JPH10284755A - Photocoupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify assembling and improve coupling efficiency of light by directly bonding electrically insulating a light-emitting element chip on the surface of a light-receiving element chip state. SOLUTION: The substrate of an LED chip 1 is composed of a material which transmits the light generated in the light-emitting part which is laminated on the substrate. The LED chip 1 is bonded on a PD chip 2 which are mutually electrically insulated. That is, the LED chip 1 is bonded on the PD chip 2 by using an adhesive agent 4 or the like, which transmits light generated from the LED chip 1. The light generated from the LED chip 1 is outputted on the rear of the substrate, enters the PD chip 2 through the adhesive agent 4, and is received by the PD chip 2. Since the substrate of the LED chip 1 is composed of an electrically insulating material, the electric insulation between the LED chip 1 and the PD chip 2 is maintained very high, in the state of direct bonding of the chips 1, 2. Thereby the possibility of mutual contact of wires is excluded, and assembling is very much facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocoupler in which a light emitting element and a light receiving element are electrically insulated and housed in a package, and two circuits are electrically insulated while being electrically insulated. More specifically, the present invention relates to a photocoupler having a structure that can be easily assembled.

[0002]

2. Description of the Related Art A conventional photocoupler of this type is, for example, as shown in FIG.
A D chip 31 is die-bonded to a first lead 32 of the lead frame, one electrode of which is electrically connected, and the other electrode is wire-bonded to a second lead 34 by a gold wire 33 or the like. The light emitting element portion 35 formed by the above method and a light receiving element chip (hereinafter, referred to as a PD chip) 36 are die-bonded to a third lead 37 so that one electrode is electrically connected and the other electrode is gold. A light receiving element portion 40 formed by wire bonding to a fourth lead 39 with a wire 38 or the like is opposed to the light receiving element portion 40, and the opposed portion is fixed by a transparent resin 41, and a package 42 made of an opaque resin or the like is provided around the portion.
It is formed by being covered by.

In order to manufacture this photocoupler, a simple manufacturing method using one lead frame can be achieved by using an LED chip 31 and a PD on one surface of one lead frame.
After the chips 36 are respectively die-bonded and wire-bonded, the leads on the light emitting element section 35 or the light receiving element section 40 side must be bent to face each other. After that, the opposing portion must be filled with a transparent resin by potting or the like, and then the periphery thereof must be molded.

[0004]

Even if a conventional photocoupler uses a lead frame for mass production, as described above, after forming a light emitting element portion and a light receiving element portion, one of the leads is bent. Both must be opposed. Each of the light emitting element portion and the light receiving element portion has a gold wire for wire bonding protruding on its surface side, and it is necessary to prevent them from coming into contact with each other. As a result, the assembly process is very complicated, and the man-hour is increased.
There is a limit to cost reduction.

Further, as described above, a gold wire protrudes from the opposing portion of the light emitting element portion and the light receiving element portion, and the insulating property of the transparent resin filled therebetween is not sufficient, and the assembling accuracy is low. From the point of view, there is a limit in narrowing the facing distance, and the distance cannot be reduced to 0.5 mm or less. Therefore, there is a problem in that the distance between the two becomes large, the efficiency of light transmission and reception is reduced, a light emitting element with higher luminance is required, the current consumption of the light emitting element is increased, and miniaturization of the element is restricted. .

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and can greatly simplify the assembling and improve the light coupling efficiency so that even a light emitting element with low luminance can be sufficiently used. An object of the present invention is to provide an inexpensive, compact, and efficient photocoupler that can be coupled.

[0007]

In a photocoupler according to the present invention, a semiconductor layer forming a light emitting portion is laminated on a substrate,
The substrate includes a light emitting element chip made of a material that transmits light emitted by the light emitting unit, and a light receiving element chip capable of receiving light emitted by the light emitting element chip, wherein the light emitting element chip is a light emitting element chip. It is directly adhered to the surface of the light receiving element chip while being electrically insulated therefrom.

As a result, it is not necessary to oppose the light emitting element portion and the light receiving element portion so as to have a fixed gap, and it is only necessary to stack and bond the light emitting element portion and the light receiving element portion. The portions are almost in contact with each other, and the efficiency of light coupling between the two is improved.

The electrical insulation between the light emitting element chip and the light receiving element chip is, for example, that an insulating film that transmits light emitted by the light emitting element chip is formed on the surface of the light receiving element chip, Since the substrate is made of an electrically insulating substrate, it can be obtained even if the substrate is directly adhered with an adhesive or the like.

[0010]

Next, a photocoupler of the present invention will be described with reference to the drawings.

The photocoupler of the present invention, as shown in FIG. 1, is a schematic view of one embodiment of the present invention, in which the substrate of the LED chip 1 is made of a material that transmits light emitted by a light emitting portion laminated thereon. And the LED chip 1 is P
It is characterized in that it is provided on the D chip 2 by bonding so as to be electrically insulated from each other. That is, in the example shown in FIG. 1, the LED chip 1 is a blue LED chip in which a gallium nitride-based compound semiconductor is laminated on a sapphire substrate, and light emitted from the LED chip 1 on a PD chip 2. It is formed by bonding with an adhesive 4 or the like that transmits light.

The LED chip 1 has, for example, an n-type GaN and / or AlGaN-based (the ratio of Al to Ga can be variously changed on a sapphire substrate 11 as shown in the sectional structure of FIG. 2, for example. An n-type layer (cladding layer) 13 on which a compound semiconductor is epitaxially grown, and a material whose band gap energy is smaller than that of the cladding layer, for example, InG
an active layer 14 made of an aN-based (which means that the ratio of In to Ga can be varied, the same applies hereinafter) compound semiconductor;
For example, a p-type layer (cladding layer) 15 made of p-type GaN and / or an AlGaN-based compound semiconductor is laminated, and a p-side electrode 18 is laminated by being electrically connected to the p-type layer 15 on the surface thereof. It is formed by providing n-side electrodes 19 electrically connected to the n-type layer 13 which is partially exposed by etching the semiconductor layer. In the ordinary LED chip 1, the p-side electrode 18 is formed to be small so as not to block the light in order to extract light from the upper surface side.
A current diffusion layer made of a thin metal film that transmits light may be provided on the surface of the p-type layer 15. However, in the present invention, since light emitted to the back side of the substrate 11 is used, the entire surface of the p-type layer is used. An electrode metal from which an ohmic contact can be made can be provided thick. Alternatively, an insulating film and Al
A reflective film such as a reflective film may be formed. The sapphire substrate 11 of the LED chip 1 is transparent, transmits blue light, and has good electrical insulation. Therefore, even if the LED chip 1 is directly adhered onto the PD chip 2, the electrical insulation between the two is sufficient. Can be obtained.

The PD chip 2 has an LED chip 1 thereon.
As shown in FIG. 3, a semiconductor substrate 21 made of n-type silicon or the like,
A photodiode in which a pn junction is formed by a p-type region 22 formed by diffusion of a p-type dopant in the semiconductor substrate 21 and the n-type layer (semiconductor substrate 2).
1) and n electrically connected to the p-type region 22 respectively.
It is formed by providing the side electrode 23 and the p-side electrode 24. When light is irradiated in a state where a reverse bias is applied to the pn junction via the electrodes 23 and 24, a current flows. This PD chip 2 can use another light receiving element chip such as a phototransistor, instead of a photodiode.

As shown in FIG. 1, this PD chip 2 is die-bonded on a die pad 3e at the tip of a first lead 3a of a lead frame, and an LED is mounted on the surface thereof.
The chip 1 is bonded with an adhesive 4 made of, for example, a transparent epoxy resin. The n-side electrode 23 of the PD chip 2 is electrically connected to the lead 3a by die bonding, and the p-side electrode 24 is electrically connected to the second lead 3b by wire bonding or the like by wire bonding. Is composed. Also, n of the LED chip 1
The side electrode 19 and the p-side electrode 18 are also wire-bonded with the third and fourth leads 3c and 3d and the gold wire 5 to constitute the light emitting element section 7. Then, in order to prevent light from entering the light receiving element portion 6 from the outside, the entire periphery is molded with an opaque epoxy resin or the like to form a package (not shown), thereby forming the photocoupler of the present invention. .

According to the present invention, the substrate of the LED chip 1 is made of a material such as sapphire that transmits light emitted by the LED chip. Therefore, the light emitted from the LED chip 1 exits to the back surface of the substrate and passes through the adhesive 4
The light enters the D chip 2 and is received. On the other hand, in the above example, LE
Since the substrate of the D chip 1 is made of an electrically insulating material such as sapphire, the electrical insulation between the two is kept very high even if the substrate is directly adhered to the PD chip 2. Therefore, there is no need to separate them and face each other.
Since there is no need to bend the lead frame, there is no need to worry about contact between wires, and assembly becomes very easy. Moreover, since there is a gap between the LED chip 1 and the PD chip 2 and the space between the LED chip 1 and the PD chip 2 is not filled with resin or the like, the coupling efficiency between the LED chip 1 and the PD chip 2 is improved, and even the LED chip 1 having a small luminance can be sufficiently used. At the same time, the overall height can be reduced, and the device becomes compact.

In the above-described example, the substrate of the LED chip is an insulating substrate. However, the substrate may not be an insulating substrate as long as light emitted by the LED chip is transmitted. In this case, in order to obtain electrical insulation from the PD chip, a material having good insulation may be used for both adhesives. An insulating film such as a transparent polyimide may be provided. In this case, in order to secure about several tens to 100 V used for the photocoupler, the theoretical value of the normal withstand voltage of the insulating material is about 20 MV / m, and a thickness several times the theoretical value is required. 1
A thick film having a thickness of 0 μm or more is required, and preferably a thickness of 20 μm or more.

When an insulating film that transmits light is formed on the surface of the light receiving element chip, for example, wiring can be formed on the surface by patterning. Therefore, LED
Even when the chip substrate is a semiconductor substrate or the like and both electrodes are provided on the upper and lower surfaces thereof, the wiring on the insulating film and the L
By bonding the LED chip so that the electrode provided on the back side of the ED chip is in contact with the LED chip, the electrodes of the LED chip can be easily connected. Therefore, L
The ED chip is not limited to a blue light emitting element in which a gallium nitride compound semiconductor is stacked on a sapphire substrate as described above.
All light-emitting elements having a substrate made of a material that transmits light, such as an As substrate or a GaP substrate for red and green, can be used. Even when a conductive substrate such as a semiconductor is used as the substrate, if both n-side and p-side electricity are formed on the surface on which the semiconductor layer is laminated, connection of the electrodes can be easily performed only by wire bonding. I can do it.

[0018]

According to the present invention, a photocoupler can be formed by simply bonding a light receiving element chip and a light emitting element chip in sequence on a die pad of a lead frame, and then by wire bonding and molding in the same manner as a normal IC. Can be manufactured. Therefore, unlike the related art, the trouble of assembling the light-emitting element portion and the light-receiving element portion in alignment and facing each other is eliminated, and the assembling process is very easy and can be manufactured in a short time. Further, since the insulation properties of the two element portions can be reliably maintained irrespective of the alignment in assembling, the yield is improved and the reliability is also improved.

Further, since the light emitting element portion and the light receiving element portion are very close to each other, the coupling efficiency between the light emitting element and the light receiving element is increased, and the current consumption of the light emitting element can be reduced.
Furthermore, since there is no need to provide an interval between the two elements, the thickness can be reduced and the device can be made compact.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a state in which a chip is bonded on a lead frame of an embodiment of the photocoupler of the present invention.

FIG. 2 is an explanatory side view of a PD chip and an LED chip unit of FIG. 1;

FIG. 3 is an explanatory perspective view of a PD chip and an LED chip unit of FIG. 1;

FIG. 4 is an explanatory sectional view of a main part of an example of a conventional photocoupler.

[Explanation of symbols]

 1 LED chip 2 PD chip 4 Adhesive

Claims (3)

[Claims] A light emitting element chip formed of a material through which light emitted by the light emitting unit is transmitted; and a light emitting element chip for receiving light emitted by the light emitting element chip. Light-receiving element chip
A photocoupler in which the light emitting element chip is directly adhered to the surface of the light receiving element chip while being electrically insulated from the light receiving element chip. 2. The light-emitting element chip is electrically insulated from the light-receiving element chip by forming an insulating film that transmits light emitted by the light-emitting element chip on a surface of the light-receiving element chip. Item 7. The photocoupler according to Item 1. 3. The photocoupler according to claim 1, wherein the substrate of the light emitting element chip comprises an electrically insulating substrate.