Multilayer substrate

Abstract

To provide a multilayer substrate capable of suppressing propagation of noise generated in a power supply IC to a power supply line and EMI radiation while suppressing an increase in the size of a substrate and layout constraints.SOLUTION: Multilayer substrates (1, 2, 3, and 4) have a power supply line (20) connected to a power supply IC (10). The power supply line (20) has: a bandpass filter (12) configured to cut off a fundamental wave of an operating frequency of the power supply IC (10); and an open stub (26) or a branch wiring (27) configured to cut off a harmonic of the operating frequency of the power supply IC (10). The open stub (26) or the branch wiring (27) includes first vias (14 to 18) and wiring (28 and 29) provided in an inner layer of each multilayer substrate (1, 2, 3 and 4).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer substrate, and more particularly to a multilayer substrate having a power supply line connected to a power supply IC. [Background technology]

[0002] In recent years, as electronic circuits have become faster and more compact, the effects of electromagnetic noise generated inside electronic devices have become a problem. In particular, when a power supply IC mounted on a printed circuit board switches, noise that flows into the power plane is radiated by parallel plate resonance between the power plane and the ground plane, causing adverse effects such as malfunctions and reception interference in other electronic devices. One solution to this problem is to place decoupling capacitors between the power terminals and the power plane, but this has problems such as increased costs due to the increased number of components, an increase in board size, and an inability to completely block high-frequency noise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-140210 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-35222 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-204297 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-113402 Summary of the Invention [Problem to be solved by the invention]

[0004] To address this issue, technologies such as those described in Patent Documents 1 to 4 exist that reduce noise without increasing the number of components by using an open stub to cancel out noise components in reverse phase. However, installing the open stub vertically on the same plane as the power line requires space, which increases the size of the board and restricts layout. Furthermore, the noise path spreads on the surface of the board, increasing noise propagation and making EMI radiation more likely.

[0005] The present invention aims to provide a multilayer board that can suppress the propagation of noise generated by a power supply IC to the power supply line and EMI radiation, while minimizing increases in board size and layout restrictions. [Means for solving the problem]

[0006] The above-mentioned problems can be solved by a multilayer substrate having a power supply line connected to a power supply IC, the power supply line having a band-pass filter configured to block the fundamental wave of the operating frequency of the power supply IC, and an open stub or branch wiring configured to block harmonics of the operating frequency of the power supply IC, the open stub or branch wiring having a first via and wiring provided in an inner layer of the multilayer substrate.

[0007] In other words, the bandpass filter and open stub or branch wiring can suppress the propagation of noise caused by the fundamental and harmonics of the power supply IC's operating frequency through the power supply line. Also, by configuring the open stub or branch wiring with vias and inner layer wiring, it is possible to suppress increases in board size and layout restrictions, and further suppress the spread of noise on the board surface, thereby suppressing EMI radiation.

[0008] It is desirable that the open stub have an electrical length that is 1 / 4 the wavelength λ of the harmonic of the power supply IC's operating frequency, and that the branch wiring have an electrical length that is 1 / 2 the wavelength λ of the harmonic of the power supply IC's operating frequency. With this configuration, the open stubs and branch wiring with the above-mentioned electrical lengths can cancel out noise propagating through the power line with an anti-phase wave.

[0009] Furthermore, it is desirable that at least one of the upper and lower layers of the layer where the open stub or branch wiring is provided is connected to ground, as the shielding effect of the upper and lower layers connected to ground can suppress noise propagation.

[0010] It is also desirable to have a second via arranged around the first via and connected to ground, which makes it possible to suppress radiation of noise that has not been canceled by the open stub or branch wiring from the via.

[0011] In this case, a plurality of second vias are provided, and the distance d between adjacent second vias is

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[0012] It is also desirable that the open stub or branch wiring has a plurality of first vias. By increasing the number of vias, it becomes possible to reduce the impedance of the open stub or branch wiring and to enhance the noise reduction effect.

[0013] Furthermore, it is desirable that the bandpass filter has an LRC filter, or an open stub or branch wiring having a third via and wiring provided on an inner layer of the multilayer substrate. The LRC filter, or the open stub or branch wiring composed of a third via and inner layer wiring makes it possible to block a predetermined frequency. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a multilayer substrate that can suppress the propagation of noise generated by a power supply IC to the power supply line and EMI radiation, while suppressing an increase in the size of the substrate and limitations on layout. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic plan view of a multilayer substrate 1 according to a first embodiment of the present invention. [Figure 2] 2 is a schematic cross-sectional view of the multilayer substrate 1 of FIG. 1 taken along the line AA'. [Figure 3] FIG. 2 is a schematic plan view of a multilayer substrate 2 according to a second embodiment of the present invention. [Figure 4] 4 is a schematic cross-sectional view of the multilayer substrate 2 of FIG. 3 taken along the line BB'. [Figure 5] FIG. 10 is a schematic plan view of a multilayer substrate 3 according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a schematic plan view of a multilayer substrate 4 according to a fourth embodiment of the present invention. [Figure 7] 1 is a schematic plan view showing an example of the configuration of a band-pass filter according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Fig. 1 shows a schematic plan view of a multilayer substrate 1 according to a first embodiment of the present invention, and Fig. 2 shows a schematic cross-sectional view taken along the line A-A' in Fig. 1. Multilayer substrate 1 is composed of multiple conductive layers having wiring made of conductive materials, and insulating layers provided between each conductive layer. In the following description, the topmost conductive layer of the multilayer substrate will be referred to as the "surface layer," and the conductive layers sandwiched between the insulating layers will be referred to as the "inner layers."

[0017] A power supply line 20 is provided on the surface layer of the multilayer substrate 1. One end of the power supply line 20 is connected to a power supply IC 10, such as a linear regulator or a switching regulator, which operates at a predetermined operating frequency and supplies power to the power supply line 20. The other end of the power supply line 20 is connected to an electronic component 11, which is a load that consumes the power supplied from the power supply IC 10.

[0018] Furthermore, the power supply line 20 is provided with a bandpass filter 12, which is an electronic component or circuit such as a low-pass filter that has the function of blocking a predetermined frequency, and a via 14 that forms part of the open stub 26. The bandpass filter 12 is located closer to the power supply IC 10 than the via 14, and is configured to block the fundamental wave of the operating frequency of the power supply IC 10.

[0019] On both sides of the power supply line 20, ground wirings 21 and 22 insulated from the power supply line 20 are provided. In addition, a plurality of vias 30 and 31 connected to the ground wirings 21 and 22 are arranged around the via 14. Adjacent vias 30 and 31 are arranged in a direction parallel or non-parallel to the power supply line 20, spaced apart by a distance d defined by equation (1).

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[0020] where c is the speed of light (3×10 8 where er_eff is the relative permittivity of the insulating layers of the multilayer substrate 1, and f is the frequency of a harmonic of the operating frequency of the power supply IC 10. Arranging multiple vias 30, 31 at intervals d makes it possible to suppress EMI caused by noise of frequency f that is not canceled by the open stub 26 being emitted from the via 14. Note that the harmonics of the operating frequency of the power supply IC 10 include multiple harmonics such as the third and fifth harmonics, but it is desirable to set f so as to suppress EMI at the frequencies of low-order harmonics with large amplitude levels.

[0021] Furthermore, in the multilayer substrate 1, to obtain a greater EMI radiation suppression effect, the ground wiring 21, 22 and vias 30, 31 are provided on both sides of the power line 20, but they may be provided on only one side. However, if they are provided on only one side, the EMI suppression effect will be smaller than if they are provided on both sides. Furthermore, in the multilayer substrate 1, to obtain a greater EMI suppression effect at a specific frequency f, the multiple vias 30, 31 connected to the ground wiring 21, 22 are arranged at intervals of the distance d defined by equation (1), but the number of vias may be one. If there is one via around the via 14, an EMI suppression effect that is not frequency-dependent can be obtained.

[0022] An inner layer of the multilayer substrate 1 is provided with an inner layer wiring 28 that forms part of an open stub 26. The open stub 26 is configured by connecting one end of the inner layer wiring 28 to one end of a via 14. The other end of the via 14 is connected to the wiring of a power supply line 20 provided on the surface layer of the multilayer substrate 1. The open stub 26 is configured to block harmonics of the operating frequency of the power supply IC 10. More specifically, the length s of the open stub 26, i.e., the electrical length s defined along the center line of the via 14 and the inner layer wiring 28 as shown in FIG. 2, is configured to be ¼ of the wavelength λ of the harmonic of the operating frequency of the power supply IC 10. This generates a reflected wave that is out of phase with the harmonic of wavelength λ, thereby canceling out the noise of wavelength λ propagating through the power supply line 20. Although there are multiple harmonics of the operating frequency of the power supply IC 10, such as the third harmonic and the fifth harmonic, it is desirable to set the electrical length s to 1 / 4 of the wavelength λ of the lower-order harmonics, which have a larger amplitude level. Furthermore, the frequency of the noise canceled by the open stub 26 may be the same as or different from the frequency f of the EMI suppressed by the multiple vias 30, 31 provided in the ground wirings 21, 22.

[0023] Wiring 23, 24 connected to ground are provided in the upper and lower conductive layers of inner layer wiring 28. The shielding effect of ground wiring 23, 24 can suppress noise propagation in the inner layers of multilayer substrate 1. Note that although the shielding effect is achieved when ground wiring 23, 24 is provided only on the upper layer or only on the lower layer of inner layer wiring 28, a higher shielding effect can be achieved by providing ground wiring 23, 24 on both the upper and lower layers.

[0024] Next, a schematic plan view of multilayer substrate 2 according to a second embodiment of the present invention is shown in Fig. 3, and a schematic cross-sectional view of multilayer substrate 2 taken along line B-B' in Fig. 3 is shown in Fig. 4. Multilayer substrate 2 differs from multilayer substrate 1 in that it has branch wiring 27 instead of open stub 26 of multilayer substrate 1, but otherwise has the same configuration as multilayer substrate 1. For this reason, in the figure, components of multilayer substrate 2 that have the same functions as components of multilayer substrate 1 are given the same reference numerals.

[0025] A power supply line 20 is provided on the surface layer of the multilayer substrate 2. A power supply IC 10 is connected to one end of the power supply line 20, and an electronic component 11 is connected to the other end. The power supply line 20 also has a band-pass filter 12 and two vias 15 and 16 that form part of a branch wiring 27. The band-pass filter 12 is arranged closer to the power supply IC 10 than the two vias 15 and 16, and is configured to block the fundamental wave of the operating frequency of the power supply IC 10. Ground wiring 21 and 22 are provided on both sides of the power supply line 20, and a plurality of vias 30 and 31 are connected to each of the ground wiring 21 and 22, and are spaced apart by a distance d expressed by equation (1).

[0026] An inner layer of the multilayer substrate 2 is provided with an inner layer wiring 29 that forms part of a branch wiring 27. The branch wiring 27 is configured by connecting one end of each of two vias 15 and 16 to each end of the inner layer wiring 29. The other ends of the two vias 15 and 16 are connected to the wiring of a power supply line 20 provided on the surface layer of the multilayer substrate 2. The branch wiring 27 is configured to block harmonics of the operating frequency of the power supply IC 10. More specifically, the electrical length b of the branch wiring 27, i.e., the electrical length b defined along the center line of the two vias 15 and 16 and the inner layer wiring 29 as shown in FIG. 4, is configured to be half the wavelength λ of the harmonic of the operating frequency of the power supply IC 10. This generates a wave that is out of phase with the harmonic propagating through the power supply line 20, thereby canceling out the noise with wavelength λ propagating through the power supply line 20. The harmonics of the operating frequency of the power supply IC 10 include multiple harmonics such as the third and fifth harmonics, and it is desirable to set the electrical length b to half the wavelength λ of the lower harmonics, which have a larger amplitude level. The frequency of the noise canceled by the branch wiring 27 may be the same as or different from the frequency of the EMI suppressed by the multiple vias 30, 31 provided in the ground wirings 21, 22.

[0027] Wiring 23, 24 connected to ground are provided in the conductive layers above and below the inner layer wiring 29. The shielding effect of the ground wiring 23, 24 can suppress noise propagation in the inner layers of the multilayer substrate 1. Note that although the shielding effect is achieved when the ground wiring 23, 24 is provided only on the upper layer or only on the lower layer of the inner layer wiring 29, a greater shielding effect can be achieved by providing the ground wiring 23, 24 on both the upper and lower layers.

[0028] Next, a schematic plan view of a multilayer substrate 3 according to a third embodiment of the present invention is shown in FIG. 5. Multilayer substrate 3 differs from multilayer substrate 1 in that via 17, which constitutes part of open stub 26, has a larger cross-sectional area than via 14 of multilayer substrate 1, but otherwise has a similar configuration to multilayer substrate 1. Therefore, in the figure, components of multilayer substrate 3 that have similar functions to those of multilayer substrate 1 are given the same reference numerals. In multilayer substrate 3, increasing the cross-sectional area of ​​via 17, which constitutes part of open stub 26, can reduce the impedance of open stub 26 and enhance the noise reduction effect. Regarding two vias 15 and 16 that constitute part of branch wiring 27 of multilayer substrate 2 according to the second embodiment, increasing the cross-sectional area of ​​one or both of the two vias 15 and 16 can also reduce the impedance of branch wiring 27 and enhance the noise reduction effect.

[0029] Next, a schematic plan view of a multilayer substrate 4 according to a fourth embodiment of the present invention is shown in FIG. 6. Multilayer substrate 4 differs from via 14 of multilayer substrate 1 in that via 18 constituting part of open stub 26 is composed of multiple vias. However, multilayer substrate 4 otherwise has a similar configuration to multilayer substrate 1. Therefore, in the figure, components of multilayer substrate 4 that have similar functions to those of multilayer substrate 1 are given the same reference numerals. In multilayer substrate 4, increasing the number of vias 18 constituting part of open stub 26 reduces the impedance of open stub 26 and enhances noise reduction. Regarding two vias 15 and 16 constituting part of branch wiring 27 of multilayer substrate 2 according to the second embodiment, configuring one or both of the two vias 15 and 16 with multiple vias reduces the impedance of branch wiring 27 and enhances noise reduction.

[0030] Finally, Fig. 7 shows an example of the configuration of the bandpass filter 12 of the above-mentioned multilayer substrates 1, 2, 3, and 4. Fig. 7(a) is a schematic plan view of a bandpass filter 50 configured with an LRC filter, Fig. 7(b) is a schematic plan view of a bandpass filter 51 configured with open stubs, and Fig. 7(c) is a schematic plan view of a bandpass filter 52 configured with branched wiring.

[0031] The band-pass filter 50 shown in FIG. 7(a) is an LCR filter with low-pass characteristics. The band-pass filter 50 includes at least one element 40, which is an inductive element such as a coil or a resistive element such as a resistor, and a capacitive element 41, such as a capacitor. In other words, the term "LCR filter" in this application includes LC filters without resistive elements and RC filters without inductive elements. The inductive element and / or resistive element 40 is disposed in the wiring path of the power supply line 20, and one end of the capacitive element 41 is connected to the wiring of the power supply line 20 and the other end is connected to the ground wiring 25. The band-pass filter 50 has a cutoff frequency determined by the time constant of the inductive element and / or resistive element 40 and the capacitive element 41, such as a capacitor.

[0032] 7(b) has a similar configuration to the open stub 26. That is, one end of a via 42 is connected to one end of an inner layer wiring. The other end of the via 42 is connected to the wiring of the power supply line 20 provided on the surface layer of the multilayer substrates 1, 2, 3, and 4. The band-pass filter 51 can cancel noise with a wavelength λ that is four times the electrical length of the open stub.

[0033] 7(c) has a similar configuration to the branch wiring 27. That is, the branch wiring is configured by connecting one end of each of two vias 43 and 44 to the respective ends of the inner layer wiring. The other ends of the two vias 43 and 44 are connected to the wiring of the power supply line 20 provided on the surface layer of the multilayer substrates 1, 2, 3, and 4. The band-pass filter 52 can cancel noise with a wavelength λ that is twice the electrical length of the branch wiring.

[0034] Although the multilayer substrate according to the present invention has been described above, the present invention is not limited to the above-described embodiments and includes all aspects encompassed by the concept of the present invention and the scope of the claims. For example, while the multilayer substrates 1, 2, 3, and 4 shown in the above-described embodiments each include only one open stub 26 or one branch line 27, multiple open stubs or branch lines may be arranged in series or parallel to one another in the power supply line 20. In this case, the multiple open stubs or branch lines may be configured to block the same harmonic of the operating frequency of the power supply IC 10, or each open stub or branch line may be configured to block different harmonics. [Explanation of symbols]

[0035] 1, 2, 3, 4 multilayer board 10 Power IC 11 Electronic Components 12, 50, 51, 52 bandpass filters 14, 15, 16, 17, 18, 30, 31, 42, 43, 44 vias 20 Power Line 21, 22, 23, 24, 25 Ground wiring 26 Open Stub 27 Branch wiring 28, 29 Inner layer wiring 40 Inductive / Resistive Elements 41 Capacitive elements

Claims

1. A multilayer substrate having a power supply line connected to a power supply IC, The power supply line is a bandpass filter configured to block a fundamental wave of an operating frequency of the power supply IC; an open stub or branch wiring configured to block harmonics of the operating frequency of the power supply IC; and The open stub or branch wiring has a first via and a wiring provided on an inner layer of the multilayer substrate. A multilayer substrate characterized by:

2. 2. The multilayer board according to claim 1, wherein the open stub has an electrical length that is 1 / 4 of the wavelength λ of a harmonic of the operating frequency of the power supply IC.

3. 2. The multilayer board according to claim 1, wherein the branch wiring has an electrical length that is 1 / 2 the wavelength λ of a harmonic of the operating frequency of the power supply IC.

4. 2. The multilayer board according to claim 1, wherein at least one of the upper and lower layers above and below the layer on which the open stub or branch wiring is provided is connected to ground.

5. 2. The multilayer board according to claim 1, further comprising a second via arranged around the first via and connected to ground.

6. a plurality of the second vias; The distance d between adjacent second vias is [Equation 1] where c is the speed of light, f is the frequency of a harmonic of the operating frequency of the power supply IC, and er_eff is the relative permittivity of the insulating layer of the multilayer substrate.

6. The multilayer substrate according to claim 5.

7. The multilayer board according to claim 1 , wherein the open stub or branch wiring has a plurality of first vias.

8. 2. The multilayer substrate of claim 1, wherein the bandpass filter comprises an LRC filter.

9. 2. The multilayer substrate according to claim 1, wherein the bandpass filter has an open stub or branch wiring having a third via and a wiring provided on an inner layer of the multilayer substrate.

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