JP2014110397A - Light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device with high reliability.SOLUTION: A light-emitting device according to an embodiment comprises: a ceramic substrate 1; a first metal layer 2 and a second metal layer 3 formed on a first surface 11; a third metal layer 4 formed on a second surface; a light-emitting part 5 including a light-emitting element 52 with one end electrically connected to one end of the first metal layer 2 and the other end electrically connected to one end of the second metal layer 3; a first connector 8 provided on the other end of the first metal layer 2; a second connector 9 provided on the other end of the second metal layer 3; and a metal heat-radiating plate 10 connected to the third metal layer 4 via a solder layer 64. The light-emitting part 3 is arranged such that a central portion C of the light-emitting part 3 approximately coincides with a central portion C' of the ceramic substrate 1. The central portion C of the light-emitting part 3, the first connector 8, and the second connector 9 are arranged on the X-axis. The first connector 8 and the second connector 9 are arranged so as to interpose the light-emitting part 3 in between.

Description

  Embodiments described herein relate generally to a light emitting device.

  A light-emitting device is a light source using a light-emitting element, and is used for lighting and display applications, for example. Since the light emitting element is a point light source, it is known that the light emitting device has a higher heat generation density than a linear light source such as a fluorescent lamp. In recent years, there has been a demand for a light-emitting device that emits high-intensity light with a small light-emitting area. Therefore, it is necessary to secure a structure that efficiently releases heat generated in a light-emitting element.

  As an example for ensuring this heat dissipation, a metal heat dissipation plate may be provided on the surface of the substrate opposite to the surface on which the light emitting element is mounted. The connection between the substrate and the heat radiating plate is performed by forming a metal layer on the back surface of the substrate and joining the metal layer and the heat radiating plate with solder. As a result, a heat radiating path capable of transmitting heat from the light emitting element to the heat radiating plate is formed.

  However, when the substrate is made of ceramic, a large stress is applied to the solder due to a difference in thermal expansion coefficient from the heat dissipation plate, which is a metal, and cracks are generated. If stress continues to be applied, cracks progress and reliability decreases.

JP 2012-84733 A JP 2011-171320 A JP 2012-9886 A

  The problem to be solved by the present invention is to provide a highly reliable light emitting device.

  In order to achieve the above object, a light emitting device according to an embodiment has a first surface and a second surface located on the opposite side of the first surface, and a pair of first end sides and the first surface. A ceramic substrate having a pair of second end sides that are orthogonal to the first side and have the same or shorter length as the first end side, a first metal layer formed on the first surface, and a first Two metal layers, a third metal layer formed on the second surface, one end electrically connected to one end side of the first metal layer, and the other end electrically connected to one end side of the second metal layer. A light emitting unit including a connected light emitting element, a first connector provided on the other end side of the first metal layer, and a second connector provided on the other end side of the second metal layer; A metal heat dissipating plate face-to-face connected to the ceramic substrate via a solder layer on the third metal layer, When passing through the central part and the axis along the first end side is the first axis, passing through the central part of the ceramic substrate and the axis along the second end side is the second axis, The light emitting portion is arranged so that a central portion thereof substantially coincides with the central portion of the ceramic substrate, and the central portion of the light emitting portion, the first connector, and the second connector are arranged in the first portion. The first connector and the second connector are arranged on the shaft so as to sandwich the light emitting portion therebetween.

  According to the present invention, a highly reliable light-emitting device can be provided.

It is a figure for demonstrating the light-emitting device of 1st Embodiment. It is a figure for demonstrating the cross section of the light-emitting device of 1st Embodiment. It is a figure for demonstrating the state which removed members, such as a light emitting element and a connector, in the light-emitting device of 1st Embodiment. It is a figure for demonstrating the conventional light-emitting device. It is a figure for demonstrating the light-emitting device of 2nd Embodiment. It is a figure for demonstrating the light-emitting device of 3rd Embodiment. It is a figure for demonstrating the light-emitting device of other embodiment.

(First embodiment)
The first embodiment will be described with reference to FIGS. 1, 2, and 3. FIG. 1 is a diagram for explaining a light emitting device according to a first embodiment of the present invention, FIG. 2 is a diagram for explaining a cross section of the light emitting device according to the first embodiment, and FIG. It is a figure for demonstrating the state which removed members, such as a light emitting element and a connector, in the light-emitting device of 1 embodiment.

  The light-emitting device of this embodiment is a light-emitting device used for illumination and display applications. As a main part, a ceramic substrate 1 composed of a ceramic material such as alumina or alumina nitride, or a ceramic material and a composite ceramic material is used. I have. The ceramic substrate 1 has a first surface 11 as a front surface and a second surface 12 as a back surface. The first end sides 13 and 14 and the first end side 13 are orthogonal to the pair of first end sides 13 and 14, and the second end sides 15 and 16 are shorter than the first end sides 13 and 14. That is, the ceramic substrate 1 of the present embodiment is a thin plate in which the first surface 11 and the second surface 12 are rectangular in shape and have a thickness of 1 mm or less.

  The ceramic substrate 1 is configured as a DPC (Direct Plated Copper) substrate. That is, at least the first metal layer 2 and the second metal layer 3 are formed on the first surface 11 and the third metal layer 4 is formed on the second surface of the ceramic substrate 1. The 1st metal layer 2, the 2nd metal layer 3, and the 3rd metal layer 4 can be comprised with the same material. For example, a first plating layer made of copper and having a thickness of 0.1 mm or less is laminated on a titanium oxide layer formed by sputtering. A second plating layer made of nickel / gold or nickel / palladium / gold may be further laminated on the first plating layer. The total volume of the metal layer formed on the first surface 11 is preferably smaller than the total volume of the metal layer formed on the second surface 12. With such a relationship, it is possible to widen the formation region of the solder layer 64 interposed between the heat sink 10 to be described later, and therefore heat is transmitted from the light emitting element 52 serving as a heat generating portion to the heat sink 10. A wide heat dissipation path can be secured, and thus heat dissipation can be improved.

  The wiring pattern on the first surface 11 of the ceramic substrate 1 will be described in detail with reference to FIG. A first axis passing through the central portion C ′ of the ceramic substrate 1 and extending along the first end sides 13 and 14 is the X axis, and a second axis passing through the central portion C ′ and extending along the second end sides 15 and 16 When the axis is the Y axis, the first metal layer 2 is formed in the vicinity of the second end 15 on the ceramic substrate 1 so as to coincide with the X axis. At this time, the end portion of the first metal layer 2 does not reach the second end side 15. In the first metal layer 2, a power supply metal layer 21 is formed at the end portion on the second end side 15 side so as to protrude along the Y axis and in the direction of the first end side 13. The first metal layer 2 has an inspection metal layer 22 protruding along the Y axis in the direction of the first edge 14 between the end portion on the light emitting unit 5 side and the power supply metal layer 21. Is formed. Further, the first metal layer 2 has a component mounting metal layer 23 protruding along the Y axis in the direction of the first edge 13 between the end portion on the light emitting unit 5 side and the inspection metal layer 22. Is formed.

  On the other hand, the second metal layer 3 is formed in the vicinity of the second end 16 on the ceramic substrate 1 so as to coincide with the X axis. At this time, the end portion of the first metal layer 2 does not reach the second end side 15. In the second metal layer 3, a power supply metal layer 31 that protrudes along the Y axis in the direction of the first edge 13 is formed at the end on the second edge 16 side. The second metal layer 3 includes an inspection metal layer 32 that protrudes along the Y axis in the direction of the first edge 14 between the end portion on the light emitting unit 5 side and the power supply metal layer 31. Is formed.

  A light emitting unit 5 is provided on the first surface 11 of the ceramic substrate 1. The light emitting unit 5 has a cylindrical shape and includes a light emitting surface 51 from which light is emitted. The light emitting part 5 is arranged so that the central part C substantially coincides with the central part C ′ of the ceramic substrate 1. That is, in the light emitting portion 5, the distance from the corner of the ceramic substrate 1 to the central portion C 'is substantially the same length. In this embodiment, “substantially” means that the same is optimal, but a deviation of about an error, for example, a deviation of about 3 mm is allowed.

  The light emitting unit 5 includes a light emitting element 52. The light emitting element 52 is, for example, a flip chip type light emitting element that generates blue light. Specifically, a transparent sapphire layer, an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer are laminated in order from one side to the other side, and electrodes are respectively formed on the n-type semiconductor layer and the p-type semiconductor layer. Is a light emitting element formed. By supplying power to the n-type semiconductor layer and the p-type semiconductor layer through a pair of electrodes, light is generated in the light-emitting layer located below the element, and the light is emitted from the sapphire layer. In the light emitting element 52, one electrode is electrically connected to one end side of the first metal layer 2, and the other electrode is electrically connected to the other end side of the second metal layer 3 by the solder layer 61.

  In the present embodiment, a plurality of light emitting elements 52 are configured. For example, there are 96 light emitting elements 52. The plurality of light emitting elements 52 are divided into a first section 53 and a second section 54. The first section 53 includes half (48) light emitting elements 52, which are connected in series by an element mounting metal layer 55, one end connected to the first metal layer 2, and the other end. Is connected to the second metal layer 3. Further, the connection side of the first section 53 with the second metal layer 3 is branched in the middle, and the component mounting metal layer 56 extends in the direction of the first metal layer 2. Two capacitors 71 and 72 are connected between the component mounting metal layer 56 and the component mounting metal layer 23 via the component mounting metal layer 73. Capacitors 71 and 72 are for preventing dark lighting. The reason for using a plurality of capacitors is that if one capacitor is used, the size, particularly the height of the capacitor increases, and the light generated by the light emitting unit 5 may be blocked. Similarly, the second section 54 is composed of half (48) light-emitting elements 52, which are connected in series by the element mounting metal layer 55, and one end is connected to the first metal layer 2. The other end is connected to the second metal layer 3.

  The light emitting unit 5 includes a cylindrical wall portion 57. The wall portion 57 is higher than the height of the light emitting element 52 and is formed on the first surface 11 of the ceramic substrate 1 so as to surround the light emitting element 52 in the cylinder. A part of the metal layer is formed on the metal layer. In order to cover the light emitting element 52, the wall portion 57 is desirably formed of a highly light reflective material. You may have the bank which inclines toward the front side.

A space formed by the wall portion 57 and the ceramic substrate 1 is filled with a sealing resin 58 made of a resin such as silicone so as to cover the light emitting element 4. The sealing resin 58 contains a yellow phosphor material. That is, part of the blue light generated in the light emitting element 52 is excited by the phosphor included in the sealing resin 58 to become yellow light, and part of the blue light passes through the sealing resin 58 while remaining blue light. The light in which they are mixed is emitted from the light emitting surface 51 of the light emitting unit 5 as white light. The total luminous flux with respect to the area of the light emitting surface 51, the so-called luminous flux divergence is 10 lm / mm ^{2 to} 100 lm / mm ² , and the total luminous flux with respect to the total input power is 50 lm / W to 150 lm / W. Thus, the light emitting device of this embodiment emits high-intensity light with a narrow light emitting area.

  The first connector 8 is provided on the other end side of the first metal layer 2, that is, on the power feeding metal layer 21. The first connector 8 is a member for supplying electric power to the light emitting element 52 and is connected to a power supply line extended from the lighting circuit. The first connector 8 has a metal terminal and is connected to the first metal layer 2 via a solder layer 62. A second connector 9 is provided on the other end side of the second metal layer 3, that is, on the power feeding metal layer 31. Similarly to the first connector 8, the second connector 9 has a metal terminal and is connected to the second metal layer 3 through the solder layer 63. At that time, the first connector 8 and the second connector 9 are arranged so as to be symmetrical with respect to the Y axis. That is, the distance L1 between the light emitting unit 2 and the first connector and the distance L2 between the light emitting unit 2 and the first connector are substantially the same distance. Note that the temperature of the first connector 8 and the second connector 9 can be increased by transferring heat from the light emitting element 52 that is a heat source through the first metal layer 2 and the second metal layer 3. It is a characteristic member. Therefore, in order to prevent the heat from being biased toward the center of the ceramic substrate 1, the distances L1 and L2 are desirably 2 mm or more. On the other hand, the distance between the end of the ceramic substrate 1 and the connector, particularly the shortest distance L3, is 5 mm or more in order to avoid a member that can reach a high temperature in the vicinity of the crack starting point and the crack from being easily advanced. Is desirable. The metal terminal may be covered with an insulating case such as resin.

  A heat sink 10 is disposed on the second surface 12 of the ceramic substrate 1. The heat sink 10 is a metal plate that functions as a heat spreader and has a thickness of 5 mm or less. The heat radiating plate is connected to the third metal layer 4 through the solder layer 64 so as to face the second surface 12 of the ceramic substrate 1.

  As described above, in the present embodiment, the light emitting unit 5 is arranged so that the central portion C thereof substantially coincides with the central portion C ′ of the ceramic substrate 1, and the first connector 2 and the second connector that are single pole connectors are arranged. Since the connector 3 is spaced from both ends of the light emitting section 5, a highly reliable light emitting device can be provided. That is, in the case of a light-emitting device that emits high-intensity light with a narrow light-emitting area, in which the ceramic substrate 1 and the heat sink 10 are connected by the solder layer 64, a large stress is applied to the solder layer 64 due to a difference in thermal expansion between lighting and extinguishing. As a result of the occurrence of cracks and selective progress of the cracks, there is a risk of lowering reliability, but this embodiment can suppress them.

  More specifically, referring to a conventional light emitting device, as shown in FIG. 4, the light emitting portion 5 is disposed at a biased position on the first surface 11 of the ceramic substrate 1, and the bipolar connector 8 ′ is disposed. In the light emitting device that has been used, there is a high risk of lowering the reliability. In the light emitting device, the portion where the temperature rises is a light emitting portion 5 including a light emitting element that is a heat source, and a connector 8 ′ including an anode connector and a cathode connector in which the heat is transmitted through the metal layers 2 and 3. This is because, if the arrangement of members that can become high temperature is biased on the ceramic substrate 1 as in 4, the heat distribution is also biased. That is, a crack is generated in the solder layer near the corner of the ceramic substrate 1 and gradually progresses toward the center of the substrate. Leads to the development of local cracks. Even if the crack of the solder layer partially progresses to the back side of the light emitting portion 5, the heat radiation path from the light emitting element to the heat radiating plate is cut off, and the light emitting element is broken.

  Therefore, in the first embodiment, since the light emitting unit 5 is arranged at the center of the ceramic substrate 1 and the single-pole connectors are arranged at both ends, the heat source is dispersed and the heat distribution in the ceramic substrate 1 is uneven. Is eliminated, the occurrence of local cracks can be suppressed, and the progress can be delayed. Further, since the light emitting portion 5 is separated from the corner of the ceramic substrate 1 where the crack starts, the time for the crack to reach the back side of the light emitting portion 5 can be sufficiently delayed. Thus, a highly reliable light-emitting device can be provided. Although the capacitors 71 and 72 are disposed only in the vicinity of the first connector 8, since the heat generation of the capacitors 71 and 72 is not large, such an arrangement does not cause a large deviation in heat distribution.

  Further, since the first connector 8 and the second connector 9 are provided so as to be symmetric with respect to the Y axis, the heat distribution is made uniform and the reliability is further improved. Further, since the plurality of light emitting elements 52 are provided so as to be symmetric with respect to the X axis and the Y axis, the heat distribution is made uniform and the reliability is further improved. In addition, since the first connector 8 and the second connector 9 are connected to the first metal layer 2 and the second metal layer 3 so that the longitudinal direction thereof is along the Y axis, the reliability is further improved.

(Second Embodiment)
FIG. 5 is a diagram for explaining a light emitting device according to a second embodiment of the present invention. About each part of this 2nd Embodiment, the same part as each part of 1st Embodiment is shown with the same code | symbol, and the description is abbreviate | omitted.

  In this embodiment, an elliptical substrate is used for the first surface 11 of the ceramic substrate 1. In addition, the central portion C of the light emitting portion 5 and the second central portion C are arranged on the X axis passing through the central portion C ′ of the ceramic substrate 1 and along the edge of the heat radiating plate 10 and passing through the longest portion of the ceramic substrate 1. One connector 8 and a second connector 9 are arranged.

  Also in the second embodiment, as in the first embodiment, since the uneven distribution of heat is made uniform, a highly reliable light-emitting device can be provided.

(Third embodiment)
FIG. 6 is a diagram for explaining a light emitting device according to a third embodiment of the present invention.

  In this embodiment, a substrate having a polygonal shape is used by forming the notches 17 obliquely at the four corners of the ceramic substrate 1 whose first surface 11 is rectangular. In addition, the central portion C of the light emitting portion 5 and the second central portion C are arranged on the X axis passing through the central portion C ′ of the ceramic substrate 1 and along the edge of the heat radiating plate 10 and passing through the longest portion of the ceramic substrate 1. One connector 8 and a second connector 9 are arranged.

  In the third embodiment as well, as in the first embodiment, since the uneven distribution of heat is made uniform, a highly reliable light-emitting device can be provided.

  The present invention is not limited to the above embodiments, and various modifications are possible.

  For example, the light emitting unit 5 is not limited to a cylindrical shape, and may be an elliptical column shape or a polygonal column shape.

  The light-emitting element 52 is not limited to a flip-chip type light-emitting element, and may be a face-up type light-emitting element that performs electrical connection using a bonding wire.

  The first connector 8 and the second connector 9 may be arranged symmetrically with respect to the center C of the ceramic substrate 1 as shown in FIG. The same applies to some patterns of the first metal layer 2 and the second metal layer 3.

  Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Ceramic substrate 11 1st surface 12 2nd surface 13, 14 1st edge 15, 16 2nd edge 2 1st metal layer 3 2nd metal layer 4 3rd metal layer 5 Light emission part 52 Light Emitting Element 64 Solder Layer 8 First Connector 9 Second Connector 10 Heat Dissipation Plate

Claims (4)

A first surface and a second surface located on the opposite side of the first surface; and a pair of first end sides and the first end sides orthogonal to each other; the first end side and the length Ceramic substrates having a pair of second edges that are the same or short,
A first metal layer and a second metal layer formed on the first surface;
A third metal layer formed on the second surface;
One end is one end side of the first metal layer, the other end is a light emitting unit including a light emitting element electrically connected to one end side of the second metal layer,
A first connector provided on the other end side of the first metal layer;
A second connector provided on the other end side of the second metal layer;
A metal heat dissipating plate facing the ceramic substrate via a solder layer on the third metal layer,
An axis passing through the central portion of the ceramic substrate and extending along the first end side is a first axis, and an axis passing through the central portion of the ceramic substrate and extending along the second end side is a second axis. When
The light emitting portion is arranged so that a central portion thereof substantially coincides with the central portion of the ceramic substrate, and the central portion of the light emitting portion, the first connector, and the second connector are arranged in the first portion. A light emitting device, wherein the light emitting device is disposed on an axis, and the first connector and the second connector are disposed so as to sandwich the light emitting portion therebetween.   The light emitting device according to claim 1, wherein the first connector and the second connector are provided so as to be substantially symmetric with respect to the second axis.   The light emitting portion covers a cylindrical wall portion, a plurality of light emitting elements disposed in the cylinder of the wall portion, an inter-element metal layer that electrically connects the plurality of light emitting elements, and the light emitting element. As described above, the sealing resin filled in the cylinder of the wall portion is provided, and the light emitting element is provided so as to be symmetric with respect to the first axis and the second axis. The light-emitting device according to claim 1 or 2. A circular or polygonal ceramic substrate having a first surface and a second surface;
A first metal layer and a second metal layer formed on the first surface;
A third metal layer formed on the second surface;
One end is one end side of the first metal layer, the other end is a light emitting unit including a light emitting element electrically connected to one end side of the second metal layer,
A first connector provided on the other end side of the first metal layer;
A second connector provided on the other end side of the second metal layer;
A metal heat dissipating plate facing the ceramic substrate via a solder layer on the third metal layer,
An axis passing through the central portion of the ceramic substrate and passing through the portion with the longest width of the ceramic substrate is a first axis, and an axis passing through the central portion of the ceramic substrate and perpendicular to the first axis. As the second axis,
The light emitting portion is arranged so that a central portion thereof substantially coincides with the central portion of the ceramic substrate, and the central portion of the light emitting portion, the first connector, and the second connector are arranged in the first portion. A light emitting device, wherein the light emitting device is disposed on an axis, and the first connector and the second connector are disposed so as to sandwich the light emitting portion therebetween.

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