Patent ID: 12243972

DETAILED DESCRIPTION

Certain embodiments of the present invention will be explained below with reference to the accompanying drawings. The embodiments explained below are provided for the purpose of giving shape to the technical ideas of the present invention, which do not limit the present invention unless otherwise specifically noted. The sizes of and positional relationships between the members shown in the drawings might be exaggerated for clarity of explanation.

The present invention will be explained in detail below based on the drawings. In the explanation below, terms indicating specific directions or positions (e.g., “upper,” “lower,” or terms including these words) will be used as needed. These terms are used to make the embodiments in the drawings more easily understood, and the meaning of such terms does not restrict the technical scope of the present invention. The members or parts denoted by the same reference numerals are the same or equivalent members or parts.

Furthermore, the embodiments described below are backlights shown as examples for the purpose of embodying the technical ideas of the present invention. However, the present invention is not limited to the examples described below. The dimensions, materials, shapes, and relative positions of the constituent elements described below are not meant to limit the scope of the invention unless otherwise specifically noted, but are intended to provide examples. The content described with reference to one embodiment or example is applicable to another embodiment or example. Moreover, the sizes of and positional relationships between the members shown in the drawings might be exaggerated for clarity of explanation.

Embodiment 1

FIG.1is a schematic upper face view of a light emitting device according to Embodiment 1.FIG.2is a schematic lower face view of the light emitting device of the embodiment.FIG.3is a schematic cross-sectional view taken along line inFIG.1.FIG.4is a schematic end face view only showing the cross section along line IV-IV inFIG.1.FIG.5is a schematic cross-sectional view enlarging a portion of the bonding member and the vicinity thereof in the light emitting device according to the embodiment.

The light emitting device100shown inFIG.3includes a base10having an upper face10a, a light emitting element20mounted on the upper face10a, bonding members30disposed on the upper face10aoutward of the light emitting element20, a light transmissive member40bonded to a portion of the upper face10aby the bonding members30, and a protective film60covering the upper face10aof the base10and the light emitting element20. The device has, between the upper face10aof the base10and the lower face40bof the light transmissive member40, gaps70that allow the space in which the light emitting element20is mounted to be in communication with the outside of the light emitting device100. The gaps70are defined by the upper face10aof the base10, the lower face40bof the light transmissive member40, and the bonding members30. The protective film60continuously covers the light emitting element20, the upper face10aof the base10, the lateral faces30cof the bonding members30, and the lower face40bof the light transmissive member40.

In the example shown inFIG.1, the base10has a flat sheet-shaped base part11, and a lateral wall part12disposed on the base part11. The base part11and the lateral wall part12may be formed integrally, or as separate parts. The base part11and the lateral wall part12define a first recessed part. The first upper face11aof the base part11is the bottom of the first recessed part. The light emitting element20is disposed on the first upper face11a. The shape of the first upper face11awhen viewed from above is quadrangular, for example. As shown inFIG.6, the second upper face12a, which is the upper face of the lateral wall part12, is positioned outward of the light emitting element20when viewed from above. The second upper face12ais frame shaped having, for example, a quadrangular outline when viewed from above.

Positive and negative first wires14are arranged on the first upper face11aof the base10. The light emitting element20is flip-chip mounted on the base10. Specifically, using a light emitting element20having positive and negative electrodes on the same face, the positive and negative electrodes of the light emitting element20are electrically connected to the positive and negative first wires14of the base10, respectively, via conductive members. For the conductive members, for example, (i) eutectic solder using gold and tin, or tin, silver, and copper as main components, (ii) conductive paste containing silver, gold, or palladium, or (iii) bumps containing silver or gold can be used. The light emitting element20may be connected to the first wires14of the base10using wires (mounted face up). Second wires15are arranged on the lower face10bof the base10. The base part11of the base10has through holes, and internal wires (not shown) are disposed in the through holes. The first wires14and the second wires15are connected using the internal wires. The base10may or may not have second recessed parts16on the lower face10bside. The second recessed parts16are provided from the lower face10bto the outer lateral faces10cof the base10. In the case in which second recessed parts16are provided, the second wires15are also disposed on the outer lateral faces16cof the base10that define the second recessed parts16. When bonding the second wires15of the light emitting device100to another mounting substrate or the like by using solder or the like, the solder can enter the second recessed part16. This can electrically connect the second wires15in a more stable manner.

A light transmissive member40is a member having light transmissivity that transmits at least the light from the light emitting element20, transmitting at least 60%, preferably at least 90% of the emitted light from the light emitting element20. The shape of the light transmissive member40is, for example, quadrangular when viewed from above. The light transmissive member40, besides the flat sheet shape shown inFIG.1andFIG.2, may be such that the upper face and/or the lower face are/is spherical or aspherical lens shaped.

A bonding member30bonds the second upper face12aof the lateral wall part12of the base10and the light transmissive member40. Because the lateral wall part12is disposed to surround the light emitting element20when viewed from above, the bonding member30is preferably disposed to surround the light emitting element20as well. The bonding member30is disposed on a portion of the second upper face12a, not across the entire surface, of the base10. In the portions in which the bonding members30are not disposed, as shown inFIG.4, there are gaps70between the second upper face12aof the base10and the lower face of the light transmissive member40that are defined by the second upper face12aof the base10, the lower face40bof the light transmissive member40, and the bonding members30. The gaps70allow the space in which the light emitting element20is disposed to be in communication with the outside of the light emitting device100. In other words, the space in which the light emitting element20is disposed is not an airtight space in the light emitting device100.

In the example shown inFIG.6, a plurality of bonding members30are arranged. The bonding members30are disposed at the four corners of the second upper face12athat is quadrangular when viewed from above. In the case of arranging a plurality of bonding member30as described above, arranging them to have point symmetry about the center of the base10or line symmetry using the line connecting the centers of two opposing sides of the base10when viewed from above can increase the bonding quality between the base10and the light transmissive member40. There is no particular restriction on the number and positions of the bonding members30, as long as the gaps70secured after bonding the light transmissive member40and the base10are large enough to allow a gaseous raw material to be supplied to the space in which the light emitting element20is disposed during the process of forming a protective film60described below. In the example shown inFIG.6, the bonding members30are arranged such that two pieces are present per side of the base10. The bonding members30may be arranged such that one, three, or more pieces are present per side of the base10. A bonding member30may be disposed in any position other than the four corners of the base10, such as the center of a side of the base10. A bonding member30may be disposed continuously over two or more sides. For example, one bonding member30can be disposed over three or four sides while leaving a gap at one location. In the case of disposing multiple bonding members30, at least one bonding member30may be disposed over two or more sides of the base10.

In the example shown inFIG.6, one gap70is provided per side of the base10. There may be a single gap70, or multiple gaps70per side of the base10. Two or more gaps70may be provided per side of the base10. The height of a gap70(the thickness of the bonding member30between the second upper face12aand the lower face40bof the light transmissive member40) can be set, for example, in a range of 1 μm to 100 μm. The height of a gap70is preferably set as 10 μm to 50 μm. In the case in which the first metal film51and the second metal film52described below are included, the height refers to the thickness of the bonding member30between the first metal film51and the second metal film52. There is no particular restriction on the width of a gap70, as long as it is large enough to allow a gaseous raw material to be supplied through the gap70into the space in which the light emitting element20is disposed in the process of forming a protective film60described below. The percentage of the width of the bonding member30(30W inFIG.5) of the base10in the width of the second upper face12a(12W inFIG.5) in the direction perpendicular to the sides of the base10is preferably set, for example, as at least 50%. The width of the second upper face12ain the direction perpendicular to the sides of the base10can be set, for example, in a range of 0.3 mm to 0.7 mm. The width of the bonding member30in the direction perpendicular to the sides of the base10can be set, for example, in a range of 0.2 mm to 0.5 mm.

On the second upper face12aof the base10, a first metal film51may be disposed or not. In the example shown inFIG.6, the first metal film51is positioned between the bonding members30and the second upper face12aof the base10. The first metal film is quadrangular frame shaped when viewed from above, and the four corners are rounded. In the case in which a first metal film51is provided, the bonding members30are disposed on the first metal film51.

In the peripheral portion of the lower face40bof the light transmissive member40, a second metal film52may be disposed or not. In the example shown inFIG.7, the second metal film52is disposed between the bonding members30and the lower face40bof the light transmissive member40. The second meal film52opposes the second upper face12aof the base10. The second metal film52is frame-shaped and has a quadrangular outline with arc-shaped chamfers (indentations) at the corners in a plan view of the lower face40bof the light transmissive member40. In the case in which a second metal film52is provided, the bonding members30are bonded to the second metal film52.

A protective film60is made of an inorganic material and continuously covers the base10, the light emitting element20, the bonding members30, and the light transmissive member40. The protective film60in the example shown inFIG.3andFIG.4covers the lower face10bexcluding the surfaces of the second wires15and the outer lateral faces10cof the base10, the lateral faces30cof the bonding members30, and the surfaces of the light transmissive member40, making up the lower face and the lateral faces in part and the upper face among the outer surfaces of the light emitting device100. In the case in which a second recessed part16is provided, the protective film60preferably also covers the downward facing face16bof the base10that defines the second recessed part16. Furthermore, the protective film60covers the inner lateral faces10dof the lateral wall part12and the first upper face11aof the base part11of the base10that define the first recessed part of the base10. Moreover, under the light emitting element20, the protective film60covers the lower face of the light emitting element20, the lateral faces of the conductive members, and the first upper face11aof the base10positioned under the light emitting element20. The protective film60preferably covers the light emitting element20, the second upper face12aof the base10, the lateral faces30cof the bonding members30interposed between the second upper face12aof the base10and the lower face of the light transmissive member40, and the lower face40bof the light transmissive member40without any gap, such as an opening or break. In the light emitting device100shown inFIG.3andFIG.4, the protective film60covers the surfaces of the base10excluding the surfaces of the second wires15, the surfaces of the light emitting element20, the lateral faces30cof the bonding members30, and the surfaces of the light transmissive member40.

The light emitting device100may have a protective device, such as a Zener diode, or not. In the example shown inFIG.6, a protective device80is disposed on the first upper face11aof the base10.

Each constituent element of the light emitting device100will be explained below.

Base10

A base10is provided for mounting a light emitting element20. In the example shown inFIG.3, the base10has a flat sheet shaped base part11and a lateral wall part12disposed on the base part11. A light emitting element20is disposed on the first upper face11aof the base part11, and bonding members30are disposed on the second upper face12aof the lateral wall part12. The shape of the first upper face11aof the base part11defined by the lateral wall part12when viewed from above is, for example, quadrangular.

The base10includes an insulation base material, first wires14, and second wires15. Examples of the insulation base materials include ceramics, glass epoxy, and resins. For ceramics, a highly heat resistant and highly weather resistant material is preferably used. Examples of such ceramics include alumina, aluminum nitride, mullite and the like.

The first upper face11aof the base10has first wires14. The lower face10bof the base10has second wires15. The first wires14and the second wires15can be formed of any material known in the art. For the first wires14and the second wires15, for example, a metal, such as copper, aluminum, gold, silver, or the like can be used.

Light Emitting Element20

A light emitting element20is disposed on the first upper face11aof the base part11of the base10. For the light emitting element20, a light emitting diode, laser diode, or the like can be used.

There is no particular restriction for the peak emission wavelength for the light emitting element20, and any peak emission wavelength can be suitably selected, for example, 250 nm to 600 nm. For example, a light emitting diode that emits ultraviolet light can be used as a light source for sterilization or sanitization purposes. The peak emission wavelength for an ultraviolet light emitting element20is, for example, 400 nm at most. Because an ultraviolet light emitting element20tends to be readily degraded by moisture or the like, covering the element with a protective film60can notably improve the effect of reducing such degradation.

The light emitting element20is preferably made of nitride semiconductor layers, such as InXAlYGa1-X-YN (0≤X, 0≤Y, X+Y≤1), for example. In the case of using a light emitting element that emits light in the deep ultraviolet to ultraviolet wavelength range, it preferably includes a nitride semiconductor layer containing at least Al. The light emitting element20includes semiconductor layers that include at least an emission layer, and positive and negative electrodes. In the light emitting element20according to this embodiment, the positive and negative electrodes are disposed on the same face. Accordingly, the light emitting element20can be flip-chip mounted on the base10, thereby reducing the size of the light emitting device100as compared to the case in which the light emitting element20and the base10are electrically connected using wires. The face of the light emitting element that is opposite the face having the electrodes can be bonded to the first upper face11aof the base10while electrically connecting the positive and negative electrodes of the light emitting element20to the positive and negative first wires14using wires, respectively. Alternatively, a light emitting element having one of the positive and negative electrodes on the upper face and the other electrode on the lower face can be used.

The light emitting element20can have a substrate for growing a semiconductor layer in addition to the semiconductor layers and the electrodes described above. Examples of such a substrate include an insulating substrate, such as sapphire, lithium niobate, or neodymium gallate, or a conductive substrate, such as SiC, ZnO, Si, GaAs, or the like. The substrate preferably has light transmissivity. The substrate may be removed by utilizing a laser lift-off technique or the like.

In the example shown inFIG.6, the light emitting element20is disposed in the center of the first upper face11a. In the example shown inFIG.6, moreover, the light emitting device100has one light emitting element20. The light emitting device100may have multiple light emitting elements20arranged therein. The light emitting element20in a top view can have a quadrangular shape, for example. In this case, the length of a side of the light emitting element20when viewed from above is preferably in a range of 50 μm to 3,000 μm, for example, more preferably 300 μm to 2,000 μm. The top view shape of the light emitting element20may be another polygon, such as a triangle, hexagon, or the like.

Bonding Member30

A bonding member30bonds the base10and the light transmissive member40. The bonding member30, in the case in which the light emitting device100includes a first metal film51and a second metal film52, is disposed between the first metal film51and the second metal film52. Examples of the bonding member30include solder, low melting point glass, resins, and the like. Examples of solder include Au—Sn, Au—In, and the like. Examples of resins include silicone resins, epoxy resins, and the like.

FIG.8is a schematic top view showing another layout of the bonding members30. In the example shown inFIG.8, multiple bonding members30are annularly arranged at certain intervals. The bonding members30are arranged in the regions excluding the four corners of the base10. In the example shown inFIG.8, three or more bonding members30are arranged per side of the base10. This can increase the bonding strength between the base10and the light transmissive member40.

Light Transmissive Member40

A light transmissive member40has the function of transmitting the light from the light emitting element20disposed on the base10to be output from the light emitting device100. The light transmissive member40preferably transmits at least 60%, more preferably at least 90% of the emitted light from the light emitting element20. Examples of materials for use as the light transmissive member40include an inorganic material made of at least one selected from the group consisting of sapphire, borosilicate glass, quartz glass, calcium fluoride glass, aluminoborosilicate glass, oxynitride glass, and chalcogenide glass. The thickness of the light transmissive member40may be, for example, in a range of 0.1 mm to 7 mm.

Protective Film60

A protective film60has the function of protecting the light emitting element, the base, and the bonding members from dust and moisture. The protective film60has light transmissivity and insulation properties, and as shown inFIG.2, continuously covers at least the light emitting element20, the upper face10aof the base10, and the lateral faces of the bonding members30. As shown inFIG.2, the protective film60preferably covers substantially all surfaces of the light emitting device100except for the lower face. This can reduce the chance of allowing the protective film60to be separated from the surfaces of the light emitting device100.

Examples of materials for the protective film60include inorganic materials, such as aluminum oxide, silicon dioxide, tantalum oxide, niobium oxide, titanium oxide, aluminum nitride, silicon nitride, and the like. The protective film60preferably is a film that contains aluminum oxide or silicon dioxide as a primary component. The protective film60can be of a single layer film of one material, or a multilayer film made of two or more different materials. Specifically, it is preferable to use a stack composed of a layer made of aluminum oxide as a primary component and a layer made of silicon dioxide as a primary component, or a stack in which these layers are repeatedly alternately stacked. The thickness of the protective film60is, for example, in a range of 3 nm to 250 nm. The thickness of the protective film60is preferably in a range of 40 nm to 150 nm. In the case of employing a multilayer film for the protective film60, the total thickness of all layers is preferably set to fall within the ranges described above.

The light emitting device100according to this embodiment is such that the light emitting element20, the base10, and the lateral faces of the bonding members30are continuously covered by the protective film60to protect these members from the external factors, such as dust and moisture. Thus, deterioration attributable to oxidation or the like can be prevented. Accordingly, a highly reliable light emitting device100can be provided.

Method of Manufacturing Light Emitting Device100

FIG.9AandFIG.9Bare schematic cross-sectional views explaining a method of manufacturing a light emitting device100of Embodiment 1.

Process of Preparing Intermediate Body110

As shown inFIG.9A, an intermediate body110, which includes a base10having an upper face10a, a light emitting element20mounted on the upper face10a, a bonding member30disposed on the upper face10aoutward of the light emitting element20, and a light transmissive member40bonded to a portion of the upper face10aby the bonding member30, is prepared. The intermediate body110has, between the upper face10aof the base10and the lower face40bof the light transmissive member40, a gap70that allows the space in which the light emitting element20is mounted to be in communication with the outside of the intermediate body110. The gap70is created by the bonding member30interposed between the upper face10aof the base10and the lower face40bof the light transmissive member40.

One example of the method of manufacturing such an intermediate body110will be explained. First, a light emitting element20is mounted on the first upper face11aof the base10. A bonding member30is disposed on a portion of the second upper face12aoutward of the light emitting element20. Subsequently, by bonding the portion of the second upper face12aand the light transmissive member40using the bonding member30, an intermediate body110like that shown inFIG.9Ais obtained. Such an intermediate body110may be purchased, or prepared by following the intermediate body preparation process in part or whole.

Process of Forming Protective Film60

Next, as shown inFIG.9B, a protective film60that covers the upper face10aof the base10and the light emitting element20is formed.

The protective film60is preferably formed by atomic layer deposition (ALD). Forming the protective film60by atomic layer deposition can thinly form a dense protective film60across all surfaces that extend in different planar directions. Employing atomic layer deposition allows the gaseous raw material for forming the protective film60to be supplied through the gap created between the upper face10aof the base10and the lower face40bof the light transmissive member40.

The protective film60can be formed to continuously cover at least the upper face10aof the base10, the light emitting element20, and the lateral faces of the bonding member30, but is preferably formed to substantially cover all surfaces of the light emitting device excluding the second wires15as shown inFIG.9B. Examples of methods of selectively forming the protective film60as described above include one that forms a protective film60on all surfaces of the light emitting device100followed by removing the protective film60positioned on the second wires15by grinding or laser beam irradiation, one that uses a mask to cover the second wires15before forming a protective film60, and the like.

Embodiment 2

FIG.10is a schematic end face view showing only a cross section of a light emitting device200according to Embodiment 2.

The light emitting device200has a light emitting element20and a light transmissive member240on a flat sheet shaped base210. The light transmissive member240has a flat sheet part241, and a lateral wall part242positioned under the flat sheet part241. The lower face242bof the lateral wall part242is bonded to the base210via a bonding member30. The flat sheet part241and the lateral wall part242of the light transmissive member240can be formed integrally. A light emitting element is positioned in the recessed part243defined by the flat sheet part241and the lateral wall part242. The shape of the opening of the recessed part243is, for example, quadrangular. A gap70that allows the space in which the light emitting element20is mounted to be in communication with the outside of the light emitting device100is present between the base210and the lower face242bof the light transmissive member240. The gap70is defined by the upper face10aof the base10, the lower face240bof the light transmissive member240, and the bonding member30. The protective film60covers the surfaces of the base210, the surfaces of the light emitting element20, the lateral faces of the bonding member30, and the surfaces of the light transmissive member. In the light emitting device200shown inFIG.10, the light emitting element20, the base210, and the lateral faces of the bonding member30, which are continuously covered by the protective film60, can be protected from dust and moisture to thereby prevent the deterioration attributable to oxidation and the like.