Imaging unit, method for manufacturing imaging unit, and endoscope

Abstract

[Problem] To provide an imaging unit 1 having superior characteristics and high reliability. [Solution] An imaging unit 1 comprises an image sensor 10, a wiring board 20, and an electronic component 40. The image sensor 10 includes an external electrode 13 on a rear surface 10SB. The wiring board 20 is a multilayer rigid wiring board obtained by laminating a first block 21, a second block 22, a third block 23, and a fourth block 24. The first block 21 includes a first electrode 31 on a first surface F1, and a second electrode 32 connected to the first electrode 31 via a first internal wiring line 37 on a second surface F2. The second block 22 is such that a third electrode 33 on a third surface F3 is in contact with the second electrode 32. The third block 23 includes a fourth electrode 34 on a fourth surface F4 and a fifth electrode 35 on a fifth surface F5. A third end 36A of a sixth electrode 36 of a sixth surface F6 of the fourth block 24 is in contact with the fifth electrode. The electronic component 40 is joined to the third electrode 33.

Description

Imaging unit, imaging unit manufacturing method, and endoscope

[0001] The present invention relates to an imaging unit having a wiring board on which electronic components are mounted, a method for manufacturing an imaging unit having a wiring board on which electronic components are mounted, and an endoscope including an imaging unit having a wiring board on which electronic components are mounted.

[0002] An endoscope has an insertion section equipped with an imaging unit that is inserted into, for example, a living body to capture and display images of the inside. The user then observes and treats the affected area based on the endoscopic images. To make endoscopes less invasive, imaging units are becoming increasingly miniaturized.

[0003] Japanese Patent Application Publication No. 2020-39427 discloses an imaging unit in which electronic components are soldered to lands on the concave bottom surface of a circuit board in which multiple substrates are stacked parallel to the optical axis of an imaging element.

[0004] International Publication No. 2020 / 244133 discloses an imaging unit in which a green sheet having a conductor via is cut along a cutting line that straddles the conductor via, thereby forming a so-called half-split via in which the cut surface of the conductor is exposed on the surface, and an electronic component is solder-joined to the half-split via.

[0005] JP 2020-39427 A International Publication No. 2020 / 244133

[0006] It is not easy to bond ultra-small electronic components to ultra-small wiring boards, and if the bonding positions of the electronic components are misaligned from the positions of the lands on the wiring board, the characteristics and reliability of the imaging unit will deteriorate.

[0007] An object of the embodiments of the present invention is to provide an imaging unit with high performance and high reliability, an endoscope having an imaging unit with high performance and high reliability, and an easy method for manufacturing an imaging unit with high performance and high reliability.

[0008] An imaging unit according to an embodiment of the present invention includes an image sensor, a wiring board, and electronic components. The image sensor has a light-receiving surface and a back surface opposite to the light-receiving surface, and has an external electrode on the back surface. The wiring board is a multilayer rigid wiring board in which a first block, a second block, a third block, and a fourth block are stacked in this order in the optical axis direction of the image sensor. The first block has a first surface and a second surface opposite to the first surface, and has a first electrode joined to the external electrode on the first surface, and a second electrode connected to the first electrode via a first internal wiring on the second surface. The lock has a third surface orthogonal to the second surface and a third electrode on the third surface, a first end of the third electrode in contact with the second electrode; the third block has a fourth surface orthogonal to the third surface and a fifth surface opposite the fourth surface, a fourth electrode on the fourth surface in contact with a second end of the third electrode, and a fifth electrode on the fifth surface connected to the fourth electrode via second internal wiring; the fourth block has a sixth surface orthogonal to the fifth surface and a sixth electrode on the sixth surface, a third end of the sixth electrode in contact with the fifth electrode; and the electronic component is bonded to the third electrode.

[0009] An endoscope according to an embodiment of the present invention has an imaging unit at the tip of an insertion section, the imaging unit having an image sensor, a wiring board, and electronic components, the image sensor having a light receiving surface and a back surface opposite the light receiving surface, and an external electrode on the back surface, the wiring board being a multilayer rigid wiring board in which a first block, a second block, a third block, and a fourth block are stacked in the above order in the optical axis direction of the image sensor, the first block having a first surface and a second surface opposite the first surface, a first electrode joined to the external electrode on the first surface, and a fourth block connected to the first electrode via a first internal wiring on the second surface. a second electrode, the second block having a third surface perpendicular to the second surface and a third electrode on the third surface, a first end of the third electrode in contact with the second electrode; the third block having a fourth surface perpendicular to the third surface and a fifth surface opposite the fourth surface, a fourth electrode on the fourth surface in contact with a second end of the third electrode, and a fifth electrode on the fifth surface connected to the fourth electrode via second internal wiring; the fourth block having a sixth surface perpendicular to the fifth surface and a sixth electrode on the sixth surface, a third end of the sixth electrode in contact with the fifth electrode; and the electronic component being bonded to the third electrode.

[0010] A method for manufacturing an imaging unit according to an embodiment of the present invention includes laminating a first sheet, a second sheet, a third sheet, and a fourth sheet, each of which is formed by laminating a plurality of green sheets, in the above order, to produce a laminated sheet, the first sheet having a first surface and a second surface opposite to the first surface, a first electrode on the first surface, and a second electrode on the second surface connected to the first electrode via a first internal wiring, the second sheet having a third surface orthogonal to the second surface, a third electrode on the third surface, a first end of the third electrode being in contact with the second electrode, the third sheet having a fourth surface orthogonal to the third surface and a second electrode on the second surface opposite to the fourth surface, a fifth surface on the opposite side, a fourth electrode in contact with the second end of the third electrode on the fourth surface, a fifth electrode connected to the fourth electrode via a second internal wiring on the fifth surface, the fourth sheet having a sixth surface perpendicular to the fifth surface and a sixth electrode in contact with the fifth electrode on the sixth surface, the laminated sheet being fired, a plating film being disposed on each surface of the first electrode, the third electrode, and the sixth electrode, to fabricate a multilayer rigid wiring board, an external electrode of an image sensor being joined to the first electrode on the first surface of the multilayer rigid wiring board, and an electronic component being joined to the third electrode on the third surface.

[0011] According to the embodiments of the present invention, it is possible to provide an imaging unit with high characteristics and high reliability, an endoscope having an imaging unit with high characteristics and high reliability, and an easy method for manufacturing an imaging unit with high characteristics and high reliability.

[0012] FIG. 1 is a perspective view of an imaging unit of a first embodiment. FIG. 2 is an exploded perspective view of the imaging unit of the first embodiment. FIG. 3 is an exploded cross-sectional view of a wiring board of the imaging unit of the first embodiment. FIG. 4 is a transparent perspective view showing the wiring structure of the wiring board of the imaging unit of the first embodiment. FIG. 5 is a transparent cross-sectional view showing the wiring state between blocks of the wiring board of the imaging unit of the first embodiment. FIG. 6 is a top view of the wiring board of the imaging unit of the first embodiment. FIG. 7 is a flowchart of a manufacturing method of the imaging unit of the first embodiment. FIG. 8 is a perspective view for explaining a manufacturing method of the wiring board of the imaging unit of the first embodiment. FIG. 9 is a perspective view for explaining a manufacturing method of the wiring board of the imaging unit of the first embodiment. FIG. 10 is a perspective view for explaining a manufacturing method of the wiring board of the imaging unit of the first embodiment. FIG. 11 is a perspective view of an imaging unit of a second embodiment. FIG. 12 is a perspective view of an endoscope of a third embodiment.

[0013] 1 and 2 show an imaging unit 1 of this embodiment. The imaging unit 1 includes an image sensor 10, a multilayer rigid wiring board 20 (hereinafter referred to as the “wiring board 20”), electronic components 40, and a cable 50.

[0014] The drawings based on the embodiments are schematic. The relationship between the thickness and width of each part, the thickness ratio of each part, etc., differ from the actual ones. The drawings also include parts with different dimensional relationships and ratios. In addition, illustrations and reference numerals of some components are omitted.

[0015] The image sensor 10 has a light-receiving surface 10SA and a back surface 10SB opposite the light-receiving surface 10SA. The image sensor 10 also has an imaging element 11 and a cover glass 12. A plurality of external electrodes 13 are disposed on the back surface 10SB of the imaging element 11, which receives imaging light. Note that a semiconductor element that performs primary processing of an imaging signal may be stacked on the back surface of the imaging element 11, and the external electrodes 13 may be disposed on the back surface of the semiconductor element.

[0016] Wiring board 20 is an irregular ceramic wiring board. That is, wiring board 20 is a multilayer ceramic wiring board in which first block 21, second block 22, third block 23, and fourth block 24, each of which has a ceramic base, are stacked in this order in the optical axis direction of image sensor 10 and integrated together. Note that wiring board 20 is not limited to a multilayer ceramic wiring board whose base material is ceramic, as long as it is a multilayer rigid wiring board, but may also be, for example, a multilayer resin wiring board whose base material is a hard resin such as glass epoxy resin.

[0017] The electronic component 40 (41, 42) is soldered to the third electrode 33 of the wiring board 20, and the cable 50 is soldered to the sixth electrode 36. The electronic component 40 (41, 42) is, for example, a chip capacitor with two terminals having two electrodes 21A, 21B at its end. There may be one electronic component 40, or multiple electronic components of different sizes.

[0018] 3 and 4 , the first block 21 has a plurality of first electrodes 31 on its first surface F1 and a plurality of second electrodes 32 on its second surface F2. Each of the plurality of first electrodes 31 is joined to each of the plurality of external electrodes 13 of the image sensor 10. Each of the plurality of first electrodes 31 and each of the plurality of second electrodes 32 are connected via a respective first internal wiring 37.

[0019] The second block 22 has a third surface F3 that is perpendicular to the second surface F2. The second block 22 has a plurality of third electrodes 33 on the third surface F3. The first end surface 33A of each of the plurality of third electrodes 33 is in surface contact with the corresponding second electrode 32, and the electrodes are integrated by firing. The plurality of third electrodes 33 are capacitor lands to which electronic components 40, such as chip capacitors, are solder-bonded.

[0020] The third block 23 has a fourth surface F4 perpendicular to the third surface F3 and a fifth surface F5 opposite the fourth surface F4. The fourth surface F4 and the fifth surface F5 are parallel to the first surface F1 and the second surface F2. A recess is formed between the second surface F2 and the fourth surface F4. The bottom of the recess is the third surface F3. The third block 23 has a plurality of fourth electrodes 34 on the fourth surface F4 and a plurality of fifth electrodes 35 on the fifth surface F5. Each of the plurality of fourth electrodes 34 is in surface contact with the second end surface 33B of each of the plurality of third electrodes 33 and is integrated by firing. Each of the plurality of fourth electrodes 34 and each of the plurality of fifth electrodes 35 are connected via a corresponding one of the plurality of second internal wirings 38.

[0021] The fourth block 24 has a sixth surface F6 that is perpendicular to the fifth surface F5. The sixth surface F6 is parallel to the third surface F3. The fourth block 24 has a plurality of sixth electrodes 36 that have third end surfaces 36A that are in surface contact with the fifth electrodes 35 on the sixth surface F6. The plurality of sixth electrodes 36 are cable lands to which the plurality of cables 50 are solder-bonded. The second block 22 and the fourth block 24 have smaller dimensions in a direction perpendicular to the optical axis than the second block 22 and the fourth block 24. Therefore, the electronic component 40 and the ends (joints) of the plurality of cables 50 are housed in a virtual space VS (see FIG. 11 ) that is an extension of the image sensor 10 along the optical axis.

[0022] The third electrode 33 is a first half-split via wiring buried in the third face F3. The sixth electrode 36 is a second half-split via wiring buried in the sixth face F6. As will be described later, a half-split via wiring is a wiring having a substantially rectangular exposed surface formed by cutting a long and narrow internal wiring in a plane parallel to the longitudinal direction. A half-split via wiring is formed, for example, by cutting a via connecting layers in a substrate in half.

[0023] The surfaces of the first electrode 31, the third electrode 33, and the sixth electrode 36 are each covered with a two-layer plating film 60 made of, for example, a nickel layer and a gold layer. The plating film 60 is disposed by electroplating.

[0024] The plating film 60 is disposed for soldering. The first electrode 31 is soldered to the external electrode 13 of the image sensor 10, the third electrode 33 is soldered to an electronic component, and the sixth electrode 36 is soldered to the cable 50. The first electrode 31, the third electrode 33, and the sixth electrode 36, which are covered with the plating film 60, can be easily soldered, and the soldering reliability is high.

[0025] Note that the second electrode 32, the fourth electrode 34, and the fifth electrode 35 are not exposed on the outer surface of the wiring board 20. For example, as shown in FIG. 5 , at the boundary between the second surface F2 and the third surface F3, the second electrode 32 is entirely disposed within the first end surface 33A of the third electrode 33. The surfaces of the second electrode 32, the fourth electrode 34, and the fifth electrode 35 are not covered with the plating film 60.

[0026] As will be described later, in the process of providing plating film 60 on the surfaces of first electrodes 31, etc., if plating film 60 is also provided on second electrodes 32, etc., there is a risk of peeling at the block interface. A wiring board 20 in which plating film 60 is not formed on first electrodes 31, etc. is highly reliable.

[0027] As shown in FIG. 6 , the maximum dimension (top surface diagonal dimension) L41 of the electronic component 41 is greater than the distance W33 between the second surface F2 and the fourth surface F4. The length of the third electrode 33 in the optical axis direction is the same as the distance W33 between the second surface F2 and the fourth surface F4. Furthermore, the distance D between the two electrodes 41A of the two-terminal electronic component is substantially the same as the distance between the two third electrodes 33 to which it is bonded. Therefore, even if the electronic component 41 is rotated in a direction along the third surface F3 from a predetermined position, the maximum dimension L41 is greater than the distance W33, preventing it from rotating by more than a certain angle, and the electrode 41A is always bonded to the third electrode 33. Furthermore, even if the electronic component 41 is misaligned in the direction of the optical axis O, the electrode 41A is always bonded to the third electrode 33. The imaging unit 1 allows for stable mounting of the electronic component 41.

[0028] The electronic components 40 are entirely housed in the recess between the first block 21 and the third block 23. Therefore, the size of the imaging unit 1 perpendicular to the optical axis O is small, and the imaging unit 1 is compact.

[0029] In the imaging unit 1, the electronic component 40 can be easily mounted on the third electrode 33, and the bonding reliability is high. Although the electronic component 42 is smaller than the electronic component 41, by adjusting the dimensions and arranging two electronic components 42 at the same time, the same effect as the electronic component 41 can be achieved. Furthermore, the third electrode 33 may include an electrode 33X that is not bonded to any electronic component.

[0030] The second electrode 32, the third electrode 33, the fourth electrode 34, the fifth electrode 35, and the sixth electrode 36 are arranged in a substantially straight line. Because the wiring path is short, the wiring board 20 has low internal resistance of the wiring and high performance.

[0031] The second electrode 32, the third electrode 33, the fourth electrode 34, the fifth electrode 35, and the sixth electrode 36 may not be arranged in a substantially straight line, and some of the electrodes may be arranged inside the wiring board.

[0032] As shown in FIG. 4, an end face of an electroplating current-carrying wiring 39 for forming a plating film 60, which is connected to the second internal wiring 38, is exposed on a side surface F23S perpendicular to the third surface F3 of the third block 23.

[0033] Although not shown, in order to improve the bonding reliability, the bonded portions are sealed with underfill resin after the image sensor 10, electronic components 40, and cables 50 are bonded to the wiring board 20. The underfill resin is an insulating resin such as epoxy resin, acrylic resin, polyimide resin, silicone resin, or polyvinyl resin.

[0034] As described above, the imaging unit 1 has high performance and high reliability.

[0035] <Method of Manufacturing Imaging Unit> A method of manufacturing an imaging unit will be described with reference to the flowchart of FIG.

[0036] <Step S10> Preparation of Green Sheets A plurality of unfired wiring sheets called green sheets having surface wiring and internal wiring made of conductive paste or the like are prepared.

[0037] <Step S20> Preparation of First to Fourth Sheets As shown in FIG. 8, a first sheet 21S, which will become the first block, is prepared by stacking a plurality of wiring sheets 21S1 to 21S3. The first sheet 21S, which is made up of a plurality of wiring sheets 21S1 to 21S3, is a block sheet that will become a plurality of first blocks. In the wiring sheets 21S1 to 21S3, the lines extending in the stacking direction are vias, and the wiring extending horizontally to the stacking direction are patterns. The vias are prepared by punching holes in the sheets and pouring a conductive paste into the holes. The patterns are prepared by screen-printing the conductive paste. After these processes, the wiring sheets are stacked and pressed to prepare the block sheet.

[0038] Conductor regions 31S that become first electrodes 31 are exposed on the surface of wiring sheet 21S1. Similarly, second sheet 22S that becomes the second block, third sheet 23S that becomes the third block, and fourth sheet 24S that becomes the fourth block are produced (see FIG. 11 ).

[0039] 9, the second sheet 22S has a through hole H22 formed therein that straddles the conductor filled in the via, which is the internal wiring, and has a half-split wiring 33S that serves as the third electrode 33. Note that the first sheet 21S shown in FIG. 8 also has a through hole H21 formed therein that communicates with the through hole H22.

[0040] Although not shown, a through hole that straddles the conductor filled in the via, which is the internal wiring, is also formed in the fourth sheet 24S, forming a half-split wiring, and a through hole that communicates with the through hole H22 is also formed in the third sheet 32S. During plating, the plating solution reaches the surface of the half-split wiring 33S of the second sheet 22S through the through hole.

[0041] <Step S30> Preparation of laminated sheet As shown in Figure 10, laminated sheet 20S is prepared by stacking first sheet 21S, second sheet 22S, third sheet 23S, and fourth sheet 24S in the above order, each of which is a block sheet in which multiple wiring sheets are stacked.

[0042] <Step S40> The fired laminated sheet 20S is fired under predetermined conditions (temperature, atmosphere, time).

[0043] <Step S50> A plating film is formed by electroplating on the plated and baked laminated sheet 20S. Although not shown, the electroplating current-carrying wiring 39 of each of the plurality of third sheets 23S is connected, and a terminal that serves as a plating cathode is exposed on the outer circumferential surface.

[0044] That is, the plating film 60 is disposed on the surfaces of the first electrode 31, the third electrode 33, and the sixth electrode 36 that are exposed to the outside.

[0045] <Step S60> As shown in cutting diagram 10, laminated sheet 20S including a plurality of wiring boards 20 after plating is cut along cutting lines CL to be separated into a plurality of wiring boards 20.

[0046] <Step S70> A light receiving section such as a CMOS light receiving element is formed on the light receiving surface of the bonded semiconductor wafer by a known semiconductor manufacturing method, and by providing through wiring (not shown), an image sensor wafer (not shown) is produced that has external electrodes 13 connected to the light receiving section on its back surface 10SB. A glass wafer is bonded to the light receiving surface of the image sensor wafer. The image sensor wafer with the bonded glass wafer is cut to produce image sensors 10.

[0047] External electrodes 13 (e.g., solder bumps) of image sensor 10 are solder-joined to first electrodes 31 of wiring board 20. Electronic component 40 is solder-joined to third electrodes 33 of wiring board 20. Cable 50 is solder-joined to sixth electrodes of wiring board 20.

[0048] The maximum dimension of the electronic component 41 is smaller than the distance between the first block 21 and the third block 23. Therefore, the electronic component 41 is reliably bonded to the third electrode 33.

[0049] According to the manufacturing method of this embodiment, it is possible to easily manufacture an imaging unit 1 with high characteristics and high reliability.

[0050] <Modification of First Embodiment> An imaging unit 1A according to a modification of the first embodiment is similar to the imaging unit 1 of the first embodiment and has the same effects. For this reason, components having the same functions as those of the imaging unit 1 are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0051] 11 , wiring board 20A also has, on its seventh face F7 opposite to third face F3, an electrode (not shown) on which electronic component 43 (40) having the same configuration as third electrode 33 is mounted. Electronic component 40 is housed in a recess between first block 21 and third block 23. Furthermore, wiring board 20A also has, on its eighth face F8 opposite to sixth face F6, an electrode (not shown) that is the same as sixth electrode 36 to which component cable 50A is connected. In other words, wiring board 20A has two sets of wiring configurations that are substantially the same as the wiring structure of wiring board 20.

[0052] In wiring board 20A, length L1 from the inner surface of virtual space VS, which is obtained by extending image sensor 10 in the optical axis direction, to eighth surface F8 is longer than length L2 from the inner surface of the virtual space to sixth surface F6. Therefore, cable 50A connected to eighth surface F8 is thicker than cable 50, but the joint of cable 50A is contained within the virtual space. Note that length L3 from the inner surface of virtual space VS to third surface F3 and length L4 from the inner surface of virtual space VS to seventh surface F7 may also be different so that the electronic component 40 (43) to be disposed is contained within the virtual space.

[0053] The imaging unit 1A can be preferably used as an image sensor with higher performance than the imaging unit 1.

[0054] 12 , the endoscope 9 of this embodiment has a distal end portion 9A on which the imaging unit 1 is disposed, a freely bendable bending portion 9B connected to the proximal end of the distal end portion 9A, and an elongated flexible portion 9C connected to the proximal end of the bending portion 9B. The bending portion 9B is bent by the user operating an operating portion 9D. The distal end portion 9A, bending portion 9B, and flexible portion 9C form an insertion portion that is inserted into the body. A universal cord 9E extending from the operating portion 9D is connected to a processor or the like (not shown).

[0055] The endoscope 9 has high reliability and high performance because it has the imaging units 1 and 1A.

[0056] The endoscope 9 is a so-called flexible endoscope for medical use, but an endoscope in another embodiment may be an industrial endoscope or a so-called rigid endoscope having a rigid straight tube instead of the flexible section 9C. The imaging units 1 and 1A may also be used in an oblique-viewing endoscope in which the subject is directed in a lateral direction.

[0057] As already explained, the imaging units 1 and 1A are highly reliable, and therefore the endoscope 9 is highly reliable.

[0058] The present invention is not limited to the above-described embodiments, and various modifications, combinations, and applications are possible within the scope of the invention.

[0059] REFERENCE SIGNS LIST 1, 1A... Imaging unit 9... Endoscope 10... Image sensor 11... Imaging element 12... Cover glass 13... External electrode 20, 20A... Multilayer rigid wiring board (wiring board) 21... First block 22... Second block 23... Third block 24... Fourth block 31... First electrode 32... Second electrode 33... Third electrode 34... Fourth electrode 35... Fifth electrode 36... Sixth electrode 40 (41, 42)... Electronic component 50... Cable 60... Plating film

Claims

1. An image sensor, comprising: an image sensor; a wiring board; and at least one electronic component; wherein the image sensor has a light-receiving surface and a back surface opposite the light-receiving surface, and an external electrode on the back surface; wherein the wiring board is a multilayer rigid wiring board in which a first block, a second block, a third block, and a fourth block are stacked in the above order in the direction of the optical axis of the image sensor; wherein the first block has a first surface and a second surface opposite the first surface, and has a first electrode joined to the external electrode on the first surface, and a second electrode connected to the first electrode via first internal wiring on the second surface; wherein the second block has a third surface orthogonal to the second surface, and has a third electrode on the third surface, a first end of the third electrode in contact with the second electrode; wherein the third block has a fourth surface orthogonal to the third surface and a fifth surface opposite the fourth surface, and has a fourth electrode on the fourth surface in contact with a second end of the third electrode, and a fifth electrode on the fifth surface connected to the fourth electrode via second internal wiring; the fourth block has a sixth surface perpendicular to the fifth surface, a sixth electrode on the sixth surface, a third end of the sixth electrode being in contact with the fifth electrode, and the electronic component being bonded to the third electrode.

2. The imaging unit described in claim 1, characterized in that the third electrode is a first half-split via wiring buried in the third surface, and the sixth electrode is a second half-split via wiring buried in the sixth surface.

3. The imaging unit according to claim 1, wherein the surfaces of the first electrode, the third electrode, and the sixth electrode are covered with a plating film.

4. The imaging unit according to claim 3, wherein the surfaces of the second electrode, the fourth electrode, and the fifth electrode are not covered with the plating film.

5. The imaging unit according to claim 1, wherein the maximum dimension of said electronic component is greater than the distance between said second surface and said fourth surface.

6. The imaging unit according to claim 1, wherein the length of the third electrode in the optical axis direction is the same as the distance between the second surface and the fourth surface.

7. The imaging unit according to claim 1, wherein the second electrode, the third electrode, the fourth electrode, the fifth electrode, and the sixth electrode are arranged in a substantially straight line.

8. An imaging unit as described in claim 1, characterized in that an end face of a lead-out wiring connected to the second internal wiring is exposed on a side surface of the third block perpendicular to the third surface.

9. The imaging unit according to claim 1, characterized in that the wiring board has a seventh surface on which the electronic components are mounted, opposite the third surface, and an eighth surface, opposite the sixth surface.

10. An imaging unit as described in claim 9, characterized in that the first length from the inner surface of the virtual space extending from the image sensor in the optical axis direction to the eighth surface is different from the second length from the inner surface of the virtual space to the sixth surface.

11. An imaging device having an imaging unit at the tip of an insertion portion, the imaging unit having an image sensor, a wiring board, and at least one electronic component, the image sensor having a light-receiving surface and a back surface opposite the light-receiving surface, and an external electrode on the back surface, the wiring board being a multilayer rigid wiring board in which a first block, a second block, a third block, and a fourth block are stacked in the above order in the direction of the optical axis of the image sensor, the first block having a first surface and a second surface opposite the first surface, a first electrode joined to the external electrode on the first surface, and a second electrode connected to the first electrode via first internal wiring on the second surface, the second block having a third surface perpendicular to the second surface, and a third electrode on the third surface, a first end of the third electrode being in contact with the second electrode, the third block has a fourth surface perpendicular to the third surface and a fifth surface opposite the fourth surface, a fourth electrode on the fourth surface that is in contact with a second end of the third electrode, and a fifth electrode on the fifth surface that is connected to the fourth electrode via a second internal wiring; the fourth block has a sixth surface perpendicular to the fifth surface and a sixth electrode on the sixth surface, the third end of the sixth electrode being in contact with the fifth electrode; and the electronic component is bonded to the third electrode.

12. A laminated sheet is produced by laminating a first sheet, a second sheet, a third sheet, and a fourth sheet in the above order, each of which has a plurality of wiring sheets laminated thereon; the first sheet has a first surface and a second surface opposite to the first surface, and has a first electrode on the first surface and a second electrode on the second surface connected to the first electrode via first internal wiring; the second sheet has a third surface perpendicular to the second surface and has a third electrode on the third surface, and a first end of the third electrode is in contact with the second electrode; the third sheet has a fourth surface perpendicular to the third surface and a fifth surface opposite to the fourth surface, and has a fourth electrode on the fourth surface in contact with a second end of the third electrode and a fifth electrode on the fifth surface connected to the fourth electrode via second internal wiring; the fourth sheet has a sixth surface perpendicular to the fifth surface and has a sixth electrode on the sixth surface in contact with the fifth electrode; and firing the laminated sheet; a method for manufacturing an imaging unit, comprising: providing a plating film on a surface of each of the first electrode, the third electrode, and the sixth electrode to fabricate a multilayer rigid wiring board; bonding an external electrode of an image sensor to the first electrode on the first surface of the multilayer rigid wiring board; and bonding an electronic component to the third electrode on the third surface.

13. The method for manufacturing an imaging unit described in claim 12, characterized in that the laminated sheet containing a plurality of components that will become the multilayer rigid wiring board is separated into a plurality of multilayer rigid wiring boards after the plating film is disposed thereon.

Images