JP2011258866A - Substrate for mounting light emitting element and light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for mounting a light emitting element which is excellent in thermal conductivity and high in reflectance while deterioration in a reflectance is suppressed.SOLUTION: A substrate 1 for mounting a light emitting element includes: a substrate body 2 having a mounting surface 21 on which a light emitting element 8 is mounted; and a reflective layer 6 formed in a part of the mounting surface 21 of the substrate body 2 and reflecting light emitted from the light emitting element 8. The reflective layer 6 comprises a sintered body of a composition containing titanium oxide and glass powder.

Description

  The present invention relates to a light-emitting element mounting substrate and a light-emitting device using the same, and more particularly, a light-emitting element mounting substrate having high visible light reflectivity and excellent thermal conductivity, and a light-emitting device using the same. About.

  In recent years, with the achievement of high brightness and whitening of light emitting diode elements (chips), light emitting devices using light emitting diode elements are used as illumination, various displays, backlights for large liquid crystal TVs, and the like. In general, a light emitting element mounting substrate on which a light emitting diode element is mounted is required to have high reflectivity for efficiently reflecting light emitted from the element and high heat dissipation for efficiently dissipating heat generated from the element. . Further, high corrosion resistance against corrosive gases such as hydrogen sulfide gas is also required.

Conventionally, it has been proposed to use, for example, a resin substrate as a light emitting element mounting substrate. When a resin substrate is used, a high reflectance can be obtained, but since the heat dissipation is inferior, the temperature around the substrate may be excessively increased.
It has also been proposed to use a ceramic substrate such as alumina or aluminum nitride as a substrate for mounting a light emitting element. In the ceramic substrate, although excellent heat dissipation can be obtained, the reflectance is not necessarily high, so that sufficient light emission luminance cannot be obtained.
On the other hand, a technique of providing a silver reflective layer with a silver thin film on the surface of such a substrate has also been proposed. Since the silver reflection layer can obtain a high reflectance and is also excellent in heat dissipation, excellent characteristics can be obtained as an element mounting substrate.

However, since silver tends to corrode in a high-temperature and high-humidity atmosphere or in the presence of hydrogen sulfide gas, the light reflectance deteriorates with time.
In order to prevent such a decrease in light reflectance due to corrosion of the silver reflective layer, for example, in Patent Document 1, the surface of the silver reflective layer is coated with a resin such as a silicone resin, an acrylic resin, an epoxy resin, a urethane resin, It has been proposed to prevent a decrease in light reflectance. However, the sealing properties of these resin films are not perfect, and corrosive gases or liquids may permeate the resin film or enter from the interface between the resin and the substrate after long-term use. As a result, the silver reflection layer corrodes, and there is a problem that the decrease in reflectance over time cannot be sufficiently prevented.

  In order to solve such a problem, for example, Patent Document 2 proposes to protect the light reflecting layer by providing a glass coating layer on the upper surface of the silver reflecting layer. Since the protective layer made of glass is excellent in sealing performance as compared with the protective layer made of resin, it is possible to suppress the corrosion of the reflective layer due to the corrosive gas and the deterioration of the reflectance with time due to this. Furthermore, since glass has a high light transmittance, a high reflectance can be obtained without impairing the reflectance of the light reflecting layer. For this reason, even in the presence of corrosive gas or the like, high reflectance can be maintained over a long period of time, and light from the light emitting element can be used efficiently.

By the way, it is necessary to form the protective layer made of glass with a predetermined thickness on the substrate in order to ensure sufficient sealing performance.
However, since the thermal conductivity of glass is very low as compared with metals such as silver and ceramics such as alumina, the glass layer formed as a thick film tends to be a heat retaining layer, and the heat dissipation of the substrate is significantly impaired.

On the other hand, Patent Document 3 proposes using titanium oxide as a reflective film. Titanium oxide has a higher thermal conductivity than glass and has high corrosion resistance against corrosive gases such as hydrogen sulfide gas, so it can be formed alone on a substrate without providing a protective layer. . Furthermore, since titanium oxide has a high refractive index, the reflectance can be improved by forming a thin film on the substrate.
However, in Patent Document 3, a sputtering method, which is a vacuum process, is used to form a titanium oxide film, which is not suitable for mass production and has a problem in terms of manufacturing cost. In addition, when the sputtering method is used, a uniform thin film with a thickness of about several hundred nm to several μm is generally obtained. However, even when a titanium oxide film having such a thickness is formed on the substrate, the reflectance is sufficiently improved. Without sufficient light emission brightness.

JP 2007-67116 A JP 2010-034487 A JP 2009-206294 A

  The present invention has been made in order to solve the above-described problem, and is a light-emitting element that has excellent heat dissipation, high reflectivity, and suppresses deterioration of reflectivity over time in a corrosive gas atmosphere. The object is to provide a mounting substrate. Another object of the present invention is to provide a light emitting device using the light emitting element mounting substrate.

  As a result of intensive studies, the inventor of the present invention uses a sintered body of a composition containing titanium oxide powder and glass powder as a reflective film, which has excellent heat dissipation, high reflectance, and corrosion. It was found that a substrate for mounting a light emitting element with little deterioration of reflectance over time in a reactive gas atmosphere can be obtained.

  That is, the light emitting element mounting substrate of the present invention is formed on a substrate body having a mounting surface on which the light emitting element is mounted, and a part of the mounting surface of the substrate body, and reflects light emitted from the light emitting element. A reflective layer, and the reflective layer is made of a sintered body of a composition containing titanium oxide powder and glass powder.

  The ratio of the glass and titanium oxide contained in the reflective layer is preferably a volume ratio of glass: titanium oxide = 3: 97 to 30:70. The substrate body is preferably a low-temperature fired ceramic substrate. The thickness of the reflective layer is preferably 10 μm or more and 50 μm or less.

  The light emitting device of the present invention includes the above-described light emitting element mounting substrate of the present invention and a light emitting element mounted on a mounting surface of the light emitting element mounting substrate.

According to the present invention, by providing a reflective layer composed of a sintered body of a composition containing titanium oxide powder and glass powder, the reflectance is high, and light emitted from the light emitting element can be used efficiently, and the light emitting element It is possible to provide a substrate for mounting a light emitting element in which the thermal conductivity of the mounting surface is improved. Further, even in the presence of corrosive gas or liquid, the reflective layer is hardly deteriorated, and even when used for a long time, a light-emitting element mounting substrate in which a decrease in reflectance is suppressed can be obtained.
Specifically, according to the present invention, a light-emitting element mounting substrate provided with a reflective layer having a light reflectance of 85% or more, a thermal conductivity of 5 W / m · K or more, and sufficient corrosion resistance is provided. can do.
Further, according to the present invention, a light emitting device with high light emission luminance can be obtained by mounting a light emitting element on such a light emitting element mounting substrate.

It is sectional drawing which shows an example of the light emitting element mounting substrate of this invention. It is sectional drawing which expands and shows the reflection layer 6a periphery of FIG. It is sectional drawing which shows an example of the light-emitting device of this invention.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a cross-sectional view showing an example of a light emitting element mounting substrate of the present invention.
The light emitting element mounting substrate 1 includes a substantially flat substrate body 2 having a side wall 2b provided at the end of the substrate. The substrate body 2 is formed in a shape having a cavity on one surface (the upper side in FIG. 1), and the bottom surface of the cavity is a mounting surface 21 on which a light emitting element such as a light emitting diode element is mounted. . The mounting surface 21 is provided with a connection terminal 3 that is electrically connected to the light emitting element. The other main surface of the substrate body 2 is a non-mounting surface 22 on which no light emitting element is mounted. The non-mounting surface 22 is provided with external electrode terminals 4 that are electrically connected to an external circuit. The external electrode terminals 4 are electrically connected to the connection terminals 3 by through conductors 5 that penetrate the substrate body 2. ing.

  A reflection layer 6a for reflecting light from the light emitting element is provided at a substantially central portion of the mounting surface 21 of the substrate body 2 shown in FIG. The reflective layer 6b for reflecting the light to be transmitted is provided. (Hereinafter, the reflective layer 6a and the reflective layer 6b are referred to as the reflective layer 6.) In FIG. 1, the reflective layers 6a and 6b are shown to be formed independently, but the connection terminals 3 are exposed. If the reflective layer 6 can be formed in a state, the reflective layers 6a and 6b are not necessarily formed independently.

FIG. 2 is an enlarged cross-sectional view showing the periphery of the reflective layer 6a in FIG.
The reflective layer 6 is composed of a sintered body of a composition containing titanium oxide powder (hereinafter sometimes referred to as titania powder) and glass powder. The reflective layer 6 can be formed, for example, by blending a titania powder into a glass powder to form a composition, adding a resin binder to make a paste, screen-printing this on the substrate body 2 and baking. Thereby, the reflective layer 6 of titanium oxide having a desired thickness can be efficiently formed in a short time.

The thickness of the reflective layer 6 is preferably 10 μm or more and 50 μm or less. When the thickness of the reflective layer 6 is less than 10 μm, the distance from the contact surface of the reflective layer 6 with the light emitting element 8 to the contact surface with the substrate main body 2 is short, so that the light is emitted from the light emitting element 8 to the substrate main body 2 side. Therefore, the ratio of the incident light to the substrate body 2 side increases, and the light emitted from the light emitting element 8 cannot be efficiently reflected.
On the other hand, when the thickness of the reflective layer 6 exceeds 50 μm, for example, when the reflective layer 6 is formed by screen printing or the like, the number of times of printing increases, and the manufacturing cost may increase. That is, in screen printing, the thickness that can be formed by one printing is usually about 10 to 20 μm, and when a film having a thickness of 50 μm or more is formed, the number of times of printing may increase and the manufacturing cost may increase. is there. Furthermore, when the thickness of the reflective layer 6 exceeds 50 μm, the surface waviness tends to increase, and it may be difficult to flatten the surface of the reflective layer 6. The thickness of the reflective layer 6 is more preferably 15 μm or more and 30 μm or less.

  A more preferable ratio of glass and titanium oxide contained in the reflective layer 6 is a volume ratio of glass: titanium oxide = 3: 97 to 30:70. If the proportion of glass is less than the above range, the adhesion of the reflective layer 6 to the substrate body 2 is lowered, and the reflective layer 6 may be easily separated from the substrate body 2 during firing. On the other hand, when the ratio of the glass is larger than the above range, the volume of the sintered body of the glass powder in the reflective layer 6 becomes excessive, and there is a possibility that good thermal conductivity of the reflective layer 6 cannot be obtained. Moreover, when content of the glass powder which forms the reflection layer 6 exceeds 30 volume%, reaction with a titanium oxide powder and glass powder may arise. In this case, the light from the light emitting element 8 is absorbed by the reaction product, and the reflectance of the reflective layer 6 may be reduced. In particular, the reflective layer 6 is preferably substantially composed of 3 to 30% by volume of glass powder and 70 to 97% by volume of titanium oxide powder, and preferably 3 to 15% by volume of glass powder and 85 to 97% by volume. What consists of titanium oxide powder is more preferable, and what consists of 3-7 volume% glass powder and 93-97 volume% titanium oxide powder is still more preferable.

The particle diameter of the titania powder is preferably about the same as the wavelength of light emitted from the light emitting element. By using titania powder having such a particle size, light from the light emitting element can be efficiently scattered, and high reflectance can be obtained.
For example, when the wavelength of light from the light emitting element is about 460 nm, the 50% particle size (D ₅₀ ) of the titania powder is preferably 0.1 μm or more and 2 μm or less. When the particle size of the titania powder is smaller than 0.1 μm or larger than 2 μm with respect to light having a wavelength of about 460 nm, it may be difficult to obtain sufficient reflectance. The 50% particle size (D ₅₀ ) of the titania powder is more preferably 0.3 μm or more and 0.8 μm or less.

  Although it does not specifically limit about the glass powder for reflection layers, It is preferable to have practically sufficient moisture resistance and acid resistance. Moreover, in order to suppress the fall of the reflectance of the reflection layer 6, it is preferable that a glass powder does not contain the component which absorbs light in the component. Furthermore, if the glass powder is too crystallized during firing, the reflective layer 6 may be peeled off from the substrate body 2. For this reason, it is preferable that the glass powder has a low crystallization rate during firing.

Furthermore, when the reflective layer 6 is fired simultaneously with the substrate body 2, the softening point (Ts) of the glass powder used for the reflective layer 6 is “the firing temperature of the substrate body 2 −100 ° C.” or higher, and the “baking temperature of the substrate body 2”. + 100 ° C. ”or less is preferable.
When the softening point (Ts) of the glass powder is lower than “the firing temperature of the substrate body 2 −100 ° C.”, when the substrate body 2 and the reflective layer 6 are fired simultaneously, there is a reaction between the glass component and titania. This is likely to occur, and the light from the light emitting element 8 may be absorbed by the reaction product and the reflectance of the reflective layer 6 may be reduced. On the other hand, when the softening point (Ts) of the glass powder is higher than “the baking temperature of the substrate 2 + 100 ° C.”, when the substrate body 2 and the reflective layer 6 are simultaneously fired, the glass powder is not sufficiently softened and reflected. The adhesion strength of the layer 6 to the substrate body 2 is lowered, and so-called film peeling in which the reflective layer 6 is separated from the substrate body 2 during firing may be likely to occur.

When the substrate body 2 is made of, for example, low temperature co-fired ceramic (hereinafter referred to as LTCC), the softening point of the glass powder used for the reflective layer 6 is about 750 to 950 ° C. It is preferable. LTCC is obtained by firing a mixture of a glass powder that can be fired at a temperature of about 850 ° C. and a ceramic powder.
Examples of such glass powder include SiO ₂ of 35 mol% to 84 mol%, B ₂ O ₃ of 5 mol% to 25 mol%, Al ₂ O ₃ of 0 mol% to 15 mol%, Na ₂ O and K ₂ O. A borosilicate system in which at least one selected from the group is 0 mol% or more and 10 mol% or less in total, and when any of CaO, SrO, BaO, and ZnO is contained, the total content thereof is 0% mol or more and 35% mol or less The glass powder can be used.

SiO ₂ serves as a network former of glass, and is an essential component for increasing chemical durability, particularly acid resistance. When the content of SiO ₂ is less than 35 mol%, there is a possibility that the acid resistance becomes insufficient. On the other hand, if the content of SiO ₂ exceeds 84 mol%, the glass softening point (Ts) and glass transition point (Tg) may be excessively high.

B ₂ O ₃ is a glass network former. If the content of B ₂ O ₃ is less than 5 mol%, the softening point (Ts) may be excessively high, and the glass may become unstable. On the other hand, when the content of B ₂ O ₃ exceeds 25 mol%, it is difficult to obtain a stable glass and the chemical durability may be lowered.
The content of B ₂ O ₃ is preferably 13 mol% or more.

Al ₂ O ₃ may be added in a range of 15 mol% or less in order to enhance the stability and chemical durability of the glass. When the content of Al ₂ O ₃ exceeds 15 mol%, the transparency of the glass may be lowered. On the other hand, when the content of Al ₂ O ₃ exceeds 15 mol%, a color development phenomenon (hereinafter simply referred to as color development) due to the reaction with titanium oxide tends to occur.

Na ₂ O and K ₂ O can be added in such a range that the total content does not exceed 10 mol% in order to lower the softening point (Ts) and glass point transfer (Tg). When the total content of Na ₂ O and K ₂ O exceeds 10 mol%, chemical durability, particularly acid resistance may be lowered, and electrical insulation may be lowered. Further, when the total content of Na ₂ O and K ₂ O exceeds 10 mol%, there is a possibility that color development tends to occur.
Na ₂ O and K ₂ O preferably contain one or more of them, and the total content of Na ₂ O and K ₂ O is preferably 0.5 mol% or more.

    CaO, SrO, BaO, ZnO are added in a range where the total content does not exceed 35 mol% in order to lower the softening point (Ts) and glass point transfer (Tg) and to increase the stability of the glass. Also good. If the total content of CaO, SrO, BaO and ZnO exceeds 35 mol%, the acid resistance may be reduced. Further, when the total content of CaO, SrO, BaO, and ZnO exceeds 35 mol%, there is a possibility that color development is likely to occur.

In particular, the glass powder used for the reflective layer 6 preferably has the same composition as the glass powder used for the substrate body 2. As such glass powder, for example, SiO ₂ is 57 mol% or more and 65 mol% or less, B ₂ O ₃ is 13 mol% or more and 18 mol% or less, CaO is 9 mol% or more and 23 mol% or less, and Al ₂ O ₃ is 3 mol% or more and 8 mol% or less. % Or less, and those containing at least one selected from Na ₂ O and K ₂ O in total of 0.5 mol% or more and 6 mol% or less can be used.

When the glass powder having the composition in the above range is used as the reflective layer 6, it is preferable that the substrate body 2 also uses the glass powder having the composition in the above range. When glass powder having a composition outside the above range is used in the production of the substrate body 2, glass powders having different characteristics are fired in contact with each other. For this reason, there exists a possibility that precipitation of a crystal | crystallization may arise at the time of baking, or the curvature of the board | substrate body 2 may arise from the difference in the shrinkage | contraction behavior of each glass component.
Even when the glass powder for the substrate main body 2 and the glass powder for the reflective layer 6 have different compositions, warping of the substrate main body 2 is prevented by appropriately adjusting the temperature rising rate during firing. It is possible.

In addition, the glass powder used for the reflective layer 6 can contain another component in the range which does not impair the objective of this invention. Moreover, the glass powder used for the reflection layer 6 is not limited to what has the said content rate, The glass powder which has a content rate different from this can also be used.
For example, when the glass powder for the substrate body 2 has a composition outside the above range, the glass powder for the reflective layer 6 is not limited to those within the above composition range, and the glass powder for the substrate body 2 It is also possible to use glass powder having the same composition.
In this embodiment, lead oxide is not contained. When other components are contained, the total content is preferably 10 mol% or less.

  The glass powder used for the reflective layer 6 can be obtained by producing glass having the above glass composition by a melting method and pulverizing it by a dry pulverization method or a wet pulverization method. In the case of the wet pulverization method, it is preferable to use water as a solvent. The pulverization can be performed using a pulverizer such as a roll mill, a ball mill, or a jet mill.

The glass powder used for the reflective layer 6 preferably has a 50% particle size (D ₅₀ ) of 0.5 μm or more and 4 μm or less. When the 50% particle size of the glass powder is less than 0.5 μm, the glass powder tends to aggregate, making handling difficult, and the time required for pulverization may be too long. On the other hand, if the 50% particle size of the glass powder exceeds 4 μm, the glass softening temperature may increase or the sintering may be insufficient. The 50% particle size (D ₅₀ ) for the reflective layer 6 is more preferably 1.0 μm or more and 3.0 μm or less. The particle size can be adjusted, for example, by classification as necessary after pulverization. In the present specification, the 50% particle size (D ₅₀ ) refers to a value measured using a laser diffraction / scattering particle size distribution analyzer.

The substrate body 2 is not limited to any material as long as it is an electrically insulating flat plate member that does not deform or change in quality at the firing temperature of the reflective layer 6, but ceramics, particularly alumina ceramics, LTCC, aluminum nitride, etc. are strong and manufactured. Since it is excellent in terms of cost and the like, it is preferably used.
Among the ceramics described above, in particular, when LTCC is adopted as the substrate body 2, the substrate body 2 and the reflective layer 6 can be simultaneously fired at the same time, so that the light emitting element mounting substrate 1 can be efficiently manufactured. Can do.

The substrate body 2 made of LTCC can be manufactured as follows.
First, a slurry is prepared by adding a binder, if necessary, a plasticizer, a solvent, etc. to a glass ceramic composition containing glass powder for a substrate body and a ceramic filler, and this is formed into a sheet by a doctor blade method or the like. And dry to produce a green sheet.

  Although the glass powder for substrate main bodies is not necessarily limited, a glass transition point (Tg) of 550 ° C. or higher and 700 ° C. or lower is preferable. If the glass transition point (Tg) is less than 550 ° C., degreasing described later may be difficult. On the other hand, when the glass transition point (Tg) exceeds 700 ° C., the shrinkage start temperature becomes high, and the dimensional accuracy may be lowered.

As such a glass powder for a substrate body, for example, SiO ₂ is 57 mol% to 65 mol%, B ₂ O ₃ is 13 mol% to 18 mol%, CaO is 9 mol% to 23 mol%, and Al ₂ O ₃ is 3 mol%. It is preferably 8 mol% or less and at least one selected from K ₂ O and Na ₂ O in total containing 0.5 mol% or more and 6 mol% or less.

The glass powder for a substrate body can be obtained by producing glass having the above glass composition by a melting method and pulverizing it by a dry pulverization method or a wet pulverization method.
In the case of the wet pulverization method, it is preferable to use water as a solvent. The pulverization can be performed using a pulverizer such as a roll mill, a ball mill, or a jet mill.

  In addition, the glass powder for substrate main body can also contain other components in the range which satisfies various characteristics, such as a glass transition point. When other components are contained, the total amount of the other components is preferably 10 mol% or less.

The 50% particle size (D ₅₀ ) of the glass powder for substrate body 2 is preferably 0.5 μm or more and 4 μm or less. If the 50% particle size of the glass powder for substrate main body 2 is less than 0.5 μm, the glass powder tends to aggregate, making it difficult to handle and making it difficult to disperse uniformly. On the other hand, if the 50% particle size of the glass powder exceeds 4 μm, the glass softening temperature may increase or the sintering may be insufficient. More preferably, it is 1.0 μm or more and 3 μm or less. The particle size can be adjusted, for example, by classification as necessary after pulverization.

As the ceramic filler, those conventionally used for the production of LTCC substrates can be used without particular limitation. For example, alumina powder, zirconia powder, or a mixture of alumina powder and zirconia powder can be suitably used. The 50% particle size (D ₅₀ ) of the ceramic filler is preferably, for example, 0.3 μm or more and 4 μm or less.

  Mixing and mixing such glass powder for substrate main body and ceramic filler such that glass powder for substrate main body is 30 mass% to 50 mass% and ceramic filler is 50 mass% to 70 mass%, for example. Thus, a glass ceramic composition can be obtained. Moreover, a slurry can be obtained by adding a plasticizer, a solvent, etc. to this glass ceramic composition as needed.

  As the binder, for example, polyvinyl butyral, acrylic resin and the like can be suitably used. As the plasticizer, for example, dibutyl phthalate, dioctyl phthalate, butyl benzyl phthalate and the like can be used. As the solvent, aromatic or alcoholic organic solvents such as toluene, xylene and butanol can be used. Furthermore, it is possible to use a dispersant or a leveling agent.

  A green sheet can be produced by forming this slurry into a sheet by the doctor blade method or the like and drying it. The green sheet thus manufactured can be cut into a predetermined dimension angle by using a punching die or a punching machine, and at the same time, via holes for interlayer connection can be formed by punching at predetermined positions.

An unfired conductor pattern is formed on the surface of the green sheet by printing a conductive metal paste by a method such as screen printing. In addition, an unfired interlayer connection portion is formed by filling a conductor metal paste into the via hole for interlayer connection described above. Thereby, the unfired connection terminal 3A, the unfired external electrode terminal 4A, and the unfired through conductor 5A are formed.
As the conductive metal paste used for the conductor pattern and the interlayer connection portion, for example, a metal powder mainly composed of copper, silver, gold or the like is added with a vehicle such as ethyl cellulose, and a solvent or the like is added to form a paste. Things can be used.

Next, a paste of the composition for the reflective layer 6 (hereinafter referred to as titania paste) is printed on the surface of the green sheet for the uppermost layer of the substrate body 2 at a position shown in FIG. 1 by a method such as screen printing. An unsintered reflective layer 6 is formed.
As the titania paste, for example, a paste obtained by adding a vehicle such as ethyl cellulose to a mixture of titania powder and glass powder and, if necessary, a solvent or the like can be used.

  After aligning a plurality of green sheets on which an unfired conductor pattern and an unfired reflective layer 6 are aligned, they are integrated by heating and pressing, and then, for example, 1 at a temperature of 500 ° C. or more and 600 ° C. or less. By holding for not less than 10 hours but not more than 10 hours, degreasing is performed to decompose and remove a binder such as resin contained in the green sheet. Then, the glass ceramic composition which comprises a green sheet is baked by hold | maintaining for 20 minutes or more and 60 minutes or less, for example at the temperature of 850 degreeC or more and 900 degrees C or less. By this firing, the metal paste formed inside and on the surface of the glass ceramic substrate is also fired at the same time, and the substrate body 2 having the connection terminals 3, the external electrode terminals 4, the through conductors 5, and the reflective layer 6 can be obtained.

  If the degreasing temperature is less than 500 ° C. or the degreasing time is less than 1 hour, the binder or the like may not be sufficiently removed. On the other hand, if the degreasing temperature is about 600 ° C. and the degreasing time is about 10 hours, the binder and the like can be sufficiently removed, and if it exceeds this, the productivity may be lowered.

If the firing temperature is less than 850 ° C. and the firing time is less than 20 minutes, a dense product may not be obtained. On the other hand, if the firing temperature is about 900 ° C. and the firing time is about 60 minutes, a sufficiently dense product can be obtained, and if this is exceeded, productivity and the like may be reduced.
The firing is particularly preferably performed at a temperature of 860 ° C. or higher and 880 ° C. or lower. When the firing temperature exceeds 880 ° C., the titania paste made of a mixture of titania powder and glass powder may be excessively softened and cannot maintain a predetermined shape.

  The light reflecting layer of the light emitting element mounting substrate of the present invention obtained as described above generally has the following characteristics, that is, excellent thermal conductivity of 5 W / m · K or more and reflectance of 85% or more. It has special characteristics. In addition, since the heat conductivity of the sintered compact obtained by baking the composition comprised only by titania powder without containing glass powder is about 10.5 W / m * K, the light emitting element of this invention The upper limit of the thermal conductivity of the reflective layer 6 containing glass powder applied to the mounting substrate 1 is about 10.5 W / m · K.

  For example, as shown in FIG. 3, the light emitting device of the present invention is one in which a light emitting element 8 such as a light emitting diode element is mounted on a reflective layer 6 a provided on a mounting surface 21 of a light emitting element mounting substrate 1. The light emitting element 8 is fixed to the reflective layer 6 a using an adhesive, and an electrode (not shown) is electrically connected to the connection terminal 3 by a bonding wire 9. A light emitting device 10 is configured by providing a molding material 11 so as to cover the light emitting element 8 and the bonding wire 9.

  As the molding material 11, for example, a silicone resin or an epoxy resin can be used, and a silicone resin is particularly preferable because it is excellent in light resistance and heat resistance.

By mixing or dispersing a phosphor or the like in the molding material 11, the light obtained as the light emitting device 10 can be appropriately adjusted to a desired emission color.
As the adjustment of the emission color, for example, by mixing and dispersing the phosphor in the molding material 11, the phosphor is excited by the light emitted from the light emitting element 8 to emit visible light, and the visible light and the light emitting element are emitted. The light emitted from the light 8 is mixed, and the light emitting device 10 can obtain a desired light emission color. In addition, the light emitting device 10 can obtain a desired light emission color by mixing the light emitted from the light emitting element 8 and the visible light emitted from the phosphor, or by mixing the visible lights. . The type of the phosphor is not particularly limited, and is appropriately selected according to the type of light emitted from the light emitting element and the target emission color.

  In the light emitting device 10 of the present invention, by providing the reflective layer 6 made of a sintered body of a composition containing titanium oxide powder and glass powder, the light emitted from the light emitting element 8 to the substrate body 2 side is reflected. 6 is reflected upward by the titanium oxide, and the reflected light is incident on the phosphor in the molding material 11 to emit visible light, or the reflected light collides with the phosphor and is further refracted or reflected. To do.

  The phosphor is not limited to the method of mixing and dispersing in the molding material 11 as described above. For example, a phosphor layer can be separately provided on the molding material 11.

According to the light emitting device 10 of the present invention, by using the light emitting element mounting substrate 1 having excellent thermal conductivity, an excessive temperature rise of the light emitting element 8 can be suppressed and light can be emitted with high luminance. In addition, since oxidation or sulfurization of the reflective layer 6 is difficult to occur, the reflectance is hardly reduced, and light can be emitted with high brightness over a long period of time.
Such a light emitting device 10 of the present invention can be suitably used as a backlight for a mobile phone, a large liquid crystal display, etc., illumination for automobiles or decoration, and other light sources.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
First, a composition of titania powder and glass powder (hereinafter referred to as a glass ceramic composition for a reflective layer) used for the reflective layer 6 was produced.
That, SiO ₂ is _60.1mol%, B 2 _{O 3} is 15.9mol%, _Al 2 _{O 3} is 6.1mol%, CaO is 14.9mol%, Na ₂ O is 2.0mol%, _{K 2} O is The raw materials were blended and mixed so as to be 1.0 mol%. The raw material mixture was put in a platinum crucible and melted at 1600 ° C. for 60 minutes, and then the molten glass was poured out and cooled. This glass was pulverized with an alumina ball mill for 20 hours to produce a glass powder for a reflective layer. Note that ethyl alcohol was used as a solvent for grinding.

The average particle diameter D ₅₀ (μm) of the glass powder for the reflection layer thus obtained was measured using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Shimadzu Corporation, trade name: SALD2100). The average particle diameter _{D 50} of the glass powder was 2.0 .mu.m.
Further, the softening point (Ts) of the glass powder for the reflective layer is raised to 1000 ° C. under the condition of a heating rate of 10 ° C./min using a differential thermal analyzer (trade name: TG-DTA2000, manufactured by Bruker AXS). And measured. The softening point (Ts) of the glass powder for a reflective layer was 835 ° C.

Next, the above-mentioned glass powder for the reflective layer is blended with the titania powder (Toho Titanium Co., Ltd., trade name: HT1311) having a 50% particle size (D ₅₀ ) of 0.6 μm so as to have the ratio shown in Table 1. Then, glass ceramic compositions 1 to 3 for Examples 1 to 3 and glass ceramic compositions 4 to 6 for Comparative Examples 1 to 3 were produced by mixing. In the table, the mixing ratio of titania powder and glass powder is expressed in volume%.

The glass ceramic composition and the resin component are blended at a ratio of 70% by mass of the glass ceramic composition G1 and 30% by mass of the resin component, kneaded in a porcelain mortar for 1 hour, and further in three rolls Dispersion was performed three times to produce a titania paste P1 for the reflective layer. In addition, the resin component used what prepared and disperse | distributed ethyl cellulose and alpha terpineol by the ratio of mass ratio 15:85.
Further, reflective layer titania pastes P2 to P6 were prepared in the same manner as the reflective layer titania paste P1 except that the glass ceramic compositions G2 to G6 were used instead of the glass ceramic composition G1.

Next, a green sheet for a substrate body was manufactured.
First, the _{SiO 2 60.4mol%, B 2 O} 3 to 15.6mol%, _Al 2 _{O 3} to 6 mol%, CaO and 15 mol%, 1 mol% of _{K 2} O, the Na ₂ O such that 2 mol% The raw materials were blended and mixed. The raw material mixture was put in a platinum crucible and melted at 1600 ° C. for 60 minutes, and then the molten glass was poured out and cooled. This glass was pulverized for 40 hours by an alumina ball mill to produce a glass powder for a substrate body. Note that ethyl alcohol was used as a solvent for grinding.

  A glass ceramic composition for a substrate body is produced by blending and mixing the glass powder for the substrate body to 40% by mass and the alumina filler (trade name: AL-45H, manufactured by Showa Denko KK) to 60% by mass. did. 50 g of this ceramic composition for a glass substrate body, 15 g of an organic solvent (a mixture of toluene, xylene, 2-propanol and 2-butanol in a mass ratio of 4: 2: 2: 1), a plasticizer (di-2 phthalate) -Ethylhexyl) 2.5g, polyvinyl butyral as a binder (trade name: PVK # 3000K, manufactured by Denka Co., Ltd.) 5g, and further a dispersant (trade name: BYK180, manufactured by Big Chemie) were mixed and mixed to prepare a slurry. .

  This slurry was applied onto a PET film by a doctor blade method and dried to produce a green sheet for a main body having a thickness after firing of 0.15 mm.

  On the other hand, conductive metal powder (manufactured by Daiken Chemical Industry Co., Ltd., trade name: S550) was mixed so that the solid content was 85 mass%. The vehicle is a mixture of ethyl cellulose and α-terpineol as a solvent in a mass ratio of 15:85. The mixture of the conductive metal powder and the vehicle was kneaded for 1 hour in a porcelain mortar, and further dispersed three times with three rolls to produce a conductive metal paste.

  Next, using the obtained titania paste, conductive metal paste, and green sheet, a sample for evaluating the luminous flux was prepared. First, a through hole having a diameter of 0.3 mm is formed in a portion corresponding to the unfired through conductor 5 of the green sheet 2 for the main body by using a hole puncher, and filled with a metal paste by a screen printing method to obtain an unfired through conductor paste. While forming the layer 5, the unfired connection terminal conductor paste layer 3 and the unfired external electrode terminal conductor paste layer 4 were formed. The green sheets were overlapped and integrated by thermocompression bonding to obtain a green sheet for a main body with a conductive paste layer.

  The reflective layer titania paste 1 was applied to the center of the mounting surface 21 of the main body green sheet with the conductive paste layer by a screen printing method to form the reflective layer 6, thereby forming the unfired light emitting element mounting substrate 1.

  The non-fired light emitting element mounting substrate 1 obtained above was degreased by holding at 550 ° C. for 5 hours, and further fired by holding at 870 ° C. for 30 minutes to produce a light emitting element mounting substrate 1. The thickness of the reflective layer 6 formed on the light emitting element mounting substrate 1 was 20 μm.

(Examples 2-3, Comparative Examples 1-3)
The reflective layer 6 was formed by applying the reflective layer titania pastes P2 to P6 using the glass ceramic compositions G2 to G6 to the central portion of the mounting surface 21 by the screen printing method instead of the reflective layer titania paste P1. A light emitting element mounting substrate 1 was manufactured in the same manner as Example 1 except for the above.

[Thermal conductivity]
The thermal conductivity of each reflective layer 6 provided on the light emitting element mounting substrate 1 of each example and comparative example was measured as follows. First, the glass powder for reflection layer and the titania powder are mixed in the proportions described in each example and comparative example in Table 1, and the obtained glass ceramic compositions 1 to 6 are pressed and fired by 3 g each. Thus, a sintered body having a diameter of 10 mm and a height of 10 mm was obtained. Next, each sintered body was ground and polished to produce a sintered body block having a diameter of 10 mm and a height of 1 mm. About each obtained sintered compact block, thermal conductivity was measured by the laser flash method using the thermal conductivity measuring apparatus (The ULVAC-RIKO Co., Ltd. make, brand name: TC-7000). The thermal conductivity was measured under the conditions of a measurement temperature of 20 ° C., a pressure of 25 kg / m ⁻² , and atmospheric conditions. The measurement results are shown in Table 1.

[Reflectance]
The reflectance of each reflective layer 6 provided on the light emitting element mounting substrate 1 of each example and comparative example was measured by the following method.
First, on a square transparent quartz substrate having a length of about 30 mm × width of about 30 mm, the titania pastes P1 to P6 for the reflective layer are applied by a screen printing method so that the thickness after firing becomes approximately 15 μm and 30 μm, respectively. Two types of titania films were formed.
Each titania film was baked by holding at 875 ° C. for 45 minutes using a spectroscope (Ocean Optics, trade name: USB2000) and a small integrating sphere (Ocean Optics, trade name: ISP-RF). The reflectance was measured. The obtained reflectance was linearly complemented with respect to the thickness, and the reflectance (unit:%) of the 20 μm thick titania film fired body, that is, the reflective layer was calculated.
The reflectance was for light having a wavelength of 460 nm, and barium sulfate was used as a reference. The measurement results are shown in Table 1.

[Adhesiveness]
The adhesion of the reflective layer 6 provided on the light emitting element mounting substrate 1 of each example and comparative example to the substrate body 2 was evaluated by the following method.
That is, the reflective layer titania pastes P1 to P6 were applied on a square green sheet having a length of about 30 mm and a width of about 30 mm by screen printing to form a titania film having a thickness of 20 μm. This green sheet with a titania film was degreased by holding at 550 ° C. for 5 hours, and further fired by holding at 870 ° C. for 30 minutes to obtain a green sheet sintered body with a reflective layer.
The obtained sintered body is put into water in a beaker, subjected to ultrasonic cleaning, and the titania film fired body, that is, the presence or absence of film peeling of the reflective layer is visually observed to determine whether the reflective layer and the substrate body are Adhesion was evaluated. In Table 1, the case where film peeling was confirmed was described as “x”, and the case where film peeling was not observed visually was described as “◯”.

  In addition, a light emitting diode 10 was mounted on the light emitting element mounting substrate 1 of each example and comparative example, thereby producing a light emitting device 10. One light emitting diode element 8 (trade name: GQ2CR460Z, manufactured by Showa Denko KK) is fixed on the reflective layer 6 with a die bond material (trade name: KER-3000-M2 manufactured by Shin-Etsu Chemical Co., Ltd.), and the electrode (not shown) It was electrically connected to the connection terminal 3 by the bonding wire 9. Furthermore, it sealed so that the molding material 11 shown in FIG. 3 might be comprised using the sealing agent (The Shin-Etsu Chemical Co., Ltd. make, brand name: CSR-1016A). As the sealant, a phosphor (chemical chemicals, trade name: P46-Y3) containing 20% by mass with respect to the sealant was used.

[Light flux]
Next, for the light emitting device 10 of each example and comparative example, 35 mA was applied to the light emitting element 8 (light emitting diode element) using a voltage / current generator (trade name: R6243, manufactured by Advantest Corporation) The total luminous flux of light obtained from the light emitting device 10 was measured. Measurement of the total luminous flux is carried out by installing the light emitting device 10 in an integrating sphere (6 inches in diameter) and using a total luminous flux measuring device (Spectracorp, product name: SOLIDLAMBDA, CCD, LED, MONITOR, PLUS). It was. The measurement results are shown in Table 1. In Table 1, the measured value of the total luminous flux in Comparative Example 2 is assumed to be 100%, and for Examples 1 to 3 and Comparative Examples 1 and 3, the percentage based on the measured value of Comparative Example 2 is calculated. Indicated.
In Comparative Example 1, the amount of light flux was not evaluated because the reflective layer 6 was separated from the substrate body 2 and peeled off during firing.

From Table 1, in the light emitting element mounting substrates of Examples 1 to 3, each reflective layer has a very high reflectance of 90% or more, and sufficiently reflects light from the light emitting element forward. Is possible. Moreover, in the light emitting element mounting substrates of Examples 1 to 3, all the reflective layers have a thermal conductivity of 5 W / m · K or more, and it is possible to efficiently dissipate heat from the light emitting elements. is there. Moreover, since a high reflectance was obtained in this way, it was confirmed that the light emitting devices of Examples 1 to 3 can obtain a higher light flux amount than the light emitting devices of Comparative Examples 1 to 3.
On the other hand, in the light emitting element mounting substrate of Comparative Example 2, the reflectance of the reflective layer was low and the light flux of the light emitting device was low as compared with Examples 1 to 3. Moreover, in the light emitting element mounting substrate 1 of the comparative example 1, the adhesiveness with respect to the board | substrate body of a reflection layer was inferior, and it was recognized that practical application is difficult. Moreover, in the light emitting element mounting substrate of Comparative Example 3, the thermal conductivity of the reflective layer was low, the heat dissipation of the light emitting element mounting substrate was inferior, and the light flux in the light emitting device was small.

DESCRIPTION OF SYMBOLS 1 ... Light emitting element mounting substrate, 2 ... Board | substrate body, 21 ... Mounting surface, 22 ... Non-mounting surface, 3 ... Connection terminal, 4 ... External electrode terminal, 5 ... Through-conductor, 6 ... Reflective layer, 8 ... Light emitting element, 9 ... Bonding wire, 10 ... Light emitting device, 11 ... Mold material

Claims (7)

A substrate body having a mounting surface on which the light emitting element is mounted;
A reflective layer that is formed on a part of the mounting surface of the substrate body and reflects light emitted from the light emitting element;
The substrate for mounting a light emitting element, wherein the reflective layer is made of a sintered body of a composition containing titanium oxide powder and glass powder. 2. The light-emitting element mounting substrate according to claim 1, wherein a ratio of glass and titanium oxide contained in the reflective layer is, as a volume ratio, glass: titanium oxide = 3: 97 to 30:70. The light emitting element mounting substrate according to claim 1, wherein the substrate body is a low-temperature fired ceramic substrate. 4. The light-emitting element mounting substrate according to claim 1, wherein the reflective layer has a thickness of 10 μm to 50 μm. The light emitting element mounting substrate according to claim 1, wherein the reflective layer has a thermal conductivity of 5 W / m · K or more. The light emitting element mounting substrate according to claim 1, wherein the reflectance of the reflective layer is 85% or more. The light emitting element mounting substrate according to any one of claims 1 to 6,
A light emitting device mounted on a mounting surface of the light emitting device mounting substrate.

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