JP7186935B2 - lighting equipment - Google Patents

Description

The present application relates to lighting devices.

Since the lighting device has a heat-generating part such as a light source, it is necessary to keep the inside of the device below an allowable temperature in order to suppress thermal runaway due to temperature rise of the device. In order to cool the inside of the device, for example, a metal heat sink is attached to the heat generating portion, heat is transferred to the heat sink, and then the heat sink is air-cooled. Furthermore, in order to enhance the cooling effect of the heat sink, it is known to provide cooling fins to increase the surface area (see Patent Document 1, for example).

Also, it is known to use a ceramic heat sink instead of a metal heat sink (see, for example, Patent Document 2).

JP 2018-041576 A Japanese Patent Publication No. 2012-528439

In Patent Document 1, a metal heat sink having cooling fins is used to cool the light source of the LED headlight. However, in order to improve the cooling performance, it is necessary to increase the height or size of the fins, making it difficult to reduce the size of the device.

Even the ceramic material exemplified in Patent Document 2 has a lower thermal conductivity than metal, so the heat radiation efficiency on the radiation surface opposite to the surface on which the light source is mounted cannot be said to be sufficient.

The present application has been made to solve the above problems, and an object of the present application is to provide a lighting device that uses a ceramic heat sink to achieve both improved heat radiation efficiency and reduced size.

A lighting device disclosed in the present application includes a light source, a substrate provided with the light source on one surface, a plate-shaped heat sink for cooling the substrate, the other surface of the substrate and one surface of the heat sink. a heat conductive layer provided in close contact between the heat sink, the heat sink made of a ceramic material, and having a plurality of via holes penetrating in a thickness direction and filled with a metal inside, the plurality of via holes comprising: When the thermal diffusion coefficient of the heat sink is D [m ² /sec] , the distance L between the via holes satisfies the following: L≧√(0.02D).

According to the lighting device disclosed in the present application, by using a heat sink made of a ceramic material in which via holes filled with metal are appropriately arranged, heat is efficiently transferred from the light source side, and heat dissipation efficiency is improved. By providing fins or the like, the heat radiation efficiency can be improved without increasing the size. As a result, it is possible to provide a lighting device that uses a ceramic heat sink and is capable of achieving both improved heat radiation efficiency and reduced size.

1 is a schematic configuration diagram showing an LED headlight according to Embodiment 1; FIG. FIG. 2 is a cross-sectional view showing the structure of the heat sink of the LED headlight according to Embodiment 1; FIG. 2 is a plan view of the heat sink of the LED headlight according to Embodiment 1 as seen from the heat dissipation surface side; 4 is a diagram for explaining the relationship between the arrangement of via holes formed in the heat sink according to Embodiment 1 and the radiation efficiency; FIG. 4 is a diagram for explaining the relationship between the arrangement of via holes formed in the heat sink according to Embodiment 1 and the radiation efficiency; FIG. 4 is a diagram for explaining the relationship between the arrangement of via holes formed in the heat sink according to Embodiment 1 and the radiation efficiency; FIG. FIG. 2 is a cross-sectional view of the heat sink according to Embodiment 1, and is a diagram for explaining the relationship between the arrangement of via holes and the radiation efficiency; FIG. 2 is a cross-sectional view of the heat sink according to Embodiment 1, and is a diagram for explaining the relationship between the arrangement of via holes and the radiation efficiency; FIG. 2 is a cross-sectional view of the heat sink according to Embodiment 1, and is a diagram for explaining the relationship between the arrangement of via holes and the radiation efficiency; 4 is a diagram for explaining the relationship between the radius of via holes formed in the heat sink according to Embodiment 1 and the radiation efficiency; FIG. FIG. 10 is a cross-sectional view showing the structure of the heat sink of the LED headlight according to Embodiment 2; FIG. 8 is a plan view of the heat sink of the LED headlight according to Embodiment 2 as viewed from the heat dissipation surface side; FIG. 10 is a schematic configuration diagram showing an LED headlight according to Embodiment 3; FIG. 11 is another schematic configuration diagram showing the LED headlight according to Embodiment 3; FIG. 5 is a diagram for explaining the effects of Examples 1 to 12;

The present embodiment will be described below with reference to the drawings. In each figure, the same reference numerals indicate the same or corresponding parts. Moreover, although an LED headlight is mentioned as an example of a lighting device, it is not limited to this. The light source that generates heat is not limited to the LED, and the lighting device that requires miniaturization is not limited to the headlight.

Embodiment 1.
An LED headlight, which is an example of the lighting device according to Embodiment 1, will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of an LED headlight according to Embodiment 1. FIG. The LED headlight 1 includes a housing 11 containing a light source 2 that is a heating element, a substrate 3 on one side of which the light source 2 is attached, a condenser lens 4 that collects light emitted from the light source 2, and a light source. A projection lens 5 for emitting light to the outside, a holding member 6 for holding the condenser lens 4, a mounting member 7 for holding the condenser lens 4 and mounting the projection lens 5, and a heat conductive layer provided on the other surface of the substrate 3. 8, a heat sink 9 provided on the surface of the heat conductive layer 8 opposite to the substrate 3, and a radiation heat absorption layer 10 provided apart from the heat sink 9. Each component of the LED headlight 1 is arranged in a sealed space under air by a housing 11 .

The assembly of the LED headlight 1 is performed, for example, by the following method. The light source 2 is attached to one surface of the substrate 3, the condenser lens 4 held by the holding member 6 is installed on the substrate 3 so as to be positioned in front of the light source 2, and the condenser lens 4 is fixed by the mounting member 7. . After that, the projection lens 5 is attached to the attachment member 7 . A heat conductive layer 8 and a heat sink 9 are attached in this order to the other surface of the substrate 3 . A substrate 3 on which a light source 2 is attached and which serves as a heat generating portion is in close contact with a heat sink 9 via a heat conductive layer 8 . In the heat sink 9, the surface in close contact with the heat conductive layer 8 is the heat generating surface 9a, and the opposite surface is the heat radiating surface 9b. The light source unit assembled in this manner is installed in a housing 11 having a radiation heat absorbing layer 10 attached to the inner surface thereof. At this time, the heat radiation surface 9b of the heat sink 9 and the radiation heat absorption layer 10 are arranged so as to be separated from each other and face each other. Each component constituting the light source section is attached, for example, with screws or an adhesive, but may be attached by other methods.

The heat sink 9 absorbs heat from the light source 2 and the substrate 3, radiates heat from the heat radiating surface 9b on the side opposite to the light source 2, and the radiated heat absorption layer 10 absorbs the radiated heat and cools it. . The size of the radiation heat absorbing layer 10 should be at least the size of the heat sink 9 or larger, and should not be smaller. This is because if it is smaller than the heat sink 9, radiant heat from the heat sink 9 is reflected by the housing 11, resulting in a decrease in cooling efficiency. However, in the case where the housing 11 is made of resin, even if the radiant heat absorbing layer 10 is not provided, the heat radiation effect is not deteriorated due to the reflection of the radiant heat.

The heat sink 9 is made of ceramic with via holes 12 formed therein. As ceramics, for example, aluminum oxide, titanium oxide, chromium oxide, silicon oxide, glass, silicon nitride, silicon carbide, zirconium dioxide, mullite, stearite, forsterite, cordierite, aluminum nitride are used. Although materials in which two or more kinds of ceramics are combined are also used, aluminum oxide is preferable from the viewpoint of workability and cost.

The substrate 3, the heat conductive layer 8, and the heat sink 9 should be brought into close contact with each other so that there is no gap between the contacting surfaces. This is because heat conduction is hindered if there is a gap, making it difficult for heat to be conducted. Therefore, it is desirable to use a metallic bonding material for the thermally conductive layer 8 to bond the substrate 3 and the heat sink 9 together. When using a bonding material, a silver-based material is used from the viewpoint of high thermal conductivity. However, from the point of view of coefficient of thermal expansion and manufacturing process, the joining material may not be used. In that case, a metal foil may be used as the thermally conductive layer 8, and the substrate 3, the thermally conductive layer 8, and the heat sink 9 may be screwed together. If it is a metal foil, it conforms to the shape and can suppress a decrease in thermal conductivity. The material of the metal foil is preferably a silver-based material from the viewpoint of high thermal conductivity.

Ceramic or resin is used as the radiation heat absorbing layer 10 . In the case of ceramics, for example, aluminum oxide, titanium oxide, chromium oxide, silicon oxide, glass, silicon nitride, silicon carbide, zirconium dioxide, mullite, stearite, forsterite, cordierite, aluminum nitride are used. A bulk body processed from a ceramic mass may be used, or the housing 11 may be provided with a ceramic coating. Any ceramic material can be used. Examples of resins that can be used include polycarbonate, polypropylene, polyvinyl alcohol, acrylic, epoxy, phenol, polyvinyl chloride, polystyrene, unsaturated polyester, polyimide, and acrylonitrile-butadiene-styrene copolymer. Fiber-reinforced plastics using these resins as a matrix are also used. Furthermore, two or more of these may be used in combination. It may be formed by processing a block of resin and provided on the inner surface of the housing 11, or may be provided on the housing 11 by coating or painting.

FIG. 2 is a cross-sectional view showing the structure of the heat sink 9 of the LED headlight according to Embodiment 1. As shown in FIG. The heat sink 9 is processed with via holes 12 penetrating in the thickness direction of the ceramic. The inside of the via hole 12 is filled with metal having high thermal conductivity. As a method of filling the metal, a method such as filling with a metal paste or filling with metal plating on the inner surface is used.

The heat sink 9 is manufactured by, for example, the following method. First, a plate-shaped ceramic substrate is prepared. Next, a via hole 12 is processed at a predetermined position using a technique such as laser or mechanical drilling. After that, the via hole 12 is filled with a silver-based paste. It should be noted that alignment can be easily performed by using screen printing for filling. After that, the silver-based paste is sintered. At this time, a gap may occur between the via hole 12 and the paste due to the shrinkage rate of the paste, but this can be improved by controlling the shrinkage rate by adjusting the solid content concentration and blending of the paste. In addition, it is also possible to use a ceramic molded body before firing as the ceramic substrate, to process the via holes 12 in the ceramic body, to fire the ceramic body, and to fill the ceramic body with the paste. Alternatively, a method may be used in which the via holes 12 are processed in the ceramic molded body before firing, and the paste is filled and then fired. The molded body can be easily processed because it is softer and easier to process than the fired body. However, since ceramic shrinks during firing, there is a problem that dimensional accuracy is low when it is processed as a molded body. By these techniques, the heat sink 9 in which the inside of the via hole 12 is filled with a material having high thermal conductivity can be produced. Moreover, when performing a metal plating process, it is good to perform copper plating from an electrical conductivity, adhesiveness, and corrosive viewpoint.

The structure shown in FIG. 2 can be produced by attaching the thermally conductive layer 8 and the substrate 3 to one side of a heat sink 9 having via holes 12 filled with metal therein. The other surface of the heat sink 9 is a heat radiation surface 9b, and since the light source 2 is attached to the substrate 3, it becomes a heat generating portion.

FIG. 3 is a plan view of the heat sink 9 as viewed from the heat dissipation surface side, and corresponds to the top view of FIG. Most of the heat radiating surface of the heat sink 9 is exposed to ceramic, and only the via holes 12 are made of a material with high thermal conductivity. The via hole 12 preferably has a circular cross-section rather than a square, triangular, elliptical, or elongated shape, and has a cylindrical shape as a via hole, from the viewpoint of diffusing heat uniformly around it. In addition, from the viewpoint of making the distances between the via holes 12 uniform, it is desirable to arrange the via holes 12 so as to be positioned at the vertices of an equilateral triangle.

4, 5, and 6 are diagrams for explaining the relationship between the arrangement of the via holes 12 formed in the heat sink 9 on the heat radiation surface of the heat sink 9 and the radiation efficiency. The average heat diffusion distance d _t is expressed as d _t =√(2Dt) using the thermal diffusion coefficient D [m ² /sec] of the material forming the heat sink and the time t [sec]. The time during which the heat from the via hole 12 is transferred to the heat radiation surface of the heat sink 9 and the temperature of the heat radiation surface of the heat sink 9 is instantaneously increased is assumed to be 0.01 [sec]. At this time, in the drawing, the radius of the via hole 12 is r, the area of the via hole is A (=πr ² ), and the edge of the via hole 12 where heat is diffused and the radiation efficiency is high is d _0.01 =√(0. 02D), and let C be the area of the range beyond the distance d _0.01 from the end of the via hole 12 with poor radiation efficiency. The area occupied by the area A and the area B corresponds to the area contributing to heat dissipation.

As shown in FIG. 4, when the via hole 12 is arranged so that circles with a radius of r+d _0.01 from the center of the via hole 12 are in contact with each other, the total surface area occupied by the area A and the area B is 90.7% of the total surface area. %( ≈( A+B)/(A+B+C)), which allows the most efficient radiation without overlapping circles with a radius of r+d _0.01 . The relationship in which circles having a radius of r+d _0.01 do not overlap means that L≧d0 _{. 01} relationship.

As shown in FIG. 5, when the via hole 12 is arranged away from the circle having a radius of r+d _0.01 from the center of the via hole 12, the area C of the range with poor radiation efficiency increases, and the area A and the area Although the total surface area occupied by B is less than 90.7% of the total, the effect of radiation is sufficiently obtained.

On the other hand, as shown in FIG. 6, when the via holes 12 are arranged so that circles having a radius of r+d _0.01 from the center of the via holes 12 overlap each other, the area C of the range with poor radiation efficiency decreases, and the area A and area B occupy more than 90.7% of the total surface area. However, since the circles with a radius of r+d of _0.01 are overlapped, the radiation effect per via hole is lowered, resulting in inefficiency. Moreover, it is necessary to increase the number of via holes per unit area of the heat sink 9, which increases the processing cost.

7, 8, and 9 are cross-sectional views of the heat sink 9 for explaining the relationship between the arrangement of the via holes 12 and the radiation efficiency. Let H [mm] be the thickness of the heat sink 9 and L [mm] be the interval between the via holes 12 . 7 and 8 show the case where the thickness of the heat sink 9 is sufficiently thick. If the via hole 12 is not formed, the distance d _0.01 from the heat generating surface 9a of the heat sink 9 in FIG. 7 becomes an effective range for radiation, but the heat does not reach the heat radiation surface 9b and the heat radiation efficiency is inferior. As shown in FIG. 7, when the distance L between the via holes 12 is 2×d _0.01 , the heat is instantaneously uniform between the via holes 12, and the area E from which the heat radiation surface 9b can be radiated becomes the entire surface of the heat radiation surface 9b. , heat is radiated from the heat radiation surface 9b, and radiation efficiency is improved.

FIG. 8 shows the case where the distance L between the via holes 12 exceeds 2×d _0.01 . In this case, the heat instantly becomes uniform except for the U-shaped inner region between the via holes 12 . A region within d _0.01 from the via hole 12 of the heat dissipation surface 9b is a region E where heat can be radiated, and heat is radiated from this region, improving the radiation efficiency.
7 and 8, when the thickness H of the heat sink 9 is thick and is d _0.01 or more (H≧d _0.01 ), the effective range for radiation depends on the interval L between the via holes 12 .

On the other hand, when the thickness H of the heat sink 9 is thin and smaller than _d0.01 (H< _d0.01 ) as shown in FIG. The heat becomes uniform, and the entire surface of the heat dissipation surface 9b becomes a region E where heat can be radiated. Therefore, in the structure having the via hole 12, the effect of the via hole 12 is produced when the relationship with the thickness H of the heat sink 9 satisfies the relational expression of H≧d _0.01 .

FIG. 10 is a diagram for explaining the relationship between the radius r of the via hole 12 formed in the heat sink 9 and the radiation efficiency. FIG. 10 shows the ratio of the area A of the via hole 12 to the entire heat dissipation surface when the via hole 12 is arranged so that circles having a radius of r+d _0.01 from the via hole 12 are in contact with each other as shown in FIG. The dashed line indicates the ratio of the area B of the range included in the distance d _0.01 =√(0.02D) from the end of the via hole 12 where the heat diffuses and reaches a temperature at which the radiation efficiency is high. is shown.

From FIG. 10, the smaller the radius r of the via hole 12, the larger the area B where the radiation efficiency is high, and the higher the radiation efficiency as a whole, which is desirable. If the radius r of the via hole 12 is 3.5 mm or less, the ratio of the area B with high radiation efficiency exceeds the area A of the via hole, resulting in high radiation efficiency. In addition, in FIG. 10, the radius r of the via hole 12 excludes zero.

As described above, according to the lighting device according to the first embodiment, the substrate made of a plate-shaped ceramic material is used as the heat sink 9 for cooling the substrate 3 provided with the light source 2 as a heating element. A via hole 12 penetrated and filled with metal is provided to efficiently transfer heat from the heat-generating surface 9a on the light source side of the heat sink 9 to the heat-dissipating surface 9b, thereby improving heat-dissipating efficiency. The heat radiation efficiency can be improved without changing the size of the ceramic substrate. As a result, it is possible to provide a lighting device that uses a ceramic heat sink 9 and that can achieve both improved heat radiation efficiency and reduced size.

In addition, since the heat conductive layer 8 is provided between the substrate 3 on which the light source 2 is provided and the heat generating surface 9a of the heat sink 9, the heat from the light source 2, which is a heating element, can be more easily transferred to the heat sink 9. Improves heat dissipation efficiency.
Furthermore, since the radiation heat absorption layer 10 is provided in the housing 11 in which the light source 2 is arranged so as to face the heat radiation surface 9b of the heat sink 9, the radiation heat absorption layer 10 absorbs the heat from the heat sink 9, Heat dissipation efficiency improves more.

Embodiment 2.
An LED headlight, which is an example of a lighting device according to Embodiment 2, will be described below with reference to the drawings.
FIG. 11 is a cross-sectional view showing the structure of the heat sink 9 of the LED headlight according to Embodiment 2. As shown in FIG. In the second embodiment, the heat dissipation layer 13 is provided in the via hole 12 of the heat sink 9 so as to protrude toward the heat dissipation surface 9b. Other configurations are the same as those of the first embodiment.

By providing the heat dissipation layer 13 in the via hole 12 so as to protrude toward the heat dissipation surface 9b side, the heat dissipation area can be increased as compared with the case where the heat dissipation layer 13 is not provided, and the heat dissipation effect by radiation from the heat dissipation layer 13 can also be obtained. can be done. The heat dissipation layer 13 is a layer containing ceramic, for example, and can be formed using a paste containing ceramic particles. As the ceramic particles, aluminum oxide is preferable from the standpoint of availability. After applying a paste containing ceramic particles to the apex of the via hole 12, the heat dissipation layer 13 is provided by heating to a predetermined temperature. can be done.

FIG. 12 is a plan view of the heat sink 9 as seen from the heat dissipation surface side. A heat dissipation layer 13 is provided in the portion of the via hole 12, and the heat dissipation area can be increased by the amount protruding from the via hole 12. - 特許庁

As described above, according to the lighting device according to the second embodiment, the same effects as those of the first embodiment can be obtained. Furthermore, since the heat dissipation layer 13 is provided in the via hole 12 of the heat sink 9 so as to protrude toward the heat dissipation surface 9b, the heat dissipation area can be increased compared to the case where the heat dissipation layer 13 is not provided. A heat dissipation effect can be obtained. As a result, the heat radiation efficiency is further improved, and it is possible to provide a lighting device with high heat radiation efficiency.

Embodiment 3.
An LED headlight, which is an example of a lighting device according to Embodiment 3, will be described below with reference to the drawings.
FIG. 13 is a schematic configuration diagram showing an LED headlight according to Embodiment 3. FIG. The difference from the first embodiment shown in FIG. 1 is that the heat conductive layer 8 and the heat sink 9 provided in close contact with the substrate 3 on which the light source 2 is provided are made larger than the substrate 3 . As shown in the cross-sectional view of FIG. 13, the width of the heat conductive layer 8 and the heat sink 9 is wider than the width of the substrate 3 . If the substrate 3 is smaller than the thermal conductive layer 8 and the heat sink 9, the heat transfer from the substrate 3 that is not in contact with the thermal conductive layer 8 and the heat sink 9 will be insufficient. When the thickness is larger, the heat from the light source 2 can be efficiently transferred through the substrate 3 and radiated. In this case, the size of the radiation heat absorption layer 10 should also be increased corresponding to the heat conduction layer 8 and the heat sink 9 . In FIG. 13, the width of the radiant heat absorbing layer 10 is widened corresponding to the width of the heat conducting layer 8 and the heat sink 9 .

FIG. 14 is another schematic configuration diagram showing the LED headlight according to the third embodiment. In FIG. 14, the width of the heat conductive layer 8 is made larger than that of the substrate 3, but the width of the heat sink 9 may be made wider than the width of the heat conductive layer 8. In this case, it is better to adjust the arrangement of the via holes 12 so that the via holes 12 are in contact with the edge portions of the heat conductive layer 8 in order to conduct heat smoothly. Since the heat dissipation area spreads around the via hole 12, in FIG. 14, the area outside the heat generating surface 9a of the heat sink 9 in the via hole 12 in the edge portion of the thermally conductive layer 8 (dotted oval area in FIG. 14) also contributes to heat dissipation. As a result, the heat dissipation efficiency is improved. In FIG. 14 as well, the width of the radiant heat absorption layer 10 is widened corresponding to the width of the heat sink 9 .

As described above, according to the lighting device according to the third embodiment, the thermal conductive layer 8 and the heat sink 9 provided in close contact with the substrate 3 provided with the light source 2 are made larger than the substrate 3 to dissipate heat. Improve efficiency. Further, if the heat sink 9 is made larger than the heat conductive layer 8 and the via holes 12 are arranged in the edge portion of the heat conductive layer 8, the heat generating surface 9a side of the heat sink 9 also contributes to the heat dissipation. Improve efficiency.

Examples 1-12.
Next, the effects of the metal-filled via hole 12 and the heat dissipation layer 13 will be described based on an embodiment. The test conditions are as follows.
1. Size of substrate 3, thermally conductive layer 8, heat sink 9: 100 mm x 100 mm
2. Material of heat sink 9: aluminum oxide
D=1.1×10 ⁻⁵ [m ² /sec]
√(0.02D)=0.47mm
3. Light source 2: For the LED headlight via hole 12, samples were prepared by changing the radius r of the via hole 12, the distance L between the via holes 12, and the presence or absence of the heat dissipation layer 13, and after the LED headlight was turned on, the saturated temperature was applied to the optical fiber. The temperature was measured with a thermometer or thermocouple, and the temperature rise from the test start temperature was compared.

FIG. 15 summarizes the test results, showing examples 1 to 12 and comparative examples 1 to 5 of the heat dissipation effect of the via holes 12 and the heat dissipation layer 13 formed in the heat sink 9 shown in the first and second embodiments. It is a figure for demonstrating based on the result of . In addition, it has shown that the heat dissipation effect is so high that the rising temperature is low.
[Effect of via hole]
When the thickness H of the heat sink 9 is 5.0 mm and the via hole 12 is provided (Examples 1 to 6, 8 to 12) and the via hole is not provided (Comparative Example 1), the temperature rise of 120 K in Comparative Example 1 is compared with that of the example. 1 to 6 and 8 to 12, the temperature rise was lower than 120K, and the effect of providing via holes was confirmed. Further, when the thickness H of the heat sink is 1.5 mm and the via holes are provided (Example 7) and the via holes are not provided (Comparative Example 4), the temperature rise is 108 K and 118 K, respectively, and the effect of providing the via holes is similarly confirmed. rice field.

[Regarding distance L between via holes]
In Examples 1 to 6, the thickness H of the heat sink 9 is 5.0 mm and the heat dissipation layer 13 is not provided, and only the distance L between the via holes is different. As the distance L between the via holes decreases sequentially from Example 6, the temperature rise decreases, but in Examples 1 to 3, the temperature rise is constant at 99K. In the third embodiment, as shown in FIG. 4, the via holes 12 are arranged so that circles having a radius of r+√(0.02D) centering on the via hole 12 are in contact with each other. Examples 1 and 2, in which the via holes 12 are closer than this, correspond to the state shown in FIG. 6, in which the heat dissipation effect per via hole does not increase and the heat dissipation efficiency saturates. Therefore, in Examples 1 to 3, the temperature rise is constant. Also, providing via holes close to each other increases the number of via holes per unit area, increases the number of via hole processing steps, and affects the cost. 0.94 mm).

[About heat sink thickness H]
Examples 4 and 7 and Comparative Example 2 have via holes 12, the distance L between the via holes is 1.2 mm, the radius r of the via holes is 0.1 mm, and only the thickness H of the heat sink is different. In Example 4, the heat sink thickness H is 5.0 mm and the temperature rise is 105 K. In Example 7, the heat sink thickness H is 1.5 mm and the temperature rise is 108 K. In Comparative Example 2, the heat sink thickness H is 0.3 mm. The temperature was 125K. Comparative Example 2, in which the thickness H of the heat sink 9 is smaller than √(0.02D) (=0.47 mm), has a higher temperature rise, and Examples 4 and 7, in which the thickness H of the heat sink 9 is larger than √(0.02D), are comparative examples. Lower temperature rise. That is, when the thickness H of the heat sink 9 is larger than √(0.02D), the effect of having the via holes 12 is obtained.

As described above for the effect of the via hole, when the temperature rise in Example 4 with the same heat sink thickness H of 5.0 mm is compared with the temperature rise in Comparative Example 1, the results are 105 K and 120 K, respectively. Comparing the temperature rises of Example 7, in which the thickness H of the heat sink is 1.5 mm, and Comparative Example 4, the results are 108 K and 118 K, respectively. That is, when the thickness H of the heat sink is larger than √(0.02D), the effect of heat transfer and heat dissipation by the via holes is exhibited.

On the other hand, Comparative Example 2 in which the thickness H of the heat sink is smaller than √(0.02D) corresponds to the state shown in FIG. The thickness H of the heat sink is 0.3 mm, which is the same as in Comparative Example 2. Compared to Comparative Example 3, which does not have via holes, the temperature rise is the same 125 K, and the effect of heat transfer and heat dissipation by the via holes is not recognized. .

[Regarding via hole radius r]
In Examples 8 to 10 and Comparative Example 5, the thickness H of the heat sink 9 is 5.0 mm, the distance L between the via holes 12 is 1.2 mm, the heat dissipation layer 13 is not provided, and the radius r of the via holes 12 is different. The temperature rise was 107 K for Example 8, 108 K for Example 9, 113 K for Example 10, and 117 K for Comparative Example 5. In Examples 8 to 10, in which the radius r of the via hole is 3.5 mm or less, it can be confirmed that the temperature rise is lower than in Comparative Example 1, which does not have the via hole. However, in Comparative Example 5 in which the radius r of the via hole exceeds 3.5 mm, the temperature rise is large, and the difference from Comparative Example 1, which does not have a via hole, is only 3K, confirming that the effect is small.

[Effect of heat dissipation layer]
In Examples 11 and 12, the heat dissipation layer 13 is provided. Comparing the temperature rise with and without the heat dissipation layer 13 under the same other conditions, the temperature rise was 96 K in Example 11 and 99 K in Example 3, confirming that the provision of the heat dissipation layer 13 reduced the temperature rise. Similarly, the temperature rises of Examples 12 and 8 were 104 K and 107 K, respectively, with and without the heat dissipation layer 13 under the same other conditions, and the effect of providing the heat dissipation layer 13 was confirmed.

While this disclosure describes various exemplary embodiments and examples, various features, aspects, and functions described in one or more of the embodiments may vary from particular embodiment to embodiment. The embodiments are applicable singly or in various combinations without being limited to the application.
Accordingly, numerous variations not illustrated are envisioned within the scope of the technology disclosed herein. For example, modification, addition or omission of at least one component, extraction of at least one component, and combination with components of other embodiments shall be included.

1: LED headlight 2: Light source 3: Substrate 4: Condensing lens 5: Projection lens 6: Holding member 7: Mounting member 8: Thermal conductive layer 9: Heat sink 9a: Heat generating surface 9b: heat dissipation surface, 10: radiation heat absorption layer, 11: housing, 12: via hole, 13: heat dissipation layer.

Claims (8)

a light source;
a substrate provided with the light source on one surface;
a plate-shaped heat sink that cools the substrate;
a heat conductive layer provided in close contact between the other surface of the substrate and one surface of the heat sink;
The heat sink is made of a ceramic material, has a plurality of via holes that penetrate in the thickness direction and are filled with metal,
When the thermal diffusion coefficient of the heat sink is D [m ² /sec] , the plurality of via holes have a distance L between the via holes of
L≧√(0.02D)
A lighting device arranged to satisfy The thickness H of the heat sink is
H≧√(0.02D)
2. The lighting device according to claim 1, wherein the thickness satisfies the following: 3. The lighting device according to claim 1, wherein the via hole has a radius of 3.5 mm or less. 4. The lighting device according to any one of claims 1 to 3, further comprising a heat dissipation layer provided on the via hole on the other surface of the heat sink. The lighting device according to claim 4, wherein the heat dissipation layer is a layer containing ceramic. the light source is disposed in a housing with a radiant heat absorbing layer on the inner surface;
6. The lighting device according to any one of claims 1 to 5, wherein the radiation heat absorbing layer and the heat sink are spaced apart and opposed to each other. The lighting device according to any one of claims 1 to 6, wherein the heat conductive layer and the heat sink are formed larger than the substrate. The lighting device according to claim 7, wherein the heat sink is formed larger than the heat conductive layer.

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