cooling mechanism to the thermally conductive substrate on a side opposite to the mounting substrate;
The present invention is characterized by having the following.

1 is a plan view showing a light source device having a heat conducting structure according to a first embodiment. 2 is a cross-sectional view taken along line AA of FIG. 1. FIG. 3 is a partially enlarged view of FIG. 2 . FIG. 11 is a cross-sectional view showing a first modified example of a mounting substrate. FIG. 11 is a cross-sectional view showing a second modified example of the mounting substrate. FIG. 11 is a plan view showing a light source device having a heat conducting structure according to a second embodiment. This is a cross-sectional view taken along line B-B of FIG. FIG. 11 is a cross-sectional view showing a light source device having a heat conduction structure according to a modified example of the second embodiment. 10 is a flowchart illustrating a method for manufacturing a thermal conduction structure according to a third embodiment. 10A to 10C are cross-sectional views illustrating a method for manufacturing the thermal conduction structure shown in FIG. 9 . 10A to 10C are cross-sectional views illustrating a method for manufacturing the thermal conduction structure shown in FIG. 9 . 10A to 10C are cross-sectional views illustrating a method for manufacturing the thermal conduction structure shown in FIG. 9 . 10A to 10C are cross-sectional views illustrating a method for manufacturing the thermal conduction structure shown in FIG. 9 .

The heat conduction structure and the method for manufacturing the heat conduction structure of the present invention will be described in detail below with reference to the attached drawings.

1. First Embodiment First, a thermal conduction structure according to a first embodiment will be described.

1.1. Heat Conduction Structure FIG. 1 is a plan view showing a light source device having a heat conduction structure according to the first embodiment. FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1. In each drawing of the present application, an X-axis, a Y-axis, and a Z-axis are set as three mutually orthogonal axes. Each axis is represented by an arrow, with the tip end side being "plus" and the base end side being "minus". In the following description, the plus side of the Z-axis is described as "upper" and the minus side of the Z-axis is described as "lower". Furthermore, in this specification, a view from a position on the Z-axis is referred to as a "planar view". In addition, "connection" and "joining" in this specification each include not only a state in which the target members are directly connected or joined to each other, but also a state in which the target members are indirectly connected or joined via any member.

The light source device 1 shown in Figures 1 and 2 has a plano-convex lens 11, a spacer 13, and a heat conducting structure 15. The heat conducting structure 15 includes a phosphor 14 (heat source), a mounting substrate 12, a heat conducting substrate 16, and a heat sink 17.

The plano-convex lens 11 is a convex lens with one surface that is curved and convex outward in the optical axis direction, and the other surface that is a flat surface 11a. As shown in FIG. 2, the plano-convex lens 11 has its flat surface 11a fitted into the recess 13b of the spacer 13. The flat surface 11a of the plano-convex lens 11 is bonded to the bottom surface 13c of the recess 13b of the spacer 13 and to the top surface 14a of the phosphor 14.

The material of which the plano-convex lens 11 is made is not particularly limited as long as it is a transparent material, but examples include glass, quartz, etc.

The mounting substrate 12 is a flat plate material. The mounting substrate 12 is thermally connected to the phosphor 14, which is a heat source. The shape of the mounting substrate 12 in a plan view is not particularly limited, and may be a rectangular shape as shown in FIG. 1, or a circular shape. The size of the mounting substrate 12 is not particularly limited, as long as the spacer 13 and the phosphor 14 can be placed on the upper surface 12a of the mounting substrate 12.

The mount substrate 12 has a plurality of diamond substrates 120 bonded to each other. The diamond substrates 120 have a particularly high thermal conductivity and also have little anisotropy in thermal conduction. Therefore, the mount substrate 12 having the diamond substrates 120 can efficiently diffuse and dissipate heat from the phosphor 14. The diamond substrates 120 will be described later.

As shown in FIG. 2, the spacer 13 is adhered to the upper surface 12a of the mounting substrate 12 via adhesive 31. The spacer 13 has a recess 13b that opens in the center of the upper surface 13d in a plan view, and a through hole 13a that penetrates the center of the recess 13b in the thickness direction in a plan view.

The material that the spacer 13 is made of is not particularly limited as long as it has low thermal resistance, but examples include oxygen-free copper and pure aluminum.

The phosphor 14 emits fluorescence LF when it receives the excitation light LE. Therefore, the phosphor 14 generates heat as a result of receiving the excitation light LE, and serves as a heat source. Examples of phosphors 14 include YAG (yttrium aluminum garnet) phosphors.

The phosphor 14 is an example of a heat source that dissipates heat by the heat conduction structure 15, but it can be replaced with other heat sources. Examples of heat sources other than the phosphor 14 include light-emitting elements such as light-emitting diodes and semiconductor lasers, and power semiconductors such as IGBTs (insulated gate bipolar transistors) and power MOSFETs (metal oxide semiconductor field effect transistors). Depending on the type of heat source, the plano-convex lens 11 and spacer 13 may be replaced with other members or may be omitted.

The phosphor 14 is surrounded by the plano-convex lens 11, the spacer 13, and the mounting substrate 12. As described above, the phosphor 14 is thermally connected to the mounting substrate 12. A filler (not shown) is provided between the upper surface 14a of the phosphor 14 and the plano-convex lens 11. This fills the gap between the upper surface 14a of the phosphor 14 and the plano-convex lens 11, allowing the light emitted from the phosphor 14 to be efficiently captured by the plano-convex lens 11.

The lower surface 14b of the phosphor 14 is bonded to the upper surface 12a of the mounting substrate 12 via a reflective film 140 and a thermally conductive adhesive 21, which will be described later, to provide a thermal connection. The thermally conductive adhesive 21 is not particularly limited as long as it has thermal conductivity, and may be an adhesive whose main material is a conductive polymer, but is preferably composed of a paste-like adhesive containing conductive particles or a hardened sheet-like adhesive. Examples of the conductive particles include silver particles, gold particles, aluminum particles, and resin particles coated with a conductive metal. The average particle size of the conductive particles is preferably about 0.1 μm or more and 100 μm or less, and more preferably about 1.0 μm or more and 10 μm or less. Examples of the shape of the conductive particles include a spherical shape, a flake shape, and a fibrous shape. Note that the lower surface 14b and the upper surface 12a may simply be in contact as long as they are thermally connected.

A reflective film 140 is provided on the lower surface 14b of the phosphor 14. The reflective film 140 is a thin film that reflects the light emitted by the phosphor 14. The reflective film 140 is made of a material with high thermal conductivity, such as silver.

The space surrounded by the plano-convex lens 11, the spacer 13, and the mounting substrate 12 is preferably sealed, forming a sealed space 19. This sealed space 19 is preferably filled with an inert gas. This makes it possible to suppress the deterioration of the phosphor 14 due to oxidation or moisture absorption. An example of an inert gas is nitrogen.

The upper surface 16a of the thermally conductive substrate 16 is joined to the lower surface 12b of the mounting substrate 12 via a thermally conductive adhesive 22. The thermally conductive substrate 16 is thicker than the mounting substrate 12. As a result, the thermally conductive substrate 16 has a larger heat capacity than the mounting substrate 12, and can efficiently absorb the heat of the mounting substrate 12. This makes it possible to prevent the temperature of the phosphor 14 from continuing to rise, even when the phosphor 14 is continuously irradiated with light.

The thickness of the thermally conductive substrate 16 is not particularly limited as long as it is thicker than the diamond substrate 120 of the mounting substrate 12. Considering the balance between the heat capacity expected of the thermally conductive substrate 16 and the thermal diffusivity expected of the diamond substrate 120, the difference in thickness between the two is preferably 0.1 mm or more, more preferably 0.3 mm or more, and even more preferably 0.5 mm or more.

The upper limit of the difference is not particularly limited, but in order to reduce the size and weight of the light source device 1, it is preferable that the upper limit be 10 mm or less, and more preferably 5 mm or less.

The material of the thermally conductive substrate 16 is not particularly limited as long as it has a high thermal conductivity, but examples include aluminum or an aluminum alloy, copper or a copper alloy, and a composite material of copper or a copper alloy and carbon.

The thermally conductive adhesive 22 is appropriately selected from the adhesives used as the thermally conductive adhesive 21. The type and composition of the thermally conductive adhesive 22 may be different from those of the thermally conductive adhesive 21.

The heat sink 17 is bonded to the lower surface 16b of the thermally conductive substrate 16 via a thermally conductive adhesive 23. The heat sink 17 includes a base 172 and a plurality of flat fins 174 extending from the base 172. The plurality of fins 174 are arranged at equal intervals along the lower surface of the base 172.

The material of the heat sink 17 is not particularly limited as long as it is a material that can dissipate heat from the thermally conductive substrate 16, but examples include aluminum alone or an aluminum alloy, copper alone or a copper alloy, etc.

The heat sink 17 is a type of cooling mechanism, but may be replaced by other cooling mechanisms. Examples of other cooling mechanisms include a heat pipe and a vapor chamber.

The thermally conductive adhesive 23 is appropriately selected from the adhesives used as the thermally conductive adhesive 21. The type and composition of the thermally conductive adhesive 23 may be different from those of the thermally conductive adhesive 21.

In the light source device 1 as described above, the light emitted by the phosphor 14 is reflected upward by the reflective film 140. The light reflected by the reflective film 140 is then emitted to the outside via the plano-convex lens 11. For this reason, the light source device 1 is suitable for use as a reflective wavelength conversion element for a projector, for example. Note that the heat conductive structure 15 can also be used as a transmissive wavelength conversion element by providing through holes (not shown) in the heat conductive substrate 16 and the heat sink 17.

The heat conducting structure 15 may not include the phosphor 14 and the heat sink 17. In other words, the heat conducting structure 15 may be composed of at least the mounting substrate 12 and the heat conducting substrate 16.

In this way, the heat conduction structure 15 according to this embodiment is used, as an example, to dissipate heat from the phosphor 14, which serves as a heat source. This makes it possible to prevent the phosphor 14 from becoming too hot, even when light is continuously irradiated onto the phosphor 14. Therefore, for example, a reflective or transmissive wavelength conversion element can be realized.

1.2 Diamond Substrate As described above, the mount substrate 12 has a plurality of diamond substrates 120 bonded together. The method of bonding the diamond substrates 120 together is not particularly limited, and examples thereof include a method of bonding the diamond substrates 120 together via a surface modification film (metallized coating), a method of bonding the diamond substrates together via a bonding material, and a method of directly bonding the diamond substrates together to integrate them.

Figure 3 is a partially enlarged view of Figure 2. The diamond substrate 120 shown in Figure 3 includes a base 121 made of diamond, and a surface modification film 122 containing a metal material that is provided on the surface of the base 121. By providing such a surface modification film 122, it is possible to impart adhesiveness to other members to the surface of the base 121. This makes it possible to realize a diamond substrate 120 that combines the excellent thermal conductivity of diamond with the excellent adhesiveness of the surface modification film 122.

The base 121 is a portion whose main material is diamond. In this specification, the term "main material" refers to a material that occupies 70% or more by volume fraction. The main material of the base 121 may be single crystal diamond or polycrystalline diamond.

The heat of the phosphor 14 first flows quickly along the in-plane direction of the base 121, as shown by heat flow HF1 in FIG. 3. This allows the heat of the phosphor 14 to be diffused quickly. The diffused heat is then transferred from the base 121 to the thermally conductive substrate 16 via the surface modification film 122 and the thermally conductive adhesive 22, as shown by heat flow HF2 in FIG. 3. In this way, the mounting substrate 12 functions as a heat spreader.

The diamond substrate 120 of the mounting substrate 12 preferably contains single crystal diamond. In other words, the base 121 is preferably composed of single crystal diamond. Among diamond-based materials, single crystal diamond has particularly high thermal conductivity. In addition, the thermal conductivity of single crystal diamond has very small anisotropy. For this reason, the diamond substrate 120 containing single crystal diamond can efficiently spread the heat of the phosphor 14 in the in-plane direction and efficiently conduct it in the thickness direction to the thermally conductive substrate 16. As a result, the phosphor 14 can be efficiently cooled, and even if the phosphor 14 is continuously irradiated with light, the characteristics of the phosphor 14 can be prevented from deteriorating.

Methods for manufacturing the base 121 include, for example, high-temperature and high-pressure methods and chemical vapor synthesis (CVD) methods. Among these, the chemical vapor synthesis method described below allows the production of substrate-shaped single crystal diamond at relatively low cost.

The thermal conductivity of the diamond that constitutes the base 121 is preferably 1000 [W/m·K] or more, and more preferably 1500 [W/m·K] or more.

The planar shape of the diamond substrate 120 is not particularly limited, but as an example, it is a rectangle with sides preferably having a length of 2 mm to 50 mm, more preferably 3 mm to 10 mm. This makes it possible to prevent the number of diamond substrates 120 from increasing significantly when arranging multiple diamond substrates 120 in a tiled pattern, thereby improving the efficiency of the tiling work and avoiding the diamond substrates 120 from becoming significantly expensive. In addition, by preventing the number of diamond substrates 120 from increasing significantly, it is possible to prevent the thermal resistance inside the mount substrate 12 from increasing.

The planar shape of the diamond substrate 120 shown in FIG. 1 is a square. This can improve the isotropy of thermal conduction in the in-plane direction of the XY plane of the diamond substrate 120.

The length of one side of the diamond substrate 120 shown in FIG. 1 is L2. The lower surface 14b of the phosphor 14 is the connection surface to the mounting substrate 12, and is square in FIG. 1. The length of one side of the lower surface 14b is L1. The length L2 may be equal to or greater than the length L1, but in this embodiment, the length L2 is set to be shorter than the length L1.

In other words, the heat conducting structure 15 shown in Figures 1 and 2 has a phosphor 14 (heat source) having a lower surface 14b which is the connection surface with the mounting substrate 12, but the upper surface 120a and the lower surface 120b of the diamond substrate 120 are each set smaller than the lower surface 14b. The upper surface 120a and the lower surface 120b are the two main surfaces of the diamond substrate 120 which are in a front-back relationship with each other.

With this configuration, even if the lower surface 14b, which is the connection surface between the phosphor 14 and the mounting substrate 12, is large, the diamond substrate 120 can be made small, making it easy to reduce the cost of the mounting substrate 12. In other words, since the thermal conductivity of the diamond substrate 120 is sufficiently high, even if multiple small diamond substrates 120 are arranged side by side, a sufficiently high thermal conductivity can be ensured for the entire mounting substrate 12. Therefore, a light source device 1 with sufficiently low cost can be realized regardless of the size of the phosphor 14, which is the heat source.

As an example, the area of the diamond substrate 120 is preferably 90% or less of the area of the lower surface 14b, which is the connection surface, and more preferably 10% to 80%.

Furthermore, such a size relationship is not essential, and the upper surface 120a and the lower surface 120b of the diamond substrate 120 may be larger than the lower surface 14b of the phosphor 14.

In addition, in the mount substrate 12 shown in FIG. 1, four diamond substrates 120 are arranged in a matrix of two rows and two columns. This makes it possible to increase the isotropy of heat conduction in the in-plane direction of the XY plane of the mount substrate 12. Furthermore, since the heat spread evenly in the in-plane direction can be transferred to the thermally conductive substrate 16, it becomes possible to dissipate heat by making the most of the thermal capacity of the thermally conductive substrate 16. Note that the number of diamond substrates 120 that the mount substrate 12 has is not particularly limited as long as there is more than one. Furthermore, the size and shape of the diamond substrates 120 that the mount substrate 12 has may be the same or different from each other.

From the viewpoint of isotropy of thermal conduction, it is preferable that the arrangement of the diamond substrates 120 in the mount substrate 12 has rotational symmetry of an arbitrary angle when the center of the mount substrate 12 is taken as the center of symmetry. Examples of the arbitrary angle include 45°, 60°, 90°, 120°, and 180°. In the mount substrate 12 shown in FIG. 1, four diamond substrates 120 are arranged in a matrix of 2 rows and 2 columns, and therefore the arrangement can be said to have rotational symmetry of 90°.

Furthermore, in the light source device 1 shown in FIG. 1, the phosphor 14 is disposed in the center of the mount substrate 12 in a planar view. Therefore, in a planar view, the phosphor 14 overlaps with a portion of each diamond substrate 120. In other words, in a planar view, the phosphor 14 is disposed so as to straddle each diamond substrate 120. This reduces the variation in thermal resistance between the phosphor 14 and each diamond substrate 120. Therefore, from this perspective as well, the mount substrate 12 shown in FIG. 1 can equalize the spread of heat in the in-plane direction, and can diffuse heat more efficiently.

The thickness of the diamond substrate 120 is preferably 0.1 mm or more and 2.0 mm or less, and more preferably 0.2 mm or more and 1.0 mm or less. A diamond substrate 120 of such a thickness can easily achieve low costs while ensuring a sufficient cross-sectional area to spread the heat of the phosphor 14 in the in-plane direction of the X-Y plane.

The surface modification film 122 contains a metal material as described above. This metallizes the surface of the base 121, and the adhesion of the adhesive 31 and the thermally conductive adhesives 21 and 22 to the diamond substrate 120 can be improved. As a result, the adhesive strength can be increased and the thermal resistance between the phosphor 14 and the diamond substrate 120, and between the diamond substrate 120 and the thermally conductive substrate 16 can be reduced. This makes it possible to suppress peeling of the adhesive due to heat cycles, etc. Note that if the thermally conductive adhesives 21 and 22 have sufficient adhesion to diamond, the surface modification film 122 may be omitted.

Methods for forming the surface modification film 122 include, for example, plating, vapor phase film formation, liquid phase film formation, metal paste method, metal film transfer method, etc.

Among these, examples of plating methods include copper plating, gold plating, silver plating, nickel plating, etc., and one or more of these can be used in combination. Of these, copper plating is preferably used from the standpoint of cost, adhesion, thermal conductivity, etc.

Examples of vapor-phase film formation methods include sputtering and vacuum deposition. Of these, sputtering is preferably used. Examples of materials that can be used to form films using sputtering include copper, gold, and silver. When forming films using these materials using sputtering, it is preferable to use an undercoat film in combination. Examples of materials that can be used to form undercoats include titanium (Ti), titanium-tungsten (TiW), and titanium nitride (TiN).

Before forming the surface modification film 122, the base 121 may be subjected to a surface treatment, if necessary. Examples of the surface treatment include a roughening treatment, a plasma treatment, and an ozone treatment. By performing such a surface treatment, it is possible to increase the adhesion of the surface modification film 122 to the base 121. Examples of the roughening treatment include a sputter etching treatment.

The average thickness of the surface modification film 122 is preferably 0.05 μm or more and 50 μm or less, and more preferably 0.10 μm or more and 10 μm or less. This ensures a sufficient thickness for metallizing the surface of the base 121 and also sufficiently reduces the thermal resistance of the surface modification film 122.

In the mounting substrate 12 shown in FIG. 3, the diamond substrates 120 are bonded together via a surface modification film 122. For example, if the surface modification film 122 is copper plating, the diamond substrates 120 are bonded together by direct bonding of the copper plating. As a result, only the surface modification film 122 is interposed between the bases 121, and the distance between the bases 121 can be shortened, thereby minimizing the thermal resistance associated with bonding.

To perform direct bonding, first, a surface activation process is performed on the bonding surfaces to remove any oxide films or adsorption layers, and then the treated surfaces are brought into contact with each other. Examples of surface activation processes include ion irradiation and neutral atom beam irradiation.

FIG. 4 is a cross-sectional view showing a first modified example of the mounting substrate.
In the mount substrate 12A shown in Fig. 4, the diamond substrates 120 are bonded together via a bonding material 24. The bonding material 24 may be, for example, an adhesive similar to the thermally conductive adhesives 21 and 22 described above. When this adhesive is used as the bonding material 24, the process of arranging the diamond substrates 120 and the process of bonding the mount substrate 12A to the thermally conductive substrate 16 can be performed simultaneously, which is also useful from the viewpoint of reducing the number of steps.

FIG. 5 is a cross-sectional view showing a second modified example of the mounting substrate.
In the mount substrate 12B shown in Fig. 5, the diamond substrates 120 are integrated by direct bonding between the diamonds. This allows the bases 121 to be directly bonded to each other, minimizing the thermal resistance between them. In addition, the mechanical strength of the mount substrate 12 can be particularly increased.

One example of a method for manufacturing the mounting substrate 12B is to create a large substrate in which diamonds are integrated together using the mosaic method, and then form a surface modification film 122 on the large substrate.

As described above, the heat conduction structure 15 according to this embodiment includes at least the mount substrate 12 connected to the phosphor 14 (heat source) and the heat conduction substrate 16 bonded to the mount substrate 12. The mount substrate 12 has a plurality of diamond substrates 120 bonded to each other. The heat conduction substrate 16 is bonded to the mount substrate 12 on the side opposite the phosphor 14, and is thicker than the diamond substrate 120.

With this configuration, the mount substrate 12 can function as a high-performance heat spreader due to the low anisotropy and high thermal conductivity derived from diamond. This allows the heat of the phosphor 14 to be efficiently diffused and dissipated. In addition, since the mount substrate 12 is bonded to the thermally conductive substrate 16 that is thicker than the diamond substrate 120, the heat diffused by the mount substrate 12 can be transferred to the thermally conductive substrate 16, which has a large heat capacity, and the heat of the mount substrate 12 can be efficiently taken into the thermally conductive substrate 16. This allows the heat of the phosphor 14 to be efficiently transferred, and a thermally conductive structure 15 with excellent cooling efficiency for the phosphor 14 to be realized.

In addition, since the mounting substrate 12 is composed of multiple diamond substrates 120 bonded together, it is easier to manufacture than when a single large diamond substrate is used. Therefore, the heat conducting structure 15 is also useful from the viewpoint of being able to reduce costs.

By providing such a heat conduction structure 15, the light source device 1 is able to suppress the decrease in the wavelength conversion efficiency of the phosphor 14, thereby realizing high brightness and high luminous flux. In addition, the heat conduction structure 15 is made compact due to the high thermal conductivity of diamond. This makes it easy to miniaturize the light source device 1 and electronic devices such as projectors that include it.

The thermally conductive structure 15 according to this embodiment also includes a heat sink 17 (cooling mechanism) that is joined to the thermally conductive substrate 16 on the side opposite the mounting substrate 12.

By providing such a heat sink 17, the thermally conductive substrate 16 can be cooled particularly efficiently. Therefore, for example, even if the phosphor 14 is continuously irradiated with light, the temperature of the phosphor 14 can be prevented from continuing to rise.

2. Second Embodiment Next, a heat conducting structure according to a second embodiment will be described.

Figure 6 is a plan view showing a light source device having a heat conduction structure according to the second embodiment. Figure 7 is a cross-sectional view taken along line B-B of Figure 6.

The second embodiment will be described below, focusing on the differences from the first embodiment and omitting the description of the similarities. Note that in Fig. 6 and Fig. 7, the same reference numerals are used to designate the same components as those in the first embodiment.
The second embodiment is similar to the first embodiment except for the configuration of the mounting substrate.

In the first embodiment described above, the mount substrate 12 has four diamond substrates 120. In contrast, in this embodiment, as shown in Figures 6 and 7, the mount substrate 12C has nine diamond substrates 120. Specifically, in the mount substrate 12C shown in Figure 6, the nine diamond substrates 120 are arranged in a matrix of three rows and three columns. This makes it possible to increase the isotropy of thermal conduction in the in-plane directions of the X-Y plane of the mount substrate 12C.

In addition, since the number of diamond substrates 120 in this embodiment is greater than that in the first embodiment, if the size of the mounting substrate 12C does not change, the size of each diamond substrate 120 can be made smaller than that in the first embodiment. As a result, it is possible to realize a mounting substrate 12C that can reduce the cost of the mounting substrate 12C or can accommodate a larger phosphor 14.

Figure 8 is a cross-sectional view showing a light source device having a heat conduction structure according to a modified example of the second embodiment.

In the mount substrate 12C shown in FIG. 7, the nine diamond substrates 120 have the same thickness. In contrast, in the mount substrate 12D shown in FIG. 8, the thickness t1 of the first substrate 1201 located in the center of the nine diamond substrates 120 is thicker than the thickness t2 of the remaining eight second substrates 1202.

The thermally conductive substrate 16D shown in FIG. 8 has a recess 16c that opens to the upper surface 16a facing the mounting substrate 12D. A part of the multiple diamond substrates 120, i.e., the first substrate 1201 located in the center, is inserted into the recess 16c.

With this configuration, the first substrate 1201 located at the center can spread the heat of the phosphor 14 in the in-plane direction of the X-Y plane while also efficiently transmitting it in the Z-axis direction. Since the most heat flows to the first substrate 1201 located at the center, the heat can be quickly diffused toward the thermally conductive substrate 16D. In addition, since the thermally conductive substrate 16D has a recess 16c, the contact area between the first substrate 1201 and the recess 16c can be made larger than in the embodiment of FIG. 7. As a result, the thermal resistance between the mounting substrate 12D and the thermally conductive substrate 16D can be sufficiently reduced, and the cooling efficiency of the phosphor 14 can be particularly improved.

As described above, the mount substrate 12D shown in FIG. 8 has a first substrate 1201, which is a diamond substrate 120 inserted into the recess 16c, and a second substrate 1202, which is a diamond substrate 120 provided on the upper surface 16a facing the mount substrate 12D. The thickness t1 of the first substrate 1201 is greater than the thickness t2 of the second substrate 1202.

This configuration allows the upper surface 12a of the mounting substrate 12D to be flat. As a result, gaps are less likely to form between the phosphor 14 and the mounting substrate 12D, and the thermal resistance can be sufficiently reduced.

When thickness t1 is 1, thickness t2 is preferably 1.05 to 2.00, more preferably 1.10 to 1.80, and even more preferably 1.15 to 1.70. This makes it possible to obtain the above-mentioned effects more significantly.

The depth of the recess 16c is appropriately set according to the thickness difference t1-t2 described above.
In the second embodiment as described above, the same effects as in the first embodiment can be obtained.

3. Third Embodiment Next, a method for manufacturing a heat conducting structure according to a third embodiment will be described.

Figure 9 is a flow chart for explaining a method for manufacturing a heat conduction structure according to the third embodiment. Figures 10 to 13 are cross-sectional views for explaining the method for manufacturing the heat conduction structure shown in Figure 9.

The third embodiment will be described below, focusing on the differences from the first embodiment and omitting a description of similar points. Note that in Figures 10 to 13, the same reference numerals are used for configurations similar to those of the first embodiment.

The method for manufacturing the heat conducting structure shown in FIG. 9 includes a diamond film forming step S102, a peeling step S104, a cutting step S106, a surface modification step S108, a mounting substrate fabrication step S110, a lamination step S112, a heat source connection step S114, and a heat sink bonding step S116. Each step will be explained in order below. Note that the following explanation uses the method for manufacturing the heat conducting structure 15 shown in FIG. 2 as an example.

3.1 Diamond Film Forming Step In the diamond film forming step S102, as an example of a method for manufacturing the base 121 mainly made of diamond, a diamond film is epitaxially grown on a seed crystal substrate by chemical vapor deposition (CVD). The seed crystal substrate may be, for example, a single crystal diamond substrate.

3.2. Peeling Step In the peeling step S104, the diamond film formed on the seed crystal substrate is peeled off from the seed crystal substrate. This results in a free-standing diamond film. For example, a peeling processing technique such as a lift-off method using laser ablation can be used for the peeling.

3.3 Cutting Step In the cutting step S106, the peeled diamond film is cut into a desired shape and separated into individual pieces. This results in obtaining the base portion 121 (individual piece) shown in Fig. 10. Laser processing, for example, is used to cut the diamond film.

11, a surface modification film 122 is formed on the surface of the base 121. This results in a diamond substrate 120 (surface-modified piece). The method for forming the surface modification film 122 is as described above.

3.5 Mount Substrate Fabrication Step In the mount substrate fabrication step S110, the diamond substrates 120 are bonded to each other. This results in the mount substrate 12 shown in Fig. 12. The diamond substrates 120 can be bonded to each other by any of the various bonding methods described above.

3.6. Lamination Step In the lamination step S112, as shown in FIG. 13, the mount substrate 12 is laminated on the thermally conductive substrate 16, and the two are bonded together. For example, the thermally conductive adhesive 22 described above is used for bonding. It is preferable to perform a surface cleaning treatment on the thermally conductive substrate 16 in advance. This can increase the bonding strength between the mount substrate 12 and the thermally conductive substrate 16, and between the thermally conductive substrate 16 and the heat sink 17, and can suppress peeling of the bonding portion due to heat cycles, etc. In addition to increasing the bonding strength, it can also reduce the thermal resistance. Examples of surface cleaning treatments include oxygen plasma cleaning and cleaning with an organic solvent.

3.7. Heat Source Connection Step In the heat source connection step S114, the phosphor 14 (heat source) is connected to the surface of the mounting substrate 12 opposite to the thermally conductive substrate 16, i.e., the upper surface 12a of the mounting substrate 12. For the connection, for example, the thermally conductive adhesive 21 described above is used.

In the heat sink bonding step S116, the heat sink 17 (cooling mechanism) is bonded to the surface of the thermally conductive substrate 16 opposite to the mount substrate 12, i.e., the lower surface 16b of the thermally conductive substrate 16. For example, the thermally conductive adhesive 23 described above is used for bonding. As a result, the thermally conductive structure 15 shown in FIG. 2 is obtained.

Note that the order of the above steps is not limited to the order of the present embodiment. Some steps may be omitted. For example, when manufacturing a heat conductive structure 15 having a mount substrate 12B as shown in FIG. 5, first, in a diamond film formation step S102, multiple diamond films are epitaxially grown from the same seed crystal substrate, and then, in a peeling step S104, the diamond films are peeled off to obtain multiple bases 121 (individual pieces). Thereafter, the cutting step S106 is omitted, and the bases 121 are directly bonded together in a mount substrate fabrication step S110, and then, in a surface modification step S108, a surface modification film 122 is formed on the bonded bases 121. As a result, the mount substrate 12B as shown in FIG. 5 is obtained.

As described above, the manufacturing method of the heat conduction structure according to this embodiment includes a surface modification step S108, a mount substrate preparation step S110, a lamination step S112, a heat source connection step S114, and a heat sink bonding step S116. In the surface modification step S108, a surface modification film 122 containing a metal material is formed on the surface of a base 121 (piece) mainly made of diamond, to obtain a diamond substrate 120. In the mount substrate preparation step S110, the diamond substrates 120 are bonded together to obtain a mount substrate 12. In the lamination step S112, the mount substrate 12 is bonded to a heat conductive substrate 16 that is thicker than the diamond substrate 120. In the heat source connection step S114, a phosphor 14 (heat source) is connected to the side of the mount substrate 12 opposite to the heat conductive substrate 16. In the heat sink bonding step S116, a heat sink 17 (cooling mechanism) is bonded to the side of the heat conductive substrate 16 opposite to the mount substrate 12.

This configuration provides a heat conduction structure 15 that efficiently diffuses and dissipates heat from the phosphor 14. Furthermore, by going through the process of bonding multiple diamond substrates 120, it is possible to realize a large mount substrate 12 made primarily of diamond without manufacturing a single large diamond substrate. This makes it possible to easily and inexpensively manufacture a heat conduction structure 15 that includes a mount substrate 12 that is diamond-derived and has low anisotropy and high thermal conductivity.

In addition, by appropriately changing the number of diamond substrates 120, it is possible to easily accommodate design changes to the mounting substrate 12.

The method for manufacturing a heat conduction structure according to this embodiment further includes a diamond film formation step S102, a peeling step S104, and a cutting step S106. In the diamond film formation step S102, a diamond film is epitaxially grown on the seed crystal substrate by chemical vapor synthesis. In the peeling step S104, the diamond film is peeled off from the seed crystal substrate. In the cutting step S106, the diamond film is cut to obtain a base 121 (individual piece).

With this configuration, a diamond film can be stably produced by chemical vapor synthesis, and then the plate-shaped base 121 can be mass-produced by cutting. This allows the diamond substrate 120 to be produced efficiently and at low cost.

The heat conduction structure and the method for manufacturing the heat conduction structure of the present invention have been described above based on the illustrated embodiment, but the heat conduction structure of the present invention is not limited to the embodiment, and for example, each part of the embodiment may be replaced with an arbitrary configuration having a similar function, or an arbitrary component may be added to the embodiment. Furthermore, the manufacturing method of the heat conduction structure of the present invention is not limited to the embodiment, and for example, a process for an arbitrary purpose may be added to the embodiment.

1...light source device, 11...plano-convex lens, 11a...flat surface, 12...mounting substrate, 12A...mounting substrate, 12B...mounting substrate, 12C...mounting substrate, 12D...mounting substrate, 12a...upper surface, 12b...lower surface, 13...spacer, 13a...through hole, 13b...recess, 13c...bottom surface, 13d...upper surface, 14...phosphor, 14a...upper surface, 14b...lower surface, 15...thermal conductive structure, 16...thermal conductive substrate, 16D...thermal conductive substrate, 16a...upper surface, 16b...lower surface, 16c...recess, 17...heat sink, 19...sealed space, 21...thermal conductive adhesive, 22...thermal conductive adhesive, 23...thermal conductive adhesive, 24...bonding material, 31...adhesive , 120...diamond substrate, 120a...upper surface, 120b...lower surface, 121...base, 122...surface modification film, 140...reflective film, 172...base, 174...fin, 1201...first substrate, 1202...second substrate, HF1...heat flow, HF2...heat flow, L1...length, L2...length, LE...excitation light, LF...fluorescence, S102...diamond film deposition step, S104...peeling step, S106...cutting step, S108...surface modification step, S110...mounting substrate preparation step, S112...lamination step, S114...heat source connection step, S116...heat sink bonding step, t1...thickness, t2...thickness

Claims (13)

a mounting substrate having a plurality of diamond substrates bonded together and connected to a heat source;
a thermally conductive substrate bonded to the mounting substrate on an opposite side to the heat source, the thermally conductive substrate being thicker than the diamond substrate;
A heat conducting structure comprising: The heat source further comprises:
the heat source has a connection surface that is connected to the mounting substrate;
The diamond substrate has two main surfaces which are reverse to each other,
The thermal conductive structure according to claim 1 , wherein the two main surfaces are smaller than the connecting surface. The diamond substrate is
A base mainly made of diamond;
A surface modification film including a metal material provided on a surface of the base;
The thermally conductive structure according to claim 1 or 2, comprising: The heat conducting structure according to claim 3, wherein the diamond substrates are bonded together via the surface modification film. The heat conducting structure according to any one of claims 1 to 3, wherein the diamond substrates are bonded together via a bonding material. The heat conducting structure according to claim 1 or 2, in which the diamond substrates are integrated by direct bonding of the diamonds. The thermal conduction structure according to any one of claims 1 to 6, further comprising a cooling mechanism joined to the thermal conduction substrate on the side opposite to the mounting substrate. the thermally conductive substrate has a recess that opens onto a surface facing the mounting substrate;
8. The thermal conductive structure according to claim 1, wherein a portion of the diamond substrate is inserted into the recess. the mount substrate includes a first substrate which is the diamond substrate inserted into the recess, and a second substrate which is the diamond substrate provided on a surface facing the mount substrate;
The thermally conductive structure of claim 8 , wherein the first substrate is thicker than the second substrate. The thermal conduction structure according to any one of claims 1 to 9, wherein the heat source is a phosphor. The thermal conduction structure according to any one of claims 1 to 10, wherein the diamond substrate includes single crystal diamond. forming a surface modification film containing a metal material on a surface of an individual piece mainly made of diamond to obtain a diamond substrate;
bonding the diamond substrates together to obtain a mount substrate;
bonding the mounting substrate to a thermally conductive substrate that is thicker than the diamond substrate;
connecting a heat source to the mounting substrate opposite the thermally conductive substrate;
bonding a cooling mechanism to the thermally conductive substrate on a side opposite to the mounting substrate;
A method for producing a thermal conduction structure, comprising the steps of: epitaxially growing a diamond film on a seed crystal substrate by chemical vapor deposition;
peeling the diamond film from the seed crystal substrate;
cutting the diamond film to obtain the individual pieces;
The method for producing a thermally conductive structure according to claim 12, comprising the steps of:

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