Printed circuit board

Abstract

To prevent static electricity from entering a ground region on which a connector is mounted.SOLUTION: A front layer of a printed circuit board 100 includes: frame ground regions 102a, 102b on which connectors 202, 203 to be connected with external apparatuses or communication cables are mounted and which are connected with a ground; a signal ground region 101 which is separated from the frame ground regions 102a, 102b at the front layer, on which electronic devices 200, 201 configured to receive signals from the connectors 202, 203 are mounted, and which is connected with the ground; and a static electricity removal ground region 103 separated from the frame ground regions 102a, 102b and the signal ground region 101 at the front layer, situated outside the frame ground regions 102a, 102b, and connected with the ground.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a printed circuit board.

Background Art

[0002] Electronic devices incorporate a printed circuit board (PCB), and the printed circuit board is fixed to a housing or the like. Passive components such as resistors and capacitors, and active components such as ICs (Integrated Circuits) are mounted on the printed circuit board.

[0003] In recent years, due to the influence of the miniaturization of electronic devices, the size of the printed circuit board has also been decreasing. In addition, for power consumption reduction and performance improvement, the miniaturization and high integration of ICs mounted on the printed circuit board have been progressing.

[0004] As the substrate size decreases, the area of the ground serving as the reference potential on the printed circuit board becomes smaller, making it difficult for noise such as static electricity to escape, and the stabilization of the voltage level has become severe. In addition, as the ICs are miniaturized and highly integrated, the electrostatic resistance has decreased, and malfunctions and destruction due to external disturbance noise such as static electricity are likely to occur.

[0005] In the control board 5 described in Patent Document 1, a frame ground region 53 and a signal ground region 52 are provided with an insulation distance ΔL2 therebetween.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Document 1, the frame ground area 53 and the signal ground area 52 are separated by an insulating distance ΔL2, so that the propagation of signals from the frame ground area 53 to the signal ground area 52 can be suppressed. However, it is not possible to suppress the intrusion of static electricity into the frame ground area 53. For example, if a connector for connecting cables or external devices is mounted in the frame ground area 53, static electricity charged on the hands of the person holding the cables or external devices, the cables, and the external devices can enter the frame ground area 53. In Patent Document 1, the propagation of signals from the frame ground area 53 to the signal ground area 52 can be suppressed, but it is not possible to prohibit the propagation of all static electricity. Therefore, suppressing the intrusion of static electricity into the frame ground area 53 is more effective in suppressing the intrusion of static electricity into the signal ground area 52.

[0008] Therefore, the present invention has been made to solve the above problems, and the object of the present invention is to provide a printed circuit board that can suppress the intrusion of static electricity into the ground area on which the connector is mounted. [Means for solving the problem]

[0009] To achieve the above objective, the printed circuit board of the present invention has a first ground region provided in an annular shape on the outer edge of the surface layer of the printed circuit board and connected to the ground, and on the surface layer of the printed circuit board, inside the first ground region Electrically It has a second ground area which is provided separately and on which a connector to which an external device or communication cable is connected is mounted and which is connected to ground, and the first ground area and the second ground area are mutual Electrically It is characterized by being separated. [Effects of the Invention]

[0010] According to the present invention, This provides a printed circuit board that can suppress the intrusion of static electricity into the ground area where the connector is mounted. . [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram showing the structure of an image forming apparatus. [Figure 2] This is a block diagram showing the controller. [Figure 3] This is a diagram showing the details of a printed circuit board. [Figure 4] This is a magnified view of a portion of a printed circuit board. [Figure 5] This is a cross-sectional view of AA' in Figure 3. [Figure 6] This diagram shows the path through which static electricity propagates. [Figure 7] This figure shows the relationship between the resonant frequencies and gains of the signal layer and ground layer. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments are not intended to limit the invention as defined in the claims, and not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. [Examples]

[0013] The embodiments for carrying out the present invention will be described below with reference to the drawings.

[0014] <Overall configuration of the image forming apparatus> Figure 1 shows the structure of an image forming apparatus according to Embodiment 1 of the present invention. As shown in Figure 1, the image forming apparatus 10 includes a scanner unit 12 which is an image input device and a printer unit 13 which is an image output device.

[0015] The scanner unit 12 is a device that reads an image formed on a document and acquires image data. By inputting the reflected light from the light irradiated onto the image formed on the document into the CCD, the information of the image is converted into an electrical signal. This electrical signal is converted into a luminance signal consisting of R, G, and B colors and output to the controller 11, which will be described later.

[0016] The document set on the tray 1250 of the scanner unit 12 is fed one by one by the document feeder 1260 to the reading position of the optical unit 1213 on the platen glass 1211. Then, the document read by the optical unit 1213 is discharged to the discharge tray 1219. The light irradiated from the lamp 1212 of the optical unit 1213 and reflected by the document is input to the CCD image sensor 1218 via the mirrors 1214, 1215, 1216, and the lens 1217. Note that the method of reading the document may be a method of scanning the carriage on which the optical unit 1213 is mounted with respect to the document placed on the platen glass 1211, instead of the automatic feeding method by the document feeder 1260. In the first embodiment, the image forming apparatus 10 capable of monochrome printing will be described, but the image forming apparatus 10 may be capable of color printing.

[0017] The printer unit 13 is a device that forms an image on paper using the input image data. Note that the image forming method of the printer unit 13 in this embodiment is an electrophotographic method using a photoreceptor drum or a photoreceptor belt, but the present invention is not limited to this. For example, the printer unit 13 may be an inkjet method that ejects ink from a minute nozzle array and prints on paper.

[0018] The image forming apparatus 10 also has a plurality of paper cassettes 1311, 1312, 1313, 1314 for storing sheets on which images are formed by the printer unit 13 and a manual feed tray 1315. The laser driver 1321 of the printer unit 13 drives the laser emitting unit 1322. The laser driver 1321 causes the laser emitting unit 1322 to emit laser light corresponding to the image data output from the controller 11. The laser light is irradiated onto the photosensitive drum 1323, and a latent image corresponding to the laser light is formed on the photosensitive drum 1323. A developer is attached to the latent image portion of the photosensitive drum 1323 by the developing unit 1324. The transfer unit 1325 transfers the developer attached to the photosensitive drum 1323 to the recording paper that has passed through the conveyance path 1331. The recording paper with the developer thereon is conveyed to the fixing unit 1327 by the conveyance belt 1326. The fixing unit 1327 fixes the developer onto the recording paper by heat and pressure. The recording paper that has passed through the fixing unit 1327 passes through the conveyance paths 1335 and 1334 and is discharged to the paper output tray 1328. Alternatively, when discharging with the printed surface reversed to the paper output tray 1328, the recording passes through the conveyance paths 1336 and 1338 and then through the conveyance paths 1337 and 1334.

[0019] When double-sided printing is performed, the recording paper is guided from the fixing unit 1327 to the conveyance path 1336 and is then guided to the conveyance path 1333 by the flapper 1329. Thereafter, the recording paper is conveyed in the reverse direction and is guided to the conveyance paths 1338 and the re-feed conveyance path 1332 by the flapper 1329. The recording paper guided to the re-feed conveyance path 1332 passes through the conveyance path 1331 and is fed to the transfer unit 1325.

[0020] <Description of the Controller 11 of the Image Forming Apparatus 10> FIG. 2 is a block diagram showing a controller that controls the entire image forming apparatus. Referring to FIG. 2, the details of the controller 11 that controls the overall operation of the image forming apparatus 10 will be described.

[0021] As shown in Figure 2, the controller 11 is electrically connected to the scanner unit 12, printer unit 13, and operation unit 12 described above. In this embodiment, each device of the controller 11 is mounted on a single printed circuit board. However, the devices of the controller 11 may be mounted on two or more printed circuit boards. For example, the controller 11 may be composed of a printed circuit board on which the operation unit I / F 1105 and human presence sensor 1110 are mounted, and a printed circuit board on which the CPU 1101 and the like are mounted. This controller 11 includes a CPU 1101, RAM 1102, ROM 1103, operation unit I / F 1105, LAN controller 1106, human body detection sensor 1110, paper detection sensor 1112, and power control unit 1114. The CPU 1101, RAM 1102, ROM 1103, operation interface 1105, LAN controller 1106, human body detection sensor 1110, paper detection sensor 1112, and power control unit 1114 are connected to the system bus 1107. The controller 11 also includes an HDD 1104, image processing unit 1109, scanner interface 1111, and printer interface 1113. The HDD 1104, image processing unit 1109, scanner interface 1111, and printer interface 1113 are connected to the image bus 1108.

[0022] The CPU 1101 comprehensively controls access to various connected devices based on control programs stored in the ROM 1103, and also comprehensively controls various processes executed by the controller 11.

[0023] RAM1102 is the system work memory for the operation of CPU1101. This RAM1102 also serves as memory for temporarily storing image data. RAM1102 has SRAM, which can retain stored data even when the power is off, and DRAM, which erases stored data when the power is off. ROM1103 stores the device's boot program and other data. HDD1104 is a hard disk drive that stores programs for controlling the image forming apparatus 10 and image data.

[0024] The control unit I / F 1105 is an interface unit for connecting the system bus 1107 and the control unit 12. This control unit I / F 1105 receives image data for display on the control unit 12 from the system bus 1107 and outputs it to the control unit 12, and also outputs information input from the control unit 12 to the system bus 1107.

[0025] The LAN controller 1106 controls the input and output of information between the image forming apparatus 10 and the external device 50 connected to the network 60.

[0026] The human body detection sensor 1110 is an infrared sensor array in which infrared sensors that receive infrared light are arranged in a matrix. The human body detection sensor 1110 detects when a person approaches the image forming apparatus 10 by receiving infrared light emitted from a person or other object. In this embodiment, an example of the human body detection sensor 1110 detecting a person is described, but any object that emits infrared light can be detected by this human body detection sensor 1110. Note that the human body detection sensor is not limited to the infrared sensor described above. Any sensor that can detect when an object approaches the image forming apparatus 10 may be a device other than an infrared sensor (such as an optical sensor that detects light, a strain sensor that deforms with physical force, a magnetic sensor that detects magnetism, or a temperature sensor that detects temperature).

[0027] The paper detection sensor 1112 detects when paper is loaded into the manual feed tray 1315.

[0028] The power supply control unit 1114 controls the power supply to each part of the image forming apparatus 10. Details of the power supply control unit 1114 will be described later.

[0029] The image bus 1108 is a transmission path for exchanging image data and consists of buses such as the PCI bus and IEEE 1394.

[0030] The image processing unit 1109 is for image processing. It reads image data stored in the RAM 1102 and performs image processing such as scaling (enlargement or reduction) of JPEG, JBIG, etc., and color adjustment.

[0031] The scanner unit 12 includes a scanner control unit 1201 and a scanner drive unit 1202. The scanner drive unit 1202 is a physically driven device that includes a paper transport motor for transporting the document set in the tray 1250 to the reading position of the scanner unit 12. The scanner control unit 1201 controls the operation of the scanner drive unit 1202. When performing scanning processing, the scanner control unit 1201 receives setting information set by the user through communication with the CPU 1101 and controls the operation of the scanner drive unit 1202 based on this setting information.

[0032] The printer unit 13 includes a printer control unit 1301 and a printer drive unit 1302. The printer drive unit 1302 is a physically driven device that includes a motor for rotating the photosensitive drum 1323, a motor for rotating the fuser 1327, and a paper transport motor. The printer control unit 1301 controls the operation of the printer drive unit 1302. When performing a print operation, the printer control unit 1301 receives setting information set by the user through communication with the CPU 1101 and controls the operation of the printer drive unit 1302 based on this setting information.

[0033] <Explanation of Printed Circuit Boards> Figures 3 and 4 show details of the printed circuit board. The printed circuit board 100 is fixed to the metal housing 300 by metal screws 20 to 24. ICs 200 and 201 are mounted on the printed circuit board 100. IC 200 is the CPU 1101 described above, and IC 201 is the LAN controller 1106 described above. Connectors 202 and 203 are mounted on the printed circuit board 100, to which external devices and cables (e.g., USB devices, USB cables) are connected. IC 200 is connected to connector 202 via signals 110, 111, 112, and 113. IC 201 is connected to connector 203 via signals 114 and 115. IC 200 can communicate with external devices via connector 202. IC 201 can communicate with external devices via connector 203. Signals 110-115 may transmit a clock signal, a data signal, supply power, or be connected to ground. In this embodiment, connector 202 is a 4-pin connector (pins 400, 401, 402, 403), and connector 203 is a 2-pin connector (pins 405, 405). The number of pins in connectors 202 and 203 is not limited to 4 pins or 2 pins.

[0034] IC200 may be a PGA (Prigrammable Gate Array) or an ASIC (Application Specific Integrated Circuit). The power control unit 1114 described above is a PGA, and the image processing unit 1109 described above is an ASIC. IC200 and IC201 are highly integrated, and their semiconductor processes are on the nanometer order. The smaller the semiconductor process, the lower the electrostatic discharge resistance, so the higher the probability of malfunction due to external noise such as static electricity.

[0035] Connector 202 is fixed to the printed circuit board 100 by locking pins 406 and 407. Connector 203 is also fixed to the printed circuit board 100 by locking pins 408 and 409. If connector 202 is a surface-mount device (SMD) connector, locking pins 406 and 407 are joined to the surface layer (signal layer 30) of the printed circuit board 100 by solder. If connector 202 is a dual in-line package (DIP) component, locking pins 406 and 407 penetrate from the surface layer (signal layer 30) to the back layer (signal layer 36) of the printed circuit board 100 and are similarly joined by solder. The same applies to connector 203, so its explanation is omitted.

[0036] The surface layer (signal layer 30) of the printed circuit board 100 in this embodiment has three ground regions separated by slits. The three ground regions are the signal ground region 101, the frame ground region 102b, and the static electricity protection ground region 103.

[0037] The signal ground region 101 is the region where ICs 200 and 201, which receive signals from connectors 202 and 203, are mounted. This signal ground region 101 is connected to ground via the inner ground layer 32. The potential of the inner ground layer 32 is the reference potential for signals 110 to 115 and the reference potential for the power supply to ICs 200 and 201. This signal ground region 101 is located outside the frame ground region 102a and frame ground region 102b.

[0038] The frame ground area 102a is where the connector 202 is mounted and is electrically connected to the metal housing 300. The frame ground area 102a is connected to the metal frame of the connector 202.

[0039] The frame ground area 102b is where the connector 203 is mounted and is electrically connected to the metal housing 300. The frame ground area 102b is connected to the metal frame of the connector 203.

[0040] In this embodiment, in addition to the signal ground region 101, frame ground region 102a, and frame ground region 102b, a static electricity prevention ground region 103 is formed on the signal layer 30 of the printed circuit board 100. The static electricity prevention ground region 103 is provided on the periphery of the printed circuit board 100. Furthermore, the static electricity prevention ground region 103 is formed in a continuous ring shape. Furthermore, the static electricity prevention ground region 103 is provided so as to continuously surround the signal ground region 100. Moreover, the static electricity prevention ground region 103 is provided so as to continuously surround the frame ground region 102a. Furthermore, the static electricity prevention ground region 103 is provided so as to continuously surround the frame ground region 102b. In this embodiment, the static electricity prevention ground region 103 is provided so as to continuously surround the signal ground region 101.

[0041] Furthermore, the static electricity protection ground area 103 is located outside the frame ground area 102a and at least in a position corresponding to the insertion opening 202a into which the external devices and cables of the connector 202 are inserted. Additionally, the static electricity protection ground area 103 is located outside the frame ground area 102b and at least in a position corresponding to the insertion opening 203a into which the cables of the connector 203 are inserted.

[0042] The static electricity protection ground area 103 is connected to the ground layer 32. The frame ground area 102a, frame ground area 102b, and signal ground area 101 are also connected to the ground layer 32. In other words, the static electricity protection ground area 103 is connected to the frame ground area 102a, frame ground area 102b, and signal ground area 101 in the ground layer 32.

[0043] The ground area 103 for static electricity protection has through holes through which screws 20-23 pass. Screws 20-23 fix the printed circuit board 100 to the metal housing 300. The through holes may also be notches. Screws 20-23 are made of metal and are connected to ground when the printed circuit board 100 is fixed to the metal housing 300.

[0044] The static electricity protection ground region 103 is completely isolated in the signal layer 30 from the frame ground region 102a, frame ground region 102b, and signal ground region 101 by a slit 502. This slit 502 is provided only in the signal layer 30 and does not reach the ground layer 32.

[0045] The static electricity protection ground region 103 is provided in the signal layer 30 and the signal layer 36. The static electricity protection ground region 103 of the signal layer 30 and the static electricity protection ground region 103 of the signal layer 36 are provided at the periphery of the printed circuit board 100. In this embodiment, there is no frame ground region in the signal layer 36. Of course, a frame ground region may be provided in the signal layer 36.

[0046] In this embodiment, a signal ground region 101 is located between the static electricity protection ground region 103 and the frame ground region 102a. Furthermore, a signal ground region 101 is located between the static electricity protection ground region 103 and the frame ground region 102b. Note that a signal ground region 101 may not be provided between the static electricity protection ground region 103 and the frame ground region 102a. Similarly, a signal ground region 101 may not be provided between the static electricity protection ground region 103 and the frame ground region 102b.

[0047] A via 107 is formed in the static electricity protection ground region 103, and the static electricity protection ground region 103 is connected to the ground layer 32.

[0048] Static electricity that enters the peripheral edge of the printed circuit board 100 is less likely to propagate to the signal ground region 101 and frame ground regions 102a and 102 due to the slit 502. Static electricity that enters the peripheral edge of the printed circuit board 100 propagates to the metal housing 300 via vias 107 and screws 20-23 in the static electricity-reducing ground region 103. Static electricity generated by discharge from people when inserting or removing devices or cables from connectors 202 and 203 can be prevented from entering the inside of the static electricity-reducing ground region 103. Static electricity discharged around connectors 202 and 203 can be prevented from entering the high-frequency operating active elements (ICs 200 and 201) mounted on the printed circuit board 100.

[0049] The frame ground region 102a is connected from the signal layer 30 via via 103 to the ground region 32 and the static electricity shielding ground region 103 of the signal layer 36. Static electricity discharged on the frame of the connector 202 propagates to the frame ground region 102a via lock pins 406 and 407. The static electricity then propagates through via 103 to the static electricity shielding ground region 103 of the signal layer 36 and escapes into the metal housing 300.

[0050] Furthermore, the frame ground region 102a is separated from the signal ground region 101 by the slit 500. Also, the frame ground region 102b is separated from the signal ground region 101 by the slit 501. In addition, in this embodiment, the static electricity prevention ground region 103 and the frame ground region 102a are separated by slits 502 and 500. Also, the static electricity prevention ground region 103 and the frame ground region 102b are separated by slits 502 and 501. Also, the static electricity prevention ground region 103 and the signal ground region 101 are separated by slit 502. A slit is a groove that physically separates the conductor (copper film) constituting the signal layer 30 of the printed circuit board 100, making it electrically non-conductive. In other words, in the signal layer 30, the signal ground 100 and the frame ground 101 are separated by the slit 500. Furthermore, in the signal layer 30, the signal ground 100 and the frame ground 102 are separated by the slit 501.

[0051] Connector 202 is connected to the ground layer 32 of the printed circuit board 100 via via 103. The via in this embodiment is a through-via. A through-via is a hole that penetrates from the surface layer to the back layer. A through-via is made by drilling a hole from the surface layer to the back layer and coating the hole with a conductor, thereby joining multiple layers. Pins 400 to 403 of connector 202 are connected outside the frame ground area 102a, i.e., to the signal ground 100. This is to avoid signals 110 to 113 having to cross two different ground areas.

[0052] Figure 5 is a cross-sectional view of the printed circuit board along AA' in Figure 3. In Figure 5, the shaded area is the signal ground region, the vertical lines are the frame ground region, and the dots are the power supply layer.

[0053] The printed circuit board 100 in this embodiment has a four-layer structure. However, the number of layers in the printed circuit board 100 is not limited to four. The printed circuit board 100 may have six layers or eight layers.

[0054] Signal layers 30 and 36 are provided to transmit signals output from IC200 and IC201 to other ICs. Signals output from IC200 and IC201 may be transmitted to signal layer 36, or they may be transmitted within signal layer 30.

[0055] Signal layer 30 is wired with the aforementioned signals 110 to 115, etc. In addition to signal lines such as signals 110 to 115, signal layer 30 also has a power plane and ground areas 101 to 103. The frame ground area 102a provided in signal layer 30 is connected to the signal ground 100 of the ground layer 32 and signal layer 36 by via 103.

[0056] The ground layer 32 stabilizes the voltage level of the ground. In this embodiment, the entire ground layer 32 is the signal ground region 101.

[0057] The power layer 34 is provided with multiple power planes used by IC200, IC201, connector 202, and connector 203. The power planes of power layer 34 supply power to the ICs mounted on the signal layer 30 via via 105. Since via 105 is at the same potential as the power plane, it is not connected to the signal layer 30, the ground layer 32, or the ground of the signal layer 36. Via 103 is not connected to the power plane of power layer 34.

[0058] Each layer is made of a conductor such as copper. Prepregs 31, 35, and 33 are placed between each layer. Prepregs 31 and 35 are substrates made by impregnating glass cloth with a resin such as epoxy and semi-curing it, and are used for insulation between layers when forming the printed circuit board 100 by stacking the copper of each layer and the 33 core material.

[0059] The screw 20 is fixed to the metal housing 300.

[0060] When inserting or removing cables from connectors 202 or 203, static electricity is discharged from charged human bodies, devices, cables, etc., and there is a possibility that static electricity may enter the frames of connectors 202 or 203 that come into contact with them, or the signals 110 etc. that are wired from connectors 202 or 203.

[0061] Figure 6 shows the path through which static electricity propagates.

[0062] When inserting or removing devices or cables from connectors 202 or 203, the close physical distance makes it highly likely that charged human bodies or devices will discharge into the static electricity-reducing ground area 103 provided on the insertion side of connector 202. The static electricity discharged into the static electricity-reducing ground area 103 propagates through vias 107 to the ground layer 32 and signal layer 36. The static electricity then propagates to the metal housing 300 via screws 20 (path 2000).

[0063] Furthermore, static electricity that enters the frame of connector 202 propagates to the frame ground area 102a via lock pins 406 and 407, and then propagates to the ground layer 32 and signal layer 36 via via 103. Since via 103 is connected to the static electricity escape ground area 103 in the signal layer 36, the static electricity escapes to the metal housing 300 via screws 20 (path 2001).

[0064] Furthermore, noise that enters signals 110 to 113 connected to connector 202 may reach IC 200 (path 2002).

[0065] There is a path (path 2003) through which static electricity that has entered the static electricity-reducing ground area 103 and the frame ground 101 propagates to the signal ground area 101 via parasitic capacitance formed in the slits 500 and 502. In this embodiment, the static electricity-reducing ground area 103 is provided on the outside of the connector 202, and furthermore, two slits 500 and 502 are formed between the connector and the signal ground area 101, making it difficult for static electricity to propagate to the signal connector.

[0066] As shown in Figure 7, the signal layer 30 and the ground layer 32 of the printed circuit board 100 have different frequencies at which they are prone to vibration. This is because the signal layer 30 has three ground regions separated by slits, while the ground layer 32 does not have such slits, and the shapes of the signal layer 30 and the ground layer 32 are significantly different. Even if static electricity propagated along path 2003 causes a resonance phenomenon in the signal ground region 101 of the signal layer 30, a resonance phenomenon of the same intensity as in the signal layer 30 is less likely to occur in the ground layer 32. Therefore, static electricity propagated in the signal layer 30 is attenuated based on the frequency characteristics as it propagates to the ground layer 32 and the signal layer 36. Consequently, it becomes less likely to be superimposed as noise as it propagates to the inner layers.

[0067] In this embodiment, the slit 502 allows for the provision of a static electricity-reducing ground region 103 at the periphery of the printed circuit board 100, separated from the signal ground region 101, the frame ground region 101, and the frame ground region 102b. As a result, static electricity is concentrated in the static electricity-reducing ground region 103 at the periphery of the printed circuit board 100. Therefore, static electricity accumulated on people, cables, and devices can be discharged to the metal housing 300.

[0068] Furthermore, by differentiating the shapes of the surface signal layer 30 and the inner ground layer 32, the resonant frequency can be shifted, thus attenuating static electricity propagating to the inner layer. As a result, electronic devices such as printing equipment incorporating the printed circuit board 100 have improved electrostatic resistance, and the possibility of malfunctions of mounted ICs 200 and other components is reduced.

[0069] <Variation> In the embodiments described above, an example was given in which the printed circuit board of the present invention is mounted on an image forming apparatus. However, the apparatus on which the printed circuit board of the present invention is mounted is not limited to an image forming apparatus. For example, the printed circuit board of the present invention can be mounted on various devices such as notebook PCs, tablet PCs, desktop PCs, smartphones, automobiles, air conditioners, amusement machines, and robots. [Explanation of symbols]

[0070] 1. Image forming apparatus 100 Printed Circuit Boards 101 Signal Ground Region 102a Frame ground area 102b Frame ground area 103 Ground area for static electricity protection 200 IC 201 IC 202 Connector 203 Connector

Claims

1. A first ground region is provided in an annular shape on the outer edge of the surface layer of the printed circuit board and is connected to the ground, The surface layer of the printed circuit board has a second ground region, which is electrically separated from the first ground region and on which a connector for an external device or communication cable is mounted and connected to ground, A printed circuit board characterized in that the first ground region and the second ground region are electrically isolated from each other.

2. The printed circuit board according to claim 1, characterized in that the first ground region is provided in an annular shape without interruption.

3. The surface further has a third ground region connected to the ground, The printed circuit board according to claim 1 or 2, wherein the third ground region is provided inside the first ground region on the surface layer, is provided separately from the first ground region and the second ground region, and an electronic device that receives signals from the connector is mounted on it.

4. The surface further has a fourth ground region connected to the ground, The printed circuit board according to claim 3, characterized in that the fourth ground region is separated from the first ground region, the second ground region and the third ground region on the surface, and other connectors to which external devices or communication cables are connected are mounted.

5. The printed circuit board according to any one of claims 1 to 4, characterized in that the printed circuit board is a multilayer printed circuit board having at least a signal layer, a power layer, and a ground layer.

6. The printed circuit board according to claim 3 or 4, characterized in that the first ground region, the second ground region, and the third ground region are connected in the ground layer.

7. The printed circuit board according to any one of claims 1 to 6, characterized in that the second ground region is connected to the metallic frame of the connector.

8. A printing apparatus comprising a printed circuit board according to any one of claims 1 to 7, and a metal housing to which the printed circuit board is fixed.

9. The printing apparatus according to claim 8, characterized in that the first ground region and the second ground region are connected to the housing.

10. The printing apparatus according to claim 8 or 9, characterized in that the first ground region has a hole or notch through which a fixing member for fixing the printed circuit board to the housing passes.

11. The printing apparatus according to claim 10, characterized in that the fixing member is made of metal.

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