Light detection device

Abstract

To provide a light detection device capable of appropriately suppressing breakage while suppressing a protrusion of an underfill material.SOLUTION: A light detection device 1 includes a wiring board 2, a light-receiving board 3 which is disposed on a surface 2a of the wiring board 2, a plurality of conductive members 6 electrically connecting a plurality of pad electrodes 21 and a plurality of photodiodes 31, and an underfill material 4 which is disposed between the wiring board 2 and the light-receiving board 3. In a view in a Z direction, an outer edge E of the surface 2a of the wiring board 2 has a pair of long side parts E1 and E1 which are opposed to each other and a pair of short side parts E2 and E2 and in each of the pair of long side parts E1 and E1 and the pair of short side parts E2 and E2 of the wiring board 2, a plurality of recesses 22 is disposed which is opened on the surface 2a and extends from the outer edge E toward the inside of the wiring board 2 in the view in the Z direction. An inner side face 22c of each of the plurality of recesses 22 is formed in a shape which is tapered toward the inside of the wiring board 2 in the view in the Z direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a light detection device. [Background technology]

[0002] There is known a photodetector that includes a wiring board, a light receiving board (light receiving element array board) arranged on the wiring board, and a conductive member that electrically connects the wiring board and the light receiving board (see, for example, Patent Document 1). For example, in a radiation detection unit used in a CT scanner or the like, a plurality of such photodetectors may be arranged with reduced spacing between them. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-000291 Summary of the Invention [Problem to be solved by the invention]

[0004] In the photodetector described above, an underfill material may be disposed between the wiring board and the light-receiving board to protect the conductive member electrically connecting the two. During the manufacture of such a photodetector, the underfill material may overflow from between the wiring board and the light-receiving board when filling the gap between the wiring board and the light-receiving board or when heating the filled underfill material. In this case, the overflowing underfill material may interfere with the other components, making it difficult to arrange multiple photodetectors with reduced spacing between them. Alternatively, to resolve the above issue, process workers may need to wipe off the overflowing underfill material, which may increase the labor required by the process workers. Furthermore, if an underfill material is used as described above, if a void (cavity) forms between the underfill material and the wiring board, the air in the void may expand when the photodetector is exposed to high temperatures, potentially causing the underfill material to peel off and ultimately damaging the photodetector.

[0005] An object of the present disclosure is to provide a light detection device that can effectively prevent damage while suppressing the overflow of underfill material. [Means for solving the problem]

[0006] a light-receiving substrate disposed on the first surface of the wiring board and including a plurality of light-receiving elements arranged two-dimensionally to correspond to the plurality of pad electrodes; a plurality of conductive members electrically connecting the plurality of pad electrodes to the plurality of light-receiving elements; and an underfill material disposed between the wiring board and the light-receiving substrate, wherein, when viewed from a first direction in which the wiring board and the light-receiving substrate face each other, an outer edge of the first surface of the wiring board has at least a pair of sides facing each other, and each of the pair of sides of the wiring board has a plurality of recesses that open to the first surface and extend from the outer edge toward an inside of the wiring board when viewed from the first direction, and an inner surface of each of the plurality of recesses opposite the outer edge is formed in a shape that tapers toward the inside of the wiring board when viewed from the first direction.

[0007] According to the photodetector described in [1] above, a portion of the underfill material disposed (filled) between the wiring substrate and the light-receiving substrate can be appropriately guided into the recesses provided on each of a pair of sides. This effectively prevents the underfill material from spilling out from the side of the photodetector. Furthermore, by providing multiple recesses on at least each of a pair of opposing sides, the stress balance of the wiring substrate can be improved compared to when recesses are provided on only one side. Furthermore, the inner surface of each of the multiple recesses is tapered toward the inside of the wiring substrate when viewed from the first direction. This improves adhesion between the portion of the underfill material disposed between the wiring substrate and the light-receiving substrate and the inner surface of the recess when the portion of the underfill material spills out into the recess during manufacturing of the photodetector. As a result, it is possible to effectively prevent voids from forming between the portion of the underfill material flowing into the recess and the inner surface of the recess. As a result, the photodetector described above effectively prevents damage while preventing the underfill material from spilling out.

[0008] The photodetector may be [2] "the photodetector according to [1], wherein the wiring substrate has a bottom surface that closes the second surface side of each of the plurality of recesses." According to the above configuration, the underfill material that flows into the recesses can be blocked by the bottom surface of the recesses, thereby preventing the underfill material from flowing around (spilling out) toward the second surface side of the wiring substrate. Furthermore, by providing a bottom surface for the recesses, the strength of the wiring substrate can be improved compared to when a recess is formed that penetrates from the first surface to the second surface. Therefore, according to the above configuration, spilling out of the underfill material and damage to the photodetector can be more effectively prevented.

[0009] The photodetector may be [3] "the photodetector according to [1] or [2], wherein the inner surface of each of the plurality of recesses is formed into a curved surface that is convex toward the inside of the wiring substrate when viewed from the first direction." According to the above configuration, when a portion of the underfill material disposed between the wiring substrate and the light-receiving substrate moves and protrudes into the recess, the portion of the underfill material can be brought into smooth contact with the inner surface of the recess, compared to when the inner surface of the recess is formed into an angular shape when viewed from the first direction, thereby further improving adhesion between the portions. As a result, the generation of voids between the portion of the underfill material flowing into the recess and the inner surface of the recess can be more effectively suppressed.

[0010] The photodetector may be [4] "the photodetector according to any one of [1] to [3], wherein the plurality of pad electrodes include two pad electrodes adjacent to each other in a second direction along the side portion, the plurality of recesses include a first recess located between the two pad electrodes in the second direction, and the inner surface of the first recess is located closer to the outer edge than a first line connecting the centers of the two pad electrodes when viewed from the first direction." According to the above configuration, by tapering the inner end of the recess (first recess) toward the inside of the wiring substrate and providing the first recess so as not to extend beyond the first line connecting the centers of the two adjacent pad electrodes, an increase in the arrangement interval (pitch) between the two adjacent pad electrodes can be suppressed. Therefore, while providing a plurality of recesses for suppressing overflow of the underfill material as described above, a decrease in the integration rate of the pad electrodes on the wiring substrate can be suppressed.

[0011] The photodetector may be [5] "the photodetector according to [4], wherein the inner surface of the first recess reaches inside a second straight line connecting the outer edge ends of the two pad electrodes when viewed from the first direction." According to the above configuration, by extending the first recess as far inside the wiring board as possible while suppressing an increase in the arrangement interval (pitch) between two adjacent pad electrodes, it is possible to suitably ensure the volume of the first recess as an escape area for the underfill material.

[0012] The photodetector may be [6] "a photodetector according to any one of [1] to [5], wherein the plurality of pad electrodes include two pad electrodes adjacent to each other in the second direction along the side portion, the plurality of recesses include a first recess located between the two pad electrodes in the second direction, and the width of the first recess in the second direction is smaller than the shortest distance between the two pad electrodes in the second direction." According to the above configuration, even if the recess (first recess) is arranged so as to extend to some extent between two pad electrodes adjacent to each other in the second direction, it is possible to reliably prevent interference between the first recess and the two pad electrodes. As a result, the reliability (quality) of the photodetector can be improved.

[0013] The photodetector may be [7] "the photodetector according to [6], in which the width of the first recess is greater than the shortest distance between the first recess and at least one of the two pad electrodes." According to the above configuration, by arranging the first recess as close as possible to the pad electrode adjacent to the first recess, it is possible to suitably ensure the volume of the first recess as a place for the underfill material to escape.

[0014] The photodetector may be [8] "a photodetector according to any one of [1] to [7], in which, when each of the pair of side portions is equally divided into a first side region and a second side region, two or more of the recesses are provided in the first side region and two or more of the recesses are provided in the second side region." According to the above configuration, by providing a plurality (two or more) of recesses in each side region (first side region and second side region) obtained by equally dividing each side portion, it is possible to arrange a large number of recesses in an overall balanced arrangement. As a result, internal stress generated in the wiring board is evenly distributed, and deformation (breakage) of the wiring board due to the internal stress can be suitably suppressed.

[0015] The photodetector may be the photodetector according to [9] "in which the number of recesses provided in the first side region of one of the pair of sides, the number of recesses provided in the second side region of one of the pair of sides, the number of recesses provided in the first side region of the other of the pair of sides, and the number of recesses provided in the second side region of the other of the pair of sides are equal to one another." According to the above configuration, by providing the same number of recesses in each side region obtained by dividing each side into two equal parts, a large number of recesses can be arranged in a more balanced arrangement. As a result, internal stress generated in the wiring substrate can be more evenly distributed.

[0016] The photodetector may be

[10] "the photodetector according to [9], wherein the arrangement of the plurality of recesses on the wiring substrate, when viewed from the first direction, is symmetrical with respect to a line passing through the center of the wiring substrate and perpendicular to the pair of sides, and is also symmetrical with respect to a line passing through the center of the wiring substrate and parallel to the pair of sides." This configuration allows for a more balanced arrangement of multiple recesses. As a result, internal stress generated in the wiring substrate can be more evenly distributed.

[0017] The photodetector may be

[11] "a photodetector according to any one of [1] to

[10] , wherein the distance between the centers of adjacent recesses in the plurality of recesses is 0.5 mm or more and 2.5 mm or less." According to the above configuration, for example, when recesses and pad electrodes are arranged alternately, an increase in the pitch between the pad electrodes can be suppressed by setting the pitch between the recesses to 2.5 mm or less. On the other hand, by ensuring that the pitch between the recesses is at least a certain value (0.5 mm or more), the spacing between adjacent recesses is prevented from becoming too narrow, and the degree of freedom in arranging the pad electrodes to be arranged therebetween can be improved.

[0018] The photodetector device has a width of the recess in the second direction along the side of the side of the photodetector, which is 0.15 mm or more and 0.5 mm or less, a length of the recess in the direction perpendicular to the first direction and the second direction of the photodetector, which is 0.25 mm or more and 2.0 mm or less, and a volume of the recess of 0.018 mm. 3 More than 0.4mm 3 The photodetector may be the photodetector according to any one of [1] to

[11] , which is as follows: If the size of each recess (the size (length, width, and volume) when viewed from the first direction) is too small, the effect of allowing the underfill material to properly escape into the recess (i.e., the effect of suppressing the overflow of the underfill material) becomes insufficient. On the other hand, if the size of each recess is too large, a large amount of underfill material is likely to enter the recess when filling the underfill material, and as a result, there is a risk that the underfill material will not be sufficiently distributed throughout the entire space between the wiring board and the light-receiving board. By keeping the length, width, and volume of each recess within the above-mentioned ranges, the occurrence of the above-mentioned problems can be suitably suppressed. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide a light detection device that can effectively prevent damage while suppressing the overflow of underfill material. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view of a radiation detector including a photodetector according to an embodiment. [Figure 2] FIG. 2 is a bottom view of a portion of the light-receiving substrate shown in FIG. [Figure 3] FIG. 3 is a plan view of the wiring board shown in FIG. [Figure 4] Fig. 4(a) is a side view of the wiring board when viewed from the X direction, and Fig. 4(b) is a side view of the wiring board when viewed from the Y direction. [Figure 5] FIG. 5 is an enlarged view of a portion A of the wiring board shown in FIG. [Figure 6]FIG. 6 is a diagram showing a first example of the arrangement of a plurality of recesses. [Figure 7] FIG. 7 is a diagram showing a second example of the arrangement of a plurality of recesses. [Figure 8] Fig. 8(a) is a diagram showing a recess according to a first modified example, and Fig. 8(b) is a diagram showing a recess according to a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0022] [Radiation detector configuration] 1, radiation detector 10 includes photodetector 1, scintillator layer 11, a plurality of integrated circuit devices 12, a flexible printed circuit board 13, and a heat sink 14. In radiation detector 10, when radiation (e.g., gamma rays, X-rays, etc.) is incident on scintillator layer 11, scintillation light is generated in scintillator layer 11, and the scintillation light is detected by photodetector 1. Radiation detector 10 is used as a radiation imaging device, for example, in a medical radiation image diagnostic device, a non-destructive testing device, etc.

[0023] The light-detecting device 1 includes a wiring board 2, a light-receiving board 3, an underfill material 4, a plurality of conductive members 6, and a plurality of conductive members 7 (see FIG. 2). Hereinafter, the direction in which the wiring board 2 and the light-receiving board 3 face each other will be referred to as the Z direction (first direction), the direction perpendicular to the Z direction will be referred to as the X direction (second direction), and the direction perpendicular to the Z direction and the X direction will be referred to as the Y direction (second direction).

[0024] The wiring board 2 has a front surface 2a (first surface) and a back surface 2b (second surface) opposite to the front surface 2a. In this embodiment, the wiring board 2 is formed in a rectangular plate shape. A plurality of pad electrodes 21 are two-dimensionally arranged on the front surface 2a (see FIG. 3). The plurality of pad electrodes 21 are conductive and made of a metal such as copper or silver. The plurality of pad electrodes 21 include a plurality of pad electrodes 21a (see FIG. 3) electrically and physically connected to the plurality of conductive members 6 and a plurality of pad electrodes 21b (see FIG. 3) electrically and physically connected to the plurality of conductive members 7. The wiring board 2 is made of a ceramic material such as alumina (Al2O3) or aluminum nitride (AlN).

[0025] The light-receiving substrate 3 has a surface 3a and a back surface 3b opposite to the surface 3a. The light-receiving substrate 3 is mounted on the surface 2a of the wiring substrate 2 with the back surface 3b facing the surface 2a of the wiring substrate 2. The light-receiving substrate 3 has a plurality of light-receiving elements arranged two-dimensionally along the back surface 3b. In other words, the light-receiving substrate 3 is a light-receiving element array substrate in which a plurality of light-receiving elements are arranged in an array. As an example, the light-receiving elements are photodiodes 31 (see FIG. 2) that function as photoelectric conversion regions. The multiple photodiodes 31 are arranged two-dimensionally so as to correspond to the multiple pad electrodes 21 (i.e., so as to overlap each other in the Z direction). The light-receiving substrate 3 is, for example, a back-illuminated area sensor.

[0026] The plurality of conductive members 6, 7 electrically connect the wiring substrate 2 and the light-receiving substrate 3. The plurality of conductive members 6 are disposed between the plurality of pad electrodes 21a and the plurality of photodiodes 31, and electrically connect the plurality of pad electrodes 21a and the plurality of photodiodes 31. The plurality of conductive members 6 are provided so that one conductive member 6 corresponds to one pad electrode 21a. The plurality of conductive members 7 electrically connect the plurality of pad electrodes 21b to a cathode electrode (not shown) provided on the rear surface 3b of the light-receiving substrate 3, which will be described later. The plurality of conductive members 7 are provided so that one conductive member 7 corresponds to one pad electrode 21b. The conductive members 6, 7 are, for example, bump electrodes.

[0027] The underfill material 4 is disposed between the wiring substrate 2 and the light-receiving substrate 3. The underfill material 4 is a resin that hardens when subjected to a predetermined hardening process (for example, heating or exposure to ultraviolet light or the like). In this embodiment, the underfill material 4 is an underfill resin formed from a thermosetting resin that hardens when heated. The resin material of the underfill material 4 is, for example, an epoxy-based resin. The underfill material 4 fills the gap between the front surface 2a of the wiring substrate 2 and the back surface 3b of the light-receiving substrate 3, filling the spaces between adjacent conductive members 6 and 7. The underfill material 4 protects the multiple conductive members 6 and 7, thereby improving the reliability of the electrical connection between the wiring substrate 2 and the light-receiving substrate 3. In addition, the underfill material 4 functions as an adhesive layer that enhances the adhesive strength between the wiring substrate 2 and the light-receiving substrate 3, thereby improving the structural stability of the light-detecting device 1.

[0028] The scintillator layer 11 is disposed on the surface 3a of the light-receiving substrate 3. When viewed from the Z direction, the scintillator layer 11 is optically separated into individual photodiodes 31. The material of the scintillator layer 11 is, for example, LYSO when gamma rays are to be detected, and is, for example, CsI, GOS when X-rays are to be detected.

[0029] The multiple integrated circuit devices 12 are mounted on the back surface 2b of the wiring board 2. Each integrated circuit device 12 is electrically and physically connected to the wiring board 2 by multiple bump electrodes 12a. The multiple integrated circuit devices 12, for example, process electrical signals transmitted from the wiring board 2. The multiple integrated circuit devices 12 may control the operation of the light receiving substrate 3. The flexible printed circuit board 13 is electrically and physically connected to the wiring board 2 by multiple bump electrodes 13a. The flexible printed circuit board 13, for example, serves to output electrical signals transmitted from the wiring board 2 to the outside of the radiation detector 10 and to input electrical signals from the outside to the wiring board 2. The heat sink 14 is attached to the back surface 2b of the wiring board 2 in contact with the multiple integrated circuit devices 12. The heat sink 14 cools each integrated circuit device 12.

[0030] In the radiation detector 10, incident radiation is converted into scintillator light in the scintillator layer 11, and electrical signals corresponding to the intensity of the scintillator light are generated in the multiple photodiodes 31 included in the light-receiving substrate 3. The generated electrical signals are then transmitted to the wiring substrate 2 via the multiple conductive members 6 and multiple pad electrodes 21a. The electrical signals are transmitted to the integrated circuit devices 12 and the flexible printed circuit board 13 via the bump electrodes 12a, 13a, and are output from the flexible printed circuit board 13 to the outside of the radiation detector 10.

[0031] [Configuration of the light receiving board] 2, for example, the light-receiving substrate 3 includes an n-type semiconductor substrate 30 made of silicon. The thickness of the n-type semiconductor substrate 30 is, for example, 30 to 300 μm. The impurity concentration of the n-type semiconductor substrate 30 is, for example, 1×10 12 ~1×10 15 / cm 3 is.

[0032] A plurality of p-type regions 32 are formed in a portion of the n-type semiconductor substrate 30 along the rear surface 3b. The plurality of p-type regions 32 are arranged two-dimensionally with the X and Y directions being the column and row directions. The plurality of p-type regions 32 form a plurality of pn junction regions with the n-type semiconductor substrate 30. In the light-receiving substrate 3, the plurality of pn junction regions function as a plurality of photodiodes 31. The thickness of each p-type region 32 in the Z direction is, for example, 0.05 to 20 μm. The impurity concentration of each p-type region 32 is, for example, 1×10 13 ~1×10 20 / cm 3 is.

[0033] A plurality of high-concentration n-type regions 33 are formed in a portion of the n-type semiconductor substrate 30 along the back surface 3b. When viewed from the Z direction, each high-concentration n-type region 33 extends in a frame shape so as to surround each p-type region 32. The multiple high-concentration n-type regions 33 electrically isolate the multiple photodiodes 31 from one another, thereby suppressing the occurrence of crosstalk between adjacent photodiodes. The thickness of each high-concentration n-type region 33 in the Z direction is, for example, 0.1 to several tens of μm. The impurity concentration of each high-concentration n-type region 33 is, for example, 1×10 13 ~1×10 20 / cm 3 is.

[0034] A p-type region 34 is formed in a portion of the n-type semiconductor substrate 30 along the back surface 3b. When viewed from the Z direction, the p-type region 34 extends in a lattice pattern so as to pass between adjacent high-concentration n-type regions 33. The p-type region 34 forms a pn junction region with the n-type semiconductor substrate 30. The width of the p-type region 34 in the Z direction is, for example, 0.05 to 20 μm. The impurity concentration of the p-type region 34 is, for example, 1×10 13 ~1×10 20 / cm 3 is.

[0035] A plurality of conductive members 6 are formed on the back surface 3b of the light-receiving substrate 3. Each conductive member 6 is formed on an anode electrode (not shown) electrically connected to each p-type region 32 (photodiode 31). Each anode electrode is formed on the back surface of the n-type semiconductor substrate 30 and is located on each p-type region 32. When light is incident on each photodiode 31 from the front surface 3a side, carriers are generated in each photodiode 31, and a photocurrent generated by the generation of these carriers is output to the wiring substrate 2 via each conductive member 6.

[0036] A plurality of conductive members 7 are formed on the rear surface 3b of the light-receiving substrate 3. Each conductive member 7 is formed on a cathode electrode (not shown) electrically connected to a plurality of high-concentration n-type regions 33 and p-type regions 34. The cathode electrode is formed on the rear surface of the n-type semiconductor substrate 30 and extends in a lattice pattern so as to cover the plurality of high-concentration n-type regions 33 and p-type regions 34. The plurality of conductive members 7 are formed on a plurality of intersections of the cathode electrode extending in a lattice pattern. However, the plurality of conductive members 7 do not have to be formed on all intersections, but may be formed on a plurality of intersections at intervals of a predetermined number of intersections in both the X and Y directions (in this embodiment, at positions corresponding to a plurality of pad electrodes 21b shown in FIG. 3). Each conductive member 7 is electrically connected to a ground potential, for example, via the wiring substrate 2 (pad electrode 21b).

[0037] [Wiring board configuration] The configuration of the wiring board 2 will be described with reference to FIGS. 3 to 5. As shown in FIG. 3, in this embodiment, the wiring board 2 (surface 2a) is formed in a rectangular shape with the X direction as the short side direction and the Y direction as the long side direction when viewed from the Z direction. When viewed from the Z direction, the outer edge E of the surface 2a of the wiring board 2 has a pair of long sides E1, E1 (a pair of sides) facing each other and a pair of short sides E2, E2 (a pair of sides) facing each other. The pair of long sides E1, E1 are parallel to the Y direction and face each other in the X direction. The pair of short sides E2, E2 are parallel to the X direction and face each other in the Y direction. That is, in this embodiment, the Y direction is the long side direction along the long sides of the wiring board 2, and the X direction is the short side direction along the short sides of the wiring board 2.

[0038] 3, the plurality of pad electrodes 21 are two-dimensionally arranged on the surface 2a. In the present embodiment, as an example, the plurality of pad electrodes 21 includes a total of 512 (=32×16) pad electrodes 21a arranged in a grid pattern with 32 electrodes lined up along the long side E1 and 16 electrodes lined up along the short side E2, and a total of 32 (=8×4) pad electrodes 21b arranged in a grid pattern with 8 electrodes lined up along the long side E1 and 4 electrodes lined up along the short side E2. When viewed from the Z direction, the pad electrode 21b located outermost in the X direction among the plurality of pad electrodes 21b (i.e., the pad electrode 21b closest to the long side E1) is located more inward than the pad electrode 21a located outermost in the X direction among the plurality of pad electrodes 21a (i.e., the pad electrode 21a closest to the long side E1). Similarly, when viewed from the Z direction, the pad electrode 21b located outermost in the Y direction among the multiple pad electrodes 21b (i.e., the pad electrode 21b closest to the short side E2) is located more inside than the pad electrode 21a located outermost in the Y direction among the multiple pad electrodes 21a (i.e., the pad electrode 21a closest to the short side E2). Therefore, in this embodiment, the pad electrode 21a (the pad electrode 21a arranged along the outer edge E) among the multiple pad electrodes 21a whose positional relationship with the recess 22 described later matters.

[0039] 3, the distance p1 (pitch) between the centers of adjacent pad electrodes 21a in the Y direction (long side direction) is constant, and the distance p2 (pitch) between the centers of adjacent pad electrodes 21a in the X direction (short side direction) is also constant. In this embodiment, as an example, the distance p1 is slightly shorter than the distance p2. However, the distance p1 may be the same as the distance p2 or may be longer than the distance p2.

[0040] In this embodiment, each pad electrode 21b is formed in a circular shape when viewed from the Z direction. Furthermore, the remaining pad electrodes 21a, excluding the 32 pad electrodes 21a arranged along each short side E2, among the plurality of pad electrodes 21a, are also formed in a circular shape when viewed from the Z direction. Meanwhile, each of the 32 pad electrodes 21a arranged along each short side E2 has a shape in which a portion of the pad electrode 21a on the short side E2 side along which the pad electrode 21a is aligned is cut out in an arch shape when viewed from the Z direction. However, the shape of the plurality of pad electrodes 21 is not limited to the above example. For example, the 32 pad electrodes 21a arranged along each short side E2 may also be formed in a circular shape similar to the other pad electrodes 21a, 21b. Alternatively, the 64 pad electrodes 21a arranged along each long side E1 may be formed in the same shape as the 32 pad electrodes 21a arranged along each short side E2 (for example, a shape in which a portion of the pad electrode 21a on the long side E1 side along which each pad electrode 21a is aligned is cut out in an arched shape).

[0041] A plurality of recesses 22 are provided on each of the pair of long sides E1, E1 and the pair of short sides E2, E2 of the wiring board 2. In this embodiment, the recesses 22 are not provided at the corners of the wiring board 2 (surface 2a) when viewed from the Z direction. By not providing the recesses 22 at the corners of the wiring board 2 in this way, a decrease in the strength of the wiring board 2 is suppressed.

[0042] The plurality of recesses 22 (31 per side in this embodiment) provided on each long side E1 are arranged at equal intervals along the Y direction. The plurality of recesses 22 provided on the long side E1 and the plurality of pad electrodes 21a (32 in this embodiment) provided along the long side E1 are arranged alternately along the Y direction. More specifically, each recess 22 provided on the long side E1 is located between two pad electrodes 21a adjacent to each other along the long side E1 in the Y direction. In this embodiment, each recess 22 provided on the long side E1 is located exactly midway between two adjacent pad electrodes 21a. That is, the midway position in the Y direction between two adjacent pad electrodes 21a coincides with the center position in the Y direction of the recess 22 located between the two pad electrodes 21a.

[0043] The plurality of recesses 22 (15 per side in this embodiment) provided on each short side E2 are arranged at equal intervals along the X direction. The plurality of recesses 22 provided on the short side E2 and the plurality of pad electrodes 21a (16 in this embodiment) provided along the short side E2 are arranged alternately along the X direction. More specifically, each recess 22 provided on the short side E2 is located between two pad electrodes 21a adjacent to each other along the short side E2 in the X direction. In this embodiment, each recess 22 provided on the short side E2 is located exactly midway between two adjacent pad electrodes 21a. That is, the midpoint in the X direction between two adjacent pad electrodes 21a coincides with the center position in the X direction of the recess 22 located between the two pad electrodes 21a.

[0044] Each recess 22 is open to the front surface 2a and extends from the outer edge E toward the inside of the wiring board 2 when viewed from the Z direction. That is, each recess 22 provided on the long side E1 extends from the long side E1 (outer edge E) along the X direction toward the inside of the wiring board 2. Each recess 22 provided on the short side E2 extends from the short side E2 (outer edge E) along the Y direction toward the inside of the wiring board 2.

[0045] Fig. 4(a) is a diagram showing the side surface 2c of the wiring board 2 shown in Fig. 3 when viewed from the X direction. As shown in this figure, each recess 22 formed along the long side E1 opens to the side surface 2c. Fig. 4(b) is a diagram showing the side surface 2d of the wiring board 2 shown in Fig. 3 when viewed from the Y direction. As shown in this figure, each recess 22 formed along the short side E2 opens to the side surface 2d.

[0046] 3 and 4, each recess 22 has a slit (groove) shape that is open to the front surface 2a and the side surface (side surface 2c or side surface 2d) but does not penetrate to the back surface 2b in the Z direction. That is, the wiring board 2 has a bottom surface 22a that closes the back surface 2b side of each recess 22. The depth d of each recess 22 (the distance from the front surface 2a to the bottom surface 22a in the Z direction) is constant, and is, for example, 0.5 mm.

[0047] Fig. 5 is an enlarged view of a portion A along the short side E2 of the wiring board 2 shown in Fig. 3. The contents (configuration and effects) described below with reference to Fig. 5 also apply to the portion along the long side E1 of the wiring board 2 (i.e., the portion where the plurality of pad electrodes 21 and the plurality of recesses 22 along the long side E1 are alternately arranged in the Y direction as described above).

[0048] As shown in FIG. 5, each recess 22 has a pair of side surfaces 22b extending with approximately equal width from an outer edge E (short side portion E2 in the example of FIG. 5) in a direction perpendicular to the outer edge E (Y direction in the example of FIG. 5), and an inner surface 22c connected to inner ends of the pair of side surfaces 22b. The pair of side surfaces 22b and the inner surface 22c extend in the Z direction to connect the bottom surface 22a and the front surface 2a. The inner surface 22c is the surface opposite the outer edge E of each recess 22. When viewed from the Z direction, the inner surface 22c is formed in a shape that tapers toward the inside of the wiring board 2. That is, the width (length in the X direction) of each recess 22 gradually decreases on the inner surface 22c from the outer edge E toward the inside of the wiring board 2. In the example of FIG. 5, the inner surface 22c is formed in a curved shape that convexly curves toward the inside of the wiring board 2 when viewed from the Z direction. The inner surface 22c has a rounded chamfered shape when viewed from the Z direction, for example.

[0049] [Method of manufacturing the photodetector] A method for manufacturing the above-described photodetector 1 will be described with reference to FIG. 1. First, a wiring board 2 and a light-receiving substrate 3 having a plurality of conductive members 6 and 7 formed on the rear surface 3b are prepared. Next, the light-receiving substrate 3 is placed on the wiring board 2 so that the conductive members 6 formed on the rear surface 3b of the light-receiving substrate 3 are positioned on the pad electrodes 21a provided on the wiring board 2, and the conductive members 7 are positioned on the pad electrodes 21b. Next, the light-receiving substrate 3 is pressed against the wiring board 2 at a predetermined heating temperature. As a result, the pad electrodes 21 provided on the wiring board 2 and the electrodes provided on the light-receiving substrate 3 are electrically and physically connected by the conductive members 6 and 7.

[0050] Next, the underfill material 4 is filled into the gap between the wiring board 2 and the light-receiving board 3 from the outer edge E side. The underfill material 4 may be injected from all sides (the pair of long sides E1 and the pair of short sides E2) or from some of the sides. The underfill material 4 may be injected using an injection molding machine, a dispenser, or a manual injection tool. For example, the underfill material 4 may be injected toward the inner surfaces 22c of some of the recesses 22. This prevents the underfill material 4 from spilling out from the side surfaces 2c and 2d during injection, and efficiently guides the underfill material 4 into the entire gap between the wiring board 2 and the light-receiving board 3. If recesses 22 were not provided in the sides where the underfill material 4 is injected, the underfill material 4 may easily spill out from the outer edge E of the wiring board 2. In contrast, by using the recess 22 provided on the outer edge E of the wiring board 2 as an injection port for the underfill material 4, it is possible to prevent the underfill material 4 from spilling out when injecting the underfill material 4, while allowing the underfill material 4 to be suitably distributed into the gap between the wiring board 2 and the light-receiving substrate 3.

[0051] After the underfill material 4 fills the gap between the wiring substrate 2 and the light-receiving substrate 3, the photodetector 1 is heated. The photodetector 1 may be heated in an oven. The oven may be an annealing furnace or a bake oven. Here, a thermosetting resin is used as the underfill material 4, and the viscosity of the underfill material 4 may temporarily decrease when heating begins. This causes the underfill material 4 to become liquid, temporarily increasing its fluidity and causing some of the underfill material 4 to migrate from the inside of the wiring substrate 2 toward the outer edge E. This migrated portion of the underfill material 4 flows into the recesses 22 provided along the outer edge E before spilling out from the outer edge E. As a result, the multiple recesses 22 function as liquid reservoirs for the underfill material 4. Subsequently, as the temperature further increases, the underfill material 4 begins to cure. As the curing reaction progresses, the viscosity of the underfill material 4 increases again, and eventually the underfill material 4 solidifies. In this manner, the photodetector 1 is manufactured.

[0052] The wiring substrate 2 included in the photodetector 1 may be manufactured as follows. That is, when forming via holes (through holes) for embedding the pad electrodes 21 in the wiring substrate 2, the multiple recesses 22 may be formed at the same time. For example, the wiring substrate 2 may be formed by stacking multiple sheet-like substrates. In this case, for each substrate constituting the lower layer of the multiple substrates constituting the wiring substrate 2 (the portion closer to the back surface 2b than the bottom surface 22a of the recess 22), only the punching process for forming the via holes is performed. On the other hand, for each substrate constituting the upper layer of the multiple substrates constituting the wiring substrate 2 (the portion closer to the front surface 2a than the bottom surface 22a of the recess 22), the punching process for forming the via holes and the multiple recesses 22 are performed. Thereafter, by stacking the substrates constituting the upper layer on the substrates constituting the lower layer manufactured as described above, the wiring substrate 2 provided with the multiple recesses 22 of this embodiment can be efficiently obtained.

[0053] [Action and effect] According to the photodetector 1, a portion of the underfill material 4 disposed (filled) between the wiring board 2 and the light-receiving board 3 can be appropriately guided to the recesses 22 provided on each of a pair of sides (a pair of long sides E1, E1 and a pair of short sides E2, E2 in this embodiment). This effectively prevents the underfill material 4 from spilling out from the side surfaces 2c, 2d of the photodetector 1. Furthermore, by providing the recesses 22 on at least a pair of opposing sides, the stress balance of the wiring board 2 can be improved compared to when the recesses 22 are provided on only one side (e.g., only one long side E1 of the pair of long sides E1, E1 or only one short side E2 of the pair of short sides E2, E2). That is, as shown in FIG. 3, by providing the recesses 22 on each of the pair of long sides E1, E1, the structural balance of the wiring board 2 in the X direction can be improved. Furthermore, by providing multiple recesses 22 on each of the pair of short sides E2, E2, the structural balance of the wiring board 2 in the Y direction can be improved. As a result, compared to when recesses 22 are provided only on one long side E1 (or only on one short side E2), the structural stability of the wiring board 2 can be improved, and the structural stability of the photodetector 1 can be improved. Furthermore, since the strength (stability) of the wiring board 2 itself is improved, not only can damage to the completed photodetector 1 be suppressed, but also damage to the wiring board 2 during manufacturing of the wiring board 2, etc., can be suppressed.

[0054] Furthermore, the inner surface 22c of each of the plurality of recesses 22 is formed in a shape that tapers toward the inside of the wiring substrate 2 when viewed from the Z direction. This improves adhesion between the part of the underfill material 4 disposed between the wiring substrate 2 and the light-receiving substrate 3 and the inner surface 22c of the recesses 22 when part of the underfill material 4 moves to protrude into the recesses 22 during manufacturing of the photodetector 1 (for example, during a process of applying (injecting) the underfill material 4 or a process of heating the underfill material 4). In other words, gaps are less likely to occur between the inner surface 22c and the underfill material 4 flowing into the recesses 22. As a result, it is possible to effectively prevent voids from occurring between the part of the underfill material 4 flowing into the recesses 22 and the inner surface 22c of the recesses 22. For example, if the shape of the recess 22 when viewed from the Z direction is formed into a simple rectangle (e.g., if the inner surface 22c and the side surface 22b of the recess 22 are perpendicular to each other when viewed from the Z direction), the inner surface 22c does not narrow inward as in the present embodiment, which may reduce adhesion between the underfill material 4 and the recess 22 near the inner surface 22c and increase the likelihood of voids forming between the underfill material 4 and the recess 22. As a result, if the photodetector 1 is exposed to high temperatures, the air in the voids may expand, causing peeling of the underfill material 4 and ultimately damage to the photodetector 1. In contrast, in the present embodiment, the inner surface 22c of the recess 22 is formed into a shape that tapers inward when viewed from the Z direction, which effectively prevents damage to the photodetector 1 due to such voids. As described above, the photodetector 1 can effectively prevent damage while preventing the underfill material 4 from spilling out.

[0055] As shown in FIGS. 4 and 5 , the wiring board 2 has a bottom surface 22a that closes the back surface 2b of each of the recesses 22. According to the above configuration, the underfill material 4 that flows into the recesses 22 can be blocked by the bottom surface 22a of the recesses 22, thereby preventing the underfill material 4 from flowing around (spilling out) onto the back surface 2b of the wiring board 2. Furthermore, by providing the bottom surface 22a of the recesses 22, the strength of the wiring board 2 can be improved compared to when recesses that penetrate from the front surface 2a to the back surface 2b are formed. Therefore, according to the above configuration, the spilling out of the underfill material 4 and damage to the photodetector 1 can be more effectively prevented. Furthermore, compared to when penetrating recesses are provided as described above, a decrease in the strength of the wiring board 2 as a whole can be prevented. Therefore, according to the above configuration, damage to the wiring board 2 can be effectively prevented, even during manufacturing of the wiring board 2.

[0056] As shown in FIG. 5 , the inner surface 22c of each of the recesses 22 is curved (in this embodiment, chamfered) and convex toward the inside of the wiring substrate 2 when viewed from the Z direction. According to the above configuration, when a portion of the underfill material 4 disposed between the wiring substrate 2 and the light-receiving substrate 3 moves to protrude toward the recess 22, the portion of the underfill material 4 can be brought into smooth contact with the inner surface 22c of the recess 22, compared to when the inner surface 22c of the recess 22 is formed into an angular shape when viewed from the Z direction. This further improves adhesion between the portion of the underfill material 4 flowing into the recess 22 and the inner surface 22c of the recess 22. Furthermore, when the inner surface of the recess 22 is cut out into an angular shape, cracks may easily occur starting from the corners. However, by forming the inner surface 22c as a curved surface as described above, the starting points for such cracks can be eliminated. As a result, even during the manufacturing of the wiring board 2, damage to the wiring board 2 can be suitably suppressed.

[0057] As shown in FIG. 5, the pad electrodes 21a include two pad electrodes 21A and 21B adjacent to each other in the X direction (second direction) along the short side E2 (side). The recesses 22 include a recess 22A (first recess) located between the two pad electrodes 21A and 21B in the X direction. When viewed from the Z direction, the inner surface 22c of the recess 22A is located closer to the outer edge E (short side E2) than the straight line L1 (first straight line) connecting the centers C of the two pad electrodes 21A and 21B. Here, the center C of the pad electrode 21 refers to the center of a circle with the smallest radius that includes the entire pad electrode 21 when viewed from the Z direction. Therefore, when the pad electrode 21 is based on a circular shape with a partially cut-out shape, as in the case of the pad electrode 21 provided along the short side E2 of this embodiment, the center C of the pad electrode 21 coincides with the center of the circle that serves as the base.

[0058] According to the above configuration, as described above, the inner surface 22c of the recess 22A is formed to taper toward the inside of the wiring substrate 2 (in the present embodiment, a convex curved surface), and the recess 22A is provided so as not to extend inside the straight line L1 connecting the centers C of the two adjacent pad electrodes 21A, 21B, thereby suppressing an increase in the arrangement interval between the two adjacent pad electrodes 21A, 21B (i.e., the distance (pitch) between the centers C of the pad electrodes 21A, 21B). Therefore, while providing a plurality of recesses 22 for suppressing overflow of the underfill material 4 as described above, it is possible to suppress a decrease in the integration rate of the pad electrodes 21 on the wiring substrate 2. Furthermore, by limiting the size of the recess 22 to an extent that the recess 22 does not extend inside the straight line L1, it is possible to suppress a degree of decrease in the strength of the wiring substrate 2 due to the provision of the recess 22.

[0059] 5, when viewed from the Z direction, the inner surface 22c of the recess 22A extends further inward than a straight line L2 (second straight line) connecting the ends EP (in this embodiment, the linear ends cut out in an arched shape) of the two pad electrodes 21A and 21B on the outer edge E side. That is, the innermost portion of the inner surface 22c of the recess 22A is located between the straight lines L1 and L2. According to the above configuration, by extending the recess 22A as far inside the wiring substrate 2 as possible while suppressing an increase in the arrangement interval (pitch) between the two adjacent pad electrodes 21A and 21B, it is possible to suitably ensure the volume of the recess 22A as a relief area for the underfill material 4.

[0060] As shown in FIG. 5, the width W of the recess 22A (recess 22) in the X direction is smaller than the shortest distance d1 between the two pad electrodes 21A and 21B in the X direction. The width W of the recess 22 here refers to the maximum width of the recess 22. In this embodiment, the width of the recess 22 has a constant maximum width at the portion where the pair of side surfaces 22b face each other, and therefore the width W of the recess 22 is the distance (spacing) between the pair of side surfaces 22b. According to the above configuration, even if the recess 22A is disposed so as to extend to some extent between the two pad electrodes 21A and 21B adjacent to each other in the X direction, interference between the recess 22A and the two pad electrodes 21A and 21B can be reliably prevented. As a result, the reliability (quality) of the photodetector 1 can be improved.

[0061] As shown in FIG. 5, the width W of the recess 22A (recess 22) is greater than the shortest distance d2 between the recess 22A and at least one of the two pad electrodes 21A and 21B. According to the above configuration, by arranging the recess 22A as close as possible to the pad electrode (at least one of the pad electrodes 21A and 21B) adjacent to the recess 22A, the volume of the recess 22A as a relief area for the underfill material 4 can be suitably secured. As described above, in this embodiment, the recess 22A is disposed midway between the two pad electrodes 21A and 21B in the X-axis direction. Therefore, the shortest distance d2 between the recess 22A and the pad electrode 21A (hereinafter referred to as the “first shortest distance”) and the shortest distance between the recess 22A and the pad electrode 21B (hereinafter referred to as the “second shortest distance”) are equal to each other. If the first shortest distance and the second shortest distance do not coincide with each other, the width W of the recess 22A only needs to be greater than the shorter of the first shortest distance and the second shortest distance. However, from the viewpoint of more suitably achieving the above-mentioned effect (ensuring the volume of the recess 22A), it is preferable that the width W of the recess 22A be larger than both the first shortest distance and the second shortest distance.

[0062] The distance between the centers of adjacent recesses 22 (pitch P (see FIG. 5)) among the plurality of recesses 22 is preferably 0.5 mm or more and 2.5 mm or less. According to the above configuration, for example, when the recesses 22 and the pad electrodes 21 are alternately arranged along the long side E1 or the short side E2 as in this embodiment, by setting the pitch P between adjacent recesses 22 to 2.5 mm or less, it is possible to suppress an increase in the pitch between adjacent pad electrodes 21 (the distance between the centers C of adjacent pad electrodes 21). On the other hand, by ensuring that the pitch P between the recesses 22 is at least a certain value (0.5 mm or more), it is possible to suppress the spacing between adjacent recesses 22 from becoming too narrow, and it is possible to improve the degree of freedom in arranging the pad electrodes 21 arranged therebetween.

[0063] The width W of the recess 22 in the X direction along the short side E2 may be 0.15 mm or more and 0.5 mm or less, the length L of the recess 22 in the Y direction perpendicular to the Z direction and the X direction may be 0.25 mm or more and 2.0 mm or less, and the volume of the recess 22 may be 0.018 mm or less.3 More than 0.4mm 3 or less. If the size of each recess 22 (the size when viewed from the Z direction (length L, width W, and volume)) is too small, the effect of allowing the underfill material 4 to properly escape into the recess 22 (i.e., the effect of suppressing the overflow of the underfill material 4) will be insufficient. On the other hand, if the size of each recess 22 is too large, a large amount of underfill material will easily enter the recess 22 when filling the underfill material 4, and as a result, there is a risk that the underfill material 4 will not sufficiently spread throughout the entire space between the wiring board 2 and the light-receiving board 3. By keeping the size (length L, width W, and volume) of each recess 22 within the above-mentioned range, the occurrence of the above-mentioned problems can be suitably suppressed.

[0064] It is preferable that a certain number or more (at least four or more on each side) of recesses 22 are arranged in a balanced manner on each of the pair of long sides E1, E1. More specifically, it is preferable that the recesses 22 provided on each long side E1 are arranged so as to satisfy the following conditions (first to third conditions) which will be described with reference to FIG. 6.

[0065] (First condition) When each of a pair of sides (long sides E1, E1) is divided into a first side region ER1 (the left side in the example of Figure 6) and a second side region ER2 (the right side in the example of Figure 6), two or more recesses 22 are provided in the first side region ER1, and two or more recesses 22 are provided in the second side region ER2.

[0066] (Second condition) The number of recesses 22 provided in the first side region ER1 of one of the pair of long sides E1, E1 (for example, the upper long side E1 in FIG. 6), the number of recesses 22 provided in the second side region ER2 of one of the pair of long sides E1, E1, the number of recesses 22 provided in the first side region ER1 of the other of the pair of long sides E1, E1 (for example, the lower long side E1 in FIG. 6), and the number of recesses 22 provided in the second side region ER2 of the other of the pair of long sides E1, E1 are all equal. In the example of FIG. 6, the number of recesses 22 provided in each side region (each first side region ER1 and each second side region ER2) is "2."

[0067] (Third condition) When viewed from the Z direction, the arrangement of the plurality of recesses 22 in the wiring board 2 (here, the plurality of recesses 22 provided on each of the pair of long sides E1, E1) is line-symmetric with respect to a line LP that passes through the center CP of the wiring board 2 and is perpendicular to each long side E1, and is also line-symmetric with respect to a line LH that passes through the center CP and is parallel to each long side E1. In other words, when viewed from the Z direction, the surface 2a includes a first region A1 (the left half region in FIG. 6) and a second region A2 (the right half region in FIG. 6) that are line-symmetric with respect to the line LP. Furthermore, each of the first region A1 and the second region A2 is line-symmetric with respect to the line LH. As a result, at least two or more recesses 22 are arranged on each of the pair of long sides E1, E1 of the first region A1 so as to be line-symmetric with respect to the line LH. Similarly, at least two or more recesses 22 are arranged on each of the pair of long sides E1, E1 of the second region A2 so as to be line-symmetric with respect to the line LH.

[0068] According to the configuration that satisfies the first condition, by providing a plurality (two or more) of recesses 22 in each side region (first side region ER1 and second side region ER2) obtained by dividing each long side portion E1 into two equal parts, it is possible to arrange a large number of recesses 22 in an overall balanced arrangement. As a result, the internal stress generated in the wiring board 2 is evenly distributed, and deformation (breakage) of the wiring board 2 due to the internal stress can be suitably suppressed.

[0069] Furthermore, according to the configuration that satisfies the second condition, by providing the same number of recesses 22 in each side region (first side region ER1 and second side region ER2) obtained by dividing each long side portion E1 into two equal parts, it is possible to arrange a large number of recesses 22 in a more balanced arrangement. As a result, it is possible to more evenly distribute the internal stress generated in the wiring board 2.

[0070] Furthermore, according to the configuration that satisfies the third condition, by arranging the recesses 22 symmetrically with respect to the straight lines LP and LH as described above, it is possible to arrange a large number of recesses 22 in a more balanced arrangement. As a result, it is possible to more evenly distribute the internal stress generated in the wiring board 2.

[0071] Similarly, it is preferable that a certain number or more of recesses 22 (at least four or more on each side) be arranged in a balanced manner on each of the pair of short side portions E2, E2. More specifically, it is preferable that the recesses 22 provided on each short side portion E2 be arranged so as to satisfy the same conditions (first to third conditions) as those described for the long side portion E1 using FIG. 6, as shown in FIG. 7. That is, as shown in FIG. 7, when each of the pair of short side portions E2, E2 is equally divided into a first side region ER1 (an upper portion in the example of FIG. 7) and a second side region ER2 (a lower portion in the example of FIG. 7), it is preferable that the above-mentioned first to third conditions be satisfied for each of these side regions (first side region ER1, second side region ER2).

[0072] The third condition for the recesses 22 provided on the short side E2 is expressed as follows: That is, when viewed from the Z direction, the arrangement of the plurality of recesses 22 in the wiring board 2 (here, the plurality of recesses 22 provided on each of the pair of short side E2, E2) is line-symmetric with respect to a line LH that passes through the center CP of the wiring board 2 and is perpendicular to each short side E2, and is also line-symmetric with respect to a line LP that passes through the center CP and is parallel to each short side E2. In other words, when viewed from the Z direction, the surface 2a includes a first region A1 (the upper half of FIG. 7) and a second region A2 (the lower half of FIG. 7) that are line-symmetric with respect to the line LH. Furthermore, each of the first region A1 and the second region A2 is line-symmetric with respect to the line LP.

[0073] When the plurality of recesses 22 provided on the pair of short side portions E2, E2 satisfy the above-mentioned first to third conditions, the same effect as when the plurality of recesses 22 provided on the pair of long side portions E1, E1 satisfy the above-mentioned first to third conditions is obtained.

[0074] The wiring board 2 of this embodiment (see FIG. 3) satisfies both the condition (arrangement condition of the plurality of recesses 22 provided in each long side portion E1) described with reference to FIG. 6 and the condition (arrangement condition of the plurality of recesses 22 provided in each short side portion E2) described with reference to FIG. 7. In this way, by providing a plurality of recesses 22 in each of the pair of long side portions E1, E1 and also providing a plurality of recesses 22 in each of the pair of short side portions E2, E2 so as to satisfy both of the above conditions, it is possible to effectively suppress the underfill material 4 from spilling out from each side portion, and by optimizing the balance of the arrangement of the plurality of recesses 22, it is possible to suitably suppress the above-mentioned deformation (breakage) of the wiring board 2.

[0075] [Variations] The present disclosure is not limited to the above-described embodiment. For example, the multiple recesses 22 may include a recess 22B as shown in FIG. 8(a). In this example, the recess 22B located between two pad electrodes 21a arranged along a side (short side E2 in this example) is located outside (toward the outer edge E) of the straight line L2 connecting the ends EP of the two pad electrodes 21a. That is, the inner surface 22c of the recess 22B is arranged so as not to extend inside the straight line L2. This recess 22B can also effectively prevent damage to the photodetector 1 while suppressing overflow of the underfill material 4. Furthermore, by preventing the recess 22B from extending into the region between the pad electrodes 21a, it becomes easier to further reduce the pitch between two adjacent pad electrodes 21a.

[0076] The recesses 22 may also include a recess 22C as shown in FIG. 8(b). In this example, the inner surface 22c of the recess 22C has a C-chamfered shape when viewed from the Z direction. That is, when viewed from the Z direction, the inner surface 22c of the recess 22C includes a pair of inclined surface portions 22c1 connected to the inner ends of the pair of side surfaces 22b and extending linearly so as to approach each other as they approach the inside, and an end surface portion 22c2 connecting the ends of the pair of inclined surface portions 22c1 opposite the side surfaces 22b. Even with this recess 22C, the inner surface 22c narrows inward, improving adhesion between the underfill material 4 and the recess 22 near the inner surface 22c compared to when the recess 22 is simply rectangular when viewed from the Z direction. As a result, voids between the underfill material 4 and the recess 22 can be effectively suppressed. However, forming the inner side surface 22c of the recess 22 into a curved surface (e.g., a rounded chamfered shape) as in the above embodiment (see FIG. 5) can further improve the adhesion between the underfill material 4 and the recess 22 and more effectively suppress the occurrence of voids between the underfill material 4 and the recess 22. Note that in the recess 22C, the end surface portion 22c2 may be omitted, and the inner ends of the pair of inclined surface portions 22c1 may be directly connected to each other. Even with such a shape, the above-mentioned effect can be obtained by forming the recess 22 to taper inward.

[0077] The wiring board 2 does not necessarily have to be rectangular when viewed from the Z direction. That is, the wiring board 2 does not have to be rectangular as long as the outer edge E of the surface 2a has at least a pair of sides that face each other. For example, the outer edge E may have a polygonal shape other than a rectangle (e.g., a hexagonal shape) when viewed from the Z direction.

[0078] Regarding the manufacturing method of the light-detecting device 1, the above embodiment has described an example in which the underfill material 4 is injected (filled) using the recess 22 of the wiring board 2 as an injection port after the light-receiving board 3 and the wiring board 2 are pressure-bonded together, but the underfill material 4 may also be injected through a gap between the rear surface 3b of the light-receiving board 3 and the front surface 2a of the wiring board 2 in a portion where the recess 22 is not provided. Also, the underfill material 4 may be disposed in advance between the rear surface 3b of the light-receiving board 3 and the front surface 2a of the wiring board 2 before the light-receiving board 3 and the wiring board 2 are pressure-bonded together.

[0079] In the recess 22, the inner surface 22c is formed in a chamfered shape (a convex curved surface in this embodiment) tapering toward the inside of the wiring substrate 2 when viewed from the Z direction. In addition, the area between the inner surface 22c and the bottom surface 22a may also be similarly chamfered. By chamfering the edges of the bottom surface 22a of the recess 22 in this manner, the adhesion between the underfill material 4 that flows along the inner surface 22c and the bottom surface 22a can be improved. As a result, the generation of voids between the recess 22 and a portion of the underfill material 4 can be more effectively suppressed. It is also possible to form only the edges of the bottom surface 22a of the recess 22 in a chamfered shape (e.g., a curved shape) without providing the recess 22 with the chamfered inner surface 22c (for example, by forming the recess 22 so that it has a simple rectangular shape when viewed from the Z direction). However, in this case, compared to the above embodiment in which the chamfered inner surface 22c is provided as described above, the effect of improving the adhesion between the underfill material 4 and the recess 22 when the underfill material 4 flows into the recess 22 from the inner end of the recess 22 cannot be obtained. Therefore, even when the edge of the bottom surface 22a of the recess 22 is formed into a chamfered shape (for example, a curved surface), forming the inner surface 22c of the recess 22 into a chamfered shape that tapers toward the inside of the wiring board 2, as in the above embodiment, is very effective in effectively suppressing the occurrence of voids.

[0080] 5, the inner surface 22c of the recess 22A may extend further inward into the wiring board 2 than the straight line L1 connecting the centers C of the two pad electrodes 21A and 21B when viewed from the Z direction. According to the above configuration, by extending the recess 22A further into the wiring board 2, the volume of the recess 22A as a place for the underfill material 4 to escape can be suitably secured.

[0081] 5, the recess 22A is provided at a position exactly midway between the two pad electrodes 21A and 21B, but the recess 22A may be disposed at a position shifted toward one of the pad electrodes (pad electrode 21A or pad electrode 21B) from the midway position. Furthermore, as in the example of FIG. 8(a), when the inner surface 22c of the recess 22 is positioned outside the straight line L2, the recess 22 and the pad electrode 21a may be disposed so as to overlap each other in the direction in which the recess 22 extends when viewed from the Z direction (the Y direction in this example).

[0082] In the above embodiment, the recesses 22 are all formed to have the same size and shape, but the recesses 22 may include multiple types of recesses having different sizes or shapes. For example, the recesses 22 provided along the long side E1 may be formed to have a different size or shape from the recesses 22 provided along the short side E2. Furthermore, multiple recesses 22 of different sizes or shapes may be provided along the same side.

[0083] In the above embodiment, the same positional relationship as that between two adjacent pad electrodes 21 (pad electrodes 21A, 21B) along the short side E2 and the recess 22 (recess 22A) located therebetween as described with reference to FIG. 5 also holds true for two adjacent pad electrodes 21 along the long side E1 and the recess 22 located therebetween. However, such a positional relationship between the pad electrodes 21 and the recess 22 may be different between the long side E1 and the short side E2. Also, different positional relationships may be mixed on the same side. For example, the recess 22A (see FIG. 5) and the recess 22B (see FIG. 8(a)) may be mixed on the same short side E2.

[0084] In the above embodiment, recess 22 includes a pair of side surfaces 22b extending parallel to each other when viewed from the Z direction, but the pair of side surfaces 22b may not be formed. That is, recess 22 may have a shape that is chamfered (R-chamfered, C-chamfered, etc.) so as to taper from the opening end of the side surface (side surface 2c or side surface 2d) toward the inside of wiring substrate 2 when viewed from the Z-axis direction.

[0085] In the above embodiment, the recesses 22 provided on a pair of sides (long side E1 or short side E2) are arranged so as to satisfy the first to third arrangement conditions described with reference to FIGS. 6 and 7. However, the recesses 22 do not necessarily have to satisfy the first to third conditions. For example, the recesses 22 provided on a pair of sides (long side E1 or short side E2) may be arranged so as to satisfy the first and second conditions but not the third condition. Furthermore, the recesses 22 provided on a pair of sides (long side E1 or short side E2) may be arranged so as to satisfy the first condition but not the second and third conditions. Alternatively, the recesses 22 do not have to satisfy all of the first to third conditions. [Explanation of symbols]

[0086] 1...photodetector, 2...wiring board, 2a...surface (first surface), 2b...back surface (second surface), 3...light-receiving board, 4...underfill material, 6, 7...conductive member, 21, 21A, 21B, 21a, 21b...pad electrode, 22, 22B, 22C...recess, 22A...recess (first recess), 22a...bottom surface, 22c...inner surface, E...outer edge, E1...long side portion (side portion), E2...short side portion (side portion), ER1...first side region, ER2...second side region.

Claims

1. a wiring substrate including a first surface on which a plurality of pad electrodes are two-dimensionally arranged, and a second surface opposite to the first surface; a light-receiving substrate disposed on the first surface of the wiring substrate, the light-receiving substrate including a plurality of light-receiving elements two-dimensionally arranged to correspond to the plurality of pad electrodes; a plurality of conductive members electrically connecting the plurality of pad electrodes and the plurality of light receiving elements; an underfill material disposed between the wiring board and the light-receiving board; When viewed from a first direction in which the wiring substrate and the light receiving substrate face each other, an outer edge of the first surface of the wiring substrate has at least a pair of side portions facing each other, a plurality of recesses are provided in each of the pair of side portions of the wiring substrate, the recesses opening to the first surface and extending from the outer edge toward an inside of the wiring substrate when viewed from the first direction; An optical detection device, wherein an inner surface of each of the plurality of recesses opposite the outer edge is formed in a shape that tapers toward the inside of the wiring substrate when viewed from the first direction.

2. The light-detecting device according to claim 1 , wherein the wiring substrate has a bottom surface that closes the second surface side of each of the plurality of recesses.

3. The photodetector according to claim 1 , wherein the inner surface of each of the plurality of recesses is formed as a curved surface that is convex toward the inside of the wiring substrate when viewed from the first direction.

4. the plurality of pad electrodes include two pad electrodes adjacent to each other in a second direction along the side portion, the plurality of recesses include a first recess located between the two pad electrodes in the second direction; The photodetector device according to claim 1 , wherein the inner surface of the first recess is located closer to the outer edge than a first straight line connecting the centers of the two pad electrodes when viewed from the first direction.

5. 5. The photodetector device of claim 4, wherein the inner surface of the first recess, when viewed from the first direction, extends further inward than a second straight line connecting the outer edge ends of each of the two pad electrodes.

6. the plurality of pad electrodes include two pad electrodes adjacent to each other in a second direction along the side portion, the plurality of recesses include a first recess located between the two pad electrodes in the second direction; The photodetector according to claim 1 , wherein a width of the first recess in the second direction is smaller than a shortest distance between the two pad electrodes in the second direction.

7. The photodetector according to claim 6 , wherein the width of the first recess is greater than the shortest distance between the first recess and at least one of the two pad electrodes.

8. 2. The optical detection device according to claim 1, wherein when each of the pair of sides is divided into a first side region and a second side region, two or more of the recesses are provided in the first side region and two or more of the recesses are provided in the second side region.

9. 9. The optical detection device of claim 8, wherein the number of recesses provided in the first side region of one of the pair of sides, the number of recesses provided in the second side region of one of the pair of sides, the number of recesses provided in the first side region of the other of the pair of sides, and the number of recesses provided in the second side region of the other of the pair of sides are equal to each other.

10. 10. The photodetector device of claim 9, wherein the arrangement of the plurality of recesses on the wiring substrate, when viewed from the first direction, is symmetrical with respect to a line passing through the center of the wiring substrate and perpendicular to the pair of sides, and is also symmetrical with respect to a line passing through the center of the wiring substrate and parallel to the pair of sides.

11. 11. The light detection device according to claim 1, wherein the distance between the centers of adjacent recesses in the plurality of recesses is 0.5 mm or more and 2.5 mm or less.

12. a width of the recess in a second direction along the side portion is 0.15 mm or more and 0.5 mm or less; a length of the recess in a direction perpendicular to the first direction and the second direction is 0.25 mm or more and 2.0 mm or less; The volume of the recess is 0.018 mm ３ 0.4mm or more ３ The photodetector according to any one of claims 1 to 10, wherein:

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