JP2007123410A - Glass-covered light emitting diode element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass-covered white LED element for overcoming a problem that much bubbles are left within the glass material of the glass-covered white LED element, and thereby transmittivity is lowered. <P>SOLUTION: The light emitting diode element 10 is covered with a glass material 1 in which phosphor material is dispersed. This light emitting diode element 10 may be manufactured by putting into a glass fusing vessel a mixed powder of the phosphor material powder and the glass powder to which the phosphor material is diffused, and one or more lumps of glass to which the phosphor material is diffused; and then obtaining the fused glass by heating the glass material together with the vessel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light emitting diode element (LED element) in which a light emitting diode (LED) is covered with glass in which a phosphor is dispersed, particularly a white LED element.

Conventionally, incandescent bulbs, fluorescent lamps and the like have been widely used as white light sources, but in recent years, so-called white LED elements have been developed as a new type of white light source, and their application to backlights for liquid crystal displays and the like has rapidly progressed. Yes.
In a one-chip type white LED element currently on the market, an LED having a quantum well structure using InGaN in which GaN is added with In as a light emitting layer is sealed with a resin containing a phosphor. In a typical white LED element, the LED is a blue LED having an emission wavelength of 460 to 480 nm, and the phosphor is a cerium-doped YAG phosphor that emits yellow fluorescence with light having the emission wavelength.

The white LED element functions as a white light source as follows. That is, when a direct current is passed through the LED, blue light is emitted from the LED, while the YAG phosphor is excited by a part of the blue light, and yellow light (fluorescence) is emitted from the phosphor. This blue light and yellow light are in a complementary color relationship, and they enter and enter the human eye and appear as white light due to the principle of additive color mixing.
However, in such a white LED element in which the LED is sealed with the resin, when it is used for a long period of time, moisture enters the resin and the operation of the LED is hindered. The resin is irradiated with ultraviolet light or blue light emitted from the LED. Discolored and the light transmittance decreased.

As a white LED element that solves such a problem, the present inventors expressed in mol%, TeO ₂ 20 to 70%, ZnO 5 to 30%, B ₂ O ₃ 0 to 55%, SiO ₂ + GeO ₂ 0 to 0%. 10%, Li ₂ O + Na ₂ O + K ₂ O 0-30%, MgO + CaO + SrO + BaO 0-20%, and a white LED element sealed with TeO ₂ —ZnO-based glass in which a phosphor is dispersed inside Etc. were proposed (see Patent Document 1).

JP 2005-11933 A

The glass-covered white LED element proposed in Patent Document 1 is manufactured by simply heating a mixture of glass powder and phosphor powder to cover the LED, and the white LED thus obtained is used. There was a problem that many bubbles remained in the coated glass of the element.
The object of the present invention is to provide a glass-covered LED element capable of solving such problems.

  The present invention is a light-emitting diode element covered with a glass in which a phosphor is dispersed, the glass comprising a glass powder in which the phosphor is to be dispersed and a mixed powder of the phosphor powder, Provided is a glass-covered LED element produced by placing one or more chunks of glass into which a body is to be dispersed in a glass melting vessel and heating the vessel to make the glass into molten glass.

According to the present invention, it is possible to obtain a white LED element in which phosphors are dispersed and covered with glass with less bubbles.
Further, such glass can be manufactured by a simple method called remelt.

FIG. 1 is a schematic sectional view of a glass-covered LED element of the present invention mounted on a wiring board, but the present invention is not limited to FIG.
In FIG. 1, an LED element 10 flip-chip mounted on a wiring board having wiring 20 formed on the surface of a substrate 30 is covered with glass 1 (phosphor dispersion glass) in which phosphors are dispersed. Has been.
A connection bump 21 is formed on an electrode (not shown) of the LED element 10, and the connection bump 21 is electrically connected to the wiring 20.
The LED element 10 covered with the glass 1 is the glass-covered LED element of the present invention.

The glass-covered LED element of the present invention mounted on a wiring board as shown in FIG. 1 is manufactured, for example, as follows.
First, a glass plate (phosphor-dispersed glass plate) made of phosphor-dispersed glass is prepared.
Typically, the thickness is 0.2 to 2 mm, and the size is 1 to 4 mm □.
Moreover, it is preferable that the surface which should contact with the LED element is mirror-polished. Otherwise, when the LED element is heated and coated with the phosphor-dispersed glass, bubbles may be trapped between the surface and the LED element.

On the other hand, a bumped LED element in which connection bumps are formed on the electrodes of the LED element (bare chip) is prepared and flip-chip mounted on the wiring of the wiring board. The typical size of the LED element is 0.2 to 1 mm □.
Examples of the substrate of the wiring board include an alumina substrate and an aluminum nitride substrate, and the wiring is typically a gold wiring obtained by applying and baking a glass powder-containing gold paste on the substrate.

  Next, the phosphor-dispersed glass plate is placed on the LED element flip-chip mounted on the wiring board and then heated, and this glass plate is softened and flowed to cover at least the upper surface and the side surface of the LED element.

The phosphor-dispersed glass comprises a powder of a glass in which the phosphor is to be dispersed (hereinafter referred to as coating glass) and a mixed powder of the phosphor powder (hereinafter also referred to simply as mixed powder) and a coating glass. One or more lumps are placed in a glass melting container and heated together with the container to make these glasses into molten glass.
The glass for coating has a softening point (Ts) of 500 ° C. or less, an average linear expansion coefficient (α) at 50 to 300 ° C. of 65 × 10 ^{−7 to} 95 × 10 ⁻⁷ / ° C., and a thickness of 1 mm for light having a wavelength of 405 nm. It is preferable that the glass has an internal transmittance (T ₄₀₅ ) of 80% or more and a refractive index (n) for the same light of 1.7 or more.

The Preferred glass _in mole% based on the following _{oxides, TeO 2 40~53%, GeO 2} 0~10%, B 2 O 3 5~30%, Ga 2 O 3 0~10%, Bi 2 _{O 3 0~10%, 3~20% ZnO} , Y 2 O 3 0~3%, La 2 O 3 0~3%, Gd 2 O 3 0~7%, Ta 2 O 5 0~5%, from What becomes essentially is illustrated. This exemplary glass may contain other components than the above components, for example, TiO _{2 and the} like within a range not impairing the object of the present invention, in which case the total content of the above components is typically 95% or more. . For example, “GeO ₂ 0 to 10%” means that GeO ₂ is not essential but may be contained up to 10%.

  The phosphor dispersed in the coating glass is typically one containing cerium-doped YAG when the LED is a blue light emitting diode element.

The maximum particle size of the coating glass powder used for the mixed powder is typically 50 μm or less.
The size of the coating glass lump is preferably 5 mm or more. If it is less than 5 mm, the specific surface area becomes large, and bubbles may be involved at the time of remelting and the light transmittance may be lowered. The size is typically 30 mm or less.

  The number of lumps should be appropriately selected, but the ratio of the mass of the mixed powder to the total mass of one or more lumps of the glass is preferably from 2: 8 to 5: 5. If it is less than 2: 8, the phosphor may be insufficiently dispersed. If it exceeds 5: 5, entrained bubbles increase and the light transmittance may be reduced.

The glass melting vessel is preferably a vessel made of gold or a gold alloy such as a gold crucible when the coating glass is TeO ₂ glass as exemplified above.

  It is preferable to heat the glass melting container containing the mixed powder and one or more coating glass ingots at 900 ° C. for 5 minutes or less. If it exceeds 900 ° C. or more than 5 minutes, the cerium-added YAG-containing phosphor may be deactivated.

(Example 1)
The composition shown in mol% is TeO ₂ 45%, GeO ₂ 5%, B ₂ O ₃ 18%, Ga ₂ O ₃ 6%, Bi ₂ O ₃ 3%, ZnO 15%, Y ₂ O ₃ 0.5. %, La ₂ O ₃ 0.5%, Gd ₂ O ₃ 3%, Ta ₂ O ₅ 3%, TiO ₂ 1%, and 450 g of the prepared raw material is prepared. It was placed in a 300 cc gold crucible and dissolved at 950 ° C. for 2.5 hours. At this time, the molten glass was homogenized by stirring with a gold stirrer for 1 hour. The homogenized molten glass was poured out into a carbon mold and formed into a plate shape having a thickness of about 20 mm.

About the obtained glass, as a result of measuring Ts, Tg, α, n, T ₄₀₅ , RW, RA by the method described below, 490 ° C., 445 ° C., 86 × 10 ⁻⁷ / ° C., 2.011, respectively. 95.2%, 1, 1, and so on. RW and RA are water resistance and acid resistance grades determined according to the evaluation methods established by the Japan Optical Glass Industry Association.

Ts: A sample processed into a cylindrical shape having a diameter of 5 mm and a length of 20 mm was measured at a heating rate of 5 ° C./min using a thermomechanical analyzer DILATOMETER 5000 (trade name) manufactured by Mac Science.
Tg: 150 mg of a sample processed into a powder form was filled in a platinum pan and measured with a thermal analyzer TG / DTA6300 (trade name) manufactured by Seiko Instruments Inc.
α: A sample processed into a cylindrical shape having a diameter of 5 mm and a length of 20 mm was measured at a heating rate of 5 ° C./min using the thermomechanical analyzer. The expansion coefficient at 50 to 300 ° C. was determined in increments of 25 ° C., and the average value was taken as α.

n: Glass was processed into a triangular prism having a side of 30 mm and a thickness of 10 mm, and measured with a precision spectrometer GMR-1 (trade name) manufactured by Kalnew Optical.
T ₄₀₅ : Two plate-like glass samples having both sides mirror-polished and having a size of 2 cm × 2 cm and thicknesses of 1 mm and 5 mm were prepared using a spectrophotometer U-3500 (trade name) manufactured by Hitachi, Ltd. The transmittance for light having a wavelength of 405 nm is measured. T ₄₀₅ (unit:%) is calculated according to the following equation, where T 1 and T 5 are the transmittances of the plate samples having a thickness of 1 mm and 5 mm obtained by the measurement, respectively.
T ₄₀₅ = 100 × exp [(2/3) × log _e (T5 / T1)].

RW: Glass particles having a diameter of 420 to 600 μm were prepared, and the mass reduction ratio when immersed in 80 ml of pure water at 100 ° C. for 1 hour was measured. When the mass reduction ratio is less than 0.05, it is grade 1, when it is 0.05 or more and less than 0.10, grade 2; Grades 60 and below 1.10 were grade 5, and grades 1 and 10 were grade 6. RW is preferably grade 1.
RA: Glass grains having a diameter of 420 to 600 μm were prepared, and the mass reduction ratio when immersed in 80 ml of a 0.01 N nitric acid aqueous solution at 100 ° C. for 1 hour was measured. If the mass reduction ratio is less than 0.20, it is grade 1, it is grade 2 if it is 0.20 or more and less than 0.35, grade 3 if it is 0.35 or more and less than 0.65, grade 4 if it is 0.65 or more and less than 1.20. Grades 20 and below 2.20 were grade 5, and grades 2.20 and above were grade 6. RA is preferably grade 1.

Next, the plate-like glass was cut to produce a block (block) of 8 to 25 mm in one piece. Several of these blocks were crushed with an alumina mortar to obtain glass powder. Although the maximum particle size of this glass powder was not measured, it is estimated that it is 50 micrometers or less from the result of visual observation.
37.5 g of this glass powder was mixed with 5 g of yellow phosphor P46-Y3 (cerium-added YAG powder) manufactured by Kasei Optonics Co., Ltd. to prepare a mixed powder.

Place 42.5 g of the mixed powder and 5 blocks (total mass = 62.5 g) in a gold crucible with a capacity of 100 cm ³ and hold the glass in an electric furnace at 900 ° C. for 5 minutes. Simultaneously with remelting, the phosphor was dispersed in the molten glass.

  After 5 minutes, the crucible was taken out, and the molten glass in which the phosphor was dispersed was poured out into a carbon mold to form a plate having a thickness of about 7 mm. The plate-like glass was immediately put in another electric furnace at 470 ° C., kept at that temperature for 1 hour, and then cooled to room temperature over 12 hours.

The fluorescence spectrum of the phosphor-dispersed glass thus obtained was measured using a fluorescence spectrophotometer F-4500 manufactured by HITACHI. That is, when excitation light of 460 nm was incident, broadband emission was observed in the range of 460 to 650 nm with a peak at 530 nm, and it was confirmed that the phosphor in the phosphor-dispersed glass was not deactivated.
For comparison, a phosphor-dispersed glass was prepared by holding it in an electric furnace at 900 ° C. for 30 minutes, and when the fluorescence spectrum was measured in the same manner, no emission was observed, and the phosphor in the phosphor-dispersed glass was lost. Life was confirmed.

The plate-like glass (phosphor-dispersed glass) was processed into a glass plate having a thickness of 1.5 mm and a size of 3 mm × 3 mm, and then both surfaces thereof were mirror-polished.
On the other hand, an alumina substrate (thickness: 1 mm, size: 25 mm × 50 mm) on which a gold wiring pattern is formed and a LED made by Toyoda Gosei (product name: E1C60-0B011-03) with connection bumps are prepared. The LED was flip-chip mounted on the alumina substrate.

A glass substrate having the phosphor-dispersed glass plate placed on the flip-chip mounted LED is placed in an electric furnace, heated to 610 ° C. at a rate of 1 ° C. per minute and held at that temperature for 15 minutes. The LED was coated by softening and flowing. Thereafter, cooling from 610 ° C. to about 400 ° C. was carried out at a rate of 1 ° C. per minute, and the temperature of 400 ° C. or lower was left in the furnace for natural cooling.
When the glass covering the LED was visually observed, no bubbles were found near the surface.

When a DC voltage was applied to the glass-coated LED element thus obtained, white light emission was confirmed.
The emission start voltage was 2.4 V, which was the same as that for the bare chip. This shows that the LED element light emitting layer is not damaged.
The voltage when the current value was 10 mA was 3.0 V, which was a little higher than 2.9 V in the bare chip. This is considered to be due to damage to the electrode, but it is considered that there is no problem in practical use.

(Example 2)
For comparison, 7.61 g of the same glass used in Example 1 was crushed using a mortar and pestle to form a glass powder, and this was mixed with 381 mg of the same yellow phosphor used in Example 1 to obtain a glass frit containing the phosphor. Obtained.
Meanwhile, a 6-inch silicon wafer (manufactured by Osaka Titanium) was prepared, and boron nitride powder (boron spray manufactured by Kaken Kogyo Co., Ltd.) was sprayed thereon as a release material.

34 mg of a glass frit containing a phosphor was placed on this substrate with a release material, heated from 25 ° C. at 5 ° C./min, held at 610 ° C. for 15 minutes, and then cooled to 25 ° C. at a rate of 5 ° C./min.
As a result, a substantially spherical phosphor-dispersed glass having a flat portion in contact with the substrate was obtained. The maximum width of the glass was 2.0 mm, the height from the flat part was 1.9 mm, and the diameter of the flat part (circular) was 0.8 mm.

Next, many blue light emitting LED bare chips GB-3070 manufactured by Showa Denko KK were sprayed from a height of about 3 cm on the same substrate as the release material-attached substrate.
The bare chip has a size of 300 μm □ and a thickness of 80 μm. The n electrode and the p electrode are arranged on one side of the chip, and the surface thereof is gold.

  Among the sprayed bare chips, one having an electrode forming surface in contact with the boron nitride powder layer and having a bare chip substrate (sapphire substrate) as an upper surface is selected, and the substantially spherical phosphor-dispersed glass is centered on the flat portion of the bare chip. The substrate was placed on the substrate, and the same heat treatment as that for producing the substantially spherical phosphor-dispersed glass was performed. As a result, the bare chip substrate was covered with glass, and a glass-covered LED element having a shape in which the bare chip was embedded in the glass was obtained. In addition, dimensions, such as the height of the coating glass and the maximum width in the horizontal direction, were almost the same as those of the substantially spherical phosphor-dispersed glass, and no glass adhered to the electrode forming surface.

When voltage was applied to the glass-coated LED element thus obtained, white light emission was confirmed. However, the luminescence was weak compared to Example 1.
When the glass covering the LED was visually observed, bubbles having a size of about 100 μm were concentrated in the vicinity of the surface, and a large number of bubbles were recognized inside. It is thought that it was due to these bubbles that the luminescence was weak.
The light emission starting voltage was 2.4 V, which was the same as that for the bare chip.

  It can be used as a white LED element.

The conceptual diagram of the cross section of the glass covering LED element of this invention mounted on the wiring board.

Explanation of symbols

1: Glass 10 in which phosphor is dispersed inside: LED element 20: Wiring 21: Connection bump 30: Substrate

Claims (7)

  A light emitting diode element coated with glass in which phosphor is dispersed, wherein the glass is dispersed in a glass powder to which the phosphor is to be dispersed and a mixed powder of the phosphor powder. A glass-coated light-emitting diode device produced by placing one or more lumps of glass to be put into a glass melting vessel and heating together with the vessel to make these glasses into molten glass.   The glass-coated light-emitting diode device according to claim 1, wherein the phosphor powder contains cerium-added YAG powder, and the light-emitting diode device is a blue light-emitting diode device.   The glass-coated light-emitting diode device according to claim 1, wherein the container is heated at 900 ° C. for 5 minutes or less.   4. The glass-coated light-emitting diode device according to claim 1, wherein a mass ratio of the mixed powder and the one or more chunks of the glass is from 2: 8 to 5: 5.   The glass-coated light-emitting diode element according to any one of claims 1 to 4, wherein a size of the lump is 5 mm or more. The glass in which the phosphor is to be dispersed has a softening point of 500 ° C. or less, an average linear expansion coefficient at 50 to 300 ° C. of 65 × 10 ^{−7 to} 95 × 10 ⁻⁷ / ° C., and a thickness of 1 mm for light with a wavelength of 405 nm. The glass-coated light-emitting diode device according to any one of claims 1 to 5, which is a glass having an internal transmittance of 80% or more and a refractive index with respect to the same light of 1.7 or more. The glass _in mole% based on the following _{oxides, TeO 2 40~53%, GeO 2} 0~10%, B 2 O 3 5~30%, Ga 2 O 3 0~10%, Bi 2 O 3 0 _{~10%, 3~20% ZnO, Y} 2 O 3 0~3%, La 2 O 3 0~3%, Gd 2 O 3 0~7%, Ta 2 O 5 0~5%, essentially from The glass-coated light-emitting diode device according to claim 6.

Images