JP2011258801A - Light-emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting diode, in which an entire upper surface of a substrate to mount a light-emitting device on is made a uniform reflection surface, and the reflection efficiency of light emitted by the light-emitting device on the substrate surface is increased.SOLUTION: The light-emitting diode includes: a substrate 12; a surface reflective layer 13 covering an upper surface of the substrate 12; a device mount surface 17 in which part of the upper surface of the substrate 12 is exposed by removing part of the surface reflective layer 13; a light-emitting device 15 placed on the device mount surface 17 and having a reflective film 20 provided on its lower surface; and a resin body 16 encapsulating the light-emitting device 15 on the substrate 12 and having light transmissivity. The light-emitting device 15 is larger than the device mount surface 17 in two dimensional shape, and the outer periphery of its lower surface is put on part of the surface reflective layer 13 on the outward periphery of the device mount surface 17.

Description

  The present invention relates to a light-emitting diode formed by mounting a light-emitting element on a substrate and sealing it with a resin body.

  Conventionally, a light emitting diode is formed by forming an electrode with a predetermined pattern on a substrate, mounting the light emitting element on the electrode by die bonding or wire bonding, and sealing with a resin body having translucency (patent) References 1, 2).

  The light-emitting diode described in Patent Document 1 includes a substrate on which a pair of electrode patterns are formed, a light-emitting element that is flip-chip mounted on the electrode pattern via solder bumps, and a resin body that seals the light-emitting element. It is configured. The light emitting element includes a reflective layer and a pair of element electrodes on the back side, and the pair of element electrodes are placed on the corresponding pair of electrode patterns via solder bumps, and then conductively connected by a reflow process. .

  Further, in Patent Document 2, one of the pair of element electrodes, one element electrode is provided at the center of the substrate, and the other element electrode is provided at the outer peripheral portion of the substrate with the insulating region interposed therebetween. A light emitting element having a position and shape corresponding to the electrode pattern is shown.

  The light emitting element obtains a predetermined brightness by light emitted from the PN junction layer directly through the resin body to the outside or by light reflected from the surface of the substrate and emitted to the outside through the resin body.

JP-A-11-168235 Japanese Utility Model Publication 4-103666

  In the light emitting diode described in Patent Document 1, a reflective layer is provided on the back surface of the light emitting element, and the reflective layer is placed on the substrate with the reflective layer facing down, thereby improving the reflection efficiency on the substrate.

  However, since the element electrode provided on the back side and the electrode pattern of the substrate are mounted via the solder bumps, the light emitting element is in a state of floating from the substrate by the thickness of the solder bumps. For this reason, a gap is generated between the reflective layer of the light emitting element and the substrate surface, and the reflectance may be lowered.

  Further, the high reflectance on the substrate is the surface of the electrode pattern formed of gold, copper, or the like. Since a plurality of electrode patterns are formed on the substrate, the resin surface on which the substrate is exposed is removed. It is necessary to form between. Since the resin surface has a lower reflectance than the electrode pattern surface, there is a problem in that the overall reflectance decreases and uneven reflection occurs.

  Furthermore, gold or copper having good conductivity is generally used for the electrode pattern, but silver having high conductivity and high reflectivity may cause migration when a high voltage is applied. For this reason, the wiring density is high and cannot be used for an electrode pattern having fine processing.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light emitting diode capable of making the entire upper surface of a substrate on which a light emitting element is mounted a uniform reflecting surface and improving the reflection efficiency of light emitted from the light emitting element on the substrate surface. That is.

  In order to solve the above problems, a light emitting diode according to the present invention includes a substrate, a surface reflection layer covering the upper surface of the substrate, and a portion of the surface reflection layer is removed to expose a portion of the upper surface of the substrate. An element mounting surface, a light-emitting element provided on a lower surface with a reflective film, and a light-transmitting resin body that seals the light-emitting element on the substrate, The planar shape of the light emitting element is formed larger than the element mounting surface, and the outer peripheral portion of the lower surface is placed on the surface reflection layer on the outer periphery of the element mounting surface.

  The lower surface of the light emitting element is provided with element electrodes at the center and the outer periphery, respectively, and the element electrode at the center is electrically connected to the substrate electrode formed on the element mounting surface. Is electrically connected to the surface reflective layer having conductivity.

  According to the light emitting diode of the present invention, the entire surface of the substrate centering on the mounted light emitting element is a uniform reflective surface, and the reflective film formed on the back surface of the light emitting element is the substrate. Since it adheres onto the surface reflection layer formed on the surface, the light emitted from the light emitting element can be efficiently reflected to increase the overall luminance.

  Further, when the surface reflective layer is used as a part of one of the substrate electrodes, the surface reflective layer can be formed using a metal member having a high reflectivity, and thus has a high reflection effect. A high-intensity light emitting diode can be obtained.

It is a perspective view of the light emitting diode of 1st Embodiment. It is sectional drawing of the light emitting diode of 1st Embodiment. It is the top view (a) and AA sectional drawing (b) which looked at the light emitting element of 1st Embodiment from the back surface side. It is sectional drawing of the light emitting diode comprised by the light emitting element which had thickness in the outer peripheral part of the reflecting film. It is an effect | action figure which shows the reflective effect | action of the light emitting diode of 1st Embodiment. It is a perspective view of the light emitting diode of 2nd Embodiment. It is sectional drawing of the light emitting diode of 2nd Embodiment. It is the top view (a) and BB sectional drawing which looked at the 1st light emitting element in the light emitting diode of 2nd Embodiment from the back surface side. It is the top view which looked at the 2nd light emitting element in the light emitting diode of 2nd Embodiment from the back surface side. It is a perspective view of the light emitting diode of 3rd Embodiment. It is sectional drawing of the light emitting diode of 3rd Embodiment.

  Hereinafter, embodiments of a light emitting diode according to the present invention will be described in detail with reference to the accompanying drawings. As shown in FIGS. 1 and 2, the light-emitting diode 11 according to the first embodiment of the present invention includes a substrate 12 having a surface reflecting layer 13 on the front surface side and a pair of substrate electrodes 14a and 14b formed from the front surface to the back surface side. A light-emitting element 15 mounted on the surface of the substrate 12 and electrically connected to the pair of substrate electrodes 14a and 14b; and a light-transmitting property that seals the light-emitting element 15 on the surface reflective layer 13. And a transparent or translucent resin body 16.

  The substrate 12 is made of an insulating material such as a general epoxy resin or BT resin, and a surface reflection layer 13 is formed on the upper surface thereof. Further, the surface reflection layer 13 is provided with an element mounting surface 17 in which a part of a substantially central portion of the surface is removed in a rectangular shape or a circular shape, and a part of the substrate 12 is exposed. The element mounting surface 17 is formed slightly smaller than the planar shape of the light emitting element 15, and a pair of through holes 18 a and 18 b are provided from the front surface to the back surface of the substrate 12. As shown in FIG. 3A, the through holes 18a and 18b are formed in accordance with the positions of the pair of element electrodes 19a and 19b provided on the back surface side of the light emitting element 15 to be mounted. It is the electrode pad 23 surface soldered to 19a and 19b. The through holes 18a and 18b are electrically connected to a pair of substrate electrodes 14a and 14b that are patterned on the back surface of the substrate 12, respectively.

  The light emitting element 15 has a planar shape larger than the element mounting surface 17, and a PN junction layer comprising an n layer 25 and a p layer 26 on a rectangular base 24 as shown in FIG. 21. The n layer 25 is provided with an element electrode 19a, the p layer 26 is provided with an element electrode 19b, and a reflective film 20 is formed on the p layer 26 via a transparent insulating film 27 made of SiO2 or the like. Is formed. The reflective film 20 is covered with a deposited film of Al or Ag on the transparent insulating film 27 so as to be separated from at least the element electrode 19a. In addition, even if the reflection film 20 is a white resin material having an insulating property, a reflection effect can be obtained. One of the element electrodes 19a and 19b is an anode and the other is a cathode, and corresponds to the pair of through holes 18a and 18b on the element mounting surface 17 as described above. The light emitting element 15 emits the strongest light from the PN junction layer 21. The irradiation range by the light emitted from the PN junction layer 21 covers the entire surface of the substrate 12 with the light emitting element 15 as the center.

  As shown in FIG. 2, in the light emitting element 15, corresponding element electrodes 19a and 19b are placed on the electrode pad 23 surface of the pair of through holes 18a and 18b via solder bumps 22. At this time, the outer peripheral portion 20 a of the reflective film 20 of the light emitting element 15 is closely disposed on the surface reflective layer 13 so as to cover the outer peripheral portion of the element mounting surface 17.

  Since the surface reflective layer 13 has a certain thickness, a step is formed between the device mounting surface 17 and the device electrodes 19a and 19b and the through holes 18a and 18b are electrically connected by the solder bumps 22 within the step. In addition, the light emitting element 15 can be fixed on the substrate 12. For this reason, a gap is not generated between the reflective film 20 of the light emitting element 15 and the surface reflective layer 13, and a decrease in reflectance due to light leakage can be prevented.

  Further, as shown in FIGS. 3B and 4, by forming the outer peripheral portion 20 a of the reflective film 20 to be thicker than the central portion, it is possible to sufficiently secure the bonding height width including the solder bumps 22. it can. As a result, lifting or peeling from the surface reflective layer 13 does not occur, and the reflective film 20 can be more closely attached to the surface reflective layer 13.

  As shown in FIGS. 1 and 2, by mounting the light emitting element 15, the element mounting surface 17 in which the through holes 18 a and 18 b are provided is completely hidden, and the periphery around the light emitting element 15 is centered. The whole becomes one uniform surface reflecting layer 13. The surface reflecting layer 13 is made of a plate-like or film-like metal member having a high light reflectance or a mirror-finished member. In this embodiment, since the surface reflective layer is not an electrode, conductivity is not required, but a high reflection effect can be obtained by using a metal member such as gold plating, silver plating, or copper plating. In particular, silver plating is most excellent in terms of reflectivity.

  As shown in FIG. 5, the light emitted downward from the PN junction layer 21 of the light emitting element 15 is reflected by the reflective film 20 of the light emitting element 15 covering the element mounting surface 17, and the reflective film 20. Can be reflected further upward on the surface reflective layer 13 in close contact with the outer peripheral portion of the surface. Further, the light emitted horizontally or upward from the PN junction layer 21 can be radiated to the outside through the resin body 16 as it is, so that the entire emission luminance is combined with the light reflected by the surface reflection layer 13. Can be greatly improved.

  6 and 7 show a light emitting diode 31 according to a second embodiment of the present invention. As shown in FIG. 8A, the light-emitting diode 31 is formed by applying to a light-emitting element 35 having a structure in which element electrodes 39a and 39b are provided at the center and outer periphery of the back surface. The light emitting element 35 is provided with a first element electrode 39a at the center of the back surface and has a common second element electrode 39b at the corners of the four corners.

  The light emitting element 35 has a planar shape larger than the element mounting surface 37, and as shown in FIG. 8B, a PN junction layer comprising an n layer 45 and a p layer 46 on a rectangular base 44. 41, the device electrode 39a is provided from the n layer 45, and the device electrode 39b is provided from the p layer 46, and is reflected on the p layer 46 through a transparent insulating film 47 made of SiO2 or the like and having insulating properties. Film 40 is formed. The reflective film 40 is covered with a deposited film of Al or Ag on the transparent insulating film 27 so as to be separated from at least the element electrode 39a. Alternatively, a white resin material having insulation may be used for the reflective film 40.

  Similar to the light emitting diode 11 of the first embodiment, a rectangular element mounting surface 37 with the substrate 32 exposed is provided at a substantially central portion of the surface reflective layer 33 on which the light emitting element 35 is placed. A first through hole 38 a that communicates with the rear surface side of the substrate 32 is formed on the surface 37. An electrode pad 23 is provided at the upper end of the first through hole 38 a, and the first element electrode 39 a of the light emitting element 15 is conductively connected to the electrode pad 23 via the solder bump 22. Conductive connection is made to the external electrode 34a extending toward the surface. The light emitting element 35 is formed so that the planar shape of the back surface on which the reflective film 40 is formed is larger than the element mounting surface 37 so as to cover the element mounting surface 37.

  The surface reflection layer 33 is formed of a conductive member made of gold plating, copper plating or silver plating. The surface reflecting layer 33 is electrically connected to the second external electrode 34b formed on the back surface side of the substrate 32 through the second through hole 38b from the surface opposite to the extending direction of the external electrode 34a. The

  As shown in FIGS. 6 and 7, the light emitting element 35 is placed on the surface reflective layer 33 so as to cover the element mounting surface 37, and the first element electrode 39a and the upper surface of the first through hole 38a are solder bumps. Is connected by conduction. On the other hand, the second element electrode 39b is placed on the surface reflective layer 33 along the outer periphery of the element mounting surface 37, whereby electrical connection with the second external electrode 34b is achieved via the second through hole 38b. .

  As in the first embodiment, the first element electrode 39a and the second through hole 38a are connected by solder bumps by providing the thickness of the surface reflection layer 33 and the outer peripheral portion of the reflection film 40 of the light emitting element 35. Can be secured. Thus, electrical connection between the first element electrode 39b and the surface reflective layer 33 formed of the conductive member is achieved in a state where the light emitting element 35 is placed on the substrate 32.

  In the light emitting diode 31 of the second embodiment, the surface reflection layer 33 is a part of the substrate electrode, and thus is formed of a conductive member. As such a conductive member, in addition to gold plating and copper plating having good conductivity, silver plating having excellent reflectance is used. In this silver plating, migration tends to occur when a high voltage is applied, but there is no possibility of causing a short circuit or the like because it is separated from the other second element electrode 39a by separating the element mounting surface 37.

  In addition to the light emitting element 35, a light emitting element 35a having an element electrode structure as shown in FIG. 9 can also be used. The light emitting element 35a has a first element electrode 39a at the center of the back surface and a second element electrode 39b at a portion continuous along the outer peripheral surface. The light emitting elements 35 and 35a have a reflective film 40 formed on the entire back surface except for the first and second element electrodes 39a and 39b. The structure of the light emitting element 35a is the same as the structure shown in FIG.

  10 and 11 show the light-emitting diode 51 of the third embodiment in which a surface reflection layer 53 and a part of the external electrodes 54a and 54b are formed on a substrate 52. FIG. First and second through holes 58a and 58b are formed in the central portion of the surface reflecting layer 53, and are electrically connected to external electrodes 54a and 54b that run from the back side of the both sides of the substrate 52 to the upper surface through the side surfaces, respectively. ing. As in the first embodiment, the light-emitting element 55 has a reflective film 60 on the back surface side, and first and second conductive layers connected from the reflective film 60 to the first and second through holes 58a and 58b through the solder bumps 22. Two element electrodes 59a and 59b are formed.

  In the substrate 52, an isolation groove 63 exposing the resin surface of the substrate 52 is formed to separate the surface reflective layer 53 and the pair of external electrodes 54a and 54b. The resin body 56 is molded along the outer peripheral portion of the surface reflection layer 53 including the isolation groove 63. Thus, by molding the resin body 56 on the planar region including the isolation groove 63, the surface reflective layer 53 can be electrically insulated and separated from the external electrodes 54a and 54b. It can be formed by conductive plating such as high gold, silver, and copper. Further, even when silver plating is used, there is no possibility of short-circuiting with the external electrodes 54a and 54b even when migration peculiar to silver occurs due to the isolation groove 63. Further, a part of the outer peripheral portion of the resin body 56 is bonded to the surface of the substrate 52 exposed by the isolation groove 63, so that the light emitting element 55 can be hermetically sealed so as not to cause light emission leakage. it can.

  As described above, according to the light emitting diode according to the present invention, the entire surface of the substrate sealed with the resin body can be formed by one continuous surface reflection layer centering on the light emitting element. As a result, the reflection efficiency of light emitted from the light emitting element is increased, and light emission unevenness does not occur. In addition to being able to separate the pair of substrate electrodes provided for driving the light emitting element and the surface reflection layer, it is possible to take a form such as using the surface reflection layer as a part of one substrate electrode. In any case, since the surface reflective layer can be formed using a highly reflective metal member, a high-intensity light-emitting diode having a high reflection effect can be obtained.

DESCRIPTION OF SYMBOLS 11 Light emitting diode 12 Board | substrate 13 Surface reflection layer 14a, 14b Board electrode 15 Light emitting element 16 Resin body 17 Element mounting surface 18a, 18b Through hole 19a, 19b Element electrode 20 Reflective film 20a Outer peripheral part 21 PN junction layer 22 Solder bump 23 Electrode pad 24 Base 25 n layer 26 p layer 27 transparent insulating film 31 light emitting diode 32 substrate 33 surface reflecting layer 34a, 34b substrate electrode 35 light emitting element 36 resin body 37 element mounting surface 38a, 38b through hole 39a, 39b element electrode 40 reflecting film 41 PN Bonding layer 44 Base 45 n layer 46 p layer 47 Transparent insulating film

Claims (8)

A substrate, a surface reflective layer covering the upper surface of the substrate, an element mounting surface from which a part of the surface reflective layer is removed to expose a part of the upper surface of the substrate, and a reflective film on the lower surface, A light-emitting element placed on the element mounting surface, and a light-transmitting resin body that seals the light-emitting element on the substrate,
The light-emitting diode is characterized in that the planar shape of the light-emitting element is formed larger than the element mounting surface, and the outer peripheral portion of the lower surface is placed on the surface reflection layer on the outer periphery of the element mounting surface.   The light emitting diode according to claim 1, wherein a pair of element electrodes is provided on a lower surface of the light emitting element, and a substrate electrode electrically connected to the element electrode is provided on the element mounting surface.   Element electrodes are provided on the lower surface of the light emitting element at the center and the outer periphery, respectively, and the element electrode at the center is electrically connected to the substrate electrode formed on the element mounting surface, and the element electrode at the outer periphery is electrically conductive. The light emitting diode of Claim 1 or 2 electrically connected to the said surface reflection layer which has property.   The light emitting diode according to claim 3, wherein the surface reflection layer is formed of a conductive member.   2. The light emitting diode according to claim 1, wherein an outer peripheral portion of the reflection film is in close contact with an upper surface of a surface reflection layer on an outer periphery of the element mounting surface.   2. The light emitting diode according to claim 1, wherein the reflective film is formed such that an outer peripheral portion placed on the upper surface of the surface reflective layer is thicker than other portions.   The light emitting diode according to claim 1, wherein the surface reflection layer is formed by silver plating.   The light emitting diode according to claim 1, wherein the resin body is formed on the substrate so as to surround a region covered with the surface reflection layer.

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