JP6564615B2 - Lighting device - Google Patents

Description

  The present invention relates to an illumination device using a semiconductor light emitting element such as a light emitting diode (LED) element.

  Recently, with the improvement of the light output of light emitting diode (LED) elements, application to applications requiring higher luminance such as outdoor lighting has progressed, and the path of higher power has been followed. On the other hand, in the LED element, about 70% of the input electric power becomes heat, and the own heat causes a decrease in performance and a shortened life. Therefore, the illuminating device using an LED element requires an appropriate heat dissipation structure.

  A conventional lighting device having a heat dissipation structure includes a metal base printed wiring board on which LED elements are mounted (die attach) via an insulating layer, and a highly heat conductive ceramic substrate provided on the back surface of the metal base printed wiring board. And a heat sink provided on the back surface of the ceramic substrate for convection and radiation of heat (refer to Patent Document 1).

JP 2011-96416 A

  However, in the conventional lighting device described above, for the purpose of ensuring the adhesion between the ceramic substrate and the heat sink, it is necessary to perform a microscopic surface processing of the installation surface to suppress the surface roughness of the installation surface of the ceramic substrate, There is a problem that the manufacturing cost is high. In addition, if the metal-based printed wiring board is formed with an insulating layer highly filled with an inorganic filler for improving heat dissipation characteristics, a high-life mold is required for press punching, which increases the manufacturing cost. . Further, when high thermal conductivity aluminum nitride is used as the ceramic substrate, the ceramic substrate is expensive to manufacture.

  Further, the above-described conventional lighting device requires an insulating layer immediately below the LED element for the metal-based printed wiring board. Therefore, as shown in FIG. 16, the thermal resistance due to the insulating layer cannot be ignored. There is also a problem that the radiation characteristics are degraded. In FIG. 16, since the adhesive layer is inserted between the ceramic substrate and the heat sink, the thermal resistance of the adhesive device as a whole is increased by adding the thermal resistance of the adhesive layer to the thermal resistance of the insulating layer. It is getting bigger.

In order to solve the above-described problems, a lighting device according to the present invention includes a semiconductor light emitting element, a columnar part having an element mounting surface on which the semiconductor light emitting element is directly or indirectly mounted, and a flange shape having a larger lateral size than the columnar part. A heat spreader formed by combining the fitting portions, an organic resin printed wiring board having a through-hole into which the columnar portion is inserted, a counterbored portion in which the fitting portion is inserted, and a frustum-like standing portion facing the counterbored portion The frustum-like standing portion is a die-casting extrusion base of the heat sink . Accordingly, the frustum-like standing portions of the semiconductor light emitting element, the heat spreader, and the heat sink are arranged on a straight line.

  According to the present invention, the heat of the semiconductor light-emitting element propagates to the heat sink through the heat spreader having good thermal conductivity without passing through the insulating layer, so that the heat resistance can be reduced by the heat spreader having the fitting portion (flange portion). The heat dissipation characteristics can be improved by heat convection and radiation effect by the frustum-like standing portion of the heat sink linearly connected to the heat spreader.

Embodiments of a lighting device according to the present invention are shown, in which (A) is a top view, (B) is a side view, and (C) is a bottom view. It is for demonstrating the heat spreader preparation process of the manufacturing method of the illuminating device of FIG. 1, (A) is a top view, (B) is a side view. It is for demonstrating the LED element die-attach process of the manufacturing method of the illuminating device of FIG. 1, (A) is a top view, (B) is a side view. It is sectional drawing for demonstrating the heat sink formation process of the manufacturing method of the illuminating device of FIG. It is sectional drawing for demonstrating the heat sink finishing process of the manufacturing method of the illuminating device of FIG. It is sectional drawing for demonstrating the heat spreader joining process of the manufacturing method of the illuminating device of FIG. It is sectional drawing for demonstrating the organic resin printed wiring board processing process of the manufacturing method of the illuminating device of FIG. It is sectional drawing for demonstrating the organic resin printed wiring board assembly process of the manufacturing method of the illuminating device of FIG. It is sectional drawing for demonstrating the light emission part completion process of the manufacturing method of the illuminating device of FIG. It is sectional drawing for demonstrating the condition of the heat flow of the illuminating device of FIG. It is a graph which shows the thermal resistance / heat capacity (thermal structure function) characteristic of the illuminating device of FIG. It is sectional drawing which shows the example of a change of the light emission part of FIG. It is sectional drawing which shows the other example of a change of the light emission part of FIG. It is sectional drawing which shows the example of a change of the organic resin printed wiring board of FIG. It is sectional drawing which shows the example of a change of the junction part of the insertion part of the heat spreader of FIG. 1, and a heat sink. It is a graph which shows the thermal resistance / heat capacity (thermal structure function) characteristic of the conventional illuminating device.

  1A and 1B show an embodiment of a lighting device according to the present invention. FIG. 1A is a top view, FIG. 1B is a side view, and FIG. 1C is a bottom view.

  In FIG. 1, the heat spreader 1 includes a columnar portion 11 and a flange-like fitting portion 12. The LED element 2 is mounted on the element mounting surface 11 a of the columnar part 11. The heat sink 3 includes a frustum-like standing portion (extrusion base) 3b having an ejector pin mark 3a and die radiating fins 3c at the time of die casting. In this case, the frustum-like standing portion 3b is formed so as to be connected by the radiation fin 3c. The upper surface of the heat sink 3 is bonded to the organic resin printed wiring board 5 by the adhesive layer 4. A control circuit board 6 is mounted on the organic resin printed wiring board 5.

  Counterbores 4d and 4d 'are formed on the upper surface of the heat sink 3. The insertion part 12 of the heat spreader 1 is inserted into the counterbore part 4d. The counterbore 4d 'is for suppressing heat from the LED element 2 from propagating to the control circuit board 6.

  Further, a through hole 5 a is formed in the organic resin printed wiring board 5. The columnar portion 11 of the heat spreader 1 is inserted into the through hole 5a.

  In FIG. 1, 8 is a bonding wire, 9 is a dam, 10 is a translucent sealing resin layer, and constitutes a light emitting portion including the LED element 2.

  In FIG. 1, the heat from the LED element 2 propagates directly to the heat sink 3 via the heat spreader 1 without passing through the insulating layer. The heat of the heat sink 3 immediately below the heat spreader 1 is dissipated by convection and radiation by the frustum-like standing portion 3b immediately below the heat spreader 1.

  A method of manufacturing the lighting device of FIG. 1 will be described with reference to FIGS.

First, referring to FIG. 2, a heat spreader 1 made of copper is prepared in a heat spreader preparation step. The heat spreader 1 includes a columnar portion 11 having an element mounting surface 11a and a flange-like fitting portion (flange portion) 12 on the bottom surface of the columnar portion 11. The thermal diffusion characteristics are improved by the presence of the fitting portion 12 having a lateral size D2 larger than the lateral size D1 of the columnar portion 11. The heat spreader 1 is plated with gold, silver palladium or the like.

  Next, referring to FIG. 3, in the LED element die attaching step, the LED element 2 is die attached to the element mounting surface 11 a of the heat spreader 1 by Au—Sn eutectic bonding (not shown). In this case, if necessary, a stress relaxation agent such as molybdenum foil may be laminated just below the die attach surface by diffusion bonding or the like.

  Next, referring to FIG. 4, in the heat sink formation step, the heat sink 3 made of aluminum alloy or the like is formed by a die casting method. At this time, the frustum-like standing portion (extrusion base) 3b having the ejector pin marks 3a is formed. This frustum-like standing portion 3b is formed so as to overlap with the radiation fin 3c (see FIG. 1).

  Next, referring to FIG. 5, in the heat sink finishing process, a counterbore portion 3 d corresponding to the fitting portion 12 of the heat spreader 1 and a counterbore portion 3 d ′ corresponding to the control circuit board 6 described later are formed by counterbore processing using a flat end mill. Form. The surface roughness of the heat sink 3 in the case of die casting is about 12.5 s. However, the surface roughness of the counterbored portions 3d and 3d ′ is set to about 1.6 s by counterboring using a flat end mill, and the heat spreader 1 and the heat sink 3 And improve thermal conductivity. In the case of a conventional metal-based printed wiring board, a finishing process using a flat end mill is low in manufacturing cost compared to the case where a contact surface of a heat sink is required to have a mirror finish.

  Next, referring to FIG. 6, in the heat spreader joining step, the fitting portion 12 of the heat spreader 1 of FIG. 3 is inserted into the sagging portion 3 d of the heat sink 3 of FIG. 5 and bonded by the high thermal conductive adhesive layer 7. As the high thermal conductive adhesive layer 7, for example, a high heat resistant ceramic adhesive containing fine powder of aluminum nitride is used. In the case of a conventional metal base printed wiring board, an expensive thermal conductive sheet is inserted between the adhesive surface of the metal base printed wiring board and the heat sink, and the warp of the metal base printed wiring is further performed. The manufacturing cost is high because it is necessary to apply a uniform pressure while correcting the above.

  Next, referring to FIG. 7, in the organic resin printed wiring board processing step, the through hole 5 a for the heat spreader 1 is opened in the organic resin printed wiring board 5 and the control circuit board 6 is mounted.

  Next, referring to FIG. 8, in the organic resin printed wiring board assembly process, the heat spreader 1 of FIG. 6 is inserted into the organic resin printed wiring board 5 of FIG. 7 in which the through hole 5a is formed and the control circuit board 6 is mounted. The heat sink 3 is adhered by an adhesive layer 4. At this time, the columnar portion 11 of the heat spreader 1 is inserted into the through hole 5 a of the organic resin printed wiring board 5. As the adhesive layer 4, a silicone epoxy sheet adhesive is used.

Finally, referring to FIG. 9, a bonding wire 8 is provided between the pad of the LED element 2 and the wiring pattern of the organic resin printed wiring board 5 in the light emitting unit completion process. Next, a ring-shaped dam 9 is formed by a dispenser so as to surround the LED element 2 and the bonding wire 8. The dam 9 is made of a high aspect ratio silicone high thixotropic resin. Then, it sealed with translucent sealing resin layer 10 by instillation of silicone resin or Epokiji resin inside the dam 9. Thereby, the illuminating device of FIG. 1 is completed.

  FIG. 10 is a view for explaining propagation of heat flow in the irradiation apparatus of FIG.

The heat flow Q _d generated in the LED element 2 spreads through the columnar portion 11 of the heat spreader 1 and propagates to the fitting portion 12 of the heat spreader 1. At this time, the heat flow _Qcs propagated to the organic resin printed wiring board 5 due to the interfacial thermal resistance and the low heat temperature of the organic resin printed wiring board 5 is very small.

Heat flow Q _d propagating in the fitting portion 12 of the heat spreader 1 is divided into the fitting portion 12 and the large vertical heat flow by thermal diffusion to 2π space by the high thermal conductive adhesive layer 7 Q _u and horizontal heat flow Q _s. Since the heat spreader 1 and the frustum-like standing portion 3b of the heat sink 3 are arranged linearly facing each other, the heat flow _Qu is increased. At this time, if the diameter of the root portion of the frustum-like standing portion 3b is increased, the heat flow _Qu is further increased. Heat flow Q _u propagated to the tip portion from the base portion of the frustum-shaped erected portion 3b convection, is dissipated by radiation effect. On the other hand, although the heat flow Q _s diffusing perpendicular to the heat flow Q _d is small, it is radial when viewed from above the irradiation device, and is dissipated by the convection and radiation effect of the radiation fins 3c, and is totally dissipated by the diffusion effect. The effect of heat diffusion is great.

The partial heat flow Q _t of the heat flow Q _s also propagates directly under the control circuit board 6, but the heat flow Q _r to the control circuit board 6 becomes very small due to the presence of the counterbore portion 3d ′. As a result, the propagation of heat from the LED element 2 to the control circuit board 6 is suppressed.

  FIG. 11 is a graph showing the thermal resistance / heat capacity (thermal structure function) characteristics of the irradiation apparatus of FIG. As shown in FIG. 11, the heat from the LED element 2 propagates directly to the heat sink 3 via the heat spreader 1 without passing through the insulating layer, so that the thermal resistance becomes very small as compared with the conventional case. Therefore, the heat spreader 1 absorbs the rapid heat generation of the LED element 2, and the rapid deterioration of the device and the occurrence of an accident due to the application of a large current such as a surge are reduced.

Figure 12 is a sectional view showing a modification of the light emission portion of Fig.

  In the first modification shown in FIG. 12A, the LED element 2 is mounted on the heat spreader 1 via a submount 21 made of ceramic on which a metallized pattern is formed. In this case, electrodes are formed on the front and back of the LED element 2, and the bonding wire 8 is also provided on the submount 21.

  In the second modified example shown in FIG. 12B, the electrode pattern is formed on the front and back of the LED element 2, and the electrode pattern is formed on the element mounting surface 11 a of the columnar portion 11 of the heat spreader 1. In this case, the bonding wire 8 is also provided on the heat spreader 1. However, an insulating layer 22 that electrically insulates the bottom surface of the fitting portion 12 of the heat spreader 1 is provided.

In the third modification shown in FIG. 12C, the LED element 2 is an LED package 24 with a copper core 23, and the electrode terminals 25 are spot welded onto the organic resin printed wiring board 5. In this case, the copper core 23 is not electrically connected.

  FIG. 13 is a cross-sectional view showing another modification of the light emitting section of FIG. In FIG. 13, the LED element 2 with the electrode and heat dissipation terminal 26 is used as the LED element 2. In this case, a part of the electrode / heat radiating terminal 26 is spot welded to the columnar portion 11 of the heat spreader 1, while the other part of the electrode / heat radiating terminal 26 is spot welded to the organic resin printed wiring board 5. In this case, an insulating layer 27 or the like is required between the fitting portion 12 of the heat spreader 1 and the heat sink 3.

  As described above, the LED element 2 is indirectly mounted via the copper core 23 or the electrode terminal 25 in addition to being directly mounted on the upper surface of the columnar portion 11 of the heat spreader 1.

  FIG. 14 is a cross-sectional view showing a modified example of the organic resin printed wiring board. In FIG. 14, the organic resin printed wiring board 5 is a three-dimensional organic resin printed wiring board 5 ′. The three-dimensional organic resin printed wiring board 5 ′ has a reflection frame 51 ′ around the LED element 2, and holds a lens 52 ′ on the reflection frame 51 ′.

  FIG. 15 is a cross-sectional view showing a modified example of the joint portion between the fitting portion 12 and the heat sink 3 of the heat spreader 1 of FIG. In FIG. 15, a high heat resistant resin insulating thin film sheet 28 made of polyimide is inserted between the high heat conductive adhesive layer 7 having an insulating property of about 8 kV / cm (= 200 V / mil) and the heat sink 3. The polyimide high heat-resistant resin insulating thin film sheet 27 has a thickness of about 12.7 μm (= 0.5 mil) and a thermal resistance of 1 ° C./W or less. In this case, the side wall of the sagging portion 3d is tapered to enhance the adhesive holding force of the high thermal conductive adhesive layer 7. If arc resistance is required for the high heat-resistant insulating thin film sheet 27, peel-off mica may be selected.

  The LED element 2 in the above-described embodiment can be replaced with another semiconductor light emitting element such as a laser diode (LD) element.

  The present invention can be applied to any changes within the obvious range of the above-described embodiment.

  The illuminating device according to the present invention can be used for an infrared radiation unit such as a night vision camera and a distance image forming camera, in particular, an illuminating device that requires variations in small-lot production and light source design.

1: Heat spreader 11: columnar part 11a: element mounting surface 12: fitting part 2: LED element 3: heat sink 3a: ejector pin mark 3b: frustum-shaped solid part (extrusion base)
3c: Radiation fins 3d, 3d ': Counterbore part 4: High thermal conductive adhesive layer 5: Organic resin printed wiring board 5': Three-dimensional organic resin printed wiring board 51 ': Reflective frame 52': Lens 5a: Through hole 6: the control circuit board 7: adhesive layer 8: bonding wire 9: dam 10: translucent sealing resin layer 21: submount 22: insulating layer 23: copper core 24: LED package 25: electrode terminal 26: an electrode and heat radiation terminals 27 : Insulating layer 28: High heat resistant resin thin film sheet

Claims (6)

A semiconductor light emitting device;
A heat spreader formed by coupling a columnar part having an element mounting surface on which the semiconductor light emitting element is directly or indirectly mounted, and a flange-shaped fitting part having a larger lateral size than the columnar part;
An organic resin printed wiring board having a through-hole into which the columnar part is inserted;
A heat sink having a first counterbore part into which the fitting part is inserted and a frustum-like standing part facing the first counterbore part ;
The frustum-like standing portion is an illuminating device that is a die-cast extrusion base of the heat sink . And a control circuit board mounted on the organic resin printed wiring board.
The lighting device according to claim 1, wherein the heat sink has a second counterbore portion facing the control circuit board.   Furthermore, the illuminating device of Claim 1 which comprises the highly heat conductive adhesive layer provided between the said fitting part and the said heat sink. Furthermore, the illuminating device of Claim 3 which comprises the high heat-resistant resin insulating layer provided between the said high heat conductive adhesive layer and the said heat sink.   The lighting device according to claim 1, wherein a side wall of the first counterbore portion is tapered.   The lighting device according to claim 1, wherein the organic resin printed wiring board is a three-dimensional organic resin printed wiring board.

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