Source: https://patents.justia.com/patent/7690817
Timestamp: 2019-06-19 01:48:01
Document Index: 593057720

Matched Legal Cases: ['art 3', 'arts 114', 'arts 113', 'art 114', 'art 113', 'arts 114', 'arts 114', 'arts 114', 'arts 114', 'arts 114', 'art 201', 'arts 201']

US Patent for Illumination device with semiconductor light-emitting elements Patent (Patent # 7,690,817 issued April 6, 2010) - Justia Patents Search
Justia Patents With Ventilating, Cooling Or Heat Insulating MeansUS Patent for Illumination device with semiconductor light-emitting elements Patent (Patent # 7,690,817)
Nov 29, 2007 - Toshiba Lighting & Technology Corporation
The base board 2 has, for example, a rectangular shape in order to obtain a light emission area that is required by the illumination device 1. The material of the base board 2 should preferably be a metal with good heat radiation properties, such as copper or an aluminum alloy. As shown in FIG. 2, the base board 2 has a front surface 2a and a back surface 2b which is located opposite to the front surface 2a. A plurality of columnar projection portions 8 are integrally formed on the front surface 2a of the base board 2. The number of projection portions 8 corresponds to the number of semiconductor light-emitting elements 5.
The thickness A of that part of the base board 2, which excludes the projection portions 8, is, e.g. 0.25 mm. The back surface 2b of the base board 2 is used as a heat radiation surface, or a heat conduction surface which is thermally connected to a heat sink.
As shown in FIG. 2, the projection portion 8 has a flat distal end face 8a. The distal end face 8a of the projection portion 8 is parallel to the front surface 2a of the base board 2. The projection portion 8 is formed to be thicker at a proximal portion 8b thereof, which is continuous with the front surface 2a of the base board 2, than at the distal end face 8a thereof. In the present embodiment, the projection portion 8 is formed to become gradually thicker from the distal end face 8a toward the proximal portion 8b. In other words, the cross-sectional area of the projection portion 8a in its diametrical direction increases continuously from the distal end face 8a toward the proximal portion 8b. Accordingly, the projection portion 8 has a tapered outer peripheral surface 8c which flares from the distal end face 8a toward the proximal portion 8b. The outer peripheral surface 8c of the projection portion 8 is continuous with the front surface 2a of the base board 2, describing a gentle arcuate curve. According to the present embodiment, the diameter of the distal end face 8a is, e.g. 0.57 mm, and the diameter of the proximal portion 8b is, e.g. 1.08 mm.
A light reflective layer 10 is stacked on the distal end face 8a of the projection portion 8. The light reflective layer 10 is formed of a thin film of, e.g. silver, and the thickness B thereof is 0.003 mm to 0.005 mm. The light reflectance of the light reflective layer 10 is 90% or more.
A white glass epoxy base plate, for instance, is used as the insulator 3 in order to obtain a light reflecting performance. The thickness C of the insulator 3 may be 0.060 mm at minimum, and is, e.g. 0.25 mm in this embodiment. As shown in FIG. 1 and FIG. 3, the insulator 3 includes a plurality of through holes 11, through which the projection portions 8 penetrate. The through hole 11 has a circular shape, for instance, and its diameter is greater than the diameter of the proximal portion 8b that is the thickest part of the projection portion 8. The number of through holes 11 agrees with the number of projection portions 8.
The insulator 3 is attached to the front surface 2a of the base board 2 via an adhesive layer 12. The adhesive layer 12 is formed by impregnating a sheet of fibrous material, such as paper or cloth, with a thermosetting resin adhesive, and has electrical insulating properties. The adhesive layer 12 is interposed between the insulator 3 and the base board 2 and has a plurality of holes, through which the projection portions 8 penetrate. The diameter of each hole is greater than the diameter of the proximal portion 8b of the projection portion 8. The thickness of the adhesive layer 12 should preferably be, e.g. 0.005 mm or less.
In the state in which the insulator 3 is attached to the front surface 2a of the base board 2, the projection portions 8 of the base board 2 coaxially penetrate the through holes 11 of the insulator 3. In other words, the insulator 3 is stacked on that area of the front surface 2a of the base board 2, which excludes the projection portions 8. Thereby, the projection portions 8 are exposed to the outside of the insulator 3 through the through holes 11.
Since each of the through hole 11 of the insulator 3 has a greater diameter than the proximal portion 8b of the projection portion 8, the insulator 3 can be prevented from interfering with the projection portions 8 when the insulator 3 is stacked on the front surface 2a of the base board 2. Thus, the insulator 3 does not lift from the front surface 2a of the base board 2. Therefore, the insulator 3 properly overlaps the front surface 2a, and the position of the insulator 3, relative to the base board 2, is fixed. In other words, by overlapping the insulator 3 on the front surface 2a of the base board 2 so as to prevent interference between the through holes 11 of the insulator 3 and the projection portions 8, the insulator 3 can be stacked at a proper position on the front surface 2a.
When the insulator 3 is attached to the base board 2 by using the adhesive layer 12, the insulator 3 is pressed toward the base board 2. Thereby, the adhesive layer 12 is clamped between the base board 2 and the insulator 3, and an excess portion of the adhesive is pushed out into the inside of the through hole 11. More exactly, an excess portion 12a of the adhesive is pushed out and stays in an annular gap g between the outer peripheral surface 8c of the projection portion 8 and the through hole 11. The excess portion 12a of the adhesive hardens in the state in which the excess portion 12a spreads between the outer peripheral surface 8c of the projection portion 8 and the insulator 3.
Thereby, the insulator 3 is also attached to the projection portions 8, and the strength of adhesion of the insulator 3 to the base board 2 is increased. Moreover, the excess portion 12a of the adhesive functions as an insulator having a volume resistivity of 10−2 to 10−15Ω·m. As a result, the withstand voltage between the insulator 3 and the outer peripheral surface 8c of the projection portion 8 is improved.
The first conductor string 13 includes a plurality of conductor portions 15 and a first terminal portion 16a. Similarly, the second conductor string 14 includes a plurality of conductor portions 15 and a second terminal portion 16b. The conductor portions 15 are arranged in line at intervals in the longitudinal direction of the base board 2. In the present embodiment, the conductor portions 15 and the through holes 11 of the insulator 3 are alternately arranged with a pitch of, e.g. 4 mm. In other words, the through hole 11, in which the projection portion 8 is passed, is positioned between neighboring conductor portions 15.
The first terminal portion 16a is formed integral with the conductor portion 15 which is located at one end of the first conductor string 13. The second terminal portion 16b is formed integral with the conductor portion 15 which is located at one end of the second conductor string 14. Power cables are electrically connected to the first and second terminal portions 16a and 16b by means of, e.g. soldering.
As shown in FIG. 2 and FIG. 3, an end edge 15a of each conductor portion 15 is spaced apart by a predetermined distance from the opening edge of the through hole 11. Thereby, a portion 3a of the white insulator 3 is exposed from between the end edge 15a of each conductor portion 15 and the opening edge of the through hole 11. As a result, a distance for insulation, which is greater than the gap g between the outer peripheral surface 8c of the projection portion 8 and the through hole 11, can be secured between the end edge 15a of each conductor portion 15 and the outer peripheral surface 8c of the projection portion 8. In addition, since the portion 3a of the insulator 3 is exposed from between the end edge 15a of each conductor portion 15 and the opening edge of the through hole 11, light which is incident on the part 3a of the insulator 3 can be reflected in a light-extraction direction opposite to the base board 2. Exactly speaking, the end edge 15a of the conductor portion 15 refers to an end edge of the light reflective layer 18 that covers the conductor portion 15.
A double-wire type blue LED chip which uses, e.g. a nitride semiconductor, is used as each semiconductor light-emitting element 5. The semiconductor light-emitting element 5 includes a light-transmissive substrate 20 and a light-emitting layer 21. A sapphire substrate, for instance, is used as the substrate 20. The substrate 20 has a first surface 20a and a second surface 20b which is located on a side opposite to the first surface 20a. The semiconductor light-emitting layer 21 is formed by successively stacking, on the first surface 20a of the substrate 20, a buffer layer, an n-type semiconductor layer, a light emission layer, a p-type clad layer and a p-type semiconductor layer. The light emission layer has such a quantum well structure that barrier layers and well layers are alternately arranged. The n-type semiconductor layer includes an n-side electrode 22. The p-type semiconductor layer includes a p-side electrode 23. Besides, the semiconductor light-emitting layer 21 has no reflective film, and light can be emitted in both directions along the thickness thereof.
As shown in FIG. 2, the semiconductor light-emitting elements 5 are mounted on the distal end faces 8a of the projection portions 8 that project from the base board 2. Specifically, the second surface 20b of the substrate 20 of each semiconductor light-emitting element 5 is adhered to the distal end face 8a of the projection portion 8 via a bonding material 24. Accordingly, the semiconductor light-emitting elements 5 and the conductor portions 15 are alternately arranged with a pitch of, e.g. 4 mm.
That one of the conductor portions 15 of the first conductor string 13, which is located on the side opposite to the first terminal portion 16a, and that one of the conductor portions 15 of the second conductor string 14, which is located on the side opposite to the second terminal portion 16b, are electrically connected via another bonding wire 26 (see FIG. 1). Thus, the plural semiconductor light-emitting elements 5 are connected in series on the base board 2.
When the semiconductor light-emitting element 5 is wire-bonded to the conductor portion 15, a bonding machine is made to recognize a boundary between the end edge 15a of the conductor portion 15 and the insulator 3, and the bonding wire 25 is bonded to that part of the conductor portion 15, which is apart from this boundary, or a reference position, by a predetermined distance G. In the present embodiment, in order to minimize a stress remaining at the bonding part of the bonding wire 25, each of a distance H1 between the end edge 15a of the conductor portion 15 and the n-side electrode 22 of the semiconductor light-emitting element 5 and a distance H2 between the end edge 15a of the conductor portion 15 and the p-side electrode 23 is set at, e.g. 0.25 mm to 6.0 mm.
The reflector 6 is attached to the insulator 3. In the present embodiment, all the conductor portions 15 of the conductor 4 are located within the region surrounded by the reflector 6. The first and second terminal portions 16a and 16b of the conductor 4 are located outside the reflector 6.
The reflector 6 is formed of, e.g. a synthetic resin, and its inner peripheral surface is formed as a light reflective surface 6a. In this embodiment, in order to obtain the light reflective surface 6a, white powder is mixed in the resin material, of which the reflector 6 is to be formed, and thereby the light-reflective surface 6a itself is formed in a white color with high reflectance of visible light. The reflector 6 is usable, for example, as an attachment part of a lens for controlling distribution of light.
As shown in FIG. 2, the sealing member 7 is filled in the region surrounded by the reflector 6. The sealing member 7 is solidified, for example, by heating treatment, and covers the semiconductor light-emitting elements 5, insulator 3 and bonding wires 25 and 26 which are located inside the reflector 6. Further, the sealing member 7 is continuously filled in the gap g between the through hole 11 of the insulator 3 and the outer peripheral surface 8c of the projection portion 8. The sealing member 7 thus covers the excess portion 12a of the adhesive, which protrudes into the through hole 11 and the outer peripheral surface 8c of the projection 8.
In addition, since the reflector 6 is formed in such a frame shape as to surround all semiconductor light-emitting elements 5 as a group, most of the light, which is extracted to the outside of the illumination device 1 through the sealing member 7, travels through the sealing member 7 without being reflected by the light reflective surface 6a of the reflector 6. Therefore, the loss of light due to reflection decreases, and the light emitted from the semiconductor light-emitting elements 5 can efficiently be taken out of the illumination device 1.
In the illumination device 1 of the first embodiment, the excess portion 12a of the adhesive, which forms the adhesive layer 12, protrudes into the through hole 11 of the insulator 3. Thus, the adhesive layer 12 is entirely filled between the base board 2 and the insulator 3. Therefore, no gap, which is continuous with the through hole 11, is formed between the base board 2 and the insulator 3.
In the first embodiment, the insulator 3, which effects electrical insulation between the conductor portion 15 of the conductor 4 and the base board 2, is excluded from between the semiconductor light-emitting element 5 and the distal end face 8a of the projection portion 8, and the substrate 20 of the semiconductor light-emitting element 5 is bonded to the light reflective layer 10 of the projection portion 8.
Thus, the heat produced by the semiconductor light-emitting element 5 is directly conducted to the base board 2, without interference by the insulator 3. To be more specific, the heat of the semiconductor light-emitting element 5 is conducted to the projection portion 8 of the base board 2 via the light reflective layer 10 of the silver thin film from the bonding material 24 that is so thin that its thermal resistance is substantially ignorable. Furthermore, since the projection portion 8 is so formed as to have a gradually increasing thickness from the distal end face 8a toward the proximal portion 8b and the cross-sectional area of the projection portion 8 gradually increases toward the front surface 2a of the base board 2, the heat of the semiconductor light-emitting element 5 can efficiently be conducted from the distal end face 8a of the projection portion 8 to the base board 2. The heat that is conducted to the base board 2 is radiated from the back surface 2b of the base board 2 to the outside of the base board 2.
Moreover, part of the light emitted from the semiconductor light-emitting element 5 toward the base board 2 and part of the light emitted from the phosphor within the sealing member 7 are incident on the white insulator 3 and are reflected by the white insulator 3 in the light-extraction direction. In addition, the part of the light emitted toward the base board 2 is incident on the light reflective layer 18 covering the conductor portion 15, and is reflected by the light reflective layer 18 in the light-extraction direction. Besides, the portion 3a of the insulator 3 is not covered with the conductor portion 15 and is exposed to the periphery of the through hole 11. In other words, the portion 3a of the insulator 3 can be regarded as a white reflection surface which is continuous in the circumferential direction of the through hole 11. Thus, the light, which is incident on the portion 3a of the insulator 3, can be reflected in the light-extraction direction.
Furthermore, according to the first embodiment, the annular gap g is present between the outer peripheral surface 8c of the projection portion 8 and the through hole 11 of the insulator 3, and a part of the sealing member 7 is filled in the gap g. Thus, part of the light emitted from the phosphor in the sealing member 7 is made incident on the outer peripheral surface 8c of the projection portion 8 without being blocked by the insulator 3. The outer peripheral surface 8c of the projection portion 8 is inclined so as to flare from the distal end face 8a of the projection portion 8 toward the proximal portion 8b. Thereby, the light incident on the outer peripheral surface 8c can positively be reflected in the light-extraction direction opposite to the base board 2. Therefore, the light emitted from the semiconductor light-emitting element 5 can efficiently be extracted by making use of the projection portion 8 that promotes heat radiation of the semiconductor light-emitting element 5.
Moreover, the bonding material 24, which bonds the semiconductor light-emitting element 5 to the distal end face 8a of the projection portion 8, is the transparent silicone resin. There is very little possibility that the degradation of the silicone resin, including a change in color due to heat, progresses. As a result, the extraction of light reflected by the light reflective layer 10 can be maintained in good condition for a long time, without the light incident on the light reflective layer 10 being blocked by the bonding material 24, or without the extraction of the light reflected by the light reflective layer 10 being hindered by the bonding material 24.
In the first embodiment, one semiconductor light-emitting element 5 is disposed on the distal end face 8a of one projection portion B. The present invention, however, is not limited to this configuration. For example, a plurality of semiconductor light-emitting elements 5 may be disposed on the distal end face 8a of one projection portion 8. In this case, a plurality of semiconductor light-emitting elements 5, which emit light of the same color, or a plurality of semiconductor light-emitting elements 5, which emit lights of different colors, may be employed. In the case where the semiconductor light-emitting elements 5 which emit lights of different colors are employed, three semiconductor light-emitting elements 5 which emit lights of red, yellow and blue, for instance, may be arrayed in line. By arraying the plural semiconductor light-emitting elements 5 on the distal end face 8a of one projection portion 8, the entire luminous flux of the illumination device 1 can be more improved.
As shown in FIG. 6, the reflector has a plurality of reflection holes 31 (only one of them being shown) which are associated with the semiconductor light-emitting elements 5. The semiconductor light-emitting element 5, which is bonded to the projection portion 8 of the base board 2, is individually disposed in the reflection hole 31. The reflection hole 31 is a taper hole with a diameter which gradually increases from the base board 2 in the light-extraction direction. The sealing member 7 is filled in each of the reflection holes 31. The sealing member 7 is continuously filled in the gap g between the through hole 11 of the insulator 3 and the outer peripheral surface 8c of the projection portion 8, and the sealing member 7 covers the excess portion 12a of the adhesive, which protrudes into the through hole 11 and the outer peripheral surface 8c of the projection portion 8.
In the third embodiment, the semiconductor light-emitting element 5, which is bonded to the projection portion 8 of the base board 2, is individually sealed by a sealing member 41. The sealing member 41 is formed by dispensing a non-solidified resin on each of the semiconductor light-emitting element 5 from a dispenser (not shown). The non-solidified resin, after dispensed from the dispenser, is solidified in a hemispherical shape. The sealing member 41 includes a phosphor. The phosphor is uniformly dispersed in the sealing member 41. Further, the sealing member 41 is continuously filled in the gap g between the through hole 11 of the insulator 3 and the outer peripheral surface 8c of the projection portion 8, and covers the excess portion 12a of the adhesive, which protrudes into the through hole 11 and the outer peripheral surface 8c of the projection 8.
The resist layer 51 includes a plurality of openings 52 which correspond to the projection portions 8. The resist layer 51 includes a first stack portion 51a which covers the conductor portions 15, and a second stack portion 51b which covers the insulator 3. The first stack portion 51a and second stack portion 51b are integrally continuous with each other. As is clear from the comparison between FIG. 10 and FIG. 11, the height of the first stack portion 51a relative to the insulator 3 and the height of the second stack portion 51b relative to the insulator 3 are different by a degree corresponding to the thickness of the conductor portion 15 including the light reflective layer 18.
The sealing member 53 continuously covers the semiconductor light-emitting element 5 located within each opening 52, the two bonding wires 25 and the end portions of the conductor portions 15, to which the bonding wires 25 are connected. Moreover, the sealing member 7 is continuously filled in the gap g between the through hole 11 of the insulator 3 and the outer peripheral surface 8c of the projection portion 8. The sealing member 7 thus covers the excess portion 12a of the adhesive, which protrudes into the through hole 11 and the outer peripheral surface 8c of the projection 8.
In the fifth embodiment, a resin adhesive sheet is used as the adhesive layer 12. The color of the adhesive layer 12, which is formed by using the resin adhesive sheet, is brown, and the light reflectance of the adhesive layer 12 is lower than that of the white insulator 3. The adhesive layer 12 has a plurality of holes corresponding to the projection portions 8 of the base board 2. The diameter of each hole is greater than the diameter of the proximal portion 8b of the projection portion 8. The thickness I of the adhesive layer 12 is several times greater than the thickness of the adhesive layer 12 in the first embodiment.
The adhesive layer 12 is laid over the front surface 2a of the base board 2 in the state in which the projection portion 8 is passed through the associated hole. After the adhesive layer 12 is laid over the base board 2, the insulator 3 is laid over the adhesive layer 12. The mutually stacked base board 2, adhesive layer 12 and insulator 3 are pressed in the direction of stacking, and thereby the base board 2 and the insulator 3 are bonded by the adhesive layer 12. As shown in FIG. 12, since the adhesive layer 12 is pressed between the base board 2 and the insulator 3, the opening edge of the hole of the adhesive layer 12 protrudes into the through hole 11. Specifically, the excess portion 12a of the adhesive layer 12 is protruded into the annular gap g between the outer peripheral surface 8c of the projection portion 8 and the through hole 11. The excess portion 12a is solidified in the state in which the excess portion 12a is continuous in the circumferential direction of the through hole 11. The dimension J of protrusion of the excess portion 12a is, e.g. 0.2 mm or less. The dimension J of protrusion can be adjusted by adjusting the thickness of the adhesive layer 12 and the pressing force on the adhesive layer 12. Moreover, the excess portion 12a of the adhesive layer 12 covers the front surface 2a of the base board 2 and rises in the through hole 11.
In the fifth embodiment, a side light reflective layer 61 is stacked on the outer peripheral surface 8c of each projection portion 8. The side light reflective layer 61 is continuous with the light reflective layer 10 stacked on the distal end face 8a of the projection portion 8 and with the excess portion 12a of the adhesive layer 12. The side light reflective layer 61 is a silver thin film which is similar to the light reflective layer 10, and is formed together with the light reflective layer 10 by electroless plating on the projection portion 8. Since the electroless plating is performed before the insulator 3 is attached to the base board 2, the side light reflective layer 61 is not formed on the excess portion 12a of the adhesive layer 12. Thus, the side light reflective layer 61 does not reach that part of the base board 2, which is covered with the excess portion 12a of the adhesive layer 12.
Further, the sealing member 7 is continuously filled in the gap g between the through hole 11 of the insulator 3 and the outer peripheral surface 8c of the projection portion 8, and the sealing member 7 thus covers the excess portion 12a of the adhesive layer 12, which protrudes into the through hole 11 and the outer peripheral surface 8c of the projection 8.
Moreover, in the fifth embodiment, the outer peripheral surface 8c of the projection portion 8 is covered with the side light reflective layer 61, and the side light reflective layer 61 is continuous with the light reflective layer 10 that covers the distal end face 8a of the projection portion 8. Thus, part of the light emitted from the phosphor in the sealing member 7 is incident not only on the light reflective surface 10 at the distal end of the projection portion 8, but also on the side light reflective layer 61 via the gap g. Accordingly, the side light reflective layer 61 reflects the light, which travels toward the outer peripheral surface 8c of the projection 8, in the light-extraction direction opposite to the base board 2. Thereby, the light can efficiently be extracted.
According to experiments conducted by the inventor, the entire luminous flux of the illumination device 1, in which the distal end face 8a and outer peripheral surface 8c of the projection 8 are covered with the light reflective layers 10 and 18, was 110, in the case where the entire luminous flux of the illumination device, in which no light reflective layer is provided on the projection portion 8, was set at 100. Therefore, according to the illumination device 1 of the fifth embodiment, the light extraction efficiency can be increased by 10%.
In the fifth embodiment, the excess portion 12a of the adhesive layer 12 rises from the base board 2 between the outer peripheral surface 8c of the projection section 8 and the through hole 11. It is hence undeniable that the area of the side light reflective layer 61 is decreased by the excess portion 12a. However, since the dimension J of protrusion of the excess portion 12a is 0.2 mm or less and is very small, the decrease in area of the side light reflective layer 61 is practically ignorable. In addition, even if the color of the adhesive layer 12 is, for example, brown or black, other than white, the light absorbing function of the excess portion 12a of the adhesive layer 12 is also substantially ignorable.
In the fifth embodiment, the height of the excess portion 12a of the adhesive layer 12, which protrudes into the through hole 11, can be made substantially equal to the height of the surface of the insulator 3. Even in the case where the height of the excess portion 12a of the adhesive layer 12 is increased, the distal end face 8a of the projection portion 8, which is covered with the light reflective layer 10, projects higher than the surface of the insulator 3. Thus, all the side light reflective layer 61 is not covered with the excess portion 12a. Therefore, even if the adhesive layer 12 is colored, the light traveling toward the projection portion 8 can be reflected by the side light reflective layer 61, and the light can efficiently be extracted.
Furthermore, if the height of the excess portion 12a of the adhesive layer 12 is increased and made substantially equal to the height of the surface of the insulator 3, most of the gap g is filled with the excess portion 12a. Thus, when a non-solidified resin is filled in the region surrounded by the reflector 6, air hardly remains in the through hole 11. Therefore, by virtue of the presence of the adhesive layer 12, no gap occurs between the base board 2 and the insulator 3, and bubbles are prevented from remaining in the sealing member 7.
According to the fifth embodiment, since the adhesive layer 12 is brown, there is a sharp contrast between the excess portion 12a of the adhesive layer 12, which protrudes into the through hole 11, and the white insulator 3. Thereby, the position of the through hole 11 of the insulator 3 can easily be recognized. Accordingly, the semiconductor light-emitting element 5 can be bonded to the projection portion 8 by using the position of the through hole 11 as a reference position.
In the fifth embodiment, the color of the excess portion 12a of the adhesive layer 12 is brown, and the light reflectance of the excess portion 12a is lower than that of the white insulator 3. Thus, the image recognition unit can easily recognize the through hole 11 that is located at the boundary between the insulator 3 and the excess portion 12a of the adhesive layer 12. As a result, when the semiconductor light-emitting element 5 is to be bonded to the projection portion 8 that penetrates the through hole 11, the reference for determining the position of the semiconductor light-emitting element 5, relative to the projection portion 8, can surely be acquired.
In the fifth embodiment, it is not necessary that the adhesive layer 12 be colored in brown. The adhesive layer 12 may be transparent. In the case where the excess portion 12a of the adhesive layer 12 is transparent, the color of the image of the base board 2, which is captured through the excess portion 12a, becomes the color of the material of the base board 2. For example, if the base board 2 is formed of copper, the color of the base board 2 is brown. If the base board 2 is formed of a carbon-based material, the color of the base board 2 is black. The brown or black base board 2 has a lower reflectance than the white insulator 3.
As a result, the color of the base board 2, which is recognized through the excess portion 12a of the adhesive layer 12, is different from the color of the peripheral portion of the through hole 11 of the insulator 3, and the through hole 11, which is located at the boundary between the insulator 3 and the excess portion 12a of the adhesive layer 12, can easily be recognized. Hence, when the semiconductor light-emitting element 5 is to be bonded to the projection portion 8 that penetrates the through hole 11, the reference for determining the position of the semiconductor light-emitting element 5, relative to the projection portion 8, can surely be acquired.
As shown in FIG. 14, the reflector 6 has a plurality of reflection holes 71 (only one of them being shown) which are associated with the semiconductor light-emitting elements 5. The semiconductor light-emitting element 5, which is bonded to the light reflective layer 10 of the projection portion 8, is individually disposed in the reflection hole 71. The reflection hole 71 is a taper hole with a diameter which gradually increases from the base board 2 in the light-extraction direction. The sealing member 7 is filled in each of the reflection holes 71. The sealing member 7 is continuously filled in the gap g between the through hole 11 of the insulator 3 and the outer peripheral surface 8c of the projection portion 8, and the sealing member 7 covers the excess portion 12a of the adhesive layer 12, which protrudes into the through hole 11 and the outer peripheral surface 8c of the projection portion 8.
The base board 101 is formed in a rectangular shape in order to obtain a light emission area that is required by the illumination device 100. The material of the base board 101 should preferably be a metal with good heat radiation properties, such as copper. The base board 101 has a front surface 101a. An insulator 106 is stacked on the front surface 101a. The insulator 106 is formed of, e.g. a white synthetic resin. The thickness of the base board 101 including the insulator 106 is, e.g. 0.5 mm.
The reflector 103 is formed of, e.g. a synthetic resin, and its inner peripheral surface is formed as a light reflective surface 103a. In the present embodiment, in order to obtain the light reflective surface 103a, a white filler, such as magnesium oxide, is mixed in the resin, of which the reflector 103 is to be formed. The thickness of the reflector 103 is, e.g. 1.0 mm.
The reflector 103 includes first to fourth edge portions 117a, 117b, 117c and 117d. The first edge portion 117a extends along one longitudinal side edge of the base board 101. The second edge portion 117b extends along the other longitudinal side edge of the base board 101. The third edge portion 117c extends between one end of the first edge portion 117a and one end of the second edge portion 117b. The fourth edge portion 117d extends between the other end of the first edge portion 117a and the other end of the second edge portion 117b. Accordingly, the third and fourth edge portions 117c and 117d extend in a direction perpendicular to the longitudinal direction of the base board 101, and cross over the terminal portions 111 of the conductor strings 109. To be more specific, the third and fourth edge portions 117c and 117d of the reflector 103 cross over the connection parts 114 of the terminal portions 111. Thereby, all the conductor portions 110 of the conductor 108 are located within the region surrounded by the reflector 103, and all the land parts 113 of the conductor 108 are located outside the reflector 103.
As shown in FIG. 16 and FIG. 17, the adhesive member 104 bonds the reflector 103 to the insulator 106 of the base board 101. The adhesive member 104 is formed in a rectangular shape and has a size corresponding to the reflector 103. The adhesive member 104 is formed by impregnating a frame-shaped base with a thermosetting adhesive resin. A silicone resin is usable as the adhesive resin. The thickness of the adhesive member 104 is greater than that of the conductor portion 110 and is less than that of the reflector 103. Specifically, the thickness of the adhesive member 104 is, e.g. 0.15 mm. The width of the adhesive member 104 is equal to, or slightly less than, the width of each of the first to fourth edge portions 117a, 117b, 117c and 117d.
The adhesive member 104, when heated, is clamped between the reflector 103 and the insulator 106 of the base board 101 and is deformed. Thereby, part of the adhesive resin, which is contained in the base, protrudes to the inside and outside of the reflector 103. As shown in FIG. 16, protrusion portions 104a of the adhesive resin cover at least corner portions which are defined by the inner surfaces of the third and fourth edge portions 117c and 117d of the reflector 103 and the surface of the insulator 106. Furthermore, the protrusion portions 104a extend continuously along the inner surfaces of the third and fourth edge portions 117c and 117d in the direction perpendicular to the longitudinal direction of the base board 101. The protrusion portions 104a are naturally formed when the adhesive member 104 is pressed between the reflector 103 and the insulator 106. Thus, the formation of the protrusion portions 104a is not time-consuming, and this is advantageous in that the reflector 103 is easily attached.
The length K of protrusion of the protrusion portion 104a from the inner surface of each of the third and fourth edge portions 117c and 117d should preferably be set at 0.2 mm or less. The reason is as follows.
For example, in the case where the adhesive resin is colored in a color other than white, there is a concern that light emitted from the semiconductor light-emitting element 102 is absorbed by the protrusion portion 104a of the adhesive resin. However, since the length K of protrusion of the protrusion portion 104a is 0.2 mm or less and is very small, the area of the protrusion portion 104a is very small. Accordingly, the light absorption function of the protrusion portion 104a becomes ignorable, and it is possible to prevent the protrusion portion 104a from hindering efficient extraction of light.
In addition, when wire bonding is applied to the semiconductor light-emitting element 102 after the reflector 103 is attached to the base board 102, interference between the bonding tool and the protrusion portion 104a of the adhesive resin can be avoided. Thus, the bonding tool is prevented from being stained and damaged by the adhesive resin.
As shown in FIG. 16, the sealing member 105 is filled in the region surrounded by the reflector 103. The sealing member 105 covers all the semiconductor light-emitting elements 102 located inside the reflector 103, insulator 106 and bonding wires 116. Further, the sealing member 105 covers the protrusion portion 104a of the adhesive resin, which is located inside the reflector 103.
Besides, the width of the connection part 114 of each of the terminal portions 111, over which the third and fourth edge portions 117c and 117d of the reflector 103 cross, is less than the width of the land part 113 of each terminal portion 111. Thereby, the pitch P between neighboring connection parts 114 can be increased. In other words, even in the case where the pitch between neighboring conductor strings 109 is reduced as small as possible, the pitch P between the connection parts 114 can be increased.
As a result, when the reflector 103 is pressed toward the base board 101, that part of the adhesive member 104, which extends along the third and fourth edge portions 117c and 117d of the reflector 103, deforms and easily enter between the neighboring connection parts 114. In the present embodiment, since the interval between the neighboring connection parts 114 is set at 2.5 mm, the adhesive member 104 more easily enter between the neighboring connection parts 114.
A plurality of grooves 201 are formed in the surface of the sealing member 105. The grooves 201 extend in the longitudinal direction of the base board 101 and are arranged in parallel at intervals in the direction perpendicular to the longitudinal direction of the base board 101. The grooves 201 are positioned at boundaries between the neighboring light emission sections 200. A bottom part 201a of each groove 201 lies between the neighboring light emission sections 200.
The sealing member 105 may be formed by, for example, injection molding. Thereby, the non-solidified resin, of which the sealing member 105 is to be formed, is filled in the mold, and thus the thickness of the light emission sections 200 becomes uniform. Furthermore, since the grooves 201 having bottom parts 201a are formed between the light emission sections 200, deformation of the sealing member 105 due to blow-hole can be prevented.
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2002-94122 March 2002 JP
English Abstract of JP-2002-94122, Mar. 29, 2002.
Patent Publication Number: 20080128739
Assignee: Toshiba Lighting & Technology Corporation (Tokyo)
Inventors: Tomohiro Sanpei (Yokosuka), Yumiko Hayashida (Yokosuka), Masahiro Izumi (Fujisawa), Kiyoshi Otani (Yokosuka), Yutaka Honda (Yokohama), Shinji Nogi (Tokyo)
Application Number: 11/947,075
Current U.S. Class: With Ventilating, Cooling Or Heat Insulating Means (362/294); Having Light-emitting Diode (362/249.02); With Sealing Means Or Artificial Atmosphere (362/267)