Abstract:
Providing a lighting device wherein provisions are made to be able to provide a sufficiently high dielectric strength while retaining the required heat-sink property even when a module substrate with a plurality of LED elements mounted thereon is reduced in size. A lighting device includes a module substrate on an upper surface of which are mounted a plurality of LED elements, a heat-sink member, having a raised portion, for dissipating heat generated by the plurality of LED elements, and an insulating sheet formed with an opening and interposed between a portion of the lower surface of the module substrate and the heat-sink member, and wherein the raised portion is formed so as to be located via the opening in close proximity to the lower surface of a region where the plurality of LED elements are mounted on the module substrate.

Description:
CROSS-REFERENCES TO RELATED APPLICATION 
     This application is a new U.S. patent application that claims benefit of JP 2012-126035, filed on Jun. 1, 2012, the entire content of JP 2012-126035 is hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a lighting device that comprises a module substrate with a plurality of LED elements mounted thereon and a heat-sink member for dissipating heat generated by the LED elements. 
     BACKGROUND ART 
     Lighting equipment using LED elements has come into widespread use. To simplify design of lighting equipment such as desk lamps and other lighting lamps, it is common to modularize light source units. For example, FIG. 1 in a Japanese Unexamined Patent Publication No. 2009-218204 shows a light-emitting module  1  constructed by mounting a plurality of light-emitting elements  3  (packaged LED elements), a lighting circuit  4 , and a connector  5  on the surface of a substrate  2  (a module substrate). 
       FIG. 11  is a plan view showing the surface of the light-emitting module  1  disclosed in the Japanese Unexamined Patent Publication No. 2009-218204. 
     The light-emitting module  1  shown in  FIG. 11  comprises a disc-shaped substrate  2 , and the light-emitting elements  3 , lighting circuit components  4 , and power supply connector  5  mounted on the substrate  2 . The substrate  2  is made of aluminum formed in the shape of a disc, and has a thickness of about 1.5 mm and a diameter of about 70 mm. The upper surface  2   a  of the substrate  2  is a component mounting surface, and the lower surface  2   b  thereof provides a planar heat-sink surface. Further, an insulating layer is formed on the upper surface  2   a  of the substrate  2 , and an interconnection pattern not shown is formed on the insulating layer. 
     Eight light-emitting elements  3 , one spaced from another by a prescribed distance, are mounted in the center of the component mounting surface. The outer dimensions of each light-emitting element  3  are 3.5 mm square and about 1.5 mm high, and each element is a surface-mount LED element containing four LED dies. The lighting circuit components  4  are arranged along the outer periphery of the component mounting surface. The lighting circuit components  4  are components for controlling the lighting of the LED chips, and include a fuse F, a capacitor C, a rectifier REC, a voltage-regulating diode ZD, resistive elements R 1  and R 2 , and a transistor Q. The connector  5  for connecting to utility power is located outside the array of the light-emitting elements  3 . A white resist having high reflectivity is applied by printing over the component mounting surface of the substrate  2 , and mounting screw holes  6  are formed at three places passing through the substrate  2 . 
       FIG. 12  is a schematic diagram of a lighting device  10  constructed using the light-emitting module  1  disclosed in the Japanese Unexamined Patent Publication No. 2009-218204. 
     Since the light-emitting elements (LED elements)  3  generate heat during operation, the heat must be efficiently dissipated outside the lighting device. FIG. 4 in the Japanese Unexamined Patent Publication No. 2009-218204 shows how the light-emitting elements  3  are mounted on a heat sink (heat-sink member)  12  via the substrate  2 . The lighting device  10  shown in  FIG. 12  is a downlight and has a casing  11  fixedly mounted in a ceiling. The metal heat sink  12  provided with radiating fins is placed inside the casing  11 , and the light-emitting module  1  equipped with a reflector  13  is mounted on the heat sink  12 . The light-emitting module  1  is screwed to the casing  11  so that the heat-sink lower surface  2   b  of the substrate  2  is held in intimate contact with the heat sink  12  by interposing a silicone rubber sheet (not shown) therebetween. The reflector  13  is formed in the shape of a cup having a gently curved face, and its upper end has a mounting opening  13   a , while its lower end provides a lighting opening  13   b.    
     SUMMARY 
     An electrically conductive resin or a metal such as aluminum may be used as the material for the heat-sink member in order to enhance heat conductance. When applying a high voltage to the module substrate adjacent to the heat-sink member, the module substrate must be provided with a sufficiently high dielectric strength. One method known in the art to increase the dielectric strength is to increase the distance between the power supply terminal of the module substrate and the edge face of the module substrate. This method, however, increases the size of the module substrate. Another method known to provide increased dielectric strength is to interpose an insulating sheet between the module substrate and the heat-sink member; the silicone rubber sheet described with reference to  FIG. 12  corresponds to this insulating sheet. The silicone rubber sheet also has the function of enhancing adhesion and providing stable heat conductance. However, if the dielectric strength is to be increased by using such an insulating sheet, the thickness of the insulating sheet has to be increased, and as a result, the heat-sink property has to be compromised. 
     It is an object of the present invention to provide a lighting device that comprises a module substrate with a plurality of LED elements mounted thereon and a heat-sink member for dissipating heat generated by the LED elements, wherein provisions are made to be able to provide a sufficiently high dielectric strength while retaining the required heat-sink property even when the module substrate is reduced in size. 
     There is provided a lighting device that includes a module substrate on an upper surface of which are mounted a plurality of LED elements, a heat-sink member, having a raised portion, for dissipating heat generated by the plurality of LED elements, and an insulating sheet formed with an opening and interposed between a portion of the lower surface of the module substrate and the heat-sink member, and wherein the raised portion is formed so as to be located via the opening in close proximity to the lower surface of a region where the plurality of LED elements are mounted on the module substrate. 
     Preferably, in the lighting device, the raised portion is in contact with the lower surface of the region where the plurality of LED elements are mounted on the module substrate. 
     Preferably, in the lighting device, a thermally conductive resin layer is interposed between the lower surface of the module substrate and the raised portion. 
     Preferably, in the lighting device, the insulating sheet is thicker than the raised portion, and the insulating sheet is formed in the shape of a box. 
     Preferably, in the lighting device, the module substrate is provided with a dam member enclosing the plurality of LED elements, and the LED elements are covered with a fluorescent resin. 
     Preferably, in the lighting device, a portion of a lighting circuit is mounted on the module substrate in a region outside the dam member, and the lighting circuit is covered with the fluorescent resin. 
     Preferably, in the lighting device, a portion of the dam member is used as a portion of a dam member enclosing the portion of the lighting circuit. 
     Preferably, in the lighting device, the module substrate is provided with a dam member enclosing the plurality of LED elements, and the plurality of LED elements are covered with a fluorescent resin. 
     Preferably, in the lighting device, the plurality of LED elements are packaged by being covered with a resin. 
     Preferably, in the lighting device, a portion of a lighting circuit for the plurality of LED elements is mounted on the module substrate. 
     Preferably, in the lighting device, the portion of the lighting circuit includes a diode bridge circuit, a bypass circuit, and an LED array formed by connecting the plurality of LED elements in series, wherein the diode bridge circuit is provided with a terminal for connecting to a utility AC power supply, the bypass circuit is provided with a first current input terminal, a second current input terminal, and a current output terminal, and the LED array is constructed from a plurality of sub-LED arrays, and wherein the first current input terminal of the bypass circuit is connected to a connection node between the sub-LED arrays, and a current input to the first current input terminal is controlled on and off according to a current input to the second current input terminal. 
     Preferably, in the lighting device, the bypass circuit includes a depletion-mode FET, wherein a drain of the FET is connected to the first current input terminal, and a source of the FET is connected to the second current input terminal. 
     Preferably, in the lighting device, the module substrate is formed from a ceramic as a base material. 
     Preferably, in the lighting device, the ceramic is white in color. 
     Preferably, the lighting device further comprises a holder, provided with a spring contact, for fixedly holding the module substrate in position, wherein the spring contact presses a power supply terminal on the module substrate and provides an electrical connection between the power supply terminal and external circuitry. 
     In the above lighting device, the module substrate is placed on the heat-sink member by interposing the insulating sheet therebetween. However, the insulating sheet is formed with an opening only in a region directly below the mounting region of the LED elements that generate heat, and the module substrate directly contacts the heat-sink member through this opening. That is, since the region directly below the terminal for receiving the power supply and the peripheral region of the module substrate are protected with the insulating sheet interposed between the module substrate and the heat-sink member, a high dielectric strength can be maintained. On the other hand, an efficient heat sink path can be secured because the module substrate directly contacts the heat-sink member in and near the mounting region of the LED elements. Accordingly, in the above lighting device, because of the use of the insulating sheet, sufficiently high dielectric strength can be provided while retaining the required heat-sink property even when the module substrate is reduced in size. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantageous of the present lighting apparatus will be apparent from the ensuing description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1(   a ) is a plan view of a module substrate  20 , and  FIG. 1(   b ) is a front view of the module substrate  20 . 
         FIG. 2(   a ) is a plan view of an insulating sheet  26 , and  FIG. 2(   b ) is a front view of the insulating sheet  26 . 
         FIG. 3(   a ) is a plan view showing a portion of a heat-sink member  28 , and  FIG. 3(   b ) is a front view showing the same portion of the heat-sink member  28 . 
         FIG. 4  is a diagram illustrating how the module substrate  20 , insulating sheet  26 , and heat-sink member  28  shown in  FIGS. 1 to 3  are assembled together. 
         FIG. 5  is a cross-sectional view of a light source section  100  of a lighting device. 
         FIG. 6  is a circuit diagram showing one example of a lighting circuit  300  accommodated on the module substrate  20 . 
         FIG. 7(   a ) is a cross-sectional view of a packaged LED (LED element)  70  having a strong light distribution in the upward direction, and  FIG. 7(   b ) is a cross-sectional view of a packaged LED (LED element)  71  having a light distribution in the sideways directions as well. 
         FIG. 8  is a cross-sectional view of an alternative light source section  110  of the lighting device. 
         FIG. 9  is a perspective view of a lighting device  90 . 
         FIG. 10  is a cross-sectional view taken along AA′ in  FIG. 9 . 
         FIG. 11  is a plan view showing the surface of a light-emitting module  1  disclosed in the Japanese Unexamined Patent Publication No. 2009-218204. 
         FIG. 12  is a schematic diagram of a lighting device  10  constructed using the light-emitting module  1  disclosed in the Japanese Unexamined Patent Publication No. 2009-218204. 
     
    
    
     DESCRIPTION 
     A lighting device will be described below with reference to the drawings. It will, however, be noted that the technical scope of the present invention is not limited to the specific embodiment described herein but extends to the inventions described in the appended claims and their equivalents. Further, throughout the drawings, the same or corresponding component elements are designated by the same reference numerals, and the description of such component elements, once given, will not be repeated thereafter. 
       FIG. 1(   a ) is a plan view of a module substrate  20 , and  FIG. 1(   b ) is a front view of the module substrate  20 . 
     As shown in  FIG. 1 , a circular dam member  24  is provided in the center of the upper surface of the module substrate  20 , and a rectangular dam member  23  connecting to the dam member  24  is provided outside the dam member  24 . The region enclosed by the dam member  24 , and the region enclosed by the dam member  23  and a portion of the dam member  24 , are both filled with a fluorescent resin  25 . A terminal wiring line  22  which passes under the dam member  23  extends in the left and right directions and is connected at each end to a power supply terminal  21 . As will be described later (see  FIG. 5 ), LED dies  51  are mounted in the region enclosed by the dam member  24 , while electronic components  52  are mounted in the region enclosed by the dam member  23  and a portion of the dam member  24 . In the lighting circuit  300  to be described later (see  FIG. 6 ), the electronic components  52  correspond to the electronic components other than the LED dies  51 , and constitute part of the lighting circuit  300 . In  FIG. 1(   b ), neither the terminal wiring line  22  nor the power supply terminal  21  is shown. 
     The module substrate  20  is a white ceramic whose base material is AlO 2 , and has a thickness of about 300 to 1000 μm. White ceramic is an insulating material having high reflectivity and high thermal conductivity, and is therefore advantageous when it comes to reducing the size of the module substrate  20 . Various kinds of materials can be selected for the module substrate  20  according to the required specifications; for example, use may be made of a material whose base material is aluminum nitride and whose surface is treated to provide a reflective surface, or a material whose base material is aluminum and whose surface is coated with an insulating layer. The dam members  23  and  24  are each formed from a silicone resin, and are 0.7 to 1.0 mm in thickness and 0.5 to 0.8 mm in height. The fluorescent resin  25  is a phosphor-containing silicone resin, and is about 400 to 700 μm in thickness. The terminal wiring line  22  and the power supply terminal  21  are each formed by depositing Ni and Au on top of Cu. 
       FIG. 2(   a ) is a plan view of an insulating sheet  26 , and  FIG. 2(   b ) is a front view of the insulating sheet  26 . 
     As shown in  FIG. 2 , the insulating sheet  26  has a top plan size slightly larger than that of the module substrate  20  shown in  FIG. 1(   a ), and has an opening  27  in the center. The insulating sheet  26  is formed from an insulating resin, for example, a PI (polyimide) or PET (polyethylene terephthalate) resin. When forming the insulating sheet  26  from a PI resin, it is preferable to form it with a thickness of about 0.1 mm in order to secure a dielectric strength of 4 kV. 
       FIG. 3(   a ) is a plan view showing a portion of a heat-sink member  28 , and  FIG. 3(   b ) is a front view showing the same portion of the heat-sink member  28 . 
     As shown in  FIG. 3 , the heat-sink member  28  has a raised portion  29  on a flat upper surface. The heat-sink member  28  is formed from a thermally conductive material such as die-cast aluminum or a resin having high thermal conductivity. When forming the heat-sink member  28  from a resin, a suitable electrical insulation must be provided because the resin is made electrically conductive by mixing a carbon material in order to enhance thermal conductivity. It goes without saying that a suitable electrical insulation must also be provided when forming the heat-sink member  28  from die-cast aluminum. 
       FIG. 4  is a diagram illustrating how the module substrate  20 , insulating sheet  26 , and heat-sink member  28  shown in  FIGS. 1 to 3  are assembled together. 
     The light source section of the lighting device is constructed by stacking the insulating sheet  26  and the module substrate  20  one on top of the other on the heat-sink member  28 . At this time, the raised portion  29  of the heat-sink member  28  is fitted into the opening  27  of the insulating sheet  26 . In  FIG. 4 , the heat-sink member  28  is hatched differently from that shown in  FIG. 3  in order to make the raised portion  29  easily distinguishable. 
       FIG. 5  is a cross-sectional view of the light source section  100  of the lighting device. 
       FIG. 5  shows a cross section of the light source section  100  of the lighting device fabricated by assembling together the module substrate  20 , insulating sheet  26 , and heat-sink member  28  shown in  FIG. 4 . The upper surface of the raised portion  29  of the heat-sink member  28  is covered with a thermally conductive silicone resin layer  55  via which the upper surface of the raised portion  29  and the lower surface of the module substrate  20  are connected together. The thermally conductive resin layer  55  serves to improve adhesion between the heat-sink member  28  and the module substrate  20  and to achieve smooth thermal conduction. The module substrate  20  is held fixedly to the heat-sink member  28  by a holder  54 . The raised portion  29  may be made to directly contact the lower surface of the module substrate  20  without interposing the thermally conductive resin layer  55 . That is, it is important that the raised portion  29  and the module substrate  20  be located in close proximity to each other to ensure good thermal conduction. 
     The LED dies (LED elements)  51  are mounted on the module substrate  20  by die bonding, and the connection between each LED die  51  is made by a wire  53 . The LED die  51  located at each of the left and right ends is connected to a wiring line on the upper surface of the module substrate  20  (not shown in  FIG. 5 ) by a wire  53 . The array of the LED dies  51  is enclosed by the dam member  24  and covered with the fluorescent resin  25 . In the region enclosed by the dam member  24  and the dam member  23 , the electronic components  52  other than the LED dies  51  are mounted by die bonding and covered with the fluorescent resin  25 . The electronic components  52  are connected to an interconnection pattern (not shown) by wires  53 . The power supply feed line connecting to the power supply terminal  21  is not shown. The top plan size of each LED die  51  is, for example, about 500 μm×290 μm. In  FIG. 5 , four LED dies  51  are shown in the cross section, and each electronic component  52  is shown as being connected by one wire; however, this is only illustrative, and various other configurations are also possible. 
     Since the heat-sink member  28  and the module substrate  20  are made to contact with each other via the thermally conductive resin layer  55  in the region directly below the mounting region of the LED dies  51 , as shown in  FIG. 5 , the light source section  100  of the lighting device achieves high heat-sink efficiency. 
     Further, the presence of the insulating sheet  26  directly below the power supply terminal  21  serves to provide high dielectric strength. 
       FIG. 6  is a circuit diagram showing one example of the lighting circuit  300  accommodated on the module substrate  20 . 
     The lighting circuit  300  comprises a diode bridge circuit  305 , a sub-LED array  310 , a sub-LED array  330 , a bypass circuit  320 , and a current limiting circuit  340 . In  FIG. 6 , the lighting circuit  300  is shown as being connected to a utility AC power supply  306  and a fuse  307 . That is, the lighting circuit  300  can be connected to the utility AC power supply  306  by just adding a protective device such as the fuse  307 . Further, since the number of LED elements operated to emit light varies according to the applied AC voltage, as will be described later, the lighting circuit  300  has the feature that the non-emission period is short, making flicker less noticeable and reducing high-frequency noise. Furthermore, since the number of electronic components other than the LED elements is small, the configuration of the lighting circuit  300  lends itself to reducing the size of the module substrate  20  (see  FIGS. 1 and 5 ). 
     The diode bridge circuit  305  is constructed from four diodes  301 ,  302 ,  303 , and  304 , and has a full-wave rectified waveform output terminal A, a reference voltage application terminal B, and power supply terminals C and D. The power supply terminals C and D each correspond to the power supply terminal  21  in  FIG. 1 . The utility AC power supply  306  is connected to the terminal D and also to the terminal C via the fuse  307 . 
     The LED array contained in the lighting circuit  300  is formed by connecting the sub-LED arrays  310  and  330  in series. Within the sub-LED array  310 , a large number of LED dies  51  (see  FIG. 5 ) including LED dies  310   a  and  310   b  are connected in series. Likewise, within the sub-LED array  330  also, a large number of LED dies  51  (see  FIG. 5 ) including LED dies  330   a  and  330   b  are connected in series. The anode of the sub-LED array  310  is connected to the terminal A of the diode bridge circuit  305 , and the cathode of the sub-LED array  310  is connected to the anode of the sub-LED array  330 . The connection node between the sub-LED arrays  310  and  330  is connected to a current input terminal (first current input terminal)  321  of the bypass circuit  320 . The cathode of the sub-LED array  330  is connected to a current input terminal  341  of the current limiting circuit  340 . 
     The bypass circuit  320  includes, in addition to the current input terminal (first current input terminal)  321 , a current input terminal (second current input terminal)  322  and a current output terminal  323 . The current input terminal  322  is connected to a current output terminal  343  of the current limiting circuit  340 , and the current output terminal  323  is connected to the terminal B of the diode bridge circuit  305 . The bypass circuit  320  comprises a depletion-mode FET  324  and a resistor  325 ; the drain of the FET  324  is connected to the current input terminal  321 , and the source of the FET  324  and one end of the resistor  325  are connected to the current input terminal  322 , while the gate of the FET  324  and the other end of the resistor  325  are connected to the current output terminal  323 . In the bypass circuit  320 , the current flowing into the circuit from the current input terminal  321  is limited by the current flowing into the circuit from the current input terminal  322 . 
     The current limiting circuit  340  has a circuit configuration substantially identical to that of the bypass circuit  320 , the only difference being the absence of a terminal corresponding to the current input terminal  322  of the bypass circuit  320 . An FET  344  and a resistor  345  are connected in the same manner as in the bypass circuit  320 . The resistor  345  is smaller in value than the resistor  325 , and the ratio of the resistance value of the resistor  345  to that of the resistor  325  is chosen to be 1:2. 
     The method of operation of the lighting circuit  300  will be described below. 
     The voltage of the full-wave rectified waveform begins to rise from 0 V, and when the voltage exceeds the threshold value of the sub-LED array  310 , current flows through the sub-LED array  310  into the bypass circuit  320 , and the sub-LED array  310  lights. At this time, feedback is applied through the resistor  325  to the source of the FET  324 , and the bypass circuit  320  thus operates in a constant current mode. Since the forward voltage drop of each LED die ( 310   a , etc.) is about 3 V, if the number of LED dies ( 310   a , etc.) connected in series in the sub-LED array  310  is, for example, 20, the threshold value of the sub-LED array  310  is about 60 V. Similarly, if the number of LED dies ( 330   a , etc.) connected in series in the sub-LED array  330  is, for example, 20, the threshold value of the sub-LED array  330  is about 60 V. Therefore, when the sub-LED arrays  310  and  330  are each formed by connecting 20 LED dies in series, the lighting circuit  300  can efficiently operate with the utility AC power supply  306  whose root-mean-square value is 100 V. 
     When the voltage of the full-wave rectified waveform further rises and exceeds the sum of the threshold values of the sub-LED arrays  310  and  330 , current also begins to flow through the sub-LED array  330  into the current limiting circuit  340 . When the current at the current input terminal  322  exceeds a predetermined value, the source voltage of the FET  324  increases, increasing the source-gate voltage, and the FET  324  turns off. At this time, feedback is applied through the resistor  345  to the FET  344 , and the current limiting circuit  340  thus operates in a constant current mode. Accordingly, the sub-LED array  330  as well as the sub-LED array  310  lights. The process that takes place during the period that the voltage of the full-wave rectified waveform drops is the reverse of the process that takes place during the period that the voltage of the full-wave rectified waveform rises. 
     Since the connection configuration of the lighting circuit  300  is symmetrical and simple, the diodes  301  and  302  and the bypass circuit  320  are mounted, for example, in the electronic component mounting region to the right of the dam member  24  (the region enclosed by the dam members  23  and  24 ) in  FIG. 1 . On the other hand, the diodes  303  and  304  and the current limiting circuit  340  are mounted in the electronic component mounting region to the left of the dam member  24  (the region enclosed by the dam members  23  and  24 ). By thus mounting the electronic components, the LED dies  51  (see  FIG. 5 ) and the other electronic components  52  (see  FIG. 5 ) can be connected to the power supply terminals  21  (see  FIG. 5 ) by providing wiring only on the upper surface of the module substrate (see  FIGS. 1 and 5 ). On the other hand, if all of the diodes  301  to  304  are to be mounted in one or the other of the electronic component mounting regions, wire  53  (see  FIG. 5 ) has to be routed so as to run over the wiring on the module substrate  20  only at one place. 
     While the lighting circuit  300  has been shown in  FIG. 6  as including two sub-LED arrays  310  and  330 , the lighting circuit  300  may be expanded to include three or more sub-LED arrays to construct the LED array. In that case, a bypass circuit is provided for each connection node between one sub-LED array and the next, and the connection node is connected to the first current input terminal of the bypass circuit. Further, the current output terminal of the bypass circuit located on the downstream side as viewed from the diode bridge circuit (if there is no downstream bypass circuit, then the current output terminal of the current limiting circuit) is connected (in cascade) with the second current input terminal of the upstream bypass circuit. 
     In the lighting circuit  300  of  FIG. 6 , the bypass circuit  320  has been shown as comprising the depletion-mode FET  324  and the resistor  325 . However, the bypass circuit  320  may be constructed using two resistors in combination with an enhancement-mode FET and an NPN bipolar transistor. In that case, one resistor and the drain of the FET are connected to the current input terminal (first current input terminal), and the other end of the resistor is connected to the gate of the FET and the collector of the transistor. Then, the other resistor, the source of the FET, and the base of the transistor are connected to the second current input terminal. Further, the other end of that other resistor and the emitter of the transistor are connected to the current output terminal. In the bypass circuit thus constructed, the current input to the first current input terminal is limited by the current input to the second current input terminal. This bypass circuit can be constructed as a current limiting circuit by allowing the second current input terminal to float. 
     In the light source section  100  of the lighting device shown in  FIG. 5 , the LED dies  51  and the electronic components  52  are mounted on the module substrate  20  by die bonding and connected by wires  53 . However, each LED element need not be limited to a bare chip LED die, but may be provided in the form of a packaged LED element (hereinafter called the packaged LED) constructed by covering an LED die with a resin or the like. Further, the mounting method of the electronic components need not be limited to die bonding and wiring, but a surface mounting method using solder joining may be employed. An alternative light source section  110  which uses packaged LEDs and in which the electronic components are mounted by soldering will be described below. 
       FIG. 7(   a ) is a cross-sectional view of a packaged LED (LED element)  70  having a strong light distribution in the upward direction, and  FIG. 7(   b ) is a cross-sectional view of a packaged LED (LED element)  71  having a light distribution in the sideways directions as well. 
     In  FIG. 7(   a ), the LED die includes a sapphire substrate  73 , a semiconductor layer  74 , and electrode bumps  75 ; here, the semiconductor layer  74  is formed on the lower surface of the sapphire substrate  73 , and the two electrode bumps  75  are attached to the semiconductor layer  74 . The side faces of the LED die and the bottom face thereof excluding the portions where the electrode bumps are formed are coated with a reflective member  76 , and the top face of the LED die is coated with a fluorescent sheet  72 . The reflective member  76  is formed by kneading fine reflective particles such as titanium oxide into a silicone resin, and is applied to a thickness of about 100 μm on the side faces. The reflective member  76  on the bottom face is provided to protect the bottom face of the LED die, and is about 10 μm in thickness. The fluorescent sheet  72  is formed by kneading fluorescent particles into a silicone resin and has a thickness of about 100 μm. The packaged LED  70  is a chip-size package (called a CSP) about the same size as the LED die. 
     In  FIG. 7(   b ), the LED die is the same as that used in  FIG. 7(   a ). The top and side faces of the LED die and the bottom face thereof excluding the portions where the electrode bumps are formed are coated with a fluorescent member  77 . The fluorescent member  77  is formed by kneading fluorescent particles into a silicone resin, and is applied to a thickness of about 100 μm on the top face as well as on the side faces. The fluorescent member  77  on the bottom face is provided to protect the bottom face of the LED die, and is about 10 μm in thickness. The packaged LED  71  also is a chip-size package. While the packaged LED  70  has a strong light distribution in the upward direction because of the presence of the reflective member  76 , the packaged LED  71  has a light distribution in the sideways directions as well because the side faces are also coated with the fluorescent member  77 . 
       FIG. 8  is a cross-sectional view of the alternative light source section  110  of the lighting device. 
     The alternative light source section  110  shown in  FIG. 8 , like the light source section  100  shown in  FIG. 5 , is constructed by stacking the insulating sheet  26  and the module substrate  20  one on top of the other on the heat-sink member  28 , with the raised portion  29  of the heat-sink member  28  fitted into the opening  27  of the insulating sheet  26 . The upper surface of the raised portion  29  of the heat-sink member  28  is covered with the thermally conductive silicone resin layer  55  via which the upper surface of the raised portion  29  and the lower surface of the module substrate  20  are directly connected together. The module substrate  20  is held fixedly to the heat-sink member  28  by the holder  54 . 
     The packaged LEDs (LED elements)  70  and  71  are flip-chip mounted on a predefined interconnection pattern (not shown) on the module substrate  20 . In this case, the packaged LEDs  70  and  71  are each connected to the predefined interconnection pattern (not shown) by solder. The electronic components  81  such as the diodes, resistors, and FETs (see  FIG. 6 ) are also connected to the predefined interconnection pattern (not shown) by solder  82 . Using the packaged LEDs  70  and  71  and the surface-mount electronic components  81  serves to simplify the fabrication process because it eliminates the need for a wire bonder and a dispenser (which were used to form the dam members  23  and  24  (see  FIGS. 1 and 5 ) and to dispense the fluorescent resin  25  (see  FIGS. 1 and 5 )). In the alternative light source section  110 , the light distribution area is enlarged by arranging the packaged LEDs  71  along the periphery of the LED element mounting region and placing the packaged LEDs  70  in the center. 
     In the alternative light source section  110  also, high heat-sink efficiency can be achieved, because the heat-sink member  28  and the module substrate  20  are made to directly contact with each other in the region directly below the mounting area of the packaged LEDs  70  and  71 . The alternative light source section  110  also provides high dielectric strength because of the presence of the insulating sheet  26  directly below the power supply terminals  21 . In the alternative light source section  110 , the circuit diagram of the lighting circuit formed on the module substrate  20  is the same as that shown in  FIG. 6 . 
     In the light source section  100 , the LED dies  51  and the electronic components  52  are mounted on the module substrate  20  (see  FIG. 5 ), while in the alternative light source section  110 , the packaged LEDs  70  and  71  and the electronic components  81  are mounted on the module substrate  20  (see  FIG. 8 ). However, in the light source section, the components other than the LED elements (the LED dies  51  or the packaged LEDs  70  and  71 ) may not be mounted on the module substrate. For example, the light source section may be constructed using a technology known as a COB (Chip On Board) module in which the LED dies mounted in the center of the module substrate are enclosed by a dam member and are entirely covered with a fluorescent resin. Since the COB module generates heat in the center of the module substrate, and a reduction in the size of the module substrate is demanded, the above-described light source structure is effective in satisfying both the heat-sink and dielectric strength requirements. 
     In the light source sections  100  and  110 , the module substrate  20  has been described as being formed from a ceramic. However, since the ceramic, by its nature, easily breaks, the insulating sheet  26  may be made thicker than the raised portion  29  of the heat-sink member  28  by about 50 μm. In this case, the space between the bottom surface of the module substrate  20  and the upper surface of the raised portion  29  is filled with a thermally conductive resin such as silicone. 
     In the light source sections  100  and  110 , the holder  54  may be extended toward the center of the module substrate  20  and may be provided with spring contacts. The spring contacts not only work to press the module substrate  20  fixedly in position, but also serve to electrically connect the power supply terminals on the module substrate  20  to external circuitry. This simplifies the electrical connection configuration, while at the same time, preventing the breakage of the module substrate made of ceramic. 
       FIG. 9  is a perspective view of a lighting device  90 , and  FIG. 10  is a cross-sectional view taken along AA′ in  FIG. 9 . 
     The lighting device  90  is one example of the lighting device using the above-described light source section  100  (see  FIG. 5 ), and includes a diffusing cover  91  for diffusing the light emitted from the light source section  100 , and a heat-sink member  28  provided with many radiating fins  94 . A power feed terminal  92  and two fixing members  93  protrude horizontally from the diffusing cover  91 , as shown in  FIG. 9 . The power feed terminal  92  is used to supply dimmer control power to be described later, as well as power for lighting, to the circuit substrate  96  housed inside the diffusing cover  91 . The fixing members  93  constitute part of the heat-sink member  28 , and are formed integrally with the heat-sink member  28 . The fixing members  93  and the power feed terminal  92  are used to mount the lighting device  90  fixedly to a lighting fixture or to a ceiling or the like. 
     The heat-sink member  28  includes the radiating fins  94  and the raised portion  29 . The edge portion of the insulating sheet  26  provided around the raised portion  29  is bent downward in the figure. More specifically, the insulating sheet  26  is formed by a mold into the shape of a box whose top is provided with an opening in the center thereof and whose bottom is open. The bent portion of the insulating sheet  26  serves to improve the dielectric strength between the module substrate  20  and the heat-sink member  28 . The light source section  100  containing the module substrate  20  and the fluorescent resin  25  (see  FIG. 5 ) is mounted on the raised portion  29 . The light source section  100  is fixed in position by a holder  95 , and the circuit substrate  96  is fixed on the holder  95 . Electronic components (not shown), including a controller for adjusting the brightness of the light source section  100 , are mounted on the circuit substrate  96 . 
     The diffusing cover  91  is fixed to the heat-sink member  28 , and houses the upper part of the heat-sink member  28 , the light source section  100 , the holder  95 , and the circuit substrate  96 . In the figure, the insulating sheet  26 , the holder  95 , and the circuit substrate  96  are each shown as being separated between left and right, but actually each of these components is a single one-piece component. Further, the lighting device  90  incorporating the light source section  100  has been shown in  FIGS. 9 and 10 , but the lighting device  90  may be constructed to incorporate the light source section  110  (see  FIG. 8 ). 
     The preceding description has been presented only to illustrate and describe exemplary embodiments of the present lighting apparatus. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope.