JP2002217459A - Light-emitting diode, and backlight device of liquid crystal display using the light-emitting diode as light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting diode which can efficiently extract the light emitted from a LED chip from a light-emitting surface, and also to provide a backlight device using the same. SOLUTION: The LED chip 4 is electrically connected by flip-chip bonding to a pair of external electrodes 3 on a substrate 2 via bumps 5. On the substrate 2, whereon the LED chip 4 is flip-chip bonded, a lamp house 6, having a through- hole 6a surrounding the LED chip 4 is provided. The through-hole 6a is filled with a molding resin 8. By controlling the height and tilt angle of the through- hole 6a of the lamp house 6, the directional characteristics of the light emitting diode 1 can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode used as a light source for a backlight device of a liquid crystal display section of a notebook personal computer, a portable telephone, or the like, and the light emitting diode is arranged at an end of a light guide plate. And a backlight device.

[0002]

2. Description of the Related Art Heretofore, as a light source for a backlight device of this type, a light guide plate provided with a cold cathode fluorescent tube (CFL) or an electroluminescent (EL) element on an end face has been used. However, a device using a CFL or EL element as a light source requires a lighting circuit such as an inverter, and thus has a problem in that the overall size is increased.

[0003] Therefore, there has been proposed a backlight device using a light emitting diode having a feature of being small in size, having a long service life and low power consumption as a light source. The light emitting diode 90 used in this type of backlight device is configured as shown in, for example, FIGS. 5 and 6, FIG. 5 (a) is a plan view, FIG. 5 (b) is a vertical sectional view, and FIG. Diode 9
FIG. 9 is a perspective view showing a state where the light emitting device is mounted on a printed circuit board 96 when 0 is used as a light source of a backlight device.

A light emitting diode 90 shown in FIG. 5 has an LED chip 91 fixed on a plate-like insulating substrate 93 on which an electrode pattern forming a pair of external electrodes is appropriately formed.
The electrodes of the chip 91 and the electrode patterns on the insulating substrate 93 are electrically connected by wires 92 such as gold wires. The substrate 93 on which the LED chip 91 is mounted is sealed with a substantially semi-cylindrical mold resin 94.

At this time, since the light emitting diode 90 is required to emit white light as a light source for a backlight device of a liquid crystal display portion for performing full color display, an LED chip 91 is required.
For example, GaN, GaAlN, InGaN, In
A light-emitting layer is formed from a nitride-based compound semiconductor such as GaAlN, ZnSe (zinc selenide), or the like.
m, which emits blue light, and this LED chip 9
As the mold resin 94 for sealing the entire structure, a resin in which an yttrium / aluminate phosphor having a garnet structure is uniformly dispersed in an epoxy resin is used. As a result, the phosphor absorbs a part of the blue light emitted from the LED chip 91 and converts it into light (yellow-orange) having a wavelength longer than the wavelength of the blue light of the LED chip 91, The yellow-orange light converted in wavelength by the phosphor and the blue light from the LED chip 91 are mixed into white light, and the mixed white light is emitted to the outside. FIG. 8 shows an emission spectrum of the light-emitting diode 90, in which white light is obtained by mixing color of blue light having a peak near 470 nm and yellow-orange light having a peak near 570 nm. .

Next, as a method of manufacturing the light emitting diode 90, first, a plurality of LED chips 91 are die-bonded on a substrate 93 on which a plurality of electrode patterns corresponding to each light emitting diode 90 are formed. The electrodes and the electrode pattern on the insulating substrate 93 are connected to wires 92 such as gold wires.
To make an electrical connection. Then, the LED chip 91
The mold resin 94 in which the phosphor is uniformly dispersed is hardened into a substantially semi-cylindrical shape by transfer molding or the like on the substrate 93 on which is mounted, and is sealed. Thereafter, the substrate 93 is cut, and individual light emitting diodes 90 are formed.

The light emitting diode 90 thus formed
As shown in FIG. 6, the substrate 93 is placed on a printed circuit board 96 such that the substrate 93 has a vertical direction, that is, the light emitting direction is horizontal to the direction of the printed circuit board 96, and the external electrode pattern of the substrate 93 of the light emitting diode 90 is printed. The wiring pattern on the substrate 96 is soldered 95 so that electrical connection is achieved and fixed. Then, as shown in FIG. 7, on a printed circuit board 96 on which the light emitting diode 90 is mounted, a light guide plate 97 having a semicylindrical recess 97a formed on an end face in which a molding resin 94 of the light emitting diode 90 is fitted.
, And a liquid crystal display 99 supported by a frame 98 is mounted thereon to assemble a liquid crystal display unit 100. Although not particularly shown, the light guide plate 97 is formed of a translucent material such as an acrylic resin, and the upper surface is appropriately diffused to obtain uniform surface light emission. In order to increase the reflectance and efficiently guide the light to the light emitting surface, an appropriate reflecting member is provided.

As described above, the conventional liquid crystal display unit 100 is configured, and the light from the light emitting diode 90 is transmitted through the recess 97.
a, the light enters the light guide plate 97, is reflected by the reflection member on the lower surface of the light guide plate 97, or is directly incident on the upper surface of the light guide plate 97, and is diffused by the diffusion processing performed on the upper surface of the light guide plate 97 to be uniformly spread. It emits light and illuminates the liquid crystal display 99 from behind to display on the liquid crystal display unit 100.

[0009]

However, such a conventional light emitting diode 90 requires a plurality of LED chips 9.
Since the individual light emitting diodes 90 are manufactured by a method of cutting the resin-molded substrate 93 on which 1 is mounted, light leaks from the side surface (cut surface) of the mold resin 94 which is not in contact with the end surface of the light guide plate 97. There is a problem that luminous efficiency is poor. In addition, in order to control the directivity of the light emitting diode 90, it is necessary to change the lens shape (the shape of the mold resin 94), and there is a problem that changing the mold requires cost and labor. Further, in recent years, the liquid crystal display unit 100 of such a mobile phone has been required to be thinner and have higher luminance. In order to make the liquid crystal display unit 100 thinner, it is necessary to make the light guide plate 97 thinner. However, in the conventional light emitting diode 90, the luminous efficiency is further reduced, and it is inevitable to increase the number of the light emitting diodes 90 in order to increase the brightness of the liquid crystal display unit, which is a factor of cost increase. However, solving these problems has been an issue.

[0010]

According to the present invention, as a specific means for solving the above-mentioned conventional problems, there is provided a substrate on which an LED chip and a pair of external electrodes respectively connected to electrodes of the LED chip are formed. And a mold resin covering a light emitting surface of the LED chip, wherein the LED chip is electrically connected to a pair of external electrodes on the substrate by flip chip bonding via bumps, A light emitting diode, wherein a lamp house having a through hole surrounding the periphery of the LED chip is mounted on a substrate to which the LED chip is flip-chip bonded, and the through hole is filled with the molding resin. Is to solve the problem.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on an embodiment shown in the drawings.

FIGS. 1 and 2 show a first embodiment of a light emitting diode 1 according to the present invention. FIG.
FIG. 2 shows a plan view. This light emitting diode 1
An electrode pattern 3 forming a pair of external electrodes is formed on a plate-shaped insulating substrate 2, and an LED chip 4 is fixed on the electrode pattern 3. The LED chip 4 has a pair of positive and negative electrodes on the back side, and each of these electrode portions is connected to each of a pair of external electrodes of the electrode pattern 3 on the substrate 2 by a bump 5 such as an Au bump or a solder bump. And is so-called flip-chip bonded. At this time, the material of the LED chip 4 is, for example, GaN, GaAlN, InGaN, InGaN, or the like.
A light-emitting layer is formed from a nitride-based compound semiconductor such as GaAlN, ZnSe (zinc selenide), or the like.
m, a device that emits blue light.

Further, the lamp house 6 is placed on the substrate 2 on which the LED chip 4 is flip-chip bonded.
Are provided by bonding with an adhesive 7. At this time, a through hole 6a having a substantially elliptical horizontal cross section is formed in the lamp house 6, as shown in FIG. 2, and the LED chip 4 is accommodated in the through hole 6a.
At this time, as shown in FIG. 1, the through hole 6a has an inner surface inclined so that the opening diameter decreases from the upper surface to the lower surface, and the light is emitted from the LED chip 4 toward the inner surface of the through hole 6a. By reflecting the light on the inner surface and outputting the light upward, the light emitted from the LED chip 4 can be efficiently extracted from the emission surface.

The material of the lamp house 6 is desirably a material having a high reflectance of light from the LED chip 4, excellent heat resistance, and easy to form. For example, nylon-based materials such as polyphthalamide (trade name: Amodel) And thermoplastic resins such as various liquid crystal polymers such as Vectra (trade name).
If necessary, various ceramics such as silica and titanium oxide, glass fibers, and the like are blended in an amount of about 50 wt%, whereby a material having a high heat resistance of a deflection temperature under load of 240 ° C. or higher can be obtained. Furthermore, the through hole 6 of the lamp house 6
On the inner surface of a, a film made of a high-reflectance material such as a metal such as Al, Ag and W or a metal oxide such as TiO ₂ is formed, or the light from the LED chip 4 is coated by applying a white pigment. Processing for increasing the reflectance can be performed.

Then, a mold resin 8 in which an yttrium-aluminate-based phosphor having a garnet structure is uniformly dispersed in an epoxy resin or the like is placed in a through hole 6a of a lamp house 6 bonded to the substrate 2. Inject and LE
The entire periphery of the D chip 4 is sealed with a mold resin 8, and the mold resin 8 is cured to fix the phosphor, thereby forming the light emitting diode 1. By this, LED
The phosphor absorbs a part of the blue light emitted from the chip 4 and converts it into light (yellow orange) having a wavelength longer than the wavelength of the blue light of the LED chip 4. The wavelength-converted yellow-orange light and the blue light from the LED chip 4 are mixed to form white light, and the mixed white light is reflected directly or by the inner surface of the through hole 6a of the lamp house 6. And is emitted from the emission surface to the outside.

The light emitting diode 1 thus formed is
As shown in FIG.
The substrate 2 is placed so that the vertical direction, that is, the light emitting direction is horizontal to the direction of the printed circuit board 9, and the light emitting diode 1
The external electrode pattern 3 of the substrate 2 and the wiring pattern on the printed circuit board 9 are soldered to achieve electrical connection and are fixed. Then, the light guide plate 10 is mounted on the printed board 9 on which the light emitting diodes 1 are mounted, and the backlight device 11 is assembled. Further, a liquid crystal display (not shown) is mounted thereon to assemble a liquid crystal display. Although not specifically shown, the light guide plate 10 is formed in a thin plate shape with a light-transmitting material such as an acrylic resin, and the upper surface is subjected to a diffusion process to obtain uniform surface light emission, or the lower surface is subjected to a diffusion process. In order to increase the internal reflectivity and efficiently guide light to the light emitting surface, a reflecting member or the like is appropriately provided.

At this time, the light emitting surface of the light emitting diode 1 is parallel and close to the end face of the light guide plate 10, and the height of the light emitting diode 1 is substantially equal to the vertical length (thickness) of the end face of the light guide plate 10. It is formed with the same length. That is, the lamp house 6 of the light-emitting diode 1 is formed in a rectangular parallelepiped shape having a horizontally long cross section in accordance with the vertical length of the end face of the light guide plate 10. Along the long axis, a long axis is formed in a horizontally long elliptical shape along the horizontal direction of the end surface of the light guide plate 10. The substrate 2 is naturally formed in a horizontally long rectangular shape in accordance with this.

By forming the light-emitting diode 1 as described above, the directional characteristics of the light-emitting diode 1 can be controlled by controlling the height and the inclination angle of the through hole 6a of the lamp house 6. This not only increases the degree of freedom in designing the device, but also prevents light leakage from the side (cut surface) that is not in contact with the end surface of the light guide plate, which was a problem of the conventional light emitting diode, and the light intensity of the backlight device Can be enhanced.

Further, since the LED chip 4 has a structure in which the LED chip 4 is flip-chip bonded on the substrate 2, the light extraction efficiency is improved as compared with the conventional wire-bonded structure, and the wire is cut off during resin molding. It is also possible to prevent a light emitting diode from being turned off accidentally.

Further, by configuring the entire liquid crystal display section in this way, light emitted from the light emitting diode 1 enters the light guide plate 10 from the end face of the light guide plate 10 and is reflected by the reflection member on the lower surface of the light guide plate 10. Or directly incident on the upper surface of the light guide plate 10 and diffused by a diffusion process performed on the upper surface of the light guide plate 10 to uniformly emit light, and illuminate the liquid crystal display from behind to perform display on the liquid crystal display unit. It is.

In the above embodiment, the phosphor dispersed in the mold resin 8 of the light emitting diode 1 is an yttrium / aluminate phosphor having a garnet structure. When a phosphor doped with Ce) and praseodymium (Pr) is used, 610 is obtained as shown in the graph of the emission spectrum shown in FIG.
New peaks appear in the vicinity of nm and 630 nm, and the emission in the red region increases, whereby a white light emitting diode having good color rendering properties can be obtained. This means that, when used as a light source for a backlight device of a full-color liquid crystal display unit, a conventional white light emitting diode has 600 n as shown in FIG.
In this case, bright and warm white light emission can be obtained by increasing the light in the red region from what was observed as a dark and warm display with little light emission in the red region of m or more.

In the above embodiment, the blue LED
Although a light-emitting diode that emits white light using a chip and a phosphor has been described as an example, the present invention is not limited to this, and other light-emitting colors required as a light source for a backlight device of a liquid crystal display unit may be used. LE that emits color
A light emitting diode that emits mixed colors by appropriately combining a D chip and a phosphor may be used, and the phosphor does not need to be mixed into the mold resin as long as the LED chip emits light of a required color.

In the above embodiment, the through hole of the lamp house 6 of the light emitting diode 1 has been described as having a substantially elliptical shape. However, the present invention is not limited to this, and may be circular depending on the thickness and size of the light guide plate. It may be square or rectangular.

The number of the light emitting diodes 1 used in the backlight device 11 is also appropriately selected according to the size of the liquid crystal display unit, and is not limited to the above embodiment.

[0025]

As described above, according to the present invention, L
The ED chip is electrically connected to a pair of external electrodes on the substrate by flip chip bonding via bumps, and a through hole surrounding the LED chip is provided on the substrate on which the LED chip is flip chip bonded. By attaching a lamp house having a light emitting diode in which the resin is filled in the through hole,
By controlling the height and inclination angle of the through hole in the lamp house, the directional characteristics of the light emitting diode can be controlled, which not only increases the degree of freedom in designing a backlight device, but also increases the Light leakage from a side surface (cut surface) that is not in contact with the end surface of the light guide plate, which is a problem, can be prevented, and the amount of light of the backlight device can be increased. In addition, because the LED chip is flip-chip bonded on the substrate, the light extraction efficiency is improved as compared with the conventional wire-bonded structure, and the light-emitting diode is turned off due to wire cutting during resin molding. Can also be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a light emitting diode according to the present invention.

FIG. 2 is a plan view showing a first embodiment of a light emitting diode according to the present invention.

FIG. 3 is a plan view showing a backlight device using a light emitting diode according to the present invention.

FIG. 4 is a graph showing an emission spectrum of the light emitting diode according to the present invention.

5A and 5B are explanatory views showing a light emitting diode in a conventional example, where FIG. 5A is a plan view and FIG. 5B is a cross-sectional view.

FIG. 6 is a perspective view showing a state in which a light emitting diode in a conventional example is mounted on a printed circuit board.

FIG. 7 is a plan view showing a conventional backlight device using light emitting diodes.

FIG. 8 is a graph showing an emission spectrum of a light emitting diode in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light emitting diode 2 ... Substrate 3 ... Electrode pattern 4 ... LED chip 5 ... Bump 6 ... Lamp house 6a ... Through-hole 7 ... Adhesive 8 ... Mold resin 9 ... Printed circuit board 10 ... ... Light guide plate 11 ... Backlight device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // F21Y 101: 02 F21Y 101: 02 F-term (reference) 2H091 FA23Z FA45Z FB02 LA09 LA16 4M109 AA01 BA03 CA21 DB14 EB18 GA01 5F041 AA04 AA06 AA14 CA34 CA40 CA43 DA09 DA20 DA43 DA74 DA75 DA78 DB09 EE25 FF11

Claims (4)

[Claims] 1. A light emitting diode comprising: an LED chip; a substrate on which a pair of external electrodes connected to electrodes of the LED chip are formed; and a mold resin covering a light emitting surface of the LED chip. The LED chip is electrically connected to the pair of external electrodes on the substrate by flip chip bonding via bumps, and the LED chip is provided on the substrate to which the LED chip is flip chip bonded and surrounds the periphery of the LED chip. A light emitting diode, wherein a lamp house having a hole is attached, and the mold resin is filled in the through hole. 2. The LED chip emits blue light, and the mold resin has a phosphor that absorbs a part of the light emitted from the LED chip and generates light having a longer wavelength than the light emitted from the LED chip. The light emitting diode according to claim 1, wherein the light emitting diode emits white light by being mixed and mixed with light emitted from the LED chip and light generated from the phosphor. 3. The light emitting diode according to claim 2, wherein said phosphor is a phosphor obtained by doping cerium and praseodymium as an inactivating agent to an yttrium aluminate phosphor having a garnet structure. . 4. A light emitting diode according to claim 1, wherein said light emitting diode is mounted on a printed circuit board so that a light emitting direction thereof is substantially horizontal to said printed circuit board. A backlight device for a liquid crystal display, wherein a light guide plate is provided on the printed circuit board so as to be parallel and close to each other at substantially the same height.