JP2011176060A - Light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device radiating heat produced by a light-emitting element 2 and having a high reliability. <P>SOLUTION: A first conductive material 4 and a second conductive material 5 are laminated and filled in a through-hole 3 of a substrate 1, and a light-emitting element is disposed over them. This forms a through electrode having a high airtightness and a high thermal conductivity to radiate the heat produced by the light-emitting element 2 outside, and prevents an external filtration of water and gas. It is preferable that the first conductive material is manufactured with a sintered conductive paste with binders added to a conductive filler, and the second conductive material is manufactured with resin hardening conductive paste with conductive filler added to a thermosetting resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light emitting device having a configuration in which a light emitting element is packaged.

  In recent years, semiconductor light emitting devices have been improved in light emission efficiency and brightness, and their practical application to backlights for liquid crystal displays and illumination applications is accelerating. However, along with the improvement of characteristics, the amount of heat generated by the light emitting element has increased, and there has been a demand for lower thermal resistance and higher reliability of the package.

  FIG. 4 illustrates a cross-sectional structure of a light emitting device using a substrate in which a through hole filled with a conductive material or a high thermal conductivity material is formed. Through holes 3, 3a, 3b are formed in a substrate 1, such as ceramics, glass, or resin, and a conductive material 16 is embedded therein. A glass epoxy substrate 21 having an opening made of a slope is bonded to the substrate 1. The opening is filled with a sealing material 9 so as to cover the light emitting element. A metal pattern 12 is provided on the upper surface of the conductive material 16. In the figure, the metal patterns 12 on both sides are provided with wires 14 that are electrically connected to a pair of electrodes of the light emitting element. Therefore, a voltage can be applied to the light emitting element 2 from a pair of terminal electrodes 8 a and 8 b formed on the lower surface of the substrate 1. Further, the light emitting element 2 is disposed above the through hole 3 in the center of the figure, and the heat generated by the light emitting element 2 passes through the conductive material 16 having high thermal conductivity filled in the through hole 3 from the metal pattern 12. It is possible to dissipate heat from the lower surface of the substrate more efficiently. At this time, a heat radiating metal pattern 18 that promotes heat radiation is provided on the lower surface of the substrate. Thereby, low thermal resistance can be achieved, and a highly reliable and high-performance light emitting device can be obtained (see, for example, Patent Document 1).

  Moreover, as a method of embedding a conductive material or a heat-dissipating material in the through hole 3, a method of forming a through hole in a substrate and filling it with a metal paste by printing, or plating the side wall of the through hole with Cu is performed. A method of depositing a metal film such as Ni or Ni, or a method of embedding metal in a through hole formed in a substrate to form a through electrode is known.

JP 2005-209663 A

  However, in the case of the light emitting device described in Patent Document 1, one type of conductive material or high thermal conductivity material is embedded in the through hole, and the thermal conductivity of the through electrode obtained by the embedded material, Characteristics such as reliability are determined. For example, in general, in the case of a through electrode formed by filling a through hole formed in a substrate made of ceramic, glass, resin, or the like with a resin-curing metal paste, the metal paste is good with the substrate by the resin. Adhesiveness can be obtained, but the thermal conductivity decreases rapidly depending on the amount of resin added. For example, 20-30% resin is blended in a general resin curable silver paste, but the thermal conductivity is 1-10 W / mK, and the thermal conductivity for a recent high-brightness light emitting device is low. being insufficient. If the amount of resin added is reduced, the thermal conductivity can be improved, but the adhesiveness with the substrate is insufficient and moisture, gas, etc. are easily infiltrated, leading to a decrease in reliability.

  Further, as a material having high thermal conductivity, a sintered metal paste is known, and a through electrode having high thermal conductivity can be obtained by filling the through hole with this material, but it is fired at a high temperature of 400 ° C. or higher. Therefore, the shrinkage of the paste itself is large, and the influence of the difference in thermal expansion coefficient between the paste and the substrate is also large. For this reason, a gap is generated between the side wall of the through hole and the metal paste, so that moisture, gas, and the like can easily enter, thereby reducing reliability.

  In addition, there is a method of forming a through electrode by embedding a metal in a through hole formed in a substrate made of ceramics or glass, but a crack or the like is likely to occur in the substrate due to a difference in thermal expansion coefficient between the substrate and the metal. For this reason, the strength of the substrate is reduced, and moisture or gas easily enters from the generated gap, which causes a decrease in reliability. For this reason, it is not easy to form a through electrode having good characteristics.

  The present invention has been made in order to solve the above-described problems, and has a gap between the through hole side wall and the conductive paste to be filled, no cracks in the substrate, and a through electrode having high thermal conductivity. An object of the present invention is to provide a light-emitting device with high reliability and low thermal resistance.

  Accordingly, the present invention provides a light emitting device including a substrate having a through hole formed therein, a conductive material filled in the through hole, a light emitting element mounted on the surface of the substrate, and a sealing material for covering and sealing the light emitting element. In the apparatus, the light emitting element is disposed on the conductive material, and the conductive material is configured by stacking the first conductive material and the second conductive material.

  Further, the first conductive material was prepared from a sintered conductive paste obtained by adding a binder to a conductive filler, and the second conductive material was prepared from a resin curable conductive paste obtained by adding a conductive filler to a thermosetting resin. At this time, the thickness of the second conductive material was 10 to 20% of the thickness of the substrate.

  In addition, a sintered conductive paste containing 90% or more of a conductive filler was used as the sintered conductive paste. Furthermore, this conductive filler is composed of a first conductive filler having an average particle size of 100 nm or less and a second conductive filler having an average particle size of 1 to 5 μm, and the blending ratio of the first conductive filler is 30 to 50%. did.

  In the light emitting device of the present invention, heat generated from the light emitting element is efficiently dissipated through two kinds of conductive materials, and it is possible to reduce moisture and gas entering from the through hole. A light emitting device having high and high thermal conductivity can be realized.

It is a cross-sectional schematic diagram of the light-emitting device which concerns on the Example of this invention. It is a cross-sectional schematic diagram of the light-emitting device which concerns on the Example of this invention. It is a cross-sectional schematic diagram of the light-emitting device which concerns on the Example of this invention. It is a cross-sectional schematic diagram of a conventionally well-known light-emitting device.

  Hereinafter, the light-emitting device of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a cross-sectional structure of a light emitting device of the present invention. A plurality of through holes 3 are formed in the substrate 1 and each of the through holes is filled with two kinds of conductive materials. That is, the conductive material is formed by laminating the first conductive material 4 and the second conductive material 5. And the light emitting element 2 is mounted on the upper part of the several through-hole 3 via the die attach material 13. As shown in FIG. Although there are a plurality of through holes 3 in FIG. 1, only one may be used. Moreover, the light emitting element 2 is covered with a sealing material (not shown), and is blocked from the outside air. The first conductive material 4 is formed from a sintered conductive paste in which a binder is added to a conductive filler, and the second conductive material 5 is formed from a resin curable conductive paste in which a conductive filler is added to a thermosetting resin. At this time, the thickness (t5) of the second conductive material 5 is 10 to 20% of the thickness of the through hole 3, that is, the thickness of the substrate 1, and the thickness (t4) of the first conductive material 4 is 80 of the thickness of the substrate 1. Need to be -90%. As described above, the conductive material filled in the through hole 3 has a configuration in which the first conductive material 4 and the second conductive material 5 are laminated, and the through hole 3 is provided immediately below the light emitting element 2. The heat generated in the element 2 can be efficiently dissipated and moisture and gas entering from the through hole can be prevented. As described above, a light-emitting device having high airtightness and high thermal conductivity can be realized. In FIG. 1, the second conductive material 5 is provided on the side close to the light emitting element 2, but the first conductive material 4 may be provided on the side close to the light emitting element 2 by reversing the stacking order. A metal layer for promoting heat dissipation may be formed on the back surface of the substrate 1 (the surface on which the light emitting element is not mounted).

  Further, the conductive filler contained in the sintered conductive paste may be configured by mixing a first conductive filler having an average particle size of 100 nm or less and a second conductive filler having an average particle size of 1 to 5 μm.

  Here, the content of the conductive filler contained in the sintered conductive paste constituting the first conductive material 3, and the reliability and thermal conductivity when the average particle size and content ratio of the conductive filler are changed are evaluated. The results are shown in Table 1 below.

表１では、焼結型導電ペーストに含まれる導電性フィラーの含有率（重量比）を８５〜９５％とし、平均粒径１００ｎｍ以下の第一導電性フィラーと平均粒径１〜５μｍの第二導電性フィラーの含有比率（重量比）を変えたときの特性を調べた。ここで、間隙／クラックは、導電ペーストの焼結時の収縮によって生じるクラックまたは貫通孔壁との隙間を言い、発生がないものを○、微小なクラック／隙間が生じたものを△、大きなクラックが発生するものを×としている。×評価のものは、第二導電材料５となる樹脂硬化型導電ペーストを充填しても気密性を確保できないことを確認している。また、熱伝導性は、熱伝導率を評価しており、１００Ｗ／ｍ・ｋ以上のものを○、５０〜１００Ｗ／ｍ・ｋの範囲のものを△、５０Ｗ／ｍ・ｋ以下のものを×としている。

In Table 1, the content (weight ratio) of the conductive filler contained in the sintered conductive paste is 85 to 95%, the first conductive filler having an average particle size of 100 nm or less and the second conductive particle having an average particle size of 1 to 5 μm. The characteristics when the content ratio (weight ratio) of the conductive filler was changed were examined. Here, the gap / crack refers to a crack caused by shrinkage during sintering of the conductive paste or a gap with the through-hole wall. The thing which generate | occur | produces is set as x. X The thing of evaluation has confirmed that airtightness cannot be ensured even if it fills with the resin hardening type electrically conductive paste used as the 2nd electrically-conductive material 5. FIG. Moreover, thermal conductivity is evaluating thermal conductivity, the thing of 100 W / m * k or more is (circle), the thing of the range of 50-100 W / m * k is (triangle | delta), and the thing of 50 W / m * k or less. X.

  From the evaluation results in Table 1, when there are many first conductive fillers having a particle size of 100 nm or less, shrinkage during sintering is large and gaps / cracks are generated. On the other hand, when there are many 2nd conductive fillers with a large average particle diameter, thermal conductivity falls. In order to satisfy both characteristics, the first conductive filler having an average particle diameter of 100 nm or less and the second conductive filler having an average particle diameter of 1 to 5 μm are mixed, and the mixing ratio of the first conductive filler is 30 to 50%. And it is sufficient. In addition, with a sintered conductive paste with a low conductive filler content, the thermal conductivity decreases, and the amount of binder increases, resulting in a large shrinkage during sintering and an increase in gaps / cracks. It is necessary that the content of

  Therefore, as a sintered conductive paste, the content of the conductive filler is 90%, the first conductive filler having an average particle size of 50 nm is 40%, and the second conductive filler having an average particle size of 2.5 μm is 60%. Using the added material, the through hole 3 was filled by a printing method, and a resin curable conductive paste was filled thereon by a dispenser method. Table 2 shows the evaluation results when the filling ratio of the sintered conductive paste and the resin curable conductive paste was changed.

表２では気密性と熱伝導性を評価しており、前者は浸透液による試験を、後者は発光素子２２のジャンクションからケースまでの熱抵抗が１０℃／Ｗ以下を○、２０℃／Ｗ以下を△、それ以上を×としている。

In Table 2, airtightness and thermal conductivity are evaluated. The former is a test using a penetrating liquid, and the latter is a case where the thermal resistance from the junction to the case of the light emitting element 22 is 10 ° C./W or less, and 20 ° C./W or less. △, and more than that.

  From the results shown in Table 2, the resin-cured conductive paste for ensuring airtightness starts to exert its effect when it is filled at 10% or more, but when it is filled at 30% or more, the thermal conductivity sharply decreases. By filling the resin-curing conductive paste with 10 to 20%, that is, 90 to 80% of the sintered conductive paste, a through electrode having both airtightness and thermal conductivity can be obtained. Here, the filling ratio can also be expressed by the thickness of the first conductive material 4 formed of a sintered conductive paste and the second conductive material 5 formed of a resin curable conductive paste. That is, the thickness of the second conductive material 5 is 10 to 20% of the substrate thickness, and the thickness of the first conductive material 4 is 80 to 90% of the substrate thickness. When the importance of heat dissipation is high as in a recent high-luminance light emitting device, the filling ratio of the sintered conductive paste is set to 90%, that is, the thickness of the first conductive material 4 is set to 90% of the substrate thickness. % Is desirable.

Further, the sintered conductive paste and the resin curable conductive paste may contain low melting point glass powder having good adhesion to ceramics and glass. Thereby, the airtightness of the conductive material is further increased and the adhesion with the through hole is improved.
Hereinafter, the light emitting device according to the present invention will be described in detail.

Example 1
2A and 2B schematically show a cross-sectional configuration of the light-emitting device of this example. In the present embodiment, a case where a through hole filled with a conductive material in which the first conductive material 4 and the second conductive material 5 are stacked is used as a through electrode will be described. Here, a glass substrate 11 having a recess 6 formed in the center is used as a base. Through holes 3 a and 3 b are formed on the bottom surface of the recess 6. The first conductive material 4 and the second conductive material 5 are stacked and filled in the through hole. Through electrodes 7a and 7b are formed of a conductive material filled in the through holes 3a and 3b. The light emitting device shown in FIG. 2A has a configuration in which one through electrode is formed immediately below one light emitting element. The light-emitting device shown in FIG. 2B has a configuration in which a through electrode extending radially at an angle of 45 ° from the bottom surface of the recess 6 to the back surface of the glass substrate 11 is formed immediately below one light-emitting element. The light emitting element 2 is disposed on the through electrode 7a via the bonding material 15. The bonding material 15 includes a bump and a conductive adhesive, and bonds and fixes the light emitting element 2 to the bottom of the recess 6. An electrode (not shown) is formed on the lower surface of the light emitting element 2 and is electrically connected to the through electrode 7 a through the bonding material 15. Further, an electrode (not shown) is also formed on the upper surface of the light emitting element 2, and is connected to the through electrode 7 b by a wire 14. Terminal electrodes 8a and 8b are formed separately from each other on the back surface of the glass substrate 11, and are connected to the through electrodes 7a and 7b, respectively. Therefore, the light emitting element 2 can receive power supply from the terminal electrodes 8a and 8b. In this embodiment, the terminal electrodes 8a and 8b were formed by printing and curing a conductive paste on the back surface of the glass substrate 11.

  With such a configuration, heat generated in the light emitting element 2 is effectively dissipated through the bonding material 15, the through electrode 7a in which the first conductive material 4 and the second conductive material 5 are laminated, and the terminal electrode 8a. At the same time, it becomes possible to prevent moisture and gas entering from the through hole.

  Although not shown, a reflection film is formed on the inner wall surface and the bottom surface of the recess 6 and functions as a reflection surface that reflects light emitted from the light emitting element 2. Further, the recess 6 is filled with a sealing material for preventing impurities, moisture and the like from entering from the outside, and covers the light emitting element 2 and the wire 14.

  In this embodiment, the glass substrate 11 is integrally formed by molding a normal glass material mainly composed of silicon oxide. At this time, the recess 6 and the through holes 3a and 3b can be formed simultaneously. Therefore, it is not necessary to process and bond the substrate and the frame part individually.

(Example 2)
3A to 3C schematically show a cross-sectional configuration of the light emitting device of this example. In the present embodiment, a configuration in which the through hole 3 positioned immediately below the light emitting element is not used as a through electrode will be described. Others are the same as those in the first embodiment, and therefore, redundant description is omitted as appropriate. Through holes 3, 3 a, 3 b are formed in the bottom surface of the recess 6 of the glass substrate 11. The first conductive material 4 and the second conductive material 5 are stacked and filled in each through hole. The light emitting element 2 is fixed to the upper portion of the through hole 3 filled with the first conductive material 4 and the second conductive material 5 by a die attach material 13.

  In the light emitting device shown in FIG. 3A, the through hole 3 is filled with the conductive material until the first conductive material 4 protruding from the back surface of the glass substrate 11 has the same thickness as the terminal electrodes 8a and 8b. Yes. In the light emitting device shown in FIG. 3B, the first conductive material 4 protruding from the back surface of the glass substrate 11 spreads over a range wider than the area of the through hole. Also here, the through hole 3 is filled with the conductive material to the same height as the terminal electrodes 8a and 8b. In the light emitting device shown in FIG. 3C, the through-hole 3 is formed to radially spread at an angle of 45 ° from the bottom surface of the recess 6 to the back surface of the glass substrate 11, and is protruded from the back surface of the glass substrate 11. The through hole 3 is filled with the conductive material up to a height at which the one conductive material 4 has the same thickness as the terminal electrodes 8a and 8b. Here, the size of the portion from which the first conductive material 4 protrudes is the same as the size of the through hole in the back surface of the glass substrate 11. As described above, when the conductive material is protruded, the conductive material is easily brought into close contact with a member on which the light-emitting device is mounted.

  Further, the through electrodes 7a and 7b are formed by the through holes 3a and 3b in the region where the light emitting element 2 is not disposed. The first conductive material 4 and the second conductive material 5 are stacked and filled in the through holes 3a and 3b. A pair of electrodes (not shown) are formed on the upper surface of the light emitting element 2 and are connected to the through electrodes 7 a and 7 b by a pair of wires 14. Terminal electrodes 8a and 8b are formed on the back surface of the glass substrate 11 separately from each other, and are connected to the through electrodes 7a and 7b, respectively. Therefore, the light emitting element 2 can receive power supply from the terminal electrodes 8a and 8b.

  In each of the above-described embodiments, one light emitting element 2 is arranged in one recess 6 and one through hole 3 is formed in one light emitting element 2, but this is not limitative. For example, a plurality of light emitting elements may be arranged in one recess 6. Moreover, the structure by which the several through-hole 3 was provided with respect to one light emitting element may be sufficient.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Light emitting element 3 Through-hole 4 First conductive material 5 Second conductive material 6 Depression 7a, 7b Through electrode 8a, 8b Terminal electrode 11 Glass substrate 13 Die attach material 14 Wire 15 Bonding material

Claims (9)

A substrate having a through hole formed thereon, a conductive material filled in the through hole, a light emitting element mounted on the surface of the substrate, and a sealing material for covering and sealing the light emitting element,
The light emitting element is disposed on the conductive material, and the conductive material is formed by stacking a first conductive material and a second conductive material.   The first conductive material is made from a sintered conductive paste in which a binder is added to a conductive filler, and the second conductive material is made from a resin curable conductive paste in which a conductive filler is added to a thermosetting resin. The light-emitting device according to claim 1.   The light emitting device according to claim 2, wherein the thickness of the second conductive material is 10 to 20% of the thickness of the substrate.   The light emitting device according to claim 2 or 3, wherein the sintered conductive paste contains 90% or more of a conductive filler.   The conductive filler is composed of a first conductive filler having an average particle size of 100 nm or less and a second conductive filler having an average particle size of 1 to 5 μm, and the blending ratio of the first conductive filler is 30 to 50%. The light-emitting device according to claim 4.   The light emitting device according to claim 1, wherein the second conductive material is provided closer to the light emitting element than the first conductive material.   The light emitting device according to claim 1, wherein the conductive material is provided so as to protrude from a back surface of the substrate.   The light emitting device according to claim 7, wherein an area of the protruding portion of the conductive material is larger than an area of the through hole.   The substrate is a glass substrate having a recess, the through hole is formed in the recess, the light emitting element is formed on a bottom surface of the recess, and the sealing material is supplied to the recess. The light-emitting device according to claim 1.

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