JP2010135729A - Substrate for mounting light-emitting element and light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for mounting a light-emitting element in which its reflection layer has a reflection property equivalent to that of silver and the reflection property does not deteriorate due to sulfurization, and a light-emitting device. <P>SOLUTION: The substrate for mounting a light-emitting element is provided with: a base member 1; a mounting part 2 configured to mount a light-emitting element 4 in a predetermined area of the upper surface of the base member 1; and a refection film 3 on surrounding areas of the mounting part 2, wherein the reflection film 3 is an alloy of silver and gold mutually soluble in solid phase at any ratio. The surface of the reflection film 3 is hard to be sulfurized even in a sulfurizing atmosphere, and the reflection property can be preserved. In the case the content percentage of gold in the reflection film 3 is 7 to 45 mass%, the reflection film 3 has a satisfactory reflection property equivalent to that of silver, and is satisfactory since the reflection property can be preserved even in a sulfurizing atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light emitting element mounting substrate and a light emitting device for mounting a light emitting element such as a light emitting diode.

  Conventionally, a ceramic substrate has been used as a light emitting element mounting substrate (hereinafter also referred to as a substrate) for mounting a light emitting element such as a light emitting diode. A conventional ceramic substrate is, for example, for mounting a substantially rectangular parallelepiped ceramic base having a recess for housing the light emitting element in the center of the upper surface, and a light emitting element disposed on the bottom surface of the recess. And a pair of wiring conductors led out from the mounting portion and its periphery to the lower surface. Further, in order to reflect and emit the light emitted from the light emitting element housed in the recess, a reflective layer in which a metallized metal layer and a plating layer are sequentially formed is formed on the side surface of the recess. The outermost layer is known as a plating layer made of a silver (Ag) metal having a high reflectance of light emitted from a light emitting element (see, for example, Patent Document 1).

  The light emitting element is fixed to the mounting portion of the light emitting element mounting substrate connected to one wiring conductor with a conductive bonding material, and the electrode of the light emitting element and the other wiring conductor are connected via a bonding wire. A light emitting device is obtained by electrical connection and filling the recess with a transparent sealing resin to seal the light emitting element.

JP 2004-207672 A

  However, in a light-emitting device using a light-emitting element mounting substrate in which the outermost layer of the reflective layer is a silver plating layer, when the light-emitting element is used by emitting light, the surface of the reflective layer changes color over time. In some cases, the luminance of the light emitting device is lowered. In particular, when left in a sulfur atmosphere, there is a problem that the silver plating layer is sulfided and the reflection characteristics are lowered.

  In order to prevent sulfidation of the surface of the reflective layer, instead of silver plating, there are those using platinum group plating with excellent corrosion resistance such as rhodium (Rh), palladium (Pd) or platinum (Pt). Since the platinum group does not have the reflective properties as silver, a high-luminance light emitting device could not be obtained.

  The present invention has been completed in order to solve the above-described problems, and the object thereof is to provide a light-emitting element mounting substrate in which the reflective layer has a reflective property equivalent to that of silver, and the reflective property does not deteriorate due to sulfuration, and A light emitting device using the light emitting element mounting substrate is provided.

  The light emitting element mounting substrate of the present invention includes a base, a mounting portion for mounting the light emitting element on the upper surface of the base, and a reflective film around the mounting portion, and the reflective film includes silver and gold. It is characterized by being a solid solution alloy of the above.

  The light emitting element mounting substrate of the present invention is characterized in that, in the above configuration, the upper surface of the substrate includes a concave portion having the mounting portion on the bottom surface, and the reflective film is formed on a side surface of the concave portion. It is what.

  The light emitting element mounting substrate of the present invention is characterized in that, in each of the above structures, the reflective film has a gold content of 7 mass% to 45 mass%.

  The light-emitting device of the present invention includes the light-emitting element mounting substrate having the above-described configuration, the light-emitting element mounted on the mounting portion, and a transparent sealing material that covers the light-emitting element. It is what.

  According to the light emitting element mounting substrate of the present invention, since the reflective film is a solid-solid alloy of silver and gold, there is no silver single particle on the surface of the reflective film. In particular, the surface of the reflective film is not easily sulfided, and the reflection characteristics can be maintained.

  Further, according to the light emitting element mounting substrate of the present invention, in the above configuration, when the concave portion having the mounting portion on the bottom surface is provided on the upper surface of the base, and the reflective film is formed on the side surface of the concave portion, the substrate is mounted. The light emitted from the light emitting element can be efficiently reflected upward by the reflective film on the side surface of the recess, so that the light emitting element mounting substrate from which a light emitting device with higher luminance can be obtained.

  In addition, according to the light emitting element mounting substrate of the present invention, in each of the above-described configurations, when the reflective film has a gold content of 7% by mass to 45% by mass, it has good reflection characteristics equivalent to silver. The reflection characteristics can be maintained even in a sulfurized atmosphere.

  In addition, according to the light emitting device of the present invention, since the reflective film of the light emitting element mounting substrate is not easily sulfided even in a sulfurizing atmosphere and the reflection characteristics can be maintained, the light emitted from the light emitting element is excellent over a long period of time. Thus, the light emitting device can be radiated to a light source with little reduction in luminance.

(A) is a top view which shows an example of embodiment of the light emitting element mounting substrate of this invention, (b) is sectional drawing in the AA of (a). (A) is a top view which shows the other example of embodiment of the light emitting element mounting substrate of this invention, (b) is sectional drawing in the AA of (a). (A) is a top view which shows the other example of embodiment of the light emitting element mounting substrate of this invention, (b) is sectional drawing in the AA of (a). It is sectional drawing to which the principal part which shows an example of a structure of the reflecting film of the light emitting element mounting substrate of this invention was expanded. (A) is a top view which shows the other example of embodiment of the light emitting element mounting substrate of this invention, (b) is sectional drawing in the AA of (a). It is sectional drawing to which the principal part which shows an example of a structure of the reflecting film of the light emitting element mounting substrate of this invention was expanded. (A) is a top view which shows the other example of embodiment of the light emitting element mounting substrate of this invention, (b) is sectional drawing in the AA of (a). (A) is a top view which shows the other example of embodiment of the light emitting element mounting substrate of this invention, (b) is sectional drawing in the AA of (a). It is a graph which shows the relationship between the gold content rate of a reflecting film, and a reflectance.

  The light emitting element mounting substrate of the present invention will be described with reference to the accompanying drawings. 1 to 3 and FIGS. 5, 7, and 8, (a) is a plan view showing an example of an embodiment of a light-emitting element mounting substrate of the present invention, and (b) is (a). It is sectional drawing in the AA of. 4 is an enlarged cross-sectional view of a portion A in FIG. 1, and FIG. 6 is an enlarged cross-sectional view of the portion A in FIG. 1 to 8, 1 is a base, 1a is a recess, 1b is a base, 1c is a heat dissipation part, 2 is a mounting part, 2a is a mounting electrode, 2b is a connection electrode, 3 is a reflective film, 3a is a metallized metal layer, 3b is an adhesion layer, 4 is a light emitting element, 5 is a connection member, 6 is an internal wiring, and 7 is a terminal electrode. 1, 2, and 5 show a state in which the light emitting element 4 is mounted on the mounting electrode 2 a of the mounting portion 2 of the light emitting element mounting substrate, and the light emitting element 4 and the connection electrode 2 b are connected using the bonding wires as the connection members 5. Is shown. FIG. 3 shows a state in which the connection electrodes 2b and 2b of the mounting portion 2 of the light emitting element mounting substrate and the electrodes (not shown) of the light emitting element 4 are mounted by connecting bumps such as solder bumps as connection members 5. Show. 7 and 8 show an example in which the base 1 is composed of a base portion 1b and a heat radiating portion 1c. The light emitting element 4 is mounted on the mounting portion 2 provided on the heat radiating portion 1c, and the electrode and base portion of the light emitting element 4 are mounted. A state is shown in which the connection electrodes 2b and 2b provided on 1b are connected with bonding wires as connection members 5.

  The light emitting element mounting substrate of the present invention includes a base 1, a mounting portion 2 for mounting the light emitting element 4 on the bottom surface of the upper surface of the base 1, and a reflective film 3 around the mounting portion 2. 3 is an alloy that is a solid solution of silver and gold. Due to such a configuration, there is no silver single particle on the surface of the reflective film 3, so that the surface of the reflective film 3 is less likely to be sulfided even in a sulfurized atmosphere, and the reflection characteristics can be maintained. .

  Moreover, the light emitting element mounting substrate of the present invention has the above-described configuration, wherein the top surface of the substrate 1 is provided with the concave portion 1a having the mounting portion 2 on the bottom surface, and the reflective film 3 is formed on the side surface of the concave portion 1a. It is a feature. With such a configuration, light emitted from the mounted light emitting element 4 can be efficiently reflected upward by the reflective film 3 on the side surface of the recess 1a, so that a light emitting device with higher luminance can be obtained. It becomes a light emitting element mounting substrate.

  In the above structure of the light emitting element mounting substrate of the present invention, the reflective film 3 preferably has a gold content of 7 mass% to 45 mass%. In this case, it has good reflection characteristics equivalent to silver and can maintain the reflection characteristics even in a sulfurized atmosphere.

  If the substrate 1 is the case shown in FIGS. 1 to 6, the aluminum oxide sintered body (alumina ceramic), the aluminum nitride sintered body, the mullite sintered body, and the glass ceramic sintered body. It consists of ceramics such as.

  If the substrate 1 is made of, for example, an aluminum oxide sintered body, an appropriate organic binder and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide to form a slurry. Then, this is formed into a sheet shape by a conventionally known doctor blade method, calendar roll method or the like to obtain a green sheet. After that, the green sheet is subjected to appropriate punching processing and a plurality of sheets are laminated to obtain a high temperature (about It is manufactured by firing at 1600 ° C.

  The concave portion 1a of the substrate 1 is formed by forming a through-hole whose inner surface is the side surface of the concave portion 1a in a green sheet by laser processing or punching with a mold and laminating it with another green sheet. The Alternatively, the substrate having the recesses 1a can also be produced by firing the green sheet in which the through-holes are formed to produce a frame, and joining the separately produced substrate. In this case, the frame body of the base 1 and the substrate may be made of the same material or different materials. In order to join the frame body and the substrate, a metallized layer may be formed on each joining surface, and joined by a joining material such as an Ag brazing material.

  The angle between the side surface of the recess 1a and the bottom surface of the recess 1a (angle θ shown in FIG. 5) is preferably 35 to 70 degrees. When the angle θ is in such a range, the angle θ is not too small, so that it is easy to stably and efficiently form the inner surface of the through hole 2a by punching, and the package can be easily downsized. Moreover, the light emitted from the light emitting element 4 can be favorably reflected to the outside. The concave portion 1a having such a side surface is formed by punching a green sheet using a punching die having a large clearance between the punch diameter and the die hole diameter. That is, by setting the diameter of the die hole larger than the diameter of the punch of the punching die, when the green sheet is punched from one main surface side to the other main surface side, the green sheet Shearing is performed from the edge of the contact surface with the punch toward the edge of the contact surface with the die hole, and the through hole is formed to spread from one main surface side to the other main surface side. By setting the clearance between the diameter of the punch and the diameter of the die hole in accordance with the thickness of the green sheet, the angle of the side surface of the through hole formed in the green sheet is adjusted. After forming a through hole with an angle of about 90 degrees by processing with a punching die having a small clearance between the diameter of the normal punch and the diameter of the die, the mold can be pressed against the inner surface of the through hole as described above. Although it is possible to form a through hole having an angle that spreads from one main surface side to the other main surface side, the above method can be formed only by punching, so the productivity is high and the mold is pressed This is preferable because there is little influence of deformation on the green sheet.

  A mounting electrode 2 a for mounting the light emitting element 4 and a connection electrode 2 b connected to the electrode of the light emitting element 4 are formed on the mounting portion 2 for mounting the light emitting element 4 of the substrate 1. When the flip chip type light emitting element 4 as shown in FIG. 3 is mounted, the connection electrodes 2b and 2b also function as mounting electrodes. The mounting electrode 2 a and the connection electrode 2 b are connected to terminal electrodes 7 and 7 for connecting the light emitting device to the external circuit board, which are formed on the lower surface of the base 1 by internal wiring 6. In the example shown in FIGS. 1 to 3 and 5, the terminal electrodes 7 and 7 are formed on the lower surface of the substrate 1, but may be formed on the side surface of the substrate 1 or formed from the side surface to the lower surface of the substrate 1. May be.

  The mounting electrode 2a, the connection electrode 2b, the internal wiring 6, and the terminal electrode 7 are made of metal powder such as tungsten (W), molybdenum (Mo), manganese (Mn), Ag, copper (Cu). For example, when the substrate 1 is made of an aluminum oxide sintered body, a conductor paste obtained by adding and mixing an appropriate organic binder and solvent to a refractory metal powder such as W, Mo, or Mn is used as the substrate 1. The green sheet is preliminarily printed and applied in a predetermined pattern by a known screen printing method, and is fired at the same time as the green sheet to be the base 1 to be deposited on a predetermined position of the base 1. When the internal wiring 6 is a through conductor as in the examples shown in FIGS. 1 to 3 and 5, before forming the conductor paste pattern to be the mounting electrode 2 a, the connection electrode 2 b, and the terminal electrode 7, A through hole is formed in the green sheet by punching by a die or punching or laser processing, and the through hole is filled with a conductive paste by a printing method.

  The reflective film 3 is formed on the metallized metal layer 3a formed around the mounting portion 2 when the substrate 1 has a flat plate shape as in the examples shown in FIGS. 1 to 3, and the example shown in FIG. When the substrate 1 has the concave portion 1a as described above, it is formed on the metallized metal layer 3a formed on the side surface of the concave portion 1a, and in any case, it is made of a completely solid solution alloy of silver and gold. An alloy layer. If this alloy is not a solid solution alloy but a simple alloy of silver and gold, particles made of silver are present on the surface of the reflective film 3, and the portion is easily sulfided, and the reflection characteristics are likely to deteriorate. It becomes a thing. Whether or not an all-solid alloy of silver and gold is formed as the reflective film 3 can be determined by examining the distribution of silver and gold on the surface of the reflective film 3 from the silver and gold mapping by Auger analysis. Is possible. When a completely solid solution alloy is formed, the distribution of silver and gold is uniform, and there is no single particle of each, but when an alloy that is not completely solid solution is formed, silver or gold The part where gold is mapped as 100% is observed. Note that, when performing Auger analysis, it is preferable to observe by removing argon from the surface by sputtering argon ions.

  The metallized metal layer 3a is obtained by sintering metal powder such as W, Mo, Mn, Ag, and Cu, and a metal paste obtained by adding and mixing an appropriate organic binder and solvent to the metal powder is conventionally known. By this screen printing method, printing is applied to the inner surface of the through-hole of the green sheet to be the recess 1a, and it is fired at the same time as the green sheet, thereby being deposited on the side surface of the recess 1a. Thereby, the side surface of the recessed part 1a becomes a smoother surface, and the favorable reflective film 3 can be formed. The metal paste may be the same as the above-described conductor paste, or may be one in which the type and amount of the organic binder or solvent are changed in consideration of printability.

  The reflective film 3 made of a solid solution alloy layer of silver and gold is formed by forming an alloy layer of silver and gold by electrolytic plating, electroless plating, sputtering, or vapor deposition, or gold It is possible to interdiffuse silver and gold by forming a layer and a silver layer on top of each other and then performing a heat treatment. When the plating method is used, in order to improve the adhesion between the metallized metal layer 3a and the silver plated layer or the gold plated layer, a nickel plated layer is formed on the metallized metal layer 3a as in the example shown in FIGS. It is desirable to provide an adhesion layer 3b made of

  If the heat treatment at this time exceeds the temperature of the liquidus of the alloy of silver and gold (for example, 970 ° C. when gold is 10% by mass), the alloy of silver and gold is dissolved. Therefore, the reflective film 3 made of an alloy layer having good reflection characteristics cannot be formed on the metallized metal layer 3a, so that the temperature does not exceed the liquidus line temperature of the alloy.

  Also, if the temperature at which the heat treatment is performed is lower than the liquidus temperature by 100 ° C. or more, silver and gold will not diffuse sufficiently, and it will be difficult to form a solid solution alloy, and it will take time to form. The temperature is preferably the liquidus temperature of the alloy of gold and silver minus 100 ° C. or less.

  The atmosphere for the heat treatment may be in an inert atmosphere, but more preferably in a reducing atmosphere that is less susceptible to oxidation.

  The gold content of the reflective film 3 is preferably 7% by mass to 45% by mass. When the gold content is less than 7% by mass, the ratio of silver is large, so that the initial reflection characteristics are good, but there is a tendency that the reflectance is reduced by sulfuration. On the other hand, when the gold content exceeds 45% by mass, since the gold ratio is large, the initial reflectance that is not sulfided tends to decrease. If the content of gold in the reflective film 3 is within this range, the reflectance is higher than that of expensive platinum group palladium or platinum, and the reflectance can be set to the same level as rhodium. Furthermore, it is more preferable that the gold content of the reflective film 3 is 15% by mass to 35% by mass because the reflectance can be higher than that of rhodium.

  The thickness of the reflective film 3 is preferably 1 μm or more. If it is thinner than 1 μm, the metallized metal layer 3a or the adhesion layer 3b cannot be sufficiently covered, and the reflectance may be lowered. In addition, there is no particular problem with the characteristics of the thick reflective film 3, but it is preferably less than 15 μm from the viewpoint of film formation time and cost.

  Further, although the metallized metal layer 3a is not directly shown in FIG. 2, the metallized metal layer 3a may be connected to the mounting electrode 2a as in the example shown in FIG. It may be connected to the electrode 2b.

  The exposed surfaces of the mounting electrode 2a, connection electrode 2b, and terminal electrode 7 are coated with a metal having excellent corrosion resistance, such as nickel, gold, and silver, and excellent brazing material wettability to a thickness of about 1 to 20 μm. These can be effectively prevented from being oxidized and corroded, the connection between the mounting electrode 2a and the light emitting element 4, the connection between the connection electrode 2b and the connection member 5 such as a bonding wire, and the terminal electrode 7 and the external circuit board Bonding with brazing filler metal can be strengthened.

  In addition, if a film of a solid solution alloy of silver and gold, which is the same as the reflective film 3, is formed on the surface of the mounting electrode 2a and the connection electrode 2b, radiation is emitted downward (from the mounting portion 2 side) from the light emitting element 4. It is preferable because the luminance of the light emitting device can be further increased by reflecting the emitted light. The formation of the alloy layer film can be performed simultaneously with the formation of the reflective film 3. Further, the ratio of silver and gold may be different between the alloy layer formed on the surface of the mounting electrode 2a or the connection electrode 2b and the alloy layer of the reflective film 3, or either the mounting electrode 2a or the connection electrode 2b. The same alloy layer as the reflective film 3 may be formed on only one surface. For example, when the light emitting element 4 and the connection electrode 2b are connected using a bonding wire mainly composed of gold as the connection member 5, in order to make the connection between the bonding wire and the connection electrode 2b stronger, It is preferable to form a gold film on the surface of the connection electrode 2b, and to form an alloy layer made of a solid solution alloy of silver and gold, similar to the reflective film 3, on the surface of the mounting electrode 2a. In this case, as in the example shown in FIG. 2, the mounting electrode 2a and the metallized metal layer 3a are connected and integrated, for example, so that the reflective film 3 has a larger area so that the reflection efficiency is increased. It is good to improve.

  The base body 1 may be composed of a plurality of members such as a base portion 1b and a heat radiating portion 1c. For example, as in the example shown in FIGS. 7 and 8, a base 1b having a reflective film 3 and a heat radiating part having a mounting portion 2 for the light emitting element 4 disposed in a central through hole 1d of the base 1b. It may be composed of 1c. In the case of these examples, the base 1b is similar to the base 1 of the example shown in FIGS. 1 to 6 described above, and is an aluminum oxide sintered body (alumina ceramic), an aluminum nitride sintered body, and a mullite sintered body. The heat radiating portion 1c is made of a material having a higher thermal conductivity than the base portion 1b, for example, a metal such as copper or copper-tungsten, or the base portion 1b. What is necessary is just to consist of ceramics with a high rate. By adopting such a configuration, the heat generated by the light emitting element 4 can be released to the outside from the heat radiating portion 1c satisfactorily. Therefore, when the light emitting element 4 having a large calorific value is mounted to form a light emitting device, It is possible to suppress a decrease in luminous efficiency due to.

  When the base 1 is thus composed of the base 1b and the heat radiating portion 1c, the base 1b has a through hole 1d at the center thereof, and the mounting portion 2 on the upper surface side of the base 1b is formed in the through hole 1d. It is comprised by attaching and dissipating the thermal radiation part 1b so that may be exposed. The through hole 1d of the base portion 1b is formed by forming a through hole to be the through hole 1d in the green sheet to be the base portion 1b by a method similar to the method of forming the recess in the base 1 described above.

  The base 1b and the heat radiating part 1c are bonded to each other by, for example, providing a metallizing layer (not shown) for bonding at a part in contact with the heat radiating part 1c of the base 1b if the heat radiating part 1c is made of metal. It can be performed using a bonding material such as an Ag-Cu brazing material. Alternatively, if an active metal brazing material in which an active metal such as Ti is added to the brazing material is used, the base portion 1b and the heat radiating portion 1c can be joined without providing a metallized layer on the base portion 1b. In any case, a metal having excellent corrosion resistance and excellent wettability of the brazing material, such as nickel, gold, and silver, is deposited on the surface of the heat radiating portion 1c to a thickness of about 1 to 20 μm. In addition, it is possible to effectively prevent these from being oxidized and corroded, and to join the heat radiating portion 1c and the base portion 1b, to join the heat radiating portion 1c to the light emitting element 4, and to join the heat radiating portion 1c and the external circuit board with a brazing material. Can be strong. When the heat radiating portion 1c is made of metal, the connection electrode 2b, the internal wiring 6 and the terminal electrode 7 are formed on the base portion 1b.

  Further, when the heat radiating portion 1c is made of ceramics having a higher thermal conductivity than the base portion 1b, for example, an aluminum oxide sintered body is used for the base portion 1b and an aluminum nitride based sintered body is used for the heat radiating portion 1c. Can be configured. In this case, for example, the mounting electrode 2a and the connection electrode 2b can be formed on the heat dissipating part 1c, and in this way, the plating layer is deposited on the metal parts of the respective surfaces of the base part 1b and the heat dissipating part 1c. Therefore, it is possible to easily make the ratio of silver and gold different between the plating layer on the surface of the mounting electrode 2a and the connection electrode 2b and the reflective film 3. Further, in this case, the base 1b and the heat radiating part 1c may be joined by providing a metallization layer for joining to each of the base 1b and the heat radiating part 1c and joining them with a brazing material. You may join by an active metal brazing material, without providing a layer.

  The heat dissipating part 1c and the through hole 1d may have the same shape in the upper and lower sides, and the outer peripheral surface of the heat dissipating part 1c may be joined to the inner wall of the through hole 1d. However, in the example shown in FIG. The lower surface of the base portion 1b and the upper surface of the flange portion of the heat radiating portion 1c are joined around the opening of the through hole 1d on the lower surface. Moreover, in the example shown in FIG. 8, the base 1b and the heat radiating part 1c are joined by the lower surface of the level | step difference provided in the through-hole 1d of the base 1b, and the upper surface of the collar part of the heat radiating part 1c. In any example, the heat radiating part 1c is provided with a flange part in the lower part, and has a shape having a larger step at the lower part than the upper part where the light emitting element 4 is mounted. Since this step surface (upper surface of the flange portion) is a joint surface with the base portion 1b, the positioning of the heat radiating portion 1c is facilitated, and the positional relationship between the light emitting element 4 and the reflective film 3 is easily made constant.

  Further, the heat radiating portion 1c may be joined to the bottom surface (upper surface) of the recess, assuming that the base 1b is replaced with the through hole 1d and has a recess having an opening on the lower surface of the base 1b. The mounting portion 2b in this case is the upper surface of the base portion 1b located above the recess. At this time, since the heat conduction from the mounting portion 2b to the heat radiating portion 1c joined to the bottom surface (upper surface) of the recess may not be sufficient depending on the material of the base portion 1b, the lack of the heat conduction is compensated. Therefore, a through conductor for heat transfer may be provided between the upper surface and the bottom surface (upper surface) of the recess. Alternatively, a recess may not be provided on the lower surface of the base portion 1b, and the heat sink 1c may be joined to the flat lower surface of the base portion 1b using the flat base 1 as in the example shown in FIGS. In this case as well, a through conductor for heat transfer may be provided in order to compensate for the lack of heat conduction from the mounting portion 2b to the heat radiating portion 1c.

  The light emitting device of the present invention includes the light emitting element mounting substrate having the above-described configuration, the light emitting element 4 mounted on the mounting portion 2, and a transparent sealing resin that covers the light emitting element 4 and the reflective film 3. It is characterized by that. As described above, since the reflective film 3 of the substrate for mounting a light emitting element of the present invention is not easily sulfided even in a sulfurizing atmosphere and can maintain reflection characteristics, the light emitted from the light emitting element 4 can be emitted well over a long period of time. Thus, a light-emitting device with little reduction in luminance is obtained.

  The light-emitting element 4 is a light-emitting diode (LED) or a semiconductor laser (LD). For example, the light-emitting element 4 is formed of a conductive bonding material such as a brazing material made of an Au-silicon (Si) alloy or an epoxy resin containing silver (Ag). While being fixed on the mounting electrode 2a, the electrode of the light emitting element 4 and the connection electrode 2b are electrically connected via a connection member 5 such as a bonding wire mainly composed of Au. In the case of the flip chip type light emitting device 4 as shown in FIG. 3, the bumps made of metal such as solder or gold connected to the electrodes of the light emitting device 4 are heated and melted, or ultrasonic vibration is applied. It connects by adding, or it connects to the connection electrode 2b via solder or a conductive adhesive.

  Although not illustrated, the sealing material is transparent (having translucency) made of silicon resin, epoxy resin, or the like that seals the light emitting element 4. For example, after applying a liquid sealing resin so as to cover the light emitting element 4, the sealing resin is cured to obtain a light emitting device. When the substrate 1 includes the recess 1a as in the example shown in FIG. 5, the sealing resin may be filled in the recess 1a. Alternatively, a box-shaped sealing material may be placed on the substrate 1 so as to cover the light emitting element 4 and fixed with an adhesive. When the base body 1 includes the recess 1a, the opening of the recess 1a may be closed with a sealing material formed in a plate shape. When a sealing material molded in a box shape or a plate shape is used, the light emitted from the light emitting element 4 can be condensed by the lens-shaped portion if a part of the sealing material is molded into a lens shape. Therefore, the light-emitting element mounting substrate from which a light-emitting device with higher luminance can be obtained.

  Moreover, the phosphor may be contained in the sealing material. The phosphor can receive light having a predetermined wavelength emitted from the light emitting element 4 and can emit light of other wavelengths, or can receive light of a specific wavelength from the outside to match the light receiving sensitivity of the light receiving element. Thus, an arbitrary emission color can be obtained by a combination of light emitted from the light emitting element 4 and a phosphor capable of emitting light. For example, if the light emitted from the light-emitting element 4 is blue light and the light emitted from the phosphor is yellow light, white light can be emitted from the light-emitting device by a mixture of both lights.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the light emitting element 4 may be directly mounted on the base 1 without forming the mounting electrode 2a on the mounting portion 2, and the connection electrode 2b connected to the internal wiring 6 may be formed around the light emitting element 4. Alternatively, a plurality of light emitting elements 4 may be mounted, and mounting electrodes 2a and connection electrodes 2b corresponding to the light emitting elements 4 may be formed.

Examples of the light emitting element mounting substrate of the present invention will be described below.
First, an acrylic resin is used as an organic binder with respect to 100% by weight of ceramic powder prepared by mixing 96% by weight of aluminum oxide and 4% by weight of silicon oxide, magnesium oxide and calcium oxide as a sintering aid. A solid content of 9% by mass, 0.1% by mass of dibutyl phthalate as a plasticizer was added, and toluene was used as a solvent to mix for 40 hours to prepare a ceramic slurry. This ceramic slurry was formed into a sheet shape by a doctor blade method, and green sheets having thicknesses of 0.2 mm and 0.4 mm, which were to be the base 1, were produced.

  Next, a through hole having a diameter of 100 μm in which the internal wiring 6 is arranged was formed by punching at a predetermined position of a green sheet having a thickness of 0.2 mm. Obtained by adding 0.8% by mass of cellulose nitrate as an organic binder to 100% by mass of W powder having an average particle size of 1.90 μm, and adding and mixing diethylene glycol monobutyl ether acetate and dibutyl phthalate as solvents for viscosity adjustment The conductive paste was filled in the through holes by a screen printing method. Furthermore, a conductor paste having adjusted viscosity was printed and applied to form a conductor paste layer to be the mounting electrode 2a, the connection electrode 2b, and the terminal electrode 7. Further, by punching a green sheet having a thickness of 0.4 mm with a punching die, a through-hole that becomes a recess 1a and spreads from one main surface side to the other main surface side at an angle θ of 45 ° was formed. . In addition, diethylene glycol monobutyl ether acetate and dioctyl as solvents for viscosity adjustment were added to the side surface of the through-holes in which 3% by mass of cellulose nitrate was added as an organic binder to 100% by mass of W powder having an average particle size of 1.25 μm. The metal paste obtained by adding and mixing the phthalate was printed and applied by a screen printing method to form a metal paste layer to be the metallized metal layer 3a.

  Then, two green sheets are laminated and pressure-bonded, and the organic components are removed by heating at a temperature of about 1000 ° C. for about 3 hours in a nitrogen atmosphere containing water vapor, and then in a nitrogen atmosphere containing water vapor. And calcining at a temperature of about 1500 ° C. for about 6 hours. Further, a nickel plating layer having a thickness of 3 μm is deposited as an adhesion layer 3b on the mounting electrode 2a, the connection electrode 2b, the terminal electrode 7 and the metallized metal layer 3a by an electrolytic plating method. Then, a silver plating layer having a thickness of 3.19 μm and a gold plating layer having a thickness of 0.63 μm were sequentially deposited by electrolytic plating.

  Then, the silver plating layer and the gold plating layer are mutually diffused by heating for about 10 minutes at a temperature of about 900 ° C. in a reducing atmosphere (75% by volume of hydrogen + 25% by volume of nitrogen). An alloy layer having a solid content of silver and gold having a gold content of 26.5% by mass is formed, and silver and gold are formed on the side surface of the recess 1a as shown in FIG. A substrate for mounting a light-emitting element including the reflective film 3 made of a completely solid alloy was produced. At this time, the same alloy layer film of silver and gold as in the reflective film 3 was also formed on the mounting electrode 2a.

  Moreover, the thickness of the silver plating layer and the gold plating layer is changed by changing the immersion time in the plating solution and the application time of the current when forming the silver plating layer and the gold plating layer. Eleven types of light emitting element mounting substrates (samples) with different gold contents were prepared.

  The gold content in the reflective film 3 is the thickness of the silver plating layer and the gold plating layer of the sample not subjected to the heat treatment for forming an all-solid alloy layer of silver and gold, and the fluorescent X-ray film. Using a thickness gauge (SFT3300, manufactured by SII Nano Technology Co., Ltd., X-ray tube: W), X-ray output: 45 kV-1 mA, measurement time: measured for 10 seconds, measured silver plating thickness The mass ratio was calculated from the thickness of the gold plating and the specific gravity of silver and gold. At this time, the thickness of the silver plating layer and the gold plating layer on the mounting electrode 2a which is flat and easy to measure was measured.

  In addition, the gold content in the reflective film 3 is measured by using a fluorescent X-ray film thickness meter and quantitatively converted after forming a solid solution alloy layer of silver and gold by heat treatment. It can also be measured. The results measured in this way were confirmed to be the same as the results calculated as described above.

  Next, using a spectrocolorimeter (CM-3700d manufactured by Minolta Co., Ltd.), reference light source: D65, measurement wavelength range: 360-740 nm, field of view: 10 °, measurement reflectance: total reflectance, mask: SAV The reflectance was measured under the following conditions. After conducting a sulfurization test in which a 0.5% ammonium sulfide aqueous solution is placed in a petri dish and placed in a desiccator, the inside of the desiccator is a sulfurizing atmosphere, and the sample whose reflectance is measured in the sulfurizing atmosphere is left at room temperature for 8 hours. The reflectance was measured again under the same conditions as above.

  The results of measuring the reflectance of each sample having a different gold content in the reflective film 3 are summarized as shown in the diagram of FIG. In FIG. 9, the vertical axis represents the reflectance of light of 440 nm, which is the blue wavelength where silver wavelength is likely to change due to sulfuration, and the horizontal axis represents the gold content in the reflective film 3. The black rhombus indicates the reflectance of each sample before the sulfidation test (initial), and the white square indicates the reflectance of each sample after the sulfidation test (after sulfidation).

  From the results shown in FIG. 9, when the gold content of the reflective film 3 is 0% by mass (silver is 100% by mass), the reflectance before the sulfidation test (initial) is 90.7% after the sulfidation test ( It can be seen that after the sulfidation, the reflectivity is reduced to 31.8%, whereas when the reflective film 3 is made of an alloy containing gold, the sulfidation is suppressed and the decrease in reflectivity is suppressed. In addition, when the gold content increases, the color tone of the surface of the reflective film 3 approaches a low gold color tone with a reflectance of about 32%, so the initial reflectivity exceeds 25% by mass. There is a tendency to gradually decrease from around. It can be seen that when the gold content is 7 mass% to 45 mass%, a reflectance of 70% or more is exhibited even after the sulfurization test. When the reflectance (initial) of a sample in which the reflective film 3 is a plating film of palladium (Pd), rhodium (Rh), and platinum (Pt) is measured in the same manner, Pd is about 57%, Rh is 71%, Pt shows a reflectance of 57%. Compared with these, when the gold content is 7% by mass to 45% by mass, the reflectance is equal to or higher than that of the platinum group plating film having excellent corrosion resistance both before and after the sulfidation test. I understand that. Therefore, it can be said that a light-emitting element mounting substrate with a small reduction in reflection characteristics due to sulfuration is obtained without using expensive platinum group plating. Also, if the gold content is 15 mass% to 35 mass%, it shows a reflectance of 80% or more both before and after the sulfidation test, and has a reflectance higher than that of a reflection film made of platinum group plating, It can be seen that high reflectance can be maintained even when exposed to a sulfurized atmosphere.

1: Base 1a: Recess 1b: Base 1c: Radiator 1d: Through hole 2: Mounting portion 2a: Mounting electrode 2b: Connection electrode 3: Reflective film 3a: Metallized metal layer 3b: Adhesion layer 4: Light emitting element 5: Connection member 6: Internal wiring 7: Terminal electrode

Claims (4)

A substrate, a mounting portion for mounting the light emitting element on the upper surface of the substrate, and a reflective film around the mounting portion, and the reflective film is a completely solid alloy of silver and gold A substrate for mounting a light emitting element. 2. The light emitting element mounting substrate according to claim 1, wherein a concave portion having the mounting portion on a bottom surface is provided on an upper surface of the base, and the reflective film is formed on a side surface of the concave portion. The light-emitting element mounting substrate according to claim 1, wherein the reflective film has a gold content of 7 mass% to 45 mass%. A light emitting element mounting substrate according to any one of claims 1 to 3, a light emitting element mounted on the mounting portion, and a transparent sealing material covering the light emitting element. A light emitting device.

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