Electronic circuit board, laminated board, and method of manufacturing electronic circuit board

An electronic circuit board includes: electronic components; a silicon board that is plate shaped, includes a wiring pattern provided on at least one of a surface and a reverse surface thereof, and includes recessed portions where the electronic components are individually mounted; and a supporting board that is layered over the reverse surface of the silicon board, and includes a wiring pattern provided on at least one of a surface and a reverse surface thereof. Side faces of the recessed portions are perpendicular to the surface of the silicon board, the wiring pattern is connected to at least one of the electronic components mounted in the recessed portions, via at least one of a via and a bottom surface electrode provided in of the at least one of the recessed portions, and the recessed portions penetrate through the silicon board.

BACKGROUND

The present disclosure relates to an electronic circuit board, a laminated board, and a method of manufacturing the electronic circuit board.

Endoscopes have been widely used for various examinations in the medical field and the industrial field. Especially, medical endoscopes are widely used, because by insertion of an elongated and flexible insertion unit having a solid state imaging element provided at a distal end thereof into a body cavity of a subject, such as a patient, in-vivo images inside the subject are able to be acquired without incision of the subject, and further, curative treatment is able to be carried out by protrusion of a treatment tool from the distal end of the insertion unit, as necessary.

In an imaging device used in such an endoscope, generally: a light receiving surface of a CCD chip thereof is covered by cover glass; an inner lead of a TAB tape is connected to an electrode provided at an outer peripheral edge portion of the light receiving surface; and the CCD chip is connected to electronic components and an external information processing device (see, for example, Japanese Unexamined Patent Application, Publication No. H11-76152).

In recent years, the number of electronic components used in an imaging device has increased, but for reduction of burdens on subjects, decrease in diameters and decrease in lengths of distal ends of insertion units of endoscopes are demanded, and thus a technique for improving mounting density of electronic components has been desired.

As a technique for improving mounting density of electronic components, a technique of forming a recessed portion in a silicon board and mounting a mounted component in the recessed portion has been proposed (see, for example, Japanese Unexamined Patent Application, Publication No. 2002-151801).

Further, a technique of forming an opening in a metal core, blocking the opening by forming an insulating layer on at least one of principal surfaces of the metal core, and mounting an electronic component in the opening has been proposed (see, for example, Japanese Unexamined Patent Application, Publication No. 2013-141028).

SUMMARY

An electronic circuit board according to one aspect of the present disclosure includes: electronic components; a silicon board that is plate shaped, includes a wiring pattern provided on at least one of a surface and a reverse surface thereof, and includes recessed portions where the electronic components are individually mounted; and a supporting board that is layered over the reverse surface of the silicon board, and includes a wiring pattern provided on at least one of a surface and a reverse surface thereof, wherein side faces of the recessed portions are perpendicular to the surface of the silicon board, the wiring pattern is connected to at least one of the electronic components mounted in the recessed portions, via at least one of a via and a bottom surface electrode provided in of the at least one of the recessed portions, and the recessed portions penetrate through the silicon board.

The above and other features, advantages and technical and industrial significance of this disclosure will be better understood by reading the following detailed description, when considered in connection with the accompanying drawings.

DETAILED DESCRIPTION

In the following description, as modes for carrying out the present disclosure (hereinafter, referred to as “embodiments”), electronic circuit boards, a laminated board having electronic circuit boards layered over each other, and methods of manufacturing the electronic circuit boards will be described. Further, the present disclosure is not limited by these embodiments. Furthermore, the same portions are assigned with the same reference signs, throughout the drawings. Moreover, the drawings are schematic, and it needs to be noted that a relation between a thickness and a width of each member and ratios among respective members are different from the actual relation and ratios. In addition, there may be portions that differ in their dimensions and ratios among the drawings, too.

First Embodiment

FIG. 1is a sectional view of an electronic circuit board according to a first embodiment. An electronic circuit board100according to the first embodiment includes: a silicon board20having recessed portions21ato21dwhere electronic components40ato40dare mounted; a supporting board10that is layered over a reverse surface f2of the silicon board20; and an insulating protective layer30that is layered over a surface f1of the silicon board20.

The silicon board20is plate-shaped, and has the recessed portions21ato21dformed therein, the recessed portions21aand21dpenetrating therethrough from the surface f1to the reverse surface f2. Side faces of the recessed portions21ato21dare perpendicular to the surface f1of the silicon board20. The recessed portions21ato21dare formed by dry etching, preferably inductively coupled plasma (ICP) anisotropic etching. By the formation of the recessed portions21ato21dby ICP etching, the recessed portions21ato21dare able to be formed with high positional accuracy and narrow pitches.

The supporting board10is layered by being laminated on the reverse surface f2side of the silicon board20. The supporting board10is formed of a glass epoxy board, a flexible printed circuit board, or the like, and functions as a bottom face of the recessed portions21ato21don the reverse surface f2side thereof. The electronic components40ato40dare connected onto the supporting board10serving as the bottom face of the recessed portions21ato21d. The recessed portions21ato21dhaving the electronic components40ato40daccommodated therein have sealing resin22filled therein. The electronic components40ato40dused in this first embodiment each have a size with a length of each side thereof being equal to or less than 1 mm, for example, the so-called0402size (0.4 mm×0.2 mm), or the like.

The insulating protective layer30is layered by being laminated on a surface f1side of the silicon board20. Electrically conductive vias31ato31dare formed in the insulating protective layer30on the recessed portions21ato21d. A wiring pattern that is formed on a surface f3side of the insulating protective layer30and not illustrated in the drawings is electrically connected to the electronic components40ato40daccommodated in the recessed portions21ato21dvia the vias31ato31d.

An example, in which an insulating protective layer is stuck and via openings are formed by laser or the like, has been described above; but instead, processing, in which, after application of resin, the resin is polished so as to make the resin uniform and expose a plane, and vias up to electronic components are formed by etching of a protective layer after photolithography, may be adopted. In particular, if a photosensitive resin material is used, processing of vias by photolithography and formation of a protective film may be carried out simultaneously.

Further, if application of resin is adopted as a method of forming an insulating protective layer, the insulating protective layer may also serve as the sealing resin22.

Next, by reference toFIG. 2AtoFIG. 2E, a manufacturing process for the electronic circuit board100will be described.FIG. 2AtoFIG. 2Eare diagrams for explanation of a method of manufacturing the electronic circuit board according to the first embodiment.

As illustrated inFIG. 2A, after the supporting board10and the silicon board20are layered over each other by being laminated onto each other, the silicon board20is subjected to etching from the surface f1side of the silicon board20, and thereby the recessed portions21ato21dare formed. The recessed portions21ato21dare formed by dry etching, preferably ICP etching, by: a photoresist layer being layered over the surface f1of the silicon board20, and a pattern of the recessed portions21ato21dbeing formed on the photoresist layer by photolithography, with this photoresist layer being a mask. By the recessed portions21ato21dbeing etched by ICP, the recessed portions21ato21dhaving the side faces that are perpendicular to the surface f1of the silicon board20are able to be formed. Since the side faces of the recessed portions21ato21dare perpendicular to the surface f1of the silicon board20, the recessed portions21ato21dare able to be formed with narrow pitches and mounting density thereof is able to be improved. In ICP etching, intervals between the recessed portions21ato21dare each able to be made about 10 μm, but for increase in mechanical strength thereof, the intervals between the recessed portions21ato21dare each preferably made about 20 μm. Further, insulating protective layers are preferably formed on inner wall faces of the recessed portions21ato21d. The insulating protective layers may be formed by, for example, formation of silicon oxide films by plasma CVD or the like in the recessed portions21ato21dafter ICP etching. By the formation of the insulating protective layers on the inner wall faces of the recessed portions21ato21d, even if sizes of the recessed portions21ato21dare slightly larger than those of the electronic components40ato40d, insulation is able to be obtained.

After the recessed portions21ato21dare formed, as illustrated inFIG. 2C, the electronic components40ato40dare arranged to be individually accommodated in the recessed portions21ato21d. A joining material of solder, electrically conductive resin, or insulating resin is applied in the recessed portions21ato21d, the electronic components40ato40dare accommodated in the recessed portions21ato21d, and thereafter, the electronic components40ato40dare fixed in the recessed portions21ato21dby heating or the like.

After the electronic components40ato40dare accommodated in the recessed portions21ato21d, the sealing resin22is filled in the recessed portions21ato21d, and the insulating protective layer30is layered over the surface f1of the silicon board20by being laminated thereon (seeFIG. 2D).

After the insulating protective layer30is layered, as illustrated inFIG. 2E, holes32ato32dare made by laser or the like in the insulating protective layer30on the recessed portions21ato21d, the electrically conductive vias31ato31dare formed by plating being performed and/or by an electrically conductive material being filled, inside the holes32ato32d, and thereby the electronic circuit board100illustrated inFIG. 1is manufactured.

In the first embodiment, the recessed portions21ato21dare formed after the silicon board20and the supporting board10are layered over each other, but the supporting board10may be laminated on the silicon board20after the recessed portions21ato21dare formed in the silicon board20.

The recessed portions illustrated inFIG. 1andFIG. 2have recessed shapes formed by: their side faces being surrounded by the silicon board20having through hole portions; and the supporting board10serving as their bottom faces.

Further, a silicon board having bottomed recessed portions may be used in the electronic circuit board.FIG. 3is a sectional view of an electronic circuit board according a first modified example of the first embodiment.

InFIG. 3, recessed portions have recessed shapes formed by their side faces and bottom faces being surrounded by a silicon board20A.

An electronic circuit board100A: includes a silicon board20A having bottomed recessed portions21ato21d(with heights of the recessed portions21ato21dbeing lower than a thickness of the silicon board20A); and does not have a supporting board. The recessed portions21ato21dare formed, similarly to the first embodiment, by dry etching, preferably by ICP etching, and thus side faces of the recessed portions21ato21dare perpendicular to a surface f1of the silicon board20A. Since the side faces of the recessed portions21ato21dare perpendicular, the recessed portions21ato21dare able to be formed with narrow pitches in the silicon board20A, and mounting density of electronic components40ato40dis able to be improved.

Further, an insulating protective layer may be not layered over the silicon board.FIG. 4is a sectional view of an electronic circuit board according a second modified example of the first embodiment.

In an electronic circuit board100B, bottom surface electrodes11ato11delectrically and mechanically connecting electronic components40ato40cand40d′ are formed, and a wiring pattern not illustrated in the drawings is formed; on a connected surface f4side of a supporting board10B (on a surface side of the supporting board10B), the connected surface f4side being toward a silicon board20B. The electronic components40ato40cand40d′ arranged in the recessed portions21ato21dare connected to the bottom surface electrodes11ato11dvia solder or electrically conductive resin. In the electronic circuit board100B, sealing resin is not filled around the electronic components40ato40cand40d′ in the recessed portions21ato21d, and an insulating protective layer is not layered over a surface f1of the silicon board20B, either.

The wiring pattern formed on the connected surface f4side of the supporting board10B and not illustrated in the drawings is connected to the electronic components40ato40cand40d′ via the bottom surface electrodes11ato11d. A wiring pattern may be formed on a surface f5side reverse to the connected surface f4side of the supporting board10B, or inside the supporting board10B, and when the wiring pattern is formed on the reverse surface f5side of the supporting board10B or inside the supporting board10B, vias are provided in the supporting board10B, and the wiring pattern is connected to the electronic components40ato40cand40d′ via the vias and the bottom surface electrodes11ato11d. Since side faces of the recessed portions21ato21din the second modified example are also perpendicular, the recessed portions21ato21dare able to be formed in the silicon board20B with narrow pitches, and mounting density of the electronic components40ato40cand40d′ is able to be improved. Further, the electronic component40d′ having a height higher than a height of the recessed portion21dis also able to be mounted thereon.

Second Embodiment

In an electronic circuit board according to a second embodiment, side faces of recessed portions have: portions tapered relatively to a surface of a silicon board; and portions that are perpendicular to the surface.FIG. 5is a sectional view of the electronic circuit board according to the second embodiment.

An electronic circuit board100C has a silicon board20C having recessed portions21a′ to21c′ having electronic components40ato40cmounted therein. The recessed portions21a′ to21c′ respectively include: first recessed portions21a′-1to21c′-1, which are formed on a surface f1side of the silicon board20C, and have side faces that are tapered relatively to a surface f1of the silicon board20C such that the first recessed portions21a′-1to21c′-1decrease in their diameters from opening sides thereof; and second recessed portions21a′-2to21c′-2, which have side faces that are perpendicular to the surface f1of the silicon board20C.

The first recessed portions21a′-1to21c′-1are formed, as illustrated inFIG. 6A, by execution of tapered etching, preferably anisotropic etching through wet etching in particular, on the surface f1of the silicon board20C, over which a supporting board10has been layered.

The second recessed portions21a′-2to21c′-2are formed, as illustrated inFIG. 6B, by further etching through dry etching, preferably ICP etching, on the first recessed portions21a′-1to21c′-1of the silicon board20C.

In the silicon board20C having the recessed portions21a′ to21c′ configured as described above, arrangement of electronic components40ato40cin the recessed portions21a′ to21c′ is facilitated.FIG. 7Ais a top view of the recessed portions21a′ to21c′ of the electronic circuit board100C according to the second embodiment.FIG. 7BandFIG. 7Care diagrams for explanation of the arrangement of the electronic components40ato40cin the recessed portions21a′ to21c′ of the electronic circuit board100C according to the second embodiment.

The electronic components40ato40care arranged near the recessed portions21a′ to21c′ illustrated inFIG. 7A(seeFIG. 7B), and the silicon board20C is vibrated. By the silicon board20C being vibrated, the electronic components40ato40care respectively accommodated in the recessed portions21a′ to21c′. Since the surface f1side of the silicon board20C in the recessed portions21a′ to21c′, on which the electronic components40ato40care mounted, has the first recessed portions21a′-1to21c′-1having the side faces that are tapered relatively to the surface f1of the silicon board20C, the arrangement of the electronic components40ato40cinto the recessed portions21a′ to21c′ is facilitated. This is particularly effective when the electronic components40ato40care small and arrangement thereof in the recessed portions by grasping is difficult.

In terms of balance between ease of the arrangement of the electronic components40ato40cinto the recessed portions21a′ to21c′ and mounting density of the electronic components40ato40con the silicon board20C, a height r1of the first recessed portions21a′-1to21c′-1is preferably equal to or less than a height r2of the second recessed portions21a′-2to21c′-2, particularly equal to or less than 40% thereof.

Third Embodiment

An electronic circuit board according to a third embodiment has a through electrode formed in a silicon board thereof.FIG. 8is a sectional view of the electronic circuit board according to the third embodiment.

A silicon board20D of an electronic circuit board100D has a through electrode32formed therein, which penetrates from a surface f1of the silicon board20D to a reverse surface f2thereof. A side face in a hole portion, in which the through electrode32is formed, has an insulating protective layer formed thereon, similarly to inner wall faces of recessed portions21ato21d, and the insulating protective layer insulates the silicon board20D and the through electrode32from each other. Further, a side surface of the silicon board20D has a side surface electrode33formed thereon, and the side surface electrode33also functions as a through electrode by being formed from the surface f1of the silicon board20D to the reverse surface f2thereof.

On a connected surface f4side of a supporting board10D, the connected surface f4side being toward the silicon board20D, bottom surface electrodes11aand11c, to which electronic components40aand40care electrically and mechanically connected, are formed, and the bottom surface electrodes11aand11care connected to a wiring pattern, which is formed on the connected surface f4side of the supporting board10D and not illustrated in the drawings. The electronic components40aand40carranged in the recessed portions21aand21care respectively connected to the bottom surface electrodes11aand11cvia solder or electrically conductive resin.

An insulating protective layer30D is layered by being laminated on a surface f1side of the silicon board20D. The insulating protective layer30D is also layered on the side surface of the silicon board20D, the side surface being where the side surface electrode33is formed, and insulates the silicon board20D and the side surface electrode33from each other. Electrically conductive vias31band31dare formed in the insulating protective layer30D on the recessed portions21band21d. The electrically conductive vias31band31dare respectively connected electrically to the electronic components40band40daccommodated in the recessed portions21band21d, and are connected to a wiring pattern, which is formed on a surface f3side of the insulating protective layer30D and is not illustrated in the drawings.

The through electrode32and the side surface electrode33are connected to: the wiring pattern formed on the connected surface f4side of the supporting board10D; and the wiring pattern formed on the surface f3side of the insulating protective layer30D.

The electronic circuit board100D according to the third embodiment enables mounting density of the electronic components40ato40dto be improved, since the side faces of the recessed portions21ato21dare perpendicular to the surface of the silicon board20D. Further, since the wiring pattern formed on the supporting board10D and the wiring pattern formed on the insulating protective layer30D are connected to each other via the through electrode32and the side surface electrode33, wiring freedom is able to be improved.

Fourth Embodiment

An electronic circuit board according to a fourth embodiment has semiconductor circuits formed on a silicon board thereof.FIG. 9is a sectional view of the electronic circuit board according to the fourth embodiment.

A silicon board20E of an electronic circuit board100E has semiconductor circuits34aand34bformed at a surface f1side thereof. The semiconductor circuits34aand34bare formed by semiconductor processes. A silicon wafer having the plural semiconductor circuits34aand34bformed thereon is subjected to singulation and formed into the silicon board20E, and thereafter, recessed portions21ato21dare formed by ICP etching.

An insulating protective layer30E is layered by being laminated on the surface f1side of the silicon board20E, and electrically conductive vias31b,31d,35a, and35bare formed in the insulating protective layer30E on the recessed portions21band21dand on the semiconductor circuits34aand34b. A wiring pattern, which is formed on a surface f3side of the insulating protective layer30E and not illustrated in the drawings, is electrically connected to electronic components40band40dand the semiconductor circuits34aand34b, via the vias31b,31d,35a, and35b.

On a connected surface f4side of a supporting board10E, the connected surface f4side being toward the silicon board20E, bottom surface electrodes11aand11c, to which the electronic components40aand40care electrically and mechanically connected, are formed, and the bottom surface electrodes11aand11care connected to a wiring pattern, which is formed on the connected surface f4side of the supporting board10E and not illustrated in the drawings. The electronic components40aand40carranged in the recessed portions21aand21care respectively connected to the bottom surface electrodes11aand11cvia solder or electrically conductive resin, and are connected to a wiring pattern, which is formed on the surface f3side of the insulating protective layer30E, via the through electrode32and the side surface electrode33.

The electronic circuit board100E according to the fourth embodiment has the semiconductor circuits34aand34bin the silicon board20E, and thus downsizing and integration of the electronic circuit board100E are enabled as there is no need for semiconductor circuits to be newly provided therein.

Fifth Embodiment

A fifth embodiment is a laminated board having electronic circuit boards layered over each other.FIG. 10is a sectional view of the laminated board according to the fifth embodiment.

A laminated board200has a first electronic circuit board100D-1and a second electronic circuit board100D-2that are layered over each other. The first electronic circuit board100D-1has a configuration similar to that of the electronic circuit board100D according to the third embodiment, and has an intermediate layer36having an insulating function, such as a resist layer, the intermediate layer36being layered on a surface of an insulating protective layer30D-1.

The second electronic circuit board100D-2has an insulating protective layer layered therein, instead of the supporting board10D on a reverse surface f2side of the silicon board20D according to the third embodiment. The second electronic circuit board100D-2is able to be manufactured by formation of vias31b-2and31d-2, a through electrode32-2, and a side surface electrode33-2, after an insulating protective layer30D-2is layered and electronic components40a-2to40d-2are arranged in recessed portions21a-2to21d-2, after the recessed portions21a-2to21d-2are formed in a silicon board20D-2.

Since the laminated board200has the first electronic circuit board100D-1and the second electronic circuit board100D-2that are layered over each other, mounting density of electronic components is able to be improved.

The laminated board according to the fifth embodiment is able to be suitably used in an imaging unit of an endoscope system described later.FIG. 11is a diagram schematically illustrating an overall configuration of the endoscope system, in which the laminated board according to the fifth embodiment is used.FIG. 12is a side view of the imaging unit used in an endoscope ofFIG. 11.

As illustrated inFIG. 11, an endoscope system1includes an endoscope2, a universal cord5, a connector6, a light source device7, a processor (control device)8, and a display device9.

The endoscope2captures an in-vivo image of a subject and outputs an imaging signal, by insertion of an insertion unit3into the subject. A cable inside the universal cord5is extended to a distal end of the insertion unit3of the endoscope2, and is connected to the imaging unit provided at a distal end portion3bof the insertion unit3.

The connector6is provided at a proximal end of the universal cord5, is connected to the light source device7and the processor8, executes predetermined signal processing on the imaging signal (output signal) output by an imaging unit300at the distal end portion3bconnected to the universal cord5, executes analog/digital conversion (A/D conversion) on the imaging signal, and outputs the converted imaging signal as an image signal.

The light source device7is, for example, configured by use of a white LED. Pulsed white light lighted by the light source device7serves as illumination light to be emitted toward the subject from the distal end of the insertion unit3of the endoscope2via the connector6and the universal cord5.

The processor8executes predetermined image processing on the image signal output from the connector6, and controls the whole endoscope system1. The display device9displays thereon the image signal processed by the processor8.

An operating unit4provided with various buttons and knobs, through which endoscopic functions are operated, is connected at a proximal end side of the insertion unit3of the endoscope2. The operating unit4has a treatment tool insertion opening4aprovided therein, through which a treatment tool, such as biopsy forceps, an electric knife, or an inspecting probe, is inserted in a body cavity of the subject.

The insertion unit3includes: the distal end portion3bwhere the imaging unit300is provided; a bent portion3a, which is connected consecutively to a proximal end side of the distal end portion3band is freely bendable in an up-down direction; and a flexible tube portion3c, which is connected consecutively to a proximal end side of this bent portion3a. The bent portion3ais bent in the up-down direction by operation on a bending operation knob provided in the operating unit4, and is freely bendable in two directions, for example, upward and downward, in association with pull and relaxation of a bending wire inserted through the insertion unit3.

A light guide that transmits the illumination light from the light source device7is arranged in the endoscope2, and an illumination window is arranged at an illumination light emission end of the light guide. This illumination window is provided at the distal end portion3bof the insertion unit3, and the illumination light is emitted toward the subject from this illumination window.

The imaging unit300provided at the distal end portion3bof the endoscope2includes, as illustrated inFIG. 12: an imaging element310having a light receiving unit311that photoelectrically converts incident light and generates an electric signal; an optical member320that seals the light receiving unit311; a flexible printed circuit board (hereinafter, referred to as “FPC board”)330; and a hard board340. The laminated board200has functions of the FPC board330and the hard board340, of the imaging unit300.

The imaging element310includes an electrode pad not illustrated in the drawings, around the light receiving unit311formed at a central portion of a principal surface thereof, and a bump (not illustrated in the drawings) made of solder or the like is formed on the electrode pad.

The optical member320is formed of a material having excellent optical properties, such as glass, and is adhered to the imaging element310by an adhesive.

The FPC board330has an insulating base and a wiring layer formed inside or on a surface of the base, and an inner lead is connected to the electrode pad of the imaging element310, the inner lead being a part of the wiring layer, the part being exposed from the base. A connected portion between the inner lead and the electrode pad is sealed by a sealing resin331. The FPC board330extends from a side surface (bottom surface) side to a reverse surface side of the imaging element310, and the hard board340having plural conductor layers is connected onto an extended surface of the FPC board330. A conductor361of a cable360is connected to a proximal end side of the hard board340.

By use of the laminated board200according to the fifth embodiment in the imaging unit300, decrease in diameter and decrease in length of the imaging unit are enabled.

According to the present disclosure, an electronic circuit board is able to be downsized even when many electronic components are mounted thereon, because mounting density of electronic components thereon is able to be improved.