JP2005251223A - Method for evaluating characteristic of printed circuit board, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate whether or not a printed circuit board, in which a power supply voltage fluctuation is suppressed and unwanted electromagnetic wave radiation caused by the resonance of a power supply system circuit is prevented, has been designed during or after board layout preparation before board manufacturing. <P>SOLUTION: The layout information of the entire board is fetched by an input device (S10), only the layout information of the power supply system circuit is extracted by an extraction means (S11), it is stored in the storage part of a storage device (S12), and it is fetched by a conversion means and converted to electric circuit information (S13). By using this electric circuit information, impedance characteristics of the power supply system circuit viewed from the power supply terminal connecting position of a certain designated active element are calculated (S14) and the result thereof is displayed (S15). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a printed circuit board characteristic evaluation method for evaluating electrical characteristics and the like of a printed circuit board, and a storage medium for realizing the evaluation method.

  Conventionally, as a technique for evaluating whether a printed circuit board can operate normally by a numerical analysis method, for example, a circuit simulator called PSPICE as described in non-patent literature is generally known, and a patent There was what was disclosed in Document 1.

  FIG. 23 is a block diagram showing the configuration of the transmission line simulator disclosed in the above publication. According to this transmission line simulator, when a symbolized element and connection are input at the design stage, the display control unit 101 displays the physical shape and wiring topology of the connection application board on the display unit 102, A property is selected via the input unit 103. The property is given to the electromagnetic field simulator 106, which calculates the line constant of the connection and creates a line model. The element symbol is given to the replacement unit 105, and the replacement unit 105 extracts the device model from the element library 105a. The line model and the device model are combined by the combination unit 107 to form an equivalent circuit of the evaluation target circuit. The circuit simulator 108 performs transmission line analysis such as transmission lines such as delay and reflection characteristics on the equivalent circuit.

  By using these techniques, for example, as shown in FIG. 24, in the printed circuit board 200 on which the driver IC 201 and the receiver IC 202 are mounted, the electrical characteristics of signals transmitted from the IC 201 to the IC 202 via the wiring 203 are as follows: Can be evaluated. 25A and 25B are diagrams showing an example of an analysis model and an analysis result of the circuit configured on the substrate 200 of FIG. 24, where FIG. 25A is an analysis model and FIG. 25B is an analysis. Results are shown.

  The analysis model shown in FIG. 25A is a circuit in which a driver IC 201 and a receiver IC 202 are connected by a wiring 203. The driver IC 201 is represented by an equivalent circuit composed of a voltage source or a current source and a certain value of impedance, the receiver IC 202 is represented by an equivalent circuit of a certain value of impedance, and the wiring 203 is simply a wiring or resistor having the same potential, an inductor, It is expressed as a transmission line composed of a combination of capacitors.

  The analysis result shown in FIG. 25B represents the voltage waveform at the input terminal of the receiver IC 202. This voltage waveform has a large overshoot at the time of rising and an undershoot at the time of falling, so that the normal operation of the circuit cannot be guaranteed as it is, and a product mounted with this board cannot be commercialized.

  Therefore, as in the analysis model shown in FIG. 26A, the filter circuit 204 is inserted between the driver IC 201 and the wiring 203 to suppress the overshoot and undershoot (FIG. 26B). ).

  As described above, if the above technique is used, the circuit parameters can be easily changed, so that the optimum design of the circuit can be easily performed. In addition, since the signal waveform of the circuit can be grasped before the printed circuit board is manufactured, reprinting of the board due to a circuit design error is reduced, leading to a reduction in manufacturing cost.

On the other hand, in the printed circuit board, there is a power supply system circuit for supplying a stable DC voltage to an active element such as an IC or an LSI in addition to the above-described circuit for exchanging signals. FIG. 27 is an equivalent circuit focusing only on the power supply system, and the circuit within the range indicated by the one-dot chain line is the power supply system circuit 210. In this example, a capacitor 208 serving as a power supply system circuit 210 and a DC power supply 209 outside the substrate are connected to the power supply terminal 206 and the ground terminal 207 of the IC 205. The capacitor 208 plays a role of replenishing charges necessary for the switching operation of the IC 205 instead of the DC power supply 209 by being connected near the IC 205. If a capacitor having a low impedance is used as the capacitor 208, the voltage between the power supply terminal 206 and the ground terminal 207 does not fluctuate even if the IC 205 performs a switching operation. Such a capacitor 208 is called a decoupling capacitor. Until now, if it is connected, the power supply system circuit can be handled as a DC circuit, and it is not necessary to analyze the high-frequency characteristics with a circuit simulator. .

January 1993, R.F. Design, pages 25-27 (RF Design January 1993, pp. 25-27) JP-A-9-274623

  However, in recent years, the operating frequency of active elements such as ICs and LSIs has rapidly increased, so that this type of high frequency is required despite the fact that the high frequency characteristics of the power supply circuit as described above should be evaluated. There has never been a technique for evaluating characteristics by numerical analysis techniques. As a result, (1) the circuit operation of the printed circuit board cannot be sufficiently guaranteed, and (2) unnecessary electromagnetic waves are emitted from the printed circuit board.

  First, the problem (1) will be described in detail. When the operating frequency of the active element increases, the impedance due to the parasitic inductance of the decoupling capacitor itself and the impedance due to the parasitic inductance of the pads and via holes for mounting the capacitor on the substrate is the impedance due to the capacitance of the capacitor. Therefore, it becomes difficult to supply a stable DC voltage to the active elements, and it is difficult to guarantee their stable operation. This point will be specifically described with reference to FIG.

  FIG. 28 is a cross-sectional view showing a typical mounting example of the decoupling capacitor. In this example, the capacitor 220 is connected to the inner power supply layer 221 and the ground layer 222 via pads 223 and 224 and via holes 225. The parasitic inductance of the capacitor 220 itself is about 1 nH in the case of a chip component, and the parasitic inductances of the pads 223 and 224 and the via hole 225 are at least about 1 nH in total. Thus, it no longer works as a capacitive element but as an inductive element. Therefore, unless these inductances are designed to be as small as possible, power supply voltage fluctuations increase and circuit operation cannot be guaranteed.

  Next, the problem (2) will be described in detail. When the operating frequency of the active element increases, the wiring in the power supply system circuit acts as a transmission line, not just a wiring of the same potential, and the entire circuit behaves as a resonance circuit of the transmission line. Electromagnetic waves are emitted. This point will be specifically described with reference to FIG.

  FIG. 29 shows an example of a power supply system circuit in which a plurality of decoupling capacitors are connected as a model closer to an actual substrate. As shown in the figure, a decoupling capacitor 230a is connected to the IC 205, and thereafter, a wiring 231 serving as a transmission line, a decoupling capacitor 230b connected to another IC, and a DC power supply outside the substrate. 209 is connected. The decoupling capacitors 230 a and 230 b are connected to a parasitic inductance 232 in series with the capacitance 233. The power supply system circuit 234 is a circuit within a one-dot chain line, and this circuit may cause resonance.

  The solid line in FIG. 30 is an example of the impedance (Zin) characteristic when the power supply system circuit 234 is viewed from the connection position of the IC 205, and the broken line in FIG. 30 is the impedance (Zc) characteristic of the capacitor 230a. The characteristics of Zin substantially coincide with the characteristics of Zc, but are large at frequencies f01 and f02. This is because the impedance of the capacitor 230a acts as an inductive reactance as shown by the broken line, and the impedance of the power supply system circuit 234 connected thereafter acts as a capacitive reactance, and the magnitudes thereof coincide to cause parallel resonance. It is. When such resonance occurs, the impedance Zin when the power supply system circuit 234 is viewed from the IC 205 becomes large, which causes a large fluctuation in power supply voltage. In addition, energy by resonance is stored in the power supply system circuit, and strong electromagnetic waves are radiated therefrom, which makes it difficult to clear the standard regarding unnecessary electromagnetic radiation (EMI).

  In view of the above-described conventional problems, the present invention focuses on the high-frequency characteristics of the power supply system circuit to determine whether a printed circuit board that suppresses fluctuations in the power supply voltage and prevents unnecessary electromagnetic radiation due to resonance of the power supply system circuit can be designed. An object of the present invention is to provide a printed circuit board characteristic evaluation apparatus, a printed circuit board characteristic evaluation method, and a storage medium for realizing the evaluation method, which are evaluated by a numerical analysis method.

  In order to achieve the above object, a printed circuit board characteristic evaluation method according to the present invention is a method for evaluating a printed circuit board characteristic by a programmed computer, the power supply of each active element mounted on the printed circuit board. Calculating the impedance characteristic of the power supply system circuit in the substrate viewed from the terminal connection position, calculating the impedance characteristic from the power terminal connection position to the capacitor element connected to the closest position, and the power source By comparing the impedance characteristic of the supply system circuit with the magnitude, phase, real part, or imaginary part of the impedance characteristic up to the capacitor element, it is determined whether resonance occurs in the power supply system circuit. And a process.

  The printed circuit board characteristic evaluation method according to the present invention is a method for evaluating a printed circuit board characteristic by a programmed computer, and is closest to the power supply terminal connection position of each active element mounted on the printed circuit board. When the impedance characteristic of the capacitor element connected to the position is calculated, the impedance characteristic of the power supply system circuit after the capacitor element is calculated, the impedance characteristic of the capacitor element calculated by the calculation means, and the power supply system circuit And determining whether resonance occurs in the power supply system circuit by comparing any one of the magnitude, phase, real part, and imaginary part of the impedance characteristics.

  Further, a recording medium on which a printed circuit board characteristic evaluation control program according to the present invention is recorded is a recording medium on which a control program for evaluating a printed circuit board characteristic by a computer is recorded. Calculate the impedance characteristics of the power supply system circuit in the board viewed from the power supply terminal connection position of each active element mounted on the board, and the impedance characteristics from the power supply terminal connection position to the capacitor element connected to the nearest position Resonance in the power supply circuit by comparing the impedance characteristic of the power supply system circuit and the magnitude, phase, real part, or imaginary part of the impedance characteristic up to the capacitor element. Including processing for determining whether or not To.

  Further, a recording medium on which a printed circuit board characteristic evaluation control program according to the present invention is recorded is a recording medium on which a control program for evaluating a printed circuit board characteristic by a computer is recorded. A process for calculating the impedance characteristic of the capacitor element connected to the position closest to the power supply terminal connection position of each active element mounted on the substrate; a process for calculating the impedance characteristic of the power supply system circuit after the capacitor element; It is determined whether resonance occurs in the power supply system circuit by comparing the impedance characteristic of the capacitor element and the magnitude, phase, real part, or imaginary part of the impedance characteristic of the power supply system circuit. And a processing to be performed.

  As described above in detail, according to the present invention, the following effects can be obtained. (1) Since the impedance characteristic of the power supply system circuit can be calculated using the board layout information, the impedance of the power supply system circuit can be calculated during or after the layout creation before the board production without producing the board. Is designed to be sufficiently low, or whether the power supply system circuit does not resonate can be evaluated. (2) Since the current distribution and voltage distribution in the power supply system circuit can be grasped, when the power supply system circuit resonates, it becomes possible to grasp the cause and the optimum place for applying the suppression method. . (3) Since the resonance suppression method can be prepared in advance and the layout can be changed by applying the method, it is possible to confirm the effect of the resonance suppression method. (4) Since the board layout information after the optimum design can be output, it is possible to design and manufacture a printed circuit board that guarantees stable operation of the active element and suppresses electromagnetic radiation in a short time.

  Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing the configuration of a printed circuit board characteristic evaluation apparatus according to a first embodiment of the present invention. The printed circuit board characteristic evaluation apparatus includes an input device 1, a data processing device 2, a storage device 3, and an output device 4. Among them, the data processing device 2 includes an extraction unit 10, a conversion unit 11, and a calculation unit 12, and the storage device 3 includes a storage unit 13.

  Next, the operation of the present embodiment will be described with reference to FIGS. Here, FIG. 2 is a flowchart showing the operation of the present embodiment, and FIGS. 3A and 3B are diagrams showing a configuration example of a four-layer printed circuit board to be evaluated. a) is a plan view, and FIG.

  The printed circuit board 20 to be evaluated shown in FIG. 3 includes four layers, ie, a signal layer 26a, a ground layer 27, a power supply layer 28, and a signal layer 26b from the top of the figure. In the first signal layer 26a, in addition to the oscillator 21, the driver IC 22, the receiver IC 23, and the four signal wirings 24, a decoupling capacitor is connected to a power supply terminal of each active element and a terminal for supplying power from the outside. 25a, 25b, 25c, and 25d are mounted. Both the second-layer ground layer 27 and the third-layer power supply layer 28 are conductor planes covering the entire substrate. The fourth signal layer 26b has neither wiring nor parts. All of these conductors were made of copper. The substrate material 29 is, for example, a glass epoxy resin, and has a relative dielectric constant of 4.7 and a dielectric loss tangent of 0.015.

  First, in this embodiment, the layout information of each layer including the mounted components of the entire printed circuit board is captured by the input device 1 (step S10). Next, in this information, only the layout information of the power supply system circuit is extracted by the extracting means 10 (step S11). As the layout information of the power supply system circuit, in the substrate of FIG. 3, the power supply terminal connection pad and the ground terminal connection pad of the active element mounted on the first layer 26 a are connected to the power supply layer 28 or the ground layer 27 from there. This corresponds to the layout information of the wirings and via holes, the decoupling capacitors 25a, 25b, 25c, and 25d, the second ground layer 27, and the third power supply layer 28. As an extraction method, for example, a symbol such as “V” or “G” that is easy to distinguish may be added to the layout information of the power supply system circuit in advance.

  Next, after this information is stored in the storage unit 13 (step S12), the information is taken into the conversion means 11 and converted into electrical circuit information (step S13). The processing in step S13 will be described with reference to FIG. 4 representing an equivalent circuit model of the power supply system circuit. First, the power layer 28 and the ground layer 27 are handled as parallel plate lines formed by two conductor planes. . The parallel plate line is divided at a position (a position indicated by a broken line in FIG. 4) where the decoupling capacitors 25a, 25b, 25c, and 25d are connected perpendicularly to the long side (X) direction of the substrate. The characteristics of the divided parts are expressed by the F matrix shown in the following formula (1), and the characteristics of other components such as decoupling capacitors and pads are shown in the following formula (2) or the following formula (3). The F matrix is used.

  Expression (1) is an F matrix expressing the characteristics of the transmission line. Z0 is the characteristic impedance of the line, and is determined by the physical constant of the line and the electric constants such as the relative permittivity and the relative permeability of the support forming the line. For example, “November 1977, Proceedings of the IE, Vol. 65, No. 11, pages 1611-1612 (Proceedings of the IEEE, Vol. 65, No. 11, November 1977). , Pp. 1611-1612) ”. γ (f) is a propagation constant of the line. This constant is constituted by an attenuation constant α of the real part and a phase constant β of the imaginary part. Both the attenuation constant α and the phase constant β are determined by the physical shape of the line and the electrical constant of the support, as with the characteristic impedance. The attenuation constant α is, for example, “June 1968, IEE E Transaction on MT, MMT-46, No. 6, pages 342-350 (IEEE Transaction on MTT, Vol. MTT-16, No. 6, June 1968, pp. 342-350 ) ”May be used. The phase constant β is obtained from 2π√εr / λ√μr, εr and μr are the relative permittivity and relative permeability of the support, and λ is the wavelength. Finally, l is the line length.

  Expression (2) is an F matrix representing the characteristics of the impedance Z connected in parallel to the line, and Expression (3) is an F matrix when the impedance Z is connected in series. When expressing a decoupling capacitor, the following equation (4) may be used as the equation (2) and Z.

Ｒはその寄生抵抗、Ｌは寄生インダクタンス、Ｃはキャパシタンスである。ここで、コンデンサ２５ａ，２５ｂ，２５ｃ，２５ｄと直列につながるパッドやビアホールの寄生インダクタンスや寄生抵抗は、コンデンサの等価回路内に含めた。説明は省略するが、同様に、基板の長辺（Ｘ）方向と直交する基板の短辺（Ｙ）方向についても同じようなモデルを作る。これによってステップＳ１３の処理が完了する。

R is the parasitic resistance, L is the parasitic inductance, and C is the capacitance. Here, the parasitic inductance and parasitic resistance of pads and via holes connected in series with the capacitors 25a, 25b, 25c, and 25d are included in the equivalent circuit of the capacitor. Although explanation is omitted, similarly, a similar model is made for the short side (Y) direction of the substrate orthogonal to the long side (X) direction of the substrate. Thereby, the process of step S13 is completed.

  Next, the calculation means 12 uses this electrical circuit information to calculate an impedance characteristic when the power supply system circuit is viewed from a specified power supply terminal connection position (step S14). Here, a calculation example of the impedance characteristic Zin viewed from the power supply terminal connection position of the receiver IC 23 is shown. In FIG. 4, the impedance Zin is obtained by paralleling the impedance ZCc of the capacitor 25c, the impedance Z1 viewed from the right side of the capacitor 25c, and the impedance Z2 viewed from the left side. The impedances ZCc, Z1, and Z2 can be calculated using the following equations (5) to (9), respectively.

ＺＣｃは次式（５）、Ｚ１は次式（６）のＦマトリクス要素から次式（７）を用いて算出できる。Ｚ２も同様に、次式（８）のＦマトリクス要素から次式（９）を用いて算出できる。Ｆマトリクスで処理するメリットは、次式（８）のように、接続順に伝送線路や部品のＦマトリクスの積を取れば、その要素によってインピーダンスを算出できることにある。最終的にインピーダンスＺｉｎは、次式（１０）によって求められる。

ZCc can be calculated using the following formula (5), and Z1 can be calculated from the F matrix element of the following formula (6) using the following formula (7). Similarly, Z2 can be calculated from the F matrix element of the following equation (8) using the following equation (9). The advantage of processing with the F matrix is that the impedance can be calculated by the element if the product of the transmission matrix and the F matrix of the parts are taken in the order of connection as in the following equation (8). Finally, the impedance Zin is obtained by the following equation (10).

  Next, the calculation result is displayed (step S15). FIG. 5 shows an example of the calculation result. The solid line in FIG. 5 is the result of calculation in the long side direction of the substrate, and the broken line is the measurement result, which is indicated by the magnitude of the impedance. The measurement results were calculated using the following equation (11) from the measurement results of the reflection (S11) characteristics at the power terminal connection position using a network analyzer after the board shown in FIG. It is.

この結果から、電源供給系回路のインピーダンスが約４ＭＨｚ以上でインダクティブな素子として働いていること、１００ＭＨｚで約１オームであること、電源供給系回路が８ＭＨｚ、２３０ＭＨｚ、５１０ＭＨｚで共振を起こしていることがわかる。また、測定結果と計算結果がよく一致していることから、本計算手法の妥当性が確認できること、基板の短辺（Ｙ）方向には共振がなかったことから、これらは長辺（Ｘ）方向の共振であることがわかる。

From this result, the impedance of the power supply system circuit works as an inductive element at about 4 MHz or more, it is about 1 ohm at 100 MHz, and the power supply system circuit resonates at 8 MHz, 230 MHz, and 510 MHz. I understand. Moreover, since the measurement result and the calculation result are in good agreement, the validity of the present calculation method can be confirmed, and since there was no resonance in the short side (Y) direction of the substrate, these are the long side (X). It can be seen that the resonance is in the direction.

  As described above, by using the first embodiment, it is possible to grasp the impedance characteristics of the power supply system circuit as viewed from the power terminal connection position of the active element mounted on the substrate, and whether the power supply system circuit has resonance or not. The resonance frequency can be grasped. In other words, since the impedance characteristics of the power supply system circuit can be calculated using the board layout information, the impedance of the power supply system circuit can be calculated during the layout creation before or after the board production without creating the board. It can be evaluated whether the design is sufficiently low or the power supply system circuit does not resonate.

  Further, since the board layout information after the optimum design can be output, it is possible to design and manufacture a printed circuit board that ensures stable operation of the active element and suppresses electromagnetic radiation in a short time.

  [Second Embodiment] FIG. 6 is a block diagram showing the configuration of a printed circuit board characteristic evaluation apparatus according to a second embodiment of the present invention. In the present embodiment, in the configuration of the first embodiment shown in FIG. 1, the comparison unit 14 is further added to the data processing apparatus 2, and this comparison unit 14 is provided, so that resonance in the power supply system circuit is achieved. This makes it possible to determine whether or not there is any.

  The operation of this embodiment will be described with reference to the flowchart of FIG. The present embodiment is characterized in that the processing from step S20 to step S23 is performed after the processing from step S10 to step S13 shown in the first embodiment is performed. First, after obtaining the electric circuit information of the power supply system circuit in step S13, the magnitude | Zin | of the impedance viewed from the designated power terminal connection position is obtained (step S20). Next, the impedance magnitude | Zc | from the designated power supply terminal connection position to the decoupling capacitor connected to the closest position is calculated (step S21). Next, the two are compared (step S22). Finally, the comparison result is output and displayed (step S23).

  FIG. 8 shows the calculation results of | Zin | and | Zc | superimposed. At 8 MHz, 230 MHz, and 510 MHz where resonance occurs, | Zin | is larger than | Zc |. By comparing this magnitude relationship, the presence or absence of resonance can be determined. The reason why | Zin | and | Zc | are almost the same except for a resonance frequency of 10 MHz or more is that the impedance of the capacitor connected closest to the power supply terminal is lower than other elements constituting the power supply system circuit. This is because Zin | is determined by this impedance | Zc |.

  Next, another method for examining the presence or absence of resonance while maintaining the configuration of the present embodiment will be described. As shown in the flowchart of FIG. 9, after step S13, the magnitude | Zc '| of the decoupling capacitor connected to the position closest to the power supply terminal connection position of each active element mounted on the printed circuit board is set to Calculate (step S25). Next, the impedance magnitude | Zin2 | of the power supply system circuit connected thereafter is calculated without the capacitor (step S26). Next, by comparing these, the presence or absence of resonance is determined (step S27). Finally, the impedance calculation result, the presence / absence of resonance, and the resonance frequency are output and displayed (step S28).

  FIG. 10 shows the calculation result. As shown in the figure, at 8 MHz, | Zc ′ | which behaves as a capacitive reactance (capacitive element) and | Zin2 | which behaves as an inductive reactance (inductive element) intersect. At 230 MHz and 510 MHz, | Zc ′ | that behaves as an inductive reactance and | Zin2 | that behaves as a capacitive reactance intersect.

  As described above, when the capacitive reactance and the inductive reactance have the same magnitude, the power supply system circuit causes a parallel resonance. Therefore, the existence of resonance can be examined by examining the existence of the intersecting point. it can. Further, the resonance frequency can be examined from the intersecting frequency.

  As another method for determining the presence or absence of resonance, as shown in the flowchart of FIG. 11, after step S13, the active element mounted on the printed circuit board is connected to a position closest to the power supply terminal connection position. The reactance Im (Zc ′) of the impedance of the capacitor element thus calculated is calculated (step S30). Next, the reactance Im (Zin2) of the impedance after this capacitor is calculated (step S31). Next, these are compared (step S32), and finally, the calculation result of impedance, the presence / absence of resonance, and the resonance frequency are output and displayed (step S33).

  FIG. 12 shows an example of the calculation result. In the figure, the vertical axis represents reactance and the horizontal axis represents frequency. At the positions indicated by W1 to W4, the signs are reversed and the sizes are almost the same, and it can be seen that resonance occurs at 230 MHz and 510 MHz. Therefore, it can be understood that the presence or absence of resonance can be determined by examining whether there is a frequency with the reactance having the opposite sign and the reactance having the same magnitude.

  Next, a modification in which another calculation function is added to the calculation means 12 while the configuration remains the same will be described with reference to the flowchart of FIG. As processing subsequent to the display of the comparison results (step S23, step S28, step S33) in FIGS. 7, 9, and 11, first, when the power supply system circuit resonates, a sine wave of the resonance frequency is Input is made from the power terminal connection position of interest (step S35). Next, the current value and voltage value at each point in the power supply system circuit are calculated (step S36). Finally, the calculation result is displayed (step S37). Or, as shown in FIG. 14, before the step S37, a place where the current value or the voltage value is large is clearly indicated (step S38). Here, as a signal model for inputting a signal of a resonance frequency, for example, a voltage source capable of outputting a sine wave signal and a series circuit of a certain impedance, or a parallel circuit of a certain impedance and a current source capable of outputting a sine wave signal may be used. Good.

  The solid lines in the graphs of FIGS. 15 and 16 show the calculation results of the voltage distribution and the current distribution in the power supply system circuit when a 230 MHz sine wave signal is input from the power supply terminal connection position of the receiver IC 23 (in the figure). The broken line will be described later in the third embodiment). The signal was input from a series circuit of a 1 V voltage source and a 10 ohm resistor. In this example, it can be seen that the voltage is large at the right end of the substrate and the current is maximum at a position about 50 mm from the left end. That is, if this modification is used, a place where a voltage or current is large due to resonance can be specified, and a place suitable for resonance suppression can be grasped.

  Furthermore, as shown in the flowchart of FIG. 17, a modified example in which the calculation unit 12 has another calculation function with the same configuration will be described. After step S15 in FIG. 2, a time axis waveform is input to the power supply system circuit using an equivalent circuit model between the power supply terminal and the ground terminal of the active element (step S39). Next, a current waveform and a voltage waveform at each point in the power supply system circuit are calculated (step S40). These are output and the location where the waveform amplitude is large is clearly indicated (step S41). Alternatively, although not shown, all these waveforms are Fourier transformed to display a specific current distribution or voltage distribution of a frequency component having a large amplitude, for example.

  Thus, it is possible to grasp the behavior of current and voltage at each point in the power supply system circuit during circuit operation. Further, it is possible to grasp the frequency and magnitude of the current and voltage in the power supply system circuit during circuit operation. Furthermore, it is possible to quantitatively determine whether or not to take suppression measures depending on the size.

  [Third Embodiment] FIG. 18 is a block diagram showing a configuration of a printed circuit board characteristic evaluation apparatus according to a third embodiment of the present invention. The present embodiment is characterized in that the layout changing means 15 is added to the data processing device 2 of the second embodiment shown in FIG. 6 and the second storage unit 16 is further added to the storage device 3. The layout changing means 15 can change the layout information of the entire board, and is mainly used here to change the layout of the power supply system circuit. The second storage unit 16 stores in advance a technique for suppressing resonance of the power supply system circuit.

  The operation of the present embodiment will be described using the flowchart of FIG. In the modification shown in FIG. 13 or FIG. 14, the current value and voltage value in the power supply system circuit when the sine wave signal of the resonance frequency is input are calculated (step S36 or step S38), and the current When the value or the voltage value is large, the layout changing unit 15 applies the resonance suppression method stored in the second storage unit 16 in advance to a place where the current value or voltage value is large or the power supply terminal connection position (step S42). Next, with respect to the circuit after the change, the process returns to step S11 in FIG. 2 again, starting from the process of extracting the layout information of only the power supply system circuit part, and finally determining the presence or absence of resonance (step S23 or Step S28 or step S33) is performed (step S43).

  If it is determined that there is resonance also as a result of this, the power supply system circuit is changed by the layout changing means 15 any number of times (step S44). If it is determined that there is no resonance, the layout change means 15 outputs the layout information of the entire board after the change via the output device 4 (step S45). As a result, the layout information of the board on which the power supply system circuit is optimally designed can be obtained.

  As a resonance suppression technique stored in the second storage unit 16, for example, there is a method of mounting a low impedance element such as a capacitor in a place where the voltage value is large and the current value is small in the power supply system circuit. Further, as in the equivalent circuit of the power supply system shown in FIG. 20, a method is used in which two decoupling capacitors 50a and 50c are connected to the power supply terminal connection position of the active element by a wiring 41 having a length l1. Also good. It is known that by setting the length l1 of this wiring to a quarter wavelength of the upper limit frequency that is a problem with unnecessary electromagnetic radiation, resonance can be suppressed within a frequency band in which unnecessary electromagnetic radiation is a problem. Details are described in Japanese Patent Application No. 10-184469.

  FIG. 21 is a graph showing impedance characteristics in the power supply system circuit as seen from the position of the receiver IC 30 when the resonance suppression method shown in FIG. 20 is applied to all active elements. The length 41 of the wiring 41 and the capacitor 50c are arranged in the first layer in the substrate of FIG. The solid line in the graph of FIG. 20 is the calculated value, and the broken line is the measured value. Resonance remains at 6 MHz, but there is no resonance at 30 MHz to 1 GHz, which is currently a problem with unnecessary electromagnetic radiation. Thereby, it can be confirmed that the resonance can be suppressed. Furthermore, since the calculated value matches the measured value, the validity of the present invention can be confirmed.

  The broken lines in the graphs of FIGS. 15 and 16 represent the distribution characteristics of the current value and the voltage value at each point in the power supply system circuit when this resonance suppression method is applied. Compared to the results before applying the solid line resonance suppression method in these graphs, the amplitudes of both current and voltage are suppressed. From this result, it is understood that the resonance suppression method can be applied and the effect can be confirmed in this embodiment.

  Moreover, the measurement result of the radiation electric field characteristic before and behind application of this resonance suppression method is shown to Fig.22 (a), (b). The figure (a) is the result before application, and the figure (b) is the result after application. This measurement was performed in an anechoic chamber in which the floor surface was a metal plate and a radio wave absorber was attached to the other. The substrate was placed on a wooden desk with a height of 75 cm in parallel with the floor, and an antenna was placed at a position 3 m away from the substrate. The circuit was driven by a 20 MHz crystal oscillator, and the method shown in FIG. 20 was used as a resonance suppression method. As a whole, the radiation level decreases, and in particular, the radiation levels around 230 MHz and 510 MHz where resonance occurred are lowered by about 15 dB. This result confirms that the presence or absence of resonance of the power supply system circuit that causes electromagnetic radiation can be determined, and that the resonance suppression method can be applied.

  As described above, in this embodiment, the resonance suppression method can be prepared in advance, and the layout can be changed by applying the resonance suppression method. Therefore, the effect of the resonance suppression method can be confirmed.

  As a form for providing the present invention, for example, each function of the printed circuit board characteristic evaluation apparatus and the printed circuit board characteristic evaluation method described in the above embodiments is realized by a computer program, and a storage medium storing the program is provided. May be provided.

  The present invention can be used for design support of a printed circuit board.

It is a block diagram which shows the structure of the printed circuit board characteristic evaluation apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows operation | movement of 1st Embodiment. It is a figure which shows the structural example of the 4-layer printed circuit board which is evaluation object. It is a figure showing the equal circuit model of a power supply system circuit. It is an impedance characteristic view of the power supply system circuit according to the first embodiment. It is a block diagram which shows the structure of the printed circuit board characteristic evaluation apparatus which concerns on 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of 2nd Embodiment. It is an impedance characteristic figure of the power supply system circuit concerning a 2nd embodiment. It is a flowchart which shows the other operation | movement of 2nd Embodiment. It is another impedance characteristic view of the power supply system circuit concerning a 2nd embodiment. It is a flowchart which shows the other operation | movement of 2nd Embodiment. It is another impedance characteristic view of the power supply system circuit concerning a 2nd embodiment. It is a flowchart which shows the other operation | movement of 2nd Embodiment. It is a flowchart which shows the other operation | movement of 2nd Embodiment. It is a voltage distribution diagram in the power supply system circuit according to the second embodiment. FIG. 6 is a current distribution diagram in a power supply system circuit according to a second embodiment. It is a flowchart which shows the other operation | movement of 2nd Embodiment. It is a block diagram which shows the structure of the printed circuit board characteristic evaluation apparatus which concerns on 3rd Embodiment of this invention. It is a flowchart which shows operation | movement of 3rd Embodiment. It is a figure which shows the equivalent circuit model of the power supply system circuit explaining a resonance suppression method. It is an impedance characteristic view of a power supply system circuit. It is a figure which shows the measurement result of the radiation electric field characteristic before and behind resonance suppression technique application. It is a block diagram which shows the structure of the conventional transmission line simulator. It is a figure which shows an example of a printed circuit board. It is a figure which shows the circuit analysis model before a countermeasure. It is a figure which shows the circuit analysis model after a countermeasure. FIG. 3 is an equivalent circuit diagram focusing only on a power supply system. It is sectional drawing which shows the typical mounting example of a decoupling capacitor. It is a figure which shows the equivalent circuit model of a power supply system. It is an impedance characteristic view of a power supply system circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input device 2 Data processing device 3 Storage device 4 Output device 10 Extraction means 11 Conversion means 12 Calculation means 13 Storage part 14 Comparison means 15 Layout change means 16 Second storage part

Claims (12)

  A method of evaluating printed circuit board characteristics by a programmed computer, wherein the impedance characteristics of a power supply system circuit in the board viewed from the power terminal connection position of each active element mounted on the printed circuit board is calculated And calculating the impedance characteristic from the power terminal connection position to the capacitor element connected to the nearest position, the impedance characteristic of the power supply system circuit and the magnitude, phase, and phase of the impedance characteristic to the capacitor element, And determining whether resonance occurs in the power supply system circuit by comparing either the real part or the imaginary part.   A method of evaluating printed circuit board characteristics by a programmed computer, the method comprising calculating impedance characteristics of a capacitor element connected to a position closest to a power supply terminal connection position of each active element mounted on the printed circuit board; The step of calculating the impedance characteristic of the power supply system circuit after this capacitor element, the impedance characteristic of the capacitor element calculated by the computing means and the magnitude, phase, real part of the impedance characteristic of the power supply system circuit, And determining whether resonance occurs in the power supply system circuit by comparing any of the imaginary parts.   When resonance occurs, a sine wave signal of the resonance frequency is input to the voltage supply system circuit from the power terminal connection position, and the current value and voltage value at each point in the power supply system circuit are calculated. The printed circuit board characteristic evaluation method according to claim 1, further comprising a step of finding a place having a large value or voltage value.   4. The printed circuit board characteristic evaluation method according to claim 3, further comprising a step of applying a resonance suppression method prepared in advance to a place where a current value or a voltage value is large or a power supply terminal connection position and evaluating the presence or absence of resonance again. .   When it is determined that resonance occurs, a sine wave signal of the resonance frequency is input to the power supply system circuit from the power terminal connection position, and the current value and voltage value at each point of the power supply system circuit are calculated. 3. A printed circuit board characteristic evaluation method according to claim 1, further comprising a step of mounting a capacitor element in a place where the current value is small or a place where the voltage value is large, and evaluating the presence or absence of resonance again. .   Using the electrical equivalent circuit model between the power supply terminal and ground terminal of the active element to be mounted, a signal is input to the power supply system circuit from the power supply terminal connection position of a specified active element, and the power supply system circuit 6. The printed circuit board characteristic evaluation according to claim 1, further comprising a step of calculating a current value and a voltage value at each point and finding a place where the current value or the voltage value is large. Method.   A recording medium for recording a control program for evaluating printed circuit board characteristics by a computer, the control program being stored in the board as viewed from the power terminal connection position of each active element mounted on the printed circuit board in the computer The impedance characteristic of the power supply system circuit is calculated, the impedance characteristic from the power terminal connection position to the capacitor element connected to the closest position to the capacitor element is calculated, the impedance characteristic of the power supply system circuit and the capacitor element A circuit for determining whether resonance occurs in the power supply system circuit by comparing the magnitude, phase, real part, or imaginary part of the impedance characteristic. A recording medium on which a characteristic evaluation control program is recorded.   A recording medium on which a control program for evaluating printed circuit board characteristics is recorded by a computer, and the control program is connected to the computer at a position closest to the power supply terminal connection position of each active element mounted on the printed circuit board Processing for calculating the impedance characteristic of the capacitor element, processing for calculating the impedance characteristic of the power supply system circuit after the capacitor element, magnitude and phase of the impedance characteristic of the capacitor element and the impedance characteristic of the power supply system circuit A printed circuit board characteristic evaluation control program is recorded, including a process for determining whether resonance occurs in the power supply system circuit by comparing either the real part or the imaginary part. recoding media.   When resonance occurs, a sine wave signal of the resonance frequency is input from the power supply terminal connection position to the voltage supply system circuit, and a current value and a voltage value at each point in the power supply system circuit are calculated, and the current 9. The recording medium recorded with the printed circuit board characteristic evaluation control program according to claim 7, further comprising a process of finding a place where the value or the voltage value is large.   The printed circuit board characteristics according to claim 9, further comprising a process of applying a resonance suppression method prepared in advance to a place where the current value or the voltage value is large or a power supply terminal connection position, and evaluating the presence or absence of resonance again. A recording medium on which an evaluation control program is recorded.   When it is determined that resonance occurs, a sine wave signal of the resonance frequency is input to the power supply system circuit from the power terminal connection position, and the current value and voltage value at each point of the power supply system circuit are calculated. 9. A printed circuit board characteristic evaluation control according to claim 7, further comprising a process of mounting the capacitor element in a place where the current value is small or a place where the voltage value is large and evaluating the presence or absence of resonance again. A recording medium that records the program. Using an electrical equivalent circuit model between the power supply terminal and ground terminal of the active element to be mounted, a signal is input to the power supply system circuit from the power supply terminal connection position of a specified active element, and the power supply system circuit The printed circuit board according to claim 7, further comprising a process of calculating a current value and a voltage value at each point and finding a place where the current value or the voltage value is large. A recording medium on which a characteristic evaluation control program is recorded.

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