Patent Application
20140042472
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2012-175842, filed on Aug. 8, 2012, the entire contents of which are incorporated herein by reference.
Embodiments described herein generally relates to a semiconductor light-emitting device.
In the background art, some semiconductor light-emitting devices have included a nitride semiconductor light-emitting element and translucent resin. The element is mounted at a lead frame and bonded to the lead frame. The translucent resin containing a fluorescent body is provided on the lead frame so as to bury the light-emitting element.
A semiconductor white-light-emitting device is provided by combining a blue-light-emitting element with yellow-light-emitting translucent resin containing a fluorescent body absorbing blue light.
Blue light emitted from the element passes through the resin. The fluorescent body absorbs a portion of the blue light during the pass to convert the portion into yellow light. Remaining blue light except the portion is emitted outside. A ratio of the intensity of the yellow light to the blue light emitted outside depends on a distance that the blue light traveled inside the translucent resin. The longer the distance, the higher the intensity of the yellow light, the lower the intensity of the blue light.
As a result, blue light and yellow light are different from each other in intensity distribution. The ratio of the intensity of the yellow light to the blue light changes with a light distribution angle. Unfortunately, the light-emitting devices of the background art show large variations in the chromaticity of light with a viewing direction.
According to an embodiment, a semiconductor light-emitting device includes a substrate, a semiconductor light-emitting element, a frame body, a first translucent resin, and a second translucent resin. The substrate has a convex portion. The semiconductor light-emitting element placed on the convex portion. The frame body is provided so as to surround the convex portion. The first translucent resin covers an upper surface and a side surface of the light-emitting element, extends from the convex portion to the frame body, and contains a fluorescent body. The second translucent resin is provided on the substrate so as to bury the light-emitting element and the frame body.
An embodiment will be described with reference to drawings. In the drawing, the same reference numerals denote the same or similar portions.
A semiconductor light-emitting device in accordance with a first embodiment will be described with reference to
The semiconductor light-emitting device includes a nitride semiconductor light-emitting element and translucent resin to emit white light, in the device, the resin containing a fluorescent body conformally covers the blue-light-emitting element to mold the element. The fluorescent body absorbs blue light emitted from the element to emit yellow light. As a result, the device is capable of emitting white light.
As shown in
The convex portion 12 has a sloped side surface, and the cross section thereof is trapezoidal in shape. The convex portion 12 serves as a base to place a semiconductor light-emitting element 13.
The semiconductor light-emitting element 13 is placed on the convex portion 12 to be fixed thereon with an adhesive 14. The semiconductor light-emitting element 13 has first-electrode and second-electrode terminals (both not shown) on an upper surface 13a. The first-electrode, terminal is electrically connected to the first substrate 11a through a wire 15a. The second electrode terminal is electrically connected to the second substrate 11b through a wire 15b.
A frame body 16 with a height H2 from the upper surface 11c is provided so as to surround the convex portion 12.
A first translucent resin 17 containing a fluorescent body (not shown) covers the upper surface 13a and the side surface 13b of the semiconductor light-emitting element 13, and extends to the frame body 16 from the convex portion 12. The first translucent resin 17 has a redundant portion that does not cover the semiconductor light-emitting element 13, and the redundant portion falls into a space between the convex portion 12 and the frame body 16.
The second translucent resin 18 is provided so as to bury the semiconductor light-emitting element 13 covered with the first translucent resin 17.
The semiconductor light-emitting device 10 will be specifically described. The substrate 11 is a copper or iron plate with a thickness of 200 μm, and is plated with Ni. The convex portion 12 is formed by processing a portion of the substrate 11, and the height H1 is about 100 μm, for example.
The semiconductor light-emitting element 13 is an InGaN-series semiconductor light-emitting element, which emits blue light with a wavelength of about 450 nm, for example. The semiconductor light-emitting element 13 is 500 μm in width and 100 to 150 μm in thickness, for example.
The semiconductor light-emitting element 13 in turn includes a sapphire substrate, an N-type GaN clad layer, a semiconductor light-emitting layer, a P-type GaN clad layer, and a P-type GaN contact layer, all of which are laminated. The semiconductor light-emitting layer includes a multiple quantum well structure with in GaN well layers and GaN barrier layers each laminated alternately.
The semiconductor light-emitting element 13 has a notch (not shown) for exposing the N-type GaN clad layer. A first electrode (P-side electrode) terminal is provided on the P-type GaN contact layer. A second electrode (N-side electrode) terminal is provided on the N-type GaN clad layer, which is exposed at the notch.
The first electrode terminal is made up of a gold (Au) film enabling an ohmic contact with a P-type GaN layer. The second electrode terminal is made up of a laminated film of titanium (Ti)/platinum (Pt)/gold (Au). The laminated film enables an ohmic contact with an N-type GaN layer. The first electrode terminal is an anode terminal. The second electrode terminal is a cathode terminal.
The frame body 16 is made up of white resin, for example. The white resin is epoxy resin containing much inorganic filler, such as titanium oxide (TiO2), for example. When the frame body 16 is too short, the first translucent resin 17 will overflow outside the frame body 16. When the frame body 16 is too tall, the frame body 16 blocks light emitted from the semiconductor light-emitting element 13.
Preferably, the frame body 16 has a height as low as possible. Specifically, the height of the frame body 16 is not less than a height H1 of the convex portion 12 and not more than the sum of the height H1 and the thickness H3 of the semiconductor light-emitting element 13. The frame body 16 appropriately has a height of about 100 to 120 μm.
The first translucent resin 17 is made up of epoxy resin, silicone resin, or acrylic resin, all of which are translucent. The first translucent resin 17 contains the fluorescent body by 40 to 50 wt %.
A fluorescent body is a YAG (yttrium/aluminum/garnet) fluorescent body to emit yellow light by absorbing blue light. The YAG fluorescent body is expressed by the following general formula.
The formula is (RE1-xSmx)3(AlyGa1-y)5O12:Ce, assuming that 0≦x≦1, 0≦y≦1, and RE is at least one element selected from Y and Gd.
The second translucent resin 18 has a shape of a rectangular parallelepiped with an upper surface 18a that is parallel to a plane including the substrate 11. The second translucent resin 18 buries the semiconductor light-emitting element 13 covered with the first translucent resin 17 and the wires 15a and 15b in the resin. The second translucent resin 18 covers the upper surface 11c of the substrate 11, but does not cover the lower surface 11d.
In the semiconductor light-emitting device 10, the first electrode terminal of the semiconductor light-emitting element 13 is extracted to the first substrate 11a, and the second electrode terminal is extracted to the second substrate 11b. When the first substrate 11a is connected to a positive terminal of a power supply and when the second substrate 11b is connected to a negative terminal of the power supply, current flows through the semiconductor light-emitting element 13 to permit the element 13 to emit blue light.
The fluorescent body absorbs a portion of the emitted blue light to emit yellow light. The remaining portion of the emitted blue light, which has not been absorbed by the fluorescent body, is mixed with the yellow light emitted from the fluorescent body to make white light.
The convex portion 12 makes a difference in height between the upper surface of the substrate 11 and the surface on which the element 13 is placed. The difference enables the above-mentioned semiconductor light-emitting device 10 to be conformally covered with the first translucent resin 17
The semiconductor light-emitting device 10 stores an excess of the first translucent resin 17 in the inside area of the frame body 16 to prevent an adverse effect from an outflow of the first translucent resin 17, and thus facilitates fabrication of the device 10.
Chromaticity of the semiconductor light-emitting device 10 of the first embodiment will be described in comparison with a semiconductor light-emitting device of a comparative example. First, the semiconductor light-emitting device of the comparative example will be described.
As shown in
In
The following formula is established as
(ΔCx,ΔCy)=(Cxθ−Cx0,Cyθ−Cy0),
provided that the chromaticity coordinate at an angle of 0° is expressed as (Cx0, Cy0), and the chromaticity coordinate at an angle of θ is expressed as (Cxθ, Cyθ). For example, “ΔCx=0.025 at θ=60°” and “ΔCy=0.045 at θ=60°” are established on the solid line 26.
The intensity ratio of blue light to yellow light varies at θ=60° with respect to θ=0°. The relative intensity of yellow light at θ=60° is higher than the intensity thereof at θ=0°, meaning that the chromaticity coordinate (Cx, Cy) shifts in the direction denoted by the arrow (yellow shift) in
The angular dependence of the chromaticity arises from a difference in the distance that blue light travels in the translucent resin containing the fluorescent body. The longer the distance, the more the blue light is absorbed by the fluorescent body to be converted into yellow light.
In contrast, the shorter the distance, the less the blue light is absorbed by the fluorescent body to be emitted as it is. As a result, the ratio of blue light to yellow light changes with the angle θ.
As shown in
Meanwhile, the semiconductor light-emitting element 10 of the first embodiment shows the same tendency as the semiconductor light-emitting element 20 of the comparative example. The tendency is that ΔCx and ΔCy increase with the angle θ nearly symmetrically both in the positive and negative axes. The gradients of ΔCx and ΔCy, however, differ from each other at low angles, and the angles at which ΔCx and ΔCy increase rapidly also differ from each other.
ΔCx and ΔCy increase by a second gradient K2 lower than the first gradient K1 until the angle 0 reaches about ±80. The first gradients K1 of ΔCx and ΔCy are five times as high as the second gradients K2 thereof. ΔCx and ΔCy increase rapidly when the angle θ exceeds 80°.
The angular dependence of the chromaticity of the semiconductor light-emitting device 10 has been revealed to be much less than that of the semiconductor light-emitting device 20.
In the semiconductor light-emitting element 20, the translucent resin 23 containing the fluorescent bodies 22 has various thicknesses depending on directions. The translucent resin 23 is thicker in a direction parallel to the substrate than in a direction perpendicular thereto. That is, the fluorescent bodies 22 seem to be contained more in the direction parallel to the substrate than in the direction perpendicular thereto when viewed from the semiconductor light-emitting element 13.
As a result, blue light emitted from the semiconductor light-emitting element 13 has various probabilities for colliding with fluorescent bodies 22. The probabilities depend on the direction in which the blue light travels. A large difference in the intensity ratio of blue light to yellow light causes variations in the chromaticity (color breakup), depending on the viewing directions.
By contrast, the semiconductor light-emitting element 13 is thinly covered with the first translucent resin 17 at the upper surface 13a and the side surface 13b in the semiconductor light-emitting device 10. In other words, the element 13 is conformally covered with the first translucent resin 17 by a substantially equivalent thickness. The fluorescent bodies distribute around the element 13 when the fluorescent bodies are viewed from the element 13.
As a result, blue light emitted from the semiconductor light-emitting element 13 has an equal probability for colliding with the fluorescent bodies independently of the traveling directions (viewing directions). Variations in the chromaticity with viewing directions are, therefore, enabled to decrease. Causing the chromaticity of blue light to approach the chromaticity of yellow light enables it to reduce the variations in the chromaticity with viewing directions.
A method for manufacturing the semiconductor light-emitting device 10 will be described.
As shown in
As shown in
As shown in
As shown in
As shown by the dashed line, the translucent resin 31 covers the upper surface 13a of the semiconductor light-emitting element 13 in a convex. The translucent resin 31 also covers the side surface 13b of the semiconductor light-emitting element 13 in a skirt shape. An excess of the translucent resin 31 does not cover the semiconductor light-emitting element 13, and falls along a sloped surface of the convex portion 12 to reach the frame body 16. The excess is stored between the convex portion 12 and the frame body 16.
The covering amount depends on a balance between the weight and viscosity of the translucent resin 31 and depends on the friction against the surface to which the resin 31 is applied. A storable amount to store the excess between the convex portion 12 and the frame body 16 depends on the height H2 of the frame body 16 and a distance L1 from the convex portion 12 to the frame body 16.
A drip amount of the translucent resin 31 is not less than a covering amount of the translucent resin 31, and not more than the sum of the covering amount and the storable amount of the translucent resin 31 therebetween. As a result, the drip amount of the translucent resin 31 is easily controlled, thereby enabling it to cover the upper surface 13a and the side surface 13b of the semiconductor light-emitting element 13 with the translucent resin 31.
As shown in
As shown in
The cured epoxy resin is ejected from the metallic mold. A second translucent resin 18 is formed on the substrate 11 so as to bury the semiconductor light-emitting element 13 within the second translucent resin 18. The second translucent resin 18 has an upper surface 18a substantially parallel to the substrate 11, while the lower surface 11d of the substrate 11 is exposed. As a result, the semiconductor light-emitting device 10 shown in
As described above, the first embodiment includes the convex portion 12 and the frame body 16 surrounding the convex portion 12. The semiconductor light-emitting element 13 is placed on the convex portion 12, the translucent resin 31 containing fluorescent bodies is dripped over the semiconductor light-emitting element 13 to cover the element 13, and the first translucent resin 17 is provided so as to extend from the convex portion 12 to the frame body 16.
As a result, the chromaticity of blue light from the semiconductor light-emitting element 13 is enabled to be similar to the chromaticity of yellow light from the first translucent resin 17 containing fluorescent bodies. The semiconductor light-emitting element is, therefore, achieved to have little variations in the chromaticity with a viewing direction.
The excess of the translucent resin 31 which does not cover the semiconductor light-emitting element 13 is stored between the convex portion 12 and the frame body 16, and is not in contact with the wires 15a and 15b. Thus, the wires 15a and 15b do not undergo deformation due to resin stress occurring when the translucent resin 31 is cured.
The adhesion between the substrate 11 and the second translucent resin 18 does not lower because the first translucent resin 17 (cured translucent resin 31) is not inserted between the substrate 11 and the second translucent resin 18.
In the above description, just one semiconductor light-emitting element 13 is placed on the convex portion 12. Alternatively, two or more semiconductor light-emitting elements 13 may be placed on the convex portion 12. The semiconductor light-emitting element 13 may be an aggregate including two or more semiconductor light-emitting elements.
Placing two or more semiconductor light-emitting elements on the convex portion 12 reduces variations in the chromaticity with a viewing direction to achieve a semiconductor light-emitting device of COB (Chip On Board) type with high light output.
Excessive numbers of semiconductor light-emitting elements on the convex portion 12 are likely to cause the first translucent resin 17 to be stored between adjacent semiconductor light-emitting elements. In such a case, two or more convex portions 12 may be provided. All that is required for frame body 16 is to surround the convex portions 12.
The fluorescent bodies are YAG fluorescent bodies in the above description, but not limited to the YAG ones. Alternatively, the fluorescent bodies may be sialon-series red fluorescent bodies or sialon-series green fluorescent bodies. Alternatively, the fluorescent bodies may be a composite including two or more kinds of fluorescent materials, which emit light with wavelengths that are different from one another.
Mixing blue light properly with yellow light, red light, and green light also reduces variations in the chromaticity with a viewing direction to achieve a semiconductor light-emitting element which emits light of neutral colors.
In the above description, the second translucent resin 18 is clear resin. Alternatively, the second translucent resin 18 may be smoke resin containing a diffusion agent, which diffuses light emitted from the semiconductor light-emitting element 13 and light emitted from the fluorescent body. Examples of a diffusion agent include silica (SiO2) and zirconia (ZrO2). The diffusion agent achieves a semiconductor light-emitting device having little variations in the chromaticity with a viewing direction and emitting diffusion light. The first translucent resin 17 may contain a diffusion agent that diffuses light from the semiconductor light-emitting element 13 and light from a fluorescent body. The diffusion agent of the first translucent resin 17 may be the same as the diffusion agent of the second translucent resin 18. It is suitable to use a diffusion agent that diffuses light from a fluorescent body more strongly than light from the semiconductor light-emitting element 13. Diffusing light from the fluorescent body preferentially has a merit to cause chromaticity the characteristic of blue light to approach the chromaticity of yellow light.
In the above description, the semiconductor light-emitting device 10 includes the second translucent resin 18 being rectangular parallelepiped-like in shape to emit light from the upper surface and side surface of the second translucent resin 18. The semiconductor light-emitting device 10 may be modified to emit light focused in one direction. The semiconductor light-emitting element 10 has little variations in the chromaticity with a viewing direction, and emits highly directional light.
The semiconductor light-emitting element 13 is arranged at the bottom of the opening of the case 41. The frame body 16 prevents the liquid translucent resin 31 from flowing out and climbing a slope 41a of the case 41.
The aperture of the case 41 is filled with the second translucent resin 18 by potting. The case 41 does not cover the lower surface of the substrate 11. The case 41 made up of light-blocking resin, ceramics or the like.
Light 42 is emitted from the side surface 13b of the semiconductor light-emitting element 13, and enters the case 41. Most of the light 42 is reflected by the slope 41 to be focused in one direction.
As shown in
In addition, the semiconductor light-emitting device 50 includes a submount substrate 53 as a convex portion of a substrate. The submount substrate 53 is mounted on the flat substrate 54 with adhesives (not shown).
Various materials can be used for the submount substrate 53. An alumina ceramic substrate with high heat conductivity is used as an electrically insulating substrate. A silicon substrate or a metal substrate is used as an electrically conducting substrate, for example.
The semiconductor light-emitting device 50 may include a protection diode to protect the semiconductor light-emitting element 13 from ESD (Electro Static Discharge). The protection diode can be used as the submount substrate 53. The protection diode is a zener diode, for example.
In the above description, the frame body 16 is used to capture excessive liquid translucent resin 31. Other bodies may be used as long as the bodies are capable of capturing the excessive resin.
As shown in
A region around the convex portion 12 of the substrate 11 is roughed to form the concavo-convex portions 61 by pressing, etching, sandblasting, and cutting. The depth D1 of the concavo-convex portion 61 is much smaller than the height H1 of the convex portion 12.
For this reason, the concavo-convex portion 61 has a smaller storable amount of the translucent resin 31 than the frame body 16. The semiconductor light-emitting device 60 is suitable for a comparatively small semiconductor light-emitting element 13 and a small drip amount of the translucent resin 31.
In the above description, the semiconductor light-emitting element 13 has the first and second electrode terminals on the upper surface 13a, but is not limited to the structure. A semiconductor light-emitting element with electrode terminals on upper and lower surfaces of the element (vertical energization type) may be used. A semiconductor light-emitting element of a flip chip type may be used.
The semiconductor light-emitting element of vertical energization type has one of the first and second electrode terminals on the upper surface and the other on the lower surface.
The semiconductor light-emitting element of vertical energization type is mounted on the convex portion 12 with a conductive adhesive to eliminate the need for one of the two wires. Examples of the vertical energization type include a semiconductor light-emitting element formed on a GaN substrate or a SiC substrate.
In the above description, the substrate 11 is a metal plate. A lead frame may be used for the substrate 11. When a substrate is a lead frame, a semiconductor light-emitting device of PLCC (Plastic Lead Chip Carrier) type is acquired.
In the above description, the frame body 16 is made up of white resin. The frame body 16 may be made up of translucent resin. When the frame body 16 is made up of the translucent resin, the frame body 16 has no upper limit of the height thereof because the frame body 16 does not block light emitted from the semiconductor light-emitting element 13.
In the above description, the semiconductor light-emitting device emits white light by converting blue light into the white light. It is also possible to compose a light-emitting device capable of emitting white light by using a semiconductor light-emitting element that emits ultraviolet.
A semiconductor light-emitting device in accordance with a second embodiment will be described with reference to
The same portions or the like will be denoted by the same reference numerals also in the second embodiment. The same explanations will not be repeated. The second embodiment differs from the first embodiment in that the second embodiment includes a closed-path-like concave portion.
As shown in
The semiconductor light-emitting element 13 is placed on a region 71e surrounded by the concave portion 72 with the adhesives 14.
A first translucent resin 73 containing a fluorescent body (not shown) covers the upper surface 13a and the side surface 13b of the semiconductor light-emitting element 13. The first translucent resin 73 covering the upper surface 13a and the side surface 13b of the semiconductor light-emitting element 13 extends from the region 71 to the concave portion 72.
An excess of the first translucent resin 73, which does not cover the semiconductor light-emitting element 13, is stored in the concave portion 72.
The product of a width W1 and a height H4 is set as to be equal to the product of a distance L1 and a height H2. The W1 and the height H4 are of the convex portion 12. The distance L1 is a distance from the convex portion 12 to the frame body 16. Both the distance L1 and the height H2 of the frame body 16 are shown in
The above-mentioned semiconductor light-emitting device 70 places the semiconductor light-emitting element 13 on the region 71e surrounded by the concave portion 72 of the substrate 71 to store the excess of the translucent resin 31 in the concave portion 72, such that the first translucent resin 73 covers the upper surface 13a and the side surface 13b of the semiconductor light-emitting element 13.
As a result, variations in the chromaticity with a viewing direction are reduced, and the first translucent resin 73 is prevented from flowing out. The semiconductor light-emitting device 70 enables it to downsize the device 70 by the height 111 of the convex portion 12 in comparison with the size of the semiconductor light-emitting device 10 shown in
Steps of manufacturing the semiconductor light-emitting device 70 are the same as the manufacturing steps shown
As described above, the second embodiment includes the concave portion 72 in the substrate 71 to store the excess of the first translucent resin 73 in the concave portion 72, thereby enabling it to reduce variations in the chromaticity with a viewing direction and downsize the device 70 in comparison with the size of the semiconductor light-emitting device 10 shown in
The semiconductor light-emitting device 70 of the second embodiment may be modified to emit light focused in one direction.
As shown in
As shown in
The second embodiment can also combine the concave portion 72 with the convex portion 12 shown in
As shown in
The first translucent resin 102 containing a fluorescent body (not shown) covers the upper surface 13a and the side surface 13b of the semiconductor light-emitting element 13. An excess of the first translucent resin 102 extends from the slope of the convex portion 12 to the inside of the concave portion 72.
As a height difference (H1+H2) denoted by the sum of H1 and H2 becomes larger, the liquid translucent resin 31 shown in
It is considered, therefore, that the thickness of the first translucent resin 102 covering the upper surface 13a of the semiconductor light-emitting element 13 becomes closer to the thickness of the first translucent resin 102 covering the side surface 13b of the element 13.
A semiconductor light-emitting element in accordance with a third embodiment will be described with reference to
The same portions or the like will be denoted by the same reference numerals also in the third embodiment. The same explanations will not be repeated. The third embodiment differs from the first embodiment in that two different types of regions are alternately provided on the upper surface of the semiconductor light-emitting element in the third embodiment. Liquid translucent resin containing a fluorescent body easily flows over one of the two kinds of the regions. The liquid translucent resin hardly flows over the other.
As shown in
The first region 111 and the second region 112 are different from each other in surface roughness, for example. The first region 111 has a smooth surface, and the second region 112 has a rough surface. The smooth surface has lower friction than the rough surface to cause liquid translucent resin to easily flow over the smooth surface.
When the surface roughness of the first region 111 is identical with that of the second region 112, liquid translucent resin dripped onto a semiconductor light-emitting element to round thereon by surface tension. As a result, the liquid translucent resin is thicker in the central portion of the semiconductor light-emitting element than in the circumference of the element, becoming convex.
Targeting the thickness of the liquid translucent resin in the central portion causes the circumference portion to be thinner than the target thickness. Targeting the thickness of the liquid translucent resin in the circumference portion causes the central portion to be thicker than the target thickness. Potting is limited in the capability thereof to uniform the thickness of the first translucent resin over the upper surface of the semiconductor light-emitting element.
In contrast, as shown in
Concave portions of liquid translucent resin become larger in the second region 112 as a result of an increase in the dripped amount of the liquid translucent resin, so that the adjacent concave portions attract each other to aggregate and collapse. This phenomenon causes the thicknesses of the central portion and the circumference of liquid translucent resin to approach each other. It is, therefore, possible to enhance the uniformity in the thickness of the first translucent resin 113 over the upper surface 110a of the semiconductor light-emitting element 110.
The first region 111 and the second region 112 will be specifically described as follows. When the upper surface 110a of the semiconductor light-emitting element 110 is a surface of a P-type GaN contact layer, and an ITO (Indium Tin Oxide) film is provided on the P-type GaN contact layer; the first region 111 is a surface of the ITO film, and the second region 112 is an uneven surface formed by etching the ITO film.
When the upper surface 110a of the semiconductor light-emitting element 110 is a surface of an N-type GaN layer; the first region 111 is a surface of the N-type GaN layer, and the second region 112 is an uneven surface formed on the N-type GaN layer by etching etc.
As described above, the first region 111 and the second region 112 are alternately provided on the upper surface 110a of the semiconductor light-emitting element 110 in the third embodiment. Liquid translucent resin easily flows in the first region 111, and hardly flows in the second region 112. As a result, the third embodiment has a merit that uniformity in the thickness is enhanced of the first translucent resin 113 on the upper surface 110 of the semiconductor light-emitting element 110.
In the above description of the embodiment, the first region 111 is lattice-shaped. Nevertheless, the shape of the first region 111 is not limited as long as the first region 111 and the second region 112 are alternately arranged.
Semiconductor light-emitting devices in accordance with a fourth embodiment will be described with reference to
The same portions or the like will be denoted by the same reference numerals also in the fourth embodiment. The same explanations will not be repeated. The fourth embodiment differs from the first embodiment in that the lateral size of a semiconductor light-emitting element on the side in contact with a substrate of the element is larger than that on the side opposite to the substrate.
As shown in
When the angle between the upper surface and side surface of the element is 90° or smaller, the first translucent resin covering the element tends to become thinner at an edge where the upper surface and the side surface intersect with each other. Such a sharp edge with an angle of not more than 90° has caused the first translucent resin covering the element to be inhomogeneous in thickness.
In contrast, the semiconductor light-emitting element 121 has an obtuse angle at which the upper surface 121a and the side surface 121b intersect with each other. As a result of the obtuse angle, the first translucent resin 122 covering the semiconductor light-emitting element 121 is unlikely to be thin at the edge. The first translucent resin 122 covering the sloped side surface 121b is likely to have an improved skirt shape. The fourth embodiment, therefore, enables it to enhance homogeneity in the thickness of the first translucent resin 122 covering the semiconductor light-emitting element 121.
The semiconductor light-emitting element 121 with a trapezoidal section can be formed by cutting as sapphire substrate with a blade having a V-shaped section.
As described above, the fourth embodiment makes the size W2 of the upper surface 121a smaller than the size W1 of the lower surface 121c in the semiconductor light-emitting element 121. As a result, the fourth embodiment prevents the first translucent resin 122 covering the semiconductor light-emitting element 121 from becoming thinner at the corner of the element 121 to enhance homogeneity in the thickness of the first translucent resin 122.
In the above description of the fourth embodiment, the semiconductor light-emitting element with the size of the upper surface W2 smaller than the size of the upper surface W3 has a shape of a truncated pyramid, but the shape is not limited to the truncated pyramid.
The semiconductor light-emitting element 125 with a step on the side of the upper surface 125a is produced as follows. First, a sapphire substrate is cut to a depth of the certain thickness of the substrate with a thick blade to form a trench. Subsequently, the trench of the substrate is further cut to a depth of the full thickness of the substrate with a thin blade.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-175842 | Aug 2012 | JP | national |
