Patent Publication Number: US-2013234181-A1

Title: Semiconductor light-emitting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-050025, filed Mar. 7, 2012; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to a semiconductor light-emitting device. 
     BACKGROUND 
     In a package for semiconductor light-emitting devices, a polyamide thermoplastic resin has frequently been used as an envelope that encloses a sealing resin to control the luminous intensity distribution and to raise light extraction from the package. 
     However, with the polyamide thermoplastic resin, its degradation due to heat and light is larger than that of silicone resins, etc., which are used as sealing resins, and there are issues with reliability over the long term. Accordingly, polyamide thermoplastic resin have not been used as sealing resins for packages. 
     A semiconductor light-emitting device in which a nitride semiconductor light-emitting element is mounted and bonded to a lead frame is known. A transparent resin body with a rectangular parallelepiped shape containing fluorescent materials is installed on the lead frame of the device and the nitride semiconductor light-emitting element is embedded into this resin body. 
     With the use of the nitride semiconductor light-emitting element for emitting blue light and the transparent resin body containing fluorescent materials for absorbing the blue light and emitting yellow light, the semiconductor light-emitting device for emitting white light is obtained. 
     However, in this semiconductor light-emitting device, the ratio of the intensity of the blue light and the intensity of the yellow light depends upon the viewing direction, because of directional scattering of the chromaticity. 
     Examples of related art include Patent References of JP-A-2009-94351 and JP-A-2009-260234. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross section showing the semiconductor light-emitting device of an embodiment. 
         FIG. 2  is a perspective view showing the semiconductor light-emitting device of the embodiment. 
         FIG. 3  is a cross section showing a semiconductor light-emitting device of a comparative example. 
         FIG. 4  is a flow chart showing the manufacturing processes of the semiconductor light-emitting device of the embodiment. 
         FIGS. 5A to 5C  are cross sections sequentially showing the main parts of the semiconductor light-emitting device of the embodiment. 
         FIGS. 6A and 6B  are cross sections showing the main parts of another semiconductor light-emitting device of the embodiment. 
         FIG. 7  is a cross section showing another semiconductor light-emitting device of the embodiment. 
         FIG. 8  is a perspective view showing another semiconductor light-emitting device of the embodiment. 
         FIGS. 9A and 9B  are cross sections showing the main parts of the manufacturing processes of another semiconductor light-emitting device of the embodiment. 
         FIG. 10  is a cross section showing another semiconductor light-emitting device of the embodiment. 
         FIG. 11  is a perspective view showing another semiconductor light-emitting device of the embodiment. 
         FIG. 12  is a cross section showing the main parts of the manufacturing processes of another semiconductor light-emitting device of the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an explanation given will be given with reference to the FIGS. 
     According to an embodiment, there is provided a semiconductor light-emitting device capable of operating with little scattering of the chromaticity due to direction. 
     According to an embodiment, in a semiconductor light-emitting device, first and second lead frames are arranged with a separation on the same plane. A semiconductor light-emitting element has first and second terminals. The first terminal is electrically connected to the first lead frame, and the second terminal is electrically connected to the second lead frame. A resin body is installed to cover the first and second lead frames so that the semiconductor light-emitting element is embedded in the resin body. In the resin body, the size of the upper side opposite to the first and second lead frames is smaller than the size of the lower side at the first and second lead frames. The resin body includes fluorescent materials that absorb light, which is emitted from the semiconductor light-emitting element. These fluorescent materials emit light with a wavelength longer than the wavelength of the light that they absorb. 
     Embodiment 
     The semiconductor light-emitting device of this embodiment will be explained with reference to  FIGS. 1 and 2 .  FIG. 1  is a cross sectional diagram showing the semiconductor light-emitting device of this embodiment.  FIG. 2  is a perspective diagram showing the semiconductor light-emitting device of this embodiment. 
     The semiconductor light-emitting device of this embodiment is a semiconductor light-emitting device in which a nitride semiconductor light-emitting element which emits blue light is embedded in a transparent resin containing fluorescent materials that absorb blue light and emit yellow light. 
     As shown in  FIGS. 1 and 2 , a semiconductor light-emitting device  10  of this embodiment includes a semiconductor light-emitting element  11  that is electrically connected to first and second lead frames  12  and  13 . A dome-shaped resin body  15  containing fluorescent materials  14  is installed so that the semiconductor light-emitting element  11  is covered thereby. In addition, a transparent resin body  16  with a rectangular parallelepiped shape is installed so that the resin body  15  is covered thereby. 
     The semiconductor light-emitting element  11  is a nitride semiconductor light-emitting element that emits blue light with a wavelength of about  450  nm, for instance. In the semiconductor light-emitting element  11 , an N-type GaN clad layer, a semiconductor luminous layer having a multiple quantum well structure in which InGaN well layers and GaN barrier layers are laminated in an alternating manner, a P-type GaN clad layer, and a P-type GaN contact layer are sequentially laminated on a sapphire substrate. 
     Referring now to  FIG. 2 , a first terminal (P side electrode)  11   a  is installed on the P-type GaN contact layer. A second terminal (N side electrode)  11   b  is installed in a notch (not shown in the FIG.) for exposing the N-type GaN clad layer. 
     The first and second lead frames  12  and  13  have a tabular shape. The first and second lead frames  12  and  13  are on the same plane and are arranged with a separation in the X direction of the paper. 
     In the first lead frame  12 , one base part  12   a  with a rectangular shape from the view in the Z-axis direction is installed; four suspension pins  12   d,    12   e,    12   f,  and  12   g  extend from the base part  12   a.  In the second lead frame  13 , one base part  13   a  with a rectangular shape from the view in the Z-axis direction is installed; four suspension pins  13   d,    13   e,    13   f,  and  13   g  extend from the base part  13   a.  Compared with the first lead frame  12 , the length of the second lead frame  13  in the X direction is short and the length in the Y direction is the same. 
     At position  12   b,  which is located at the central part in the X direction of the base part  12   a  on the lower surface  12   c  of the first lead frame  12 , a convex part is formed. At position  13   b,  which is located at the central part in the X direction of the base part  13   a  on the lower surface  13   c  of the second lead frame  13 , a convex part is formed. 
     On the base part  12   a  of the first lead frame  12 , the semiconductor light-emitting element  11  is mounted using a die mount medium  17  such as an adhesive. The first terminal  11   a  of the light emitting-element  11  is electrically connected to the base part  12   a  of the first lead frame  12  via a wire  18 . The second terminal  11   b  is electrically connected to the base part  13   a  of the second lead frame  13  via a wire  19 . 
     The fluorescent materials  14  may be, for example, YAG (yttrium-aluminum-garnet) fluorescent materials that absorb blue light and emit yellow light. The YAG fluorescent materials can be expressed by the following general formula. 
       (RE 1−x Sm x ) 3 (Al y Ga 1−y ) 5 O 12 :Ce 
     Here, 0≦x≦1, 0≦y≦1, and RE represents at least one kind of element that is selected from the elements Y and Gd. 
     The resin body  15 , for example, is a silicone resin with transparency to blue light and yellow light. The resin body  15  includes the fluorescent materials  14  at about 40-50 wt %, for instance. The resin body  15  covers the semiconductor light-emitting element  11  and the wires  18  and  19 . 
     The resin body  15  has a dome shaped and its size continuously decreases with increased distance from the first and second lead frames  12  and  13 . In other words, the size of the upper portion of the resin body  15  is smaller than the size of the lower portion of the resin body  15 , which is near the first and second lead frames  12  and  13 . 
     Since the resin body  15  has a dome shape and does not have a side surface that is approximately perpendicular to the first and second lead frames  12  and  13 , the resin body  15  is not exposed to the exterior by the transparent resin body  16 . 
     The transparent resin body  16  has a rectangular parallelepiped shape, and its upper surface  16   a  is approximately parallel with the same plane on which the first and second lead frames  12  and  13  lie. The transparent resin body  16  covers the resin body  15 , exposes the lower surfaces  12   c  and  13   c  of the first and second lead frames  12  and  13 , and covers the first and second lead frames  12  and  13 . The transparent resin body  16  may be, for example, a thermosetting epoxy resin or silicone resin. 
     The transparent resin body  16  is formed to protect the resin body  15  and to improve the handling properties of the semiconductor light-emitting device  10 , such as for pickup when the semiconductor light-emitting device  10  is mounted on a substrate. 
     In the semiconductor light-emitting device  10 , directional scattering of the chromaticity is reduced by making the luminous intensity distribution characteristics of the resin body  15  approach the luminous intensity distribution characteristics of the semiconductor light-emitting element  11 . 
     Next, the luminous intensity distribution characteristics of the semiconductor light-emitting device  10  of this embodiment will be explained by comparing with the luminous intensity distribution characteristic of a semiconductor light-emitting device known in the art. 
       FIG. 3  is a cross sectional diagram showing a semiconductor light-emitting device of a comparative example. As shown in  FIG. 3 , in a semiconductor light-emitting device  30  of the comparative example, a semiconductor light-emitting element  11  is embedded in a resin body  31  with a rectangular parallelepiped shape containing fluorescent materials  14 . 
     In the semiconductor light-emitting device  30  of the comparative example, the resin body  31  has a rectangular parallelepiped shape, and multiple fluorescent materials  14  are distributed obliquely upwards from the semiconductor light-emitting element  11 . As a result, since the probability that blue light emitted obliquely upwards from the semiconductor light-emitting element  11  will make contact with the fluorescent materials is high, it is difficult for the blue light to exit out of the resin body  31 . 
     Therefore, the intensity ratio of the blue light and the yellow light depends upon the viewing direction, as well as chromaticity scattering (color breakup). The chromaticity scattering (color breakup) is a phenomenon in which the whiteness is changed in accordance with the viewing direction when the blue light and the yellow light are mixed. 
     On the other hand, in the semiconductor light-emitting device  10  of this embodiment, the resin body  15  has a dome shape, and the fluorescent materials  14  are entirely distributed from a view of the semiconductor light-emitting element  11 . As a result, the probability that the blue light will be emitted obliquely upward from the semiconductor light-emitting element  11  with the fluorescent materials is lowered, compared with the resin body  31  of the comparative example, the blue light easily exits to the outside of the resin body  15 . 
     Therefore, even if the intensity ratio of the blue light and the yellow light depends upon the viewing direction, its difference is decreased, reducing the chromaticity scattering due to the viewing direction. 
     In other words, even if there is a difference in the intensity between the blue light and the yellow light, there is no problem as long as the intensity ratio of the blue light and the yellow light is the same. The luminous intensity distribution characteristic of the blue light and the luminous intensity distribution characteristic of the yellow light are made similar, thus being able to reduce the chromaticity scattering due to the direction. 
     Next, the method for manufacturing the semiconductor light-emitting device  10  will be explained with reference to  FIGS. 4 and 5A  to  5 C.  FIG. 4  is a flow chart showing the manufacturing processes of the semiconductor light-emitting device  10 ;  FIGS. 5A to 5C  are cross sectional diagrams which sequentially show the main stages of the manufacturing processes of the semiconductor light-emitting device  10 . 
     As shown in  FIG. 5A , the lead frames  12  and  13  are prepared. The lead frames  12  and  13  are parts of a lead frame from which the lead frames  12  and  13  are repeatedly formed as one unit in the Y direction. 
     The semiconductor light-emitting element  11  is mounted on the base part  12   a  of the lead frame  12  by using the die mount medium  17 . The wire  18  is bonded to the first terminal  11   a  of the semiconductor light-emitting element  11  and the base part  12   a  of the lead frame  12 . The wire  19  is bonded to the second terminal  11   b  of the semiconductor light-emitting element  11  and the base part  13   a  of the lead frame  13  (step S 01 ). 
     As shown in  FIG. 5B , for example, a liquid silicone resin  52  containing the fluorescent materials  14  is injected with a dispenser (not shown) into a mold  51  having a dome-shaped, concave part which can surrounds the semiconductor light-emitting element  11 . Next, the lead frames  12  and  13  are turned over, and the semiconductor light-emitting element  11  is inserted into the concave part of the mold  51 , and the silicone resin  52  is cured at a prescribed temperature. The cured silicone resin  52  is drawn out of the mold  51  (step S 02 ). 
     Therefore, the dome-shaped resin body  15 , which covers the semiconductor light-emitting element  11  and the wires  18  and  19  mounted and bonded to the lead frames  12  and  13  and which includes the fluorescent materials  14 , can be obtained. 
     As shown in  FIG. 5C , a dispenser (not shown) is used to inject, for example, a liquid epoxy resin  54  into a mold  53  having a concave part with a rectangular parallelepiped shape, which can house the resin body  15 . Next, the lead frames  12  and  13  are turned over, and the resin body  15  is placed in the concave part of the mold  53 , and thereafter the epoxy resin  54  is cured at a prescribed temperature. Once cured, the epoxy resin  54  is drawn out of the mold (step S 03 ). 
     Therefore, the transparent resin body  16  with a rectangular parallelepiped shape, which covers the dome-shaped resin body  15 , can be obtained. The transparent resin body  16  has an upper surface  16   a  that is approximately parallel with the plane on which the lead frames  12  and  13  have been arranged. 
     As explained above, in the semiconductor light-emitting device  10  of this embodiment, the dome-shaped resin body  15  containing the fluorescent materials  14  is installed on the lead frames  12  and  13  arranged with a separation on the same plane in a manner such that the semiconductor light-emitting element  11  is embedded in the resin body. 
     As a result, as compared with the rectangular resin body  31  having a rectangular parallelepiped shape and containing the fluorescent materials  14 , the intensity of blue light increases from the oblique upper side toward the lower side, and the ratio of yellow light is close to the ratio in the front direction. Therefore, a semiconductor light-emitting device with little scattering of the chromaticity due to the direction can be obtained. 
     Here, the dome shape of the resin body  15  is not particularly limited but can be appropriately configured in accordance with the luminous intensity distribution characteristics of blue light of the semiconductor light-emitting element so that scattering of the chromaticity due to the direction is improved. 
     The case in which the first and second terminals  11   a  and  11   b  are installed on the upper surface of the semiconductor light-emitting element  11  has been explained, but the surface on which the first and second terminals  11   a  and  11   b  are installed is not limited to this upper surface or the particular locations depicted in  FIG. 2 . 
       FIGS. 6A and 6B  are cross sectional diagrams showing the main parts of another semiconductor light-emitting device. As shown in  FIG. 6A , when the semiconductor light-emitting element  55  is a vertical conductive type, a first terminal is installed on the lower surface of the semiconductor light-emitting element  55  and a second terminal is installed on the upper surface of the semiconductor light-emitting element  55 . The semiconductor light-emitting element  55  is mounted on the lead frame  12  by a conductive die mount medium  56 . The wire  18  is thus not required. 
     As shown in  FIG. 6B , when the semiconductor light-emitting element  57  is a flip chip, bumps  58   a  and  58   b  are installed on a surface of the semiconductor light-emitting element  57 . The bumps  58   a  and  58   b  are thermocompression-bonded to the lead frames  12  and  13 , thereby enabling a flip-chip mounting of the semiconductor light-emitting element  57  on the lead frames  12  and  13 . The wires  18  and  19  are thus not required. 
     The case in which the fluorescent materials  14  are YAG fluorescent materials has been explained, but the kinds of fluorescent materials are not limited to that case. For example, SIALON red fluorescent materials or SIALON green fluorescent materials may be used. Blue light, red light, or green light is mixed, thus being able to form a semiconductor light-emitting device that emits light with little chromaticity scattering. 
     The case in which the resin body has a dome shape has been explained. However, this disclosure is not limited to such a shape. Rather, any shape that lessens directional scattering of the chromaticity may be adopted in accordance with the luminous intensity distribution characteristic of blue light of the semiconductor light-emitting element. For example, a shape in which the lower side has a rectangular parallelepiped shape and the upper surfaces have a quadrangular pyramidic trapezoidal shape may be adopted. A shape in which the lower portion has a first rectangular parallelepiped shape and the upper portion has a second rectangular parallelepiped shape which is smaller than the first rectangular parallelepiped shape may be adopted. A shape in which the area of the upper side of the resin body containing the fluorescent materials  14  is smaller than the area of the lower side may be adopted. 
       FIGS. 7 and 8  show another semiconductor light-emitting device.  FIG. 7  is its cross section and  FIG. 8  is its perspective view. 
     As shown in  FIGS. 7 and 8 , in another semiconductor light-emitting device  60 , the lower part  61   a  (lower side) of a resin body  61  containing the fluorescent materials  14  has a rectangular parallelepiped shape while its upper part  61   b  (upper side) has a quadrangular pyramidic trapezoidal shape. The volume of the upper part  61   b  is less than the volume of the lower part  61   a.    
     The transparent resin body  62  with a rectangular parallelepiped shape exposes the side surface (the side surface of the lower part  61   a ) of the resin body  61  approximately perpendicular to the lead frames  12  and  13  and covers the resin body  61 . 
     In the resin body  61 , the concentration of the fluorescent materials  14  is lowered, compared with the resin body  31  of the comparative example shown in  FIG. 3 . Therefore, similarly to the resin body  15  of the embodiment shown in  FIG. 1 , blue light is relatively increased toward the lower part  61   a  and yellow light is reduced, increasing the ratio of the blue light and the yellow light. In light that is emitted from the lower part of the semiconductor light-emitting device  60 , yellowness is reduced. Thus, directional scattering of the chromaticity can be lessened. 
       FIGS. 9A and 9B  are cross sections showing the main parts of the manufacturing processes of the semiconductor light-emitting device  60  of the embodiment described with respect to  FIGS. 7 and 8 . As shown in  FIG. 9A , for example, a liquid silicone resin  52  containing fluorescent materials  14  is injected with a dispenser (not shown) into a mold  64  having a concave part with a rectangular parallelepiped shape, which can house the semiconductor light-emitting element  11 . Next, the lead frames  12  and  13  are turned over, the semiconductor light-emitting element  11  is placed within the mold  64 , and the silicone resin  52  therein is cured at a prescribed temperature. The cured silicone resin  52  is drawn out of the mold  64  (step S 02 ). 
     Therefore, a resin body  65  with a rectangular parallelepiped shape, which covers the semiconductor light-emitting element  11  and the wires  18  and  19  mounted and bonded to the lead frames  12  and  13 , and which includes the fluorescent materials  14 , can be obtained. 
     As shown in  FIG. 9B , using a blade  66  with a V-shaped cross section, the resin body  65  is half cut along a prescribed dicing line. Therefore, the resin body  65  with a rectangular parallelepiped shape becomes a resin body  61  having a lower part  61   a  with a rectangular parallelepiped shape and an upper part  61   b  with a quadrangular pyramidic trapezoidal shape. 
     Here, the resin body  61  can also be formed by placing the semiconductor light-emitting element  11  in a mold having a concave part with a lower rectangular parallelepiped shaped part and an upper quadrangular pyramidic trapezoidal shaped part, and molding the liquid silicone resin  52  containing the fluorescent materials  14 . 
     The ratio of the height of the lower part  61   a  and the height of the upper part  61   b,  and the ratio of the width of the lower part  61   a  and the width of the upper part  61   b,  are not restricted by this disclosure, but rather, may be appropriately set so that directional scattering of the chromaticity is lessened. 
       FIG. 10  and  FIG. 11  show another semiconductor light-emitting device.  FIG. 10  is a cross-section view and  FIG. 11  is a perspective view. 
     As shown in  FIGS. 10 and 11 , in a semiconductor light-emitting device  80 , the lower part  81   a  (lower side) of a resin body  81  containing fluorescent materials  14  has a first rectangular parallelepiped shape, and its upper part  81   b  (upper side) has a second rectangular parallelepiped shape smaller in size than the first rectangular parallelepiped shape. 
     The transparent resin body  82  with a rectangular parallelepiped shape exposes the side surface (the side surface of the lower part  81   a ) of the resin body  81  approximately perpendicular to the lead frames  12  and  13  and covers the resin body  81 . 
     In the resin body  81 , the content of the oblique upward fluorescent materials  14  is lowered, compared with the resin body  31  of the comparative example shown in  FIG. 3 . Therefore, similarly to the resin body  15  of the embodiment shown in  FIG. 1 , blue light is relatively increased toward the lower part  81   a  and yellow light is reduced, increasing the ratio of the blue light to yellow light. In light that is emitted from the lower part of the semiconductor light-emitting device  80 , yellowness is reduced. Directional scattering of the chromaticity due to the direction can be lessened. 
       FIG. 12  is a cross section showing the main parts of the manufacturing processes of the semiconductor light-emitting device  80 . As shown in  FIG. 12 , for example, using a blade  85  with a rectangular cross section, the resin body  65  is half cut along a prescribed dicing line. Therefore, the resin body  65  with a rectangular parallelepiped shape becomes the resin body  81  having the lower part  81   a  with a first rectangular parallelepiped shape and the upper part  81   b  with a second rectangular parallelepiped shape smaller than the first rectangular parallelepiped shape. 
     Here, the resin body  81  can also be formed by placing the semiconductor light-emitting element  11  in a mold having a concave part having a lower part with a first rectangular parallelepiped shape and an upper part with a second rectangular parallelepiped shape smaller than the first rectangular parallelepiped shape, and molding the resin body  81  using liquid silicone resin  52  containing the fluorescent materials  14 . 
     The ratio of the height of the lower part  81   a  and the height of the upper part  81   b,  and the ratio of the width of the lower part  81   a  and the width of the upper part  81   b,  are not to be limited herein, but rather, can be appropriately set so that scattering of the chromaticity due to the direction is improved. 
     In addition, the case in which the sides of the first rectangular parallelepiped and the sides of the second rectangular parallelepiped are parallel to each other has been explained, but the sides of the first rectangular parallelepiped and the sides of the second rectangular parallelepiped may be arranged so that they intersect with each other. 
     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 invention. Indeed, the novel embodiment 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 invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.