JP2005260436A - Imaging module and imaging apparatus employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an imaging module in which performance is enhanced while reducing the size and thickness. <P>SOLUTION: A concave curved part 41 is provided in a base substrate 4 and the curved part 41 is curved in correspondence with curvature of an image plane caused by aberration of the lens module in an imaging apparatus. The base substrate 4 is provided with a shock absorbing material film 2 which is curved along the shape at the curved part of the base substrate 4, and an imaging element 1 is provided on the shock absorbing material film 2 while bending its imaging plane according to the shape at the curved part. The shock absorbing material film 2 relaxes effect of difference in thermal expansion coefficient between the base substrate 4 and the imaging element 1 due to temperature rise on the imaging element 1. Upper and lower surfaces of the shock absorbing material film 2 also bend along the shape at the curved part, and both the imaging element 1 and the shock absorbing material film 2 are layered while keeping the curved shape similar to that at the curved part of the base substrate 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an imaging module using a curved imaging device and an imaging device mounted on a digital camera or a camera-equipped mobile phone using the imaging module.

Digital camera devices and camera-equipped mobile phones are required to improve the imaging performance and make the devices lighter and thinner. For this purpose, there is a solid-state imaging device in which the imaging element is thinned to a film thickness that can be curved, and fixed on the base material with an adhesive or the like while maintaining the curved shape, and a lens for correcting aberrations in the imaging optical system Is not necessary, and lightness, thinness and miniaturization are realized (see, for example, Patent Document 1).
The semiconductor bare chip is flip-chip mounted on the wiring substrate on one side, and a curved surface corresponding to the curvature of field caused by the aberration of the imaging lens of the imaging optical system is formed on the other side. In addition, there is a solid-state imaging device in which the back surface of the imaging element is bonded along the curved shape (see, for example, Patent Document 2).

JP 2001-156278 A (first page) JP 2003-188366 A (first page)

However, as described above, the image pickup device chip is curved for the purpose of downsizing, thinning, and high performance of the image pickup module. However, the image pickup device is thin enough to be bent, so that it is easily affected by temperature. It has become.
In the above-mentioned Patent Document 1, since the thermal expansion coefficients of the base material and the imaging element are different, a stress due to the difference in the thermal expansion coefficient is generated due to the temperature rise, and the thinned imaging element is deformed and the focus is blurred. there were.
In Patent Document 2, since both the image pickup element and the semiconductor bare chip are silicon substrates, stress generation due to the difference in thermal expansion coefficient between them can be prevented. A curved surface corresponding to the curvature of field caused by the aberration of the imaging lens is provided. There is a difference in film thickness due to the provision of the curved surface in the semiconductor bare chip.Therefore, the semiconductor bare chip is warped due to the film thickness difference as the temperature rises, and the imaging element is deformed and the image is blurred. there were.

  The present invention has been made to solve such a problem, and an object of the present invention is to obtain an imaging module and an imaging apparatus that are small, thin, and have higher performance.

  The first imaging module according to the present invention includes a pedestal substrate provided with a curved portion that is curved in a concave shape, and a buffer material film that is provided on the curved portion of the pedestal substrate and is curved along the shape of the curved portion. And an imaging element provided on the curved surface of the buffer material film and having an imaging surface curved in the shape of the curved portion.

  The first imaging module of the present invention includes a pedestal substrate provided with a curved portion that curves in a concave shape, and a buffer material film that is provided on the curved portion of the pedestal substrate and is curved along the shape of the curved portion. The image pickup surface is provided on the curved surface of the buffer material film, and the image pickup surface is curved in the shape of the curved portion. Can be resolved.

Embodiment 1 FIG.
FIG. 1 is an explanatory diagram of the imaging module according to Embodiment 1 of the present invention. The pedestal substrate 4 is provided with a curved portion 41 that is curved in a concave shape, and the curved portion 41 has the following aberrations of the lens module. Is curved corresponding to the curvature of field caused by.
Although the buffer material film 2 is provided on the pedestal substrate 4, the buffer material film 2 is curved along the shape of the curved portion of the pedestal substrate 4, and the imaging element 1 is provided on the buffer material film 2. The imaging surface is provided to be bent in the shape of the bending portion.
The buffer material film 2 is a film for alleviating the influence on the image pickup device 1 due to the difference in thermal expansion coefficient between the base substrate 4 and the image pickup device 1 due to a temperature rise, and imaging due to the difference in the coefficient of thermal expansion. In order to prevent the stress from being generated on the element 1, the upper and lower surfaces of the buffer film 2 are also curved along the curved shape, and both the imaging element 1 and the buffer film 2 are the same as the curved portion of the base substrate 4. Are stacked while maintaining the curved shape.

In an imaging device, an object is imaged on an imaging surface of an imaging device using a lens module incorporating an imaging lens. When an object is imaged with an imaging lens, a lens concentration called field curvature is used. Occurs. However, in the imaging module of the present embodiment, as described above, since the imaging element 1 is curved in response to the curvature of field caused by the aberration of the lens, an aberration correction lens becomes unnecessary, and the lens Since the number of sheets can be reduced, the height of the lens housing portion can be reduced.
In the present embodiment, in order to bend and fix the image pickup device 1 and the buffer material film 2, the film thickness of the image pickup device 1 and the buffer material film 2 is desirably 100 μm or less, and more desirably 50 μm or less.
In addition, the size of the image pickup device is not particularly limited, but it is desirable that the size is smaller than the size of the buffer material film 2 because alignment in the case of stacking becomes easy.
Further, the vertical / horizontal dimension ratio of the chip is not particularly limited, but is preferably within 1.2 times in order to make the deformation at the time of bending uniform. From the point of uniformity of stress generated when the chip is bent, it is the same. It is further desirable that

In the imaging module of the present embodiment, the imaging element 1 is not directly fixed to the pedestal substrate 4, but is laminated via the buffer member film 2, thereby causing a difference in thermal expansion coefficient from the pedestal substrate 4. Since it becomes difficult to be affected by the generated stress, the image pickup device 1 is prevented from being deformed due to a temperature rise, and the image is prevented from being blurred, thereby improving the reliability.
The imaging device 1 according to the present embodiment is not particularly limited to an artificial retina chip, a CCD (Charge Coupled Device), a CMOS (Complementary Metal-Oxide Semiconductor) type imaging device, or the like, but in this case, the buffer member film When the same Si substrate as that of the image sensor 1 is used as 2, the thermal expansion coefficient is the same as that of the image sensor 1. The same effect can be obtained even if the difference in thermal expansion coefficient between the buffer material film 2 and the image sensor 1 is ± 50% or less of the thermal expansion coefficient of the image sensor 1.
Further, since the upper and lower surfaces of the buffer material film 2 are similarly curved along the curved shape, the variation in the film thickness of the buffer material film 2 is small, and it is possible to prevent the warp accompanying the temperature rise, There is an effect that deformation of the image sensor can be prevented. Note that the variation in the film thickness is preferably substantially close to 0, but the effect as the buffer material film 2 can be obtained even if the variation in the film thickness is ± 15% or less.

  The pedestal substrate 4 is generally a multilayer wiring board such as a glass epoxy board, but an aramid fiber epoxy board or a wiring board using a thermoplastic resin can also be used. Even if the wiring board is not a multilayer wiring board, the material is not limited as long as the rigidity capable of fixing the curved imaging element is maintained.

Embodiment 2. FIG.
FIG. 2 is a process diagram for explaining a method of manufacturing the imaging module according to the second embodiment of the present invention. An ASIC (Application Specific Integrated Circuit) such as a DSP (Digital Signal Processor) that performs signal processing as the buffer material film 2, etc. A case where an active element is used will be described.
Further, although the buffer material film 2 is described as being limited to active elements, it may be a Si substrate not having an active element but a transistor circuit, or a Si substrate having a conductor circuit such as a through wiring, There is no particular limitation as long as the conditions described in the first embodiment are satisfied.
The active element is not limited to signal processing and is not particularly limited as long as it is an element that can be thinned, and the number of stacked buffer material films is not particularly limited.

First, the adhesive 3 is applied on the base substrate 4 provided with the curved portion 41, and the active element 2 made of the Si substrate serving as a buffer material film is aligned at a predetermined position {FIG. 2 (a)}. .
Further, the cover 5 is covered so as to cover the surface of the base substrate 4 and the active element (buffer material film) 2, but before the cover 5 is covered, the film 26 is covered so as to cover the base substrate 4 and the active element 2 {FIG. 2 (b)}. In addition, the cover 5 is used for pressurizing the base substrate 4 and the film 26, and the contact portion between the cover 5 and the film 26 so that there is no gap between the base substrate 4 and the film 26 so that air to be pressurized in a subsequent process does not leak. It is.
Next, the active element 2 is indirectly pressurized by deforming and bending the film 26 with a pressure 6 of air sufficient to bend the active element 2 from the hole 51 provided in the cover 5, thereby causing the base substrate 4 to be curved. The active element 2 is fixed on the pedestal substrate 4 by causing the adhesive 3 to adhere and curing the adhesive layer by heat treatment or ultraviolet irradiation {FIG. 2 (c) }.
In the above process, the active element 2 is indirectly deformed by using the film 26. This is for the purpose of uniforming the pressure. If not particularly necessary, the active element 2 is directly connected without using the film. You may pressurize with the pressure of air and make it curve. In addition, an inert gas such as nitrogen can be used instead of air, and there is no particular limitation.

Next, the cover 5 is removed {FIG. 2 (d)}, the adhesive 3 is applied on the active element 2 fixed to bend, and the imaging element 1 that is thinned at a predetermined position on the active element 2 is contained in the adhesive. Are laminated so as not to contain bubbles, and after covering with the film 26 in the same manner as described above, the cover 5 is covered so as to cover the laminate of the base substrate 4 and the image pickup device 1 {FIG. 2 (f)}.
Next, air 6 is sent from the hole 51 provided in the cover 5 to pressurize the image pickup device and deform it into a shape along the curved portion of the base substrate, and to adhere the adhesive layer and cure the adhesive such as heat treatment. Processing is performed to fix the imaging device 1 on the active device 2 {FIG. 2 (g)} to obtain the imaging module 11 {FIG. 2 (h)}.

The adhesive is not particularly limited, such as a thermosetting adhesive that cures by heating, an ultraviolet curable adhesive that cures by irradiation of energy rays such as ultraviolet rays, an adhesive that cures at room temperature, or an anaerobic adhesive. The adhesive is not particularly limited as long as it is an adhesive that can maintain the curved shape of the imaging element and the buffer material film, and the shape of the adhesive may be liquid or a sheet or film.
Further, in the case where the imaging element 1 is applied to the active element 2 that is a buffer material film, the adhesive is applied to the active element 2 in the present embodiment, but may be applied to the back surface of the imaging element, and the bonding area is also particularly limited. If it is liquid, it may be applied as long as the excess resin does not contaminate the surface of the image sensor after being fixed. If it is a sheet or film adhesive, the area larger than the chip size. May be formed.

As the adhesive, for example, an ultraviolet curable adhesive {trade name: TB3000, manufactured by Three-bond Co., Ltd.}, {trade name: 3100, manufactured by Three-bond Co., Ltd.}, {trade name: DESOLITE, JSR Manufactured by Co., Ltd.} can be preferably used. However, when an ultraviolet curable resin is used, it is necessary to use a base material that is transparent to ultraviolet rays, such as an acrylic resin, for the base substrate 4. It is. Further, although the ultraviolet ray permeability is low, an FR4 glass epoxy base material {trade name: GEPL170, manufactured by Mitsubishi Gas Chemical Co., Ltd.} may be used.
In addition, when a metal such as aluminum or ceramic is used as the opaque base material, a heat-curable adhesive that does not require ultraviolet irradiation may be used.
When it is difficult to control the thickness of the adhesive layer, it is also effective to use a spacer. The material of the spacer is not particularly limited, and particles of resin, metal, ceramic, or a composite thereof can be used. .

Embodiment 3 FIG.
FIG. 3 is an explanatory diagram of the image pickup apparatus according to the third embodiment of the present invention, which is obtained by combining the image pickup module obtained by the above embodiment and the lens module 9. Therefore, since the mounting area of the active element can be omitted, the image pickup apparatus can be thinned and miniaturized at the same time.
The lens 91 portion of the lens module 9 uses a three-element lens, and is fixed to a ring-shaped plastic support member that is superposed and threaded using an adhesive. A plastic cylindrical housing is formed, and the above-described lens is fitted by threading the inside. The number of lenses is not particularly limited, and a lens designed according to a curved shape, a curved curvature thereof, a type of an imaging element to be used, and the number of pixels is not particularly limited. Depending on the required image, it may be two or four, and may be five or more. Furthermore, these materials are not particularly limited, and may be organic or inorganic. Further, while confirming the image, the lens module 9 manufactured in this way is adjusted and fixed at a position where the image is the best, and fixed with an adhesive or the like.
The number of pixels of the image sensor is 5 million pixels for digital cameras and 2 million pixels for mobile phones with cameras. Passive elements such as active conductor elements and capacitors are used to increase the number of pixels and increase signal processing speed and capacity. Both the quantity and area of the imaging device are increasing, and by stacking the above elements as the buffer material film 2 as in the present embodiment, the imaging device can be made thinner and smaller.

Example 1.
An imaging module is manufactured by the manufacturing method of the second embodiment, using a CCD (Charge Coupled Device) as an imaging element and an ASIC of a DSP as an active element serving as a buffer member film. The film thickness of the imaging element and the active element is 40 μm, the in-plane film thickness variation is within ± 15%, the planar dimension of the imaging element is 5.6 mm × 6 mm, and the dimension of the active element is 9 mm × 9 mm.
As a base substrate provided with a curved portion, a 6-layer FR4 multilayer wiring board having a thickness of 0.6 mm is used. The curved portion has a diameter of 15 mm, the curvature of the curved portion has a radius of 20 mm, and the central portion has a depth of 0.3 mm. is there.
In addition, passive components such as capacitors and resistors are already mounted, and a cationic ultraviolet curing adhesive {trade name: TB3100, as an adhesive for joining the back surface of the active element and the base substrate. In the process of fixing the active element using the Three-bond Co., Ltd.}, after sealing with a cover, the active element is curved by pressurizing the active element with 98 N / cm ² (10 kg / cm ² ) of pressurized air. Let
Further, the adhesive is cured by irradiating with ultraviolet rays from the base substrate side for 180 seconds using an ultraviolet irradiation device {trade name: Spot Cure UIS-50101AA, manufactured by USHIO Co., Ltd.} while being fixed in this state. Thereafter, the cover was removed, but the thickness of the adhesive layer was 1 μm.
Further, in order to bond the image pickup element on the active element, a thermosetting adhesive {trade name: TB2202F, manufactured by Three-bond Co., Ltd.} is used as an adhesive, and is applied onto the active element using a micro dispenser. Keep it. Then, after aligning the image sensor at a predetermined point on the active ^element, thereby pressurizing curved imaging device with pressurized air 98N / cm 2 (10kg / cm 2). Furthermore, with the imaging module obtained by fixing the imaging element while maintaining the curved shape on the active element by heating the adhesive in the oven at 90 ° C. for 30 minutes while curing the imaging element and curing the adhesive, The thickness of the adhesive layer between the element and the active element is 2 μm.

Example 2
In Example 1, an imaging module obtained by using a CCD with 2 million pixels as an imaging element is used, and a lens module 9 is combined with the imaging module as shown in Embodiment 3 to obtain the imaging apparatus shown in FIG.

Comparative Example 1
In the first embodiment, similarly to the first embodiment, the pedestal substrate 4 is provided with a bending portion 41 to bend the CCD (imaging device) 1, but the signal processing LSI (active device) 22 is a printed wiring board which is a pedestal substrate. The imaging device shown in FIG. 4 is obtained in the same manner as in the second embodiment using the imaging module manufactured in the same manner as in the first embodiment so as to be mounted on the back surface of the first embodiment.

Comparative Example 2
In the first embodiment, the pedestal substrate 4 is not provided with a bending portion, the CCD (imaging device) 1 is not curved, and the signal processing LSI (active device) 22 is mounted on the back surface of the printed wiring board which is the pedestal substrate. Thus, using the imaging module manufactured in the same manner as in the first embodiment, the imaging device shown in FIG. 5 is obtained in the same manner as in the second embodiment.

  Table 1 shows the thicknesses of the imaging devices of Example 2, Comparative Example 1 and Comparative Example 2. As shown in Table 1, the imaging device of Example 2 is made thinner than the comparative example, and the maximum thickness is as follows. It is shown that the film thickness can be reduced by 30% or more.

  Using the imaging device of Example 2, Comparative Example 1 or Comparative Example 2, a black and white pattern of each Spatial Frequency (Ip / mm) shown in Table 2 was imaged, and modulation (modulation: total distortion of the image signal) If it is output according to the designed pattern, it is 100%.) Is measured and the measurement results are shown in Table 2.

As shown in FIGS. 4 and 5, in Comparative Example 1 and Comparative Example 2, the video signal of the image sensor 1 is transmitted to a wiring board (base board) through a wire bond and then transmitted to a DSP (active element) 22. .
On the other hand, since the signal processing DSP (active element) 2 is provided immediately below the image sensor 1 in the image pickup apparatus according to the second embodiment, the image sensor and the DSP are electrically bonded by wire bonding, so that the signal is transmitted to the wiring board. Since signal processing is performed without flowing over, transmission loss can be reduced by reducing the signal transmission distance and the influence of external noise can be reduced. As a result, the modulation has increased as shown in Table 2. It is.

Comparative Example 3
In the first embodiment, the base substrate is not provided with a curved portion, and instead of the buffer material film 2, a substrate obtained by processing a spherical curved surface at the center of the Si substrate 42 is used. The thickness of the thinnest part of the Si substrate 42 was 200 μm, and the difference from the film thickness of the thickest part was 50%.
Further, as an adhesive for bending and fixing the thinned CCD on the curved portion of the Si substrate 42, a thermosetting adhesive is used in place of the ultraviolet curing adhesive used in Example 1, and the CCD is curved and fixed. Using the imaging module manufactured in the same manner as in Example 1 so that the signal processing LSI (active element) 22 is mounted on the back surface of the pedestal substrate 4 and cured at the temperature of Thus, the imaging device shown in FIG. 6 is obtained.

  In order to evaluate the temperature dependence of the resolution of the imaging device, a black and white pattern with a spatial frequency (lp / mm) of 60 was captured using the imaging device of Example 2, Comparative Example 1 or Comparative Example 3. However, the temperature of the imaging device was raised from −25 ° C. to 80 ° C. to measure modulation, and the measurement results are shown in Table 3.

As shown in Table 3, in the imaging module of the second embodiment, the signal processing DSP chip, which is an active element, is provided immediately below the imaging element. Therefore, compared to the first and third comparative examples, the signal transmission distance is shortened. It is shown that the transmission loss can be reduced and the influence of external noise can be reduced, resulting in an increase in modulation.
Furthermore, in Example 2, the material of the active element is the same as that of the imaging element and the film thickness is uniform, so that the generation of stress due to the difference in thermal expansion coefficient between the imaging element and the base substrate can be reduced. It is shown that the temperature dependence of the modulation is improved.

It is explanatory drawing of the imaging module of Embodiment 1 of this invention. It is process drawing explaining the manufacturing method of the imaging module of Embodiment 2 of this invention. It is explanatory drawing of the imaging device of Embodiment 3 of this invention. It is explanatory drawing of the imaging device of the comparative example of this invention. It is explanatory drawing of the imaging device of the comparative example of this invention. It is explanatory drawing of the imaging device of the comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image pick-up element, 2 Buffer material film (active element), 4 base board, 41 Bending part, 11 Image pick-up module, 9 Lens module.

Claims (5)

A pedestal substrate provided with a concavely curved curved portion, a buffer material film provided on the curved portion of the pedestal substrate, curved along the shape of the curved portion, and provided on a curved surface of the buffer material film And an imaging device having an imaging surface curved into the shape of the bending portion. The imaging module according to claim 1, wherein a difference in thermal expansion coefficient between the buffer material film and the imaging element is ± 50% or less of the thermal expansion coefficient of the imaging element. The imaging module according to claim 1, wherein the thickness variation of the buffer material film is within ± 15%. The imaging module according to claim 1, wherein the buffer material film is an active element. An imaging apparatus comprising: the imaging module according to claim 1; and a lens module disposed on a light incident side of the imaging module.

Images