Light-emitting device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a resin-molded LED light emitting device in which an LED chip is arranged on a circuit board.

【0002】

[Conventional technology]

As a dot matrix type LED display for displaying characters and figures, an LED display having a structure in which an LED chip is directly arranged on a circuit board and resin-molded has been proposed (for example, Japanese Patent Application Laid-Open No. 9-6259). This LED chip direct mounting type display can be made thinner and lighter, but since it has a structure with a wide viewing angle, light is easily dispersed throughout and it is not possible to increase the brightness. Therefore, in order to increase the brightness so that it can be used outdoors, a recess is formed in the circuit board, and the electrodes and the like formed in the recess are used as a reflective material to improve the directivity in the front direction. It has been proposed to increase its brightness (see, for example, Japanese Patent Application No. 11-17303).

【0003】

However, when the circuit board is thick, the dent can be formed as described above, but as the thickness of the circuit board becomes thinner, it becomes difficult to form the dent as described above. Further, even if the circuit board has a sufficient thickness to form a dent, forming a dent in the circuit board or forming a circuit pattern in the dent can complicate the manufacturing process and the work process. It has the problem of inviting an increase.

【0004】

[Problems to be Solved by the Invention]

An object of the present invention is to provide an LED light emitting device with improved directivity and increased brightness. Another object is to simplify the manufacturing process of the LED light emitting device.

【0005】

[Means for solving problems]

As described in claim 1, the LED light emitting device of the present invention is an LED light emitting device in which an LED chip is arranged on the surface of a circuit board having a flat surface and the LED chip is molded with a light transmissive resin. It is characterized in that a thick reflective film is formed on the surface of the substrate so as to surround the chip by coming into contact with the light-transmitting resin.

【0006】

Further, as described in claim 2, the LED light emitting device of the present invention is characterized in that the thickness of the reflective coating is made thicker than 1/3 of the height of the LED chip.

【0007】

Further, as described in claim 3, the LED light emitting device of the present invention is characterized in that the circuit board has a plate thickness comparable to the height of the LED chip.

【0008】

Further, as described in claim 4, the LED light emitting device of the present invention is characterized in that the circuit board has a plate thickness thinner than the height of the LED chip.

【0009】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, examples of the present invention will be described by taking a dot matrix type LED light emitting device as an example and referring to the drawings. As shown in FIG. 3, the LED light emitting device 1 has 16 × 16 display dots 3 having a diameter of 2 to 3 mm and a pitch of 3 to 4 mm on the surface of a circuit board 2 having a side length of about several cm. It is arranged in a matrix of.

【0010】

The circuit board 2 is composed of a printed circuit board made of glass epoxy or the like, and a circuit pattern made of copper foil or the like and a resist coating (neither shown) are formed on the surface thereof. Since the thickness of the circuit pattern and the resist film covering it is extremely thin, the surface of the circuit board 2 is flat. The thickness of the circuit board 2 is about 0.3 mm, which is equivalent to the height of the LED chip described later. Therefore, it is difficult to form a recess having a depth in which the LED chip is embedded in the circuit board 2.

【0011】

The display dots 3 are an LED chip 4 as a light emitting element fixed on the circuit board 2 as shown in FIG. 1, and a reflective coating film 5 arranged on the circuit board 2 so as to surround the chip 4 in an annular shape. And a light-transmitting resin 6 that covers the LED chip 4 are provided.

【0012】

The LED chip 4 is a rectangular parallelepiped with a side length of about 0.3 mm, is fixed to the surface of the circuit board 2 with a conductive adhesive such as silver paste or solder, and is circuited using a wire bond wire 7 made of gold or the like. Wiring is applied to the pattern on the board 2. The LED chip 4 as a light emitting element can be composed of one or more, and can also be composed of a plurality of chips having different colors if necessary.

【0013】

The reflective film 5 is formed of a thick film using a film having good light reflectivity, for example, white resin, and is about 45 degrees in order to efficiently reflect the light of the LED chip 4 in the normal direction of the circuit board 2. It has an angled reflective surface. The height of the reflective coating 5 is set to be about the same as the height dimension of the LED chip 4. If the height dimension of the reflective film 5 is too low, the light reflection efficiency of the LED chip 4 deteriorates, and conversely, if the height dimension is too high, the process for forming the light transmissive resin 6 may be hindered. , It becomes difficult to place it in the limited area between the LED chips 4. Therefore, it is preferable that the height dimension of the reflective coating 5 is within the range of 1/3 to 2 times (100 μm to 600 μm) of the height dimension of the LED chip 4, and the wire bond wire is connected from the upper end position of the LED chip 4. It is most preferable to set it so that it falls within the range of the upper end position of 7.

【0014】

The light-transmitting resin 6 is composed of an epoxy-based resin mixed with a light diffusing agent of silica fine particles, and is heat-cured after being arranged in a region surrounded by the reflective coating 5.

【0015】

Next, the manufacturing procedure of the LED light emitting device 1 will be described with reference to FIG. First, as shown in FIG. 6A, a circuit board 2 on which a circuit pattern and a resist are formed in advance is prepared. Next, as shown in FIG. 6B, the LED chip 4 is chip-bonded and fixed on the circuit board 2, and then wiring is performed by the wire bond wire 7.

【0016】

Next, as shown in FIG. 6C, a reflective coating 5 is formed on the circuit board 2. For the reflective film 5, for example, a white epoxy resin having an increased viscosity is applied onto the circuit board 2 in a thick film state by a method such as screen printing. Immediately after application, a resin having a rectangular cross section changes its cross-sectional shape depending on its own fluidity, and changes to a triangular or arc-shaped cross section. In the arc shape, a sufficient reflection angle and reflection area may not be selected, or the base of the reflection coating 5 may be too wide. To improve these, the circuit board 2 is held upside down while holding the resin. Perform thermosetting. By inverting and holding the circuit board 2, the cross-sectional shape of the resin is formed into a substantially triangular shape, and it is possible to improve the reflection characteristics and prevent the spread of its own base.

【0017】

Next, the light transmissive resin 6 is formed in the same procedure as the formation of the reflective film 5. That is, a transparent epoxy resin having an increased viscosity is applied to the inside of the reflective film 5 on the circuit board 2 in a thick film state by a method such as screen printing. Immediately after application, a resin having a rectangular cross section changes its cross-sectional shape into an arc shape due to its own fluidity. In that state, or in a state where the circuit board 2 is turned upside down, the resin is thermally cured to form a convex lens-shaped resin 6.

【0018】

Through such a process, the LED light emitting device 1 as shown in FIGS. 1 and 3 can be manufactured. In the LED light emitting device 1 configured in this way, when the LED chip 4 is turned on, a part of the light that comes out of the chip 4 and travels in the light transmitting resin 6 reaches the reflective film 5, and the reflective surface inside the reflective film 5 Is reflected in the normal direction of the circuit board 2. Therefore, it is possible to increase the directivity of the light emitted from the LED chip 4 and at the same time increase the brightness in the front direction of the LED light emitting device 1. Here, it is conceivable to use a material having a poor affinity with the resin 6 as the reflective film 5, for example, a resin having a high oil repellency such as silicon, but in this case, the resin 6 is repelled by the reflective film 5 and both are repelled. There is a risk that it will be in a non-contact state and the reflective function of the reflective film 5 will not be exhibited. However, in this embodiment, since the reflective film 5 and the light transmissive resin 6 are made of materials having good affinity with each other, such as by using the same type of resin, substantially the entire region of the reflective surface inside the reflective film 5 is formed. The light-transmitting resin 6 can be kept in contact with the resin 6, and the light passing through the resin 6 can be effectively reflected by the coating film 5.

【0019】

In the above embodiment, the circuit board 2 used has a thickness similar to the height dimension of the LED chip, but the present invention is thicker than the height dimension of the LED chip 4 as shown in FIG. This is useful when a thin circuit board 20 is used. For example, it is useful when a film-like flexible circuit board 20 having a circuit pattern and a thin film resist covering the circuit pattern and a thickness of about 100 μm is used as the circuit board. The present invention is also useful when a circuit board having a thickness larger than the height dimension of the LED chip 4 is used as the circuit board 2.

【0020】

Further, the above embodiment shows an example in which only one surface that functions as a reflective surface of the reflective coating 5 is in contact with the outer peripheral portion of the resin 6 and the other surface is arranged outside the resin 6, as shown in FIG. In addition, the reflective coating 5 can be arranged so as to be completely embedded in the outer peripheral portion of the resin 6.

【0021】

The present invention is not limited to the dot matrix type LED light emitting device, and other LED light emitting devices such as a linear light source and a planar light source having an LED chip and a light transmitting resin for molding the LED chip on a circuit board. It can also be applied to.

【0022】

[Effect of the invention]

As described above, according to the present invention, it is possible to provide a thin LED light emitting device having improved directivity and increased brightness and having good assembly workability.

[Simple explanation of drawings]

[Figure 1]

It is sectional drawing of the main part of one Example of this invention.

[Figure 2]

It is sectional drawing which shows the manufacturing process of one Example of this invention.

[Fig. 3]

It is a top view of one Example of this invention.

[Fig. 4]

It is sectional drawing of the main part which shows the other Example of this invention.

[Fig. 5]

It is sectional drawing of the main part which shows the other Example of this invention.

[Explanation of symbols]

1 LED light emitting device 2 Circuit board 3 display dots 4 LED chip 5 Reflective coating 6 Light-transmitting resin