JP2021100086A - Light source device - Google Patents

Abstract

To provide a light source device with improved cooling efficiency of a light emitting element.SOLUTION: A light source device comprises: a substrate; a light-emitting element placed on a first main surface side of the substrate; a heat-dissipating member placed on a second main surface side of the substrate opposite the first main surface side; and a wiring pattern which is formed between the first main surface side and the light-emitting element and electrically connected to the light-emitting element, and the substrate has a heat conduction path that is filled with a plating material having higher thermal conductivity than a material that makes up the substrate so as to penetrate from the first main surface to the second main surface at a position not electrically connected to the wiring pattern.SELECTED DRAWING: Figure 2B

Description

The present invention relates to a light source device.

As an alternative to the conventionally used discharge lamps, the range of application of light source devices using light emitting elements such as LED elements and semiconductor lasers is expanding. With the expansion of the applicable range, it is required to increase the output of the emitted light of the light emitting element.

In order to increase the output of the emitted light of the light emitting element, it is necessary to supply a larger current to the light emitting element. However, when a large current is supplied to the light emitting element, the amount of heat generated by the light emitting element increases, which causes a decrease in output and a shortened life. Therefore, conventionally, measures against heat generation of light emitting elements have been studied. For example, Patent Documents 1 and 2 disclose cooling means for cooling an LED substrate by arranging a heat radiating member (for example, a heat sink) on the back surface side of the LED substrate.

Special Table 2015-515101 JP-A-2017-091945

In recent years, there has been a demand for improvement in cooling efficiency of light emitting elements. In order to improve the cooling efficiency, the present inventor focused not on improving the heat radiating member but on improving the thermal conductivity from the substrate on which the light emitting element is arranged to the heat radiating member. For such improvement, first, it is conceivable to use a material having excellent thermal conductivity for the substrate. However, when selecting a substrate on which the light emitting element is placed, for example, it is necessary to consider restrictions such as high insulation and less adverse effect on the light emitting element due to thermal expansion of the substrate. Therefore, a material having excellent thermal conductivity. It is not possible to select the material with the first priority. Therefore, the present inventor has examined a method for improving the thermal conductivity from the substrate to the heat radiating member from various points, not limited to the selection of the material of the substrate.

An object of the present invention is to provide a light source device having improved cooling efficiency of a light emitting element.

The light source device is a substrate and
A light emitting element arranged on the first main surface side of the substrate and
A heat radiating member arranged on the second main surface side of the opposite surface of the first main surface of the substrate, and
A wiring pattern formed between the first main surface and the light emitting element and electrically connected to the light emitting element is provided.
The substrate is provided with a plating material having a higher thermal conductivity than the material constituting the substrate so as to penetrate from the first main surface to the second main surface at a position not electrically connected to the wiring pattern. It has a filled heat conduction path.

As a result, the heat conduction path promotes the transfer of the heat generated by the light emitting element on the first main surface side to the heat radiating member on the second main surface side.

An interlayer film made of the plating material may be provided on the second main surface at least in a region facing the wiring pattern provided on the first main surface side. Although the details will be described later, the interlayer film reduces the difference in thermal expansion between the first main surface and the second main surface of the substrate, suppresses the deflection of the substrate, and enhances the adhesion with the heat radiating member to heat. Conductivity is improved.

The plating material filled in the heat conduction path may be connected to the interlayer film. As a result, the heat of the heat conduction path is diffused to the interlayer film, and the heat conductivity to the heat radiating member is improved.

The end surface of the heat conduction path on the first main surface side may include a portion located on the second main surface side with respect to the first main surface.

The wiring pattern may be made of the same material as the plating material.

In at least one of the heat conduction paths, the distance from the at least one heat conduction path to the wiring pattern may be smaller than the thickness of the substrate. Although the details will be described later, the heat passing through the heat conduction path propagates to the heat radiating member side faster than the heat propagating through the thickness of the substrate, so that the heat conductivity is improved.

When the thermal conductivity from the first main surface of the substrate to the heat radiating member is improved, the cooling efficiency of the light emitting element is improved. Thus, it is possible to provide a light source device having improved cooling efficiency.

It is a perspective view of one Embodiment of a light source device. It is an enlarged view of A1 part of FIG. FIG. 2 is a cross-sectional view taken along the line B1-B1 of FIG. 2A. FIG. 2B is an enlarged view of a main part of the cross section of the substrate shown in FIG. 2B. It is a schematic diagram for demonstrating the relationship between the heat conduction path and the thickness of a substrate. It is sectional drawing of the main part of another embodiment of a light source device.

The light source device according to the present invention will be described with reference to the drawings. It should be noted that the drawings disclosed in the present specification are merely schematically illustrated. That is, the dimensional ratio on the drawing and the actual dimensional ratio do not always match, and the dimensional ratio does not always match between the drawings.

Hereinafter, the description will be given with reference to the XYZ coordinate system as appropriate. Further, in the present specification, when the positive and negative directions are distinguished when expressing the directions, they are described with positive and negative signs such as "+ X direction" and "-X direction". Further, when expressing a direction without distinguishing between positive and negative directions, it is simply described as "X direction". That is, in the present specification, when simply described as "X direction", both "+ X direction" and "-X direction" are included. The same applies to the Y direction and the Z direction.

FIG. 1 is a schematic perspective view of an embodiment of a light source device. The light source device 100 of the present embodiment includes an LED 1 which is a light emitting element, a heat radiating member 2, a substrate 3, and a wiring pattern 4.

The substrate 3 is a plate-like member having two main surfaces (3a, 3b) and a side surface sandwiched between the two main surfaces (3a, 3b). The two main surfaces (3a, 3b) are surfaces having a much larger area than the side surfaces. In the substrate 3, the LED 1 is arranged on the first main surface 3a side, and the heat radiating member 2 is arranged on the second main surface 3b side opposite to the first main surface 3a. The substrate 3 and the LED 1 come into contact with each other via a wiring pattern, another layer, or the like, which will be described later. The substrate 3 and the heat radiating member 2 are in direct contact with each other, or are in contact with each other via another layer or the like described later. The substrate 3 is selected in consideration of the various restrictions described above, and is formed of, for example, a material containing aluminum nitride or silicon nitride as a main component. The shape of the main surface (3a, 3b) of the substrate 3 is not particularly limited.

The wiring pattern 4 is located between the first main surface 3a of the substrate 3 and the LED 1, and is electrically connected to the LED 1. The wiring pattern 4 is in contact with the first main surface 3a on one surface and in contact with the LED 1 on the other surface (see FIG. 2B). The wiring pattern 4 constitutes an electric circuit together with the wire 6, and transmits the electric power supplied from the electrode 5 to the LED 1. A material having excellent conductivity is used for the wiring pattern 4. Further, for the wiring pattern 4, it is preferable that a material having excellent thermal conductivity is used. For the wiring pattern 4, for example, a material containing copper as a main component is used.

The heat radiating member 2 is used to dissipate the heat generated by the light emission of the LED 1. The heat radiating member 2 is formed of a material having excellent thermal conductivity (for example, a material containing copper or aluminum as a main component). In the present embodiment, the heat radiating member 2 has a flow path 2c through which the cooling fluid flows, as shown in FIG. The specifications of the heat radiating member 2 are not particularly limited. For example, the heat radiating member 2 may have heat radiating fins.

Although not shown, a layer for improving thermal conductivity may be arranged between the substrate 3 and the heat radiating member 2. Examples of the layer for improving thermal conductivity include a phase change sheet and a layer coated with heat-dissipating grease.

The substrate 3 has a heat conduction path 7. The heat conduction path 7 will be described with reference to FIGS. 2A and 2B. FIG. 2A is an enlarged view of the A1 portion of FIG. 1 as viewed from the first main surface 3a side (+ Z direction side). FIG. 2B is a cross-sectional view taken along the line B1-B1 shown in FIG. 2A in the YZ plane. The heat conduction path 7 is formed so as to penetrate from the first main surface 3a to the second main surface 3b of the substrate 3.

The heat conduction path 7 is formed by forming a through hole penetrating from the first main surface 3a to the second main surface 3b on the substrate 3 and filling the formed through hole with a plating material. The through hole is formed by using, for example, a laser, electric discharge machining, a drill, or the like. For example, an electrolytic plating method can be used to fill the through holes with the plating material. As the plating material to be filled in the through holes, a material having a higher thermal conductivity than the material constituting the substrate 3 is used. As a result, even if a material having less excellent thermal conductivity than the heat radiating member 2 is selected as the substrate 3, heat is transferred through the thermal conduction path 7 formed in the substrate 3 to transfer the heat to the substrate 3. It is possible to secure the thermal conductivity from the first main surface 3a of the above to the heat radiating member 2. As the plating material, for example, a material containing copper as a main component can be used. The heat conduction path 7 is arranged apart from the wiring pattern 4 so as not to be electrically connected to the wiring pattern 4. As a result, insulation is ensured between the heat conduction path 7 and the wiring pattern 4, and the heat conduction path 7 is ensured in a non-conducting state.

In the present embodiment, the heat conduction path 7 is formed in a cylindrical shape having a constant inner diameter in the depth direction (Z direction). The diameter d1 of the heat conduction path 7 is preferably 0.1 mm or more, preferably 0.2 mm or more. Thereby, the heat conductivity in the heat conduction path 7 can be improved. Further, the diameter d1 (see FIG. 2A) is preferably 0.5 mm or less, preferably 0.3 mm or less. As a result, the plating material can be easily filled without gaps (without mixing air), and the thermal conductivity of the heat conduction path 7 can be improved.

The shape of the heat conduction path 7 is not limited to the shape of the present embodiment. For example, the heat conduction path 7 may have a groove extending in one direction or a shape in which the groove meanders or bends when viewed from the + Z direction. The heat conduction path 7 may have a tapered shape in which the opening width decreases as the depth increases from at least one of the first main surface 3a and the second main surface 3b in a cross-sectional view as shown in FIG. 2B. ..

Regarding the arrangement of the heat conduction path 7, in the present embodiment, the heat conduction path 7 is arranged based on two types of arrangement policies. The first arrangement policy is to arrange the two heat conduction paths 7 so as to sandwich the one LED 1 from the + Y direction and the −Y direction (see FIG. 2A). In the second arrangement policy, a large number of heat conduction paths 7 are arranged so as to surround the plurality of LEDs 1 and the plurality of wiring patterns 4 (see FIG. 1). The arrangement policy and arrangement configuration of the heat conduction path 7 of the present embodiment shows an example and does not limit the contents of the present disclosure.

As seen in FIG. 2B, the interlayer film 8 is provided between the second main surface 3b and the heat radiating member 2. The action and effect of the interlayer film 8 will be described.

Since the substrate 3 uses a material different from that of the conductive wiring pattern 4, the substrate 3 has a difference in thermal expansion coefficient from that of the wiring pattern 4. Therefore, when the wiring pattern 4 and the substrate 3 expand due to the heat generated by the LED 1, the first main surface 3a in the vicinity of the wiring pattern 4 receives a force due to the difference in thermal expansion coefficient from the wiring pattern 4. Since this force acts only on the first main surface 3a near the wiring pattern 4, it causes the substrate 3 to bend. Therefore, the intermediate film 8 is arranged in contact with the second main surface 3b so that the second main surface 3b in the vicinity of the intermediate film 8 receives a force from the intermediate film 8 due to the difference in the coefficient of thermal expansion. The interlayer film 8 alleviates the difference in the magnitude of the force received between the first main surface 3a and the second main surface 3b. As a result, the bending of the substrate 3 due to the temperature change is suppressed. When the bending of the substrate 3 is suppressed, the adhesion with the heat radiating member 2 is enhanced, and the thermal conductivity is improved.

The interlayer film 8 may be provided on the second main surface 3b at least in a region facing the wiring pattern 4 provided on the first main surface 3a side. The difference in thermal expansion between the first main surface 3a and the second main surface 3b in the local region of the substrate 3 can be reduced to suppress the local bending of the substrate 3.

The plating material filled in the heat conduction path 7 may be connected to the interlayer film 8 formed on the second main surface 3b. As a result, the heat of the heat conduction path 7 is diffused to the interlayer film 8, and the heat conductivity to the heat radiating member 2 is improved.

In the present embodiment, the interlayer film 8 is made of the same material as the plating material filled in the heat conduction path 7. The interlayer film 8 shown in FIG. 2B is provided on the entire surface in contact with the heat radiating member 2, including a region facing the wiring pattern 4 provided on the first main surface 3a side and a region connected to the heat conduction path 7. Has been done. As a result, the interlayer film 8 and the heat conduction path 7 are integrated, and the heat conductivity from the interlayer film 8 to the heat radiating member 2 is further improved.

An electrolytic plating method may be used for forming the interlayer film 8. The formation of the heat conduction path 7 (filling of the through holes of the plating material) and the film formation of the interlayer film 8 may be integrally formed in the same plating step. Further, in order to improve the adhesion to the heat radiating member 2, after the heat conduction path 7 and the intermediate film 8 are formed, the surface of the intermediate film 8 may be polished to reduce the unevenness on the surface. Further, a material different from the plating material filled in the heat conduction path 7 may be used for the interlayer film 8.

By the way, the heat conduction path 7 is preferably a flat surface having no protrusions or dents with respect to the second main surface 3b. In the case of the interlayer film 8 integrated with the heat conduction path 7, it is preferable that the surface of the interlayer film 8 facing the heat radiating member 2 is flat. As a result, the adhesion between the heat conduction path 7 or the interlayer film 8 and the heat radiating member 2 is improved.

FIG. 3 is an enlarged view of a main part of the cross section of the substrate 3 shown in FIG. 2B. The end surface 10 of the heat conduction path 7 on the first main surface 3a side includes a portion located on the second main surface 3b side with respect to the first main surface 3a. That is, the end surface 10 on the first main surface 3a side of the heat conduction path 7 has a recess recessed in the −Z direction with respect to the first main surface 3a. When the first main surface 3a is irradiated with light on the end surface 10 having a recess, the reflected light of the end surface 10 shows a different mode from the reflected light of the first main surface 3a. Therefore, for example, in the step of attaching the LED 1 to the substrate 3 after forming the substrate 3, the end face 10 having a recess can be used as a positioning mark of the LED 1. The dent of the end face 10 can be formed by adjusting the plating processing speed, the plating processing time, the size of the diameter of the through hole, and the etching conditions for removing the unnecessary portion of plating after the plating film formation.

The wiring pattern 4 may be made of the same material as the plating material to be filled in the through holes. The film formation of the wiring pattern 4 and the formation of the heat conduction path 7 (filling of the through holes with the plating material) may be formed by the same plating step. Further, the wiring pattern 4, the heat conduction path 7, and the interlayer film 8 are made of the same material, and the wiring pattern 4 is formed and the heat conduction path 7 is formed (filling of the through holes with the plating material). , The film formation of the interlayer film 8 may be formed by the same plating step. The wiring pattern 4 can be formed and the wiring pattern 4 and the heat conduction path 7 can be separated by etching after film formation, mechanical cutting, or the like.

The heat conduction path 7 may have a heat conduction path in which the distance from the heat conduction path 7 to the wiring pattern 4 is smaller than the thickness of the substrate 3. The action and effect of such a heat conduction path will be described with reference to FIG.

FIG. 4 is a schematic view for explaining the relationship between the heat conduction path 7 and the thickness t1 of the substrate 3. In FIG. 4, the distance d2 from the wiring pattern 4 to the heat conduction path 7 is smaller than the thickness t1 of the substrate 3. In this figure, it is schematically shown that the heat at the point p1 at the end of the wiring pattern 4 and in contact with the first main surface 3a of the substrate 3 propagates in the substrate 3 and the interlayer film 8 from the LED 1. The heat at the point p1 diffuses spherically around the point p1 in the substrate 3. L1 to L3 shown in FIG. 4 indicate a heat front (a line indicating the position of the heat propagated farthest) from the point p1, respectively, and the first front L1 (indicated by a broken line) in chronological order. The second front L2 (indicated by the alternate long and short dash line) and the third front L3 (indicated by the alternate long and short dash line) are formed in this order. The hatched region surrounded by the point p1 and each front (L1 to L3) serves as a heat propagation path.

The hatched region surrounded by the point p1 and the first front L1 (the region where the interval between diagonal lines is the narrowest) propagates in the −Z direction from the point p1 and the heat that has passed through the propagation path h11 that propagates in the −Y direction from the point p1. It contains heat that has passed through the propagation path h21. Since the distance d2 is smaller than the thickness t1, the heat passing through the propagation path h11 travels the distance d2 and reaches the heat conduction path 7, but the heat passing through the propagation path h21 reaches the second main surface 3b. Absent. In the hatching region surrounded by the first front line L1 and the second front line L2 (the region where the interval between the diagonal lines is the second narrowest), the heat h1 transmitted to the heat conduction path 7 passes through the heat conduction path having excellent thermal conductivity. It propagates significantly in the −Z direction (propagation path h12) and approaches the second main surface 3b, but the heat that has passed through the propagation path h21 travels slightly in the −Z direction (propagation path h22). In the hatched region surrounded by the second front L2 and the third front L3 (the region where the interval between the diagonal lines is the widest), the heat that has passed through the propagation path h12 has already reached the second main surface 3b and propagates through the interlayer film 8. (Propagation path h13), the heat that has passed through the propagation path h22 has finally reached the second main surface 3b.

Thus, when the distance d2 from the heat conduction path 7 to the wiring pattern 4 is smaller than the thickness t1 of the substrate 3, the heat passing through the heat conduction path 7 is faster than the heat propagating through the thickness t1 of the substrate 3. Since it propagates to the heat radiating member 2 side, the thermal conductivity is further improved. Even if the distance d2 from the heat conduction path 7 to the wiring pattern 4 is larger than the thickness t1 of the substrate 3, the provision of the heat conduction path 7 increases the number of exhaust heat paths having excellent heat conductivity. The effect of improving sex can be obtained.

The present invention is not limited to the above-described embodiment, and various improvements and changes can be made without departing from the spirit of the present invention. In the above-described embodiment, the light source device 100 having the interlayer film 8 is shown, but unlike the light source device 200 shown in FIG. 5, the interlayer film 8 is not provided between the substrate 3 and the heat radiating member 2. It doesn't matter. Further, although an example of using an LED as a light emitting element is shown, another solid-state light source such as an LD (laser diode) may be used.

1: LED
2: Heat dissipation member 2c: Flow path 3: Substrate 3a: First main surface 3b: Second main surface 4: Wiring pattern 5: Electrode 6: Wire 7: Heat conduction path 8: Intermediate film 10: End faces 100, 200: Light source apparatus

Claims (6)

With the board
A light emitting element arranged on the first main surface side of the substrate and
A heat radiating member arranged on the second main surface side of the opposite surface of the first main surface of the substrate, and
A wiring pattern formed between the first main surface and the light emitting element and electrically connected to the light emitting element is provided.
The substrate is provided with a plating material having a higher thermal conductivity than the material constituting the substrate so as to penetrate from the first main surface to the second main surface at a position not electrically connected to the wiring pattern. A light source device characterized by having a filled heat conduction path. The second main surface, according to claim 1, wherein an interlayer film made of the plating material is provided at least in a region facing the wiring pattern provided on the first main surface side. Light source device. The light source device according to claim 2, wherein the plating material filled in the heat conduction path is connected to the interlayer film. Any one of claims 1 to 3, wherein the end surface of the heat conduction path on the first main surface side includes a portion located on the second main surface side with respect to the first main surface. The light source device according to the section. The light source device according to any one of claims 1 to 4, wherein the wiring pattern is made of the same material as the plating material. The invention according to any one of claims 1 to 5, wherein in at least one of the heat conduction paths, the distance from the at least one heat conduction path to the wiring pattern is smaller than the thickness of the substrate. The light source device described.

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