JP2008277561A - Luminaire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luminaire capable of suppressing a lighting defect of a semiconductor light emitting element array due to breaking of a bonding wire for forming the semiconductor light emitting element array by connecting a semiconductor light emitting element group buried in a sealing member in series. <P>SOLUTION: The luminaire has a device substrate 2, a plurality of LEDs (semiconductor light emitting elements) 5, bonding wires 6, and a transparent sealing member 10. Each of the LEDs 5 has a first element electrode 17 and a second element electrode 18. The respective LEDs 5 are disposed in an array on one surface 2e of the device substrate 2. The bonding wires 6 electrically connecting the LEDs 5 have a wire diameter of 20-30 μm. The wires 6 are connected to first element electrodes 17 and second element electrodes 18 of LEDs 5 which are adjacent in the extension direction of the array in an arc shape reaching both the element electrodes and leaving one surface 2e. The bonding height (h) of the bonding wires 6 from the LEDs 5 is 50-150 μm. The LEDs 5 and bonding wires 6 are bured in the sealing member 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lighting device having a semiconductor light emitting element such as a plurality of LED (light emitting diode) chips and used for, for example, a lighting fixture or a display.

  Conventionally, a plurality of LED chips are arranged at high density in a unit area by arranging a plurality of LED chips vertically and horizontally on a substrate and electrically connecting these LED chips and the like with a bonding wire, for example, in series. An apparatus is known (for example, refer to Patent Document 1).

In addition, in order to protect the LED chip and the bonding wire connecting the electrode of the chip and the external electrode from external force, dust, moisture, etc., a protective member made of a translucent synthetic resin material is used. A light emitting device in which an LED chip and a bonding wire are embedded in a member is known (for example, see Patent Document 2).
JP 2003-52719 A (paragraphs 0014, 0019-0025, FIG. 1) Japanese Patent No. 3852465 (paragraphs 0026, 0028, 0036, 0045, 0053, FIG. 1A, FIG. 1B, FIG. 4)

  The illumination device of Patent Document 1 that does not include a protective member has low durability because the LED chip and the bonding wire connected to the electrode of the chip are exposed to external force, dust, moisture, and the like. Therefore, if the protective member described in Patent Document 2 is applied to the lighting device of Patent Document 1, it is possible to improve the durability of the lighting device.

  By the way, in the lighting device in which LED chip groups arranged in a row as in Patent Document 1 are connected in series via a bonding wire, for example, when one bonding wire is disconnected, an electrical device including this wire is electrically included. It becomes impossible to energize a group of LEDs connected in series. It is not disclosed in the cited document 2 using a protection member about solving such a subject.

  As a result of diligent research, the present inventor has found that there is a case where a protective sealing member in which the LED chip and the bonding wire are embedded is related to the disconnection of the bonding wire in which the adjacent LED chips are directly connected in series. It was.

  That is, the bonding wire is provided so as to bend away from the device substrate on which the LED chip is disposed, and both ends thereof are connected to the electrodes of the adjacent LED chip by wire bonding. For this reason, when the length of the bonding wire is too long and the bonding height of the bonding wire to the LED chip is increased, the amount of the sealing member used in the sealing after the wire bonding is increased and the thickness thereof is increased. Become thicker. In this specification, the bonding height refers to the height position of the electrode of the LED chip to which one end of the bonding wire that has been wire-first bonded in advance at both ends of the bonding wire and the height of the apex of the bending of the bonding wire. It indicates the difference from the position.

  If the amount of the sealing member used increases because it is necessary to securely embed the bonding wire in this way, the weight of the sealing member acting on the bonding wire during the manufacturing process until the uncured sealing member is cured. Therefore, there is a high possibility that the bonding wire is greatly deformed toward the device substrate, and stress is applied to the end portion of the bonding wire near the electrode of the LED chip due to the occurrence of this deformation.

  On the other hand, when the bonding wire is too short and the bonding height is low, the bonding wire is in a tight tension state, so that the bonding wire may be deformed by the weight of the sealing member. Decrease. However, in the wire bonding in this case, since the bonding wire is bent sharply near the electrode of the LED chip, a large stress is applied to the end portion of the bonding wire.

  Due to the stress applied to the end portion of the bonding wire as described above, the bonding wire is easily broken during the manufacturing process. Not only that, the stress associated with the thermal expansion and contraction of the sealing member accompanying the lighting / extinguishing of the lighting device is repeatedly applied to the end of the bonding wire, and this also breaks the bonding wire. Sometimes.

  Therefore, in a lighting device that obtains the required amount of light emission by connecting LED chip groups arranged in a row in series via bonding wires, the lighting failure caused by the disconnection of the bonding wires as described above However, the above-mentioned patent documents cannot satisfy such a request.

  An object of the present invention is to provide a lighting device capable of suppressing a lighting failure of a semiconductor light emitting element array due to disconnection of a bonding wire for connecting semiconductor light emitting element groups embedded in a sealing member in series to form a semiconductor light emitting element array Is to provide.

  The invention according to claim 1 is an apparatus substrate; a plurality of semiconductor light emitting elements each having a first element electrode and a second element electrode and arranged in a row on one surface of the element substrate; Connected to the first element electrode and the second element electrode of the semiconductor light emitting element adjacent to each other by wire bonding and curved so as to be away from the one surface across both element electrodes, and the wire diameter is 20 μm A bonding wire of ˜30 μm, which is wire-bonded such that the height of the wire with respect to the semiconductor light emitting element is 50 μm or more and 150 μm or less, and the semiconductor light emitting elements are electrically connected in series; And a translucent sealing member in which the semiconductor light emitting element and the bonding wire are embedded.

  In the invention of claim 1, the device substrate can be made of an insulating plate made of synthetic resin, glass or ceramics. In this case, the device substrate may be a single plate or a laminate of a plurality of devices. You may laminate | stack the metal plate for heat dissipation on the back surface of an insulating plate. In the invention of claim 1, for example, an LED (light emitting diode) chip can be suitably used as the semiconductor light emitting element. In the invention of claim 1, the first element electrode and the second element electrode of the semiconductor light emitting element may be at the same height position or at different height positions. In the first aspect of the present invention, the bonding wire is formed of a fine metal wire, but a fine Au wire can be suitably used, and the wire diameter is preferably 20 μm to 30 μm. In the invention of claim 1, a silicone resin can be preferably used for the light-transmitting sealing member, but other epoxy-based light-transmitting resins and light-transmitting low melting point glass can also be used. It is.

  In the invention of claim 1, both ends are directly connected to the first element electrode and the second element electrode of the semiconductor light emitting elements arranged in a row and adjacent to each other in the extending direction of the row by wire bonding, The height of the bonding wire, which is provided so as to be bent away from the surface on which the semiconductor light emitting element of the device substrate is mounted, is set to 50 μm or more and 150 μm or less.

  As described above, the bonding height of the bonding wire is 150 μm at the highest, so that the amount of the sealing member necessary for sufficiently burying the bonding wire is reduced, and the thickness of the sealing member is reduced. Accordingly, the weight of the uncured sealing member that acts on the bonding wire when sealing is reduced, and deformation of the bonding wire toward the device substrate can be suppressed. In addition, since the bonding height of the bonding wire is 50 μm at the lowest, it is possible to prevent the end of the bonding wire near the element electrode of the semiconductor light emitting element from being bent suddenly along with the wire bonding.

  The invention according to claim 2 is characterized in that one end of the bonding wire is connected to the first element electrode by ball bonding, and the other end of the bonding wire is connected to the first element electrode via a bump provided on the second element electrode. It is characterized by being connected to the second element electrode by wire bonding by high frequency welding.

  In the invention of claim 2, the bump is preferably made of Au, but can be made of inexpensive solder. Further, the shape of the bump may be a trapezoid having a flat apex portion or a semicircular shape when the bump is viewed from the side.

  In the invention of claim 2, since the bonding wire is ball bonded to the first element electrode, the pressure applied to the semiconductor light emitting element by the bonding tool at that time is small. In addition, the bonding wire is connected to the second element electrode not by ball bonding but by high-frequency welding, but at this time, the bumps previously attached to the second element electrode are melted and bonded at high frequency. In this bonding, the pressure applied to the semiconductor light emitting element is small. Therefore, when manufacturing, damage to the semiconductor light emitting element due to wire bonding can be suppressed.

  According to the lighting device of the first aspect of the present invention, lighting of the semiconductor light-emitting element array by disconnecting the bonding wires for connecting the semiconductor light-emitting element groups embedded in the sealing member in series to form the semiconductor light-emitting element array, etc. Defects can be suppressed.

  According to the illumination device of the second aspect of the present invention, since damage to the semiconductor light emitting element due to wire bonding of the bonding wire to the first element electrode and the second element electrode between adjacent semiconductor light emitting elements is suppressed, the semiconductor Lighting failure of the light emitting element array can be suppressed.

  Reference numeral 1 in FIGS. 1 and 2 denotes an illumination device that forms an LED package. The lighting device 1 includes a device substrate 2, a plurality of power supply terminals 3 and 4, a plurality of semiconductor light emitting elements such as LED chips (hereinafter abbreviated as LEDs) 5, bonding wires 6, 7, 8a and 8b, a reflector 9, and The sealing member 10 is provided.

  As shown in FIG. 2, for example, a metal-based substrate formed by laminating a metal plate 12 on the back surface of a laminated substrate, preferably a resin plate 11 is used for the device substrate 2. The resin plate 11 is made of an epoxy resin containing white glass powder to obtain good light reflection performance. The metal plate 12 that releases the heat of the LED 5 in the lit state to the outside is made of, for example, aluminum or an alloy thereof. As shown in FIG. 1, the device substrate 2 has a predetermined shape, for example, a quadrangular shape, specifically a rectangular shape, in order to obtain a light emitting area required for the lighting device 1.

  Each of the power supply terminals 3 and 4 is formed by laminating a metal layer, for example, an Au or Ni plating layer on copper, and is electrically connected to one end and the other end of an LED array that forms a semiconductor light emitting element array to be described later. It is provided on one surface 2e (in other words, the surface of the resin plate 11) which is a reflection surface of the device substrate 2. Specifically, as illustrated in FIG. 1, the power supply terminals 3 and 4 are arranged alternately and parallel to each other in the direction in which the side 2 a extends toward the side 2 a of the device substrate 2. .

  Each LED 5 employs a double wire type using a nitride semiconductor, for example. These LEDs 5 are formed, for example, by laminating a semiconductor light emitting layer 16 on one surface of a light-transmitting element substrate 15 made of sapphire or the like as shown in FIG. 4B. The semiconductor light emitting layer 16 emits blue light, for example. Further, each LED 5 has a first element electrode 17 and a second element electrode 18 as shown in FIGS. 4A and 4B, and the second element electrode 18 is made of, for example, solder. Bumps 19 are provided in advance. One of the first element electrode 17 and the second element electrode 18 is for the positive electrode, and the other is for the negative electrode.

  As shown in FIG. 1, the LEDs 5 are two-dimensionally arranged in rows and columns on one surface 2 e of the device substrate 2. When the LED 5 is mounted on the device substrate 2, the other surface of the element substrate 15 on which the semiconductor light emitting layer 16 is not laminated is parallel to the surface on which the light-transmitting semiconductor light emitting layer 16 is laminated, as shown in FIG. It is made by adhering using the translucent die-bonding material 20 shown as a representative. For example, the first element electrode 17 having no bump 19 is positioned on the other side 2b side parallel to the one side 2a of the apparatus substrate 2 and the second element electrode 18 having the bump 19 is disposed on the apparatus substrate. The direction of each LED 5 is made uniform so that it may be located on the one side 2a side. Thus, the LEDs 5 are arranged so that the first element electrodes 17 and the second element electrodes 18 of the LEDs 5 are alternately arranged in the direction in which the columns described below extend.

  The LEDs 5 in a row of a plurality of LEDs 5 arranged in a direction in which the sides 2c and 2d perpendicular to the one side 2a and the other side 2b of the device substrate 2 extend (this row is referred to as a column for convenience with reference to FIG. 1). The arrangement pitch A is, for example, 0.5 mm to 4.0 mm. The arrangement pitch B of the LEDs 5 in a row of a plurality of LEDs 5 arranged in the direction in which the one side 2a and the other side 2b of the device substrate 2 extend (this row is referred to as a row for convenience with reference to FIG. 1) The arrangement pitch A or more.

  Each of the bonding wires 6 and 7 is made of, for example, Au wire and has a wire diameter of 20 μm to 30 μm. The LEDs 5 in the column are connected to each other by bonding wires 6. Specifically, one end of the bonding wire 6 that is first bonded is connected to the first element electrode 17 of the LED 5 adjacent in the direction in which the column extends by ball bonding, and the other end of the bonding wire 6 that is second bonded is connected to the first element electrode 17. The second element electrodes 18 of the LEDs 5 adjacent to each other in the extending direction of the column are connected via bumps 19 by wire bonding by high frequency welding. Here, the first bonding refers to bonding performed prior to the second bonding.

  The plurality of LEDs 5 electrically connected by the bonding wires 6 as described above are adjacent to the column in the direction in which the one side 2a and the other side 2b extend, and are also electrically connected by the bonding wires 6. The plurality of LEDs 5 are electrically connected to each other by a bonding wire 7 provided over the LEDs 5 at the position closest to the other side 2b opposite to the power supply terminals 3 and 4. Both ends of the bonding wire 7 are bonded to the first element electrode 17 of the LED 5 at the position closest to the other side 2b.

  With this connection, the pair of columns form an LED array (semiconductor light emitting element array) electrically connected in series. Such an LED row may be at least one, but in this embodiment, five rows are provided as shown in FIG.

  The second element electrode 18 of the LED 5 positioned at one end of each LED row and the power supply terminal 3 arranged in the vicinity thereof are electrically connected by a bonding wire 8a bonded over them. . Similarly, the second element electrode 18 of the LED 5 positioned at the other end of each LED row and the power supply terminal 4 arranged in the vicinity thereof are electrically connected by a bonding wire 8b bonded over them. It is connected. The bonding wires 8 a and 8 b are first bonded to the power supply terminals 3 and 4 and are second bonded to the second element electrode 18 of the LED 5.

  Each of the bonding wires 6, 7, 8 a, 8 b provided by the above bonding is curved so as to be away from the one surface 2 e of the device substrate 2 as represented by the bonding wire 6 shown in FIG. 3. Of these bonding wires 6, 7, 8a and 8b, at least the bonding height h (see FIG. 3) of the bonding wires 6 and 7 with respect to the first element electrode 17 of the LED 5 is set to 50 μm or more and 150 μm or less. Yes. Moreover, in this embodiment, the bonding height h is set to be equal to or less than the thickness h1 of the LED 5 while satisfying this condition.

  The reflector 9 is not provided corresponding to each LED or each of a plurality of LEDs, but is a single frame member that surrounds all the LEDs 5 on the device substrate 2. For example, as shown in FIG. It has a shape. The reflector 9 is formed of a synthetic resin mixed with a white filler made of magnesium oxide or the like. In the plan view shown in FIG. 1, the reflector 9 is bonded to one surface 2 e of the device substrate 2 with a frame portion 9 a forming a part thereof intersecting with the power supply terminals 3 and 4. The height ½ of the height H of the reflector 9 shown in FIG. 3 is set higher than the total of the bonding height h and the thickness h1 of the LED 5. Thereby, the bonding wires 6, 7, 8 a, 8 b are surely embedded in the sealing member 10 regardless of variations in the injection amount of the sealing member 10 described later.

  The sealing member 10 is filled in the reflector 9 in a substantially full state, seals all the LEDs 5 and the bonding wires 6, 7, 8a, 8b, etc. accommodated in the reflector 9, The life of the lighting device 1 is prevented from being reduced by protecting it from the outside air. The sealing member 10 is made of a translucent material, for example, a translucent resin, specifically, a thermosetting silicone resin. The sealing member 10 is provided by being cured by being heated in a heating furnace after a predetermined amount is injected into the reflector 9 in an uncured liquid state.

  In the sealing member 10, phosphors (not shown) are preferably mixed in a uniformly dispersed state. The phosphor is excited by a part of the light emitted from each LED 5 and emits light of a color different from the color of the light emitted from the LED 5, thereby changing the color of the illumination light emitted from the illumination device 1. Used to define. In the present embodiment, in order to change the color of the illumination light emitted from the illumination device 1 to white light, a phosphor that emits yellow light that is complementary to the blue light emitted from each LED 5 is used. Has been.

  Each LED row emits light by being fed through the feed terminals 3 and 4 connected thereto. Therefore, the white light generated by mixing the blue light emitted from each LED 5 and the yellow light emitted from the phosphor excited in the sealing member 10 by a part thereof is illuminated. The light is emitted from the device 1 toward the object to be illuminated.

In the illuminating device 1, both ends of bonding wires 6, 7 that are curved so as to be away from the one surface 2 e of the device substrate 2 to which the LEDs 5 are attached are adjacent to each other in the direction in which the rows of the LED rows extend. The first element electrode 17 and the second element electrode 18 are connected to each other by wire bonding, and their bonding height h is set to 50 μm or more and 150 μm or less. Therefore, in this lighting device 1, it is possible to suppress the lighting failure of the LED array due to the disconnection of the bonding wires 6 and 7 by the sealing member 10 for obtaining durability. That is, the upper limit value of the bonding height h is 150 μm. As a result, the amount of the sealing member 10 necessary for sufficiently burying the bonding wires 6 and 7 is reduced, and the thickness of the sealing member 10 can be reduced. Thereby, when the LED 5 or the like is sealed with the sealing member 10, the weight of the uncured sealing member 10 acting on the bonding wires 6 and 7 warped toward the device substrate 2 is reduced. The deformation of the bonding wires 6 and 7 so as to approach the device substrate 2 side is suppressed.

  For this reason, stress applied to the end portions of the bonding wires 6 and 7 close to the first element electrode 17 and the second element electrode 18 of the LED 5 is reduced, and in particular, the bonding wire 6 close to the first element electrode 17. 7 can also be prevented from breaking at the ends when the ends are crystallized and become brittle due to ball bonding. Since the disconnection of the bonding wires 6 and 7 at the time of manufacture can be suppressed as described above, the lighting failure of the LED array due to the disconnection can be suppressed.

  Further, since the lower limit value of the bonding height h is 50 μm, the end portions of the bonding wires 6 and 7 near the first element electrode 17 and the second element electrode 18 of the LED 5 abruptly accompany with the wire bonding. Since it can be prevented from being bent, the stress applied to the ends of the bonding wires 6 and 7 close to the first element electrode 17 and the second element electrode 18 of the LED 5 is reduced. Therefore, particularly when the end portions of the bonding wires 6 and 7 close to the first element electrode 17 are crystallized and become brittle due to ball bonding, the end portions can be prevented from being disconnected. When the bonding height h is as small as 50 μm in this way, the length of the bonding wires 6 and 7 is shorter than that when the upper limit value of the bonding height h is 150 μm, and the bonding wires 6 and 7 are stronger. Since it is in a stretched state, the bonding wires 6 and 7 are prevented from being deformed to the device substrate 2 side by the weight of the uncured sealing member 10. Since the disconnection of the bonding wires 6 and 7 at the time of manufacture can be suppressed as described above, the lighting failure of the LED array due to the disconnection can be suppressed.

  In addition, since the stress at the ends of the bonding wires 6 and 7 is reduced as described above, the sealing member 10 is thermally expanded and contracted as the lighting device 1 is turned on / off, and the stress associated therewith is increased. In spite of being repeatedly applied to the end portions of the bonding wires 6 and 7, it is possible to suppress the disconnection of the bonding wires 6 and 7.

  Moreover, since the lighting device 1 having the above-described structure directly connects the LEDs 5 adjacent to each other in the extending direction of the LED rows by the bonding wires 6 and 7 provided as described above, It is not necessary to provide a pad as a relay electrode for relaying on the device substrate 2. For this reason, there are no following disadvantages.

  That is, the configuration in which the relay electrode is provided is disadvantageous in that the effective reflection area on the one surface 2e that forms the white color of the device substrate 2 is reduced by this electrode. In addition, the relay electrode often has an Au plating layer on its surface, and in this case, the light reflected by the relay electrode is mixed with the white light projected from the lighting device 1, so that the illumination light This is disadvantageous in that the color may change slightly.

  Further, since the relay electrode is not required as described above, the arrangement pitch A of the LEDs 5 can be narrowed when it is necessary to secure a larger amount of light emitted from the lighting device 1. By the way, when a relay electrode is provided between adjacent LEDs 5 and a bonding wire is second bonded to this electrode and the adjacent LEDs 5 are electrically connected in series, the pitch of the LEDs 5 needs to be 100 μm or more. To do. Compared to this configuration, under the condition that the amount of emitted light is the same, it is possible to configure the lighting device 1 to be smaller if the arrangement pitch A of the LEDs 5 is narrowed, and conversely, under the condition that the size of the device is the same, The lighting device 1 that can narrow the arrangement pitch A of the LEDs 5 has a higher mounting density of the LEDs 5, so that there is an advantage that the amount of emitted light can be increased and the appliance efficiency can be improved.

  As described above, in the lighting device 1 that does not use the relay electrode, the end of the bonding wire 6 is connected to the second element electrode 18 of the LED 5 by wire bonding by high-frequency welding. In this connection, since the bump 19 previously attached to the second element electrode 18 is melted at a high frequency for bonding, the pressure applied to the LED 5 by a bonding tool (not shown) along with this bonding is small. Further, since the bonding wire 6 is connected to the first element electrode 17 of the LED 5 by ball bonding, the pressure applied to the LED 5 by a bonding tool (not shown) at that time is small.

  Therefore, as the damage of the LED 5 due to the wire bonding is suppressed, the lighting failure of the LED array due to the damage of the LED 5 can be suppressed.

The front view shown in the state which partly cut away the illuminating device which concerns on one Embodiment of this invention. Sectional drawing of the illuminating device shown along the arrow F2-F2 line | wire in FIG. Sectional drawing which expands and shows a part of FIG. (A) is a front view which shows the LED chip with which the illuminating device of FIG. 1 is provided. (B) is a side view showing the LED chip.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Illuminating device, 2 ... Device substrate, 2e ... One surface of device substrate, 5 ... LED (semiconductor light emitting element), 6, 7 ... Bonding wire, 10 ... Sealing member, 15 ... Element substrate, 16 ... Semiconductor light emitting layer, 17 ... 1st element electrode, 18 ... 2nd element electrode, 19 ... Bump, h ... Bonding height

Claims (2)

A device substrate;
A plurality of semiconductor light emitting elements each having a first element electrode and a second element electrode and arranged in a row on one surface of the element substrate;
Connected to the first element electrode and the second element electrode of the semiconductor light emitting element adjacent to each other in the extending direction of the row by wire bonding, and is provided so as to be curved away from the one surface across the both element electrodes; and A bonding wire having a wire diameter of 20 μm to 30 μm, wherein the semiconductor light emitting elements are electrically connected in series by wire bonding so that the height of the wire with respect to the semiconductor light emitting elements is 50 μm or more and 150 μm or less With bonding wires;
A translucent sealing member in which the semiconductor light emitting element and the bonding wire are embedded;
An illumination device comprising:   One end of the bonding wire is connected to the first element electrode by ball bonding, and the other end of the bonding wire is connected to the second element electrode via a bump provided on the second element electrode. The lighting device according to claim 1, wherein the lighting device is connected by wire bonding by welding.

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