Abstract:
A semiconductor light emitting device includes a mold resin having a cup shape portion on an upper surface of the mold resin. One or more holes penetrate through the cup shape portion to outside of the mold resin and/or one or more trenches extend from the cup-shaped portion to outside the mold resin. A first lead is provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a first direction, and a second lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a second direction which is opposite to the first direction. A light emitting element is mounted on the first lead in the cup shape portion, and a wire electrically connects the light emitting element and the second lead. A sealing resin is embedded in the one or more holes and the one or more trenches and is configured to seal the light emitting element and the wire.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2005-48312, filed on Feb. 24, 2005, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   SMD (Surface Mounting Device) type semiconductor light emitting devices have a wide field of applications since such devices can be surface mounted to a printed circuit board. 
   With the application field being broadened, the semiconductor light emitting device may be used in a wide range ambient temperature. For example, in the automotive use, the semiconductor light emitting device may be required to be operable in a range of −40–+80 degree Centigrade. 
   On the other hand, a LED chip, a mold resin, a sealing resin and a metal lead frame have a different heat expansion coefficient and a different Young&#39;s modulus. In case an ambient temperature of the semiconductor light emitting device is raised and lowered, the sealing resin is expanded and compressed. So the optical characteristic of the semiconductor light emitting device may be worsened, or damage, such as peeling of the sealing resin from another constituent element and/or cracks in the LED chip, may occur in the semiconductor light emitting device. 
   SUMMARY 
   According to one aspect of the present invention, there is provided a semiconductor light emitting device including a mold resin having a cup shape portion on an upper surface of the mold resin and a hole extending from the cup shape portion to outside of the mold resin; a first lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a first direction; a second lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a second direction which is opposite to the first direction; a light emitting element mounted on the first lead in the cup shape portion; a wire electrically connecting the light emitting element and the second lead; and a sealing resin configured to seal the light emitting element and the wire, embedding the hole. 
   According to another aspect of the present invention, there is provided a semiconductor light emitting device including a mold resin having a cup shape portion on an upper surface of the mold resin; a first lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a first direction; a second lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a second direction which is opposite to the first direction; and the mold resin having a first trench extending from the cup shape portion to outside of the mold resin in a third direction and a second trench extending from the cup shape portion to outside of the mold resin in a fourth direction which is opposite to the third direction; a light emitting element mounted on the first lead in the cup shape portion; a wire electrically connecting the light emitting element and the second lead; and a sealing resin configured to seal the light emitting element and the wire, embedding the first trench and the second trench. 
   According to a further aspect of the present invention, there is provided a semiconductor light emitting device may include a mold resin having a cup shape portion on an upper surface of the mold resin and a hole penetrating from the cup shape portion to a bottom surface of the mold resin; a first lead having a first inner lead portion and a first outer lead portion, the first outer lead portion extending from the cup shape portion to outside of the mold resin in a first direction, the first inner lead portion provided in the cup shape portion and being thicker than the first outer lead portion; a second lead having a second inner lead portion and a second outer lead portion, the second outer lead portion extending from the cup shape portion to outside of the mold resin in a second direction which is opposite to the first direction, the second inner lead portion provided in the cup shape portion; a semiconductor light emitting element mounted on the first inner lead portion of the first lead; a wire connecting the semiconductor light emitting element and the second inner lead portion of the second lead; a sealing resin configured to seal the light emitting element and the wire, embedding the hole. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a top view of a semiconductor light emitting device in accordance with a first embodiment of the present invention. 
       FIG. 2  is a cross sectional view taken along line A—A in  FIG. 1 . 
       FIG. 3  is a cross sectional view taken along line B—B in  FIG. 1 . 
       FIG. 4  is a cross sectional view taken along line B—B in  FIG. 1 , showing a heat expansion of a sealing resin in a high temperature. 
       FIG. 5  is a cross sectional view taken along line B—B in  FIG. 1 , showing a heat compression of a sealing resin in a low temperature. 
       FIG. 6  is a top view of a semiconductor light emitting device in accordance with a comparative example. 
       FIG. 7  is a cross sectional view taken along line E—E in  FIG. 6 , showing a heat expansion of a sealing resin in a high temperature. 
       FIG. 8  is a cross sectional view taken along line E—E in  FIG. 6 , showing a heat compression of a sealing resin in a low temperature. 
       FIG. 9  is a top view of a semiconductor light emitting device in accordance with a second embodiment of the present invention. 
       FIG. 10  is a cross sectional view taken along line C—C in  FIG. 9 . 
       FIG. 11  is an end view of the semiconductor light emitting device shown in  FIG. 9 . 
       FIG. 12  is a top view of a semiconductor light emitting device in accordance with a third embodiment of the present invention. 
       FIG. 13  is a cross sectional view taken along line D—D in  FIG. 12 . 
       FIG. 14  is a top view of a semiconductor light emitting device in accordance with a fourth embodiment of the present invention. 
       FIG. 15  is a cross sectional view taken along line F—F in  FIG. 12 . 
       FIG. 16  is a cross sectional view taken along line G—G in  FIG. 12 , showing a heat expansion and compression of a sealing resin in a high and low temperature. 
       FIG. 17  is a cross sectional view taken along line G—G in  FIG. 12 , showing a semiconductor light emitting device before applying a sealing resin. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Various connections between elements are hereinafter described. It is noted that these connections are illustrated in general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. 
   Embodiments of the present invention will be explained with reference to the drawings as next described, wherein like reference numerals designate identical or corresponding parts throughout the several views. 
   FIRST EMBODIMENT 
   A first embodiment of the present invention will be explained hereinafter with reference to  FIGS. 1–5 . 
     FIG. 1  a top view of a semiconductor light emitting device  100  in accordance with a first embodiment of the present invention.  FIG. 2  is a cross sectional view taken along line A—A in  FIG. 1 .  FIG. 3  is a cross sectional view taken along line B—B in  FIG. 1 . 
   In the semiconductor light emitting device  100 , a semiconductor light emitting element  15  (LED) is mounted on a first lead  13 . A first electrode (not shown in  FIG. 1 ) provided on a top surface of the LED chip  15 , is connected to a second lead  14  via a bonding wire  16 . The first lead  13  and the second lead  14  are molded by a mold resin  11 . The mold resin  11  may be formed by, for example an injection mold. The mold resin  11  may be a thermoplastic resin. A cup shape portion  12  is provided on an upper surface of the mold resin  11  such that an upper surface of the first lead  13  and the second lead  14  are exposed from the mold resin  11 . As shown in  FIG. 3 , the bottom surface of the cup shape portion  12  is on the substantially same plane as the upper surface of the first lead frame  13 . The LED chip  15 , the first lead  13  and the second lead  14  and the wire  16  are sealed by a sealing resin  17 . The sealing resin  17  may be an epoxy resin or a silicone resin. The sealing resin  17  may be preferably transparent to light emitted from the LED chip  15 . 
   A hole  19  is provided in the mold resin  11 . As shown in  FIG. 3 , the hole  19  is penetrating to a bottom surface of the mold resin  11 , which is on the same plane as a bottom surface of the semiconductor light emitting device  100 . The sealing resin  17  is embedded in the hole  19 . For example, the sealing resin  17  is introduced into the hole  19  when the LED chip  15  and the wire  16  are sealed by the sealing resin  17 . 
   In  FIG. 1 , the hole  19  is penetrated from a bottom surface of the cup shape portion  12  to the bottom surface of the mold resin  11 . However, the hole  19  may be provided on the slanted portion of the cup shape portion  12 . Furthermore, the hole  19  may be angled from the vertical direction. 
   The sealing resin  17  is exposed form the hole  19  to outside of the semiconductor light emitting device  100 . The hole  19  may be formed by a injection mold of the mold resin  11 . 
   As shown in  FIG. 1 , two holes  19  is provided upper and below the LED chip  15 . A portion of the first lead  13 , on which the LED chip  15  is mounted, is narrower than the other part of the first lead  13 . 
   A damage such as peeling or cracking to the LED chip  15  is reduced by a hole  19  filled with the sealing resin  19  even in case an expansion and compression cycle occurs in the sealing resin  17 . 
   The mold resin  11  provided under the LED chip  15  may be adapted a good thermal resistance material. Generally the mold resin  11  is a higher thermal resistance than the sealing resin  17 . So the stable operation may be obtained in a high ambient temperature. Namely a heat generated by the LED chip  15  is released downward via the first lead  13  and the mold resin  11  to outside of the semiconductor light emitting device  100 . This structure is capable of operating in a higher temperature than a structure having the sealing resin provided under the LED chip  15 . So the maximum operating temperature may be increased. 
   The LED chip  15  is explained. 
   The LED chip  15  may be used an InGaAlP base semiconductor light emitting element, which emits visible light or an GaN base semiconductor light emitting element, which emits blue light or ultraviolet light. A florescent material such as a phosphor may be dispersed in the sealing resin  17  and a secondary light such as white light may be extracted from the semiconductor light emitting device  100 . 
   The function of the hole  19  is explained. 
     FIGS. 4–5  are cross sectional views taken along line B—B in  FIG. 1 , showing a heat expansion and a compression of a sealing resin in a high and low ambient temperature. 
   Generally a Cu board is used as lead frame is about 16.7×10 −6 /□ in heat expansion index and an iron board is used as lead frame is about 11.8×10 −6 /□ in heat expansion index. On the other hand, the sealing resin  17  (incase epoxy resin) is about 6.3×10 −5 /□ in heat expansion index, which is higher heat expansion index than a material used as a lead frame. So as shown in  FIG. 4 , in a high temperature, the LED chip  15 , the first lead  13 , the second lead  14 , the wire  16  and the mold resin  11  are pulled by the sealing resin  17 . However in this first embodiment, the hole  19  is provided. A tensile stress T is released upward form the cup shape portion  12  and downward from the hole  19 . Thus the tensile stress T to the LED chip  15 , the wire  16 , the first lead  13  and the second lead  14  is reduced. 
   In a low ambient temperature, the LED chip  15 , the wire  16 , the first lead  13  and the second lead  14  are compressed by the mold resin  11 . As shown in  FIG. 5 , in this embodiment, a compression stress C is released upward form the cup shape portion  12  and downward from the hole  19 . Thus the compression stress C to the LED chip  15 , the wire  16 , the first lead  13  and the second lead  14  is reduced. 
   As described above, in this first embodiment, damage to the LED chip  15  or the wire  16  is reduced, since the tensile stress T and the compression stress C are reduced. So peeling or cracking of the LED chip  15  may be prevented. The wire  16  is hardly to be cut. 
   COMPARATIVE EXAMPLE 
   A comparative example is explained with reference to  FIGS. 6–8 , wherein  FIG. 6  is a top view of a semiconductor light emitting device in accordance with a comparative example;  FIG. 7  is a cross sectional view taken along line E—E in  FIG. 6 , showing a heat expansion of a sealing resin in a high temperature, and  FIG. 8  is a cross sectional view taken along line E—E in  FIG. 6 , showing a heat compression of a sealing resin in a low temperature. 
   In this comparative example, the hole  19  is not provided in the mold resin  11 . As shown in  FIG. 7 , the sealing resin  17  is expanded at high ambient temperature, so that the expanded sealing resin  17  in the cup shape portion  12  of the mold resin  11  is protruded upward of the cup shape portion  12 , and in a bottom of the cup shape portion  12 , a tensile stress T to LED chip  15  and a boundary between the wire  16  and the second lead  14 , which has low heat expansion index, is generated. 
   As shown in  FIG. 8 , the sealing resin  17  is compressed and the compression stress C is generated so that the sealing resin  17  is peeled form the first lead  13  or the second lead  14  in the bottom of the sup shape portion  12 . 
   After the heat expansion and compression cycle, the sealing resin  17  may be peeled from the bottom of the cup shape portion  12 . A stress strain to the LED chip  15  may be accumulated. A cracking in the LED chip  15  and a weakening in an adhesive boundary between the lead and the wire may occur, especially at the bonding portion on the LED chip  15 . 
   However, in the first embodiment, the hole  19 , penetrating from the cup shape portion  12  to the bottom surface of the mold resin  11 , is provided in the mold resin  11 . So stress may be released to bottom side of the mold resin  11 , and peeling of the sealing resin  17 , cutting of the wire  16  or damage to the LED chip  15  may be reduced, in case a wide range heat cycle is applied to the semiconductor light emitting device  100 . 
   SECOND EMBODIMENT 
   A second embodiment is explained with reference to  FIGS. 9–11 , wherein  FIG. 9  is a top view of a semiconductor light emitting device in accordance with the second embodiment of the present invention, and  FIG. 10  is a cross sectional view taken along line C—C in  FIG. 9 , and  FIG. 11  is an end view of the semiconductor light emitting device shown in  FIG. 9 . 
   In this second embodiment, trenches  20  are provided in the mold resin  11 . The trench  20  extends from the cup shape portion to outside of the mold resin along the first lead  13  and the second lead  14 , respectively. The trenches  20  are provided on the first lead  13  and the second lead  14 , and in contact with the first lead  13  and the second lead  14 , respectively. The sealing resin  17  is embedded in the trenches  20 . 
   Similar to the effect provided by the hole  19  in the first embodiment, the tensile stress T or the compression stress C generated in the cup shape portion  12  is released by the trench  20 . A stress along a horizontal direction, which is generated between the LED chip  15  mounted surface and the sealing resin  17 , is reduced by the trench  20 . Thus peeling of the sealing resin  17 , cutting of the wire  16  or damage to the LED chip  15  may be reduced in case a wide range heat cycle is applied to the semiconductor light emitting device  200 . 
   THIRD EMBODIMENT 
   A third embodiment is explained with reference to  FIGS. 12–13 . In this third embodiment, a trench  21  is provided in the mold resin  11  in a direction, which is perpendicular to the lead extending direction. Two trenches  21  extend in a direction perpendicular to the trench  20  extending direction. The tensile stress T or the compression stress C generated in the cup shape portion  12  is released by the trenches  20  and  21 . 
   Furthermore, the holes  19  are also provided in the mold resin  11 . So the tensile stress T or the compression stress C generated in the cup shape portion  12  is released by the holes  19  and trenches  20  and  21 . 
   The stress generated in the cup shape portion is released in the horizontal direction by the hole  19 . The stress generated in the cup shape portion is released in the vertical direction by the trench  20  and  21 . Thus the peeling of the sealing resin  17 , cutting of the wire  16  or damage to the LED chip  15  may be reduced in case a wide range heat cycle is added to the semiconductor light emitting device  300 . 
   In the third and the fourth embodiment, the trenches  20  and  21  extend parallel to or perpendicular to the direction in which leads  13  and  14  extend. However, the trenches may extend in another direction. 
   FOURTH EMBODIMENT 
   A fourth embodiment will be explained with reference to  FIGS. 14–17 , in which  FIG. 14  is a top view of a semiconductor light emitting device in accordance with a fourth embodiment of the present invention;  FIG. 15  is a cross sectional view taken along line F—F in  FIG. 12 ;  FIG. 16  is a cross sectional view taken along line G—G in  FIG. 12 , showing a heat expansion and compression of a sealing resin in a high and low temperature; and  FIG. 17  is a cross sectional view taken along line G—G in  FIG. 12 , showing a semiconductor light emitting device before applying a sealing resin. 
   This fourth embodiment is suitable to a high luminosity (high optical output) type semiconductor light emitting device  400 . 
   A first lead  33  and a second lead  34  are made of a high heat conductivity metal. The first lead  33  has an outer lead portion  42  and an inner lead portion  37  which is thicker than the outer lead portion  42 . A cavity  36 , on which the LED chip  15  is mounted, is provided on the inner lead portion of the first lead  33 . The LED chip  15  may be mounted on a bottom of the cavity  36  via eutectic solder such as AuSn. A bottom surface of the first lead  33  and the second lead  34  are exposed to the outside. A heat sink (not shown in  FIGS. 14–17 ) may be provided on the bottom surface of the first lead  33  and the second lead  34  so that heat generated in the LED chip  15  may easily be released to the outside. Light extracted from the semiconductor light emitting device  400  may be increased by the cavity  36 , since light emitted from the LED chip  15  is reflected from an inner surface of the cavity  36 . 
   The mold resin  31  is injection molded. The first lead  33  and the second lead  34  extend in opposite directions. The cup shape portion  12  is provided in the mold resin  31 . As shown in  FIG. 14 , a hole  39 , which is not a round shape in the top view, is provided in both sides (upper and below) of the first lead  33 . Sealing resin  17  is embedded in the holes  19 . 
   The diameter at the bottom surface of the cup shape portion  12  along line G—G is greater than the width of the first lead  13  in the cup shape portion  12 . So the hole  39 , which has a semicircle shape in the top view, is provided. 
   A gap  40  between the first lead  33  and the second lead  34  is embedded by the mold resin  31 . However, the gap  40  may be embedded by the sealing resin  17  or another resin. 
   The tensile stress T at high temperature and the compression stress C at low temperature are released via the cup shape portion  12 , which opens upward and the hole  39 , which opens downward. Thus the peeling of the sealing resin  17 , cutting of the wire  16  or damage to the LED chip  15  may be reduced, in case a wide range heat cycle is applied to the semiconductor light emitting device  400 . 
   In this embodiment, a region under the LED chip  15  is the inner lead portion  37  and the sealing resin  17  is not provided under the LED chip  15 . So the semiconductor light emitting device  400  has good heat release efficiency by virtue of the inner lead  37  of the first lead  33  being exposed to a bottom surface of the semiconductor light emitting device  400 . Heat generated in the LED chip  15  is easily released to the outside via the inner lead  37 . So, for example, driving the semiconductor light emitting device at a higher output may be possible compared to a structure having a sealing resin  17  provided under the LED chip  15 . So the operating temperature may be improved. 
   The trenches  20  and  21 , which extend in a direction parallel to or perpendicular to the lead extending direction, may be provided in the mold resin  31  in a manner similar to the second embodiment or the third embodiment. In such a case, the stress generated in the cup shape portion  12  is reduced. 
   As described in the first to the fourth embodiments, stress release by means of a hole and/or a trench, is provided in a mold resin. Thus the peeling of the sealing resin  17 , cutting of the wire  16  or the damage to the LED chip  15  may be reduced, in case a wide range heat cycle is applied to the semiconductor light emitting device. 
   Furthermore, the shape of the hole in the mold resin is not limited to a circle. The shape of the hole in the mold resin may be oval, semicircle, square, rectangular, polygonal shape or the like, as long as the hole penetrated through the mold resin, as shown, e.g., in  FIGS. 16–17 . 
   Likewise, the shape of the cup shape portion in the mold resin is not limited to a circle, but may also be oval, semicircle, square, rectangular, polygonal shape or the like. 
   Other embodiments of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and example embodiments be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following.