JP3497971B2 - Optical coupling device and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupling device (for example, a photo coupler) in which a light emitting element and a light receiving element are opposed to each other and are optically coupled.

[0002]

2. Description of the Related Art In an optical coupling device which uses a light emitting element and a light receiving element to electrically insulate an input side and an output side and transmits a signal by light, a lead frame is used. A light emitting element and a light receiving element are mounted on the optical path, an optical path is formed by a translucent resin, and they are covered by a light shielding resin.

FIG. 9 is a diagram showing the internal structure of the above-described optical coupling device which has been conventionally used. In the figure, 21
Is a light emitting element, and is a metal (Cu, Fe, 42Alloy)
Is mounted on a light emitting side lead frame 22 made of, for example, a conductive paste (Ag paste or the like), and is wire-bonded to a connection lead frame (not shown) by a gold wire 23 by ultrasonic thermocompression bonding. Reference numeral 24 denotes a light receiving element, which is mounted on the light receiving side lead frame 25 with a conductive paste or the like, and is wire-bonded to a connection lead frame (not shown) with a gold wire 26, like the light emitting element 21. The light emitting element 21 and the light receiving element 24 are arranged so as to face each other, and are transfer-molded with a translucent resin such as a white epoxy resin that transmits infrared light to form a translucent molded body 27. Further, in order to shield ambient light, it is transfer-molded with a light-blocking resin such as a black epoxy resin to form a light-blocking mold body 28.

The electric signal sent through the light emitting side lead frame 22 is converted into an optical signal by the light emitting element 21 and passes through the light transmitting mold body 27 to receive the light receiving element 2.
4 is propagated. The light receiving element 24 converts the optical signal into an electric signal again and propagates it to the light receiving side lead frame 25.

By the way, one of the important characteristics of the optical coupling device is the so-called primary-secondary electrical isolation between the light emitting element and the light receiving element. The characteristic of this electrical isolation is usually expressed as withstand voltage. Factors that determine the withstand voltage include the insulation performance of the substance interposed between the light emitting element and the light receiving element and the distance between the elements.

Generally, the substance interposed between both elements is
Highly insulating resin such as epoxy resin or silicone resin is used, and its insulating performance is very high. Further, in the case of the optical coupling device shown in FIG. 9, the distance between both elements is the lead frame 2
It depends on the bending condition of 2, 25, the height of both elements 21, 24 and the loop height of the gold wires 23, 26. In this case, in order to have high insulation characteristics, both elements 21, 2
The thickness of the insulating resin interposed between the four, that is, the insulating distance must be a certain distance or more. For example, the overseas safety standard (reinforced insulation of IEC950) requires a width of 0.4 mm or more. However, if this distance is set too long, the current transfer ratio (hereinafter, referred to as “CTR (Current Transfer Ratio)”) between the light emitting element 21 and the light receiving element 24 is reduced.

Therefore, in order to maintain a high insulation characteristic and obtain a high CTR, it is necessary to adjust the distance between both elements so as to be as close as possible to the insulation distance that complies with the above-mentioned overseas safety standards. For that purpose, it is important to make adjustments to increase the bending accuracy of the lead frame and the loop height accuracy of the gold wire. However, these adjustments are limited in accuracy.

In view of the above, the present invention provides an optical coupling device capable of obtaining a high insulation characteristic between input and output and a high CTR without adjusting the accuracy of bending the lead frame or loop height of the gold wire. For the purpose of provision.

[0009]

A means for solving the problems according to the present invention is an optical coupling device in which a light emitting element mounted on a light emitting side lead frame and a light receiving element mounted on a light receiving side lead frame are provided so as to face each other. A part of the light emitting surface of the light emitting element is connected to the outer surface of the light emitting side lead frame opposite to the inner surface facing the light receiving side lead frame, and is opposite to the inner surface of the light receiving side lead frame facing the light emitting side lead frame. A part of the light receiving surface of the light receiving element is connected to the outer surface on the side. A light-transmitting mold body formed by molding each lead frame so that the outer surface of each lead frame is exposed, and a light-shielding mold body obtained by molding the light-transmitting mold body and each element are provided.

According to this structure, the light emitting surface of the light emitting element is directly connected to the outer surface of the lead frame, and the light receiving surface of the light receiving element is directly connected to the outer surface of the lead frame. The gold wire that was connected to is no longer necessary. Therefore, the distance between the light emitting element and the light receiving element is
Since it depends on the distance between the inner surfaces of the lead frames, the distance between the two elements can be defined with high accuracy by accurately positioning the lead frame.

Therefore, if each lead frame is integrally molded to form a translucent mold so that the outer surface of each lead frame is exposed, that is, except for the portion where the light emitting / receiving element is mounted, both leads are formed. The distance between the frames can be defined by this mold body. for that reason,
The distance between the light emitting element and the light receiving element can be defined with higher accuracy without the need to adjust the bending of the lead frame as in the conventional case.

Further, a protective mold body may be formed around the light emitting element, and a light collecting body may be arranged on the optical path from the light emitting element to the light receiving element. With the light collector,
The light transfer rate from the light emitting element to the light receiving element is improved.

According to the method of manufacturing the optical coupling device of the present invention, the light emitting side lead frame on which the light emitting element is mounted and the light receiving side lead frame on which the light receiving element is mounted are respectively bent and opposed to each other so that the outer surface of each lead frame is exposed. The lead frame is molded to form a translucent molded body, and the light emitting surface and part of the light receiving surface are connected to the exposed parts of each lead frame so that the light emitting surface of the light emitting element faces the light receiving surface of the light receiving element. Then, the light-transmitting mold body and each element are molded to form a light-shielding mold body.

In another method of manufacturing the optical coupling device, a protective potting body is formed on the inner surface of the light emitting side lead frame,
The light emitting side lead frame and the light receiving side lead frame are bent to face each other, and each lead frame is molded so that the outer surface of each lead frame is exposed to form a translucent molded body. The light emitting surface of the light emitting element and the light receiving element The light-emitting surface and a part of the light-receiving surface are connected to the exposed portion of each lead frame so that the light-receiving surface of the light-emitting element faces each other, and a protective potting body is formed around the light-emitting element. Is used to form a light-blocking mold.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a diagram showing an internal structure of an optical coupling device according to a first embodiment of the present invention, and FIG. 2 shows a connection structure between a light emitting / receiving element and a lead frame. It is a figure. With reference to FIGS. 1 and 2, in this optical coupling device, a light emitting element 1 (for example, a light emitting diode) and a light receiving element 2 (for example, a phototransistor) are arranged to face each other and are optically coupled.

The light emitting element 1 is mounted on the outer surface 3b of the pair of light emitting side lead frames 3 opposite to the light receiving side lead frame 4 so as to straddle the pair of light emitting side lead frames 3. ing. The light emitting element 1 has its light emitting surface 1
An electrode is formed on a part of a, and a part of the light emitting surface 1a is electrically connected to the outer surface 3b of the light emitting side lead frame 3 by a bump of solder, silver or the like.

The light receiving element 2, like the light emitting element 1,
It is mounted on the outer surfaces 4b of the pair of light-receiving side lead frames 4 so as to straddle them. The light receiving element 2 has a light receiving surface 2
An electrode is formed on a part of a, and a part of the light receiving surface 2a thereof is electrically connected to the outer surface 4b of the light receiving side lead frame 4 by a bump.

The outer surface 3 of each lead frame 3, 4
Each of the lead frames 3, 4b and 4b is exposed, that is, except for the portions where the light emitting and receiving elements 1 and 2 are mounted.
A transparent mold body 5 is formed by injection molding 4 of the transparent resin with a transparent resin. A light-shielding mold body 6 is formed by injection-molding the light-transmitting mold body 5 and each of the elements 1 and 2 with a light-shielding resin.

As a result, the light emitting area of the light emitting surface 1a of the light emitting element 1 faces the inner surface 3a side through the gap of the light emitting side lead frame 3, and similarly, the light receiving area of the light receiving surface 2a of the light receiving element 2 is The light receiving surface 1a and the light receiving surface 2a of the light receiving and emitting elements 1 and 2 are opposed to each other, facing the inner surface 4a side through the gap of the light receiving side lead frame 4.

The electric signal sent through the light emitting side lead frame 3 is converted into an optical signal by the light emitting element 1, and the optical signal is emitted from the light emitting area of the light emitting surface 1a which is not connected to the light emitting side lead frame 3. Is irradiated. Then, the light passes through the light-transmissive mold body 5, is received by a light-receiving region of the light-receiving surface 2 a that is not connected to the light-receiving side lead frame 4, and is propagated to the light-receiving element 2. The light receiving element 2 converts the optical signal into an electric signal again and propagates it to the light receiving side lead frame 4.

As described in the section of "Prior Art and Problems to be Solved by the Invention", in order to obtain high insulation characteristics and high CTR between the light emitting element and the light receiving element in the conventional optical coupling device, insulation is required. It is necessary to adjust the accuracy of the distance, specifically, the accuracy of bending the lead frame and the accuracy of the loop height of the gold wire.

In the optical coupling device of this embodiment, the light emitting element 1
The light emitting surface 1a is directly connected to the outer surface 3b of the light emitting side lead frame 3, and the light receiving surface 2a of the light receiving element 2 is directly connected to the outer surface 4b of the light receiving side lead frame 4. The gold wire connected to the lead frame is no longer necessary. Therefore, the precision adjustment of the insulation distance is facilitated by directly connecting the element to the lead frame, which is easy to obtain precision, instead of the gold wire, which is difficult to adjust the insulation distance with precision. Therefore, the distance between the light emitting element 1 and the light receiving element 2 can be defined with higher accuracy.

The outer surface 3 of each lead frame 3, 4
If the lead frames 3 and 4 are integrally molded to form the translucent mold body 5 so that the exposed portions b and 4b are exposed, the distance between the lead frames 3 and 4 can be defined by the mold body 5. . Therefore, it is not necessary to adjust the bending accuracy of the lead frame as in the prior art, and even if the bending accuracy is poor, the distance between the light emitting element 1 and the light receiving element 2 can be adjusted by positioning the lead frames 3 and 4.
The distance between the light emitting element 1 and the light receiving element 2 can be defined with higher accuracy. Therefore, with the above configuration, the shortest insulation distance with respect to the distance required for insulation can be secured, and high C
TR can be obtained.

Next, a method of manufacturing this optical coupling device will be described. First, the light emitting side lead frame 3 on which the light emitting element 1 is mounted and the light receiving side lead frame 4 on which the light receiving element 2 is mounted are respectively bent to face each other. Then, each lead frame 3 is formed by the upper die 7 and the lower die 8 of the mold as shown in FIG.
Fix so that 4 is sandwiched. The mold cavity 9 is
The outer surfaces 3b and 4b of the lead frames 3 and 4 are arranged so that the outer surfaces 3b and 4b of the lead frames 3 and 4 are partially exposed.
Is in contact with a part of the base and the outer bases 3c and 4c to enclose the lead frames 3 and 4. At this time, the mold contacts a part of the outer surfaces 3b, 4b of the lead frames 3, 4 so that the inner surfaces 3a, 4a of the lead frames 3, 4 face each other in parallel.

Then, the respective lead frames 3 and 4 are integrally injection-molded with a transparent resin or the like to form a transparent molded body 5. In this case, as the translucent resin, a thermoplastic polycarbonate resin that transmits infrared light, a white PPS (polyphenylene sulfide) resin that transmits infrared light, or the like is used.

Next, bumps are formed on the exposed portions of the lead frames 3 and 4 so that the light emitting surface 1a of the light emitting element 1 and the light receiving surface 2a of the light receiving element 2 face each other. Installed via and electrically connected to each other. Next, the translucent mold body 5 and the respective elements 1 and 2 are integrally injection-molded with a black thermoplastic resin to form the light-shielding mold body 6. And
External lead plating is performed, and external lead molding such as cutting and bending of the lead frames 3 and 4 protruding to the outside is performed to obtain a product.

By the way, as a mode for connecting the light emitting element 1 and the light receiving element 2 to the lead frames 3 and 4, for example, as shown in FIG. 4, electrodes are formed on the side surfaces of the elements 1 and 2. The lead frames 3 and 4 may be connected to part of the side surfaces of the elements 1 and 2 by bumps or by bonding with a heat-resistant conductive adhesive.

By doing so, the light emitting / receiving surfaces 1a, 2a of the respective elements 1, 2 and the respective lead frames 3, 4 are flush with each other, and therefore the light emitting element 1 is further provided by the thickness of the respective lead frames 3, 4. The distance between the light receiving element 2 and the light receiving element 2 can be reduced to a distance required for insulation. Therefore, the entire thickness of the optical coupling device can be made thinner than that of the structure of FIG. 1, and the optical coupling device can be downsized. In addition, the light emitting surface 1a and the light receiving surface 2a
Since a part of is not covered by the lead frames 3 and 4, the irradiation and light receiving areas of the light receiving and emitting surfaces 1a and 2a are expanded, and the amount of light transmitted is increased, so that the transmission efficiency can be further improved.

As a method of defining the distance between the lead frames 3 and 4, an insulating spacer that contacts the inner surfaces 3a and 4a of the lead frames 3 and 4 may be used. Alternatively, as shown in FIG. 5, a translucent resin body or glass body 11 having a predetermined thickness may be interposed between the lead frames 3 and 4. The glass body 11 is composed of a main body 11a formed in a substantially rectangular parallelepiped and a protrusion 11b formed at the center of the upper and lower surfaces of the main body 11a.

The thickness of the main body portion 11a is preliminarily produced so as to substantially match the distance required for insulation. Further, the thickness of the central portion of the glass body 11 including the protruding portion 11b is preliminarily produced so as to be the distance between the light emitting / receiving elements 1 and 2. That is, by arranging the lead frames 3 and 4 along the upper and lower surfaces of the body 11a of the glass body 11 and connecting the light emitting and receiving elements 1 and 2 to the lead frames 3 and 4, respectively, The frames 3 and 4 and the elements 1 and 2 can be smoothly positioned, and the distance between the light emitting element 1 and the light receiving element 2 can be defined with higher accuracy. Therefore, the shortest insulation distance with respect to the distance required for insulation can be secured, and high CTR can be obtained.

<Second Embodiment> FIG. 6 is a view showing the arrangement of an optical coupling device according to the second embodiment. A feature of the second embodiment is that a protective mold body 12 for protecting the light emitting element 1 is formed around the light emitting element 1. That is, the inner surface 3a of the light emitting side lead frame 3 corresponding to the region to which the light emitting element 1 is connected and the protective potting bodies 12a and 12b made of a translucent silicone resin or the like for molding the periphery of the light emitting element 1 are formed. . The protective potting bodies 12a and 12b prevent the light emitting element 1 from being impacted by an injection mold performed thereafter.
It is possible to prevent damage, connection failure, and the like. Other configurations are similar to those of the first embodiment.

Next, a method of manufacturing the optical coupling device according to the second embodiment will be described. First, a transparent silicone resin is dropped on the inner surface 3a of the light emitting side lead frame 3 and then thermally cured to form a protective potting body 12a. Next, the light emitting side lead frame 3 and the light receiving side lead frame 4 are bent to face each other. For convenience of manufacturing, after bending the light emitting side lead frame 3, a transparent silicone resin is dropped on the inner surface 3a to protect the potting body 12a.
May be formed. Next, the lead frames 3 and 4 are integrally injection-molded so that the outer surfaces 3b and 4b of the lead frames 3 and 4 are partially exposed to form the translucent mold body 5.

Next, the light emitting surface 1a of the light emitting element 1 and the light receiving surface 2a of the light receiving element 2 face the exposed portions of the lead frames 3 and 4 respectively so that the light emitting surface 1a and the light receiving surface 2a are partially exposed. Make electrical connections with bumps. After attaching the transparent silicone resin to the light emitting element 1, it is thermally cured to form the protective potting body 12b. Then, the light-transmitting mold body 5 and the respective elements 1 and 2 are integrally injection-molded to form the light-shielding mold body 6. After that, exterior plating is performed and external lead molding is performed to obtain a product.

The protective potting body 12a,
12b may be formed on the inner surface 4a of the light-receiving side lead frame 4 and around the light-receiving element 2 for the purpose of protecting the light-receiving element 2.

<Third Embodiment> FIG. 7 is a view showing the arrangement of an optical coupling device according to the third embodiment. The feature of the third embodiment is that an insulative lens-shaped light condensing body 13 such as transparent glass for condensing light from the light emitting element 1 is arranged on the optical path from the light emitting element 1 to the light receiving element 2. There is a point. According to the figure, the light collector 13 has a substantially hemispherical shape, and the inner surface 3a of the light emitting side lead frame 3 on which the light emitting element 1 is mounted is shown.
It is provided in.

The light collector 13 collects the light from the light emitting element 1 and reaches the light receiving element 2 without unnecessarily diffusing the light, so that the light transmission efficiency is improved and a high CTR can be obtained. Other configurations are similar to those of the first embodiment.

The present invention is not limited to the above embodiment, and many modifications and changes can be added to the above embodiment within the scope of the present invention. For example, the condenser 13 described in the third embodiment may be arranged on the light receiving element 2 side as shown in FIG.

[0039]

As described above, according to the present invention, the light emitting surface of the light emitting element is directly connected to the outer surface of the lead frame,
Since the light-receiving surface of the light-receiving element is directly connected to the outer surface of the lead frame, the gold wire that conventionally connected the element and the lead frame is no longer required, and accurate positioning of the lead frame ensures high accuracy. The distance between the light emitting element and the light receiving element can be specified. Further, except for the portion where the light emitting / receiving element is mounted, if each lead frame is integrally molded to form a translucent molded body, the distance between both lead frames can be defined by this molded body. The distance between the light emitting element and the light receiving element can be defined with higher accuracy without the need to adjust the bending of the lead frame as in the conventional case. Therefore, it is possible to provide the optical coupling device that can secure the shortest insulation distance with respect to the distance required for insulation and can obtain high CTR.

Further, by forming a protective mold body around the light emitting element, it is possible to prevent the element from being damaged, the connection being defective, and the like from being impacted by another mold.

Furthermore, if a light collecting body is arranged on the optical path from the light emitting element to the light receiving element, the light collecting body allows
The light transfer rate from the light emitting element to the light receiving element can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an internal configuration of an optical coupling device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a connection configuration between a light emitting / receiving element and a lead frame.

FIG. 3 is a diagram showing a mold when forming a translucent mold body.

FIG. 4 is a view showing a modified example of the connection configuration of the light emitting / receiving element and the lead frame.

FIG. 5 is a diagram showing another modification of the connection configuration of the light emitting / receiving element and the lead frame.

FIG. 6 is a diagram showing an internal configuration of an optical coupling device according to a second embodiment.

FIG. 7 is a diagram showing an internal configuration of an optical coupling device according to a third embodiment.

FIG. 8 is a diagram showing a modified example of the internal configuration of the optical coupling device.

FIG. 9 is a diagram showing an internal configuration of a conventional optical coupling device.

[Explanation of symbols]

1 Light emitting element 1a Light emitting surface 2 Light receiving element 2a Light receiving surface 3 Light emitting side lead frame 4 Light receiving side lead frame 5 Translucent mold body 6 Light-blocking mold 12 Protective mold 13 Light collector

Claims (6)

(57) [Claims] 1. A pair of light emitting side lead frames and a pair of light receiving side lead frames are arranged to face each other, electrodes are formed on a light emitting surface of a light emitting element, and both light emitting side lead frames face the light receiving side lead frames. On the outer surface opposite to the inner surface, the light emitting element is mounted so as to straddle, a part of the light emitting surface is electrically connected, and electrodes are formed on the light receiving surface of the light receiving element. The optical coupling device, wherein the light receiving element is mounted so as to straddle an outer surface of the opposite side of the inner surface facing the light emitting side lead frame, and a part of the light receiving surface is electrically connected. 2. A light-transmitting mold body obtained by molding each lead frame so that the outer surface of each lead frame is exposed, and a light-shielding mold body obtained by molding the light-transmitting mold body and each element. The optical coupling device according to claim 1, further comprising: 3. The optical coupling device according to claim 1, wherein a protective mold body is formed around the light emitting element. 4. A condensing body is arranged on an optical path from the light emitting element to the light receiving element.
The optical coupling device according to any one of 1. 5. A pair of light emitting side lead frames on which light emitting elements having electrodes formed on part of their light emitting surfaces are mounted, and a pair of light receiving side lead frames on which light receiving elements having electrodes formed on part of their light receiving surfaces are mounted. Are bent to face each other, and each lead frame is molded so that the outer surface of each lead frame is exposed to form a translucent molded body, and the light emitting surface of the light emitting element and the light receiving surface of the light receiving element face each other. As described above, a part of the light emitting surface and a part of the light receiving surface are mounted on the exposed portion of the outer surface of each lead frame and electrically connected, and the light-transmitting mold body and each element are molded to form a light-shielding mold. A method for manufacturing an optical coupling device, which comprises forming a body. 6. A light emitting element and a light receiving element are arranged to face each other.
Which are optically coupled, and a pair of light emitting side lead frame and a pair of light receiving side lead frame is disposed opposite the front
An electrode is formed on a side surface of the light emitting element, the light emitting side lead frame is connected to a part of the side surface of the light emitting element, an electrode is formed on a side surface of the light receiving element, and the electrode is formed on a part of the side surface of the light receiving element. An optical coupling device, wherein a light receiving side lead frame is connected, and a light emitting / receiving surface of each element and each lead frame are flush with each other.