JP2006147333A - Led-mounting printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for avoiding influence on an LED by heat generated from a control circuit without using a high-heat-radiation board, in a printed circuit board including the LED and its control circuit. <P>SOLUTION: This printed circuit board is provided with: a first area for mounting the LED; a second area for mounting a heat-radiation element out of elements constituting the control circuit of the LED; and a slit-like through-hole formed between the first area and the second area in order to restrict conduction of heat generated in the second area. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a printed circuit board for LED mounting and an LED lighting device using the same.

  LEDs having advantages such as high brightness and long life are being used as light sources for lighting devices. In such a background, there is a demand for further increasing the brightness of lighting devices using LEDs. By the way, normally, if the amount of current is increased, the luminance of the LED increases. However, if the amount of current is increased, the heat generated from the LED control circuit increases accordingly, and the LED may be damaged under the influence. For this reason, it has been common to achieve thermal relaxation by using a high heat dissipation substrate.

However, the use of a high heat dissipation substrate increases the manufacturing cost. In addition, component mounting is also one-sided mounting, and the size of the board must be increased.
SUMMARY OF THE INVENTION An object of the present invention is to provide a printed circuit board for LED mounting that can reduce the manufacturing cost, has few restrictions on component mounting, and is advantageous in terms of size.

The present invention comprises the following configuration in order to solve at least one of the above problems. That is,
A first region where the LED is mounted;
A second region in which a heating element among the elements constituting the LED control circuit is mounted;
A slit-shaped through hole formed between the first region and the second region to limit conduction of heat generated in the second region;
Is a printed circuit board.

In the above configuration, the printed circuit board is divided into a first region where the LED is mounted and a second region where the control circuit is mounted, and a slit-shaped through hole is formed at the boundary between these regions. As described above, since the first region and the second region are partly divided by the slit-shaped through hole, it is possible to effectively limit the heat generated in the second region from being conducted to the first region. . That is, the LED mounted in the first area is not easily affected by the heat generated by the control circuit in the second area.
As described above, with a simple structure in which the slit-shaped through hole is provided, a printed circuit board that can significantly reduce the thermal influence on the mounted LED is obtained. Therefore, it is possible to realize a printed circuit board that is reduced in cost, has fewer restrictions on component mounting, and is advantageous in terms of size.

  Hereinafter, the components of the present invention will be described.

(Printed circuit board and slit-shaped through hole)
The printed circuit board is used for mounting the LED and its control circuit. Although the material is not particularly limited, for example, a phenol resin, an epoxy resin, or the like is used.
The printed circuit board includes a first region and a second region. A light emitting element such as an LED is mounted in the first region. In the second region, at least heating elements (resistors, transistors, diodes, etc.) among the elements constituting the control circuit of the light emitting element are mounted. All components of the control circuit may be mounted in the second region. Moreover, even if it is a heat generating element, what must be arrange | positioned in the vicinity of a light emitting element on the characteristic of a control circuit is mounted in a 1st area | region.
In order to avoid the heat generated in the second region from being directly conducted to the first region via the printed circuit board and affecting the LED, a slit-shaped through hole is provided at the boundary between the first region and the second region. This limits the conduction of heat generated in the second region to the first region. That is, it is possible to reduce the LED from being affected by heat. On the other hand, when the slit-shaped through hole is formed, it is expected that part of the heat generated in the second region is conducted from a continuous portion of the first region and the second region. However, since the path length from the second area to the first area becomes longer, the heat radiation amount increases in proportion to the length of the path length, and the amount of heat finally reaching the first area decreases. Therefore, the LED is not easily affected by heat.

  It is preferable to form the slit-shaped through hole so that a virtual straight line connecting the LED and the heat generating element passes over the slit-shaped through hole. The length of the long side of the slit-shaped through hole is preferably as long as possible in order to limit the heat generated in the second region. However, the length of the slit is set so that sufficient strength of the printed circuit board can be secured and there is no problem in wiring. For example, the length of the long side of the slit-like through hole is preferably 70% or more of the boundary between the first region and the second region. More preferably, it is 80% or more. Although the upper limit of the length with respect to a boundary is not specifically limited, For example, it is 90%.

  In order to efficiently dissipate the heat in the printed circuit board, it is preferable to form a heat radiation pattern on a part of the surface of the printed circuit board. In particular, in order to reduce the thermal influence on the LED mounted in the first region, it is preferable to form a heat radiation pattern on the surface of the first region. The material of the heat radiation pattern is not particularly limited. An example of the material is copper. In order to dissipate heat more efficiently, it is preferable to form a heat dissipation pattern on the back surface of the printed circuit board. The heat dissipating pattern is preferably 30% or more of the first region on both the LED mounting surface and the back surface. Furthermore, it is preferably 50% or more. The upper limit of the region for forming the heat radiation pattern is not particularly limited, but is about 90%.

(LED)
The LED is used as an illumination light source. The type of LED is not particularly limited. For example, a bullet type or SMD type (surface mount type) element having a lens-shaped sealing member is used. The emission color of the LED is not particularly limited, and for example, a white LED can be used.

(Control circuit)
The control circuit is used to control the operating state of the LED. Specifically, for example, a control circuit is used to control the current flowing through the LED to be constant. For example, a resistor, a transistor, or the like is used as an element constituting the control circuit. These elements generate a large amount of heat when the amount of current is increased, and the heat may be conducted through the printed circuit board to damage the LED. Therefore, in the present invention, the conduction of heat from the elements (heat generating elements) constituting the control circuit is positively suppressed using the slit-shaped through holes formed in the printed board as described above.

(cover)
The cover is used together with a printed circuit board to constitute a lighting device. It also has a role of preventing contact with the outside. The cover is attached to the outer surface side of the LED so as to cover the printed board. The material of the cover is not particularly limited, and for example, a polycarbonate resin, an acrylic resin, or the like can be used.
A part of the outer surface of the cover can be formed into a convex lens shape to give a lens effect to the cover. With this configuration, the light from the LED is converged when passing through the cover. In addition to or in addition to the lens formed on such a cover, a lens may be used to control the light of the LED.

In particular, when the printed circuit board is covered with a cover, the heat generated in the second region may be conducted to the first region through the space above the printed circuit board. Therefore, it is preferable to form a shielding plate on the printed circuit board side of the cover and to make the tip of the shielding plate come into contact with or near the boundary between the first region and the second region of the printed circuit board. Thereby, since heat conducted to the first region through the space can be limited, the LED is not easily affected by heat.
In addition, the material of a shielding board is not specifically limited. When the cover and the shielding plate are integrally molded, the material of the shielding plate is the same as that of the cover.

  When the shielding board whose tip is in contact with the printed circuit board is formed at or near the boundary between the first area and the second area by covering the printed circuit board with the cover as described above, the space above the first area and the second area Both of the spaces above are highly sealed. In particular, when the slit-shaped through hole is blocked by a shielding plate, a substantially sealed state is obtained. This space is filled with the heat discharged from the printed circuit board into the space, and the LED is thermally affected. Therefore, it is preferable to form a vent hole in both the first region and the second region of the printed circuit board.

  The cover is fixed to the printed board in one embodiment of the present invention. When a screw is used as a fixing method, a screw hole is formed in a part of the cover, and a screw hole is also formed at a corresponding position on the printed board. Here, it is preferable to use a slit-like through hole as a part of the screw hole. Thereby, the trouble of forming a separate screw hole can be saved. In addition, the limited printed circuit board can be used effectively.

FIG. 1 is a plan view of a printed circuit board 1 according to an embodiment of the present invention. FIG. 1A is a diagram of the printed circuit board 1 on the LED mounting surface side, and FIG. 1B is a diagram of the back surface side of the printed circuit board 1. The printed circuit board 1 is used in an LED lighting device, and an LED and its control circuit are mounted.
The printed circuit board 1 includes a first area 10 and a second area 20. A slit-shaped through hole 2 is formed at the boundary between the first region 10 and the second region 20. The LED is mounted on AA in the first region 10. The printed board 1 is a double-sided copper-clad laminate.

The printed circuit board 1 includes a first area 10 and a second area 20. Elements such as LEDs are mounted in the first region 10. In the second region 20, an element of a control circuit (resistance) is mounted. In order to avoid heat generated in the second region 20 from being directly conducted to the first region 10 through the printed circuit board 1 and affecting the LED, a slit is formed at the boundary between the first region 10 and the second region 20. A through-hole 2 is provided. Thereby, the conduction of heat generated in the second region 20 to the first region 10 can be limited. That is, it is possible to reduce the influence of heat from the heat generating element transmitted from the substrate to the LED. On the other hand, when the slit-shaped through hole 2 is formed, it is expected that a part of the heat generated in the second region 20 is conducted from a continuous portion of the first region 10 and the second region 20. However, since the path length from the second area 20 to the first area 10 becomes longer, the heat dissipation amount increases in proportion to the length of the path length, and the amount of heat finally reaching the first area decreases.
In this embodiment, the area of the first region 10 is four times the area of the second region 20. Thereby, the heat generated in the first region 10 and the heat conducted from the second region 20 to the first region 10 are efficiently radiated from the surface of the first region 10.
Further, the heat radiation pattern 3 can be formed in the first region 10 to efficiently radiate heat. In particular, by forming the heat radiation pattern 3 in a region including the LED, the influence of heat on the LED can be reduced. A similar heat radiation pattern 3 can be formed on the back surface side to dissipate heat more efficiently. In this embodiment, the area of the pattern 3 on the LED mounting surface and the back surface is 60% of the area of the first region 10.

  With the configuration as described above, by forming the slit-like through hole 2 at the boundary between the first region 10 and the second region 20, the path length from the second region 20 to the first region 10 can be increased. . Therefore, even if the amount of current is increased by mounting the LED in the first region 10 of the printed circuit board 1 and mounting the heating element (resistance) in the second region 20, the LED is hardly affected by heat. That is, the cost is reduced, there are no restrictions on component mounting, and a printed circuit board that is advantageous in terms of size can be realized.

FIG. 2 shows an exploded perspective view of an LED lighting device 30 according to another embodiment of the present invention. In the LED lighting device 30, a cover 31 is attached to the LED mounting surface side of the printed circuit board 36, and the cover 31 and the printed circuit board 36 are fixed to the mounting surface 41 using screws 33. The LED 38 is mounted in the first region 100. An SMD type white LED is used as the LED 38. The LED lighting device 30 is used for lighting in the vehicle.
Since the printed circuit board 36 is the same as that in the above embodiment, its description is omitted.

The cover 31 is used together with the printed circuit board 36 to constitute the LED lighting device 30. The cover 31 also has a role of preventing contact between the printed circuit board 36 and the outside. The material of the cover 31 is a polycarbonate resin.
A region directly above the LED mounting portion of the printed board 10 is formed in a convex lens shape on the outer surface of the cover 31. With this configuration, the light of the LED 38 is converged when passing through the cover, and light that irradiates a desired range is generated.
Since the printed circuit board 36 is covered with the cover 31, the heat generated in the second region 200 may be conducted to the first region 100 through the space above the printed circuit board 36. Therefore, in the cover 31, a shielding plate 34 whose tip is in contact with the printed circuit board 36 is formed above or near the boundary between the first region 100 and the second region 200. Thereby, since the heat conducted to the first region 100 through the space can be limited, the LED 38 is hardly affected by heat. The material of the shielding plate 34 is a polycarbonate resin made of the same material as the cover.
When the shielding board 34 whose tip is in contact with the printed circuit board 36 is formed at or near the boundary between the first area 100 and the second area 200 by covering the printed circuit board 36 with the cover 31, the space above the first area 100 and the second area Both the space above the region 200 and the sealed state become high. This space is filled with the heat released from the surface of the printed circuit board 36, and there is a possibility that the LED 38 is thermally affected. Therefore, vent holes 39 are provided in the first region 100 and the second region 200 of the printed circuit board 36, respectively.

  Screws 33 are used to fix the cover 31 and the printed circuit board 36. Therefore, the screw hole 35 is formed in a part of the cover 31 and the screw hole 40 is also formed at a corresponding position on the printed circuit board 36. Moreover, in order to reduce the manufacturing process of the printed circuit board 36 and effectively use the inside of the printed circuit board 36, a part of the slit-like through hole 37 is used as a screw hole.

  A screw hole 42 for fixing the cover 31 and the printed circuit board 36 is provided in the mounting surface 41. In addition, an opening 43 is formed to dissipate the heat generated in the wiring from the inside of the vehicle body to the LED lighting device 30 and the printed board 36.

The LED lighting device 30 configured as described above is used for lighting in a vehicle. An opening is formed in the wall surface in the vehicle, and a screw hole for fixing the LED lighting device 30 is formed. After performing the electrical wiring of the LED lighting device 30, the LED lighting device 30 is fixed with screws.
Since the outer surface of the cover 31 is formed in a convex lens shape, the light of the LED is converged at a desired distance. Therefore, it can be suitably used as a map lamp or the like in vehicle interior lighting.

  With the above configuration, the heat generated in the printed circuit board is efficiently radiated to the outside. Therefore, even if the current to the LED is increased, the LED is not easily affected by heat. Therefore, high brightness of the LED can be realized also in this configuration.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications are also included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

FIG. 1 shows a surface view of a printed circuit board used in an embodiment of the present invention. (a) is the surface view of the LED mounting surface side of a printed circuit board. (b) is a front view of the back side of the printed circuit board. FIG. 2 is an exploded perspective view of an LED lighting device according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 36 Printed circuit board 2 37 Slit-like through-hole 3 Radiation pattern 10 100 1st area | region 20 200 2nd area | region 30 LED illuminating device 31 Cover 34 Shielding board

Claims (10)

A first region where the LED is mounted;
A second region in which a heating element among the elements constituting the LED control circuit is mounted;
A slit-shaped through hole formed between the first region and the second region to limit conduction of heat generated in the second region;
Printed circuit board.   2. The printed circuit board according to claim 1, wherein an imaginary straight line connecting the LED and the heat generating element passes through the slit-shaped through hole.   3. The printed circuit board according to claim 1, wherein a length of a long side of the slit-shaped through hole is 70% or more of a length of a boundary between the first region and the second region. .   The printed circuit board according to claim 1, wherein the surface area of the first region is twice or more the surface area of the second region.   The printed circuit board according to claim 1, wherein a heat dissipation pattern is formed on each of the LED mounting surface side and / or the back surface side of the first region. A printed circuit board according to any one of claims 1 to 5,
An LED and a control circuit mounted on the printed circuit board;
A cover attached to cover the LED mounting surface side of the printed circuit board;
LED lighting device comprising:   A shielding plate is formed on the printed circuit board side of the cover, and a tip of the shielding plate is in contact with or near the boundary between the first region and the second region of the printed circuit board and above the first region. The LED lighting device according to claim 6, wherein a space above and a space above the second region are separated.   8. The LED lighting device according to claim 6, wherein a region immediately above the LED mounted on the printed circuit board is formed in a convex lens shape on the outer surface of the cover. 9.   9. The printed circuit board according to claim 6, wherein the printed circuit board has at least one through hole, and the cover is fixed to the printed circuit board by using the through hole and a part of the slit-shaped through hole. The LED lighting apparatus in any one. The heat dissipation vent is formed in the printed circuit board in order to discharge heat generated in the space surrounded by the cover and the printed circuit board. LED lighting device.

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