JP7828245B2 - Semiconductor light-emitting device - Google Patents

Description

The present invention relates to a semiconductor light-emitting device that emits ultraviolet light.

Semiconductor light-emitting devices are known in which a light-emitting element is die-bonded onto a substrate and then sealed (packaged). When using a light-emitting element that emits visible light, it is common to embed the light-emitting element and seal it with resin.

On the other hand, when using a light-emitting element that emits ultraviolet light, resin is broken down by ultraviolet light, so instead of using resin, the space around the light-emitting element is filled with a low-oxygen gas and the surrounding area is sealed with a transparent material such as quartz glass or sapphire. A ceramic substrate, which is resistant to degradation by ultraviolet light, is used as the substrate to which the ultraviolet-emitting light-emitting element is die-bonded. Metal is used as the bonding material to bond the transparent material to the substrate to prevent degradation by ultraviolet light.

Specifically, Patent Documents 1 and 2 each disclose a semiconductor light-emitting device in which a glass window member is bonded to a ceramic substrate with a recess by a sealing member. The sealing member in Patent Document 1 is made of a low-melting-point metal material and is formed in a fillet shape. In Patent Document 2, the window member and substrate are bonded using an AuSn bonding material while a load is applied from above the window member. This bonding process is performed in an atmosphere with a low oxygen concentration to prevent oxidation of the AuSn bonding material.

Patent Documents 3 and 4 disclose a semiconductor light-emitting device in which a spacer made of single crystal silicon is fixed around the periphery of a glass window member, and the underside of the spacer is bonded to a ceramic substrate. An AuSn bonding material is used to bond the underside of the spacer to the ceramic substrate.

JP 2015-18873 A JP 2018-93137 A Japanese Patent Application Laid-Open No. 2016-127255 JP 2016-127249 A

Conventional ultraviolet-emitting semiconductor light-emitting devices use a metal bonding material to bond the transparent member to the substrate, but bonding with a metal bonding material requires that a metal layer (metallization) be applied beforehand on both the transparent member and the substrate. This makes the structure of the semiconductor light-emitting device more complex and increases manufacturing costs. Furthermore, to prevent oxidation during bonding, the metal bonding material must be heated to high temperatures in a non-oxidizing atmosphere, necessitating large-scale equipment.

On the other hand, when resin is used as the bonding material, there is no need to form metallization on the transparent member or substrate beforehand, simplifying the structure. Furthermore, there is no risk of oxidation during bonding, so the bonding process can be carried out in the atmosphere. However, resin bonding materials have the problem of deteriorating (yellowing and decomposing) due to the ultraviolet rays emitted by the light-emitting element.

The object of the present invention is to provide a structure in which a transparent member of a semiconductor light-emitting device that emits ultraviolet light is bonded to a substrate with resin, without compromising bonding reliability.

To achieve the above objective, the semiconductor light-emitting device of the present invention comprises a light-emitting element that emits ultraviolet light, a substrate on which the light-emitting element is mounted, a cap that airtightly covers the space around the light-emitting element on the substrate, and a bonding material that airtightly bonds the cap to the top surface of the substrate. The cap comprises a top plate and a frame that supports the underside of the top plate against the substrate. The top plate and frame are integrally formed from a material that transmits ultraviolet light and has a critical angle between the ultraviolet light and the atmosphere of 45° or less. The bottom surface of the frame is bonded to the top surface of the substrate using a resin bonding material. The upper part of the outer side surface of the frame is an inclined surface that is inclined at a predetermined angle with respect to the normal to the top plate, and some of the ultraviolet light that has been guided within the top plate reaches the inclined surface and is emitted to the outside from the inclined surface.

According to this invention, ultraviolet light that has been guided through the top plate of the transparent member is emitted to the outside through the inclined surface of the frame body, preventing it from reaching the bottom end of the frame body. This makes it possible to bond the frame body and substrate with resin while suppressing deterioration of the bonding material due to ultraviolet light, thereby achieving the effect of not compromising bonding reliability.

1 is a cross-sectional view of a semiconductor light emitting device according to an embodiment. (a), (b), and (c) are respectively a top view, a side view, and a bottom view of a semiconductor light-emitting device of an embodiment, (d) is a top view showing the wiring pattern on the substrate of the semiconductor light-emitting device, and (e) is a top view of a light-emitting element mounted on the wiring pattern. 3A and 3B are enlarged views of a cap 13 of the semiconductor light emitting device according to the embodiment and a diagram showing trajectories of light rays. 1A is an explanatory diagram showing the optical path of light that is incident on the interface between the upper surface of the top plate 131 of the cap 13 of the semiconductor light-emitting device and air at an incident angle that satisfies the critical angle θc≦incident angle θi≦critical angle θc+2δ, is reflected, and reaches the side surface 131a; and FIG. 1B is an explanatory diagram showing the optical path of light that is incident on the interface between the upper surface of the top plate 131 and air at an incident angle that satisfies the critical angle θc+2δ<incident angle θi, and reaches the side surface. FIG. 2 is a side view of an example of the light-emitting element 11. 5 is a flowchart showing a manufacturing process of the cap of the semiconductor light emitting device according to the embodiment. FIG. 5A to 5C are cross-sectional views illustrating a manufacturing process of the cap of the semiconductor light emitting device according to the embodiment. FIG. 4 is a flowchart showing an assembly process of the semiconductor light emitting device according to the embodiment. 5A to 5C are cross-sectional views showing an assembly process of the semiconductor light emitting device according to the embodiment. 10A and 10B are diagrams showing an enlarged view of a cap 13 of a semiconductor light emitting device according to a first modified example of the embodiment and ray trajectories. 10A and 10B are enlarged views of a cap 13 of a semiconductor light emitting device according to a second modification of the embodiment. 11A and 11B are enlarged views of a cap 13 of a semiconductor light emitting device according to a third modified example of the embodiment and a diagram showing ray trajectories. 10A and 10B are top views of a semiconductor light emitting device according to a fourth modification of the embodiment. 1A is a graph showing the relationship between the angle of incidence and reflectance at the interface between the top plate 131 of the semiconductor light-emitting device of the fifth embodiment and air, and FIG. 1B is a diagram showing an enlarged view of the cap 13 of the semiconductor light-emitting device of the first embodiment and the trajectory of light rays.

The following describes a semiconductor light-emitting device according to one embodiment of the present invention.

(Embodiment)
The configuration of a semiconductor light-emitting device 1 according to an embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a cross-sectional view of the semiconductor light-emitting device 1 according to an embodiment, and FIGS. 2(a), 2(b), and 2(c) are a top view, a side view, and a bottom view of the semiconductor light-emitting device 1, respectively. FIG. 2(d) is a top view showing the wiring pattern on the substrate of the semiconductor light-emitting device 1, and FIG. 2(e) is a top view showing a state in which a light-emitting element is mounted on the wiring pattern. Although FIGS. 2(b) to 2(e) are not cross-sectional views, the wiring is hatched to facilitate understanding of the structure. FIG. 3 is an enlarged view of the cap 13 and a diagram showing the trajectories of light rays.

As shown in Figures 1 and 2(a) to 2(c), the semiconductor light-emitting device 1 of this embodiment has a light-emitting element 11 that emits ultraviolet light die-bonded to one (first wiring 15a) of a pair of wirings 15a, 15b provided on a substrate 10 using an element bonding layer 12. The space 20 surrounding the light-emitting element 11 is airtightly covered by a cap 13. The lower end of the cap 13 is airtightly bonded to the upper surface of the substrate 10 using a bonding material 14. The bonding material 14 is resin.

The cap 13 includes a top plate 131 parallel to the substrate 10 and a frame 132 supporting the underside of the top plate 131. The top plate 131 and frame 132 are integrally formed from a material that transmits ultraviolet light of the wavelength emitted by the light-emitting element 11. The bottom surface of the frame 132 is bonded to the top surface of the substrate 10 with a resin bonding material 14.

A sloped surface 133 that is inclined at a predetermined angle relative to the normal to the top plate 131 is formed on the upper part of the outer side of the frame body 132. As shown in Figure 3, some of the ultraviolet light that has been guided within the top plate 131 reaches the sloped surface 133 and is emitted to the outside from the sloped surface 133.

The structure of each part will be explained in more detail below.

(Cap 13)
The frame 132 of the cap 13 is provided continuously along the entire periphery of the edge of the bottom surface of the top plate 131. Because the top plate 131 is square in this example, the shape of the upper end of the outer surface of the frame 132 when viewed from above is also square. The shape of the inner surface of the frame 132 when viewed from above is also square. However, an inclined surface 133 that is inclined toward the inner surface of the frame 132 is formed partway from the upper end to the lower end of the outer surface of the frame 132.

Specifically, as shown in FIG. 3, at position B of the upper end of the outer side surface of frame 132, an imaginary extension plane of the main plane on the light-emitting element 11 side (back side) of top plate 131 coincides with the lower end of side surface 131a of top plate 131. Furthermore, position C at a predetermined height on outer side surface 132a of frame 132 (a position a height H below the upper end of frame 132) is located a predetermined distance e2 closer to the light-emitting element 11 than side surface 131a of top plate 131. The range of height H from upper end B of outer side surface 132a of frame 132 to position C at the predetermined height forms an inclined surface 133 inclined at a predetermined angle φ with respect to the normal to top plate 131.

Here, we will explain how some of the ultraviolet light emitted from the light-emitting element 11 is guided through the top plate 131 and follows an optical path on the side of the top plate 131.

Most of the light emitted upward from the light-emitting element 11 passes through the top plate 131 in the thickness direction and is emitted from the top surface of the top plate 131, but some of the light is reflected from the top surface of the top plate 131 and then repeatedly reflected from the top and bottom surfaces of the top plate 131, thereby being guided within the top plate 131 in the direction of the main plane. The condition for waveguiding is that the angle of incidence when light from within the top plate 131 is incident on the top and bottom surfaces of the top plate 131 is greater than or equal to the critical angle θc, i.e., total reflection occurs.

For example, if the cap 13 (top plate 131 and frame 132) is made of quartz glass, for ultraviolet light with a wavelength of 265 nm, the refractive index of quartz glass is 1.50, and the critical angle θc at the interface between the quartz glass and air is 41.8°. For ultraviolet light with a wavelength of 380 nm, the refractive index of quartz glass is 1.47, and the critical angle θc at the interface between the quartz glass and air is 42.9°. Furthermore, for blue light with a wavelength of 500 nm, the refractive index of quartz glass is 1.46, and the critical angle θc at the interface between the quartz glass and air is 43.2°.

In other words, the critical angle θc of ultraviolet light at the interface between quartz glass or borosilicate glass and air is in the range of 41.8 to 43.2°, less than 45°, for ultraviolet light with a wavelength of 265 nm to blue light with a wavelength of 500 nm. Ultraviolet light that is incident on the upper and lower surfaces of the top plate 131 at an angle of incidence equal to or greater than this critical angle θc is guided within the top plate 131.

As shown in Figure 4(a), the angle of incidence at which ultraviolet light guided through the top plate 131 strikes the top surface of the top plate 131 is θi. Here, if the angle of incidence θi is the critical angle θc, the ultraviolet light that strikes the top surface of the top plate 131 at the angle of incidence θi (= critical angle θc) is totally reflected and reaches the side surface 131a of the top plate 131. The angle of incidence θs at the side surface 131a is (θs = 90° - θi = 90° - θc). As mentioned above, the critical angle θc of ultraviolet light is less than 45°, so the angle of incidence θs at the side surface is 45° or greater. In other words, because the angle of incidence θs at the side surface 131a of the top plate 131 is equal to or greater than the critical angle θc, this light is totally reflected at the side surface 131a, enters the frame 132, and is guided within the frame 132.

Similarly, ultraviolet light incident on the top surface of the top plate 131 at an incident angle θi greater than the critical angle θc is totally reflected by the top surface, reaches the side surface 131a, and is then totally reflected by the side surface 131a as shown in Figure 4(a) and guided within the frame 132. However, if the absolute value of the difference between the critical angle θc and 45° is taken as the difference angle δ (= |45 - θc|), when the incident angle θi is greater than the critical angle θc by more than 2δ (θi > θc + 2δ = 45° + δ), as shown in Figure 4(b), the incident angle θs of the ultraviolet light on the side surface 131a of the top plate 131 becomes smaller than the critical angle θc (θs < 90° - θi = 90° - (45° + δ) = 45° - δ = θc), and the ultraviolet light that reaches the side surface 131a passes through the side surface 131a and is emitted to the outside.

Therefore, of the ultraviolet rays that are guided through the top plate 131 with a critical angle θc of less than 45°, those with an incident angle θi on the top surface of the top plate 131 that is greater than or equal to the critical angle θc (θc + 2δ) (critical angle θc ≦ incident angle θi ≦ critical angle θc + 2δ) are totally reflected by the side surface 131a, guided through the frame 132, and reach the bonding material 14 at the bottom end of the frame 132, causing degradation of the bonding material 14.

In this embodiment, as shown in FIG. 3, the end face of the cap 13 is configured so that, of the ultraviolet rays guided within the top plate 131, those with an incident angle θi on the top surface of the top plate 131 that is in the range of the critical angle θc or more (θc + 2δ) or less (critical angle θc ≦ incident angle θi ≦ critical angle θc + 2δ) reach the inclined surface 133. Furthermore, the inclined surface 133 has an inclination angle that allows the ultraviolet rays guided within the top plate 131 to be incident at an angle that is less than the critical angle θc and as close to perpendicular as possible. This allows ultraviolet rays with an incident angle θi on the top surface of the top plate 131 that is in the range of the critical angle θc or more (θc + 2δ) or less to be emitted to the outside from the inclined surface 133.

In this way, ultraviolet light that has reached the vicinity of the side surface 131a of the top plate 131 is guided through the top plate 131 and then emitted to the outside from the side surface 131a or the inclined surface 133, thereby preventing the ultraviolet light from being guided within the frame body 132. This prevents the ultraviolet light from reaching the bonding material 14. Therefore, even when resin is used as the bonding material 14, deterioration due to ultraviolet light can be suppressed, and bonding reliability is not impaired.

The end face structure of the cap 13 will be described in detail below using Figure 3. In Figure 3, the critical angle θc for the range from ultraviolet to blue light is estimated to be 41.8 to 43.2 degrees, and the critical angle θc is hypothetically estimated to be 40 degrees. Furthermore, of the ultraviolet rays emitted to the outside from the inclined surface 133 (critical angle θc ≦ incident angle θi ≦ critical angle θc + 2δ), the lower limit incident angle θi (= θc) is referred to as the lower limit incident angle θa (= 40 degrees). Furthermore, when the critical angle θc = 40 degrees, the difference angle δ (= |45 - θc|) = 5 degrees, so the upper limit incident angle θi (= (θc + 2δ) = (40 degrees + 2 × 5 degrees)) of the ultraviolet rays emitted to the outside from the inclined surface 133 is referred to as the upper limit incident angle θb (= 50 degrees). The cap 131 is structured so that ultraviolet light whose incident angle θi on the top surface of the top plate 131 is in the range from a lower limit incident angle θa to an upper limit incident angle θb is incident on the inclined surface 133. Figure 3 shows the trajectories of light rays at the lower limit incident angle θa and the upper limit incident angle θb. In the figure, light incident at the lower limit incident angle is denoted as L40°, and light incident at the upper limit incident angle is denoted as L50°.

The angle φ of the inclined surface 133 is designed in advance so that when ultraviolet light guided through the top plate 131 reaches the inclined surface 133 at a lower limit incident angle θa = 40° and an upper limit incident angle θb = 50°, it is incident on the inclined surface 133 at an angle smaller than the critical angle θc. Note that the side surface 131a of the top plate 131 can also be an inclined surface that is an extension of the inclined surface 133.

The refractive index of the cap 13 varies depending on the material, and because the refractive index is wavelength-dependent, the critical angle θc varies depending on the material of the cap 13 and the wavelength of the UV light. Therefore, the critical angle θc is calculated in advance according to the wavelength of the UV light emitted by the light-emitting element 11, and the angle of the inclined surface 133 is determined in advance. Here, the critical angle θc can also be set 1° to 3° smaller than the actual critical angle.

Furthermore, the angle φ of the inclined surface 133 at which guided light (light between L40° and L50°) can be emitted from the inclined surface 133 can range from 45°-(θc-δ) to 45°+(θc-δ). However, since it is preferable for light to be incident at an angle close to the normal to the inclined surface 133 (perpendicular incidence), the angle φ relative to the normal to the top plate 131 should preferably be in the range of approximately 40° to 50°. 45° is preferred.

In addition, at the boundary between the frame body 132 and the underside of the top plate 131, a planar slit 16 is provided around the entire periphery of the frame body 132, extending from the inside to the outside of the frame body 132 on the underside of the top plate a predetermined distance Wa.

This slit 16 allows the underside of the top plate 131 to be extended in the lateral direction of the top plate 131, so that the range in which light is reflected on the underside of the top plate 131 can be extended in the lateral direction of the top plate 131, regardless of the width Wb from the inner side to the outer side of the base of the frame body 132. Therefore, position A of the tip of the slit 16 can be set to an appropriate position, and the guided light on the top plate 131 can be guided to near the edge of the top plate 131 and reach the inclined surface 133.

To explain this in more detail, position A at the tip of the slit 16 in the direction from the inside to the outside of the frame 132 is the branching end where light that has been guided through the top plate 131 branches off either toward the lower side surface 132a of the frame 132 or toward the top surface of the top plate 131.

Here, the light that passes through position A (proximity point) and heads toward the position on the lower outer surface 132a of the frame 132 closest to the substrate 10 is light with a lower limit incident angle θa (here, Ld 40°). The position where this light reaches the outer surface of the frame 132 is position C, which is the lower end of the inclined surface 133. Similarly, of the light that is reflected at position A, heads toward the upper surface of the top plate 131, and is re-reflected to reach the outer surface of the cap 13, the light that is reflected at the smallest incident angle by a surface parallel to the normal to the top plate 131 is light with an upper limit reflection angle θb (here, Lr 50°). The distance from position A to the upper end B of the inclined surface 133 is set to E so that this light reaches the upper end B of the outer surface of the frame 132.

From the above explanation, the distance E from the position A of the tip of the slit 16 to the side surface 131a of the top plate 131 is expressed by the following formula 1 based on the thickness t of the top plate 131 and the upper limit incident angle θb (=50°).
E=2×t×tanθb...Formula 1

The distance e1 from the position A of the tip of the slit 16 to the outer side surface of the frame body 132 is expressed by the following equation 2 based on the height H of the range in which the inclined surface 133 is formed and the lower limit incident angle θa (=40°).
e1=H×tanθa...Formula 2

Furthermore, the distance e2 from the lower end C of the inclined surface 133 (the outer side surface of the base of the frame body 132) to the side surface 131a of the top plate 131 is expressed by the following formula 3 based on the height H and the angle φ of the inclined surface 133.
e2=H×tanφ...Formula 3

Here, the distances E, e1, and e2 satisfy the relationship of the following formula 3.
E=e1+e2...Formula 4

Therefore, the height H of the range where the inclined surface 133 is formed from the upper end of the frame 132 is determined from Equation 5, which is obtained by substituting Equations 2 and 3 into Equation 4.
H=(2×t×tanθb)/(tanθa +tanφ) ...Formula 5

In other words, the height H of the range forming the inclined surface 133 is a range calculated using Equation 5 based on the thickness t of the top plate 131, the lower limit incident angle θa = 40° and the upper limit incident angle θb = 50°, which are determined taking into account the wavelength of the ultraviolet light and the wavelength dependence of the refractive index of the top plate 131, and the set angle φ of the inclined surface 133.

The distances E, e1, e2, and H calculated using the above formulas are calculated values for emitting ultraviolet light with a critical angle θa (= lower limit incident angle) to θb (= upper limit incident angle) from the inclined surface 133 at an angle equal to or less than the critical angle and as close to the normal of the inclined surface 133 as possible, depending on the position A of the tip of the slit 16. Therefore, in practice, the distance E from the position A of the tip of the slit 16 may be extended in the direction A-B to allow for some leeway. Similarly, the lower end position C of the height H of the range in which the inclined surface 133 is provided may be extended downward. In other words, the side surface 131a and the inclined surface 133 of the top plate 131 may be shaped to protrude outward, as indicated by the dashed line 141 in Figure 3. The thickness (t') of the end of the top plate 131 may also be thinned. By extending or thinning these portions, the area of the outer slope can be expanded. Specifically, by setting the distance E and height H to be 5% to 20% larger than the distance E and height H determined by the above formula, the guided light can be reliably emitted from the inclined surface 133.

Note that it is desirable to determine the angle φ of the inclined surface 133 so that light incident on the inclined surface 133 is at an angle close to perpendicular to the inclined surface 133, but it is sufficient if it does not deviate from the angle at which light can be emitted to the outside.

The base width Wb of the frame body can also be widened inward. Increasing the width Wb improves the joining strength. It may also be possible to set the width with consideration given to workability.

Furthermore, by providing the slits 16, the width Wb of the frame body 132 can be increased, allowing the cap 13 to be designed with a stable structure. This allows a large area to be secured for bonding the lower end surface of the frame body 132 to the substrate 10 using the resin bonding material 14, thereby improving the reliability of airtightness.

Note that the slit 16 does not necessarily have to be provided. If the slit 16 is not provided, the connection between the upper end of the inner side surface of the frame body 132 and the underside of the top plate 131 will be the above-mentioned position A.

(Substrate 10)
The substrate 10 is made of ceramic that can keep the enclosed gas airtight. For example, a substrate 10 made of aluminum nitride (AlN) with a thermal conductivity of 150 to 170 W/mK can be used. Alternatively, a substrate 10 made of alumina or silicon nitride can also be used.

As shown in FIG. 1, the substrate 10 has first wiring 15a and second wiring 15b on its top surface, and first vias 17a and second vias 17b connected to the first wiring 15a and second wiring 15b, respectively. The substrate 10 has first mounting electrodes 18a and second mounting electrodes 18 connected to the first vias 17a and second vias 17b, respectively, on its back surface. The first mounting electrodes 18a and second mounting electrodes 18b can be formed by sequentially laminating copper-tungsten (CuW), nickel (Ni), and gold (Au) (hereinafter referred to as CuW/Ni/Au), or by sequentially laminating nickel-chromium (NiCr)/Au/Ni/Au.

As shown in Figure 2(d), the first wiring 15a to which the light-emitting element 11 is die-bonded using the element bonding layer 12 has an alignment slit 17c to limit the spreading of the molten element bonding layer 12 to a specified range of the first wiring 15a. This prevents misalignment of the light-emitting element 11 and enables positioning when the element bonding layer 12 is melted to bond the light-emitting element 11 to the first wiring 15a.

The size of the substrate 10 is desirably designed so that the sides of the substrate 10 extend outward beyond the sides of the top plate 131. This protects the edges of the top plate 131 of the cap 13 from coming into contact with surrounding components and being chipped when the semiconductor light-emitting device 1 of this embodiment is mounted on a circuit board.

In addition, ultraviolet light emitted diagonally downward from the inclined surface 133 of the cap 13 is irradiated onto the protruding substrate 10, preventing the ultraviolet light from reaching the circuit board.

(Light-emitting element 11)
The light-emitting element 11 used is one that emits ultraviolet light in the visible light range (for example, ultraviolet light of 200 nm to 380 nm, or purple light of 380 nm to 415 nm) that modifies the resin from ultraviolet light. Note that ultraviolet light in this description also includes ultraviolet light in the visible light range. Here, as shown in FIG. 5 , one having a bottom electrode 11a and a bonding electrode pad 11b on its top surface is used. The light-emitting element 11 may have any structure, and may be a flip-chip type or one having a bonding electrode pad on its top surface. When using a flip-chip type light-emitting element 11 or one having a bonding electrode pad, the shape of the wiring 15 is changed to correspond to the electrode structure of the light-emitting element 11.

In addition to the light-emitting element 11, it is preferable to connect a Zener diode as a protective element 21 between the first wiring 15a and the second wiring 15b (see Figure 2(e)).

(Element bonding layer 12)
For example, a gold-tin alloy (Au-20 wt % Sn) can be used for the element bonding layer 12. The element bonding layer 12 bonds the lower electrode of the light emitting element 11 to the first wiring 15a.

(Wire 19)
An electrode pad 11b on the upper surface of the light emitting element 11 is connected to the second wiring 15b by a bonding wire 19. The bonding wire 19 is made of, for example, Au and has a diameter of 30 μm.

(Joining material 14)
The bonding material 14 may be any resin that can provide airtight sealing, such as silicone resin or acrylic resin.

(Gas filled in space 20)
The space 20 around the light-emitting element 11, which is airtightly covered by the cap 13, is filled with an inert gas such as dry air or dry nitrogen gas. Alternatively, the space 20 may be a decompressed space that is decompressed to a predetermined pressure.

Since the resin bonding material 14 is not susceptible to oxidation during hardening, dry air containing oxygen as a component gas can be used as the gas sealed in the space 20. Furthermore, the hardening process of the bonding material 14 can be carried out in the atmosphere.

<Operation and effect of each part when lighting>
The semiconductor light emitting device 1 of this embodiment is mounted on a circuit board. When a current is supplied from the circuit board between the first mounting electrode 18a and the second mounting electrode 18b on the back surface of the substrate 10, the light emitting element 11 emits ultraviolet light from the upper surface.

Most of the emitted UV light passes through the top plate 131 of the cap 13 and is emitted upward, but some UV light is guided within the top plate 131 and reaches near the edge of the top plate 131.

At this time, of the ultraviolet rays guided through the top plate 131, light whose incident angle on the upper and lower surfaces of the top plate 131 is greater than 45° is emitted to the outside from the edge surfaces of the top plate 131. On the other hand, of the ultraviolet rays guided through the top plate 131, light whose incident angle on the upper and lower surfaces of the top plate 131 is greater than or equal to the critical angle θc and less than or equal to the critical angle θc + 2δ reaches the inclined surface 133 and is emitted to the outside from the inclined surface 133.

As a result, the ultraviolet light is not guided to the lower end of the frame 132 and does not reach the bonding material 14. This prevents deterioration of the bonding material 14.

Furthermore, because resin can be used as the bonding material 14, there is no need to reduce the oxygen content of the gas sealed in the space 20 or the surrounding atmosphere when bonding the bonding material 14. This makes it possible to provide a highly reliable semiconductor light-emitting device 1 at low cost.

(Manufacturing method)
A method for manufacturing the semiconductor light emitting device 1 of the embodiment will be described with reference to the flow charts of FIGS. 6 and 8 and the cross-sectional views of FIGS.

(Cap manufacturing method)
First, a method for manufacturing the cap 13 will be described. Here, an example in which quartz glass or borosilicate glass is used will be described. Hereinafter, quartz glass or borosilicate glass will be simply referred to as glass.

(Step S1)
First, as shown in FIG. 7A, a glass plate (thickness 160 μm) for the top plate 131, a glass plate (thickness 70 μm) for the slit 16, and a glass plate (thickness 900 μm) for the frame 132 are prepared.

As shown in Figure 7(b), the glass plate for the slit 16 is cut to form the desired slit 16. Cutting can be done using laser cutting, water jet cutting, a glass milling machine, etching, or the like.

(Step S2)
7C, the glass plate for the frame 132 is cut so as to form the space 20. The cutting method is the same as in step S1.

(Step S3)
7(d), the glass plate for the frame 132, the glass plate for the slit 16, and the glass plate for the top plate 131 are stacked in this order from the bottom up. They are set in a pressure bonding device, and the contacting portions of the glass plates are pressure-welded (thermocompression bonded) to be integrated by pressing and heating.

(Step S4)
As shown in FIG. 7( e ), grooves that will become the outer side surfaces and inclined surfaces 133 of the frame body 132 are formed from the lower surface of the glass plate for the frame body 132 by dicing.

(Step S5)
As shown in FIG. 7F, the portions of the top plate 131 that will become the side surfaces 131a are diced and separated into individual pieces.

This completes the manufacturing process for the cap 13.

Next, we will explain the assembly process.

(Assembly method)
(Step S51)
The substrate 10 on which the first wiring 15a, the second wiring 15b, etc. are formed in advance, the light emitting element 11, and the cap 13 are prepared.

As shown in Figure 9(a), the underside of the light-emitting element 11 is die-bonded to the first wiring 15a of the substrate 10 using AnSn volatile solder paste.

(Step S52)
As shown in FIG. 9B, the second wiring 15 b of the substrate 10 and the electrode pad 11 b on the upper surface of the light emitting element 11 are connected by a bonding wire 19 .

(Step S53)
As shown in FIG. 9( c), for example, a silicone resin is applied as the bonding material 14 to the portion of the substrate 10 where the lower end surface of the frame body 132 of the cap 13 is to be bonded, and the cap 13 is placed on top of it. After that, the bonding material is heated and hardened in the air atmosphere to bond (seal).

In addition, silicone resin may be applied to the lower end surface of the frame 132 of the cap 13.

When sealing the cap 13, dry air or an inert gas may be sealed into the internal space 20. The pressure in the space 20 may also be reduced.

Through the above steps, the semiconductor light-emitting device 1 can be completed. In this way, in the semiconductor light-emitting device 1 of this embodiment, the cap 13 can be easily bonded to the substrate 10 using the resin bonding material 14.

(Variation 1)
A semiconductor light emitting device according to the first modification of the embodiment will be described with reference to FIG.

As shown in the cross-sectional view of Figure 10, the semiconductor light-emitting device of variant 1 has a configuration in which a light-absorbing light-shielding plate 101 is provided on the side of the substrate 10. In this case, the light-shielding plate 101 is fixed so that its main plane is perpendicular to the main plane of the substrate 10. The height of the upper end of the light-shielding plate 101 is the same as the height of the upper surface of the top plate 131 of the cap 13.

The light-shielding plate 101 can be, for example, a black ceramic or black anodized aluminum plate. Alternatively, the light-shielding plate 101 can be a plate-shaped member made of Teflon (registered trademark) resin or the like containing carbon black, fluorescent pigment, and phosphorescent pigment.

By positioning the light-shielding plate 101 from the side of the substrate 10 to the height of the upper surface of the top plate 131 in this way, the ultraviolet light of the guided light emitted from the side surface 131a and inclined surface 133 of the top plate 131 is blocked by the light-shielding plate 101. This prevents the ultraviolet light emitted from the side surface 131a and inclined surface 133 from reaching other devices arranged to the side of the semiconductor light-emitting device of this embodiment, or the circuit board on which the semiconductor light-emitting device is mounted.

Other configurations are the same as in the embodiment, so explanations will be omitted.

(Variation 2)
A semiconductor light emitting device according to the second modification of the embodiment will be described with reference to FIG.

In variant 2, the inclined surface 133 of the cap 13 is curved. The curvature is designed so that the angle of incidence of the guided light incident on the inclined surface 133 is equal to or less than the critical angle (θc).

The direction of curvature may be outwardly convex as shown in Figure 11(a), or concave as shown in Figure 11(b).

In particular, the concave curved inclined surface 133 is preferable as it makes glass processing easier and is expected to reduce manufacturing costs.

Other configurations are the same as in the embodiment, so explanations will be omitted.

(Variation 3)
A semiconductor light emitting device according to the third modification of the embodiment will be described with reference to FIG.

When the directional characteristics of the light emitted from the light-emitting element 11 that emits ultraviolet light are 90° or greater, some of the light HL1 enters the frame 132 of the cap 13 from the inner side of the frame 132, as shown in Figure 12. If the light HL1 reaches the bonding material 14, it may cause degradation of the bonding material 14.

Therefore, in variant example 3, when using a light-emitting element 11 with a directional characteristic of 90° or more, a light-shielding reflective surface 121 is provided on the bottom surface of the frame 132.

The light-shielding reflective surface 121 is formed by cutting out a portion (approximately half the width Wb) of the bottom surface of the frame 132 on the inner periphery (the side closest to the space 20) to form an inclined surface. The light-shielding reflective surface 121 is provided along the entire inner periphery of the frame 132. The height of the light-shielding reflective surface 121 from the top surface of the substrate 10 increases with increasing distance from the inner periphery, and is highest at the center of the width Wb of the frame 132.

The bonding material 14 bonds the area of the bottom surface of the frame 132 outside the center of the width Wb of the frame 132, where the light-blocking reflective surface 121 is not formed, to the top surface of the substrate 10.

Light HL1 that is incident on the inner side surface of the frame body 132 from the light-emitting element 11 and travels directly toward the bottom surface of the frame body 132 is reflected by the light-shielding reflective surface 121, preventing it from reaching the bonding material 14 and traveling upward.

In addition, light HL2 that is incident on the inner side surface of the frame body 132 from the light-emitting element 11 and travels directly toward the inclined surface 133 is also reflected by the inclined surface 133 and travels upward.

Therefore, when using a light-emitting element 11 with a directivity characteristic of 90° or more, adopting the structure shown in Figure 12 not only prevents deterioration of the bonding material 14, but also improves the light output from above with ultraviolet light.

(Variation 4)
A semiconductor light emitting device according to a fourth modification of the embodiment will be described with reference to FIG.

If the directional characteristics of the ultraviolet light emitted by the light-emitting element 11 are circular when viewed from above, it is desirable that the shape of the top plate 131 and frame 132 of the cap 13 when viewed from above be rectangular with rounded (curved) corners, as shown in Figure 3(a), or that the shape of the top plate 131 and frame 132 of the cap 13 when viewed from above be circular, as shown in Figure 3(b).

By using a cap 13 with rounded corners (Figure 13(a)) or a cap 13 that is entirely circular (Figure 13(b)), the angle between the light emitted from the light-emitting element 11 and the side of the cap 13 can be made perpendicular. This suppresses the generation of unexpected stray light and prevents stray light from reaching the bonding material 14 and degrading it.

(Variation 5)
A semiconductor light emitting device according to the fifth modification of the embodiment will be described with reference to FIGS.

When the angle of incidence is gradually increased, the reflectance of light at the interface from glass to air (vacuum) increases immediately before the critical angle θc, as shown in Figure 13(a). In particular, for P-polarized light, the reflectance drops to zero at the Brewster angle and then increases sharply.

Therefore, in order to prevent further deterioration of the bonding material 14, in variant 5, the end face structure of the cap 13 is designed based on the Brewster angle, and the ultraviolet light guided through the top plate 131 is made to enter the inclined surface 133 at an angle smaller than the Brewster angle θw.

Specifically, the critical angle θc in this embodiment is set to Brewster's angle θw. Therefore, the lower limit incident angle θa is 34° (lower limit incident angle θa = critical angle θc = Brewster's angle θw), the difference angle δ is 11° (absolute value of Brewster's angle θw - 45°), and the upper limit incident angle θb is 56° (Brewster's angle θw + 2δ). The end face structure will be the same as in the embodiment, using the aforementioned values.

The end surface structure of the cap 13, designed based on the Brewster angle, is positioned further outward than the end surface structure in Figure 3, as shown in Figure 13(b).

The semiconductor light-emitting device of variant 5 can further reduce the amount of light that reaches the bonding material 14, making it highly reliable.

The semiconductor light-emitting devices of the above-described embodiments and variants 1 to 5 can be used as light sources for resin curing devices, sterilization, disinfection, or sterilization devices, dental whitening devices, counterfeit bill detection devices, auxiliary light sources for plant cultivation, and light sources for ozone concentration detection sensors, etc.

REFERENCE SIGNS LIST 1 semiconductor light emitting device 10 substrate 11 light emitting element 11a lower electrode 11b electrode pad 12 element bonding layer 13 cap 14 bonding material 15 wiring 15a first wiring 15b second wiring 16 slit 17a first via 17b second via 17c alignment slit 18a first mounting electrode 18b second mounting electrode 19 wire 20 space 21 protective element 101 light shielding plate 121 light shielding reflecting surface 131 top plate 131a side surface 132 frame body 132a side surface 133 inclined surface 141 dashed line

Claims (8)

A light emitting element that emits ultraviolet light;
a substrate on which the light-emitting element is mounted;
a cap that airtightly covers a space around the light-emitting element on the substrate;
a bonding material that airtightly bonds the cap to the upper surface of the substrate,
the cap has a top plate and a frame body that supports a lower surface of the top plate with respect to the substrate, the top plate and the frame body being integrally formed from a material that transmits ultraviolet rays and has a critical angle between the ultraviolet rays and the atmosphere of 45° or less;
the bottom surface of the frame is bonded to the top surface of the substrate using a resin as the bonding material;
A planar slit is provided at the boundary between the frame body and the underside of the top plate, extending the underside of the top plate by a predetermined distance from the inside to the outside of the frame body, over the entire periphery of the frame body ;
A semiconductor light-emitting device characterized in that an inclined surface inclined at a predetermined angle with respect to the normal to the top plate is formed on the upper part of the outer side of the frame body, and a portion of the ultraviolet light that has been guided within the top plate reaches the inclined surface and is emitted to the outside from the inclined surface . A light emitting element that emits ultraviolet light;
a substrate on which the light-emitting element is mounted;
a cap that airtightly covers a space around the light-emitting element on the substrate;
a bonding material that airtightly bonds the cap to the upper surface of the substrate,
the cap has a top plate and a frame body that supports a lower surface of the top plate with respect to the substrate, the top plate and the frame body being integrally formed from a material that transmits ultraviolet rays and has a critical angle between the ultraviolet rays and the atmosphere of 45° or less;
the bottom surface of the frame is bonded to the top surface of the substrate using a resin as the bonding material;
a slit extending a predetermined distance from the inside to the outside of the frame body is provided around the entire periphery of the frame body at the boundary between the frame body and the underside of the top plate;
An inclined surface inclined at a predetermined angle with respect to the normal line of the top plate is formed on the upper part of the outer side surface of the frame body,
an angle of the inclined surface is 40° or more and 50° or less with respect to a normal to the top plate so that when the ultraviolet light that has been guided through the top plate reaches the inclined surface, the angle is smaller than a critical angle;
a part of the ultraviolet light that has been guided through the top plate reaches the inclined surface and is emitted to the outside from the inclined surface;
A semiconductor light-emitting device characterized in that the angle formed by the line connecting the tip of the slit and the lower end of the inclined surface of the frame body and the normal to the top plate is less than the critical angle of the ultraviolet light at the interface between the top plate and air. a substrate having an upper surface and a lower surface;
a light-emitting element mounted on an upper surface of the substrate and emitting ultraviolet light;
a cap bonded to an upper surface of the substrate to form a space around the light emitting element;
the cap has a top plate facing an upper surface of the light-emitting element and a frame body supporting a lower surface of the top plate relative to the substrate, the top plate and the frame body being made of a material that transmits ultraviolet light and has a critical angle between the ultraviolet light and the atmosphere of 45° or less;
a slit extending a predetermined distance from the inside to the outside of the frame body is provided at the boundary between the frame body and the underside of the top plate;
a base of the frame body joined to the upper surface of the substrate is joined to the substrate with a base width that extends from an outer side surface of the frame body located outside a normal line of the substrate that passes through the position of the tip of the slit to an inner side of the normal line ,
An inclined surface is formed on an upper portion of the outer side surface of the frame body, the inclined surface protruding outward more than a lower portion of the outer side surface of the frame body and inclined at a predetermined angle with respect to a normal line of the top plate,
A part of the ultraviolet light that has been guided through the top plate reaches the inclined surface, and the inclined surface is set at an inclination angle such that the light that has been reflected on the upper surface of the top plate and passed through the frame body outside the tip of the slit is emitted obliquely downward from the inclined surface to the outside.
A semiconductor light emitting device characterized by: 4. The semiconductor light emitting device according to claim 1 , wherein an upper end of the frame body is positioned in a direction of a main plane of the top plate so as to coincide with a side surface of the top plate;
the inclined surface is formed in a range from the upper end of the frame body to a predetermined height below the upper end,
The semiconductor light emitting device according to claim 1, wherein the side surface of the frame at the position of the lower end of the inclined surface is positioned closer to the light emitting element by a predetermined distance than the side surface of the top plate. 5. The semiconductor light emitting device according to claim 4 , wherein the side surface of the substrate protrudes outward beyond the side surface of the top plate of the cap. 6. The semiconductor light emitting device according to claim 5 , wherein a light blocking plate (101) is fixed to an end portion of the substrate perpendicular to a main surface of the substrate;
The semiconductor light emitting device is characterized in that the height of the light blocking plate is the same as the height of the top plate. 4. The semiconductor light emitting device according to claim 1 , wherein the inclined surface of the frame is curved convexly or concavely outward. 4. The semiconductor light emitting device according to claim 1, wherein the cap has a shape in a top view of either a rectangle with four curved corners or a circle.