GB2158641A

GB2158641A - Optoelectronic coupling element

Info

Publication number: GB2158641A
Application number: GB08511486A
Authority: GB
Inventors: Helmut Schultz
Original assignee: Telefunken Electronic GmbH
Current assignee: Telefunken Electronic GmbH
Priority date: 1984-05-08
Filing date: 1985-05-07
Publication date: 1985-11-13
Also published as: JPS60241279A; GB8511486D0; IT1183568B; IT8520610A0; GB8511061D0; FR2564266A1

Abstract

An optoelectronic coupling element comprises transmitter 1 and receiver 2 enclosed in a clear transparent plastics material which forms the housing 4 and which is subsequently coated with a reflecting plastics layer 5. The layer 5 is preferably applied by an immersion or mould process. <IMAGE>

Description

SPECIFICATION Optoelectronic coupling element The present invention relates to an optoelectronic coupling element and more particularly to an element consisting of a light emitting semiconductor component and a light receiving semiconductor component, wherein the two components are attached in isolation from one another on a carrier member and are enclosed by a transparent plastic material.

Optoelectronic coupling elements are used to transmit an electric signal via a light signal from a transmitter circuit to a receiver circuit which is completely isolated from and, therefore, galvanically separated i.e. electrically insulated from the transmitter circuit. Optoelectronic coupling elements are used, for example, in telephone exchange systems for private branch exchanges, and in data processing for the separation of potential and increase in the interference immunity. Optoelectronic coupling elements are also used for separation of potential of control and load circuits in power electronics for driving triacs and thyristors.

In a known process for the manufacture of an optoelectronic coupling element, the transmitter semiconductor component and the receiver semiconductor component are attached in one plane on adjacent portions spaced at a defined distance from one another on a coherent, structured contacting strip. A plastics reflector is then slipped over the two semiconductor components, and the space between the components and the reflector is filled up with a transparent plastics material which also encloses the contacting prongs. The reflector is then cast together with the transparent plastics material in a transparent plastics material forming the external housing. The webs holding the contacting strips together are subsequently severed off.

In a coupling element of the above type, the two semiconductor components, for example, of a light emitting diode and a phototransistor. Instead of a phototransistor, a photo-field-effect transistor, a photodiode or another photosensitive semiconductor component or a light sensitive integrated circuit may also be used.

The above optoelectric coupling element has a high insulation voltage, but is unsuitable for miniaturisation and use for film circuits in hybrid technology, as the housing dimensions are relatively large on account of the design.

The present invention seeks to provide an optoelectronic coupling element which has smaller dimensions and is suitable for use in hybrid circuits, and a process for its manufacture.

According to a first aspect of the present invention, there is provided an optoelectronic coupling element comprising a light emitting semiconductor component and a light receiving semiconductor component enclosed by a transparent member which forms the housing of the optoelectronic coupling element and is coated with a thin layer of reflecting material.

The reflecting layer preferably consists of light, infrared reflecting epoxide resin or epoxide moulding compound material.

According to a second aspect of the invention, there is provided a method of manufacturing an optoelectronic coupling element as set forth in the last but one paragraph wherein the transparent housing is coated with the reflecting layer by an immersion or mould process.

The housing is practically exclusively formed by the transparent plastics material and, by way of the plastics material, there is obtained the mechanical stability required for a housing. The reflection layer should be as thin as possible and makes practically no contribution towards the mechanical stability of the housing. The reflection layer should, if possible, be only so thin that its thickness is adequate for it to meet its reflection requirements.

Preferably the miniaturized plastics housing is coated in an immersion process with a plastics layer of white epoxide resin reflecting the light in order to obtain a high coupling factor.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a perspective partially sectional view of an optoelectronic coupling element in accordance with the present invention; Figure 2 shows a section taken through an optoelectronic coupling element similar to that of Figure 1, but without the light reflecting layer; and Figure 3 shows a section taken through the optoelectronic coupling element of Figure 1 with the reflection layer.

Referring now to the drawings, there is used, for contacting the transmitter semiconductor component 1 and the receiver semiconductor component 2, a contacting strip in the form of a continuous band which with regard to the manufacturing process comprises transverse webs, external bars and centre webs. After casting of transmitter 1 and receiver 2 with transparent plastic material 4, cutting tools are used to sever off transverse webs, external bars and centre webs.

In the embodiment shown in Figure 1, the transparent plastics material 4 consists of clear epoxide resin.

The plastics material 4 containing the transmitter semiconductor component 1 and the receiver semiconductor component 2 is coated with a lightproof reflection layer 5 in an immersion or mould process. The thus produced block-shaped, miniature housing of the standardized SOT 143 type has the following dimensions: length x width x height = 2.9 x 1.3 x 1 mm.

The light-proof reflection layer 5 consists, for example, of white epoxide resin with titanium oxide added thereto. Similar reflectors may also be made by mixing magnesium oxide and other transparent plastics such as, for example, polycarbonate.

The connecting legs 3a, 3b and 6a, 6b as shown in Figure 1, which are necessary for the electrical connection of transmitter semiconductor component 1 and receiver semiconductor component 2, are made in a bending process.

The reference numerals used in Figure 2 correspond to those of Figure 1. The light 7 issuing from the transmitter semiconductor component 1 leaves the plastics material 4 on all sides, as shown in Figure 2.

The immersion process and the coating of the plastics material 4 with a light reflecting mass 5 produces total reflection 7 in the interior of the plastics material 4, whereby a coupling factor of typically 100- is obtained, as is shown in Figure 3.

The reference numerals of Figure 3 correspond to those of Figures 1 and 2.

The insulation voltage between the transmitter semiconductor component 1 and the receiver semiconductor component 2 required for the potential separation is at least 500 V.

The optoelectronic coupling element described above in connection with Figures 1 and 3 has the substantial advantage that the transparent plastics material (together with the very thin, reflecting coating of approximately 0.3 mm) forms the housing, thereby enabling elimination of a separate external housing made of light-proof plastics material. This results in a substantial reduction in the housing dimensions.

In addition the optoelectronic coupling element is suitable for mass production use in hybrid circuits for separation of potential and interferenceproof decoupling. If the housing dimensions are selected so as to correspond to those of a standardized miniature housing, for example, of the SOT 143 type, there is the additional advantage that these components may be processed with the automatic insertion machines customary in the trade.

Besides the SOT 143 type, the housing may be of standard size TO 143 or SO 6.

Claims

1. An optoelectronic coupling element comprising a light emitting semiconductor component and a light receiving semiconductor component enclosed by a transparent member which forms the housing of the optoelectronic coupling element and is coated with a thin layer of reflecting mate rival.

2. An element according to claim 1, wherein the transparent member is of plastics material.

3. An element according to claim 2, wherein the transparent plastics material consists of clear epoxide resin.

4. An element according to any preceding claim, wherein the reflecting layer is light-proof.

5. An element according to any preceding claim, where the two semiconductor components are arranged on a carrier member and lie in one plane.

6. An element according to any preceding claim, wherein the surface of the housing is covered on all sides by the reflecting layer.

7. An element according to any preceding claim, wherein the dimensions of the housing correspond to a block-shaped, standardized miniature housing such as SOT 143, TO 143 or SO 6 type.

8. An element according to any preceding claim, wherein the reflecting layer consists of light, infrared reflecting epoxide resin or epoxide moulding compound material.

9. An element according to any preceding claim, wherein the reflecting layer has a thickness of approximately 0.3 mm and produces total internal reflection.

10. An optoelectronic coupling element substantially as herein described with reference to Figures 1 and 3 of the accompanying drawings.

11. As an independent invention the additional feature of any of claims 2 to 9.

12. A method of manufacturing an optoelectronic coupling element according to any preceding claim, wherein the transparent housing is coated with the reflecting layer by an immersion or mould process.

13. A method of manufacturing an optoelectronic coupling element substantially as herein described with reference to Figs 1 and 3 of the accompanying drawings.