CN115191914A

CN115191914A - Camera module

Info

Publication number: CN115191914A
Application number: CN202210164450.9A
Authority: CN
Inventors: 浅冈卓郎
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2021-03-16
Filing date: 2022-02-22
Publication date: 2022-10-18
Also published as: JP2022142220A

Abstract

The invention provides an image pickup module capable of preventing adhesion and peeling between an imaging element and a prism on a circuit board when an endoscope is operated. In an image pickup module including an imaging element, a lens, and an optical member disposed between the imaging element and the lens, a light receiving surface of the imaging element and the optical member are bonded and fixed to each other over the entire surface, a 1 st layer having a thermal expansion coefficient higher than that of the imaging element is bonded to a surface of the imaging element on a side opposite to the light receiving surface, and a curing temperature of an adhesive bonding the imaging element and the optical member is lower than a temperature at which the imaging element operates.

Description

Camera module

Technical Field

The present invention relates to a camera module.

Background

An image pickup module having an imaging element, a lens barrel, and the like is disposed at a distal end portion of the endoscope. The imaging element is mounted on the circuit substrate.

An optical member such as a prism for guiding light passing through the lens to an imaging surface of the imaging element is disposed between the imaging element and the lens barrel. The imaging element and the optical member are adhesively fixed to prevent positional displacement.

For example, patent document 1 describes an imaging unit for an endoscope, which includes: an objective lens disposed at the distal end of an insertion section of an endoscope; a lens barrel holding an object lens; a light incident surface connected to one end of the lens barrel; a prism having a light exit surface perpendicular to the light entrance surface; a cover glass, one surface of which is bonded to the light emitting surface of the prism via an adhesive; and an imaging element substrate arranged to face the light emitting surface of the prism, wherein any one of the lens barrel, the prism, and the cover glass includes a protruding portion provided at a position covering one side of an interface between the prism and the cover glass on the lens barrel side, and the protruding portion includes a recessed portion facing the one side to form a closed space between the prism and at least one side surface of the cover glass.

Patent document 1: japanese patent laid-open publication No. 2019-030421

In an endoscope, the following problems may occur when the endoscope is operated: the circuit board is pulled by a load applied to the cable connected to the circuit board, and the imaging element on the circuit board is also pulled, which causes the adhesion between the imaging element and the prism to peel off.

Disclosure of Invention

An object of the present invention is to solve the above-described problems of the conventional art and to provide an image pickup module capable of preventing the adhesion and separation of an imaging element and a prism on a circuit board when an endoscope is operated.

In order to solve the above problems, the present invention has the following configurations.

[1] An image pickup module includes an imaging element, a lens, and an optical member disposed between the imaging element and the lens,

the light receiving surface of the imaging element and the optical member are bonded and fixed over the entire surface,

a1 st layer having a thermal expansion coefficient larger than that of the imaging element is bonded to a surface of the imaging element on the side opposite to the light receiving surface,

the curing temperature of the adhesive bonding the imaging element and the optical member is lower than the temperature at which the imaging element operates.

[2] The camera module according to [1], wherein,

layer 1 is a circuit substrate.

[3] The camera module according to [2], wherein,

the circuit substrate is a flexible substrate.

[4] The camera module according to [2] or [3], wherein,

the imaging element and the layer 1 are connected via solder balls.

[5] The camera module according to any one of [1] to [4], wherein,

the space between the imaging element and the layer 1 is filled with adhesive.

[6] The camera module according to any one of [1] to [5], which has a 3 rd layer having a thermal expansion coefficient lower than that of the 1 st layer on a face of the 1 st layer on a side opposite to the imaging element.

[7] The camera module according to any one of [1] to [6], wherein,

the imaging element has a sensor chip and a cover glass disposed on an imaging surface of the sensor chip,

the sensor chip and the cover glass are bonded and fixed to each other over the entire surface.

Effects of the invention

According to the present invention, it is possible to provide an image pickup module capable of preventing the adhesion and peeling of the imaging element and the prism on the circuit board when the endoscope of the image pickup module is operated.

Drawings

Fig. 1 is a schematic configuration diagram showing an example of a configuration of an endoscope system using an endoscope including an image pickup module according to the present invention.

Fig. 2 is a perspective view schematically showing an example of the image pickup module of the present invention.

Fig. 3 is a side view of the camera module shown in fig. 2 in a state where the anchor and the cover member are removed.

Fig. 4 is an enlarged side view showing a part of the camera module of fig. 3.

Fig. 5 is a partially enlarged side view of another example of the camera module of the present invention.

Fig. 6 is an enlarged side view of a part of the camera module.

Fig. 7 is a side view schematically showing another example of the image pickup module of the present invention.

Fig. 8 is a side view schematically showing another example of the image pickup module of the present invention.

Fig. 9 is a side view schematically showing another example of the image pickup module of the present invention.

Detailed Description

Hereinafter, an embodiment of an image pickup module according to the present invention will be described with reference to the drawings.

The following description of the constituent elements may be made in accordance with a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In the drawings of the present specification, the proportions of the respective portions are appropriately changed for easy visual recognition.

In the present specification, the numerical range expressed by the term "to" means a range including the numerical values described before and after the term "to" as the lower limit value and the upper limit value.

[ Camera Module ]

The camera module of the invention comprises an imaging element, a lens and an optical component arranged between the imaging element and the lens,

Fig. 1 conceptually shows an example of an endoscope system including an endoscope having an image pickup module according to the present invention.

The endoscope system 1 includes an endoscope 2, a light source unit 3, and a processor unit 4. The endoscope 2 has the same structure as a general endoscope except for a portion of the image pickup module 10 described later.

The endoscope 2 includes an insertion portion to be inserted into a subject, an operation portion connected to the insertion portion, and a universal cable extending from the operation portion, and the insertion portion includes a distal end portion, a bending portion connected to the distal end portion, and a soft portion connecting the bending portion and the operation portion.

The distal end portion is provided with an illumination optical system that emits illumination light for illuminating an observation site, and an image pickup module (camera head) having an imaging element for picking up an image of the observation site, an image pickup optical system, and the like. The bending portion is configured to be bendable in a direction orthogonal to the longitudinal axis of the insertion portion, and the bending operation of the bending portion is operated by the operation portion. The soft portion is configured to be relatively soft to such an extent that the soft portion can deform following the shape of the insertion path of the insertion portion.

The operation portion is provided with a button for operating the image pickup operation of the image pickup module at the distal end portion, a knob for operating the bending operation of the bending portion, and the like. The operation portion is provided with an introduction port through which a medical tool such as an electric scalpel is introduced, and the insertion portion is provided therein with a medical tool channel through which the medical tool such as a forceps is inserted, the medical tool channel extending from the introduction port to the distal end portion.

A connector is provided at the distal end of the universal cable, and the endoscope 2 is connected via the connector to a light source unit 3 that generates illumination light emitted from an illumination optical system at the distal end portion and a processor unit 4 that processes an image signal acquired by an imaging device at the distal end portion.

The processor unit 4 processes the input video signal to generate video data of the observation site, displays the generated video data on a monitor, and records the video data. In addition, the processor unit 4 may be constituted by a processor such as a PC (personal computer).

The light source unit 3 is used for: illumination light such as white light composed of three primary color light such as red light (R), green light (G), and blue light (B) or specific wavelength light is generated and supplied to the endoscope 2, propagates through a light guide or the like in the endoscope 2, and is emitted from an illumination optical system at the distal end portion of the insertion portion of the endoscope 2, thereby illuminating an observation target site in a body cavity, and an image pickup device of the endoscope 2 picks up an image of the observation target site in the body cavity to acquire an image signal.

The optical waveguide and the electric wire group (signal cable) are housed inside the insertion portion, the operation portion, and the universal cable. The illumination light generated in the light source unit 3 is guided to the illumination optical system of the tip portion via the light guide, and signals and/or power are transmitted between the image pickup device of the tip portion and the processor unit 4 via the wire group.

The endoscope system 1 may further include a water supply tank for storing washing water or the like, a suction pump for sucking the suctioned material in the body cavity (the supplied washing water or the like is also included), and the like. Further, a supply pump or the like may be provided for supplying gas such as washing water in the water supply tank or outside air into a pipe (not shown) in the endoscope.

Fig. 2 is a perspective view schematically showing an example of the image pickup module according to the present invention. The side view of fig. 2 is shown in fig. 3. Fig. 3 is a side view of the camera module of fig. 2 with the anchor 24 and the cover member 42 removed.

The camera module 10 shown in fig. 2 and 3 includes a lens 12, a lens barrel 14 for holding the lens 12, an imaging element 15, an optical component 18, an optical component holding jig 20, a layer 2 19, a circuit board 22, an anchor 24, a cover member 42, and a cable 26.

The example shown in fig. 2 and 3 is an example in which the optical member 18 is a prism and the image forming surface of the sensor chip 16 is arranged parallel to the optical axis of the lens 12. In the following description, the optical member 18 is also referred to as a prism 18.

The lens 12 is an optical system that images incident light on an imaging surface of the sensor chip 16. The lens 12 is held by a lens barrel 14.

The lens barrel 14 is a cylindrical member that holds one or more lenses 12. The lens barrel 14 holds the lens 12 such that an optical axis of the lens 12 is perpendicular to a surface of the prism 18 facing the lens 12.

The structures of the lens 12 and the lens barrel 14 are not particularly limited. For example, the configuration may be one lens 12, or may be two or more lenses 12. Each lens 12 may be a convex lens or a concave lens.

The imaging element 15 has a sensor chip 16 and a cover glass 17.

The sensor chip 16 is an element that performs imaging by converting light imaged on an imaging surface of the sensor chip 16 by the lens 12 into an electric signal by photoelectric conversion. The sensor chip 16 is a conventionally known Device such as a CCD (Charge-Coupled Device) sensor or a CM () S (Complementary MOS) sensor.

The cover glass 17 is disposed on the imaging surface of the sensor chip 16 to protect the imaging surface. The size of the cover glass 17 in plan view is substantially the same as the size of the imaging surface of the sensor chip 16. The cover glass 17 is bonded and fixed to the entire imaging surface of the sensor chip 16. In the case where the imaging element 15 has the structure of the cover glass 17, an incident surface (a surface on the opposite side from the sensor chip 16) of the cover glass 17 may be regarded as a light receiving surface of the imaging element 15.

A prism 18 is disposed on the cover glass 17 (incident surface).

The imaging element 15 is disposed on the base end side of the lens barrel 14. As shown in fig. 3, the imaging element 15 is mounted on the circuit board 22 such that the light-receiving surface is parallel to the optical axis of the lens 12.

The circuit board 22 is the layer 1 in the present invention, and is a board on which the imaging element 15 is mounted. Further, electronic components other than the imaging element 15 may be mounted on the circuit board 22. The circuit board 22 is provided with a plurality of connection terminals for inputting/outputting signals or power to/from the imaging element 15 and the electronic components. The connection terminals are electrically connected with signal lines of the cable 26 (refer to fig. 3).

In the illustrated example, the circuit board 22 has a shape in which a substantially L-shaped plate-like member is bent at two places. Specifically, the circuit board 22 includes a 1 st bent portion 22b bent about a direction orthogonal to the optical axis direction (hereinafter also referred to as an axial direction) of the lens and a 2 nd bent portion 22c bent about the axial direction, and the imaging element 15, the electronic component, and the connection terminal are mounted on three plate-like portions connected by the two bent portions. In the illustrated example, the imaging element 15 is mounted on the upper surface side of the lower plate-like portion in fig. 3.

The circuit board 22 is a conventionally known circuit board used for an image pickup module of an endoscope. The circuit board 22 may be a flexible board having flexibility. The flexible substrate 22 is not particularly limited, and a conventionally known flexible substrate can be used. For example, a flexible substrate is formed by forming a circuit made of a copper foil or the like on a base film made of a resin material such as polyimide or polyethylene terephthalate (PET).

The circuit board 22 may be bent at one or three or more positions. The arrangement of the imaging element 15, the electronic component, the connection terminal, and the like on the circuit board 22 is not particularly limited.

The imaging element 15 and the cable 26 are connected to the circuits on the circuit board 22. The light is converted into an electrical signal by the imaging element 15 (sensor chip 16), and the electrical signal is transmitted to the cable 26 via the circuit of the circuit substrate 22. The cable 26 is inserted into an insertion portion, an operation portion, a universal cable, and the like of the endoscope and connected to the processor unit 4.

The cable 26 includes one or more signal lines such as a coaxial cable or a uniaxial cable, a shield line covering the outer periphery of the one or more signal lines, a protective coating (sheath) covering the outer peripheries of the signal lines and the shield line, and the like.

The circuit substrate 22 and the imaging element 15 (sensor chip 16) may be electrically connected through the 2 nd layer 19. Fig. 6 shows an enlarged view of the vicinity of the imaging element 15. In the example shown in fig. 6, the 2 nd layer 19 has a plurality of solder balls 19a, and the circuit of the circuit substrate 22 and the sensor chip 16 are electrically connected via the solder balls 19 a. In the example shown in fig. 6, the underfill 19b is preferably filled in a portion of the space between the imaging element 15 and the circuit board 22 where the solder ball 19a is not present. The underfill 19b is an adhesive that fills a space between the imaging element and the layer 1 in the present invention.

As the solder balls 19a, conventionally known solder balls for electrically connecting a sensor and a substrate in an imaging module of an endoscope can be suitably used. For example, a Sn-Ag-Cu alloy can be used as a material of the solder ball.

As the underfill material 19b, conventionally known underfill materials used as an underfill material in an imaging module of an endoscope can be suitably used. For example, as the underfill, a resin material such as an epoxy resin can be used.

The 2 nd layer 19 is not limited to the structure having the solder balls 19a and the underfill 19b. For example, the 2 nd layer 19 may have only the solder balls 19 a. Alternatively, an Anisotropic Conductive Film (ACF) may be used.

The layer 2 19 is configured to have solder balls 19a and an underfill 19b, whereby the warpage amount of an imaging element described later can be increased.

The prism 18 is disposed between the lens barrel 14 and the imaging element 15 (cover glass 17). The prism 18 bends the light passing through the lens 12 held by the lens barrel 14 by 90 ° to change the optical path, and guides it to the light receiving surface of the imaging element 15. In the illustrated example, the prism 18 is a rectangular prism having an incident surface orthogonal to an exit surface. The prism 18 is disposed such that an incident surface faces the base end side surface of the lens barrel 14, and an output surface faces the light receiving surface of the imaging element 15 (cover glass 17). The prism 18 is bonded and fixed to the entire surface of the imaging element 15 (cover glass 17).

The optical component holding tool 20 is a member that holds the lens barrel 14 and the prism 18. The optical component holder 20 is a substantially cylindrical member, and the lens barrel 14 is fitted into the cylindrical portion to hold the lens barrel 14. The inner surface of the optical component holding tool 20 and the outer peripheral surface of the lens barrel 14 are bonded and fixed.

As the adhesive for bonding the optical component holding tool 20 and the lens barrel 14, various known adhesives used in conventional endoscopes can be used. The same applies to the adhesive for bonding the other members to each other at this point.

The optical component holding tool 20 has a polygonal flange portion 20a on the end surface of the cylindrical portion on the base end side, and the incident surface of the prism 18 abuts against the flange portion. Thereby, the prism 18 is positioned. The optical component holding tool 20 holds the lens barrel 14 and the prism 18 at predetermined positions to fix the relative position between the lens barrel 14 and the prism 18, that is, the relative position between the lens barrel 14 and the imaging element 15.

Here, the relative position between the lens barrel 14 and the optical component holder 20 in the optical axis direction (hereinafter also referred to as the axial direction) of the lens 12 is adjusted so as to be in focus on the image forming surface of the sensor chip 16, and the lens barrel 14 is bonded and fixed to the optical component holder 20.

Anchors 24 retain cable 26 relative to optical component holding tool 20. In the illustrated example, the anchor 24 has two plate-shaped portions 24c extending in the optical axis direction, and an arm portion 24a on the leading end side of each plate-shaped portion 24 c. The arm portion 24a engages with the flange portion 20a of the optical component holding tool 20. As shown in fig. 2, the two plate-like portions 24c are arranged such that the main surfaces thereof are perpendicular to the surface of the circuit board 22 (the surface on which the imaging element 15 is arranged). The two plate-like portions 24c are arranged to face each other across a connection portion with the cable 26 on the circuit board 22.

The anchor 24 has a holding portion 24b that connects two plate-shaped portions 24c at the proximal end side and holds the cable 26. The holding portion 24b is caulked so as to press the cable 26 to hold the cable 26. That is, the holding portion 24b is bent along the outer sheath of the cable 26.

The arm portions 24a of the anchor 24 and the flange portion 20a of the optical component holding jig 20, and the holding portions 24b of the anchor 24 and the sheath of the cable 26 may be fixed by adhesive bonding, respectively.

In this way, since the anchor 24 is connected to the optical component holding tool 20 and the cable 26, the connection between the connection terminal and the signal line is prevented from being broken due to the connection portion between the connection terminal and the signal line on the circuit board 22 being pulled when the cable 26 is pulled.

The cover member 42 is a plate-like member disposed on the opposite side of the anchor 24 from the circuit board 22. The cap member 42 covers the connecting portions of the connecting terminals and the signal lines on the circuit board 22 together with the anchors 24 to protect them.

The material for forming the anchor 24 and the cover member 42 is not particularly limited, and various resin materials and metal materials used as members constituting an imaging module of an endoscope can be used. From the viewpoint of heat dissipation, a metal material is preferable. In consideration of workability, acquisition properties, strength, and the like, stainless steel and copper alloy are preferable as the anchor 24 and the lid member 42.

In addition, the cover member 42 may be formed integrally with the anchor 24. Alternatively, the cover member 42 may not be provided.

In the camera module 10, an observation image captured by the lens 12 on the imaging element 15 is formed on the imaging surface of the sensor chip 16, converted into an electric signal, output to the processor unit 4 via the cable 26, and converted into a video signal, and the observation image is displayed on a monitor connected to the processor unit 4.

Here, as described above, the following problems may occur when operating an endoscope or the like: the circuit board 22 is pulled by a load applied to the cable 26 connected to the circuit board 22, and the imaging element 15 on the circuit board 22 is also pulled, resulting in peeling of the adhesion between the imaging element 15 and the prism (optical member) 18. Further, since the anchor 24 is filled with an adhesive and a load of the cable 26 is applied to the imaging element 15 and the prism 18 via the adhesive, the adhesion between the imaging element 15 and the prism 18 is peeled off. Further, the adhesive for bonding the imaging element 15 and the prism 18 is also affected by deterioration due to environmental factors such as sterilization gas at the time of cleaning the endoscope and repeated temperature changes, and is likely to be damaged.

In contrast, the camera module of the present invention has the following structure: a layer 1 having a thermal expansion coefficient higher than that of the imaging element 15 is bonded to a surface of the imaging element 15 on the side opposite to the light receiving surface, and the curing temperature of the adhesive for bonding the imaging element 15 and the optical member 18 is lower than the temperature at which the imaging element 15 operates.

In the endoscope, when the endoscope is operated, the temperature of each member of the imaging module 10 is increased by heat generated from the imaging element 15, the light guide, and the like. Therefore, the components of the camera module 10 expand due to heat. At this time, if the thermal expansion coefficient of the 1 st layer (circuit board) 22 is larger than that of the imaging element 15, the 1 st layer 22 extends more than the imaging element 15 in the plane direction, and therefore a force of deforming the imaging element 15 into a concave shape toward the optical member 18 side is applied. Basically, the temperature at which the adhesive is cured is in a state where the stress applied to the adhesive layer is about 0, and therefore, if the curing temperature of the adhesive is lower than the temperature at the time of operation, a force that stretches in the direction of separating is applied to the central portion between the imaging element 15 and the optical member 18, and a force that compresses is applied to the end portions, as indicated by arrows in fig. 4. In this way, when the endoscope is operated with a load applied to the cable 26, the light receiving surface side of the imaging element 15 is deformed in the concave direction by heat generation of the imaging element 15 or the like, and a compressive force is applied to the outer peripheral portion of the adhesion surface between the imaging element 15 and the optical member 18, so that the imaging element 15 and the optical member 18 are brought into close contact with each other, and even when the cable 26 is pulled, the imaging element 15 and the optical member 18 can be prevented from being peeled off from each other.

Here, in the present invention, the temperature at which the imaging element operates is defined as follows.

The temperature of the center of the side face of the imaging element after reaching the equilibrium state under the following conditions is set: the endoscope having the image pickup module is set in an ambient gas at 37 ℃, the imaging element of the image pickup module is driven, and light having a light quantity half of the maximum light quantity is made incident on the light guide member provided in the endoscope.

In general, a CMOS sensor and a CCD sensor used as the sensor chip 16 have a structure in which an electrode layer, an insulating film, and the like are formed on a silicon wafer. Therefore, the thermal expansion coefficient of the sensor chip 16 is about 2.5 ppm/deg.C to 4 ppm/deg.C. When the imaging element 15 has the cover glass 17, the thermal expansion coefficient of the imaging element 15 in which the sensor chip 16 and the cover glass 17 are laminated is about 2.5 ppm/degree centigrade to 5 ppm/degree centigrade.

Examples of the circuit board 22 having a higher thermal expansion coefficient than the imaging element 15 include a flexible board and a rigid board made of a resin material such as polyimide or polyethylene terephthalate. For example, the thermal expansion coefficient of the flexible substrate is about 20 ppm/DEG C to 100 ppm/DEG C.

The thermal expansion coefficients of the respective members were measured as follows.

The thermal expansion coefficient was obtained as a length change rate per unit temperature change by measuring the length between the measurement points of the test piece for each of a plurality of temperatures.

The elastic modulus was determined by applying a load to a test piece by a tensile test, measuring the change in length between measurement points of the test piece, and calculating the stress and strain. Alternatively, a method of obtaining the young's modulus of each material by a nanoindentation method and obtaining the composite elastic modulus from the volume ratio may be used.

As the adhesive for bonding the image forming element 15 and the optical member 18, any adhesive may be used as long as it can appropriately bond the image forming element 15 and the optical member 18 and the curing temperature is lower than the temperature at which the image forming element 15 operates. The temperature of the imaging element 15 during operation is usually about 50 to 85 ℃. Therefore, as the adhesive for bonding the imaging element 15 and the optical member 18, an adhesive whose curing temperature is 50 ℃ or lower is preferable, an adhesive whose curing temperature is 40 ℃ or lower is more preferable, and an adhesive which cures at normal temperature is further preferable.

Examples of the adhesive having a curing temperature in such a range include a UV (ultraviolet) curable adhesive, a UV + heat curable adhesive, and an epoxy adhesive curable at normal temperature.

In the example shown in fig. 4, the imaging element 15 is configured to include the sensor chip 16 and the cover glass 17, but is not limited thereto. As in the example shown in fig. 5, the imaging element 15 may be configured to have the sensor chip 16 without the cover glass 17. In this case, the imaging surface of the sensor chip 16 is the light receiving surface of the imaging element 15. In this configuration, the emission surface of the optical member 18 and the image forming surface of the sensor chip 16 are bonded and fixed.

In fig. 4 and 5, the illustration of the 2 nd layer 19 between the imaging element 15 and the circuit board 22 is omitted.

The camera module of the present invention preferably has a 3 rd layer having a lower thermal expansion coefficient than the 1 st layer on the surface of the 1 st layer opposite to the imaging element.

Fig. 7 is a side view conceptually showing another example of the image pickup module of the present invention. In fig. 7, the lens and the like are not shown.

The camera module shown in fig. 7 includes an optical member 18, an imaging element 15 including a cover glass 17 and a sensor chip 16, a circuit board 22, and a 3 rd layer 40.

The optical member 18, the cover glass 17, the sensor chip 16, and the circuit board 22 have the same configuration as in the above example.

The 3 rd layer 40 is disposed on the 1 st layer, i.e., the surface (back surface) of the circuit board 22 opposite to the imaging element 15. The 3 rd layer 40 is formed of a material having a lower thermal expansion coefficient than the circuit substrate 22.

By disposing the 3 rd layer 40 having a lower thermal expansion coefficient than the circuit board 22 on the rear surface of the circuit board 22, a force for restricting thermal expansion of the circuit board 22 acts. That is, the concave warping of the imaging element 15 toward the optical member 18 side is suppressed. By disposing the 3 rd layer 40 having a low thermal expansion coefficient on the rear surface of the circuit board 22, the amount of concave warpage of the imaging element 15 toward the optical member 18 side can be adjusted, and the imaging element 15 can be prevented from being excessively warped and damaged.

Examples of the material of the 3 rd layer 40 include invar materials, kovar materials, glass, silicon, stainless steel, and ceramics such as aluminum nitride and silicon nitride.

The thickness of the 3 rd layer 40 may be appropriately set according to the adjustment amount of the warping amount of the imaging element 15.

The size of the 3 rd layer 40 in a plan view is preferably equal to or larger than the size of the imaging element 15, and the 3 rd layer 40 is preferably arranged to include the imaging element 15 in a plan view.

For example, in the example shown in fig. 7, the 3 rd layer 40 is configured such that the size (length) in the optical axis direction of the lens 12 is larger than the imaging element 15 and includes the imaging element 15 in the optical axis direction. That is, the side of the 3 rd layer 40 protrudes further than the side of the imaging element 15.

Also, a circuit may be formed on the 3 rd layer 40. The circuit formed on the 3 rd layer 40 can be connected with the circuit of the 1 st layer (flexible substrate) 22 to constitute a multilayer circuit substrate. When a circuit is formed on the 3 rd layer 40, an insulating material such as ceramic may be used for the 3 rd layer.

In the example shown in fig. 3, the imaging surface of the sensor chip 16 (the light-receiving surface of the imaging element 15) is arranged parallel to the optical axis of the lens 12, and the optical member 18 arranged between the lens 12 and the imaging element 15 is a prism that bends light by 90 °.

Fig. 8 is a side view showing another example of the image pickup module of the present invention.

The image pickup module shown in fig. 8 includes a lens barrel 14 for holding a lens 12, an optical component holding jig 20, an optical component 18, an imaging element 15 having a cover glass 17 and a sensor chip 16, a layer 2 19, a circuit board 22, and an adhesive layer 44.

In the image pickup module shown in fig. 8, the circuit board 22 has a bent portion bent substantially at 90 °, and has a flat plate-like portion parallel to the optical axis of the lens 12 and a flat plate-like portion perpendicular to the optical axis. The 2 nd layer 19, the sensor chip 16, and the cover glass 17 are laminated on the surface (the surface on the lens 12 side) of the portion perpendicular to the optical axis of the circuit board 22. Therefore, the imaging surface of the sensor chip 16 (the light receiving surface of the imaging element 15) is arranged perpendicular to the optical axis of the lens 12.

The optical member 18 guides the light passing through the lens 12 to an imaging surface of the sensor chip 16. The optical member 18 is disposed such that the light incident surface and the light emitting surface are perpendicular to the optical axis. The optical member 18 may transmit only light or may have an effect of condensing light. The optical member 18 has an effect of condensing light, and thus the distance between the lens 12 and the sensor chip 16 can be made shorter, thereby enabling miniaturization.

The lens barrel 14 holding the lens 12, the optical component holding jig 20, the imaging element 15 having the cover glass 17 and the sensor chip 16, and the 2 nd layer 19 are the same as those of the image pickup module shown in fig. 3, and therefore, descriptions thereof are omitted.

The optical component 18 is held by the optical component holding tool 20 so as to be positioned together with the lens barrel 14 held by the optical component holding tool 20.

As described above, even in the case of the image pickup module of the present invention having a structure in which the imaging surface of the sensor chip 16 is arranged perpendicular to the optical axis of the lens 12, the image pickup module has the following structure: the layer 1 (circuit board 22) having a thermal expansion coefficient higher than that of the imaging element 15 is bonded to the surface of the imaging element 15 on the side opposite to the light-receiving surface, and the curing temperature of the adhesive for bonding the imaging element 15 and the optical member 18 is lower than the temperature at which the imaging element 15 operates. This can prevent the imaging element 15 and the optical member 18 from being peeled off even if the cable is pulled during the operation of the endoscope.

Here, in the example shown in fig. 8, it is preferable that the adhesive layer 44 is provided so as to cover at least a part of the side surface of the sensor chip 16. In the example shown in fig. 8, the adhesive layer 44 is disposed at a position covering a side surface (a lower side surface in fig. 8) on the bent portion side of the circuit board 22 and a side surface (an upper side surface in fig. 8) facing the side surface.

By having the adhesive layer 44 covering at least a part of the side surface of the sensor chip 16, breakage due to warping of the imaging element can be suppressed. The adhesive layer 44 may have functions such as light shielding, gas barrier (e.g., a sterilizing gas), and moisture prevention.

The adhesive layer 44 preferably covers the entire circumference of the sensor chip 16.

As a material of the adhesive layer 44, an adhesive or a sealant can be used.

As the adhesive, various adhesives used in endoscopes can be used. For example, an epoxy adhesive can be used. Further, black epoxy is preferable because of its light-shielding property.

As the sealant, various sealants used in endoscopes can be used.

The adhesive and the sealant preferably have higher thermal conductivity, but preferably have insulating properties.

In the case of the configuration shown in fig. 3 and the like in which the image forming surface of the sensor chip 16 is arranged parallel to the optical axis of the lens 12, the adhesive layer 44 is preferably provided so as to cover at least a part of the side surface of the sensor chip 16, and more preferably is applied so as to cover the entire circumference.

In the example shown in fig. 8, the adhesive layer 44 is filled between the circuit board 22 and the prism 18, but the present invention is not limited to this, and the adhesive layer 44 may be filled between the circuit board 22 and the optical component holder 20 as in the example shown in fig. 9.

As in the example shown in fig. 8, even when the image forming surface of the sensor chip 16 is arranged so as to be perpendicular to the optical axis of the lens 12, the back surface of the circuit board 22 may have a layer 3 made of a material having a lower thermal expansion coefficient than the circuit board 22. Thereby, the warping amount of the imaging element 15 can be adjusted.

In the above example, the 1 st layer is a circuit board, but is not limited thereto. As the 1 st layer, a member having no circuit and having a thermal expansion coefficient larger than that of the imaging element may be disposed. From the viewpoint of space efficiency, a circuit board is preferably used as the 1 st layer. Further, from the viewpoints of assemblability, cost, and the like, a flexible substrate is preferably used as the 1 st layer.

While the image pickup module according to the present invention has been described in detail with reference to various embodiments, the present invention is not limited to the above examples, and various modifications and variations can be made without departing from the scope of the present invention.

Description of the symbols

1-endoscope system, 2-endoscope, 3-light source unit, 4-processor unit, 10-camera module, 12-lens, 14-lens barrel, 15-imaging element, 16-sensor chip, 17-cover glass, 18-optical component (prism), 19-2 nd layer, 19 a-solder ball, 19 b-underfill, 20-optical component holding tool, 20 a-flange portion, 22-circuit substrate (1 st layer), 22 a-back surface, 22 b-1 st bend portion, 22 c-2 nd bend portion, 24-anchor, 24 a-arm portion, 24 b-holding portion, 24 c-plate portion, 26-cable, 40-3 rd layer, 42-cover member, 44-adhesive layer.

Claims

1. An image pickup module includes an imaging element, a lens, and an optical member disposed between the imaging element and the lens,

a 1 st layer having a thermal expansion coefficient larger than that of the imaging element is bonded to a surface of the imaging element on a side opposite to the light receiving surface,

2. The camera module of claim 1,

the layer 1 is a circuit substrate.

3. The camera module of claim 2,

the circuit substrate is a flexible substrate.

4. The camera module of claim 2 or 3,

the imaging element and the layer 1 are connected via a solder ball.

5. The camera module of any of claims 1-3,

the space between the imaging element and the layer 1 is filled with an adhesive.

6. The camera module of any of claims 1-3,

a 3 rd layer having a lower thermal expansion coefficient than the 1 st layer is provided on a surface of the 1 st layer opposite to the image forming member.

7. The camera module of any of claims 1-3,

the sensor chip and the cover glass are bonded and fixed on the whole surface.