Image pickup apparatus and endoscope

An image pickup apparatus includes an image pickup device on which a light receiving section is formed, a heat transfer member made of a material having thermal conductivity equal to or higher than 15 W/(m·K), the heat transfer member including a wiring board, a joining section joined to the image pickup device, a bending section extended from the joining section, and a fixed section extended from the bending section, and a housing made of metal, an inner surface of which is in contact with a part of the fixed section of the heat transfer member housed on an inside.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup apparatus in which an image pickup device and a heat transfer member joined to the image pickup device are housed in a housing and an endoscope including the image pickup apparatus.

2. Description of the Related Art

An image pickup device including a semiconductor, on a principal plane of which a light receiving section is formed, is small in size. Therefore, the image pickup device is used in an electronic endoscope and the like. However, when temperature of the image pickup device rises during operation, in some case, the image pickup device is deteriorated or image quality is deteriorated by thermal noise.

Therefore, an image pickup apparatus that suppresses a temperature rise of an image pickup device by transferring, with a member having high thermal conductivity, heat generated by the image pickup device is reported.

For example, Japanese Patent Application Laid-Open Publication No. 2011-200338 discloses an electronic endoscope including an image pickup apparatus in which one end portion of a flexible substrate is connected to a CCD (an image pickup device) and the other end of the flexible substrate is closely attached to an inner wall surface of a protection frame made of metal having high thermal conductivity. The protection frame includes a spring section and surely comes into contact with an inner circumferential surface of a cylindrical section. Consequently, heat generated from the CCD is radiated to the protection frame.

SUMMARY OF THE INVENTION

An image pickup apparatus in an embodiment of the present invention includes: an image pickup device including a first principal plane and a second principal plane, in which a light receiving section is formed on the first principal plane; a wiring board including a device electrode pad connected to an external connection terminal of the image pickup device and a wire, one end of which is connected to the device electrode pad; a heat transfer member, which is made of a material having thermal conductivity equal to or higher than 15 W/(m·K), including a joining section joined to the second principal plane of the image pickup device, a bending section extended from the joining section, and a fixed section extended from the bending section; and a housing made of metal, an inner surface of which is in contact with a part of the fixed section of the heat transfer member housed on an inside.

An endoscope in another embodiment of the present invention includes an image pickup apparatus including: an image pickup device including a first principal plane and a second principal plane, in which a light receiving section is formed on the first principal plane; a wiring board including a device electrode pad connected to an external connection terminal of the image pickup device and a wire, one end of which is connected to the device electrode pad; a heat transfer member, which is made of a material having thermal conductivity equal to or higher than 15 W/(m·K), including a joining section joined to the second principal plane of the image pickup device, a bending section extended from the joining section, and a fixed section extended from the bending section; and a housing made of metal, an inner surface of which is in contact with a part of the fixed section of the heat transfer member housed on an inside.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

An image pickup apparatus1in the present embodiment is small in diameter and very small in size because the image pickup apparatus1is disposed, for example, at a distal end portion of an electronic endoscope.

As shown inFIG. 1,FIG. 2, andFIG. 3, the image pickup apparatus1includes a cover glass10, an image pickup device20, a heat transfer member30, a wiring board40, a cable50, and a housing60. An image pickup unit including the cover glass10, the image pickup device20, the heat transfer member30, and the wiring board40is housed on an inside of the housing60. Note that, as shown inFIG. 2and the like, resin62is filled in the inside of the housing60. However, the resin62is not shown inFIG. 1and the like.

The image pickup device20exchanges electric signals with a processor (not shown in the figure) connected to the cable50via the wiring board40. That is, a plurality of external connection terminals23of the image pickup device20are joined to respective device electrode pads42(hereinafter referred to as “electrode pads42”) at one end of a wire43of the wiring board40. A plurality of cable electrode pads45(hereinafter referred to as “electrode pads45”) at the other end of the wire43are respectively connected to lead wires52of the signal cable50.

The image pickup apparatus1includes the heat transfer member30. A part of the heat transfer member30is joined to the image pickup device20and transfers heat generated by the image pickup device20to the housing60with which another part of the heat transfer member30is in contact.

The components of the image pickup apparatus1are explained below.

The image pickup device20is a substantially rectangular parallelepiped chip in which a light receiving section21including a solid-state image pickup circuit is formed on a first principal plane20SA. Note that the solid-state image pickup circuit includes a CCD or a CMOS sensor. The image pickup device20may be a back illuminated type.

The external connection terminal23for exchanging signals with the light receiving section21is formed on a second principal plane20SB via a through-wire22. That is, the plurality of external connection terminals23are disposed on the second principal plane20SB in an array shape. Note that a wire from the light receiving section21to the through-wire22is present on the first principal plane20SA and a wire from the through-wire22to the external connection terminal23is present on the second principal plane20SB. However, the wires are not shown in the figure.

The cover glass10is bonded to the first principal plane20SA of the image pickup device20via an adhesive layer (not shown in the figure). As explained below, in the image pickup apparatus1, after a transparent wafer is bonded to a semiconductor wafer on which a plurality of light receiving sections and the like are fondled, the bonded wafers are singulated by dicing. Therefore, a plan view dimension of the image pickup device20and a plan view dimension of the cover glass10are the same. Note that, although the cover glass10has a protection function for the light receiving section21, the cover glass10is not an essential component of the image pickup apparatus1.

The wiring board40is a flexible wiring board including flexible resin such as polyimide as a base material and including the wire43made of copper or the like. The wiring board40may be a single-layer wiring board or may be a multi-layer wiring board in which wiring layers are formed at least on both surfaces. The electrode pad42is formed on a distal end side of the wiring board40. The electrode pad45(seeFIG. 2) is formed on a rear end side. The electrode pad42and the electrode pad45are electrically connected by the wire43. A connection pad (not shown in the figure) is formed in the wire43of the wiring board40. An electronic component44such as a chip capacitor is mounted on the connection pad. That is, the wire43configures an electronic circuit that processes a signal inputted from the image pickup device20and outputs the signal to the signal cable50.

Note that, as shown inFIG. 1toFIG. 3and the like, the wiring board40is bent halfway and fit within a projection surface of a principal plane of the image pickup device20.

The heat transfer member30includes a joining section30X joined to the second principal plane20SB of the image pickup device20, bending sections30V1and30V2extended from the joining section30X, and fixed sections30Y1and30Y2extended from the respective bending sections30V1and30V2. Note that, in the following explanation, when a plurality of components having the same function are referred to, a last one numerical character of a sign of the components is sometimes omitted. For example, each of the bending sections30V1and30V2is referred to as bending sections30V.

When the heat transfer member30is housed on the inside of the housing60, the fixed section30Y is pressed against an inner surface of the housing60by an urging force and surely comes into contact with the inner surface of the housing60made of metal. That is, the bending section30V, which is a spring, presses the fixed section30Y against the inner surface of the housing60.

Since heat generated by the image pickup device20is transferred to the housing60via the heat transfer member30having high thermal conductivity, the heat is efficiently radiated. Therefore, temperature of the image pickup device20does not excessively rise during operation. Therefore, the image pickup device20is not deteriorated. Image quality is not deteriorated by thermal noise.

Note that, in the image pickup apparatus1, the external connection terminal23is present on the second principal plane20SB of the image pickup device20. Therefore, a through-hole30H is present in a position opposed to the external connection terminal23of the heat transfer member30, in other words, in a position opposed to the electrode pad42of the wiring board40.

As shown inFIG. 4, a plan view shape of the joining section30X of the heat transfer member30is substantially rectangular like the image pickup device20. The bending section30V and the fixed section30Y extend from two opposed sides among four sides of the joining section30X. That is, the heat transfer member30includes an extended plurality of bending sections30V and an extended plurality of fixed sections30Y. However, the bending sections30V and the fixed sections30Y are integral. A boundary between the bending sections30V and the fixed sections30Y cannot be clearly distinguished.

The heat transfer member30is a thin plate made of a metal material having high thermal conductivity and elasticity such as stainless steel, copper, phosphor bronze, or a copper alloy. As shown inFIG. 3, the bending section30V is bent and plastically deformed before being housed in the inside of the housing60.

InFIG. 3, length between an end portion of the fixed section30Y1and an end portion of the fixed section30Y2of the heat transfer member30, in which the bending section30V is plastically deformed, is shown as W3. The length W3is larger than an inner dimension W1of the housing60.

Therefore, when being housed in the inside of the housing60, the fixed section30Y is pressed against the inner surface of the housing60by an urging force and surely comes into contact with the housing60.

A material of the heat transfer member30has thermal conductivity λ of 15 W/(m·K) or more. That is, as the heat transfer member30, for example, copper (λ=398 W/(m·K)), aluminum (λ=237 W/(m·K)), iron (λ=84 W/(m·K)), phosphor bronze (λ=60 W/(m·K)), or stainless steel (λ=17 W/(m·K)) is used.

As the housing60, a material having high thermal conductivity λ, for example, a material same as the material of the heat transfer member30may be used. However, as the material of the heat transfer member30, it is desirable to use a material having the thermal conductivity λ higher than the thermal conductivity λ of the housing60. For example, it is particularly desirable that the housing60is formed of stainless steel and the heat transfer member30is formed of copper.

Note that, as a joining member for joining the heat transfer member30and the image pickup device20, it is desirable to use an adhesive made of resin having high thermal conductivity. The thermal conductivity of the joining member is desirably 1 W/(m·K) or more and particularly desirably 15 W/(m·K) or more.

As the joining member, low-melting point metal such as solder may be used. By joining the heat transfer member30and the image pickup device20using metal having higher thermal conductivity compared with the resin, it is possible to more efficiently transfer heat. When a conductive material such as a metal material is used for the joining, it goes without saying that it is necessary to prevent contact with an electric connection section.

A method of manufacturing the image pickup apparatus1is explained.

First, a plurality of image pickup devices20including the light receiving sections21are formed on a silicon substrate using a publicly-known semiconductor process. After a glass wafer having substantially the same size as the silicon substrate is bonded on a formation surface of the light receiving sections21as a protection material, cutting is performed from a rear surface side of the silicon substrate. After thickness of the silicon substrate is reduced by the cutting, a through-hole is formed by etching or the like from the rear surface side. An insulating film is formed on a sidewall of the formed through-hole. An inside of the through-hole is made conductive by conductive paste, a plating method, a sputtering method, or the like, whereby the through-wire22is formed. Thereafter, the silicon substrate bonded with the glass wafer is singulated by cutoff, whereby the image pickup device20bonded with the cover glass10is manufactured.

In the wiring board40, the electrode pads42and45and the wire43are manufactured by sticking together and etching a copper foil and a polyimide or the like, which is a base material, and using the plating method. The electronic component44is mounted on the wiring board40.

The heat transfer member30is manufactured by, for example, pressing and etching a copper plate. To facilitate bending of the bending section30V, local heat treatment or the like may be applied to only the bending section30V by laser radiation or the like. Then, the bending section30V is bent and plastically deformed to set the length between the end portion of the fixed section30Y1and the end portion of the fixed section30Y2to W3.

The length W3only has to be larger than the inner dimension W1of the housing60. However, when easiness of insertion into the housing and a balance with intensity of an urging force are taken into account, it is desirable that the length W3is 110% or more and 200% or less of W1.

Note that a shape memory alloy such as a titanium-nickel alloy may be used as the material of the heat transfer member30. That is, after the bending section30V of the heat transfer member30, which memorizes a state in which the bending section30V is deformed and the fixed section30Y is largely open, is bent and housed in the housing, by heating the heat transfer member30to a predetermined temperature, the fixed section30Y can be pressed against the inner surface of the housing60by an urging force.

The joining section30X of the heat transfer member30is joined to the second principal plane20SB of the image pickup device20by a joining member. At this point, the joining section30X is joined such that the external connection terminal23of the image pickup device20is located on the inside of the through-hole30H of the heat transfer member30.

Subsequently, the electrode pad42of the wiring board40, to which the cable50is connected, and the external connection terminal23of the image pickup device20are joined. A periphery of the joining section30X may be sealed by resin such that the resin is injected into the through-hole30H.

An image pickup unit, in which the cover glass10, the image pickup device20, the heat transfer member30, the wiring board40, and the signal cable50are integrated, is inserted into the inside of the housing60. A plan view shape and an inner dimension of the housing60are substantially the same as and slightly larger than a plan view shape and an outer dimension of the image pickup device20. For example, the inner dimension W1in a longitudinal direction of the housing60shown inFIG. 3is almost the same as the outer dimension W2in the longitudinal direction of the image pickup device20.

The resin62is filled in the inside of the housing60, whereby the image pickup apparatus1is completed.

As explained above, the heat transfer member30is in contact with the housing60made of metal while being pressed against the housing60. Note that, an elastic body is used as a material of the heat transfer member30. The heat transfer member30is pressed against the inner surface of the housing60to be deformed by adjusting thickness, dimensions, a shape, and the like of the heat transfer member30. The heat transfer member30can be set in surface contact with the housing60. By setting the heat transfer member30in surface contact with the housing60, it is possible to more efficiently transfer heat generated in the image pickup device20to the housing60.

The image pickup apparatus1can efficiently radiate the heat generated by the image pickup device20. The image pickup apparatus1is small in diameter because the heat transfer member30and the wiring board40are housed in a housing having an inner dimension same as an outer dimension of the image pickup device20.

<Modification of the First Embodiment>

As shown inFIG. 4, in the heat transfer member30of the image pickup apparatus1, the bending sections30V1and30V2and the fixed sections30Y1and30Y2respectively extend from two opposed sides of the joining section30X.

On the other hand, in a heat transfer member30A in a modification1shown inFIG. 5, the bending section30V1and the fixed section30Y1extend from one side of the joining section30X.

In a heat transfer member30B in a modification2shown inFIG. 6, bending sections30V1,30V2, and30V3and fixed sections30Y1,30Y2, and30Y3extend from three sides of the joining section30X.

In a heat transfer member30C in a modification3shown inFIG. 7, the bending sections30V1and30V3and the fixed sections30Y1and30Y3extend from orthogonal two sides of the joining section30X.

Image pickup apparatuses in the modifications1to3including the heat transfer members30A,30B, and30C have effects same as the effects of the image pickup apparatus1in the first embodiment. Note that a shape of the heat transfer member is selected according to disposition of the wiring board40, the electronic component44, and the signal cable50disposed on the inside of the housing60, a heat value of the image pickup device, that is, a heat quantity that should be radiated, and the like.

Second Embodiment

An image pickup apparatus1D in a second embodiment is explained. Since the image pickup apparatus1D is similar to the image pickup apparatus1and the like, the same components are denoted by the same reference numerals and signs and explanation of the components is omitted.

As shown inFIG. 8andFIG. 9, a heat transfer member30D of the image pickup apparatus1D includes a bending section30YV in the fixed section30Y. The bending section30YV is plastically deformed in advance such that, when the heat transfer member30D is housed in the housing60, a distal end portion30YA of the fixed section30Y is parallel to the inner surface of the housing60. Therefore, an entire surface of the distal end portion30YA is in surface contact with the inner surface of the housing60.

The image pickup apparatus1D has effects same as the effects of the image pickup apparatus1. Further, since a contact area of the heat transfer member30D and the housing60is large, it is possible to more efficiently radiate the heat generated by the image pickup device20.

Third Embodiment

An image pickup apparatus1E in a third embodiment is explained. Since the image pickup apparatus1E is similar to the image pickup apparatus1and the like, the same components are denoted by the same reference numerals and signs and explanation of the components is omitted.

As shown inFIG. 10, on an inner surface of a housing60E of the image pickup apparatus1E, a positioning section63that defines a position in a longitudinal direction of the fixed section30Y on an inside of the housing60E, that is, a position in the longitudinal direction of an image pickup unit is disposed.

As explained above, an image pickup unit, in which the cover glass10, the image pickup device20, the heat transfer member30, the wiring board40, and the signal cable50are integrated, is inserted into the inside of the housing60E from a distal end side. At this point, a disposition position in the longitudinal direction of the image pickup unit is defined by the positioning section63.

The positioning section63may be formed by disposing a separate member or may be formed by machining a part of the housing60E. A part of the fixed section30Y may be machined to provide a convex section to be locked to or engaged with the positioning section63.

The image pickup apparatus1E has effects same as the effects of the image pickup apparatus1and the like. Further, it is possible to easily secure accuracy of a disposition position of the image pickup unit, for example, the image pickup device20.

<Modification of the Third Embodiment>

In an image pickup apparatus1F of a modification shown inFIG. 11, an elongated hole60FH is formed on a contact surface of a heat transfer member30F of a housing60F. A part of the fixed section30Y of the heat transfer member30F is machined into a convex section30FH to fit with a hole60FH. That is, the hole60FH of the housing60F is a positioning section having a function of a positioning member that defines a position of a fixed section.

Note that, after the heat transfer member30F and the housing60F are fit, a material having high thermal conductivity such as high thermal conduction resin, solder, or Ag paste may be injected into the hole60FH to fix and seal a part where the housing60F and the heat transfer member30F are in contact.

The image pickup apparatus1F in the modification has the effects of the image pickup apparatus1E. Further, since the hole60FH of the housing60F and the convex section30FH of the fixed section30Y are fit, a contact area is large. When a contact portion of the housing60F and the convex section30FH of the heat transfer member30F is sealed by a high thermal conductivity material, heat is more efficiently transferred.

Fourth Embodiment

An image pickup apparatus1G in a fourth embodiment is explained. Since the image pickup apparatus1G is similar to the image pickup apparatus1and the like, the same components are denoted by the same reference numerals and signs and explanation of the components is omitted.

As shown inFIG. 12, in an image pickup device20G of the image pickup apparatus1G, an external connection terminal23G is disposed on the first principal plane20SA. One end portion of a wiring board40G is connected to the external connection terminal23G on the first principal plane20SA of the image pickup device20G. The other end portion is disposed on a rear end side via a bending section.

The image pickup apparatus1G has the effects of the image pickup apparatus1and the like. Further, it is easy to manufacture the image pickup device20G without a through-wire. The through-hole30H is absent in a joining section30XG of a heat transfer member30G. Therefore, it is easy to manufacture the heat transfer member30G. Further, since a contact area of the image pickup device20G and the heat transfer member30G is large, it is possible to efficiently radiate heat generated by the image pickup device20G.

Fifth Embodiment

An endoscope9in a fifth embodiment is explained. As shown inFIG. 13, the endoscope9is an electronic endoscope including the image pickup apparatus1in the first embodiment at a distal end portion2of an insertion section3.

The endoscope9includes an operation section4disposed on a proximal end side of the insertion section3and a universal cord5extending from the operation section4. In the operation section4, various switches and the like, which a surgeon operates while grasping the operation section4, are disposed. The cable50of the image pickup apparatus1is inserted through the insertion section3and the universal cord5and connected to a main body section (not shown in the figure), which performs image processing and the like, via a connector6disposed at a proximal end portion of the universal cord5.

Since the image pickup apparatus1is small in diameter and very small is size, the endoscope9including the image pickup apparatus1at the distal end portion is less invasive. In the endoscope9, it is unlikely that the image pickup apparatus1is deteriorated by an excessive temperature rise and image quality is deteriorated by thermal noise.

Note that it goes without saying that endoscopes including the image pickup apparatuses1A to1G in the embodiments and the modifications instead of the image pickup apparatus1in the first embodiment also have effects same as the effects of the endoscope9in the present embodiment.

The present invention is not limited to the embodiments, the modifications, and the like. Various changes, alterations, and the like can be made in a range in which the gist of the present invention is not changed.