JP6226393B2 - Optical coupling device - Google Patents

Description

  Embodiments described herein relate generally to an optical coupling device.

  An optical coupling device (including a photocoupler and a photorelay) can convert an input electric signal into an optical signal by using a light emitting element, and can output the electric signal after receiving the light by the light receiving element. For this reason, the optical coupling device can transmit an electrical signal in a state where the input and output are insulated.

  In industrial equipment, office equipment, and home appliances, different power supply systems such as a DC voltage system, an AC power supply system, a telephone line system, and a control system are arranged in one apparatus. However, if different power supply systems and circuit systems are directly coupled, malfunction may occur.

  In this case, when an optical coupling device is used, different power sources are insulated from each other, so that the operation can be kept normal.

  For example, in inverters and air conditioners, a large number of photocouplers including those for AC loads are used. Further, when used for signal switching for a tester application, a large number of photocouplers are mounted, and the downsizing area is strongly required because the mounting area on the substrate needs to be reduced.

JP-A-9-36413

  Provided is an optical coupling device which can be easily reduced in thickness and mounting area.

An optical coupling device according to an embodiment includes a substrate having a first surface including a light emitting surface and a second surface opposite to the first surface, and light emission provided on the second surface of the substrate. A semiconductor stacked body including a layer, a light emitting element having first and second electrodes provided on a surface of the semiconductor stacked body on a side opposite to the substrate, a plurality of the light emitting elements provided facing the light emitting element, A light receiving surface formed by connecting a plurality of pn junctions in series, a third electrode provided on the light receiving surface side and connected to a pn junction at one end of the plurality of pn junctions, and the plurality of pn junctions A light receiving element having a fourth electrode connected to the pn junction at the end, and a resin molded body that covers the light emitting element and the light receiving element and has a light shielding property. 2 electrodes. The second electrode covers the light emitting layer and reflects most of the emitted light from the light emitting layer toward the second electrode toward the light emitting surface.

FIG. 1A is a schematic plan view of the optical coupling device according to the first embodiment, and FIG. 1B is a schematic cross-sectional view taken along the line AA. 2A is a schematic side view of the light emitting element, FIG. 2B is a schematic plan view of the light emitting element, and FIG. 2C is a schematic plan view of the light receiving element. 2D is a schematic cross-sectional view taken along the line AA of the EX portion, and FIG. 2E is a schematic side view of the EX portion. FIG. 3A is a schematic plan view of the pattern of the light receiving surface of the light receiving element, and FIG. 3B is a connection diagram of the photodiode array. It is a schematic plan view of the 1st modification of the pattern of a light-receiving surface. 4A is a schematic plan view of a second modification of the pattern of the light receiving surface, and FIG. 5B is a connection diagram of the photodiode array. It is a schematic cross section of the optical coupling device concerning a comparative example. FIG. 7A is a schematic plan view of the optical coupling device according to the second embodiment, FIG. 7B is a schematic cross-sectional view along the line BB, and FIG. 7C is a configuration diagram thereof. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a schematic plan view of the optical coupling device according to the first embodiment, and FIG. 1B is a schematic cross-sectional view taken along the line AA.
The optical coupling device includes a light emitting element 10, a light receiving element 20, an adhesive layer 34, an input terminal 30, an output terminal 40, and a resin molded body 70.

  The light-emitting element 10 includes a light-transmitting support substrate, a semiconductor stacked body, and a first electrode and a second electrode provided in the semiconductor stacked body. The light emitting element 10 can be, for example, a surface emitting LED (Light Emitting Diode).

  The light receiving element 20 has a first electrode and a second electrode on the light receiving surface side. The light receiving element 20 is made of silicon or the like, and can be a photodiode, a photodiode array including a plurality of pn junction regions, a phototransistor, a light receiving IC in which a control circuit or an amplifier circuit is further integrated, and the like.

The adhesive layer 34 has translucency and insulation, and bonds the light emitting element 10 and the light receiving surface side of the light receiving element 20 together. The adhesive layer 34 can be inorganic materials including glass and SiO _2, or an acrylic, silicone, and a resin material such as polyimide. Light emitted downward from the light emitting layer passes through the adhesive layer 34 and enters the light receiving surface.

  The optical coupling device may include a resin molded body 70 provided on the insulating substrate 60 so as to cover the light emitting element 10 and the light receiving element 20. Alternatively, the optical coupling device may include a light receiving element 20 provided on the lead and a resin molded body 70 provided so as to cover the light emitting element 10 provided on the light receiving element 20. The resin molded body 70 can include acrylic, epoxy, silicone, and the like. The resin molded body 70 is represented by a broken line in FIG. 1B, and is omitted in FIG.

  The input terminal 30 and the output terminal 40 provided on the surface of the insulating substrate 60 are electrically insulated. For this reason, the optical coupling device can transmit an electrical signal in a state where the input and output are insulated.

2A is a schematic side view of the light emitting element, FIG. 2B is a schematic plan view of the light emitting element, and FIG. 2C is a schematic plan view of the light receiving element. FIG. 2D is a schematic cross-sectional view of the EX portion, and FIG. 2E is a schematic side view of the EX portion.
As shown in FIG. 2A, the translucent support substrate 11 has a first surface 11a and a second surface 11b opposite to the first surface 11a. The semiconductor stacked body 13 including the light emitting layer 12 (dot line) is provided on the second surface 11b. The semiconductor stacked body 13 includes a stepped portion that reaches from the surface to the lower side of the light emitting layer 12 on the surface opposite to the support substrate 11. The step portion has a bottom surface 13a.

  If the support substrate 11 is made of GaAs, its band gap wavelength is approximately 870 nm. For this reason, the wavelength of the emitted light G from the light emitting layer having an MQW (Multi Quantum Well) structure or the like can be made longer than 870 nm and shorter than 1100 nm, for example. If the support substrate 11 is GaP having a band gap wavelength of approximately 500 nm, the wavelength of the emitted light G can be set to 700 to 1100 nm or the like.

  A first electrode 14 is provided on the bottom surface 13a of the step portion, and a second electrode 15 is provided on the surface of the semiconductor stacked body 13 excluding the step portion. When the second electrode 15 covers the upper side of the light emitting layer 13, most of the upward emitted light is reflected by the second electrode 15, and the upward emitted light can be reduced. Light emitted downward from the light emitting layer 12 is emitted from the light emitting surface 18 on the back surface of the support substrate 11 and enters the light receiving surface of the light receiving element 20. As shown in FIG. 2B, the light emitting surface 18 overlaps the light emitting layer 12 when seen in a plan view, that is, from a direction perpendicular to the first surface 11a (or the second surface 11b).

  The light receiving surface 22 of the light receiving element 20 shown in FIG. 2C is preferably included in the light emitting surface 18 on the back surface of the light emitting element 10 in plan view. In this way, since the light receiving surface 22 does not protrude from the semiconductor light emitting element 10, disturbance light can be prevented from entering the light receiving surface. For this reason, malfunction of the optical coupling device can be reduced. The light receiving element includes a first electrode 24 connected to one conductivity type layer of the pn junction, and a second electrode 26 connected to the other conductivity type layer of the pn junction.

  FIG. 2D is a schematic cross-sectional view of the EX portion represented by a broken line in FIG. As shown in FIG. 2D, the emitted light G emitted from the light emitting surface 18 and transmitted through the adhesive layer 34 enters the light receiving surface 22. Since the adhesive layer 34 is thin, the emitted light G from the light emitting element 10 efficiently enters the light receiving surface 22 from the light emitting surface 18. FIG. 2E is a schematic side view of the EX portion, and the electrodes of the light emitting element 10 and the light receiving element 20 can be connected to the input terminal 30 and the output terminal 40 using bonding wires or the like, respectively.

FIG. 3A is a schematic plan view of the pattern of the light receiving surface of the light receiving element, and FIG. 3B is a connection diagram of the photodiode array.
For example, a plurality of light receiving elements 20 are formed by insulating one photodiode made of one pn junction on a Si substrate. Further, a plurality of silicon photodiodes are connected in series to form a photodiode array 20a. This is preferable because a voltage higher than the threshold voltage Vth of the gate of the MOSFET built in the optical coupling device can be supplied.

  Further, as shown in FIG. 3A, the twelve photodiodes are connected in series by the metal wiring portion 20b. Each of the photodiodes has a light receiving surface made of a pn junction, and functions as a solar cell that receives light emitted from the light emitting element and generates photovoltaic power. In this case, the light receiving surface 22 is a region including 12 photodiodes. One end of the photodiode array 20a is connected to the first electrode 24 by a metal wiring portion 20b. The other end of the photodiode array 20a is connected to the second electrode 26 by a metal wiring 20b.

  The photovoltaic power per stage of the photodiode is approximately 0.6V. On the other hand, it is not easy to set the threshold voltage Vth of the MOSFET to 0.6 V or less. That is, when at least two photodiodes are connected in series, the MOSFET can be reliably controlled to be turned on or off.

FIG. 4 is a schematic plan view of a first modification of the pattern of the light receiving surface.
The plurality of pn junction regions may include regions of different sizes. The light emitted from the light emitting element 10 has the maximum light intensity on the optical axis passing through the light emission center (for example, represented by a point O in FIG. 2B), and the light intensity decreases as the region is separated from the optical axis. In the present embodiment, since the light receiving surface 22 does not protrude outside the light emitting surface 18 of the semiconductor light emitting element 10, it is possible to prevent the photovoltaic power from being extremely reduced.

  However, the current density in the regions R4 and R10 separated from the optical axis may decrease. In this case, if the areas of the pn junctions in the regions R4 and R5 are increased, the currents in the regions R4 and R5 can be easily brought close to the currents in the pn junction region having a high light intensity and a small planar size. That is, the maximum output point Pmax as a solar cell can be improved by setting the planar size of the pn junction region to an appropriate value.

FIG. 5A is a schematic plan view of a second modification of the light receiving surface pattern, and FIG. 5B is a connection diagram of the photodiode array.
As shown in FIG. 5A, the light receiving element 20 can further include a control circuit 28. The control circuit 28 is connected to the first electrode 27 and the second electrode 26 of the photodiode array 20a. With such a configuration, a voltage can be supplied to each gate of the MOSFET (M1, M2).

  The MOSFETs (M1, M2) can be, for example, n-channel enhancement type. As shown in FIG. 5B, the MOSFETs (M1, M2) are connected to the common source and connected to the second electrode 26 of the photodiode array 20a. Each gate is connected to the first electrode 27, and each drain serves as an output terminal 40.

  When the optical signal is on, the MOSFETs (M1, M2) are both on and connected to an external circuit via the output terminal 40. On the other hand, when the optical signal is off, the MOSFETs (M1, M2) are both turned off and are disconnected from the external circuit.

FIG. 6 is a schematic cross-sectional view of a counter-type optical coupling device according to a comparative example.
In the comparative example, the light emitting element 110 bonded to the input lead 130 and the light receiving element 120 bonded to the output lead 140 are provided so as to face each other within the translucent resin layer 168 while maintaining a separation distance L1. It is done. For this reason, the emitted light spreads, only a part of the light can reach the light receiving surface, and the current is as low as about 2.5 μA. Further, it is necessary to provide the light shielding resin layer 170 so as to cover the light transmitting resin layer 168. In the opposed type, there is a limit in reducing the separation distance L1.

  In contrast, in the first embodiment, since the separation distance is the thickness of the adhesive layer 34 and is small, the spread of the emitted light is reduced, and the current can be increased to about 13 μA. Further, it is easy to make the optical coupling device thinner and reduce the mounting area.

FIG. 7A is a schematic plan view of an optical coupling device according to the second embodiment, FIG. 7B is a schematic cross-sectional view along the line BB, and FIG. 7C is a configuration diagram thereof.
The optical coupling device according to the second embodiment includes a light emitting element 10, a light receiving element 20, a MOSFET (M1, M2), an adhesive layer 34, an input terminal 30, an output terminal 40, and a resin molded body 70. Have.

  In this figure, MOSFETs (M1, M2) are n-channel enhancement type, but the present invention is not limited to this. The channel conductivity type of the MOSFETs (M1, M2) and the polarity of the photodiode array 20a may be opposite conductivity types. The MOSFET may be a depletion type.

  In this figure, the optical coupling device further includes an insulating substrate 60. On the upper surface 60a, the lower surface 60b, and the side surface 60c of the insulating substrate 60, a thick film containing a metal and a plated conductive layer made of Au, Ag, Cu or the like provided thereon are provided. The conductive layer includes a die pad portion 42 made of a conductive layer such as Au, Ag, and Pd to which the input terminal 30 (30a, 30b), the output terminal 40 (40a, 40b), and the light receiving element 20 are bonded.

  The light emitting element 10 is bonded onto the light receiving element 20 by an adhesive layer 34. After the wire bonding, a resin molded body 70 is provided so as to cover the light emitting element 10, the light receiving element 20, the conductive layer, and the insulating substrate 60. FIG. 7A is a schematic plan view before the resin molded body 70 is provided. The insulating substrate 60 can be a glass epoxy material, a ceramic material, or the like. It is preferable that the resin molded body 70 is light-shielding because malfunction can be further reduced by ambient light.

  The input terminal 30 and the output terminal 40 can be conductive layers provided continuously on the upper surface 60a, the lower surface 60b, and the side surface 60c of the insulating substrate 60. In this case, for example, a recess may be provided on the side surface 60c of the insulating substrate 60, and a conductive layer may be provided on the surface to form a solder fret. The lower surfaces of the input terminal 30 and the output terminal 40 are exposed from the resin molding 70 and can be bonded to the mounting substrate. That is, the second embodiment can be an optical coupling device having four terminals 30a, 30b, 40a, 40b, for example, as shown in FIG. 7C.

  The optical coupling device assembled on the insulating substrate 60 does not require bending of the lead frame or lead cutting, and only one resin layer is required, so that mass productivity is high. Further, it is easy to reduce the thickness.

  The light receiving element 20 may include a control circuit 28, for example. The control circuit 28 gate-drives MOSFETs (M1, M2) connected in a source-common manner by the photovoltaic power of the photodiode array 20a. When an AC load is connected between the first lead 40a and the second lead 40b of the output terminal 40 connected to the drain, a continuous sine wave can be output while maintaining low loss as in the mechanical relay. it can.

  The optical coupling device having the configuration shown in FIG. 7C can be called a photorelay, and can be used for many fax modems, integrated circuit testers, and the like.

  Note that the light receiving element 20 (including the control circuit 28) and the MOSFETs (M1, M2) in FIG. The one-chip IC can be bonded to the die pad portion 42.

  According to the first and second embodiments, it is possible to provide an optical coupling device that generates a photovoltaic power, and that can be easily reduced in thickness and mounting area. Such an optical coupling device can be used for an inverter air conditioner or an integrated circuit tester.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Light emitting element, 11 Support substrate, 11a 1st surface, 11b 2nd surface, 12 Light emitting layer, 14 (1st light emitting element) 1st electrode, 15 (2nd light emitting element) 2nd electrode, 18 Light-emitting surface , 20 Light receiving element, 20a Photodiode array, 20b Metal wiring part, 22 Light receiving surface, 24 First electrode (for light receiving element), 26 Second electrode (for light receiving element), 30 Input terminal, 34 Adhesive layer, 40 Output terminal, 70 resin molding, M1, M2 MOSFET, G emission light

Claims (4)

A substrate having a first surface including a light emitting surface and a second surface opposite to the first surface, a semiconductor laminate including a light emitting layer provided on the second surface of the substrate, and A light emitting device having first and second electrodes provided on the surface of the semiconductor laminate opposite to the substrate;
A light receiving surface provided opposite to the light emitting element and formed by connecting a plurality of pn junctions in series, and a light receiving surface provided on the light receiving surface side and connected to a pn junction at one end of the plurality of pn junctions. A light receiving element having a third electrode and a fourth electrode connected to the pn junction at the other end of the plurality of pn junctions;
A resin molding that covers the light emitting element and the light receiving element and has a light shielding property;
With
The light receiving surface is included in the second electrode in plan view ,
The second electrode is an optical coupling device that covers an upper part of the light emitting layer and reflects most of emitted light from the light emitting layer toward the second electrode toward the light emitting surface .
Further comprising a MOSFET,
The optical coupling device according to claim 1, wherein the MOSFET has a gate connected to the third electrode and a source connected to the fourth electrode.   3. The optical coupling device according to claim 2, wherein the MOSFET includes two MOSFETs connected by a source common. The plurality of pn junctions are connected in series by a metal wiring portion,
Among the plurality of pn junctions, the area of the pn junction of the outer peripheral portion of the light receiving surface is greater than the area of the inner pn junction than the outer peripheral portion, the light according to any one of claims 1 to 3 Coupling device.

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