JP7580206B2 - Semiconductor light emitting device - Google Patents

Description

Related to semiconductor light-emitting devices such as light-emitting diodes (LEDs).

A semiconductor light-emitting device is known in which a light-transmitting member is placed on the emission surface of a semiconductor light-emitting element, and the side surfaces of the semiconductor light-emitting element and the light-transmitting member are covered with a light-reflective member (for example, Patent Document 1, etc.). It is known that the light-reflective member is a member called a white resin, in which light-scattering particles are dispersed in a light-transmitting resin.

Patent No. 5746335

In the semiconductor light-emitting device described above, in addition to high light extraction efficiency, it is expected that high contrast will be obtained between the area from which light is emitted and other areas.

The present invention has been made in consideration of the above points, and aims to provide a semiconductor light-emitting device with high light extraction efficiency and high contrast.

The device is characterized by having a substrate having a recess on its upper surface, a light-emitting element disposed on the bottom surface of the recess, a light-transmitting member disposed on the light-emitting element and having light-transmitting properties with respect to the light emitted by the light-emitting element, and a covering member disposed within the recess so as to cover the side surfaces of the light-emitting element and the light-transmitting member, the covering member being made of resin as a medium and containing suspended particles that are resin particles and scattering particles that have light-scattering properties in the medium.

FIG. 2 is a top view of a semiconductor light emitting device according to an embodiment. 1 is a cross-sectional view of a semiconductor light emitting device according to an embodiment. FIG. 3 is an enlarged schematic diagram showing a part of FIG. 2 . 1A to 1C are diagrams illustrating the movement of scattering particles during the manufacturing process. 4 is a flowchart showing an example of a manufacturing process for a semiconductor light emitting device according to an embodiment. FIG. 4 is a schematic diagram of a portion corresponding to FIG. 3 according to a comparative example. 4 is a graph showing an example of a luminance distribution of a semiconductor light emitting device according to an example. 11 is a graph showing an example of a luminance distribution of a semiconductor light emitting device according to a comparative example.

In the following, preferred embodiments of the present invention will be described, but these may be modified and combined as appropriate. In the following description and accompanying drawings, substantially the same or equivalent parts are denoted by the same reference numerals.

The configuration of a semiconductor light-emitting device 10 according to an embodiment of the present invention will be described with reference to Figures 1 to 3. Figure 1 is a top view that shows a semiconductor light-emitting device 10 according to an embodiment of the present invention. Figure 2 is a cross-sectional view that shows a schematic cross section of the semiconductor light-emitting device 10 shown in Figure 1 taken along line 2-2. Figure 3 is an enlarged view of part A surrounded by a dotted line in Figure 2.

[Light-emitting device]
As shown in Figures 1 and 2, the semiconductor light-emitting device 10 (hereinafter also referred to as the light-emitting device 10) of this embodiment is configured to include a substrate 11 having a recess 11C, a semiconductor light-emitting element 13 (hereinafter also referred to as the light-emitting element 13) mounted on a bottom surface 11S of the recess 11C of the substrate 11, a translucent member 25 mounted above the light-emitting element 13, an adhesive member 37 that bonds the upper surface of the light-emitting element 13 to the lower surface of the translucent member 25, and a covering member 27 that covers the bottom surface 11S of the substrate 11 and the side surfaces of the light-emitting element 13 and the translucent member 25.

[Substrate 11]
The substrate 11 is rectangular in top view and has a recess 11C that opens to the top surface. The recess 11C is defined by a flat bottom surface 11S and a frame portion 11W that surrounds the outer periphery of the bottom surface 11S. An anode wiring 21 and a cathode wiring 29 are provided on the bottom surface 11S of the recess 11C of the substrate 11, so that the light emitting element 13 can be mounted. An anode mounting electrode 33 and a cathode mounting electrode 31 are provided on the surface opposite to the bottom surface 11S, so that the light emitting device 10 can be mounted on a circuit board. That is, the substrate 11 is composed of a substrate base 11A including the bottom surface 11S, which is the mounting surface for the light emitting element 13, and a frame portion 11W.

In this embodiment, the substrate base 11A forming the bottom surface 11S of the substrate 11 and the portion forming the frame 11W are integrally formed. That is, the substrate 11 is made of one member. For example, the substrate 11 is made of ceramics such as alumina, aluminum nitride, silicon nitride, etc. Note that the substrate base 11A including the bottom surface 11S of the substrate 11 and the frame 11W may be formed by joining separate members. For example, the substrate 11 may be formed by joining a ceramic flat-plate-shaped substrate base 11A to a resin or ceramic frame 11W.

The cathode wiring 29 and anode wiring 21 provided on the bottom surface 11S are metal wiring electrode patterns. Similarly, the cathode mounting electrode 31 and anode mounting electrode 33 provided on the surface opposite the bottom surface 11S are also metal electrode patterns. The cathode mounting electrode 31 is electrically connected to the cathode wiring 29 via the conductive via 31H, and the anode mounting electrode 33 is electrically connected to the anode wiring 21 via the conductive via 33H.

For example, the anode wiring 21, the cathode wiring 29, the cathode mounting electrode 31, and the anode mounting electrode 33 are made of a silver alloy, and their surfaces are plated with nickel/gold (Ni/Au). The conductive vias 31H and 33H are also made of a silver alloy.

[Semiconductor Light Emitting Device]
The semiconductor light emitting element 13 is composed of, for example, a conductive support substrate 15 and a semiconductor laminate 17 made of an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer bonded onto the support substrate 15. Furthermore, the light emitting element 13 is provided with an anode element electrode 19 provided on the same surface as the surface of the support substrate 15 to which the semiconductor laminate 17 is bonded, and a cathode element electrode (not shown) is provided on the surface of the support substrate 15 opposite to the surface to which the semiconductor laminate 17 is bonded.

Specifically, the anode element electrode 19 is provided on the support substrate 15 via an insulating layer, and is connected to a p-side electrode (not shown) provided on the p-type semiconductor layer of the semiconductor laminate 17 via a p-side bonding member (not shown). That is, the anode element electrode 19 is electrically bonded to the p-type semiconductor layer of the semiconductor laminate 17 and is insulated from the support substrate 15.

The cathode element electrode (not shown) is an electrode provided on the surface of the support substrate 15 opposite to the surface to which the semiconductor laminate 17 is bonded, i.e., on the back surface of the support substrate 15 (the underside of the light-emitting element 13). The cathode element electrode is connected to an n-side electrode provided on the n-type semiconductor layer via the support substrate 15 and an n-side bonding member (not shown). In other words, the cathode element electrode is electrically connected to the n-type semiconductor layer of the semiconductor laminate 17.

In this embodiment, the support substrate 15 is made of conductive silicon (Si), the semiconductor laminate 17 includes an indium gallium nitride (InGaN) light-emitting layer, and the light-emitting element 13 emits light with a peak wavelength (λp) of 430 to 460 nm.

In this embodiment, the light-emitting element 13 is electrically connected via a bonding member 35 between the cathode element electrode provided on the lower surface of the support substrate 15 and the cathode wiring 29 provided on the bottom surface 11S of the recess 11C of the substrate 11. Also, the anode element electrode 19 provided on the upper surface of the support substrate 15 and the anode wiring 21 provided on the bottom surface 11S of the recess 11C of the substrate 11 are electrically connected via a bonding wire 23.

[Light-transmitting member]
The light-transmitting member 25 is disposed above the light-emitting element 13, and is a plate-like body having a size that almost overlaps the contour of the semiconductor laminate 17 (the light-emitting surface of the light-emitting element 13) when viewed from above. The size of the light-transmitting member 25 is preferably equal to or larger than the contour of the semiconductor laminate 17 and equal to or smaller than the contour of the light-emitting element 13 when viewed from above. The light-transmitting member 25 of this embodiment has a size that covers the light-emitting element 13 excluding the anode element electrode 19 when viewed from above.

The light-transmitting member 25 is translucent to the light emitted from the light-emitting element 13 and the light emitted from the wavelength conversion material described below. The light-transmitting member 25 can be made of glass, translucent ceramics such as alumina and yttrium aluminum garnet (YAG), or translucent resins such as silicone resin, epoxy resin, polycarbonate resin, acrylic resin, and polyimide resin. Note that glass is used for the light-transmitting member 25 in this embodiment.

The light-transmitting member 25 may contain a wavelength conversion material such as a phosphor that absorbs the radiation light from the light-emitting element _{13 and emits light of a longer wavelength. For example, as the wavelength conversion material, YAG:Ce phosphor particles in which a cerium (Ce) activator is contained in yttrium aluminum garnet crystal (YAG:Y3Al5O12 )} , phosphor particles in which an europium (Eu) activator is contained in α-sialon or β- _sialon , nanoparticles of metal nitride or metal sulfide, etc. can be used.

In this embodiment, the surface (lower surface) of the translucent member 25 opposite the upper surface 25T is adhered to the upper surface of the light-emitting element 13 by an adhesive member 37.

[Adhesive member]
The adhesive member 37 is translucent to the light emitted from the light emitting element 13 and the light emitted from the wavelength conversion material, and bonds the upper surface (emission surface) of the light emitting element 13 to the lower surface (incident surface) of the light transmissive member 25. The adhesive member 37 has a function of guiding the light emitted from the upper surface of the light emitting element 13 to the lower surface of the light transmissive member 25.

The adhesive member 37 embeds part or all of the semiconductor laminate 17 and the anode element electrode 19 on the surface of the light-emitting element 13 (more specifically, on the upper surface of the support substrate 15). For example, it is preferable that the adhesive member 37 has a side that connects the edge that defines the lower surface of the translucent member 25 with the edge that defines the upper surface of the support substrate 15. It is also preferable that the connection between the anode element electrode 19 and the bonding wire 23 is covered with the adhesive member 37. By providing the adhesive member 37 in this manner, the semiconductor laminate 17, which is prone to deterioration, can be sealed and the connection portion of the bonding wire 23 connected to the anode element electrode 19 can be fixed to prevent the wire from coming loose.

However, if the adhesive member 37 covers the side surface of the support substrate 15, the light emitted from the semiconductor laminate 17 will be absorbed by the support substrate 15, which is not preferable.

For the adhesive member 37, resins such as silicone resin, epoxy resin, and acrylic resin can be used. Inorganic polymers including silica polymer and alumina-silica geopolymer can also be used. In this embodiment, silicone resin was used as the adhesive member 37.

The adhesive member 37 may also contain a wavelength conversion material such as a phosphor that absorbs the radiation from the light-emitting element 13 and emits fluorescence. The wavelength conversion material may be contained in at least one of the translucent member 25 or the adhesive member 37. In this embodiment, the adhesive member 37 contains YAG:Ce phosphor particles as the wavelength conversion material.

[Covering member]
The covering member 27 covers the bottom surface 11S of the recess 11C of the substrate 11, the supporting substrate 15 of the light-emitting element 13, the adhesive member 37, the side surface of the translucent member 25, and the bonding wires 23, and is filled into the recess 11C of the substrate 11 so as to expose the upper surface 25T of the translucent member 25.

The covering member 27 seals the light-emitting element 13 and has the function of reflecting the light emitted from the light-emitting element 13 and the light emitted from the wavelength conversion material.

The covering member 27 of this embodiment contains a medium 39 made of a resin that is translucent to the light emitted from the light emitting element 13 and the light emitted from the wavelength conversion material, and scattering particles 41 that have a refractive index different from that of the medium 39 and scatter (Mie scattering) the light that is guided through the medium 39 (i.e., have light scattering properties), and the covering member 27 as a whole is a member with light reflectivity. Furthermore, the covering member 27 contains floating particles 43 that have approximately the same specific gravity as the medium 39. And, the scattering particles 41 and floating particles 43 are uniformly dispersed at a predetermined concentration in the medium 39 of the covering member 27, as shown in FIG. 3.

For example, the covering member 27 in this embodiment can be formed by uniformly dispersing the scattering particles 41 and the floating particles 43 in a resin material having fluidity before hardening that becomes the medium 39 (hereinafter, the "resin material having fluidity before hardening" is also referred to as the "precursor resin material") and then hardening the material. As will be described in detail later, the floating particles 43 have the function of preventing the scattering particles 41 dispersed in the precursor resin material of the medium 39 from settling during the process of forming the covering member 27.

In this way, the covering member 27 with the suspended particles 43 dispersed therein maintains a state in which the scattering particles 41 are uniformly dispersed, so that, of the light emitted from the light-emitting surface of the light-emitting element 13 (the upper surface of the semiconductor laminate 17) and incident on the translucent member 25, the light that enters the covering member 27 from the side of the translucent member 25 can be uniformly reflected back to the translucent member 25.

As a result, direct light that is emitted from the light emission surface of the light-emitting element 13, enters the translucent member 25, and is emitted from the top surface 25T is combined with indirect light that is reflected by the covering member 27 that covers the side surface of the translucent member 25 and is emitted from the top surface 25T, thereby increasing the optical output of the light that is emitted from the top surface 25T of the translucent member 25. In addition, a high contrast is obtained with respect to the surrounding area of the top surface 25T of the translucent member 25 (for example, the top surface 27T of the covering member 27).

The medium 39 of the covering member 27 may be, for example, a thermosetting resin or a photosetting resin such as silicone resin (specific gravity 0.99), epoxy resin (specific gravity 1.11 to 1.40), acrylic resin (specific gravity 1.17 to 1.20), polycarbonate resin (specific gravity 1.1 to 1.6), or polyimide resin (specific gravity 1.33 to 1.43). The scattering particles 41 may be, for example, particles of metal oxide such as titanium oxide (TiO ₂ ), zinc oxide (ZnO), or alumina (Al ₂ O ₃ ). The floating particles 43 may be, for example, particles of cured resin such as silicone resin, epoxy resin, acrylic resin, polycarbonate resin, or polyimide resin (particles of resin that do not liquefy at the curing temperature of the medium 39 may be used).

In this embodiment, the medium 39 of the covering member 27 is a silicone resin with a specific gravity of 0.99, a refractive index of 1.41, and light resistance that does not yellow when exposed to the blue light (wavelength 430 nm to 460 nm) from the light-emitting element 13.

In addition, spherical anatase-type titanium oxide (TiO ₂ ) particles with a specific gravity of 4.0, a refractive index of 2.52, and a particle size of 250 nm were used as the scattering particles 41. For example, light with a wavelength of 430 nm is 305 nm in the medium 39 (wavelength in the medium=wavelength in vacuum/refractive index of the medium: 430 nm/1.41), and the particle size of the scattering particles is 0.82 times the wavelength (250 nm/305 nm). In addition, light with a wavelength of 780 nm is 553 nm (780 nm/1.41) in the medium 39, and the particle size of the scattering particles is 0.45 times the wavelength (250 nm/553 nm). In this way, in the region where the particle size of the scattering particles 41 is 1/4 to 2 times the wavelength in the medium 39, it is a Mie scattering region, and a high reflectance is obtained.

The amount of scattering particles 41 added was 25 wt% (weight percent concentration). The amount can be 8 wt% to 40 wt%, but if it is less than 8 wt%, the reflectance is low, and if it exceeds 40 wt%, resin cracks may occur in the coating member 27, so this is not recommended.

As the floating particles 43, spherical cured silicone resin with a specific gravity of 0.99, a refractive index of 1.41, and a particle diameter of 800 nm was used. The amount of floating particles 43 added was 2 wt%. The amount of floating particles 43 added is preferably 1 wt% to 6 wt%, but if it is less than 1 wt%, the effect of preventing the scattering particles 41 from settling is weak, and if it exceeds 6 wt%, the effect of preventing the settling is saturated. The floating particles 43 may be added in an amount of more than 6 wt%, but it is desirable to keep the amount added to a level that does not cause flow obstruction due to a decrease in the liquid amount of the coating member 27 before curing. For example, the amount of floating particles 43 added is preferably 18 wt% or less. If the flow obstruction of the coating member 27 before curing is taken into consideration, it is preferable that the amount of floating particles 43 added is less than the amount of scattering particles 41 added (amount of floating particles 43 added < amount of scattering particles 41 added).

2 and 3, the top surface 27T of the covering member 27 is lower than the top surface 25T of the translucent member 25 in a cross-sectional view of the light-emitting device 10. Such a shape of the covering member 27 occurs when the precursor resin material of the medium 39 shrinks slightly when cured. However, the suspended particles 43 are resin particles that have been cured in advance, so they do not shrink when cured. This makes it possible to prevent the top surface 27T of the covering member 27 from becoming lower. In particular, the slope of the boundary between the periphery of the top surface 25T of the translucent member 25 and the top surface 27T of the covering member 27 can be made gentler.

For example, if the slope of the boundary is steep, the coating member 27 covering the side surface near the upper surface 25T of the translucent member 25 becomes thin, reducing the contrast. Adding suspended particles 43 makes the slope of the boundary gentler, preventing the reduction in contrast.

[Functions of suspended particles]
Next, the function of the suspended particles 43 will be described. The suspended particles 43 added to the covering member 27 prevent the scattering particles 41 from settling until the precursor resin material that becomes the medium 39 during manufacturing is cured. In other words, the suspended particles 43 have the function of maintaining the scattering particles 41 in a state where they are uniformly dispersed in the medium 39.

Figure 4 is a diagram that shows a schematic of the movement of scattering particles 41 and floating particles 43 during the manufacturing process of the light-emitting device 10, which will be described later. Specifically, the figure shows the movement of scattering particles 41 and floating particles 43 until the precursor resin material that becomes the medium 39 is cured when forming the covering member 27.

The dashed arrows attached to the scattering particles 41 in FIG. 4 show the settling of the scattering particles 41. The dashed arrows attached to the floating particles 43 show the movement of the floating particles 43 from before the scattering particles 41 pass by them to while they are passing by them. The solid arrows attached to the floating particles 43 show the movement of the floating particles from while the scattering particles 41 pass by them to after they have passed by them.

In this embodiment, the specific gravity of the titanium oxide particles serving as scattering particles 41 is 4.00, which is about four times the specific gravity of the silicone resin serving as medium 39, which is 0.99. Furthermore, when the silicone resin, which is the precursor resin material serving as medium 39, is heated and cured, it becomes more fluid (its viscosity decreases) during the temperature rise process prior to curing. Therefore, the scattering particles 41 in the silicone resin, which is the precursor resin material, tend to settle from the top surface 27T toward the bottom surface 11S of the substrate 11 (from top to bottom in FIG. 4).

On the other hand, the floating particles 43 are particles made from the same hardened resin as the silicone resin, which is the precursor resin material that becomes the medium 39, and so have the same specific gravity. Therefore, the floating particles 43 do not sink or float even when the silicone resin, which is the precursor resin material that becomes the medium 39, is in a high fluidity state. In other words, they are suspended in the silicone resin.

First, as shown in FIG. 4, in order for the scattering particles 41 to settle, they need to push aside the silicone resin that serves as the medium 39. At this time, the silicone resin flows around the scattering particles 41. The flow speed of the silicone resin is fast near the scattering particles 41 and slow farther away. In such a fluid, the solid suspended particles 43 impede the flow of the silicone resin, which has a difference in speed. As a result, the settling resistance of the scattering particles 41 increases, and the settling of the scattering particles 41 is suppressed.

Next, the suspended particles 43 move laterally as the silicone resin is pushed aside by the scattering particles 41, as shown by the dashed arrows in Figure 4. For example, it is possible for the suspended particles 43 to move laterally while rotating. In other words, in order for the scattering particles 41 to move downward, it is necessary to move the suspended particles 43 while pushing aside the silicone resin. Even in this case, the solid suspended particles 43 impede the flow of the silicone resin, which has a speed difference (the suspended particles rotate by impeding the flow with a speed difference). As a result, the settling resistance of the scattering particles 41 increases, and the settling of the scattering particles 41 is suppressed.

The space created by the scattering particles 41 moving downward is replaced by silicone resin. In this case, as in the case described above, the solid floating particles 43 impede the flow of the silicone resin, which has a difference in speed. As a result, the settling resistance of the scattering particles 41 increases, and the settling of the scattering particles 41 is suppressed.

In this way, by adding the floating particles 43 together with the scattering particles 41 to the silicone resin precursor resin material that forms the medium 39, the settling resistance of the scattering particles 41 can be increased, and the settling of the scattering particles 41 can be suppressed.

In other words, the floating particles 43, which are solid granules in the silicone resin precursor resin material that forms the medium 39 and do not settle or rise, impede the flow of the silicone resin and suppress the settling of the scattering particles 41.

On the other hand, when the floating particles 43 settle in the precursor resin material that becomes the medium 39, the scattering particles 41 settle. When the floating particles 43 rise to the surface in the precursor resin material that becomes the medium 39, the settling of the scattering particles 41 is promoted. Therefore, it is desirable that the floating particles 43 are suspended in the silicone resin of the precursor resin material that becomes the medium 39.

This method does not change the chemical properties of the silicone resin that forms the medium 39, and does not impair the sealing performance or adhesion of the coating member 27.

For example, one method for preventing the scattering particles 41 from settling is to add silica or alumina, which become inorganic polymers through hydrogen bonding or reaction, or a gelling agent or surfactant to the medium 39 to impart viscosity and thixotropy. However, these methods may impair the filling properties, sealing performance, and adhesion of the coating member 27.

The range of specific gravity in which the suspended particles 43 can be suspended in the precursor resin material that forms the medium 39 and prevent the scattering particles 41 from settling is relatively wide when the medium 39 is a resin material such as silicone resin or epoxy resin.

The time required for suppressing the settling of the scattering particles 41 by the floating particles 43 may be about 30 minutes to 2 hours from when the covering member 27 is filled into the recess 11C of the light-emitting device 10 until it hardens. The specific gravity of the silicone resin or epoxy resin that is the medium 39 of the covering member 27 is small (low density) at about 0.9 to 1.3, whereas the viscosity before hardening is relatively large at 0.5 to 10 Pa·s (for example, the viscosity of water is 1 mPa·s). Therefore, the relative specific gravity, which is the specific gravity of the floating particles 43 to the medium 39 (density of the floating particles/density of the medium, or specific gravity of the floating particles/specific gravity of the medium), may be in the range of 0.7 to 1.3. If the relative specific gravity is 0.9 to 1.1, the floating particles 43 do not substantially settle or rise during the time until hardening (for example, movement of about the particle size of the floating particles), which is even more preferable. A relative specific gravity of about 1 is preferable.

In this specification, the resins used for the medium 39 and the suspended particles 43 are referred to as the same resin if they have the same main skeleton (the molecular skeleton that determines the type of resin) and the same substituents (groups that change the characteristics of the same resin type), and are referred to as the same type of resin if they have the same main skeleton but different substituents.

In the present invention, it is preferable that the medium 39 and the floating particles 43 are made of the same type of resin, and preferably the same resin. For example, if they are the same or the same type of resin, the floating particles 43 will disperse in the medium 39 without agglomerating. In addition, after hardening, the floating particles 43 will assimilate with the medium 39, so the addition of the floating particles 43 will not cause a change in the characteristics of the covering member 27.

On the other hand, if the resin is a different type, the floating particles 43 may aggregate in the medium 39. In such a case, this can be resolved by coating the surface of the floating particles 43 with a coating film that has good lyophilicity with the medium 39.

The size of the floating particles 43 is preferably a size that can block the flow of the resin having fluidity that becomes the medium 39 generated by the settling (movement) of the scattering particles 41. In general, the particle size of the floating particles 43 is preferably 1/2 to 4 times the particle size of the scattering particles 41. Here, when comparing the particle size of the floating particles 43 with the particle size of the scattering particles 41, for example, they may be compared by the volume average particle size calculated from the particle size distribution measured by the laser diffraction/scattering method, or may be compared by the median diameter (50% diameter). If the particle size of the floating particles 43 is smaller than 1/2, the floating particles 43 move by assimilating with each of the fast and slow flows caused by the scattering particles 41, and do not generate a large resistance. Also, if it exceeds 4 times, the floating particles 43 act as a stationary object, and the scattering particles 41 simply settle (move) along the edge of the floating particles 43, and do not generate a large resistance. A particularly preferred particle size for the suspended particles 43 is one in which the weight of the suspended particles 43 is approximately equal to the weight of the scattering particles 41.

For example, if the particle size of the scattering particles 41 is 250 nm, the preferred particle size of the suspended particles 43 is 125 nm to 1000 nm. A particularly preferred particle size is about 400 nm, which means that if the specific gravity of the scattering particles 41 is 4 and the specific gravity of the suspended particles 43 is 1, the volume of the suspended particles 43 is four times the volume of the scattering particles 41.

The shape of the floating particles 43 may be any shape that can block the flow of the fluid resin that forms the medium 39 caused by the settling (movement) of the scattering particles 41. For example, the floating particles 43 may be of various shapes, such as spherical, elliptical, disc-shaped, or cylindrical.

In the light-emitting device 10 of this embodiment, the blue light emitted from the light-emitting element 13 and the orange light emitted by the phosphor added to the adhesive member 37 after absorbing part of the blue light are mixed in the translucent member 25, and white light is emitted from the top surface 25T. The light emission color of the light-emitting device 10 can be adjusted to any color, from the color of light emitted by the light-emitting element 13 to the color of light emitted by the wavelength conversion material, by adjusting the presence or absence of the wavelength conversion material and the amount of the material added.

As described above, the light emitting device 10 of this embodiment uses a covering member 27 in which floating particles 43 are added in addition to scattering particles 41 in the medium 39, and thereby the scattering particles 41 in the medium 39 can be uniformly dispersed at a predetermined concentration without settling, and the light incident on the covering member 27 from the translucent member 25 side can be uniformly reflected, so that the light output (light emission brightness) emitted from the upper surface 25T of the translucent member 25 can be increased, and the contrast of the light emitted from the upper surface 25T can be increased.

[Manufacturing method of light emitting device according to the embodiment]
Next, a method for manufacturing the light emitting device 10 of this embodiment will be described with reference to Fig. 5. Fig. 5 is a flow chart showing the manufacturing process of the light emitting device 10. Note that the manufacturing method shown in Fig. 5 is merely one method for manufacturing the light emitting device 10, and is not limited thereto.

[Component preparation process]
The member preparation step S11 is a step of preparing the substrate 11 on which wiring and electrodes have been formed in advance, and the light emitting element 13. For example, the substrate 11 made of alumina on which the anode wiring 21, the cathode wiring 29, the cathode mounting electrode 31, and the anode mounting electrode 33 are formed, as shown in Fig. 2, and the light emitting element 13 including the support substrate 15 made of silicon (Si) are prepared.

[Die bonding process]
The die bonding step S12 is a step of mounting the light emitting element 13 on the wiring provided on the bottom surface 11S of the substrate 11.

First, a solder paste containing powder made of a gold-tin (AuSn) alloy is applied onto the cathode wiring 29. Next, the cathode element electrode surface of the light-emitting element 13 is placed on the solder paste so that it is in contact with the solder paste. After that, the light-emitting element 13 is joined to the cathode wiring 29 by heating to approximately 300°C in a reflow device, while forming a joining member 35 made of an AuSn alloy, and the light-emitting element 13 is fixed and electrically connected. Note that the flux contained in the solder paste evaporates during joining.

[Wire bonding process]
The wire bonding step S 13 is a step of connecting the anode electrode 19 of the light emitting element 13 and the anode wiring 21 with a bonding wire 23 .

First, the substrate 11 that has been subjected to the die bonding process S12 is set in the wire bonding device. Next, one end of a gold (Au) bonding wire 23 is bonded (first bonding) to the anode wiring 21, and then the other end of the bonding wire 23 is bonded (second bonding) to the anode element electrode 19 of the light emitting element 13 to establish an electrical connection.

[Transparent member adhesion process]
The light-transmitting member bonding step S14 is a step of bonding the light-transmitting member 25 via an adhesive member 37 onto the semiconductor laminate 17 of the light-emitting element 13 bonded to the substrate 11.

First, an appropriate amount of liquid silicone resin that will become the adhesive member 37 is dropped onto the surface of the semiconductor laminate 17. Next, the translucent member 25 is placed on the liquid silicone resin and pressed to temporarily bond the upper surface of the support substrate 15 and the lower surface of the translucent member 25 so that they are covered with silicone resin. Finally, the silicone resin is hardened by heating at 150°C for 3 minutes, and the light emitting element 13 and the translucent member 25 are bonded together. At the same time, the adhesive member 37 is formed.

In this embodiment, 50 wt% of yellow phosphor (YAG:Ce) with a particle size of 15 nm to 30 nm is added to the adhesive member 37. The light-transmitting member 25 is a glass plate with a thickness of 200 μm and has a shape roughly equivalent to the upper surface of the support substrate 15 excluding the anode element electrode 19.

[Coating member filling process]
The covering member filling step S15 is a step of filling the gap defined by the recess 11C of the substrate 11, the light emitting element 13, the adhesive member 37, and the side surface of the light transmissive member 25 with the covering member 27 after the light transmissive member bonding step S14 is performed.

First, 25 wt % of titanium oxide (TiO ₂ ) particles having a particle diameter of 250 nm as scattering particles 41 and 2 wt % of cured silicone resin particles having a particle diameter of 800 nm as suspended particles 43 are added to the silicone resin precursor resin material to be the medium 39, and uniformly dispersed (mixed). Next, a degassing process is performed to prepare a precursor to be the covering member 27. Next, the gap defined by the recess 11C of the substrate 11, the light emitting element 13, the adhesive member 37, and the side surface of the translucent member 25 is filled with the precursor of the covering member 27. The precursor of the covering member 27 is filled to a height approximately equal to the height of the upper surface 25T of the translucent member 25.

[Covering member curing process]
The covering member hardening step S16 is a step of heating and hardening the precursor of covering member 27 filled in recess 11C of substrate 11, light emitting element 13, adhesive member 37, and the side surface of light-transmitting member 25 to tightly seal them.

First, the substrate 11 filled with the precursor of the coating member 27 after the coating member filling step S15 is placed in a heat curing furnace and left to stand for 30 minutes to allow the silicone resin that will become the medium 39 to blend with the bottom surface 11S of the substrate 11, the light-emitting element 13, the adhesive member 37, and the side surfaces of the translucent member 25. Next, the precursor of the coating member 27 is cured by heating to 180°C over 90 minutes to form the coating member 27.

At this time, the floating particles 43 prevent the scattering particles 41 from settling until the silicone resin that becomes the medium 39 hardens. In particular, in the temperature range where the fluidity of the silicone resin is high (viscosity is low) just before hardening, the titanium oxide particles that are the scattering particles 41 have a large specific gravity and are prone to settling. In this embodiment, hardened silicone resin particles are added to the silicone resin as the floating particles 43, so that the settling of the scattering particles 41 is suppressed, and a coating member 27 is formed in which the scattering particles 41 are uniformly dispersed in the medium 39 at a predetermined concentration.

The light emitting device 10 of this embodiment is manufactured by the above process. The light output of the light emitted from the upper surface 25T of the light-transmitting member 25 of the light emitting device 10 manufactured in this manner is high, and has a high contrast with the upper surface 27T of the surrounding covering member 27.

Comparative Example

Next, we will explain a semiconductor light-emitting device as a comparative example.

The semiconductor light-emitting device 50 (hereinafter also referred to as light-emitting device 50) of the comparative example is configured similarly to the light-emitting device 10, except that it has a covering member 51 instead of the covering member 27. Figure 6 is a schematic diagram of the light-emitting device 50 of the comparative example, showing a portion corresponding to part A surrounded by a dotted line in Figure 2.

The covering member 51 does not contain suspended particles 43, and is configured with scattering particles 41 dispersed in the medium 39. Therefore, the scattering particles 41 settle in the covering member 51, and the concentration of the scattering particles 41 is low near the top surface 51T and high toward the bottom surface 11S of the substrate 11. Specifically, the concentration of the scattering particles 41 is low on the side surface of the translucent member 25 and high on the side surface of the light-emitting element 13. Therefore, the reflectance of light incident on the covering member 51 side from the translucent member 25 side is lower than a predetermined reflectance.

Furthermore, as shown in FIG. 6, a portion in which the concentration of scattering particles 41 is particularly low is formed near the upper surface 51T of the covering member 51. Specifically, a region B in which the concentration of scattering particles 41 is low is formed, which is surrounded by a dashed line in FIG. 6.

In this region B, the light incident on the covering member 51 from the light-transmitting member 25 is not reflected toward the light-transmitting member 25, but is attenuated within the covering member 51 while propagating through region B. Alternatively, in region B, the light incident on the covering member 51 from the light-transmitting member 25 is reflected by the scattering particles 41 below the region and exits toward the upper surface 51T.

As a result of the above, the optical output of the light emitted from the upper surface 25T of the light-transmitting member 25 of the semiconductor light-emitting device 50 decreases. In addition, the contrast of the light emitted from the upper surface 25T of the light-transmitting member 25 with respect to the covering member 51 also decreases. At the same time, stray light is also generated when the light that entered the covering member 51 exits from the upper surface 51T.

[Comparative Example: Manufacturing Method of Light-Emitting Device]
The manufacturing method of the light emitting device 50 of the comparative example differs from the manufacturing method of the light emitting device 10 of the present embodiment only in that the covering member 27 does not contain suspended particles 43 and a covering member 51 is used. All other manufacturing steps are the same, so only the differences will be explained.

In the covering member 51 of the light emitting device 50 of the comparative example, the scattering particles 41 start to settle in the covering member 51 from the time when the precursor of the covering member 51 is filled in the recess 11C of the substrate 11 in the covering member filling step S15, and the scattering particles 41 continue to settle until the precursor of the covering member 51 is hardened in the covering member hardening step S16. Therefore, in the medium 39 of the covering member 51, the density (concentration) of the scattering particles 41 is low near the top surface 51T and high at the bottom surface 11S of the substrate 11. In other words, the density of the scattering particles 41 becomes non-uniform.

[Light Emitting Characteristics of Light Emitting Device]
The light emitting characteristics of the light emitting device 10 of this embodiment and the light emitting device 50 of the comparative example will be described below with reference to FIGS.

Figure 7 is a graph showing the luminance distribution obtained by measuring the luminance of the semiconductor light-emitting device 10 along line 2-2 in Figure 1. The horizontal axis of the graph shown in Figure 7 indicates the position along line 2-2 in Figure 2, with the center of the upper surface 25T of the light-transmitting member 25 being 0 mm. The vertical axis of the graph shown in Figure 7 indicates normalized luminance, with the maximum luminance set to 1. Furthermore, "R1" in the graph shown in Figure 7 indicates the light-emitting surface of the semiconductor light-emitting device 10, i.e., the area corresponding to the upper surface 25T of the light-transmitting member 25.

As shown in FIG. 7, the normalized luminance of the semiconductor light-emitting device 10 forms a high-luminance region that maintains high luminance within the light-emitting surface R1. In addition, in both regions outside the light-emitting surface R1, a luminance attenuation region is formed in which the luminance attenuates sharply with increasing distance from the center. In this way, the luminance distribution of the light-emitting device 10 clearly has high-luminance regions and luminance attenuation regions, and high contrast is obtained.

Figure 8 is a graph showing the luminance distribution of a semiconductor light-emitting device 50 of a comparative example, measured in the same manner as Figure 7.

As shown in FIG. 8, the normalized luminance of the semiconductor light-emitting device 50 forms high-luminance regions within the light-emitting surface R1, although there are luminance depressions. In addition, in both regions outside the light-emitting surface R1, a luminance attenuation region is formed in which the luminance attenuates sharply with distance from the center. However, at the edge of the attenuation region (the portion surrounded by the dashed line in the figure), a stray light portion is generated where the attenuation of the normalized luminance slows down or increases. In this way, the contrast of the light-emitting device 50 that does not contain suspended particles 43 may be reduced by stray light. In addition, the light output radiated from the upper surface 25T of the translucent member 25 is reduced by the amount lost as stray light.

In this way, the semiconductor light-emitting device 10 using the covering member 27 containing suspended particles 43 has a high light output radiated from the upper surface 25T of the light-transmitting member 25, and has a high contrast with the upper surface 27T of the covering member 27 surrounding the upper surface 25T of the light-transmitting member 25. This is because the scattering particles 41 contained in the covering member 27 covering the side surface of the light-transmitting member 25 are uniformly dispersed.

On the other hand, a semiconductor light-emitting device 50 using a covering member 51 that does not contain suspended particles 43 emits high light output from the upper surface 25T of the light-transmitting member 25, but emits stray light from the upper surface 51T of the covering member 51. In other words, light is leaking from the side of the light-transmitting member 25 to the covering member 51. This stray light also reduces the contrast. This is because the scattering particles 41 contained in the covering member 51 that covers the side of the light-transmitting member 25 settle and become disproportionate. In particular, this is due to the concentration of scattering particles 41 becoming thinner on the upper surface 51T of the covering member 51, as shown in region B of Figure 6.

As described above, the semiconductor light-emitting device of the present invention comprises a light-emitting element, a light-transmitting member disposed on the light-emitting surface of the light-emitting element and translucent for the light emitted by the light-emitting element, and a covering member disposed to cover the side surfaces of the light-emitting element and the light-transmitting member. The covering member uses resin as a medium, has a refractive index different from that of the resin, and contains scattering particles with light-scattering properties and suspended particles made of the same resin.

By adding suspended particles to the covering member, the scattering particles are uniformly dispersed without settling in the fluid resin that is the precursor of the medium. Therefore, even if the light emitted from the light-emitting element passes through the translucent member and enters the covering member, it is reflected with a predetermined reflectance and returned to the translucent member. Therefore, it is possible to provide a semiconductor light-emitting device that has a high light output emitted from the upper surface of the translucent member and has a high contrast.

In addition, the semiconductor light-emitting device according to the present invention is less likely to have regions with low concentration of scattering particles formed near the upper surface of the covering member due to the scattering particles settling in the covering member. Therefore, it is possible to prevent a decrease in optical output and a decrease in contrast caused by the light emitted from the light-emitting element being guided from the translucent member to the covering member.

In the above embodiment, the light-emitting element 13 is a light-emitting element having a support substrate 15, but the present invention is not limited to this. The light-emitting element 13 may be a semiconductor light-emitting element whose light-emitting surface is the top surface, which is the surface opposite to the bottom surface 11S of the substrate 11. For example, a flip-chip type light-emitting element having a translucent growth substrate may be used as the light-emitting element 13.

The semiconductor light-emitting device according to the present invention may also be configured to include a plurality of light-emitting elements. For example, a unit including the light-emitting element 13, the light-transmitting member 25, and the adhesive member 37 of the above embodiment may be used as a light-emitting structure, and a plurality of light-emitting structures may be arranged in a matrix shape at predetermined intervals on the bottom surface 11S of the substrate 11. In this case, the gaps defined by the recess 11C of the substrate 11, the side surfaces of the light-emitting elements 13, the side surfaces of the adhesive members 37, and the side surfaces of the light-transmitting members 25 are filled with a precursor of the covering member 27, which is then heated and cured to form the covering member 27.

With this configuration, a covering member 27 with scattering particles 41 uniformly dispersed therein is present between each translucent member 25 and the adjacent translucent member 25. This prevents light leakage from each light-emitting structure to the adjacent light-emitting structure, and prevents crosstalk. Therefore, for example, when letters or numbers are represented by an arrangement of multiple light-emitting structures, they can be displayed clearly. In addition, for example, the emission colors of the multiple light-emitting structures can be made different from each other by increasing or decreasing the amount of wavelength conversion material added to the adhesive member 37. In this case, too, a high contrast can be obtained for each light-emitting structure, and color mixing between adjacent light-emitting structures can be prevented, making it possible to achieve color coding as designed.

The configurations in the above-mentioned embodiments and manufacturing methods are merely examples and can be modified as appropriate depending on the application, etc.

REFERENCE SIGNS LIST 10 Semiconductor light emitting device 11 Substrate 11S Bottom surface 13 Light emitting element 15 Support substrate 17 Semiconductor laminate 19 Anode element electrode 21 Anode wiring 23 Bonding wire 25 Light-transmitting member 25T Top surface 27, 51 Covering member 31 Cathode mounting electrode 33 Anode mounting electrode 35 Bonding member 37 Adhesive member 39 Medium 41 Scattering particles 43 Suspended particles

Claims (6)

A substrate having a recess on an upper surface thereof;
A light emitting element disposed on a bottom surface of the recess;
a light-transmitting member provided on the light-emitting element and having a light-transmitting property with respect to light emitted by the light-emitting element;
a covering member provided in the recess so as to cover side surfaces of the light-emitting element and the light-transmitting member, the covering member having a resin material as a base material, scattering particles having light scattering properties and suspended particles made of a light-transmitting resin dispersed in the base material;
the scattering particles are particles made of a metal oxide,
the floating particles are thermosetting or photocurable resin particles,
The particle size of the floating particles is between 1/2 and 4 times the particle size of the scattering particles,
The specific gravity of the suspended particles is 0.9 to 1.1 times the specific gravity of the base material;
The base material has a physical property that the minimum viscosity when hardened is 0.5 to 10 Pa·s . A substrate having a recess on an upper surface thereof;
A light emitting element disposed on a bottom surface of the recess;
a light-transmitting member provided on the light-emitting element and having a light-transmitting property with respect to light emitted by the light-emitting element;
a covering member provided in the recess so as to cover side surfaces of the light-emitting element and the light-transmitting member, the covering member having a resin material as a base material, scattering particles having light scattering properties and suspended particles made of a light-transmitting resin dispersed in the base material;
the scattering particles are particles made of a metal oxide,
the suspended particles are thermosetting or photocurable resin particles,
The particle size of the floating particles is between 1/2 and 4 times the particle size of the scattering particles,
the base material includes at least one of a silicone resin, an epoxy resin, an acrylic resin, a polycarbonate resin, and a polyimide resin;
The semiconductor light emitting device is characterized in that the suspended particles are made of the same or the same type of resin as the base material. an upper surface of the light-transmitting member is exposed from the covering member;
the covering member covers the entire side surface of the light-transmitting member,
the upper surface of the covering member is inclined downward in a region near the side surface of the translucent member as it moves away from the boundary with the upper surface of the translucent member;
3. The semiconductor light emitting device according to claim 1, wherein the first insulating layer is a semiconductor light emitting device. 4. The semiconductor light emitting device according to claim 1 , wherein the covering member is a light blocking member that blocks light from the light emitting element. 5. The semiconductor light emitting device according to claim 1, wherein the light transmitting member contains a phosphor. an adhesive member provided between the light emitting element and the translucent member to bond the light emitting element and the translucent member;
5. The semiconductor light emitting device according to claim 1, wherein at least one of the light transmissive member and the adhesive member contains a phosphor.

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