JP2011061056A - Linear light-emitting device, method of manufacturing the same, and surface light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a warp occurs due to stress generated by a difference between thermal expansion coefficients of two members since a plurality of light-emitting element chips are disposed in a long groove formed by sticking a circuit board to a reflective frame or by sticking the circuit board to a heat radiating substrate. <P>SOLUTION: Light-emitting element chips 2-1, 2-2, ..., and circuit chips 3-1, 3-2, ..., are alternately arranged on the bottom of a long groove 1a of a substrate 1 having the long groove 1a, and electrically connected in series via bonding wires 4-1, 4-2 .... <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a linear light-emitting device in which a plurality of light-emitting element chips, for example, light-emitting diode (LED) chips, are linearly arranged, a manufacturing method thereof, and a surface light source device using the linear light-emitting device. The surface light source device is used as a backlight of a liquid crystal display device, for example.

  As a high-luminance light-emitting device, a linear light-emitting device in which a plurality of LED chips are arranged linearly, that is, linearly, is known.

  FIG. 9 is a perspective view showing a first conventional linear light emitting device (see FIG. 5 of Patent Document 1).

  As shown in FIG. 9, a bowl-shaped reflecting frame 102 is attached to a rectangular circuit board 101 made of epoxy or the like with an adhesive (not shown). Next, three LED chips 104-1, 104-2, and 104-3 are arranged in a line in the longitudinal direction in the long groove 103 formed by the circuit board 101 and the reflection frame 102. Note that the number and interval of the LED chips 104-1, 104-2, and 104-3 are set according to the lateral width and luminance of the long groove 103.

  FIG. 10 is a perspective view showing a second conventional linear light emitting device (see FIG. 2 of Patent Document 2).

  As shown in FIG. 10, the lower circuit board 202 is attached to the heat dissipation board 201 such as copper with an adhesive 203, and the upper circuit board 204 is attached to the lower circuit board 202 with an adhesive 205. The circuit pattern (wiring pattern) 202a of the lower circuit board 202 and the circuit pattern (wiring pattern) 204a of the upper circuit board 204 are electrically connected by a through hole (not shown) of the upper circuit board 204. Next, a plurality of LED chips 207 are arranged linearly in a long groove 206 formed by the heat dissipation substrate 201, the lower circuit substrate 202, and the upper circuit substrate 204. Each LED chip 207 is electrically connected to the circuit pattern 202 a of the lower circuit board 202 by a bonding wire 208. The number and interval of the LED chips 207 are set according to the lateral width and luminance of the long groove 206.

Japanese Patent Application Laid-Open No. 2006-216821 JP 2007-109945 A

  In the first conventional linear light emitting device shown in FIG. 9, there is a problem that stress is generated and warped due to a difference in thermal expansion coefficient between the circuit board 101 and the reflection frame 102 during heat treatment. In addition, since the adhesive for attaching the circuit board 101 and the reflection frame 102 protrudes into the region where the LED chips 104-1, 104-2, 104-3 are mounted, the LED chips 104-1, 104-2. , 104-3 must be made larger than necessary, resulting in an increase in the size of the linear light emitting device. In particular, when the linear light-emitting device is applied to a surface light source device using a light guide plate, if the linear light-emitting device increases in size, the light capture efficiency decreases, and if the LED chip is a white LED chip, the light emission color Unevenness increases.

  Also in the second conventional linear light emitting device shown in FIG. 10, there is a problem that stress is generated and warped due to a difference in thermal expansion coefficient between the heat dissipation substrate 201 and the circuit substrates 202 and 204 during heat treatment. In addition, since the adhesive 203 for attaching the heat dissipation board 201 and the lower circuit board 202 protrudes into the area where the LED chip 207 is mounted, the space around the area where the LED chip 207 is mounted becomes larger than necessary. As a result, there is a problem that the linear light emitting device is increased in size.

  In order to solve the above-described problems, a linear light emitting device according to the present invention includes a substrate having a long groove, a plurality of light emitting element chips arranged linearly at the bottom of the long groove of the substrate, and a long groove of the substrate. A plurality of circuit chips arranged linearly on the bottom, and the light emitting element chip and the circuit chip are electrically connected in series by bonding wires. Thereby, instead of the different parts pasted with the conventional adhesive, an integrally formed substrate is used, so that stress due to the difference in thermal expansion coefficient does not occur, and therefore warpage does not occur. Further, no adhesive is required. Furthermore, even when the number of light emitting element chips is increased or decreased according to the luminance, the bonding wire length is always shortened by adjusting the size of the circuit chip between the light emitting element chips according to the interval between the light emitting element chips. It becomes easy to do.

  Further, the light emitting element chips and the circuit chips were alternately arranged on the same line in the longitudinal direction of the long groove, the bonding wires were connected between the adjacent circuit chip and the light emitting element chip, and the wiring was drawn from both ends of the long groove.

  Furthermore, the method for manufacturing the linear light emitting device according to the present invention includes a step of arranging a plurality of light emitting element chips in the longitudinal direction of the long groove on the bottom of the long groove of the substrate on which the long groove is formed, and a plurality of circuit chips on the bottom of the long groove. And a step of electrically connecting the light emitting element chips and the circuit chips in series by bonding wires, and the circuit chips are alternately arranged on the same line as the light emitting elements. If the circuit chip arrangement step is performed after the light emitting element arrangement step, the influence of heat generated by the AuSn solder bonding used at the time of light emitting element bonding does not reach the circuit chip.

  Furthermore, the light source plate facing the long groove of the substrate of the above-described linear light emitting device is provided to realize a surface light source device. If the substrate of the linear light-emitting device is brought into contact with the light guide plate, the light-emitting element is arranged in the long groove of the substrate, so that the efficiency of taking light into the light guide plate is improved.

  According to the present invention, it is possible to prevent the linear light emitting device from warping and to reduce the size. Further, even when the number of light emitting element chips is increased or decreased, the bonding operation can be facilitated and the manufacturing cost can be reduced.

It is a perspective view which shows embodiment of the linear light-emitting device concerning this invention. It is a graph which shows the reflective characteristic of the material used for the board | substrate of FIG. It is a perspective view which shows fluorescent substance resin sealing of the linear light-emitting device of FIG. The 1st example of arrangement | positioning of the LED chip of FIG. 1 and a circuit chip is shown, (A) is a side view, (B) is a top view. FIGS. 2A and 2B show a second example of the arrangement of the LED chip and the circuit chip in FIG. 1, and FIG. FIG. 2 is a perspective view showing a modified example of the substrate in FIG. It is a flowchart for demonstrating the manufacturing method of the linear light-emitting device of FIG. 1, FIG. It is a perspective view which shows the surface light-emitting device using the linear light-emitting device of FIG. 1, FIG. It is a perspective view which shows the 1st conventional linear light-emitting device. It is a perspective view which shows the 2nd conventional linear light-emitting device.

  FIG. 1 is a perspective view showing a first embodiment of a linear light-emitting device according to the present invention.

  As shown in FIG. 1, the substrate 1 on which the long groove 1a is formed is made of a material having high reflectivity and high thermal conductivity, for example, Al. When Cu or ceramic with low reflectivity but high thermal conductivity is used, an Al film or Ag film with high reflectivity shown in FIG. 2 may be formed thereon. The long groove 1a communicates from one short side of the substrate 1 to the other side.

  As shown in FIG. 2, the reflectivity of Al and Ag in the ultraviolet light to green light region is higher than the reflectivity of Au. Therefore, it is particularly effective for white LEDs to use Al and Ag instead of Au. However, the reflectance of Ag decreases in a relatively short time due to light heat, halogen ions in the atmosphere, and S in the atmosphere. On the other hand, since a very dense natural oxide film having a strong protective force is formed on the surface of Al, it is excellent in corrosion resistance and weather resistance. As a result, there is almost no decrease in the reflectance of Al. Further, a strong alumite treatment may be performed instead of the natural oxide film of Al.

  LED chips 2-1, 2-2, 2-3 and circuit chips (wiring chips) 3-1, 3-2, 3-3, and 4-4 are linearly arranged in the long groove 1 a of the substrate 1. Yes. In this case, the LED chips 2-1, 2-2, 2-3 are arranged between the circuit chips 3-1, 3-2, 3-3, 3-4. As described above, the length of the LED chip in the short direction can be reduced as compared with the case where the circuit chip is provided on the upper surface of the side wall portion of the substrate 1.

  The LED chips 2-1, 2-2, 2-3 and the circuit chips 3-1, 3-2, 3-3, 3-4 are electrically connected by bonding wires 4-1, 4-2,. Connected in series.

  Power supply wirings 5-1 and 5-2 are connected to the outermost circuit chips 3-1 and 3-4. That is, the power supply wirings 5-1 and 5-2 are led out from the short side surfaces of the substrate 1.

  When the LED chips 2-1, 2-2, 2-3 are blue LED chips, as shown in FIG. 3, the long groove 1a is sealed with a phosphor resin 6 to form a white LED. This phosphor resin 6 suppresses uneven color. Furthermore, although not shown in the drawing, a white silicone resin having high thixotropy, for example, a silicone resin containing TiO filler, is disposed so as to block both ends of the long groove 1a so that the phosphor resin does not flow out of the long groove 1a. Thus, since the side surface of the phosphor resin 6 is in contact with the substrate 1 having a high heat dissipation property, the heat dissipation property can be improved.

  In the linear light emitting device of FIGS. 1 and 3, the long groove 1a as the reflective frame 102 of the conventional FIG. 9 is formed and the lower circuit board 202 of the conventional FIG. 10 is a circuit chip. The stress due to the difference in thermal expansion coefficient is not generated in the substrate 1, and therefore no warping occurs.

  In the linear light emitting device of FIGS. 1 and 3, the adhesive for the conventional reflective frame 102 of FIG. 9 and the lower circuit board 202 of FIG. It is not necessary to increase the space around the area where the −2 and 2-3 are mounted more than necessary, and as a result, the linear light emitting device can be reduced in size.

  Further, in the linear light emitting device of FIGS. 1 and 3, the substrate 1 is an Al substrate having a high reflectivity and a high thermal conductivity, or a high reflectivity Al or Ag on a Cu substrate or a ceramic substrate having a high thermal conductivity. Since the heat dissipation is improved by coating, the luminance can be increased by increasing the current to the LED chips 2-1, 2-2, 2-3.

  The number and interval of the LED chips are set according to the lateral width and luminance of the long groove 1a. For example, when the brightness of the LED chip is low, the number of LED chips is three as shown in FIG. 4, while when the brightness of the LED chip is high, the number of LED chips is set as shown in FIG. Two.

  In FIG. 4, three LED chips 2-1, 2-2, 2-3 are mounted on the substrate 1 by transparent silicone adhesive layers 2-1a, 2-2a, 2-3a that are less susceptible to deterioration by light and heat. ing. Thereby, since the light from the lower side of the LED chips 2-1, 2-2, 2-3 is reflected through the transparent silicone adhesive layers 2-1a, 2-2a, 2-3a, the luminance can be increased. . The four circuit chips 3-1, 3-2, 3-3, and 3-4 are printed wiring boards, for example, insulating boards 3-1 a, 3-2 a, such as FP-4 or a flexible insulating board, 3-3a, 3-4a and Au plated Cu conductive layers 3-1b, 3-2b, 3-3b, 3-4b formed thereon, and are made of silicone paste, Ag paste, epoxy paste, etc. (not shown) Mounted on the substrate 1. However, since the circuit chips 3-1, 3-2, 3-3, 3-4 do not emit light, the transparency of the adhesive layer is not necessary. At this time, the circuit chips 3-1, 3-2, 3-3 and 3-4 having the same shape and the same configuration are processed into appropriate dimensions, and as a result, the bonding wires 4-1, 4-2 and 4. -3, 4-4, 4-5 and 4-6 are short and have an appropriate length W1, which facilitates the wire bonding operation. Thereby, since the bonding wires 4-1, 4-2,..., 4-6 are usually made of Au, expensive Au material can be saved, and an increase in manufacturing cost can be suppressed. Further, the transparent silicone adhesive layers 2-1a, 2-2a, and 2-3a are island-like adhesive layers that are not continuous between the power supply wirings 5-1 and 5-2 at both ends of the long groove 1a. As a result, the adhesive that is likely to generate stress is not continuous but scattered, and thus it is difficult for the substrate 1 to warp.

  In FIG. 5, two LED chips 2-1, 2-2, 2-3 and three circuit chips 3-1, 3-2, 3-3 are mounted on the substrate 1 as in FIG. However, the dimensions of the circuit chips 3-1, 3-2 and 3-3 having the same shape and the same configuration are processed larger than the case of FIG. 4, and as a result, the bonding wires 4-1 and 4-2 are processed. , 4-3, 4-4 are also short and have an appropriate length W 2 (≈W 1), which facilitates wire bonding work and saves Au material.

  4 and 5, when performing the wire bonding operation, the LED ball is placed on the LED chip side with the first ball with the Au ball as a cushion, and the circuit chip side with the second ball without the Au ball. Reduces the impact on the chip and protects the LED chip.

  As described above, the number of LED chips may be increased or decreased according to the required luminance of various linear light emitting devices and the luminance of the LED chips. To adjust the length of the bonding wire. As a result, the manufacturing cost can be reduced.

  FIG. 6 is a perspective view showing a modified example of the substrate 1 of FIG. That is, as shown in FIG. 6A, long grooves 1b and 1b ′ parallel to the long groove 1a are provided on the lower surface side of the substrate 1 so as not to face the long groove 1a, or as shown in FIG. The long grooves 1c and 1c ′ parallel to the long grooves 1a are provided on the upper surface side of the substrate 1, or the long grooves 1d and 1d ′ parallel to the long grooves 1a are provided on the side surface of the substrate 1 as shown in FIG. . Thereby, the curvature of the board | substrate 1 is further suppressed and heat dissipation can be improved by the increase in the surface area of the board | substrate 1. FIG. Although not shown, a heat radiating fin may be provided on the lower surface side or the side surface side of the substrate 1 to improve heat dissipation.

  FIG. 7 is a flowchart for explaining a method of manufacturing the linear light emitting device of FIGS. 1 and 3.

  First, in step 701, a plurality of LED chips 2-1, 2-2,... Are arranged at the bottom of the long groove 1a of the substrate 1 in which the long groove 1a is formed.

  Next, in step 702, a plurality of circuit chips 3-1, 3-2,... Are arranged at the bottom of the long groove 1 a of the substrate 1. At this time, the LED chips are arranged between the circuit chips, and the LED chips and the circuit chips are alternately arranged in a linear shape.

  Next, in step 703, the LED chips 2-1, 2-2,... And the circuit chips 3-1, 3-2,. In this case, the first stroke of each bonding wire 4-1, 4-2,... Is placed on the LED chip side, and the second stroke is placed on the circuit chip side, so that the impact on the LED chip is reduced.

  Finally, in step 704, the phosphor resin 6 is applied to the long groove 1 a of the substrate 1 and the long groove 1 a is filled with the phosphor resin 6.

  In the manufacturing method of FIG. 7, since the circuit chip is disposed after the LED chip is disposed, when the circuit chip is joined to the substrate 1 by solder such as AuSn, there is no influence due to heat loss to the circuit chip.

  FIG. 8 is a perspective view showing a surface light emitting device using the linear light emitting device of FIGS. 1 and 3. As shown in FIG. 8, the surface light-emitting device is configured by mounting the light guide plate 6 along the arrangement of the LED chips 2-1, 2-2,... On the linear light-emitting device of FIGS. . In this case, there is no circuit (wiring) pattern on the upper surface of the side wall portion of the substrate 1 of the linear light emitting device of FIGS. It can be brought close to the light plate 6. For example, the substrate 1 of the linear light emitting device can be brought into contact with the light guide plate 6. Further, since the LED chips 2-1, 2-2,... Are arranged in the long groove 1a, the horizontal light of the substrate 1 decreases and the upward light of the substrate 1 increases. Therefore, the light capturing efficiency can be increased with respect to the light guide plate 6, and the luminance can be increased when the surface emitting device is used as a backlight of a liquid crystal display device. Moreover, since it can respond to the light guide plate 6 of various sizes, manufacturing cost can be reduced.

1: Substrates 1a, 1b, 1b ′, 1c, 1c ′, 1d, 1d ′: Long grooves 2-1, 2-2,...: LED chips 2-1a, 2-2a,. , 3-2, ...: Circuit chip (wiring chip)
3-1a, 3-2a, ...: Insulating substrates 3-1b, 3-2b, ...: Cu conductive layers 4-1, 4-2, ...: Bonding wires 5-1, 5-2: Power supply wiring 101: Circuit board 102: Reflection frame 103: Long grooves 104-1, 104-2, 104-3: LED chip 201: Heat dissipation board 202: Lower circuit board 202a: Circuit pattern (wiring pattern)
203: Adhesive 204: Upper circuit board 204a: Circuit pattern (wiring pattern)
205: Adhesive 206: Long groove 207: LED chip 208: Bonding wire

Claims (9)

A substrate on which a long groove is formed;
A plurality of light emitting device chips arranged linearly at the bottom of the long groove of the substrate;
A plurality of circuit chips arranged linearly at the bottom of the long groove of the substrate,
A linear light emitting device in which the light emitting element chip and the circuit chip are electrically connected in series by bonding wires. Furthermore, the light emitting element chip and the circuit chip are alternately arranged on the same line in the longitudinal direction of the long groove,
The bonding wire is connected between the circuit chip and the light emitting element chip adjacent to each other;
The linear light-emitting device according to claim 1, wherein wiring is drawn from both ends of the long groove.   The linear light-emitting device according to claim 1, wherein the light-emitting element chip is bonded to the bottom of the long groove of the substrate with a transparent adhesive layer. Each of the circuit chips is
An insulating substrate;
The linear light-emitting device according to claim 1, further comprising: a conductive layer formed on the insulating substrate.   The linear light-emitting device according to claim 1, further comprising a phosphor resin embedded in the long groove, wherein the light-emitting element chip, each circuit chip, and the bonding wire are sealed with the phosphor resin.   The linear light-emitting device according to claim 1, wherein another long groove parallel to the long groove of the substrate is provided. A step of arranging a plurality of light emitting element chips in the longitudinal direction of the long groove on the bottom of the long groove of the substrate on which the long groove is formed;
Arranging a plurality of circuit chips at the bottom of the long groove;
And a step of electrically connecting the light emitting element chip and the circuit chip in series by a bonding wire, wherein the circuit chip is alternately arranged on the same line as the light emitting element.   The method for manufacturing a linear light emitting device according to claim 7, wherein the circuit chip arranging step is performed after the light emitting element arranging step. A linear light-emitting device according to claim 1;
A surface light emitting device comprising: a light guide plate facing a long groove of a substrate of the linear light emitting device.

Images