JP2010171251A - Substrate unit and wiring unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for suppressing the radiation of electromagnetic waves in a substrate unit having sheet metal and a wiring board fixed to this sheet metal. <P>SOLUTION: A clock line 22 is provided on a second surface 21b that is the opposite side of a first surface 21a opposed to the sheet metal 3 on a wiring board 2. On the first surface 21a, a ground 23a is provided in such a manner as to be positioned between the clock line 22 and the sheet metal 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a substrate unit including a sheet metal and a substrate, and a wiring unit including the substrate unit.

  Conventionally, various proposals have been made on how to form a wiring pattern on a wiring board (Patent Document 1).

For example, Patent Document 1 describes an optical transceiver, and this optical transceiver is
An optical receiving subassembly (ROSA), a printed circuit board on which a receiving circuit for processing an electrical signal from the ROSA is mounted, and a flexible circuit board that connects the ROSA and the printed circuit board. A provided surface and a surface provided with a signal line. In order to reduce crosstalk noise, the flexible substrate is disposed with the surface on which the ground layer is provided facing the printed circuit board.

JP 2007-43496 A (FIG. 6 etc.)

  For example, in order to obtain accurate data, sensors such as an image sensor are required to have their positions strictly defined. Therefore, in order to prevent warpage of the wiring board (printed circuit board) due to heat and displacement of the position of the imaging element due to vibration, it is preferable that the wiring board on which the imaging element is mounted is fixed to a sheet metal. When the substrate is fixed to the sheet metal in this way, a large amount of electromagnetic waves are radiated from the sheet metal. However, in the prior art, electromagnetic radiation from the sheet metal has not been considered.

  An object of the present invention is to suppress radiation of electromagnetic waves from a sheet metal in view of such problems of the prior art.

  In order to solve the above problems, the wiring unit according to claim 1 includes a sheet metal and a wiring board, and the wiring board is fixed to the sheet metal so that the first surface faces the sheet metal, and the first A ground disposed on the surface, and a high-frequency signal line disposed on the second surface of the substrate so as to overlap the ground on the first surface.

  In this wiring unit, the high-frequency signal line is arranged on the second surface opposite to the first surface facing the sheet metal of the two surfaces of the substrate so as to overlap the ground on the first surface. Return current flows more easily to ground than sheet metal. That is, since return current does not easily flow through the sheet metal, radiation of electromagnetic waves from the sheet metal is suppressed.

  According to a second aspect of the present invention, in the substrate unit of the first aspect, the high-frequency signal line may be a clock line.

  In addition, as described in claim 3, the board unit according to claim 1 or 2 may further include an image pickup device mounted on the wiring board.

  According to a fourth aspect of the present invention, there is provided a wiring unit including the two or more board units according to any one of the first to third aspects, the high-frequency signal line of the certain board unit, and the other board. A first wiring that connects the high-frequency signal line of the unit; a second wiring that connects the grant of the certain board unit and the ground of the other board unit;

  The wiring unit according to claim 4, wherein the certain board unit further includes a clock source disposed on the wiring board, and the high frequency signal for the certain board unit is provided. The line may be a clock line connected to the clock source.

  According to a sixth aspect of the present invention, in the wiring unit according to the fourth or fifth aspect, the other board unit further includes an image pickup device mounted on the wiring board, and the high frequency of the other board unit. The signal line may be connected to the image sensor.

  In the substrate unit of the present invention, the return current flows more easily to the ground than the sheet metal. That is, since return current does not easily flow through the sheet metal, radiation of electromagnetic waves from the sheet metal is suppressed.

The disassembled perspective view which shows the principal part structure of the board | substrate unit 1 which concerns on one Embodiment of this invention. FIG. 3 is a cross-sectional view showing the main configuration of the substrate unit 1. FIG. 2 is a perspective view showing an external appearance of a multifunction machine 100 in which the substrate unit 1 is incorporated. FIG. 3 is a perspective view illustrating a part of an internal configuration of the multifunction peripheral 100 (an example of a wiring unit). Sectional drawing which shows the principal part structure of the board | substrate unit 13. FIG. FIG. 3 is a diagram schematically showing a flow of a loop current formed in the multifunction machine 100. Sectional drawing which shows the principal part structure of the board | substrate unit 14 which concerns on other embodiment of this invention. The disassembled perspective view which shows the principal part structure of the board | substrate unit 15 which concerns on further another embodiment of this invention. Sectional drawing of the board | substrate unit 500 which concerns on a comparison form. The figure which shows typically the flow of the loop current in a comparison form.

[1] First Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(1-1) Board unit 1
First, a schematic configuration of the substrate unit 1 of the present embodiment will be described with reference to FIG. FIG. 1 is an exploded perspective view showing a main configuration of the substrate unit 1.

  As shown in FIG. 1, the substrate unit 1 includes an image sensor mounting substrate 2, a substrate fixing sheet metal 3, an image sensor 4, and screws 5.

  Screw holes 20 and 30 are provided in the image pickup device mounting substrate 2 and the substrate fixing sheet metal 3, respectively. When the screw 5 penetrates the screw holes 20 and 30, the imaging element mounting substrate 2 is fixed to the substrate fixing sheet metal 3. Details of the imaging element mounting substrate 2 will be described later.

  The substrate fixing sheet metal 3 is a metal plate member. It is formed in an L shape in a cross section in a direction perpendicular to the mounting surface of the image sensor mounting substrate 2, that is, the surface provided with the screw holes 30. That is, the substrate fixing sheet metal 3 further includes a portion extending in a direction perpendicular to the mounting surface, and a screw hole 32 is further provided in the portion. The substrate fixing sheet metal 3 is fixed to the bottom plate 6 (described later) with screws (not shown) through the screw holes 32.

  The image sensor 4 is mounted on the image sensor mounting substrate 2. For example, a CCD is preferably used as the imaging element 4.

  In addition to the image sensor 4, the image sensor mounting substrate 2 may be mounted with various elements such as an image sensor timing generator, an image sensor drive circuit, and an analog front end. Further, these elements other than the imaging element 4 may be mounted on another substrate.

  Next, the configuration of the substrate unit 1 will be described in more detail with reference to FIG. FIG. 2 is a cross-sectional view showing the main configuration of the substrate unit 1. In FIG. 2, the illustration of the screw holes 20 and 30, the screw 5, and the image sensor 4 is omitted for convenience of explanation.

  As shown in FIG. 2, the imaging device mounting substrate 2 includes a core 21, a first pattern layer 201 formed on the first surface 21 a of the core 21, and a second pattern formed on the second surface 21 b of the core 21. A resist layer 24 covering each of the layer 202, the first pattern layer 201, and the second pattern layer 202 is provided. As shown in FIG. 2, the imaging element mounting substrate 2 is fixed by the above-described screws 5 so that the first surface 21 a of the core 21, which is an example of the substrate, faces the substrate fixing sheet metal 3.

  As shown in FIG. 2, the first pattern layer 201 is entirely the ground 23a. This ground 23 a is the ground of the clock line 22. A plurality of clock lines 22 are formed in the second pattern layer 202. In addition to the clock line, the second pattern layer 202 is also formed with a ground 23b, a power supply line, and other wiring.

  Thus, the clock line 22 is not formed on the first surface 21a, but is formed only on the second surface 21b. The ground 23a is formed over substantially the entire first surface 21a. As a result, the clock line 22 on the second surface 21b is arranged so as to overlap the ground 23a on the first surface 21a with the core 21 in between. In other words, the ground 23 a on the first surface 21 a is disposed between the clock line 22 and the substrate fixing sheet metal 3. That is, a line segment connecting the clock line 22 and the substrate fixing sheet metal 3 with the shortest distance (a line segment extending perpendicularly from the clock line 22 to the surface of the substrate fixing sheet metal 3) is blocked by the ground 23a. In particular, in the present embodiment, as shown in FIG. 2, the distance L1 from the clock line 22 on the second surface 21b to the ground 23a on the first surface 21a and the substrate from the clock line 22 on the second surface 21b are fixed. The distance L2 to the sheet metal 3 is L1 <L2.

  By arranging the ground 23a in this way, a return current due to the flow of the clock signal through the clock line 22 can easily flow in the ground 23a. That is, the return current is prevented from flowing through the substrate fixing sheet metal 3. The return current will be described in detail later.

  Note that wirings other than the clock line 22 may be formed on the second surface 21b.

(1-2) MFP 100
The multi-function device 100 on which the substrate unit 1 is mounted will be described with reference to the drawings. In the following description, “up” and “down” mean an upward direction and a downward direction, respectively, in the normal installation posture of the multifunction machine.

  First, an overview of the multifunction peripheral 100 will be described with reference to FIG. FIG. 3 is a perspective view showing the external appearance of the multifunction peripheral 100.

  As shown in FIG. 3, the multifunction peripheral 100 includes a main body 101 and a document conveying device 102. The document feeder 102 is disposed on the main body 101.

  The main body 101 includes a scanner 104, a printing unit 105, a paper cassette 106, and a platen glass 107. The platen glass 107 is disposed on the upper surface of the main body unit 101 at a position facing the document conveying device 102, the scanner 104 is provided on the upper side of the main body unit 101, that is, directly below the platen glass 107, and the printing unit 105 The sheet cassette 106 is provided at the bottom and further on the bottom of the main body 101.

  The scanner 104 includes the substrate unit 1 described above, and includes a light source, a mirror, a lens, and the like. The light from the light source is guided to the platen glass 107 by the mirror, and the light reflected by the original on the platen glass is guided to the image sensor 4 by the mirror and the lens. The image sensor 4 converts light into an analog electrical signal. Thereafter, an analog signal is converted into a digital signal by an analog front end circuit (not shown). This digital signal is used for printing or transmission as image data through an image processing circuit (not shown). The scanner 104 can read an image from both a document placed on the platen glass 107 and a document conveyed by the document conveying device 102 and passing on the platen glass 107.

  The printing unit 105 prints image data on a sheet. Specifically, an image forming apparatus using an electrophotographic method or an inkjet method is used.

  The paper cassette 106 stores paper supplied to the printing unit 105.

  The document conveying device 102 includes a plurality of rollers and a driving device that rotates these rollers, and conveys the document so as to pass over the platen glass 107 by the rotating rollers.

(1-3) Internal Configuration of Multifunction Device 100 With reference to FIG. 4, a portion related to the substrate unit 1 in the internal configuration of the multifunction device 100 will be described. FIG. 4 is a perspective view illustrating a part of the internal configuration of the multifunction peripheral 100.

  As shown in FIG. 4, the multifunction peripheral 100 further includes a bottom plate 6 that forms the bottom surface of the scanner 104, and a side plate 7 that is arranged in parallel to the back surface of the main body 101. Both the bottom plate 6 and the side plate 7 are metal plate members. The bottom plate 6 and the side plate 7 are arranged so as to be perpendicular to each other with a gap G therebetween. A substrate unit 1, particularly a substrate fixing sheet metal 3, is fixed on the bottom plate 6. A clock generation board 8 is fixed on the side plate 7. Assuming that one unit including the sheet metal and the wiring board fixed thereto is a substrate unit, a new substrate unit 12 is formed by the bottom plate 6 and the substrate unit 1, and a separate substrate is formed by the side plate 7 and the clock generation substrate 8. It can be said that the unit 13 is configured.

  As shown in FIG. 4, a clock source 81 is mounted on the clock generation board 8. The clock source 81 includes a clock generation circuit that generates a clock signal.

  The multi-function device 100 further includes a cable 91 that connects the clock generation board 8 and the image sensor mounting board 2.

  The cable 91 is an example of wiring. In the cable 91, the clock line 22 of the image sensor mounting board 2 extends so as to be connected to a clock line 82 described later of the clock generation board 8. Further, a later-described ground 83 a of the clock generation board 8 extends in the cable 91 so as to be connected to the ground 23 a of the imaging element mounting board 2.

  The clock line 22 and the ground 83a in the cable 91 are preferably arranged so as to be as parallel as possible to each other and as short as possible. For example, the cable 91 is preferably arranged so as to connect the imaging element mounting substrate 2 and the clock generation substrate 8 with the shortest distance. By arranging in this way, the loop area described later is reduced.

(1-4) Board unit 13
The board unit 13, particularly the clock generation board 8 included therein, will be described with reference to the cross-sectional view of FIG.

  As shown in FIG. 5, the clock generation substrate 8 includes a core 811, a first pattern layer 801 formed on the first surface 811 a of the core 811, and a second pattern layer formed on the second surface 811 b of the core 811. 802, a resist layer 84 covering each of the first pattern layer 801 and the second pattern layer 802 is provided. The clock generation board 8 is fixed with the first surface 811 a facing the side plate 7. For fixing the clock generation board 8, screws can be used as in the case of fixing the image sensor mounting board 2.

  The first pattern layer 801 is all a ground 83a. A clock line 82 connected to the clock source 81 is formed in the second pattern layer 802. In addition to the clock line 82, other wiring such as the ground 83b is also formed in the second pattern layer 802.

  In this way, the clock line 82 is not formed on the first surface 811a, but only on the second surface 811b. The ground 83a is formed over substantially the entire first surface 811a. As a result, the ground 83a on the second surface 811b is disposed so as to overlap the ground 23a on the first surface 82a with the core 811 interposed therebetween. In other words, the ground 23 a on the first surface 811 a is located between the clock line 82 and the substrate fixing sheet metal 3. That is, the line segment connecting the clock line 82 and the side plate 7 with the shortest distance (the line segment extending perpendicularly from the clock line 23a to the surface of the side plate 7) is blocked by the ground 83a. In particular, as shown in FIG. 5, the distance L81 from the clock line 82 to the ground 83a and the distance L82 from the clock line 82 to the side plate 7 are L81 <L82.

  That is, the arrangement of the clock line 82 and the ground 83a on the clock generation board 8 is substantially the same as the arrangement of the clock line 22 and the ground 23a on the imaging element mounting board 2. By arranging the ground 83a in this way, a return current caused by a clock signal flowing through the clock line 82 can easily flow through the ground 83a, and the return current can be prevented from flowing into the side plate 7. The return current will be described in detail later.

(1-5) Loop Current With reference to FIG. 6, the loop current flowing in the multi-function device 100 will be described. FIG. 6 is a drawing schematically showing the flow of loop current formed in the multi-function device 100. Since FIG. 6 is a schematic drawing, the orientation and arrangement of each member such as the substrate fixing sheet metal 3, the bottom plate 6, and the side plate 7 are changed from actual ones for convenience of explanation.

  As shown by a dotted arrow in FIG. 6, the clock signal generated by the clock generation board 8 is transmitted to the image sensor mounting board 2 through the clock line 82 and the cable 91 of the clock generation board 8.

  As indicated by a dotted arrow in FIG. 6, in the image pickup device mounting substrate 2, as described above, the return current generated by transmitting the clock signal through the clock line 22 flows in the ground 23a. The return current is transmitted to the clock generation board 8 through the cable 91. This return current flows through the ground 83a in the clock generation board 8.

  In this way, a loop current flows between the two substrate units 12 and 13 as shown by the dotted arrows in FIG. That is, the loop antenna is formed by the clock line 82, the cable 91, the clock line 22, the ground 23a, and the ground 83a.

  However, since the return current passes through the grounds 23a and 83a and does not pass through the sheet metals 3, 6, and 7, the loop area (the area surrounded by the dotted arrow in FIG. 6) can be kept small. Therefore, the amount of electromagnetic radiation is also reduced.

  Note that when all the clock lines are arranged on one side of the wiring board as in the imaging device mounting board 2 and the clock generation board 8, via holes are not used for wiring of the clock lines. When providing clock lines on both sides of the substrate, via holes are provided in the substrate, and the clock lines are passed through the via holes. However, passing the clock line through the via hole in this manner may increase electromagnetic radiation. Therefore, also from this viewpoint, the configuration of the present embodiment is preferable. In the wiring board, when crossing of signal lines occurs on the surface where the clock line is arranged, wiring on one side is enabled by using a jumper resistor.

[2] Other Embodiments (2-1) In the first embodiment, the board units 1, 12, and 13 are given as examples of the board unit. That is, the substrate fixing sheet metal 3, the bottom plate 6, and the side plate 7 are examples of sheet metal, and the image sensor mounting substrate 2 and the clock generation substrate 8 are examples of wiring boards.

  However, the substrate unit only needs to include a sheet metal and a wiring substrate fixed thereto, and the other configurations are not limited. For example, in the board unit, two or more wiring boards may be fixed on one sheet metal, or a plurality of (for example, three or more) sheet metals may be combined. In addition to the sheet metal and the wiring board, another configuration may be provided, and the method for fixing the wiring board to the sheet metal is not particularly limited.

  (2-2) The clock lines 22 and 82 are merely examples of high-frequency signal lines provided on the wiring board. The high-frequency signal line is a wiring that transmits a high-frequency signal. “High frequency” is a term used when the lower limit of the frequency of a signal is, for example, 1 MHz or more, or several MHz or more, more specifically 5 MHz or more, and more specifically 10 MHz or more.

  The high-frequency signal line is formed on the second surface opposite to the first surface facing the sheet metal on the wiring board, and is disposed so as to overlap the ground of the first surface, thereby Since the ground is disposed between the sheet metal and the return current, the return current easily flows in the ground and does not easily flow in the sheet metal.

  One wiring board may include both a clock line and other high-frequency signal lines as high-frequency signal lines.

  If all the high-frequency signal lines in one wiring board are formed on the second surface and all the high-frequency signal lines are arranged so as to overlap the ground, the effect of suppressing electromagnetic radiation is high. However, even when only a part of the high-frequency signal line overlaps the ground on the second surface, an effect of suppressing electromagnetic wave radiation can be expected. That is, a part of the high-frequency signal line is formed on the first surface, or a part of the high-frequency signal line formed on the second surface is shifted from the ground (so as not to overlap the ground). It is permissible. Of the high-frequency signal lines in one wiring board, the ratio of the arrangement is preferably 50% or more, more preferably 70% or more, further preferably 80% or more, more preferably 90% or more, 95 % Or more is particularly preferable.

  (2-3) The ground is arranged to cover the clock line on the second surface on the first surface, and more preferably to cover the periphery of the clock line on the second surface. Is preferable to prevent the return current from flowing.

  In the first embodiment, the grounds 23a and 83a cover the entire area where the wiring patterns on the first surfaces 21a and 811a can be formed. Thus, the ground can cover the first surface widely, so that the return current can be effectively prevented from flowing through the sheet metal.

  However, the ground may be formed only in a part of the pattern formation region on the first surface.

  (2-4) Further, wiring other than the ground may be provided on the first surface of the substrate. Examples of the wiring include a power line and a low frequency signal line. The low frequency signal line is a wiring for transmitting a low frequency signal. Low frequency is a term used when the upper limit of the frequency of a signal is, for example, less than 1 MHz or several hundred kHz or less.

  For example, the horizontal synchronizing signal of the image sensor has a frequency of about several hundred kHz and can be said to be a low frequency signal. The horizontal synchronization signal is used to generate an image sensor driving signal in a timing generator (not shown) together with the vertical synchronization signal and the clock signal.

  FIG. 7 shows a specific form. As shown in FIG. 7, the substrate unit 14 of the present embodiment has the same configuration as that of the image sensor mounting substrate 2 of the first embodiment, except that a wiring substrate 200 is provided instead of the image sensor mounting substrate 2. Therefore, members having the same functions as those already described are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 7, the wiring board 200 has the same configuration as that of the imaging element mounting board 2 except that the power supply line 231 and the low frequency signal line 232 are formed on the first surface 21a. In the wiring board 200, like the imaging device mounting board 2 of the first embodiment, the clock line 22 on the second surface 21b is arranged so as to overlap the ground 23a on the first surface 21a. As shown in FIG. 7, the ground 23 a is preferably provided so as to overlap the clock line 22 and the surrounding area. That is, by providing a wider area than the clock line 22, it is possible to more effectively prevent the return current from flowing through the substrate fixing sheet metal 3.

  The power supply line and the low frequency signal line may be formed not only on the first surface 21a but also on the second surface 21b.

(2-5) In the first embodiment, the image pickup device 4 and the clock source 81 are exemplified as the elements arranged on the wiring board. However, the elements and circuits arranged on the wiring board are limited to this. Is not to be done. A plurality of elements and circuits may be provided on one wiring board. In particular, since a wiring board on which a component that dislikes position variation is often fixed on a sheet metal, the present invention can be suitably used. Examples of such components include various sensors, particularly optical sensors, and also a laser light source for drawing in an electrophotographic image forming apparatus. (2-6) The board unit may be incorporated in the wiring unit. . The wiring unit includes two or more board units and wirings for connecting the high-frequency signal lines and the grounds of these board units. The configuration shown in FIG. 4 includes substrate units 1 (12) and 13 as an example of the configuration of the wiring unit, and includes a cable 91 that is an example of the first wiring and the second wiring.

  In FIG. 4, the sheet metal is separated between the substrate units 12 and 13, but in two or more substrate units, the sheet metal may be connected or the sheet metal may be continuous. That is, when two wiring boards are arranged on one sheet metal and the wiring boards are connected by wiring, the sheet metal and the two wiring boards may be considered as two board units. .

  (2-7) In the first embodiment, in both the substrate unit 1 (12) and the substrate unit 13 connected thereto, the clock line is arranged on the surface opposite to the surface facing the sheet metal, and the sheet metal and the clock line are arranged. The ground is arranged between the two. That is, both of the two substrate units connected to each other have the configuration described in (2-1) to (2-4) above.

  If the plurality of substrates connected to each other have such a configuration as in the first embodiment, the effect of reducing the amount of electromagnetic wave radiation is high. However, if any one of a plurality of substrates connected to each other has such a configuration, it is expected that the loop area will be reduced and consequently the amount of electromagnetic radiation will be reduced.

  (2-8) FIG. 8 shows a substrate unit 15 according to still another embodiment. As illustrated in FIG. 8, the imaging element 4 may be provided on the first surface 21 a side on the imaging element mounting substrate 2. In this case, the substrate fixing sheet metal 3 is provided with an opening 31 large enough to allow the imaging element 4 to pass therethrough. When the image pickup device mounting substrate 2 is fixed on the substrate fixing sheet metal 3 with the screws 5, the image pickup device 4 is fitted into the opening 31, so that the image pickup device 4 can receive light from the outside and image pickup is possible.

  (2-9) As an embodiment of the present invention, the MFP 100 including the scanner 104 has been described in the first embodiment, but the present invention can be applied to various other electric devices.

  (2-10) Techniques obtained by combining the embodiments described above are also included in the embodiments of the present invention.

[3] Comparative Embodiment FIG. 9 shows a cross-sectional view of a substrate unit 500 according to the comparative embodiment. As shown in FIG. 9, the board unit 500 of this comparative embodiment has the same configuration as that of the board unit 1 of the first embodiment except that a wiring board 502 is provided instead of the image sensor mounting board 2. Therefore, members having the same functions as those already described may be denoted by the same reference numerals and description thereof may be omitted.

  As shown in FIG. 9, in the wiring board 502, the clock line 22 is disposed on the first surface 21 a of the core 21. Therefore, although the ground 23 is formed on the second surface 21b, no ground is formed between the clock line 22 on the first surface 21a and the substrate fixing sheet metal 3, and the clock line 22 is It is arranged close to the substrate fixing sheet metal 3. Therefore, the return current generated when the clock signal flows through the clock line 22 easily flows through the substrate fixing sheet metal 3. That is, in the substrate unit 500 of this comparative embodiment, the clock line 22 and the substrate fixing sheet metal 3 are configured to easily form a loop antenna. Specifically, in this comparative embodiment, the distance L501 from the clock line 22 on the first surface 21a to the ground 23 on the second surface 21b and the distance from the clock line 22 on the first surface 21a to the substrate fixing sheet metal 3 Since L501 is L501> L502, the return current is more likely to flow to the substrate fixing sheet metal 3 than the ground 23 of the second surface 21b.

  FIG. 10 schematically shows a loop antenna formed when the substrate unit 500 is applied to a multifunction machine instead of the substrate unit 1 of the first embodiment. Except for the substrate units 12 and 13 being replaced by the substrate units 512 and 513, the configuration of the present embodiment is the same as that of the MFP 100 of the first embodiment. Therefore, members having the same functions as those already described with reference to FIGS. 3 to 6 and the like may be denoted by the same reference numerals and description thereof may be omitted.

  The board unit 512 has the same configuration as that of the board unit 12 of the first embodiment except that the wiring board 502 is provided instead of the imaging element mounting board 2.

  The board unit 513 has the same configuration as that of the board unit 12 of the first embodiment, except that a clock generation board 508 is provided instead of the clock generation board 8. In the clock generation board 508, the clock line connected to the clock source is arranged on the first surface facing the side plate 7 like the wiring board 502 shown in FIG.

  As shown in FIG. 10, the clock signal reaches from the clock generation board 508 to the wiring board 502 via the cable 91 as in the first embodiment (FIG. 6). Since the return current generated at this time flows through the substrate fixing sheet metal 3 in the substrate unit 500 as described above, the return current flows through the substrate fixing sheet metal 3 and further through the bottom plate 6 as shown in FIG.

  As described with reference to FIG. 4, due to the presence of the gap G, the bottom plate 6 and the side plate 7 are not in direct contact with each other. However, the bottom plate 6 and the side plate 7 are electrically connected via a conductive member such as another sheet metal. Therefore, as shown in FIG. 10, the return current reaches the side plate 7 from the bottom plate 6 through various conductive members. That is, the loop antenna is formed by the substrate units 512 and 513 and other conductive members. As indicated by the dotted line in FIG. 10, the return current is largely bypassed as compared with the first embodiment (FIG. 6). The path through which the loop current formed in this way is as shown by a dotted line in FIG.

  As is clear when FIG. 6 and FIG. 10 are compared, the loop area in the comparative embodiment is larger than the loop area in the first embodiment. As a result, the amount of radiated electromagnetic waves also increases.

  In particular, as described with reference to FIG. 4, the distance between the cable 91 and the bottom plate 6 is not uniform, and there is a wide portion such as a distance L3. Therefore, the loop area is further increased as compared with the first embodiment in which the clock signal and the return current flow through the cable 91.

  In FIG. 10, the bottom plate 6 and the side plate 7 are drawn in a flat shape, but in reality, the bottom plate 6 and the side plate 7 have complicated shapes such as being bent or having unevenness according to the arrangement of the members in the multifunction machine. ing. Therefore, the loop area is very large compared to the above-described embodiments.

  The substrate unit of the present invention can be widely used in imaging devices such as scanners and digital cameras, multifunction devices, and other electrical devices.

1, 12 to 15 Substrate unit 2 Imaging device mounting substrate (an example of a wiring substrate)
21, 81 core (example of substrate)
21a First surface 21b Second surface 22, 82 Clock line (an example of a high-frequency signal line)
23a, 23b, 83a, 83b Ground 3 substrate fixing sheet metal (an example of sheet metal)
4 Image sensor 5 Screw 6 Bottom plate (an example of sheet metal)
7 Side plate (an example of sheet metal)
8 Clock generation board (an example of wiring board)
91 cable (first and second wiring)

Claims (6)

Sheet metal,
The substrate fixed so that the first surface faces the sheet metal, the ground disposed on the first surface, and the second surface of the substrate are disposed so as to overlap the ground on the first surface. A wiring board comprising a high-frequency signal line;
A substrate unit comprising: 2. The board unit according to claim 1, wherein the high-frequency signal line is a clock line. The board unit according to claim 1, further comprising an image pickup device mounted on the wiring board. While comprising two or more substrate units according to any one of claims 1 to 3,
A first wiring connecting the high-frequency signal line of a certain substrate unit and the high-frequency signal line of another substrate unit;
A second wiring connecting the grant of the certain board unit and the ground of the other board unit;
A wiring unit further comprising: The certain board unit further includes a clock source disposed on the wiring board,
5. The wiring unit according to claim 4, wherein the high-frequency signal line of the certain board unit is a clock line connected to the clock source. The other board unit further includes an image sensor mounted on the wiring board,
The wiring unit according to claim 4 or 5, wherein the high-frequency signal line of the other board unit is connected to the imaging element.

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