JP2013157447A - Light-emitting element mounting substrate and light-emitting device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting element mounting substrate which has high heat conductivity and can reduce light transmission at a frame part and has high luminous efficiency; and provide a light-emitting device using the light-emitting element mounting substrate.SOLUTION: In a light-emitting element mounting substrate, a sintered body included in each of a base part 3 and a frame part 5 has a porosity of 5% or less; the base part 3 and the frame part 5 include ceramic particles 7 having average aspect ratios different from each other in which the ceramic particles 7 included in the frame part 5 have a smaller average aspect ratio than that of the ceramic particles 7 included in the base part 3. Because of this, the light-emitting element mounting substrate which has high heat conductivity and low light transmittance at the frame part, and a light-emitting device using the light-emitting element mounting substrate can be obtained.

Description

  The present invention relates to a light-emitting element mounting substrate having high reflectivity and a light-emitting device using the same.

  2. Description of the Related Art In recent years, light emitting devices equipped with light emitting elements typified by LED (Light Emission Diode) bulbs have been improved for high brightness and whitening, and are used as backlights for mobile phones, large liquid crystal televisions, and the like. . Among them, not only has high reflectivity, but also has higher thermal conductivity and mechanical strength, superior heat resistance and durability, and longer than the synthetic resin used for conventional light emitting element mounting substrates. A light emitting element mounting substrate based on alumina ceramics or glass ceramics has attracted attention because it does not deteriorate even when exposed to ultraviolet rays for a period of time.

  In addition, the light emitting element mounting substrate has a so-called frame-like light emission having a wall surface surrounding the light emitting element on the surface of the substrate on which the light emitting element is mounted in order to increase the light emission efficiency of light emitted from the light emitting element. An element mounting substrate has been proposed (see, for example, Patent Document 1).

  In recent years, LED bulbs have been used as lighting for small electronic devices such as mobile phones. However, as represented by smartphones, small electronic devices have become increasingly sophisticated and highly functional. For this reason, LED bulbs mounted on such small electronic devices are required to be further reduced in size and brightness, and therefore, there is an increasing demand for downsizing of light-emitting element mounting substrates.

JP 2006-261290 A

  However, although the ceramic light-emitting element mounting substrate is excellent in thermal conductivity as described above, a light-emitting element mounting substrate with a frame body is manufactured using ceramics as a base material, and the size thereof is reduced. In this case, since the thickness of the frame body is reduced along with the area of the substrate, there is a problem that light emitted from the light emitting element is easily transmitted through the frame body and the light emission efficiency is lowered.

  Accordingly, an object of the present invention is to provide a light-emitting element mounting substrate having high thermal conductivity, and capable of reducing light transmission in the frame body portion and having high light emission efficiency, and a light-emitting device using the same.

  The substrate for mounting a light emitting element of the present invention is formed integrally with a base part having a light emitting element mounting surface at the center part of the upper surface made of a sintered body of ceramic particles, and the base part is formed on the base part. A light emitting element mounting substrate including a frame body portion disposed so as to surround the mounting surface, wherein both the base body portion and the sintered body constituting the frame body portion have a porosity of 5% or less. And the base body portion and the frame body portion are composed of ceramic particles having different average aspect ratios, and the ceramic particles constituting the frame body portion have an average aspect ratio higher than that of the ceramic particles constituting the base body portion. The ratio is small.

The light emitting device of the present invention is characterized in that a light emitting element is provided in the mounting portion of the light emitting element mounting substrate.

  ADVANTAGE OF THE INVENTION According to this invention, while having high thermal conductivity, the transmission of the light in a frame part can be reduced, and the light emitting element mounting substrate with high luminous efficiency, and a light-emitting device using the same can be obtained.

(A) and (b) are the cross-sectional schematic diagram and top view which show typically an example of the light emitting element mounting substrate of this embodiment. It is an enlarged view of A part and B part of Drawing 1 (a). It is a cross-sectional schematic diagram which shows the light-emitting device of this embodiment. It is a schematic diagram which shows the manufacturing process of the light emitting element mounting substrate of this embodiment.

  FIGS. 1A and 1B are a schematic cross-sectional view and a plan view schematically showing an example of a light-emitting element mounting substrate according to the present embodiment. FIG. 2 is an enlarged view of a portion A and a portion B in FIG.

  In the light emitting element mounting substrate of the present embodiment, a base body portion 3 having a mounting surface 1 for mounting a light emitting element and a frame body portion 5 arranged so as to surround the mounting surface 1 are integrally formed. It has been done. The base 3 and the frame 5 are both formed of a sintered body of ceramic particles 7 and have a porosity of 5% or less. Further, the base body portion 3 and the frame body portion 5 are composed of ceramic particles 7 having different average aspect ratios, and the ceramic particles 7 constituting the frame body portion 5 are more average than the ceramic particles 7 constituting the base body portion 3. It is characterized by a small aspect ratio.

  Thereby, it is possible to obtain a light emitting element mounting substrate having a high thermal conductivity and a high light emission efficiency including the frame portion 5 that can reduce the transmission of light.

  That is, the light emitting element mounting substrate of the present embodiment makes a difference in the average aspect ratio of the ceramic particles 7 between the ceramic particles 7 constituting the frame portion 5 and the ceramic particles 7 constituting the base portion 3. The characteristics of the frame body part 5 that contributes to the improvement of the directivity and reflectance of light emitted from the light emitting element and the characteristics of the base body part 3 that is a part that releases heat from the light emitting element can be improved. it can.

  That is, when the average aspect ratio of the ceramic particles 7 constituting the frame body portion 5 is small, the ceramic particles 7 have a shape close to a sphere, and thus each ceramic particle 7 can reflect light radially. Therefore, the scattering of light in the frame body part 5 is increased, whereby the transmission of light in the frame body part 5 can be suppressed, and as a result, the light emission efficiency can be improved.

  On the other hand, when the base part 3 side is formed of ceramic particles 7 having a large average aspect ratio, the base part 3 is made to have high thermal conductivity by utilizing the fact that the thermal conductivity of the ceramic particles 3 is high in the longitudinal direction. Thus, a light emitting element mounting substrate having both high thermal conductivity and high reflectivity can be obtained. In this case, for example, the frame 5 has a sintered state in which the number of ceramic particles 7 present per unit area is large when the cross-sectional view is seen, and the outline of the ceramic particles 7 can be clearly seen. It is good to have.

  On the other hand, when the porosity of the sintered body of the base body portion 3 and the frame body portion 5 is higher than 5%, the mechanical strength of the sintered body is lowered and the water absorption is increased. As a result, the reliability of the light emitting element mounting substrate is lowered. Moreover, when the porosity of the frame body part 5 is higher than 5%, light is easily transmitted by the pores, and the light emission efficiency is lowered.

  Further, in the configuration in which the average aspect ratio of the ceramic particles 7 does not differ between the ceramic particles 7 constituting the frame body portion 5 and the ceramic particles 7 constituting the base portion 3, high thermal conductivity and light directivity and It is difficult to obtain a light emitting element mounting substrate that can efficiently achieve a high reflectance.

  As the light emitting element mounting substrate of the present embodiment, in particular, the frame part 5 is composed of ceramic particles 7 having an average aspect ratio of 1.5 or less, and the base part 3 has an average aspect ratio of 1.5 or more. It is desirable that the ceramic particle 7 is composed of a sintered body.

  In this case, the average particle diameter of the ceramic particles 7 constituting the respective sintered bodies of the base body portion 3 and the frame body portion 5 should be about 1 to 10 μm, and in particular, the ceramic particles 7 constituting the frame body portion 5. Is preferably smaller than the average particle diameter of the ceramic particles 7 constituting the base portion 5 in terms of increasing the thermal conductivity in the base portion 3 while increasing the light reflectance.

  Further, the average aspect ratio of the ceramic particles 7 constituting the sintered body of the base portion 3 is preferably 3 or less, particularly 2 or less in that the mechanical strength of the base portion 3 can be increased.

  Here, the porosity of the sintered body was determined by image analysis of the total area of pores found on the photograph, using an electron micrograph of the cross-section polished sample, and then the total area of the pores was photographed. Divide by the area of In this case, pores having a maximum diameter of 0.1 μm or more are selected, and pores smaller than that are excluded.

  The average aspect ratio and average particle size of the ceramic particles 7 constituting the sintered bodies of the base body 3 and the frame body 5 are obtained by cross-sectional polishing the obtained light emitting element mounting substrate and observing it with a scanning electron microscope. This is obtained by image analysis.

  Specifically, on a photograph taken with a scanning electron microscope, a circle containing about 10 to 30 ceramic particles 7 is drawn, and each ceramic particle 7 existing in the circle has a long side and a long side. The aspect ratio of each ceramic particle 7 is obtained from the ratio of the long side / short side, and then the average aspect ratio is obtained from the average value thereof.

  The average particle diameter of the ceramic particles 7 is obtained by calculating the area from the contours of the ceramic particles 7 in the same region, calculating the diameter from the area of the circle, and determining the average value of the diameters thus obtained. The particle size.

  Further, in the light emitting element mounting substrate of this embodiment, the frame body portion 5 has a mortar shape in which the wall surface 9 of the portion surrounding the mounting surface 1 has a larger opening diameter on the upper side. It is desirable that the number of ceramic particles 7 present per unit area increases from the mounting surface 1 side to the upper side when the frame 5 is viewed in plan.

  When the frame body part 5 has a mortar-like structure as described above, the thickness t of the frame body part 5 gradually decreases from the mounting surface 1 side to the upper side. In the mounting substrate, the number of ceramic particles 7 constituting the frame body portion 5 per unit area increases from the mounting surface 1 side to the upper side, so that the reflectance of light by the grain boundaries of the ceramic particles 7 is increased. As a result, the light can be more uniformly reflected from the entire surface of the frame body portion 5 provided on the light emitting element mounting substrate.

  The configuration of the present embodiment is suitable for a light-emitting element mounting substrate having a very thin configuration in which the thickness t of the frame body portion 5 is 100 to 1000 μm, particularly 100 to 500 μm.

  Here, the fact that the frame body portion 5 is formed integrally with the base body portion 3 means that the frame body portion 5 and the base body portion 3 are simultaneously fired and sintered.

  Further, in this light emitting element mounting substrate, the base body portion 3 and the frame body portion 5 are preferably made of the same material. When the base body 3 and the frame body 5 are made of the same material, when the base body 3 and the frame body 5 are sintered at the same time, the sintering speed of the base body 3 and the frame body 5 is close. This is because it can be reduced. In this case, the same material means that the ceramic components of the main components contained in the base body portion 3 and the frame body portion 5 are the same. Here, the main component refers to a case where the content of the ceramic component contained in the base body portion 3 and the frame body portion 5 is 80% by mass or more.

  In addition, the base | substrate part 3 and the frame part 5 have a high thermal conductivity and high intensity | strength, and the thing which contains an additive, such as Si and Mg, to this is desirable in the point.

  FIG. 3 is a schematic cross-sectional view showing the light emitting device of this embodiment. The light emitting device of this embodiment is characterized in that the light emitting element 11 is provided in the mounting portion 1 of the light emitting element mounting substrate described above. This light emitting device employs a substrate in which the base portion 3 and the frame portion 5 are formed of a dense sintered body, and the base portion 3 and the frame portion 5 are formed of ceramic particles having different average aspect ratios. Therefore, the light emitted from the light emitting element 11 can be emitted from the frame portion 5 with high directivity and high efficiency, and the light emitting device is also excellent in thermal conductivity.

  In addition, the light emitting element mounting substrate of this embodiment may be provided with a conductor layer for connecting to the light emitting element or an external power source on the surface or inside thereof as necessary.

  Next, a method for manufacturing the light emitting element mounting substrate and the light emitting device of the present embodiment will be described. FIG. 4 is a schematic view showing a manufacturing process of the light emitting element mounting substrate of the present embodiment.

First, as shown in FIG. 4A, a sheet-like molded body 21 for forming the base body portion 3 and the frame body portion 5 is produced. The composition is, for example, a mixed powder in which Al ₂ O ₃ powder is a main component and a predetermined amount of SiO ₂ powder and MgO powder is added thereto.

  Next, an organic binder is added to the mixed powder together with a solvent to prepare a slurry or a kneaded product, which is then formed into a sheet shape using a molding method such as a press method, a doctor blade method, a rolling method, or an injection method. Formed body 21 is formed.

  In addition, when manufacturing a light emitting element mounting substrate, you may form the conductor pattern used as the conductor layer for connecting with a light emitting element or an external power supply in the surface and inside of the sheet-like molded object 21 as needed. .

  Next, as shown in FIG. 4 (b), a mold having a convex portion 23 on one surface is prepared, and the produced sheet-like molded body is press-molded using this mold to form the convex portion 23. A molded body 25 is formed in which the corresponding part is a recess.

  In this press molding step, the density of the compact 25 after pressing is different between the portion pressed by the convex portion 23 of the mold and the portion around the convex portion 23. come.

That is, as shown in FIG. 4 (c), the region 27 pressed in the peripheral portion of the convex portion 23 of the mold is formed into a sheet shape as compared with the region 29 pressed in the convex portion 23 portion. Since the change in the thickness of the body 21 is small, the green density in the molded body 25 is lower in the region 27 than in the region 29. That is, the density of the region 29 is higher than that of the region 27.

  Next, the molded body 25 is fired under a predetermined temperature condition, whereby a light emitting element mounting substrate can be obtained.

  The thus obtained light emitting element mounting substrate has a different sintered state after firing depending on the green density of the region 27 (low density) and the region 29 (higher density than the region 27) in the molded body 25. come.

  In the region 27 where the green density is low, the ceramic powder is less in contact with the region 29 than in the region 29 in the state of the molded body 25, so that the diffusion of the components of the ceramic powder is compared with the ceramic powder in the region 29 even during the firing process. Therefore, the grain growth of the ceramic powder in the region 27 is slower than that of the ceramic powder in the region 29.

  On the other hand, in the high density region 29, the ceramic powder is more firmly in contact with the region 27 in the state of the molded body 25, so that the components of the ceramic powder are easily diffused during the firing process. The powder tends to grow.

  As a result, even if the molded body 25 is sintered to have a porosity of 5% or less, the region 27 having a lower density of the molded body 25 has a small degree of grain growth of the ceramic powder, so that the average aspect ratio is reduced. On the other hand, the area 29 having a higher density of the molded body 25 has a higher degree of grain growth of the ceramic powder, so that the average aspect ratio can be increased.

  Thus, both the sintered bodies constituting the base portion 3 and the frame portion 5 have a porosity of 5% or less, and the ceramic particles 7 constituting the frame portion 5 are more average than the ceramic particles 7 constituting the base portion 3. A light emitting element mounting substrate having a small aspect ratio can be obtained.

After mixing SiO ₂ powder at 5% by mass and MgO powder at 2% by mass with respect to 93% by mass of Al ₂ O ₃ powder, 19% by mass of acrylic binder as organic binder and paraffin wax as wax 3% by mass, toluene as an organic solvent was mixed to prepare a slurry, and a sheet-like molded article having an average thickness of 800 μm was prepared by a doctor blade method.

  Next, with respect to the obtained sheet-like molded object, it heat-presses at the temperature of 80 degreeC using the metal mold | die of the structure shown in FIG.4 (b), cut | disconnects, and it shows in FIG.4 (c) A molded body having such a structure was formed. Next, baking was performed in the air at a temperature of 1510 to 1550 ° C. for 1 hour.

  The obtained light emitting element mounting substrate has a plane area of 3 mm × 3 mm, a thickness of the frame portion (a thickness at a height of the mounting portion on the surface of the base portion) of 300 μm, and a height from the mounting surface of the frame portion. Was 200 μm (the thickness of the region of the mounting surface of the base portion was 400 μm).

  As a comparative example, the whole sheet-like molded body was pressed at the same pressure as the pressure received by the convex region during molding using the mold having the convex portions described above, and then subjected to cutting work to obtain a frame. A molded body in which the part and the base part were integrated was produced, and then a product fired under the same firing conditions was produced.

  Each of the produced light emitting element mounting substrates had a mortar shape in which the wall surface of the portion surrounding the mounting surface had an opening diameter increased upward.

  Next, the obtained light emitting element mounting substrate was processed to cut out the base portion of the mounting surface, and the thermal conductivity was measured.

  Further, when the LED element was mounted on the mounting surface of the obtained light-emitting element mounting substrate, this light-emitting element was connected to a power source with a lead wire, and the light-emitting element was mounted when the light emission intensity of the light-emitting element was 100%. The upper surface of the frame body portion was covered with a black plate, and the ratio of the amount of light detected from the side surface of the frame body portion was evaluated.

  The porosity of the sintered body is determined by image analysis of the total area of pores found on the photograph, using an electron micrograph of the sample whose cross-section is polished, and then the total area of the pores is the area of the photograph. It was calculated by dividing. In this case, pores having a maximum diameter of 0.1 μm or more were selected, and pores smaller than that were excluded.

  The average aspect ratio and average particle size of the ceramic particles constituting the sintered body of the base portion and the frame portion are obtained by polishing the cross-section of the obtained light emitting element mounting substrate and observing it with a scanning electron microscope. Obtained by image analysis. Specifically, on a photograph taken with a scanning electron microscope, a circle containing about 20 ceramic particles 7 is drawn, and the lengths of the long side and the short side are measured for each ceramic particle present in the circle. Then, the aspect ratio of each ceramic particle was determined from the ratio of the long side / short side, and then the average aspect ratio was determined from these average values.

  The average particle size of the ceramic particles is obtained by calculating the area from the contour of each ceramic particle in the same region, calculating the diameter from the area of the circle, and determining the average value of the diameters thus obtained, and calculating the average particle size. It was.

  When the ceramic body in each region was evaluated by dividing the frame body into three equal parts in the height direction, all the samples of the present invention had the number of ceramic particles from the mounting surface side to the upper side of the frame body part. The number of ceramic particles present per unit area from the mounting surface side to the upper side of the frame portion of the sample of the comparative example (sample No. 1) was not changed, although increased. The results are shown in Table 1.

  As is clear from Table 1, sample No. In Nos. 2 to 5, the porosity of the base part and the frame part was 3.8% or less, and the ratio of the amount of light detected from the side surface of the frame part was 20% or less. All of these samples had a thermal conductivity of 15 W / mK or more.

  In addition, Sample No. 2 in which the average aspect ratio of the ceramic particles in the frame portion is 1.5 or less and the average aspect ratio of the ceramic particles in the base portion is 1.5 or more. In 3-5, the ratio of the quantity of the light detected from the side surface of a frame part was 18% or less, and the heat conductivity was 15 W / mK or more.

  On the other hand, sample No. In No. 1, the porosity of the base portion and the frame portion was 3.1% or less and the thermal conductivity was 17 W / mK, but the ratio of the amount of light was 28% and the transmittance was high.

  Sample No. Since No. 6 had a porosity of 5% or more, the thermal conductivity was 11 W / m · K, and the ratio of the amount of light was 35%.

DESCRIPTION OF SYMBOLS 1 ... Mounting surface 3 .... Base part 5 .... Frame part 7 .... Ceramic particle 11 ... Light emitting element 21... Sheet-like molded body 23... Convex part 25... Molded body 27. Region 29... Region pressed by the convex portion of the mold

Claims (4)

  A base part made of a sintered body of ceramic particles, having a light emitting element mounting surface at the center of the upper surface, and formed integrally with the base part, and disposed so as to surround the mounting surface on the base part A light emitting element mounting substrate comprising: a base body portion; and a sintered body constituting the base body portion and the frame body portion, each having a porosity of 5% or less; The frame part is composed of ceramic particles having different average aspect ratios, and the ceramic particles constituting the frame part have a smaller average aspect ratio than the ceramic particles constituting the base part. Device mounting board.   The frame part is made of ceramic particles having an average aspect ratio of 1.5 or less, and the base part is made of a sintered body of ceramic particles having an average aspect ratio of 1.5 or more. The light emitting element mounting substrate according to claim 1.   The frame body portion has a mortar shape in which the wall surface of the portion surrounding the mounting surface increases the opening diameter upward, and when the frame body portion is viewed in plan, the sintered body of the frame body portion is The light emitting element mounting substrate according to claim 1, wherein the number of the ceramic particles present per unit area increases from the mounting surface side to the upper side.   A light emitting device comprising a light emitting element in the mounting portion of the light emitting element mounting substrate according to claim 1.