JP2011181754A - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device that can suppress stray light due to resin while protecting a bonding wire with the resin. <P>SOLUTION: The protective resin 6 enclosing the bonding wire 5 has at least a partial region 6a on a surface facing a light emitting element 3, processed so as to suppress reflection of light from the light emitting element 3. Specifically, the region 6a is cut away, and the surface after the cutting is shaped perpendicularly to a principal plane of a substrate 1. For example, a plurality of holes can be bored in the resin 6a of the protective resin 6. Alternatively, the surface of the resin 6a of the protective region can be processed so as to be a rough surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light emitting device in which a light emitting element is mounted on a substrate, and more particularly to a light emitting device in which a bonding wire is disposed on a substrate.

  2. Description of the Related Art In a light emitting device in which a light emitting element such as an LED chip is mounted on a substrate having a pair of electrodes formed on the surface, a structure using bonding wires for widely connecting electrodes is widely used. For example, Patent Document 1 discloses a light emitting device in which the lower surface electrode of an LED chip is die-bonded to one electrode on a substrate, and the upper surface electrode of the LED chip is connected to the other electrode on the substrate by a bonding wire. The entire LED chip and bonding wire are sealed with a translucent resin.

  As described above, in a light emitting device having a structure in which a bonding wire is sealed with resin, when the light emitting device is mounted on a printed circuit board or the like by solder reflow processing, the resin is softened and cured by heat due to solder reflow, and the expansion at that time In some cases, the bonding wire may break due to shrinkage. For this reason, in patent document 1, fillers, such as glass and carbon, are mixed in resin around a bonding wire, and the glass transition point of resin is raised. This prevents the resin around the bonding wire from being softened by the heat during solder reflow, thereby reducing thermal stress on the bonding wire. When the filler-containing resin is disposed only around the bonding wire, potting (dropping) or a method of injecting into the mold is used.

JP 2002-110864 A

  In Patent Document 1, since the filler-containing resin is disposed only around the bonding wire by potting or the like, the filler-containing resin is formed in a raised shape so as to wrap around the bonding wire. For this reason, a part of the light emitted from the LED chip with a light distribution characteristic close to a sphere is reflected upward on the surface of the raised filler-containing resin, which may cause leakage light or stray light. . When such leakage light or stray light occurs, light deviating from the optical design is emitted, so that the characteristics of the apparatus are impaired.

  The objective of this invention is providing the light-emitting device which can suppress the stray light by resin, protecting a bonding wire with resin.

  In order to achieve the above object, according to the first aspect of the present invention, the following light emitting device is provided. That is, a light-emitting device having a light-emitting element and a bonding wire mounted on a substrate and a protective resin that encloses the bonding wire, the tangent of the surface facing the light-emitting element being 45 degrees with respect to the main plane Processing for suppressing upward reflection of light from the light emitting element is performed on at least a part of the region described above.

  For example, as the above process, a process of removing the protective resin by cutting so as not to expose the bonding wire is performed.

  Further, for example, a plurality of holes can be formed in the aforementioned region of the protective resin. Alternatively, the surface of the aforementioned region of the protective resin can be processed into a rough surface.

  According to the second aspect of the present invention, the following light emitting device is provided. That is, a light-emitting device that includes a light-emitting element and a bonding wire mounted on a substrate and a protective resin that wraps the bonding wire, and at least a part of a surface facing the light-emitting element is a main plane of the substrate. It is a plane perpendicular to. For example, the outer shape of the protective resin can be made columnar.

  According to the present invention, since stray light due to reflection from the slope of the protective resin of the bonding wire disposed in the vicinity of the light emitting element can be suppressed, the optical design of the light distribution becomes easy and the light distribution characteristics are excellent. A high-quality light-emitting device can be provided.

The top view of the light-emitting device of a 1st embodiment. FIG. 3 is a cross-sectional view taken along the line A-A ′ of the light emitting device according to the first embodiment. (A) Explanatory drawing which shows the area | region 6a which should be cut in 1st Embodiment, and the reflection direction of light, (b) Explanatory drawing which shows the reflection direction of the light after cutting. Sectional drawing of the light-emitting device of 2nd Embodiment. The top view of the light-emitting device of 3rd Embodiment. (A)-(c) Explanatory drawing which shows the process of forming protective resin around the bonding wire 5 in 4th Embodiment. (A)-(c) Explanatory drawing which shows another example of the process of forming protective resin around the bonding wire 5 in 4th Embodiment. (A) And (b) Explanatory drawing which shows the process of forming protective resin around the bonding wire 5 in 5th Embodiment.

  Hereinafter, an embodiment of the present invention will be described.

  In the present invention, the light reflected by the resin is reduced by controlling the shape of the resin covering the bonding wire.

(First embodiment)
The light-emitting device of 1st Embodiment is demonstrated using FIG. 1 and FIG. FIG. 1 is a top view of the light emitting device, and FIG. 2 is a cross-sectional view taken along the line AA ′.

  As shown in FIGS. 1 and 2, the four LED chips 3 are fixed to the submount substrate 12 in a row. The submount substrate 12 includes a predetermined electrode pattern 13 on an insulating substrate such as ceramic. The electrode pattern 13 is connected to a pair of electrode pads (not shown) on the LED chip 3 by a bonding wire 8 such as Au. On the upper surface of the LED chip 3, a phosphor resin layer 4 formed of a resin in which a predetermined phosphor is dispersed is provided. Thereby, the four LED chips 3 are connected in series. The submount substrate 12 on which the LED chip 3 is mounted is fixed on a mounting substrate 1 having power supply electrodes 2 at both ends. The electrode patterns 13 at both ends on the submount substrate 12 are connected to the power supply electrode 2 on the mounting substrate 12 by bonding wires 5 such as Au. In FIG. 2, the bonding wire 8 is not shown.

  The bonding wire 5 connected to the power supply electrode 2 is thicker than the bonding wire 8 connected to the LED chip 3.

  Since the bonding wires 5 are located at both ends, they may come into contact with other objects in the manufacturing process or the like. For this reason, it is covered with the protective resin 6.

  In this embodiment, as shown in FIG. 2, the protective resin 6 has a region 6a facing the LED chip 3 cut vertically.

  Thereby, of the light emitted from the LED chip 3, the light directed to the protective resin 6 is not easily reflected upward, and the protective resin 6 does not shine when viewed from above, that is, the upper (front) by the reflection of the protective resin 6 ) Can be suppressed.

  The region 6a where the protective resin 6 has been removed will be described with reference to FIGS. 1, 3A, and 3B. The area 6a for scraping off the protective resin 6 is a surface area facing the LED chip 3 as viewed from above as shown in FIG. 1, and the tangent to the surface of the protective resin 6 before scraping is 45 degrees or more with respect to the main plane. This is a range that includes a portion and does not expose the bonding wire 5. As a result, among the light emitted from the LED chip 3 and passing through the phosphor resin layer 4, the light emitted parallel to the main plane or upward is reflected vertically upward by the protective resin 6. There is nothing to do. Moreover, since the bonding wire 5 is not exposed, the function of the protective resin 6 is not impaired.

  In order to reduce the reflectance of light emitted from the phosphor resin layer 4, the protective resin 6 is preferably formed of a black resin containing a filler such as carbon. Since the black resin absorbs the laser beam, the region 6a of the protective resin 6 can be cut with the laser beam in the manufacturing process described later. Specifically, for example, a silicone resin containing 10 wt% of carbon particles having a particle diameter of 75 μm can be used.

  The operation of each part of the light emitting device will be described. The current supplied to the power feeding electrode 2 is supplied to the electrode pattern 13 on the submount substrate 12 through the bonding wire 5 and supplied to the LED chip 3 through the bonding wire 8. Thereby, light of a predetermined wavelength, for example, blue light is emitted from the upper surfaces of the four LED chips 3. The phosphor resin layer 4 contains a phosphor that absorbs light from the LED chip 3 and is excited to emit fluorescence having a predetermined wavelength. For example, a YAG phosphor that absorbs blue light and emits yellow fluorescence is contained. Thereby, a part of blue light is absorbed by the phosphor, and yellow fluorescence is generated. The yellow fluorescence is mixed with blue light that passes through the phosphor resin layer 4, becomes white light, is diffused by the phosphor resin layer 4, and is emitted.

  A part of the light emitted from the phosphor resin layer 4 is also emitted in the direction of the protective resin 6, but the protective resin 6 has at least a region facing the LED chip 3 cut off vertically as described above. Therefore, it is not reflected vertically upward. Therefore, when the protective resin 6 is viewed from above, the protective resin 6 does not shine, and upward stray light due to reflection of the protective resin 6 can be suppressed.

  Next, a method for manufacturing the light emitting device will be described. First, four LED chips 3 are arranged on the submount substrate 12 at a predetermined interval and fixed. For fixing, AuSn solder or the like is used. A pair of electrodes (not shown) on the LED chip 3 are connected to the electrode pattern 13 by bonding wires 8 such as Au. A phosphor resin layer 4 is formed by preparing a resin such as a silicone resin in which a predetermined amount of the phosphor is dispersed, applying the resin on the LED chip 3 using a dispenser, and then curing the resin under predetermined conditions.

  The submount substrate 12 is fixed on the mounting substrate 1 on which the pair of power supply electrodes 2 are formed, and the electrode patterns 13 on both sides of the submount substrate 12 are connected to the power supply electrodes 12 by bonding wires 5 such as Au. Since the position where the bonding wire 5 is bonded is determined as alignment based on the shapes of the electrode pattern 13 and the feeding electrode 12, the bonding wire 5 is arranged at a certain position with a predetermined accuracy.

  Prepare a black resin mixed with a filler such as carbon, drop and apply around the bonding wire 5 using a dispenser, etc., and then cure it under specified conditions to protect the bonding resin 5 in a shape that wraps the bonding wire 5 Form. The position and shape of the protective resin 6 can be formed at a predetermined position and shape with a predetermined accuracy by moving a nozzle such as a dispenser as an alignment based on the shape of the electrode pattern 13 or the feeding electrode 12.

  Based on the position and shape of the protective resin 6, a region 6a for cutting the protective resin 6 is determined in advance. As described above, the region 6a is a surface region facing the LED chip 3 as viewed from the top as shown in FIG. 1, and the tangent to the surface of the protective resin 6 before scraping is 45 ° with respect to the main plane. And a range in which the bonding wire 5 is not exposed. The range of the region 6a is determined with reference to a predetermined position of the electrode pattern 13 or the feeding electrode 12.

Next, the region 6a of the protective resin 6 is irradiated with laser light to cut the protective resin 6 in the region 6a. The wavelength of the laser light is a wavelength that is absorbed by the black protective resin 6 and is set to an intensity that allows the protective resin 6 at the irradiation position to be cut almost vertically. Specifically, for example, laser light having a wavelength of 1064 nm, an intensity of 0.5 J / cm ² , and a beam diameter of 100 μm is used. By repeatedly irradiating the region 6a with this laser light while gradually shifting the irradiation position, the protective resin 6 in the region 6a can be cut almost vertically.

  Thus, in this embodiment, the protective resin 6 is cut in the region 6a to form a vertical surface, so that the light from the LED chip 3 is reflected in the upward (front) direction and becomes stray light. Can be prevented. Although stray light (reflected light) from the vicinity of the light source is not preferable because it complicates the optical design of the light-emitting device, this embodiment can prevent stray light and provide a light-emitting device with excellent light distribution characteristics.

  When determining the region 6a of the protective resin 6 to be cut, the LED chip 3 surface area on the LED chip 3 side of the protective resin 6 by actually emitting the LED chip 3 or emitting a monitor light source instead. It is also possible to set the region 6a so that the light is incident on the surface, the stray light is observed by observing the light from the upper surface, and the region where the stray light is generated is removed.

  In the present embodiment, since the black resin mixed with a filler such as carbon is used as the protective resin 6, it absorbs 1064 nm laser light, which is the fundamental wave of the YAG laser. Therefore, it is possible to easily perform the cutting process by irradiating the protective resin 6 without converting the wavelength of the laser light into a harmonic or the like.

  In addition, since the absorption rate of the laser beam of the protective resin 6 is high, the output of the laser beam can be kept low, so that even if the laser beam hits the bonding wire 5, it prevents the bonding wire 5 from being disconnected. Can do.

(Second Embodiment)
FIG. 4 is a cross-sectional view of the light emitting device of the second embodiment.

  In the first embodiment, the region 6a of the protective resin 6 is cut, but in the present embodiment, the region 6a is not cut, and fine irregularities are formed in the surface region 6a of the protective resin 6 as shown in FIG. To do. Thereby, the region 6a is roughened to reduce the light reflectance, and the region 6a suppresses the reflected light.

As a method of manufacturing the light emitting device having the configuration shown in FIG. 4, in the manufacturing method of the first embodiment, when the region 6 a of the protective resin 6 is irradiated with laser light, the intensity of the laser light is reduced. Although it is not completely removed, it is controlled so that irregularities are formed on the surface. Specifically, for example, the wavelength is controlled to 1064 nm, the intensity is about 0.5 J / cm ² , and the beam diameter is 100 μm. Other steps are the same as those in the first embodiment.

(Third embodiment)
FIG. 5 is a top view of the light emitting device of the third embodiment.

  In this embodiment, a plurality of holes 9 whose axial direction is perpendicular to the main plane of the substrate 1 are formed in the region 6a of the protective resin 6 as shown in FIG. The arrangement of the holes 9 is desirably random. In this way, by randomly providing a plurality of holes 9 whose inner wall surfaces are perpendicular to the main plane of the substrate in the region 6a of the protective resin 6, light reflected upward (front) is reduced, and stray light is reduced. Is possible.

Specifically, for example, the region 6a of the protective resin 6 is randomly irradiated with pulsed laser light almost vertically from above. At this time, the intensity of the laser beam is controlled so that a hole 6 having a predetermined depth is opened in the shape of the laser beam in the protective resin 6. Specifically, for example, the wavelength is controlled to 1064 nm, the intensity is about 0.5 J / cm ² , and the beam diameter is 100 μm. Other steps are the same as those in the first embodiment.

  In the present embodiment, the step of making the hole 9 in the region 6a of the protective resin 6 can be easily performed with a laser beam having a smaller diameter than when the entire region 6a is cut. Further, since the amount of the protective resin 6 to be removed by the laser beam is small, there is also an advantage that the amount of the protective resin 6 to be evaporated is small and the exhaust can be easily performed.

(Fourth embodiment)
In the fourth embodiment, when the protective resin 6 is cured, the outer side surface of the protective resin 6 is made vertical.

  The basic structure and manufacturing process of the light emitting device are the same as those in the first embodiment except for the protective resin 6. The protective resin 6 is formed as follows. As shown in FIG. 6A, after bonding the bonding wire 5, a release film 61 wound in a cylindrical shape is disposed around the bonding wire 5 as shown in FIG. 6B. As the release film 61, a film that is difficult to adhere to the protective resin 6 is used. As shown in FIG. 6C, the cylindrical release film 61 is used as a mold, and an uncured protective resin 6 is filled therein by dropping or the like, and then the protective resin 6 is cured under predetermined curing conditions. After curing, the release film 61 is removed. Thereby, a light emitting device including the cylindrical protective resin 6 can be manufactured.

  In the light emitting device of the present embodiment, since the protective resin 6 has a cylindrical shape, the peripheral side surface is perpendicular to the substrate main plane. Therefore, it is difficult to reflect light emitted from the phosphor resin layer 4 upward (front), and stray light can be suppressed.

  In this embodiment, since the protective resin 6 is not processed using laser light, the protective resin 6 does not have to have a property of absorbing laser light, and the range of selection of the material of the protective resin 6 is widened.

  In this embodiment, the cylindrical release film 61 is used as a mold to form the cylindrical protective resin 6. However, the material of the mold is not limited to the release film 61, and after the protective resin 6 is cured. Anything that can be removed is acceptable. For example, as shown in FIGS. 7A to 7C, it is possible to use a metal tube 62 having a mirror-finished inner surface and provided with two slits 63. After bonding the bonding wire 5 (FIG. 7A), the metal tube 62 is disposed around the bonding wire 5 (FIG. 7B), and the inside is filled with uncured protective resin 6, and predetermined curing conditions are set. Cured with. After curing, the metal tube 62 is divided into two members at the slit 63 and removed (FIG. 7C). Thereby, the cylindrical protective resin 6 can be formed.

  The protective resin 6 is not limited to a cylindrical shape, and may be a quadrangular prism or a polygonal column as long as the side surface is perpendicular to the main surface of the substrate.

  In the present embodiment, the entire side surface of the protective resin 6 is vertical. However, as described in the first embodiment, it is sufficient that at least the region 6a is vertical, and the portion excluding the region 6a is not left. Other shapes such as a shape raised by the surface tension of the cured protective resin 6 may be used.

(Fifth embodiment)
In the fifth embodiment, the surface of the protective resin 6 is processed into a rough surface without using laser light. Specifically, as shown in FIGS. 8A and 8B, after forming the bonding wire 5, the periphery of the bonding wire 5 is covered with an uncured protective resin 6 and the protective resin 6 is cured. Further, the release film 64 having a concavo-convex shape formed on the surface is almost pressed against the resin surface 6. The area where the release film 64 is pressed is the area 6a as in the second embodiment. The protective resin 6 is cured while the release film 64 is pressed, and the release film 64 is removed. Thereby, similarly to the second embodiment, it is possible to manufacture a light emitting device in which at least the surface region 6a of the protective resin 6 is processed into a rough surface. Other manufacturing steps are the same as those in the second embodiment. The stray light suppression effect of the light emitting device is also the same as in the second embodiment.

  In this embodiment, since the protective resin 6 is not processed using laser light, the protective resin 6 does not have to have a property of absorbing laser light, and the range of selection of the material of the protective resin 6 is widened.

  In addition, instead of pressing the release film 64 whose surface is processed into irregularities against the protective resin 6, the surface of the cured protective resin 6 can be projected with a sharpened needle or the like to form an irregular shape. It is. The region where the concavo-convex shape is formed by protruding with a needle or the like is at least the region 6a described above.

  In Examples 4 and 5, as the release film 64, an Opyran (registered trademark) manufactured by Mitsui Chemicals, Inc., processed into irregularities was used. Since this film has a heat resistant temperature of 200 ° C., it can withstand the curing temperature of the silicone resin of 150 ° C., and it is possible to transfer irregularities by embossing or the like.

  The light emitting device of the present invention is suitable as a light source that is desired to reduce stray light from the periphery of an LED chip, such as a headlamp light source.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Feed electrode, 3 ... LED chip, 4 ... Phosphor resin layer, 5 ... Bonding wire, 6 ... Protective resin, 6a ... Area | region, 8 ... Bonding wire, 9 ... Hole, 12 ... Submount substrate, 13 ... Electrode pattern, 61 ... Release film, 62 ... Metal tube, 63 ... Slit, 64 ... Release film with irregularities on the surface

Claims (5)

A light-emitting element and a bonding wire mounted on the substrate, and a protective resin for enclosing the bonding wire;
The protective resin is processed to suppress upward reflection of light from the light emitting element in at least a part of the region where the tangent of the surface facing the light emitting element is 45 degrees or more with respect to the main plane. A light emitting device characterized by being provided.   2. The light emitting device according to claim 1, wherein the processing is processing for removing the protective resin by cutting so as not to expose the bonding wire.   2. The light emitting device according to claim 1, wherein a plurality of holes are formed in the region of the protective resin.   The light emitting device according to claim 1, wherein a surface of the region of the protective resin is processed into a rough surface. A light-emitting element and a bonding wire mounted on the substrate, and a protective resin for enclosing the bonding wire;
The light emitting device according to claim 1, wherein at least a part of the surface of the protective resin facing the light emitting element is a surface perpendicular to the main plane of the substrate.

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