JP3704794B2 - Method for forming LED display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an LED display using two or more light emitting diodes, and more particularly to an LED display excellent in light emission characteristics, visibility and productivity while preventing deterioration of the light emitting diodes.
[0002]
[Prior art]
Today, with the development of light-emitting diodes that can emit RGB (red, green, blue) three primary colors with high brightness, the lamps, signals, letters, LED displays are beginning to be used for displays capable of displaying full-color image information. The LED display which is such a collective lamp is generally fixed to a wall or the like at a certain angle. On the other hand, the position of the viewer, the irradiation angle of the extraneous light, and the like change from moment to moment. It is desirable that the visibility of the LED display does not change greatly even with such a change.
However, in order to improve the front luminance, the light-emitting diode covers the LED chip with a lens-processed resin or the like, thereby condensing light emitted to spread around the front to raise the luminance. For this reason, there is a problem in that the light emission luminance in the direction deviating from the front surface (directing direction) of the light emitting diode is low, and the visibility is greatly reduced as the viewer moves.
[0003]
Therefore, various collective lamps have been developed to widen the viewing range.
Specifically, JP-A-7-302931 and utility model registration number 3019845 can be mentioned. Japanese Patent Laid-Open No. 7-302931 has a configuration in which a plurality of light emitting surfaces of LEDs having RGB three primary colors are provided and the light distribution directions of the light emitting surfaces are different. Alternatively, it is disclosed that visibility is improved by arranging LEDs on a flexible substrate and providing an angle to the flexible substrate. However, it cannot substantially cope with wider visibility in the outdoors. That is, in order to deal with wider visibility, a plurality of substrates that are light emitting surfaces must be used for each angle, and devices such as wiring and mounting become complicated and cannot be formed with high productivity. In addition, it is difficult to mount LEDs on a flexible board, and if a flexible board is always under stress, it can be bent at a certain angle or more in an environment where the temperature and humidity cycle is intense, such as temperature rise due to heat generation of the light emitting diode or the outdoors. There arises a problem that the electrical connection such as soldering is defective.
[0004]
In addition, in Utility Model Registration No. 3019845, a large number of light emitting diodes are arranged vertically and horizontally on a square base surface with a printed circuit board superimposed on the back surface, and the mounting angle of one row of light emitting diodes is centered. An attachment in which the wire is gradually changed from the line to the end is disclosed. By gradually changing the mounting angle of the light emitting diode, it is possible to sufficiently cope with relatively wide visibility. However, in order to change the mounting angle of the light emitting diodes with respect to the substrate, the individual light emitting diodes must be accurately changed with respect to the substrate. In this arrangement, it is difficult to arrange the directional characteristics. Also, if the light emitting diode and the substrate are soldered while being held at a predetermined angle or more, the temperature rise due to soldering may cause the lead terminal subjected to bending stress to move partially. There also arises a problem that the electrical connection member to be connected is partially dissociated. Further, it is practically difficult and impractical to place the light-emitting diodes that are once bent exactly at a desired angle on the substrate and fix them with solder or the like while maintaining the angle.
[0005]
[Problems to be solved by the invention]
Therefore, in the present day when wide visibility is required in a harsher environment, the collective lamp having the above configuration is not sufficient, and further improvement in characteristics is required. In view of such a problem, the present invention is to provide an LED display excellent in visibility and productivity while preventing deterioration of light emission characteristics.
[0006]
[Means for Solving the Problems]
The present invention relates to a method for forming an LED display, comprising: a plurality of light emitting diodes each having a lead electrode and a mold member; a substrate on which the light emitting diodes are arranged at different inclination angles; and a housing on which the substrate is disposed. The lead member of the light emitting diode is disposed in the opening of the substrate, and the mold member is inserted into the hole in a jig having a plurality of holes each having an inclination angle adjusted with respect to the substrate. And a step of fixing the light emitting diode, and a step of fixing the lead electrode of the light emitting diode to the substrate with the jig attached thereto. is there.
[0007]
Moreover, it has the process of removing the said jig | tool after fixing the said lead electrode to the said board | substrate. In addition, the method includes a step of arranging the plurality of substrates on which the light emitting diodes are fixed on the housing at different angles.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As a result of various experiments, the inventor of the present application has performed a wide viewing angle without impairing the light emission characteristics by tilting the light-emitting diode for improving visibility by tilting the linear lead terminal with respect to the substrate instead of bending the lead terminal. It was found that the LED display can be made, and the present invention has been made.
[0009]
That is, when the linear lead terminal is inclined and penetrated with respect to the substrate as in the present invention, it is considered that it is difficult to be affected by external force or stress due to temperature change. Specifically, since the lead terminal itself is linear, it is strong against bending stress, and deterioration due to metal fatigue, lead plating damage, etc., and deterioration of color mixing due to bending variations are unlikely to occur. In addition, since the opening is large and the amount of solder between the linear lead terminal and the conductive pattern provided on the substrate is large, it has good adhesion to the conductive pattern, lead terminal, etc., and also has high heat dissipation and stable light emission characteristics. Can be Therefore, the LED display of the present invention is an LED display that is excellent in visibility without deteriorating the light emission characteristics of the substrate and the lead terminal by adjusting the light emitting diode directivity angle by the inclination angle of the linear lead terminal with respect to the substrate. Can be a container. Hereinafter, the photoelectric conversion device of the present invention will be described with reference to the drawings.
[0010]
As shown in FIGS. 1 and 2, the lead terminal 201 of the light emitting diode 102 is linearly inserted into the opening of the substrate 101, and is gradually inclined from one end of the substrate to the other end. The light emitting diode 102 is electrically connected and fixed by the conductive pattern 202 of the substrate 101 and the solder 203. The same substrate on which the light emitting diodes 102 are formed is arranged in the casing so as to be line-symmetrical by changing the direction. A filler 103 is disposed between the light emitting diode 102 and the housing 104 for the purpose of protecting the substrate from moisture, dust, and external force from the outside. In addition, a light shielding member 105 is fitted in the housing to shield extraneous light. The LED display formed in this way can improve the visibility from the left-right direction. Hereinafter, each configuration of the present invention will be described in detail.
[0011]
(Substrate 101)
The substrate 101 used in the present invention is used for arranging and electrically connecting the light emitting diodes 102 in a desired arrangement and a desired angle. Further, it may also be used as a substrate for a drive circuit. The arrangement of the light emitting diodes may be a matrix shape when used for a display. In addition, when diverting to a desired application such as an arrow signal, a light emitting diode may be arranged in accordance with its shape.
[0012]
As the substrate 101 of the present invention, a substrate having high mechanical strength and little thermal deformation is preferable. Specifically, ceramic substrates on which conductors such as copper foil are formed, metal substrates such as glass and aluminum, and printed substrates using various resins can be suitably used. Since the surface of the substrate on which the light emitting diode is mounted coincides with the LED display surface, it is preferable that the substrate surface is colored to improve contrast. Further, in order to improve the adhesion with the filler, sand blasting may be performed to form irregularities. Furthermore, by changing the direction of the substrate on which each light emitting diode is mounted at a desired angle without bending the lead terminal and arranging it symmetrically in the housing, the substrate can have different inclination angles. Thereby, mass productivity can be improved.
[0013]
(Board opening)
The opening part of the board | substrate of this invention is a hole for the linear lead terminal 201 penetration provided in the board | substrate. Usually, the through-hole is opened slightly larger than the lead terminal diameter so that the lead terminal 201 of the light emitting diode can be easily fixed perpendicularly to the substrate and for the mounting process of the electronic component automatic insertion machine. On the other hand, the opening of the present invention is smaller than the stopper attached to the lead terminal 202 but larger than the lead terminal diameter, and is actively opened to a size that allows the light emitting diode to form a desired inclination with respect to the substrate. Yes. This difference in aperture diameter can increase the viewing angle of the LED display without forming internal stress as a result. Further, the connection area between the lead terminal and the substrate can be increased to improve the adhesion. The opening diameter can be variously selected depending on the size of the stopper provided on the lead terminal, the thickness of the substrate, and the performance of the mounting device. As for the inclination angle of the lead terminal that can be determined by the opening diameter and the lead terminal diameter, the maximum inclination angle with respect to the substrate is preferably 40 degrees to 140 degrees in order to fix the lead terminals without causing poor contact even in solder mounting. In addition, since the opening of the substrate is larger than the conventional one, it is necessary to cut the lead terminal penetrating the substrate longer in consideration of making the lead terminal oblique. Thereby, it is possible to efficiently dissipate the adhesion to the substrate and the heat generation of the light emitting diode.
[0014]
(Light emitting diode 102)
As the light emitting diode 102 used in the present invention, a light emitting element formed by molding various optical semiconductor elements with resin is used. One type of semiconductor element in the light emitting diode may be used for single color emission, or a plurality of semiconductor elements may be used for single color or multicolor emission. Specifically, a material in which a semiconductor such as GaAlN, ZnS, ZnSe, SiC, GaP, GaAlAs, AlInGaP, InGaN, GaN, and AlInGaN is formed as a light emitting layer on a substrate by liquid phase growth method or MOCVD method is preferably used. It is done. Examples of the structure of the semiconductor element include a homo structure having a MIS junction and a PN junction, a hetero structure, and a double hetero structure. Depending on the material of the semiconductor layer and the degree of mixed crystal, the emission wavelength can be selected from ultraviolet light to infrared light. Furthermore, the light emitting layer may have a single quantum well structure or a multiple quantum well structure in order to give a quantum effect. A desired electrode is formed on the semiconductor thus formed by vapor deposition, sputtering, CVD, or the like to form an LED chip. After each electrode of such an LED chip is electrically connected to a lead terminal or the like using an electrical connecting member such as a gold wire or silver paste, a light emitting diode can be formed by covering with a mold member.
[0015]
In addition, when the LED display is used in an environment with relatively strong external light such as outdoors, it is preferable to use a gallium nitride compound semiconductor as a green system and a blue system, and in the red system, a gallium / aluminum / arsenic system is used. A semiconductor or an aluminum / indium / gallium / phosphorous semiconductor is preferably used. Moreover, it can also be set as the multicolor light emitting element which has arrange | positioned multiple LED chips from which a wavelength differs depending on necessity on the cup provided in the lead terminal. For example, two LED chips, one green chip and one red chip, are installed on the lead terminals. In order to use a light emitting diode as a full-color LED display, it is necessary to use a light emitting diode using a semiconductor having a red emission wavelength of 600 nm to 700 nm, a green color of 495 nm to 565 nm, and a blue emission wavelength of 430 nm to 490 nm. preferable.
[0016]
The mold of the light emitting diode is provided to protect each LED chip, the electrical connection member, and the like from the outside and enhance directivity. In general, an epoxy resin is used. Moreover, a lens effect can be given by making a resin mold into a desired shape. The resin mold uses a plurality of types of resins, and may have a convex lens shape, a concave lens shape, or a laminated structure in which a plurality of them are combined. Furthermore, it can also serve as a filter that cuts off undesired wavelengths by coloring the mold itself by attaching a paint or containing dyes and pigments in the mold member. Moreover, directivity can also be eased by containing a diffusing agent in the mold member. As such a diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide or the like is preferably used. As a material for the resin mold, a transparent resin having strength and excellent weather resistance such as epoxy resin, urea resin, silicone resin, fluororesin, and polycarbonate resin is preferably used.
[0017]
(Housing 104)
The housing 104 mechanically protects the light emitting diodes arranged in a desired shape such as a matrix on the substrate from the outside, and can be formed in a desired size. As the housing, a material having a small coefficient of thermal expansion is preferable in consideration of adhesion to the filler. Moreover, it is preferable that the housing has an inclination angle so that the substrate can be inclined as desired to compensate for the inclination of the light emitting diode. Furthermore, as materials for the housing, polycarbonate resin, ABS resin, epoxy resin, phenol resin, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), acrylic resin, PBT resin, etc. are used from the viewpoint of ease of molding and weather resistance. preferable. Further, the inner surface of the housing may be embossed to increase the adhesion area, or plasma treatment may be performed to improve the adhesion with the filler.
[0018]
(Filler 103)
The filler 103 is provided to protect the internal circuit of the LED display from moisture, dust, and external force. Accordingly, the filler 103 is required to have mechanical strength and weather resistance. In addition, good adhesion to the light emitting diode 102, the housing, the substrate on which the light emitting diode is disposed, the light shielding member, and the like is also required. Specific examples of such a filler 103 include epoxy resin, urethane resin, and silicone resin. Further, a dark colored dye may be contained in the filler for improving the contrast. Furthermore, a heat conductive member may be included for the purpose of improving heat conduction, or a resin with high heat dissipation may be used. Since the heat conducting member is also disposed between the light emitting diodes, it is required not to conduct electricity. Specifically, copper oxide and silver oxide are preferable. Examples of the heat radiating resin include heat radiating silicone.
[0019]
(Light shielding member 105)
As the light shielding member 105, each of the light emitting diodes 102 is prevented from being difficult to be visually recognized by external light. More preferably, the light shielding member is colored black or the like for the purpose of suppressing reflected light. It is preferable that the angle of the light shielding member can be changed according to the viewing distance. In this case, it can be selected as desired depending on the viewing angle and distance, but preferably from 80 degrees to 100 degrees with respect to the substrate.
[0020]
(Jig 301)
The jig 301 used in the present invention is for fixing various inclinations of the light emitting diode 102 with respect to the substrate 101 as desired, and various types can be used. Specifically, as shown in FIG. 3, members 303 having holes 303 into which the light emitting diodes can be inserted are fixed by screws 302 or the like. In order to change the inclination angle of the light-emitting diode with respect to the substrate using such a jig, the light-emitting diodes are arranged in the openings of the substrate and the lead terminals are cut to a desired length, and then FIG. The light emitting diode 102 is inserted and fixed in the hole 303 of the jig described in the above. Fixing is performed by soldering the wiring pattern of the substrate and the respective lead terminals of the light emitting diode with the fixed jig attached.
[0021]
(Driving means)
The drive means is electrically connected to an LED display having a lighting circuit or the like and a plurality of light emitting diodes arranged therein. Specifically, an LED display arranged in a matrix or the like is driven by an output pulse from the drive circuit. As a drive circuit, a RAM (Random Access Memory) that temporarily stores input display data and a gradation signal for lighting a light emitting diode to a predetermined brightness are calculated from the data stored in the RAM. A gradation control circuit; and a driver that is switched by an output signal of the gradation control circuit to turn on the light emitting diode. Such a driving means can be formed using a CPU. The gradation control circuit calculates the lighting time of the light emitting diode from the data stored in the RAM and outputs a pulse signal. A gradation signal, which is a pulse signal output from the gradation control circuit, is input to the driver of the light emitting diode to switch the driver. The light emitting diode can be turned on when the driver is turned on and turned off when the driver is turned off. Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to specific examples.
[0022]
[Example 1]
A gallium nitride semiconductor having a PN junction is formed on a sapphire substrate using MOCVD as an optical semiconductor element. Thereafter, P-type and N-type electrodes are respectively formed on the semiconductor using a sputtering apparatus, and the sapphire substrate is individually divided to obtain LED chips. Next, the LED chip is die-bonded using a die bonder on a cup provided on a lead terminal having a lead terminal diameter of 0.5 mm. The die-bonded LED chip is wire-bonded between the electrode of the LED chip and the lead terminal with a gold wire as an electrical connection member. This was cured into a bullet shape with epoxy resin as shown in FIG.
[0023]
The light-emitting diodes thus formed are placed on a 1.6 mm thick printed circuit board having an aperture diameter of 1.5 mm and arranged in a matrix with an electronic component automatic insertion machine, and extra lead terminals are cut longer. The maximum inclination angle of the light emitting diode at this time is 35 degrees with respect to the substrate. The substrate on which the light emitting diodes are arranged on the substrate is fitted and fixed to a jig as shown in FIG. 3 in order to make the light emitting diodes have respective desired angles. As a result, the light emitting diode at one end is fixed at an inclination angle of 75 degrees with respect to the substrate, and the light emitting diode at the other end is fixed at 125 degrees, which is the maximum inclination angle with respect to the substrate. The inclination angle is 100 degrees. The fixed substrate is simultaneously soldered and fixed by an automatic soldering apparatus.
[0024]
After removing the jig, the two substrates on which the respective light-emitting diodes are mounted at a desired angle without changing the lead terminals are changed in direction and arranged symmetrically with respect to the approximate center line of the housing, and the left and right inclination angles 15 It was fixed in the case set at the time. In the case, an LED display was formed by injecting and curing the filler to such an extent that the tip of the mold part of the light emitting diode was exposed. The light-emitting diodes are tilted from a tilt angle of 90 degrees, which is the front of the housing, to a maximum of 140 degrees. Accordingly, the viewing angle can be increased while suppressing a decrease in luminance from the front of the LED display. One thousand such LED displays were produced and connected to a drive circuit and a power source, respectively. Both can emit light well. The LED display in which the light emitting diode was repeatedly turned on and off every 10 minutes was subjected to a temperature cycle of −20 ° C. for 1 hour and a temperature cycle of 80 ° C. for 1 hour, and the weather resistance was examined. In any of the LED displays, it was not possible to confirm light emission unevenness or characteristic deterioration due to peeling of the electrical connection member or peeling of the solder.
[0025]
[Comparative Example 1]
This was carried out except that the opening of the substrate was 0.6 mm, the light emitting diodes were arranged vertically with respect to the flexible substrate, and after fixing by soldering, the light emitting diodes were inclined from 75 to 125 degrees with respect to the substrate, and the substrate was arranged as shown in FIG. Formed as in Example 1. The light emission characteristics were examined by the same temperature cycle test as in Example 1. When the LED is bent at an angle of 85 to 95 degrees, the average defect occurrence rate that causes uneven light emission and characteristic deterioration is 3% or less, whereas the average defect occurrence of the light emitting diode bent to 85 degrees or less or 95 degrees or more is generated. The rate is over 21%.
[0026]
【The invention's effect】
With the configuration of the present invention as described above, an LED display having a wide vertical, horizontal, and horizontal viewing angle can be easily manufactured without deteriorating the light emission characteristics of the light emitting diode even in a severe environment.
[0027]
[Brief description of the drawings]
FIG. 1 is a schematic view showing an LED display according to the present invention, FIG. 1 (A) is a schematic front view showing the LED display according to the present invention, and FIG. 1 (B) is a diagram of FIG. 1 (A). It is AA sectional drawing.
FIG. 2 is a partially enlarged view of a linear lead terminal used in the present invention passing through a substrate.
3A and 3B are schematic views of a jig for tilting each light emitting diode with respect to the substrate of the present invention. FIG. 3A is a schematic plan view of the jig, and FIG. 3B is a plan view of FIG. It is AA sectional drawing of).
4 is a schematic view showing an LED display shown for comparison with the present invention, FIG. 4 (A) is a schematic front view showing the LED display, and FIG. 4 (B) is FIG. It is AA sectional drawing of A).
[Explanation of symbols]
101 ... Inclined substrate 102 ... Light-emitting diodes with linear lead terminals 103 ... Filler 104 ... Housing 105 ... Shading member 201 ... Linear lead terminal 202 ... Pattern wiring 203 provided on the substrate Solder 301 Jig 302 for fixing the light emitting diode in an inclined manner Adjusting screw 303 for adjusting the inclination angle of the light emitting diode Inserting hole for the light emitting diode 401 ... Inclined flexible substrate 402 ... Light emitting diode 403 with lead terminals bent ... Filler 404 ... Housing 405 ... Light shielding member

Claims (3)

A method for forming an LED display, comprising: a plurality of light emitting diodes having lead electrodes and a mold member; a substrate on which the light emitting diodes are arranged at different inclination angles; and a housing on which the substrate is arranged.
Placing the light emitting diode lead electrode in the opening of the substrate;
Fixing the light emitting diode by inserting the mold member into the hole in a jig having a plurality of holes each having an inclination angle adjusted with respect to the substrate;
And a step of fixing the lead electrode of the light emitting diode to the substrate in a state where the jig is attached.   The method for forming an LED display according to claim 1, further comprising a step of removing the jig after fixing the lead electrode to the substrate.   The method for forming an LED display according to claim 1, further comprising a step of arranging the plurality of substrates on which the light emitting diodes are fixed on the housing at different angles.

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