Circuit boards, image forming apparatus

Abstract

We provide circuit boards that can universally mount multiple electronic components with different specifications or different functions. [Solution] The circuit board 300 includes a front surface on which a motor driver IC 406 can be mounted, a back surface on which a motor driver IC 416 can be mounted, a first connection portion on the front surface to which the terminals of the motor driver IC 406 are connected, a current sensing resistor R12 on the front surface, a second connection portion on the back surface to which the terminals of the motor driver IC 416 are connected, a current sensing resistor R22 on the back surface, and a wiring pattern that connects the current sensing resistor R12 and the current sensing resistor R22 in parallel and electrically conducts with the first connection portion and the second connection portion, respectively.

Description

Technical Field

[0001] The present invention relates to a circuit board on which electronic components for operating components such as built-in actuators 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 generally includes a plurality of circuit boards. On the 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 functions to be realized. The electronic components on the circuit board are connected by conductors (wiring patterns) such as printed wiring. Examples of the electronic components include integrated circuits, elements such as resistors, capacitors, and inductors connected to the input / output terminals of the integrated circuit. These electronic components constitute an electronic component component.

[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 fixing of the image on the sheet. For this purpose, the image forming apparatus controls various actuators such as an optical sensor, a temperature sensor, a motor, and a solenoid. Patent Document 1 discloses a control circuit board mounted on an image forming apparatus. A plurality of electronic components are mounted on the circuit board of Patent Document 1 for actuator control. For example, a driver board for driving a motor has an integrated circuit (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. Also, a plurality of control circuit boards themselves are provided in the image forming apparatus.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] Some electronic components, such as motor driver ICs, differ in size and terminal arrangement depending on the manufacturer and slight variations in specifications. This makes it difficult to route different electronic components using common footprints on a circuit board. Therefore, it is desirable to pre-design a single circuit board with footprints corresponding to multiple electronic components that perform the same function, and then switch between mounting and not mounting the electronic components to achieve the same functionality.

[0006] However, in conventional technology, appropriate wiring patterns have not been considered for circuit boards that can universally mount electronic components with different specifications. Therefore, in view of the above-mentioned problems, the present invention aims to provide a circuit board that can universally mount multiple electronic components with different specifications or multiple electronic components with different functions. [Means for solving the problem]

[0007] The circuit board of the present invention is characterized by comprising: a first surface including a first region on which a first electronic component can be mounted; a second surface different from the first surface including a second region on which a second electronic component can be mounted; a first connection portion disposed on the first surface for which the terminals of the first electronic component are connected; a first element disposed on the first surface; a second connection portion disposed on the second surface for which the terminals of the second electronic component are connected; a second element disposed on the second surface; and a wiring pattern that connects the first element and the second element in parallel and electrically conducts with the first element and the second element, and with the first connection portion and the second connection portion, respectively. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a circuit board on which multiple electronic components can be mounted. [Brief explanation of the drawing]

[0009] [Figure 1]System configuration diagram of an image forming apparatus. [Figure 2] A diagram illustrating the configuration of an image forming apparatus. [Figure 3] Functional block diagram of a circuit board. [Figure 4] Diagram illustrating electronic components. [Figure 5] A diagram illustrating the wiring pattern of a circuit board. [Figure 6] A diagram illustrating the wiring pattern of a conventional circuit board. [Figure 7] Cross-sectional view of a circuit board. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present invention will be described below with reference to the attached drawings.

[0011] (Configuration of an image forming apparatus) Figure 1 is a system configuration diagram of an image forming apparatus having a circuit board according to this embodiment. Unless otherwise specified, the image forming apparatus 100 may be a system composed of multiple devices connected via a network, as long as the functions of the image forming apparatus 100 are performed.

[0012] In this embodiment, the image forming apparatus 100 is connected to a host computer 101 via a network 105 for communication. The network 105 consists of communication lines such as a LAN (Local Area Network), WAN (Wide Area Network), or public network. Multiple image forming apparatuses 100 and host computers 101 may be connected to the network 105. The host computer 101 generates print jobs and transmits the generated print jobs to the image forming apparatus 100 via the network 105.

[0013] The image forming apparatus 100 comprises a controller board 110, storage 115, paper feed unit 140, printer engine 150, and operation panel 180. The controller board 110, storage 115, paper feed unit 140, printer engine 150, and operation panel 180 are interconnected via a system bus 116 so as to be able to communicate with each other.

[0014] The controller board 110 comprises 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, ROM 112, RAM 113, and CPU 114 are mounted on a circuit board. The controller board 110 functions as the main control unit of the image forming apparatus 100 and controls the operation of the entire image forming apparatus 100. The circuit board is, for example, a printed circuit board with printed wiring formed on it.

[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 the operation of the image forming apparatus 100, such as image forming processing, by executing computer programs stored in the ROM 112 and storage 115. The computer programs include a startup program, control program, and operating system. The startup program, control program, and operating system are stored in the ROM 112 and storage 115. The RAM 113 provides a workspace for the CPU 114 when it executes processing and stores temporary data. The storage 115 stores large amounts of data, such as image data and print data, temporarily or long-term. For example, the storage 115 stores image data for generating adjustment images to adjust image forming conditions. The storage 115 is a large-capacity storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive).

[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, etc. The output interface is a display, a speaker, etc. The operation panel 180 receives instructions, etc. 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 image. The image position detection unit 154 detects the image position 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 formed on the paper based on the image position 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 on 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 of 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 an optical processing mechanism for forming an electrostatic latent image, visualizing the electrostatic latent image, and transferring the visualization 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 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 the colors of the images to be formed are different. 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 laser light modulated according to 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 CPU 114, a rotating polygon mirror 208, and a reflection 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 reflection mirror 209. When the surface of the photosensitive drum 205 is exposed, an electrostatic latent image is formed.

[0023] The developer unit 212 uses toner to reveal the electrostatic latent image, forming a toner image on the surface of the photosensitive drum 205. A yellow toner image is formed on the photosensitive drum 205 of station Y 220. A magenta toner image is formed on the photosensitive drum 205 of station M 221. A cyan toner image is formed on the photosensitive drum 205 of station C 222. A black toner image is formed on the photosensitive drum 205 of station K 223.

[0024] The intermediate transfer belt 252 is mounted on rollers such as the secondary transfer inner roller 240 and rotates clockwise in the figure. The toner images of each color formed on each photosensitive drum 205 are transferred onto the rotating intermediate transfer belt 252 so as to be superimposed. The transfer of the toner image from the photosensitive drum 205 to the intermediate transfer belt 252 is performed by applying a bias voltage to the intermediate transfer belt 252 that has characteristics opposite to those of the toner image. As a result, the intermediate transfer belt 252 carries the full-color toner image. As the intermediate transfer belt 252 rotates, it transports the carried toner image to the secondary transfer section, which consists 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 for the paper S and includes a storage compartment 210 for storing the paper S, a transport path, transport rollers, etc. The paper feeding unit 140 transports the paper S one sheet at a time from the storage compartment 210 to the secondary transfer unit. The secondary transfer unit uses the secondary transfer inner roller 240 and the secondary transfer outer roller 251 to grip and transport the intermediate transfer belt 252 and the paper S. At this time, a bias voltage with the opposite polarity to the toner image is applied to the secondary transfer outer roller 251, so that the toner image is transferred from the intermediate transfer belt 252 to the paper S.

[0026] The paper S onto which the toner image has been transferred is transported to the fixing unit 260, which is a fixing mechanism. The fixing unit 260 includes a fixing roller 261 having a heat source inside, a pressure roller 262 that is biased toward the fixing roller 261, and a circuit board 300 that controls the fixing process by the fixing unit 260. The fixing unit 260 fixes the toner image to the paper S by gripping and transporting the paper S with the toner image 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 pressurizes the paper S between itself and the pressure roller 262.

[0027] As a result, the image is printed on the paper S. In the case of double-sided printing, the paper S with the image printed on the first side is transported again to the secondary transfer section via the inversion path 270. By being transported to the secondary transfer section via the inversion path 270, the image formation surface of the paper S is inverted. The paper S with the inverted image formation surface is then used by the secondary transfer section and the fixing section 260 to print the image on a second side that is different from the first side.

[0028] The paper S on which the image is printed passes through the image reading unit 290, which is located downstream of the fixing unit 260 in the paper transport 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 paper S is an adjustment image for image forming conditions.

[0029] To perform the image forming process described above, the image forming apparatus 100 is equipped with various actuators such as motors and sensors. The actuators are connected to a circuit board on which control electronic components are mounted. Each electronic component mounted on the circuit board is electrically connected by conductors. The circuit board in this embodiment is, for example, a printed circuit board that uses a wiring pattern made of printed wiring on the conductors.

[0030] Electronic components control the operation of actuators. For this purpose, numerous circuit boards are provided within the image forming apparatus 100, corresponding to the actuators. One or more actuators are controlled by a single circuit board. The circuit boards are controlled by a CPU 114. The controller board 110 on which the CPU 114 is mounted is also an example of a circuit board. Below, an example of a circuit board, specifically a circuit board 300 provided in the fixing unit 260, will be described.

[0031] (Circuit board) Figure 3 is a functional block diagram of the circuit board 300 provided in the fixing unit 260. Multiple motors 309 to 311 and multiple sensors 312 to 314 within the fixing unit 260 are electrically connected to the circuit board 300. Motor 309 is a drive source for driving the fixing roller 261, which is a rotating body. Motor 310 is a drive source for biasing the pressure roller 262 toward the fixing roller 261. Motor 311 is a drive source for driving the roller, which is a rotating body that transports the paper S after the fixing process to the next stage. Sensor 312 is a detector for detecting the paper S that has been transported to the fixing unit 260. Sensor 313 is a temperature detector for detecting the temperature of the fixing roller 261. Sensor 314 is a detector for detecting the paper S after the fixing process.

[0032] The circuit board 300 implements various functions using multiple electronic components. In the example shown in Figure 3, the circuit board 300 includes an AC / DC converter 302 used to generate a predetermined DC voltage from an AC voltage and a DC / DC converter 303 that converts the voltage value of the DC voltage. Furthermore, the circuit board 300 includes a CPU 304, an ASIC (Application Specific Integrated Circuit) 305, and motor driver ICs 306-308 used to control the actuator. The circuit board 300 has multiple integrated circuits (hereinafter referred to as "ICs") as described above, and peripheral electronic components corresponding to the ICs mounted on it.

[0033] The AC-DC converter 302 generates a first DC power supply voltage having a predetermined voltage value from the AC power supplied from the commercial power supply 301. The DC-DC converter 303 generates a second DC power supply voltage with a voltage value different from the first power supply voltage supplied from the AC-DC converter 302. The second power supply voltage generated by the DC-DC converter 303 is supplied to the CPU 304 and ASIC 305, etc. The CPU 304 and ASIC 305 operate using the second power supply voltage supplied from the DC-DC converter 303. The first power supply voltage output from the AC-DC converter 302 is also supplied to electronic components and motors 309-311 that operate at voltage values ​​different from those of the CPU 304 and ASIC 305.

[0034] The CPU 304 is connected to the motor driver ICs 306-308 and sensors 312-314 via the ASIC 305. The CPU 304 acquires the detection results from sensors 312-314 and detects the state of the fixing unit 260 based on these results. The CPU 304 controls the operation of motors 309-311 by controlling the motor driver ICs 306-308 via the ASIC 305 according to the detected state of the fixing unit 260. In this way, the CPU 304 and ASIC 305 control the operation of the fixing unit 260.

[0035] The circuit board 300 controls the operation of the fixing unit 260 because it is located on the fixing unit 260, but other circuit boards located within the image forming apparatus 100 similarly control the operation of their corresponding components. Each circuit board within the image forming apparatus 100 (including the circuit board 300 and other circuit boards) is communicated to the controller board 110. Communication is possible between the circuit boards via the controller board 110. Each circuit board appropriately controls the components within the image forming apparatus 100 while sharing information about the detection results of each sensor and the control status of the motors with each other.

[0036] Numerous electronic components are mounted on a circuit board. However, there is a possibility that some of these standard electronic components may become difficult to procure. To address situations where electronic components become difficult to procure, one method is to pre-investigate alternative components that are identical or similar in shape and specifications to each standard component. If a problem occurs with component procurement, the manufacturing of circuit board 300 can continue by procuring alternative components and mounting them on the circuit board.

[0037] However, in the case of circuit board 300, for example, certain ICs such as the DC-DC converter IC 303 and motor driver ICs 306, 307, and 308 may require specific peripheral electronic components for use. Furthermore, the number, arrangement, or electrical specifications of the ICs may differ, and there may be no readily available substitute ICs. In such cases, to address the difficulty in procuring each IC, electronic component components identical in function to the ICs and their peripheral components are prepared. These electronic component components are exclusively mounted on the circuit board. This approach allows for the continued manufacture of circuit board 300 by mounting ICs that are available depending on the availability of the components to be mounted.

[0038] The circuit board 300 of this embodiment has a configuration that can address situations where component procurement is difficult, and it is possible to reduce the area required for mounting. The specific circuit configuration and wiring (conductor pattern) of the circuit board 300 will be described below. In this embodiment, the configuration of a motor driver IC that controls a two-phase bipolar driven stepping motor will be used for the explanation.

[0039] (Electronic components) Figure 4 is an explanatory diagram of an electronic component set including a motor driver IC and its peripheral electronic components. The electronic component set includes a first electronic component set 410 containing a motor driver IC 406, a second electronic component set 420 containing a motor driver IC 416 which is a replacement for the motor driver IC 406, and a shared electronic component set 430. The shared electronic component set 430 is shared by the motor driver ICs 406 and 416. The first electronic component set 410 can be mounted on the first side (front) of the circuit board 300. The second electronic component set 420 can be mounted on a second side (back) of the circuit board 300, which is different from the first side. The first electronic component set 410 and the second electronic component set 420 are exclusively mounted on the circuit board 300.

[0040] The first electronic component 410 includes, in addition to the motor driver IC 406, a resistor R11 and capacitors C11, C12, and C13. The resistor R11 and capacitor C11 are components for determining the chopping frequency of constant current PWM (Pulse Width Modulation) control when controlling the motor current. Capacitors C12 and C13 are provided for noise suppression, respectively. Similarly, the second electronic component 420 includes, in addition to the motor driver IC 416, a resistor R21 and capacitors C21, C22, and C23. The resistor R21 and capacitor C21 are resistors for determining the chopping frequency of constant current PWM control when controlling the motor current. Capacitors C22 and C23 are provided for noise suppression, respectively.

[0041] The shared electronic component 430 comprises current sensing resistors R12, R13, R21, and R23. Current is detected based on the voltage across the current sensing resistors R12, R13, R21, and R23. Current sensing resistors R12 and R22 are positioned opposite each other on the front and back surfaces. Current sensing resistors R12 and R22 are connected in parallel via vias and are connected via the shortest distance to the current sensing terminals that detect the B-phase current of each motor driver IC 406, 416.

[0042] In other words, the circuit board 300 has a wiring pattern that connects current sensing resistors R12 and R22 in parallel. The wiring pattern also includes portions that connect current sensing resistors R12 and R22 to the connection portion to which the terminals of motor driver IC 406 are connected and to the connection portion to which the terminals of motor driver IC 416 are connected. Furthermore, in this embodiment, this wiring pattern includes vias that penetrate the board. Similarly, current sensing resistors R13 and R23 are positioned opposite each other on the front and back surfaces. Current sensing resistors R13 and R23 are connected in parallel via vias and are connected by the shortest distance to the current sensing terminals that detect the A-phase current of each motor driver IC 406 and 416. The shared electronic component 430 is an electronic component that is always mounted, unlike the first electronic component 410 and the second electronic component 420 which are mounted exclusively.

[0043] The motor driver ICs 406 and 416 receive control signals branched from the ASIC 305 via damping resistors R1 to R6. These control signals include the ENABLE signal, CLK signal, VREF signal, MODE signal (MODE_1 and MODE_2 signals), and DIR signal. The ENABLE signal enables the output of the motor driver ICs 406 and 416. The CLK signal controls the motor speed. The VREF signal controls the current flowing to the motor. The MODE signal controls the motor excitation pattern. The DIR signal controls the motor's rotation direction. The motor driver ICs 406 and 416 can drive the motor in response to these control signals. The phase output signals (OUTA, OUTA*, OUTB, OUTB*) output from the motor driver ICs 406 and 416 are connected via vias using the shortest possible path and input to the motor. The motor's operation is controlled by these signals input from the motor driver ICs 406 and 416.

[0044] In the above description, the first electronic component 410 and the second electronic component 420 are mounted exclusively on the circuit board 300. However, the circuit board 300 may be configured to mount components exclusively on an IC basis, rather than on an electronic component basis. For example, the motor driver IC 406 and the motor driver IC 416 may be mounted exclusively on the circuit board 300. In this case, for example, the resistor R11 and capacitors C11, C12, and C13 may be shared with the motor driver IC 416, and the resistor R21 and capacitors C21, C22, and C23 may be unnecessary.

[0045] (Circuit board mounting area) Figure 5 is an explanatory diagram of the wiring pattern in the area of ​​the circuit board 300 where electronic components are mounted. The circuit board 300 has a multilayer structure. In this embodiment, the circuit board 300 has a four-layer structure, with the second layer being the power supply layer and the third layer being the ground layer. The explanation of the wiring patterns of the second and third layers is omitted. Electronic components can be mounted on the first and fourth layers. In other words, electronic components are mounted on the outermost layers of the multilayer structure. The wiring pattern is formed using a conductor such as copper foil, for example, by a printing method.

[0046] In this embodiment, as explained in Figure 4, the first electronic component 410 and the second electronic component 420 are exclusively provided on the front (first layer) and back (fourth layer) of the circuit board 300. The current sensing resistors R12 and R22, which constitute the shared electronic component 430, are mounted on the front (first layer) and back (fourth layer) of the circuit board 300, respectively, and are connected to the motor driver ICs 406 and 416 via vias 52 over the shortest distance. The current sensing resistors R13 and R23 have a similar configuration. Note that a large current flows through the wiring pattern between the motor driver IC and the current sensing resistors. For this reason, it is preferable that the wiring pattern to which control signals for controlling the motor driver IC are transmitted is provided away from the wiring pattern between the current sensing resistors to prevent malfunctions.

[0047] The first electronic component 410 includes a motor driver IC 406. The second electronic component 420 includes a motor driver IC 416, which is a replacement for the motor driver IC 406. The mounting area 406a for the motor driver IC 406 on the front surface and the mounting area 416a for the motor driver IC 416 on the back surface are located in the same position (coordinate region) opposite each other, separated by the circuit board 300 (second and third layers). Wiring patterns are formed in these mounting areas 406a and 416a so that the motor driver ICs 406 and 416 can be mounted.

[0048] The first layer of the circuit board 300 is configured so that a motor driver IC 406 can be mounted in the mounting area 406a. The fourth layer of the circuit board 300 is configured so that a motor driver IC 416 can be mounted in the mounting area 416a. The motor driver IC 406 has a die pad 50a on its back surface for supporting and fixing semiconductor elements. The motor driver IC 416 has a die pad 50b on its back surface for supporting and fixing semiconductor elements.

[0049] The die pads 50a and 50b are connected to the grounding pattern of the circuit board 300 by soldering, allowing heat from the motor driver ICs 406 and 416 to be released to the circuit board 300. Furthermore, to enhance heat dissipation, multiple common heat dissipation vias 51 are provided at the point where the circuit board 300 connects to the die pads 50a and 50b of the motor driver ICs 406 and 416, so as to accommodate both motor driver ICs 406 and 416. In other words, multiple heat dissipation vias 51 are provided so as to penetrate and connect the mounting area 406a and the mounting area 416a.

[0050] (Difference from the conventional configuration) Figure 6 is an explanatory diagram of the wiring pattern in the area where electronic component parts are mounted on a conventional circuit board 300. The number and size of current sensing resistors differ between Figure 5 and Figure 6. In the conventional configuration, current sensing resistors R12 and R13 are also shared by motor driver ICs 406 and 416. However, in the conventional configuration, current sensing resistors R12 and R13 are placed on either the front surface (first layer) or the back surface (fourth layer) and connected to motor driver ICs 406 and 416 via vias.

[0051] In this case, a large current flows through the current sensing resistors R12 and R13, so it is necessary to select resistor elements with high wattage for R12 and R13. This results in larger sizes for the current sensing resistors R12 and R13. For example, when driving a motor with 2[A], considering derating, current sensing resistors of 0.1[Ω], 1[W], and 5025 size are used. In addition, the sides on which current sensing resistors are not mounted become wasted space without wiring patterns.

[0052] As explained in Figure 5, in this embodiment, the current sensing resistors R12, R13, R22, and R23 are arranged separately on the front surface (first layer) and the back surface (fourth layer). This eliminates wasted space and increases mounting density, making it possible to minimize the substrate area.

[0053] Specifically, 0.2[Ω], 0.5[W], 3216 size resistors are used as current sensing resistors R12, R13, R22, and R23, and are arranged separately on the front (first layer) and back (fourth layer). The wiring pattern is designed so that the combined resistance of current sensing resistors R12 and R22 is 0.1[Ω] when connected in parallel. Current sensing resistors R12 and R22 are connected via via 52, providing the shortest possible connection to motor driver ICs 406 and 416. When connected in parallel, the current flowing through each current sensing resistor becomes 1[A]. This makes it possible to use 0.5[W], 3216 size resistors, reducing the board area for current sensing by approximately 60% compared to conventional configurations. The same applies to current sensing resistors R13 and R23.

[0054] Figure 7 is a cross-sectional view of the portion of the circuit board 300 on which the motor driver IC and current sensing resistor are mounted. As described above, the circuit board 300 consists of four layers: the first layer 61, the second layer 62, the third layer 63, and the fourth layer 64. The circuit board 300 is double-sided reflow coated, and electronic components are mounted on the first layer 61 and the fourth layer 64.

[0055] As described above, the first electronic component 410, which includes the motor driver IC 406, is mounted on the first layer 61, which is the front surface, and the second electronic component 420, which includes the motor driver IC 416, is mounted on the fourth layer 64, which is the back surface. The first electronic component 410 and the second electronic component 420 are mounted exclusively. The current sensing resistors R12 and R13, which constitute the shared electronic component 430, are mounted on the first layer 61, which is the front surface, and the current sensing resistors R22 and R23 are mounted on the fourth layer 64, which is the back surface. In other words, the circuit board 300 will have either the first electronic component 410 or the second electronic component 420, and the shared electronic component 430 mounted on it.

[0056] Current sensing resistors R12 and R22 are positioned opposite each other on the first layer 61 and the fourth layer 64 (front and back sides). Current sensing resistors R12 and R22 are connected in parallel via via 52 and connected to motor driver ICs 406 and 416. Current sensing resistors R13 and R23 are positioned opposite each other on the front and back sides. Current sensing resistors R13 and R23 are connected in parallel via via 53 and connected to motor driver ICs 406 and 416.

[0057] Motor driver IC 406 is a semiconductor device encased in case 60a and mounted on die pad 50a. Motor driver IC 406 is bonded within case 60a by wire 65a. Motor driver IC 416 is a semiconductor device encased in case 60b and mounted on die pad 50b. Motor driver IC 416 is bonded within case 60b by wire 65b.

[0058] The second layer 62 is the power supply layer. The second layer 62 consists of wiring that supplies power to the motor driver ICs 406 and 416, and wiring that supplies low voltage to drive logic circuits such as the CPU and ASIC. The third layer 63 is the GND (ground) layer and is connected via vias to the ground patterns of the first layer 61 and the fourth layer 64. The third layer 63 provides the ground voltage for the first layer 61 and the fourth layer 64.

[0059] The multiple vias enclosed by the dashed line 67 are heat dissipation vias 51, provided to enhance the heat dissipation effect of the motor driver ICs 406 and 416. The heat dissipation vias 51 can contact the die pads 50a and 50b of both motor driver ICs 406 and 416 and are shared by both motor driver ICs 406 and 416. The heat from motor driver ICs 406 and 416 is dissipated by the heat dissipation vias 51 via the die pads 50a and 50b.

[0060] The heat dissipation via 51 and the die pad 50a are in contact via the heat dissipation wiring pattern 66a. The heat dissipation via 51 and the die pad 50b are in contact via the heat dissipation wiring pattern 66b. The heat dissipation wiring pattern 66a is formed on the first layer 61 so as to contact the entire surface of the die pad 50a. The heat dissipation wiring pattern 66b is formed on the fourth layer 64 so as to contact the entire surface of the die pad 50b. The heat dissipation wiring patterns 66a and 66b enhance heat dissipation efficiency by contacting the entire surfaces of the die pads 50a and 50b, respectively.

[0061] In the circuit board 300 with the above configuration, electronic components such as ICs (semiconductor devices) or electronic component components including multiple electronic components are mounted exclusively on the front and back surfaces to achieve the same function. The remaining electronic component components are always mounted on the front and back surfaces, thus minimizing the board area. With this configuration, even if it becomes difficult to procure regular parts, the manufacture of the circuit board 300 can continue using alternative parts.

[0062] In this embodiment, motor driver ICs 406 and 416 were used as examples of electronic components (semiconductor devices), and current sensing resistors R12, R13, R22, and R23 were used as examples of peripheral electronic components. However, the electronic components (semiconductor devices) and peripheral electronic components are not limited to these. The functions of the electronic component are not limited as long as the configuration allows for separate implementation of the electronic component's functions. The electronic components (semiconductor devices) may be, for example, DC-DC converters, switching ICs, FETs (Field-effect transistors), etc. The peripheral electronic components may be capacitors for charge pumps, power inductors for smoothing, etc.

Claims

1. A first surface including a first region on which a first electronic component can be mounted, A second surface different from the first surface, which includes a second region on which a second electronic component can be mounted, The first surface is provided with a first connection portion for which the terminals of the first electronic component are connected, A first element arranged on the first surface, The second surface is provided with a second connection portion for which the terminals of the second electronic component are connected, The second element arranged on the second surface, The first element and the second element are connected in parallel, and the wiring pattern is characterized by providing electrical conductivity between the first element and the second element and the first connection part and the second connection part, respectively. Circuit board.

2. The first electronic component and the second electronic component are characterized in that they are exclusively mounted on the circuit board. The circuit board according to claim 1.

3. The position of the first surface on which the first element is mounted and the position of the second surface on which the second element is mounted are characterized in that they face each other across the circuit board. The circuit board according to claim 1.

4. The circuit board has a multilayer structure, The first and second surfaces are the outermost layers of the multilayer structure. The first element and the second element, which are divided and arranged on the first and second surfaces, are connected by vias that penetrate from the first surface to the second surface. The circuit board according to claim 1.

5. The first region can be used to mount a semiconductor device for a motor driver that drives the motor, as the first electronic component. The second region is characterized in that a semiconductor device for a motor driver that drives the motor can be mounted as the second electronic component. The circuit board according to claim 4.

6. The first element is a resistor for detecting the current of the first electronic component, and the second element is a resistor for detecting the current of the second electronic component. The circuit board according to claim 5.

7. The second electronic component is characterized in that it is a replacement component for the first electronic component. The circuit board according to claim 1.

8. The first surface can be used to mount a first electronic component including the first electronic component and the first element. The second surface is characterized in that a second electronic component including the second electronic component and the second element can be mounted on it. The circuit board according to claim 1.

9. The circuit board according to claim 1, The present invention is characterized by comprising a component that forms an image, controlled by either the first electronic component or the second electronic component mounted on the circuit board, Image forming apparatus.

10. The aforementioned component is a motor, The first electronic component is a semiconductor device for a motor driver that drives the motor, The second electronic component is characterized by being a semiconductor device for a motor driver that drives the motor. The image forming apparatus according to claim 9.

11. The first element is a resistor for detecting the current of the first electronic component, and the second element is a resistor for detecting the current of the second electronic component. The image forming apparatus according to claim 9.

Images