JP3974739B2 - Light emitting element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting element used in a photo interrupter that detects a light emitting element and a light receiving element facing each other and passing between them. More specifically, in order to be small and inexpensive to manufacture, a light emitting element chip is die-bonded on a flat island instead of a parabolic reflector, and light can be condensed on the front surface of the light emitting element chip. The present invention relates to a light emitting element in which a dome-shaped package is formed of a translucent mold resin so that the reliability of a wire bonding portion can be improved.
[0002]
[Prior art]
Conventionally, a photo interrupter is, for example, as shown in FIG. 4A, in which a light emitting element 1 and a light receiving element 2 are opposed to each other with a predetermined gap and fixed with a non-translucent resin package 3 or a case. It is configured such that the presence or absence of an object to be detected passing between the light emitting element 1 and the light receiving element 2 facing each other can be detected. The light-emitting element 1 used for these is shown in FIG. 4B as a plan view illustrating the state in which the light-emitting element chip is bonded to the lead frame, and the tip of the first lead 11 formed by the lead frame 10 is shown. A light emitting element chip (hereinafter referred to as an LED chip) 13 is bonded to the island 11a and is electrically connected to the second lead 12 via a wire 14 such as a gold wire.
[0003]
Then, as shown in the side view of FIG. 4C, the periphery thereof is formed by primary molding with a translucent resin 15 so that a dome-shaped convex portion 15a is formed on the front side. Yes. Only the front surface is exposed, and as described above, the light receiving element 2 and the non-translucent resin are molded to form the package 3.
[0004]
This type of light-emitting element 1 is formed of a lead frame because it needs to be manufactured at a very low cost, and needs to be assembled so as to irradiate light in a direction perpendicular to the direction in which the leads extend. The LED chip 13 is die-bonded directly to the island at the leading end of the lead, and is molded with a translucent resin 15 so that light can be collected as much as possible on the front side. A dome-shaped convex portion 15a is formed on the front side. ing.
[0005]
That is, if the structure is such that the LED chip is die-bonded to the tip of the lead (ie, die-bonded so that light is emitted in a direction parallel to the direction in which the lead extends) as in the conventional lamp-type light emitting device. Although it is possible to form a bowl-shaped recess at the tip, it is preferable to eliminate the bending of the lead in order to make it as inexpensive and compact as possible, and the frame surface of the lead frame is preferably a die bonding surface In a thin lead frame, it is difficult to form a recess when the lead frame is punched. In addition, it is not preferable to add a molding process to form a recess in the die bonding part because of increased cost. Therefore, as shown in FIGS. 4B to 4C, the LED chip 13 is directly die-bonded to the flat island 11a.
[0006]
[Problems to be solved by the invention]
As described above, in a light-emitting element that is small and inexpensive, an LED chip is directly die-bonded to a lead frame-like flat island part. Therefore, even when a dome-shaped convex part is formed on the front side when molding with a translucent resin, the light cannot be sufficiently collected, the input to the LED chip is increased, and the light emission characteristics Therefore, there is a problem in that it is necessary to use an excellent LED chip, resulting in a cost increase.
[0007]
That is, the LED chip emits light not only from the top surface but also from the side surface, but there is no light reflecting on the side surface, and the translucent resin has a dome-shaped convex portion. Even if formed, the position is about h = 0.1 to 0.2 mm from the surface of the LED chip 13 (the dimension H from the lead frame surface to the upper surface of the convex portion is about 0.5 to 0.6 mm), As shown by the arrow in FIG. 4C, the light emitted in the oblique direction is deflected sideways before entering the convex portion 15a, and the light that is sufficiently emitted cannot be used. In particular, in order to avoid noise due to ambient light, such as a photo interrupter, when the light emitting element and light receiving element receive and emit light only through a thin slit provided in front of it, it is effectively used unless the light is collected at the center. Can not do it.
[0008]
Furthermore, as the translucent resin covering the periphery of the LED chip described above, epoxy resin or the like is used and formed by transfer molding or the like, but from the viewpoint of optical characteristics such as sealing property and light transmission property. Epoxy resins are excellent. However, there is a problem in that the shrinkage force acting upon curing is strong, and in particular, the portion that is wire-bonded to the surface of the LED chip is easily scratched from the surface of the LED chip.
[0009]
The present invention has been made to solve such problems, and is an inexpensive light-emitting element that protects the wire bonding portion on the surface of the LED chip, and has a planar shape without a reflective recess formed on the island portion. Even in such a case, an object is to provide a light emitting element capable of efficiently condensing light traveling in an oblique direction close to the lateral direction onto a dome-shaped convex portion on the front side.
[0010]
[Means for Solving the Problems]
In the light emitting device according to the present invention, a flat island formed integrally with a first lead, a light emitting device chip bonded on the island, and one electrode of the light emitting device chip are connected via a wire. a second lead provided on said island coating, with light-transmitting covering the light-emitting element chip in a dome shape, and an electrically insulating covering layer with a resilient, by the electrically insulating covering layer the distal end of the first lead of the tip portion and the second lead being found Ri Do from a translucent molding resin to be coated as a dome-shaped convex portion is formed on the front side of the light emitting device chip, The light emitting element chip is die-bonded so as to be equidistant from two opposing sides or two adjacent sides of the island, and an outer peripheral portion of the bottom surface of the electrically insulating coating layer is formed on the two sides. Wherein the match so electrically insulating covering layer is formed.
[0011]
Here, the light-transmitting and elastic electrically insulating coating layer means an impurity concentration so as to be suitable for protecting a junction, such as a junction coat resin (hereinafter referred to as JCR). It means silicone, polyimide, etc. that have low elasticity. The light-transmitting property means a property that hardly attenuates light having a wavelength emitted by the light-emitting element, and does not necessarily mean that it is transparent to visible light.
[0012]
By adopting this structure, the LED chip is covered with a resilient electrically insulating coating layer. Therefore, even if the shrinkage force of the translucent resin covering the outer periphery acts, the wire bonding portion on the LED chip surface In this case, an electrically insulating coating layer (hereinafter also simply referred to as an insulating coating layer or a coating layer) serves as a buffer layer and is protected by its elasticity, and is not directly applied. As a result, the reliability of wire bonding of the light emitting element chip is greatly improved. In addition, this insulating coating layer is formed in a convex shape so as to form a dome shape, and the light emitted from the light emitting element chip is first refracted to the center side by the convex curved surface of the insulating coating layer, and the light transmission It is easy to condense in the dome of the functional resin. And the light which refracted further by the dome-shaped convex part of translucent resin, and came out in the diagonal direction near a side can also be used effectively. Furthermore, since the electrically insulating coating layer is formed so that the outer peripheral portion of the bottom surface of the electrically insulating coating layer coincides with the two opposite sides or the two adjacent sides, the insulating coating layer is a dome. The bottom surface of the light-emitting element chip is formed with a convex portion with the outer periphery of the island as the outer shape, and even when the material of the insulating coating layer is potted, the center axis of the light-emitting element chip and the insulating coating will be The center axis of the dome of the layer can be made coincident, and light is easily collected at the center.
[0013]
By forming the dome shape of the electrically insulating coating layer and the dome shape of the mold resin so as to be substantially coaxial, light can be further condensed in the central axis direction. Here, being coaxial means that the central axes of the dome shapes of the insulating coating layer and the translucent resin substantially coincide.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, the light emitting device of the present invention will be described with reference to the drawings. The light emitting device according to the present invention has a light emitting device chip (LED) on a flat island 11a formed integrally with the first lead 11, as shown in FIG. 1 (a). Chip) 13 is bonded. One electrode of the light-emitting element chip 13 is connected to the second via a wire 14 such as a gold wire, as shown in FIG. 1B, which is a plan view illustrating the LED chip 13 bonded in the lead frame state. It is connected to the lead 12.
[0016]
The LED chip 13 is covered with an insulating coating layer 16 that is potted and hardened from the surface thereof. This insulating covering layer 16 is formed in a dome shape having a convex front surface side by potting and curing a light-transmitting and electrically insulating resin such as JCR. ing. The tip portion of the first lead 11 and the tip portion of the second lead 12 covered with the insulating coating layer 16 are made of the translucent resin 15 so that the dome-shaped convex portion 15a is formed on the front side thereof. Molded.
[0017]
The leads 11 and 12 and the island 11a are formed, for example, by punching a plate-like body such as copper or iron. As shown in FIG. Are formed on a lead frame 10 in which a first lead 11 and a second lead 12 are connected. The island 11a has upper and lower sides (opposite sides) in FIG. 1B so that it substantially coincides with the outer periphery of the bottom surface as indicated by the alternate long and short dash line in FIG. 1B. 2 sides) is formed, and the LED chip 13 is bonded at positions that are equidistant from the two opposing sides. That is, since the width of the island 11a is formed so as to have a desired size, even if there is too much insulating coating material to be potted, it does not sag due to its surface tension, and its end is limited. The bottom shape is as follows.
[0018]
The reason why bonding is performed at a position that is substantially equidistant from the two opposing sides will be described. The insulating coating layer 16 that covers the surface of the LED chip 13 is formed in a dome shape by dripping (potting) a resin, which is usually called JCR, onto the surface of the LED chip 13 and curing it. That is, this type of JCR has a certain degree of viscosity, and even when potted due to its viscosity and surface tension, it does not become flat, but forms a dome shape and cures.
[0019]
However, as shown in FIG. 3A, when the island 11a is sufficiently larger than the diameter of the bottom surface of the insulating coating layer 16, the dome-shaped insulating coating layer 16 is formed around the dropped position. . Therefore, if it does not drop at the center of the LED chip 13, the central axis of the LED chip 13 and the central axis of the insulating coating layer 16 do not coincide with each other as shown in FIG. If the central axes do not coincide with each other, the wire bonding portion is exposed from the insulating coating layer 16 as shown in FIG. 3A, and sufficient protection against stress at the time of shrinkage of the epoxy resin described later can be sufficiently performed. This is not preferable because it cannot be performed and the light from the LED chip 13 cannot be condensed on the central axis so as to be sufficiently directed toward the inside of the dome-shaped convex portion 15a.
[0020]
Further, as shown in FIG. 3B, if the size of the island 11 a is substantially the same as or smaller than the bottom surface of the insulating coating layer 16, the end of the island 11 a is the insulating coating layer 16. A dome shape is formed so as to be the bottom surface of the material (due to viscosity and surface tension, the potting material does not sag from the island, and a dome shape with its end as a limit is formed). Therefore, the insulating coating layer 16 is always formed with reference to the end of the side of the island 11a. If the LED chip 13 is bonded to the center thereof, the central axis of the LED chip 13 and the dome shape of the insulating coating layer 16 are formed. It is easy to match the central axis of
[0021]
The LED chip 13 is bonded to the center of the island 11a as shown in FIG. 1B even if the four sides of the island 11a do not become the end of the insulating coating layer 16. If two sides become end portions and are equidistant from the two sides, the horizontal position can easily achieve the purpose because the position of the dispenser by the automatic machine can be easily adjusted. Further, as shown in FIG. 2, when the LED chip 13 is bonded in the vicinity of two adjacent sides, the bottom surface of the insulating coating layer 16 can be obtained by bonding so as to be equidistant from the two sides. Is formed in a circle in contact with the two sides, the LED chip 13 is located at the center of the circle, and the central axis of the LED chip 13 coincides with the central axis of the insulating coating layer 16.
[0022]
The LED chip 13 is formed by a pn junction structure or a double heterostructure of a semiconductor that emits light of a desired wavelength, such as a conventionally used AlGaAs compound semiconductor, InAlGaP compound semiconductor, GaP, or GaN compound semiconductor. Is done.
[0023]
The insulating coating layer 16 is for the purpose of protecting the wire bonding portion of the LED chip 13 and for taking out light emitted from the LED chip 13 as efficiently as possible, and has elasticity that can absorb external force, A material that easily forms a dome shape that refracts light inside is used. As described above, the JCR has viscosity and is formed into a dome shape by being potted.
[0024]
The translucent resin 15 is made of, for example, epoxy resin, and die bonding and wire bonding are performed on the lead frame 10 as shown in FIG. 1B, and the insulating coating layer 16 is formed on the surface side of the LED chip 13. In a state in which is formed, the mold is set in a mold, and a translucent resin is poured and cured to form a desired shape having the dome-shaped convex portion 15a. The translucent resin 15 only needs to be translucent with respect to the emission wavelength of the LED chip 13. For example, in the case of an infrared LED chip, the translucent resin 15 is formed of a black resin mixed with a dye that cuts visible light. It may be.
[0025]
According to the present invention, since the periphery of the LED chip is covered with the insulating coating layer having elasticity, the wire bonding portion of the LED chip is protected by the insulating coating layer, and the translucent resin that covers the outer periphery of the LED chip is protected. The influence of external force due to the rigidity of the wire can be excluded, and the reliability of wire bonding is greatly improved. In addition, the insulating coating layer is formed to have a dome shape around the LED chip, and the refractive index is between the refractive index of the LED chip and the refractive index of the translucent resin. Therefore, the light traveling in the oblique direction is also refracted to the center side as shown in FIG. Further, since the dome-shaped convex portion of the translucent resin covering the outer periphery is formed substantially coaxially, it can be refracted again on the central axis side and condensed on the central axis by double refraction. it can.
[0026]
As shown in FIG. 4A, the light-emitting element is opposed to the light-receiving element, and a light-transmitting element and a front surface of the light-receiving element are formed with a slit-like through-hole. A photo interrupter is formed by forming the package from the conductive resin, and the state of the inspection object can be detected by passing the inspection object so as to block the opposite portion. However, this type of light-emitting element is not limited to a photointerrupter, and can be applied to a light-emitting element that is inexpensive and needs to be focused on the central axis.
[0027]
【The invention's effect】
As described above, according to the present invention, even in an inexpensive light-emitting element that does not have a curved reflecting wall and bonds an LED chip on a flat island, the emitted light is efficiently collected in the central axis direction. A light emitting device that can be made to emit light and has a very high external quantum efficiency and high reliability without being damaged by the rigidity of an epoxy resin or the like covering the periphery of the LED chip surface. Can be obtained at low cost.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of a light emitting device according to the present invention.
FIG. 2 is an explanatory view showing a modification of the island part for bonding the LED chip of FIG. 1;
FIG. 3 is an explanatory diagram of a problem in the case where the central axes of the LED chip and the dome shape of the insulating coating layer in the structure of FIG. 1 when the insulating coating layer is provided do not match.
FIG. 4 is an explanatory diagram of a conventional photo interrupter and a light emitting device used therefor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light emitting element 11 1st lead | read | reed 11a Island 12 2nd lead | read | reed 13 LED chip 14 Wire 15 Translucent resin 15a Domed convex part 16 Electrically insulating coating layer

Claims (2)

A flat island formed integrally with the first lead; a light-emitting element chip bonded on the island; a second lead to which one electrode of the light-emitting element chip is connected via a wire; and the island provided in the upper, with light-transmitting covering the light-emitting element chip in a dome shape, and an electrically insulating covering layer with a resilient, the first lead to be coated by the electrically insulating covering layer tip tip parts and the second lead, Ri Do from a translucent molding resin to be coated as a dome-shaped convex portion is formed on the front side of the light emitting element chip, the light emitting device chip, wherein It is die-bonded so as to be equidistant from two opposing sides or two adjacent sides of the island, and the electrical outer covering portion of the bottom surface of the electrically insulating coating layer is aligned with the two sides. Emitting element edge covering layer is ing formed.   The light emitting device according to claim 1, wherein the dome shape of the electrically insulating coating layer and the dome shape of the mold resin are formed so as to be substantially coaxial.

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