JP2005353638A - Printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress high-frequency current propagation and reduce the size, weight and cost for noise countermeasures.
In the printed circuit board 1 on which the microcomputer 2 is mounted, the inductance value of the power wiring 4 connecting the power supply connector 3 for supplying power to the printed circuit board from the outside to the microcomputer 2 is halved from the midpoint 40 where the inductance value is halved. A current concentration portion 43 is provided near the power connector 3, and the capacitor 5 is mounted between the power supply round trip paths 41 and 42.
[Effect] The amount of high-frequency current generated by the microcomputer propagating from the printed circuit board to the cable is reduced by an average of 20 dB and a maximum of 35 dB compared to the conventional mounting. As a result, effective noise countermeasures can be achieved with a smaller number of capacitors than before.
[Selection] Figure 1

Description

  The present invention relates to a printed circuit board on which an integrated circuit (IC) such as a microcomputer is mounted.

  In electronic devices, problems that adversely affect other electronic devices and their own circuit operations due to unnecessary conduction and radiation noise associated with circuit operations are becoming more serious. In particular, the countermeasures against noise have become complicated due to the recent increase in operating frequency of microcomputers in ICs and the high density mounting of components.

  During circuit operation, high-frequency current is generated by high-speed switching operation inside the microcomputer. This high-frequency current propagates to the wiring pattern of the printed circuit board on which the microcomputer is mounted, and further to the cable connected to the printed circuit board. In particular, in radio and television radio wave transmission bands having a frequency band of 200 MHz or less, unnecessary electromagnetic radiation is generated by the cable acting as an antenna. Therefore, a capacitor is mounted on the printed circuit board in order to suppress high-frequency current propagation to the cable.

  Patent Document 1 discloses a technique for narrowing a power supply wiring as close as possible to an integrated circuit on a printed circuit board and mounting a capacitor for suppressing high-frequency current propagation in the narrow width portion.

  Patent Document 2 discloses mounting a capacitor for suppressing high-frequency current propagation in a package that houses an IC chip.

JP 2003-8153 A (Overall)

JP 2002-184933 A (Overall)

  In the above-described conventional technology, a capacitor is mounted as close as possible to the integrated circuit to suppress the propagation of high-frequency current to the cable and to prevent unnecessary conduction and radiation noise. However, due to the high density mounting of components and the increase in the number of pins of an integrated circuit package, it is difficult to mount a large number of capacitors in the vicinity of the integrated circuit, and there is a problem that high-frequency current cannot be sufficiently suppressed. Further, when a capacitor is mounted on an integrated circuit package, there is a problem that the manufacturing cost is high and uneconomical.

  An object of the present invention is to provide a printed circuit board that effectively suppresses high-frequency current propagation with a small number of capacitors.

  Another object of the present invention is to provide a printed circuit board capable of suppressing the cost for noise countermeasures.

  In one embodiment of the present invention, in a printed circuit board in which a high-frequency short circuit element is mounted between a reciprocating path on a power supply wiring path connecting an integrated circuit from a power supply connector in the printed circuit board, directly between both poles of the power supply connector, Alternatively, a high-frequency short-circuiting element is mounted in the vicinity of the power supply connector between the reciprocating paths of the power supply wiring.

  In a preferred embodiment of the present invention, there is provided a current concentration portion in which the width of the power supply wiring is narrowed closer to the power supply connector than the midpoint on the power supply wiring path connecting the power supply connector and the integrated circuit, and the power supply reciprocation of the current concentration portion is provided. A high-frequency short-circuit element is mounted between the roads.

  In another desirable embodiment of the present invention, a current concentration portion provided closer to the power connector than the midpoint on the power wiring path connecting the power connector to the integrated circuit, and narrowing the width of the power wiring, and the current A first high-frequency short-circuit element mounted between the power supply round-trip paths of the concentrated portion and a second high-frequency short-circuit element mounted between the power supply round-trip paths near the integrated circuit.

  According to the embodiment of the present invention, high-frequency current propagation that occurs in an integrated circuit and causes unnecessary conduction and radiation noise can be effectively suppressed with a small number of capacitors.

  Also, according to a preferred embodiment of the present invention, effective noise countermeasures can be taken, and a small, light and economical printed circuit board can be provided.

  Other objects and features of the present invention will become apparent from the embodiments described below.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a plan view schematically showing a printed circuit board on which an integrated circuit (hereinafter referred to as a microcomputer) is mounted according to the first embodiment of the present invention. A microcomputer 2 and a power connector 3 for supplying power to the microcomputer 2 are mounted on the printed circuit board 1. Furthermore, the forward path 41 and the return path 42 of the power supply wiring 4 for electrically connecting the microcomputer 2 and the power connector 3 are mounted. A current concentrating portion 43 that narrows the width of the power supply wiring 4 is provided closer to the power supply connector 3 than the midpoint 40 where the inductance value of the power supply wiring 4 extending from the power supply connector 3 to the microcomputer 2 is halved. It is. The current concentration portion 43 refers to a portion where the width of the power supply wiring 4 (41, 42) through which the current flows is narrowed down, and can also be referred to as a narrow width portion of the power supply wiring 4. A high-frequency short-circuit element 5 for high-frequency current bypass is mounted on the current concentrating portion 43. The high-frequency short-circuit element 5 is a capacitive circuit element that passes only a high-frequency current typified by a capacitor.

  FIG. 2 is a plan view schematically showing a printed circuit board according to a modification of the first embodiment of the present invention. The same parts as those in FIG. The difference from FIG. 1 is that a high frequency short circuit element 5 for high frequency current bypass is mounted between the bipolar terminals 31 and 32 of the power connector 3.

  Next, the effect of the first embodiment of the present invention will be described based on the actual measurement result using the evaluation board.

  FIG. 3 is a plan view schematically showing the circuit configuration of the evaluation board. The forward path 41 and the return path 42 of the power supply wiring 4 connecting the microcomputer 2 and the power supply connector 3 are designed to be parallel. A portion where the reciprocating paths 41 and 42 of the power supply wiring 4 are parallel to each other corresponds to the current concentration portion (narrow width portion) 43 in the embodiment of FIG. The mounting position c of the capacitor 5 is provided within the range of the power supply wiring path ab connecting the microcomputer 2 and the power supply connector 3 of the power supply wiring 4. That is, pads for mounting the capacitors 5 are provided at 10 positions 405 to 414 in the power supply wiring path a-b. Evaluation was performed by mounting one capacitor 5 on any one of these pads. Here, 40 is the midpoint of the path of the power supply wiring 4. The center point 40 of the path is preferably a point where the inductance between a and c is substantially the same as the inductance between c and b, but may be a dimensional midpoint in many cases.

  FIG. 4 shows the inductance value of the power supply wiring 4 for each mounting position c of the capacitor. That is, the inductance between a and c in FIG. 3 and the inductance between c and b are displayed in a bar graph. The midpoint 40, that is, the position where the inductance value is halved is between the capacitor mounting positions 409 and 410.

  FIG. 5 is a graph showing the amount of noise reduction according to the first embodiment of the present invention. This is a result of measuring the amount of high-frequency current propagation to the cable for each frequency when only one capacitor 5 is mounted at each mounting position of the evaluation board shown in FIG.

  The case where the capacitor 5 is mounted at a position 405 in the vicinity of the microcomputer 2 corresponds to the conventional mounting method described in Patent Documents 1 and 2 described above. On the other hand, the case where the capacitor 5 is mounted in the region from positions 410 to 414 closer to the power connector 3 than the position 40 where the inductance value is halved corresponds to the first embodiment of the present invention shown in FIG. To do. From the figure, it can be seen that at frequencies of 48 MHz, 64 MHz, 80 MHz, and 96 MHz, the closer the mounting position of the capacitor 5 is to the power supply connector 3, in other words, the further away from the microcomputer 2, the lower the high-frequency current that propagates to the cable. Compared to the case where the capacitor 5 is mounted at the position 405 in the vicinity of the microcomputer 2 corresponding to the conventional mounting, the capacitor 5 is mounted at the positions 410 to 414 according to the first embodiment of the present invention shown in FIG. The effect of suppressing high-frequency current propagation is greater as 20 dB. In particular, at 32 MHz, according to the first embodiment shown in FIG. 1 of the present invention, it can be seen that the effect of suppressing high-frequency current propagation is larger by about 35 dB when mounted at the position 410 than by the conventional mounting method. .

  The first embodiment of the present invention shown in FIG. 1 is summarized as follows. First, a power connector 3 for supplying power into the board from the outside of the printed circuit board 1 on which the integrated circuit 2 is mounted, and a power wiring 4 for connecting the integrated circuit 2 to the power connector 3 are mounted. And the printed circuit board which mounts the high frequency short circuit element 5 between the reciprocating paths 41 and 42 on the path of this power supply wiring 4 is made into object. Here, a current concentrating portion 43 that narrows the width of the power supply wiring 4 is provided closer to the power supply connector 3 than the midpoint 40 on the power supply wiring 4 path connecting the power supply connector 3 and the integrated circuit 2. And the high frequency short circuit element 5 is mounted between the reciprocating paths 41 and 42 of this current concentration part 43.

  Here, as a modification of the first embodiment, although not shown in the drawings, if the power connector 4 is closer to the power connector 3 than the midpoint 40 on the power cable 4 path, a current concentrating portion 43 that narrows the width of the power cable 4 is provided. Even if it is not provided, it is sufficiently effective.

  As shown in FIG. 2, when the high frequency short circuit element (capacitor) 5 for high frequency current bypass is directly mounted between the bipolar terminals 31 and 32 of the power connector 3, the capacitor mounting position 414 in FIG. Similarly, it has a sufficient effect.

  As described above, according to the first embodiment of the present invention, the amount of high-frequency current that is generated in the microcomputer 2 and causes unnecessary conduction and radiation noise is propagated from the printed circuit board 1 to the cable. Compared to the mounting method, the average was reduced by 20 dB and a maximum of 35 dB. As a result, the number of capacitors is smaller than before, and it is possible to reduce the size and weight of the noise effectively.

  FIG. 6 is a plan view schematically showing a printed circuit board on which an integrated circuit (hereinafter referred to as a microcomputer) is mounted according to the second embodiment of the present invention. The same parts as those in FIG. The difference from FIG. 1 is that a high frequency short circuit element 51 for high frequency current bypass is mounted in the current concentrating portion 43, and a high frequency current bypass second circuit is also provided between the round trip paths 41 and 42 of the power supply wiring 4 in the vicinity of the microcomputer 2. Two capacitors 52 are mounted.

  FIG. 7 is a plan view schematically showing a printed circuit board on which an integrated circuit (hereinafter referred to as a microcomputer) is mounted according to the third embodiment of the present invention. The same parts as those in FIG. The difference from FIG. 6 is that a relatively long current concentration portion 431 is provided in the power supply wiring 4 closer to the power supply connector 3 than the middle point 40 of the power supply wiring path, and two high frequency short circuit elements 53 and 54 for high frequency current bypassing are provided. Is implemented at intervals.

  Next, functions and effects of the second and third embodiments of the present invention will be described with reference to FIGS.

  8 shows a combination of mounting positions when two capacitors 51, 52 or 53, 54 are mounted at any two positions c1, c2 of the capacitor mounting positions 405 to 414 of the evaluation board shown in FIG. The inductance value of the power supply wiring 4 with respect to is shown. That is, the inductance value between the position a of the power connector 3 and the mounting position c1 of the first capacitor 51 or 53 is shown at the top of the figure. In the center of the figure, an inductance value between the mounting position c1 of the first capacitor 51 or 53 and the mounting position c2 of the second capacitor 52 or 54 is shown. Similarly, the lowermost part of the drawing shows the inductance value between the mounting position c2 of the second capacitor 52 or 54 and the mounting position b of the microcomputer 2.

  FIG. 9 is a graph showing noise reduction amounts according to the second and third embodiments of the present invention. It is the result of measuring the amount of high-frequency current propagation to the cable for each frequency when two capacitors are mounted in a combination of positions.

  The case where two capacitors are mounted at positions 405 and 406 in the vicinity of the microcomputer 2 corresponds to the conventional mounting method.

  On the other hand, when one capacitor 51, 52 is mounted at a position 405 near the microcomputer 2 and a position 414 near the power connector 3, respectively, the print according to the second embodiment of the present invention shown in FIG. It is a circuit board. As is clear from comparison between the two, it can be seen that the second embodiment of the present invention has a greater effect of suppressing the propagation of high-frequency currents by an average of about 15 dB at all measured frequencies, compared to the conventional mounting method. . In particular, at 32 MHz, it has been found that the mounting according to the second embodiment of the present invention has a large effect of suppressing the propagation of high-frequency current by about 25 dB compared to the conventional mounting method.

  The second embodiment of the present invention shown in FIG. 6 is summarized as follows. First, a power connector 3 for supplying power into the board from the outside of the printed circuit board 1 on which the integrated circuit 2 is mounted, and a power wiring 4 for connecting the integrated circuit 2 to the power connector 3 are mounted. A printed circuit board on which a high-frequency short-circuiting element is mounted between the reciprocating paths 41 and 42 on the path of the power supply wiring 4 is intended. Here, a current concentrating portion 43 that narrows the width of the power supply wiring 4 is provided closer to the power supply connector 3 than the midpoint 40 on the power supply wiring 4 path connecting the power supply connector 3 and the integrated circuit 2. The first high-frequency short-circuit element 51 mounted between the round-trip paths 41 and 42 of the current concentrating portion 43 and the second high-frequency short-circuit mounted between the round-trip paths 41 and 42 of the power supply wiring 4 near the integrated circuit 2. An element 52 is provided.

  Here, as a modification of the second embodiment, although not shown, if the first high-frequency short-circuit element (capacitor) 51 is closer to the power connector 3 than the midpoint 40 on the power wiring 4 path, Even if it is not provided in the current concentration part 43 with the narrowed width of the wiring 4, a sufficient effect can be expected.

  Similarly to the example of FIG. 2, when the first high frequency short circuit element (capacitor) 51 for bypassing the high frequency current is directly mounted between the bipolar terminals 31 and 32 of the power connector 3, the capacitor mounting of FIG. Similar to the combination of the positions 405 and 414, a sufficient effect can be expected.

  As described above, according to the second embodiment of the present invention, as in the first embodiment, a high-frequency current generated in the microcomputer 2 and causing unnecessary conduction and radiation noise is generated from the printed circuit board 1. The amount of propagation to the cable was reduced by an average of 15 dB and a maximum of 25 dB compared to the conventional mounting method. As a result, the number of capacitors is smaller than before, and it is possible to reduce the size and weight of the noise effectively.

  Next, the effect of the third embodiment of the present invention shown in FIG. 7 will be described.

  The noise reduction amount characteristic according to the third embodiment of the present invention shown at the right end of FIG. 9 represents the effect of the embodiment shown in FIG. That is, the first capacitor 53 is mounted at a position 414 in the vicinity of the power connector 3 in the relatively long current concentration portion 431. Further, the second capacitor 54 is mounted in the vicinity of the right positions 410 to 412 of the current concentration portion 431, which is slightly closer to the power connector 3 than the midpoint 40 of the power wiring path. This result is the noise reduction amount characteristic of the printed circuit board 1 according to the third embodiment of the present invention shown at the right end of FIG. As is clear from comparison with the conventional characteristic shown at the left end of FIG. 9, the third embodiment of the present invention has an average high frequency current of about 15 dB at all measured frequencies as compared with the conventional mounting method. It can be seen that the effect of suppressing propagation is large. In particular, at 32 MHz, it has been found that the mounting according to the third embodiment of the present invention has a large effect of suppressing the propagation of high-frequency current by about 30 dB as compared with the conventional mounting method.

  The third embodiment of the present invention shown in FIG. 7 is summarized as follows. First, a power supply connector 3 for supplying power from the outside of the printed circuit board 1 on which the integrated circuit 2 is mounted to the board and a power supply wiring 4 connecting the power supply connector 3 to the integrated circuit 2 are mounted. The printed circuit board 1 in which a high-frequency short-circuit element is mounted between the reciprocating paths 41 and 42 on the path of the power supply wiring 4 is intended. Here, a relatively long current concentrating portion 43 in which the width of the power supply wiring 4 is narrowed is provided closer to the power supply connector 3 than the midpoint 40 on the power supply wiring 4 path connecting the power supply connector 3 and the integrated circuit 2. The first high-frequency short-circuiting element 53 mounted between the reciprocating paths 41 and 42 in the vicinity of the power connector 3 at the left end of the current concentrating portion 43 and the power source closer to the power connector 3 than the middle point 40 on the power wiring path. A second high-frequency short-circuit element 54 mounted between the wiring reciprocating paths 41 and 42 is provided.

  Here, as a modification of the third embodiment, although not shown, if the two high-frequency short-circuit elements (capacitors) 53 and 54 are closer to the power supply connector 3 than the midpoint 40 on the power supply wiring 4 path, A sufficient effect can be expected without providing the current concentrating portion 43 that narrows down the width of the wiring 4.

  The first high-frequency short-circuiting element (capacitor) 53 is substantially the same as the capacitor mounting position 414 in FIG. 9 even when directly mounted between the bipolar terminals 31 and 32 of the power connector 3, as in the example of FIG. The same effect can be expected.

  Thus, according to the third embodiment of the present invention, the amount of high-frequency current that is generated in the microcomputer 2 and causes unnecessary conduction and radiation noise is propagated from the printed circuit board 1 to the cable. Compared to the mounting method, the average was reduced by 15 dB, and the maximum was 30 dB. As a result, the number of capacitors is smaller than before, and it is possible to take an effective noise countermeasure that is small and light and economical.

1 is a plan view schematically showing a printed circuit board according to a first embodiment of the present invention. The top view which shows typically the printed circuit board by the modification of FIG. The top view which shows typically the evaluation board | substrate used for the effect verification of this invention. The graph of the power supply wiring inductance value with respect to each mounting position of the evaluation board | substrate of FIG. The graph which shows the noise reduction amount by the 1st Embodiment of this invention. The top view which showed typically the printed circuit board by the 2nd Embodiment of this invention. The top view which showed typically the printed circuit board by the 3rd Embodiment of this invention. The graph which shows the inductance value of the power supply wiring 4 with respect to the combination of the mounting position of the evaluation board | substrate of FIG. The graph which shows the noise reduction amount by the 2nd and 3rd embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Printed circuit board, 2 ... Integrated circuit (microcomputer), 3 ... Power supply connector 31,32 ... Power supply connector bipolar terminal, 4 ... Power supply wiring, 40 ... Midpoint of power supply wiring (inductance), 41, 42 ... Power supply Wire reciprocation path, 43, 431 ... current concentration part (narrow width part), 405-414 ... high frequency short circuit element (capacitor) mounting position on power supply wiring, 5, 51-54 ... high frequency short circuit element (capacitor).

Claims (12)

  An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power from the outside of the printed circuit board into the printed circuit board, a power supply wiring connecting the integrated circuit from the power connector, and In a printed circuit board in which a high-frequency short-circuit element is mounted between reciprocating paths on a power wiring path, the width of the power wiring is set closer to the power connector than a midpoint on the power wiring path connecting the integrated circuit from the power connector. A printed circuit board, wherein a narrowed current concentration portion is provided and the high-frequency short-circuiting element is mounted between the reciprocating paths of the current concentration portion.   An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power from the outside of the printed circuit board into the printed circuit board, a power supply wiring connecting the integrated circuit from the power connector, and A printed circuit board in which a high-frequency short-circuit element is mounted between round-trip paths on a power-supply wiring path, wherein the high-frequency short-circuit element is mounted between round-trip paths of the power-supply wiring near the power-supply connector.   An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power from the outside of the printed circuit board into the printed circuit board, and a power supply wiring connecting the integrated circuit from the power connector are mounted. A printed circuit board, wherein a high-frequency short-circuit element is mounted between both poles of the power connector.   An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power from the outside of the printed circuit board into the printed circuit board, a power supply wiring connecting the integrated circuit from the power connector, and In a printed circuit board in which a high-frequency short-circuit element is mounted between reciprocating paths on a power supply wiring path, the power supply wiring is provided closer to the power supply connector than a midpoint on the power supply wiring path connecting the integrated circuit to the power supply connector. A current concentration part with a narrowed width, a first high-frequency short-circuit element mounted between the round-trip paths of the current-concentration part, and a second high-frequency short circuit mounted between the round-trip paths of the power supply wiring near the integrated circuit A printed circuit board comprising an element.   An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power from the outside of the printed circuit board into the printed circuit board, a power supply wiring connecting the integrated circuit from the power connector, and In a printed circuit board in which a high-frequency short-circuiting element is mounted between reciprocating paths on a power supply wiring path, a first high-frequency shorting element mounted between the reciprocating paths of the power supply wiring in the vicinity of the power connector and the integrated circuit in the vicinity of the integrated circuit. A printed circuit board comprising a second high-frequency short-circuiting element mounted between reciprocating paths of power supply wiring.   An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power to the printed circuit board from the outside of the printed circuit board, and a power supply wiring connecting the integrated circuit from the power connector are mounted. The printed circuit board includes a first high-frequency short-circuit element mounted between both poles of the power connector and a second high-frequency short-circuit element mounted between reciprocating paths of the power supply wiring near the integrated circuit. Printed circuit board.   An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power from the outside of the printed circuit board into the printed circuit board, a power supply wiring connecting the integrated circuit from the power connector, and In the printed circuit board in which the high frequency short circuit element is mounted between the reciprocating paths on the power supply wiring path, the first high frequency short circuit element mounted between the reciprocating paths in the vicinity of the power connector and the midpoint on the power supply wiring path. A printed circuit board comprising a second high-frequency short-circuiting element mounted between reciprocating paths of the power supply wiring near the power supply connector.   An integrated circuit, a printed circuit board on which the integrated circuit is mounted, a power connector for supplying power from the outside of the printed circuit board into the printed circuit board, a power supply wiring connecting the integrated circuit from the power connector, and In a printed circuit board in which a high-frequency short-circuiting element is mounted between the reciprocating paths on the power wiring path, the current concentrating part in which the width of the power wiring near the power connector is narrowed and the current concentrating part is mounted between the reciprocating paths. A printed circuit board comprising: a first high-frequency short-circuit element; and a second high-frequency short-circuit element mounted between a reciprocating path of the power supply wiring closer to the power supply connector than a midpoint on the power supply wiring path .   9. The printed circuit board according to claim 1, wherein a midpoint on the power supply wiring path is a midpoint of a wiring inductance value of the power supply wiring.   9. The printed circuit board according to claim 1, wherein the midpoint on the power supply wiring path is a midpoint on the dimensions of the power supply wiring path.   The printed circuit board according to claim 1, further comprising a capacitor as the high-frequency short-circuit element. The printed circuit board according to claim 1, wherein the integrated circuit includes a microcomputer.

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