JP2022076829A - Light-emitting device - Google Patents

Abstract

To provide a light-emitting device capable of realizing satisfactory performance characteristics and temperature characteristics when mounting a plurality of light-emitting elements on a single substrate.SOLUTION: A light-emitting device 1 comprises: a substrate 10 including a mounting surface 34 extending in a first direction; a first power supply pattern 41 and a second power supply pattern 42 which are disposed in a proximate manner in one end of the mounting surface 34 in the first direction and to which power can be supplied from the outside; a plurality of wiring patterns 43 to 46 which are arrayed on the mounting surface 34 in the first direction; and a plurality of light-emitting elements 11 to 14 each electrically connected to adjacent two of the first power supply pattern 41 and the plurality of wiring patterns 43 to 46. An area of each of the plurality of wiring patterns 43 to 46 is three times or more as large as an area of the light-emitting elements 11 to 14.SELECTED DRAWING: Figure 1

Description

The present invention relates to a light emitting device.

Various techniques for improving operating characteristics and temperature characteristics are known in vertical-cavity surface-emitting lasers (VCSELs). For example, in Patent Document 1, by mounting a VCSEL in a recess formed in a silicon substrate which is a conductive substrate having high thermal conductivity, heat generated from the VCSEL can be efficiently dissipated, thereby providing operational characteristics and characteristics. A light emitting device that improves the temperature characteristics is described.

Japanese Unexamined Patent Publication No. 2009-27088

In recent years, in an optical transmission system including a light emitting device, in order to reduce the size of the light emitting device, it is desired to mount various electronic components such as a driving element, a capacitor and a resistor for driving the light emitting element on a substrate together with the light emitting element. There is. In the light emitting device described in Patent Document 1, when a single VCSEL is mounted and a plurality of light emitting elements are mounted, it is not easy to realize good operating characteristics and temperature characteristics.

The present invention solves such a problem, and an object of the present invention is to provide a light emitting device capable of realizing good operating characteristics and temperature characteristics when a plurality of light emitting elements are mounted on a single substrate. do.

The light emitting device according to the present invention has a substrate having a mounting surface extending in the first direction, a first power supply pattern and a second power supply pattern which are arranged close to one end of the mounting surface in the first direction and can be supplied with electric power from the outside. A power supply pattern, a plurality of wiring patterns arranged on a mounting surface along a first direction, and a plurality of light emitting elements each electrically connected to two adjacent first power supply patterns and a plurality of wiring patterns. The area of each of the plurality of wiring patterns is three times or more the area of the light emitting element.

Further, in the light emitting device according to the present invention, it is preferable that the plurality of wiring patterns are arranged over the entire surface in the second direction orthogonal to the first direction of the mounting surface.

Further, in the light emitting device according to the present invention, the substrate is arranged so that the front surface faces the back surface of the mounting board on which the mounting surface is arranged on the front surface, and the grounding pattern is arranged on one surface at least. One grounding board, a first conductor that electrically connects the wiring pattern and the grounding pattern that are farthest from the first power supply pattern and the second power supply pattern among a plurality of wiring patterns, and the second power supply pattern and the grounding. It is preferable to have a second conductor that electrically connects the pattern.

Further, in the light emitting device according to the present invention, the light emitting current flowing when a plurality of light emitting elements emit light is a first power supply pattern on the mounting substrate from one end of the mounting surface close to the first power supply pattern and the second power supply pattern. And flows along the first direction toward the other end of the mounting surface separated from the second power supply pattern, and flows on at least one grounding board from the other end of the mounting surface separated from the first power supply pattern and the second power supply pattern. Generated by the emission current by canceling the magnetic field generated by the emission current flowing in the first direction by flowing along the first direction toward one end of the mounting surface close to the first power supply pattern and the second power supply pattern. It is preferable to reduce the inductance to be applied.

Further, in the light emitting device according to the present invention, it is preferable that the substrate further has a third conductor that electrically connects between the grounding patterns arranged on each of the at least one grounding substrates.

Further, it is preferable that the light emitting device according to the present invention further has a capacitor connected between the first power supply pattern and the second power supply pattern.

Further, in the light emitting device according to the present invention, the area of each of the plurality of wiring patterns is preferably 10 times or more the area of the light emitting element.

Further, in the light emitting device according to the present invention, the area of each of the plurality of wiring patterns is preferably 30 times or more the area of the light emitting element.

Further, in the light emitting device according to the present invention, the thickness of each of the plurality of wiring patterns is preferably 10 μm or more and 100 μm or less.

The light emitting device according to the present invention can realize good operating characteristics and temperature characteristics when a plurality of light emitting elements are mounted on a single substrate.

It is a perspective view of the light emitting device which concerns on embodiment. (A) is a plan view of the light emitting device shown in FIG. 1, and (b) is a side view of the light emitting device shown in FIG. FIG. 2A is an enlarged plan view showing a region shown by a broken line A in FIG. 2A. (A) is a plan view of the mounting board shown in FIG. 2 (b), (b) is a plan view of the first grounding board shown in FIG. 2 (b), and (c) is shown in FIG. 2 (b). It is a plan view of the 2nd grounding board shown, and FIG. 2D is a plan view of the 3rd grounding board shown in FIG. 2B. FIG. 4A is an enlarged plan view showing a region shown by a broken line B in FIG. 4A. It is a figure which shows the connection relationship of the mounting board, the 1st grounding board, the 2nd grounding board, and the 3rd grounding board shown in FIG. 2B. It is a circuit diagram of the light emitting device shown in FIG. (A) is a diagram showing an example of a switching signal supplied to the light emitting device shown in FIG. 1, (b) is an enlarged view of a portion indicated by parentheses C in (a), and (c) is (b). ) Is an enlarged view of the portion indicated by parentheses D. It is a figure which shows the path of the light emission current which flows when the light emitting element shown in FIG. 1 emits light. (A) is a diagram showing a simulation result showing a temperature change of a light emitting element when the area ratio of a light emitting element and a wiring pattern is changed, and (b) is a wiring for a light emitting element in the simulation result shown in (a). It is a figure which shows the relationship between the area ratio of a pattern, and the temperature of a light emitting element. (A) is a diagram showing the simulation result showing the area ratio between the light emitting element and the wiring pattern and the temperature change of the light emitting element when the film thickness of the copper thin film is changed, and (b) is the figure showing the light emitting element and the wiring pattern. It is a figure which shows the simulation result which shows the temperature change of a light emitting element at the time of changing the film thickness of a copper thin film, keeping the area ratio with and at 3000% constant.

Hereinafter, the light emitting device according to the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to those embodiments and extends to the inventions described in the claims and their equivalents.

(Configuration and function of light emitting device according to the embodiment)
1 is a perspective view of a light emitting device according to an embodiment, FIG. 2A is a plan view of the light emitting device shown in FIG. 1, and FIG. 2B is a side view of the light emitting device shown in FIG. 3 is an enlarged plan view showing a region shown by a broken line A in FIG. 2A.

The light emitting device 1 includes a substrate 10, a first light emitting element 11, a second light emitting element 12, a third light emitting element 13, and a fourth light emitting element 14. The light emitting device 1 includes a frame material 15, a first diffusion plate 16, a second diffusion plate 17, a third diffusion plate 18, a fourth diffusion plate 19, a first charging capacitor 20a, and a second charging capacitor 20b. And further has a third charging capacitor 20c and a fourth charging capacitor 20d. The light emitting device 1 further includes a light emitting control circuit 21, a control power supply capacitor 22, a current adjusting resistor 23, a current adjusting capacitor 24, and a switching resistor 25. The light emitting device 1 further includes a temperature sensor 26 and a temperature condenser 27. The light emitting device 1 is used, for example, as a light source for a TOF (Time Of Flight) sensor.

The board 10 has a mounting board 30, a first grounding board 31, a second grounding board 32, and a third grounding board 33. The mounting substrate 30, the first grounding substrate 31, the second grounding substrate 32, and the third grounding substrate 33 are substantially rectangular insulating substrates formed of a resin such as glass epoxy, and are arranged in an overlapping manner.

4A is a plan view of the mounting board 30, FIG. 4B is a plan view of the first grounding board 31, and FIG. 4C is a plan view of the second grounding board 32. 4 (d) is a plan view of the third grounding substrate 33. 5 is an enlarged plan view showing a region shown by a broken line B in FIG. 4A, and FIG. 6 is a connection relationship between the mounting board 30, the first grounding board 31, the second grounding board 32, and the third grounding board 33. It is a figure which shows.

The mounting substrate 30 has a mounting surface 34 on which electronic components such as the first light emitting element 11 to the fourth light emitting element 14 and the light emitting control circuit 21 are mounted. The light emitting device 1 includes a first power supply pattern 41, a second power supply pattern 42, a first wiring pattern 43, a second wiring pattern 44, a third wiring pattern 45, a fourth wiring pattern 46, a first grounding pattern 47, and a control circuit discharge. It also has a pattern 48. The light emitting device 1 further includes a control power supply pattern 49, a current adjustment signal pattern 50, a first switching signal pattern 51, a second switching signal pattern 52, an error signal pattern 53, a sensor power supply pattern 54, an SCL pattern 55, and an SDA pattern 56. .. The first power supply pattern 41 to SDA pattern 56 are conductive thin films such as copper foil having a thickness of 70 μm, and are mounted via an insulating layer 35 such as a solder resist arranged over the entire surface of the mounting surface 34. 34 are arranged adjacent to each other in the longitudinal direction. The longitudinal direction of the substrate 10 may be referred to as the first direction, and the lateral direction of the substrate 10 orthogonal to the longitudinal direction may be referred to as the second direction.

The first power supply pattern 41 is arranged close to one end of the mounting surface 34 and over the entire surface of the mounting surface 34 in the lateral direction. The first power supply pattern 41 has a planar shape that extends from one end to the other end of the mounting surface in the lateral direction and has a convex portion that protrudes at the center toward the adjacent first wiring pattern 43. Have.

The first power supply pattern 41 is electrically connected to four first power supply electrodes 61 arranged in the vicinity of one end of a pair of long sides of the substrate 10, and is connected to a plurality of positive electrodes of the first light emitting element 11. 1 It is electrically connected via the bonding wire 81. The plurality of first bonding wires 81 are preferably substantially parallel to the direction of the electric current when viewed in a plan view from the upper surface of the product. The route can be shortened the most. Further, the first power supply pattern 41 is electrically connected to one end of the first charging capacitor 20a, the second charging capacitor 20b, the third charging capacitor 20c, and the fourth charging capacitor 20d. The first power supply pattern 41 is an anode power supply pattern in which electric power can be supplied from the outside.

The second power supply pattern 42 is a cathode power supply pattern that is arranged between one end of the mounting surface 34 and the first power supply pattern 41 and is grounded. The second power supply pattern 42 has a substantially rectangular planar shape in which the corners of the sides extending in parallel with one side of the first power supply pattern 41 arranged adjacent to the short side of the mounting surface are notched.

The second power supply pattern 42 includes five second power supply electrodes 62 arranged on the short side of the substrate 10, nine third power supply electrodes 63 arranged on each of the pair of long sides of the substrate 10, and a fourth power supply electrode. It is electrically connected to 64 and one fifth power supply electrode 65 arranged on the short side of the substrate 10. The second power supply electrode 62, the third power supply electrode 63, the fourth power supply electrode 64, and the fifth power supply electrode 65 are grounded. The second power supply pattern 42 is directly connected to the second power supply electrode 62, and is connected to the third power supply electrode 63, the fourth power supply electrode 64, and the fifth power supply electrode 65 with the first grounding board 31, the second grounding board 32, and the third. It is electrically connected via the grounding board 33.

A second grounding pattern 57, a third grounding pattern 58, and a fourth grounding pattern 59 are arranged on each of the first grounding board 31, the second grounding board 32, and the third grounding board 33. The second grounding pattern 57 to the fourth grounding pattern 59 are arranged over the entire surface of each of the first grounding board 31, the second grounding board 32, and the third grounding board 33.

When the second grounding pattern 57 to the fourth grounding pattern 59 are arranged in a region exceeding 90% of the area of the surface of the first grounding board 31 to the third grounding board 33, they are arranged over the entire surface of the surface. do.

Through holes 57a, 58a and 59a, which are also referred to as vias, are formed in each of the second grounding pattern 57, the third grounding pattern 58 and the fourth grounding pattern 59, respectively. The second grounding pattern 57, the third grounding pattern 58, and the fourth grounding pattern 59 have a first grounding pattern 47 via a first conductor 60a arranged so as to penetrate each of the through holes 57a, 58a, and 59a. Is electrically connected to. The first conductor 60a electrically connects the fourth wiring pattern 46 farthest from the first power supply pattern 41 and the second power supply pattern 42 to the second grounding pattern 57, the third grounding pattern 58, and the fourth grounding pattern 59. do.

The second grounding pattern 57, the third grounding pattern 58, and the fourth grounding pattern 59 have a second power supply pattern 42 via a second conductor 60b arranged so as to penetrate each of the through holes 57a, 58a, and 59a. Is electrically connected to. Further, the second grounding pattern 57, the third grounding pattern 58, and the fourth grounding pattern 59 are electrically connected to each other via a third conductor 60c arranged so as to penetrate each of the through holes 57a, 58a, and 59a. Will be done.

The first wiring pattern 43 is arranged on the opposite side of the second power supply pattern 42 so as to be adjacent to the first power supply pattern 41 in the longitudinal direction of the mounting surface 34 and over the entire surface of the mounting surface 34 in the lateral direction. The first wiring pattern 43 extends from the vicinity of one end in the lateral direction of the mounting surface to the vicinity of the other end. The first wiring pattern 43 is arranged so as to face the convex portion protruding in the central portion from the first power supply pattern 41 arranged adjacent to one, and the second wiring pattern 44 is arranged adjacent to the other. It has a planar shape in which a convex portion protruding toward the center is formed. The area of the first wiring pattern 43 is 10 times or more the area of the first light emitting element 11 arranged in the first wiring pattern 43, and functions as a heat sink that dissipates heat generated from the first light emitting element 11. It is more preferable that the area of the first wiring pattern 43 is 30 times or more. This is because the heat dissipation is improved. When it exceeds 30 times, the increase in heat dissipation becomes small.

Since the grounded third power supply electrode 63 and the fourth power supply electrode 64 are arranged at both ends in the lateral direction in the region where the first wiring pattern 43 is arranged, the first power supply pattern 41 has both ends in the lateral direction. Not stretched to. When the length of the wiring pattern in the lateral direction exceeds 90% of the length in the lateral direction of the substrate 10, the wiring pattern is arranged over the entire surface of the mounting surface 34 in the lateral direction.

The first wiring pattern 43 is electrically connected to a negative electrode formed on the back surface of the first light emitting element 11 via a conductive adhesive member such as a DB paste containing fine particle metal powder, and is also electrically connected to the second light emitting element. It is electrically connected to the positive electrode of 12 via a plurality of second bonding wires 82.

The second wiring pattern 44 is arranged on the opposite side of the first power supply pattern 41 so as to be adjacent to the first wiring pattern 43 in the longitudinal direction of the mounting surface 34 and over the entire surface of the mounting surface 34 in the lateral direction. The second wiring pattern 44 extends from the vicinity of one end in the lateral direction of the mounting surface to the vicinity of the other end. The second wiring pattern 44 is arranged so as to face the convex portion protruding in the central portion from the first wiring pattern 43 arranged adjacent to one, and the third wiring pattern 45 is arranged adjacent to the other. It has a planar shape in which a convex portion protruding toward the center is formed. The area of the second wiring pattern 44 is 10 times or more the area of the second light emitting element 12 arranged in the second wiring pattern 44, and functions as a heat sink that dissipates heat generated from the first light emitting element 12.

The second wiring pattern 44 is electrically connected to a negative electrode formed on the back surface of the second light emitting element 12 via a conductive adhesive member such as a DB paste containing fine particle metal powder, and is also electrically connected to the third light emitting element. It is electrically connected to the positive electrode of 13 via a plurality of third bonding wires 83.

The third wiring pattern 45 is arranged on the opposite side of the first wiring pattern 43 so as to be adjacent to the second wiring pattern 44 in the longitudinal direction of the mounting surface 34 and over the entire surface of the mounting surface 34 in the lateral direction. The third wiring pattern 45 extends from the vicinity of one end in the lateral direction of the mounting surface to the vicinity of the other end. The third wiring pattern 45 is arranged so as to face the convex portion protruding in the central portion from the second wiring pattern 44 arranged adjacent to one, and the fourth wiring pattern 46 is arranged adjacent to the other. It has a planar shape in which a convex portion protruding toward the center is formed. The area of the third wiring pattern 45 is 10 times or more the area of the third light emitting element 13 arranged in the third wiring pattern 45, and functions as a heat sink that dissipates heat generated from the first light emitting element 13.

The third wiring pattern 45 is electrically connected to a negative electrode formed on the back surface of the third light emitting element 13 via a conductive adhesive member such as a DB paste containing fine particle metal powder, and is also electrically connected to the fourth light emitting element. It is electrically connected to the positive electrode of 14 via a plurality of fourth bonding wires 84.

The fourth wiring pattern 46 is arranged on the opposite side of the second wiring pattern 44, adjacent to the third wiring pattern 45 in the longitudinal direction of the mounting surface 34, over the entire surface of the mounting surface 34 in the lateral direction. The planar shape of the fourth wiring pattern 46 is different from the planar shape of the first wiring pattern 43 to the third wiring pattern 45, and is longer in the longitudinal direction than the first wiring pattern 43 to the third wiring pattern 45. The fourth wiring pattern 46 has a substantially U-shaped planar shape surrounding the control circuit discharge pattern 48, the current adjustment signal pattern 50, and the like. The area of the fourth wiring pattern 46 is 10 times or more the area of the fourth light emitting element 14 arranged in the fourth wiring pattern 46, and functions as a heat sink that dissipates heat generated from the first light emitting element 14.

The fourth wiring pattern 46 is electrically connected to a negative electrode formed on the back surface of the fourth light emitting element 14 via a conductive adhesive member such as a DB paste containing fine particle metal powder. Further, the fourth wiring pattern 46 is electrically connected to the current input terminal of the light emission control circuit 21 via a conductive adhesive member such as a DB paste containing fine particle metal powder.

The first grounding pattern 47 is electrically connected to the grounding terminal of the light emission control circuit 21 via a conductive adhesive member such as a DB paste containing fine particle metal powder. In the first grounding pattern 47, a plurality of through holes 47a are formed, and the second grounding pattern 57, the third grounding pattern 58, and the fourth grounding pattern 59 are formed via the first conductor 60a arranged inside the through holes 47a. Is electrically connected to.

The control circuit discharge pattern 48 is adhered to the back surface of the light emission control circuit 21 via an insulating adhesive. The control circuit discharge pattern 48 may be connected to the back surface of the light emission control circuit 21 with solder. In the first grounding pattern 47, a plurality of through holes 48a are formed, and the second grounding pattern 57 and the third grounding pattern 58 pass through a heat conductive member having a high thermal conductivity such as metal arranged inside the through holes 48a. And is connected to the fourth grounding pattern 59.

One end of the control power supply pattern 49 is electrically connected to the power supply terminal of the light emission control circuit 21 via a conductive adhesive member such as DB paste containing fine particle metal powder, and the other end is electrically connected to the control electrode 66. Will be done. The control electrode 66 is arranged on the short side of the substrate 10.

One end of the current adjustment signal pattern 50 is electrically connected to the current adjustment signal terminal of the light emission control circuit 21 via a conductive adhesive member such as DB paste containing fine metal powder, and the other end is a current adjustment signal electrode 67. Is electrically connected to. The current adjustment signal electrode 67 is arranged at the longitudinal end of the substrate 10.

One end of the first switching signal pattern 51 is electrically connected to the first switching signal terminal of the light emission control circuit 21 via a conductive adhesive member such as DB paste containing fine particle metal powder. The other end of the first switching signal pattern 51 is electrically connected to the first switching signal electrode 68. The first switching signal electrode 68 is arranged on the short side of the substrate 10.

One end of the second switching signal pattern 52 is electrically connected to the second switching signal terminal of the light emission control circuit 21 via a conductive adhesive member such as DB paste containing fine particle metal powder. The other end of the second switching signal pattern 52 is electrically connected to the second switching signal electrode 69. The second switching signal electrode 69 is arranged on the short side of the substrate 10.

One end of the error signal pattern 53 is electrically connected to the error signal terminal of the light emission control circuit 21 via a conductive adhesive member such as DB paste containing fine metal powder, and the other end is electrically connected to the error signal electrode 70. Connected to. The error signal electrode 70 is arranged at the longitudinal end of the substrate 10.

One end of the sensor power supply pattern 54 is electrically connected to the sensor power supply terminal of the temperature sensor 26 via a conductive adhesive member such as DB paste containing fine metal powder, and the other end is electrically connected to the sensor power supply electrode 71. Be connected. The sensor power electrode 71 is arranged on the short side of the substrate 10.

One end of the SCL pattern 55 is electrically connected to the SCL terminal of the temperature sensor 26 via a conductive adhesive member such as a DB paste containing fine particle metal powder, and the other end is electrically connected to the SCL electrode 72. .. The SCL electrode 72 is arranged at the longitudinal end of the substrate 10.

One end of the SDA pattern 56 is electrically connected to the SDA terminal of the temperature sensor 26 via a conductive adhesive member such as a DB paste containing fine particle metal powder, and the other end is electrically connected to the SDA electrode 73. .. The SDA electrode 73 is arranged at the longitudinal end of the substrate 10.

Each of the first light emitting element 11 to the fourth light emitting element 14 is also referred to as a VCSEL, and a plurality of emitters that emit laser light are arranged on the surface in an array at equal intervals. Each of the first light emitting element 11 to the fourth light emitting element 14 has, for example, 364 (26 × 14) emitters, and the 364 emitters are arranged at a pitch of 0.0385 mm.

The first light emitting element 11 to the fourth light emitting element 14 are arranged along the longitudinal direction of the substrate 10 via the first wiring pattern 43 to the fourth wiring pattern 46. The first light emitting element 11 to the fourth light emitting element 14 have a first power supply pattern 41 and a second power supply pattern 42 via the first wiring pattern 43 to the fourth wiring pattern 46, the light emission control circuit 21, the first grounding pattern 47, and the like. It is connected in series with.

The positive electrode of the first light emitting element 11 is electrically connected to the first power supply pattern 41, and the negative electrode of the first light emitting element 11 is electrically connected to the first wiring pattern 43. The positive electrode of the second light emitting element 12 is electrically connected to the first wiring pattern 43, and the negative electrode of the second light emitting element 12 is electrically connected to the second wiring pattern 44. The positive electrode of the third light emitting element 13 is electrically connected to the second wiring pattern 44, and the negative electrode of the third light emitting element 13 is electrically connected to the third wiring pattern 45. The positive electrode of the fourth light emitting element 14 is electrically connected to the third wiring pattern 45, and the negative electrode of the fourth light emitting element 14 is electrically connected to the fourth wiring pattern 46.

Each of the first light emitting element 11 to the fourth light emitting element 14 responds to the application of a predetermined voltage such as 12V between the first power supply electrode 61 and the second power supply electrode 62 to the fifth power supply electrode 65. , Coherent laser light is emitted from the emitter toward the first diffuser plate 16 to the fourth diffuser plate 19. The emitted laser light may have a directivity of ± 15 °.

The frame material 15 is formed of a resin such as epoxy or silicone, or a member such as alumina, is arranged so as to surround each of the first light emitting element 11 to the fourth light emitting element 14, and is arranged so as to surround each of the first light emitting element 11 to the fourth light emitting element 14. Each of the diffuser plates 19 is covered at a position where the laser beam does not hit, and each of the first light emitting element 11 to the fourth light emitting element 14 and the plurality of first bonding wires 81 to the plurality of fourth bonding wires 84 is covered with the minimum distance. Hold in position.

Each of the first diffusion plate 16 to the fourth diffusion plate 19 is a light transmissive member formed of a thermoplastic resin such as a polyarylate resin, a thermosetting resin such as a silicone resin, and an ultraviolet curable resin such as an epoxy resin. Is. On at least one of the front surface and the back surface of each of the first diffusion plate 16 to the fourth diffusion plate 19, the light emitted from each of the first light emitting element 11 to the fourth light emitting element 14 is diffused by embossing or the like. A surface is formed. Each of the first diffusion plate 16 to the fourth diffusion plate 19 preferably takes in 90% or more, preferably 95% or more, of light emitted from each of the first light emitting element 11 to the fourth light emitting element 14. 100% is more preferable. The luminous efficiency of the device does not decrease.

The first charging capacitor 20a to the fourth charging capacitor 20d are connected in parallel between the first power supply pattern 41 and the second power supply pattern 42, and the charged charge is emitted by the first light emitting element 11 to the fourth light emitting element 14. It is supplied as a light emitting current that flows when the capacitor is used.

The light emission control circuit 21 is electrically connected to the negative electrode of the fourth light emitting element 14 via the fourth wiring pattern 46, and is also connected to the negative electrode of the fourth light emitting element 14 via the first grounding pattern 47 and the second grounding pattern 57 to the fourth grounding pattern 59. Is electrically connected to the second power supply pattern 42.

FIG. 7 is a circuit diagram of the light emitting device 1.

The light emission control circuit 21 has a current adjusting element 211, a switching element 212, and an error detection circuit 213, and controls the light emitting current flowing through the first light emitting element 11 to the fourth light emitting element 14. In the light emission control circuit 21, a predetermined voltage such as 5V is applied as the power supply voltage from the control electrode 66 via the control power supply pattern 49.

The current adjusting element 211 is, for example, a plurality of n MOSFETs connected in parallel. The gate of the current adjusting element 211 is electrically connected to the current adjusting signal electrode 67, the source of the current adjusting element 211 is electrically connected to one end of the switching element 212, and the drain of the current adjusting element 211 is the fourth light emitting element 14. It is electrically connected to the negative electrode of. The amount of light emission current flowing through the first light emitting element 11 to the fourth light emitting element 14 is controlled according to the magnitude of the current adjustment signal, which is the voltage applied to the gate via the current adjustment signal electrode 67 of the current adjustment element 211. do. The current adjusting element 211 receives, for example, a current adjusting signal in which the beak current of the light emitting current becomes 7 A.

The switching element 212 is, for example, a plurality of n MOSFETs connected in parallel, and by turning on and off between the source and the drain according to the voltage applied to the gate which is the control terminal, the first light emitting element 11 to 4th. The light emitting current flowing through the light emitting element 14 is turned on and off. A differential signal is applied as a switching signal from the first switching signal electrode 68 and the second switching signal electrode 69 to the control terminal of the current adjusting element 211 via the first switching signal pattern 51 and the second switching signal pattern 52. ..

The error detection circuit 213 monitors the operation of the current adjusting element 211 and the switching element 212, and when the current adjusting element 211 and the switching element 212 perform an abnormal operation, the error signal is transmitted to the error signal electrode via the error signal pattern 53. Output to 70.

One end of the control power supply capacitor 22 is electrically connected to the power supply terminal of the light emission control circuit 21 via the control power supply pattern 49, and the other end is grounded. One end of the current adjustment resistor 23 is electrically connected to the current adjustment signal electrode 67, and the other end is electrically connected to the current adjustment signal terminal of the light emission control circuit 21 and one end of the current adjustment capacitor 24. The other end of the current adjusting capacitor 24 is grounded via the first grounding pattern 47. One end of the switching resistance 25 is electrically connected to the first switching signal pattern 51, and the other end is connected to the second switching signal pattern 52.

The temperature sensor 26 is a diode temperature sensor and has a two-wire serial interface such as I2C. The temperature sensor 26 detects the ambient temperature that rises in response to the light emission of the first light emitting element 11 to the fourth light emitting element 14, and outputs a temperature signal indicating the detected ambient temperature to the SDA electrode 73 based on the I2C communication standard. Is output as a temperature signal from. The temperature capacitor 27 is connected in parallel with the temperature sensor 26 between the control power supply pattern 49 and the first grounding pattern 47.

8 (a) is a diagram showing an example of a switching signal supplied to the light emitting device 1, FIG. 8 (b) is an enlarged view of a portion shown in parentheses C in FIG. 8 (a), and FIG. 8 (b) is an enlarged view. c) is an enlarged view of the portion shown by parentheses D in FIG. 8 (b). The switching signal is a differential signal supplied between the first switching signal electrode 68 and the second switching signal electrode 69, and is shown here as a single-ended signal.

In one example, the switching signal is supplied to the light emitting device 1 as a repeating signal having a frame rate of 25 Hz. In one example, the width of the pulse group, also referred to as burst, is 7.6 ms and the burst interval is 40 ms. The burst is an aggregate of pulse groups repeated at intervals of 2.2 ms, and the width of the pulse group included in the burst is 100 to 500 μs. The burst is determined by the detection target of the TOF sensor in which the light emitting device 1 is used as a light source. The pulse group included in the burst has a pulse width of 10 ns and includes a plurality of pulses repeating at intervals of 25 ns. The duty ratio of the pulse included in the switching signal is specified so that the power consumption is about 0.2 W.

FIG. 9 is a diagram showing a path of a light emitting current flowing when the first light emitting element 11 to the fourth light emitting element 14 emit light.

When the light emitting device 1 emits light, the light emitting current is transmitted from the first power supply pattern 41 via the first light emitting element 11 to the fourth light emitting element 14, the first wiring pattern 43 to the fourth wiring pattern 46, and the like. It flows on the mounting board 30 toward 21. When the light emission current reaches the light emission control circuit 21, the second ground pattern 57 to the fourth ground are arranged from the first ground pattern 47 to the first ground board 31 to the third ground board 33 via the first conductor 60a. Flow to pattern 59.

The light emitting current flows from the end of the second grounding pattern 57 to the fourth grounding pattern 59 separated from the first power supply pattern 41 toward the second conductor 60b electrically connected to the second power supply pattern 42. When the emission current reaches the second conductor 60b electrically connected to the second power supply pattern 42, it flows through the second power supply pattern 42 via the second conductor 60b.

The direction of the light emitting current flowing in the longitudinal direction of the substrate 10 on the mounting substrate 30 is opposite to the direction of the light emitting current flowing in the longitudinal direction of the second grounding pattern 57 to the fourth grounding pattern 59. Since the emission currents are oriented in opposite directions when flowing in the longitudinal direction of the substrate 10, the magnetic fields generated by the emission currents flowing in the longitudinal direction of the substrate 10 cancel each other out.

(Action and effect of the light emitting device according to the embodiment)
In the light emitting device 1, since the first power supply pattern 41 and the second power supply pattern 42 are arranged close to one end in the longitudinal direction of the mounting surface 34, they flow to the mounting board 30 and the first grounding board 31 to the third grounding board. The direction of the emission current in the longitudinal direction is opposite. In the light emitting device 1, since the directions of the light emitting currents flowing in the mounting board 30 and the first grounding board 31 to the third grounding board are opposite to each other in the longitudinal direction, the magnetic fields generated by the light emitting currents flowing in the longitudinal direction of the substrate 10 cancel each other out. Therefore, the inductance generated by the light emission current can be reduced. In the light emitting device 1, the inductance generated by the light emitting current is low, so that a high-speed response is possible.

Further, in the light emitting device 1, the first light emitting element 11 to the fourth light emitting element 14 are arranged, and the area of the first wiring pattern 43 to the fourth wiring pattern 46 that functions as a heat dissipation plate is the first light emitting element 11 to the fourth light emitting element. It is 10 times or more the area of the element 14. In the light emitting device 1, the area of the first wiring pattern 43 to the fourth wiring pattern 46 is very large, which is 10 times or more the area of the first light emitting element 11 to the fourth light emitting element 14, so that good heat dissipation characteristics can be realized.

Further, in the light emitting device 1, since the first wiring pattern 43 to the fourth wiring pattern 46 are arranged over the entire surface of the mounting surface 34 in the lateral direction, good heat dissipation characteristics are achieved while minimizing the area of the mounting surface. Can be realized. The first wiring pattern 43 to the fourth wiring pattern 46 spread heat in a well-balanced manner over the entire area of each wiring and accumulate the heat, so that each wiring pattern does not have to be directly provided with a hole called Via. Heat can be dissipated to the first grounding board 31 to the third grounding board 33.

Further, since the light emitting device 1 has the first grounding board 31 to the third grounding board 33 arranged so as to be superimposed on the mounting board 30 in addition to the mounting board 30, the mechanical strength can be improved.

Further, since the first charging capacitor 20a, the second charging capacitor 20b, the third charging capacitor 20c, and the fourth charging capacitor 20d are connected in parallel to the first light emitting element 11 to the fourth light emitting element 14, the first light emitting element 11 to A light emitting current can be stably supplied to the fourth light emitting element 14.

Further, in the light emitting device 1, between the second grounding pattern 57 and the fourth grounding pattern 59 arranged on the first grounding board 31 to the third grounding board 33, the third conductor 60c electrically covers the entire surface. Since it is connected, the grounding resistance can be reduced.

(Modified example of the light emitting device according to the embodiment)
The light emitting device 1 has the first light emitting element 11 to the fourth light emitting element 14, but the light emitting device according to the embodiment may have a plurality of two, three, or five or more light emitting elements. Further, in the light emitting device 1, the first light emitting element 11 to the fourth light emitting element 14 are connected in series, but in the light emitting device according to the embodiment, a plurality of light emitting elements may be connected in parallel or serially in parallel.

Further, in the light emitting device 1, the electrodes for external connection such as the first power supply electrode 61 are arranged on the side surface of the substrate 10, but in the light emitting device according to the embodiment, the electrodes for external connection are on the surface of the substrate or. It may be placed on the bottom surface. Further, in the light emitting device according to the embodiment, the first power supply electrode 61 and the second power supply electrode 62 to the fifth power supply electrode 65 are omitted, and the first power supply pattern 41 and the second power supply pattern 42 are used as electrodes for external connection. May be good.

Further, in the light emitting device 1, the first direction, which is the arrangement direction of the first light emitting element 11 to the fourth light emitting element 14, is the longitudinal direction of the mounting surface 34, but in the light emitting device according to the embodiment, it is orthogonal to the first direction. The second direction in which the wiring pattern extends may be the longitudinal direction of the mounting surface 34.

Further, in the light emitting device 1, the substrate 10 is formed by the mounting board 30, the first grounding board 31 to the third grounding board 33, but in the light emitting device according to the embodiment, the board on which a plurality of light emitting elements are mounted is , It may be a single substrate having a multi-layer structure.

Further, in the light emitting device 1, the first charging capacitor 20a, the second charging capacitor 20b, the third charging capacitor 20c, and the fourth charging capacitor 20d are connected in parallel to the first light emitting element 11 to the fourth light emitting element 14. However, in the light emitting device according to the embodiment, the charging capacitor connected in parallel to the plurality of light emitting elements may be omitted.

Further, in the light emitting device 1, electronic components other than the first light emitting element 11 to the fourth light emitting element 14 such as the light emitting control circuit 21 are mounted on the substrate 10, but in the light emitting device according to the embodiment, other than the plurality of light emitting elements. Electronic components do not have to be mounted on the substrate.

Further, in the light emitting device 1, the area of the first wiring pattern 43 to the fourth wiring pattern 46 is 10 times or more the area of the first light emitting element 11 to the fourth light emitting element 14. However, in the light emitting device according to the embodiment, the area of the wiring pattern in which the light emitting element is arranged may be three times or more the area of the light emitting element.

FIG. 10A is a diagram showing a simulation result showing a temperature change of the light emitting element when the area ratio of the light emitting element and the wiring pattern is changed. FIG. 10B is a diagram showing the relationship between the area ratio of the wiring pattern to the light emitting element and the temperature of the light emitting element in the simulation result shown in FIG. 10A. In FIG. 10A, the column of "wiring pattern / element area [%]" shows the ratio of the area of the wiring pattern to the area of the light emitting element, and the column of "copper thin film thickness [μm]" shows the thickness of the copper thin film. The column of "element power [W]" indicates the power supplied to the light emitting element. In addition, the column of "temperature of light emitting element [° C]" indicates the temperature of the light emitting element, and the column of "temperature ratio" is when the area of the wiring pattern is the same as the area of the light emitting element, that is, "wiring pattern / element area [%". ] ”Column indicates the ratio of the temperature of the light emitting element to the temperature of the light emitting element when the column is 100%. In FIG. 10B, the horizontal axis shows the ratio of the area of the wiring pattern to the area of the light emitting element, and the vertical axis shows the temperature of the light emitting element.

The light emitting element used in the simulation shown in FIGS. 10 (a) and 10 (b) has a shape having an area of 1 mm ² and a height of 0.1 mm when viewed in a plan view, and has a shape of 0.2 W. It is a single element to which power is supplied. The substrates used in the simulations shown in FIGS. 10 (a) and 10 (b) are a copper thin film having a film thickness of 18 μm and a film film arranged on the surface of the copper thin film having a film thickness of 0.1 mm and thermal conductivity. Has an insulating layer of 0.3 W / mK.

When the ratio of the area of the wiring pattern to the area of the light emitting element is 200%, the temperature of the light emitting element is 81.9 degrees, while the ratio of the area of the wiring pattern to the area of the light emitting element is 300%. The temperature of the light emitting element is 71.8 degrees. The ratio of the area of the wiring pattern to the area of the light emitting element is 300%, that is, 80 degrees or less when the area of the light emitting element is three times the area of the wiring pattern. Generally, the melting temperature of a conductive connecting member such as solder or a paste containing fine metal powder is about 80 degrees, and when the area of the light emitting element is three times or more the area of the wiring pattern, the temperature of the light emitting element is conductive. The melting temperature of the sex connecting member is not reached. Further, since the heat generation temperature of the light emitting element is lowered by 10.1 degrees, it is possible to suppress the decrease in the luminous efficiency due to the heat of the light emitting element, and it is possible to suppress the deterioration due to the heat of the light emitting element even if it is lit for a long time.

Further, the temperature ratio when the ratio of the area of the wiring pattern to the area of the light emitting element is 200% is 51%, whereas the temperature when the ratio of the area of the wiring pattern to the area of the light emitting element is 50,000%. The ratio is 35%. When the ratio of the area of the wiring pattern to the area of the light emitting element is 1000% or more, that is, when the area of the light emitting element is 10 times or more the area of the wiring pattern, the decrease in the temperature ratio is saturated. When the area of the light emitting element becomes 10 times or more the area of the wiring pattern, the decrease in the temperature ratio is substantially saturated. Therefore, by making the area of the light emitting element 10 times the area of the wiring pattern, heat is dissipated with the minimum size. A highly efficient light emitting device can be realized.

FIG. 11A is a diagram showing simulation results showing the area ratio between the light emitting element and the wiring pattern and the temperature change of the light emitting element when the film thickness of the copper thin film is changed. FIG. 11B is a diagram showing a simulation result showing a temperature change of the light emitting element when the area ratio of the light emitting element and the wiring pattern is kept constant at 3000% and the film thickness of the copper thin film is changed. In FIG. 11A, the horizontal axis shows the ratio of the area of the wiring pattern to the area of the light emitting element, and the vertical axis shows the temperature of the light emitting element. Further, the waveform W101 indicates the temperature of the light emitting element when the thickness of the copper thin film is 18 μm, the waveform W102 indicates the temperature of the light emitting element when the thickness of the copper thin film is 35 μm, and the waveform W103 indicates the temperature of the light emitting element when the thickness of the copper thin film is 35 μm. Shows the temperature of the light emitting element when is 70 μm. The waveform W104 shows the temperature of the light emitting element when the thickness of the copper thin film is 200 μm, and the waveform W105 shows the temperature of the light emitting element when the thickness of the copper thin film is 500 μm. In FIG. 11B, the horizontal axis represents the thickness of the wiring pattern, and the vertical axis represents the temperature of the light emitting element.

Even if the thickness of the copper thin film is increased from 18 μm, the change in the temperature characteristics of the light emitting element is small. Therefore, by reducing the thickness of the wiring pattern formed by the copper thin film, the amount of copper used The manufacturing cost can be reduced by reducing the amount of copper. The thickness of the wiring pattern is preferably 10 μm or more and 100 μm or less.

1 Light emitting device 10 Board 11 1st light emitting element 12 2nd light emitting element 13 3rd light emitting element 14 4th light emitting element 30 Mounting board 31 1st grounding board 32 2nd grounding board 33 3rd grounding board 41 1st power supply pattern 42 2 Power supply pattern 43 1st wiring pattern 44 2nd wiring pattern 45 3rd wiring pattern 46 4th wiring pattern

Claims (9)

A substrate having a mounting surface extending in the first direction,
A first power supply pattern and a second power supply pattern that are arranged close to one end of the mounting surface in the first direction and can be supplied with electric power from the outside.
A plurality of wiring patterns arranged on the mounting surface along the first direction, and
It has a plurality of light emitting elements, each of which is electrically connected to two adjacent two of the first power supply pattern and the plurality of wiring patterns.
The area of each of the plurality of wiring patterns is three times or more the area of the light emitting element.
A light emitting device characterized by that. The light emitting device according to claim 1, wherein the plurality of wiring patterns are arranged over the entire surface of the mounting surface in a second direction orthogonal to the first direction. The substrate is
A mounting board on which the mounting surface is arranged on the surface, and
At least one grounding board arranged so that the front surface faces the back surface of the mounting surface and the grounding pattern is arranged over one surface.
A first conductor that electrically connects the first power supply pattern, the wiring pattern most distant from the second power supply pattern, and the grounding pattern among the plurality of wiring patterns.
A second conductor that electrically connects the second power supply pattern and the grounding pattern, and
The light emitting device according to claim 1 or 2. The emission current that flows when the plurality of light emitting elements emit light is
The mounting board is viewed from one end of the mounting surface close to the first power supply pattern and the second power supply pattern toward the other end of the mounting surface separated from the first power supply pattern and the second power supply pattern. Flowing along the first direction,
On the at least one grounding board, from the other end of the mounting surface separated from the first power supply pattern and the second power supply pattern to one end of the mounting surface close to the first power supply pattern and the second power supply pattern. By flowing along the first direction towards
The light emitting device according to claim 3, wherein the inductance generated by the light emitting current is lowered by canceling the magnetic field generated by the light emitting current flowing in the first direction. The light emitting device according to claim 3 or 4, wherein the substrate further comprises a third conductor that electrically connects between the grounding patterns arranged on each of the at least one grounding substrate. The light emitting device according to any one of claims 1 to 5, further comprising a capacitor connected between the first power supply pattern and the second power supply pattern. The light emitting device according to any one of claims 1 to 6, wherein the area of each of the plurality of wiring patterns is 10 times or more the area of the light emitting element. The light emitting device according to claim 7, wherein the area of each of the plurality of wiring patterns is 30 times or more the area of the light emitting element. The light emitting device according to any one of claims 1 to 8, wherein the thickness of each of the plurality of wiring patterns is 10 μm or more and 100 μm or less.

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