JP2013239546A - 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, high in reflectance at a light emitting element mounting face, less in optical loss due to silver coloring when used in a light emitting device, and high in light extraction efficiency.SOLUTION: A substrate 1 for mounting a light emitting element includes: a substrate body 2; a silver reflective layer 6 formed in the substrate body 2 and comprising silver or a silver alloy as a main body; and a coating layer 7 formed so as to cover the entire face of the silver reflective layer 6 and comprising a glass ceramic sintered body comprising glass as a main body and containing ceramic powder. The coating layer substantially contains no alumina-based ceramic powder, and contains ceramic powder including one kind or more of powder of ceramic having high refractive index, the difference between the high refractive index and a refractive index of the glass being 0.4 or more.

Description

  The present invention relates to a light-emitting element mounting substrate and a light-emitting device, and more particularly to a light-emitting element mounting substrate with high light extraction efficiency and a light-emitting device using the same.

  2. Description of the Related Art In recent years, light emitting devices using light emitting elements have been used as lighting, various displays, backlights for large liquid crystal TVs, and the like with increasing brightness and whitening of light emitting elements such as light emitting diodes (LEDs). In general, since a light emitting element mounting substrate on which a light emitting element is mounted is required to have high reflectivity for efficiently reflecting light emitted from the element, attempts have been made to provide a reflective layer (light reflecting layer) on the substrate surface. . A reflective layer mainly composed of silver having a high reflectance (hereinafter referred to as a silver reflective layer) is used as the reflective layer.

  However, since silver is easily corroded, if left in an exposed state, oxidation or sulfuration occurs on the surface of the silver reflection layer, the reflectance is lowered, and sufficient light extraction efficiency cannot be obtained. In order to prevent corrosion of the silver reflection layer, a method of covering the surface with a coating layer has been proposed. In recent years, a glass material containing ceramic powder has been studied as a material that can form a coating layer that has high sealing properties, is less likely to be deformed during firing, and has high surface flatness (see, for example, Patent Document 1). ). By configuring the coating layer with a sintered body of a mixture of glass powder and ceramic powder (hereinafter sometimes referred to as a glass ceramic sintered body), the surface flatness is increased. In addition, the reflection direction of light incident on the coating layer from the light emitting element can be dispersed, and variations in light distribution characteristics can be reduced.

  However, in the structure in which a coating layer made of a glass ceramic sintered body is provided on the surface of the silver reflection layer, there is a problem that the reflectance is greatly reduced as compared with the case of only the silver reflection layer.

Moreover, for example, when a coating layer of a glass ceramic sintered body containing alumina (Al ₂ O ₃ ) ceramic powder is provided on the surface of the silver reflection layer, the coating layer is discolored for the following reason. There has been a problem that the light intensity (luminance) of the light emitting device is lowered. That is, during the firing process, silver ions diffuse and migrate from the silver reflective layer to the coating layer containing the alumina-based ceramic powder, and the transferred silver ions are exposed from the surface of the coating layer. And when a light emitting element is mounted on such a coating layer and a sealing layer such as a silicone resin is formed, high-concentration silver ions (Ag ⁺ ) exposed on the surface of the coating layer are contained in the sealing layer. Is reduced to Ag ⁰ by contact with a platinum catalyst, and the like, agglomerates into colloidal particles, and develops a phenomenon called so-called silver coloring that develops color at the interface between the coating layer and a sealing layer such as a silicone resin. . As a result, the reflectivity may be reduced, and the luminance as the light emitting device may be reduced.

JP2011-228672A

  The present invention has been made to solve the above-described problems, and has a high reflectance of a light emitting element mounting surface, a small light loss due to silver coloring when used as a light emitting device, and a high light extraction efficiency. It is an object to provide a light-emitting element mounting substrate and a light-emitting device using the substrate.

  The substrate for mounting a light emitting element of the present invention includes a substrate body having a mounting surface on which the light emitting element is mounted, a metal layer mainly composed of silver or a silver alloy formed on the mounting surface of the substrate body, and the metal layer. A substrate for mounting a light-emitting element, which is formed so as to cover the entire surface of the substrate and has a coating layer made of a glass-ceramic sintered body mainly composed of glass and containing ceramic powder, the coating layer comprising an alumina-based ceramic A ceramic powder containing substantially no powder and containing at least one high refractive index ceramic powder having a refractive index difference of 0.4 or more from glass is contained.

In the light-emitting element mounting substrate of the present invention, the content of Al ₂ O _{3 in} the glass is preferably less than 2% in terms of mol% based on oxide. Moreover, it is preferable that the light reflectance of the area | region where the said coating layer was formed on the said metal layer is 94% or more in the said mounting surface of the said board | substrate body. The concentration of the silver contained in the coating layer is preferably in terms of Ag 2 _O is 0.5 wt% or less.

  Furthermore, in the light emitting element mounting substrate of the present invention, the content of the high refractive index ceramic powder contained in the coating layer is preferably 0.8 volume% or more and 20 volume% or less. And the said coating layer is a layer formed by baking the printing layer of the paste containing the said powder of glass and the said ceramic powder, The total content of the said ceramic powder contained in this coating layer is 15 volume% The content is preferably 40% by volume or less. The coating layer is a layer formed by firing a green sheet containing the glass powder and the ceramic powder, and the total content of the ceramic powder contained in the coating layer is 40% by volume or more and 50%. It is preferable that it is less than volume%.

  The light emitting device of the present invention includes the light emitting element mounting substrate of the present invention and a light emitting element mounted on the mounting portion of the mounting surface of the light emitting element mounting substrate. In the light emitting device of the present invention, it is preferable that a part or all of the surface of the coating layer is sealed with a silicone resin.

According to the substrate for mounting a light emitting element of the present invention, it is possible to prevent gas or liquid from entering a metal layer mainly composed of silver or a silver alloy to prevent oxidation or sulfidization, and silver from the metal layer to the coating layer. By preventing ion migration / diffusion, silver ions can be prevented from agglomerating and colloidal particles on the surface of the coating layer, and a decrease in reflectance due to silver coloring can be prevented.
Furthermore, since the coating layer contains ceramic powder including high refractive index ceramic powder, it is high by suppressing the decrease in reflectance due to the formation of the coating layer on the metal layer mainly composed of silver or silver alloy. In addition to achieving the reflectance, a light emitting element mounting substrate with improved flatness of the light emitting element mounting portion can be obtained. Furthermore, since the metal layer on the substrate and the coating layer provided thereon can be fired at the same time, the load on the process can be suppressed.

  In the light emitting device of the present invention, by using the light emitting element mounting substrate described above, the reflectance of the mounting surface is high and the reflectance is not easily lowered, so that high emission luminance can be maintained for a long time. In addition, since the tilt and damage of the light-emitting element are suppressed, favorable light emission with no variation in alignment characteristics can be obtained.

It is sectional drawing which shows an example of embodiment of the light emitting element mounting substrate of this invention. It is sectional drawing which shows an example of embodiment of the light-emitting device of this invention.

  Embodiments of the present invention will be described below.

<Light emitting element mounting substrate>
FIG. 1 is a cross-sectional view showing an example of an embodiment of a light emitting element mounting substrate of the present invention. The light emitting element mounting substrate 1 has a substantially flat substrate body 2. One main surface of the substrate body 2 is a mounting surface 2a on which a light emitting element such as an LED element is mounted. The mounting surface 2 a is provided with an element 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 2b on which no light emitting element is mounted. The non-mounting surface 2b is provided with external electrode terminals 4 that are electrically connected to an external circuit. ing. A through conductor 5 that electrically connects the element connection terminal 3 and the external electrode terminal 4 is provided inside the substrate body 2. In the present specification, the “substantially flat substrate body” means a level at which the upper main surface and the lower main surface, that is, the mounting surface 2a and the non-mounting surface 2b can be recognized as a flat plate shape at the visual level. A substrate body that is a flat surface. Similarly, the abbreviations indicate levels that can be recognized at the visual level unless otherwise specified.

  Furthermore, in order to reduce the thermal resistance of the substrate body 2, thermal vias (not shown) can be embedded in the substrate body 2. The thermal via is, for example, a columnar one that is smaller than the mounting portion of the light emitting element to be described later, and is preferably disposed from the non-mounting surface 2b to an intermediate position in the thickness direction of the substrate body 2. With this arrangement, the flatness of the entire mounting surface 2a, particularly the mounting portion, can be improved, the thermal resistance can be reduced, and the inclination when the light emitting element is mounted can be suppressed.

  A silver reflecting layer (center reflecting layer) 6 which is a metal layer mainly composed of silver or silver alloy for reflecting light emitted from the light emitting element is provided at a substantially central portion of the mounting surface 2a of the substrate body 2. It has been. The metal layer mainly composed of silver or silver alloy is preferably a reflective layer as described above, but is not limited to a reflective layer, and may be a conductive layer having a conductive function, for example.

And the coating layer 7 is provided on the said silver reflection layer 6 so that the whole surface (upper surface and side surface) may be covered, and a part of coating layer 7 is the mounting part 10 in which a light emitting element is mounted, and It has become. A silver reflection layer (peripheral reflection layer) 6 mainly composed of silver or a silver alloy is also provided on the periphery of the mounting surface 2 a of the substrate body 2, and all of the silver reflection layer 6 is also provided on the silver reflection layer 6. A covering layer 7 is provided so as to cover the surface. Each of the coating layers 7 provided so as to cover the surface of the silver reflective layer (the central reflective layer and the peripheral reflective layer) 6 is mainly a glass powder sintered body (hereinafter sometimes simply referred to as glass). And a ceramic ceramic powder containing ceramic powder containing substantially no alumina ceramic powder and containing at least one high refractive index ceramic powder having a refractive index difference of 0.4 or more from glass It is comprised by. In this specification, “alumina-based ceramic powder” refers to a ceramic powder containing 50% by mass or more of alumina (Al ₂ O ₃ ) as a chemical component.

By providing such a covering layer 7 so as to cover the entire surface of the silver reflective layer 6, it is possible to prevent gas or liquid from entering the silver reflective layer 6 and prevent oxidation and sulfurization of the silver reflective layer 6. The silver ion migration and diffusion from the silver reflective layer 6 to the coating layer 7 can be prevented, and the aggregation and colloidalization of silver ions on the surface of the coating layer 7 can be prevented, and the reflectance is lowered due to silver coloring. Can be prevented.
Incidentally, the glass powder sintered body constituting the coating layer 7, by less than 2% content of Al ₂ O ₃ in mole% based on oxides, the diffusion of silver ions into the coating layer 7 more It can suppress well and can prevent the fall of the reflectance of the surface of the coating layer 7 much more.

  In the light emitting element mounting substrate 1 of the embodiment of the present invention, the substrate body 2 is a substantially flat plate member, but a recess (cavity) is formed so that the light emitting element mounting portion 10 is positioned one step below. It can also be used as a member. Although the material which comprises the board | substrate body 2 is not specifically limited, The thing which does not deform | transform at the formation process of the above-mentioned coating layer 7 is preferable, and an inorganic material is used preferably. Among inorganic materials, alumina, low temperature co-fired ceramics (hereinafter referred to as LTCC), aluminum nitride, and the like are excellent in terms of thermal conductivity, heat dissipation, strength, and manufacturing cost. And is preferably used. In particular, from the viewpoints of high reflectivity, ease of manufacture, easy processability, economy, etc., LTCC is preferred as the inorganic material constituting the substrate body 2. The raw material composition, sintering conditions, and the like of the glass ceramic sintered body constituting the substrate body 2 will be described in a method for manufacturing a light emitting element mounting substrate described later.

  The constituent material of the element connection terminal 3, the external electrode terminal 4 and the through conductor 5 described above can be used without particular limitation as long as it is the same constituent material as the wiring conductor normally used for the light emitting element mounting substrate. Specific examples of the constituent material of the element connection terminal 3, the external electrode terminal 4, and the through conductor 5 include conductive metal materials mainly composed of metals such as copper, silver, and gold. Note that “mainly comprising metal” means that when a simple metal layer (for example, a copper metal layer, a silver metal layer, or a gold metal layer) is formed from this metal material, the metal component is 70 mass. It means to contain more than%. In the case of a metal layer that imparts high reflection performance, a metal material composed of silver, a metal material composed of silver and platinum, or a metal material composed of silver and palladium is preferably used. The silver content at this time is preferably 95% by mass or more. These metal materials will be specifically described in a method for manufacturing a light emitting element mounting substrate described later. The thicknesses of the element connection terminal 3 and the external electrode terminal 4 are preferably 5 to 15 μm.

  Further, the surface of the element connection terminal 3 or the external electrode terminal 4 is electrically conductive in order to protect this layer from oxidation and sulfuration and to improve solder wettability and bonding characteristics when connecting a bonding wire or the like. A protective layer (not shown) is preferably provided. The conductive protective layer is not particularly limited as long as it is made of a conductive material having a function of protecting the conductive metal layer. Specific examples include layers made of nickel plating, chromium plating, silver plating, nickel / silver plating, gold plating, nickel / gold plating, and the like. A method for forming the element connection terminals 3 and the like will also be described in the method for manufacturing a light emitting element mounting substrate.

  The silver reflection layer 6 is a layer made of a silver alloy such as silver, a silver palladium alloy, or a silver platinum alloy. The silver reflection layer 6 preferably has a high reflectance, and is particularly preferably a silver layer. The silver reflecting layer 6 is a paste formed by adding a vehicle such as ethyl cellulose to a powder of silver or the above silver alloy and, if necessary, a solvent or the like to form a paste, by a method such as screen printing. It can be formed by printing at a predetermined position and firing.

  The coating layer 7 is a layer for protecting the lower silver reflection layer 6 from corrosion such as oxidation and sulfurization, and is composed of a glass ceramic sintered body mainly composed of glass and containing ceramic powder. Note that “mainly composed of glass” means that glass is contained in a proportion exceeding 50% by volume. The ceramic powder contained in the coating layer 7 is substantially free of alumina-based ceramic powder, and includes one or more of high-refractive index ceramic powders having a refractive index difference of 0.4 or more from glass. .

The glass constituting the coating layer 7 is at least one selected from the group consisting of 20 to 85% of SiO ₂ , 0 to 40% of B ₂ O ₃ , MgO, CaO, SrO and BaO in terms of oxide-based mol%. It is preferably a sintered body obtained by firing a glass powder containing 0 to 16%, 0 to 16% of at least one selected from Na ₂ O and K ₂ O.

  Hereinafter, the components of the glass powder will be described. In the following description, unless otherwise specified, the composition is expressed in mol%, and is simply expressed as%.

SiO ₂ serves as a network former of glass, and is an essential component for increasing chemical durability, particularly acid resistance. If the SiO ₂ content is less than 20%, the acid resistance may be insufficient. On the other hand, if the content of SiO ₂ exceeds 85%, the glass softening point (Ts) and glass transition point (Tg) may be excessively high.

B ₂ O ₃ serves as a glass network former, and may be added within a range of 40% or less. When the content of B ₂ O ₃ exceeds 40%, it is difficult to obtain stable glass, and chemical durability may be lowered. The content of B ₂ O ₃ is preferably 12% or more.
The content ratio of Al ₂ O ₃ in the glass powder is preferably less than 2%. By making it less than 2%, the diffusion of silver ions to the coating layer 7 can be suppressed more favorably, and the decrease in reflectance due to silver coloring on the surface of the coating layer 7 can be further prevented.

  MgO, CaO, SrO and BaO may be added in a range where the total content does not exceed 50% in order to lower Ts and Tg and to increase the stability of the glass. If the total content of MgO, CaO, SrO, and BaO exceeds 50%, the acid resistance may decrease. Moreover, there is a possibility that silver coloring is likely to occur.

Na ₂ O and K ₂ O can be added within a range where the total content does not exceed 16% in order to lower Ts and Tg. When the total content of Na ₂ O and K ₂ O exceeds 16%, chemical durability, particularly acid resistance may be lowered, and electrical insulation may be lowered.

When Al ₂ O ₃ is used as a constituent component of the multi-layer 7, there is a possibility that silver coloring is likely to occur. That is, in the glass, Al ³⁺ attracts non-bridging oxygen and takes the form of tetracoordinate [AlO ₄ ], and the central Al becomes negatively charged. For this charge compensation, Ag ⁺ (silver ion) having a positive charge is attracted, so that the silver ion is stably present as such a tetracoordinate aluminum counter cation. It is considered that diffusion / migration from the glass to the coating layer 7 containing glass proceeds. Therefore, by a glass composition containing no Al ₂ O _3, can suppress the diffusion of the silver ions into the glass ceramic sintered body in, it can be prevented silver coloring of the coating layer 7 surface.

The glass powder used for forming the coating layer 7 (hereinafter sometimes referred to as glass powder for the coating layer) is not necessarily limited to the one consisting only of the above components, and may be other as long as the object of the present invention is not impaired. It can contain ingredients. When other components are contained, the total content is preferably 10% or less. In the embodiment of the present invention, the glass powder does not contain lead oxide.
Moreover, the glass powder for coating layers 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.

  The glass powder for coating layer 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 50% particle size (D ₅₀ ) of the glass powder for coating layer is preferably 0.5 μm or more and 4 μm or less. In this specification, D ₅₀ refers to a value measured using a laser diffraction / scattering particle size distribution measuring apparatus. When D ₅₀ of the glass powder for the coating layer is less than 0.5 [mu] m, the glass powder is likely to agglomerate, handle with is difficult, fear is the time required for pulverization is too long. On the other hand, D ₅₀ of the glass powder for the coating layer is more than 4 [mu] m, increase and insufficient sintering of Ts may occur. The particle size can be adjusted, for example, by classification as necessary after pulverization. The maximum particle size of the glass powder for coating layer is preferably 20 μm or less. When the maximum particle size exceeds 20 μm, the sinterability of the glass powder is lowered, and undissolved components remain in the sintered body, which may reduce the reflectivity of the coating layer 7. The maximum particle size of the glass powder for coating layer is more preferably 10 μm or less.

Examples of the high refractive index ceramic powder contained in the coating layer 7 include titania powder, zirconia powder, and stabilized zirconia powder. While the refractive index of glass is about 1.5, the refractive index of titania is about 2.7 and the refractive index of zirconia is about 2.2, which is higher than the refractive index of glass by 0.4 or more. have. D ₅₀ of these high refractive index ceramic powders is preferably 0.5 μm or more and 4 μm or less. The content of the high refractive index ceramic powder in the glass ceramic sintered body constituting the coating layer 7 is preferably 0.8 volume% or more and 20 volume% or less. The reflectance of the coating layer 7 can be improved by making content of high refractive index ceramic powder 0.8 volume% or more. Moreover, the glass ceramic sintered compact of a uniform composition can be obtained because content of high refractive index ceramic powder shall be 20 volume% or less.

The coating layer 7 can contain ceramic powders such as silica (SiO ₂ ), ceria (CeO ₂ ), and zinc oxide (ZnO) in addition to these high refractive index ceramic powders. D _{50 of} these ceramic powders is also preferably 0.5 μm or more and 4 μm or less, like the high refractive index ceramic powder. As described above, the coating layer 7 does not substantially contain an alumina ceramic powder such as an alumina powder.

  The preferable range of the total content (total content) of the ceramic powder contained in the coating layer 7 varies depending on the method of forming the coating layer 7. When the coating layer 7 is a layer formed by firing a printed layer of a paste containing glass powder and ceramic powder, the total content of the ceramic powder contained in the coating layer 7 is 15 volume% or more and 40 volumes. % Or less is preferable. When the coating layer 7 is a layer formed by firing a green sheet containing glass powder and ceramic powder, the total content of the ceramic powder contained in the coating layer 7 is 40% by volume or more and less than 50% by volume. It is preferable that In any of the forming methods, when the total content of the ceramic powder contained in the coating layer 7 is not less than the lower limit value, the surface flatness of the coating layer 7 is improved and the heat dissipation is improved. Moreover, when the total content of the ceramic powder is not more than the upper limit value, a glass ceramic sintered body having a uniform composition can be obtained.

  The thickness of the covering layer 7 is preferably 5 to 30 μm. If it is less than 5 μm, the covering property may be insufficient, and therefore it is preferably 5 μm or more. If it exceeds 30 μm, heat dissipation may be hindered and the light emission efficiency may be reduced.

  The method for forming the coating layer 7 is not particularly limited as long as the method can form a 5 to 30 μm thick layer. For example, a paste of a mixture of glass powder and ceramic powder containing one or more of the high refractive index ceramic powders can be printed by screen printing or the like and fired. Moreover, the green sheet produced from the mixture of glass powder and the ceramic powder containing 1 or more types of the said high refractive index ceramic powder can be arrange | positioned in a predetermined part, and can be formed by baking. The method for forming the coating layer 7 will be described in the method for manufacturing the light emitting element mounting substrate 1.

  According to the light emitting element mounting substrate 1 of the embodiment of the present invention, the coating layer 7 made of a glass ceramic sintered body is provided so as to cover the entire surface of the silver reflective layer 6. In addition to suppressing the intrusion of gas or liquid to prevent oxidation or sulfidation of the silver reflective layer 6, the coating layer 7 does not substantially contain alumina ceramic powder. 7 can be prevented from moving and diffusing to silver 7, and aggregation and colloidal formation of silver ions on the surface or inside of the coating layer 7 can be prevented. In addition, since the coating layer 7 contains one or more kinds of high refractive index ceramic powder, a decrease in reflectance due to the provision of the coating layer 7 on the silver reflective layer 6 is suppressed to 94% or more. High reflectivity can be achieved.

In the light emitting element mounting substrate 1 of the embodiment, the concentration of silver contained in the coating layer 7 is 0.5% by mass in terms of Ag ₂ O due to migration / diffusion of silver ions from the silver reflecting layer 6. Or less, more preferably 0.2% by mass or less.

  Furthermore, according to the light emitting element mounting substrate 1 of the embodiment, since the silver reflection layer 6 and the coating layer 7 provided thereon can be simultaneously fired, the load on the process can be suppressed.

<Method for manufacturing substrate for mounting light-emitting element>
A light emitting element mounting substrate 1 having a substrate body 2 made of LTCC includes, for example, (A) a green sheet manufacturing process for a substrate, (B) a conductor paste layer forming process, (C) a laminating process, ( It can be produced by a method comprising D) a silver paste layer forming step for a reflective layer, (E) an unfired coating layer forming step, and (F) a firing step. In addition, about the member used for manufacture, the same code | symbol as the member of a finished product is attached | subjected and demonstrated.

(A) Substrate green sheet manufacturing process First, a substrate green sheet is formed. The green sheet for a substrate is prepared by adding a binder, and if necessary, a plasticizer, a solvent, etc., to a glass ceramic composition containing a glass powder for a substrate and a ceramic powder for a substrate, and adjusting the slurry to obtain a doctor blade method or the like. Can be obtained by molding into a sheet and drying.

  Although the glass powder for substrates is not necessarily limited, those having a Tg of 550 ° C. or more and 700 ° C. or less are preferable. When Tg is less than 550 ° C., degreasing described later may be difficult. On the other hand, when Tg exceeds 700 ° C., the shrinkage start temperature increases, and the dimensional accuracy may decrease.

Such a glass powder for a substrate is expressed in mol% on the basis of oxide, for example, SiO ₂ is 57% to 65%, B ₂ O ₃ is 13% to 18%, CaO is 9% to 23%. Hereinafter, it is preferable to contain Al ₂ O _{3 in a range} of 3% to 8% and one or more selected from K ₂ O and Na ₂ O in a total amount of 0.5% to 6%.

  The glass powder for a substrate 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 or ethyl alcohol 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 substrates is not necessarily limited to what consists only of the said component, It can also contain another component in the range with which various characteristics, such as Tg, are satisfy | filled. When other components are contained, the total content is preferably 10% or less.

It is preferable that _{D 50} of the glass powder for substrate is 0.5 to 2 [mu] m. If D ₅₀ of the glass powder for substrate is less than 0.5 [mu] m, the glass powder is likely to agglomerate, handle not only difficult, it is difficult to uniformly disperse. On the other hand, if the D ₅₀ of the glass powder for substrate exceeds 2 [mu] m, there is a possibility that the increase and insufficient sintering of Ts occurs. The particle size can be adjusted, for example, by classification as necessary after pulverization.

As the ceramic powder for the substrate, those conventionally used for the production of LTCC substrates can be used. For example, alumina powder, zirconia powder, or a mixture of alumina powder and zirconia powder can be suitably used. _{D 50} of the ceramic powder for substrate, for example, preferably 0.5 to 4 .mu.m.

  By mixing and mixing such glass powder for a substrate and ceramic powder for a substrate, for example, so that the glass powder is 30% by mass to 50% by mass and the ceramic powder is 50% by mass to 70% by mass. A glass ceramic composition can be obtained.

  Moreover, a slurry can be obtained by adding a binder and, if necessary, a plasticizer, a solvent, and the like to the glass ceramic composition. 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.

  The slurry is formed into a sheet by a doctor blade method or the like and dried to produce a green sheet for a substrate. Next, the substrate green sheet thus obtained is cut into a predetermined dimensional angle by using a punching die or a punching machine, and at the same time, via holes for interlayer connection are punched and formed at predetermined positions. Furthermore, if necessary, holes for thermal vias are punched and formed at predetermined positions on the green sheet for substrates.

(B) Conductive paste layer forming step By forming a conductive paste layer at a predetermined position on each substrate green sheet, the unfired element connection terminals 3 and the unfired external electrode terminals 4 are formed. Further, the unfired through conductor 5 is formed by filling the above-described via hole with a conductive paste. Furthermore, if necessary, an unfired thermal via is formed by filling a metal paste into the hole for the thermal via formed in the above step.

  Examples of the method for forming the conductor paste layer and the conductor paste filling layer include a method in which the conductor paste is applied by screen printing or filled into a hole. The film thickness of the formed conductive paste layer is adjusted so that the film thicknesses of the finally obtained element connection terminals 3, external electrode terminals 4 and the like become predetermined film thicknesses. In addition, as a method for forming a metal paste filling layer that becomes an unfired thermal via, a method of filling a metal paste into a hole by screen printing can be given.

  As a conductive paste used for forming the unfired element connection terminal 3, the unfired external electrode terminal 4, and the unfired through conductor 5, a conductive metal powder mainly composed of copper, silver, gold or the like, a vehicle such as ethyl cellulose, etc. If necessary, a paste can be used by adding a solvent or the like. As the conductive metal powder, silver powder, metal powder composed of silver and platinum, or metal powder composed of silver and palladium are preferably used. As the metal paste used for forming the unfired thermal via, a paste obtained by adding the above-described metal powder mainly composed of silver to a vehicle such as ethyl cellulose and, if necessary, a solvent or the like can be used.

(C) Laminating process A plurality of green sheets for a substrate on which unfired element connection terminals 3, unfired external electrode terminals 4, unfired through conductors 5 and the like are formed are stacked while being aligned and integrated by thermocompression bonding. To do. Thus, the unfired substrate body 2 is obtained.

(D) Silver paste layer forming step for reflective layer The silver paste for reflective layer is printed at a predetermined position on the mounting surface 2a of the unfired substrate body 2 by a method such as screen printing to form the unfired silver reflective layer 6. . As the silver paste for the reflective layer, a paste obtained by adding a vehicle such as ethyl cellulose to a silver alloy powder such as silver, a silver palladium alloy or a silver platinum alloy, and a solvent if necessary, is used.

(E) Unsintered coating layer forming step The above-described glass powder for coating layer and the ceramic for coating layer so as to cover the entire surface of the unsintered silver reflecting layer 6 formed on the mounting surface 2a of the unfired substrate body 2 in the above step. A glass paste for a coating layer, which is made into a paste by adding a vehicle such as ethyl cellulose and a solvent as necessary to the mixture with the powder, is printed by a method such as screen printing to form the unfired coating layer 7.

  Moreover, the unbaking coating layer 7 can also be formed by disposing a green sheet. That is, a slurry is prepared by adding a binder, and, if necessary, a plasticizer, a solvent, etc. to a glass ceramic composition containing a glass powder for a coating layer and a ceramic powder for a coating layer. And then dried to produce a green sheet for a coating layer. And this green sheet for coating layers is arrange | positioned so that the whole surface of the unbaking silver reflection layer 6 may be covered, and the unbaking coating layer 7 is formed.

  The thickness of the unfired coating layer 7 to be formed is preferably adjusted to be the thickness of the coating layer 7 finally obtained.

(F) Firing step For sintering the glass ceramic composition or the like after degreasing the binder or the like, if necessary, on the unfired substrate body 2 on which the unfired coating layer 7 is formed in the step (E). Baking is performed to obtain a light-emitting element mounting substrate 1.

  Degreasing is, for example, held at a temperature of 500 ° C. to 600 ° C. for 1 hour to 10 hours. In this way, degreasing is performed to decompose and remove the binder such as resin contained in the green sheet and each layer. Then, for example, the glass ceramic composition which comprises a green sheet is baked by hold | maintaining at the temperature of 850-900 degreeC for 20 minutes-60 minutes. By this firing, conductor paste, metal paste, silver paste, glass paste, and the like formed on and inside the substrate body 2 are simultaneously fired, and the element connection terminals 3 and the external electrode terminals 4 are placed at predetermined positions on the substrate body 2. The through conductor 5, the silver reflecting layer 6 and the covering layer 7 can be formed respectively.

  When the degreasing temperature is less than 500 ° C. or the degreasing time is less than 1 hour, it is difficult to sufficiently remove the binder and the like. 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.

  In addition, in the firing, the time can be appropriately adjusted in the temperature range of 800 ° C. to 930 ° C. in consideration of obtaining a dense structure of the substrate body 2 and productivity. Specifically, it is preferable to hold at a temperature of 850 ° C. or more and 900 ° C. or less for 20 minutes or more and 60 minutes or less, and a temperature of 860 ° C. or more and 880 ° C. or less is particularly preferable. If the firing temperature is less than 800 ° C., the substrate body 2 may not be obtained as a dense structure. On the other hand, when the firing temperature exceeds 930 ° C., productivity and the like may be reduced due to deformation of the substrate body 2. On the other hand, when the firing temperature exceeds 880 ° C., the silver reflective layer 6 and the like are excessively softened, so that the predetermined shape may not be maintained.

  In this way, the light emitting element mounting substrate 1 is obtained. After firing, nickel plating, chrome plating, silver plating, nickel / nickel plating, nickel / plating so as to cover the entire element connection terminals 3 and external electrode terminals 4 as necessary. Conductive protective layers, such as silver plating, gold plating, nickel / gold plating, etc., which are usually used for conductor protection in the light emitting element mounting substrate 1 can be formed. Among these, nickel / gold plating is preferably used. For example, the nickel / gold plating can be formed by electrolytic plating using a nickel sulfamate bath for the nickel plating layer and a potassium gold cyanide bath for the nickel plating layer.

  The light emitting element mounting substrate 1 of the present invention has been described above. However, the configuration thereof can be changed as appropriate as long as it does not contradict the spirit of the present invention.

<Light emitting device>
Next, the light emitting device of the present invention will be described. In the light emitting device 20 of the present invention, for example, as shown in FIG. 2, a light emitting element 11 such as an LED element is mounted on the mounting portion 10 of the coating layer 7 provided on the mounting surface 2 a of the light emitting element mounting substrate 1. It is a thing. The light emitting element 11 is fixed on the coating layer 7 using an adhesive, and an electrode (not shown) is electrically connected to the connection terminal 3 by a bonding wire 12. And the sealing layer 13 which consists of mold resin is provided so that the light emitting element 11 and the bonding wire 12 may be covered, and the light-emitting device 20 is comprised.

  As mold resin which comprises the sealing layer 13, since it is excellent in terms of light resistance and heat resistance, a silicone resin is preferably used. By adding a catalyst such as platinum or titanium to such a mold resin, the mold resin can be quickly cured.

  By mixing or dispersing a phosphor or the like in the sealing mold resin, the light obtained as the light emitting device 20 can be appropriately adjusted to a desired emission color. That is, by mixing and dispersing the phosphor in the sealing layer 13, the phosphor excited by the light emitted from the light emitting element 11 emits visible light, and the visible light and the light emitted from the light emitting element 11. And the desired light emission color as the light emitting device 20 can be obtained. 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 11 and the target emission color. The arrangement of the phosphor is not limited to the method of mixing and dispersing in the sealing layer 13 as described above. For example, a phosphor layer may be provided on the sealing layer 13. is there.

  In the light emitting device 20 of the present invention, by using the light emitting element mounting substrate 1, since the reflectance of the mounting portion 10 is high and the reflectance is not easily lowered, high emission luminance can be obtained for a long time. Further, by using the light-emitting element mounting substrate 1 having excellent flatness of the mounting portion 10 and low thermal resistance, an excessive temperature rise of the light-emitting element 11 is suppressed, and high-luminance light emission without variation in alignment characteristics is obtained. be able to.

  Such a light emitting device 20 can be suitably used, for example, as a backlight for a mobile phone or a large liquid crystal display, illumination for automobiles or decoration, and other light sources.

  Examples of the present invention will be described below. The present invention is not limited to these examples.

Examples 1-3, Comparative Examples 1-3
<Manufacture of substrate for reflectance measurement>
A glass ceramic composition for a coating layer was prepared.
First, a glass raw material is prepared and mixed so that each component of SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , CaO, Na ₂ O and K ₂ O has the composition (mol%) shown in the upper part of Table 1. The raw material mixture was put in a platinum crucible and melted at 1500-1600 ° C. for 60 minutes, and then the molten glass was poured out and cooled. The obtained glass was pulverized with an alumina ball mill for 20 to 60 hours to obtain a glass powder for a coating layer. In addition, ethyl alcohol was used as a solvent for pulverization.

The average particle diameter D ₅₀ of the glass powder for the resulting coating layer, a laser diffraction / scattering particle size distribution analyzer (manufactured by Shimadzu Corporation, trade name: SALD2100) was used for the measurement. Glass powder of any composition _{may, D 50} was in the range of 1 to 3 [mu] m.

Next, the glass powder for coating layer and the ceramic powder shown in Table 1 were mixed and mixed so as to have the composition (volume%) shown in the middle part of the same table to prepare a glass ceramic composition for coating layer. .
As the ceramic powder, the following were used.
Zirconia (ZrO ₂ ) powder;
1st rare element chemical company make, brand name: HST-3F, D ₅₀ = 0.5 μm
Titania (TiO ₂ ) powder;
Product name: HT1311, D ₅₀ = 0.6 μm, manufactured by Toyo Titanium
Silica (SiO ₂ ) powder;
Product name: FB-3SDC, D ₅₀ = 3.4 μm, manufactured by Denki Kagaku Kogyo Co., Ltd.
Alumina (Al ₂ O ₃ ) powder;
Product name: AL-47H, D ₅₀ = 2.1 μm, manufactured by Showa Denko

  Subsequently, in Examples 1-2 and Comparative Example 1, 50 g of the obtained glass ceramic composition for coating layer was mixed with an organic solvent (toluene, xylene, 2-propanol, 2-butanol in a mass ratio of 4: 2: 2: 15 g, a plasticizer (di-2-ethylhexyl phthalate) 2.5 g, polyvinyl butyral (manufactured by Denka Co., Ltd., trade name: PVK # 3000K) as a binder, and a dispersant (manufactured by BYK Chemie) (Product name: BYK180) 0.5 g was mixed and mixed to prepare a slurry. The slurry was applied onto a PET film by the doctor blade method and dried, and the thickness after baking was a green sheet for a coating layer of 50 μm. Was made.

  Moreover, in Example 3 and Comparative Examples 2-3, the glass ceramic composition for coating layers and the resin component were blended at a mass ratio of 60:40, kneaded in a porcelain mortar for 1 hour, and further three Dispersion was performed three times with a roll to prepare a glass paste for a coating layer. Here, as the resin component, ethyl cellulose and α-terpineol were prepared and dispersed at a mass ratio of 85:15. In addition, the green sheet for coating layers and the glass paste for coating layers used the thing of the same composition also in manufacture of the light emitting element mounting substrate mentioned later.

Next, a green sheet for a substrate body was manufactured. First, SiO ₂ is _60.4mol%, B 2 _{O 3} is 15.6mol%, _Al 2 _{O 3} is 6 mol%, CaO is 15mol%, _{K 2} O is 1 mol%, as Na ₂ O is 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 with ethyl alcohol as a solvent for 40 hours by an alumina ball mill to obtain a glass powder for a substrate body.

  35% by mass of the glass powder for the substrate body, 40% by mass of alumina powder (manufactured by Showa Denko KK, trade name: AL-45H), zirconia powder (manufactured by Daiichi Rare Element Chemical Co., Ltd., trade name: HSY-3F- A glass ceramic composition for a substrate body was obtained by blending and mixing such that J) was 25% by mass. 50 g of this glass ceramic composition, 15 g of an organic solvent (toluene, xylene, 2-propanol, 2-butanol mixed at a mass ratio of 4: 2: 2: 1), plasticizer (di-2-ethylhexyl phthalate) 2.5 g of polyvinyl butyral (trade name: PVK # 3000K, manufactured by Denka Co., Ltd.) as a binder, 5 g, and 0.5 g of a dispersant (trade name: BYK180, manufactured by Big Chemie) were blended 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 substrate main body having a thickness after firing of 0.15 mm. In addition, this board | substrate main body green sheet used similarly was used also in manufacture of the light emitting element mounting substrate mentioned later.

  Next, the obtained six green sheets for the substrate main body were superposed and integrated by thermocompression bonding, and then a silver paste for reflecting layer was printed on one side by a screen printing method. The reflective layer silver paste is composed of silver powder (manufactured by Daiken Chemical Industry Co., Ltd., trade name: S400-2) and ethyl cellulose as a vehicle in a mass ratio of 85:15, resulting in a solid content of 85% by mass. Thus, it disperse | distributed to (alpha) terpineol as a solvent, It knead | mixed for 1 hour in the porcelain mortar, and also obtained by disperse | distributing 3 times with a three roll.

  In Examples 1-2 and Comparative Example 1, the above-described green sheet for coating layer was stacked and pressure-bonded on the silver paste layer thus formed to obtain an unfired substrate. Moreover, in Example 3 and Comparative Examples 2-3, the above-mentioned glass paste for coating layers was apply | coated by the screen printing method on the silver paste layer, and the unbaking board | substrate was obtained.

  Next, the unfired substrate obtained above was held at 550 ° C. for 5 hours to decompose and remove the resin component, and then held at 870 ° C. for 30 minutes for firing. In this way, a substrate for reflectance measurement was manufactured.

<Measurement of reflectance>
Thus, the reflectance of the area | region in which the coating layer was formed on the silver reflection layer was measured in the board | substrate for a reflectance measurement obtained in Examples 1-3 and Comparative Examples 1-3, respectively. In the measurement, the reflectance in the entire visible light region (wavelength 400 to 700 nm) was measured using a spectroscope USB2000 and a small integrating sphere ISP-RF manufactured by Ocean Optics. Barium sulfate was used as a reference, and the reflectance of the surface coated with barium sulfate was calculated as 100%. The reflectance measurement results are shown in Table 1.

As is apparent from Table 1, the coating is composed of a glass ceramic sintered body which does not contain alumina powder and contains at least one of zirconia (ZrO ₂ ) powder and titania (TiO ₂ ) powder which are high refractive index ceramic powders. In the substrates of Examples 1 to 3 having layers, the reflectance of the region where the coating layer is formed is 95% or more, and it can be seen that a high reflectance can be achieved.
On the other hand, in the substrates of Comparative Examples 1 and 2, the coating layer contains a high refractive index ceramic powder, but also contains an alumina powder, so a high reflectance is not obtained. Moreover, in the board | substrate of the comparative example 3, since a coating layer does not contain high refractive index ceramic powder, it turns out that a reflectance is not high enough.

Examples 4-6, Comparative Examples 4-6
<Manufacture of light-emitting element mounting substrate>
First, conductive silver powder (manufactured by Daiken Chemical Industry Co., Ltd., trade name: S550) and ethyl cellulose as a vehicle are blended at a mass ratio of 85:15, and the solvent is used so that the solid content is 85% by mass. After being dispersed in α-terpineol, kneading was carried out for 1 hour in a porcelain mortar, and further dispersing was performed three times with three rolls to prepare a conductor paste (silver paste for conductor).

  Next, a through hole having a diameter of 0.3 mm was formed in the portion corresponding to the unfired through conductor of the green sheet for the substrate body produced in the same manner as in the production of the reflectance measurement substrate described above using a hole punch. . The through-hole is filled with the conductor paste by screen printing to form an unfired through conductor, and the same conductor paste is screen-printed at a predetermined position to form unfired connection terminals and unfired external electrode terminals. Each was formed.

  Next, after stacking 6 sheets of the green sheet for the substrate main body on which the unfired through conductors, unfired connection terminals and the like are formed and integrating them by thermocompression bonding, a silver paste for the reflective layer is applied to the central portion of the mounting surface. Printing was performed by a screen printing method to form an unsintered silver reflecting layer. In addition, the silver paste for reflective layers used what was similarly prepared by the same composition as the silver paste for reflective layers used in the said Examples 1-3 and Comparative Examples 1-3.

  And on this unbaked silver reflective layer, in Examples 4-5 and Comparative Example 4, the same green sheets for coating layers as those used in Examples 1-2 and Comparative Example 1 were stacked and pressure-bonded, An unsintered light emitting element mounting substrate was obtained. In Example 6 and Comparative Examples 5 to 6, the same coating layer glass paste as that used in Example 3 and Comparative Examples 2 to 3 was applied by a screen printing method, and an unsintered light emitting element mounting substrate and did.

  Next, after the unfired light emitting element mounting substrate obtained above is held at 550 ° C. for 5 hours to decompose and remove the resin component, it is held at 870 ° C. for 30 minutes to perform firing, and the light emitting element mounting substrate is obtained. Manufactured.

<Measurement of Ag ion concentration>
Thus, the concentration (mass%) of silver ions (Ag ⁺ ) contained in the coating layer of the light emitting element mounting substrate obtained in each of Examples 4 to 6 and Comparative Examples 4 to 6 was set to an arbitrary 10 μm × In the 10 μm region, measurement was performed by two-dimensional concentration mapping analysis using an Electron Probe Micro Analyzer (EPMA). The measurement results are shown in Table 2 as values converted to Ag ₂ O.

<Measurement of change in luminous flux of light emitting device over time>
Next, a light emitting diode (LED) element was mounted on each of the light emitting element mounting substrates obtained in Examples 4 to 6 and Comparative Examples 4 to 6 to manufacture the light emitting device shown in FIG. That is, one LED element (product name: GQ2CR460Z, manufactured by Showa Denko KK) is fixed on the mounting portion of the coating layer with a die bond material (product name: KER-3000-M2 manufactured by Shin-Etsu Chemical Co., Ltd.), and the electrode is fixed. It electrically connected to the element connection terminal by the bonding wire. Furthermore, the mold sealing layer was formed using the sealing agent. In addition, as the sealant, a silicone resin for sealing (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: SCR-1016A) was used.

Next, 35 mA was applied to the light emitting device thus obtained using a voltage / current generator (trade name: R6243, manufactured by Advantest Co., Ltd.) to cause the LED element to emit light. The total luminous flux of light obtained from the light emitting device at the time of the initial light emission (after 0 hours), after leaving for 48 hours in an environment of 80% temperature and 80% humidity, and after leaving for 96 hours in the same environment. (Lumen) was measured. Measurement of the total luminous flux was carried out using a luminous device installed in an integrating sphere (diameter 6 inches) and using a total luminous flux measuring instrument (Spectracorp, trade name: SOLIDLAMBDA / CCD / LED / MONITOR / PLUS). . The measurement results are shown in Table 2.
In Table 2, the measured value of the luminous flux in each of Examples 4 to 6 and Comparative Examples 4 to 6 at the initial light emission (after 0 hours) is set to 100, and the luminous fluxes measured after 48 hours and 96 hours are measured. The value was expressed as a relative value based on the measured value of the luminous flux after 0 hour.

As is apparent from Table 2, the coating is composed of a glass ceramic sintered body which does not contain alumina powder and contains at least one of zirconia (ZrO ₂ ) powder and titania (TiO ₂ ) powder which are high refractive index ceramic powders. In the light emitting element mounting substrates of Examples 4 to 6 having the layers, the silver ion concentration contained in the coating layer is suppressed to 0.5% by mass or less in terms of Ag ₂ O, and after the silicone resin sealing There is almost no decrease in luminance (total light flux) over time of the light emitting device.

  On the other hand, in the light emitting element mounting substrates of Comparative Examples 4 and 5, since the coating layer contains alumina powder, the silver ion concentration contained in the coating layer is high, and the transition from the silver reflective layer to the coating layer is performed. Diffused silver (ions) is present in the coating layer at a high concentration. In the light emitting device after sealing with the silicone resin, it can be seen that the total luminous flux is decreased with time, and the luminance is greatly decreased due to silver coloring or the like.

  Furthermore, in the light emitting element mounting substrate of Comparative Example 6, since the coating layer does not contain alumina powder, the Ag concentration in the coating layer is low, and the amount of light emission after sealing with the silicone resin hardly decreases with time. Since the layer does not contain high refractive index ceramic powder, a sufficiently high reflectance as a light emitting element mounting substrate cannot be obtained as in Comparative Example 3.

  DESCRIPTION OF SYMBOLS 1 ... Light emitting element mounting substrate, 2 ... Board | substrate body, 3 ... Element connection terminal, 4 ... External electrode terminal, 5 ... Through conductor, 6 ... Silver reflection layer, 7 ... Covering layer, 10 ... Mounting part, 11 ... Light emitting element , 12 ... bonding wires, 13 ... sealing layer, 20 ... light emitting device.

Claims (9)

A substrate body having a mounting surface on which the light emitting element is mounted;
A metal layer mainly composed of silver or a silver alloy formed on the mounting surface of the substrate body;
A light-emitting element mounting substrate having a coating layer formed of a glass ceramic sintered body mainly composed of glass and containing ceramic powder, which is formed so as to cover the entire surface of the metal layer,
The coating layer substantially contains no alumina-based ceramic powder and contains ceramic powder containing at least one kind of high-refractive index ceramic powder having a refractive index difference of 0.4 or more with respect to the glass. A substrate for mounting a light-emitting element. _2. The light-emitting element mounting substrate according to claim 1, wherein the content of Al ₂ O ₃ in the glass is less than 2% in terms of mol% based on oxide.   3. The light emitting element mounting substrate according to claim 1, wherein, in the mounting surface of the substrate body, a light reflectance of a region where the coating layer is formed on the metal layer is 94% or more. The light emitting element mounting substrate according to claim 1, wherein the concentration of silver contained in the coating layer is 0.5% by mass or less in terms of Ag ₂ O.   5. The light-emitting element mounting substrate according to claim 1, wherein a content of the high refractive index ceramic powder contained in the coating layer is 0.8 volume% or more and 20 volume% or less.   The coating layer is a layer formed by firing a printing layer of a paste containing the glass powder and the ceramic powder, and the total content of the ceramic powder contained in the coating layer is 15% by volume or more and 40%. The light emitting element mounting substrate according to any one of claims 1 to 5, wherein the substrate is a volume% or less.   The coating layer is a layer formed by firing a green sheet containing the glass powder and the ceramic powder, and the total content of the ceramic powder contained in the coating layer is 40% by volume or more and 50% by volume. The light emitting element mounting substrate according to any one of claims 1 to 5, wherein the light emitting element mounting substrate is less than. A substrate for mounting a light emitting element according to any one of claims 1 to 7,
A light emitting device mounted on a mounting portion of the mounting surface of the light emitting element mounting substrate.   The light emitting device according to claim 8, wherein a part or all of the surface of the coating layer is sealed with a silicone resin.

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