JP2004079946A - Photoelectric conversion circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion circuit insusceptible to external noise in which generation of radiation radio wave is suppressed. <P>SOLUTION: The photoelectric conversion circuit 1 comprises a substrate 10, and an image sensor 20 having a lead terminal 22 projecting outward. A ground pattern 14 being connected electrically with the ground level is provided on the substrate 10, a metal plate 40 having a hole 41 being fitted idly with the lead terminal 22 is interposed between the substrate 10 and the image sensor 20 to touch the ground pattern 14, and the image sensor 20 is mounted on the substrate 10 while fitting the lead terminal 22 idly in the hole 41. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photoelectric conversion circuit in which an image sensor is mounted on a substrate, and more particularly, to a photoelectric conversion circuit that suppresses generation of radiated radio waves from an image sensor.
[0002]
[Prior art]
An image reading apparatus such as an image scanner, a copying machine, and a facsimile apparatus is provided with, for example, a photoelectric conversion circuit 100 as shown in FIG. The photoelectric conversion circuit 100 includes a CCD (Charge Coupled Device) 110 serving as an image sensor, a driving integrated circuit 120 for driving the CCD 110, and the like mounted on a printed circuit board 130. The CCD 110 has a large number of photoelectric conversion elements 111 for converting received light into electric charges on the light receiving surface 110a. The packaging case 110b (see FIG. 8) for accommodating the CCD chip is made of ceramic, glass, metal, or the like, and has a plurality of lead terminals 112 on both sides of the packaging case 110b.
[0003]
In recent years, the speed of operation of electronic devices has increased, and the frequency of drive signals input to the CCD 110 from the drive integrated circuit 120 has also increased accordingly. With the high-speed operation, measures for heat generation are important for stabilizing the operation of the CCD 110. In order to efficiently dissipate the heat generated from the CCD 110, the packaging case 110b of the CCD 110 is made of a material in which ceramic or metal is laminated on glass (for example, see Patent Document 1). This improves the thermal conductivity of the glass and prevents heat from being stored in the packaging case 110b.
For example, as shown in FIGS. 7 to 10, a heat radiating plate 140 made of a metal such as Al (aluminum) is inserted into a gap formed by the printed board 120, the linear CCD image sensor 110, and the lead terminal 112. Things have also been done. As a result, the heat generated from the CCD 110 is radiated to the outside by the heat radiating plate 140, thereby making the CCD 110 less affected by the heat.
[0004]
[Patent Document 1]
JP-A-10-154804 (paragraphs 0014 to 0019, FIG. 3)
[0005]
[Problems to be solved by the invention]
Meanwhile, the lead terminal 111 of the above-described conventional CCD 110 (Patent Document 1) is provided to protrude outside the packaging case 110b as shown in FIGS. A high-speed and repetitive large pulse current flows through the lead terminal 111 as the driving frequency increases. At this time, radio waves are radiated from the exposed portion of the lead terminal 111. The radiated radio waves become noise and may cause electromagnetic interference (EMI) on other circuits, devices, and the like. Also, noise generated from other circuits or devices may be taken in from the exposed portion of the lead terminal 111, and the operation of the image sensor itself may be unstable.
An object of the present invention is to provide a photoelectric conversion circuit that suppresses the generation of radiated radio waves and is not easily affected by other radiated radio waves.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, an invention according to claim 1 is a photoelectric conversion circuit including a substrate and an image sensor having lead terminals protruding to the outside, wherein the photoelectric conversion circuit is provided between the substrate and the image sensor. A metal plate having a hole in which the lead terminal can be loosely fitted, and the image sensor is mounted on the substrate with the lead terminal loosely fitted in the hole.
[0007]
According to the first aspect of the invention, since the image sensor is mounted on the board with the lead terminals loosely fitted in the holes of the metal plate, the periphery of the lead terminals is surrounded by the metal plate. In addition, the degree to which the lead terminals are exposed to the outside can be reduced. Therefore, a radiated radio wave generated by driving the image sensor is absorbed by the metal plate and dropped to the ground level by the ground pattern provided on the substrate. Therefore, it is possible to reduce electromagnetic interference with other components provided on the substrate and other circuits. In addition, since noise radio waves from other sources are shielded by the metal plate around the lead terminals, it is also possible to reduce the electromagnetic interference caused by the image sensor itself. Therefore, generation of radiation waves from the photoelectric conversion circuit can be suppressed, and influence of radiation waves from other sources can be reduced.
[0008]
According to a second aspect of the present invention, in the photoelectric conversion circuit according to the first aspect, a driving integrated circuit for driving the image sensor is provided, and the driving integrated circuit can be loosely fitted to the metal plate. A driving integrated circuit hole is provided, and the driving integrated circuit is mounted on the substrate while being buried in the driving integrated circuit hole.
[0009]
According to the second aspect of the present invention, the driving integrated circuit for driving the image sensor is loosely fitted in the driving integrated circuit hole and is mounted on the substrate while being buried in the metal plate. Even if a radiated radio wave that becomes noise is generated from the lead terminal of the driving integrated circuit, the radiated radio wave can be absorbed by the metal plate. For this reason, it is possible to reduce electromagnetic interference caused by other components or circuits due to the driving integrated circuit. Further, since a noise radio wave from other sources can be shielded by the metal plate, it is possible to reduce the electromagnetic interference caused by the driving integrated circuit.
[0010]
According to a third aspect of the present invention, in the photoelectric conversion circuit according to the second aspect, the driving integrated circuit is provided with a driving signal generating integrated circuit that supplies a driving signal for driving the image sensor, The metal plate is provided with a drive signal generation integrated circuit hole into which the drive signal generation integrated circuit can be loosely fitted, and the drive signal generation integrated circuit is buried in the drive signal generation integrated circuit hole. It is characterized by being mounted on the substrate in a state.
[0011]
According to the third aspect of the present invention, the drive signal generating integrated circuit is loosely fitted into the drive signal generating integrated circuit hole and mounted on the substrate while being buried in the metal plate. Even if a radiated radio wave as noise is generated from the lead terminal of the generating integrated circuit, the radiated radio wave can be absorbed by the metal plate and dropped to the ground level. Also, noise radio waves from other sources can be shielded by the metal plate.
[0012]
According to a fourth aspect of the present invention, in the photoelectric conversion circuit according to any one of the first to third aspects, an analog signal processing integrated circuit for A / D converting a signal output from the image sensor is provided. The metal plate is provided with an analog signal processing integrated circuit hole into which the analog signal processing integrated circuit can be loosely fitted, and the analog signal processing integrated circuit is buried in the analog signal processing integrated circuit hole. It is mounted on the substrate in a state where it is made.
[0013]
According to the fourth aspect of the present invention, the analog signal processing integrated circuit is loosely fitted into the analog signal processing integrated circuit hole and mounted on the substrate while being buried in the metal plate. Even if a radiated radio wave as noise is generated from the lead terminal of the processing integrated circuit, the radiated radio wave can be absorbed by the metal plate and dropped to the ground level. Also, noise radio waves from other sources can be shielded by the metal plate.
[0014]
According to a fifth aspect of the present invention, in the photoelectric conversion circuit according to any one of the first to fourth aspects, unevenness is provided on a surface of the ground pattern or a contact surface of the metal plate with the ground pattern, The metal plate and the ground pattern are in point contact with each other.
[0015]
According to the fifth aspect of the present invention, the surface of the ground pattern or the contact surface of the metal plate with the ground pattern is provided with irregularities, and the ground pattern and the metal plate are point-contacted and electrically connected. . If the surface of the ground pattern and the contact surface of the metal plate with the ground pattern have no irregularities and are smooth, respectively, the metal plate and the ground pattern are in surface contact. At this time, if one of the surfaces is warped, poor contact occurs. However, by providing a large number of fine irregularities on the surface of the ground pattern or the contact surface with the ground pattern of the metal plate and making point contact with each other, it is possible to increase the effective contact area as a result as compared with the case of surface contact. it can. Therefore, the radiation wave absorbed by the metal plate can be more efficiently reduced to the ground level.
[0016]
According to a sixth aspect of the present invention, in the photoelectric conversion circuit according to any one of the first to fifth aspects, the metal plate is a heat radiating plate that dissipates heat generated from the image sensor. I do.
[0017]
According to the sixth aspect of the present invention, since the metal plate can dissipate the heat generated from the image sensor, the metal plate is less affected by the heat applied to the image sensor, and the operation of the circuit can be stabilized. . In addition, since the metal plate has both a function as an absorber of the radiated radio wave and a heat radiation function, an increase in the number of components can be prevented.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a photoelectric conversion circuit according to the present invention will be described with reference to the drawings.
The photoelectric conversion circuit 1 shown in FIG. 1 is one in which an image sensor 20 and a driving integrated circuit 30 and the like are mounted on a printed board 10, and converts image information input as an optical signal to the image sensor 20 into an electric signal. .
[0019]
The image sensor 20 is a linear CCD and is packaged in a lead insertion mounting type. The lead terminals 22 are provided in a line on both sides of the packaging case 20b, and are arranged in a dual in-line type. As shown in FIGS. 3 and 6, the lead terminal 22 is inserted into the through hole 12 provided in the printed board 10, and is fixed by soldering on the back side of the printed board 10.
[0020]
The driving integrated circuit 30 shown in FIGS. 1 and 4 inputs a high-frequency driving signal to the image sensor 20 and outputs the charge generated by the image sensor 20 to the outside.
The driving integrated circuit 30 is packaged in a surface mount type. The lead terminals 32 are provided in a row on both sides of the packaging case 32b, and are arranged in a gull-wing type. The lead terminal 32a provided substantially at the center of the case 30b is a GND connection terminal electrically connected to a ground (GND) level which is a ground potential, and is formed wider than the other lead terminals 32b. Have been. These lead terminals 32 are directly soldered to a soldering pattern formed on the printed circuit board 10, as shown in FIG.
[0021]
The photoelectric conversion circuit 1 further includes a drive signal generation integrated circuit 50 that supplies a drive pulse to the drive integrated circuit 30, an analog signal processing integrated circuit that converts an electric signal output from the image sensor 20 into a digital signal. 60 (A / D conversion circuit), and various ICs such as a transmission circuit (not shown) for transmitting an electric signal converted into a digital signal to another circuit such as an image processing circuit are provided.
[0022]
As shown in FIGS. 3 and 4, mounting patterns such as through holes 12 and soldering patterns 13 are formed on a printed circuit board on which these ICs are mounted.
Further, a GND pattern 14 is formed on the entire surface of the printed circuit board 10 excluding the mounting surfaces of the ICs 20 and 30. As shown in FIG. 5, the GND pattern 14 is provided so as to be folded on the back side of the printed circuit board 10, and is electrically connected to the GND level at the folded portion 14a. In addition, the surface of the GND pattern 14 is finished in an uneven shape.
[0023]
Further, as shown in FIGS. 2 to 5, a heat radiating plate 40 is provided on the printed board 10 so as to be in contact with the above-mentioned GND pattern 14. The heat radiating plate 40 is formed in substantially the same size as the printed board 10. The contact surface between the heat sink 40 and the GND pattern 14 is a point contact. That is, the surface contact between the heat radiating plate and the printed circuit board is substantially less in contact due to the warpage of the plate and the like, and the effective contact area is larger in the case of a large number of point contacts which are in contact with fine uneven surfaces. This is because it can be secured.
[0024]
The heat radiating plate 40 is made of a metal plate such as Al, Fe (iron) or a magnetic material, and is located between the image sensor 20 and the substrate 10, and dissipates heat generated from the image sensor 20 during operation to the outside.
[0025]
As shown in FIG. 3, the heat sink 40 has a long hole 41a into which a lead terminal 22a provided on one side of the package case 20b of the image sensor 20 can be loosely fitted, and a lead terminal provided on the other side. A long hole 41b into which the 22b can be loosely fitted is provided. Then, as shown in FIGS. 5 and 6, the image sensor 20 is mounted on the printed circuit board 10 with the lead terminals 22 inserted through the elongated holes 41. At this time, most of the lead terminals 22 are covered by the inner peripheral wall of the elongated hole 41 in a state of not electrically contacting the heat sink 40.
[0026]
As shown in FIGS. 1 and 4, a rectangular hole 42 having substantially the same size as the driving integrated circuit 30 is formed in a portion corresponding to the mounting position of the driving integrated circuit 30 on the heat sink 40. I have. As shown in FIG. 1, the driving integrated circuit 30 is housed in the rectangular hole 42 so as to be buried. The periphery of the lead terminal 32 of the driving integrated circuit 30 is surrounded by a heat sink 40, and the GND connection lead terminal 32 a is in contact with the heat sink 40.
[0027]
Further, as shown in FIG. 1, the drive signal generating integrated circuit 50 and the analog signal processing integrated circuit 50 are mounted on portions corresponding to the mounting positions of the drive signal generating integrated circuit 50 and the analog signal processing integrated circuit 60, respectively. Rectangular holes 45 and 46 having substantially the same size as the integrated circuit 60 are formed. The circuits 50 and 60 are loosely fitted in the rectangular holes 45 and 46 and mounted on the printed circuit board 10 while being buried in the heat sink 40, similarly to the drive integrated circuit 30.
[0028]
In addition to the above-described circuits, other ICs such as a transmission circuit provided in the photoelectric circuit 1 are also mounted in the same manner as the image sensor 20 for those packaged in a lead insertion mounting type like the image sensor 20. The IC packaged in a surface mount type is mounted in the same manner as the integrated circuit 30 for driving.
[0029]
According to the photoelectric conversion circuit 1 described above, since the lead terminals 22 of the image sensor 20 are mounted on the printed circuit board 10 in a state of being loosely fitted in the long holes 41 formed in the heat sink 40, the periphery of the lead terminals 22 Is surrounded by the heat radiating plate 40, and the degree to which the lead terminals 22 are exposed to the outside can be reduced. Therefore, the radiated radio wave generated by driving the image sensor 20 is absorbed by the heat sink 40 and dropped to the GND level by the GND pattern 14, so that the electromagnetic wave to another IC provided on the printed circuit board 10 or another circuit is provided. Obstacles can be reduced. Further, noise radio waves from other sources are shielded by the heat radiating plate 40 around the lead terminals 22, so that the electromagnetic wave interference received by the image sensor 20 itself can be reduced.
[0030]
The driving integrated circuit 30 is also mounted on the printed circuit board 10 so as to be buried in the heat sink 40, and the lead terminals 32 of the driving integrated circuit 30 are surrounded by the heat sink 40. Therefore, even when a radiated radio wave is generated from the lead terminal 32 when the drive integrated circuit 30 is operated, the radiated radio wave can be absorbed by the heat sink 40. For this reason, it is possible to reduce electromagnetic interference caused by other components or circuits due to the driving integrated circuit 40. In addition, since noise radio waves from other sources can be shielded by the heat radiating plate 40, it is possible to reduce electromagnetic interference caused by the driving integrated circuit 40.
[0031]
Similarly to the drive integrated circuit 30, the drive signal generation integrated circuit 50 and the analog signal processing integrated circuit 60 are mounted on the printed circuit board 10 while being buried in the rectangular holes 45 and 46 formed in the heat sink 40. Therefore, the radiated radio waves generated from these circuits 50 and 60 can be absorbed and reduced to the GND level. Further, noise radio waves from other sources can be shielded by the heat sink 40.
[0032]
Furthermore, by providing many fine irregularities on the surface of the GND pattern 14 and making the GND pattern 14 and the heat sink 40 point-contact, as described above, a larger effective contact area can be secured than in the case of surface contact, The contact state is improved. Therefore, the radiation wave absorbed by the heat sink 40 can be more efficiently reduced to the GND level.
[0033]
Further, as described above, since the heat radiating plate 40 has both a heat radiating function and a function as an absorber that absorbs radiated radio waves, it is possible to reduce electromagnetic interference without increasing the number of components.
[0034]
Further, in the present embodiment, since the heat radiating plate 40 is formed to have substantially the same size as the printed circuit board 10, the heat radiating area becomes larger as compared with the related art, and the heat accumulated in the entire substrate is efficiently radiated. can do. In general, a CCD has a phenomenon called dark current in which electric charges are accumulated over time even when light is blocked. However, since the amount of generation of the dark current depends on the temperature, the generation of the dark current can be reduced by increasing the size of the heat sink and dissipating the heat efficiently as in the present embodiment.
[0035]
Note that the photoelectric conversion circuit of the present invention is not limited to the above-described embodiment, and it is needless to say that the photoelectric conversion circuit can be appropriately changed without departing from the spirit of the present invention.
For example, in the above-described embodiment, the image sensor 20 is a linear CCD, but the image sensor 20 is not limited to this. The input surface is formed in a planar shape, and an area type that can input a two-dimensional image is used. It may be a CCD. Further, the image sensor 20 is not limited to a CCD, but may be any photoelectric conversion element that converts an input optical signal into an electric signal.
[0036]
In addition, the surface of the GND pattern 14 is provided with an uneven surface finish, but the present invention is not limited to this. The contact surface of the heat radiating plate 40 that comes into contact with the GND pattern 14 may be provided with an uneven surface finish. In short, any configuration is possible as long as the GND pattern and the heat radiating plate 40 are electrically connected by point contact. It may be.
[0037]
It is preferable that the heat radiating plate 40 be thick. As shown in FIG. 2, FIG. 3, FIG. 5, and FIG. 6, it is preferable that the height at which the image sensor 20 rises from the printed circuit board 10 by the lead terminals 22 and the thickness of the heat radiation plate 40 be made substantially equal. is there. Furthermore, when the photoelectric conversion circuit 1 is viewed from the side, the heat dissipation plate 40 may have a thickness such that the base end of the lead terminal 22 is completely hidden. In that case, a recessed portion for accommodating the package case 20b of the image sensor 20 may be formed in a portion sandwiched between the long hole 41a and the long hole 41b shown in FIG. By making the heat radiating plate 40 thick and surrounding the lead terminals 22 and 32 of the image sensor 20 and the driving integrated circuit 30 with the heat radiating plate 40, radio waves radiated from the lead terminals 22 and 32 are more reliably absorbed. This makes it possible to more reliably shield noise radio waves from other sources.
[0038]
【The invention's effect】
According to the first aspect of the present invention, even if a radio wave serving as a noise is radiated from the lead terminal, it can be absorbed by the metal plate around the lead terminal and dropped to the ground level by the ground pattern. Electromagnetic wave interference to other components provided and other circuits can be reduced. In addition, since a noise radio wave from another can be shielded by the metal plate, it is possible to reduce the electromagnetic wave interference received by the image sensor itself. Therefore, it is possible to suppress the generation of the radiated radio wave from the photoelectric conversion circuit and to make the photoelectric conversion circuit less susceptible to the radiated radio wave from the other.
[0039]
According to the second aspect of the present invention, the same effects as those of the first aspect can be obtained, and the radiated radio waves generated from the lead terminals of the driving integrated circuit can be transmitted to the metal plate around the driving integrated circuit. Can be absorbed. Further, the driving integrated circuit can be shielded from the noise radio wave by the metal plate.
[0040]
According to the third aspect of the present invention, the same effects as those of the first or second aspect can be obtained, and radiated radio waves generated from the lead terminals of the integrated circuit for driving signal generation are integrated with the integrated circuit for driving signal generation. It can be absorbed by a metal plate around the circuit and dropped to ground level. Further, the driving signal generating integrated circuit can be shielded from noise radio waves by the metal plate.
[0041]
According to the fourth aspect of the present invention, the same effect as any one of the first to third aspects can be obtained, and the radiated radio wave generated from the lead terminal of the analog signal processing integrated circuit can be obtained. It can be absorbed by the metal plate around the analog signal processing integrated circuit and dropped to the ground level. Further, the integrated circuit for analog signal processing can be shielded from noise radio waves by the metal plate.
[0042]
According to the fifth aspect of the present invention, the same effect as any one of the first to fourth aspects can be obtained, and the ground pattern and the metal plate are electrically connected by point contact. Therefore, a larger effective contact area can be secured than in the case of surface contact where there is a risk of contact failure due to warpage of the substrate or metal plate, and the contact state is improved. Therefore, the radiated radio wave absorbed by the metal plate can be more efficiently reduced to the ground level.
[0043]
According to the sixth aspect of the invention, the same effect as any one of the first to fifth aspects can be obtained, and the metal plate can dissipate the heat generated from the image sensor. Therefore, the image sensor is hardly affected by heat, and the operation of the circuit can be stabilized. In addition, since the metal plate has both a function as an absorber of the radiated radio wave and a heat radiation function, an increase in the number of components can be prevented.
[Brief description of the drawings]
FIG. 1 is a plan view illustrating an example of a photoelectric conversion circuit according to the present invention.
FIG. 2 is an exploded perspective view showing a portion where an image sensor is mounted in the photoelectric conversion circuit shown in FIG.
FIG. 3 is an exploded perspective view showing a portion where a driving integrated circuit is mounted in the photoelectric conversion circuit shown in FIG.
FIG. 4 is a perspective view showing a state in which a lead terminal of an image sensor is inserted into a hole provided in a heat sink in the photoelectric conversion circuit shown in FIG. 1;
FIG. 5 is a sectional view taken along the line AA in FIG. 1;
FIG. 6 is a sectional view taken along the line BB in FIG. 1;
FIG. 7 is a plan view illustrating an example of a conventional photoelectric conversion circuit.
8 is an exploded perspective view showing a portion where an image sensor is mounted in the photoelectric conversion circuit shown in FIG.
9 is a sectional view taken along the line AA in FIG. 7;
FIG. 10 is a sectional view taken along the line BB in FIG. 7;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photoelectric conversion circuit 10 Substrate 14 Ground pattern 20 Image sensor 22 Lead terminal 30 Driving integrated circuit 40 Metal plate (heat sink)
41 holes (long holes)
42 hole for driving integrated circuit (rectangular hole)
45 Drive signal generation integrated circuit hole (rectangular hole)
46 Integrated circuit hole for analog signal processing (rectangular hole)
50 Integrated Circuit for Generating Drive Signals 60 Integrated Circuit for Analog Signal Processing

Claims (6)

In a photoelectric conversion circuit including a substrate and an image sensor having a lead terminal protruding outside,
A metal plate having a hole in which the lead terminal can be loosely inserted is interposed between the substrate and the image sensor, and the image sensor is mounted on the substrate with the lead terminal loosely fitted in the hole,
A photoelectric conversion circuit, wherein a ground pattern electrically connected to a ground level is provided on the substrate, and the metal plate and the ground pattern are in contact with each other and are electrically connected. The photoelectric conversion circuit according to claim 1,
A driving integrated circuit for driving the image sensor is provided,
The metal plate is provided with a driving integrated circuit hole into which the driving integrated circuit can be loosely fitted, and the driving integrated circuit is mounted on the substrate while being buried in the driving integrated circuit hole. A photoelectric conversion circuit characterized in that: The photoelectric conversion circuit according to claim 2,
A drive signal generation integrated circuit that supplies a drive signal for driving the image sensor to the drive integrated circuit is provided,
The metal plate is provided with a drive signal generation integrated circuit hole into which the drive signal generation integrated circuit can be loosely fitted, and the drive signal generation integrated circuit is buried in the drive signal generation integrated circuit hole. A photoelectric conversion circuit, wherein the photoelectric conversion circuit is mounted on the substrate in a state where the photoelectric conversion circuit is in a state where the photoelectric conversion circuit is in a state where the photoelectric conversion circuit is closed. The photoelectric conversion circuit according to any one of claims 1 to 3,
An analog signal processing integrated circuit for A / D converting a signal output from the image sensor;
The metal plate is provided with an analog signal processing integrated circuit hole into which the analog signal processing integrated circuit can be loosely fitted, and the analog signal processing integrated circuit is buried in the analog signal processing integrated circuit hole. A photoelectric conversion circuit, wherein the photoelectric conversion circuit is mounted on the substrate in a state where the photoelectric conversion circuit is in a state where the photoelectric conversion circuit is in a state where the photoelectric conversion circuit is closed. In the photoelectric conversion circuit according to any one of claims 1 to 4,
A photoelectric conversion circuit, wherein the surface of the ground pattern or the contact surface of the metal plate with the ground pattern has irregularities, and the metal plate and the ground pattern are in point contact with each other. The photoelectric conversion circuit according to any one of claims 1 to 5,
The photoelectric conversion circuit according to claim 1, wherein the metal plate is a heat radiating plate for dissipating heat generated from the image sensor.

Images