Wiring board, imaging unit, and endoscope

Abstract

The invention provides a wiring board, an imaging unit, and an endoscope. The wiring board has a first main surface and a second main surface, a first pad, a second pad, and a wiring pattern are disposed on the first main surface, the wiring pattern connects the first pad and the second pad, an electronic component is bonded to the first pad using a solder, and the second pad is bonded to the second pad using a solder. A solder non-wetting region is formed on the second pad that is not soldered to another member.

Description

Technical Field

[0001] The present invention relates to a wiring board to which electronic components are soldered, an imaging unit having a wiring board to which a camera unit is soldered, and an endoscope including the imaging unit. The imaging unit has a wiring board to which a camera unit is soldered. Background Art

[0002] In recent years, three-dimensional circuit devices, such as molded circuit devices (MID), have been used to achieve miniaturization and high functionality of electronic devices.

[0003] Japanese Patent Publication No. 2017-23234 discloses a camera unit of an endoscope using a special-shaped circuit board as a three-dimensional circuit device. The camera unit includes an imaging element, a flat wiring board (flat wiring board) on which electronic components are mounted, and a special-shaped circuit board (three-dimensional wiring board). A plurality of cables are connected to the plurality of side surfaces of the special-shaped circuit board.

[0004] International Publication No. 2021 / 181530 discloses an imaging unit in which a camera unit is mounted in a cavity of a molded circuit device. The external electrode of the camera unit is connected to a signal cable via a through wiring that penetrates the bottom surface of the cavity and reaches a through hole on the back surface.

[0005] When soldering the camera unit to the three-dimensional circuit device, if the solder flows out of the through hole, not only the bonding reliability is reduced, but also the camera unit may move from the specified position. When the optical axis of the camera unit deviates from the specified position, the desired field of view cannot be obtained, and the performance of the camera device may be reduced.

[0006] Japanese Patent Application Laid-Open No. 2020-181856 discloses a wiring board in which a gold layer on a wiring surface is removed and diffused by irradiating a laser in order to suppress outflow of solder into the wiring, thereby exposing a nickel layer under the gold layer. Summary of the invention

[0007] A wiring board of one embodiment of the present invention comprises a first main surface and a second main surface on the opposite side of the first main surface, and one or more first solder pads, one or more second solder pads and one or more wiring patterns are arranged on the first main surface, the wiring pattern connects the first solder pad with the second solder pad, there is an area on the first solder pad to which electronic components can be joined, and a solder non-wetting area is formed on the second solder pad that is not soldered to other components.

[0008] A camera unit according to one embodiment of the present invention comprises: a wiring board having a first main surface and a second main surface on the opposite side of the first main surface, the wiring board being provided with one or more first solder pads, one or more second solder pads and one or more wiring patterns on the first main surface, the wiring patterns respectively connecting the first solder pads with the second solder pads; and a camera unit, which is joined to the first solder pad using solder, and a solder non-wetting area is formed on the second solder pad which is not joined to other components by soldering.

[0009] An endoscope according to one embodiment of the present invention has a camera unit at the front end of the insertion portion, the camera unit comprising: a wiring board having a first main surface and a second main surface on the opposite side of the first main surface, the wiring board being provided with one or more first solder pads, one or more second solder pads and one or more wiring patterns on the first main surface, the wiring patterns respectively connecting the first solder pads with the second solder pads; and a camera unit, which is joined to the first solder pad using solder, and a solder non-wetting area is formed on the second solder pad which is not soldered to other components. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a perspective view of the imaging unit according to the first embodiment.

[0011] Figure 2 It is a perspective view of the imaging unit according to the first embodiment.

[0012] Figure 3 It is along Figure 1 Cross-sectional view along line III-III.

[0013] Figure 4 yes Figure 3 A partial enlarged view of .

[0014] Figure 5 It is a bottom view of the camera unit of the image pickup unit according to the first embodiment.

[0015] Figure 6 It is a bottom view of the cavity of the wiring board of the image pickup unit according to the first embodiment.

[0016] Fig. 7A This is an enlarged bottom view of the cavity of the wiring board of the image pickup unit according to the first embodiment.

[0017] Figure 7B This is an enlarged view of the bottom surface of the cavity before the solder non-wetting region is formed on the wiring board of the image pickup unit according to the first embodiment.

[0018] Figure 8 This is a flowchart of the method for manufacturing the image pickup unit according to the first embodiment.

[0019] Fig. 9A This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0020] Fig. 9B This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0021] Fig. 9C This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0022] Fig.9D This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0023] Fig.9E This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0024] Fig.9F This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0025] Figure 9G This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0026] Figure 9H This is an enlarged bottom view of a cavity of a wiring board of an image pickup unit according to a modification of the first embodiment.

[0027] Fig.10 It is a partial plan view of the second main surface of the wiring board of the image pickup unit according to the modification of the first embodiment.

[0028] Fig.11 This is a partial cross-sectional view of a wiring board of an image pickup unit according to a modified example of the first embodiment.

[0029] Fig.12 It is a perspective view of an endoscope according to a second embodiment. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described using the drawings.

[0031] In addition, the drawings based on the embodiments are schematic. The relationship between the thickness and width of each part, the ratio of the thickness of each part, etc. are different from reality. The drawings also include parts where the relationship and ratio of each other's dimensions are different.

[0032] <First Embodiment>

[0033] Figure 1 to Figure 4The present embodiment shows an image pickup unit 1 having a wiring board 20. The image pickup unit 1 has a wiring board 20 and a camera unit 10 as an electronic component. As described later, the wiring board 20 is a three-dimensional wiring board as a molded circuit device (MID: Molded Interconnect Device).

[0034] The wiring board 20 is a three-dimensional (stereoscopic) molded circuit component in which a plurality of conductor patterns are arranged on a three-dimensional molded base body made of injection-molded resin. Regarding the wiring board 20, unlike a flat wiring board, the shape of the wiring board 20 is functional, and the conductor patterns can be arranged on an inclined surface, a vertical surface, a curved surface, a through hole, etc.

[0035] The wiring board 20 has an assembly part 20A and a convex part 20B protruding from the assembly part 20A. The convex part 20B surrounded by a frame-like wall constitutes a cavity C20 which is a hole with a bottom for accommodating the camera unit 10. The gap between the camera unit 10 accommodated in the cavity C20 and the inner wall surface 20SS of the cavity C20 is filled with a sealing resin 32. Hereinafter, the bottom surface of the cavity C20 is referred to as the first main surface 20SA, and the surface on the opposite side of the first main surface 20SA is referred to as the second main surface 20SB.

[0036] A plurality of solder resist patterns 31 are arranged on the wiring patterns 26 of the second main surface 20SB. Electronic components, such as chip capacitors 40, are mounted on the upper surfaces of two wiring patterns 26 between two solder resist patterns 31. The solder resist patterns 31 are arranged to mount electronic components on the two parallel wiring patterns 26. Although not shown, a signal cable is connected to the fourth pad 27.

[0037] like Figure 3 and Figure 4 As shown, the camera unit 10 includes an imager 11 and an optical element 12. The optical element 12 includes a plurality of lenses. The imager 11 is an imaging element such as a CCD or a CMOS that converts a subject image focused by the optical element 12 into an electrical signal.

[0038] like Figure 5 As shown, the camera unit 10 (imager 11) has a plurality of external electrodes 13 for transmitting and receiving electric signals on the bottom surface 10SB. Solder bumps 14X are respectively provided on the plurality of external electrodes 13. The plurality of solder bumps 14X constitute a ball grid array. The camera unit 10 is joined to the wiring board 20 by the solder 14 as a joining member formed by melting the solder bumps 14X.

[0039] like Figure 6As shown, a plurality of first pads 21, a plurality of wiring patterns 22, and a plurality of second pads 23 are arranged on the first main surface 20SA of the wiring board 20. The wiring board 20 has a plurality of through holes H20 that penetrate the first main surface 20SA and the second main surface 20SB. A through wiring layer 24 is arranged on the inner surface of the through hole H20. The second pads 23 are connected to the through wiring layer 24. A third pad 25 and a wiring pattern 26 extending from the through wiring layer 24, and a fourth pad 27 arranged at the end of the wiring pattern 26 are arranged on the second main surface 20SB.

[0040] As described later, the first pad 21, the wiring pattern 22, the second pad 23, the through wiring layer 24, the third pad 25, the wiring pattern 26, and the fourth pad 27 are conductor multilayer films formed simultaneously using a plating method, and their boundaries are not clear. However, in this specification, for the convenience of description, for example, a structure in which the second pad 23 is arranged on the first main surface 10SA and the through wiring layer 24 is extended from the bottom surface of the second pad 23 is described.

[0041] In addition, the "pad" means an electrode formed of a conductor pattern. The "pad" is not limited to, for example, an electrode bonded by soldering or an electrode provided around a through hole.

[0042] The first pad 21, the wiring pattern 22, the second pad 23, the through wiring layer 24, the third pad 25, the wiring pattern 26 and the fourth pad 27 are composed of, for example, a Cu / Ni / Au multilayer film in which a nickel layer (Ni) and a gold layer (Au) are sequentially stacked on a copper layer (Cu). The nickel layer is a diffusion prevention layer for solder and has poor solder wettability. The gold layer has very good solder wettability. The thickness of each layer of Cu / Ni / Au is, for example, 12μm / 3μm / 0.03μm.

[0043] The inner diameter of the through hole H20 is larger than twice the thickness of the through wiring layer 24. Therefore, the through hole H20 is not blocked by the through wiring layer 24, and has an opening O23 at the center of the second pad 23.

[0044] When the camera unit 10 (electronic component) is soldered to the wiring board 20, when the solder bump 14X melts, the camera unit 10 may move in the direction where the solder 14 flows out. In particular, if the solder 14 flows from the opening O23 into the through hole H20 via the wiring pattern 22, the connection between the external electrode 13 and the first pad 21 may become weak, or the camera unit 10 may be connected obliquely.

[0045] like Figure 6As shown, in the camera unit 1, the plurality of wiring patterns 22 are each led out from each of the plurality of first pads 21 to each of the plurality of second pads 23 symmetrically with the optical axis O of the camera unit 10 as the center. The second pads 23 are located in an area (an area close to the outer edge) that is closer to the outside of the first main surface 20SA than the first pads 21. The plurality of wiring patterns 22 have substantially the same length L22. Therefore, the second distance D2 between the plurality of second pads 23 adjacent to each other is longer than the first distance D1 between the plurality of first pads 21 adjacent to each other.

[0046] Furthermore, “substantially the same length” means that the length L22 of each wiring pattern 22 exceeds 90% of the average value of the lengths of the plurality of wiring patterns 22 and is less than 110% (including 100%) of the average value.

[0047] The camera unit 1 is ultra-small, so Fig. 7A As shown, the width W22 of the wiring pattern is, for example, 100 μm, and the length L22 is 200 μm. Fig. 7A : This is a partial enlarged view of the first main surface 10SA before the solder non-wetting area is formed. The outer diameter D21 of the first pad is, for example, 130 μm, and the outer diameter D23 of the second pad is, for example, 250 μm. That is, the area A23 of the second pad 23 is larger than the area A21 of the first pad 21. In addition, the opening diameter DO23 of the opening O23 of the second pad 23 is, for example, 50 μm to 150 μm.

[0048] Moreover, if Figure 7B As shown, an annular solder non-wetting area S23 is formed on the second pad 23 so as to surround the opening O23. The outer diameter DS23 of the solder non-wetting area S23 is smaller than the outer diameter D23 of the second pad 23. The inner diameter of the solder non-wetting area S23 is substantially the same as the opening diameter DO23 of the opening O23 of the second pad 23.

[0049] As described later, the solder non-wetting region S23 is a region where the gold layer of the second pad 23 is removed and diffused by laser irradiation, and the nickel layer under the gold layer is exposed.

[0050] In the imaging unit 1, when the camera unit 10 is soldered to the wiring board 20, the outflowing solder 14 does not diffuse into the solder non-wetting area S23, so the solder 14 does not flow into the through hole H20 from the opening O23 via the second pad 23. In addition, the solder 14 provided on the plurality of first pads 21 flows into the plurality of wiring patterns 22 symmetrically arranged around the center (optical axis O) of the camera unit 10. Therefore, the camera unit 10 does not move during bonding and is bonded accurately at a predetermined position.

[0051] Since the camera unit 10 is accurately bonded to a predetermined position of the wiring board 20 , the image pickup unit 1 has high performance.

[0052] In addition, for example, the outflow of the solder 14 can be prevented by forming an annular solder non-wetting area on the first pad 21 to be soldered to the camera unit 10. However, if the solder non-wetting area is formed on the pad to be soldered, the soldering area is further reduced, so the bonding reliability may be reduced.

[0053] In particular, if the solder non-wetting region is formed on the smaller first pad 21, the solder joint area becomes further reduced. On the other hand, since no other components are joined by solder on the second pad 23, the reliability will not be reduced even if the solder non-wetting region is formed.

[0054] Furthermore, by forming a solder non-wetting area on the wiring pattern 22, it is also possible to prevent the solder 14 from flowing out. However, it is not easy to accurately irradiate the narrow wiring pattern 22 with a laser. If the laser is mistakenly irradiated to the resin around the wiring pattern 22, the MID will be damaged. In contrast, the second pad 23 has a relatively large area, so there is no worry about the laser being mistakenly irradiated.

[0055] <Method of Manufacturing Image Capture Unit>

[0056] Below, according to Figure 8 The manufacturing method of the imaging unit is described with reference to the flowchart of FIG.

[0057] <Step S10> Molding process (making a molding substrate)

[0058] The three-dimensional substrate is produced by injection molding by injecting MID resin into a mold having a concave portion of the outer shape of wiring board 20. A precursor such as a non-conductive metal complex that becomes a plating catalyst by light irradiation is added to the MID resin.

[0059] <Step S20> Laser Irradiation Steps 1 and 2 (Forming Through Holes and Forming Active Layers)

[0060] By irradiating the second main surface 20SB of the three-dimensional substrate with a high-output first laser, a through hole H20 is formed from the second main surface 20SB to the first main surface 20SA (laser irradiation 1). The opening of the through hole H20 on the second main surface 20SB is larger than the opening of the through hole H20 on the first main surface 20SA. An activated catalyst layer is formed on the wall surface of the through hole H20.

[0061] Furthermore, the first main surface 20SA and the second main surface 20SB are pattern-irradiated with a second laser in order to arrange the first pad 21, the wiring pattern 22, the second pad 23, the third pad 25, the wiring pattern 26, and the fourth pad 27. By irradiating the molded substrate with the second laser, a catalyst layer having catalytic activity of electroless plating is formed on the molded substrate (laser irradiation 2).

[0062] <Step S30> Plating process

[0063] By sequentially performing electroless copper plating, electroless nickel plating, and displacement gold plating on the molded substrate having the catalyst layer pattern formed thereon, the molded substrate becomes a wiring board 20 having a plurality of conductor patterns arranged on the first main surface 20SA, the second main surface 20SB, and the through hole H20. The plurality of conductor patterns constitute the first pad 21, the wiring pattern 22, the second pad 23, the through wiring layer 24, the third pad 25, the wiring pattern 26, and the fourth pad 27.

[0064] like Figure 5 As shown, the plurality of external electrodes 13 disposed on the bottom surface 10SB of the camera unit 10 are disposed at four-fold symmetrical positions with the optical axis O as the center. In other words, the plurality of external electrodes 13 are disposed at positions where they overlap when rotated 90 degrees relative to the optical axis O. A solder bump 14X is disposed on each of the plurality of external electrodes 13 .

[0065] like Figure 6 As shown, a plurality of first pads 21, a plurality of wiring patterns 22, and a plurality of second pads 23 are provided on the first main surface 20SA of the wiring board 20. The first pads 21 are bonded to the external electrodes 13 of the camera unit 10 by solder 14.

[0066] The wiring pattern 22 is radially extended from each of the plurality of first pads 21. At the end of the wiring pattern 22, a second pad 23 connected to the through wiring layer 24 is provided.

[0067] Furthermore, the plurality of first pads 21 , the plurality of wiring patterns 22 , and the plurality of first pads 21 are arranged at four-fold symmetrical positions with the optical axis O as the center.

[0068] In addition, the plurality of external electrodes 13, the plurality of first pads 21, and the like may be arranged at N-fold symmetrical positions (N is a natural number greater than or equal to 2) with the optical axis O as the center.

[0069] <Step S40> Resist (resin) placement step

[0070] A solder resist pattern 31 is disposed on the second main surface 20SB using a dispenser.

[0071] In addition, step S40 may also be performed after step S50.

[0072] <Step S50> Solder Non-Wetting Area Formation Step (Laser Irradiation Step 3)

[0073] By laser irradiation, at least a portion of the gold layer of the second pad 23 is removed and diffused, thereby forming a solder non-wetting region S23 where the nickel layer is exposed. The laser spot diameter is, for example, 5 μm to 150 μm.

[0074] Since the second pad 23 having a large area is irradiated with the laser, even if the irradiation position is shifted, the laser is unlikely to irradiate the resin in the surrounding area where no electrode is provided.

[0075] Solder wettability is measured, for example, by the "solder tank balance method" specified in Japanese Industrial Standard Z3198-4. The area with a longer zero crossing time (the time until the contact angle reaches 90 degrees after immersion) has poor solder wettability compared to the area with a shorter zero crossing time. The area with a zero crossing time of more than 5 seconds is called a solder non-wetting area. In addition, the solder wettability is measured using a solder non-wetting area on a test piece with the same structure as the conductor pattern of the first main surface 20SA formed under the same conditions as step S50.

[0076] <Step S60> Camera Unit Mounting Process

[0077] The camera unit 10 is a CSP (Chip Size Package) produced by bonding a glass wafer to a semiconductor wafer having a plurality of imagers 11 and then cutting the wafer. The size of the camera unit 10 is, for example, 1 mm square to 3 mm square. The camera unit 10 may also further have a semiconductor chip for processing imaging signals bonded to the back of the imager 11.

[0078] The camera unit 10 is housed in the cavity C20 in a state where each of the plurality of external electrodes 13 is aligned with each of the plurality of first pads 21. Before the camera unit 10 is housed in the cavity C20, solder paste may be applied to the first pads 21.

[0079] Furthermore, a two-terminal electronic component, such as a chip capacitor 40, is temporarily fixed between the two solder resist patterns 31 on the second main surface 20SB of the wiring board 20. The two terminals of the chip capacitor 40 have, for example, a solder coating. Solder paste may also be applied to the joint position of the wiring pattern 26. In addition, the interval between the two parallel wiring patterns 26 is substantially the same as the interval between the two terminals of the chip capacitor 40.

[0080] <Step S70> Reflow process

[0081] For example, the camera unit 1 is heated to a temperature at which the solder 14 melts using a reflow furnace. When the camera unit 1 returns to room temperature, the external electrode 13 of the camera unit 10 is soldered to the first pad 21 of the wiring board 20. In addition, the chip capacitor 40 is soldered to the wiring pattern 26.

[0082] After the reflow process, when the sealing resin 32 is injected between the cavity C20 and the camera unit 10 and a curing process is performed, the image pickup unit 1 is completed.

[0083] When the solder bump 14X melts during the reflow process, the camera unit 10 may move in the direction where the solder 14 flows out. If the solder 14 flows into the through hole H20, the connection between the external electrode 13 and the first pad 21 may be weakened or the camera unit 10 may be connected obliquely.

[0084] In the image pickup unit 1, the plurality of wiring patterns 22 through which the solder 14 flows out are equal in width and length. In other words, after reflow, the plurality of wiring patterns 22 through which the solder 14 flows out have the same area.

[0085] The solder 14 flows out along the plurality of wiring patterns 22 arranged at four-fold symmetric positions around the camera unit 10 (optical axis O). Therefore, the camera unit 10 is automatically and accurately joined to a desired position by a self-alignment effect during the reflow process. According to this manufacturing method, a high-performance camera unit 1 can be manufactured.

[0086] In addition, the plurality of first pads 21, the plurality of second pads 23, and the plurality of wiring patterns 22 may be arranged at N-fold symmetrical positions (N is a natural number equal to or greater than 2).

[0087] <Solder Non-Wettable Area and Pad of Image Pickup Unit of Modified Example>

[0088] Hereinafter, an image pickup unit of a modified example of the first embodiment will be described. The image pickup unit of the modified example is similar to the image pickup unit of the first embodiment and has the same effects as the image pickup unit of the first embodiment. Therefore, description of the same structure as the image pickup unit of the embodiment will be omitted.

[0089] The solder non-wetting region S23 can be appropriately selected from a plurality of shapes in which the solder 14 does not flow into the through-hole H20 via the opening O23 .

[0090] Fig. 9A The annular solder non-wetting area S23 shown is formed on the entire surface of the second pad 23 .

[0091] about Fig. 9BThe annular solder non-wetting area S23 shown has an inner diameter larger than the opening diameter of the opening O23 and an outer diameter smaller than the outer diameter of the second pad 23 .

[0092] Fig. 9C The solder non-wetting region S23 shown is formed so that the outer peripheral diameter is smaller than the outer peripheral diameter of the second pad 23 , but a part thereof is in contact with the end portion T22 of the wiring pattern 22 .

[0093] about Fig.9D The annular solder non-wetting area S23 shown has an inner diameter larger than the opening diameter of the opening O23 and an outer diameter substantially the same as the outer diameter of the second pad 23 .

[0094] Fig.9E The illustrated annular solder non-wetting area S23 surrounds the opening O23 of the rectangular second pad 23 .

[0095] Fig.9F The illustrated annular solder non-wetting area S23 surrounds the opening O23 of the elliptical second pad 23 .

[0096] Figure 9G The solder non-wetting area S23 shown is a rectangle surrounding the opening O23 of the second pad 23 .

[0097] If the solder non-wetting area S23 is formed to the outer periphery of the second pad 23, the solder 14 will not flow into the second pad 23. Therefore, the reliability of the joint is high. The solder non-wetting area S23 ( Fig. 9C ) also has a solder non-wetting area S23 ( Fig. 9A , Fig.9D ) to the same effect.

[0098] Figure 9H The solder non-wetting area S23 shown is formed on the entire surface of the second pad 23 without an opening. Even if the second pad 23 has no opening, that is, the second pad 23 is arranged in a region without a through hole, if the solder non-wetting area S23 is formed, the solder 14 will not flow into the second pad 23. Therefore, the reliability of the joint is high.

[0099] The outer shape of the second pad 23 is not limited to a circle. Similarly, the outer shape of the first pad 21 is not limited to a circle.

[0100] A dummy electrode may be provided on the optical axis O of the bottom surface 10SB of the camera unit 10. In the case of the above structure, a dummy pad soldered to the dummy electrode is also provided on the optical axis O of the first main surface 20SA of the wiring board 20. No wiring pattern is extended from the dummy pad. The dummy electrode may also be connected to the external electrode 13 of the ground potential at the imager 11, for example.

[0101] <Installation of chip capacitors>

[0102] The camera unit 10 is described above as an example of an electronic component soldered to the first pad 21 of the first main surface 20SA of the wiring board 20. Next, a modified example of an imaging unit in which a chip capacitor 40 is also soldered near the through hole H20 of the second main surface 20SB is described.

[0103] exist Fig.10 , Fig.11 In the image pickup unit 1 of the illustrated modification, the chip capacitor 40 is mounted in the region 20SB1 on the second principal surface 20SB on the opposite side to the bottom surface (first principal surface 20SA) of the convex portion 20B.

[0104] The third pad 25A has an opening that is disposed on the wall surface of the through hole H20 and passes through the wiring layer. The two fourth pads 27A that are soldered to the chip capacitor 40 are substantially rectangular. The fourth pad 27A is connected to the third pad 25A via the wiring pattern 26A.

[0105] The third pad 25A surrounding the through hole H20 is formed with, for example, Figure 7B The solder non-wetting area S23 has the same shape as the solder non-wetting area S25. The third pad 25A is not solder-bonded to other components.

[0106] Two wiring patterns 26A are led out from the respective fourth pads 27A to the respective third pads 25A symmetrically with respect to the center O40 of the chip capacitor 40 .

[0107] The melted solder 15 at both ends of the chip capacitor 40 spreads to each wiring pattern 26A symmetrically with respect to the center O40 of the chip capacitor 40. Since the solder non-wetting area S25 is formed, the solder 15 does not flow into the through hole H20 via the third pad 25A.

[0108] Therefore, the chip capacitor 40 is bonded to a desired position using a self-alignment effect, and the bonding reliability is high.

[0109] In addition, the wiring board for soldering electronic components such as chip capacitors is not limited to a three-dimensional wiring board. For example, even if it is a planar wiring board, the reliability of the joint can be ensured by forming a solder non-wetting area on the second pad connected to the first pad soldered to other components using a wiring pattern.

[0110] <Second Embodiment>

[0111] like Fig.12 As shown in FIG. 1 , the endoscope 9 of this embodiment includes: a front end portion 9A, which is provided with an imaging unit 1; a bendable bending portion 9B, which is connected to the base end of the front end portion 9A; and an elongated soft portion 9C, which is connected to the base end of the bending portion 9B. The bending portion 9B is bent by the user operating an operating portion 9D. The front end portion 9A, the bending portion 9B, and the soft portion 9C are insertion portions to be inserted into the body. A universal cable 9E extending from the operating portion 9D is connected to a processor, etc., not shown.

[0112] Since the endoscope 9 includes the imaging unit 1 , it has high reliability and high performance.

[0113] The endoscope 9 is a side-viewing flexible endoscope for medical use, but the endoscopes of other embodiments may be industrial endoscopes or rigid endoscopes having a rigid straight tube instead of the flexible portion 9C. Furthermore, the imaging unit 1 may also be used for a direct-viewing endoscope in which the object direction is the tip direction.

[0114] The three-dimensional circuit device is not limited to MID, and can be manufactured by, for example, processing with a 3D printer or cutting. The material of the three-dimensional circuit device is not limited to resin, and ceramic or glass epoxy resin can also be used.

[0115] The present invention is not limited to the above-described embodiments and the like, and various changes and modifications can be made without departing from the spirit and scope of the present invention.

Claims

1. A wiring board, wherein: The wiring board has a first main surface and a second main surface opposite to the first main surface. One or more first pads, one or more second pads, and one or more wiring patterns are arranged on the first main surface. The wiring pattern connects the first pad and the second pad. The first pad has a region to which an electronic component can be bonded, and the second pad, which is not solder-bonded to other components, has a solder non-wetting region.

2. The wiring board according to claim 1, wherein The second pad is composed of a multi-layer film, and the multi-layer film is composed of a copper layer / a nickel layer / a gold layer, The solder non-wetting area is an area where the nickel layer is exposed.

3. The wiring board according to claim 1, wherein The wiring board includes a plurality of first pads, a plurality of second pads, and a plurality of wiring patterns. The plurality of wiring patterns are respectively led out from each of the plurality of first pads to each of the plurality of second pads symmetrically around a bonding region of the electronic component.

4. The wiring board according to claim 3, wherein The plurality of wiring patterns have substantially the same length.

5. The wiring board according to claim 1, wherein The solder non-wetting region is formed to be in contact with the wiring pattern.

6. The wiring board according to claim 1, wherein The solder non-wetting region is formed to the outer periphery of the second pad.

7. The wiring board according to claim 3, wherein The wiring board has a plurality of through holes extending from the first main surface to the second main surface. A through wiring layer is disposed on the wall surfaces of the plurality of through holes, respectively. The openings of the through wiring layer are respectively located at the centers of the plurality of second pads, The respective solder non-wetting regions are formed on the respective pads of the plurality of second pads so as to surround the respective openings.

8. The wiring board according to claim 7, wherein The wiring board is a three-dimensional wiring board having a frame-shaped wall constituting a cavity, The first main surface is a bottom surface of the cavity.

9. The wiring board according to claim 1, wherein An area of ​​the second pad is larger than an area of ​​the first pad.

10. The wiring board according to claim 1, wherein The second pad is located outside the first pad.

11. The wiring board according to claim 1, wherein The wiring board includes a plurality of first pads, a plurality of second pads, and a plurality of wiring patterns. A second distance between the plurality of second pads adjacent to each other is longer than a first distance between the plurality of first pads adjacent to each other.

12. A camera unit, wherein: The camera unit comprises: A wiring board having a first main surface and a second main surface opposite to the first main surface, wherein the wiring board is provided with one or more first pads, one or more second pads, and one or more wiring patterns on the first main surface, wherein the wiring patterns connect the first pads and the second pads; and a camera unit joined to the first pad using solder, A solder non-wetting area is formed on the second pad that is not solder-bonded to other components.

13. An endoscope, wherein: The endoscope has an imaging unit at the front end of the insertion portion. The camera unit comprises: A wiring board having a first main surface and a second main surface opposite to the first main surface, wherein the wiring board is provided with one or more first pads, one or more second pads, and one or more wiring patterns on the first main surface, wherein the wiring patterns connect the first pads and the second pads; and a camera unit joined to the first pad using solder, A solder non-wetting area is formed on the second pad that is not solder-bonded to other components.

Images