JP2006313555A - Apparatus and method for supporting design of printed board and recording medium recording program used in this apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for supporting design of a printed board, which is provided with a design function to suppress electromagnetic radiation in a common mode from the printed board. <P>SOLUTION: The apparatus for supporting design of the printed board, which uses an information processor, includes a means for provisionally placing electronic components on the printed board, a means for interconnecting the provisionally placed electronic components with a shortest route of wiring, and a means for re-placing the provisionally placed electronic components so as to minimize the length of the wirings of the interconnection in a long side direction of a ground plane. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed circuit board design support apparatus using an information processing apparatus, a design support method, and a recording medium recording a program used in the design support apparatus, and more particularly to a printed circuit board design support apparatus that suppresses unnecessary electromagnetic radiation. The present invention relates to a recording medium on which a program used in a design support method and a design support apparatus is recorded.

  In order to prevent unnecessary electromagnetic waves radiated from electronic devices (hereinafter referred to as EMI (Electromagnetic Interference)) from obstructing public broadcasting and communication, EMI emitted from electronic devices is regulated in various countries. . For example, international standards such as CISPR are typical, and the frequency range to be regulated is 30 MHz to 1 GHz at present. For this reason, a manufacturer cannot ship a product unless the EMI of the product is kept below the regulation value. However, since EMI measurement based on the standard cannot be performed unless the product is actually completed, if it is found that the standard is not satisfied by EMI measurement soon after shipment, measures such as adding parts or redesigning should be taken. It was. For this reason, the shipment delay of the product and the cost increase may occur.

  Therefore, as a method for solving this problem, an apparatus for designing a product with reduced EMI has been devised. That is, since the main factor that generates EMI in an electronic device is the printed circuit board, the design support device for the printed circuit board is provided with a design function for suppressing EMI. For example, Japanese Patent Application Laid-Open No. 10-49568 “Circuit Board Design Method and Recording Medium” and Japanese Patent Application Laid-Open No. 10-91663 “Printed Circuit Board CAD Device” correspond to this.

  FIG. 27 is a flowchart showing an outline of a printed circuit board layout method described in Japanese Patent Laid-Open No. 10-49568 “Circuit Board Design Method and Recording Medium”. The present invention considers that EMI radiation from the printed circuit board is dominant from the signal line, calculates the amount of radiation from the signal line, and measures are taken when the value exceeds a certain limit value. It is characterized in that the optimum arrangement of countermeasures and countermeasures is determined. In this way, an attempt is made to design a printed circuit board in which EMI caused by signal lines is suppressed.

  On the other hand, FIG. 28 is a conceptual diagram of the operation of the CAD device described in Japanese Patent Laid-Open No. 10-91663, “Printed Circuit Board CAD Device”. In the present invention, when a certain wiring is specified on the printed circuit board CAD device, the radiation amount of EMI from the wiring is calculated based on the signal waveform information of the wiring, and the intensity of the radiation amount at each place is visually determined. It is characterized by being displayed on. If this CAD device is used, the location of the signal wiring that is the main cause of electromagnetic radiation can be specified, and measures can be easily taken.

  Both of the two design support devices are intended to suppress electromagnetic radiation from the signal wiring on the printed circuit board. Such electromagnetic radiation is called normal mode radiation or differential mode radiation. However, there are other common modes of radiation from the printed circuit board. Common mode radiation is more dominant than normal mode radiation in actual products.

  Hereinafter, “normal mode current” and “common mode current”, which are sources of normal mode radiation and common mode radiation, will be described in detail.

  The high-frequency current that causes EMI includes “normal mode current” and “common mode current”. The “normal mode current” on the printed circuit board is a pair current that flows in the same amount in the signal wiring and the ground plane opposite to the signal wiring and in opposite directions, and is also called a loop current. FIG. 29 is a diagram for explaining the normal mode current and the common mode current, and the current indicated by the dotted line in FIG. 29 corresponds to the normal mode current. On the other hand, the “common mode current” refers to a difference current between the signal wiring current and the ground plane current that is caused by the balance between the “normal mode current” flowing through the signal wiring and the ground plane for some reason. The current shown by the solid line in FIG. 29 corresponds to this. The “normal mode current” is a current that flows in a closed circuit between the signal wiring and the ground plane, whereas the “common mode current” is a current that also flows in the ground plane and a cable connected thereto.

  Since “normal mode current” is the same amount and opposite phase current flows close to each other, the electromagnetic fields cancel each other, and if the current value is small, the EMI is small and does not become a problem, but “common mode current” is the reverse that cancels each other Since the current flowing in the direction is not near, strong electromagnetic radiation is caused even if the original current value is small.

  The “normal mode current” can be easily grasped as the current flowing through the signal wiring, but the cause of the “common mode current” has not yet been fully elucidated. It is extremely difficult to understand where and how it flows. Therefore, there has been no effective printed circuit board design method for suppressing the “common mode current”.

For example, on page 337 of “1990, Noise Reduction Technique, Jacks Publishing”, “Normal mode (differential mode) radiation can be easily suppressed by product design and layout, while common mode (common mode ) Radiation is difficult to suppress and usually determines the overall radiation performance of the product. "
JP 10-49568 A Japanese Patent Laid-Open No. 10-91663

  There were printed circuit board design support devices that suppressed normal mode radiation by signal wiring, such as the “circuit board design method” and “printed circuit board CAD device” described in the section of the conventional example, but printing that suppressed common mode radiation. There has never been a substrate design support device.

  An object of the present invention is to provide a support device for designing a printed circuit board that suppresses common mode radiation.

  In order to achieve the above object, a printed circuit board design support apparatus according to the present invention temporarily arranges electronic components on a printed circuit board in a printed circuit board design support apparatus using an information processing apparatus. Means for connecting electronic parts with the shortest path wiring, and means for rearranging the temporarily arranged electronic parts so as to minimize the wiring length in the long side direction of the ground plane of the connected wiring It is characterized by that.

  The printed circuit board design support apparatus according to the present invention is a printed circuit board design support apparatus that uses an information processing device. The shortest path between the means for temporarily placing electronic components on the printed circuit board and the temporarily placed electronic components. Characterized in that it comprises means for connecting by wiring, and means for rearranging the electronic components temporarily arranged so that the length of the connected wiring in the long side direction of the ground plane is not more than a predetermined reference value. And

  According to another aspect of the printed circuit board design support method of the present invention, the information processing apparatus temporarily arranges an electronic component on the printed circuit board in the printed circuit board design support method using the information processing apparatus. A step in which the information processing apparatus connects the temporarily arranged electronic components with the shortest path wiring; and the information processing apparatus minimizes the wiring length in the long side direction of the ground plane of the connected wiring. Thus, the step of rearranging the electronic components temporarily arranged is included.

  According to another aspect of the printed circuit board design support method of the present invention, the information processing apparatus temporarily arranges an electronic component on the printed circuit board in the printed circuit board design support method using the information processing apparatus. A step in which the information processing apparatus connects the temporarily arranged electronic components with the wiring of the shortest path, and the wiring length in the long side direction of the ground plane of the wiring connected by the information processing apparatus is a predetermined reference A step of rearranging the electronic components temporarily arranged so as to be equal to or lower than the value.

  The recording medium of the present invention is a computer-readable recording medium that records a program used in a design support device for a printed board using an information processing apparatus, and a code for temporarily placing electronic components on the printed board And the code for the step of connecting the temporarily arranged electronic components with the wiring of the shortest path, and the temporarily arranged electronic components so as to minimize the wiring length in the long side direction of the ground plane. The code of the process to arrange | position is recorded, It is characterized by the above-mentioned.

  The recording medium of the present invention is a computer-readable recording medium that records a program used in a design support device for a printed board using an information processing apparatus, and a code for temporarily placing electronic components on the printed board And the provisionally arranged so that the wiring length in the long side direction of the ground plane of the connected wiring is equal to or less than a predetermined reference value, the cord of the step of connecting the temporarily arranged electronic components with the wiring of the shortest path It is characterized by recording a code of a process of rearranging the electronic components.

  The operation of the present invention will be described. From the experiment and the results of its investigation, the common mode current of the printed circuit board is based on the normal mode current of the signal wiring on the printed circuit board, flows to the ground plane facing it, and the direction in which the common mode current flows is the normal mode current It is found that when the length of the ground plane in that direction matches the length of an integral multiple of ½ wavelength, or a frequency close to that, a large amount of common mode current flows and the common mode radiation becomes stronger. did. From this result, if the frequency of each side of the ground plane is close to the integral multiple of 1/2 wavelength at the design stage of the printed circuit board, the frequency at which common mode radiation is likely to occur and the frequency It can be seen whether it is included in the frequency range subject to EMI regulation, and it is possible to determine in which direction of the printed circuit board the signal wiring of the high-speed signal (meaning “signal frequency is high”) that causes common mode radiation. it can.

  Further, according to the experiment and the result of the examination, the present invention shows that, in the case of a wide metal plate such as a ground plane, strictly, the frequency is slightly lower than the frequency at which the length of one side coincides with the length of an integral multiple of 1/2 wavelength. It was found that the ground plane resonated strongly at a low frequency. The value was a value obtained by multiplying the frequency at which the length of one side coincides with the length of an integral multiple of ½ wavelength by about 0.75. Therefore, a frequency obtained by multiplying a frequency (or a frequency close thereto) by which the length of one side is equal to an integral multiple of 1/2 wavelength by 0.75 (or a value close thereto) is output and displayed, or A value obtained by multiplying the length of one side by 1.3 (or a value close thereto) is a frequency (or a frequency close thereto) that matches the length of an integral multiple of ½ wavelength, and is output and displayed. As a result, it is possible to know the frequency at which common-mode radiation is likely to occur at the design stage of a printed circuit board, and whether the frequency is included in the frequency range subject to EMI regulation, and a high-speed signal that causes common-mode radiation. It becomes easy to determine in which direction of the printed circuit board the wiring should be drawn.

  Further, according to the present invention, when a printed circuit board is configured by connecting a plurality of electronic components by wiring from an experiment and the result of the examination, if the position on the ground plane changes even if the positional relationship between the electronic components and the wiring is the same, It was found that the radiation level is different, and that the common mode radiation level is higher when the wiring is arranged along the long side direction of the ground plane than when the wiring is arranged along the short side direction. Therefore, in the present invention, electronic components are temporarily arranged, and the components are connected by the shortest path wiring, and then the wiring length of the wiring in the long side direction of the ground plane is obtained, and the temporary value is set so that the value is minimized. Rearrange the placed electronic components. As a result, a printed circuit board that suppresses common mode radiation can be designed.

  Further, according to the present invention, in the above-described invention, the “condition for rearranging the temporarily arranged electronic components” is set such that “the wiring length in the long side direction of the ground plane is obtained, and the value is less than a certain value. ". This value should be as small as possible, but design conditions can be relaxed by allowing the value to be changed according to the size of the printed circuit board and the total wiring length. Even if the conditions are relaxed in this way, a printed circuit board that suppresses common mode radiation can be designed in the same manner as the invention described above.

  Further, according to the present invention, when the signal wiring is arranged along the long side direction of the ground plane, the signal wiring is arranged at the edge (end side) of the ground plane from the experiment and the examination result. It was found that the common mode radiation from the printed circuit board is larger than that in the case where the circuit board is disposed in the circuit board. Therefore, in the present invention, first, the ground plane is divided into N regions in the short side direction. Next, terminals of a plurality of electronic components are designated, and wirings connecting the designated terminals are arranged in M areas inside the divided ground planes. Thereby, the printed circuit board which suppressed common mode radiation can be designed.

  Further, according to the present invention, in the invention described above, the ground plane is divided into four regions in the short side direction of the printed circuit board, and the region where the signal wiring is arranged is two regions inside the ground plane. It is. This value is an empirically obtained value. As a result, a printed circuit board that suppresses common mode radiation can be designed.

  Further, according to the present invention, the length of a certain ratio or more with respect to a certain signal wiring that has already been arranged is within M areas inside the area divided into N pieces in the short side direction of the ground plane. It is to check whether it is arranged. In the present invention, the number of area divisions is four, and the arrangement area to be checked is two areas inside the ground plane. In this way, by checking whether or not the signal wiring is arranged at the edge, it is possible to check whether or not the printed circuit board design that suppresses the common mode radiation is made. If not, it becomes clear that it must be redesigned.

  Further, according to the present invention, the signal wiring already arranged is longer than a certain proportion of the wiring in the outer P areas among the areas divided into N pieces in the short side direction of the ground plane. It is to check whether it is arranged in. In the present invention, the number of divisions of the area is four, and the arrangement area to be checked is two areas outside the ground plane. It should be noted that the same characteristics are checked for the signal wirings only in the position to be checked is different from the above-described invention. In this way, by checking whether or not the wiring is arranged at the edge, it is possible to check whether or not the printed circuit board design that suppresses the common mode radiation has been made, and if not, the design must be redesigned. It becomes clear.

  According to the printed circuit board design support apparatus of the present invention, it is possible to know the frequency at which common mode radiation is likely to occur and whether the frequency is included in the frequency range subject to EMI regulation at the board design stage. It becomes easier to determine in which direction of the printed circuit board the signal wiring of the high-speed signal that causes mode radiation. Further, the frequency to be obtained is a frequency in which 1.3 times the length of each side of the ground plane is close to an integral multiple of ½ wavelength, or the length of each side of the ground plane is an integral multiple of ½ wavelength. By setting the frequency close to the length to 0.75 multiplied by the frequency, it is possible to grasp the frequency that causes the common mode radiation closer to the actual frequency.

  According to the printed circuit board design support apparatus of the present invention, by re-arranging the temporarily arranged electronic components so that the wiring length in the long side direction of the ground plane is minimized or less than a certain value, A printed circuit board that suppresses mode radiation can be designed.

  According to the printed circuit board design support apparatus of the present invention, the long-side portion of the ground plane of the signal wiring connecting the terminals is arranged in the M areas inside the ground plane divided into N areas. Thus, it is possible to realize a wiring layout in which common mode radiation is difficult to occur.

  According to the design support apparatus of the present invention, by arranging the portion of the wiring connecting the terminals in the direction of the long side of the ground plane into two regions inside the ground plane divided into four regions, the common mode It is possible to realize a wiring layout that hardly generates radiation.

  According to the design support apparatus of the present invention, the long side portion of the ground plane of the wiring connecting the terminals is arranged in M areas inside the ground plane divided into N areas at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the design support apparatus of the present invention, the portion of the long side direction of the ground plane of the wiring connecting the terminals is arranged in two regions inside the ground plane divided into four regions at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the design support apparatus of the present invention, the long-side portion of the ground plane of the wiring connecting the terminals is arranged in P areas outside the ground plane divided into N areas at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the design support apparatus of the present invention, the portion of the long side direction of the ground plane of the wiring connecting the terminals is arranged in two regions outside the ground plane divided into four regions at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the printed circuit board design support method of the present invention, at the board design stage, it is possible to know the frequency at which common mode radiation is likely to occur and whether the frequency is included in the frequency range subject to EMI regulation. It becomes easier to determine in which direction of the printed circuit board the signal wiring of the high-speed signal that causes mode radiation. Further, the frequency to be obtained is a frequency in which 1.3 times the length of each side of the ground plane is close to an integral multiple of ½ wavelength, or the length of each side of the ground plane is an integral multiple of ½ wavelength. By setting the frequency close to the length to 0.75 multiplied by the frequency, it is possible to grasp the frequency that causes the common mode radiation closer to the actual frequency.

  According to the printed circuit board design support method of the present invention, it is possible to re-arrange the temporarily arranged electronic components so that the wiring length in the long side direction of the ground plane is minimized or less than a certain value. A printed circuit board that suppresses mode radiation can be designed.

  According to the printed circuit board design support method of the present invention, the long-side portion of the ground plane of the signal wiring connecting the terminals is arranged in M regions inside the ground plane divided into N regions. Thus, it is possible to realize a wiring layout in which common mode radiation is difficult to occur.

  According to the design support method of the present invention, the portion of the wiring connecting the terminals in the direction of the long side of the ground plane is arranged in two regions inside the ground plane divided into four regions. It is possible to realize a wiring layout that hardly generates radiation.

  According to the printed circuit board design support method of the present invention, the M areas inside the ground plane in which the portion of the long side direction of the ground plane of the wiring connecting the terminals is divided into N areas at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the printed circuit board design support method of the present invention, the two areas inside the ground plane in which the long-side portion of the wiring ground plane connecting the terminals is divided into four areas at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the printed circuit board design support method of the present invention, P areas outside the ground plane in which the portion of the long side direction of the ground plane of the wiring connecting the terminals is divided into N areas at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the printed circuit board design support method of the present invention, the two areas outside the ground plane in which the long-side portion of the ground plane of the wiring connecting the terminals is divided into four areas at a certain ratio or more. It is possible to check whether or not the signal wiring is arranged so that common mode radiation is less likely to occur.

  According to the recording medium of the present invention, the code of the process of obtaining the length of each side of the ground plane in the printed circuit board from the layout information of the printed circuit board, and the length of each side and the integral multiple of 1/2 wavelength Recorded the code of the process for obtaining the frequency that is substantially the same and within the scope of the regulation of unnecessary electromagnetic radiation, and the code for the process of outputting and displaying the value of the obtained frequency. By applying to a printed circuit board design support device, it is possible to know the frequency at which common mode radiation is likely to occur at the printed circuit board design stage and whether the frequency is included in the frequency range subject to EMI regulations. This makes it easier to determine in which direction the signal wiring of the high-speed signal that causes common mode radiation should be drawn.

  According to the recording medium of the present invention, a code for the step of obtaining the length of each side of the ground plane in the printed circuit board from the layout information of the printed circuit board, a value obtained by multiplying the length of each side by a predetermined coefficient, and 1 / 2 is a frequency that is approximately equal to the length of an integral multiple of two wavelengths, or is a frequency that is a frequency that is approximately equal to the length of each side and the length of an integral multiple of ½ wavelength multiplied by a predetermined coefficient. In addition, a code for a process for obtaining a frequency within the scope of the regulation of unnecessary electromagnetic radiation and a code for a process for outputting and displaying the obtained frequency value are recorded. By applying it to the equipment, it is possible to know at the design stage of the printed circuit board the frequency close to the actual frequency at which common mode radiation is likely to occur, and whether the frequency is included in the frequency range subject to EMI regulation. Nmodo determined such either to draw in the direction of the printed circuit board the signal wiring of the high-speed signal which causes radiation is likely to.

  According to the recording medium of the present invention, the code of the step of temporarily arranging electronic components on the printed circuit board, the code of the step of connecting the temporarily arranged electronic components by the shortest path wiring, and the ground plane of the connected wiring In order to minimize the wiring length in the long side direction, the code of the process of rearranging the electronic components temporarily arranged is recorded, so that the ground can be applied by applying to a versatile printed circuit board design support device. By rearranging the temporarily arranged electronic components so that the wiring length in the long side direction of the plane is minimized, it is possible to design a printed circuit board that suppresses common mode radiation.

  According to the recording medium of the present invention, the code of the step of temporarily arranging electronic components on the printed circuit board, the code of the step of connecting the temporarily arranged electronic components by the shortest path wiring, and the ground plane of the connected wiring Since the code of the process of rearranging the temporarily arranged electronic components is recorded so that the wiring length in the long side direction is equal to or less than a predetermined reference value, it is applied to a versatile printed circuit board design support apparatus. Thus, a printed circuit board in which common mode radiation is suppressed can be designed by rearranging the temporarily arranged electronic components so that the wiring length in the long side direction of the ground plane is not more than a predetermined value.

  According to the recording medium of the present invention, the code of the step of dividing the ground plane of the printed circuit board into N regions in the short side direction, the code of the step of designating the terminals of a plurality of electronic components arranged on the printed circuit board, Since the long side direction portion of the ground plane of the wiring connecting the designated terminals is arranged in M areas inside the ground plane divided into N areas, the code of the process is recorded. By applying it to a flexible printed circuit board design support device, the long side portion of the ground plane of the signal wiring connecting the terminals is divided into N areas into M areas inside the ground plane. By arranging the wiring, it is possible to realize a wiring layout in which common mode radiation is difficult to occur.

  According to the recording medium of the present invention, the code of the process of dividing the ground plane of the printed circuit board into four regions in the short side direction, the code of the process of designating the terminals of a plurality of electronic components arranged on the printed circuit board, Since the long-side portion of the ground plane of the wiring connecting the designated terminals is recorded in two areas inside the ground plane divided into four areas, the general-purpose code is recorded. By applying it to a flexible printed circuit board design support device, the portion of the wiring connecting the terminals in the direction of the long side of the ground plane is arranged in two regions inside the ground plane divided into four regions. Thus, it is possible to realize a wiring layout in which common mode radiation is difficult to occur.

  According to the recording medium of the present invention, the code of the process of dividing the ground plane of the printed circuit board into N regions in the short side direction, the code of the process of designating the wiring connecting the electronic components on the printed circuit board, A code of a process for inspecting that the long-side portion of the specified wiring in the long side direction of the designated wiring is in the M areas inside the divided ground plane at a predetermined ratio or more and the inspection result are output and displayed. Since the process code is recorded, when applied to a general-purpose printed circuit board design support apparatus, the length of the long side direction of the ground plane of the wiring connecting the terminals is greater than a certain percentage. Whether or not signal wiring is arranged so that common mode radiation is less likely to occur. It is possible to check.

  According to the recording medium of the present invention, the code of the process of dividing the ground plane of the printed circuit board into four regions in the short side direction, the code of the process of designating the wiring connecting the electronic components on the printed circuit board, Outputs and displays the code of the process for inspecting that the long side direction portion of the specified plane of the specified wiring is in two areas inside the divided ground plane at a predetermined ratio or more, and the inspection result Since the process code is recorded, when applied to a general-purpose printed circuit board design support device, the long-side direction portion of the ground plane of the wiring connecting the terminals has a certain ratio of four areas or more. Check whether the signal wiring is arranged so that it is difficult to generate common mode radiation. It is possible to check.

  According to the recording medium of the present invention, the code of the process of dividing the ground plane of the printed circuit board into N regions in the short side direction, the code of the process of designating the wiring connecting the electronic components on the printed circuit board, A code of a process for inspecting that the long-side portion of the specified wiring in the long side direction of the designated wiring is in P areas outside the divided ground plane at a predetermined ratio or more and the inspection result are output and displayed. Since the process code is recorded, when applied to a general-purpose printed circuit board design support apparatus, the length of the long side direction of the ground plane of the wiring connecting the terminals is greater than a certain percentage. Whether or not signal wiring is arranged so that common mode radiation is less likely to occur. It is possible to check.

  According to the recording medium of the present invention, the code of the process of dividing the ground plane of the printed circuit board into four regions in the short side direction, the code of the process of designating the wiring connecting the electronic components on the printed circuit board, Outputs and displays a code of a process for inspecting that the long side direction portion of the specified plane of the specified wiring is in two areas outside the divided ground plane at a predetermined ratio or more, and the inspection result Since the process code is recorded, when applied to a general-purpose printed circuit board design support device, the long-side direction portion of the ground plane of the wiring connecting the terminals has a certain ratio of four areas or more. Check whether the signal wiring is arranged so that it is difficult to generate common mode radiation. It is possible to check.

  The present invention is realized by adding a design function for suppressing EMI to a printed circuit board design support apparatus using an information processing apparatus (so-called computer system) such as a workstation or a personal computer. Moreover, the realization means depends on software. Therefore, the present invention is not limited to the type of hardware constituting the system, and the hardware configuration of the system to be used is not particularly illustrated.

[First Embodiment]
A first embodiment of the present invention will be described.

  In this example, a printed circuit board design support device using an information processing device such as a workstation or a personal computer obtains the length of each side of the ground plane (ground layer) in the printed circuit board from the printed circuit board layout information. A processing unit, a processing unit for obtaining a frequency that is a length that is an integral multiple of a half wavelength and the length of each of the sides, and that is within a range subject to regulation of unnecessary electromagnetic radiation, and a value of the frequency The system is configured by providing a processing unit for outputting and displaying the above.

  FIG. 1 shows an example of a printed circuit board for explaining the operation of the first embodiment of the present invention, in which LSIs (Large Scale Integrated Circuits) 3a, 3b, 3c, 3d are arranged on a rectangular printed circuit board 1. It is.

  In this example, first, information on the ground plane 2 is extracted from the layout information of the printed circuit board 1, and the length of each side of the ground plane 2 is obtained from the information. Here, the long side is L1 and the short side is L2.

  Next, a frequency at which the lengths L1 and L2 are ½ wavelength is obtained. Since the relationship between frequency and wavelength is (frequency Hz) = (3 × 10E + 8) / (wavelength m), the frequency fr is

  It is obtained by. Here, the frequency fr [Hz] and the side length L [m], and 3 × 10E + 8 [m / s] is the speed at which the electromagnetic wave propagates in the vacuum. Finally, the obtained frequency is output to the display unit of the design support apparatus.

  Thus, by outputting and displaying the frequency at which the length of each side is ½ wavelength, the printed circuit board designer can grasp the frequency at which the common mode radiation becomes strong at the design stage. It can be judged whether or not a measure to suppress common mode radiation is necessary for the printed circuit board.

  Here, the half wavelength has been described as an example, but resonance can occur even at a frequency that is an integral multiple of the half wavelength, such as one wavelength, three-half wavelength, or the like. Therefore, if not only the half wavelength but also an integer multiple of the frequency is within the frequency range subject to EMI regulation, this is output and displayed.

  Next, a more specific printed board will be described as an example. FIG. 9 is an example of a printed circuit board for explaining the detailed operation of the first embodiment. With this example, the common mode radiation becomes strong at the frequency of the ground plane having a length close to ½ wavelength. Explain that.

  The printed circuit board shown in FIG. 9 is a four-layer printed circuit board having a size of 210 mm × 100 mm × 1.6 mm. The layer structure is, from the top, a signal layer, a ground layer (ground plane), a power supply layer (power supply plane), and a signal layer. All circuits were placed in the first signal layer. A printed circuit board circuit was composed of a 40 MHz crystal oscillator, an FPGA (Field Programmable Gate Array) LSI, a load capacity of 7 pF, a decoupling capacitor of 0.1 μF, and an initialization circuit. A 40 MHz rectangular wave signal was output from the crystal oscillator to the LSI, and a 20 MHz rectangular wave signal was output from the LSI to 16 load capacitors. Since the initialization circuit determines the operation mode of the LSI, only the circuit between the crystal oscillator and the LSI and between the LSI and the load capacitor operates in a steady state.

  10 and 11 show the radiation electric field characteristics of the printed circuit board. According to the standard of EMI measurement, it measured in the range of 30 MHz to 1 GHz. The measurement was performed in an anechoic chamber in which a radio wave absorber was also laid on the floor surface. The printed circuit board was arranged parallel to the floor surface. 10 shows horizontal polarization characteristics, and FIG. 11 shows vertical polarization characteristics. Both had characteristics with a peak in the vicinity of 500 MHz. In addition, the level of radiation was higher in horizontal polarization in the range of 300 MHz to 700 MHz, and there was almost no difference between horizontal and vertical at other frequencies.

  In order to find out the cause of the higher level of horizontal polarization, the radiation pattern of 520 MHz where the radiation level was the highest was measured. FIG. 12 shows the result. The solid line is horizontal polarization, and the broken line is vertical polarization. The horizontal polarization has an 8-shaped pattern with peaks at 90 ° and 270 °, and the vertical polarization has a characteristic close to that of an 8-shaped pattern with peaks at 0 ° and 180 °. This radiation pattern can be explained by the radiation model shown in FIGS. FIG. 13 shows a normal mode radiation model in which the signal wiring between the crystal oscillator and the LSI or the signal wiring between the LSI and the load capacitor acts as a minute loop antenna. In this model, the vertical polarization where the loop surface and the antenna reception surface coincide with each other is the main polarization, and an 8-shaped radiation pattern having peaks at angles φ of 0 ° and 180 °. The vertical polarization component of the measurement result corresponds to that. FIG. 14 shows a common mode radiation model in which the long side of the ground plane functions as a half-wave dipole antenna. In this model, the horizontally polarized wave in which the length direction of the ground plane serving as an antenna and the antenna receiving surface coincide with each other is a main polarized wave, and an 8-shaped radiation pattern having peaks at angles of 90 ° and 270 °. The horizontal polarization component of the measurement result corresponds to that. From this result, it can be expected that the cause of the horizontally polarized component having a high radiation level is the common mode radiation from the ground plane.

  In order to verify the validity of this result, a radiation pattern was obtained by calculation using an electromagnetic analysis model as shown in FIG. The main cause of the common mode current flowing through the ground plane was assumed to be LSI. The LSI chip portion is represented by a voltage source, the LSI lead frame and signal wiring are represented by complete conductor wires, the load capacitance is represented by a 1 ohm resistor, and the ground plane is represented by a complete conductor plane. This is a radiation model in which the normal mode radiation model of FIG. 13 and the common mode radiation model of FIG. 14 are combined. The radiation pattern was calculated | required using the electromagnetic field simulator by FDTD (Finite Difference Time Domain) method. FIG. 16 shows the calculation result at 520 MHz. The vertical axis represents the absolute gain proportional to the radiation electric field characteristics. The tendency agrees well with the measurement result shown in FIG. From the result of this calculation, the validity of the radiation model shown in FIGS. 13 and 14 can be confirmed, and it can be confirmed that the common mode radiation from the ground plane is dominant in this printed circuit board.

  Furthermore, in order to investigate the characteristics of the common mode current on the ground plane, which is the cause of radiation, the electromagnetic field intensity distribution near the ground plane was obtained. FIG. 17 shows the electric field strength distribution, and FIG. 18 shows the magnetic field strength distribution. This is a distribution at a position 10 mm away from the ground plane on the side where there is no signal wiring, and is the sum of squares of the three-direction components of the electromagnetic field. The electric field is strong at the edge of the long side of the ground plane and weak at the center. Conversely, the magnetic field is strong at the center and weak at the edges. This indicates that the ground plane works as a half-wave dipole antenna.

  The frequency at which the long side 210 mm of the ground plane plane becomes a half wavelength is 714 MHz. Although it is actually about 0.75 times smaller than the highest radiation level of 520 MHz, it can be seen that the ground plane is strongly excited at a frequency at which the long side is about ½ wavelength, causing common mode radiation.

  From the above results, it can be seen that the common mode radiation from the printed circuit board becomes strong in the vicinity of the frequency at which the length of the ground plane is ½ wavelength. Therefore, by displaying the frequency at which the length of each side of the ground plane is ½ wavelength or close to it, it is possible to inform the designer of the frequency at which the common mode radiation is generated, and the print considering the common mode radiation. Supports board design.

  Further, resonance can occur not only at ½ wavelength but also at an integral multiple thereof. Therefore, a printed circuit board that suppresses common mode radiation can be designed by outputting a frequency in which the length of the ground plane is an integral multiple of ½ wavelength among the frequencies that are problematic for unnecessary electromagnetic radiation.

  In the first embodiment, the frequency at which the long side of the ground plane is ½ wavelength is output. However, as can be seen from this example, in the case of a flat plate such as a ground plane, the resonance frequency is 1. / Slightly lower than the frequency of 2 wavelengths. From this experimental result, a frequency where 1.3 times the length of one side becomes a half wavelength, or a frequency obtained by multiplying a frequency where the length becomes a half wavelength by 0.75 is more realistic. . In addition, it can be estimated that the same result can be obtained not only at 1/2 wavelength but also at a frequency that is an integral multiple of 1/2 wavelength.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.

  In this example, a printed circuit board design support device using an information processing device such as a workstation or a personal computer has a shortest path wiring between a processing unit that temporarily places electronic components on the printed circuit board and the temporarily placed electronic components. And a processing unit for rearranging the temporarily arranged electronic components so as to minimize the wiring length of the connected wiring in the long side direction portion of the ground plane.

  FIG. 2 is an example of a printed circuit board for explaining the operation of the second embodiment of the present invention. FIG. 2 is an example in which LSIs 3e and 3f are provisionally arranged on the printed circuit board 1 as electronic parts and the signal wiring 4 of the shortest path is connected therebetween. In this case, all the signal wirings 4 are oriented in the long side direction of the ground plane 2. Next, the LSIs 3e and 3f are moved so that all the signal wirings facing the long side direction face the short side direction. An example of this change is shown in FIG. FIG. 4 is a flowchart illustrating this series of operations. If the signal wiring 4 for high-speed signals that can cause EMI is not drawn in the long side direction of the ground plane, common mode radiation can be effectively suppressed.

  Next, a more specific printed board will be described as an example. FIG. 19 is an example of a printed circuit board for explaining the second embodiment in detail. The printed circuit board shown in FIG. 19 has the same circuit configuration as the printed circuit board shown in FIG. 9, but the whole circuit is rotated 90 ° clockwise around the LSI. This is an example in which most of the signal wiring between the crystal oscillator and the LSI and between the LSI and the load capacitor faces the short side direction of the ground plane. 20 shows the radiated electric field characteristic of the printed circuit board of FIG. 9, and FIG. 21 shows the radiated electric field characteristic of the printed circuit board of FIG. As in the previous case, the measurement results were obtained in an anechoic chamber in which a radio wave absorber was also laid on the floor. However, (1) When the printed circuit board is arranged parallel to the floor surface, (2) When the long side of the printed circuit board is arranged perpendicular to the floor surface, (3) The short side of the printed circuit board is arranged perpendicular to the floor surface In this case, the horizontal polarization characteristics and the vertical polarization characteristics were measured, and all of them were superimposed. From this result, it can be seen that the printed circuit board of FIG. 19 has a lower radiation level than the printed circuit board of FIG.

In order to explain the reason why the radiation level of the printed circuit board of FIG. 19 is lowered in this way, a radiation pattern of 520 MHz in which the radiation level is significantly lowered is shown. FIG. 22 shows the measurement results when the printed circuit board is arranged parallel to the floor surface. Since the position of the signal wiring is shifted by 90 ° from the printed circuit board of FIG. 9, the figure 8 characteristic of vertical polarization due to normal mode radiation is also shifted by 90 ° compared to the result of FIG. On the other hand, horizontal polarization due to common mode radiation is low. From this result, it is understood that the common mode radiation is lowered by rearranging the signal wiring in the short side direction of the ground plane. In the electric field and magnetic field distribution in the vicinity of the ground plane shown in FIGS. 17 and 18, the direction of the signal wiring and the excitation direction of the ground plane are the same.
Predicting from this result, in the printed circuit board of FIG. 19, since most of the signal wirings are arranged in the short side direction, it is considered that the long side direction is hardly excited and the short side direction is excited. However, since the length in which the length of 100 mm in the short side direction becomes a half wavelength was about 1.5 GHz, strong excitation was not generated at a frequency of 1 GHz or less measured here, and strong radiation did not occur. .

  From the above results, it can be seen that a printed circuit board that suppresses common mode radiation can be designed by rearranging components so that the wiring length in the long side direction of the ground plane is minimized using the present invention.

  Note that the printed circuit boards shown in FIGS. 2 and 3 are very simple examples. In an actual printed circuit board, components and wiring are intertwined in a complicated manner. In such a case, the temporarily arranged electronic components may be rearranged so that the wiring length in the long side direction of the ground plane is not more than a specified value. As the value, what percentage or less of the total length, or what m, cm, mm or less may be specified. As an empirical value, 20% or less is a reasonable value.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.

  In this example, a printed circuit board design support apparatus using an information processing apparatus such as a workstation or a personal computer has a processing unit that divides the ground plane of the printed circuit board into N areas in the short side direction, and a printed circuit board. A processing unit for designating terminals of a plurality of arranged electronic components and a process for arranging a portion of a long side direction of a ground plane of wiring connecting between the designated terminals in M areas inside the divided ground plane The system is configured by providing a section.

  The operation of the third embodiment of the present invention will be described with reference to the printed circuit boards shown in FIGS. In this example, the ground plane 2 of the printed circuit board 1 is equally divided into four regions in the short side direction. The two outer areas are “Bad” areas, and the two inner areas are “Good” areas. Further, the terminals of the LSIs 3g and 3h are designated, and the signal wiring 4 connects between them. The example of FIG. 5 is an example of wiring without considering common mode radiation, and the example of FIG. 6 is an example of wiring by applying the present invention. As described above, when the signal wiring 4 is arranged in the long side direction of the ground plane, the common mode radiation is increased. Further, as will be described in detail later, when the signal wiring 4 is arranged at the edge of the ground plane, the common mode radiation is stronger than when the signal wiring 4 is arranged at the center. As a matter of fact, it is impossible to route the wiring at all in the long side direction of the ground plane. In such a case, the signal wiring in the long side direction is arranged at the center of the ground plane as much as possible to suppress common mode radiation. A printed circuit board can be designed. FIG. 7 shows a flowchart illustrating the above operation.

Hereinafter, the board model will be described as an example in more detail. FIG. 23 shows a board model when the signal wiring is arranged at a position 10 mm from the edge of the ground plane. FIG. 24 shows a board model when the signal wiring is arranged in the center of the ground plane. Other conditions are the same as those of the substrate model shown in FIG. Radiation patterns obtained based on these models are shown in FIGS. The frequency is 520 MHz as before. When the signal wiring is at the center of the ground plane, as shown in FIG.
However, if the signal wiring is at the edge, as shown in FIG. 25, the directivity becomes sharp in the direction in which the wiring approaches. In EMI measurement, since the maximum radiation level is measured while placing the substrate on the turntable and rotating the substrate, it can be seen that the radiation level is higher when the signal wiring is arranged at the edge.

  From the above results, it is possible to design a printed circuit board that suppresses common mode radiation by directing the long side portion of the signal wiring ground plane in the center of the ground plane as much as possible.

  In the example shown in FIG. 5, the number N of areas to be divided is 4 and the number M of areas to be wired is 2 and the combination of these values is basic. And M = N−2.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described.

  In this example, a printed circuit board design support apparatus using an information processing apparatus such as a workstation or a personal computer includes a processing unit that divides the ground plane of the printed circuit board into N regions in the short side direction, A process for checking whether or not the processing unit for specifying the wiring connecting the electronic components and the long side direction portion of the ground plane of the specified wiring are in a certain number of M areas inside the divided ground plane. And a processing unit for outputting and displaying the result of the examination are configured.

  The operation will be described with reference to FIGS. First, the ground plane 2 of the printed circuit board 1 is divided into four regions in the short side direction. Next, the signal wiring to be checked is designated. Here, three signal wires 4 are designated. Next, for the portion of the designated signal wiring 4 in the long side direction of the ground plane, the length existing in the two regions inside the ground plane is obtained, and the length is the total length in the long side direction of the ground plane. If the ratio is less than the specified value, and if it is less than the specified value, the wiring is output as an error. In this example, N = 4 and M = 2. A combination of these values is fundamental, but in order to increase the effect, the number N of regions may be increased and M = N−2. Further, the ratio of the judgment criteria may be 100% in order to improve the effect, but about 80% is considered a reasonable value. In this example, one outer line is an error.

  As described above, according to this example, it is possible to examine whether or not the long side portion of the ground plane of the signal wiring is disposed near the center of the ground plane with respect to the already disposed signal wiring. It is possible to confirm whether or not a suppressed printed circuit board has been designed.

[Fifth Embodiment]
Finally, a fifth embodiment of the present invention will be described.

  In this example, a printed circuit board design support apparatus using an information processing apparatus such as a workstation or a personal computer includes a processing unit that divides the ground plane of the printed circuit board into N regions in the short side direction, A processing unit for designating wiring connecting between electronic components, and a processing unit for checking that a certain proportion or more of the long side direction portion of the ground plane of the designated wiring is in P areas outside the divided ground plane; The system is configured by providing a processing unit for outputting and displaying the result of the examination. In this example, the ground plane region for examining the arrangement of the signal wiring in the long side direction of the ground plane is set as the outer region, not the inner region.

  For example, the determination criterion ratio of 80% in the fourth embodiment is the same as the determination criterion ratio of 20% in this example. Therefore, according to this example, it is possible to check whether the long side direction part of the ground plane of the signal wiring is arranged near the center of the ground plane for the signal wiring that has already been arranged, and print that suppresses common mode radiation. It is possible to check whether the board is designed.

  By the way, in the printed circuit board design support apparatus using the information processing apparatus such as the workstation and the personal computer from the first embodiment to the fifth embodiment described above, the computer is recorded therein. The program code is read and the process is executed. Therefore, the program code for realizing the functions of the above-described embodiments is recorded on a computer-readable recording medium, and the program code recorded on the recording medium is read by the computer of the printed circuit board design support apparatus and executed. Thus, a design support process for the printed circuit board may be performed.

  Note that the “computer-readable recording medium” herein refers to a storage medium such as a floppy disk, a magneto-optical disk, a portable medium such as a ROM or a CD-ROM, or a hard disk built in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In this way, it is assumed to include those that hold a program for a certain period of time.

  The program code may be transmitted from a computer system storing the program code in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program code refers to a medium having a function of transmitting information, such as a network (communication line) such as the Internet or a communication line (communication line) such as a telephone line.

  The program code may be for realizing a part of the design support function described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program code already recorded on the computer system, what is called a difference file (code of a difference program) may be sufficient.

It is an example of the printed circuit board for demonstrating the operation | movement of the 1st Embodiment of this invention. It is Example 1 of the printed circuit board for demonstrating the operation | movement of the 2nd Embodiment of this invention. It is Example 2 of the printed circuit board for demonstrating the operation | movement of the 2nd Embodiment of this invention. It is a flowchart for demonstrating the operation | movement of the 2nd Embodiment of this invention. It is an example of the printed circuit board for demonstrating operation | movement of the 3rd, 4th, 5th embodiment of this invention. It is an example of the printed circuit board by the 3rd Embodiment of this invention. It is a flowchart for demonstrating the operation | movement of the 3rd Embodiment of this invention. It is a flowchart for demonstrating the operation | movement of the 4th Embodiment of this invention. It is an example of the printed circuit board for demonstrating the detailed operation | movement of the 1st Embodiment of this invention. 10 is a measurement result of horizontal polarization characteristics of the printed circuit board shown in FIG. 9. 10 is a measurement result of vertical polarization characteristics of the printed board shown in FIG. 9. It is a measurement result of the radiation pattern of the printed circuit board shown in FIG. It is a normal mode radiation model of the printed circuit board shown in FIG. It is a common mode radiation model of the printed circuit board shown in FIG. 10 is an electromagnetic field analysis model of the printed circuit board shown in FIG. 9. It is a calculation result of the radiation pattern of the printed circuit board shown in FIG. 10 is a calculation result of electric field strength distribution in the vicinity of the printed board shown in FIG. 9. 10 is a calculation result of a near magnetic field strength distribution of the printed circuit board shown in FIG. 9. It is an example of the printed circuit board for demonstrating the detailed operation | movement of 2nd Embodiment. It is a radiation electric field characteristic of the printed circuit board shown in FIG. It is a radiation electric field characteristic of the printed circuit board shown in FIG. It is a radiation pattern measurement result of the printed circuit board shown in FIG. It is the board | substrate model 1 for demonstrating operation | movement of 3rd Embodiment. It is the board | substrate model 2 for demonstrating operation | movement of 3rd Embodiment. It is a radiation pattern calculation result of the board | substrate model shown in FIG. It is a radiation pattern calculation result of the board | substrate model shown in FIG. It is a flowchart which shows the outline of the layout method of the printed circuit board of a prior art example. It is an operation | movement conceptual diagram of the CAD apparatus of a prior art example. It is a figure for demonstrating a normal mode electric current and a common mode electric current.

Explanation of symbols

1 Printed circuit board 2 Ground plane (ground layer)
3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h LSI
4 signal wiring

Claims (6)

In a printed circuit board design support device using an information processing device,
Means for temporarily placing electronic components on a printed circuit board;
Means for connecting the temporarily placed electronic components with the shortest path wiring;
A printed circuit board design support apparatus, comprising: means for rearranging the electronic components temporarily arranged so as to minimize the wiring length of the connected wiring in the long side direction of the ground plane. In a printed circuit board design support device using an information processing device,
Means for temporarily placing electronic components on a printed circuit board;
Means for connecting the temporarily placed electronic components with the shortest path wiring;
A printed circuit board design support comprising: means for rearranging the electronic components temporarily arranged so that the wiring length in the long side direction of the ground plane of the connected wiring is equal to or less than a predetermined reference value apparatus. In a printed circuit board design support method in a printed circuit board design support apparatus using an information processing device,
The information processing apparatus temporarily placing electronic components on a printed circuit board;
The information processing apparatus is a step of connecting the temporarily arranged electronic components by wiring of the shortest path;
The information processing apparatus includes a step of rearranging the electronic components temporarily arranged so as to minimize the wiring length of the connected wiring in the long side direction of the ground plane. Support method. In a printed circuit board design support method in a printed circuit board design support apparatus using an information processing device,
The information processing apparatus temporarily placing electronic components on a printed circuit board;
The information processing apparatus is a step of connecting the temporarily arranged electronic components by wiring of the shortest path;
The information processing apparatus includes a step of rearranging the electronic components temporarily arranged so that the wiring length of the connected wiring in the long side direction of the ground plane is equal to or less than a predetermined reference value. A printed circuit board design support method. In a computer-readable recording medium recording a program used in a printed circuit board design support device using an information processing device,
A code for temporarily placing electronic components on the printed circuit board;
A code for the process of connecting the temporarily placed electronic components with the shortest path wiring;
A recording medium in which a code of a process of rearranging the electronic components temporarily arranged so as to minimize the wiring length of the connected wiring in the long side direction of the ground plane is recorded. In a computer-readable recording medium recording a program used in a printed circuit board design support device using an information processing device,
A code for temporarily placing electronic components on the printed circuit board;
A code for the process of connecting the temporarily placed electronic components with the shortest path wiring;
A recording medium in which a code of a process of rearranging the electronic components temporarily arranged so that the wiring length of the connected wires in the long side direction of the ground plane is equal to or less than a predetermined reference value is recorded.

Images