JPH07226533A - Photocoupler and its manufacture - Google Patents

Abstract

PURPOSE:To provide a means for improving dielectric strength which can be easily formed without requiring particular material and setting delicate manufacturing condition or the like. CONSTITUTION:A light emitting element 1 is mounted on an input side lead frame 3a, a light receiving element 2 is mounted on an output side lead frame 3b, and bonding wires 4 connect the part between pads of each of the elements and lead frames corresponding with each of the pads. A resin film 5 is formed by using transparent resin at the tip part of the output side lead frame 3b so as to cover the end portions of the light receiving element 2 and the lead frame. The space between the light emitting element 1 and the light receiving element 2 is filled with transparent resin 6, and an optical path is formed. The whole body is packaged with mold resin 7.

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 such as a photo coupler and a solid state relay, and more particularly to a primary
The present invention relates to an optical coupling element having an improved breakdown voltage between the secondary and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view of a conventional optical coupling element of this kind. As shown in the figure, the light emitting element 1 is mounted on the input side lead frame 3a and wired by the bonding wire 4, and similarly, the light receiving element 2 is mounted on the output side lead frame 3b and the bonding wire 4 is mounted.
Is wired by. The light emitting element 1 and the light receiving element 2 are arranged to face each other, and are optically coupled by a translucent resin 6 filled between the elements, and the entire mold is made of a non-translucent resin such as a black epoxy resin. It is packaged with resin 7.

The optical coupling element is being downsized in response to the recent tendency of various parts to become lighter, thinner, shorter, and smaller, but one of the problems here is the problem of lowering the withstand voltage. The dielectric breakdown of the optical coupling element occurs as follows. When the potential difference of the voltage applied between the input side lead frame 3a and the output side lead frame 3b becomes as large as several kV, the discharge path A is formed at the interface of the translucent resin at the shortest distance between the two lead frames. Are formed, where dielectric breakdown occurs.

In order to prevent this dielectric breakdown, it is known that it is effective to lengthen the creepage distance where the discharge path is formed. Next, a few examples of the optical coupling device provided with this kind of dielectric strength improving means will be described. In addition,
In the following drawings, the same parts as those of FIG. 5 are designated by the same reference numerals, and the duplicated description will be omitted. FIG. 6 is a cross-sectional view of an optical coupling element proposed in JP-A-61-255076, which shows an output side lead frame 3
The side surface of the tip portion of b is coated with a highly insulating insulator 8 such as ceramic, whereby the discharge path can be lengthened from A to B.

Further, in Japanese Patent Laid-Open No. 57-143889, as shown in FIG. 7, a resin thin film 9 such as a polyimide film is provided on the back surface of the input side lead frame 3a and the output side lead frame 3b with a translucent resin. It is described that it is adhered by 10 and the discharge distance is increased from A to B. FIG. 8 is a cross-sectional view of the one proposed in Japanese Examined Patent Publication No. 59-15501 (Japanese Patent Laid-Open No. 57-66679), in which an insulating film is provided between the light emitting element 1 and the light receiving element 2. 11 is inserted and the translucent resin 6 is filled between both the elements in that state. As a result, the discharge path is lengthened from A to B.

[0006]

The above-mentioned conventional examples have the following problems, respectively. The conventional example shown in FIG. 6 has a drawback in that the lead frame becomes extremely expensive because an insulator such as ceramic is attached to the lead frame in advance. Further, since the insulator covers only the side surface of the lead frame, as shown in FIG. 6, the creepage distance is not greatly extended and the withstand voltage improving effect is not so large.

Further, in the conventional example shown in FIG. 7, since the light emitting element or the light receiving element is mounted on the lead frame and wiring is performed by wire bonding, the resin thin film 9 is attached to the back surface of the lead frame. The workability was poor and the cost was increased. Further, in this conventional example, when the lead frame is protruding to the outside of the resin thin film, a predetermined withstand voltage improving effect cannot be obtained, so that it is necessary to set the size of the resin thin film to a large size, which is disadvantageous to downsizing. It was. Further, as shown in FIG. 7, since the effect of increasing the creepage distance is not so great, the withstand voltage improving effect is also relatively low.

In the conventional example of FIG. 8, the discharge distance can be made considerably long as shown in the figure, but it is difficult to stably insert the soft insulating film 11 into the optical coupling path. However, there is a problem that productivity is reduced, resulting in cost increase. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a withstand voltage improving means that has good workability and can sufficiently lengthen a discharge path, and is therefore small and high. It is intended to provide an optical coupling element having a withstand voltage at low cost.

[0009]

In order to achieve the above object, according to the present invention, a light emitting device (1) is mounted on a primary side lead frame (3a) and is mounted on a secondary side lead frame (3b). A light receiving element (2) is mounted, a light emitting element and a light receiving element are arranged to face each other, and both are optically coupled by a translucent resin (6). At least a primary side lead frame and a secondary side lead frame are provided. There is provided an optical coupling element in which a resin coating film (5) is formed on one of the tip portions so as to cover the tip portion from the front surface to the back surface.

According to the present invention, the step of mounting the light emitting element (1) on the primary side lead frame (3a) and the step of mounting the light receiving element (2) on the secondary side lead frame (3b). A step of forming a resin coating film (5) on the tip of at least one of the primary side lead frame and the secondary side lead frame, and the input side lead frame (3a so that the light emitting element and the light receiving element face each other. ) And an output side lead frame (3b), and a translucent resin (6) for optically coupling the light emitting element and the light receiving element.
And a step of filling the space between both the elements with each other.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view showing the element structure of the first embodiment of the present invention. As shown in the figure, the light emitting element 1 is mounted on the input side lead frame 3a, and the pads of the light emitting element and other input side lead frames 3a are connected by bonding wires 4. Similarly,
The light receiving element 2 is mounted on the output side lead frame 3b, and the pads of the light receiving element and other output side lead frames 3 are mounted.
A bonding wire 4 is used to connect to b.

At the tip of the output side lead frame 3b,
A resin coating 5 is formed so as to surround the end of the light receiving element 2 and the end of the lead frame. A transparent resin 6 is filled between the light emitting element 1 and the light receiving element 2 to form an optical coupling path. Here, the resin film 5 is formed by using the same material as the translucent resin 6. All of these are packaged with a mold resin 7 made of black epoxy resin or the like. In the optical coupling element configured as described above, when the discharge path does not have the resin film 5,
Since it extends from B to B, high breakdown voltage can be realized.

2A to 2D are process sectional views showing a manufacturing process of the first embodiment of the present invention. First, the light emitting element 1 and the light receiving element 2 are mounted on the input side lead frame 3a and the output side lead frame 3b, respectively, and the necessary connections are made by the bonding wires 4 [FIG. 2 (a)]. Next, a translucent resin is attached to the tip of the lead frame 3b on which the light receiving element 2 is mounted by a potting method, and the tip of the lead frame 3b is held downward to cure the resin. The resin drops and a resin coating film 5 having a thickness of about 0.1 to 0.2 mm is formed on the tip portion [FIG. 2 (b)].

Next, the lead frame 3a on the input side and the lead frame 3b on the output side are opposed to each other and welded together, and the light-transmitting resin 6 is filled between the light emitting element 1 and the light receiving element 2 by the potting method. Then, an optical coupling path is formed [FIG. 2 (c)]. After the translucent resin 6 is hardened, the whole is covered with the molding resin 7, and the exposed portions of the lead frames 3a and 3b are cut and molded to complete the optical coupling element of the present embodiment shown in FIG. To do.

In the above embodiment, the resin film 5 is formed by the potting method and can be easily formed without the need for a special material or delicate manufacturing condition setting. The cost increase due to the addition of this is slight. Further, since the resin film 5 is extended to the back surface of the lead frame, the creepage distance can be increased and a large withstand voltage improving effect can be obtained.

FIG. 3 is a sectional view showing the element structure of the second embodiment of the present invention. In FIG. 3, portions similar to those of FIG. 1 are designated by the same reference numerals, and a duplicate description will be omitted. However, in the present embodiment, the resin coating 5 is used.
Is formed at the end of the input side lead frame 3a.
With this configuration, similarly to the case of the first embodiment, the discharge path B, which is longer than the discharge path A without the resin coating 5, can be formed, so that a sufficiently high dielectric strength voltage can be obtained. Regarding the manufacturing method, in FIG. 2B, the same manufacturing can be performed by applying the light emitting element side instead of the light receiving element side.

Whether to select the first embodiment or the second embodiment is such that the breakdown voltage is limited by the distance between the tip portion of the input side lead frame 3a and the output side lead frame 3b, or the output side. It is determined whether the breakdown voltage is limited by the distance between the tip of the lead frame 3b and the input side lead frame 3a. Further, when both have the same withstand voltage, a resin coating may be provided on both. FIG. 4 shows the distribution of the difference in withstand voltage with and without the resin coating 5. As shown in the figure, the formation of the resin coating shows a marked increase in withstand voltage.

The preferred embodiment has been described above.
The present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. For example, although the resin coating film 5 is formed by the potting method in the embodiment, it may be formed by a dipping method instead of this method. Further, this coating may be formed using a non-translucent resin. In that case, it is necessary to consider that the resin coating is not applied to the light emitting portion of the light emitting element or the light receiving surface of the light receiving element.

[0019]

As described above, in the optical coupling element according to the present invention, the tip portion of the input side lead frame or the tip portion of the output side lead frame is wrapped by the potting method or the like. Since the resin coating is formed, the pressure resistance improving means can be easily formed without requiring a special material or delicate manufacturing condition setting. Further, since the resin film can be extended to the back surface of the lead frame, the creepage distance can be made sufficiently long. Therefore, according to the present invention, it is possible to provide a small-sized optical coupling element having a high withstand voltage at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a device structure of a first embodiment of the present invention.

FIG. 2 is a process cross-sectional view for explaining the manufacturing method according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing an element structure of a second embodiment of the present invention.

FIG. 4 is a diagram showing a distribution of withstand voltage between an element according to the present invention and a conventional example.

FIG. 5 is a sectional view of a first conventional example.

FIG. 6 is a sectional view of a second conventional example.

FIG. 7 is a sectional view of a third conventional example.

FIG. 8 is a sectional view of a fourth conventional example.

[Explanation of symbols]

 1 Light emitting element 2 Light receiving element 3a Input side lead frame 3b Output side lead frame 4 Bonding wire 5 Resin coating 6 Light transmissive resin 7 Mold resin 8 Insulator 9 Resin thin film 10 Light transmissive resin 11 Insulation film A When no measures are taken Discharge route B Discharge route when countermeasures are taken

Claims (6)

[Claims] 1. A light emitting element is mounted on a primary side lead frame, a light receiving element is mounted on a secondary side lead frame, and a light emitting element and a light receiving element are arranged so as to face each other, and both are optically coupled by a translucent resin. In the optical coupling element, a resin coating film is formed on at least one tip of the primary side lead frame and the secondary side lead frame so as to cover the tip from the front surface to the back surface. Coupling element. 2. The optical coupling element according to claim 1, wherein the resin coating film also covers a part of the surface and the side surface of the light emitting element and / or the light receiving element. 3. The optical coupling element according to claim 1, wherein the resin coating film is made of the same material as the translucent resin that optically couples the light emitting element and the light receiving element. 4. A step of mounting a light emitting element on a primary side lead frame, a step of mounting a light receiving element on a secondary side lead frame, and a tip portion of at least one of the primary side lead frame and the secondary side lead frame. A step of forming a resin coating film, a step of arranging an input side lead frame and an output side lead frame so that the light emitting element and the light receiving element face each other, and the light emitting element and the light receiving element are optically coupled. And a step of filling a translucent resin between the two elements for the purpose of manufacturing the optical coupling element. 5. A step of mounting a light emitting element on a primary side lead frame, a step of mounting a light receiving element on a secondary side lead frame, and a tip portion of at least one of the primary side lead frame and the secondary side lead frame. A step of applying a resin to the resin, a step of curing the applied resin with the tip end of the lead frame coated with the resin facing down, and an input side lead frame so that the light emitting element and the light receiving element face each other. An optical coupling element comprising: a step of disposing an output side lead frame; and a step of filling a translucent resin for optically coupling the light emitting element and the light receiving element between both elements. Production method. 6. The method for manufacturing an optical coupling element according to claim 4, wherein the step of applying the resin is performed by a potting method or a dipping method.