JP7585104B2 - Imaging module - Google Patents

Description

The present invention relates to an imaging module.

An imaging module having an image sensor and a lens barrel is placed at the tip of the endoscope. The image sensor is placed on a substrate via an electrode layer that provides electrical connection via solder balls, etc.

Flexible boards made of resins such as polyimide and polyethylene terephthalate are being considered for use as substrates for a number of reasons: they are cheaper than rigid substrates, they are easy to assemble as they can be mounted together with other electronic components at once, and they can be bent so that they can be arranged three-dimensionally within a small housing.

For example, Patent Document 1 describes an endoscope that has a solid-state imaging element that photoelectrically converts the imaging light incident on the image receiving surface through a photographing lens, and a circuit board with a connection surface that faces the terminal surface, which is the surface opposite the image receiving surface of the solid-state imaging element, where multiple terminals are evenly arranged vertically and horizontally in a two-dimensional matrix on the terminal surface of the solid-state imaging element, the connection surface of the circuit board and the terminal surface of the solid-state imaging element are connected via multiple terminals, and the total area of the multiple terminals on the terminal surface occupies 10% or more of the area of the imaging area on the image receiving surface of the solid-state imaging element.

This patent document states that when mounting an image sensor on a flexible substrate, deformation of the flexible substrate, particularly during cooling, can cause warping of the substrate of the image sensor, which can lead to localized distortion at the connection between the image sensor and the circuit substrate (paragraph [0026]).

JP 2018-007714 A

As described above, when a flexible substrate is used as the substrate for an imaging element, there is a problem in that when each component thermally expands or contracts due to temperature changes, the imaging element warps due to the large difference in thermal expansion coefficient between the imaging element and the electrode layer and flexible substrate. In particular, since the material used as a flexible substrate has a large thermal expansion coefficient, it was found that when a flexible substrate is used as the substrate, there is a problem in that the imaging element warps and is damaged.

The present invention aims to provide an imaging module that can solve the problems of the conventional technology described above and suppress warping of the imaging element of the imaging module, thereby preventing damage to the imaging element.

To solve the above problems, the present invention has the following configuration.

[1] An imaging module including an imaging element,
a first layer made of a flexible substrate and disposed on a back surface side opposite to an imaging surface of the imaging element;
a second layer disposed between the image sensor and the first layer and electrically connecting the image sensor and the first layer;
a third layer disposed on the opposite side of the first layer from the second layer side,
the third layer has a thermal expansion coefficient closer to the thermal expansion coefficient of the image sensor than the average thermal expansion coefficient of the first layer and the second layer;
The imaging module, wherein the third layer has a higher elastic modulus than the first layer and the second layer.
[2] The imaging module described in [1], wherein a sum of the elastic modulus x thickness of the imaging element and the elastic modulus x thickness of the third layer is greater than a sum of the elastic modulus x thickness of the first layer and the elastic modulus x thickness of the second layer.
[3] The imaging module according to [1] or [2], wherein a cover glass having a size in a plan view equal to that of the imaging element is attached to an imaging surface of the imaging element.
[4] A lens that forms an image on an imaging surface of an imaging element by incident light,
at least one optical component disposed between the cover glass and the lens;
The light receiving surface of the cover glass is glued and fixed to the optical components.
The imaging module described in [3], wherein in at least one direction perpendicular to the side surface of the imaging element, the amount of protrusion of the third layer from the side surface of the imaging element is less than half the sum of the thickness of the cover glass, the thickness of the imaging element, and the thickness of the second layer.
[5] A lens that forms an image on an imaging surface of an imaging element by incident light,
A prism is disposed between the lens and the image sensor.
The imaging surface of the image sensor is arranged parallel to the optical axis of the lens.
The imaging module according to any one of [1] to [4], wherein the third layer forms an outermost layer of the imaging module.
[6] A prism is disposed between the lens and the image sensor,
The imaging surface of the image sensor is arranged parallel to the optical axis of the lens.
a third layer forms an outermost layer of the imaging module;
The imaging module according to [4], wherein the side of the third layer protruding from the imaging element is the side facing the lens.
[7] The imaging module according to any one of [1] to [6], wherein the third layer is made of ceramic.
[8] The imaging module according to any one of [1] to [7], wherein a circuit is formed on the third layer and is electrically connected to the first layer.
[9] The imaging module according to any one of [1] to [8], wherein the second layer has solder balls.
[10] The imaging module according to [9], wherein the second layer is at least partially filled with an underfill.

The present invention provides an imaging module that can suppress warping of the imaging element of the imaging module and prevent damage to the imaging element.

1 is a schematic diagram showing an example of the configuration of an endoscope system using an endoscope having an imaging module according to the present invention. FIG. 1 is a perspective view illustrating an example of an imaging module of the present invention. 3 is a side view of the imaging module shown in FIG. 2 with an anchor and a cover member removed. 3 is an enlarged perspective view showing a part of the imaging module of FIG. 2. FIG. 5 is a side view of FIG. FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention. FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention. FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention. FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention. FIG. 2 is a side view illustrating a schematic diagram of another example of the imaging module of the present invention.

Hereinafter, an embodiment of an imaging module of the present invention will be described with reference to the drawings.
The following description of the components may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In the drawings of this specification, the scale of each part is appropriately changed for ease of viewing.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.

[Imaging module]
The imaging module of the present invention comprises:
In an imaging module including an imaging element,
a first layer made of a flexible substrate and disposed on a back surface side opposite to an imaging surface of the imaging element;
a second layer disposed between the image sensor and the first layer and electrically connecting the image sensor and the first layer;
a third layer disposed on the opposite side of the first layer from the second layer side,
the third layer has a thermal expansion coefficient closer to the thermal expansion coefficient of the image sensor than the average thermal expansion coefficient of the first layer and the second layer;
The third layer has a modulus of elasticity greater than the modulus of elasticity of the first layer and the second layer, the imaging module.

Figure 1 conceptually illustrates an example of an endoscope system equipped with an endoscope having an imaging module of 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 configuration as a general endoscope, except for the imaging module 10, which will be described later.

The endoscope 2 has an insertion section that is inserted into the subject, an operating section that is connected to the insertion section, and a universal cord that extends from the operating section. The insertion section is composed of a tip section, a bending section that is connected to the tip section, and a flexible section that connects the bending section to the operating section.

The tip is provided with an imaging module (camera head) that has an illumination optical system that emits illumination light to illuminate the observation site, and an imaging element and imaging optical system that capture images of the observation site. The bending section is configured to be bendable in a direction perpendicular to the longitudinal axis of the insertion section, and the bending operation of the bending section is controlled by the operating section. In addition, the flexible section is configured to be relatively flexible so that it can be deformed to follow the shape of the insertion path of the insertion section.

The operation section is provided with buttons for controlling the imaging operation of the imaging module at the tip, and knobs for controlling the bending operation of the bending section. The operation section is also provided with an introduction port through which a treatment tool such as an electric scalpel is introduced, and inside the insertion section is provided with a treatment tool channel that extends from the introduction port to the tip and through which a treatment tool such as forceps is inserted.

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

The processor unit 4 processes the input video signal to generate video data of the observed area, and displays and records the generated video data on a monitor. The processor unit 4 may be configured with a processor such as a PC (personal computer).

The light source unit 3 generates illumination light such as white light or specific wavelength light composed of three primary colors such as red (R), green (G), and blue (B) light, and supplies it to the endoscope 2, where it propagates through a light guide or the like within the endoscope 2 and is emitted from the illumination optical system at the tip of the insertion section of the endoscope 2 to illuminate the area to be observed within the body cavity, in order to capture an image of the area to be observed within the body cavity using the imaging device of the endoscope 2 and obtain an image signal.

A light guide and a group of electrical wires (signal cables) are housed inside the insertion section, the operating section, and the universal cord. Illumination light generated by the light source unit 3 is guided to the illumination optical system at the tip via the light guide, and signals and/or power are transmitted between the imaging device at the tip and the processor unit 4 via the group of electrical wires.

The endoscope system 1 may further include a water tank for storing cleaning water, etc., and a suction pump for sucking up the aspirated material from within the body cavity (including the supplied cleaning water, etc.). It may also include a supply pump for supplying cleaning water from the water tank or gas such as external air to a duct (not shown) within the endoscope.

Figure 2 shows a perspective view that shows a schematic example of an imaging module of the present invention. Figure 3 shows a side view of Figure 2. Figure 3 also shows a side view of the imaging module of Figure 2 with the anchor 24 and cover member 42 removed.

The imaging module 10 shown in Figures 2 and 3 has a lens 12, a lens barrel 14 that holds the lens 12, an imaging element (hereinafter also referred to as a sensor) 16, a cover glass 17, an optical member 18, an optical member holder 20, a second layer 19, a flexible substrate 22, a third layer 40, an anchor 24, a cover member 42, and a cable 26.

2 and 3 show an example in which the optical member 18 is a prism, and the imaging surface of the imaging element 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 the prism 18. As will be described in detail later, the third layer 40 is arranged on the rear surface 22a side of the flexible substrate 22, and therefore in this configuration, the third layer 40 forms the outermost layer of the imaging module 10.

Lens 12 is an optical system that focuses incident light onto the light receiving surface of sensor 16. Lens 12 is held in 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 so that the optical axis of the lens 12 is perpendicular to the surface of the prism 18 that faces the lens 12.

The configuration of the lens 12 and the lens barrel 14 is not particularly limited. For example, the configuration may include one lens 12, or may include two lenses 12, or may include four or more lenses 12. Furthermore, each lens 12 may be a convex lens or a concave lens.

The sensor 16 is an imaging element that captures an image by converting the light focused by the lens 12 into an electrical signal through photoelectric conversion. The sensor 16 is a conventional imaging element such as a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary MOS) sensor.

The sensor 16 is disposed closer to the base end than the lens barrel 14. As shown in FIG. 3, the sensor 16 is mounted on a flexible substrate 22 so that the light receiving surface is parallel to the optical axis of the lens 12.

The flexible substrate 22 is the first layer in the present invention, and is a substrate on which the sensor 16 is mounted. Electronic components other than the sensor 16 may also be mounted on the flexible substrate 22. The flexible substrate 22 is provided with a number of connection terminals through which signals or power are input and output to and from the sensor 16 and the electronic components. The signal lines of the cable 26 are electrically connected to the connection terminals (see FIG. 3).

In the illustrated example, the flexible substrate 22 has a shape in which a roughly L-shaped plate-like member is curved at two points. Specifically, the flexible substrate 22 has a first curved portion 22b curved around an axis perpendicular to the optical axis direction of the lens (hereinafter also referred to as the axial direction), and a second curved portion 22c curved around an axis in the axial direction, and the sensor 16, electronic components, and connection terminals are mounted on the three plate-like portions connected by these two curved portions. In the illustrated example, the sensor 16 is mounted on the upper surface side of the plate-like portion on the lower side in FIG. 3.

The flexible substrate 22 is a substrate having flexibility. There are no particular limitations on the flexible substrate 22, and any conventionally known flexible substrate can be used. As an example, the flexible substrate is formed by forming a circuit made of copper foil or the like on a base film made of a resin material such as polyimide or polyethylene terephthalate (PET).

The flexible substrate 22 may be bent at one point or at three or more points. There are no particular limitations on the arrangement of the sensor 16, electronic components, connection terminals, etc. on the flexible substrate 22.

The sensor 16 and the cable 26 are connected to the circuit on the flexible substrate 22. Light is converted into an electrical signal by the sensor 16, and this electrical signal is transmitted and transmitted to the cable 26 via the circuit on the flexible substrate 22. The cable 26 is inserted through the insertion portion, operation portion, universal cord, etc. of the endoscope, and is connected to the processor unit 4.
The cable 26 includes one or more signal wires such as a coaxial cable or a single-axial cable, a shield wire covering the outer periphery of the one or more signal wires, and a protective coating (sheath) covering the outer periphery of the signal wires and the shield wire.

The flexible substrate 22 and the sensor 16 are electrically connected by the second layer 19. Figures 4 and 5 show enlarged views of the vicinity of the sensor 16. In the example shown in Figures 4 and 5, the second layer 19 has multiple solder balls 19a, which electrically connect the circuit of the flexible substrate 22 and the sensor 16. In the example shown in Figure 4, as a preferred embodiment, the spaces between the solder balls 19a are filled with underfill 19b.

As the solder ball 19a, any conventional solder ball used to electrically connect a sensor and a substrate in an endoscope imaging module can be used as appropriate. For example, a Sn-Ag-Cu alloy can be used as the material for the solder ball.

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

The second layer 19 is not limited to a configuration having solder balls 19a and underfill 19b. For example, the second layer 19 may have only solder balls 19a. Alternatively, the second layer 19 may be an anisotropic conductive film (ACF).

The cover glass 17 is placed on the light receiving surface of the sensor 16 to protect the light receiving surface. A prism 18 is placed on the cover glass 17. The size of the cover glass 17 in a plan view is approximately the same as the size of the imaging surface of the sensor 16.

The prism 18 is disposed between the lens barrel 14 and the sensor 16 (cover glass 17). The prism 18 bends the light that has passed through the lens 12 held in the lens barrel 14 by 90 degrees to change the optical path and guides it to the light receiving surface of the sensor 16. In the illustrated example, the prism 18 is a right-angle prism whose entrance surface and exit surface are perpendicular to each other. The entrance surface of the prism 18 is disposed facing the base end surface of the lens barrel 14, and the exit surface is disposed facing the light receiving surface of the sensor 16. The prism 18 may be adhesively fixed to the cover glass 17.

The optical member holder 20 is a member that holds the lens barrel 14 and the prism 18. The optical member holder 20 is a roughly cylindrical member, and the lens barrel 14 is fitted inside the cylindrical portion to hold the lens barrel 14. The inner surface of the optical member holder 20 and the outer peripheral surface of the lens barrel 14 are adhesively fixed.

A variety of known adhesives used in conventional endoscopes can be used as the adhesive for bonding the optical member holder 20 and the lens barrel 14. The same applies to adhesives for bonding other members together.

The optical element holder 20 has a polygonal flange portion 20a on the end face on the base end side of the tube portion, against which the entrance surface of the prism 18 abuts. This positions the prism 18. The optical element holder 20 holds the lens barrel 14 and prism 18 in a predetermined position, thereby fixing the relative position between the lens barrel 14 and prism 18, i.e., the relative position between the lens barrel 14 and sensor 16 (light receiving surface).

The lens barrel 14 is adhesively fixed to the optical member holder 20 after its relative position in the optical axis direction (hereinafter also referred to as the axial direction) of the lens 12 is adjusted so that the light receiving surface of the sensor 16 is in focus.

The anchor 24 holds the cable 26 relative to the optical element holder 20. In the illustrated example, the anchor 24 has two plate-like portions 24c extending in the optical axis direction, and an arm portion 24a at the tip of each plate-like portion 24c. The arm portion 24a engages with the flange portion 20a of the optical element holder 20. As shown in FIG. 2, the two plate-like portions 24c are arranged so that their main surfaces are perpendicular to the surface of the flexible substrate 22 (the surface on which the sensor 16 is arranged). The two plate-like portions 24c are arranged so that they face each other across the connection point with the cable 26 on the flexible substrate 22.

The anchor 24 also has a holding portion 24b that connects two plate-like portions 24c to the base end and holds the cable 26. The holding portion 24b is crimped to press against the cable 26 and holds the cable 26. In other words, the holding portion 24b is bent along the outer sheath of the cable 26.

The arm portion 24a of the anchor 24 and the flange portion 20a of the optical element holder 20, as well as the holding portion 24b of the anchor 24 and the outer sheath of the cable 26, may each be adhesively fixed.

In this way, the anchors 24 are connected to the optical member holder 20 and the cable 26, respectively, and prevent the connection between the connection terminals on the flexible substrate 22 and the signal lines from being pulled when the cable 26 is pulled, for example, and thus preventing the connection between the connection terminals and the signal lines from being broken.

The cover member 42 is a plate-like member that is disposed on the opposite side of the anchor 24 from the flexible substrate 22. Together with the anchor 24, the cover member 42 covers and protects the connection points between the connection terminals on the flexible substrate 22 and the signal lines.

There are no particular limitations on the materials from which the anchor 24 and the cover member 42 are made, and various resin materials and metal materials used as components constituting the imaging module of an endoscope can be used. Metal materials are preferred from the viewpoint of heat dissipation. Considering processability, availability, strength, etc., stainless steel and copper alloys are preferred for the anchor 24 and the cover member 42.

The cover member 42 may be formed integrally with the anchor 24. Alternatively, the cover member 42 may not be included.

In such an imaging module 10, the observation image captured by the sensor 16 through the lens 12 is focused on the light receiving surface of the sensor 16 and converted into an electrical signal, which is 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.

The imaging element is a heat source, and when the temperature of the imaging element rises, the materials around the imaging element thermally expand. If there is a large difference in the thermal expansion coefficient between the imaging element and the second and first layers (flexible substrate), the imaging element will warp. In particular, since the material used for the flexible substrate has a large thermal expansion coefficient, it was found that when a flexible substrate is used as the substrate, there is a problem that the imaging element will warp and be damaged.

In contrast, the imaging module of the present invention has a third layer 40 arranged on the surface of the flexible substrate 22 (first layer) opposite the second layer 19, and the thermal expansion coefficient of the third layer 40 is closer to the thermal expansion coefficient of the imaging element 16 than the average thermal expansion coefficient of the first layer 22 and the second layer 19, and the elasticity of the third layer 40 is higher than the elasticity of the first layer 22 and the second layer 19. With this configuration, the third layer 40 suppresses the thermal expansion of the first layer 22 and the second layer 19, and prevents the imaging element 16 from warping and being damaged.

In general, CMOS sensors and CCD sensors used as the image sensor 16 have a structure in which an electrode layer, an insulating film, etc. are formed on a silicon wafer. Therefore, the thermal expansion coefficient of the image sensor 16 is about 2.5 ppm/°C to 4 ppm/°C.

On the other hand, the flexible substrate 22 is mainly made of resin materials such as polyimide and polyethylene terephthalate. Therefore, the thermal expansion coefficient of the flexible substrate 22 (first layer) is about 20 ppm/°C to 100 ppm/°C. In addition, the elastic modulus of the flexible substrate 22 is about 5 GPa to 30 GPa.

For example, when the second layer 19 is made of solder balls 19a and underfill 19b, the thermal expansion coefficient of the second layer 19 is about 20 ppm/°C to 80 ppm/°C. The elastic modulus of the second layer 19 is about 5 GPa to 50 GPa.

Therefore, the average thermal expansion coefficient of the first layer 22 and the second layer 19 is approximately 20 ppm/°C to 90 ppm/°C, calculated as a volume-weighted average.

Materials for the third layer 40 that satisfy the above-mentioned conditions for the image sensor 16, first layer (flexible substrate) 22, and second layer 19 include Invar, Kovar, glass, silicon, stainless steel, and ceramics such as aluminum nitride and silicon nitride. Examples of the thermal expansion coefficients and elastic moduli of these materials are shown in Table 1.

From the viewpoint of suppressing warping of the sensor 16, the thermal expansion coefficient of the third layer 40 is preferably 10 ppm/°C or less, more preferably 5 ppm/°C or less, and even more preferably 2 ppm/°C to 4 ppm/°C.

In addition, from the viewpoint of suppressing warping of the sensor 16, the elastic modulus of the third layer 40 is preferably 70 GPa or more, more preferably 150 GPa or more, and even more preferably 300 GPa or more.

In addition, from the viewpoint of suppressing warping of the sensor 16, the material of the third layer 40 is preferably ceramics such as aluminum nitride and silicon nitride, Invar material, or Kovar material, and more preferably ceramics such as aluminum nitride and silicon nitride.

In addition, from the viewpoint of suppressing warping of the sensor 16, it is preferable that the sum of the elastic modulus x thickness of the sensor 16 and the elastic modulus x thickness of the third layer 40 is greater than the sum of the elastic modulus x thickness of the first layer 22 and the elastic modulus x thickness of the second layer 19. This restricts the first and second layers from expanding due to heat, thereby preventing the sensor 16 from warping.

The thermal expansion coefficient and elastic modulus of each member were measured as follows.
The thermal expansion coefficient is determined by measuring the length between measurement points on a test piece at multiple temperatures and calculating the rate of change in length per unit temperature change.
The elastic modulus is determined by applying a load to a test piece in a tensile test, measuring the change in length between the measurement points on the test piece, and calculating the stress and strain. Alternatively, the Young's modulus of each material can be determined by the nanoindentation method, and the composite elastic modulus can be determined from the volume ratio.

Here, as a preferred embodiment, the imaging module 10 has an adhesive layer 44 arranged to cover at least a portion of the side of the sensor 16 (see Figures 4 and 5). In the example shown in Figures 4 and 5, the adhesive layer 44 is arranged on the flexible substrate 22, and covers the second layer 19, the sensor 16, and two of the side surfaces of the cover glass 17.

By having an adhesive layer 44 that covers at least a portion of the side surface of the sensor 16, damage caused by warping of the imaging element can be suppressed. In addition, the adhesive layer 44 may have functions such as light blocking, gas barrier (sterilizing gas, etc.), and moisture resistance.

The adhesive layer 44 preferably covers the entire circumference of the sensor 16. In this case, when the adhesive layer 44 is filled between the flexible substrate 22 and the prism 18 and/or the optical component holder 20, a problem may occur in which the adhesive layer peels off between the prism and the cover glass due to the effect of thermal expansion when the temperature rises during operation, but this can be suppressed by adjusting the protrusion amount _H2 of the third layer 40 from the sensor 16 as described below.

The material for the adhesive layer 44 can be an adhesive or a sealant.

As the adhesive, various adhesives used in endoscopes can be used. For example, an epoxy resin-based adhesive can be used. In addition, black epoxy is preferable because of its light-blocking properties.

As the sealing agent, various sealing agents used in endoscopes can be used.
The adhesive and sealant should have a high thermal conductivity, but it is preferable that they have insulating properties.

Furthermore, it is preferable that the size of the third layer 40 in a planar view is equal to or larger than the size of the sensor 16, and it is also preferable that the third layer 40 is positioned so as to encompass the sensor 16 in a planar view.

For example, in the example shown in FIG. 6, the third layer 40 is arranged so that the size (length) of the lens 12 in the optical axis direction is greater than that of the sensor 16, and so as to encompass the sensor 16 in the optical axis direction. In other words, the side of the third layer 40 protrudes beyond the side of the sensor 16. In the example shown in FIG. 6, the side of the third layer 40 facing the lens 12 is arranged flush with the side of the flexible substrate 22 facing the lens 12.

7, the amount of protrusion _H2 of the third layer 40 from the sensor 16 is preferably equal to or less than half the total value _H1 of the thickness of the cover glass 17, the thickness of the sensor 16, and the thickness of the second layer 19. By setting the amount of protrusion _H2 of the third layer 40 within this range, peeling between the prism and the cover glass due to the influence of the difference in thermal expansion between the adhesive layer 44 and the cover glass 17, the sensor 16, and the second layer 19 can be suppressed.

As shown in FIG. 7, the side surface of the third layer 40 facing the lens 12 protrudes from the side surface of the sensor 16, and the amount of protrusion _H2 is preferably equal to or less than half the total thickness _H1 .

7, the protrusion amount _H2 of the third layer 40 is equal to or less than half the total thickness value _H1 , and the protrusion amount of the flexible substrate 22 protrudes outward beyond the sensor 16 and the third layer 40, but this is not limiting. As in the example shown in FIG. 8, the protrusion amount _H2 of the third layer 40 and the flexible substrate 22 may be equal to or less than half the total thickness value _H1 .

In the examples shown in Figures 3 and 6 to 8, the imaging surface of the sensor 16 is arranged parallel to the optical axis of the lens 12, and the optical member 18 arranged between the lens 12 and the sensor 16 is a prism that bends light by 90 degrees, but this is not limited to the configuration.

FIG. 9 is a side view showing another example of the imaging module of the present invention.
The imaging module shown in Figure 9 has a lens barrel 14 that holds a lens 12, an optical member holder 20, an optical member 18, a cover glass 17, a sensor 16, a second layer 19, a flexible substrate 22, a third layer 40, and an adhesive layer 44.

In the imaging module shown in FIG. 9, the flexible substrate 22 is curved at approximately 90°, and has a portion parallel to the optical axis of the lens 12 and a portion perpendicular to the optical axis. A second layer 19, a sensor 16, and a cover glass 17 are laminated on the surface of the portion perpendicular to the optical axis of the flexible substrate 22 (the surface facing the lens 12). Meanwhile, a third layer 40 is disposed on the back surface of the portion perpendicular to the optical axis of the flexible substrate 22. Therefore, the imaging surface of the sensor 16 is disposed perpendicular to the optical axis of the lens 12.

The optical element 18 guides the light that has passed through the lens 12 to the imaging surface of the sensor 16. The optical element 18 has a light entrance surface and an exit surface that are arranged perpendicular to the optical axis. The optical element 18 may simply transmit light, or may have the effect of concentrating light. By having the optical element 18 have the effect of concentrating light, the distance between the lens 12 and the sensor 16 can be made closer, allowing for a smaller size.

The optical element 18 is held by the optical element holder 20 and is positioned with respect to the lens barrel 14 held by the optical element holder 20.

In this way, even when the imaging module of the present invention is configured so that the imaging surface of the sensor 16 is arranged perpendicular to the optical axis of the lens 12, the third layer 40 suppresses the thermal expansion of the first layer 22 and the second layer 19, thereby preventing the imaging element 16 from warping and being damaged.

Here, even in the case of a configuration in which the imaging surface of the sensor 16 is arranged perpendicular to the optical axis of the lens 12 as shown in FIG. 9, it is preferable to have an adhesive layer 44 arranged so as to cover at least a portion of the side surface of the sensor 16, but it is more preferable to cover the entire circumference.

In the example shown in FIG. 9, the adhesive layer 44 is filled between the flexible substrate 22 and the optical member 18, but this is not limited thereto, and as in the example shown in FIG. 10, the adhesive layer 44 may be filled between the flexible substrate 22 and the optical member holder 20.

For example, in the example shown in Figures 9 and 10, the third layer 40 has a size (length) in the vertical direction in the figure that is greater than that of the sensor 16, and is positioned so as to encompass the sensor 16. In other words, the two sides of the third layer 40 (the upper side and the lower side in the figure) each protrude from the sensor 16.

9 and 10 , even in the case where the imaging surface of the sensor 16 is disposed perpendicular to the optical axis of the lens 12, it is preferable that the protrusion amount _H2 of the third layer 40 from the sensor 16 is equal to or less than half the total value _H1 of the thickness of the cover glass 17, the thickness of the sensor 16, and the thickness of the second layer 19. Setting the protrusion amount _H2 of the third layer 40 within this range can suppress peeling between the optical component and the cover glass.

In addition, in the imaging module of the present invention, a circuit may be formed on the third layer 40. The circuit formed on the third layer 40 may be connected to the circuit on the first layer (flexible substrate) 22 to form a multi-layer circuit board. When a circuit is formed on the third layer 40, the third layer may be made of an insulating material such as ceramic.

The imaging module according to the present invention has been described in detail above using various embodiments, but the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the spirit of the present invention.

REFERENCE SIGNS LIST 1 Endoscope system 2 Endoscope 3 Light source unit 4 Processor unit 10 Imaging module 12 Lens 14 Lens barrel 16 Imaging element (sensor)
17 Cover glass 18 Optical member (prism)
19 Second layer 19a Solder ball 19b Underfill 20 Optical member holder 20a Flange portion 22 Flexible substrate (first layer)
22a Back surface 22b First curved portion 22c Second curved portion 24 Anchor 24a Arm portion 24b Holding portion 24c Plate-shaped portion 26 Cable 40 Third layer 42 Cover member 44 Adhesive layer

Claims (10)

In an imaging module including an imaging element,
a first layer configured with a flexible substrate and disposed on a back surface side opposite to an imaging surface of the imaging element;
a second layer disposed between the image sensor and the first layer and electrically connecting the image sensor and the first layer;
a third layer disposed on the side of the first layer opposite to the second layer side,
a thermal expansion coefficient of the third layer is closer to a thermal expansion coefficient of the image sensor than an average thermal expansion coefficient of the first layer and the second layer;
The imaging module, wherein the third layer has a higher elastic modulus than the first layer and the second layer. 2. The imaging module of claim 1, wherein a sum of the elastic modulus x thickness of the imaging element and the elastic modulus x thickness of the third layer is greater than a sum of the elastic modulus x thickness of the first layer and the elastic modulus x thickness of the second layer . The imaging module according to claim 1 or 2, wherein a cover glass having a size in a plan view equal to the size of the imaging element is attached to the imaging surface of the imaging element. a lens that forms an image of incident light on an imaging surface of the imaging element;
at least one optical component disposed between the cover glass and the lens;
The light receiving surface side of the cover glass is adhesively fixed to the optical component,
4. The imaging module of claim 3, wherein in at least one direction perpendicular to the side surface of the imaging element, the amount of protrusion of the third layer from the side surface of the imaging element is less than half the sum of the thickness of the cover glass, the thickness of the imaging element, and the thickness of the second layer. a lens that forms an image of incident light on an imaging surface of the imaging element;
a prism disposed between the lens and the image sensor;
The imaging element is disposed such that an imaging surface is parallel to an optical axis of the lens,
The imaging module according to any one of claims 1 to 4, wherein the third layer forms an outermost layer of the imaging module. a prism disposed between the lens and the image sensor;
The imaging element is disposed such that an imaging surface is parallel to an optical axis of the lens,
the third layer forms an outermost layer of the imaging module;
The imaging module according to claim 4 , wherein a side surface of the third layer protruding from the imaging element is a side surface on the lens side. The imaging module according to any one of claims 1 to 6, wherein the third layer is made of ceramic. The imaging module according to any one of claims 1 to 7, wherein a circuit is formed on the third layer and is electrically connected to the first layer. The imaging module according to any one of claims 1 to 8, wherein the second layer has solder balls. The imaging module according to claim 9, wherein the second layer is at least partially filled with underfill.