JP2013171924A - Light emitting device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting device capable of efficiently dissipating heat generated by a light emitting element.SOLUTION: A light emitting device 1 comprises: a board 11 having a heat dissipating via 19 penetrating through from an upper surface to a lower surface thereof; a light reflection layer 21 formed on the board 11 so as to cover a boundary 17 between the board 11 and the heat dissipating via 19; a translucent protective layer 23 formed on the light reflection layer 21; an element mounting plate 25 disposed at a position, where at least a part of the element mounting plate overlaps with an upper region of the boundary 17, so as to be partially buried in the upper part of the protective layer 23, and comprising a material having thermal conductivity higher than that of the protective layer 23; and a light emitting element 13 mounted on the element mounting plate 25.

Description

  The present invention relates to a semiconductor light emitting device in which a light emitting element such as a light emitting diode (LED) element is mounted on a wiring board.

  A light-emitting device in which an LED element is mounted on a wiring board has been conventionally used for lighting, backlights, industrial equipment, and the like. In such a light emitting device, the luminance of the light emitting element is being increased. Also, as the brightness of the light emitting device increases, the amount of heat generated in the light emitting device increases, so the demand for increasing the heat dissipation efficiency by efficiently transferring the heat generated in the light emitting device to the outside of the light emitting device has increased. Yes.

  A technique is known in which a reflective layer made of silver is provided on the surface of a ceramic substrate on which a light emitting element is mounted to increase the light extraction efficiency. In such a device, in order to prevent silver forming the reflective layer from combining with highly reactive sulfur to produce low-reflectance silver sulfide, the reflectivity of the reflective layer is reduced. A coating layer made of glass for coating the reflective layer is formed. Further, in order to increase the heat radiation efficiency, a heat radiation via made of a material having high thermal conductivity such as silver penetrating from the upper surface to the rear surface of the substrate on which the light emitting element is mounted is formed (Patent Document 1).

JP 2010-34487 A

  In the light-emitting device as described above, it is difficult to form a glass layer flat because of the characteristics of glass, and thus there are large irregularities on the surface of the glass coating layer. In particular, in the region on the heat dissipation via, the surface of the glass coating layer in the vicinity of the via is caused by unevenness that occurs in the sintering process during manufacturing due to the difference in the thermal expansion coefficient between the ceramic substrate and the silver filled in the via. Larger irregularities were generated.

  Due to these irregularities, the distance between the back surface of the light emitting element mounted on the surface of the coating layer via the silicone resin and the top surface of the substrate is increased, and the thermal resistance between the light emitting element and the back surface of the substrate is increased. It was.

  SUMMARY An advantage of some aspects of the invention is that it provides a light emitting device that can efficiently dissipate heat generated from a light emitting element.

  The light-emitting device of the present invention includes a substrate having a heat dissipation via penetrating from the upper surface to the lower surface, a light reflection layer formed on the substrate so as to cover a boundary portion between the substrate and the heat dissipation via, The light-transmitting protective layer formed on the protective layer is disposed at a position at least partially overlapping the upper region of the boundary so as to be partially embedded above the protective layer, and has a higher thermal conductivity than the protective layer. It includes an element mounting plate made of a material and a light emitting element mounted on the element mounting plate.

  Also, the manufacturing method of the present invention provides a ceramic green sheet having a hole portion penetrating from the upper surface to the lower surface, and constituting a substrate by firing, and a heat conductive material for forming a heat radiation via in the hole portion. And apply a light reflective material for forming a light reflective layer on the upper surface of the ceramic green sheet so as to cover the boundary between the ceramic green sheet and the heat conductive material. Applying a translucent material for forming a light-sensitive protective layer, and placing the element mounting plate at a position so as to be partially embedded in the upper part of the translucent material and at least partially overlap the upper region of the boundary portion Disposing and forming a laminated structure; firing the laminated structure to form a substrate, a heat dissipation via, a light reflecting layer, and a protective layer; and mounting a light emitting element on the element mounting plate; The heat dissipation via is Higher thermal conductivity than the plate, the element mounting plate has higher thermal conductivity than the protective layer, it is characterized.

  In the light emitting device of the present invention, an element mounting plate for mounting a light emitting element is provided above the protective layer in such a manner as to be partially embedded in the protective layer. Thereby, the heat dissipation efficiency of the light emitting device can be improved.

It is a top view of the light-emitting device of the present invention. It is sectional drawing of the light-emitting device of this invention. It is sectional drawing of the light-emitting device of this invention. It is sectional drawing in each process of the manufacturing method of the light-emitting device of this invention. It is sectional drawing in each process of the manufacturing method of the light-emitting device of this invention. It is sectional drawing in each process of the manufacturing method of the light-emitting device of this invention. It is sectional drawing in each process of the manufacturing method of the light-emitting device of this invention. It is sectional drawing of the modification of the light-emitting device of this invention. It is sectional drawing of the modification of the light-emitting device of this invention. It is sectional drawing of the modification of the light-emitting device of this invention.

  Below, the light-emitting device 1 of this invention is demonstrated, referring FIG. FIG. 1a is a plan view of the light emitting device 1 of the present invention as viewed from the light emitting surface side. 1b is a cross-sectional view taken along line 1b-1b in FIG. 1a.

The substrate 11 has a rectangular planar shape made of low temperature co-fired ceramics (LTCC) or high temperature co-fired ceramics (HTCC) mainly composed of Al ₂ O _3. For example, it is formed by firing a green sheet made of Al ₂ O ₃ , glass, an organic binder, and a plasticizer. An electrode (not shown) for supplying power to the LED element 13 is formed on the upper surface of the substrate 11 by, for example, printing a paste such as Au on the green sheet and firing the green sheet later. Yes.

  In the center of the substrate 11, a cylindrical hole portion 17 that penetrates from the upper surface to the lower surface of the substrate 11, for example, has a circle having a diameter of 500 μm as a bottom surface, has a thermal conductivity better than that of the substrate 11, such as Ag. The heat dissipation via 19 filled with is formed. The heat dissipation via 19 is formed by, for example, punching the green sheet to form a cylindrical hole 17, filling the hole 17 with an Ag paste, and firing the green sheet together with the green sheet. Various materials such as other metals can be used as the material for forming the heat dissipation via 19 as long as the material has better thermal conductivity than the substrate 11.

  The reflective layer 21 is formed so as to cover the upper surface of the substrate 11. The reflective layer 21 is made of, for example, a layered light reflective member such as Ag having a thickness of 20 μm. For example, the reflective layer 21 is formed by printing a paste such as Ag on the green sheet and firing the paste together with the green sheet. Is done.

  The protective layer 23 is formed so as to cover the upper surface of the reflective layer 21. The protective layer 23 is, for example, a layered translucent member having a thickness of 30 μm, and is made of a glass material or the like. The protective layer 23 is formed, for example, by printing a paste of glass material on the paste forming the reflective layer 21 and baking it together with the green sheet or the like. The protective layer 23 seals the reflective layer 21 from the external environment and prevents the reflective layer 21 from being deteriorated in reflectivity due to the reflective layer 21 being deteriorated by sulfur or the like. The protective layer 23 may be anything other than glass as long as the reflective layer 21 can be sealed from the external environment and has translucency.

  The element mounting plate 25 is a member having a higher thermal conductivity than the member forming the protective layer 23, for example, ceramic, and has a square planar shape with a side of 800 μm and a thickness of 30 μm. . The element mounting plate 25 is formed in a plate shape by firing a green sheet similar to the green sheet used for the substrate 11 and then cutting and dividing the green sheet. The element mounting plate 25 is provided on the protective layer 23 directly above the heat radiation via 19 so as to be partially embedded in the protective layer 23 and separated from the reflective layer. In addition, the heat dissipation via 19 is covered with the element mounting plate 25 in a top view as viewed from the direction perpendicular to the surface of the substrate 11, or is disposed at a position including the entire top surface of the heat dissipation via in the top view. That is, the heat dissipation via 19 is arranged so as to be inside the element mounting plate 25 when projected onto a plane parallel to the substrate 11 (FIG. 1a).

  With this configuration, it is possible to dispose the element mounting plate 25 and the light emitting element 13 parallel to the surface of the substrate 11 on the protective layer 23 regardless of the unevenness of the surface of the reflective layer 21 caused by the heat dissipation via 19. is there. Therefore, the thermal resistance between the light emitting element and the back surface of the substrate can be reduced as compared with the conventional light emitting device in which the light emitting element is mounted on the coating layer having an uneven surface. In addition, since the element mounting plate 25 has higher thermal conductivity than the protective layer 23, the light emitting device 1 using the element mounting plate 25 is more than the conventional light emitting device in which the LED element 13 is directly mounted on the upper surface of the protective layer 23. In addition, the thermal resistance between the LED element 13 and the back surface of the substrate 11 is reduced.

  In addition, the member used for the element mounting plate 25 may be a member having a thermal conductivity better than that of the protective layer 23, and may be a metal such as Cu or Al. For example, the ceramic green sheet forming the substrate 11 is fired. It is preferable to use a high melting point member (for example, Mg or W) that hardly deforms under high heat (for example, about 900 ° C.). Further, as the element mounting plate 25, it is also preferable to use high-temperature fired ceramics (HTCC) with high thermal conductivity. Further, as shown in FIG. 2, the element mounting plate 25 covers a part of the heat radiating via 19 or overlaps only a part of the heat radiating via in a top view when viewed from the direction perpendicular to the surface of the substrate 11. It may be arranged. That is, the element mounting plate 25 is arranged at a position covering the boundary portion between the substrate 11 and the heat dissipation via 19 (ie, a position overlapping the upper region of the boundary portion) in a top view as viewed from the direction perpendicular to the surface of the substrate 11. It may be. Even in this case, the element mounting plate 25 and the LED element 13 mounted thereon are parallel to the upper surface of the substrate 11 regardless of the unevenness of the surface of the light reflecting layer 21 generated above the boundary between the heat dissipation via 19 and the substrate 11. It can arrange | position and can reduce thermal resistance. The element mounting substrate 25 is preferably made of a material having a high light reflectivity, but is preferably formed to be small enough to mount the light emitting element so that reflection by the reflection layer 21 can be used. .

  The LED element 13 has a square planar shape with a side of 450 μm and a thickness of 120 μm. The LED element 13 is mounted on the upper surface of the element mounting plate 25 via an adhesive material such as a silicone resin or epoxy resin. The adhesive is not limited to a translucent resin, and a material that increases the reflectance and thermal conductivity can be added. The LED element 13 has a P electrode and an N electrode on the upper surface, and the P electrode and the N electrode are, for example, Au (or conductors such as Cu, Pt, Al) bonding wires (not shown). Is electrically connected to an electrode (not shown).

  As described above, in the light emitting device 1 of the present invention, the LED element 13 is not directly mounted on the protective layer 23 having irregularities on the surface, but is partially embedded in the protective layer 23 and protected. It is mounted via an element mounting plate 25 having a higher thermal conductivity than the layer 23. The lower part of the element mounting plate 25 is buried in the upper part of the protective layer 23 so as not to contact the reflective layer 21, and the upper part is exposed from the upper surface of the protective layer 23. As a result, the unevenness of the interface between the reflective layer 21 surface and the protective layer 23 in the vicinity of the heat dissipation via 19, that is, the unevenness of the surface of the protective layer 23 is large when the element mounting plate 25 is not interposed. In the region near the via 19, the LED element 13 can be disposed on the protective layer 23 in parallel with the substrate 11, and the heat dissipation effect by the heat radiating via 19 having a high thermal conductivity can be utilized to the maximum. Is possible. Furthermore, it is possible to provide a highly reliable light-emitting device 1 that is free from various problems that are a concern when irregularities occur at the boundary between the substrate 11 and the heat dissipation via 19 or above the heat dissipation via 19. This is because there is a concern that the LED element 13 may be inclined with respect to the upper surface of the substrate 11 when unevenness occurs at the boundary between the substrate and the heat dissipation via or above the heat dissipation via. In the wire bonding step of connecting a power supply wire to the electrode formed on the upper surface of the element 13, when the image of the LED element 13 is recognized, the reflection state of the upper surface of the LED element 13 is different from the normal state, so that wire bonding cannot be performed. Cases can arise. Further, when the degree of unevenness is large, there is a possibility that the optical axis of the LED element 13 is shifted and desired luminance and light distribution cannot be obtained.

  Next, with reference to FIGS. 3a to 3d, a method for manufacturing the light emitting device 1 of the present invention will be described. Note that “A” is attached to the reference symbol for green sheets, pastes, and the like before firing.

First, for example, a substrate green sheet 11A prepared by cutting a ceramic green sheet made of Al ₂ O ₃ , glass, an organic binder, and a plasticizer according to the size of the substrate 11 is prepared.

  Next, as shown in FIG. 3a, a hole 17 for forming the heat dissipation via 19 is formed in the center of the substrate green sheet 11A by using, for example, punching. Then, the hole 17 is filled with a thermal conductive material paste 19A made of a material such as Ag having a higher thermal conductivity than the substrate 11 by, for example, screen printing.

  Next, as shown in FIG. 3b, a light reflective material paste 21A such as an Ag paste is applied to the entire upper surface of the substrate green sheet 11A by screen printing, for example, so as to cover the light reflective material paste 21A. Then, a paste 23A of a translucent material such as glass paste is applied by screen printing.

  Next, as shown in FIG. 3c, an element mounting plate 25, which is a plate-like member made of ceramic, metal, or the like, previously formed in a predetermined size is placed on the paste 23A of a translucent material. After the element mounting plate 25 is placed, the element mounting plate 25 is pressed from above in the direction of the substrate 11 so that a part of the element mounting plate 25 is embedded in the paste 23A of a translucent material. At this time, the pressing is performed to the extent that the element mounting plate 25 does not contact the paste 21A of the light reflecting material.

  Next, if necessary, green sheets are laminated according to the thickness of the final manufactured device, and fired in a nitrogen atmosphere (in the case of LTCC, the firing temperature is about 900 degrees). The transparent material paste 19A, the light reflective material paste 21A, and the light transmissive material paste 23A are cured. Thereafter, as shown in FIG. 3d, an adhesive made of silicone resin or the like is applied onto the element mounting plate 25, the LED element 13 is mounted on the adhesive, the adhesive is heated and cured, and the LED element is formed by wire bonding. 13 and an electrode (not shown) are electrically connected. After that, if necessary, a process such as resin sealing (not shown) of the LED element 13 is performed by dripping and curing a resin on the LED element 13, and light emission is performed by dividing and dividing the LED element 13. The device 1 is completed. In addition, it is good also as performing the division | segmentation and piece-dividing processing of the board | substrate 11 etc. before mounting the LED element 13. FIG.

  In the above embodiment, one heat dissipation via 19 is provided, but a plurality of heat dissipation vias 19 may be formed as in the light emitting device 2 shown in FIG. Moreover, the several element mounting board 25 and the LED element 13 may be distribute | arranged on one heat dissipation via like the light-emitting device 3 shown in FIG. Further, the heat radiation via 19 is not necessarily provided directly under the element mounting plate 25. For example, as in the light emitting device 4 shown in FIG. 6, the element mounting plate 25 may be arranged at a position that does not overlap the heat dissipating vias 19 in a top view as viewed from the direction perpendicular to the surface of the substrate 11. Even in this case, the element mounting plate 25 and the LED element 13 are parallel to the upper surface of the substrate 11 regardless of the unevenness generated on the surface of the protective layer 23 due to the properties of the heat dissipation via 19 or the protective layer 23. The effect of mounting and lowering the thermal resistance is obtained.

  Moreover, in the said Example, although the planar shape of the element mounting board 25 is larger than the bottom face of the thermal radiation via 19, the planar shape of the element mounting board 25 should just be larger than the bottom face of the LED element 13. FIG. . The element mounting plate 25 may be other than a square, and may have various shapes such as a rectangle, a circle, and an ellipse.

  Moreover, in the said Example, although the light reflection layer 21 is a structure which covers the whole board | substrate upper surface, if the function which reflects the light inject | emitted from the LED element 13 in the light emission direction of the light-emitting device 1 can be fulfilled. For example, only a part of the upper surface of the substrate may be covered.

  Moreover, in the said Example, although the case where the light reflection layer 21 covered the whole upper surface of the thermal radiation via 19 was demonstrated, it formed so that at least one part of the boundary part of the thermal radiation via 19 and the board | substrate 11 might be covered. Also good. The unevenness that occurs on the surface of the reflective layer 21 (the unevenness that occurs on the surface of the protective layer 23 in the configuration in which the element mounting plate 25 is not provided) can occur above the heat dissipation via 19 and above the boundary between the heat dissipation via 19 and the substrate 11. Since the unevenness generated above the boundary between the heat dissipation via 19 and the substrate 11 is larger, by disposing the element mounting plate 25 between the boundary between the heat dissipation via 19 and the substrate 11 and the bottom surface of the LED element 13, This is because the LED element 13 can be placed substantially parallel to the upper surface of the substrate 11.

  Various numerical values, dimensions, materials, and the like in the above-described embodiments are merely examples, and can be appropriately selected according to the application and the light-emitting element used.

1, 2, 3 Light-emitting device 11 Substrate 11A Substrate green sheet 13 LED element 17 Hole portion 19 Heat radiation via 19A Thermal conductive material paste 21 Reflective layer 21A Light reflective material paste 23 Protective layer 23A Translucent material paste 25 Element mounting plate

Claims (6)

A substrate having a heat dissipation via penetrating from the upper surface to the lower surface;
A light reflecting layer formed on the substrate so as to cover the boundary between the substrate and the heat dissipation via;
A translucent protective layer formed on the light reflecting layer;
An element mounting plate that is disposed at a position at least partially overlapping the upper region of the boundary portion and is made of a material having higher thermal conductivity than the protective layer so as to be partially embedded in the upper portion of the protective layer; ,
A light emitting element mounted on the element mounting plate;
A light emitting device comprising:   2. The light emitting device according to claim 1, wherein the element mounting plate is configured to include the entire top surface of the heat radiating via when viewed from a direction perpendicular to the top surface of the substrate.   The light emitting device according to claim 1, wherein the element mounting plate is made of ceramic or metal. A method of manufacturing a light emitting device,
A ceramic green sheet having a hole penetrating from the upper surface to the lower surface and forming a substrate by firing is prepared, and the hole is filled with a heat conductive material for forming a heat radiating via, and the ceramic green sheet A light-reflective material for forming a light-reflective layer is applied on the upper surface of the ceramic green sheet so as to cover the boundary between the heat-conductive material and the heat-conductive material, and a light-transmitting protection is applied to the light-reflective material. A light-transmitting material for forming a layer is applied, and an element mounting plate is disposed at a position so as to be partially embedded in the upper part of the light-transmitting material and at least partially overlap the upper region of the boundary portion. A step of forming a laminated structure,
Firing the laminated structure to form the substrate, the heat dissipation via, the light reflecting layer, and the protective layer;
Mounting a light emitting element on the element mounting plate, wherein the heat dissipation via has a higher thermal conductivity than the substrate, and the element mounting plate has a higher thermal conductivity than the protective layer. A method for manufacturing a light emitting device.   The method of manufacturing a light emitting device according to claim 4, wherein the element mounting plate is configured to include the entire upper surface of the heat dissipation via when viewed from a direction perpendicular to the upper surface of the ceramic green sheet.   6. The method for manufacturing a light-emitting device according to claim 4, wherein the element mounting plate is made of ceramic or metal.

Images