JP2007324256A - Led apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration of light extraction efficiency from an LED apparatus due to the discoloration of a metal part such as a lead frame etc. caused by the high gas transmissivity of silicon resin when the silicon resin is used as the sealant for sealing an LED chip. <P>SOLUTION: In the LED apparatus using the silicon resin as the sealant for sealing the LED chip, the metal part such as the lead frame etc. is covered with a layer of a translucent inorganic material such as sol gel glass etc. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an LED device.

In the conventional LED device, the LED chip is covered with a light-transmitting resin such as an epoxy resin as a sealing material. However, as the output of the LED chip increases, the color of the epoxy resin around the LED chip changes (yellowing). It has become a problem.
Therefore, a silicone resin, which is a material having high heat resistance and high light resistance, is being adopted as a sealing material instead of an epoxy resin.
On the other hand, surrounding the LED chip with sol-gel glass has also been studied (see Patent Document 1 and Patent Document 2).

JP 2005-11933 A Japanese Patent Laid-Open No. 2002-203989

The inventors of the present invention have intensively studied to improve the durability of the LED device, and have found the following problems.
Silicone resin hardly discolors around the LED chip. However, since the gas permeability is high, the metal in the LED chip may be gradually oxidized and discolored. Examples of such a metal include a lead frame and a reflective layer. The surface of the metal is mirror-finished to improve the light extraction efficiency from the LED device. However, the light reflectance decreases with the oxidation of the metal surface. For this reason, when a silicone resin is used as a sealing material, it is difficult for the LED device to maintain a desired light extraction efficiency.
On the other hand, when all of the sealing material is made of a glass material as disclosed in Patent Document 1, the sealing material is easily broken, and a problem remains in terms of mechanical strength.
Patent Document 2 discloses a configuration in which an LED chip is surrounded by a glass layer, instead of using all of the sealing material as a glass material. However, there is no disclosure or suggestion of coating a metal part such as a lead frame with a glass layer. Therefore, when a silicone resin is used as the sealing material, the reduction in light extraction efficiency due to the discoloration of the metal part is still inevitable.

The present invention has been made to solve the above-mentioned problems, and its configuration is defined as follows.
An LED device comprising an LED chip, a case of the LED chip, and a silicone sealing material filled in the case and surrounding the LED chip,
An LED device, wherein a metal portion is covered with a light-transmitting inorganic material layer in the case.

  According to the LED device configured as described above, since the metal portion is coated with the light-transmitting inorganic material, discoloration of the metal portion can be reliably prevented. As a result, the reflectance of the metal portion is maintained, and a decrease in light extraction efficiency as the LED device is prevented. In maintaining the light extraction efficiency, the effect of preventing discoloration due to the use of a silicone resin as the sealing material also contributes.

In the above, as the light-transmitting inorganic material, glass, a hybrid material, or the like can be used. It is preferable to use sol-gel glass as the glass. This is because sol-gel glass can be formed into a film at a low temperature. Although the density of sol-gel glass is smaller than that of ordinary glass, since the density is much higher than that of silicone resin, it has almost no air permeability. The composition of such sol-gel glass is SiO ₂ , but PBO, ZnO, Al ₂ O ₃ or the like can be blended therein.

Examples of the hybrid material include chemical formula M ¹⁺ (OR ¹ ) _m R ² _1−m (wherein R ¹ is a hydrocarbon group having 1 to 5 carbon atoms, an alkoxyalkyl group or an acyl group, R ² is vinyl, amino, imino. An organic group containing at least one selected from epoxy, acryloyloxy, methacryloyloxy, phenyl, mercapto and alkyl groups, l is a valence of M, and l and m are integers). A mixture of a decomposition product and a hydrolysis / condensation polymerization product can be used. Here, M can use an element such as Si, Al, Zr, or Ti.

Hydrolysis / condensation polymerization of the alkoxide compound represented by the general formula M ¹⁺ (OR ¹ ) _m R ² _1−m is performed as follows.

It is a mixture of a hydrolyzed / condensed polymer of such an alkoxide compound and has fluidity comparable to water.
In the above, when the metal element M is Si, the following silane compounds can be used. Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4- Epoxycyclohexyl) ethyltrimethoxysilane, γ- (3,4-epoxycyclohexyl) ethyltriethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, phenyltrimethoxysilane, phenyltriacetoxysilane, γ-mercaptopropyltri Methoxysilane, γ-chloropropyltrimethoxysilane, β-cyanoethyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyl Trimethoxysilane, ethyl triethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and the like tetrabutoxysilane.

Arbitrary fluorescent substance can be mix | blended with a translucent inorganic material. The following can be mentioned as this fluorescent substance.
The following can be employed as the inorganic phosphor. For example, 6MgO · As ₂ O ₅ : Mn, Y (PV) O ₄ : Eu, CaLa _0.1 Eu _0.9 Ga ₃ O ₇ , BaY _0.9 Sm _0.1 Ga ₃ having red emission color. O ₇ , Ca (Y _0.5 Eu _0.5 ) (Ga _0.5 In _0.5 ) ₃ O ₇ , Y ₃ O ₃ : Eu, YVO ₄ : Eu, Y ₂ O ₂ : Eu, 3.5 MgO • 0.5MgF ₂ GeO ₂ : Mn, and (Y · Cd) BO ₂ : Eu and other red phosphors, blue-based (Ba, Ca, Mg) ₅ (PO ₄ ) ₃ Cl: Eu, (Ba, Mg) ₂ Al ₁₆ O ₂₇ : Eu, Ba ₃ MgSi ₂ O ₈ : Eu, BaMg ₂ Al ₁₆ O ₂₇ : Eu, (Sr, Ca) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu, ( _{sr, Ca) 10 (PO 4} ) 6 Cl 2 · nB _{O 3: Eu, Sr 10 (} PO 4) 6 Cl 2: Eu, (Sr, Ba, Ca) 5 (PO 4) 3 Cl: Eu, Sr 2 P 2 O 7: Eu, Sr 5 (PO 4) 3 Cl: Eu, (Sr, Ca, Ba) ₃ (PO ₄ ) ₆ Cl: Eu, SrO · P ₂ O ₅ .B ₂ O ₅ : Eu, (BaCa) ₅ (PO ₄ ) ₃ Cl: Eu, SrLa _{0 .95} Tm _0.05 Ga ₃ O ₇ , ZnS: Ag, GaWO ₄ , Y ₂ SiO ₆ : Ce, ZnS: Ag, Ga, Cl, Ca ₂ B ₄ OCl: Eu, BaMgAl ₄ O ₃ : Eu, and general A blue phosphor represented by the formula (M1, Eu) ₁₀ (PO ₄ ) ₆ Cl ₂ (M1 is at least one element selected from the group consisting of Mg, Ca, Sr, and Ba), etc. Y ₃ Al ₅ O having the emission color of _{12: Ce, Y 2 SiO 5} : Ce, Tb, Sr 2 Si 3 O 8 · 2SrCl 2: Eu, BaMg 2 Al 16 O 27: Eu, Mn, ZnSiO 4: Mn, Zn 2 SiO 4: Mn, LaPO 4 : Tb, SrAl ₂ O ₄ : Eu, SrLa _0.2 Tb _0.8 Ga ₃ O ₇ , CaY _0.9 Pr _0.1 Ga ₃ O ₇ , ZnGd _0.8 Ho _0.2 Ga ₃ O ₇ , SrLa _0.6 Tb _0.4 Al ₃ O ₇ , ZnS: Cu, Al, (Zn, Cd) S: Cu, Al, ZnS: Cu, Au, Al, Zn ₂ SiO ₄ : Mn, ZnSiO ₄ : Mn, ZnS : Ag, Cu, (Zn · Cd) S: Cu, ZnS: Cu, GdOS: Tb, LaOS: Tb, YSiO 4: Ce · Tb, ZnGeO 4: Mn, GeMgAlO: Tb, SrG ^{_{S: Eu 2+, ZnS: Cu}} · Co, MgO · nB 2 O 3: Ge, Tb, LaOBr: Tb, Tm, and _La 2 _O 2 S: can be used green phosphor represented by Tb and the like. In addition, yellow fluorescence represented by CaLu _0.5 Dy _0.5 Ga ₃ O ₇ , (Y, Gd) ₃ Al ₅ O ₁₂ : Ce, (Ba, Sr) ₂ SiO ₄ : Eu having a yellow emission color. The body can also be used.
In the case of an ultraviolet light emitting LED, white light can be obtained by combining the above-described red phosphor, green phosphor and blue phosphor. In the case of a blue light emitting LED chip, white light can be obtained by a combination of the above-described red phosphor and green phosphor or a yellow phosphor.
A light diffusing material can also be used in combination with the phosphor. As a result, light emission unevenness can be reduced.

The LED chip can be face-up or flip-chip type. Further, as the LED package, a package such as a top view type or a side view type SMD, a shell type, or a COB type can be used.
The problem of yellowing of the sealing material is an LED chip that emits light of a short wavelength (green to ultraviolet), and the LED chip is generally formed of a group III nitride compound semiconductor. .
Here, the group III nitride compound semiconductor is a quaternary system of Al _X Ga _Y In _1- XYN (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1) as a general formula. A so-called binary system of AlN, GaN and InN, Al _x Ga _1-x N, Al _x In _1-x N and Ga _x In _1-x N (where 0 <x <1). Includes the system. Part of group III elements may be substituted with boron (B), thallium (Tl), etc., and part of nitrogen (N) may also be phosphorus (P), arsenic (As), antimony (Sb), bismuth. It can be replaced with (Bi) or the like.
In addition to Si, Ge, Se, Te, C, or the like can be used as the n-type impurity doped in the n-type layer.
Sapphire, spinel, silicon, silicon carbide, zinc oxide, gallium phosphide, gallium arsenide, magnesium oxide, manganese oxide, group III nitride compound semiconductor single crystal, etc. for the substrate on which the group III nitride compound semiconductor layer is grown Can be used.

  The LED chip case mounts and protects the LED chip and efficiently emits the light emitted from the LED chip to the outside. In order to improve the light extraction efficiency from the LED chip, a reflective layer made of metal such as silver may be formed on the inner surface of the case. The case is provided with a wiring material for supplying power to the LED chip. In order to improve the reflectance on the surface of this wiring material, for example, the lead frame, the lead frame may be subjected to silver plating. In addition, a metal such as silver alloy, aluminum, or aluminum alloy may be exposed and disposed in the case. In either case, the surface is mirrored to improve the light reflectance.

Since such a metal portion is discolored when oxidized, in the present invention, the metal portion is covered with an inorganic material layer. Therefore, the LED chip itself may or may not be coated with the inorganic material.
The film thickness of the inorganic material layer is not particularly limited, but can be arbitrarily selected so as to ensure a hermeticity with respect to the metal portion and to have a thickness that does not cause cracking.

  When flip chip type LED chip is covered with sol-gel glass, the refractive index of alumina substrate is 1.7, the refractive index of sol-gel glass is 1.6, and the refractive index of silicone resin is 1.4. The refractive index is gently inclined from the light source side to the atmosphere (refractive index: 1.0). Therefore, the reflection at the interface of each layer is reduced, and the light extraction efficiency is improved from this point.

Next, examples of the present invention will be described.
FIG. 1 is a cross-sectional view showing the structure of the LED device 1 of the embodiment.
A lead frame 4 having a surface plated with silver is disposed at the bottom of the cup-shaped case 2. In this embodiment, the inner surface of the case 2 is also silver-plated (reflective layer) from the viewpoint of improving the reflectance. The lead frame 4 is wired outside through the bottom wall or side wall of the case 2. A blue LED chip 5 made of a group III nitride compound semiconductor is fixed via a D / B paste 7 at substantially the center of the bottom of the case 2. The LED chip 5 is a face-up type SMD. A bonding wire 9 is suspended between two bonding pads (not shown) formed on the surface of the LED chip 5 and the lead frame 4.
Although it is preferable to use a group III nitride compound semiconductor light emitting element for the LED chip 5, it does not exclude the use of other types of LED chips.

Reference numeral 11 in the figure denotes a glass layer, and in this embodiment, the entire inner surface of the case 2 including the LED chip 5 is covered. As a result, the lead frame 4 is completely covered with the glass layer 11. The inner side surface (silver-plated) of the case 2 is also covered with the glass layer 11.
For the glass layer 11, sol-gel glass (inorganic (solvent type)) was employed. The sol-gel glass before curing is potted in the case 2 in which the LED chip 5 and the bonding wire 9 are assembled. Due to the surface tension of the sol-gel glass (before curing) and its adhesiveness, the sol-gel glass (before curing) covers the reflective surface, the surface of the lead frame 4 and the entire LED chip 5 in the case 2 with substantially the same thickness. The curing conditions for the sol-gel glass were first pretreatment of 100 ° C. × 10 minutes, and then 180 ° C. × 2 hours. According to such curing conditions, the LED chip 5 and the lead frame 4 and the case 2 are not stressed greatly.

Although the thickness of the glass layer 11 is not specifically limited, It is preferable to set it as 1 micrometer-50 micrometers. If the thickness is less than 1 μm, the airtightness with respect to the metal portion remains uneasy, and if it exceeds 50 μm, the probability of cracking increases, which is not preferable. The more preferable thickness of the glass layer 11 is 1 μm to 30 μm, and more preferably 1 μm to 20 μm.
A silicone resin (addition reaction type) was used for the sealing material 13. The silicone resin is filled onto the glass layer 11 of the case 2 in a fluid state and is cured there. The curing conditions were 150 ° C. × 1 hour.

  According to the LED device 1 shown in FIG. 1 configured as described above, the metal portion in the case 2 (the inner surface of the case 2 and the lead frame 4) is covered with the glass layer 11 made of sol-gel glass. Even if air has permeated through the sealing material made of the above, it is possible to reliably prevent the air from touching the metal portion. Therefore, the metal part is not discolored and the light reflectance is not lowered. As a result, the light extraction efficiency of the LED device is maintained for a long time.

FIG. 2 shows an LED device 21 of another embodiment. The same elements as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
The LED device 21 of this embodiment employs a flip chip type as the LED chip 25. Reference numeral 27 denotes a bump.
According to the LED device 21 having such a configuration, the light emission surface of the LED chip is a sapphire substrate (refractive index: 1.7), and a glass layer (refractive index: 1.6) and a silicone resin (refractive index: 1) thereon. 4) are stacked in order. As a result, the refractive index changes gradually from the light source to the outside, and the reflection of light between the layers is reduced. As a result, the light extraction efficiency is improved.

  The present invention is not limited to the description of the embodiments of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims. For example, the lead frame is used as the wiring material in the above-described embodiments, but the present invention can also be applied to a sintered metal paste such as a ceramic package wiring material.

It is a top view which shows the structure of the LED device of this invention. It is a top view which shows the structure of the LED apparatus of the other Example of this invention.

Explanation of symbols

1, 21 LED device 2 Case 4 Lead frame 5, 25 LED chip 11 Glass layer 13 Sealing material

Claims (3)

An LED device comprising an LED chip, a case of the LED chip, and a silicone sealing material filled in the case and surrounding the LED chip,
An LED device, wherein a metal portion is covered with a light-transmitting inorganic material layer in the case. The LED device according to claim 1, wherein the inorganic material layer is made of sol-gel glass. The LED device according to claim 1, wherein the metal portion is a wiring material and / or a reflective layer.

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