Light-emitting device and lighting device provided with the same

Abstract

A light-emitting device capable of ensuring an electric connection between a light-emitting element and an electrode without generating any problem in practical use, by both connecting methods with a solder and a connector, and a lighting device provided with the light-emitting device are provided. The light-emitting device according to the present invention has a plurality of LED chips, and a soldering electrode land and a connector connecting electrode land electrically connected to the chips, on a ceramic substrate. The soldering electrode land is formed of a first conductive material having a function to prevent diffusion to a solder, and the connector connecting electrode land is formed of a second conductive material having a function to prevent oxidation.

Claims

1. A light-emitting device comprising: a substrate; a light-emitting part formed on the substrate; a sealing body to cover the light-emitting part; a first wiring pattern formed on the substrate, the first wiring pattern being used for an anode-side connection; and a second wiring pattern formed on the substrate, the second wiring pattern being used for a cathode-side connection, wherein the light-emitting part includes a plurality of LED chips arranged in at least two LED rows including a first row and a second row, the number of the LED chips in the first row being smaller than that in the second row, a plurality of series circuits, each of which is composed of the same number of the LED chips connected in series as the others, are formed, each of the series circuits having one end connected to the first wiring pattern and the other end connected to the second wiring pattern, and at least one of the series circuits has a portion where an electric connection is made between one of the LED chips in the first row and one of the LED chips in a row adjacent to the first row.

2. The light-emitting device of claim 1, wherein the first wiring pattern and the second wiring pattern are formed in a periphery of the light-emitting part on the substrate, respectively, the first wiring pattern electrically connects to a land being used for an anode-side external electric connection, and the second wiring pattern electrically connects to another land being used for a cathode-side external electric connection.

3. The light-emitting device of claim 1, wherein the first wiring pattern and the second wiring pattern are arranged so as to be opposed to each other on the substrate.

4. The light-emitting device of claim 1, further comprising a resin dam formed so as to surround the light-emitting part, wherein the sealing body is filled inside the resin dam.

5. The light-emitting device of claim 4, wherein the resin dam has a circular ring shape.

6. The light-emitting device of claim 5, wherein the first wiring pattern and the second wiring pattern have respective arc shapes each constituting a part of the circular ring.

7. The light-emitting device of claim 4, further comprising at least one first wire and at least one second wire, wherein one end of each of the series circuits and the first wiring pattern are connected through the first wire, the other end of each of the series circuits and the second wiring pattern are connected through the second wire, and the resin dam is formed so as to cover a part of the first wire, a part of the second wire, the first wiring pattern, and the second wiring pattern.

8. The light-emitting device of claim 4, further comprising a protection element arranged under the resin dam.

9. The light-emitting device of claim 1, wherein the sealing body is composed of a phosphor containing resin.

10. The light-emitting device of claim 1, wherein an outline of a plurality of the LED rows constituting the light-emitting part is substantially similar in shape as an outline of the sealing body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A and 1B are schematic structure diagrams showing one example of alight-emitting device according to the present invention;

(2) FIGS. 2A and 2B are schematic structure diagrams showing a stage before the light-emitting device according to the present invention is completed;

(3) FIGS. 3A and 3B are schematic structure diagrams showing a connector jig, and a state in which the connector jig and the light-emitting device are overlapped, respectively.

(4) FIG. 4 is a schematic structure diagram showing a state fixed to a case under the condition that the connector jig and the light-emitting device are overlapped;

(5) FIG. 5 is an outline view of a lighting device mounting the light-emitting device;

(6) FIGS. 6A and 6B are views to explain a method for ensuring electric connection between a connector connecting electrode land and the connector jig;

(7) FIG. 7 is a schematic structure diagram showing a state in which the light-emitting device externally connected with a solder is fixed to the case;

(8) FIGS. 8A and 8B are schematic structure diagrams showing another example of the light-emitting device according to the present invention;

(9) FIGS. 9A and 9B are schematic structure diagrams showing another example of the light-emitting device according to the present invention;

(10) FIGS. 10A and 10B are schematic structure diagrams showing a state in which the connector jig and the light-emitting device are overlapped;

(11) FIGS. 11A and 11B are schematic structure diagrams showing another state in which the connector jig and the light-emitting device are overlapped; and

(12) FIG. 12 is a schematic structure diagram of a conventional lighting device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(13) FIGS. 1A and 1B are schematic structure diagrams showing one example of alight-emitting device of this embodiment. As shown in FIGS. 1A and 1B, a light-emitting device 1 according to this embodiment includes a ceramic substrate 3, wiring patterns 7 (7a and 7k), a phosphor containing resin layer 9, LED chips 11, a wire 13, a printing resistive element 15, soldering electrode lands 17 (17a and 17k), connector connecting electrode lands 19 (19a and 19k), a resin dam 21, and positioning openings 25. In addition, FIG. 1A is a top view and FIG. 1B is a cross-sectional view. In FIG. 1A, an inner side is transparently shown in order to make a connection relationship clear.

(14) In addition, FIGS. 2A and 2B are schematic views showing a state prior to the state shown in FIG. 1A. FIG. 2A is a view showing a schematic structure before the LED chips 11 are mounted and FIG. 2B is a view showing a schematic structure after the LED chips 11 are mounted and before the phosphor containing resin layer 9 and the resin dam 21 are formed.

(15) The wiring pattern 7a, and the electrode lands 17a and 19a are all electrically connected to an anode terminal, and the wiring pattern 7k, and the electrode lands 17k and 19k are all electrically connected to a cathode terminal.

(16) The ceramic substrate 3 is formed into a rectangular shape. For example, its outline is 24 mm20 mm, and its thickness is 1 mm.

(17) Thus, the electrode lands 17a and 19a connected to the anode, and the electrode lands 17k and 19k connected to the cathode are arranged at diagonally opposed corner parts of the ceramic substrate 3, respectively.

(18) The soldering electrode lands 17a and 17k are used when an external connection (for the purpose of power supply) with the wiring pattern 7 is made with a solder. Each of them is formed of AgPt by a screen printing method. An example of its thickness is 20 m.

(19) The AgPt layer is preferably formed on an uppermost layer of each of the soldering electrode lands 17a and 17k, but another metal layer may be thinly formed on the surface of the AgPt layer because it is only necessary to prevent a diffusion reaction to the solder in the AgPt layer. In addition, a metal layer having small specific resistance may be formed under the AgPt layer.

(20) The connector connecting electrode lands 19a and 19k are used when an external connection (for the purpose of power supply) with the wiring pattern 7 is made with a connector. Each of them is formed of Au by a screen printing method. An example of its thickness is 3 m.

(21) Here, the material Au used for the connector connecting electrode lands 19a and 19k has a feature that prevents an oxide film from being formed on a surface. Thus, the external electric connection can be easily ensured through a connector contact.

(22) In addition, the Au layer is preferably formed on an uppermost surface of each of the connector connecting electrode lands 19a and 19k to be easily connected at the time of the connector contact, but a hard metal layer (such as Ti or W) having small specific resistance may be thinly formed to prevent a damage at the time of the connector contact. In addition, instead of the Au layer, a hard metal which is hardly oxidized and has small specific resistance may be used.

(23) The wiring patterns 7a and 7k are formed on the ceramic substrate 3 so as to be opposed to each other. Each of them has an arc shape which is partially cut out from a circular ring when viewed from the top of the light-emitting device 1. In addition, the soldering electrode land 17a is connected to one end of the wiring pattern 7a through a leading line, and the soldering electrode land 17k is connected to one end of the wiring pattern 7k through a leading line. The connector connecting electrode land 19a is electrically connected to the soldering electrode land 17a through a leading line or a contact electrode, and the connector connecting electrode land 19k is also electrically connected to the soldering electrode land 17k in a similar way.

(24) The printing resistive element 15 is provided in order to enhance an electrostatic withstand voltage, and composed of RhO.sub.2 having a resistance value of 50, in which its width is 200 m and its width is 6 m. As shown in FIGS. 1A to 2B, the printing resistive element 15 is arranged so as to connect one end of the wiring pattern 7a and one end of the wiring pattern 7k, and has an arc shape partially cut out from a circular ring. According to this embodiment, each of the wiring pattern 7a, the printing resistive element 15, and the wiring pattern 7k constitutes a part of an outer periphery of the same circular ring.

(25) The plurality of LED chips 11 are mounted on the ceramic substrate 3. According to this embodiment, 12 series circuits each composed of 12 LED chips 11 are arranged as parallel lines.

(26) In addition, the LED chips 11 are linearly arranged so as to be roughly parallel to one side of the substrate. Thus, the number of the chips in the line is greatest in the vicinity of the center of the circular ring shape composed of the wiring patterns 7 and the printing resistive element 15, and the number of the chips is reduced toward the periphery of the substrate from the center, so that the LED chips can be densely arranged in an area surrounded by the wiring patterns 7.

(27) When the LED chips 11 are arranged as described above, the outline of the arranged LED chips 11 becomes the same (or similar) shape as the outline of the phosphor containing resin layer 9 (sealing body) when viewed from the top of the light-emitting device 1. According to this embodiment, as shown in FIGS. 1A and 1B, the shape of the sealing body has a circular shape when viewed from the top, and the outline of the arranged LED chips 11 also has a circular shape. This configuration can solve the problem that a light-emitting pattern cannot have the same shape as that of the sealing body due to a shadow caused because a light source is not arranged in the vicinity of the sealing body.

(28) Basically, the adjacent LED chips 11 are directly connected by the wire 13 in the one LED chip line. However, in the vicinity of the periphery of the substrate in which the number of the chips in the same line is smaller, the LED chip is electrically connected to the LED chip in the adjacent line so that the number of the LED chips 11 is to be the same in each series circuit. The LED chip 11 arranged in the vicinity of the wiring pattern 7 is directly and electrically connected to the wiring pattern 7 through the wire.

(29) The resin dam 21 is provided to dam the sealed resin and composed of a colored material (preferably white or milky white). According to this embodiment, the resin dam 21 is composed of a white silicon resin (containing TiO.sub.2 as a filler) and formed into a circular ring shape having a width of 1 mm and a diameter of 9 mm. It is formed such that after the resin is applied, it is subjected to a curing treatment at 150 C. for 60 minutes. As shown in FIG. 1A, the resin dam 21 is preferably formed so as to cover the wiring patterns 7, the printing resistive element 15, and a part of the wire 13.

(30) The phosphor containing resin layer 9 is formed to convert the light (such as blue light) emitted from the LED chip to white light. According to this embodiment, a material containing a green phosphor (such as Ca.sub.3(Sr.Mg).sub.2Si.sub.3O.sub.12:Ce) and a red phosphor (such as (Sr.Ca)AlSiN.sub.3:Eu) is injected into the inner side of the resin dam 21 formed into the ring shape, and thermally cured at 150 C. for 5 hours, whereby the phosphor containing resin layer 9 is formed.

(31) According to this embodiment, as shown in FIG. 1A, the two positioning openings 25 are formed at the diagonally opposed corners of the ceramic substrate 3. This opening 25 is used when a connector jig which will be described below is screwed on the light-emitting device 1.

(32) FIGS. 3A and 3B are schematic structure diagrams showing the connector jig, and a state after the connector jig and the light-emitting device 1 are overlapped. FIG. 3A shows the connector jig, and FIG. 3B shows the state after the connector jig and the light-emitting device 1 are overlapped.

(33) A connector jig 31 is provided to electrically connect the connector connecting electrode lands 19 (19a and 19k) formed on the ceramic substrate 3 to an external line, and composed of a resin plate 30 having almost the same size as that of the ceramic substrate 3. A positioning opening 33, a connector terminal opening 35, and a light-emitting surface opening 39 are formed in the resin plate 30. A slanted part 37 is formed on an outer peripheral side surface of the light-emitting surface opening 39 and serves as a reflection member. The resin plate 30 is made of a resin such as PBT (polybutylene terephthalate) resin or a PC (polycarbonate) resin. According to this embodiment, the resin plate 30 is composed of a milky white or white PBT resin having a high reflection rate with respect to light emitted from the light-emitting part.

(34) As shown in FIG. 3A, the positioning openings 33 are provided at one of two pairs of diagonally opposed corners of the connector jig 31, and the connector terminal openings 35 are provided at the other of the two pairs of diagonally opposed corners thereof. The connector terminal opening 35 is configured so that the connector can be inserted from a side surface to the inner side of the resin plate 30.

(35) As shown in FIG. 3B, after the light-emitting device 1 and the connector jig 31 are overlapped, the opening 25 provided in the ceramic substrate 3 of the light-emitting device 1 is overlapped with the positioning opening 33 provided in the connector jig 31. In addition, the light-emitting surface containing the LED chips 11 and the phosphor containing resin layer 9 is exposed in the light-emitting surface opening 39. In addition, each of the connector connecting electrode lands 19a and 19k provided in the light-emitting device 1 is partially opposed to the connector terminal opening 35 provided in the connector jig 31 in a vertical direction. In FIG. 3B, in order to clearly understand that the connector connecting electrode lands 19a and 19k exist under the connector terminal opening 35, the resin plate 30 positioned just above them is transparently shown.

(36) Thus, the connector jig 31 is set and a connector 46 is fit in the connector terminal opening 35, whereby, as shown in FIG. 4, a lead (lead in the connector) 41 attached to the connector is electrically connected to the connector connecting electrode lands 19a and 19k. Thus, a screw 43 (such as M5 screw) is fit in so as to penetrate the openings 25 and 33 and fixed to a case 51. Then, a lens dome 55 is fit in, whereby a LED lighting device 50 is completed (refer to FIG. 5). In addition, in FIG. 5, reference 53 represents a cap and may be integrally provided with the case 51.

(37) FIG. 6 is a conceptual view to explain a method to ensure the electric connection between the connector connecting electrode land 19 and the connector jig 31 when the resin plate 30 of the connector jig 31 and the ceramic substrate 3 of the light-emitting device 1 are to be overlapped. In FIG. 6, reference 45 represents a lead attached to the jig.

(38) As described above, when the light-emitting device 1 and the connector jig 31 are overlapped such that the opening 25 provided in the ceramic substrate 3 and the positioning opening 33 provided in the resin plate 30 are overlapped, the connector terminal opening 35 provided in the connector jig 31 is opposed to the connector connecting electrode land 19 in the vertical direction. The lead 45 attached to the jig is provided in the connector jig 31 to electrically connect the lead 41 in the connector to the connector connecting electrode land 19.

(39) The lead 45 attached to the jig is formed of a conductive material wound into the form of a spring. The spring shape is provided to increase a contact area between the lead 45 and the connector connecting electrode land 19 to disperse force applied at the time of contact to prevent an edge of the lead 45 attached to the jig from sharply coming in contact with the surface of the connector connecting electrode land 19 and damaging the surface after the connector jig 31 and the light-emitting device 1 are overlapped. As described above, when fixed to the case 51, the screw 43 is fit in the opening 25 and 33 so as to penetrate them, so that the lead 45 and the connector connecting electrode land 19 are surely connected electrically.

(40) In addition, as shown in FIG. 6B, it is preferable that a click 48 is previously formed in the connector terminal opening 35 to prevent the connector 46 inserted in the connector terminal opening 35 from escaping.

(41) In addition, when the light-emitting device 1 of this embodiment is externally connected with soldering, as shown in FIG. 7, the soldering electrode land 17 (17a and 17k) is soldered, whereby an external lead 42 can be electrically connected to the soldering electrode land 17 through a solder 47. Thus, the ceramic substrate 3 is fixed to the case 51 by a press part 49. According to the light-emitting device 1 of this embodiment, although both of the soldering electrode land 17 and the connector connecting electrode land 19 are provided, since each of them is arranged in the vicinity of the corner of the ceramic substrate 3, a space for providing the press part 49 can be sufficiently provided in the periphery of the substrate 3.

(42) Thus, the whole is fixed by a screw 44 with the ceramic substrate 3 and the case 51 fixed to each other by the press part 49. After that, similar to the case of the connector connection, the lens dome 55 is fit in, whereby the LED lighting device 50 is formed (refer to FIG. 5).

(43) According to the configuration of this embodiment, since each of the soldering electrode land 17 (17a and 17k) and the connector connecting electrode land 19 (19a and 19k) is previously provided on the ceramic substrate 3, either one of the methods of soldering and connector connecting can be employed according to a usage mode of a user when the wiring pattern 7 is electrically connected to the outside. In addition, in the case where the external connection is provided with soldering, the conventional problem that Au is diffused in the solder and forms an intermetallic compound so that the electric connection cannot to be ensured is not caused because the soldering electrode land 17 is not formed of Au. In addition, the LED chips can be densely arranged in the light-emitting device having the circular shape viewed from the top, which contributes to miniaturization of the lighting device having high luminance of 25 W.

(44) Furthermore, in the case where the light-emitting device 1 according to this embodiment is externally connected through the connector, the connector jig having almost the same size as that of the ceramic substrate 3 having the LED chips 11 is overlapped. At this time, since the connector jig 31 has the openings (33, 35, and 39) corresponding to the structure of the ceramic substrate 3, positioning is automatically made when it is overlapped. Thus, the light-emitting part (LED chips 11) of the light-emitting device 1 can be positioned. In addition, since the connector jig 31 is composed of the resin plate 30, the ceramic substrate 3 having the LED chips 11 can be protected.

(45) [Variation]

(46) The arrangement positions of the soldering electrode land 17 and the connector connecting electrode land 19 are not limited to those shown in FIG. 1A. Hereinafter, a variation will be described with reference to FIGS. 8A to 9B.

(47) According to a variation shown in FIG. 8A, the light-emitting device 1 is provided such that the wiring pattern 7a is electrically connected to the connector connecting electrode land 19a through a leading line connected to a region around the center of the wiring pattern 7a, and the wiring pattern 7a is electrically connected to the soldering electrode land 17a through a leading line extending from the connector connecting electrode land 19a. This is applied to the connector connecting electrode land 19k and the soldering electrode land 17k.

(48) When the wiring pattern 7 is externally connected through the connector terminal, in the light-emitting device 1 shown in FIG. 8A, the connector jig 31 shown in FIG. 8B is overlapped with the ceramic substrate 3. The connector jig 31 shown in FIG. 8B is provided such that the connector terminal openings 35 are arranged almost in the center of opposed one pair of sides, in a peripheral part of the resin plate 30, and the connector jig 31 is overlapped with the ceramic substrate 3, whereby each of the connector connecting electrode lands 19 (19a and 19k) is partially exposed in each of the connector terminal openings 35. The positioning opening 33 and the light-emitting surface opening 39 are formed similarly to the above embodiment.

(49) Thus, the external connection can be made through the connector by the same method as shown in FIG. 4, and the external connection can be made through the solder by the same method as shown in FIG. 7.

(50) In addition, according to a variation shown in FIG. 9A, the light-emitting device 1 is provided such that the connector connecting electrode lands 19a and 19k are arranged at one diagonally opposed pair of corners of the ceramic substrate 3, and the soldering electrode lands 17a and 17k are arranged at the other diagonally opposed pair of corners of the ceramic substrate 3. That is, the connector connecting electrode lands 19a and 19k, and the soldering electrode lands 17a and 17k are formed at the four corners of the ceramic substrate 3, respectively. In addition, the opening 25 is provided almost in the center of the opposed one pair of sides, in a peripheral part of the ceramic substrate 3.

(51) Thus, the connector connecting electrode land 19a is electrically connected to one terminal of the wiring pattern 7a through a leading line, and the soldering electrode land 17a is electrically connected to the other terminal of the wiring pattern 7a through a leading line. Similarly, the connector connecting electrode land 19k is electrically connected to one terminal of the wiring pattern 7k through a leading line, and the soldering electrode land 17k is electrically connected to the other terminal of the wiring pattern 7k through an leading line.

(52) When the wiring pattern 7 is externally connected through a connector terminal, in the light-emitting device 1 shown in FIG. 9A, the connector jig 31 shown in FIG. 9B is overlapped with the ceramic substrate 3. The connector jig 31 shown in FIG. 9B is provided such that the connector positioning openings 33 are arranged almost in the center of opposed one pair of sides, in a peripheral part of the resin plate 30, and the connector jig 31 is overlapped with the ceramic substrate 3, whereby the positioning openings 33 are overlapped with the openings 25, respectively. In addition, the connector terminal openings 35 are provided at one diagonally opposed pair of corners, and when the connector jig 31 is overlapped with the ceramic substrate 3, the connector connecting electrode land 19 is partially exposed in the connector terminal opening 35.

(53) Thus, the external connection can be made through the connector by the same method as shown in FIG. 4, and the external connection can be made through the solder by the same method as shown in FIG. 7.

(54) FIGS. 10A and 10B are additional schematic structure diagrams showing the state in which the connector jig 31 and the light-emitting device 1 are overlapped, in the configuration shown in FIGS. 9A and 9B. FIG. 10A is a view showing a state when viewed from the top without a part of the light-emitting device being transparently shown, and FIG. 10B is a view showing a cross-sectional state cut by a line connecting the two opposed openings 25 (33). As described above, the LED chips 11 are formed under the resin layer 9, and the lead 45 attached to the jig and the connector connecting electrode land 19 are formed under the connector connecting opening 35 although not shown in the drawing.

(55) FIGS. 11A and 11B are additional schematic structure diagrams showing the state in which the connector jig 31 and the light-emitting device 1 are overlapped, in the configurations shown in FIGS. 1A and 1B, and FIGS. 8A and 8B, respectively when viewed from the top without a part of the light-emitting device being transparently shown, similar to FIG. 10A. FIGS. 10A and 10B, and FIGS. 11A and 11B are provided to understand the structure.

(56) [Other Embodiments]

(57) Hereinafter, other embodiments will be described.

(58) (1) While the ceramic substrate is used as the substrate 3 in the above embodiment, the substrate may be a metal core substrate provided such that an insulation layer is formed on a surface of a metal substrate serving as a core.

(59) (2) While the soldering electrode land 17 is made of AgPt in the above embodiment, it only has to contain a conductive material (corresponding to a first conductive material) having a function to prevent diffusion to the solder. Thus, the material may include Ag or AgPd other than the AgPt. In addition, at this time, it is preferable that an uppermost surface part which is in contact with at least the solder is made of the first conductive material. In addition, while the connector connecting electrode land 19 is made of Au in the above embodiment, it only has to contain a conductive material (corresponding to a second conductive material) having a function to prevent oxidation from proceeding. The material Au is used as one example of the conductive material to prevent the oxidation from proceeding. In addition, at this time, it is preferable that an uppermost surface which is in contact with the lead (the lead 45 attached to the jig in the structure shown in FIG. 6) electrically connected to at least the connector is made of the second conductive material.

(60) (3) While the adjacent LED chips 11 are directly and electrically connected by the wire 13 in the above embodiment, they may be connected through a relay electrode.

(61) (4) While the soldering electrode land 17 is provided on the same side (main surface side) as the connector connecting electrode land 19, on the ceramic substrate 3 in the above embodiment, it may be provided on a back surface side of the substrate 3. In this case, a penetration electrode which penetrates the substrate to be connected to the wiring pattern 7 is provided, so that the soldering electrode land 17 provided on the back surface side is electrically connected to the penetration electrode.

(62) In addition, the soldering electrode land 17 may be provided on a side surface of the substrate 3.

(63) (5) The shapes of the electrode lands (17 and 19) and the openings (25, 33, and 35) are only shown as one example, and other shapes may be employed.

(64) (6) While the resin plate 30 constituting the connector jig 31 has almost the same size as that of the ceramic substrate 3 having the LED chips 11 in the above embodiment, the resin plate 30 may have any size. However, with a view to miniaturizing the lighting device 50, the resin plate 30 is preferably miniaturized within a range in which the openings (25 and 33) of the resin plate 30 and the ceramic substrate 3 can be overlapped. That is, it is preferable that the outer periphery of the connector jig 31 does not protrude from the outer periphery of the light-emitting device 1 when viewed from a direction perpendicular to the overlapped surface of the light-emitting device and the connector jig.

(65) (7) While one or both of the soldering electrode land 17 and the connector connecting electrode land 19 are arranged at the corners of the ceramic substrate 3 in the above embodiment, the arrangement position is not limited to the corner. However, the case where the electrode land is arranged at the corner of the ceramic substrate 3 is preferable because a space for the opening 25 can be sufficiently ensured in the ceramic substrate 3, and a ratio of the light emitted from the LED chip 11 absorbed by the electrode lands (17 and 19) can be reduced.

(66) (8) While the connector jig 31 is composed of the white or milky white resin plate 30 in the above embodiment, the connector jig 31 may be composed of a transparent member in a case where it is used only for fixing the ceramic substrate 3 to ensure the connector connection without having a function as a reflection member.

(67) (9) While the light-emitting device 1 has the printing resistive element 15 in the above embodiment, the printing resistive element is not necessarily provided when the withstand voltage protecting function is not executed. In addition, as an element having the withstand voltage protecting function, a zener diode may be mounted instead of the printing resistive element.

(68) (10) While the 12 series circuits each composed of 12 LED chips 11 connected in series are arranged as parallel lines on the substrate 3 in the above embodiment, as a matter of course, the number of the LED chips 11 connected in series, and the number of the series circuits (parallel line number) are not limited to the above numbers. In addition, the number of chips connected in series is not necessarily equal to the number of the parallel series circuits.

(69) In addition, in FIG. 1A, the LED chips 11 of the adjacent lines are appropriately connected in series in the vicinity of the peripheral part of the substrate in which the number of the chips belonging to the same line is smaller, so that the number of the LED chips 11 constituting the series circuit can be equalized. At this time, the LED chips 11 in the three or more adjacent lines may be incorporated as the components of the series circuit.

(70) In addition, in FIG. 1A, the LED chips 11 of the adjacent lines are appropriately connected in series in the vicinity of the peripheral part of the substrate in which the number of the chips belonging to the same line is smaller, so that the number of the LED chips 11 constituting the series circuit can be equalized. At this time, the LED chips 11 in the three or more adjacent lines may be incorporated as the components of the series circuit.

(71) Although the present invention has been described in terms of the preferred embodiment, it will be appreciated that various modifications and alternations might be made by those skilled in the art without departing from the spirit and scope of the invention. The invention should therefore be measured in terms of the claims which follow.