JP2018073977A - Load drive device, lighting fixture for vehicle and manufacturing method for load drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load drive device, lighting fixture for vehicle and manufacturing method for load drive device, capable of satisfactorily shielding an electromagnetic wave from an electromagnetic wave generation source while simplifying a manufacturing process.SOLUTION: A load drive device (100) includes: an electromagnetic wave generation source which supplies electric power to a load for driving and is installed on a substrate (101); a shielding case (103) whose top face has an opening part therein. The top face covers at least part of the electromagnetic wave generation source, and a terminal part of an electronic component installed on the substrate (101) is visible from the opening part in top view.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a load driving device, a vehicular lamp, and a method for manufacturing the load driving device.

  In recent years, the technology of light emitting diodes (LEDs) has been developed, and LEDs have come to be used as light sources for home lighting fixtures and vehicle lighting fixtures. In these lamps, it is necessary to convert the voltage supplied from the power source into a voltage suitable for driving the LED, and a voltage converter such as a DC / DC converter is mounted in the drive circuit. In addition, when executing LED light amount control using PWM (Pulse Width Modulation) control or the like, a PWM control unit is mounted in the drive circuit.

  Such a voltage conversion unit and PWM control unit include a switching element, a capacitor, a coil, and the like, and a weak electromagnetic wave is generated from the circuit portion when the drive circuit is driven to drive the LED as a load. Resulting in. Since electromagnetic waves generated from the drive circuit may interfere with other electronic devices provided in the vicinity as noise, it is necessary to cover the entire circuit with a metal shield for shielding electromagnetic waves (for example, Patent Document 1).

  In such a conventional technique, since the entire circuit is covered with a metal shield, it is difficult to reduce the size of the apparatus, and a process of attaching the metal shield to the circuit board is necessary, and the manufacturing process becomes complicated. Therefore, it has been proposed to reduce the size of the circuit by covering only the region where electromagnetic waves are generated with a metal shield.

  FIG. 8 is a circuit diagram showing a conventional technique in which only the electromagnetic wave generation source is covered with a metal shield. On the circuit board, a drive unit 1 which is a load driving device and a load unit 2 driven by the drive unit 1 are mounted. As shown in FIG. 8, the drive unit 1 includes an input filter 11, a DC / DC converter 12, a control circuit 13, and an output filter 14.

  The input filter 11 is a circuit unit that is connected to a power supply unit (not shown) and supplied with power, and supplies power to the DC / DC converter 12. The DC / DC converter 12 is a voltage conversion unit that converts the DC voltage supplied from the input filter 11 into a voltage suitable for the load unit 2 and supplies the voltage to the output filter 14. As shown in the figure, the entire area where the DC / DC converter 12 is mounted on the circuit board is covered with a metal shield so as to shield the electromagnetic wave emission from the circuit. Yes.

  The control circuit 13 detects the current supplied from the DC / DC converter 12 to the output filter 14 and feedback-controls the DC / DC converter 12 according to the current value. The output filter 14 outputs the direct current supplied from the DC / DC converter 12 to the load unit 2.

  The load unit 2 includes a load LED 21 to be driven by the drive unit 1, and the LED 21 is driven to emit light.

  As described above, in the conventional load driving circuit, the LED 21 of the load unit 2 is driven by the voltage converted by the DC / DC converter 12, and the DC / DC converter 12 operates by covering the DC / DC converter 12 with the metal shield. The electromagnetic wave generated by doing so is prevented from leaking outside.

JP 2012-204168 A

  In recent years, in order to increase the density of circuit boards, surface mount type electronic components are employed as various electronic components, and they are frequently mounted on a circuit board in a reflow furnace.

  When the metal shield is mounted on the circuit board after the reflow process, the connection of the metal shield to the circuit board is an insertion mounting type. FIG. 9 is a drawing-substituting photograph showing a state where the metal shield is inserted and mounted on the circuit board. FIG. 9 (a) shows a non-defective product and FIG. 9 (b) shows a defective product.

  As shown in FIG. 9, a terminal integrally formed with a metal shield is inserted into a through hole provided in the circuit board, and the metal shield is mounted on the circuit board by soldering. For such insertion mounting type soldering, processes such as a soldering apparatus, flow soldering, and manual soldering are necessary, and it is difficult to simplify the manufacturing process. In addition, since heat escapes to the large-area metal shield during the soldering operation, there is a problem that the solder creeping up to the through hole is worsened and the yield of poor connection is worsened as shown in FIG. 9B. It was.

  When the metal shield is mounted on the circuit board at the same time as the reflow process, the metal shield covers the electromagnetic wave generation source. Therefore, it is possible to inspect the solder connection state of each electronic component by image recognition using a solder appearance inspection device. It becomes impossible.

  In addition, since the temperature of the electronic component rises due to heat accumulation in the area covered with the metal shield, there is a limit to reducing the size of the metal shield.

  Accordingly, an object of the present invention is to provide a load driving device, a vehicular lamp, and a manufacturing method of the load driving device capable of satisfactorily shielding electromagnetic waves from an electromagnetic wave generation source while simplifying the manufacturing process. To do.

  In order to solve the above problems, a load driving device according to the present invention is a load driving device that drives by supplying electric power to a load, and has an electromagnetic wave source mounted on a substrate and an opening on the top surface. A shielding case provided, wherein the top surface covers at least a part of the electromagnetic wave generation source, and a terminal portion of an electronic component mounted on the substrate is visible from the opening in a top view. Features.

  In such a load driving device of the present invention, it is possible to satisfactorily shield the electromagnetic wave from the electromagnetic wave generation source while simplifying the manufacturing process.

  In one embodiment of the present invention, the shielding case is electrically connected to a ground potential provided on the substrate.

  In one embodiment of the present invention, the shielding case is made of metal and is surface-mounted on the substrate.

  In the aspect of the invention, the electromagnetic wave generation source is a voltage conversion unit including a switching element or a coil, the top surface covers substantially the entire surface of the switching element or the coil, and the switching element is formed from the opening. Alternatively, the terminal portion of the coil is visible.

  In order to solve the above problems, a vehicular lamp according to the present invention includes the load driving device according to any one of the above aspects and a semiconductor light source as the load.

  In order to solve the above problems, a method for manufacturing a load driving device according to the present invention is a method for manufacturing a load driving device that drives by supplying power to a load, and includes a step of mounting an electromagnetic wave generation source on a substrate. An opening is provided on the top surface, the top surface covers at least a part of the electromagnetic wave generation source, and a terminal portion of an electronic component mounted on the substrate is visible from the opening in a top view. And a step of mounting a shielding case on the substrate.

  In such a method for manufacturing a load driving device of the present invention, it is possible to satisfactorily shield electromagnetic waves from an electromagnetic wave generation source while simplifying the manufacturing process.

  In one embodiment of the present invention, the shielding case is a surface-mount type, and the step of mounting the electromagnetic wave generation source and the shielding case on the substrate is collectively performed in a reflow furnace.

  The present invention can provide a load driving device, a vehicular lamp, and a method for manufacturing the load driving device that can satisfactorily shield electromagnetic waves from an electromagnetic wave generation source while simplifying the manufacturing process.

It is a mimetic diagram showing load driving device 100 in a 1st embodiment. It is the schematic diagram which expands and shows the area | region in which the sample 1 of the shielding case 103 was mounted among the load drive devices 100. FIG. It is a schematic diagram which shows the example which changed the shape of the shielding case 103 of the load drive device 100, Fig.3 (a) shows a comparative example, FIG.3 (b) shows the sample 2, FIG.3 (c) is a sample. 3 is shown. FIG. 4D is a schematic diagram showing an example in which the shape of the shielding case 103 of the load driving device 100 is changed. FIG. 4D shows Sample 4, FIG. 4E shows Sample 5, and FIG. 6 is shown. 5A and 5B are schematic views showing an example in which the shape of the shielding case 103 of the load driving device 100 is changed. FIG. 5G shows the sample 7 and FIG. It is a graph which shows the noise reduction effect by the kind of shielding case 103 for every frequency band. It is a graph which shows the noise reduction effect of the whole by the kind of shielding case 103. FIG. It is a circuit diagram which shows the prior art which covers only an electromagnetic wave generation source with a metal shield. FIG. 9A is a drawing-substituting photograph showing a state in which a metal shield is inserted and mounted on a circuit board. FIG. 9A shows a non-defective product and FIG. 9B shows a defective product.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. FIG. 1 is a schematic diagram showing a load driving device 100 according to the present embodiment.

  In the load driving device 100, a socket portion 102, a shielding case 103, and a plurality of electronic components 104 are mounted on a circuit board 101. The circuit board 101 is a board on which circuit wiring (not shown) is printed on the surface, and is made of, for example, glass epoxy resin. The socket portion 102 is a component that is electrically connected to the circuit wiring on the circuit board 101, and an electrical connection with an external power source or load of the load driving device 100 is ensured by connecting a plug (not shown). The By connecting the plug to the socket unit 102, power is supplied from the power source to the load driving device 100, and an appropriate voltage and current are output to the load to be driven to drive the load. As the load, for example, an illumination device using an LED as a light source can be cited.

  The shield case 103 is a metal shield cover mounted on the circuit board 101, and is surface-mounted on a land having a ground potential provided on the circuit board 101. As shown in FIG. 1, the shielding case 103 has a substantially rectangular shape, and includes a side wall that surrounds the outer periphery and a top surface 103a, and an opening 103b is formed in the top surface 103a. In the area where the shielding case 103 is mounted, a plurality of electronic components 104 are mounted on the circuit board 101, and a part of the electronic component 104 mounted in the area can be visually observed from the opening 103b of the shielding case 103. It has become.

  The electronic component 104 is various electronic elements such as a resistor, a capacitor, and an IC (Integrated Circuit). The electronic component 104 is a surface-mount type element, and the terminal portions 104 a and 104 b are surface-mounted on lands provided on the circuit board 101 by reflow soldering to constitute a circuit of the load driving device 100. An example of the drive circuit configured by the circuit wiring formed on the circuit board 101 and the electronic component 104 is the LED drive circuit shown in FIG.

  FIG. 2 is an enlarged schematic view showing a region where the sample 1 of the shielding case 103 is mounted in the load driving device 100 of the present embodiment. Among the electronic components 104 mounted on the circuit board 101, a voltage conversion unit such as a DC / DC converter is an electromagnetic wave source that easily generates an electromagnetic wave during operation, and shields the area where the electromagnetic wave source is mounted. A case 103 is mounted. The DC / DC converter, which is an electromagnetic wave generation source, includes a coil 105 and a switching element 106, which are a kind of electronic components 104, and the electronic component 104, the coil 105, and the switching element 106 are connected to the respective terminal portions 104a. 140b, 105a, 105b, 106a, 106b are surface-mounted on the circuit board 101.

  As shown in FIG. 2, the top surface 103a of the shielding case 103 covers at least a part of the DC / DC converter that is an electromagnetic wave generation source when viewed from above, and the electronic component 104, the coil 105, and the like from the opening 103b. Terminal portions 104a, 140b, 105a, 105b, 106a, 106b of the switching element 106 are visible. The top surface 103a is formed so as to cover at least part of the coil 105 and the switching element 106, but the other electronic components 104 are not covered with the top surface 103a but exposed from the opening 103b. May be.

  In the sample 1 of the shielding case 103 of the present embodiment, the width of the top surface 103a that covers the coil 105 and the switching element 106 is made wider than the other regions, so that the electromagnetic waves emitted from the coil 105 and the switching element 106 are efficiently generated. Designed to absorb. In this case, while the terminal portions 105a, 105b, 106a, 106b of the coil 105 and the switching element 106 are visible from the opening 103b, the area of the top surface 103a covering the coil 105 and the switching element 106 is increased as much as possible. The top surface 103a is preferably formed in a shape that covers substantially the entire surface of the coil 105 and the switching element 106.

  As a method for manufacturing the load driving device of this embodiment, first, circuit wiring including lands is formed on the circuit board 101, and the electronic component 104, the coil 105, and the switching element 106 are arranged on the circuit board. Next, the shielding case 103 is disposed on the area of the DC / DC converter including the coil 105 and the switching element 106. Finally, the shielding case 103, the electronic component 104, the coil 105, and the switching element 106 are collectively soldered in a reflow furnace, and the shielding case 103, the electronic component 104, the coil 105, and the switching element 106 are mounted on the circuit board 101. Connect them electrically.

  The shielding case 103 is positioned by reflow soldering the bottom surface of the side wall of the shielding case 103 to a case land (not shown in FIG. 2) provided so as to surround the DC / DC converter region of the circuit board 101. . Therefore, the side wall constituting the outer shape of the shielding case 103 is accurately positioned around the DC / DC converter, and the region covered by the top surface 103a and the region visible from the opening 103b are also accurately aligned, thereby shielding the shielding case 103. Is mounted on the circuit board 101.

  In the present embodiment, the shielding case 103 includes a top surface 103a and an opening 103b, and the top surface 103a covers the coils 105 and the switching elements 106 that are electromagnetic wave generation sources. As a result, the electromagnetic wave generated from the coil 105 and the switching element 106 is absorbed by the top surface 103a and discharged to the ground potential of the circuit board 101. Therefore, the electromagnetic wave generated from the electromagnetic wave generation source is shielded and the leakage to the outside is suppressed. it can. Further, since the electronic parts 104, the coil 105, and the terminal parts 104a, 140b, 105a, 105b, 106a, and 106b of the switching element 106 are visible from the opening 103b, the terminal parts 104a, 140b, and 105a are used by using a solder appearance inspection device. , 105b, 106a, 106b can be confirmed.

  In addition, since the shielding case 103, the electronic component 104, the coil 105, and the switching element 106 are collectively mounted on the circuit board 101 in a reflow furnace, it is not necessary to provide an insertion mounting type soldering process separately, thereby simplifying the manufacturing process. I can plan.

  Furthermore, since the opening 103b is formed in the shielding case 103, the heat generated by the DC / DC converter of the electromagnetic wave generation source covered by the shielding case 103 can be radiated well to the outside. As a result, even if the shielding case 103 is downsized, it is possible to prevent the temperature of the electronic component 104 from rising due to heat accumulated in the shielding case 103.

  As described above, the load driving device 100 of this embodiment and the method of manufacturing the load driving device 100 can well shield electromagnetic waves from the electromagnetic wave generation source while simplifying the manufacturing process.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. A description of the same parts as those in the first embodiment will be omitted. 3 to 5 are schematic diagrams illustrating an example in which the shape of the shielding case 103 of the load driving device 100 is changed. 3A shows a comparative example, FIG. 3B shows Sample 2, and FIG. 3C shows Sample 3.

  In the comparative example shown in FIG. 3A, the shielding case 103 is not provided, and the electronic component 104, the coil 105, the switching element 106, and the shielding case 103 that are mounted on the surface of the circuit board 101 are mounted. Land 110 for use is exposed. Therefore, the connection state of all the terminal portions 104a, 140b, 105a, 105b, 106a, 106b can be inspected by the solder appearance inspection device.

  In the sample 2 shown in FIG. 3B, the shielding case 103 is only the side wall portion, and the top surface 103a is not provided, and the entire upper surface has the shape of the opening 103b. Therefore, all the terminal portions 104a, 140b, 105a, 105b, 106a, and 106b are exposed from the opening 103b, and the connection state can be inspected by the solder appearance inspection apparatus.

  In the sample 3 shown in FIG. 3C, the shielding case 103 has a shape having a side wall portion and a cross-shaped top surface 103a. In Sample 3, the top surface 103a does not cover the coil 105 and the switching element 106. Further, all the terminal portions 104a, 140b, 105a, 105b, 106a, 106b are exposed from the opening 103b, and the connection state can be inspected by a solder appearance inspection device. The width of the top surface 103a is about 1 mm as an example.

  In the sample 4 shown in FIG. 4D, the shielding case 103 has a shape having a side wall portion and a plurality of beam-like top surfaces 103a. In Sample 4, the top surface 103a covers the coil 105 and the switching element 106 only partially. Further, all the terminal portions 104a, 140b, 105a, 105b, 106a, 106b are exposed from the opening 103b, and the connection state can be inspected by a solder appearance inspection device. The width of the top surface 103a is about 1 mm as an example.

  In the sample 5 shown in FIG. 4E, the shielding case 103 has a shape having a side wall portion and a plurality of beam-like top surfaces 103a. In Sample 5, the top surface 103a covers the coil 105 and the switching element 106 only partially. Further, all the terminal portions 104a, 140b, 105a, 105b, 106a, 106b are exposed from the opening 103b, and the connection state can be inspected by a solder appearance inspection device. The width | variety of the top | upper surface 103a is formed thicker than the sample 4, and is about 2 mm as an example.

  In Sample 6 shown in FIG. 4F, the shielding case 103 has a side wall portion and a plurality of beam-like top surfaces 103a, and has a shape in which the area on the coil 105 is increased. In Sample 6, the top surface 103a covers substantially the entire surface of the coil 105 and a part of the switching element 106. Further, all the terminal portions 104a, 140b, 105a, 105b, 106a, 106b are exposed from the opening 103b, and the connection state can be inspected by a solder appearance inspection device.

  In the sample 7 shown in FIG. 5G, the shielding case 103 has a side wall portion and a plurality of beam-shaped top surfaces 103a, and has a shape in which areas on the coil 105 and the switching element 106 are increased. In this sample 7, the top surface 103a covers substantially the entire surface of the coil 105 and the switching element 106. Moreover, a part of terminal part 104a, 140b, 105a, 105b, 106a, 106b is covered with the top | upper surface 103a, and there exists a terminal which cannot test | inspect a connection state with a solder external appearance inspection apparatus.

  In the sample 8 shown in FIG. 5 (h), the shielding case 103 includes a side wall portion and a top surface 103a, and the opening portion 103b is not formed. In this sample 8, the electronic component 104, the coil 105, the switching element 106, and the terminal portions 104a, 140b, 105a, 105b, 106a, 106b are all covered with the top surface 103a, and the connection state is inspected with a solder appearance inspection device. Can not.

  FIG. 6 is a graph showing the noise reduction effect by the type of shielding case 103 for each frequency band. The vertical axis in FIG. 6 represents the level of the electromagnetic wave emitted to the outside of the load driving device 100, and the horizontal axis represents the frequency of the electromagnetic wave. The broken line in the graph is the comparative example shown in FIG. 3A, and the plot shown by the solid line is the sample 4 and FIG. 5 shown in FIG. Sample 8 shown in (h) and Sample 1 shown in FIG. 2 in the first embodiment.

  FIG. 7 is a graph showing the overall noise reduction effect depending on the type of the shielding case 103. The vertical axis in FIG. 7 represents the average noise level, and the horizontal axis represents Comparative Examples, Samples 2 to 8, and Sample 1 from the left.

  6 and 7, it can be seen that the noise level can be reduced in all the samples using the shielding case 103 as compared to the comparative example in which the shielding case 103 is not used. However, in Samples 2 and 3, since the coil 105 and a part of the switching element 106 are not covered with the top surface 103a, the noise level is not sufficiently reduced. In samples 4 to 8 and sample 1, at least a part of the coil 105 and the switching element 106 is covered with the top surface 103a, and the noise level is sufficiently reduced. In addition, as the area of the top surface 103a covering the coil 105 and the switching element 106 is larger, the effect of reducing the noise level tends to be greater.

  In samples 7 and 8, the effect of reducing the noise level is maximized, but the area of the top surface 103a is too large to cover the coil 105 and part of the terminal portions 105a, 105b, 106a, 106b of the switching element 106, Visual inspection with a solder appearance inspection device is impossible. In contrast, in sample 1, the top surface 103a covers substantially the entire surface of the coil 105 and the switching element 106, but the terminal portions 105a, 105b, 106a, and 106b of the coil 105 and the switching element 106 are exposed from the opening 103b. Therefore, visual recognition with a solder appearance inspection apparatus is also possible. In addition, the noise level reduction of sample 1 is about the same as that of sample 8 that does not have the opening 103b and covers the entire top surface with the top surface 103a, so that both the best noise level reduction and a solder appearance inspection device are possible. is made of.

  In the load driving device 100 and the method for manufacturing the load driving device 100 according to this embodiment, it is possible to satisfactorily shield the electromagnetic wave from the electromagnetic wave generation source while simplifying the manufacturing process.

(Third embodiment)
Next, a third embodiment of the present invention will be described. A description of the same parts as those in the first embodiment will be omitted. In this embodiment, the load driving device 100 is used for a vehicle lamp, and a semiconductor light source such as an LED, an organic EL, or a semiconductor laser is employed as a driving load.

  The load driving device 100 is used in a relatively high temperature environment such as a vehicular lamp because the shielding case 103 has a top surface and an opening, so that the electromagnetic wave generation source covered by the shielding case 103 is not heated. The heat dissipation is also good when used. It is also possible to reduce the size of the shielding case 103 while maintaining heat dissipation. Further, since the electromagnetic wave emission from the load driving device 100 can be satisfactorily shielded by the shielding case 103, it becomes possible to suppress the interference of electromagnetic wave noise to the in-vehicle radio device or the like.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. A description of the same parts as those in the first embodiment will be omitted. In the first embodiment, the voltage conversion unit including the switching element or the coil is shown as the electromagnetic wave generation source of the load driving device 100. However, the circuit unit is not limited to the voltage conversion unit, and any other circuit unit can generate an electromagnetic wave. There may be.

  Examples of other electromagnetic wave generation sources include a digital circuit such as a PWM control unit that drives and controls a load LED, an inverter circuit that drives a motor, and a power supply circuit.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Load drive device 101 ... Circuit board 102 ... Socket part 103 ... Shielding case 103a ... Top surface 103b ... Opening part 104 ... Electronic component 104a, 104b, 105a, 105b, 106a, 106b ... Terminal part 105 ... Coil 106 ... Switching element 110 ... Land for cases

Claims (7)

A load driving device that drives by supplying power to a load,
An electromagnetic wave source mounted on a substrate;
Provided with a shielding case with an opening on the top,
The load driving device, wherein the top surface covers at least a part of the electromagnetic wave generation source, and a terminal portion of an electronic component mounted on the substrate is visible from the opening in a top view. The load driving device according to claim 1,
The load driving device, wherein the shielding case is electrically connected to a ground potential provided on the substrate. The load driving device according to claim 1 or 2,
The load driving device, wherein the shielding case is made of metal and is surface-mounted on the substrate. The load driving device according to any one of claims 1 to 3,
The electromagnetic wave generation source is a voltage conversion unit including a switching element or a coil,
The top surface covers substantially the entire surface of the switching element or the coil, and the terminal portion of the switching element or the coil is visible from the opening. The load driving device according to any one of claims 1 to 4,
A vehicle lamp comprising a semiconductor light source as the load. A method of manufacturing a load driving device that drives by supplying power to a load,
Mounting an electromagnetic wave generation source on a substrate;
An opening is provided on the top surface, and the top surface covers at least a part of the electromagnetic wave generation source, and the terminal portion of the electronic component mounted on the substrate is visible from the opening when viewed from above. And a step of mounting the case on the substrate. It is a manufacturing method of the load drive device according to claim 6,
The shielding case is a surface mount type,
The method of manufacturing a load driving device, wherein the step of mounting the electromagnetic wave generation source and the shielding case on the substrate is performed at once in a reflow furnace.