This application claims priority to Japanese Patent Application No. 2021-212024, filed on Dec. 27, 2021, the disclosure of which is hereby incorporated by reference in its entirety.
The present disclosure relates to a method for producing a light-emitting unit and a light-emitting unit.
Light-emitting units including, in part, semiconductor light-emitting elements, represented by light-emitting diodes (LEDs), have been widely used. Japanese Patent Publication No. 2020-077870 discloses a LED unit in which a light-emitting element is mounted to a printed board using an anisotropic bonding film composed of a solid resin, solder particles and a flux.
In the field of light-emitting units including light-emitting elements on a substrate, there is a demand for further improvement in light extraction efficiency.
According to an embodiment of the present disclosure, a method for producing a light-emitting unit includes: (A) providing a solder composition on a wiring layer of a substrate, the solder composition containing a solder, a flux, and light-reflective particles; (B) placing a light-emitting element having an electrode on the solder composition such that the electrode of the light-emitting element faces the solder composition; and (C) melting the solder by a reflow process to allow the light-reflective particles to move to a surface of the solder composition, and to electrically couple the electrode with the wiring layer via the solder.
According to another embodiment of the present disclosure, a light-emitting unit includes: a light-emitting element having an upper surface and a lower surface that is opposite to the upper surface, the light-emitting element including a pair of electrodes provided at the lower surface; a substrate having a wiring layer; a bonding member located between the wiring layer of the substrate and each of the electrodes, the bonding member including a solder to electrically couple the electrode with the wiring layer; and a light reflecting layer located at a part of a surface of the bonding member that is in contact with neither the electrodes nor the wiring layer, wherein the light reflecting layer includes light-reflective particles and a flux.
According to an embodiment of the present disclosure, the light extraction efficiency of a light-emitting unit can be improved.
Embodiments of the present disclosure will now be described in detail with reference to the drawings. The following embodiments are illustrative, and the light-emitting unit and the production method thereof according to the present disclosure are not limited thereto. For example, the numerical values, shapes, materials, steps, and the order of steps, etc., to be shown in the following embodiments are merely examples, and various modifications can be made thereto so long as they do not lead to technical contradictions. The embodiments described below are merely illustrative, and various combinations are possible so long as they do not lead to technical contradictions.
The size, the shape, etc., of the components shown in the figures may be exaggerated for the ease of understanding, and they may not represent the size and the shape of the components, the size relationship therebetween in an actual light-emitting unit. Some components may be omitted in order to prevent the figures from becoming excessively complicated.
In the following description, components of like functions may be denoted by like reference signs and may not be described redundantly. Terms indicating specific directions and positions (e.g., “upper”, “lower”, “right”, “left”, and other terms including such terms) may be used in the following description. Note however that these terms are used merely for the ease of understanding relative directions or positions in the figure being referred to. The arrangement of components in figures from documents other than the present disclosure, actual products, actual manufacturing apparatuses, etc., does not need to be equal to that shown in the figure being referred to, as long as it conforms with the directional or positional relationship as indicated by terms such as “upper” and “lower” in the figure being referred to. In the present disclosure, the term “parallel” encompasses cases where two straight lines, sides, planes, etc., are in the range of about 0±5°, unless otherwise specified. In the present disclosure, the term “perpendicular” or “orthogonal” encompasses cases where two straight lines, sides, planes, etc., are in the range of about 90±5°, unless otherwise specified.
The light-emitting unit 100A shown in
The substrate 110 includes a wiring layer 10 and a base 16 that supports the wiring layer 10. The wiring layer 10 includes a first wiring 11 and a second wiring 12. Herein, the upper surface 110a of the substrate 110 has the shape of a rectangle, and one side of the rectangle is parallel to the X or Y direction.
In the configuration illustrated in
Each of the bonding members 131 and 132 electrically couples the light-emitting element 120 with the wiring layer 10 of the substrate 110. As for the bonding members 131 and 132, at least a part of the bonding member 131 is located between the electrode 21 of the light-emitting element 120 and the first wiring 11 of the wiring layer 10. Meanwhile, at least a part of the bonding member 132 is located between the electrode 22 of the light-emitting element 120 and the second wiring 12 of the wiring layer 10.
As schematically shown in
The light reflecting layers 141, 142 and the bonding members 131, 132 are realized by solidifying a solder composition 30, which will be described later. As will be described later in detail, the solder composition 30 contains solder particles, a flux, light-reflective particles, and a solvent. The bonding members 131, 132 are mainly made of the solder, and the light reflecting layers 141, 142 include the flux and light-reflective particles originally contained in the solder composition 30. The solder composition 30 may, or may not, contain a resin such as flux. Note that, however, the solder composition 30 does not contain a thermosetting resin (particularly, epoxy resin), which is likely to be discolored when irradiated with blue light.
As schematically shown in
According to an embodiment of the present disclosure, a greater part of light emitted from the light-emitting element 120 and traveling toward the bonding members 131, 132 can be reflected by the light reflecting layers 141, 142 provided over the surfaces of the bonding members 131, 132. That is, the absorption of the light by the solder is small as compared with mounting with the use of a usual solder and, as a result, a greater part of the light can be extracted from the light-emitting unit, so that the light extraction efficiency can be improved.
The light reflecting layer 141 can cover 20% to 100%, inclusive, of a portion of the surface 131a of the bonding member 131 which is not in contact with any of the electrode 21 and the first wiring 11. From the viewpoint of suppressing light absorption at the solder surface, it is more advantageous that the light reflecting layer 141 covers 50% or more of the above-described portion of the surface 131a of the bonding member 131. Also, the light reflecting layer 142 preferably covers 20% to 100%, inclusive, of a portion of the surface 132a of the bonding member 132 which is not in contact with any of the electrode 22 and the second wiring 12. More preferably, the light reflecting layer 142 covers 50% or more of that portion. When greater part of the portions of the surfaces of the bonding members 131, 132 which are not in contact with any of the electrodes of the light-emitting element 120 and the wiring layer 10 is covered with the light reflecting layers 141, 142, the extraction efficiency of the light can be further improved.
It is beneficial that the difference in refractive index (e.g., the difference in refractive index for light at the wavelength of 450 nm) between the material of the light-reflective particles 44 and the material of the flux 46 is 0.5 or greater. This is because total reflection is likely to occur at the interface between the light-reflective particles 44 and the flux 46 and, as a result, the light extraction efficiency improves. From the viewpoint of improving the light extraction efficiency, it is advantageous that the average particle size of the light-reflective particles 44 is in the range of equal to or greater than 0.1 µm and equal to or smaller than 10 µm. Here, the “average particle size” refers to a particle size at which the cumulative value reaches 50% in a cumulative distribution on a volume basis (D50: median particle size). The central particle size can be measured by a laser diffraction particle size distribution measuring device (e.g., MASTER SIZER 2000 manufactured by MALVERN).
The thickness of the light reflecting layer 141 along the normal direction of the surface 131a of the bonding member 131 is in the range of, for example, equal to or greater than 0.1 µm and equal to or smaller than 30 µm. The thickness of the light reflecting layer 142 along the normal direction of the surface 132a of the bonding member 132 is also in the range of, for example, equal to or greater than 0.1 µm and equal to or smaller than 30 µm.
In the examples shown in
As will be described later, the flux 46 in the light reflecting layers 141, 142 can be decomposed when irradiated with the light from the light-emitting element 120. Since the encapsulation member 150 is provided on the substrate 110 so as to cover the light reflecting layers 141, 142, falling off of the light-reflective particles 44 from the bonding members 131, 132 can be suppressed even if the flux 46 is partially or entirely lost by photodecomposition. Since falling off of the light-reflective particles 44 is suppressed, decrease in reflectance of the light reflecting layers 141, 142, which is attributed to the falling off of the light-reflective particles 44, can be avoided.
The flux 46 may not be substantially present on the region R1, but a light reflecting layer substantially composed of light-reflective particles 44 may be located on the region R1. The light-reflective particles 44 on the region R1 are covered with a part of the encapsulation member 150 which is present between the lower surface 120b of the light-emitting element 120 and the base 16, whereby the light-reflective particles 44 are retained on the region R1.
Due to the presence of the light-reflective particles 44 on the region R2 of the upper surface 110a of the substrate 110, reflection by the light-reflective particles 44 on the region R2 can be utilized to increase light traveling upward from the light-emitting unit 100A while absorption of light by the upper surface 110a of the substrate 110 is reduced. That is, the effect of improving the light extraction efficiency can be expected.
The flux 46 may not be substantially present on the region R2 as previously described for the region R1, but a light reflecting layer substantially composed of light-reflective particles 44 may be located on the region R2. The light-reflective particles 44 on the region R2 can also be covered with the encapsulation member 150 as well as the light-reflective particles 44 on the region R1 are. In other words, the encapsulation member 150 can cover both or one of the region R2 and the region R1.
Furthermore, in the example shown in
The flux 46 may not be substantially present on the region R3, but a light reflecting layer substantially composed of light-reflective particles 44 may be located on the region R3. The light-reflective particles 44 on the region R3 can also be covered with the encapsulation member 150 as well as the light-reflective particles 44 on the region R1 or the region R2 are.
As will be described later, the void 50 is a space formed by photodecomposition of an organic substance in the flux contained in the solder composition used for formation of the light reflecting layers 141B, 142B. Therefore, as schematically shown in
The light reflecting layer 141 is located on a part of the surface 131a of the bonding member 131 in the same fashion as in each of the above-described examples. Meanwhile, the light reflecting layer 142 is located on a part of the surface 132a of the bonding member 132. Since a part of the surface 131a of the bonding member 131 and a part of the surface 132a of the bonding member 132 are covered with the light reflecting layer 141 and the light reflecting layer 142, respectively, the extraction efficiency of the light can be improved due to diffuse reflection by the light-reflective particles 44. The configuration of each of the light-emitting elements 120 and its surroundings in the light-emitting unit 200 can be the same as that of any of the examples previously described with reference to
In the example shown in
The partition member 260 can further include a bottom 62, which is parallel to the upper surface 210a of the substrate 210. The bottom 62 has a plurality of through holes 62h, each of which has a circular opening, for example. Each of the light sources 220 is located inside a corresponding one of the through holes 62h. Since the partition member 260 has the bottom 62, part of the light emitted from the light sources 220 traveling toward the substrate 210 can be reflected by the bottom 62.
The partition member 260 is made of, for example, a resin material that contains a white filler. A part of the plurality of walls 60 which is present between two adjacent light sources 220 has slope surfaces 60a that are inclined with respect to the upper surface 210a of the substrate 210. Reflection at the slope surfaces 60a of the walls 60 is utilized so that the traveling direction of light from the light sources 220 can be oriented upward of the substrate 210. In this sense, the partition member 260 can also be referred to as a reflector.
As shown in
Firstly, a substrate 110 that has a wiring layer 10 is provided and, as shown in
In the present embodiment, as the solder composition 30, a mixture containing light-reflective particles 44 in addition to a solvent, a flux 46 and particles of solder 38 is placed at a predetermined position on the wiring layer 10.
The amount of the light-reflective particles 44 contained in the solder composition 30 is typically in the range of equal to or higher than 0.1 mass% and equal to or lower than 5 mass%, preferably in the range of equal to or higher than 0.7 mass% and equal to or lower than 2 mass%. When the solder composition 30 contains the light-reflective particles 44 in the proportion of 0.1 mass% or higher, the light reflecting layers 141, 142 formed after the reflow process can exhibit a relatively high reflectance for the light from the light-emitting element 120. By setting the proportion of the light-reflective particles 44 in the solder composition 30 to 5 mass% or lower, the solder composition 30 can be prevented from having an excessively high viscosity. Decrease in the viscosity of the solder composition 30 can facilitate application of the solder composition 30 by printing.
Next, a light-emitting element 120 is provided, and the light-emitting element 120 is placed on the solder composition 30 (Step S2 of
Next, the solder 38 in the solder composition 30 is melted by a reflow process such that the solder 38 electrically couples the electrodes 21, 22 with the wiring layer 10. When the solder 38 is solidified, the bonding member 131 having the light reflecting layer 141 located at a part of the surface 131a and the bonding member 132 having the light reflecting layer 142 located at a part of the surface 132a are formed as shown in
Heating through the reflow process melts the solder 38, and particles of the solder 38 in the solder composition 30 start to bind together. Accordingly, due to the surface tension of the solder 38, the light-reflective particles 44 and the flux 46 are pushed to the external side of the solder 38. As a result, the light-reflective particles 44 move to the surface of the solder composition 30, so that the light reflecting layer 141 or the light reflecting layer 142 can be selectively formed on a part of the surface of each of the bonding member 131 and the bonding member 132 which is not in contact with any of the electrodes 21, 22 and the wiring layer 10. Note that some of the light-reflective particles 44 in the solder composition 30 can remain inside the solidified solder 38, i.e., inside the bonding member 131 or the bonding member 132.
After the reflow process is performed to form the light reflecting layers 141, 142, when necessary, an encapsulation member 150 can be formed so as to cover the light-emitting element 120. Typically, the encapsulation member 150 also covers the light reflecting layer 141 and the light reflecting layer 142. Covering the light reflecting layers 141, 142 with the encapsulation member 150 allows the light-reflective particles 44 to be prevented from falling off. The encapsulation member 150 can be formed of a light-transmitting resin material by potting, transfer molding, or the like. A part of the encapsulation member 150 can be located in a space between the lower surface 120b of the light-emitting element 120 and the upper surface 110a of the substrate 110.
The flux 46 pushed to the external side of the solder composition 30 by melting of the solder 38 in the step of the reflow process can be gradually decomposed through irradiation with light from the light-emitting element 120 (e.g., blue light). Since the light-emitting unit 100A includes the encapsulation member 150, the light-reflective particles 44 can be retained on the surface 131a of the bonding member 131 and the surface 132a of the bonding member 132, or on the surface 131a of the bonding member 131 or the surface 132a of the bonding member 132, even if the flux 46 is subjected to photodecomposition.
After the light reflecting layer 141 and the light reflecting layer 142 have been formed, the flux 46 can be at least partially removed by, for example, photodecomposition. The molecular weight of the material used as the flux 46 is, for example, equal to or smaller than 500. When the molecular weight of the material of the flux 46 is equal to or smaller than 500, the flux 46 is likely to be decomposed by irradiation with light from the light-emitting element 120 (e.g., blue light), and it is advantageous for posterior removal of the flux 46. If the molecular weight of the material of the flux 46 is excessively large, the reflectance in the light reflecting layer can decrease due to discoloration over time of the residue after the photodecomposition. If the molecular weight of the material of the flux 46 is relatively small, the decrease in reflectance which is attributed to such a phenomenon can be avoided.
Removal of the flux 46 can be carried out by intentional light irradiation or can be realized by unintentional photodecomposition. For example, when irradiated with light emitted from the light-emitting element 120 while the light-emitting unit 100A is in operation, part of the flux 46 in the light reflecting layer 141 or the light reflecting layer 142 which is present near the light-emitting element 120 can be lost with the passage of time. In such a case, due to photodecomposition of the flux 46, void(s) 50 is posteriorly formed in the vicinity of the light-emitting element 120, and a light-emitting unit 100B having the void(s) 50 as shown in
Since the flux 46 is decomposed by photodecomposition, the surfaces of the light-reflective particles 44 covered with the flux 46 come into contact with a medium of a lower refractive index than the flux 46 (typically, air). That is, interfaces are formed between the lower refractive index medium and the light-reflective particles 44 and, accordingly, the effect of reflecting light from the light-emitting element 120 improves. Further, since the light-reflective particles 44 are also present inside the void(s) 50, the light-reflective particles 44 can remain in a region of large luminous flux, such as the vicinity of the light-emitting element 120, for example, while falling off of the light-reflective particles 44 is prevented.
The decomposition of the flux 46 by irradiation with light from the light-emitting element 120 occurs after the light-emitting element 120 has been encapsulated with a light-transmitting resin material, which is different from removal of the flux by washing. Therefore, photodecomposition of the flux 46 with the use of light from the light-emitting element 120 enables the light-reflective particles 44 to be provided inside the voids 50. On the other hand, if the step of washing away the flux 46 is performed after the light reflecting layer 141 and the light reflecting layer 142 have been formed, a large part of the flux 46 supporting the light-reflective particles 44 is removed from the light reflecting layers 141, 142. If thereafter the encapsulation member 150 is formed, the material of the encapsulation member 150 comes into the gap between the light-reflective particles 44. Thus, it is usually difficult to form a structure like the void 50. Note that, in removing the flux 46 by photodecomposition, it is not essential that the flux 46 is entirely removed. For example, part of the flux 46 can remain inside the voids 50.
The photodecomposition of the flux 46 with the use of light from the light-emitting element 120 can be more likely to occur in a region of larger luminous flux. That is, at the surfaces of the light-reflective particles 44 located in a region of larger luminous flux, the interface with air for example is more likely to be formed. This means that, in a region of larger luminous flux, a light-reflecting structure is more likely to be formed spontaneously, and the extraction efficiency of the light can be efficiently improved.
As previously described, in placing the light-emitting element 120 on the solder composition 30 after the solder composition 30 has been provided on the wiring layer 10, the light-emitting element 120 can be pressed toward the substrate 110. In this case, if the distance between the electrode 21 and the electrode 22 of the light-emitting element 120 is relatively short and accordingly the distance between the first wiring 11 and the second wiring 12 of the wiring layer 10 is short, the light-emitting element 120 can push the solder composition 30 so that a part of the solder composition 30 on the first wiring 11 and a part of the solder composition 30 on the second wiring 12 can come into contact with each other as schematically shown in
Even if the solder composition 30 on the first wiring 11 and the solder composition 30 on the second wiring 12 are in contact with each other, they can be separated thereafter by performing a reflow process to melt the solder 38. That is, by performing the reflow process, a part of the solder composition 30 which is present between the first wiring 11 and the second wiring 12 is separated into a portion lying on the first wiring 11 and a portion lying on the second wiring 12 due to the difference in wettability between the base 16 and the wiring layer 10.
In this process, the solder 38 in the solder composition 30 moves to a region on the first wiring 11 or a region on the second wiring 12 and, as a result, the light-reflective particles 44 and the flux 46 in the solder composition 30 can remain in a region overlapping none of the first wiring 11 and the second wiring 12 as schematically shown in
In the example shown in
In providing the solder composition 30 on the wiring layer 10, the solder composition 30 can be placed on the wiring layer 10 so as to extend over the first wiring 11 and the second wiring 12 as schematically shown in
The space between the lower surface 120b of the light-emitting element 120 and the upper surface 110a of the substrate 110 may be filled with a light-transmitting encapsulation member or may be filled with a resin layer 180 as a so-called underfill, as in the light-emitting unit 100C shown in
When the space between the light-emitting element 120 and the substrate 110 is filled with the resin layer 180 or the encapsulation member, occurrence of cracks in the bonding members 131, 132 due to the temperature cycle can be suppressed as compared with a case where the space is filled with a member that has a large coefficient of linear expansion and that is relatively hard, such as flux. The resin layer 180 can also cover the light reflecting layers 141, 142.
In placing the solder composition 30 on the wiring layer 10, if the amount of the solder composition 30 to be placed is large, part of the solder composition 30 can extend to the outside of a part of the wiring layer 10 overlapping the light-emitting element 120 in a plan view (for example, a portion outside the land of the first wiring 11 or a portion outside the land of the second wiring 12). Alternatively, after the solder composition 30 is placed on the wiring layer 10, when the light-emitting element 120 is pressed toward the substrate 110, the solder composition 30 can spread beyond the extent of the land of the wiring layer 10, for example. If the reflow process is performed with the thus-placed solder composition 30, mainly the solder 38 in the solder composition 30 gathers in a region between the electrodes 21, 22 of the light-emitting element 120 and the wiring layer 10 and, as a result, the light-reflective particles 44 and the flux 46 can remain on a part of the wiring layer 10 which does not overlap the light-emitting element 120 in a plan view (e.g., on the region R3 shown in
Hereinafter, components of a light-emitting unit according to an embodiment of the present disclosure are described in more detail.
The light-emitting element 120 is a semiconductor device capable of emitting light according to a supplied electric current. A typical example of the light-emitting element 120 is an LED. As previously described, in the configuration illustrated in
The semiconductor multilayer structure 25 includes an n-type semiconductor layer, a p-type semiconductor layer, and an active layer interposed between the n-type semiconductor layer and the p-type semiconductor layer. The active layer may have a single quantum well (SQW) structure or a multiple quantum wells (MQW) structure that includes a plurality of well layers. The semiconductor multilayer structure 25 includes a plurality of semiconductor layers containing a nitride semiconductor. The nitride semiconductor includes all of the compositions represented by InxAlyGa1-x-yN ( 0≤x, 0≤y, x+y≤1) where x and y represent the proportions, each being variable within a predetermined range. The emission peak wavelength of the active layer can be appropriately selected according to the purpose. The active layer is configured to be capable of emitting visible light or UV light, for example.
The semiconductor multilayer structure 25 can include a plurality of light-emitting regions each including an n-type semiconductor layer, an active layer and a p-type semiconductor layer. When the semiconductor multilayer structure 25 includes a plurality of light-emitting regions, a plurality of well layers included in the semiconductor multilayer structure 25 can have different emission peak wavelengths or can have equal emission peak wavelengths. Note that having equal emission peak wavelengths includes a case where the emission peak wavelengths have variations of about several nanometers.
The combination of the emission peak wavelengths of the plurality of light-emitting regions can be appropriately selected. For example, when the semiconductor multilayer structure 25 includes two light-emitting regions, examples of the combination of light emitted from these light-emitting regions include blue light and blue light, green light and green light, red light and red light, ultraviolet light and ultraviolet light, blue light and green light, blue light and red light, and green light and red light. For example, when the semiconductor multilayer structure 25 includes three light-emitting regions, examples of the combination of light emitted from these light-emitting regions include combinations of blue light, green light and red light. Each of the light-emitting regions can include one or more well layers whose emission peak wavelengths are different from the other well layers.
The reflective film 28 is provided on the upper surface 24a of the light-transmitting substrate 24. Since the entire upper surface 24a of the light-transmitting substrate 24 is covered with the reflective film 28, light from the semiconductor multilayer structure 25 can be mainly extracted from the side surfaces of the light-emitting element 120 while the luminance on the optical axis of the light-emitting element 120 is appropriately reduced. A typical example of the reflective film 28 is a multilayer dielectric film. The reflective film 28 can be a metal film or a white resin layer.
The light-emitting element 120 includes the electrodes 21 and 22 as a pair of the positive and negative electrodes at the lower surface 120b. The shortest distance from the periphery of the electrode 21 to the periphery of the electrode 22 is, for example, equal to or greater than 50 µm and equal to or smaller than 500 µm. Examples of the material of the electrodes 21, 22 include gold, silver, tin, platinum, rhodium, titanium, aluminum, tungsten, palladium, nickel, and alloys containing one or more of these elements.
As previously described, the solder composition 30 contains the solder 38, the light-reflective particles 44, the flux 46 and the solvent. As the solder 38 in the solder composition 30, particles of a material usually used as solder can be employed. Examples of the material of the solder 38 include Au-containing alloys, Ag-containing alloys, Pdcontaining alloys, In-containing alloys, Pb-Pd containing alloys, Au-Ga containing alloys, Au-Sn containing alloys, Sncontaining alloys, Sn-Cu containing alloys, Sn-Cu-Ag containing alloys, Au-Ge containing alloys, Au-Si containing alloys, Al-containing alloys, and Cu-In containing alloys.
As the light-reflective particles 44, titanium oxide particles, aluminum oxide particles, silicon dioxide particles, or zirconium dioxide particles can be employed. The flux 46 is a mixture of a rosin and a solvent and can further contain an additive such as active agent. As the rosin of the flux 46, any of tall rosin, gum rosin, and wood rosin can be employed. The flux 46 may contain one or more types of acid modified rosins, which are produced by treating a rosin with an acid. When the flux 46 contains the acid modified rosin, improvement in wettability can be expected. Examples of the acid modified rosin include acrylic acid modified rosins, acrylic acid modified hydrogenated rosins, maleic acid modified rosins, and maleic acid modified hydrogenated rosins.
As the active agent, organic acids, halogen based active agents (e.g., organohalogen compounds or amine hydrohalides), amines, and organophosphorous compounds (e.g., phosphonate ester or phenyl substituted phosphinic acids) can be used. The flux 46 can contain only one type of the aforementioned compounds or can contain two or more types of the aforementioned compounds. The amount of each constituent of the solder composition 30 can be measured by, for example, ICP emission spectrometry according to the method stipulated in JIS Z 3910:2017.
Some commercially-available solder compositions contain a thermosetting resin, such as epoxy resin, for the purpose of improving the bonding strength. In contrast, the solder composition 30 does not contain an epoxy resin. The epoxy resin may be discolored by blue light. Since the solder composition 30 does not contain an epoxy resin, according to an embodiment of the present disclosure, the bonding members 131, 132 (or the light reflecting layers 141, 142) that are formed from the solder composition 30 can avoid decrease of the optical output which is attributed to discoloration of the epoxy resin. That is, according to an embodiment of the present disclosure, the reliability of the light-emitting unit can be secured over a long use period.
The encapsulation member (e.g., the encapsulation member 150) is made of an epoxy resin, silicone resin or fluoric resin, a mixture thereof, glass, or the like. Typically, the encapsulation member includes a dome portion that covers the light-emitting element 120. The material of the encapsulation member can contain an additional material having a different refractive index from that of the base material such that the additional material is dispersed in the material of the encapsulation member, so that the encapsulation member can have a light diffusing function. For example, the encapsulation member can include a light diffusing material, such as particles of silicon oxide, aluminum oxide, zirconium oxide or zinc oxide. As the light diffusing material dispersed in the base material, nanoparticles whose diameter defined by D50 is equal to or greater than 1 nm and equal to or smaller than 100 nm may be used.
The encapsulation member can include a wavelength conversion material, such as phosphor, instead of or together with the light diffusing material. As the phosphor included in the encapsulation member, a known material can be employed. Examples of the phosphor include yttrium aluminum garnet based phosphors (e.g., Y3(Al,Ga)5O12:Ce), lutetium aluminum garnet based phosphors (e.g., Lu3(Al,Ga)5O12:Ce), terbium aluminum garnet based phosphors (e. g., Tb3 (Al, Ga) 5O12: Ce), β sialon based phosphors (e.g., (Si,Al)3(O,N)4:Eu), α sialon based phosphors (e.g., Ca(Si,Al) 12(O,N) 16:Eu) , nitride based phosphors, and fluoride based phosphors. Examples of the nitride based phosphors include CASN based phosphors (e.g., CaAlSiN3:Eu) and SCASN based phosphors (e.g., (Sr,Ca)AlSiN3:Eu). Examples of the fluoride based phosphors include KSF based phosphors (e.g., K2SiF6:Mn), KSAF based phosphors (e.g., K2(Si,Al)F6:Mn) and MGF based phosphors (e.g., 3.5MgO·0.5MgF2·GeO2:Mn) .
The yttrium aluminum garnet based phosphors (YAG based phosphors) are examples of a wavelength conversion material capable of converting blue light to yellow light. The β sialon based phosphors are examples of a wavelength conversion material capable of converting blue light to green light. The CASN based phosphors and the SCASN based phosphors are examples of a wavelength conversion material capable of converting blue light to red light. The KSF based phosphors, the KSAF based phosphors and the MGF based phosphors are also examples of a wavelength conversion material capable of converting blue light to red light. The phosphor can be a phosphor having a perovskite structure (e.g., CsPb(F,Cl,Br,I)3) or a quantum dot phosphor (e.g., CdSe, InP, AgInS2 or AgInSe2) .
The substrate 110 includes a base 16 and a wiring layer 10 supported by the base 16. The base 16 is an insulative member, which is made of a resin, glass, ceramic material, or the like. As the material of the base 16, a composite material, such as fiberglass-reinforced plastic (e.g., glass epoxy resin), can be used. As does the substrate 110, the substrate 210 shown in
As previously described with reference to
The shape of the partition member 260 can be realized by various molding methods with a die or by stereolithography. For example, the partition member 260 can be produced by vacuum forming from a sheet of polyethylene terephthalate (PET) containing white filler, such as oxide particles. The partition member 260 may be produced by providing a reflective material over a surface of a member produced by molding of a resin sheet that does not contain a white filler. The thickness of the resin sheet used for formation of the partition member 260 is, for example, 100 to 500 µm.
The insulator layer 270 is made of a resin material, such as epoxy resin, urethane resin, acrylic resin, polycarbonate resin, polyimide resin, oxetane resin, silicone resin, modified silicone resin, or the like, and functions as an insulative resist. The insulator layer 270 can include particles of a light reflective material, such as titanium oxide, aluminum oxide, or the like, as does the partition member 260, so that the insulator layer 270 can further have the function of reflecting incoming light. Since the insulator layer 270 includes the light reflective particles, the utilization efficiency of light can be improved. When the employed partition member 260 has the bottom 62 as shown in
In the configuration illustrated in
The wavelength conversion sheet 280 is typically made of a material containing a resin and particles of a phosphor or the like, which are dispersed in the resin. An example of the base material of the wavelength conversion sheet 280 is a material containing a silicone resin, modified silicone resin, epoxy resin, modified epoxy resin, urea resin, phenolic resin, acrylic resin, urethane resin or fluorine resin, or two or more types of these resins. As the phosphor contained in the wavelength conversion sheet 280, the aforementioned examples of the wavelength conversion material that can be dispersed in the encapsulation member can be employed. The thickness of the wavelength conversion sheet 280 can be in the range of, for example, equal to or greater than 100 µm and equal to or smaller than 200 µm.
The light diffuser sheet 284 is capable of diffusing and transmitting incoming light. The light diffusing structure can be formed in the light diffuser sheet 284 by providing recessed or raised portions in the surface of the light diffuser sheet 284 or dispersing a material of a different refractive index throughout the light diffuser sheet 284. The light diffuser sheet 284 is made of a material of low light absorption for visible light, such as polycarbonate resin, polystyrene resin, acrylic resin, polyethylene resin, or the like. As the light diffuser sheet 284, an optical sheet commercially available under names such as diffuser film can be used. The lower surface of the light diffuser sheet 284 can be separated from, or in contact with, the partition member 260.
The prism sheet 282 is configured to have an array of a plurality of prisms each extending in a predetermined direction. The prism sheet 282 has the function of refracting light incoming from various directions such that the traveling direction of the light changes to the +Z direction. For example, an Advanced Structured Optical Composite (ASOC) manufactured by 3 M can be used as the prism sheet 282.
A light-emitting unit produced according to an embodiment of the present disclosure is useful in various types of light sources for lighting, light sources for on-vehicle devices, light sources for display devices, etc. Particularly, embodiments of the present disclosure are advantageously applicable to backlight units for liquid crystal display devices.
It is to be understood that although certain embodiments of the present invention have been described, various other embodiments and variants may occur to those skilled in the art that are within the scope and spirit of the invention, and such other embodiments and variants are intended to be covered by the following claims.
Number | Date | Country | Kind |
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2021-212024 | Dec 2021 | JP | national |