Patent Publication Number: US-7719023-B2

Title: Light emitting device

Description:
This application is a continuation of Ser. No. 10/119,524, filed on Apr. 9, 2002, now U.S. Pat. No. 7,242,032. 

   CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-110674, filed on Apr. 9, 2001; the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   This invention relates to a light emitting device, in particular, having an excellent emission property and a high reliability. 
   Light emitting devices combining LEDs (light emitting diodes) or other semiconductor light emitting elements and fluorescent elements have been remarked as inexpensive, long-lived light emitting devices, and are widely used as various kinds of indicators, light sources, flat-type display devices, backlight of liquid crystal displays, and so forth. 
   As typical light emitting devices, there are those mounting semiconductors light emitting elements in resin stems. 
     FIGS. 14A and 14B  show such a typical conventional light emitting device.  FIG. 14A  is a plan view showing a configuration of the substantially part thereof, and  FIG. 14B  is a cross-sectional view thereof. 
   The light emitting device shown here is of a so-called “surface mounting” type, including a package (resin stem)  800 , semiconductor light emitting element  802  and sealing element  804  of a resin. 
   The resin stem  800  has a structure molding a pair of leads  805 ,  806  shaped from lead frames with a resin portion  803  of a thermoplastic resin. The resin portion  803  has an opening  801 , and the semiconductor light emitting element  802  is place therein. Then the semiconductor light emitting element  802  is sealed with an epoxy resin  804 . 
   The semiconductor light emitting element  802  is mounted on the lead  806 . An electrode (not shown) of the semiconductor light emitting element  802  and the lead  805  are connected to each other by a wire  809 . When en electric power is supplied to the semiconductor light emitting element  802  through those two leads  805 ,  806 , the semiconductor light emitting element  802  emits light, and the light is extracted from an emission surface  812  via the epoxy resin  804 . 
   It is often required to include two or more chips to be mounted in the opening  801  in the semiconductor devices of a type as shown in  FIGS. 14A and 14B . 
   For example, those having two or more semiconductor elements common in emission wavelength, for example, are enhanced in output. 
   Those having two or more semiconductor elements different in emission wavelength can provide mixed color, thereby to diversify the color representation. In this case, two complementary colors can produce white light. 
   It is sometimes desirable to mount an element for protecting the light emitting element in a common package. Incase of a light emitting element of a nitride semiconductor, it is often desirable to connect a Zener diode in a parallel opposite directions for the purpose of protecting the light emitting element from static electricity. 
   However, the light emitting device shown in  FIGS. 14A and 14B  cannot provide a sufficient space for mounting the chip and for bonding the wire as well. If two chips are packed in the narrow opening by force, the optical axis of the light emitting element will largely offset from the center of the opening, and the intensity profile of the emitted light, i.e., luminous intensity property, will become asymmetrical. Then, the light emitting device cannot provide a uniform emission pattern required in applications such as the back light of a liquid crystal display. 
     FIG. 15  is a schematic diagram showing a plan-viewed configuration of a light emitting device prepared by the Inventor for trial toward the present invention. 
   The light emitting device shown here has an approximately rectangular opening  901  formed in a resin portion  903 , and chips  902 A,  902 B mounted on opposed leads  905 ,  906 , respectively, at the bottom of the opening  901 . Wires  909 A,  909 B extending from the chips  902 A,  902 B are connected to the opposed leads  906 ,  905 , respectively. 
   As a result of evaluation of this light emitting device, the following problems were found. 
   The first problem is that a part of an adhesive extruding out upon mounting the chips  902 A,  902 B causes insufficient bonding of the wires  909 A,  909 B. For mounting the chips  902 A,  902 B to the leads, pastes such as silver paste or solders such as gold-tin (AuSn) or gold-germanium (AuGe) solder is usually used. 
   However, such an adhesive often extrudes on the leads  905 ,  906  upon mounting. If the extruded adhesive reaches the wire bonding region, it makes it difficult to bond wires  909 A,  909 B by thermo compression bonding or ultrasonic welding. For example, when a silver paste exists, so-called “breeding” occurs, and it makes wire bonding difficult. Even if they are once bonded, their bonding force will soon degrade significantly. 
   An attempt of locating the wire bonding site remote from the chip for the purpose of preventing that problem will need a larger opening  901  against the restriction on size. 
   The second problem lies in that the illustrated rectangular shape of the opening  901  causes side walls of the resin portion  903  to be uniformly thin, and makes the mechanical strength insufficient. This problem becomes serious especially when a soft resin is used as the sealing element buried in the opening. For example, a silicone resin used as the sealing element is advantageous for reducing the residual stress and thereby reducing cracks of the sealing element and breakage of the wire. However, in case the side wall of the resin portion  903  is thin, the relatively soft silicone resin often fails to prevent an external lateral force to act on the chip and the wire. For example, upon picking up the light emitting device by grasping from its side surfaces for assembly and a test, the force actually acted upon the chip and the wire, and often deformed the wire. 
   The third problem is that the illustrated rectangular shape of the opening  901  need a larger quantity of resin buried therein, and sometimes increases the resin stress. The resin filled in the opening  901  produces a stress upon curing, or thereafter upon an increase of decrease of the temperature. 
   The degree of the stress depends on the buried quantity of the resin, and tends to increase as the buried quantity increases. 
   Therefore, the sealing resin filled in the illustrated rectangular opening  901  produced a large stress, and is liable to cause exfoliation of the chips  902 A,  902 B, and deformation or breakage of the wires  909 A,  909 B. 
   That is, the attempt of mounting two or more chips in the light emitting device invites various problems contravening the requirements about the external dimensions. 
   As reviewed above, conventional light emitting devices were not suitable for mounting a plurality of chips, and had room for improvement from the viewpoint of reliability as well. 
   SUMMARY OF THE INVENTION 
   According to an embodiment of the invention, there is provided a light emitting device comprising: a lead; a resin portion which buries at least a part of said lead; 
   a first semiconductor light emitting element mounted on said lead in an opening formed in said resin portion; 
   a semiconductor element mounted on said lead in said opening; and a wire connecting said first semiconductor light emitting element and said lead, said lead having a slit formed between a portion where said first semiconductor light emitting element is mounted and a portion where said wire is connected. 
   According to another embodiment of the invention, there is another provided a light emitting device comprising: a first lead; a second lead; a resin portion which buries at least a part of said first and second leads; a first semiconductor light emitting element mounted on said first lead in an opening formed in said resin portion; a semiconductor element mounted on said second lead in said opening; a first wire connecting said first semiconductor light emitting element and said second lead; and a second wire connecting said semiconductor element and said first lead, said first lead having a first slit formed between a portion where said first semiconductor light emitting element is mounted and a portion where said second wire is connected, and said second lead having a second slit formed between a portion where said semiconductor element is mounted and a portion where said first wire is connected. 
   According to another embodiment of the invention, there is another provided a light emitting device comprising: a first lead; a second lead; a resin portion which buries at least a part of said first and second leads; a first semiconductor light emitting element mounted on said first lead in an opening formed in said resin portion; a semiconductor element mounted on said first lead in said opening; a first wire connecting said first semiconductor light emitting element and said second lead; and a second wire connecting said semiconductor element and said second lead, said opening having a substantially elliptical or elongate-circular opening shape, said first semiconductor light emitting element and said semiconductor element being arranged along a longer axis or a shorter axis of said elliptical or elongate-circular opening. 
   In the present application, the “elongate-circle” means a shape connecting a pair of curved portions by a pair of substantially straight portions. The curved portions may be either regularly arc-shaped or irregularly arc-shaped. 
   In the present application, the “fluorescent element” may be any having a wavelength converting function, either inorganic or organic, including inorganic dyes having a wavelength converting function. 
   In the present application, “nitride semiconductors” include III-V compound semiconductors expressed by the chemical formula B x In y Al z Ga (1−x−y−z) N (0≦x≦1, 0≦y≦1, 0≦z≦1, 0≦x+y+z≦1), where each of x, y, and z is varied throughout its respective range, and further include mixed crystals containing not only N (nitrogen) but also phosphorus (P) and/or arsenic (As) in addition to N as group V elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the embodiments of the invention. However, the drawings are not intended to imply limitation of the invention to a specific embodiment, but are for explanation and understanding only. 
     In the drawings: 
       FIGS. 1A and 1B  show schematic diagrams illustrating a configuration of the substantial part of a light emitting device according to the first embodiment of the invention, in which  FIG. 1A  is a plan view and  FIG. 1B  is a cross-sectional view taken along the A-A line of  FIG. 1A ; 
       FIG. 2  is a plan view that schematically shows the first modification of the first embodiment; 
       FIG. 3  is a cross-sectional view that schematically shows the structure of a semiconductor light emitting element made of nitride compound semiconductor which can realize a strong emission in a wavelength range between ultraviolet and green; 
       FIG. 4  is a plan view that schematically shows the second specific example of the light emitting device according to the first embodiment; 
       FIG. 5  is a cross-sectional view that shows a structure of the semiconductor light emitting element  106 D; 
       FIG. 6  is a plan view that schematically shows the third modification example of the light emitting device according to the first embodiment; 
       FIG. 7  is a plan view that schematically shows the fourth specific example of the light emitting device according to the first embodiment; 
       FIG. 8  is a plan view that schematically shows the fifth specific example of the light emitting device according to the first embodiment; 
       FIG. 9  is a plan view that schematically shows the specific example of the light emitting device according to the second embodiment; 
       FIG. 10  is a plan view that schematically shows the modification of the second embodiment; 
       FIG. 11  is a plan view that schematically shows the twelfth specific example of the light emitting device according to the first embodiment; 
       FIG. 12  is a plan view that schematically shows the modification of the third embodiment; 
       FIG. 13  is a cross-sectional view that schematically shows a configuration of the substantial part of a light emitting device according to the instant embodiment; 
       FIGS. 14A and 14B  show such a typical conventional light emitting device, where  FIG. 14A  is a plan view showing a configuration of the substantially part thereof, and  FIG. 14B  is a cross-sectional view thereof; and 
       FIG. 15  is a schematic diagram showing a plan-viewed configuration of a light emitting device prepared by the Inventor for trial toward the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Some embodiments of the invention will now be explained below with reference to the drawings. 
   First Embodiment 
     FIGS. 1A and 1B  show schematic diagrams illustrating a configuration of the substantial part of a light emitting device according to the first embodiment of the invention, in which  FIG. 1A  is a plan view and  FIG. 1B  is a cross-sectional view taken along the A-A line of  FIG. 1A . 
   The light emitting device  1 A shown here includes a resin stem  100 , a semiconductor light emitting element  106 A mounted on the resin stem  100 , a protective Zener diode  106 B and a sealing element  111  provided to embed them. 
   The resin stem  100  includes leads  101 ,  102  shaped from a lead frame, and a resin portion  103  molded integrally with the leads  101 ,  102 . The leads  101 ,  102  have opposed ends close to each other, and extend therefrom in the opposite directions to outside the resin portion  103 . 
   The resin portion  103  has formed an opening  105 , and the semiconductor light emitting element  106 A and the diode  106 B are mounted at the bottom of the opening  105 . The plan-viewed shape of the opening  105  is approximately elliptical or approximately elongate-circular as illustrated. The inner wall surface of the resin portion  103  surrounding the elements  106 A,  106 B inclines to face toward the light extraction direction to function as a reflective surface  104  for reflecting light. 
   In the opening  105 , the lead  101  and the lead  102  are isolated. Near the distal end of the lead  101 , a slit  101 G is formed to divide it into the regions  101 A and  101 B. Similarly, near the distal end of the lead  102 , a slit  102 G is formed to divide it into the regions  102 A and  102 B. 
   The light emitting element  106 A is mounted in the region  101 A with an adhesive such as silver (Ag) paste. The light emitting element  106 B is mounted in the region  102 B similarly with an adhesive  107  such as silver (Ag) paste. 
   From an electrode (not shown) formed on the light emitting element  106 A, the wire  109 A is connected to the opposed region  102 A. From an electrode (not shown) formed on the diode  106 B, the wire  109 B is connected to the opposed region  101 B. 
   The configuration explained above provides the following effects. 
   The slits  101 G,  102 G formed near distal ends of the leads  101 ,  102  separate each of them into the portion ( 101 A,  102 B) for mounting the chips  106 A,  106 B and the portion ( 101 B,  102 A) for bonding the wires  109 A,  109 B. This configuration keeps the portion for bonding the wire clean even when silver paste, for example, extrudes upon mounting the chip, and thereby eliminates defective bonding of wires. 
   Since the invention employs a shape with a longer diameter and a shorter diameter such as an approximately elliptical shape or an approximately elongate-circular shape as the shape of the opening in lieu of an approximately circular shape as shown by a broken line in  FIG. 1A , which has been used conventionally, it is possible to effectively increase the area of the opening  105  and thereby make an ample space for mounting two or more chips and bonding the wires. 
   The approximately elliptical or elongate-circular shape of the opening according to the invention makes it easy to locate the light emitting element closest to the center of the opening. 
   The use of the approximately elliptical or elongate-circular shape of the opening according to the invention also enables the corner portions  103 C to be made thicker. As a result, the light emitting device maintains a sufficient mechanical strength, and it is prevented from deformation or wires and other kinds of damage even upon application of a lateral force during assembly or tests. 
   Furthermore, the approximately elliptical or elongate-circular shape of the opening prevents an increase of the resin quantity filled inside and thereby prevents the resin stress. As already explained with reference to  FIG. 15 , the resin stress increases as the quantity of resin filled as the sealing element  111  increases. The invention, however, minimizes the increase of the resin quantity and simultaneously keeps an ample space for locating a plurality of chips. It results in eliminating the problems of exfoliation of chips, deformation or breakage of wires due to an increase of the resin stress. Moreover, the invention enables mounting of a plurality of chips while maintaining the outer dimension of the light emitting device compact. Therefore, by connecting the protective diode  106 B in a parallel, opposite direction from the light emitting element  106 A as illustrated, the invention can improve the reliability. In addition, by combining light emitting elements different in emission wavelength, the device can realize emission of white and other various colors, which has been difficult to emit conventionally. 
   The slits  101 G,  102 G formed in the leads  101 ,  102  facilitate corners of the lead patterns to be cognized inside the opening in the process of mounting chips or bonding wires. Therefore, the invention ensures more accurate mounting positions of the chips and more accurate bonding positions of the wires than conventional techniques. 
   Next referring to  FIGS. 2 through 8 , some modifications will be explained. 
     FIG. 2  is a plan view that schematically shows the first modification of the first embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A and 1B  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   The light emitting device shown here includes two semiconductor light emitting elements  106 ,  106 C on board. For connecting two elements in parallel by using the layout pattern shown here, elements  106 A,  106 C reversed in conduction type may be used. That is, one of them may be configured n-side down while the other p-side down. 
   If two light emitting elements  106 A,  106 C are equal in emission wavelength, the optical output of the light emitting device can be doubled. 
   If the light emitting elements are different in emission wavelength, the light emitting device can provide light of a mixed color. In this case, white light can be realized by combining, for example, a blue light emitting element and a yellow light emitting element that are chromatically complementary. White light can be obtained also by combining a red light emitting element and a blue-green light emitting element. 
     FIG. 3  is a cross-sectional view that schematically shows a semiconductor light emitting element made with a nitride compound semiconductor which can realize a strong emission in a wavelength range between ultraviolet through green. This structure is briefly explained here. The light emitting element  106 A (or  106 C) includes a buffer layer  122 , n-type contact layer  123 , light emitting layer  124 , p-type cladding layer  125  and p-type contact layer  126  sequentially stacked on a conductive substrate  121 . 
   The light emitting layer  124  may have a quantum well (QW) structure in which barrier layers and well layers are stacked alternately. 
   The conductive substrate  121  may be made of, for example, an n-type GaN or SiC. Respective layers on the substrate may be made of, for example, III-V compound semiconductors, II-IV compound semiconductors, IV-VI compound semiconductors and other various materials. 
   An n-side electrode  127  is provided on the rear surface of the substrate  121 . On the other hand, formed on the p-type contact layer  126  are a translucent p-side electrode  128  made of a stacked structure including a nickel (Ni) layer and a gold (Au) layer of a thickness of several ten nanometers, and a bonding pad  129  of gold (Au) connected to the p-side electrode  128 . Surface of the element is covered by a protective film  130  of SiO 2 . 
   When a voltage is applied to the n-side electrode  127  and the p-side electrode  128  of the light emitting element  106 A ( 106 C), light generated in the light emitting layer  124  is released from the surface  131 . The emission wavelength can be adjusted in a wide range by adjusting the material and thickness of the light emitting layer. 
   The embodiment shown here can realize various emission colors by using such semiconductor light emitting elements. 
     FIG. 4  is a plan view that schematically shows the second specific example according to the first embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 3  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   The light emitting device shown here includes a protective diode  106 B and a semiconductor light emitting element  106 D. The light emitting element  106 D is formed on an insulating substrate, and includes p-side and n-side electrodes (not shown) on the front surface. Wires  109 B,  109 C extending from these electrodes are connected to the leads  101 B,  102 B, respectively. The protective diode  106 B and the light emitting element  106 D are connected in the opposite directions in parallel. 
     FIG. 5  is a cross-sectional view that shows a structure of the semiconductor light emitting element  106 D. The device shown here is made by stacking nitride compound semiconductor layers on an sapphire substrate  133 . More specifically, sequentially stacked on the sapphire substrate  133  are a buffer layer  122 , n-type contact layer  123 , light emitting layer  124 , p-type cladding layer  125  and p-type contact layer  126 . Here again, the light emitting layer  124  may have a quantum well (QW) structure in which GaN barrier layers and InGaAlN well layers are stacked alternately. 
   On the n-type contact layer  123  exposed by selectively removing the multi-layered structure from its surface by etching, an n-side electrode  127  made of, for example, Ti/Al is formed. On the other hand, formed on the p-type contact layer  126  are a translucent p-side electrode  128  in form of a Ni/Au thin film having a thickness of tens of nanometers and a bonding pad  129  of gold (Au) connected to the p-side electrode  128 . Surface of the element is covered by a protective film  130  of SiO 2 . 
   When a voltage is applied to the n-side electrode  127  and the p-side electrode  128  of the light emitting element  106 D, intensive emission of light is obtained in the range from ultraviolet rays to green color depending on the composition and structure of the light emitting layer  124 . 
   The specific example shown in  FIG. 4  can compactly accommodate both the semiconductor light emitting element  106 D formed on the insulating substrate and the protective diode  106 B in a limited space, and can reliably, easily bond the predetermined wires  109 A through  109 C. Moreover, since the chips and the wire bonding portion are isolated by the slits  101 G,  102 G, defective bonding by extrusion of the adhesive can be eliminated. 
     FIG. 6  is a plan view that schematically shows the third modification example according to the first embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 4  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   The light emitting device shown here also includes the protective diode  106 B and the semiconductor light emitting element  106 D. In this specific example, however, the opening  105  is not elliptical but approximately elongate-circular. In the present application, the “elongate circle” means a shape, like that of the opening  105  shown in  FIG. 6 , having a pair of opposed approximately arc-curved portions and connecting these curved portions by substantially straight portions. The curved portions need not be strictly arc-shaped. That is, the “approximately elongate-circle” pertains to a shape made up of a pair of curved portions connected by two substantially straight portions. 
   In general, the approximately elongate circle is advantageous for easier processing upon forming the opening  105  in the resin portion  103 . In addition, since four corners  103 C are thicker, the light emitting device can maintain a sufficient mechanical strength against a lateral stress or impulse. 
   Furthermore, in the specific example shown here, shapes of the distal ends of the pair of leads  101 ,  102  are asymmetric. That is, the portion  102 B for mounting the light emitting element  106 D on is formed to extend forward toward the center of the opening  105 . Thus the light emitting element  106 D can be located in the center of the opening  105 , and the intensity profile of the emitted light, i.e. the luminous intensity property can be approximated to a uniform or symmetric profile. It is also possible to enhance the luminance. “Locating in the center” herein means to locate any portion of the light emitting element  106 D on the central axis of the opening  105 . 
   Needless to say, the specific example shown here may use the light emitting element  106 A (or  106 C) using a conductive substrate instead of the light emitting element  106 D. 
     FIG. 7  is a plan view that schematically shows the fourth specific example according to the first embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 6  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   The light emitting device shown here also includes the protective diode  106 B and the semiconductor light emitting element  106 D. In this specific example, however, the opposed distal ends of the pair of leads  101 ,  102  are aligned straight instead of being offset. Then the diode  106 B and the light emitting element  106 D are mounted at diagonal positions. 
   The light emitting element  106 D is formed to be closer to the center of the opening  105  than the diode  106 B. Locating the optical axis closer to the center of the opening  105  ensures a more uniform luminous intensity property. 
     FIG. 8  is a plan view that schematically shows the fifth specific example according to the first embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 7  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   The light emitting device shown here also includes the protective diode  106 B and the semiconductor light emitting element  106 D, and the opposed distal ends of the pair of leads  101 ,  102  are aligned straight instead of being offset. In this specific example, however, the slits  101 G,  102 G are formed to be offset from each other. This configuration can also locate the light emitting element  106 D close to the center of the opening  105 . 
   Second Embodiment 
   Next explained is a second embodiment of the invention. 
     FIG. 9  is a plan view that schematically shows the specific example according to the second embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 8  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   In this specific example, two chips are mounted on a common lead, and they are aligned along the lengthwise direction of the opening  105  having an approximately elliptical or elongate-circular shape. 
   That is, in this specific example, the semiconductor light emitting elements  106 A,  106 C are mounted side by side on the lead  101 , and the wires  109 A,  109 B are connected to the lead  102  in the opposed position with respect to the shorter axis of the opening  105 . 
   This arrangement of a plurality of chips along the longer axis, i.e. lengthwise direction, of the approximately elliptical or elongate-circular opening  105  is advantageous for effective use of the limited space. 
     FIG. 10  is a plan view that schematically shows the modification of the second embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 9  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   In this specific example, it is necessary to connect a second wire  109 C from the light emitting element  106 D to the lead  101 . For this purpose, a slit  101 G is formed in the lead  101 , and the wire  109 C is connected across the slit  101 G. In this manner, the bonding region can be isolated from extrusion of the adhesive upon mounting the light emitting element  106 D and the diode  106 B. 
   Third Embodiment 
   Next explained is a third embodiment of the invention. 
     FIG. 11  is a plan view that schematically shows the twelfth specific example according to the first embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 10  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   Also in this specific example, two chips are mounted on a common lead. These two chips, however, are disposed along the shorter axis direction of the approximately elliptical or elongate-circular opening  15 . Then the wires  109 A,  109 B are connected to the lead  102  in the opposed position with respect to the shorter axis of the opening  105 . 
   This arrangement of a plurality of chips along the shorter axis of the approximately elliptical or elongate-circular opening  105  is also advantageous for effective use of the limited space. 
     FIG. 12  is a plan view that schematically shows the modification of the third embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 11  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   In this specific example, it is necessary to connect a second wire  109 C from the light emitting element  106 D to the lead  101 . For this purpose, a slit  101 G is formed in the lead  101 , and the wire  109 C is connected across the slit  101 G. In this manner, the bonding region can be isolated from extrusion of the adhesive upon mounting the light emitting element  106 D and the diode  106 B. 
   Fourth Embodiment 
   Next explained is the fourth embodiment of the invention. 
     FIG. 13  is a cross-sectional view that schematically shows a configuration of the substantial part of a light emitting device according to the instant embodiment. Here again, the same or equivalent components as those already explained with reference to  FIGS. 1A through 12  are commonly labeled, and their detailed explanation is omitted for simplicity. 
   In this embodiment, in a slight emitting device having a plurality of chips as shown in  FIGS. 1A through 12 , light emitted from the light emitting element  106  is extracted after wavelength conversion by the fluorescent element. 
   Regarding the specific example shown in  FIG. 13 , the light emitting element  106  is connected in parallel with a protective diode, not shown. The layout pattern of these chips and the leads  101 ,  102  may be any of those explained with reference to  FIGS. 1A through 12 . 
   The opening  105  in form of an approximate ellipse or flattened circle formed in the resin portion  103  is buried by the sealing element  111  containing the fluorescent element  110 . The sealing element  111 , however, may be provided to bury a part of the opening  105  in lieu of the manner shown here. 
   The fluorescent element  110  contained in the sealing element  111  absorbs primary light emitted from the light emitting element  106  and releases light of a predetermined wavelength. 
   For example, the light emitting element  106  may be configured to emit ultraviolet rays, i.e. light having a peak wavelength shorter than 400 nm, and may be combined with a fluorescent element that absorbs this short wavelength light and releases light of a predetermined wavelength. Especially when a first fluorescent element  110 A absorbing the primary light to emit red light, a second fluorescent element  110 B absorbing the primary light to emit green light, and a third fluorescent element  110 C absorbing the primary light to emit blue light, white light can be obtained as their mixture. 
   In case the light emitting element  106  is configured to emit light of a short wavelength such as ultraviolet rays, the sealing element  111  is preferably made of a silicone resin instead of an epoxy resin used in the conventional devices. Epoxy resins deteriorate when exposed to short-wavelength light, and although originally transparent, they change in color through yellow, liver to black finally, and result in a serious decrease of the light extraction efficiency. Silicone resins are substantially free from such deterioration. 
   The present application contemplates, with the term “silicone resin”, any resin having as its skeleton a structure in which silicon atoms having organic radicals such as alkyl radicals or aryl radicals are alternately connected to oxygen atoms. Needless to say, those containing additive elements added to such skeletons are also included in “silicone resins”. 
   In order to excite the fluorescent element, a light source of a short wavelength is preferably used. On of such examples is the light source using nitride semiconductor as explained with reference to  FIG. 3  and  FIG. 5 . If, however, a light emitting element using a nitride semiconductor is used, a diode (like a Zener diode) protective against static electricity is preferably combined. In this case, it is necessary to accommodate these two chips in a limited space and reliably connect them by wire bonding. 
   The invention can reliably cope with this requirement. As already explained with reference to the first to third embodiments, the invention makes it possible to efficiently place a plurality of chips and well isolate the wire bonding region, thereby to eliminate defective bonding. As a result, the invention can realize a high-performance light emitting device combining the semiconductor light emitting element  106  using a nitride semiconductor with the fluorescent element  110  as shown in  FIG. 13 . 
   Heretofore, some embodiments have been explained by way of specific examples. The invention, however, is not limited to those specific examples. 
   For example, combination of chips mounted on the light emitting device is not limited to that illustrated, but combination of a light emitting element  106 A (or  106 C) and a diode  106 B, combination of two or more light emitting elements  106 A (or  106 C), and combination of a light emitting element  106 A (or  106 C) and a light emitting element  106 D are also acceptable. 
   The number of chips mounted in the opening is not limited to two, but three or more chips can be mounted as well. 
   The shape of the opening  105  may be either approximately elliptical or flattened-circular. 
   Regarding the shapes and relative dimensions of the leads, any changes adequately determined individually are also contemplated in the scope of the invention. 
   The light emitting elements  106 A,  106 C,  106 D used in the invention are not limited to those using a nitride semiconductor, but those using GaAs/AlGaAs compounds, InP/InGaAs compounds, InGaAlP compounds, ZeSe compounds, ZnS compounds and other various materials can be similarly used as well. This is the case also for the diode  106 B. 
   Regarding the material of the fluorescent element, concrete structure of the light emitting elements, shapes of the leads and sealing element  111 , relative dimensions of the respective components, and so on, design changes made by the ordinary person skilled in the art are also contemplated in the scope of the invention. 
   While the present invention has been disclosed in terms of the embodiment in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modification to the shown embodiments which can be embodied without departing from the principle of the invention as set forth in the appended claims.