Wiring board and LED module

Abstract

A wiring board according to the present invention comprises: a substrate having a first surface and a second surface positioned on the opposite side from the first surface; an aluminum film positioned above the first surface; and one or more first metal films positioned above the aluminum film, the first metal film including an electrode film on which a light-emitting element is mounted.

Description

Wiring board and LED module

[0001] The present disclosure relates to a wiring board and an LED (Light Emitting Diode) module.

[0002] Japanese Patent Application Laid-Open No. 2008-177445 describes a wiring board that aims to effectively dissipate heat and increase the amount of light emitted in an LED module.

[0003] The wiring board according to the present disclosure comprises a substrate having a first surface and a second surface located opposite the first surface, an aluminum film located above the first surface, and one or more metal films located above the aluminum film, wherein the metal film includes an electrode film on which a light-emitting element is mounted.

[0004] An LED module according to the present disclosure includes the above wiring board and an LED mounted on the wiring board.

[0005] 2A is a plan view showing a wiring substrate according to an embodiment of the present disclosure; FIG. 2B is a longitudinal sectional view showing an LED module according to an embodiment of the present disclosure; FIG. 2C is an enlarged view of a portion C1 of FIG. 2A; and FIG. 2D is a graph showing the relationship between the wavelength of light and the reflectance of various metal films.

[0006] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Hereinafter, the up and down directions may be used to describe various components. "Up" refers to a direction perpendicular to the first surface S11a of the substrate 11 and facing from the second surface S11b toward the first surface S11a. This direction may differ from the direction in which the wiring substrate 10 and the LED (Light Emitting Diode) module 100 are used. In the following description, the term "metal name" + "film" refers to a film whose main component is the metal of the metal name. "Main component" refers to a component that accounts for 80% or more by mass. In the following description, when referring to a planar perspective, it refers to a perspective view from above.

[0007] Fig. 1 is a plan view showing a wiring substrate 10 according to an embodiment of the present disclosure. Fig. 2A is a longitudinal cross-sectional view showing an LED module 100 according to an embodiment of the present disclosure. Fig. 2B is an enlarged view of a portion C1 of Fig. 2A. Fig. 2A shows the longitudinal cross-section of the wiring substrate 10 taken along line A-A in Fig. 1.

[0008] The wiring substrate 10 according to the embodiment of the present disclosure may be a substrate on which the light emitting element 110 is mounted. The wiring substrate 10 may include a substrate 11 that is an insulator. The substrate 11 may have a first surface S11a that is an upper surface and a second surface S11b that is a lower surface. The substrate 11 may be made of aluminum nitride (AlN) or silicon nitride (Si ３ N ４ ) as a main component.

[0009] The wiring substrate 10 may further include an aluminum film 12 located above the first surface S11a, one or more first metal films 13 located above the aluminum film 12, and a second titanium film 14 located between the aluminum film 12 and the first surface S11a.

[0010] The wiring board 10 may further include via conductors 21 and inner layer conductors 22 located on the board 11, and a second metal film 15 located below the second surface S11b. The via conductors 21 and inner layer conductors 22 may be located from the first surface S11a to the second surface S11b, and may be configured to electrically connect the second metal film 15 on the second surface S11b side to the first metal film 13 on the first surface S11a side.

[0011] The first surface S11a of the substrate 11 may include a plurality of regions R1 and R2 (see FIGS. 1 and 2A), and the structure on the first surface S11a of the substrate 11 may be divided into a plurality of parts. The "structure on the first surface S11a" refers to the second titanium film 14, the aluminum film 12, and the first metal film 13. Each of the divided parts may be located in each of the plurality of regions R1 and R2. With this structure, the first metal film 13 located in region R1 and the first metal film 13 located in region R2 are non-conductive at least on the first surface S11a.

[0012] The second surface S11b of the substrate 11 may include a plurality of regions R11 and R12, and the second metal film 15 below the second surface S11b may be divided into a plurality of parts, each of which may be located in one of the plurality of regions R11 and R12. With this configuration, the second metal film 15 located in the region R11 and the second metal film 15 located in the region R12 are not electrically connected at least below the second surface S11b.

[0013] The wiring board 10 may have a plurality of sets of via conductors 21 and inner layer conductors 22 along a plurality of wiring paths that are not electrically connected to one another. The set of via conductors 21 and inner layer conductors 22 along a first wiring path may electrically connect the first metal film 13 on a region R1 of the first surface S11a to the second metal film 15 below a region R11 of the second surface S11b. Similarly, the set of via conductors 21 and inner layer conductors 22 along a second wiring path may electrically connect the first metal film 13 on a region R2 of the first surface S11a to the second metal film 15 in a region R12 of the second surface S11b.

[0014] The via conductor 21 may be mainly composed of a high-melting-point metal such as tungsten (W), and may be formed by co-firing the via conductor 21 and the substrate 11. A high-melting-point metal means a metal having a melting point of 2000° C. or higher.

[0015] The substrate 11 may have a laminated structure having a plurality of layers 11 a and 11 b. The substrate 11 may have a configuration in which a plurality of stacked green sheets are integrated by firing, and the plurality of layers 11 a and 11 b may correspond to the layers of the plurality of green sheets before firing.

[0016] The via conductors 21 do not necessarily have to be linearly connected across the multiple layers 11a and 11b, but rather the via conductors 21 located on the layer 11a and the via conductors 21 located on the layer 11b may be positioned so as not to overlap when viewed from above, and the via conductors 21 located on the layer 11a and the via conductors 21 located on the layer 11b may be connected via the inner layer conductor 22. With this configuration, even if a void occurs between the via conductor 21 on the layer 11a and the via conductor 21 on the layer 11b, the inner layer conductor 22 interposed between the two via conductors 21 can prevent the void from migrating from the first surface S11a to the second surface S11b. Therefore, when the upper and lower spaces of the substrate 11 are different, such as when the upper part of the substrate 11 is sealed in an airtight space, the airtightness between the upper and lower spaces can be improved.

[0017] The aluminum film 12 may have a larger area than the electrode film 13a described below. That is, the aluminum film 12 may include a region R21 where the second metal film 15 is located and a region R22 where the second metal film 15 is not located. An aluminum oxide film 16 may be located in the region R22 above the aluminum film 12 where the second metal film 15 is not located.

[0018] 2B , the plurality of first metal films 13 may include an electrode film 13a on which a light-emitting element is mounted, and a conductor film 13b located between the electrode film 13a and the aluminum film 12. The conductor film 13b may include a platinum (Pt) film 13b2 serving as a barrier layer located below the electrode film 13a, and a first titanium (Ti) film 13b1 serving as an adhesive layer located on the aluminum film 12. The electrode film 13a may be a gold (Au) film 13a1, or a film in which a gold-tin (AuSn) film 13a2 is located on the gold (Au) film 13a1.

[0019] <Details of Second Metal Film 15> The second metal film 15 located on the second surface S11b may be a film formed by stacking, from top to bottom, a titanium (Ti) film 15a, a nickel chromium (NiCr) film 15b, a gold (Au) film 15c, a nickel (Ni) film 15d, and a gold (Au) film 15e.

[0020] <Effects of Wiring Board 10> As described above, the wiring board 10 of this embodiment includes the aluminum film 12 located above the first surface S11a of the substrate 11 and the first metal film 13 located above the aluminum film 12, and the first metal film 13 includes the electrode film 13a on which the light-emitting element 110 is mounted. Therefore, a portion of the output of the light-emitting element 110 can be reflected by the aluminum film 12 and sent outward. This increases the amount of light output from the light-emitting element 110 to the outside (upward in the example of FIG. 2A ).

[0021] Furthermore, according to the wiring board 10 of this embodiment, the first metal film 13 includes an electrode film 13a and a conductor film 13b electrically connected to the electrode film 13a. The wiring board 10 further includes an aluminum oxide film 16 located above the aluminum film 12 in a region R22 where the electrode film 13a and the conductor film 13b are not located. Therefore, the aluminum film 12 extends to both the region R21 where the electrode film 13a and the conductor film 13b are located and the region R22 where they are not located, allowing for a larger area of ​​the aluminum film 12 to be employed. This allows the aluminum film 12 to reflect the output of the light-emitting element 110 over a wider range. Furthermore, the aluminum oxide film 16 protects the aluminum film 12 in the region where the electrode film 13a and the conductor film 13b are not located. This allows the aluminum film 12 in the region R22 to maintain its aluminum metal properties for a long period of time. This reduces deterioration of the light reflection characteristics throughout the entire area of ​​the aluminum film 12, and maintains the effect of increasing the amount of light irradiated to the outside through reflection by the aluminum film 12 for a long period of time.

[0022] Furthermore, according to the wiring substrate 10 of this embodiment, the first metal film 13 includes a first titanium (Ti) film 13b1 located between the electrode film 13a and the aluminum film 12. The first titanium film 13b1 provides high bonding strength between the aluminum film 12 and the electrode film 13a, thereby improving the reliability of the wiring substrate 10.

[0023] Furthermore, according to the wiring board 10 of this embodiment, the aluminum film 12 is divided into multiple pieces on the first surface S11a, thereby reducing the possibility that multiple sets of electrode films 13a or conductor films 13b that are not conductive to each other will become conductive through the aluminum film 12.

[0024] Furthermore, according to the wiring substrate 10 of this embodiment, the substrate 11 is made of ceramic and further includes a second titanium (Ti) film 14 located between the aluminum film 12 and the first surface S11a. The second titanium film 14 provides high bonding strength between the ceramic substrate 11 and the aluminum film 12. This improves the reliability of the wiring substrate 10.

[0025] Furthermore, according to the wiring board 10 of this embodiment, the substrate 11 is made of ceramics and can employ aluminum nitride as its main component. By employing aluminum nitride, the heat dissipation of the light emitting element 110 can be improved.

[0026] Furthermore, according to the wiring board 10 of this embodiment, the via conductor 21 is provided which is located within the substrate 11 from the first surface S11a to the second surface S11b, and therefore the current required to drive the light-emitting element 110 can be supplied between the first surface S11a and the second surface S11b of the substrate 11 via the via conductor 21.

[0027] Furthermore, the wiring board 10 of this embodiment further includes a second metal film 15 located below the second surface S11b. The wiring board 10 may further include an aluminum film located below the second surface S11b. The aluminum film may be bonded to the second surface S11b via a titanium film, or the second metal film 15 may be located below the aluminum film. Light output from the light-emitting element 110 to the wiring board 10 may be transmitted through the substrate 11. The aluminum film below the second surface S11b reflects light transmitted through the substrate 11 by the aluminum film on the second surface S11b at a location that does not overlap with the aluminum film 12 on the first surface S11a in a plan view, thereby further increasing the amount of light irradiated to the outside.

[0028] <Configuration of LED Module> The LED module 100 according to an embodiment of the present disclosure may include a wiring substrate 10 and a light-emitting element 110 mounted on the wiring substrate 10. The light-emitting element 110 may be an LED. Furthermore, the light-emitting element 110 may have two electrodes and be mounted on the wiring substrate 10 such that one electrode is bonded to the electrode film 13a in the region R1 and the other electrode is bonded to the electrode film 13a in the region R2, as shown in FIG. 2A . The bonding may be via a conductive bonding material such as solder. The LED module 100 may be configured such that the configuration on the first surface S11a of the substrate 11, including the light-emitting element 110, is sealed in an airtight space.

[0029] 2A, in addition to the light output from the light-emitting element 110 toward the outside of the module (e.g., upward), the LED module 100 also outputs light from the light-emitting element 110 toward the wiring substrate 10, which is reflected by the aluminum film 12 and then output toward the outside of the module. This allows the LED module 100 to emit a large amount of light toward the outside. In FIG. 2A, the light output from the light-emitting element 110 is represented by a thick chain line.

[0030] The light-emitting element 110 may be an LED having a characteristic of mainly outputting light in the ultraviolet region. Mainly emitting light in a certain wavelength region means that the amount of light in that wavelength region is greater than the amount of light in other wavelength regions. The light output by the light-emitting element 110 having the above characteristics may include visible light. Light in the ultraviolet region is highly transparent to thin films, etc. Therefore, a relatively large proportion of the light output from the light-emitting element 110 having the above characteristics is output toward the wiring substrate 10. Therefore, by reflecting light through the aluminum film 12, the total amount of light output outside the module can be further increased.

[0031] The light emitting element 110 may be an LED that mainly emits UV-C light. UV-C refers to light in the wavelength range of 200 nm to 280 nm. Figure 3 is a graph showing the relationship between the wavelength of light and the reflectance of various metal films. In the graph, the UV-C wavelength range is indicated by shading. As shown in the graph, many objects have low reflectance of UV-C, but aluminum (Al) has high reflectance of UV-C.

[0032] Therefore, by having the aluminum film 12 on the wiring substrate 10 of the LED module 100, of the UV-C mainly output from the light emitting element 110, the light output toward the wiring substrate 10 can be reflected with high reflectivity by the aluminum film 12 toward the outside of the module, thereby increasing the amount of UV-C light irradiated toward the outside of the module.

[0033] The above describes the embodiments of the present disclosure. However, the wiring board and LED module of the present disclosure are not limited to the above embodiments. The details shown in the embodiments can be modified as appropriate without departing from the spirit of the invention.

[0034] An embodiment of the present disclosure is described below: (1) A wiring substrate includes: a substrate having a first surface and a second surface located opposite to the first surface, an aluminum film located above the first surface, and one or more first metal films located above the aluminum film, wherein the first metal film includes an electrode film on which a light-emitting element is mounted.

[0035] (2) The wiring board of (1) above is characterized in that the first metal film includes the electrode film and a conductor film electrically connected to the electrode film, and further includes an aluminum oxide film located above the aluminum film in an area where the electrode film and the conductor film are not located.

[0036] (3) In the wiring board of (1) or (2) above, the first metal film includes a first titanium (Ti) film located between the electrode film and the aluminum film.

[0037] (4) In the wiring board according to any one of (1) to (3), the aluminum film is divided into a plurality of pieces on the first surface.

[0038] (5) In the wiring substrate of any one of (1) to (4) above, the substrate is made of ceramics, and a second titanium (Ti) film is provided between the aluminum film and the first surface.

[0039] (6) In the wiring substrate according to any one of (1) to (5) above, the light emitting element mounted on the electrode film mainly emits light in the ultraviolet region.

[0040] (7) In the wiring board according to any one of (1) to (6), the light-emitting element mainly outputs UV-C.

[0041] (8) In the wiring substrate of any one of (1) to (7) above, the substrate is made of ceramics, and the main component of the substrate is aluminum nitride.

[0042] (9) The wiring board according to any one of (1) to (8) above includes a via conductor located within the board across from the first surface to the second surface.

[0043] (10) The wiring board according to any one of (1) to (9) above further comprises a second metal film located below the second surface.

[0044] In one embodiment, (11) an LED module includes: a wiring board according to any one of (1) to (10) above; and an LED mounted on the wiring board.

[0045] The present disclosure can be used for wiring boards and LED modules.

[0046] REFERENCE SIGNS LIST 10 Wiring substrate 11 Substrate S11a First surface S11b Second surface 12 Aluminum film R21, R22 Region 13 First metal film 13a Electrode film 13a1 Gold film 13a2 Gold-tin film 13b Conductor film 13b1 First titanium film 13b2 Platinum film 14 Second titanium film 15 Second metal film 15a Titanium film 15b Nickel-chromium film 15c Gold film 15d Nickel film 15e Gold film 16 Aluminum oxide film 21 Via conductor 22 Inner layer conductor 100 LED module 110 Light-emitting element

Claims

1. A wiring board comprising: a substrate having a first surface and a second surface located opposite the first surface; an aluminum film located above the first surface; and one or more first metal films located above the aluminum film, wherein the first metal film includes an electrode film on which a light-emitting element is mounted.

2. The wiring board according to claim 1, wherein the first metal film includes the electrode film and a conductor film electrically connected to the electrode film, and further includes an aluminum oxide film located above the aluminum film in an area where the electrode film and the conductor film are not located.

3. The wiring board according to claim 1 or 2, wherein the first metal film includes a first titanium (Ti) film located between the electrode film and the aluminum film.

4. The wiring board according to any one of claims 1 to 3, wherein the aluminum film is divided into a plurality of pieces on the first surface.

5. The wiring board according to any one of claims 1 to 4, wherein the substrate is made of ceramics and includes a second titanium (Ti) film located between the aluminum film and the first surface.

6. The wiring board according to any one of claims 1 to 5, wherein the light emitting element mounted on the electrode film mainly outputs light in the ultraviolet region.

7. The wiring board according to any one of claims 1 to 6, wherein the light emitting element mainly outputs UV-C.

8. The wiring board according to any one of claims 1 to 7, wherein the substrate is made of ceramics and the main component of the substrate is aluminum nitride.

9. The wiring board according to any one of claims 1 to 8, comprising a via conductor located within the board from the first surface to the second surface.

10. The wiring board according to any one of claims 1 to 9, further comprising a second metal film located below the second surface.

11. An LED module comprising: a wiring board according to any one of claims 1 to 10; and an LED mounted on the wiring board.

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