Image pickup unit and endoscope

An image pickup unit of the present invention includes an image sensor, a connection board, a circuit board, a cable, and protection material. If an external force acts in a direction orthogonal to an extension direction of the cable, the whole of the circuit board, which is a rigid body, is displaced relative to an electrode portion of the image sensor by the external force. In response to the displacement of the circuit board, the connection board is displaced so that a curve radius of a curved portion changes, between a first land portion connected to the image sensor and a second land portion connected to the circuit board, and thereby a load by the external force transmitted to the image sensor from the cable through the circuit board is reduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup unit in which a rigid circuit board is connected to an electrode portion of an image sensor.

2. Description of the Related Art

In general, an image pickup unit is configured as a unit in which a circuit board for driving and signal processing is connected to an image sensor for which a solid image pickup device such as a CCD or a CMOS is used. In the case of mounting such an image pickup unit, for example, in an endoscope an elongated insertion portion of which is inserted into a subject/object to pick up an image of an observation site, it is often a case that a flexible board is used as a circuit board, and a cable is connected to the flexible board to connect to an external apparatus, as disclosed in Japanese Patent Application Laid-Open Publication No. H10-33474, for example.

Nowadays, the image sensor is often formed with a small and lightweight chip size package on which high density implementation is possible. On the chip size package, an image pickup surface of an image pickup device is arranged on a front face side of the package, and an electrode portion of the image pickup device is arranged on a back face of the package.

Further, in order to improve heat resistance and mechanical strength of the circuit board, a rigid circuit board such as a ceramic board is often used. In the case of connecting the ceramic board to the electrode portion of the chip size package, the board can be directly connected via a solder ball forming a bump on the back face of the package.

In the case of including such a chip size package image sensor in a distal end portion of an endoscope, for example, as shown inFIG. 8, a glass lid201for protection is bonded to a front face side of the package where an image pickup surface200aof an image sensor200is arranged, with adhesive or the like; furthermore, a cover glass for positioning (not shown) is bonded to the glass lid201; and the cover glass is held by a holding frame (not shown) arranged in the distal end portion of the endoscope.

Then, an electrode portion300aof a ceramic board300is bonded to an electrode portion200bon a package back face of the image sensor200. And a cable310is connected to a proximal end side of the ceramic board300and extended on an operation portion side of the endoscope. In a peripheral part from the electrode portion200bof the image sensor200to the ceramic board300, resin material is filled and fixed.

SUMMARY OF THE INVENTION

An image pickup unit according to an aspect of the present invention includes: an image sensor including an image pickup device package, an image pickup surface of an image pickup device being arranged on a front face side of the package, and an electrode portion of the image pickup device being arranged on a back face of the package; a connection board including a first land portion and a second land portion, the first land portion being connected to the electrode portion of the image sensor; a rigid circuit board including a first connection portion and a second connection portion, the first connection portion being connected to the second land portion of the connection board; a cable connected to the second connection portion of the circuit board; and protection material arranged around the connection board and the image sensor; wherein the image sensor and the circuit board are arranged such that the electrode portion of the image sensor and the first connection portion face each other; the connection board includes a curved portion between the first land portion and the second land portion, the curved portion being curved in a manner of being displaceable by an external force transmitted from the cable via the circuit board; and the protection material includes first protection material and second protection material softer than the first protection material, the second protection material being arranged at least inside the curved portion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1shows an example of an endoscope apparatus to which the present invention is applied. In the present embodiment, an endoscope apparatus1is configured being provided with an endoscope2including an image pickup unit, a light source device3configured to supply illuminating light to the endoscope2, a video processor4as a signal processing device configured to perform signal processing for the image pickup unit mounted in the endoscope2, and a color monitor5as a display device configured to display an endoscopic image.

The endoscope2includes an elongated insertion portion6to be inserted into a subject/object, an operation portion7provided on a proximal end of the insertion portion6, a universal cord8extended from the operation portion7, and an endoscope connector9provided on an end portion of the universal cord8. By the endoscope connector9being detachably connected to the light source device3, illuminating light from the light source device3is supplied to a light guide not shown in the endoscope2. One end of a connection cable10is connected to the endoscope connector9, and an electrical connector10aprovided on the other end of the connection cable10is detachably connected to the video processor4. The video processor4is connected to the color monitor5via a video cable not shown.

The insertion portion6of the endoscope2is configured being provided with a rigid distal end portion11provided on a distal end, a bendable bending portion12provided on a rear end of the distal end portion11, and a flexible tube portion13having flexibility of extending from a rear end of the bending portion12to a front end of the operation portion7.

On a distal end face of the distal end portion11, an observation window15, a plurality of illumination windows16(FIG. 1shows only one), a distal end opening17aof a treatment instrument channel (not shown), and a nozzle for cleaning not shown. On an inner side (a rear face side) of the observation window15, an image pickup unit30provided in the distal end portion11is arranged as shown inFIG. 2.

Illumination lenses are attached to the illumination windows16, and a light guide for transmitting illuminating light from the light source device3is arranged being connected to the illumination lenses (neither the illumination lenses nor the light guide is shown). Illuminating light transmitted by the light guide is emitted to a front side of the distal end face via the illumination lenses, and thereby an observation target site in a subject/object, which is a visual field range of the image pickup unit30, is illuminated.

The operation portion7is provided with a bend preventing portion18afor a part from which the proximal end of the insertion portion6is extended, a treatment instrument insertion port18barranged on a side portion on a lower part side, an operation portion body18cconstituting a grip portion provided on a middle part, a bending operation portion19provided on an upper part side and including two bending operation knobs19aand19b, an air/water feeding control portion21, a suction control portion22, and a switch portion23including a plurality of switches, the switch portion23being mainly for operating an image pickup function.

Note that inside the operation portion7, the treatment instrument insertion port18bof the operation portion7communicates with the treatment instrument channel made inside the insertion portion6, and is open at the distal end opening17aof the distal end portion11.

Next, the image pickup unit30arranged inside the distal end portion11of the endoscope2will be described based onFIG. 2.

The image pickup unit30is arranged being inserted through a distal end rigid member forming the distal end portion11, and is fixed to the distal end rigid member with screws or the like from a side face direction. The image pickup unit30is configured including an observation optical system unit31constituting an objective optical system including the observation window15, and an image pickup device unit40as an image pickup portion arranged being connected to a rear end side of the observation optical system unit31.

In the present embodiment, the observation optical system unit31is configured including a lens frame32holding lenses and a lens group33including a plurality of fixed lenses held by the lens frame32. The lens frame32is formed in a substantially cylindrical shape, and a first lens33aforming the observation window15is arranged on a distal end side inside the cylindrical shape. The lens group33is configured by arranging a second lens33b, a third lens33c, a fourth lens33dand a fifth lens33ebehind the first lens33aalong an optical axis O in that order, and each lens is fixed to the lens frame32with adhesive or the like.

Note that apertures34and35are arranged behind the first lens33aand behind the second lens33b, respectively. The third lens33cand the fourth lens33dare arranged with a spacer36between the third lens33cand the fourth lens33d.

The observation optical system unit31above is combined with the image pickup device unit40, and incident light incident via the lens group33is image-formed on a light receiving surface (an image pickup surface) of an image sensor42of the image pickup device unit40. An optical image of an object is photoelectrically converted by the image sensor42, and an image pickup signal obtained by the photoelectrical conversion is transmitted to a subsequent-stage signal processing circuit via a cable70.

The image pickup device unit40includes a substantially cylinder-shaped image pickup device holding frame41holding the image sensor42, and by inserting and fitting a proximal end side of the lens frame32of the observation optical system unit31into a distal end side inner diameter portion of the image pickup device holding frame41and watertightly bonding the proximal end side and the distal end side inner diameter portion to each other, the observation optical system unit31and the image pickup device unit40are combined.

The image sensor42is configured as an image pickup device package obtained by sealing a solid image pickup device composed of a CCD, a CMOS or the like with resin or the like. In the present embodiment, the image sensor42is configured as a small and lightweight chip size package (CSP) on which high density implementation is possible. In the image sensor42, an image pickup surface42aof the image pickup device is arranged on a front face side of the package. On the image pickup surface42aside, a glass lid43for protection is bonded and fixed with adhesive or the like. Furthermore, a cover glass44for positioning is fixed to the glass lid43with adhesive or the like, and the cover glass44is fixed to a proximal end side inner diameter portion of the image pickup device holding frame41with adhesive or the like.

On a back face of the package, which is a rear face side of the image pickup surface42aof the image sensor42, an electrode portion47on which a plurality of electrode terminals are arranged is provided. A connection board50is connected to the electrode portion47of the image sensor42, and a rigid circuit board60is connected to the connection board50.

The connection board50is a board configured to relay electrical connection between the image sensor42and the circuit board60. A connection portion to the image sensor42and a connection portion to the circuit board60are mutually electrically connected by a print pattern (not shown) formed in advance. In the present embodiment, the connection board50is composed of a flexible board made of a resin film or the like having flexibility.

The circuit board60is a circuit board on which various circuit chips of the image sensor42for driving and signal processing are implemented, and is formed as a rigid and high-strength board, which is a rigid body, such as a ceramic board. A plurality of lead wires80extended from the cable70are connected to a proximal end side of the circuit board60. The cable70is insertedly arranged inside the endoscope2and electrically connected to the video processor4via the electrical connector10a.

Note that a tubular reinforcing frame45made of metal is arranged being connected to a proximal end outer circumferential portion of the image pickup device holding frame41. An outer cover71of the cable70is bound tight and fixed with a binding thread86composed of a metal wire, a nylon thread or the like on a distal end side.

A thermal contraction tube46as a protection tube covering the cable70up to the distal end side is provided on an outer circumference of the tubular reinforcing frame45. A space formed by the reinforcing frame45and the thermal contraction tube46from a proximal end part of the image pickup device holding frame41is filled with protection material90such as insulating sealing resin for holding, reinforcing and protecting the image sensor42.

Next, details of the connection portions between the image sensor42, the connection board50and the circuit board60will be described.

As shown inFIG. 3, the image sensor42including a CSP package has a configuration in which a plurality of electrode pads47aare arranged in an array on the electrode portion47formed on the rear face side of the image pickup surface42a. A spherical solder ball47bmade of solder is bonded to each electrode pad47aof the electrode portion47to form a bump.

The connection board50includes a first land portion51and a second land portion52on both sides of a flexible board, and a plurality of lands51aand a plurality of lands52ato be electrode terminals are formed on the first land portion51and the second land portion52, respectively. The lands51aof the first land portion51are associated with the respective lands52aof the second land portion52in advance, and connected by a print pattern not shown.

The circuit board60includes a first connection portion61to which the connection board50is connected, and a second connection portion62to which the cable70is connected. A plurality of electrode terminals61aand a plurality of electrode terminals62aare formed on the first connection portion61and the second connection portion62, respectively. Each electrode terminal61aof the first connection portion61is connected mainly to a terminal for drive output, image pickup signal input or the like to the image sensor42from each circuit part via the print pattern not shown, and each electrode terminal62aof the second connection portion62is connected mainly to a terminal of each circuit part for signal input/output or the like to the video processor4via the print pattern not shown. Note that the first connection portion61is configured as a bump electrode similar to the electrode portion47of the image sensor42.

The image sensor42and the connection board50are electrically connected by performing heat bonding of each of the solder balls47bof the electrode portion47and each land51aof the first land portion51, or the like. The connection board50and the circuit board60are electrically connected by the plurality of lands52aof the second land portion52being bonded to the respective electrode terminals61aof the first connection portion61of the circuit board60. To the respective electrode terminals62aof the second connection portion62of the circuit board60, a plurality of lead wires80extended from the cable70are bonded by soldering or with electrically conductive adhesive and electrically connected.

Here, the connection board50includes a curved portion53curved in a manner of being displaceable by an external force transmitted from the cable70via the circuit board60, which is a rigid body, between the first land portion51and the second land portion52. Due to the curved portion53, it is possible to prevent an excessive load from being applied to a bonding surface between the image pickup surface42aof the image sensor42and the glass lid43from the cable70side via the circuit board60.

In the present embodiment, on the circuit board60, an electrode arrangement surface of the first connection portion61and an electrode arrangement surface of the second connection portion62are orthogonal to each other, and the electrode arrangement surface of the first connection portion61is arranged facing an electrode arrangement surface of the electrode portion47of the image sensor42. The connection board50interposed between the electrode portion47of the image sensor42and the first connection portion61of the circuit board60includes the curved portion53curved like a U-shaped groove between the first land portion51and the second land portion52, and due to the curved portion53, it is possible to reduce a load transmitted to the image sensor42from the cable70via the circuit board60, which is a rigid body.

That is, if an external force acts on the second connection portion62of the circuit board60due to curving, torsion, tilt and the like of the cable70, especially the image sensor42and the circuit board60generate heat as the endoscope2is used, and the protection material90around the image sensor42becomes soft. In such a situation, the circuit board60, which is a rigid body, is displaced by the external force applied to the cable70, and a load is applied to other parts arranged being connected to the circuit board60.

For example, if an external force F acts in a direction orthogonal to an extension direction of the cable70as shown inFIG. 4, the whole circuit board60, which is a rigid body, is displaced relative to the electrode portion47of the image sensor42by the external force F. On the connection board50, in response to the displacement of the circuit board60, the curved portion53is displaced, and the curved shape changes, between the first land portion51connected to the image sensor42and the second land portion52connected to the circuit board60.

Therefore, even if the circuit board60is displaced by an external force, only a part of the connection board50near the curved portion53is displaced in response to the displacement, so that the external force can be absorbed and reduced. Thereby, it is possible to reduce a load by an external force transmitted to the image sensor42from the cable70via the circuit board60. As a result, it does not happen that such an excessive force that causes detachment of a bonding layer between the image pickup surface42aof the image sensor42and the glass lid43is applied to the bonding layer, and it is possible to effectively prevent occurrence of a trouble such as detachment.

In this case, though the protection material90such as sealing resin filled around the image sensor42and the curved portion53may be material of one kind, the protection material90may include first protection material90aand second protection material90bthat is softer than the first protection material90aas exemplified inFIG. 2. The second protection material90bis arranged at least in a space formed by the curved portion53.

In the case of forming the first and second protection materials90aand90bwith resin material, resin softer than resin material as the first protection material90ais used as resin material as the second protection material90b. By arranging the soft resin material in the space formed by the curved portion53, it is possible to cause the curved portion53to function more effectively.

As the second protection material90barranged in the curved portion53, soft material such as sponge can be used instead of resin material. It is also possible to arrange nothing around the curved portion53and leave the space as a cavity.

Though the connection board50composed of a flexible board is folded in a U shape between the first land portion51and the second land portion52to form the curved portion53in the present embodiment, the curved portion53may be formed by causing the connection board50to be curved a plurality of times between the first land portion51and the second land portion52.

FIG. 5shows a first modification of the connection board50. A connection board50A of the first modification is a flexible board that is vertically folded twice between the first and second land portions51and52. That is, a curved portion53A of the connection board50A is formed by arranging two curved portions53uand53dformed by performing vertical curving twice between the first land portion51and the second land portion52, and it is possible to reduce an external force more effectively by the two curved portions53uand53d.

FIG. 6shows a second modification of the connection board50. A connection board50B of the second modification is a flexible board that is folded twice in mutually different directions such as vertical and horizontal directions between the first and second land portions51and52. A curved portion53B of the connection board50B is formed by arranging two curved portions53xand53yformed by performing curving twice vertically and horizontally between the first land portion51and the second land portion52, and it becomes possible to reduce external forces from more directions.

Note that the connection board50(50A,50B) may be formed by a rigid flexible board obtained by integrating a flexible board and a rigid board, and the curved portion53(53A,53B) can be formed by causing a part having flexibility to be curved. It is also possible to use, for example, a metal board or the like having elasticity as the connection board50. The curved portion53may be formed by sharply folding the metal board so that not a circular-arc shaped cross section but a ridge-valley shaped cross section is obtained.

Thus, in the present embodiment, for the image pickup unit in which the circuit board60, which is a rigid body such as a ceramic board, is connected to the image sensor42configured as a CSP package, a load transmitted to the image sensor42via the circuit board60, which is a rigid body, by curving, torsion, tilt and the like of the cable70can be reduced by the curved portion53of the connection board50interposed between the image sensor42and the circuit board60. As a result, it is possible to reduce a load applied to the bonding layer between the image pickup surface42aof the image sensor42and the glass lid43and to prevent detachment of the bonding layer.

Second Embodiment

Next, a second embodiment of the present invention will be described. The second embodiment is such that the shape of the image pickup device holding frame41holding the image sensor42is slightly changed, and an extending portion extending to the connection board50side is provided.

More specifically, an image pickup device holding frame100of the second embodiment extends on a proximal end side on which the cover glass44is fixed, and has an extending portion100aincluding the glass lid43and the image sensor42and extending to a proximal end side relative to the image sensor42.

More specifically, when a distance (a projection length) from a bonding surface between the cover glass44and the glass lid43to a distal end of the extending portion100ais indicated by La, the projection length La of the extending portion100ais set to be in a relationship of La>Lb relative to a distance Lb from the bonding surface between the cover glass44and the glass lid43to an electrode surface including the electrode portion47of the image sensor42.

The extending portion100ais formed in a tubular shape having such an extension length that covers the electrode portion47side of the image sensor42or as a part extended to a proximal end side relative to the image sensor42to form a nail shape, and protection material110is arranged inside the extending portion100a. As the protection material110, the first protection material90adescribed in the first embodiment may be used. Otherwise, protection material such as resin material with a higher heat resistance may be used.

Since the projection length La of the extending portion100ais set to be in the relationship of La>Lb relative to the electrode portion47of the image sensor42, the image pickup device holding frame100of the second embodiment can, if a load larger than the load in the first embodiment is applied, receive the load by the extending portion100avia the protection material110.

Thus, in the second embodiment, even if a large load that cannot be reduced by the curved portion53of the connection board50is applied, the load can be received by the extending portion100avia the protection material110, and a load applied to the bonding layer between the image pickup surface42aof the image sensor42and the glass lid43can be reduced, in comparison with the first embodiment.