JPH11177129A - Chip type LED, LED lamp and LED display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the light-emitting efficiency of an LED by increasing the quantity of light to be incident from an LED light emitting element on a sealing body. SOLUTION: For this chip type LED 10, the LED light-emitting element 1 bonded to a printed wiring board 2 is covered with the sealing body and the sealing body is low melting point glass 3. The refractive index of the low melting point glass 3 is about 2 and the refractive index of the LED light emitting element 2 is about 2.3-4.0. In such a manner, by using the low melting point glass 3 as the sealing body, the light emitting efficiency is improved. Since the low melting glass 3 does not absorb moisture, the chip type LED 10 withstands the change of a using environment as well.

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 (LED) and an LED display used for various measuring instruments and outdoor guide boards for display.

[0002]

2. Description of the Related Art An LED light emitting element is bonded to a desired member such as a lead frame or a printed wiring board, and is molded with a sealing body made of a transparent resin. An epoxy resin is usually used for the sealing body. The LED light-emitting element emits light from the inside, and this light is emitted into the air via the epoxy resin.

[0003] As shown in FIG.
Is often bonded to the wire W via the electrode pad 5. Most of the light 6 from the light emitting point P is blocked by the bonding portion of the wire W. LE
In order to increase the luminous efficiency of D, as much light 6 as possible
It is necessary to emit light from the ED light emitting element 1 and make it incident on the epoxy resin 70. Considering an LED display in which a light diffusing agent is often added to the epoxy resin 70, increasing the amount of light 6 incident on the epoxy resin 70 from the LED light emitting element 1 is even more important in increasing the luminous efficiency. Becomes

[0004]

The amount of light incident on the epoxy resin 70 from the LED element 1 depends on the refractive index of the LED element 1 (hereinafter n _L ) and the refractive index of the epoxy resin 70 (n _E). ). Refractive index of air (hereinafter, n _a) when the a 1, n _E is usually about 1.5. n _L differs depending on the material of the LED 1. Specifically n _L about 3.4 GaP-based LED light emitting element is, n _L is about 2.3 of the GaN-based LED light emitting element, n _L of LED light emitting elements for the sapphire substrate is usually 4.0
It is about. The above n _L (≒ 2.3-4.0) and n
_In the ratio with _E (≒ 1.5), as shown in FIG.
Since the total reflection critical angle β at the boundary between the LED element 1 and the epoxy resin 70 is relatively small, the LED element 1
The amount of the light 6 which is totally reflected on the surface and returned to the element increases. Therefore, LE using epoxy resin 70 as a sealing body
D could not be said to have high luminous efficiency.

The present invention has been conceived under such circumstances, and has as its object to improve the luminous efficiency of LEDs and to maintain the quality of LEDs.

[0006]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means.

That is, a first aspect of the present invention relates to a chip-type LED in which an LED light emitting element bonded to a printed wiring board is covered with a sealing member, wherein the sealing member is made of low-melting glass. It is characterized by.

According to the present invention, an LED light emitting element is sealed with a low melting point glass to increase the amount of light incident on the low melting point glass as a sealing body from the LED light emitting element. LED
Part of the light emitted from the light emitting point in the light emitting element is the refractive index (n _G ) of the low melting glass and the refractive index (n _G ) of the LED light emitting element.
_L ), the light is totally reflected at the surface of the LED light emitting element and returned inside. The amount of light that can be incident from the LED element to the low melting point glass is determined by the critical angle of total reflection at the boundary between the low melting point glass is an LED light emitting element and the sealing member, the total reflection critical angle n _L and n It is determined by the ratio with _G. As the ratio becomes closer to 1, the critical angle for total reflection increases, and the amount of light totally reflected on the surface of the LED light emitting element and returned to the inside decreases. Light emitted from the LED light-emitting element is emitted into the air through a low-melting glass that is a sealing body.

Although the conventional chip type LED uses an epoxy resin as a sealing body, in the present invention, a low melting point glass is used as a sealing body. Low-melting glass has a melting point of about 400 ° C. and many of which have a high refractive index, and can be used as optical glass. The refractive index (n _G ) of low melting glass is about 2,
Specifically, it is in the range of 1.5 to 2.5.

As described above, the refractive index (n _G ) of the low-melting glass which is the sealing body in the present invention is about 2, and the refractive index (n _E ≒ 1.5) of the epoxy resin which is the conventional sealing body. )
The refractive index of the LED light emitting element (n _L ≒ 2.3-
4.0). Conventional chip type LED
, The ratio of n _L to n _G (n _G / n) in the chip-type LED of the present invention is higher than the ratio of n _L to n _E (n _E / n _L ).
_{Since L} ) is closer to 1, the critical angle of total reflection at the boundary between the LED light-emitting element and the sealing body in the chip-type LED of the present invention is larger than the critical angle of total reflection in the conventional chip-type LED. . By increasing the critical angle for total reflection, the amount of light emitted from the LED light-emitting element and entering the sealing body (low-melting glass) increases, and the luminous efficiency of the chip-type LED according to the present invention increases.

According to a second aspect of the present invention, in an LED lamp in which an LED light emitting element bonded to a lead frame is covered with a sealing member, the sealing member is made of low-melting glass. .

In the LED lamp of the present invention, the chip type L
As in the case of the ED, in order to increase the luminous efficiency, it is necessary to make as much light as possible incident on the sealing body. Conventional L
In an ED lamp, an epoxy resin (n _E ≒ 1.5) is a sealing body, but in the present invention, a low-melting glass (n _G ≒ 2) is a sealing body. Therefore, also in the LED lamp according to the present invention, the critical angle of total reflection at the boundary between the LED light emitting element and the sealing body is increased, and the amount of light incident from the LED light emitting element to the low melting point glass as the sealing body is reduced. As a result, the luminous efficiency of the LED lamp becomes higher than before.

In the LED display provided by the third aspect of the present invention, the LED light emitting device is bonded to a lead frame or a printed wiring board at the bottom of a segment window hole provided in a reflection case, and the LED light emitting device is provided. The element is sealed with a low-melting glass filled in the segment window and hardened.

Also in the LED display according to the present invention, a low-melting glass (n _G ≒ 2) is used as a sealing body for covering the LED light emitting element. Therefore, also in this case, the chip type LE
As already mentioned for D and LED lamps, L
The critical angle of total reflection at the boundary between the ED light emitting element and the sealing body increases, and the light incident on the low melting point glass from the LED light emitting element increases, so that the luminous efficiency of the LED display of the present invention is higher than before. .

In the present invention, the type of the low-melting glass is not particularly limited, but considering the refractive index and the melting point,
Lead glass is suitable. An LED light-emitting element sealed with lead glass can withstand a temperature around 400 ° C., which is the melting point of lead glass. Therefore, even if the lead glass is melted or hardened at a temperature around 400 ° C., the characteristics of the LED light emitting element do not change.

As described above, the chip type LE according to the present invention is provided.
D, LED lamps, and LED displays use a low-melting glass instead of an epoxy resin as a sealing body that covers the LED light emitting elements. Refractive index of low melting glass (n _G
(≒ 2.0) is the refractive index of the epoxy resin (n _E ≒ 1.5)
Higher than the refractive index of the LED light emitting element (n _L ≒ 2.3-
4.0). By sealing the LED light emitting element with low melting point glass, the amount of light that is totally reflected on the surface of the LED light emitting element and returns to the inside decreases, and the amount of light emitted from the LED light emitting element and incident on the low melting point glass increases. Become. As a result, the luminous efficiency of the chip-type LED or the like according to the present invention is higher than that of the conventional LED in which the LED light-emitting element is sealed with epoxy resin. Since the low melting point glass does not absorb moisture, the quality of the chip type LED or the LED display does not deteriorate even if the environment changes. Due to the ceramic substrate bonded to the low-melting glass, the chip type LED has higher heat resistance than before.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a chip type LED 1 according to the present invention.
FIG. 2 is a cross-sectional view of a main part showing one embodiment. Chip type LED
Reference numeral 10 mainly includes an LED element 1, a printed wiring board 2, and a low-melting glass 3 serving as a sealing body. The printed wiring board 2 has a wiring pattern 4 at a position where the LED light emitting element 1 and the wire W are bonded. LE
The D light emitting element 1 has an electrode 7 (see FIG. 2) electrically connected to the wiring pattern 4 on the entire bottom surface, and has an electrode pad 5 for wire bonding (see FIG. 2) on the upper surface. The refractive index (n _L ) of the LED light emitting element 1 varies depending on the material,
It is about 2.3 to 4.0. The low-melting glass 3 contains lead and has a refractive index (n _G ) of about 2.0.
The refractive index (n _E ) of an epoxy resin conventionally used as a sealing body is about 1.5.

The red and green LED light emitting elements 1 are GaP
It is manufactured using a conductive substrate such as a substrate or a GaAsP substrate. An n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer are sequentially laminated on the surface of the substrate. The LED light emitting element 1 has n
Light is emitted by the transition of electrons between the p-type semiconductor layer and the p-type semiconductor layer, and the material and the manufacturing process are different depending on the color of light emission.
For example, a GaP red LED has a light emitting layer in which GaP is doped with Zn and O. GaP red LED
Is as follows. First, an n-GaP layer, a light-emitting layer, and a p-GaP layer are sequentially formed on a GaP substrate by a liquid phase epitaxy (LPE) method. After polishing the obtained epiwafer, the electrode 5 is formed on the surface of the p-GaP layer, and the electrode 7 is formed on the back surface of the GaP substrate.
A plurality of LED light emitting elements 1 are obtained by dicing from the epi wafer.

FIG. 2 shows a chip type LED 1 according to the present invention.
FIG. 6 is a partially enlarged cross-sectional view showing a state of light emission by 0. Since the refractive index of the low melting point glass 3 (n _G ≒ 2.0) is lower than the refractive index of the LED 1 (n _L ≒ 2.3-4.0),
Part of the light 6 emitted from the light emitting point P in the LED light emitting element 1 is totally reflected on the surface of the LED light emitting element 1 and returned inside. Light 6 not totally reflected on the surface of LED light emitting element 1
Is interrupted at the bonding portion of the wire W. Therefore, in order to enhance the luminous efficiency of the LED, the amount of the light 6 totally reflected on the surface of the LED light emitting element 1 is reduced, that is, the total reflection critical angle α at the boundary between the LED light emitting element 1 and the low melting point glass 3. And the LED light emitting element 1
It is important to increase the amount of light 6 incident on the low-melting glass 3. When a light diffusing agent is added to the low melting point glass 3, it is more important to increase the amount of the light 6 incident on the low melting point glass 3 in order to increase the luminous efficiency of the LED.

Refractive index of low melting point glass 3 (n _G ≒ 2.0)
Is larger than the refractive index of the epoxy resin (n _E ≒ 1.5), and the refractive index of the LED 1 (n _L ．2.3-4.
0). Thus, the critical angle for total reflection α shown in FIG. 1 is larger than the critical angle for total reflection β shown in FIG. That is, the chip-type LED 1 of the above embodiment
At 0, the amount of light 6 that is totally reflected on the surface of the LED light emitting element 1 and returns to the inside is smaller than that of a conventional chip LED using an epoxy resin as a sealing body. Since the amount of light emitted from the LED light-emitting element 1 and incident on the low-melting glass 3, which is a sealing body, increases, the chip-type LED 10 has better luminous efficiency than the conventional one.

An example of a method for manufacturing the chip type LED 10 will be described below. First, a plurality of grooves are dug in the material substrate on which the wiring pattern 4 has been formed in the droplet portions on the front surface and the back surface, and a conductor film is formed on the inner surface of the groove. Next, the electrode 7 on the bottom surface side of the LED light emitting element 1 and the wiring pattern 4 of the rod-shaped part are bonded in a rod-shaped part between the grooves in the material substrate, and a wire bonding electrode pad on the upper surface of the LED light-emitting element 1 5 is bonded to a wire W. Wire W
Is bonded to the wiring pattern 4 and then covered with a mold made of, for example, carbon to cover the LED light emitting elements 1 and the wires W on the material substrate. The mold has a hole for sealing body injection. Liquid low-melting glass 3 is poured into the mold through this hole, and the low-melting glass 3 is solidified to be joined to the material substrate. After the joining is completed, the mold is removed, and the bar-shaped portion of the material substrate is cut in a direction perpendicular to the groove, whereby a plurality of chip-type LEDs 10 according to the present invention can be obtained.

Printed wiring board 2 in the above embodiment
In addition to the ceramics, a plate-like substrate made of synthetic resin or a metal substrate may be used.

FIG. 3 shows an LED lamp 30 according to the present invention.
It is principal part sectional drawing which shows one Example. LED lamp 30
Has leads 31, 32, and 33, the lower ends of which are soldered to a substrate (not shown). The lead 31 is formed with a concave reflecting dish 31a. The LED 1 is bonded to the reflection plate 31a. LE
The D light emitting element 1 is bonded to leads 32 and 33 via wires W. The peripheral portion of the reflection dish 31a is sealed with the low melting point glass 3. In addition, similarly to the above-mentioned chip type LED 10, the refractive index (n _L ) of the LED light emitting element 1 is about 2.3 to 4.0, and the refractive index (n _G ) of the low melting point glass 3 is about 2.0. is there.

Refractive index of low melting point glass 3 (n _G ≒ 2.0)
Is larger than the refractive index of the epoxy resin (n _E ≒ 1.5), and the refractive index of the LED 1 (n _L ．2.3-4.
0). As described above for the chip type LED 10, the above-described LE using the low melting point glass 3 as a sealing body
In the D lamp 30, the critical angle of total reflection at the boundary between the LED light emitting element 1 and the sealing body is larger than the critical angle of total reflection in a conventional LED lamp using an epoxy resin as a sealing body. In the LED lamp 30 of the above embodiment,
The amount of light 6 totally reflected on the surface of the LED light emitting element 1 is smaller than that of a conventional LED lamp using an epoxy resin as a sealing body. Therefore, the luminous efficiency of the LED lamp 30 is superior to the conventional LED lamp.

An example of a method for manufacturing the LED lamp 30 will be described below. First, the tip of a predetermined lead 31 of a lead frame (not shown) is subjected to pressure molding using a punch or the like to form a reflection plate 31a. LED on the bottom of the reflection dish 31a
The light-emitting element 1 is bonded, and the LED light-emitting element 1 and the ends of the leads 32 and 33 are bonded with a wire W.
Next, the liquid low-melting glass 3 is poured into a carbon mold for forming a lamp portion, and the leads 31, 32, and 33 are immersed in the low-melting glass 3. When the mold is removed after the low-melting glass 3 is solidified, the above-described LED lamp 30 can be obtained.

In the above embodiment, an example was described in which two LED light emitting elements 1 were bonded on the reflection plate 31a, but the present invention is not limited to this. The present invention can also be applied to an LED lamp to which one or three or more LED light emitting elements 1 are bonded.

FIG. 4 is a front view showing an embodiment of the LED display A according to the present invention. FIG.
It is 1-X1 line expanded sectional view. FIG. 6 is a cross-sectional view of X2-X in FIG.
It is a 2 line expanded sectional view.

This LED display A has a so-called 7
This is referred to as a segment type.
1. Lead frame 50 disposed on the back side of reflection case 11, LE bonded to lead frame 50
D light emitting element 1 is provided. The back surface of the lead frame 50 is sealed with an opaque dark synthetic resin 20.

On the surface (upper surface) of the reflection case 11, seven rod-shaped light-emitting segments 12 are arranged in an eight-shape. As shown in FIGS. 5 and 6, these light-emitting segments 12 are provided with a segment window hole 13 provided in the reflection case 11 and an LED light-emitting element bonded to a lead frame 50 at the bottom in the segment window hole 13. 1 and a low-melting glass 3 filled in the segment window hole 13 and hardened. The low melting point glass 3 contains a light diffusing agent. In addition, similarly to the case of the chip type LED 10 described above, the refractive index (n _L ) of the LED light emitting element 1 is about 2.3 to 4.0, and the refractive index (n _G ) of the low melting point glass 3 is 2.0. It is about.

The light emitted from the LED light emitting element 1 enters the low melting point glass 3 containing a light diffusing agent and diffuses in the segment window hole 13. Light diffusion causes the entire light-emitting segment 12 to appear shiny. Since the low melting point glass 3 contains a light diffusing agent, the amount of light incident on the low melting point glass 3 from the LED light emitting element 1 may be increased to increase the luminous efficiency of the LED display A.

Refractive index of low melting glass 3 (n _G ≒ 2.0)
Is larger than the refractive index of the epoxy resin (n _E ≒ 1.5), and the refractive index of the LED 1 (n _L ．2.3-4.
0). Therefore, when the low-melting glass 3 is used as a sealing body, the critical angle of total reflection at the boundary between the LED element 1 and the sealing body becomes larger than the critical angle of total reflection when the epoxy resin is used as the sealing body. . That is, L in the above embodiment
In the ED display A, the amount of light totally reflected on the surface of the LED light emitting element 1 is smaller than that of a conventional LED display in which an epoxy resin is sealed. Therefore, LED
The display A has higher luminous efficiency than the conventional LED display.

An example of a method for manufacturing the LED display A will be described below. First, masking is performed on the front surface side of the reflection case 11 so as to cover the upper opening portion of the segment window hole 13, and then the low melting point glass 3 is injected into the segment window hole 13 from the back surface side of the reflection case 11. Then
The LED light emitting element 1 bonded to the lead frame 50 is arranged at the bottom of the segment window 13 and the low melting point glass 3 is cured to obtain the LED display A.

In the above embodiment, an example of the LED display in which the LED light emitting element 1 is bonded to the lead frame 50 has been described, but the present invention is not limited to this. The present invention can be applied to an LED display in which the LED light emitting element 1 is bonded to a printed wiring board. Further, as an LED display in which the LED light emitting element 1 is bonded to a substrate, there is also a type in which a lead pin is attached to the substrate, and the present invention is applicable to any case.

As described above, in the chip type LED 10, the LED lamp 30, and the LED display A, the luminous efficiency is enhanced by using the low melting point glass 3 as a sealing body. Since the low melting point glass 3 does not absorb moisture, the above-mentioned chip type LED
10 and the like can withstand changes in the use environment.
By making the material of the printed wiring board 2 a ceramic in consideration of the bonding property with the low melting point glass 3, a chip type LED is provided.
The heat resistance of No. 10 is also improved.

As described above, the chip type LED according to the present invention, L
Although one embodiment of the ED lamp and the LED display has been described, the present invention is not limited to these, and various modifications can be made within the scope of the claims.
These include those in which each component is replaced with an equivalent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing one embodiment of a chip type LED according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a light emitting state of the chip type LED according to the present invention.

FIG. 3 is a cross-sectional view of a main part showing one embodiment of an LED lamp according to the present invention.

FIG. 4 is a front view showing an embodiment of the LED display according to the present invention.

FIG. 5 is an enlarged sectional view taken along line X1-X1 of FIG. 4; It is sectional drawing which shows one Example concerning this invention.

FIG. 6 is an enlarged sectional view taken along line X2-X2 in FIG. 4;

FIG. 7 is a partially enlarged sectional view showing a light emitting state of a conventional chip LED.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LED light emitting element 2 Printed wiring board 3 Low melting glass 6 Light 10 Chip type LED 11 Reflective case 12 Light emitting segment 13 Segment window hole 30 LED lamp 31,32,33 Lead 50 Lead frame W Wire A LED display

Claims (6)

[Claims] 1. A chip type LED in which an LED light emitting element bonded to a printed wiring board is covered with a sealing body.
In the ED, a chip-type LED, wherein the sealing body is made of low-melting glass. 2. The chip type according to claim 1, wherein the low melting point glass has a refractive index of about 2, and the LED light emitting element has a refractive index of about 2.3 to 4.0. L
ED. 3. An LED lamp in which an LED light emitting element bonded to a lead frame is covered with a sealing body, wherein the sealing body is made of low-melting glass. 4. The LED lamp according to claim 3, wherein the low melting point glass has a refractive index of about 2, and the LED light emitting element has a refractive index of about 2.3 to 4.0. . 5. An LED light emitting element is bonded to a lead frame or a printed wiring board at the bottom of a segment window provided in a reflection case, and
An LED display, wherein the light-emitting element is sealed with a low-melting glass filled in the segment window and hardened. 6. The LED display according to claim 5, wherein the low melting point glass has a refractive index of about 2, and the LED light emitting element has a refractive index of about 2.3 to 4.0. .