JP5629135B2 - Flexible board module - Google Patents

Description

  The present invention relates to a flexible substrate module, and more particularly to a flexible substrate module in which a heat source is mounted.

Conventionally, for example, when an illumination unit is configured using light emitting diodes, the amount of light can be easily increased by integrating the light emitting diodes on the printed wiring layer using a flexible substrate. Further, the use of a flexible substrate has an advantage that three-dimensional three-dimensionalization can be easily performed.
Japanese Patent Laying-Open No. 2002-184209 (Patent Document 1) discloses a lighting device in which a plurality of light emitting diodes are mounted on a flexible substrate.

JP 2002-184209 A

However, in the case of the illumination device described in Patent Document 1, in a flexible substrate on which light emitting diodes are integrated and mounted, the light emitting diodes are generally vulnerable to heat, and when the temperature of the pn junction exceeds, for example, 130 ° C., the luminance decreases and the lifetime decreases. There was a problem causing. In particular, in the case of recent high-brightness LEDs, how to solve the problem of heat dissipation has become a major issue.
Patent Document 1 discloses that the structure of a flexible substrate on which a light emitting diode is mounted is preferably a multilayer substrate including a metal layer made of copper or the like, or a graphite layer in order to obtain thermal conductivity. It is only an abstract suggestion and ends up with no concreteness.
As described above, simply attaching a flexible substrate mounted with a light-emitting heat source such as an LED to a housing such as a lighting device tends to have insufficient heat dissipation. The advantage of using a flexible substrate is that it is easy to make a three-dimensional structure because the flexible substrate can be bent and attached to the chassis after the luminescent heat source is mounted on the flexible substrate. It is difficult to press and paste the flexible board in accordance with the shape of the case, and especially under and near the light-emitting heat source such as LEDs, it is difficult to apply pressure, so the air layer is not attached to the case when bonding. There is also a problem that the heat dissipation is more difficult to improve due to the interposition between them. On the other hand, attaching the light emitting heat source after the flexible substrate is attached to the housing with a press has the problem that, as described above, it is difficult to attach the flexible substrate in accordance with the complicated shape of the housing. If the heat source is not horizontal, it is difficult to pass the mounting of the light emitting heat source through the solder reflow process because the light emitting heat source falls off when the solder melts, and the solder mounting of the light emitting heat source becomes a manual operation one by one. There is a problem that merit cannot be achieved. For this reason, when it is necessary to ensure sufficient heat dissipation, a metal PCB is often used.
In the above description, a light emitting heat source composed of a light emitting diode is described as an example of the heat source. However, there are various heat sources that need to be cooled in addition to the light emitting heat source. For example, a CPU, MPU, power transistor, laser diode, or the like generates a large amount of heat. Examples include electrical elements and devices. In recent years, with the increase in the amount of heat generated by these heat sources, the heat dissipating technology has become a major issue as in the case of the above-described light emitting diode.

  SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a flexible substrate module that solves the above-described problems in the prior art, uses a flexible substrate, is sufficiently excellent in heat dissipation with respect to a mounted heat source, and is sufficiently excellent in flexibility and integration. To do.

The flexible substrate module of the present invention that solves the above problems is a flexible substrate module in which a printed wiring layer is formed as a surface layer laminated on the surface side of a flexible insulating base material and a heat source is mounted on the printed wiring layer. A heat spot that is transferred from the heat source to the printed wiring layer as a back surface layer that is laminated on the back surface side of the flexible insulating base material when attached to the housing that is the mounting partner A plurality of thermal diffusion promotion layers made of a high thermal conductivity material for promoting the expansion of the area of the heat spot toward the housing that is the mounting partner. The layer is at least a heat diffusion layer that is directly bonded to the back surface of the flexible insulating base material as the uppermost layer of the back surface layers. A heat diffusion layer that includes a long layer and a heat diffusion facilitating layer made of a highly thermally conductive metal sheet that is in contact with the housing as the lowest layer of the back layer, and is the uppermost layer of the back layer A flexible printed wiring board is composed of the diffusion facilitating layer, the flexible insulating base material, and the printed wiring layer. A plurality of heat sources are mounted on the flexible printed wiring board, and each of the heat sources corresponds to one to a plurality of heat sources. The first feature is that the high thermal conductive metal sheet is divided and arranged .
Also flexible board module of the present invention, in addition to the first feature, and a second wherein the housing is a housing of the lighting unit.

According to the flexible substrate module according to the first feature described above, a module having excellent heat source integration and three-dimensional attachment flexibility can be provided by mounting the heat source on the flexible substrate. In particular, the back surface layer laminated on the back surface side of the flexible insulating base material has an area larger than the area of the heat spot transferred from the heat source to the printed wiring layer, and the area of the heat spot on the mounting partner. By providing a plurality of heat diffusion promoting layers made of a high thermal conductivity material to promote expansion toward a certain case, it is possible to exhibit sufficiently good heat dissipation by interposing the heat diffusion promoting layer, and the performance of the heat source It was possible to maintain a good life.

In addition, the heat diffusion heat transfer layer that is directly bonded to the back surface of the flexible insulating substrate as the uppermost layer of the back surface layer allows the heat spot transferred from the heat source to the printed wiring layer to pass through the flexible substrate. Heat can be transferred quickly to the back layer. And the expansion of the area of the heat spot transferred to the back surface layer of the flexible base material can be promoted downward. In addition, the heat diffusion promoting layer made of a highly thermally conductive metal sheet that is in contact with the casing as the lowest layer of the back surface layer further reduces the area of the heat spot with the casing. Enlargement can be encouraged to approach the contact area. That is, the heat spot transferred from the heat source can be transferred to the casing while rapidly expanding to a state close to the contact surface area with the casing. As a result, heat transferred from the heat source to the printed wiring layer can be transferred to the housing more efficiently and smoothly in a large area, and good heat dissipation can be achieved .

In addition, since the lowermost layer of the flexible board module in contact with the casing is made of a metal sheet, when the flexible board module is mounted in contact with the casing, it is easy to bring them into close contact with each other. Even if a large pressure is not applied, the air layer can be sufficiently prevented from intervening. As a result, it is possible to ensure good heat dissipation without the presence of an air layer.

In addition, since the high thermal conductivity metal sheet is divided and arranged corresponding to each of the heat sources with respect to the flexible printed wiring board on which a plurality of heat sources are mounted, Even if the thickness is increased, the flexible substrate module can be flexibly bent continuously in each gap of the divided high thermal conductive metal sheet. Therefore, the three-dimensional arrangement of the heat source can be easily made possible. In addition, since the thickness of the high heat conductive metal sheet can be increased, the area of the heat spot by the heat source can be expanded more smoothly and can be made closer to the contact surface area with the housing. Therefore, the heat dissipation efficiency can be improved more effectively.

According to the flexible substrate module according to the second aspect, in addition to the effects by the configuration according to the first aspect, by housing a housing of the lighting unit, three-dimensional structure of the housing of the lighting unit Accordingly, the flexible substrate unit can be flexibly bent and attached, and the heat generated from the heat source can be quickly dissipated to maintain the performance and life of the lighting unit favorably.

  According to the flexible substrate module of the present invention, it is possible to provide a flexible substrate module that secures good heat dissipation for a mounted heat source and also ensures good flexibility.

It is sectional drawing explaining the flexible substrate module of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining 1st Embodiment of the flexible substrate module of this invention, In each of (A), (B), (C), sectional drawing and a top view are shown on right and left. It is a figure explaining 2nd Embodiment of the flexible substrate module of this invention, In each of (A), (B), (C), (D), sectional drawing and a top view are shown on right and left.

  With reference to the following drawings, an embodiment of a flexible substrate module according to the present invention will be described for the understanding of the present invention. However, the following description is an embodiment of the present invention, and does not limit the contents described in the claims.

First, a flexible substrate module according to an embodiment of the present invention will be described with reference to FIG.
The flexible substrate module 1 according to the embodiment is a module that is attached so as to be in contact with the housing K to be attached.
As a surface layer laminated on the surface side of the flexible insulating base material 11, a printed wiring layer 12 is formed via an adhesive layer a. A light emitting heat source 14 is mounted at a predetermined mounting position of the printed wiring layer 12 via a solder 13 layer. The printed wiring layer 12 is covered with a cover lay 15 through an adhesive layer a. When the same material as the flexible insulating base material 11 and the cover lay 15 is used for the bonding, the adhesive layer a is integrated with the flexible insulating base material 11 or the cover lay 15, so that the adhesive layer a is eventually formed. It may be in a nonexistent state.
The flexible insulating substrate 11 uses an insulating resin film having flexibility such as polyimide and polyester. The thickness can be on the order of several tens of microns, for example 25 μm.
The printed wiring layer 12 can be configured by forming a wiring pattern from the copper foil using a material obtained by attaching a copper foil to the flexible insulating substrate 11 via an adhesive layer a. Although it is easy to use the thickness used for a normal flexible printed wiring board, such as 18 micrometers or 35 micrometers, as the thickness of the printed wiring layer 12, it shall not be limited to the thickness.
The solder 13 can be a general lead-free solder or a lead-containing solder made of an alloy such as Sn, Ag, or Cu. The solder 13 is preferably one having good heat conductivity in terms of heat dissipation and good heat durability in terms of life and deterioration.
The light emission heat source 14 is specifically various LEDs. Of course, the light emission heat source 14 is intended to emit light and is accompanied by the generation of heat.
The coverlay 15 may be a commonly used coverlay material, such as thin glass or epoxy, in addition to the polyimide and polyester described above. In this embodiment, polyimide is used. In the case of polyimide, the thickness can be the thickness used for a normal flexible printed wiring board, such as 12.5 μm and 25 μm. However, when using a white coverlay, the appearance is good and the reflectance is increased, so that the scattered light from the light-emitting heat source 14 such as an LED can be used effectively, which is preferable for an illumination unit such as an illumination or a backlight.
For the adhesive layer a, for example, an adhesive made of an acrylic resin or an epoxy resin which is a thermosetting type can be used. Since it is used for adhesion to the printed wiring layer 12, it is an insulating adhesive. The thickness can be a thickness generally used for an ordinary flexible printed wiring board, such as 25 μm. The adhesive layer a may be a general epoxy resin or an acrylic resin, or may be a silicone type suitable for ultraviolet use. It can also be used by hot laminating with a hot melt type resin such as a polyimide resin.

As a back surface layer laminated on the back surface side of the flexible insulating base material 11, a plurality of heat diffusion assisting layers 21 and 23 are laminated.
The heat diffusion promoting layers 21 and 23 promote, that is, expand, the area of a heat spot (region where the temperature is higher than the surroundings) transferred from the light emitting heat source 14 to the printed wiring layer 12 through the solder 13 downward. Fulfills the function.
The heat spot transferred from the light emitting heat source 14 to the printed wiring layer 12 through the solder 13 corresponds to the area of the lower surface of the solder 13. It can be said that the lower surface area of the solder 13 is very small compared to the contact surface area between the casing K and the lowermost layer of the back surface layer of the flexible insulating base material 11. When the heat spot of this small area reaches the housing K without becoming too large, the heat radiation efficiency through the housing K is poor, and the temperature of the light emitting heat source 14 and the surrounding flexible substrate module 1 can be preferably lowered. Can not. The area of the heat spot at the time when the heat spot reaches the housing K becomes closer to the contact area between the lowermost layer of the back surface layer of the flexible insulating base material 11 and the housing K. The present inventor has learned that heat dissipation can be maximized as a result of various experiments and thoughts and errors. The thermal diffusion facilitating layers 21 and 23 fulfill the function of rapidly expanding the area of the heat spot.

The thermal diffusion facilitating layer 21 is directly bonded to the immediate back surface of the flexible insulating substrate 11 via the adhesive layer b as the uppermost layer among the back layers laminated on the back surface side of the flexible insulating substrate 11.
The thermal diffusion facilitating layer 21 is intended to increase the area of the heat spot and can be a copper foil. However, even a copper foil is greatly different from a double-sided copper-clad substrate used as a substrate of a conventional flexi printed wiring board. In the conventional double-sided copper-clad substrate, both the front and back copper foils are mainly intended to form a wiring layer, and therefore the thickness of the copper foil is very thin suitable for the production of printed wiring. That is, the copper-clad substrate of the conventional printed wiring board has a thickness of about 35 μm or less even when the copper foil is thick. On the other hand, in the present invention, the thickness of the copper foil exceeds 35 μm because of the role of diffusing the heat of the heat spot. Actually, in this embodiment, the thickness of the copper foil as the thermal diffusion facilitating layer 21 is 70 μm.
The thermal diffusion promoting layer 21 does not necessarily need to use Cu. For the purpose of thermal diffusion, a highly heat conductive metal such as aluminum can be used. In addition, graphite such as natural graphite or artificial graphite can be used, or a carbon fiber material containing long carbon fiber, short carbon fiber, or the like, or other non-metallic high thermal conductivity material can be used.
Since the adhesive layer b of the back surface layer laminated on the back surface side of the flexible insulating base material 11 does not include the printed wiring layer 12 as described above, it does not necessarily require insulation, but rather has high heat dissipation. An adhesive can also be used. As such a high heat dissipation adhesive, a paste containing a high heat dissipation filler such as silver powder, copper powder, AlN powder, diamond powder, Al2O3 powder, and short carbon fiber can be used in a paste form or a sheet form. . For example, if short carbon fibers and AlN powder are mixed, the content of filler can be increased compared to the case of using only short carbon fibers by embedding AlN powder between the short carbon fibers. Can be raised. Of course, the adhesive layer b may be made of the same material as the adhesive layer a.
The adhesive layer b is integrated with the flexible insulating base material 11 or the cover lay 22 when the same material as that of the flexible insulating base material 11 or the cover lay 22 is used for the bonding. It may be in a nonexistent state.

On the other hand, the heat diffusion promoting layer 23 is a highly thermally conductive metal sheet that is in contact with the housing K as the lowest layer among the back layers laminated on the back side of the flexible insulating substrate 11. .
For example, a sheet made of an aluminum material can be used as the high thermal conductivity metal sheet as the thermal diffusion promoting layer 23. Of course, a metal sheet having high thermal conductivity such as copper or silver can be used. As a specific example of the high thermal conductivity metal sheet, for example, pure aluminum (A1) 1.5 mm thick aluminum can be used. Of course, the thickness of the aluminum can be in the range of 0.2 mm to 20 mm, for example. Further, even when the high thermal conductivity metal sheet is a copper sheet, the thickness of the copper foil used for the thermal diffusion promoting layer 21 is, for example, 70 μm, which is thicker, for example, about 0.3 mm to 20 mm. It is possible in the range.
In order to attach the highly thermally conductive metal sheet as the heat diffusion promoting layer 23 to the housing K in a contact surface state, the metal sheet can be attached by bonding via the adhesive layer b. In this case, it is preferable to use a thermosetting adhesive (bonding sheet) as an adhesive and to bond them by hot pressing so that an air layer is not interposed between them. Also, it is preferable to bond the two before mounting the light-emitting heat source 14.
Further, as a method of attaching the high thermal conductivity metal sheet as the heat diffusion promoting layer 23 and the housing K in contact with each other, if both are metal sheets and have good smoothness, attachment by screwing is also possible. . In that case, the adhesiveness of both can be ensured by interposing a cushioning material such as thermal grease or a heat conductive sheet as necessary. In the case of screwing, there is an advantage that the flexible substrate module 1 can be replaced.

In the present embodiment, the thermal diffusion promotion layers 21 and 23 are provided. However, one or more thermal diffusion promotion layers may be interposed therebetween. Thereby, the area of the heat spot can be promoted more quickly.
The heat diffusion facilitating layer 21 is important for quickly transferring a heat spot thermally conducted from the light emitting heat source 14 to the printed wiring layer 12 to the back surface side of the flexible insulating base material 11 with the housing K. And it is important for enlarging the area of a heat spot toward the lower part where the housing | casing K exists.
The heat diffusion promoting layer 23 is important for further expanding and promoting the area of the heat spot that has been transferred to transfer heat to the housing K. In addition, by using the thermal diffusion promoting layer 23 as a metal sheet, it is easy to obtain a flat surface by rolling or the like, and the adhesion between the two can be sufficiently enhanced when contacting and attaching to the housing K. As a result, even in a position directly below the light-emitting heat source 14 where it is difficult to apply pressure, it is possible to ensure good adhesion between the two without air or the like and to obtain good heat dissipation.

The flexible insulating substrate 11, the printed wiring layer 12 on the front surface side, the cover lay 15 thereon, the thermal diffusion promoting layer 21 on the back surface side, and the cover lay 22 covering it, You may make it make it independent as the high heat dissipation flexible printed wiring board H with the adhesive layers a and b interposed between them. In this case, the cover lay 22 covering the heat diffusion promoting layer 21 and the adhesive layer b joining the same protect the copper foil surface from rust in the same manner as the cover lay 15 on the surface side and the adhesive layer a joining the cover lay 15. It is provided as a thing.
When the high heat dissipation flexible printed wiring board H is an independent member, a high heat conductive metal sheet which is a heat diffusion promoting layer 23 is attached to the high heat dissipation flexible printed wiring board H via the adhesive layer b. The flexible substrate module 1 is configured by mounting and mounting the light emitting heat source 14 via the solder 13. The flexible substrate module 1 is attached to the housing K via the adhesive layer b.

In the present invention, the reason why the heat dissipation characteristics are greatly improved by providing the heat diffusion promoting layers 21 and 23 is that the area of the heat spot thermally conducted from the light emitting heat source 14 to the printed wiring layer 12 is promoted in the above case. Said that it was due to That is, the heat dissipation path through the casing K is thereby widened, thereby reducing the thermal resistance and achieving rapid heat dissipation.
The heat generated by the light-emitting heat source 14 such as an LED proceeds while spreading to other members by heat conduction, but the heat conductivity is likely to spread farther. When the thermal conductivity is isotropic, it spreads concentrically. However, by providing the thermal diffusion promoting layers 21 and 23, the heat diffusion is made smoother by the high thermal conductivity, and the casing below Heat is transmitted to K in a wider area. By increasing the area of the heat region reaching the housing K, heat dissipation from a larger heat area is expected. As a result, heat dissipation is promoted, and the temperature near the light emitting heat source 14 is lowered.
As described above, in the flexible substrate module 1 of the present invention, the heat radiation path from the light emission heat source 14 can be sufficiently expanded, and the thermal load applied to the light emission heat source 14, the solder 13, and the substrate can be reduced. .

The case where the flexible substrate module 1 of the present invention is constituted by the high heat dissipation flexible printed wiring board H, the light emission heat source 14 and the heat diffusion promoting layer 23 made of a highly heat conductive metal sheet will be further described.
One or a plurality of light-emitting heat sources 14 can be mounted on the high heat dissipation flexible printed wiring board H.
In this case, as shown in FIG. 2, as a first embodiment of the flexible substrate module 1, a thermal diffusion facilitating layer 23 made of one highly heat conductive metal sheet is provided corresponding to all the light emitting heat sources 14. The high heat dissipation flexible printed wiring board H can be arranged in common.
As shown in FIG. 3, as a second embodiment of the flexible substrate module 1, a heat diffusion assisting layer 23 made of a highly heat conductive metal sheet is formed in a high level corresponding to each of the light emitting heat sources 14. The heat dissipating flexible printed wiring board H can be divided and configured.

A first embodiment of the flexible substrate module 1 will be described with reference to FIG.
First, a highly heat-dissipating flexible printed wiring board H provided with a thermal diffusion promoting layer 21 is prepared, and a thermal diffusion promoting layer 23 made of a highly thermally conductive metal sheet is joined to the back side (A). As described above, the bonding can be performed via the adhesive layer b by hot pressing using a thermosetting adhesive (bonding sheet).
Next, a plurality of light-emitting heat sources 14 are mounted on the surface of the printed wiring layer 12 on the surface side of the highly heat-dissipating flexible printed wiring board H by a surface mounting through a reflow furnace via the solder 13 (B). Thereby, the flexible substrate module 1 is configured.
The obtained flexible substrate module 1 is attached in contact with the housing K (C).

A second embodiment of the flexible substrate module 1 will be described with reference to FIG.
First, a highly heat-dissipating flexible printed wiring board H provided with a heat diffusion promoting layer 21 is prepared, and a heat diffusion promoting layer 23 made of a highly heat conductive metal sheet is divided into a plurality of pieces on the back surface side. Arrange (A). In this case, each of the divided thermal diffusion facilitating layers 23 (high thermal conductivity metal sheet) is arranged with respect to a region corresponding to a region where one or more of the light emission heat sources 14 are to be mounted. Will be. As described above, each of the heat diffusion promoting layers 23 can be bonded through the adhesive layer b by hot pressing using a thermosetting adhesive (bonding sheet).
Next, a plurality of light-emitting heat sources 14 are mounted on the surface of the printed wiring layer 12 on the surface side of the highly heat-dissipating flexible printed wiring board H by a surface mounting through a reflow furnace via the solder 13 (B). In the drawing, one light-emitting heat source 14 is depicted corresponding to one heat diffusion assisting layer 23 (high thermal conductivity metal sheet). However, of course, as described above, a plurality of light-emitting heat sources 14 may correspond to one thermal diffusion promoting layer 23 (high thermal conductivity metal sheet). Thereby, the flexible substrate module 1 is configured.
In the obtained flexible substrate module 1, the thermal diffusion promoting layer 23 (high thermal conductive metal sheet) is divided and attached, so that the individual thermal diffusion promoting layer 23 (high thermal conductive metal sheet) is suitable for bending. Even if it is thick enough, it is possible to easily bend the highly heat-dissipating flexible printed wiring board H at a portion where the thermal diffusion promoting layer 23 is not attached, and to make a three-dimensional configuration. (C).
Therefore, the highly heat-dissipating flexible printed wiring board H can be bent in accordance with the case K having a three-dimensionally bent structure, and each heat diffusion assisting layer 23 (high heat conductive metal sheet) can be used for the case. It can be attached in contact with the body K (D). That is, the flexible substrate module 1 having excellent heat dissipation and mounting a plurality of light emitting heat sources 14 can be easily bent into a three-dimensional shape according to the three-dimensional shape of the casing K, and is in contact with the surface of the casing K. Can be installed in a state.

  In addition, as shown in the flexible substrate module 1 of the said 1st Embodiment, it is the case where the common heat diffusion assistance layer 23 (high heat conductive metal sheet) is attached to the high heat dissipation flexible printed wiring board H. Even if it exists, the flexible substrate module 1 can be made to be able to be bent positively by setting the material and the sheet thickness of the high thermal conductivity metal sheet as the heat diffusion promoting layer 23 to be bendable conditions. For example, in the case where the high thermal conductivity metal sheet that is the thermal diffusion promoting layer 23 is a pure aluminum-based aluminum rolled sheet, the thickness is set to about 0.2 mm to 0.7 mm, so that the contact surface with the housing K can be provided. The flexible substrate module 1 having a suitable flatness and suitable for bending processing following the three-dimensional shape of the housing K can be obtained.

  According to the flexible substrate module of the present invention, industrial applicability is high in the field of manufacturing various lighting units and lighting devices using the units.

DESCRIPTION OF SYMBOLS 1 Flexible substrate module 11 Flexible insulating base material 12 Printed wiring layer 13 Solder 14 Luminous heat source 15 Coverlay 21 Thermal diffusion promotion layer 22 Coverlay 23 Thermal diffusion promotion layer (high thermal conductive metal sheet)
H High heat dissipation flexible printed wiring board K Case a Adhesive layer b Adhesive layer

Claims (2)

  A flexible circuit board module in which a printed wiring layer is formed as a surface layer to be laminated on the surface side of a flexible insulating base material, and a heat source is mounted on the printed wiring layer, and is in contact with a housing to be attached. The heat spot having a surface area larger than the area of the heat spot transferred from the heat source to the printed wiring layer as the back surface layer laminated on the back surface side of the flexible insulating substrate. A plurality of thermal diffusion promotion layers made of a high thermal conductivity material for promoting expansion toward the housing that is the mounting partner, and the thermal diffusion promotion layer is at least the uppermost layer of the back surface layer A thermal diffusion facilitating layer that is directly bonded to the back surface of the flexible insulating substrate as a layer, and the bottom layer of the back surface layer as the bottom layer with respect to the housing A flexible printed wiring board comprising a heat diffusion promoting layer made of a highly thermally conductive metal sheet that is in contact with the surface, and a thermal diffusion promoting layer that is the uppermost layer of the back surface layer, the flexible insulating substrate, and the printed wiring layer The flexible printed wiring board has a plurality of heat sources mounted thereon, and the high thermal conductive metal sheet is divided and arranged corresponding to each of one to a plurality of heat sources. Board module. The flexible substrate module according to claim 1, wherein the housing is a housing of a lighting unit.

Images