JP7007180B2 - Luminescent device - Google Patents

Description

The present invention relates to a light emitting device including a metal substrate on which an LED is mounted and a resin substrate on which a control circuit for controlling a current applied to the LED is mounted.

In a light emitting device using an LED, the LED is mounted on an aluminum substrate in order to improve heat dissipation (see Patent Document 1). Further, for example, when complicated light emission control is performed on an LED, a multi-layered resin substrate such as an aluminum substrate and an FR-4 substrate may be used in combination.

In other words, by mounting the LED on an aluminum substrate, which has better thermal conductivity than the resin substrate, the heat dissipation of the LED is ensured, and by mounting the control circuit on the multi-layered resin substrate, the wiring amount and current loop are large. It can be prevented from becoming.

Conventionally, the aluminum substrate and the resin substrate are connected by a harness or a connector between the substrates, but in recent years, the demand for miniaturization of the product has increased, so a configuration in which the resin substrate is laminated on the aluminum substrate is adopted. May be done.

However, when the aluminum substrate and the resin substrate are overlapped with each other, the wiring pattern or solid formed on the bottom layer of the resin substrate and the aluminum base material of the aluminum substrate are close to each other via a thin insulating layer, resulting in a large parasitic capacitance. Is likely to occur.

If there is such a parasitic capacitance, the electric circuit including the LED and the control circuit is easily affected by noise, which causes a malfunction. For example, when the potential of the power supply or the ground fluctuates due to high frequency noise, the voltage applied to the LED fluctuates, causing flicker.

Japanese Unexamined Patent Publication No. 2011-146367

The present invention has been made in view of the above-mentioned problems, and even when a metal substrate and a resin substrate overlap each other, the influence of noise can be reduced, and the LED can continue to emit light in a desired light emitting mode. It is an object of the present invention to provide a light emitting device.

That is, the light emitting device according to the present invention includes a metal substrate on which an LED is mounted and a resin substrate on which a control circuit for controlling a current applied to the LED is mounted. , The first line wired on the metal substrate and connecting between the positive side connection terminal of the control circuit and the anode of the LED, and the negative side connection terminal of the control circuit wired on the metal substrate. A second line connecting to the cathode of the LED is provided, and the first line and the second line are wired so as to be symmetric on the metal substrate. ..

In such a case, since the first line and the second line are wired so as to be symmetric on the metal substrate, the magnitude of the parasitic capacitance generated in the first line and the said. The magnitude of the parasitic capacitance generated in the second line can be made almost the same.

Therefore, even if high-frequency noise or the like is generated, the current waveforms on the anode side and the cathode side of the LED can be changed in substantially the same manner, and the voltage applied to the LED can be kept constant. Therefore, it is possible to prevent malfunctions such as flickering of the LED due to noise.

In order to reduce the parasitic capacitance generated by separating the metals as close as possible when the metal substrate and the resin substrate are overlapped with each other, the resin substrate is a multilayer substrate and the metal substrate side. It suffices that at least one layer of the above is not formed with pattern wiring or solid in a portion other than the via or the pad connected to the metal substrate.

In order to reduce the amount of parasitic capacitance generated by shortening the wiring lengths of the first line and the second line as much as possible while realizing the desired irradiation mode by the light emitted from the LED. As a specific configuration example, a lens is provided on the light emitting side of the LED of the metal substrate, the positive side connection terminal and the negative side connection terminal are arranged at one end of the resin substrate, and the resin is provided. Examples thereof include those in which one end of the substrate is placed close to the outer edge of the lens on the metal substrate. Further, in such a case, the parasitic capacitance between the first line and the second line can be made almost the same size, and the capacitance can be reduced, so that the space between the first line and the second line can be reduced. Crosstalk can also be less likely to occur.

In order to further reduce the influence of noise such as flicker on the LED, the metal substrate may be housed in a housing having electromagnetic shielding performance.

As described above, according to the light emitting device according to the present invention, since the first line and the second line are wired so as to be symmetric on the metal substrate, the generated parasitic capacitance is substantially generated on both sides of the LED. Can be the same. Therefore, even if noise is generated, the voltage applied to the LED can be kept constant to prevent malfunction such as flicker.

The schematic diagram which shows the light emitting device which concerns on one Embodiment of this invention. The schematic diagram which shows the aluminum substrate in the same embodiment. The schematic diagram which shows the resin substrate in the same embodiment. The schematic diagram explaining the effect by making the 1st line and the 2nd line symmetry in the same embodiment.

The light emitting device 100 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 4.

The light emitting device 100 of the present embodiment is used to irradiate an inspection target with light in a predetermined irradiation mode by the LED 3.

As shown in FIG. 1, the light emitting device 100 includes an aluminum substrate 1 which is a metal substrate on which an LED 3 is mounted, and a resin substrate 2 on which a control circuit for controlling a current applied to the LED 3 is mounted. The LED 3 and the control circuit are electrically connected to each other with the resin substrate 2 mounted on the aluminum substrate 1.

In the aluminum substrate 1, an insulating layer is formed on the surface of a plate-shaped aluminum base material, and a wiring pattern made of copper foil is formed on the insulating layer. The aluminum substrate 1 has a larger area of the face plate portion than the resin substrate 2, and as shown in FIGS. 1 and 2, the face plate portion includes an LED mounting area 1A on which the surface mount type LED 3 is mounted. It is divided into a substrate mounting area 1B on which the resin substrates 2 are stacked and mounted.

FIG. 2 shows a state in which the resin substrate 2 is removed from the aluminum substrate 1. As shown in FIG. 2, on the surface of the aluminum substrate 1, the substrate mounting region 1B is formed with two connection pads 13 connected to the control circuit formed on the resin substrate 2. On the other hand, on the surface of the aluminum substrate 1, in the LED mounting region 1A, the positive side connection terminal 21 of the control circuit formed on the resin substrate 2 and the first line 11 connecting between the anodes of the LED 3 and the control circuit. The negative side connection terminal 22 and the second line 12 connecting between the cathodes of the LED 3 are wired. As shown in FIGS. 1 and 2, the first line 11 and the second line 12 pass through the center of the LED 3 and are wired so as to be symmetric with respect to the virtual line CL parallel to the face plate portion of the aluminum substrate 1. There is.

Further, as shown in FIG. 1, the wiring lengths of the first line 11 and the second line 12 are shortened as much as possible to reduce the parasitic capacitance generated between the aluminum base material of the aluminum substrate 1 and the wiring pattern. There is. Specifically, in the LED mounting area 1A, near the outer edge of the lens LN arranged on the injection surface side of the LED 3, the end surface on the resin substrate 2 on which the plus side connection terminal 21 and the minus side connection terminal 22 are formed is formed. They are arranged so that the wiring lengths of the first line 11 and the second line 12 are shortened.

FIG. 3A shows the uppermost layer of the resin substrate 2, and FIG. 3B shows the lowermost layer of the resin substrate 2. The resin substrate 2 is, for example, a multilayer substrate composed of four layers, for example, an FR-4 substrate is used. Electronic components and the like are mounted on the uppermost layer of the resin substrate 2, and only the pad connected to the connection pad 13 of the aluminum substrate 1 is formed on the lowermost layer of the resin substrate 2. This pad constitutes a positive side connection terminal 21 and a negative side connection terminal 22 of the control circuit mounted on the resin substrate 2. Further, in the resin substrate 2 of the present embodiment, the bottom layer and the third layer, which are the layers on the aluminum substrate 1 side, do not form solid or wiring patterns other than the connection terminals 21 and 22 described above. In this way, even when the resin substrate 2 is superposed on the aluminum substrate 1, the amount of metal facing the aluminum substrate and adjacent to the aluminum substrate 1 is reduced, and the parasitic capacitance is reduced.

The resistance to noise by the light emitting device 100 configured in this way will be described with reference to FIG. In this embodiment, the first line 11 and the second line 12 are wired so as to be symmetric and have the same area, and the wiring is short, so that the parasitic capacitances generated on the cathode side and the anode side of the LED 3 are almost the same. It becomes a small value in size. Further, since the first line 11 and the second line 12 are substantially formed in the LED mounting area 1A where the resin substrates 2 do not overlap, they are affected by the parasitic capacitance generated by the aluminum substrate 1 and the resin substrate 2 being close to each other. Hateful. Therefore, as shown in FIG. 4A, even if high-frequency noise enters the light emitting device 100 and the potential of the power supply or ground fluctuates, the waveforms on the cathode side and the anode side of the LED 3 are almost the same. The voltage Vf applied to the LED 3 can be kept substantially constant. Therefore, even if there is high frequency noise, there is almost no change in the radiant intensity of the light emitted from the LED 3, and it is possible to prevent malfunctions such as flicker.

On the other hand, when the first line 11 and the second line 12 are not symmetric as in the conventional case and the areas are different, parasitic capacitances having different sizes are generated on the cathode side and the anode side of the LED3. As shown in b), the response to high-frequency noise changes between the cathode side and the anode side of the LED 3, and the waveforms differ, so that the voltage Vf applied to the LED 3 fluctuates. In such a case, an error such as flickering occurs in the light emitted from the LED 3.

As described above, in the light emitting device 100 of the present embodiment, the size of the parasitic capacitance itself is reduced, and the sizes of the parasitic capacitance on the cathode side and the anode side of the LED 3 are made uniform to provide noise immunity. It is possible to prevent malfunctions such as flicker. Further, it is possible to prevent unintended noise from entering the control circuit wired to the resin substrate 2. Further, crosstalk between the first line 11 and the second line 12 can be less likely to occur.

Other embodiments will be described.

In order to further reduce the influence on noise in the above embodiment, the aluminum substrate and the resin substrate are housed in a housing having electromagnetic shielding performance such as metal, and the respective boards do not come into contact with the housing. It suffices if it is arranged like this.

Further, the metal substrate is not limited to the aluminum substrate, and may be a copper substrate or the like. In addition, the resin substrate is not limited to the substrate using the glass epoxy resin. The resin substrate is not limited to a multi-layered substrate, and may be a single-layered substrate. On the contrary, the metal substrate is not limited to a single-layered one, and a two-layered metal substrate may be used.

Even if the first line and the second line are symmetrically formed on the aluminum substrate by forming a solid or wiring pattern on the bottom layer of the resin substrate, even when noise is generated as compared with the conventional one. It is possible to stabilize the voltage applied to the LED and prevent malfunctions such as flicker.

The control circuit formed on the resin substrate may be any one that controls the current applied to the LED, and may be various circuits such as a constant current circuit and a PWM control circuit.

In addition, as long as it does not contradict the gist of the present invention, some parts of various embodiments may be combined or a part of each embodiment may be modified.

100 ・ ・ ・ Light emitting device 1 ・ ・ ・ Aluminum substrate 11 ・ ・ ・ 1st line 12 ・ ・ ・ 2nd line 2 ・ ・ ・ Resin substrate 21 ・ ・ ・ Positive side connection terminal 22 ・ ・ ・ Negative side connection terminal 3 ・・ ・ LED

Claims (6)

The metal board on which the LED is mounted and
A resin substrate that is mounted on top of the metal substrate and on which a control circuit that controls the current applied to the LED is mounted.
A first line, which is wired on the metal substrate via an insulating layer and connects between the positive side connection terminal of the control circuit and the anode of the LED,
A second line, which is wired on the metal substrate via an insulating layer and connects between the negative side connection terminal of the control circuit and the cathode of the LED, is provided.
A light emitting device, wherein the first line and the second line are wired so as to be symmetric on the metal substrate. The light emitting device according to claim 1, wherein the resin substrate is a multilayer substrate, and pattern wiring and solid are not formed in a portion other than a via or a pad in which at least one layer on the metal substrate side is connected to the via or the metal substrate. .. A lens is provided on the light emitting side of the LED on the metal substrate.
The positive side connection terminal and the negative side connection terminal are arranged at one end of the resin substrate.
The light emitting device according to claim 1 or 2, wherein one end of the resin substrate is placed close to the outer edge of the lens on the metal substrate. The light emitting device according to any one of claims 1 to 3, wherein the metal substrate is housed in a housing having electromagnetic shielding performance. The metal board on which the LED is mounted and
A resin substrate that is installed on the metal substrate and on which a control circuit that controls a current applied to the LED is mounted.
A first line, which is wired on the metal substrate via an insulating layer and connects between the positive side connection terminal of the control circuit and the anode of the LED,
A second line, which is wired on the metal substrate via an insulating layer and connects between the negative side connection terminal of the control circuit and the cathode of the LED, is provided.
The first line and the second line are wired so as to be symmetric on the metal substrate.
The light emitting device is characterized in that the resin substrate is a multilayer substrate, and pattern wiring and solid are not formed in a portion other than a via or a pad in which at least one layer on the metal substrate side is connected to the via or the metal substrate. .. The metal board on which the LED is mounted and
A resin substrate that is installed on the metal substrate and on which a control circuit that controls a current applied to the LED is mounted.
A first line, which is wired on the metal substrate via an insulating layer and connects between the positive side connection terminal of the control circuit and the anode of the LED,
A second line, which is wired on the metal substrate via an insulating layer and connects between the negative side connection terminal of the control circuit and the cathode of the LED, is provided.
The first line and the second line are wired so as to be symmetric on the metal substrate.
A lens is provided on the light emitting side of the LED on the metal substrate.
The positive side connection terminal and the negative side connection terminal are arranged at one end of the resin substrate.
A light emitting device characterized in that one end of the resin substrate is arranged on the metal substrate in close proximity to the outer edge of the lens.

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