JPS6252978A - Photocoupler - Google Patents

Abstract

PURPOSE:To make peeling off of the resin boundary from an input side conducting part to an output side conducting part difficult to occur and improve dielectric strength between the input side and output side by forming a photolinkage part with epoxy system resin which belongs to the same system as packaging resin. CONSTITUTION:A light emitting device 3 and a photodetector 4 are mounted on an element mounting part 1a and an element mounting part 2a respectively. Then wire bonding is carried out with gold wires 5 and, after the surface of the light emitting device 3 is lightly coated with silicon system resin 6, both of the light emitting device 3 and the photodetector 4 are solidly molded with transparent epoxy resin 7 which forms a phtocoupling part and further opaque epoxy resin 8, which contains light reflecting agent, is applied to the outside of the resin 7 as packageing molding and further lead terminals 1 and 2 are subjected to a bending process to complete a photocoupler. It is to be noted that the purpose of the coating of silicon system resin 6 is to avoid deterioration caused by current and, as the peeling-off at the boundary between the coating resin 6 and the transparent epoxy resin does not reach an output conducting part from an input conducting part, it can not be the cause of degradation of dielectric strength between the input side and the output side.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device that optically connects a light emitting element and a light receiving element to transmit a signal, that is, an optical coupling device. The present invention relates to an optical coupling device in which the elements are disposed on substantially the same plane, an optical coupling portion for allowing light serving as a signal medium to reach the light receiving element is formed of resin, and the exterior is molded with resin.

[Conventional technology]

The optical coupling device has an input side, that is, a light emitting element side, and an output side,
That is, since it has the advantage of being able to completely electrically isolate the light-receiving element side, it is used when a high dielectric strength voltage is required between input and output. Currently, there are two types of optical coupling devices: one in which the light-emitting element and the light-receiving element are arranged on almost the same plane, and the other in which the two elements are arranged facing each other. They must be placed close to each other, resulting in low dielectric strength between input and output. Nowadays, electronic devices are required to be more compact, and electronic devices are becoming smaller in size. Due to the limitations of insulation voltage between input and output, optical coupling devices with a light-emitting element and a light-receiving element arranged on almost the same plane are being used. It is becoming increasingly important.

The structure of a conventional optical coupling device in which a light emitting element and a light receiving element are disposed on substantially the same plane is shown in a sectional view in FIG. 1 having element mounting portions 1a and 2a on substantially the same plane, respectively;
A light-emitting element 3 and a light-receiving element 4 are respectively arranged on the element mounting portions of the pair of lead terminals 1 and 2, covered with a transparent resin 9, and covered with a resin 10 having a high surface reflectance on the outside. Furthermore, it has a structure in which the outer periphery is molded with resin 11.

The light transmission function in this structure is achieved by reflecting the light emitted from the light emitting element 3 at the interface between the transparent resin 9 and the resin 10 with high surface reflectance as shown in FIG. to communicate. Therefore, in order to prevent the resin interface that reflects light from peeling off, the transparent resin 9 and the resin 10 with high surface reflectance are usually made of the same type of resin with extremely similar coefficients of thermal expansion. Silicone resin is mainly used for the transparent resin 9 and the resin 10 with high surface reflectance, and the optical connection part 9 is usually formed by dropping the resin by a botting method and letting it air.

Moreover, epoxy resin is generally used for the exterior resin 11, and is molded by a method such as transfer molding.

[Problem that the invention seeks to solve]

As mentioned above, one of the important characteristics of an optical coupling device is the dielectric strength between the input and output sides.In the case of the conventional optical coupling device shown in Fig. 3, the silicon resin forming the optical coupling part and the exterior Since the coefficient of thermal expansion is significantly different from that of the epoxy resin, the adhesion between the two resins at the interface is extremely poor, and peeling from the input-side conductive part to the output-side conductive part is likely to occur, and insulation is lost through the peeled interface. Destruction occurs. Therefore, in order to improve the dielectric strength between input and output with this structure, it is possible to increase the amount of silicone resin and increase the distance between the interfaces of the epoxy resin, but this will cause the problems described below. , it didn't really solve the problem. That is,
Since the optical coupling device requires an optical connection part, silicone resin, etc. is included in the mold package, and there is no need to include silicone resin, etc. in the mold package.
Compared to ICs and the like, optical coupling devices are inferior in moisture resistance to ICs even though they have the same shape and dimensions. This also shows that the moisture resistance is improved when the amount of silicone resin in the optical connection portion is small. Therefore, increasing the amount of silicone resin to increase the interfacial distance will lead to deterioration of moisture resistance.

[Means for solving problems]

In the present invention, by forming the optical connection part with an epoxy resin of the same type as the exterior resin, peeling of the resin interface from the input side conductive part to the output side conductive part is made difficult to occur, and the insulation breakdown voltage between the input and output sides is improved. The aim is to

〔Example〕

Next, the present invention will be explained by examples.

FIG. 1 is a sectional view of one embodiment of the present invention, and the second factor is a plan view of the optical coupling device shown in FIG. 1 during the process.

1 and 2, 1 and 2 are a pair of lead terminals, and the respective element mounting portions 1a and 2a are t
They are lined up on the same plane. Then, the element mounting section 1a
After the light emitting element 3 is mounted on the mount part 2a and the light receiving element 4 is mounted on the element mounting part 2a, wire bonding is performed with a gold wire 5, and then the surface of the light emitting element 3 is thinly coated with a silicone resin 6. After performing this, the light emitting element 3 and the light receiving element 4 are coated with a transparent epoxy resin 7 that forms an optical coupling part.
The outside of the lead terminals is molded integrally with opaque epoxy resin 8 containing a light reflecting agent, and the lead terminals 1 and 2 are bent.
This is the completed product shown in the figure.

Note that the above-mentioned coating of silicone resin 6 is for preventing deterioration due to electrical conduction, but this interfacial peeling between the coating resin 6 and the transparent epoxy resin 7 is not peeling that reaches from the input conductive part to the output conductive part. Therefore, it cannot be the cause of deterioration of insulation between input and output. In addition, in order to reflect the light from the light emitting element 3 and reach the light receiving element 4 at the interface between the exterior resin 8 and the transparent resin 7, the transparent resin 7 is For example, it is desirable to make it a spheroid.

〔Effect of the invention〕

As explained above, in the optical coupling device according to the present invention, since the same epoxy resin as the exterior resin is used as the resin forming the optical connection part, the coefficient of thermal expansion is similar to that of the exterior resin. The adhesion between them is extremely good, making it difficult for peeling to occur at the interface, and the dielectric strength between the input and output sides is extremely high compared to conventional materials. Furthermore, the fact that peeling is less likely to occur at the resin interface means that there is less moisture infiltration through that route, and therefore, the interfacial distance can be shortened to obtain the same dielectric strength voltage as before.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a plan view of a process in progress to obtain the product shown in FIG. 1, and FIG. 3 is a cross-sectional view of a conventional optical coupling device. 1.2...Lead terminal, la, 2a...
・Element mounting part, 3...Light emitting element, 4...
- Light receiving element, 5...Gold wire, 6...Coating silicone resin, 7...Transparent epoxy resin, 8...Exterior epoxy resin containing reflective material .

Claims (1)

[Claims] A pair of lead terminals each having an element mounting part provided on substantially the same plane, a light emitting element and a light receiving element arranged in the element mounting part, a resin that includes both the elements and optically connects them; In an optical coupling device consisting of an exterior resin covering the outside,
An optical coupling device characterized in that a transparent epoxy resin is used as the optically connecting resin, and an opaque epoxy resin containing a light reflecting agent is used as the exterior resin.