Light emitting device

Abstract

To provide a light emitting device in which a protective film can be placed on the surface opposite the mounting surface of a wire.SOLUTION: A light emitting device 1 comprises: a substrate 10 on which wiring patterns 11 and 12 are formed; light emitting elements 15 mounted on the substrate 10; wires 16 connecting the light emitting element 15 to the wiring patterns 11 and 12; a first protective film 24 containing a translucent organic material and arranged to cover the surface of the wire 16 facing the substrate 10; and a second protective film 25 formed of a translucent metal oxide and positioned to cover the surface of the wire 16 opposite the substrate 10.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a light emitting device. [Background technology]

[0002] Various techniques are known for improving the reliability of light-emitting devices that use light-emitting diode (LED) dies as light-emitting elements. The light-emitting device described in Patent Document 1 can prevent corrosion of wires connected to light-emitting elements mounted on the mounting surface of a substrate by covering the wires with a protective film made of silica. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-126743 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the light-emitting device described in Patent Document 1, the protective film is placed around the wire after it is connected to the light-emitting element, because if the protective film is placed around the wire before it is connected to the light-emitting element, the flexibility of the wire will decrease. However, with the progress of miniaturization of light-emitting devices, the distance between the mounting surface of the board and the wire is decreasing, and it is not easy to place a protective film on the surface opposite the mounting surface of the wire connected to the light-emitting element.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to solve the above-mentioned problems and to provide a light-emitting device that can provide good protection for the wires from above and below using different types of materials. [Means for solving the problem]

[0006] The light-emitting device of the present invention comprises a substrate on which a wiring pattern is formed, a light-emitting element mounted on the substrate, a wire connecting the light-emitting element and the wiring pattern, a first protective film containing a light-transmitting organic material and arranged to cover the surface of the wire facing the substrate, and a second protective film formed from a light-transmitting metal oxide and arranged to cover the surface of the wire opposite the substrate.

[0007] In the light emitting device according to the present invention, the first protective film preferably covers the substrate and connects the substrate to the wire. Effect of the Invention

[0008] In the light emitting device according to the present invention, different types of materials can provide good protection for the wires from above and below. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2A is a plan view of a light emitting device according to an embodiment, and FIG. 2B is a cross-sectional view taken along line AA shown in FIG. [Diagram 2] 1(a) is a partially enlarged view of the area surrounded by dashed line B in FIG. 1(b), and (b) is a partially enlarged view of the area surrounded by dashed line B where no wires are arranged. [Diagram 3] 2(a) is a cross-sectional view taken along line CC shown in FIG. 2(a), (b) is a diagram showing a wire protection structure according to a first modified example, (c) is a diagram showing a wire protection structure according to a second modified example, and (d) is a diagram showing a wire protection structure according to a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a light emitting device according to the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to the embodiments, but extends to the inventions described in the claims and their equivalents.

[0011] 1(a) and 1(b), the light emitting device 1 includes a substrate 10, a pair of wiring patterns 11 and 12, a pair of electrodes 13 and 14, a plurality of LED dies 15, wires 16, a solder resist 17, a reflective frame 18, a sealing resin 19, etc. The light emitting device 1 is a chip on board (COB) type light emitting device.

[0012] The substrate 10 has a rectangular planar shape and includes a mounting substrate 20 and a circuit substrate 21 that are arranged in an overlapping manner. The mounting substrate 20 is made of a metal with high thermal conductivity such as aluminum, and has a mounting surface 20a on which an LED die 15 is mounted. The circuit substrate 21 is bonded to the mounting surface 20a of the mounting substrate 20, and has a circular opening 21a formed in the center. On the upper surface of the circuit substrate 21, a pair of wiring patterns 11 and 12 that surround the opening 21a, and a pair of electrodes 13 and 14 that are arranged near the opposing corners and connected to the wiring patterns 11 and 12 are formed. In response to a predetermined threshold voltage being applied between the pair of electrodes 13 and 14 from an external power source, the LED dies 15 emit light, and the light emitting device 1 emits light.

[0013] The LED die 15 is also called a light-emitting element, and is mounted on the mounting surface 20a of the mounting board 20 exposed from the opening 21a. In the light-emitting device 1, 40 LED dies 15 are mounted on the mounting surface 20a. The LED dies 15 are electrically connected between the electrodes 13 and 14 via the wiring patterns 11 and 12 so that five rows of LEDs, each of which has eight LEDs connected in series, are connected in parallel. The LED die 15 is a blue LED die that emits blue light in response to a threshold voltage that is eight times the forward voltage of the LED die 15 being applied between the electrodes 13 and 14. The wire 16 is also called a bonding wire, and is formed of a conductive material, and connects between adjacent LED dies 15, as well as between the LED die 15 and the wiring patterns 11 and 12. The wire 16 is preferably made of silver. When the wire 16 is made of silver, the reflectance of light having a wavelength in the blue light region at the wire 16 is high, and the emission efficiency of the light-emitting device 1 is increased. Wire 16 may also be a corrodible conductive material that is less expensive than gold, such as silver or copper.

[0014] The solder resist 17 is a heat-resistant insulating resin such as epoxy resin, and is arranged so as to cover the entire surfaces of the pair of wiring patterns 11 and 12 except for the pair of electrodes 13 and 14. The reflective frame 18 is a white resin in which a filler such as silica is contained in a synthetic resin such as silicone resin, and is arranged along the outer edge of the opening 21a. The sealing resin 19 is a synthetic resin in which green phosphor particles such as YAG and red phosphor particles such as CASN are mixed into a transparent resin, and is arranged inside the reflective frame 18 to seal the LED die 15 and the wire 16. The transparent resin is preferably a silicone resin with high heat resistance. The light emitting device 1 emits white light by mixing the blue light from the LED die 15 with the green light and red light obtained by exciting the green phosphor and red phosphor with a part of the blue light.

[0015] The wire protection structure in the light emitting device 1 will be described with reference to Figures 2(a), 2(b) and 3(a). In Figures 2(a), 2(b) and 3(a), the positional relationship and size of each component are shown typically, and the reflective frame 18 and the sealing resin 19 are omitted. The LED die 15 has a light emitting layer 30, an anode 31 and a cathode 32. The wire 16 connects between the anode 31 and the cathode 32 of a pair of adjacently arranged LED dies 15, connects the anode 31 of the LED die 15 to the wiring pattern 11 and connects the cathode 32 of the LED die 15 to the wiring pattern 12.

[0016] The light emitting device 1 further includes an adhesive 22, a die bond material 23, a first protective film 24, and a second protective film 25. The adhesive 22 is, for example, a silicone resin-based or epoxy resin-based adhesive member, and adheres the circuit board 21 to the mounting substrate 20. The die bond material 23 is, for example, an adhesive member containing a synthetic resin such as a silicone resin-based or polyimide silicone resin-based resin, and mounts the LED die 15 on the mounting substrate 20.

[0017] The first protective film 24 is formed of a member containing an organic material having translucency, and is arranged so as to cover the surface of the wire 16 facing the mounting surface 20a, i.e., the lower surface of the wire. The first protective film 24 is arranged so as to cover the mounting surface 20a and at least a part of the upper surface and side surface of the LED die 15 via the second protective film 25. Furthermore, the first protective film 24 is arranged so as to cover at least a part of the reflector 18. The rigidity of the first protective film 24 may be higher than the rigidity of the sealing resin 19. The first protective film 24 is preferably formed of a synthetic resin containing at least one of an acrylic resin, a fluorine compound, and a silicone resin.

[0018] The second protective film 25 is formed by sputtering a metal oxide having translucency, such as SiO2 (silica), Al2O3, ZrO2, TiO2, MgO, or Nb2O5, and is arranged so as to cover the surface of the wire 16 opposite to the mounting surface 20a, i.e., the upper surface of the wire. The second protective film 25 covers the periphery of the wire 16 together with the first protective film 24. The second protective film 25 is also arranged so as to cover at least a part of the mounting surface 20a and the upper and side surfaces of the LED die 15. The second protective layer 25 is preferably made of silica. The refractive index of silica is approximately the same as the refractive index of the transparent resin constituting the sealing resin 19, so that it is possible to reduce stray light of light reflected by the wire 16.

[0019] A method for manufacturing the light emitting device 1 will be described. First, in an aggregate substrate preparation step, an aggregate substrate in which a plurality of substrates 10 are integrated is prepared. Next, in a light emitting element mounting step, a plurality of LED dies 15 are mounted via die bond material 23 at predetermined positions on the mounting surface 20a of a plurality of substrates 10 included in the aggregate substrate. Next, in a wire bonding step, wire bonding is performed between the plurality of LED dies 15, between the plurality of LED dies 15 and the wiring pattern 11, and between the plurality of LED dies 15 and the wiring pattern 12. Next, in a reflective frame arrangement step, a reflective frame 18 is arranged to surround the mounting surface 20a.

[0020] Next, in a second protective film arrangement step, the second protective film 25 is arranged so as to cover the upper surfaces of the mounting surface 20a, the LED die 15, and the wires 16. The second protective film 25 is arranged over the entire surface of the mounting surface 20a in a plan view by sputtering a target made of a translucent metal oxide with the surfaces of the collective substrate other than the mounting surface 20a being masked. Since the target is a translucent metal oxide, the second protective film 25 is stably and robustly arranged over the entire surface of the mounting surface 20a. In the second protective film arrangement step, it is more preferable that the target to be sputtered is silica.

[0021] Next, in a first protective film arrangement step, the first protective film 24 is arranged so as to cover the mounting surface 20a and the upper and side surfaces of the LED die 15. The first protective film 24 is arranged by applying raw material of the first protective film 24 to the mounting surface 20a from above, and then solidifying the raw material applied to the mounting surface 20a. The first protective film 24 is arranged so as to cover the mounting surface 20a and to connect the mounting surface 20a and at least a part of the lower surface of the wire 16 in a planar manner.

[0022] In the first protective film arrangement step, the raw material of the first protective film 24 preferably contains an organic material having translucency. When the raw material of the first protective film 24 contains an organic material, the raw material can be solidified at a lower temperature than inorganic materials, and the raw material can be easily solidified. In addition, the raw material of the first protective film 24 before solidification is preferably liquid. When the raw material of the first protective film 24 before solidification is liquid, the mounting surface 20a can be stably covered. Furthermore, it is more preferable that the raw material of the first protective film 24 is a light-transmitting member formed of a synthetic resin containing at least one of an acrylic resin, a fluorine compound, and a silicone resin. When the raw material of the first protective film 24 is a light-transmitting member formed of a synthetic resin containing at least one of an acrylic resin, a fluorine compound, and a silicone resin, the mounting surface 20a and the lower surface of the wire 16 can be stably connected.

[0023] Next, in a sealing resin disposing step, sealing resin 19 is disposed in the area surrounded by the reflective frame 18. Then, in a cutting step, the collective substrate is cut to manufacture a plurality of light emitting devices 1.

[0024] In the light emitting device 1, a first protective film 24 made of an organic material such as a synthetic resin is disposed on the surface facing the mounting surface 20a of the wire 16, thereby protecting the surface facing the mounting surface 20a of the wire 16. In addition, a second protective film 25 made of an inorganic material such as silica is disposed on the surface opposite the surface facing the mounting surface 20a of the wire 16, thereby protecting the surface opposite the surface facing the mounting surface 20a of the wire 16. Furthermore, in the light emitting device 1, the first protective film 24 covers the mounting surface 20a and connects between the mounting surface 20a and the wire 16, thereby fixing the wire 16 integrally with the mounting surface 20a, thereby further improving the reliability of the wire 16.

[0025] Since the first protective film 24 contains an organic material, it is possible to form the first protective film 24 well on the surface of the wire 16 facing the mounting substrate 20. In particular, as shown in FIG. 3(a), when the first protective film 24 is to be connected so as to form a film between the surface of the mounting substrate 20 and the wire 16, it is preferable to form it from an organic material. On the other hand, when the second protective film 25 is to be formed uniformly on the entire inside of the opening 21a of the mounting substrate 20, it is preferable to form it from a metal oxide. Therefore, the first protective film arranged to cover the surface of the wire 16 facing the mounting substrate 20a contains a light-transmitting organic material, and the second protective film arranged to cover the surface of the wire 16 opposite the mounting substrate 20a is formed from a light-transmitting metal oxide, so that the wire 16 can be well protected from above and below.

[0026] Fig. 3(b) is a diagram showing a wire protection structure according to a first modified example, Fig. 3(c) is a diagram showing a wire protection structure according to a second modified example, and Fig. 3(d) is a diagram showing a wire protection structure according to a third modified example. Figs. 3(b) to 3(d) are cross-sectional views showing only a portion corresponding to dashed line D in Fig. 3(a). In Figs. 3(b) to 3(d), reference numerals 24b to 24d denote first protective films, and reference numerals 25b to 25d denote second protective films.

[0027] As shown in FIG. 3(b), the first protective film 24b covers a portion of the lower surface of the wire 16 in a cross-sectional view of the wire 16, and the second protective film 25b covers a portion of the upper surface of the wire 16, and portions of the upper and lower surfaces of the wire 16 are not covered by the protective films.

[0028] As shown in FIG. 3(c), in a cross-sectional view of the wire 16, the first protective film 24c covers a portion of the lower surface of the wire 16 and the lower end of the second protective film 25c, and the second protective film 25c covers a portion of the upper surface of the wire 16, so that the entire circumference of the wire 16 is covered with a protective film.

[0029] As shown in FIG. 3(d), the first protective film 24d covers the entire circumference of the wire 16 in a cross-sectional view of the wire 16, and the second protective film 25d covers a portion of the upper surface of the wire 16, so that the wire 16 is covered with a protective film around the entire circumference.

[0030] The wire protection structures according to the first to third modified examples may be configured at some locations of the wire 16. Moreover, the wire protection structures according to the first to third modified examples may be mixed. [Explanation of symbols]

[0031] 1 Light emitting device 16 Wire 24 First protective film 25 Second protective film

Claims

1. A substrate on which a wiring pattern is formed; A light emitting element mounted on the substrate; a wire connecting the light emitting element and the wiring pattern; a first protective film that contains a light-transmitting organic material and is disposed so as to cover a surface of the wire that faces the substrate; a second protective film formed of a light-transmitting metal oxide and disposed so as to cover a surface of the wire opposite to the substrate; A light emitting device comprising:

2. the first protective film covers a part of a surface of the wire facing the substrate and a lower end of the second protective film in a cross-sectional view of the wire; The second protective film covers a part of the surface of the wire opposite to the substrate. The light emitting device according to claim 1 .

3. The first protective film covers the entire circumference of the wire in a cross-sectional view of the wire, and the second protective film covers a portion of the surface of the wire 16 opposite to the substrate. The light emitting device according to claim 1 .

4. the wire is silver; The first protective film is formed of a synthetic resin including at least one of an acrylic resin, a fluorine compound, and a silicone resin, The second protective film is formed by sputtering silica. The light emitting device according to any one of claims 1 to 3.

5. the first protective film covers the substrate and connects the substrate and the wire; The light emitting device according to claim 4 .

6. the first protective film covers the substrate via the second protective film; The light emitting device according to claim 5 .

7. the first protective film covers the light emitting element via the second protective film; The light emitting device according to claim 6.

8. The light emitting device further includes a reflecting frame disposed on the substrate so as to surround the light emitting element, The first protective film covers a portion of the reflective frame. The light emitting device according to claim 7.

9. Further comprising a sealant disposed inside the reflective frame; The rigidity of the first protective film is higher than the rigidity of the sealing material. The light emitting device according to claim 8.

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