JP2009010273A - Power source noise filtering structure of printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power source noise filtering structure of a printed wiring board which structure has a bypass capacitor mounting structure that improves an effect of suppressing high-frequency noises superposed on current from a power supply system. <P>SOLUTION: A power supply line is divided into two i.e. a power supply line 2a and a power supply line 2b. Capacitor mounting power pads 5a and 5b are disposed on the surfaces of division ends of the power supply lines 2a and 2b, respectively, and the division ends are connected via an electrode 4a of a bypass capacitor 4, which is a two-terminal chip capacitor. This causes the entire high-frequency noises heading from the power supply line 2a toward the power supply line 2b to flow through the electrode 4a of the bypass capacitor 4, thus improves a performance of bypassing high-frequency noises through an electrode 4b to a GND layer 3. The division ends are also connected via a power line detouring pattern 8 to avoid disconnection between the power supply lines 2a and 2b due to the separation of the bypass capacitor 4, etc. The high-frequency impedance of the power line detouring pattern 8 is determined to be larger than the high-frequency impedance of the electrode 4a of the bypass capacitor 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power supply noise filter structure for a printed wiring board.

  Conventionally, in printed wiring boards on which LSIs and ICs are mounted, a power supply system is used as a filter structure for suppressing high frequency noise radiated from the mounted LSIs and ICs on the power supply system. A structure capable of mounting a bypass capacitor is provided (for example, Patent Documents 1 and 2).

JP 2006-120786 A Japanese Patent Laid-Open No. 11-87880

  However, since the conventional bypass capacitor mounting structure may not obtain a desired bypass performance, there is a problem that a desired suppression effect against high-frequency noise superimposed on the power supply system may not be obtained. .

  The present invention has been made in view of the above, and obtains a power supply noise filter structure for a printed wiring board having a bypass capacitor mounting structure capable of improving the effect of suppressing high frequency noise superimposed on a power supply system. With the goal.

  In order to achieve the above-described object, the present invention provides an insulation in which a power supply wiring for supplying power to an electronic component is disposed on one layer surface which is an electronic component mounting surface, and a ground layer is disposed on the other layer surface. In a printed wiring board having a layer, one terminal electrode of a two-terminal type bypass capacitor is connected to the power supply wiring, and the other terminal electrode is connected to the ground layer via a ground pad and a through hole provided in the insulating layer. A power supply noise filter structure to be connected, wherein the power supply wiring is divided into a first power supply wiring and a second power supply wiring that are spaced apart from each other by a distance shorter than the length of the terminal electrode of the two-terminal type bypass capacitor. A pad for connecting the terminal electrode of the bypass capacitor is formed on the upper surface of the wiring on the divided end side facing the first and second power supply wirings. The detour power supply wiring that is provided between the opposing divided ends of the first and second power supply wirings is disposed on the same electronic component mounting surface. It is characterized by being arranged through a route different from the route.

  According to the present invention, when one terminal electrode of a two-terminal type bypass capacitor is connected to the power supply wiring and the other terminal electrode is connected to the ground layer, the power supply wiring is divided into two, and the space between the divided ends is divided. Connect with one terminal electrode of the bypass capacitor. If the power supply wiring is not divided, high-frequency noise from one end of the power supply wiring to the other end is shunted to the power supply wiring side and the terminal electrode side of the bypass capacitor. Since all flow through the terminal electrode of the bypass capacitor, the performance of bypassing to the ground layer through the other terminal electrode is improved.

  In this case, in order to avoid a situation in which continuity between the first power supply wiring and the second power supply wiring cannot be obtained due to separation of the bypass capacitor or the like, another connection between the divided power supply wirings is performed. When connected by a conductor, high-frequency noise is diverted to the terminal electrode of the bypass capacitor and another connection conductor, so that the bypass performance is degraded.

  In other words, in order to improve the bypass performance while avoiding the situation where the continuity between the first power supply wiring and the second power supply wiring cannot be obtained due to separation of the two-terminal type bypass capacitor or the like, high frequency noise Needs to flow more on the terminal electrode side of the bypass capacitor. For this purpose, the high-frequency impedance of another connection conductor may be made larger than the high-frequency impedance of the terminal electrode of the bypass capacitor, so that another connection conductor has a different path on the same electronic component mounting surface. A bypass power supply wiring is provided, and the power supply wiring divided by the bypass power supply wiring is connected.

  In this bypass power supply wiring, the inductance component bypasses the impedance ratio (division ratio) with the terminal electrode of the two-terminal type bypass capacitor so that the high-frequency noise flows more on the terminal electrode side of the bypass capacitor. Since the arrangement path is selected so that it is larger than the terminal electrode of the bypass capacitor and the high frequency impedance is larger than the terminal electrode of the bypass capacitor, more high frequency noise flows on the terminal electrode side of the bypass capacitor. Can be. Therefore, according to the present invention, the effect of suppressing the high frequency noise superimposed on the power supply system can be improved.

  First, in order to facilitate understanding of the present invention, an outline of the prior art disclosed in Patent Documents 1 and 2 will be described with reference to FIGS.

  FIG. 5 is a perspective view showing a power supply noise filter structure of a printed wiring board having a conventional bypass capacitor mounting structure disclosed in Patent Document 1. As shown in FIG. FIG. 5 shows an application example in which a power supply wiring for supplying power to the electronic component is also provided on the electronic component mounting surface of the insulating layer.

  In FIG. 5, one layer surface (upper surface in the illustrated example) of the insulating layer 1 constituting the substrate of the printed wiring board is an arrangement surface for electronic components such as LSI and IC, and supplies power to these electronic components. A power supply wiring 2 is also provided. A ground layer (GND layer) 3 is disposed on the entire surface of the other layer surface (lower surface in the illustrated example) of the insulating layer 1.

  The bypass capacitor 4 is a two-terminal type chip capacitor that can be obtained as a commercially available part, and has terminal electrodes 4a and 4b. In the illustrated example, the terminal electrodes 4a and 4b are provided on the short side of the rectangular internal electrode. Hereinafter, the terminal electrode is simply referred to as “electrode part”.

  As a structure for mounting this bypass capacitor 4, a capacitor mounting power supply pad 5 for connecting one electrode portion 4 a is provided at a predetermined region position on the power supply wiring 2, and at a predetermined position on the upper surface of the insulating layer 1, A capacitor mounting GND pad 6 for connecting the other electrode portion 4b is provided. The GND pad 6 is connected to the GND layer 3 through a ground layer connecting through hole 7.

FIG. 6 is a circuit diagram showing an equivalent circuit of a printed wiring board on which the bypass capacitor shown in FIG. 5 is mounted. In FIG. 6, the power supply conductor 20 and the ground conductor 21 that are opposed to each other with the insulating layer 1 interposed therebetween are represented as having an inductance L _line for each unit length, and the unit between the power supply conductor 20 and the ground conductor 21 is a unit. Since the capacitance C _line is present for each length, the equivalent circuit is represented as a series-parallel circuit of the inductance L _line and the capacitance C _line .

In the mounting region 22 of the bypass capacitor 4, the capacitance Cc of the bypass capacitor 4 is inserted between the power supply conductor 20 and the ground conductor 21 instead of the capacitance C _line , and the inductance of the ground conductor 21 is unit. Although the inductance per length (L _line / 2 + L _line / 2), the inductance in the power supply conductor 20 is such that the terminal electrode 4a of the bypass capacitor 4 is connected to the power supply wiring 2, and therefore the terminal electrode of the bypass capacitor 4 4a becomes a parallel circuit of an inductance (L _cap / 2 + L _cap / 2) 23 and an inductance (L _line / 2 + L _line / 2) 24 per unit length.

That is, in the bypass capacitor mounting structure shown in FIG. 5, a part of the high-frequency noise superimposed on the power supply wiring 2 on the power supply wiring 2 side in the mounting region 22 of the bypass capacitor 4 is an inductance caused by the power supply wiring 2. Although the L _line flows, the inductance L _line due to the power supply wiring 2 and the inductance L _cap due to the terminal electrode 4a of the bypass capacitor 4 have substantially the same value, so that there is a problem that the bypass performance deteriorates to almost half.

  Next, FIG. 7 is a perspective view showing a power supply noise filter structure of a printed wiring board provided with a conventional bypass capacitor mounting structure disclosed in Patent Document 2. FIG. FIG. 7 shows an application example when the insulating layer on which the electronic component is mounted and the insulating layer on which the power supply wiring for supplying power to the electronic component is different.

  In FIG. 7, of the two insulating layers 30 and 31 in the printed wiring board, the upper surface of the upper insulating layer 30 is a mounting surface for an electronic component such as LSI or IC, and the upper insulating layer 30 and the lower insulating layer are insulated. Between the layer 31, a ground layer (GND layer) 32 is disposed, and a power supply layer 33 is disposed on the lower surface of the lower insulating layer 31.

  A capacitor mounting power supply pad 34 for connecting one electrode portion 4a of the bypass capacitor 4 is provided on the upper surface of the upper insulating layer 30 which is a mounting surface of an electronic component such as LSI or IC, and the other electrode A capacitor mounting GND pad 35 for connecting the portion 4b is provided. The capacitor mounting power supply pad 34 is connected to the power supply layer 38 through the power supply layer connecting through hole 36 provided in the two insulating layers 30 and 31, and the capacitor mounting GND pad 35 is connected to the ground provided in the insulating layer 30. The layer connection through hole 37 is connected to the GND layer 32.

FIG. 8 is a circuit diagram showing an equivalent circuit of the printed wiring board on which the bypass capacitor shown in FIG. 7 is mounted. In FIG. 8, the power supply conductor 40 and the ground conductor 41 that are opposed to each other with the insulating layer 31 interposed therebetween are each represented as having an inductance L _line for each unit length, and the unit between the power supply conductor 40 and the ground conductor 41 is a unit. Since the capacitance C _line is present for each length, the equivalent circuit is represented as a series-parallel circuit of the inductance L _line and the capacitance C _line , as in FIG.

In the mounting region 42 of the bypass capacitor 4, the inductance (L _TH ) 43 of the power layer connecting through hole 36 and the capacitance (Cc) 44 of the bypass capacitor 4 are provided between the power supply conductor 40 and the ground conductor 41. A series circuit with the inductance (L _TH ) 45 of the through hole 37 for ground layer connection is inserted.

That is, in the capacitor mounting structure for the bypass shown in Figure 7, since the inductance (L _TH) 45 inductance of the power supply layer connecting through hole 36 (L _TH) 43 the ground layer connection through-holes 37 are added, bypass As a result, the high frequency impedance of the capacitor 4 increases, and it becomes difficult for high frequency noise to flow through the bypass capacitor 4, thereby deteriorating the bypass performance.

  Therefore, the bypass capacitor mounting structure included in the power supply noise filter structure of the printed wiring board according to the present invention has a structure capable of improving the bypass performance as described above. Exemplary embodiments of a power supply noise filter structure for a printed wiring board according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG.
1 is a perspective view showing a power supply noise filter structure of a printed wiring board having a bypass capacitor mounting structure according to Embodiment 1 of the present invention. In FIG. 1, for the convenience of explanation, the same or equivalent components as those shown in FIG. 5 (conventional example) are denoted by the same reference numerals. Here, the description will focus on the parts related to the first embodiment.

  As described in FIG. 5, when the electrode portion 4 a of the bypass capacitor 4 is connected to the power supply wiring 2, high-frequency noise from one end of the power supply wiring 2 to the other end is generated between the power supply wiring 2 side and the bypass capacitor 4. Since the current is diverted to the electrode part 4a side, the bypass performance deteriorates.

  Therefore, as shown in FIG. 1, the mounting structure of the bypass capacitor according to the first embodiment is the same as that shown in FIG. 5 except that the power supply wiring 2 is connected to the place where one electrode portion 4a of the bypass capacitor 4 is mounted. The power supply wiring 2a and the power supply wiring 2b are spaced apart from each other with a distance shorter than the length of the electrode part 4a, and the electrode part 4a is formed on the upper surface of the wiring on the divided end side facing the power supply wirings 2a and 2b. Capacitor mounting power supply pads 5a and 5b to be connected are provided, respectively, and the electrode portion 4a connects between the opposed divided ends of the power supply wirings 2a and 2b.

  According to this structure, for example, if an LSI or IC (not shown) is connected to the power supply wiring 2a and a power supply source is connected to the power supply wiring 2b, the high-frequency noise radiated from the LSI or IC is generated on the power supply wiring 2a side. When all the high-frequency noise is conducted to the power supply wiring 2b side, the high-frequency noise flows through the electrode portion 4a of the bypass capacitor 4. Therefore, the conventional high-frequency noise is bypassed from the electrode portion 4b to the GND layer 3 through the internal electrode. This is an improvement over the example (FIG. 5). However, in this structure, when the bypass capacitor 4 is peeled off, a situation occurs in which the continuity between the power supply wiring 2a and the power supply wiring 2b cannot be obtained.

  In order to avoid such a situation that the continuity between the power supply wiring 2a and the power supply wiring 2b cannot be obtained, when the divided power supply wirings 2a and 2b are connected by another connection conductor, the high frequency noise is generated by the bypass capacitor 4. Since the current is divided between the electrode portion 4a and another connecting conductor, the bypass performance is lowered. Therefore, in order to improve the bypass performance while avoiding the situation where the continuity between the power supply wiring 2a and the power supply wiring 2b cannot be obtained, the high frequency impedance of another connecting conductor is higher than that of the electrode portion 4a of the bypass capacitor 4. What is necessary is just to make it increase so that more high frequency noise may flow through the electrode part 4a of the bypass capacitor 4.

  Therefore, as shown in FIG. 1, the bypass capacitor mounting structure according to the first embodiment has another path between the divided power supply wirings 2a and 2b on the same electronic component mounting surface as another connecting conductor. A detour pattern (detour power supply wiring) 8 of the power supply wiring connected through is provided. The power supply wiring detour pattern 8 is composed of detour power wiring lines 8a, 8b, and 8c so that a detour path as large as possible can be taken.

  FIG. 2 is a circuit diagram showing an equivalent circuit of the printed wiring board on which the bypass capacitor shown in FIG. 1 is mounted. In FIG. 2, a power supply conductor 10 includes power supply wires 2 a and 2 b disposed on the electronic component mounting surface of the insulating layer 1, an electrode portion 4 a of the bypass capacitor 4, and a power supply parallel to the electrode portion 4 a of the bypass capacitor 4. It is comprised with the detouring pattern 8 of wiring. The ground conductor 11 is a GND layer 3 disposed on the other layer surface of the insulating layer 1.

In the portion corresponding to the power supply wirings 2a and 2b and the ground conductor 11 in the power supply conductor 10, it is represented that the inductance L _line exists for each unit length, and the portion corresponding to the power supply wirings 2a and 2b in the power supply conductor 10 and the ground conductor 11 In between, it is expressed that there is a capacitance C _line for each unit length.

In the mounting region 12 of the bypass capacitor 4, the capacitance Cc of the bypass capacitor 4 is inserted between the power supply conductor 10 and the ground conductor 11 instead of the capacitance C _line , and the inductance of the ground conductor 11 is expressed in units. Although the inductance per length (L _line / 2 + L _line / 2), the inductance of the power supply conductor 10 is smaller than the inductance (L _cap / 2 + L _cap / 2) 13 of the electrode portion 4 a of the bypass capacitor 4. a power supply wiring bypass power supply lines 8a of the inductance in the detour pattern 8 of the _{(L line + L line) 14} , and the inductance of the bypass supply line _{8b (L line + L line)} 15, the inductance of the bypass power line 8c _{(L line} + _{L line)} A series circuit of the 6 is shaped to be connected in parallel.

The relationship among these inductance L, frequency F, and impedance Z is expressed by equation (1).
Z = 2πFL (1)

  That is, when the frequency F = 0, the impedance Z = 0, and the DC component is not affected by the inductance L. Further, as the frequency becomes higher, the impedance Z increases, and the impedance Z further increases as the inductance L increases.

  In the bypass pattern 8 of the power supply wiring, the path length can be increased to increase the inductance component, so that the high-frequency impedance can be increased and the high-frequency noise can be made difficult to flow. However, the supply of the originally necessary DC power is not affected by this inductance.

  On the other hand, since the length of the electrode portion 4a of the bypass capacitor 4 cannot be changed, the inductance 13 remains small, and the high frequency impedance is lower than that of the bypass pattern 8 side of the power supply wiring, and high frequency noise is reduced. Make it easy to flow.

  That is, the bypass pattern 8 of the power supply wiring has an impedance ratio (diversion ratio) with the electrode part 4a of the bypass capacitor 4 such that high-frequency noise flows more on the electrode part 4a side of the bypass capacitor 4. Since the arrangement path is selected so that the inductance component is larger than the electrode portion 4a of the bypass capacitor 4 and the high frequency impedance is larger than the electrode portion 4a of the bypass capacitor 4, the power supply wiring 2a and the power supply wiring 2b are selected. Even if the bypass pattern 8 of the power supply wiring that avoids the occurrence of the situation in which the continuity with the power supply cannot be obtained is provided, the bypass performance of the high frequency noise to the GND layer 3 can be improved without deteriorating.

  As described above, according to the first embodiment, the power supply wiring for supplying power to the LSI or IC is divided into two parts, and the divided power supply wirings are connected by one electrode portion of the bypass capacitor, and the bypass is bypassed. Since the connection is made with a bypass power supply wiring that realizes a high-frequency impedance larger than the high-frequency impedance of the electrode part of the capacitor for the capacitor, it is possible to avoid the situation where conduction between the divided power supply wirings cannot be obtained, such as separation of the bypass capacitor However, it is possible to improve the bypass performance, and to realize a power supply noise filter structure of a printed wiring board that can improve the suppression effect against high frequency noise superimposed on the power supply system.

  Although not clearly shown in FIG. 1, in the multilayer substrate, the insulating layer 1 is provided with a power supply wiring for supplying power to the electronic component on one layer surface which is an electronic component mounting surface, and a ground surface on the other layer surface. There may be one insulating layer on which the layer is disposed.

Embodiment 2. FIG.
3 is a perspective view showing a power supply noise filter structure of a printed wiring board provided with a bypass capacitor mounting structure according to Embodiment 2 of the present invention. In FIG. 3, the same reference numerals are given to components that are the same as or equivalent to the components shown in FIG. 1 (Embodiment 1). Here, the description will be focused on the portion related to the second embodiment.

  As shown in FIG. 3, the bypass capacitor mounting structure according to the second embodiment includes a bypass capacitor 9 in place of the bypass capacitor 4 in the configuration shown in FIG. 1 (Embodiment 1). Yes.

  The bypass capacitor 9 is a two-terminal type chip capacitor that can be obtained as a commercially available part, similar to the bypass capacitor 4, but the electrode portions 9a and 9b are provided on the long side of the rectangular internal electrode. Yes. Therefore, the interval between the divided ends of power supply wirings 2a and 2b is longer than that shown in FIG. 1 (Embodiment 1).

  Although not mentioned in the first embodiment, a parasitic capacitance always exists between the divided ends of the power supply wires 2a and 2b. Therefore, an equivalent circuit of the printed wiring board on which the bypass capacitor shown in FIG. 3 is mounted is as shown in FIG.

As shown in FIG. 4, in the bypass capacitor mounting region 18, the parasitic capacitance 19 between the power supply wires 2 a and 2 b is present on the power supply conductor 10 side, and the inductance (L _cap / 2 + L _cap) of the electrode portion 9 a of the bypass capacitor 9. / 2) In the bypass pattern 8 of the power supply line, the inductance (L _line + L _line ) 14 of the bypass power supply line 8a, the inductance (L _line + L _line ) 15 of the bypass power supply line 8b, and the bypass power supply line 8c The inductance (L _line + L _line ) 16 is connected in parallel to a parallel circuit with a series circuit.

The parasitic capacitance 19 decreases as the distance between the divided ends of the power supply lines 2a and 2b increases, and increases as the distance between the divided ends decreases. If this parasitic capacitance 19 is a parasitic capacitance C, the impedance Z of the parasitic capacitance C at a certain frequency F is:
Z = 1 / (2πFC) (2)
It is expressed.

  This equation (1) indicates the following. That is, if the frequency F is the same, the larger the parasitic capacitance C, the lower the impedance Z. Therefore, high-frequency noise is easily transmitted through the parasitic capacitance C. That is, since a route through which high-frequency noise passes through the parasitic capacitance C is generated, the ratio of passing through the inductance 13 of the electrode portion of the bypass capacitor is reduced, leading to deterioration of the bypass performance.

  On the other hand, since the impedance Z increases as the parasitic capacitance C decreases, it is difficult for high-frequency noise to be transmitted through the parasitic capacitance C. That is, since the ratio of high-frequency noise passing through the inductance 13 of the electrode portion of the bypass capacitor increases, the bypass performance can be improved.

  In short, in the second embodiment, as shown in FIG. 3, the interval between the divided ends of the power supply wirings 2a and 2b is made longer than that in the first embodiment, so that it occurs between the divided ends of the power supply wirings 2a and 2b. The parasitic capacitance C can be reduced. Therefore, since the impedance Z of the parasitic capacitance C becomes larger than that of the first embodiment with respect to the high frequency noise, the bypass performance can be further improved.

  As described above, the power supply noise filter structure of the printed wiring board according to the present invention is useful for improving the effect of suppressing high frequency noise superimposed on the power supply system.

It is a perspective view which shows the power supply noise filter structure of the printed wiring board provided with the mounting structure of the bypass capacitor by Embodiment 1 of this invention. It is a circuit diagram which shows the equivalent circuit of the printed wiring board which mounted the capacitor | condenser for bypass shown in FIG. It is a perspective view which shows the power supply noise filter structure of the printed wiring board provided with the mounting structure of the bypass capacitor by Embodiment 2 of this invention. It is a circuit diagram which shows the equivalent circuit of the printed wiring board which mounted the capacitor | condenser for bypass shown in FIG. It is a perspective view which shows the power supply noise filter structure of the printed wiring board provided with the mounting structure of the conventional bypass capacitor currently disclosed by patent document 1. FIG. FIG. 6 is a circuit diagram showing an equivalent circuit of a printed wiring board on which the bypass capacitor shown in FIG. 5 is mounted. It is a perspective view which shows the power supply noise filter structure of the printed wiring board provided with the mounting structure of the conventional bypass capacitor currently disclosed by patent document 2. FIG. It is a circuit diagram which shows the equivalent circuit of the printed wiring board which mounted the capacitor | condenser for bypass shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation layer 2a, 2b Divided power supply wiring 3 Ground (GND) layer 4 Bypass capacitor (2-terminal type chip capacitor: electrode part on short side)
4a, 4b Terminal electrode (electrode part)
5a, 5b Power supply pad for capacitor mounting 6 GND pad for capacitor mounting 7 Through hole for GND layer connection 8 Detour pattern of power supply wiring (detour power supply wiring)
8a, 8b, 8c Bypass power supply wiring 9 Bypass capacitor (2-terminal type chip capacitor: electrode part on long side)
9a, 9b Terminal electrode (electrode part)

Claims (3)

A two-terminal type bypass in a printed wiring board having an insulating layer in which a power supply wiring for supplying power to an electronic component is disposed on one layer surface, which is an electronic component mounting surface, and a ground layer is disposed on the other layer surface A power supply noise filter structure in which one terminal electrode of a capacitor for use is connected to the power supply wiring, and the other terminal electrode is connected to the ground layer through a ground pad and a through hole provided in the insulating layer,
The power supply wiring is configured to be divided into a first power supply wiring and a second power supply wiring that are separated by a distance shorter than the length of the terminal electrode of the two-terminal type bypass capacitor.
Pads for connecting the terminal electrodes of the bypass capacitors are respectively provided on the upper surfaces of the opposing divided ends of the first and second power supply wires, and
A detour power supply line connecting between the divided ends facing each other of the first and second power supply lines passes through a different path from the arrangement path of the first and second power supply lines on the same electronic component mounting surface. Arranged,
A power supply noise filter structure for a printed wiring board.   2. The power supply noise filter structure for a printed wiring board according to claim 1, wherein a terminal electrode of the two-terminal type bypass capacitor is provided on a long side of the internal electrode.   3. The bypass power supply wiring is arranged by selecting a path that realizes a high frequency impedance larger than a high frequency impedance of a terminal electrode of the two-terminal type bypass capacitor. The power supply noise filter structure of the printed wiring board as described.

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