Circuit board and image forming apparatus

Abstract

To provide a circuit board that can prevent an increase in the temperature of electronic components.SOLUTION: A circuit board 300 comprises: a first mounting surface 401a that is provided with a first mounting area 421 for mounting a first motor driver IC 405 having at least a first function; and a second mounting surface 404a that is provided with a second mounting area 422 for mounting a second motor driver IC 406 having a value of resistance during operation lower than the first motor driver IC 405 and having at least the first function.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a circuit board on which electronic components are mounted, and an image forming apparatus such as a printer, a copier, or a multifunction peripheral having such a circuit board.

Background Art

[0002] An image forming apparatus includes a plurality of circuit boards for controlling a plurality of actuators for image formation. The control circuit boards include a circuit board having a function of performing image formation control, a circuit board having a function of paper conveyance control, and the like. On each control circuit board, a plurality of electronic components such as an electronic component for performing logical operations, an electronic component for performing drive control, and an electronic component for generating a power supply voltage are mounted according to the function to be realized. The electronic components on the circuit board are connected by wirings such as printed wirings. Each electronic component constitutes an electronic component component that realizes a predetermined function including peripheral electronic components. For example, an electronic component component is constituted by a semiconductor device such as an IC (Integrated Circuit) and peripheral components such as a resistor, a capacitor, and an inductor connected to input / output terminals of the semiconductor device.

[0003] An image forming apparatus prints an image on a sheet through a plurality of steps such as sheet conveyance, image formation, image transfer to the sheet, and image fixing on the sheet. Therefore, the image forming apparatus needs to control various actuators such as an optical sensor, a temperature sensor, a motor, and a solenoid. A control circuit board mounted on the image forming apparatus has a plurality of electronic components mounted thereon for actuator control. For example, a circuit board for driving a motor has a semiconductor device (motor driver IC) for generating a drive signal for the motor based on a control signal input from a controller in order to appropriately control the motor (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventor has devised to provide mounting areas for mounting electronic components on both sides of a substrate. However, in the prior art, sufficient consideration has not been given to heat dissipation when providing mounting areas on both sides of the substrate. Electronic components mounted on the surface with low heat dissipation have a high risk of thermal shutdown and malfunction.

[0006] In view of the above problems, the main object of the present invention is to provide a circuit board capable of reducing or suppressing the temperature rise of electronic components.

Means for Solving the Problems

[0007] The circuit board of the present invention includes a first mounting surface provided with a first mounting area for mounting a first electronic component having at least a first function, and a second mounting surface provided with a second mounting area for mounting a second electronic component having a lower resistance value during operation than the first electronic component and having at least the first function. The image forming apparatus of the present invention is an image forming apparatus including a circuit board and a support member for supporting the circuit board. The circuit board includes a first mounting area for mounting a first electronic component having at least a first function, and a second mounting area for mounting a second electronic component having a lower resistance value during operation than the first electronic component and having at least the first function. The first mounting area is provided on a first mounting surface of the circuit board, the second mounting area is provided on a second mounting surface of the circuit board different from the first mounting surface, and the circuit board is supported by the support member such that the second mounting surface faces the support member.

Effects of the Invention

[0008] According to the present invention, it is possible to suppress the temperature rise of electronic components and suppress the occurrence of malfunction.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The configuration and circuit of the apparatus described in this embodiment are examples for explaining the proposed content and are not limited to the described content.

[0011] (Configuration of the image forming apparatus) FIG. 1 is a system configuration diagram of an image forming apparatus having the circuit board of this embodiment. Unless otherwise specified, it goes without saying that the image forming apparatus 100 may be a system composed of a plurality of devices connected via a network as long as the functions of the image forming apparatus 100 are executed.

[0012] The image forming apparatus 100 of this embodiment is communicably connected to a host computer 101 via a network 105. The network 105 is composed of a communication line such as a LAN (Local Area Network), WAN (Wide Area Network), or public line. The image forming apparatus 100 and the host computer 101 may be respectively connected to the network 105 in plurality. The host computer 101 generates a print job based on input information from a user acquired by an input device (not shown) and transmits the generated print job to the image forming apparatus 100 via the network 105.

[0013] The image forming apparatus 100 includes a controller board 110, a storage 115, a paper feeding unit 140, a printer engine 150, and an operation panel 180. The controller board 110, the storage 115, the paper feeding unit 140, the printer engine 150, and the operation panel 180 are connected to be communicable with each other via a system bus 116.

[0014] The controller board 110 includes an I / O control unit 111, a ROM (Read Only Memory) 112, a RAM (Random Access Memory) 113, and a CPU (Central Processing Unit) 114. The I / O control unit 111, the ROM 112, the RAM 113, and the CPU 114 are electronic components mounted on a circuit board. The controller board 110 functions as the main control unit of the image forming apparatus 100, performs various data processes, and controls the operations of the entire image forming apparatus 100. Note that the circuit board is, for example, a printed wiring board on which printed wiring is formed.

[0015] The I / O control unit 111 controls communication with external devices such as the host computer 101 via the network 105. The CPU 114 controls operations such as image forming processes by the image forming apparatus 100 by executing computer programs stored in the ROM 112 and the storage 115. The RAM 113 provides a work area when the CPU 114 executes processes and stores temporary data and the like. The storage 115 stores large-capacity data such as image data and print data temporarily or long-term. For example, the storage 115 stores image data for generating adjustment images for adjusting image forming conditions. The storage 115 is a large-capacity storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive). Computer programs such as a startup program, a control program, and an operating system executed by the CPU 114 are stored in the ROM 112 and the storage 115.

[0016] The operation panel 180 is a user interface having an input interface and an output interface. The input interface is, for example, a key button, a touch panel, or the like. The output interface is a display, a speaker, or the like. The operation panel 180 receives instructions and the like according to user operations and inputs them to the CPU 114. The CPU 114 controls the operation of the image forming apparatus 100 according to the instructions. Also, the operation panel 180 displays the state of the image forming apparatus 100 and various setting screens according to instructions from the CPU 114.

[0017] The paper feeding unit 140 includes a paper feeding device composed of one or more paper feeding stages and the entire conveying unit that conveys the paper from the paper feeding stage to the paper discharging unit. The paper feeding unit 140 feeds the paper one by one from the paper feeding stage according to an instruction from the CPU 114.

[0018] The printer engine 150 includes an image forming unit 152, a printing position control unit 153, an image position detection unit 154, a fixing unit 260, and an image reading unit 290. The image forming unit 152 forms an image (toner image) on the paper fed by the paper feeding unit 140. The fixing unit 260 fixes the image (toner image) on the paper. The image reading unit 290 reads the adjustment image printed on the paper. The image position detection unit 154 detects the position of the image printed on the paper based on the reading result of the adjustment image by the image reading unit 290. The printing position control unit 153 controls the position of the image to be printed on the paper based on the position of the image detected by the image position detection unit 154.

[0019] FIG. 2 is a configuration diagram of the image forming apparatus 100. The image forming apparatus 100 includes an operation panel 180 at the upper part of the housing 201. Inside the housing 201, the controller board 110, the storage 115, the paper feeding unit 140, and the printer engine 150 shown in FIG. 1 are provided. The printer engine 150 includes each mechanism constituting the engine unit and an engine control unit that controls the processing by each mechanism. Each mechanism constituting the engine unit includes, for example, an optical processing mechanism for forming an electrostatic latent image, visualizing the electrostatic latent image, and transferring the visualized image to the paper S, and a fixing processing mechanism for fixing the toner image transferred to the paper S.

[0020] The image forming unit 152 (see FIG. 1) of the printer engine 150 corresponds to an optical processing mechanism and includes a Y station 220, an M station 221, a C station 222, a K station 223, an intermediate transfer belt 252, and a secondary transfer outer roller 251. The Y station 220, the M station 221, the C station 222, and the K station 223 have the same configuration and only differ in the color of the image to be formed. The Y station 220 forms a yellow image. The M station 221 forms a magenta image. The C station 222 forms a cyan image. The K station 223 forms a black image. Here, the configuration of the Y station 220 will be described, and the descriptions of the configurations of the M station 221, the C station 222, and the K station 223 will be omitted.

[0021] The Y station 220 includes a photosensitive drum 205, a charger 211, an exposure device 207, and a developing device 212. The photosensitive drum 205 is a drum-shaped photoreceptor having a photosensitive layer on its surface. The charger 211 uniformly charges the surface of the photosensitive drum 205 that rotates about the drum axis. The exposure device 207 scans the surface of the charged photosensitive drum 205 with modulated laser light according to the image data.

[0022] The exposure device 207 includes a laser driver that controls the emission of a semiconductor laser (not shown) according to the image data obtained from the controller board 110 (CPU 114), a rotating polygon mirror 208, and a reflecting mirror 209. The laser light emitted from the semiconductor laser moves in the main scanning direction according to the rotation of the rotating polygon mirror 208 and is guided to the surface of the photosensitive drum 205 by the reflecting mirror 209. As a result, the laser light scans the surface of the photosensitive drum 205 in the drum axis direction. When the surface of the photosensitive drum 205 is exposed, an electrostatic latent image is formed.

[0023] The developing device 212 visualizes the electrostatic latent image with the toner of the corresponding color to form a toner image on the surface of the photosensitive drum 205. A yellow toner image is formed on the photosensitive drum 205 of the Y station 220. A magenta toner image is formed on the photosensitive drum 205 of the M station 221. A cyan toner image is formed on the photosensitive drum 205 of the C station 222. A black toner image is formed on the photosensitive drum 205 of the K station 223.

[0024] The intermediate transfer belt 252 is an endless belt wound around a plurality of rollers such as the secondary transfer inner roller 240. The intermediate transfer belt 252 rotates in the clockwise direction in the figure. The toner images of each color formed on each photosensitive drum 205 are transferred so as to overlap on the rotating intermediate transfer belt 252. The transfer of the toner image from the photosensitive drum 205 to the intermediate transfer belt 252 is performed by applying a bias voltage of the opposite polarity to the toner image to the intermediate transfer belt 252. Thereby, the intermediate transfer belt 252 carries a full-color toner image. The intermediate transfer belt 252 rotates to convey the carried toner image to the secondary transfer unit composed of the secondary transfer inner roller 240 and the secondary transfer outer roller 251.

[0025] The paper feeding unit 140 corresponds to the paper feeding mechanism of the paper S, and includes a storage bin 210 which is a paper feeding stage for storing the paper S, a conveyance path, conveyance rollers, and the like. The paper feeding unit 140 conveys the paper S from the storage bin 210 to the secondary transfer unit one by one. The secondary transfer unit sandwiches and conveys the intermediate transfer belt 252 and the paper S by the secondary transfer inner roller 240 and the secondary transfer outer roller 251. At this time, by applying a bias voltage of the opposite polarity to the toner image to the secondary transfer outer roller 251, the toner image is transferred from the intermediate transfer belt 252 to the paper S.

[0026] The sheet S onto which the toner image has been transferred is conveyed to a fixing unit 260 which is a fixing processing mechanism. The fixing unit 260 includes a fixing roller 261 having a heat source inside, a pressure roller 262 biased toward the fixing roller 261 side, and a circuit board 300 that controls the fixing process by the fixing unit 260. The fixing unit 260 fixes the toner image onto the sheet S by sandwiching and conveying the sheet S onto which the toner image has been transferred between the fixing roller 261 and the pressure roller 262. At this time, the fixing roller 261 heats and melts the toner image and presses the sheet S between it and the pressure roller 262.

[0027] As described above, an image is printed on the sheet S. In the case of double-sided printing, the sheet S with an image printed on the first side (front surface) is conveyed again to the secondary transfer unit via the reverse path 270. By being conveyed to the secondary transfer unit via the reverse path 270, the printed surface of the image on the sheet S is reversed. The sheet S with the printed surface of the image reversed has an image printed on the second side (back surface) different from the first side by the secondary transfer unit and the fixing unit 260.

[0028] The sheet S on which the image has been printed passes through an image reading unit 290 provided on the downstream side of the fixing unit 260 in the sheet conveyance direction and is discharged outside the image forming apparatus 100. The image reading unit 290 is used to read the adjustment image when the image formed on the sheet S is an adjustment image for image forming conditions.

[0029] (Circuit board) In order to perform the image forming process as described above, the image forming apparatus 100 includes various types of actuators (loads) such as motors and sensors inside. The actuators are connected to a circuit board on which control electronic components are mounted. Each electronic component mounted on the circuit board is connected by a conducting wire. The circuit board of the present embodiment is, for example, a printed wiring board using printed wiring for the conducting wire.

[0030] The electronic component controls the operation of the actuator. For this purpose, a large number of circuit boards are provided in the image forming apparatus 100 corresponding to a plurality of actuators. One or more actuators are controlled by a single circuit board. The circuit board is controlled by the CPU 114 of the controller board 110. Note that the controller board 110 on which the CPU 114 is mounted is also an example of a circuit board.

[0031] FIG. 3 is a configuration diagram of a circuit board 300 provided in the fixing unit 260. A plurality of motors 309 to 311 in the fixing unit 260 and a plurality of sensors 312 to 314 in the fixing unit 260 are electrically connected to the circuit board 300. The motors 309 to 311 are actuators (loads) whose operations are controlled by the circuit board 300.

[0032] The motor 309 is a drive source for driving the fixing roller 261 which is a rotating body. The motor 310 is a drive source for urging the pressure roller 262 toward the fixing roller 261. The motor 311 is a drive source for driving a roller which is a rotating body for conveying the sheet S after the fixing process to the subsequent stage. The sensor 312 is a detector for detecting the sheet S conveyed to the fixing unit 260. The sensor 313 is a temperature detector for detecting the temperature of the fixing roller 261. The sensor 314 is a detector for detecting the sheet S after the fixing process.

[0033] The circuit board 300 realizes various functions by a plurality of electronic components. In the example of FIG. 3, it includes an AC-DC converter 302 used for generating a predetermined DC voltage from an AC voltage and a DC-DC converter 303 for converting the voltage value of the DC voltage. Further, the circuit board 300 includes a CPU 304, an ASIC (Application Specific Integrated Circuit) 305, and motor driver ICs 306 to 308 used for controlling the actuator. The circuit board 300 has a plurality of semiconductor devices (hereinafter referred to as "ICs") as described above and peripheral electronic components corresponding to the ICs mounted thereon as electronic components.

[0034] The AC-DC converter 302 generates a DC power supply voltage having a predetermined voltage value based on the AC power supplied from the commercial power supply 301. The DC-DC converter 303 generates a DC power supply voltage having a voltage value different from that of the power supply voltage based on the power supply voltage supplied from the AC-DC converter 302. For example, the AC-DC converter 302 generates a DC voltage of 12 [V], and the DC-DC converter 303 generates a DC voltage of 5 [V]. The power supply voltage generated by the DC-DC converter 303 is supplied to the CPU 304, the ASIC 305, etc. The CPU 304 and the ASIC 305 operate with the power supply voltage supplied from the DC-DC converter 303. The power supply voltage output from the AC-DC converter 302 is also supplied to electronic components and motors 309 to 311 that operate at a voltage value different from that of the CPU 304 and the ASIC 305.

[0035] The CPU 304 is connected to the motor driver ICs 306 to 308 and the respective sensors 312 to 314 via the ASIC 305. The CPU 304 acquires detection results from each of the sensors 312 to 314, and detects the state of the fixing unit 260 based on the detection results. The CPU 304 controls the driving of each of the motors 309 to 311 by controlling each of the motor driver ICs 306 to 308 via the ASIC 305 according to the detected state of the fixing unit 260. In this way, the CPU 304 and the ASIC 305 control the operation of the fixing unit 260.

[0036] Since the circuit board 300 is provided in the fixing unit 260, it controls the operation of the fixing unit 260. Similarly, other circuit boards provided in the image forming apparatus 100 also control the operations of the corresponding components. Each circuit board (including the circuit board 300 and other circuit boards) in the image forming apparatus 100 is communicably connected to the controller board 110. Communication is possible between each circuit board via the controller board 110. Each circuit board appropriately controls the components in the image forming apparatus 100 while sharing information regarding the detection results of each sensor and the control state of the load with each other.

[0037] A large number of electronic components are mounted on a circuit board. However, due to various reasons such as distribution, environment, accidents, etc., there may be a situation where it is difficult to procure at least some of the electronic components. In order to deal with the situation where difficult-to-procure electronic components occur, electronic components with the same or similar shapes and specifications as each regular electronic component may be prepared as substitutes. If there are electronic components that cannot be procured, the production of the circuit board 300 is continued by mounting the substitute for the electronic component on the circuit board.

[0038] However, for example, in the circuit board 300, specific ICs such as the IC of the DCDC converter 303 and the motor driver ICs 306, 307, 308, etc. may require specific peripheral components during use. Also, the number of terminals, arrangement, array, or electrical specifications of the ICs may be different, and there may be no replaceable ICs. In such a case, in order to deal with the situation where it is difficult to procure each IC, another electronic component component capable of realizing the same function as the electronic component component composed of the IC and the peripheral components is prepared. These electronic component components are exclusively mounted on the circuit board. With this countermeasure method, it is possible to continue the production of the circuit board 300 in order to mount an IC that can be procured according to the availability of the mounted components.

[0039] In this way, when it is difficult to procure regular electronic components, substitutes having the same function are used. The regular product and the substitute are exclusively mounted. Therefore, the circuit board 300 needs to prepare respective mounting areas for mounting the regular product and the substitute. This means an increase in the mounting area of the circuit board 300. Also, for example, when mounting a regular product, the mounting area for the substitute becomes a wasted space where nothing is mounted.

[0040] On the other hand, a configuration has been proposed in which the regular product and the substitute are exclusively mounted on the component side (the first side) and the solder side (the second side) of the circuit board 300. However, in this configuration, due to the difference in heat dissipation between the first side and the second side of the circuit board 300, the possibility of malfunction such as thermal shutdown or failure due to the temperature rise of the electronic components mounted on one side is higher than that of the electronic components mounted on the other side.

[0041] For example, when the circuit board 300 is mounted on the housing 201 of the image forming apparatus 100, the second surface side is often mounted facing the housing 201 side. In this case, the space between the housing 201 and the second surface side of the circuit board 300 becomes narrow, and the heat dissipation property of the second surface side becomes lower than that of the first surface side. Also, even when a fan is used, air may be blown to the first surface side but not to the second surface side. Due to such reasons, the possibility of malfunction due to temperature rise of the electronic components or electronic component parts mounted on the second surface is higher than that of the electronic components or electronic component parts mounted on the first surface.

[0042] Therefore, in the present embodiment, for example, a configuration is proposed to reduce the risk of malfunction due to temperature rise of the electronic components or electronic component parts mounted on the second surface with the above configuration.

[0043] FIG. 4 is an explanatory diagram of the configuration of the circuit board 300 when the motor driver is mounted. FIG. 4 is a view of the circuit board 300 seen from the cross-sectional direction. The circuit board 300 of the present embodiment has a multilayer structure. Here, a circuit board 300 having a four-layer structure of a first layer 401, a second layer 402, a third layer 403, and a fourth layer 404 will be described, but the circuit board 300 may have any number of layers as long as it is multilayer.

[0044] The multilayer circuit board 300 is a double-sided reflow type, and electronic components can be mounted on one of the outermost layers (the first layer 401) and the other layer (the fourth layer 404) as mounting surfaces. The genuine product and the replacement product are exclusively mounted on the first mounting surface 401a of the first layer 401 which is the first surface (front surface) and the second mounting surface 404a of the fourth layer 404 which is the second surface (back surface). The second layer 402 is a power supply layer and includes a load driving power supply wiring for supplying power to the electronic components or electronic component parts, a logic power supply wiring for supplying a low voltage to the CPU 304, the ASIC 305, etc. The third layer 403 is a ground layer and is connected to the ground patterns of the first layer and the fourth layer via vias.

[0045] On the first mounting surface 401a of the first layer 401, a first mounting area 421 where the first motor driver IC 405 can be mounted is provided. On the second mounting surface 404a of the fourth layer 404, a second mounting area 422 where the second motor driver IC 406 can be mounted is provided. The first motor driver IC 405 and the second motor driver IC 406 have the same functions. The first mounting area 421 and the second mounting area 422 are provided at positions facing each other with the circuit board 300 interposed therebetween. That is, when viewed from the normal direction of the first mounting area 421, the first mounting area 421 and the second mounting area 422 overlap each other.

[0046] The first motor driver IC 405 includes a first IC chip 405a inside. On the back surface of the first motor driver IC 405, a first die pad 405b for conducting heat to the circuit board 300 is provided. The second motor driver IC 406 includes a second IC chip 406a inside. On the back surface of the second motor driver IC 406, a second die pad 406b for conducting heat to the circuit board 300 is provided.

[0047] When the first motor driver IC 405 is mounted, the first die pad 405b is soldered to the first mounting area 421. The heat of the first IC chip 405a is conducted to the first mounting area 421 through the first die pad 405b and diffused into the circuit board 300. When the second motor driver IC 406 is mounted, the second die pad 406b is soldered to the second mounting area 422. The heat of the second IC chip 406a is conducted to the second mounting area 422 through the second die pad 406b and diffused into the circuit board 300.

[0048] The leads of the first motor driver IC 405 are connected to the first output signal line 408. The leads of the second motor driver IC 406 are connected to the second output signal line 409. The first output signal line 408 and the second output signal line 409 are connected by a via 410 provided to penetrate the circuit board 300 from the first layer 401 to the fourth layer 404. The first output signal line 408 is connected to a connector 407 provided on the first mounting surface 401a.

[0049] The circuit board 300 is attached inside the housing 201 of the image forming apparatus 100 or inside the housing of the fixing unit 260. Here, an example of being attached inside the housing of the fixing unit 260 will be described. The circuit board 300 is fixedly attached to the sheet metal 411 such that the fourth layer 404 faces the sheet metal 411 side inside the housing of the fixing unit 260. The sheet metal 411 is an example of a support member that supports the circuit board 300. In such a configuration, the distance from the first mounting surface 401a of the first layer 401 to the surface of the sheet metal of the housing of the fixing unit 260 facing the normal direction of the first mounting surface 401a is larger than the distance from the second mounting surface 404a of the fourth layer 404 to the surface of the sheet metal 411. That is, the vertical space distance 413b of the first layer 401 is larger than the vertical space distance 413a of the fourth layer 404. A fan 412 is disposed on the first layer 401 side of the circuit board 300. The fan 412 cools the entire circuit board 300 by blowing air toward the first mounting region 421.

[0050] The second mounting surface 404a of the fourth layer 404 has a smaller space distance 413a compared to the first mounting surface 401a of the first layer 401, and there is less convection (forced convection when there is a fan 412, natural convection when there is no fan 412). Therefore, the second mounting surface 404a of the fourth layer has lower heat dissipation than the first mounting surface 401a of the first layer 401. For this reason, the first mounting surface 401a of the first layer 401 becomes the component surface, and a large number of electronic components such as the first motor driver IC 405, the connector 407, and other electronic components are mounted. The second mounting surface 404a of the fourth layer 404 becomes the solder surface, and a smaller number of electronic components (here, the second motor driver IC 406) are mounted compared to the component surface. That is, electronic components are mounted on the component surface such that the heat generation amount is larger than that of the solder surface.

[0051] Here, the resistance value α during the operation of the first motor driver IC405 is greater than the resistance value β during the operation of the second motor driver IC406. That is, the amount of heat generated during the operation of the first motor driver IC405 is greater than the amount of heat generated during the operation of the second motor driver IC406. Therefore, the first motor driver IC405 with a relatively large resistance value α is mounted on the first mounting surface 401a of the first layer 401 with relatively high heat dissipation. The second motor driver IC406 with a relatively small resistance value β is mounted on the second mounting surface 404a of the fourth layer 404 with relatively low heat dissipation.

[0052] In this way, the first motor driver IC405 and the second motor driver IC406 are exclusively mounted on the first mounting surface 401a of the first layer 401 and the second mounting surface 404a of the fourth layer 404 of the circuit board 300 according to their respective heat generation amounts. Therefore, the first motor driver IC405 and the second motor driver IC406 can suppress the possibility of malfunction such as thermal shutdown or failure due to temperature rise.

[0053] In this embodiment, the motor driver IC is described as an example of an electronic component, but the electronic component is not limited to this. The function of the electronic component is not limited as long as it is configured to be exclusively mounted on the front and back surfaces of the circuit board 300. For example, the electronic component may be a switching IC, a FET (Field effect transistor), etc. Also, each electronic component may be mounted simultaneously instead of exclusively, and this embodiment is still effective.

[0054] In the above example, the case where the first motor driver IC 405 and the second motor driver IC 406 are genuine products and alternative products (or alternative products and genuine products) has been described. However, the effects obtained by the present embodiment are not limited to such examples. For example, for a plurality of devices, the circuit board 300 may be designed as a common platform. At this time, in one model, a first electronic component having at least a first function is mounted on a first mounting surface, while in another model, a second electronic component having a different standard from the first electronic component but similarly having at least a first function is mounted on a second mounting surface. Even in such a case, the effects described in the present embodiment can be obtained.

Claims

1. A first mounting surface provided with a first mounting area for mounting a first electronic component having at least a first function; A second mounting surface provided with a second mounting area for mounting a second electronic component having a resistance value during operation lower than that of the first electronic component and having at least the first function, characterized in that it comprises: Circuit board.

2. The heat dissipation property of the first mounting surface is higher than that of the second mounting surface, characterized in that: The circuit board according to claim 1.

3. The circuit board is attached to a predetermined device, The distance between the surface of the device facing the first mounting surface is larger than the distance between the surface of the device facing the second mounting surface, characterized in that: The circuit board according to claim 2.

4. Further comprising a fan for blowing air onto the first mounting surface, characterized in that: The circuit board according to claim 2.

5. Comprising a via connecting the output signal lines of the first electronic component and the second electronic component, and the first electronic component and the second electronic component are mounted exclusively, characterized in that: The circuit board according to claim 1.

6. A connector to which the output signal line of the first electronic component is connected is provided on the first mounting surface, characterized in that: The circuit board according to claim 5.

7. The circuit board has a multilayer structure, the first mounting area is provided on one of the outermost layers, and the second mounting area is provided on the other of the outermost layers, characterized in that: The circuit board according to claim 1.

8. The circuit board according to claim 1, and A component that forms an image, which is controlled by either the first electronic component or the second electronic component mounted on the circuit board. The image forming apparatus is characterized by comprising the component. Image forming apparatus. **Claim 9** A circuit board, An image forming apparatus comprising a support member for supporting the circuit board, wherein the circuit board includes a first mounting area for mounting a first electronic component having at least a first function, and a second mounting area for mounting a second electronic component having at least the first function and having a lower resistance value during operation than the first electronic component. The first mounting area is provided on a first mounting surface of the circuit board. The second mounting area is provided on a second mounting surface of the circuit board different from the first mounting surface. The circuit board is supported by the support member such that the second mounting surface faces the support member. The image forming apparatus is characterized by this structure. Image forming apparatus. **Claim 10** The image forming apparatus according to claim 9, further comprising a fan for blowing air onto the first mounting surface. The image forming apparatus according to claim 9. **Claim 11** The image forming apparatus according to claim 9, comprising a via for connecting an output signal line of the first electronic component and an output signal line of the second electronic component, wherein the first electronic component and the second electronic component are mounted exclusively. The image forming apparatus according to claim 9. **Claim 12** The image forming apparatus according to claim 11, wherein a connector to which the output signal line of the first electronic component is connected is provided on the first mounting surface. The image forming apparatus according to claim 11. **Claim 13** The circuit board has a multilayer structure, the first mounting area is provided on one of the outermost layers, and the second mounting area is provided on the other of the outermost layers. The image forming apparatus according to claim 9 is characterized by this structure. The image forming apparatus according to claim 9.

Images