Abstract:
A semiconductor light emitting device includes a semiconductor light emitting element, a lead electrically connected to the semiconductor light emitting element, and a resin package covering the semiconductor light emitting element and part of the lead. The resin package includes a lens facing the front of the semiconductor light emitting element. The lead includes an elongated mounting portion projecting from the resin package. The mounting portion includes a pair of first projections spaced from each other in the longitudinal direction and a second projection positioned between the first projections. The first projections and the second projection project in opposite directions from each other in the width direction of the mounting portion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a surface mount type light emitting device incorporating a semiconductor light emitting element. 
         [0003]    2. Description of the Related Art 
         [0004]      FIG. 11  shows an example of conventional top view type semiconductor light emitting device (see JP-A-2003-188418). The semiconductor light emitting device X shown in the figure includes leads  91 A and  91 B, an LED chip  92  and a resin package  93 . The LED chip  92  is mounted on the lead  91 A. The LED chip  92  is connected to the lead  91 B via a wire. The resin package  93  covers the LED chip  92  and part of each lead  91 A,  91 B. The resin package  93  is formed with a lens  93   a.  The portions of the leads  91 A and  91 B which project from the resin package  93  are utilized as connection terminals  91 Aa and  91 Ba. The semiconductor light emitting device X is soldered to a substrate B. Specifically, the connection terminals  91 Aa and  91 Ba are inserted into through-holes formed in the substrate B, and the portions of the terminals which project from the through-holes are fixed to the substrate B with solder S. 
         [0005]    In recent years, to mount various kinds of electronic components on a circuit board, surface mounting using e.g. a reflow furnace is widely performed. With this technique, many electronic components can be collectively mounted. Thus, there is an increasing demand for a semiconductor light emitting device which can be surface-mounted unlike the above-described semiconductor light emitting device X. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention has been proposed under the circumstances described above. It is, therefore, an object of the present invention to provide a semiconductor light emitting device which can be surface-mounted. 
         [0007]    According to a -first aspect of the present invention, there is provided a semiconductor light emitting device comprising a semiconductor light emitting element, a lead electrically connected to the semiconductor light emitting element, and a resin package covering the semiconductor light emitting element and part of the lead and including a lens facing the front of the semiconductor light emitting element. The lead includes an elongated mounting portion projecting from the resin package. The mounting portion includes a pair of first projections spaced from each other in the longitudinal direction and a second projection positioned between the first projections. The first projections and the second projection project in opposite directions from each other in the width direction of the mounting portion. 
         [0008]    Preferably, the mounting portion extends in either one of a first direction which is parallel to the optical axis of the lens and a second direction which is perpendicular to the first direction. The lead includes an additional mounting portion extending in the other one of the first direction and the second direction. 
         [0009]    According to a second aspect of the present invention, there is provided a semiconductor light emitting device comprising a semiconductor light emitting element, a first and a second leads electrically connected to the semiconductor light emitting element, and a resin package covering the semiconductor light emitting element and part of each of the leads and including a lens facing the front of the semiconductor light emitting element. Each of the first and the second leads includes a mounting portion projecting from the resin package and elongated in a direction perpendicular to the optical axis direction of the lens. The mounting portion of the first lead and the mounting portion of the second lead extend parallel to each other. The position at which the first lead projects from the resin package and the position at which the second lead projects from the resin package are opposite from each other in the direction in which the mounting portions extend. 
         [0010]    Preferably, the semiconductor light emitting device provided according to the second aspect further comprises a standing portion extending from each of the mounting portions in the optical axis direction of the lens. 
         [0011]    Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]      FIG. 1  is a front view showing a semiconductor light emitting device according to a first embodiment of the present invention; 
           [0013]      FIG. 2  is a sectional view taken along lines II-II in  FIG. 1 ; 
           [0014]      FIG. 3  is a rear view of the semiconductor light emitting device shown in  FIG. 1 ; 
           [0015]      FIG. 4  is a bottom view of the semiconductor light emitting device shown in  FIG. 1 ; 
           [0016]      FIG. 5  is a side view of the semiconductor light emitting device shown in  FIG. 1 ; 
           [0017]      FIG. 6  is a bottom view showing a semiconductor light emitting device according to a second embodiment of the present invention; 
           [0018]      FIG. 7  is a plan view showing a semiconductor light emitting device according to a third embodiment of the present invention; 
           [0019]      FIG. 8  is a sectional view taken along lines VIII-VIII in  FIG. 7 ; 
           [0020]      FIG. 9  is a bottom view of the semiconductor light emitting device shown in  FIG. 7 ; 
           [0021]      FIG. 10  is a front view of the semiconductor light emitting device shown in  FIG. 7 ; and 
           [0022]      FIG. 11  is a sectional view showing an example of conventional semiconductor light emitting device. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. 
         [0024]      FIGS. 1-5  show a semiconductor light emitting device according to a first embodiment of the present invention. The illustrated semiconductor light emitting device A 1  includes leads  1 A and  1 B, an LED chip  2  and a resin package  3  and is designed as a shell type LED lamp. 
         [0025]    The leads  1 A and  1 B are utilized for mounting the light emitting device A 1  to a circuit board and supplying power to the LED chip  2  and made of e.g. Cu alloy. Each of the leads  1 A and  1 B is partially covered by the resin package  3 . As shown in  FIGS. 1 and 2 , the lead  1 A is formed with a bonding cup  10 . The bonding cup  10  is in the form of a cone having a bottom surface, and the LED chip  2  is mounted on the bottom surface. 
         [0026]    The portion of the lead  1 A which projects from the resin package  3  provides mounting portions  11 A,  12 A and a connecting portion  13 A. Similarly, the portion of the lead  1 B which projects from the resin package  3  provides mounting portions  11 B,  12 B and a connecting portion  13 B. The mounting portions  11 A and  11 B are strip portions extending parallel to each other in the direction x (see  FIG. 3 ). The mounting. portions  12 A and  12 B are strip portions extending parallel to each other in the direction z (see  FIG. 4 ). As shown in  FIG. 5 , the connecting portion  13 A is a hook-shaped portion connecting the mounting portions  11 A and  12 A to each other. Part of the connecting portion  13 A extends in the direction x, while the remaining part extends in the direction z. Similarly, the connecting portion  13 B is a hook-shaped portion connecting the mounting portions  11 B and  12 B to each other. Part of the connecting portion  13 B extends in the direction x, while the remaining part extends in the direction z. 
         [0027]    As shown in  FIG. 4 , the mounting portion  12 A includes a pair of projections  12 Aa provided at the ends and a pair of projections  12 Ab provided adjacent to the center. In the figure, the paired projections  12 Aa are spaced from each other in the direction z (i.e., the longitudinal direction of the mounting portion  12 A), and each of the projections  12 Aa projects inward (toward the mounting portion  12 B) in the direction y (i.e., the width direction of the mounting portion  12 A). The other pair of projections  12 Ab is positioned between the paired projections  12 Aa in the direction z, and each of the projections  12 Ab projects outward (away from the mounting portion  12 B) in the direction y. Similarly, the mounting portion  12 B includes a pair of projections  12 Ba provided at the ends and a pair of projections  12 Bb provided adjacent to the center. The paired projections  12 Ba are spaced from each other in the direction z, and each of the projections  12 Ba projects inward (toward the mounting portion  12 A) in the direction y. The other pair of projections  12 Bb is positioned between the paired projections  12 Ba in the direction z, and each of the projections  12 Bb projects outward (away from the mounting portion  12 A) in the direction y. In the illustrated example, each of the projections  12 Ab is a relatively narrow strip extending in the direction y and connected to the connecting portion  13 A. Similarly, each of the projections  12 Bb is a relatively narrow strip extending in the direction y and connected to the connecting portion  13 B. 
         [0028]    The LED chip  2  is the light source of the light emitting device A 1  and designed to emit light of a predetermined wavelength. The LED chip  2  is bonded to the bottom surface of the bonding cup  10 . The upper surface of the LED chip  2  is electrically connected to the lead  1 B via a wire  4 . The light emitted from the LED chip  2  in the direction x or y is reflected by the side surface of the bonding cup  10  to travel in the direction z. 
         [0029]    The resin package  3  covers the LED chip  2  and part of each lead  1 A,  1 B and is made of a resin (e.g. epoxy resin or silicone resin) which transmits the light emitted from the LED chip  2 . The resin package  3  is formed with a lens  3   a.  The lens  3   a  is positioned to face the LED chip  2  and has an optical axis L extending in the direction z. The lens  3   a  has a function to converge the light emitted from the LED chip  2 . 
         [0030]    The advantages of the semiconductor light emitting device A 1  will be described below. 
         [0031]    Due to the above-described structure, the light emitting device A 1  can be mounted on a circuit board in two different manners. Firstly, when the light emitting device is mounted by using the mounting portions  11 A and  11 B, the light emitting device A 1  is used as a top view type light source which emits light in the direction of the normal to the circuit board. Secondly, when the light emitting device is mounted by using the mounting portions  12 A and  12 B, the light emitting device A 1  is used as a side view type light source which emits light in the direction parallel to the surface of the circuit board. 
         [0032]    In surface-mounting the light emitting device A 1 , centering effect is exhibited due to the surface tension of the molten solder. Specifically, in mounting the light emitting device by using the mounting portions  12 A and  12 B, molten solder remains between the projections  12 Aa,  12 Ab,  12 Ba,  12 Bb and the circuit board. The molten solder acts to pull the object in contact with itself toward the center due to the surface tension. With respect to the mounting portion  12 A, this centering effect is produced at the projections  12 Aa and  12 Ab. The centering effect is produced similarly with respect to the mounting portion  12 B. Thus, the centering effect is exerted on each of the mounting portions  12 A and  12 B with a good balance, whereby the light emitting device A 1  is properly positioned relative to the circuit board. Particularly, when the mounting portions  12 A and  12 B are used for the mounting, the lens  3   a  overhangs largely from the mounting portions  12 A and  12 B, so that the light emitting device A 1  is in a relatively unstable posture. In such a situation, the centering effect exerting on the mounting portions  12 A and  12 B is suitable for preventing the light emitting device A 1  from deviating from its proper position. 
         [0033]      FIG. 6  shows a semiconductor light emitting device A 2  according to a second embodiment of the present invention. In this figure, the elements which are identical or similar to those of the first embodiment are designated by the same reference signs as those used for the first embodiment. The light emitting device A 2  differs from the first embodiment (see  FIG. 4 ) in shape of the mounting portions  12 A and  12 B. Specifically, the mounting portion  12 A,  12 B of the second embodiment further includes a pair of projections  12 Aa′,  12 Ba′. The additional projections  12 Aa′ are substantially the same as the projections  12 Aa in position in the direction z and project toward the opposite side of the projections  12 Aa in the direction y. Similarly, the additional projections  12 Ba′ are substantially the same as the projections  12 Ba in position in the direction z and project toward the opposite side of the projections  12 Ba in the direction y. With this arrangement, the additional projections of the mounting portions  12 A and  12 B also exhibit the centering effect. As a result, the positional deviation of the light emitting device A 2  is prevented more effectively. 
         [0034]    According to the present invention, the above-described projections may be provided at the mounting portions  11 A and  11 B. In this case, the positional deviation of the light emitting device is prevented also when the light emitting device A 1  or A 2  is used as a top view type light source. 
         [0035]      FIGS. 7-10  show a semiconductor light emitting device A 3  according to a third embodiment of the present invention. The light emitting device A 3  includes leads  1 A and  1 B, an LED chip  2  and a resin package  3 . 
         [0036]    The leads  1 A and  1 B are utilized for mounting the light emitting device A 3  to a circuit board and supplying power to the LED chip  2  and made of e.g. Cu alloy. Each of the leads  1 A and  1 B is partially covered by the resin package  3 . As shown in  FIGS. 7 and 8 , the lead  1 A is formed with a bonding cup  10 . The bonding cup  10  is in the form of a cone having a bottom surface, and the LED chip  2  is mounted on the bottom surface. 
         [0037]    The portions of the leads  1 A and  1 B which project from the resin package  3  provide mounting portions  11 A,  11 B and standing portions  14 A,  14 B. As shown in  FIG. 9 , the mounting portions  11 A and  11 B are strip portions extending in the direction y in parallel to each other. As will be understood from  FIGS. 9 and 10 , the position at which the lead  1 A projects from the resin package  3  and the position at which the lead  1 B projects from the resin package  3  differ from each other in the direction y. That is, the respective ends of the mounting portions  11 A and  11 B are oriented in opposite directions. The standing portions  14 A and  14 B extend in the direction z from the mounting portions  11 A and  11 B, respectively. In surface-mounting the light emitting device A 3 , the standing portions  14 A and  14 B serve to promote the formation of a solder fillet. In the illustrated example, each of the standing portions  14 A and  14 B includes a lower portion formed with a through-hole having a rectangular cross section. 
         [0038]    Similarly to the first and the second embodiments, the LED chip  2  is the light source of the light emitting device A 3 . The LED chip  2  is bonded to the bottom surface of the bonding cup  10 . The upper surface of the LED chip  2  is electrically connected to the lead  1 B via a wire  4 . The light emitted from the LED chip  2  in the direction x or y is reflected by the side surface of the bonding cup  10  to travel in the direction z. 
         [0039]    The resin package  3  covers the LED chip  2  and part of each lead  1 A,  1 B and is made of a resin (e.g. epoxy resin or silicone resin) which transmits the light emitted from the LED chip  2 . The resin package  3  is formed with a lens  3   a.  The lens  3   a  is positioned to face the LED chip  2  and has an optical axis L extending in the direction z. 
         [0040]    The advantages of the light emitting device A 3  will be described below. 
         [0041]    With the above-described structure, the light emitting device A 3  can be surface-mounted on a circuit board by using the mounting portions  11 A and  11 B. Unlike the conventional light emitting device X shown in  FIG. 11 , the two leads  1 A and  1 B are not easily bent even when external force is applied from any of the directions X and y. Thus, the light emitting device A 3  is stably mounted to e.g. a circuit board. Further, since a good solder fillet is formed due to the standing portions  14 A and  14 B, the light emitting device A 3  is strongly bonded. Moreover, in mounting the light emitting device by soldering, the centering effect due to molten solder is exerted at the connecting portions  15 A,  15 B (see  FIG. 9 ) connecting the standing portions  14 A,  14 B to the mounting portions  11 A,  11 B.