camera module

Abstract

Provided is an imaging module capable of suppressing warping of an imaging element and preventing breakage of the imaging element. The imaging module having an imaging element includes a first layer disposed on a back surface side opposite to an imaging surface of the imaging element and composed of a flexible substrate; a second layer disposed between the imaging element and the first layer and electrically connecting the imaging element and the first layer; and a third layer disposed on a side opposite to the second layer side of the first layer, a thermal expansion rate of the third layer being closer to a thermal expansion rate of the imaging element than an average thermal expansion rate of the first layer and the second layer, and an elastic modulus of the third layer being higher than elastic moduli of the first layer and the second layer.

Description

Technical Field

[0001] This invention relates to a camera module. Background Technology

[0002] An imaging module containing an imaging element and a lens barrel is disposed at the front end of the endoscope. The imaging element is disposed on the substrate via an electrode layer electrically connected by solder balls or the like.

[0003] For reasons such as being cheaper than rigid substrates, being able to be installed together with other electronic components at once, having good assemblability, and being able to be three-dimensionally configured in narrow housings due to their flexibility, flexible substrates made of resins such as polyimide and polyethylene terephthalate were considered as substrates.

[0004] For example, Patent Document 1 describes an endoscope comprising: a solid-state imaging element that performs photoelectric conversion on photographic light incident on an image receiving surface via a photographic lens; and a circuit board having a connection surface facing the terminal face of the solid-state imaging element on the side opposite to the image receiving surface, wherein multiple terminals are equally arranged in a two-dimensional matrix in both the longitudinal and transverse directions on the terminal face of the solid-state imaging element, and the connection surface of the circuit board is connected to the terminal face of the solid-state imaging element via multiple terminals, wherein the total area of ​​the multiple terminals on the terminal face accounts for more than 10% of the area of ​​the imaging region on the image receiving surface of the solid-state imaging element.

[0005] Patent document 1 describes that when an image sensor is mounted on a flexible substrate, the substrate of the image sensor will warp due to the deformation of the flexible substrate (especially during cooling), and the connection between the image sensor and the circuit board will sometimes be locally deformed (

[0026] paragraph).

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-007714

[0007] Therefore, when a flexible substrate is used as the substrate for an imaging element, the following problem exists: when the components expand or contract due to temperature changes, the difference in the coefficients of thermal expansion between the imaging element, the electrode layer, and the flexible substrate is large, which can cause the imaging element to warp. In particular, it has been found that because the material used as the flexible substrate has a large coefficient of thermal expansion, the imaging element may warp and break when the flexible substrate is used as the substrate. Summary of the Invention

[0008] The objective of this invention is to solve the problems of the prior art and provide a camera module that can prevent damage to the imaging element by suppressing warping of the imaging element.

[0009] To address the aforementioned issues, the present invention has the following structure.

[0010] [1] A camera module having an imaging element and having:

[0011] The first layer is disposed on the back side of the imaging element, opposite to the imaging surface, and is composed of a flexible substrate.

[0012] The second layer is disposed between the imaging element and the first layer and is electrically connected to the imaging element and the first layer; and

[0013] The third layer is located on the side of the first layer opposite to the second layer.

[0014] The thermal expansion coefficient of the third layer is closer to that of the imaging element than the average thermal expansion coefficients of the first and second layers.

[0015] The elastic modulus of the third layer is higher than that of the first and second layers.

[0016] [2] According to the camera module described in [1], wherein,

[0017] The sum of the elastic modulus × thickness of the imaging element and the elastic modulus × thickness of the third layer is greater than the sum of the elastic modulus × thickness of the first layer and the elastic modulus × thickness of the second layer.

[0018] [3] According to the camera module described in [1] or [2], wherein,

[0019] A cover glass, the same size as the imaging element when viewed from above, is attached to the imaging surface of the imaging element.

[0020] [4] The camera module according to [3] has a lens and at least one optical component.

[0021] This lens causes the incident light to be imaged onto the imaging surface of the imaging element.

[0022] The at least one optical component is disposed between the cover glass and the lens.

[0023] The light-receiving side of the cover glass is bonded and fixed to the optical components.

[0024] In at least one direction perpendicular to the side of the imaging element, the protrusion of the third layer from the side 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.

[0025] [5] The camera module according to any one of [1] to [4] has a lens and a prism.

[0026] This lens causes the incident light to be imaged onto the imaging surface of the imaging element.

[0027] The prism is positioned between the lens and the imaging element.

[0028] The imaging element is configured such that the imaging plane is parallel to the optical axis of the lens.

[0029] The third layer forms the outermost layer of the camera module.

[0030] [6] The camera module described in [4] has a prism,

[0031] The prism is positioned between the lens and the imaging element.

[0032] The imaging element is configured such that the imaging plane is parallel to the optical axis of the lens.

[0033] The third layer forms the outermost layer of the camera module.

[0034] The third layer is the side of the lens that protrudes from the imaging element.

[0035] [7] The camera module according to any one of [1] to [6], wherein,

[0036] The third layer is formed to contain ceramic.

[0037] [8] The camera module according to any one of [1] to [7], wherein,

[0038] A circuit is formed on the third layer and is electrically connected to the first layer.

[0039] [9] The camera module according to any one of [1] to [8], wherein,

[0040] The second layer has solder balls.

[0041]

[10] According to the camera module described in [9], wherein,

[0042] At least a portion of the second layer is filled with bottom filler.

[0043] Invention Effects

[0044] According to the present invention, a camera module is provided that can suppress warping of the imaging element of the camera module and prevent damage to the imaging element. Attached Figure Description

[0045] Figure 1 This is a schematic structural diagram illustrating an example of the structure of an endoscope system using an endoscope having an imaging module according to the present invention.

[0046] Figure 2 This is a perspective view schematically illustrating an example of the camera module of the present invention.

[0047] Figure 3 Is Figure 2 The side view shown shows the state of the camera module with the anchors and cover components removed.

[0048] Figure 4 It is an enlarged representation Figure 2 A stereoscopic view of a portion of the camera module.

[0049] Figure 5 yes Figure 4 Side view.

[0050] Figure 6 This is a side view schematically illustrating another example of the camera module of the present invention.

[0051] Figure 7 This is a side view schematically illustrating another example of the camera module of the present invention.

[0052] Figure 8 This is a side view schematically illustrating another example of the camera module of the present invention.

[0053] Figure 9 This is a side view schematically illustrating another example of the camera module of the present invention.

[0054] Figure 10 This is a side view schematically illustrating another example of the camera module of the present invention.

[0055] Symbol Explanation

[0056] 1-Endoscope system, 2-Endoscope, 3-Light source unit, 4-Processor unit, 10-Camera module, 12-Lens, 14-Endoscope barrel, 16-Imaging element (sensor), 17-Cover glass, 18-Optical component (prism), 19-Second layer, 19a-Solder ball, 19b-Bottom filler, 20-Optical component holding tool, 20a-Flange, 22-Flexible substrate (first layer), 22a-Back side, 22b-First bend, 22c-Second bend, 24-Anchor, 24a-Arm, 24b-Holding part, 24c-Plate part, 26-Cable, 40-Third layer, 42-Cover component, 44-Adhesive layer. Detailed Implementation

[0057] Hereinafter, embodiments of the camera module of the present invention will be described with reference to the accompanying drawings.

[0058] The following description of the constituent elements is sometimes done according to representative embodiments of the present invention, but the present invention is not limited to such embodiments. In the accompanying drawings of this specification, the proportions of the various parts have been appropriately altered for easy visual identification.

[0059] In addition, the numerical range indicated by “~” in this specification refers to the range of values ​​recorded before and after “~” as the lower limit and upper limit.

[0060] [Camera Module]

[0061] The camera module of the present invention includes an imaging element and has the following features:

[0062] The first layer is disposed on the back side of the imaging element, opposite to the imaging surface, and is composed of a flexible substrate.

[0063] The second layer is disposed between the imaging element and the first layer and is electrically connected to the imaging element and the first layer; and

[0064] The third layer is located on the side of the first layer opposite to the second layer.

[0065] The thermal expansion coefficient of the third layer is closer to that of the imaging element than the average thermal expansion coefficients of the first and second layers.

[0066] The elastic modulus of the third layer is higher than that of the first and second layers.

[0067] Figure 1 The present invention conceptually illustrates an example of an endoscope system having an endoscope with an imaging module of the present invention.

[0068] The endoscope system 1 includes an endoscope 2, a light source unit 3, and a processor unit 4. Except for the camera module 10 described later, the endoscope 2 has the same structure as a general endoscope.

[0069] The endoscope 2 has an insertion part that is inserted into the body of the patient, an operating part connected to the insertion part, and a universal cable extending from the operating part. The insertion part consists of a front end, a curved part connected to the front end, and a soft part that connects the curved part and the operating part.

[0070] The front end is equipped with an illumination optical system that emits illumination light to illuminate the observation area, and a camera module (camera head) that includes an imaging element and a camera optical system for capturing images of the observation area. The bending section is configured to bend in a direction orthogonal to the longitudinal axis of the insertion section, and the bending action of the bending section is operated by an operating section. Furthermore, the soft section is configured to be relatively flexible enough to deform according to the shape of the insertion path of the insertion section.

[0071] The operating section is equipped with buttons for controlling the camera module at the front end and knobs for controlling the bending action of the bending section. Furthermore, the operating section has an inlet for inserting medical tools such as electrosurgical scalpels, and the insertion section has a medical tool channel leading from the inlet to the front end for inserting medical tools such as forceps.

[0072] The end of the universal cable is provided with a connector, and the endoscope 2 is connected via the connector to the light source unit 3 that generates illumination light emitted from the illumination optical system at the front end and the processor unit 4 that processes the image signals acquired by the camera device at the front end.

[0073] Processor unit 4 processes the input image signal to generate image data of the observed area, displays the generated image data on a monitor, and records it. Furthermore, processor unit 4 can be configured with a processor such as a PC (personal computer).

[0074] The light source unit 3 is used to generate illumination light, such as white light or light of a specific wavelength, composed of three primary colors of light, namely red light (R), green light (G) and blue light (B), and supply it to the endoscope 2. The light propagates through the light guide or the like inside the endoscope 2 and is emitted from the illumination optical system at the front end of the insertion part of the endoscope 2, thereby illuminating the observation part inside the body cavity, so as to obtain image signals by taking pictures of the observation part inside the body cavity through the camera device of the endoscope 2.

[0075] The insertion section, operation section, and general cable internally house a light guide and a wire assembly (signal cable). The illumination light generated in the light source unit 3 is guided to the illumination optics system at the front end via the light guide, and the signal and / or power are transmitted between the camera device and the processor unit 4 at the front end via the wire assembly.

[0076] Furthermore, the endoscope system 1 may also include a water supply tank for storing washing water, a suction pump for aspirating material (including the supplied washing water) from the body cavity. Additionally, it may include a supply pump for supplying washing water from the water supply tank or external air to the tubing (not shown) inside the endoscope.

[0077] Figure 2 The diagram shows a perspective view schematically illustrating an example of the camera module of the present invention. Figure 3 The middle shows Figure 2 A side view. And, Figure 3 From Figure 2 A side view of the camera module with the anchor 24 and cover component 42 removed.

[0078] Figure 2 and Figure 3 The camera module 10 shown includes a lens 12, a lens barrel 14 for holding the lens 12, an imaging element (hereinafter also referred to as a sensor) 16, a cover glass 17, an optical component 18, an optical component holding tool 20, a second layer 19, a flexible substrate 22, a third layer 40, an anchor 24, a cover component 42, and a cable 26.

[0079] Figure 2 and Figure 3The example shown is one where the optical component 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 component 18 will also be referred to as the prism 18. Furthermore, the third layer 40 is disposed on the back side 22a of the flexible substrate 22, and thus in this structure, the third layer 40 forms the outermost layer of the camera module 10, the details of which will be described later.

[0080] Lens 12 is an optical system that images the incident light onto the light-receiving surface of sensor 16. Lens 12 is held by lens barrel 14.

[0081] The lens barrel 14 is a cylindrical component that holds one or more lenses 12. The lens barrel 14 holds the lens 12 such that the optical axis of the lens 12 is perpendicular to the plane of the prism 18 opposite to the lens 12.

[0082] There are no particular limitations on the structure of the lens 12 and the lens barrel 14. For example, it can be a structure with one lens 12, or it can be a structure with two or more lenses 12. Furthermore, each lens 12 can be a convex lens or a concave lens.

[0083] Sensor 16 is an imaging element that performs imaging by converting light imaged by lens 12 into an electrical signal through photoelectric conversion. Sensor 16 is a conventionally known imaging element such as a CCD (Charge-Coupled Device) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor.

[0084] Sensor 16 is positioned further from the base end than lens barrel 14. Furthermore, as... Figure 3 As shown, the sensor 16 is mounted on the flexible substrate 22 with the light-receiving surface parallel to the optical axis of the lens 12.

[0085] The flexible substrate 22 is the first layer in this invention and serves as the substrate for mounting the sensor 16. Furthermore, electronic components other than the sensor 16 can also be mounted on the flexible substrate 22. The flexible substrate 22 is provided with multiple connection terminals for input / output of signals or power to the sensor 16 and the electronic components. Signal lines of cables 26 are electrically connected to these connection terminals (see reference). Figure 3 ).

[0086] In the example shown, the flexible substrate 22 has a shape that bends the generally L-shaped plate-like member at two points. Specifically, the flexible substrate 22 has a first bent portion 22b that bends about an axis orthogonal to the optical axis direction of the lens (hereinafter also referred to as the axial direction) and a second bent portion 22c that bends about the axial direction. A sensor 16, electronic components, and connection terminals are mounted on the three plate-like portions connected by these two bent portions. In the example shown, the sensor 16 is mounted on... Figure 3The upper surface of the plate-like part on the lower middle side.

[0087] The flexible substrate 22 is a flexible substrate. There are no particular limitations on the flexible substrate 22, and conventionally known flexible substrates 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).

[0088] The flexible substrate 22 can also be folded in one or more places. Furthermore, there are no particular restrictions on the arrangement of the sensor 16, electronic components, and connection terminals on the flexible substrate 22.

[0089] Sensor 16 and cable 26 are connected to the circuitry on the flexible substrate 22. Light is converted into an electrical signal by sensor 16, and this electrical signal is transmitted to cable 26 via the circuitry of the flexible substrate 22. Cable 26 is inserted into the insertion part, operating part, general cable, etc. of the endoscope and connected to the processor unit 4.

[0090] Cable 26 has one or more signal lines such as coaxial cable or monoaxial cable, a shield covering the outer periphery of the one or more signal lines, and a protective coating (outer sheath) covering the outer periphery of the signal lines and the shield.

[0091] The flexible substrate 22 and the sensor 16 are electrically connected through the second layer 19. Figure 4 and Figure 5 The image shown is a magnified view of the vicinity of sensor 16. Figure 4 and Figure 5 In the example shown, the second layer 19 has multiple solder balls 19a, and the circuitry of the flexible substrate 22 and the sensor 16 are electrically connected via the solder balls 19a. Furthermore, in Figure 4 In the example shown, as a preferred embodiment, the space between the solder balls 19a is filled with bottom filler 19b.

[0092] As the solder ball 19a, conventionally known solder balls used for electrically connecting sensors and substrates in the imaging module of an endoscope can be appropriately used. For example, Sn-Ag-Cu alloys can be used as the material for the solder ball.

[0093] As the bottom filler 19b, conventionally known bottom fillers used as bottom fillers in the imaging module of an endoscope can be appropriately utilized. For example, resin materials such as epoxy resin can be used as bottom fillers.

[0094] Furthermore, the second layer 19 is not limited to a structure having solder balls 19a and bottom filler 19b. For example, the second layer 19 can also be a structure having only solder balls 19a. Alternatively, it can be an anisotropic conductive film (ACF).

[0095] A cover glass 17 is disposed on the light-receiving surface of the sensor 16 to protect the light-receiving surface. A prism 18 is disposed on the cover glass 17. The size of the cover glass 17 when viewed from above is approximately the same as the size of the imaging surface of the sensor 16.

[0096] Prism 18 is disposed between lens barrel 14 and sensor 16 (cover glass 17). Prism 18 bends light passing through lens 12 held by lens barrel 14 by 90° to change the light path and guides it to the light-receiving surface of sensor 16. In the example shown, prism 18 is a right-angle prism with its incident and exit surfaces orthogonal. Prism 18 is configured such that its incident surface faces the base end of lens barrel 14, and its exit surface faces the light-receiving surface of sensor 16. Prism 18 can be bonded and fixed to cover glass 17.

[0097] The optical component holding tool 20 is a component that holds the lens barrel 14 and the prism 18. The optical component holding tool 20 is a generally cylindrical component, in which the lens barrel 14 is embedded inside the cylindrical part to hold the lens barrel 14. The inner surface of the optical component holding tool 20 is bonded and fixed to the outer peripheral surface of the lens barrel 14.

[0098] As the adhesive for bonding the optical component holding tool 20 and the endoscope barrel 14, various known adhesives used in conventional endoscopes can be used. The same applies to the adhesives used for bonding other components to each other.

[0099] The optical component holding tool 20 has a polygonal flange 20a on the base end face of the barrel, which abuts against the incident surface of the prism 18. This positions the prism 18. The optical component holding tool 20 fixes the relative position of the barrel 14 and the prism 18, i.e., the relative position of the barrel 14 and the sensor 16 (light-receiving surface), by holding the barrel 14 and the prism 18 in a predetermined position.

[0100] Here, the relative position of the lens barrel 14 on the optical axis direction (hereinafter also referred to as the axial direction) and the optical component holding tool 20 is adjusted so that the focal point is aligned with the light-receiving surface of the sensor 16, thereby the lens barrel 14 is bonded and fixed to the optical component holding tool 20.

[0101] Anchor 24 holds cable 26 relative to optical component holding tool 20. In the example shown, anchor 24 has two plate-like portions 24c extending along the optical axis, and each plate-like portion 24c has an arm portion 24a at its front end. The arm portion 24a engages with the flange portion 20a of optical component holding tool 20. Furthermore, as... Figure 2 As shown, the two plate-shaped portions 24c are configured such that their main surfaces are perpendicular to the surface of the flexible substrate 22 (the surface where the sensor 16 is disposed). Furthermore, the two plate-shaped portions 24c are configured to sandwich the connection portion of the flexible substrate 22 to the cable 26.

[0102] Furthermore, the anchor 24 has a retaining portion 24b that connects two plate-shaped portions 24c at the base end and retains the cable 26. The retaining portion 24b is riveted to retain the cable 26 by pressing it down. That is, the retaining portion 24b is bent along the outer sheath of the cable 26.

[0103] The arm 24a of the anchor 24, the flange 20a of the optical component holding tool 20, the holding part 24b of the anchor 24, and the outer sheath of the cable 26 can be bonded and fixed with adhesive.

[0104] Thus, by connecting the anchor 24 to the optical component holding tool 20 and the cable 26 respectively, when the cable 26 is stretched, the connection between the connection terminal and the signal line is prevented from being broken due to the stretching of the connection part between the connection terminal and the signal line on the flexible substrate 22.

[0105] The cover component 42 is a plate-shaped component disposed on the side of the anchor 24 opposite to the flexible substrate 22. The cover component 42 and the anchor 24 together cover the connection parts of the connection terminals and signal lines on the flexible substrate 22 for protection.

[0106] There are no particular limitations on the materials used to form the anchor 24 and the cover component 42; various resin materials and metal materials used as components constituting the camera module of the endoscope can be used. From the viewpoint of heat dissipation, metal materials are preferred. Considering workability, availability, strength, etc., stainless steel and copper alloys are preferred for the anchor 24 and the cover component 42.

[0107] Alternatively, the cover component 42 may be integral with the anchor 24. Or, the cover component 42 may not be present.

[0108] In this camera module 10, the image of observation captured by the lens 12 on the sensor 16 is imaged onto the light-receiving surface of the sensor 16 and converted into an electrical signal. This electrical signal is output to the processor unit 4 via the cable 26 and converted into an image signal, thereby displaying the observed image on a monitor connected to the processor unit 4.

[0109] Here, the imaging element is a heat source. If the temperature of the imaging element rises, the components around the imaging element will thermally expand. However, if the difference in thermal expansion rates between the imaging element and the second and first layers (flexible substrate) is large, the imaging element will warp. In particular, it has been found that because the material used as the flexible substrate has a large thermal expansion rate, the imaging element warps and breaks when the flexible substrate is used as the substrate.

[0110] In contrast, the imaging module of the present invention has the following structure: a third layer 40 disposed on a side of the flexible substrate 22 (first layer) opposite to the side of the second layer 19, wherein the thermal expansion rate of the third layer 40 is closer to the thermal expansion rate of the imaging element 16 than the average thermal expansion rate of the first layer 22 and the second layer 19, and the elastic modulus of the third layer 40 is higher than that of the first layer 22 and the second layer 19. With this structure, the third layer 40 can suppress the thermal expansion of the first layer 22 and the second layer 19, thereby preventing the imaging element 16 from warping and breaking.

[0111] Typically, CMOS and CCD sensors used as imaging elements 16 have structures with electrode layers, insulating films, etc., formed on a silicon wafer. Therefore, the thermal expansion coefficient of imaging element 16 is approximately 2.5 ppm / ℃ to 4 ppm / ℃.

[0112] On the other hand, the flexible substrate 22 is mainly formed of resin materials such as polyimide and polyethylene terephthalate. Therefore, the coefficient of thermal expansion of the flexible substrate 22 (first layer) is about 20ppm / ℃ to 100ppm / ℃. Furthermore, the elastic modulus of the flexible substrate 22 is about 5GPa to 30GPa.

[0113] Furthermore, for example, when the second layer 19 is formed by solder balls 19a and bottom filler 19b, the thermal expansion coefficient of the second layer 19 is approximately 20 ppm / ℃ to 80 ppm / ℃. Also, the elastic modulus of the second layer 19 is approximately 5 GPa to 50 GPa.

[0114] Therefore, the average thermal expansion coefficients of the first layer 22 and the second layer 19, calculated by volume weighting, are approximately 20 ppm / ℃ to 90 ppm / ℃.

[0115] In contrast to the imaging element 16, the first layer (flexible substrate) 22, and the second layer 19, the materials for the third layer 40 that satisfy the above conditions include non-expanding steel, Kovar alloy, 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.

[0116] [Table 1]

[0117]

[0118] From the viewpoint of suppressing the warping of sensor 16, the thermal expansion rate of the third layer 40 is preferably 10 ppm / ℃ or less, more preferably 5 ppm / ℃ or less, and even more preferably 2 ppm / ℃ to 4 ppm / ℃.

[0119] Furthermore, from the viewpoint of suppressing the warping of 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.

[0120] Furthermore, from the viewpoint of suppressing the warping of sensor 16, the preferred materials for the third layer 40 are ceramics such as aluminum nitride and silicon nitride, non-expanding steel materials, and Kovar alloy materials, with ceramics such as aluminum nitride and silicon nitride being more preferred.

[0121] Furthermore, from the viewpoint of suppressing warping of sensor 16, it is preferable that the sum of the elastic modulus × thickness of sensor 16 and the elastic modulus × thickness of the third layer 40 is greater than the sum of the elastic modulus × thickness of the first layer 22 and the elastic modulus × thickness of the second layer 19. This limits the elongation of the first and second layers due to heat, thereby preventing sensor 16 from warping.

[0122] The methods for determining the thermal expansion coefficient and elastic modulus of each component are as follows.

[0123] Regarding the coefficient of thermal expansion, the length between the measurement points of each test piece at multiple temperatures is used as the rate of change of length per unit temperature change.

[0124] Regarding the elastic modulus, a tensile test is conducted on a test specimen. A load is applied, and the change in length between the test points is measured. Stress and strain are then calculated to determine the elastic modulus. Alternatively, the Young's modulus of each material can be determined using nanoindentation, and the composite elastic modulus can be calculated based on the volume ratio.

[0125] Here, as a preferred embodiment, the camera module 10 has an adhesive layer 44 configured to at least cover a portion of the side surface of the sensor 16 (see reference). Figure 4 and Figure 5 ).exist Figure 4 and Figure 5 In the example shown, adhesive layer 44 is disposed on flexible substrate 22 and covers two of the sides of second layer 19, sensor 16 and cover glass 17.

[0126] 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. Furthermore, the adhesive layer 44 can have functions such as light shielding, gas barrier (sterilizing gases, etc.), and moisture protection.

[0127] The adhesive layer 44 preferably covers the entire circumference of the sensor 16. At this time, since the adhesive layer 44 fills the space between the flexible substrate 22 and the prism 18 and / or the optical component holding tool 20, if the operating temperature is high, the adhesive layer may sometimes peel off between the prism and the cover glass due to thermal expansion. However, as will be described later, this can be suppressed by adjusting the amount H2 of the third layer 40 protruding from the sensor 16.

[0128] The adhesive layer 44 can be made of an adhesive or a sealant.

[0129] As an adhesive, various adhesives used in endoscopes can be used. For example, epoxy resin-based adhesives can be used. Furthermore, black epoxy is preferred due to its light-blocking properties.

[0130] As a sealant, various sealants used in endoscopes can be utilized.

[0131] For adhesives and sealants, the higher the thermal conductivity, the better, but insulation is preferred.

[0132] Furthermore, the size of the third layer 40 in top view is preferably larger than that of the sensor 16, and the third layer 40 is preferably configured to include the sensor 16 in top view.

[0133] For example, in Figure 6 In the example shown, the third layer 40 is configured such that its size (length) in the optical axis direction of the lens 12 is greater than that of the sensor 16, and it includes the sensor 16 in the optical axis direction. That is, the side surface of the third layer 40 protrudes more than the side surface of the sensor 16. Figure 6 In the example shown, the side of the third layer 40 on the lens 12 side is configured to be flush with the side of the flexible substrate 22 on the lens 12 side.

[0134] Here, as Figure 7 As shown, the amount H2 protruding from the sensor 16 by the third layer 40 is preferably less than half of the total thickness H1 of the cover glass 17, the sensor 16, and the second layer 19. By setting the amount H2 protruding from the third layer 40 within this range, it is possible to suppress the peeling between the prism and the cover glass caused by the difference in thermal expansion between the adhesive layer 44 and the cover glass 17, the sensor 16, and the second layer 19.

[0135] And, as Figure 7 As shown, preferably, the side of the lens 12 side of the third layer 40 protrudes from the side of the sensor 16, and the protrusion amount H2 is less than half of the total thickness H1.

[0136] In addition, Figure 7In the example shown, the protrusion H2 of the third layer 40 is less than half of the total thickness H1, and the protrusion of the flexible substrate 22 protrudes further outward than the sensor 16 and the third layer 40, but is not limited to this. Alternatively, it could be as follows... Figure 8 As shown in the example, the protrusion H2 of the third layer 40 and the flexible substrate 22 is less than half of the total thickness H1.

[0137] Here, in Figure 3 , Figures 6-8 In the example shown, the imaging surface of the sensor 16 is configured to be parallel to the optical axis of the lens 12, and the optical component 18 disposed between the lens 12 and the sensor 16 is a prism that bends light by 90°, but is not limited to this.

[0138] Figure 9 This is a side view showing another example of the camera module of the present invention.

[0139] Figure 9 The camera module shown has a lens barrel 14 for holding lens 12, an optical component holding tool 20, an optical component 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.

[0140] exist Figure 9 In the illustrated camera module, the flexible substrate 22 is bent approximately at 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 stacked on the surface of the portion of the flexible substrate 22 perpendicular to the optical axis (the surface on the side of the lens 12). On the other hand, a third layer 40 is disposed on the back side of the portion of the flexible substrate 22 perpendicular to the optical axis. Therefore, the imaging surface of the sensor 16 is configured perpendicular to the optical axis of the lens 12.

[0141] Optical component 18 guides light passing through lens 12 to the imaging surface of sensor 16. Optical component 18 is configured such that the incident and exit surfaces of light are perpendicular to the optical axis. Optical component 18 may simply transmit light, or it may have a light-converging effect. By having optical component 18 converge the light, the distance between lens 12 and sensor 16 can be brought closer, thereby enabling miniaturization.

[0142] The optical component 18 is held by the optical component holding tool 20, and is thus positioned together with the lens barrel 14 held by the optical component holding tool 20.

[0143] Thus, even when the imaging module of the present invention is configured such that the imaging surface of the sensor 16 is perpendicular to the optical axis of the lens 12, the third layer 40 can suppress the thermal expansion of the first layer 22 and the second layer 19, thereby preventing the imaging element 16 from warping and breaking.

[0144] Here, even in such Figure 9 When the imaging surface of the sensor 16 shown is configured to be perpendicular to the optical axis of the lens 12, it is also preferable to have an adhesive layer 44 configured to cover at least a portion of the side surface of the sensor 16, but more preferably to cover the entire circumference.

[0145] Furthermore, in Figure 9 In the example shown, the adhesive layer 44 fills the space between the flexible substrate 22 and the optical component 18, but is not limited to this, such as Figure 10 As shown in the example, the adhesive layer 44 can also be filled between the flexible substrate 22 and the optical component holding tool 20.

[0146] For example, in Figure 9 and Figure 10 In the example shown, the third layer 40 is configured such that its size (length) in the vertical direction is greater than and includes the sensor 16. That is, the two sides of the third layer 40 (the upper side and the lower side in the figure) protrude from the sensor 16.

[0147] And, even in cases like Figure 9 and Figure 10 When the imaging surface of the sensor 16 is configured perpendicular to the optical axis of the lens 12, the protrusion H2 of the third layer 40 from the sensor 16 is preferably less than half of the sum 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 protrusion H2 of the third layer 40 within this range, peeling between the optical components and the cover glass can be suppressed.

[0148] Furthermore, in the camera module of the present invention, circuitry can be formed on the third layer 40. The circuitry formed on the third layer 40 can be connected to the circuitry on the first layer (flexible substrate) 22 to form a multilayer circuit board. When circuitry is formed on the third layer 40, the third layer can be made of an insulating material such as ceramic.

[0149] The above describes in detail the camera module involved in the present invention by listing various embodiments. However, the present invention is not limited to the above examples. Of course, various improvements and modifications can be made without departing from the spirit of the present invention.

Claims

1. A camera module having an imaging element and comprising: The first layer is disposed on the back side of the imaging element on the side opposite to the imaging surface and is composed of a flexible substrate. A second layer, disposed between the imaging element and the first layer and electrically connected to the imaging element and the first layer; and The third layer is located on the side of the first layer opposite to the side of the second layer. The thermal expansion coefficient of the third layer is closer to that of the imaging element than the average thermal expansion coefficient of the first and second layers. The elastic modulus of the third layer is higher than that of the first and second layers. The sum of the elastic modulus × thickness of the imaging element and the elastic modulus × thickness of the third layer is greater than the sum of the elastic modulus × thickness of the first layer and the elastic modulus × thickness of the second layer.

2. The camera module according to claim 1, wherein, A cover glass, the same size as the imaging element when viewed from above, is attached to the imaging surface of the imaging element.

3. The camera module according to claim 2, wherein, The camera module has a lens and at least one optical component. The lens causes the incident light to be imaged onto the imaging surface of the imaging element. The at least one optical component is disposed between the cover glass and the lens. The light-receiving side of the cover glass is bonded and fixed to the optical component. In at least one direction perpendicular to the side of the imaging element, the protrusion of the third layer from the side 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.

4. The camera module according to claim 1 or 2, wherein, The camera module has a lens and a prism. The lens causes the incident light to be imaged onto the imaging surface of the imaging element. The prism is positioned between the lens and the imaging element. The imaging element is configured such that its imaging plane is parallel to the optical axis of the lens. The third layer forms the outermost layer of the camera module.

5. The camera module according to claim 3, wherein, The camera module has a prism. The prism is positioned between the lens and the imaging element. The imaging element is configured such that its imaging plane is parallel to the optical axis of the lens. The third layer forms the outermost layer of the camera module. The side of the third layer that protrudes from the imaging element is the side of the lens.

6. The camera module according to claim 1 or 2, wherein, The third layer is formed to contain ceramic.

7. The camera module according to claim 1 or 2, wherein, A circuit is formed in the third layer and is electrically connected to the first layer.

8. The camera module according to claim 1 or 2, wherein, The second layer has solder balls.

9. The camera module according to claim 8, wherein, At least a portion of the second layer is filled with bottom filler.

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