Patent ID: 12224386

DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments will be described with reference to the drawings, taking an ultraviolet light emitting device as an example. However, the technique of the present specification is not limited to the embodiments. A structure different from that of the embodiments may be included. The thickness ratio of each layer in each figure is conceptually shown, and does not indicate the actual thickness ratio.

First Embodiment

1. Light Emitting Device

FIG.1is a schematic configuration diagram of a light emitting device100according to a first embodiment. As illustrated inFIG.1, the light emitting device100includes a substrate110, an ultraviolet light emitting element120, a bonding layer130, a fluororesin film140, an adhesive layer150, a fluorocarbon compound160, and an air layer170. The light emitting device100is an ultraviolet light emitting device which emits ultraviolet light.

The substrate110is a substrate mounting an ultraviolet light emitting element120. The substrate110has a mounting surface110a. The mounting surface110ais a surface mounting the ultraviolet light emitting element120. The substrate110includes a base material111, circuit patterns112and113, and a through hole114. The circuit pattern112is a pattern on a mounting surface110aside in the substrate110. The circuit pattern113is a pattern on a side opposite to the mounting surface110aside in the substrate110. The through hole114electrically connects the circuit pattern112and the circuit pattern113. The through hole114is filled with a metal. The mounting surface110ais a surface of the circuit pattern112.

The ultraviolet light emitting element120is a semiconductor light emitting element which emits ultraviolet light. An emission wavelength of the ultraviolet light emitting element120is, for example, 200 nm or more and 320 nm or less. The ultraviolet light emitting element120is mounted on the substrate110via the bonding layer130. The ultraviolet light emitting element120has a first surface120a, a second surface120b, and a side surface120c. The first surface120ahas an electrode120d. The first surface120afaces the mounting surface110aof the substrate110. The second surface120bis a surface opposite to the first surface120a. The second surface120bis a light extraction surface which extracts light to the outside of the ultraviolet light emitting element120. The second surface120bfaces the fluororesin film140. The side surface120cis a surface other than the first surface120aand the second surface120b.

The bonding layer130is a layer mounting the ultraviolet light emitting element120on the substrate110. The bonding layer130bonds the electrode on the first surface120aof the ultraviolet light emitting element120and the circuit pattern112of the mounting surface110aof the substrate110. The material of the bonding layer130is, for example, an Au—Sn solder.

The fluororesin film140is a translucent fluororesin film for suitably extracting ultraviolet light emitted from the ultraviolet light emitting element120to the outside. The fluororesin film140, of course, transmits ultraviolet light. The fluororesin film140is a flexible material which can be bent. The fluororesin film140is adhered to the substrate110in a bent state. The fluororesin film140is, for example, FEP. The fluororesin film140has a refractive index higher than the refractive index of the atmosphere. The refractive index of the fluororesin film140is, for example, 1.2 or more and 1.6 or less.

The fluororesin film140has a ceiling surface141, a side wall surface142, and a flat surface143on a substrate110side. The ceiling surface141faces the second surface120bof the ultraviolet light emitting element120. The side wall surface142faces the side surface120cof the ultraviolet light emitting element120. The flat surface143is in contact with the adhesive layer150. The flat surface143is adhered to the substrate110via the adhesive layer150.

The adhesive layer150adheres the substrate110and the fluororesin film140. The substrate110and the fluororesin film140are disposed in a state where the ultraviolet light emitting element120is sandwiched therebetween. The adhesive layer150bonds the substrate110and the fluororesin film140in this state. The adhesive layer150adheres the mounting surface110aof the substrate110and the fluororesin film140. The adhesive layer150is not present between the second surface120bof the ultraviolet light emitting element120and the fluororesin film140.

The fluorocarbon compound160is located between the ultraviolet light emitting element120and the fluororesin film140.

The air layer170is a closed space located between the substrate110and the ultraviolet light emitting element120. The air layer170is filled with a gas. The gas is, for example, atmosphere. The air layer170is located between the mounting surface110aof the substrate110and the first surface120aof the ultraviolet light emitting element120. There is no air layer either between the second surface120bof the ultraviolet light emitting element120and the fluororesin film140or between the side surface120cof the ultraviolet light emitting element120and the fluororesin film140.

2. Fluorocarbon Compound

2-1. Region of Fluorocarbon Compound

The fluorocarbon compound160is a polymer having a CF bond. The fluorocarbon compound160is a liquid at normal temperature and pressure. The number of carbon atoms in the fluorocarbon compound160is 1.9 times or less the number of fluorine atoms in the fluorocarbon compound160. The fluorocarbon compound160is, for example, perfluoropolyether (PFPE). The fluorocarbon compound160may have a refractive index greater than that of the atmosphere, and equal to or less than that of the ultraviolet light emitting element120. The refractive index of the fluorocarbon compound160is, for example, 1.2 or more and 1.6 or less.

As illustrated inFIG.1, the fluorocarbon compound160fills a gap either between the second surface120bof the ultraviolet light emitting element120and the fluororesin film140or between the side surface120cof the ultraviolet light emitting element120and the fluororesin film140in a state where the second surface120band the side surface120cof the ultraviolet light emitting element120are in contact with the fluororesin film140.

The fluorocarbon compound160has an upper surface portion161and a side surface portion162. The upper surface portion161and the side surface portion162are connected to each other. The upper surface portion161faces the second surface120bof the ultraviolet light emitting element120. The side surface portion162faces the side surface120cof the ultraviolet light emitting element120.

The upper surface portion161is a region sandwiched between the second surface120bof the ultraviolet light emitting element120and the ceiling surface141of the fluororesin film140. The upper surface portion161has a rectangular parallelepiped shape. Vertical and horizontal lengths of the rectangular parallelepiped shape are equal to vertical and horizontal lengths of the ultraviolet light emitting element120.

The side surface portion162is a region surrounded by the side surface120cof the ultraviolet light emitting element120, the side wall surface142of the fluororesin film140, and the mounting surface110aof the substrate110. The side surface portion162is in contact with the side surface120cof the ultraviolet light emitting element120, the side wall surface142of the fluororesin film140, and the mounting surface110aof the substrate110. The side surface portion162surrounds a periphery of the ultraviolet light emitting element120. The side surface portion162has an annular shape.

A thickness of the side surface portion162of the fluorocarbon compound160in contact with the side surface120cof the ultraviolet light emitting element120decreases as a distance from the mounting surface110aof the substrate110increases.

The ceiling surface141of the fluororesin film140faces the second surface120bof the ultraviolet light emitting element120in a state where the upper surface portion161of the fluorocarbon compound160is sandwiched therebetween. The side wall surface142of the fluororesin film140faces the side surface120cof the ultraviolet light emitting element120in a state where the side surface portion162of the fluorocarbon compound160is sandwiched therebetween.

The fluorocarbon compound160does not fill a gap between the mounting surface110aof the substrate110and the first surface120aof the ultraviolet light emitting element120.

2-2. Effect of Fluorocarbon Compound

The fluorocarbon compound160covers the second surface120band the side surface120cof the ultraviolet light emitting element120. The refractive index of the fluorocarbon compound160is greater than the refractive index of the atmosphere and equal to or less than the refractive index of the ultraviolet light emitting element120. Therefore, the light to be emitted from the second surface120band the side surface120cof the ultraviolet light emitting element120is less likely to be totally reflected at a boundary surface with the fluorocarbon compound160. That is, the light extraction efficiency on the second surface120band the side surface120cof the ultraviolet light emitting element120is high.

3. Refractive Index

The ultraviolet light emitting element120has a refractive index of about 1.7. The fluorocarbon compound160has a refractive index of about 1.2 or more and 1.6 or less. The fluororesin film140has a refractive index of about 1.2 or more and 1.6 or less. The atmosphere has a refractive index of 1. The refractive index of the fluorocarbon compound160is preferably greater than the refractive index of the fluororesin film140. The ultraviolet light emitting element120, the fluorocarbon compound160, and the fluororesin film140have a higher refractive index in this descending order. In this case, total reflection is less likely to occur at the boundary between the materials.

In the first embodiment, the second surface120band the side surface120cof the ultraviolet light emitting element120are not in contact with the air layer170. As described above, the refractive index of the ultraviolet light emitting element120is sufficiently greater than the refractive index of the air layer170. Since in the ultraviolet light emitting element120, the second surface120band the side surface120cfrom which the light is extracted to the outside are not in contact with the air layer170having a lower refractive index, the light from the ultraviolet light emitting element120is likely to be emitted to the outside of the element. Therefore, the light extraction efficiency of the light emitting device100is high.

3. Production Method

3-1. Element Mounting Step

As illustrated inFIG.2, the ultraviolet light emitting element120is mounted on the mounting surface110aof the substrate110. A solder is placed on the mounting surface110aof the substrate110. The ultraviolet light emitting element120is placed on the solder such that the electrode120don the first surface120aof the ultraviolet light emitting element120is in contact with the solder. Then, the ultraviolet light emitting element120is mounted on the substrate110by, for example, reflow.

3-2. Fluorocarbon Compound Supply Step

As illustrated inFIG.3, the fluorocarbon compound160is supplied to the second surface120band the side surface120cof the ultraviolet light emitting element120. At this stage, the fluorocarbon compound160is not in contact with the side surface120cof the ultraviolet light emitting element120.

3-3. Adhering Step

As illustrated inFIG.4, the adhesive layer150is coated onto the mounting surface110aof the substrate110. Thereafter, the fluororesin film140is bent and adhered to the mounting surface110aof the substrate110. Accordingly, the light emitting device100is produced.

4. Effect of First Embodiment

The fluorocarbon compound160covers the second surface120band the side surface120cof the ultraviolet light emitting element120. Therefore, the light to be emitted to the outside from the second surface120band the side surface120cof the ultraviolet light emitting element120is less likely to be totally reflected at the boundary surface with the fluorocarbon compound160. That is, the light extraction efficiency on the second surface120band the side surface120cof the ultraviolet light emitting element120is high.

5. Modifications

5-1. Fluorocarbon Compound

FIG.5is a schematic configuration diagram of a light emitting device200according to a modification of the first embodiment. The light emitting device200includes the substrate110, the ultraviolet light emitting element120, the bonding layer130, a fluororesin film240, the adhesive layer150, a fluorocarbon compound260, and the air layer170.

The fluororesin film240has a ceiling surface241, an inclined surface242, and a flat surface243on the substrate110side. The ceiling surface241of the fluororesin film240is in contact with the second surface120bof the ultraviolet light emitting element120, and is not in contact with the fluorocarbon compound260. That is, there is no gap between the ceiling surface241of the fluororesin film240and the second surface120bof the ultraviolet light emitting element120, and the fluorocarbon compound260filling the gap is not present.

Even in this case, the light from the ultraviolet light emitting element120is suitably incident on the fluororesin film240. That is, the light is suitably extracted from the ultraviolet light emitting element120.

In order to produce the light emitting device200, a force for pressing the fluororesin film140against the ultraviolet light emitting element120may be increased.

5-2. Air Layer

FIG.6is a schematic configuration diagram of a light emitting device300according to a modification of the first embodiment. The light emitting device300includes the substrate110, the ultraviolet light emitting element120, the bonding layer130, the fluororesin film140, the adhesive layer150, and a fluorocarbon compound360.

The light emitting device300does not have an air layer between the mounting surface110aof the substrate110and the first surface120aof the ultraviolet light emitting element120. Instead, the fluorocarbon compound360fills the gap between the mounting surface110aof the substrate110and the first surface120aof the ultraviolet light emitting element120.

Even in this case, the light from the ultraviolet light emitting element120is transmitted through the fluorocarbon compound360and then suitably incident on the fluororesin film140. That is, the light is suitably extracted from the ultraviolet light emitting element120.

In order to produce the light emitting device300, the amount of the fluorocarbon compound360supplied to the second surface120bof the ultraviolet light emitting element120may be increased. The fluorocarbon compound360may spill out from the second surface120bof the ultraviolet light emitting element120and spread to some extent to the mounting surface110aof the substrate110. Alternatively, the fluorocarbon compound360may be separately supplied to the periphery of the bonding layer130by underfill.

5-3. Filler

The fluorocarbon compound160may contain a filler which transmits ultraviolet light. The material of the filler is, for example, fluorine powder or silica. The filler may have a refractive index about the same as the refractive index of the fluorocarbon compound160. The refractive index of the filler is, for example, 1.2 or more and 1.6 or less. The filler has a particle diameter of, for example, 20 nm or more and 50 μm or less. An abundance ratio of the filler in the fluorocarbon compound160is, for example, 0.1 wt % or more and 50 wt % or less.

When the filler is a material which does not contain fluorine, such as silica, the filler may absorb ultraviolet light. In this case, the particle diameter of the filler may be smaller than a peak value of the emission wavelength of the ultraviolet light emitting element120. The filler has a particle diameter of, for example, 20 nm or more and 100 nm or less.

The filler is suitable for adjusting a static viscosity and a kinematic viscosity of the fluorocarbon compound160. That is, the kinematic viscosity is preferably low so as to facilitate dropping. It is preferable to use a value of the static viscosity such that the side surface portion162maintains a suitable shape after the fluorocarbon compound160drips on the side surface120cof the ultraviolet light emitting element120.

5-4. Ceiling Surface

The ceiling surface141is a plane parallel to the mounting surface110aof the substrate110. However, the ceiling surface141may not be parallel to the mounting surface110aof the substrate110. The ceiling surface141may be a curved surface.

5-5. Adhesive Surface

The fluororesin film140may have an adhesive surface coated with an adhesive on the substrate110side. In this case, the adhesive on the adhesive surface is disposed between fluororesin film140and fluorocarbon compound160. The area where the adhesive on the adhesive surface comes into contact with the fluorocarbon compound160is large. Therefore, as illustrated inFIG.1, it is preferable that the adhesive is present only on the mounting surface110aof the substrate110.

5-6. Combination

The above modifications may be freely combined.

APPENDIX

An ultraviolet light emitting device according to a first aspect includes: a substrate; an ultraviolet light emitting element; a bonding layer; a fluororesin film; and a fluorocarbon compound. The substrate includes a mounting surface mounting the ultraviolet light emitting element. The ultraviolet light emitting element has a first surface having an electrode, a second surface opposite to the first surface, and a side surface. The bonding layer bonds the electrode on the first surface of the ultraviolet light emitting element and a part of the mounting surface of the substrate. The fluororesin film is a flexible material configured to transmit ultraviolet light. The substrate and the fluororesin film are disposed in a state where the ultraviolet light emitting element is sandwiched therebetween. The fluorocarbon compound is a liquid at normal temperature and pressure. The fluorocarbon compound fills a gap between the side surface of the ultraviolet light emitting element and the fluororesin film in a state of being in contact with the side surface and the fluororesin film.

In the ultraviolet light emitting device according to a second aspect, the fluorocarbon compound includes a side surface portion facing the side surface of the ultraviolet light emitting element. The fluororesin film includes a side wall surface on a substrate side. The side wall surface of the fluororesin film faces the side surface of the ultraviolet light emitting element in a state where the side surface portion of the fluorocarbon compound is sandwiched therebetween.

In the ultraviolet light emitting device according to a third aspect, a thickness of the side surface portion of the fluorocarbon compound is smaller as a distance from the mounting surface of the substrate increases.

In the ultraviolet light emitting device according to a fourth aspect, the fluorocarbon compound includes an upper surface portion facing the second surface of the ultraviolet light emitting element. The fluororesin film includes a ceiling surface on the substrate side. The ceiling surface of the fluororesin film faces the second surface of the ultraviolet light emitting element in a state where the upper surface portion of the fluorocarbon compound is sandwiched therebetween.

In the ultraviolet light emitting device according to a fifth aspect, the fluororesin film includes a ceiling surface on the substrate side. The ceiling surface of the fluororesin film is in contact with the second surface of the ultraviolet light emitting element.

In the ultraviolet light emitting device according to a sixth aspect, the fluorocarbon compound fills a gap between the mounting surface of the substrate and the first surface of the ultraviolet light emitting element.

In the ultraviolet light emitting device according to a seventh aspect, the fluorocarbon compound does not fill a gap between the mounting surface of the substrate and the first surface of the ultraviolet light emitting element.

In the ultraviolet light emitting device according to an eighth aspect, the fluorocarbon compound contains a filler configured to transmit ultraviolet light. The filler has a refractive index of 1.2 or more and 1.6 or less.

The ultraviolet light emitting device according to a ninth aspect further includes an adhesive layer. The adhesive layer adheres the mounting surface of the substrate and the fluororesin film, and is not present between the second surface of the ultraviolet light emitting element and the fluororesin film.