Reflection type optical semiconductor device

Abstract

To provide a reflection type optical semiconductor device capable of obtaining precise detection signals without generating a current due to leakage current or short circuit.SOLUTION: In a reflection type optical semiconductor device, a light-emitting element chip 1 having a light-emitting element, and a light-receiving element chip 2 having a light-receiving element and a through hole 9 are mounted to a conductive chip mounting part 31 of a mounting member 3 while the light-emitting element chip 1 is arranged in the through hole 9. The light-emitting element chip 1 is mounted, so that light-emitting element electrodes 4 are respectively arranged on a light-emitting face and a light-emitting element chip mounting face, and the light-emitting element electrode 4 arranged on the light-emitting element chip mounting face is connected to the chip mounting part 31 by a conductive adhesion member 11. The light-receiving element chip 2 is mounted, while the light-receiving element electrodes are arranged on a light-receiving face, respectively, the light-receiving element chip mounting face and an inner wall of the through hole 9 are covered by an insulation film 14, and the light-receiving element chip mounting face is adhered to the chip mounting part 31 by an adhesion member 12 via the insulation film 14 and insulated from the chip mounting part 31.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a reflective optical semiconductor device that is composed of a light-emitting element chip having a light-emitting element and a light-receiving element chip having a light-receiving element. [Background technology]

[0002] For example, a reflective optical semiconductor device used in a reflective encoder or the like is composed of a light-emitting element chip equipped with a light-emitting element and a light-receiving element chip equipped with a light-receiving element, and is configured so that light emitted from the light-emitting element is reflected by a reflector arranged opposite the reflective optical semiconductor device and enters the light-receiving element to obtain a detection signal.

[0003] A reflective optical semiconductor device has a configuration in which a light-emitting element chip and a light-receiving element chip having a through hole in which the light-emitting element chip is disposed are mounted on a die pad of a printed wiring board (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-121593 A Summary of the Invention [Problem to be solved by the invention]

[0005] Fig. 5 is an explanatory diagram showing an example of a reflective optical semiconductor device, and shows an example of a reflective optical semiconductor device 300 having a configuration in which a light emitting element chip 1 and a light receiving element chip 2 are mounted on a mounting member 3. Fig. 6 is a schematic cross-sectional view explaining the reflective optical semiconductor device shown in Fig. 5, and corresponds to a cross-sectional view in the left-right direction of the drawing that passes through the centers of the light emitting element chip 1, the wiring 10 for the light emitting element, and the lead terminal 32 connected to the wiring 10 for the light emitting element of the reflective optical semiconductor device 300 shown in Fig. 5.

[0006] A light-emitting element constituted by, for example, a light-emitting diode is disposed on the light-emitting element chip 1. A light-emitting element electrode 4 is disposed on each of the light-emitting surface on the upper surface of the light-emitting element chip 1 and the mounting surface on the lower surface of the light-emitting element chip 1, and the light-emitting element electrode 4 on the light-emitting surface is connected to the cathode of the light-emitting diode, and the light-emitting element electrode 4 on the mounting surface is connected to the anode of the light-emitting diode. A light-emitting unit 5 that emits light is disposed on the light-emitting surface.

[0007] A light receiving element array 7 consisting of a plurality of light receiving elements 6 is arranged on the light receiving surface on the upper surface of the light receiving element chip 2. The light receiving elements 6 can be composed of, for example, photodiodes. The cathode or anode of the photodiode is connected to a light receiving element electrode 8 arranged on the light receiving surface of the light receiving element chip 2 by wiring or the like (not shown). In addition, the light receiving element chip 2 has a through hole 9 arranged in the center, and wiring 10 for a light emitting element is arranged on the light receiving surface.

[0008] The light emitting element chip 1 and the light receiving element chip 2 are mounted on a mounting member 3. The mounting member 3 includes a chip mounting portion 31 and lead terminals 32, and may be formed of, for example, a printed wiring board or a lead frame. The light emitting element chip 1 and the light receiving element chip 2 are mounted on the chip mounting portion 31. Reference numeral 33 denotes a resin filled between the chip mounting portion 31 and the lead terminals 32.

[0009] The light-emitting element chip 1 is mounted on the chip mounting section 31 by connecting the light-emitting element electrode 4 arranged on the mounting surface to the upper surface of the chip mounting section 31 with a conductive adhesive member 11 made of, for example, silver paste. In the example shown in Figures 5 and 6, a part of the chip mounting section 31 functions as a lead terminal connected to the anode of the light-emitting diode.

[0010] The light receiving element chip 2 is mounted on the chip mounting portion 31 by placing the light emitting element chip 1 in the through hole 9 and adhering its lower mounting surface to the upper surface of the chip mounting portion 31 with an insulating adhesive member 12 made of, for example, an epoxy resin containing a filler.

[0011] The light-emitting element electrode 4 on the light-emitting surface of the light-emitting element chip 1 and the light-emitting element wiring 10 arranged on the light-receiving surface of the light-receiving element chip 2 are connected by metal wires 13. The light-receiving element electrode 8 on the light-receiving surface of the light-receiving element chip 2 and the lead terminal 32, and the light-emitting element wiring 10 and the lead terminal 32 are also connected by metal wires 13.

[0012] In the reflective optical semiconductor device 300 thus configured, the light receiving chip 2 is mounted on the mounting member 3 as follows. First, the insulating adhesive member 12 in a paste form is applied on the chip mounting portion 31 of the mounting member 3 in a size narrower than the size of the light receiving chip 2. Next, a load is applied so that the light receiving surface is not inclined, and the light receiving chip 2 is placed on the insulating adhesive member 12. By applying a load to the light receiving chip 2 in this manner, the insulating adhesive member 12 spreads without any gaps between the light receiving chip 2 and the chip mounting portion 31. Thereafter, the insulating adhesive member 12 is hardened, and the light receiving chip 2 is mounted on the chip mounting portion 31. Here, if the insulating adhesive member 12 does not spread without any gaps between the light receiving chip 2 and the chip mounting portion 31 and there is a portion between the light receiving chip 2 and the chip mounting portion 31 where the insulating adhesive member 12 does not exist, a leak current may occur between the light receiving chip 2 and the chip mounting portion 31. In addition, the insulating adhesive material 12 has internal stress due to shrinkage associated with hardening, and when temperature changes occur due to the passage of electricity during the manufacturing process and operation, cracks may occur in the resin in contact with the filler in the insulating adhesive material 12, causing leakage current between the light receiving element chip 2 and the chip mounting portion 31, and in some cases, a short circuit may occur.

[0013] Furthermore, if the conductive adhesive member 11 that connects the light-emitting element electrode 4 of the light-emitting element chip 1 to the chip mounting portion 31 is present in the vicinity of the light-receiving element chip 2, a leakage current may occur between the light-emitting element chip 1 and the light-receiving element chip 2, and in some cases a short circuit may occur.

[0014] When such a leakage current or current due to a short circuit occurs, it cannot be distinguished from the detection signal of the reflective optical semiconductor device 300, which causes a problem that an accurate detection signal cannot be obtained from the reflective optical semiconductor device 300.

[0015] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a reflective optical semiconductor device that is free from leakage current or current due to short circuit and capable of obtaining an accurate detection signal. [Means for solving the problem]

[0016] A reflective optical semiconductor device according to one embodiment of the present invention is a reflective optical semiconductor device in which a light-emitting element chip having a light-emitting element and a light-receiving element chip having a light-receiving element and a through hole are mounted on a conductive chip mounting portion of a mounting member by disposing the light-emitting element chip in the through hole of the light-receiving element chip, wherein the light-emitting element chip has light-emitting element electrodes disposed on its light-emitting surface and its light-emitting element chip mounting surface, respectively, and the light-emitting element electrode disposed on the light-emitting element chip mounting surface is connected to the chip mounting portion by a conductive adhesive member and mounted, and the light-receiving element chip has a light-receiving element electrode disposed on its light-receiving surface, the light-receiving element chip mounting surface and the inner wall surface of the through hole are covered with an insulating film, and the light-receiving element chip mounting surface is adhered to the chip mounting portion by an adhesive member via the insulating film, and is mounted insulated from the chip mounting portion. Effect of the Invention

[0017] According to the reflective optical semiconductor device of the present invention, the mounting surface of the light-receiving element chip and the inner wall surface of the through hole are covered with an insulating film, thereby eliminating the generation of current due to leakage current or short circuit and making it possible to obtain an accurate detection signal. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is an explanatory diagram of a reflective optical semiconductor device (embodiment 1) according to one embodiment of the present invention. [Diagram 2] 2 is a schematic cross-sectional view of the reflective optical semiconductor device of FIG. 1. [Diagram 3]FIG. 4 is a schematic cross-sectional view of a reflective optical semiconductor device (embodiment 2) according to another embodiment of the present invention. [Figure 4] 4 is a partially enlarged view of the reflective optical semiconductor device of FIG. 3. [Diagram 5] FIG. 1 is an explanatory diagram showing an example of a reflective optical semiconductor device according to a related art; [Figure 6] 6 is a schematic cross-sectional view of the reflective optical semiconductor device of FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Next, the embodiments of the reflective optical semiconductor device of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments, and the members, materials, etc. described below can be modified in various ways within the scope of the present invention. Also, in the drawings, the same reference numerals indicate the same or equivalent items, and the size and positional relationship between each component are for convenience and may not strictly reflect the actual situation.

[0020] (Embodiment 1) First, a first embodiment of the reflective optical semiconductor device of the present invention will be described. Fig. 1 is an explanatory diagram of the first embodiment of the reflective optical semiconductor device of the present invention, and Fig. 2 is a schematic cross-sectional view of the reflective optical semiconductor device of Fig. 1, which corresponds to a cross-sectional view in the left-right direction of the drawing passing through the centers of the light-emitting element chip 1, the wiring 10 for the light-emitting element, and the lead terminal 32 connected to the wiring 10 for the light-emitting element of the reflective optical semiconductor device 100 shown in Fig. 1. As shown in Figs. 1 and 2, in the reflective optical semiconductor device 100 of this embodiment, the light-emitting element chip 1 and the light-receiving element chip 2 are mounted on a mounting member 3.

[0021] A light-emitting element constituted by, for example, a light-emitting diode is disposed on the light-emitting element chip 1. A light-emitting element electrode 4 is disposed on each of the light-emitting surface on the upper surface of the light-emitting element chip 1 and the mounting surface (light-emitting element chip mounting surface) on the lower surface of the light-emitting element chip 1, and the light-emitting element electrode 4 on the light-emitting surface is connected to the cathode of the light-emitting diode, and the light-emitting element electrode 4 on the mounting surface is connected to the anode of the light-emitting diode. A light-emitting unit 5 that emits light is disposed on the light-emitting surface.

[0022] A light receiving element array 7 consisting of a plurality of light receiving elements 6 is arranged on the light receiving surface on the upper surface of the light receiving element chip 2. The light receiving elements 6 can be composed of, for example, photodiodes. The cathode or anode of the photodiode is connected to a light receiving element electrode 8 arranged on the light receiving surface of the light receiving element chip 2 by wiring or the like (not shown). In addition, the light receiving element chip 2 has a through hole 9 arranged in the center, and wiring 10 for a light emitting element is arranged on the light receiving surface.

[0023] Furthermore, the light-receiving element chip 2 of this embodiment is configured such that the mounting surface (light-receiving element chip mounting surface) on the lower surface and the inner wall surface of the through-hole 9 are covered with an insulating film 14 made of, for example, silicon dioxide. This insulating film 14 is formed to a thickness such that no leakage current or current due to short circuit occurs between the light-receiving element chip 2 and the chip mounting portion 31 even if there is a portion between the light-receiving element chip 2 and the chip mounting portion 31 where the insulating adhesive member 12 does not exist or even if a crack occurs in the insulating adhesive member 12.

[0024] As shown in FIG. 2, the light-emitting element chip 1 is mounted by connecting the light-emitting element electrode 4 arranged on the mounting surface to the conductive chip mounting portion 31 with the conductive adhesive member 11. The mounting surface and the inner wall surface of the through hole 9 of the light-receiving element chip 2 are covered with an insulating film 14, and the light-receiving element chip 2 is mounted by adhering it to the conductive chip mounting portion 31 on which the light-emitting element chip 1 is mounted with the insulating adhesive member 12 via the insulating film 14. For example, the insulating adhesive member 12 may be an epoxy resin to which a filler is added to enhance heat resistance and thermal conductivity. If the insulating adhesive member 12 containing the filler is used for adhesion as described above, there is a risk that a crack will occur in the insulating adhesive member 12 between the mounting surface of the light-receiving element chip 2 where the filler is present and the upper surface of the chip mounting portion 31, causing a leak current or a current due to a short circuit. However, in the reflective optical semiconductor device 100 of this embodiment, the mounting surface of the light-receiving element chip 2 and the inner wall surface of the through hole 9 are covered with the insulating film 14, so that no leak current or current due to a short circuit will occur between the light-receiving element chip 2 and the chip mounting portion 31. Even if there is a portion between the light receiving chip 2 and the chip mounting portion 31 where the insulating adhesive member 12 is not present, no leakage current or current due to short circuit will occur between the light receiving chip 2 and the chip mounting portion 31. The insulating film 14 covering the inner wall surface of the through hole 9 is integrated with the insulating film covering the mounting surface of the light receiving chip 2, and is formed so as to cover the inner wall surface continuously from the mounting surface without any gaps, and is formed to a thickness that does not generate leakage current or current due to short circuit between the light emitting element chip 1 and the light receiving element chip 2. Note that since leakage current and current due to short circuit occurring between the light emitting element chip 1 and the light receiving element chip 2 flow through the conductive adhesive member 11 for mounting the light emitting element chip 1 and the conductive chip mounting portion 31, it is not necessary to completely cover the entire inner wall surface of the through hole 9 from the light receiving surface of the light receiving chip 2 to the mounting surface with the insulating film 14, and it is sufficient to cover the area where leakage current and current due to short circuit can be suppressed by covering with the insulating film 14. As a result, it is possible to obtain an accurate detection signal from the reflective optical semiconductor device 100.

[0025] Furthermore, since the reflective optical semiconductor device 100 of this embodiment can mount the light-emitting element chip 1 and the light-receiving element chip 2 on a single conductive chip mounting portion 31, it is preferable that an inexpensive lead frame can be used as the mounting member 3.

[0026] The light emitting element electrode 4 on the light emitting surface of the light emitting element chip 1 and the light emitting element wiring 10 arranged on the light receiving surface of the light receiving element chip 2 are connected by a metal wire 13. The light receiving element electrode 8 on the light receiving surface of the light receiving element chip 2 and the lead terminal 32, and the light emitting element wiring 10 and the lead terminal 32 are also connected by metal wires 13. Although not shown in Figures 1 and 2, the metal wire 13 connecting either the light receiving element electrode 8 or the light emitting element wiring 10 to the lead terminal 32 may be configured to be sealed with, for example, epoxy resin or the like.

[0027] (Embodiment 2) Next, a second embodiment of the reflective optical semiconductor device of the present invention will be described. FIG. 3 is a schematic cross-sectional view of the second embodiment of the reflective optical semiconductor device of the present invention, which corresponds to FIG. 2 described in the first embodiment. FIG. 4 is a partially enlarged view of the reflective optical semiconductor device of FIG. 3, which illustrates the periphery of the through-hole. As in FIGS. 1 and 2 described in the first embodiment, the reflective optical semiconductor device 200 of this embodiment also has a light-emitting element chip 1 and a light-receiving element chip 2A mounted on a mounting member 3. The reflective optical semiconductor device 200 of this embodiment is different from the reflective optical semiconductor device 100 described in the first embodiment in the configuration of the insulating film 14A of the light-receiving element chip 2A and the mounting structure for mounting the light-emitting element chip 1 and the light-receiving element chip 2A on the chip mounting portion 31. The differences will be described in detail below.

[0028] First, the configuration of the insulating film 14A will be described. As shown in Figures 3 and 4, the light receiving element chip 2A of this embodiment is configured such that the mounting surface (light receiving element chip mounting surface) on the lower surface, the inner wall surface of the through hole 9, and the outer circumferential wall surface are covered with an insulating film 14A made of, for example, silicon dioxide. The insulating film 14A covering the mounting surface of the light receiving element chip 2A and the inner wall surface of the through hole 9 is formed to a thickness such that no leakage current or current due to short circuit occurs between the light receiving element chip 2A and the chip mounting part 31 and between the light emitting element chip 1 and the light receiving element chip 2A, like the insulating film 14 described in the above embodiment 1.

[0029] Furthermore, the insulating film 14A covering the outer peripheral wall surface of the light receiving element chip 2A is integrated with the insulating film 14A covering the mounting surface of the light receiving element chip 2A and the inner wall surface of the through hole 9, is formed so as to cover the mounting surface to the outer peripheral wall surface continuously and without any gaps, and is formed to a thickness that prevents leakage current or current due to short circuit from occurring between the light receiving element chip 2A and the chip mounting part 31. The insulating film 14A covering the outer peripheral wall surface of the light receiving element chip 2A does not need to completely cover the entire outer peripheral wall surface either, and may be configured to cover only an area where leakage current or current due to short circuit can be suppressed from occurring between the light receiving element chip 2A and the chip mounting part 31 by covering with the insulating film 14A.

[0030] As described above, in the reflective optical semiconductor device 200 of this embodiment, the mounting surface of the light-receiving element chip 2A, the inner wall surface of the through hole 9, and the outer circumferential wall surface are covered with the insulating film 14A, and a mounting structure is applied in which the light-receiving element chip 2A and the chip mounting portion 31 are bonded with a conductive adhesive member 11A. The mounting structure of this embodiment will be described below.

[0031] In the reflective optical semiconductor device 200 of this embodiment, the light-emitting element chip 1 is mounted by connecting the light-emitting element electrode 4 arranged on the mounting surface to the conductive chip mounting part 31 with the conductive adhesive member 11A. The mounting surface, the inner wall surface of the through hole 9, and the outer peripheral wall surface of the light-receiving element chip 2A are covered with the insulating film 14A, and the light-receiving element chip 2A is bonded to the conductive chip mounting part 31 on which the light-emitting element chip 1 is mounted by the conductive adhesive member 11A via the insulating film 14A. The conductive adhesive member 11A may be, for example, an epoxy resin to which a filler is added to enhance heat resistance and thermal conductivity. In the reflective optical semiconductor device 200 of this embodiment, the mounting surface of the light-receiving element chip 2A, the inner wall surface of the through hole 9, and the outer peripheral wall surface are covered with the insulating film 14A, so that no leakage current or current due to short circuit occurs between the light-receiving element chip 2A and the chip mounting part 31. In addition, even if the light receiving element chip 2A and the light emitting element chip 1 are mounted with the same conductive adhesive member 11A, the insulating film 14A is provided on the inner wall surface of the through hole 9 of the light receiving element chip 2A as shown in FIG. 4, so that no leakage current or the like occurs between the light emitting element chip 1 and the light receiving element chip 2A. Furthermore, even if the resin constituting the conductive adhesive member 11A forms a fillet 15 on the inner wall surface and the outer peripheral wall surface of the through hole 9 of the light receiving element chip 2A, the inner wall surface and the outer peripheral wall surface of the through hole 9 of the light receiving element chip 2A are covered with the insulating film 14A, so that the insulating film 14A is provided so as to cover the area where the fillet 15 is formed, so that no leakage current or current due to short circuit occurs between the light receiving element chip 2A and the chip mounting part 31. As a result, it is possible to obtain an accurate detection signal from the reflective optical semiconductor device 200.

[0032] In addition, the reflective optical semiconductor device 200 of this embodiment is also capable of mounting the light-emitting element chip 1 and the light-receiving element chip 2A on a single conductive chip mounting portion 31, and is preferable because an inexpensive lead frame can be used as the mounting member 3.

[0033] Furthermore, in this embodiment, the connection between the light receiving element chip 2A and the chip mounting portion 31 can be performed by the conductive adhesive member 11A as shown in Figures 3 and 4, and there is no need to use an insulating adhesive member. Here, the conductive adhesive member for mounting the light emitting element chip 1 and the conductive adhesive member for mounting the light receiving element chip 2A do not necessarily need to be the same conductive adhesive member. For example, in order to align the height position of the light emitting surface of the light emitting element chip 1 and the height position of the light receiving surface of the light receiving element chip 2A in the same direction, separate conductive adhesive members with adjusted thicknesses can be used. Of course, the connection between the light receiving element chip 2A and the chip mounting portion 31 may be performed by using an insulating adhesive member as described in embodiment 1.

[0034] Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiments 1 and 2. For example, the insulating film 14 and the like are not limited to silicon dioxide. In addition, the mounting member is not limited to a lead frame, and a chip mounting portion can be formed on an organic substrate.

[0035] (summary) (1) One embodiment of the reflective optical semiconductor device of the present invention is a reflective optical semiconductor device in which a light-emitting element chip including a light-emitting element and a light-receiving element chip including a light-receiving element and a through hole are mounted on a conductive chip mounting portion of a mounting member by disposing the light-emitting element chip in the through hole of the light-receiving element chip, wherein the light-emitting element chip has light-emitting element electrodes disposed on its light-emitting surface and its light-emitting element chip mounting surface, respectively, and the light-emitting element electrode disposed on the light-emitting element chip mounting surface is connected to the chip mounting portion by a conductive adhesive member and mounted, and the light-receiving element chip has a light-receiving element electrode disposed on its light-receiving surface, the light-receiving element chip mounting surface and the inner wall surface of the through hole are covered with an insulating film, and the light-receiving element chip mounting surface is adhered to the chip mounting portion by an adhesive member via the insulating film, and is mounted insulated from the chip mounting portion.

[0036] According to the reflective optical semiconductor device of (1) above, the mounting surface of the light-receiving element chip and the inner wall surface of the through hole are covered with an insulating film, thereby eliminating the generation of current due to leakage current or short circuit and making it possible to obtain an accurate detection signal.

[0037] (2) According to another embodiment, in the reflective optical semiconductor device of (1) above, the light-receiving element chip has a light-receiving element chip mounting surface, an outer wall surface, and an inner wall surface of the through hole covered with an insulating film.

[0038] According to the reflective optical semiconductor device of (2) above, the mounting surface of the light-receiving element chip, the inner wall surface of the through hole, and the outer wall surface are covered with an insulating film, thereby eliminating leakage current flowing through the outer wall surface and current due to short circuit, and making it possible to obtain an accurate detection signal.

[0039] (3) According to still another embodiment, in the reflective optical semiconductor device of (1) or (2) above, the mounting member is a lead frame. [Explanation of symbols]

[0040] 100, 200, 300 Reflective optical semiconductor device 1 Light emitting element chip 2. 2A photodetector chip 3 Mounting materials 31 Chip mounting section 32 Lead terminal 33 Resin 4 Light emitting element electrode 5 Light emitting part 6 Photodetector 7 Photodetector array 8 Photodetector electrode 9 Through holes 10 Light emitting element wiring 11, 11A Conductive adhesive material 12 Insulating adhesive material 13 Metal Wire 14, 14A Insulating film 15 Fillet

Claims

1. A reflective optical semiconductor device in which a light-emitting element chip including a light-emitting element and a light-receiving element chip including a light-receiving element and a through hole are mounted on a conductive chip mounting portion of a mounting member by disposing the light-emitting element chip in the through hole of the light-receiving element chip, The light-emitting element chip includes: A light emitting element electrode is disposed on the light emitting surface and the light emitting element chip mounting surface, respectively; the light-emitting element electrode disposed on the light-emitting element chip mounting surface is connected to the chip mounting portion by a conductive adhesive member and mounted thereon; The light receiving element chip includes: A light receiving element electrode is disposed on the light receiving surface, a light-receiving element chip mounting surface and an inner wall surface of the through hole are covered with an insulating film; The light receiving element chip mounting surface is bonded to the chip mounting portion by an adhesive material via the insulating film, and is mounted insulated from the chip mounting portion. Reflective optical semiconductor device.

2. The light receiving element chip includes: the light-receiving element chip mounting surface, the outer peripheral wall surface, and the inner wall surface of the through hole are covered with an insulating film; 2. The reflective optical semiconductor device according to claim 1.

3. The mounting member is a lead frame.

3. The reflective optical semiconductor device according to claim 1.

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