JP2004140210A - System - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system composed of semiconductor devices mounted on a substrate by which no electric power is wasted, noise can be effectively reduced up to high frequencies and power source decoupling for a semiconductor device such as a microcomputer can be achieved. <P>SOLUTION: The system is composed of an LSI package 1, a bypass capacitor 3, a filter 5 and the like which are mounted on the substrate. The filter 5 includes stub wiring 4 (λ/4) which is connected between the bypass capacitor 3 and a backbone power source and is composed of circuits which exhibit an impedance lower than that of the power source path. In this way, when noise is generated from the LSI package 1, the noise current is allowed to flow into the filter 5, is reflected from an open end of the stub wiring 4 and returns. Noise current from the LSI package 1 after λ/2 is canceled at a branch point of the stub wiring 4 by this action. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a system in which a semiconductor device is mounted, and particularly to a technology effective when applied to a system in which a semiconductor device such as a microcomputer suitable for reducing unnecessary electromagnetic radiation (EMI: Electro-Magnetic Interference) is mounted on a mounting substrate. About.
[0002]
[Prior art]
According to the study by the present inventors, the following technology can be considered for a system in which a semiconductor device such as a microcomputer is mounted on a mounting board.
[0003]
For example, in a system in which a semiconductor device of a microcomputer is mounted on a mounting board, in order to reduce EMI, a bypass capacitor of a mounted component is connected to a power supply voltage and a reference voltage of a power supply path for supplying power from a main power supply to the semiconductor device. And measures against noise so that the operating current of the microcomputer (particularly its harmonic components) is hardly drawn from the main power supply. Further, in addition to the bypass capacitor, a power supply filter may be inserted in series with the power supply voltage or the reference voltage of the power supply path.
[0004]
In order to reduce EMI, the length of the power supply line of the power supply path for supplying power from the main power supply to the semiconductor device is set to a value obtained by multiplying the specific frequency of the power supply wiring by the wavelength reduction ratio of the substrate material. (Patent Document 1) discloses a technique of a printed circuit board in which a capacitor is connected between a power supply voltage and a reference voltage.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-119110 (Summary on page 1)
[0006]
[Problems to be solved by the invention]
By the way, the present inventor has studied the system in which the above-described semiconductor device such as the microcomputer is mounted on the mounting board, and as a result, the following has become clear.
[0007]
For example, as described above, in the configuration in which the bypass capacitor is connected between the power supply voltage of the power supply path for supplying power from the main power supply to the semiconductor device and the reference voltage (see FIG. 1, but without the filter 5), With the current C, the current B from the bypass capacitor 3 does not reach 100%, and the current A from the main power supply 2 cannot be completely blocked. This is because the magnitudes of the current A and the current B are determined by the reciprocal ratio of the respective path impedances. Since the impedance of the path B can be made only about 1/10 of that of the path A, a noise current of about 1/10 of the current B flows through the path A. Since the path A is connected to a high radiation efficiency portion (acting as an antenna) such as a power cable, even a current of 1/10 causes EMI.
[0008]
Furthermore, if chip beads or a T-type filter is used in addition to the bypass capacitor, the path impedance ratio of the current A and the current B can be increased to nearly 1000: 1. However, since these can be obtained only in a relatively low frequency band and the unavoidable DC resistance (0.2 to 0.6Ω), unnecessary power consumption and fluctuations in the power supply voltage due to changes in the current of the semiconductor device are reduced. There are problems that occur.
[0009]
Further, the technique of Patent Document 1 defines the length of a power supply line of a power supply path for supplying power from a basic power supply to a semiconductor device, and as in the present invention, the other end is in an open state. This is not a technique for connecting one end of the wiring to a power supply path.
[0010]
Therefore, an object of the present invention is to provide a system in which a semiconductor device is mounted on a mounting board, which can realize power supply decoupling for a semiconductor device such as a microcomputer without wasteful power consumption and having a high noise reduction effect at high frequencies. To provide.
[0011]
The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.
[0012]
[Means for Solving the Problems]
The following is a brief description of an outline of typical inventions disclosed in the present application.
[0013]
That is, the present invention has a configuration in which a low-impedance circuit is added to a system in which a semiconductor device and a capacitor are mounted on a mounting board, and the capacitor has a power supply voltage and a reference voltage of a power supply path for supplying power from a main power supply to the semiconductor device. The low impedance circuit is connected between the capacitor and the main power supply, one end is connected to the power supply voltage and the reference voltage of the power supply path, respectively, and the other end is a pair of wires in an open state, so-called The circuit includes stub wiring and has a lower impedance than the power supply path. By providing a low-impedance circuit in the power supply path through which the noise current flows, it becomes possible to inject a current having an opposite phase to cancel the noise current from the low-impedance circuit into the power supply path.
[0014]
In this configuration, each of the pair of stub wires is formed to have a length that is １ ／ of the wavelength of the operating frequency of the semiconductor device in the mounting substrate, or is 1 / １ ／ of an integral multiple of the operating frequency of the semiconductor device. It is formed to have a length of four wavelengths, or a combination of these. As a result, the current of the opposite phase injected from the stub wiring into the power supply system generates only a frequency component that is an odd multiple of the frequency at which the stub wiring length becomes exactly 1/4 wavelength, so that the noise current is reduced and the EMI is reduced. The effect can be obtained sufficiently.
[0015]
Further, the low impedance circuit is configured by sandwiching a dielectric having a thickness of 10 μm to 0.2 μm between a pair of stub wirings, and is formed in a mounting substrate or formed as a mounting component on the mounting substrate. is there. As a result, the size of the mounting board is not affected even when it is formed in the mounting board, and when it is formed as a mounting component, it can be made to correspond to various devices as an individual component.
[0016]
It should be noted that the lower the impedance of this low impedance circuit, the greater the noise current flowing into the circuit, and thus the higher the effect of canceling noise.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for describing the embodiments, members having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted.
[0018]
An example of the configuration of the system according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic circuit diagram of a power supply system for a semiconductor device mounted on a mounting board in the system according to the present embodiment.
[0019]
Although the system of the present embodiment is not particularly limited, for example, as an example, an LSI package (semiconductor device) 1 of a microcomputer and a power supply of a power supply path for supplying power from the main power supply 2 to the LSI package 1 A bypass capacitor (capacitor) 3 connected between the voltage Vcc and the reference voltage Vss; a bypass capacitor (capacitor) 3 connected between the bypass capacitor 3 and the main power supply 2; one end of which is connected to the power supply voltage Vcc and the reference voltage Vss of the power supply path; The LSI package 1, the bypass capacitor 3, the filter 5, etc., which are connected to each other and include a pair of stub wirings 4 in an open state and a filter 5 having a lower impedance than the power supply path, are mounted. It is configured to be mounted on a substrate.
[0020]
In this system, the power supply path of the power supply voltage Vcc and the reference voltage Vss up to the connection point between the main power supply 2 and the bypass capacitor 3 and the power supply path of the power supply voltage Vcc and the reference voltage Vss up to the bypass capacitor 3 and the LSI package 1 have inductances, respectively. With components. Each output path from the LSI package 1 has a load capacitance component at the next stage.
[0021]
The LSI package 1 has a built-in chip 6 on which a plurality of modules 7 constituting a microcomputer are formed. Each module 7 is supplied with a power supply voltage Vcc and a reference voltage Vss from a power supply path on a mounting board. On the chip 6, a CPG 9 that generates a reference clock signal by using an oscillation signal from a crystal oscillator 8 provided outside the LSI package 1 as an input is formed. Supplied to Further, a buffer circuit 11 for outputting a signal to the outside of the LSI package 1 is formed on the chip 6.
[0022]
In the LSI package 1, the power supply paths of the internal power supply voltage Vcc and the reference voltage Vss each have an inductance component similarly to the above system.
[0023]
The bypass capacitor 3 is provided near the LSI package 1 and is connected between the power supply voltage Vcc and the reference voltage Vss of the power supply path on the mounting board.
[0024]
The filter 5 is provided closer to the main power supply 2 than the bypass capacitor 3 and connected to the power supply voltage Vcc and the reference voltage Vss of the power supply path on the mounting board. The filter 5 includes a pair of stub wires 4 sandwiching a dielectric. One end of each of the pair of stub wires 4 is inserted and connected in the middle of the wiring between the power supply voltage Vcc and the reference voltage Vss in the power supply path. Is open. In the filter 5, an extremely thin dielectric (thickness of about 10 μm to 0.2 μm) is used to realize a particularly low impedance. The details of the shape of the stub wiring 4 will be described later, but here, the stub wiring pattern is illustrated.
[0025]
Next, with reference to FIG. 2, an example of the concept of connection of filters and noise cancellation by the connection in the system of the present embodiment will be described. FIG. 2 shows a conceptual diagram of the connection of the filter and the noise cancellation by the connection.
[0026]
FIG. 2 shows an example of the filter 5 using the band pattern stub wiring 4. As described above, this band pattern has one end connected to the power supply voltage Vcc and the reference voltage Vss of the power supply path via the ports 1 and 2 respectively, and the other end in an open state. Is formed at a length of 1/4 wavelength (λ / 4).
[0027]
In the system of the present embodiment, when noise is generated from the LSI package 1, this noise current is partially absorbed by the bypass capacitor 3 and flows to the filter 5 ahead of the capacitor. The noise current flowing through the filter 5 is reflected at the other end of the stub wiring 4 in the open state, returns to the branch point at one end, and joins the subsequent noise current. Thus, at the branch point of the stub wiring 4, the reflected wave from the stub wiring 4 acts so as to cancel the noise current after λ / 2 from the LSI package 1. That is, it is possible to prevent the noise current from the LSI package 1 from flowing to the power supply system from the main power supply 2. This effect is effective for all odd harmonics of the fundamental frequency.
[0028]
Next, an example of the stub wiring of the filter will be described with reference to FIGS. FIG. 3 shows a band pattern, FIGS. 4 and 5 show modified examples of the band pattern, FIG. 6 shows a spiral pattern, and FIG. As shown in FIG. 2, one end of each filter is connected to the power supply voltage Vcc and the reference voltage Vss of the power supply path via the ports 1 and 2, respectively.
[0029]
As shown in FIG. 3, in the filter 5a in which the stub wiring 4a has a band pattern, the stub wiring 4a is formed in a band shape with a predetermined width and a predetermined length between the ports 1 and 2 of the filter 5a. This example may correspond to a frequency of 2.4 GHz, for example Bluetooth.
[0030]
In addition, as shown in FIG. 4, the filter using the band pattern is a stub wiring 4b having a central portion at the tip in a convex state, so that the filter 5b can increase the effective bandwidth. Alternatively, as shown in FIG. 5, the bandwidth of the filter 5c in which the tip of the stub wiring 5c is in a stepped state can also be expanded similarly. As described above, by deforming the tip of the stub wiring 4, it becomes possible to realize the filter 5 that can obtain an effect with a wide bandwidth.
[0031]
As shown in FIG. 6, in a filter 5d in which the stub wiring 4d has a spiral pattern, the stub wiring 4d is formed in a spiral shape with a predetermined width and a predetermined length between the ports 1 and 2 of the filter 5d. . In this shape, the area can be reduced by bending while maintaining the distance to the tip. Note that the width of the stub wiring 4d can be reduced within a range where the reflected wave is not attenuated (resistance loss) and the effect is not lost.
[0032]
As shown in FIG. 7, in the filter 5e, the stub wiring 4e is formed by a broken pattern, and the stub wiring 4e is formed to have a predetermined width and a predetermined length between the ports 1 and 2 of the filter 5e. As in the case of the spiral pattern, by bending while maintaining the distance to the tip, the area can be reduced.
[0033]
Next, an example in which a filter is formed in a mounting substrate will be described with reference to FIGS. 8 is a cross-sectional view of the mounting board, FIGS. 9 to 12 show layout diagrams of each layer of the mounting board, FIG. 9 shows a signal wiring layer (surface layer), FIG. 10 shows a stub wiring layer, and FIG. 11 shows a reference voltage layer. FIG. 12 shows a power supply voltage layer, and FIG. 13 shows a modification of the stub wiring layer.
[0034]
As shown in FIG. 8, the mounting substrate 20 includes a signal wiring layer (surface layer) 21, an insulating layer 22, a stub wiring layer 23, a dielectric layer 24, a reference voltage layer 25, an insulating layer 26, a power supply voltage layer 27, and an insulating layer. It is formed in a multilayer structure composed of a layer (back surface layer) 28. The filter 5 is formed inside the mounting board 20. The pair of stub wirings 4 are composed of a dielectric layer 24 and a solid pattern (plain pattern) of a stub wiring layer 23 laminated on the upper layer and a reference voltage layer 25 laminated on the lower layer. Is partially sandwiched between the shared wirings. For example, when aluminum is used for the stub wiring layer 23 and the reference voltage layer 25, the dielectric layer 24 is formed of an extremely thin aluminum oxide film having a thickness of about 10 μm to 0.2 μm, preferably 1 μm or less, and about 0.2 μm. Can be
[0035]
As shown in FIG. 9, in the signal wiring layer 21 of the mounting substrate 20, wiring patterns 32a to 32d of signals, power supply voltages, and reference voltages are routed from pads 31a to 31d on which the LSI package 1 is mounted. . The wiring pattern 32b of the power supply voltage Vcc is routed from the power supply voltage pad 31b to one of the pair of power supply voltage through holes 33a, and the other through hole 33b paired with the one through hole 33a is connected to the power supply voltage. It is connected to the voltage layer 27. The wiring pattern 32c of the reference voltage Vss is routed from the reference voltage pad 31c to the reference voltage through hole 33c.
[0036]
As shown in FIG. 10, in the stub wiring layer 23, a wiring pattern connected to the pair of through holes 33a and 33b for the power supply voltage is formed as a stub wiring 4 in a serpentine pattern (an example corresponding to FIG. 7).
[0037]
As shown in FIG. 11, the reference voltage layer 25 is formed in a solid pattern connected to the reference voltage through hole 33c. A part of the solid pattern is shared as the stub wiring 4, and the filter 5 is configured with the stub wiring 4 of the stub wiring layer 23 and the dielectric layer 24 interposed therebetween. The pair of through holes 33a and 33b for power supply voltage are not connected to a solid pattern.
[0038]
As shown in FIG. 12, the power supply voltage layer 27 is formed in a solid pattern that is connected to the other through hole 33b of the power supply voltage pair. This solid pattern is connected to the main power supply 2. Note that, of the pair for the power supply voltage, one through hole 33a and the reference voltage through hole 33c are not connected to a solid pattern.
[0039]
Further, when the stub wiring layer 23 cannot be formed in the meandering pattern as shown in FIG. 10 due to the layout of the mounting board 20, for example, as shown in FIG. It is also possible to bend and route the stub wiring 4f.
[0040]
Next, an example in which a filter is formed as a component mounted on a mounting board will be described with reference to FIGS. 14 to 16 show mounted components, FIG. 14 is a perspective view, FIG. 15 is a bottom view, FIG. 16 is an explanatory view of stub wiring, and FIGS. 17 to 19 show another mounted component. 17 is a perspective view, FIG. 18 is a sectional view, and FIG. 19 is an explanatory view of a stub wiring.
[0041]
As shown in FIGS. 14 and 15, the mounted component 40 is formed in a square pole shape, and has terminals 41 and 42 of power supply voltages Vcc1 and Vcc2 and terminals 43 and 44 of reference voltages Vss1 and Vss2 provided on the bottom surface. . Of the terminals 41 to 44, the terminals 41 and 43 of the power supply voltage Vcc1 and the reference voltage Vss1 are on the LSI package 1 side, and the terminals 42 and 44 of the power supply voltage Vcc2 and the reference voltage Vss2 are on the side of the main power supply 2 with respect to the power supply path. Connected.
[0042]
As shown in FIG. 16, a stub wiring 4g of a band pattern sandwiching a dielectric material is incorporated inside the quadrangular prism-shaped mounting component 40 in a roll shape around the open end. Further, instead of being formed in a roll shape, it is also possible to incorporate it in a broken shape. For example, the length of the stub wiring 4g is about 280 mm when adjusted to 60 MHz, and the size cannot be reduced unless the thickness is reduced including the base material. Becomes possible. For the purpose of preventing noise from entering the band used by the mobile phone (1.5 GHz), an effect can be obtained with a length of about 11 mm. In the case of a stub wiring having a short overall length, the width of the stub wiring may be reduced because the reflected wave is not easily attenuated. Part size can be reduced by reducing the overall length and width.
[0043]
As shown in FIG. 17, another mounting component 50 is formed in a columnar shape, and provided with leads 51 and 52 for power supply voltages Vcc1 and Vcc2 and leads 53 and 54 for reference voltages Vss1 and Vss2 on the bottom surface. The leads 51 and 53 for the power supply voltage Vcc1 and the reference voltage Vss1 are connected to the LSI package 1 side, and the leads 52 and 54 for the power supply voltage Vcc2 and the reference voltage Vss2 are connected to the main power supply 2 side.
[0044]
As shown in FIGS. 18 and 19, a stub wiring 4h in a zigzag pattern sandwiching a dielectric is wound inside the cylindrical mounting component 50 with an insulating material as a core and an insulating sheet (not shown). It is built in the shape. For example, the stub wiring 4h has a length of about 29 mm and a width of about 1.8 mm in ten turns. In this case, the outer shape of the mounted component 50 can be about 1 mm in diameter and about 2 mm in length.
[0045]
With respect to the filter 5 configured as described above, typical application fields and a configuration method of the filter 5 are summarized as follows.
[0046]
For example, in the case of an in-vehicle device, when the operating frequency of the microcomputer is 40 MHz, 80 MHz, or the like, the basic frequency of the filter 5 is set to the operating frequency of the microcomputer, and the filter 5 is built in the mounting substrate 20 or mounted on the mounting board 40 or 50, 50 Can be configured as In the case of a portable device, when the operating frequency of the microcomputer is 160 MHz or the like, the basic frequency of the filter 5 is set to the communication frequency of the device. Further, Bluetooth and the like can be used in the same manner as in the case of a portable device.
[0047]
Next, with reference to FIGS. 20 to 24, an example of a simulation result of the characteristic evaluation and the dependency evaluation of each stub wiring in the filter will be described. 20 is a characteristic evaluation by comparing dielectric thicknesses, FIG. 21 is a pattern dependency evaluation, FIG. 22 is a combination pattern of stub wirings, FIG. 23 is a combination evaluation of a plurality of stub wirings, and FIG. 24 is a combination of a plurality of stub wirings Are respectively shown.
[0048]
In the evaluation of the characteristics by comparing the dielectric thickness, the thickness of the dielectric was set to 400 μm and 0.2 μm for the stub wiring 4 e having the serpentine pattern (the stub wiring length was 15 mm × 15) shown in FIG. It is the simulation result which measured the attenuation value (Magnitude (dB)) with respect to the change of the frequency (Frequency (MHz)) in the case. As shown in FIG. 20, as for the transmission characteristics between the ports of the filter 5, an excellent attenuation characteristic that cannot be obtained with a dielectric thickness of 0.2 μm and a normal dielectric thickness of 400 μm is obtained.
[0049]
The evaluation of the pattern dependence is performed, for example, on the stub wiring 4d of the spiral pattern shown in FIG. 6 and the stub wiring 4e of the serpentine pattern shown in FIG. 7 when the dielectric thickness is 0.2 μm. It is the simulation result which measured the attenuation value. As shown in FIG. 21, similar characteristics are obtained in both the spiral pattern and the serpentine pattern.
[0050]
The evaluation of the combination of the plurality of stub wirings is performed by the stub wiring 4e of the serpentine pattern shown in FIG. 7, the stub of the serpentine pattern shown in FIG. 7, and the stub of the serpentine pattern by the wiring length of 1/2 of the serpentine pattern. It is the simulation result which measured the attenuation value with respect to the frequency change about the combination pattern (FIG. 22) with the wiring 4i. As shown in FIG. 23, in the meandering pattern of integral multiples, excellent attenuation characteristics can be obtained with respect to odd harmonics such as first, third, fifth, seventh,. In this case, excellent attenuation characteristics can be obtained with respect to the first, second, third, fifth, sixth, seventh,... Harmonics.
[0051]
From these results, by further combining the zigzag pattern with the wiring length of １ ／ of the zigzag pattern and the zigzag pattern with the wiring length of ４, the zigzag patterns 1 and 1 as shown in FIG. Other than the 4nth order in combination with the zigzag pattern 2 due to the wiring length of / 2, the zigzag pattern other than 8nth order in combination with the zigzag pattern 1 and the zigzag patterns 2 and 3 with the wiring lengths of 1/2 and 1/3. In the combination of the serpentine patterns 2, 3, and 4 with the wiring lengths of patterns 1, 1/2, 1/3, and 1/4, all harmonics other than the 16n-th order can be blocked.
[0052]
As described above, according to the system of the present embodiment, the connection for branching the stub wiring 4 of the filter 5 from the power supply path, the thinning of the dielectric sandwiched between the stub wirings 4 (low dielectric constant), and the applicable equipment are supported. Thus, the following effects can be obtained.
[0053]
(1) By providing a filter 5 with a stub wiring 4 having a quarter wavelength of the operating frequency in a power supply path through which a noise current flows, the noise current is canceled from the stub wiring 4 to a power supply system from the main power supply 2. Currents of opposite phases can be injected. The current having the opposite phase generates only a frequency component whose stub wiring length is an odd multiple of exactly 1/4 wavelength. Thus, the noise current is reduced, and an EMI reduction effect can be obtained.
[0054]
(2) As a result of the simulation, when the stub wiring 4 is manufactured with a microstrip line structure (including a structure with a narrow GND width) in which the dielectric is extremely thin (about 1 μm), the ratio to the characteristic impedance of the power supply system can be increased. For this reason, most of the noise current flowing through the power supply system flows into the stub wiring 4, and this is totally reflected at the other end of the stub wiring 4 in the open state, so that the noise current can be canceled at the inflow point.
[0055]
(3) The noise of the microcomputer has a peak at the higher harmonic of the operating frequency, and the filter 5 effective only at an odd multiple of the design frequency, such as the filter 5 including the stub wiring 4, effectively reduces the main peak. be able to. Further, when it is desired to eliminate even-numbered peaks, it can be realized by combining a filter 5 including a plurality of stub wirings 4 whose wiring length is adjusted to an integral multiple of the operating frequency.
[0056]
(4) In a mobile device, a communication device to which Bluetooth is applied, and the like, a noise current can be effectively reduced by using a filter 5 in which a stub wiring length (1/4 wavelength) is matched to a communication frequency of each device. Can be.
[0057]
(5) Since the filter 5 can be formed in the mounting substrate 20 with an extremely thin dielectric layer 24 such as an oxide film interposed between the stub wiring layer 23 and the reference voltage layer 25, the thickness and size of the mounting substrate 20 can be reduced. Dimensional increase can be suppressed.
[0058]
(6) When the filter 5 is formed as the mounting components 40 and 50 on the mounting board 20, it can be individually manufactured based on the frequency characteristics of various devices and the like, so that it can be adapted to various devices.
[0059]
(7) Power supply decoupling for a semiconductor device without wasteful power consumption (loss) (DC resistance of 0Ω) and high noise reduction effect at high frequencies (covering a communication frequency band of a mobile phone) can be realized. As a result, a system with low noise and low power consumption can be realized. Further, since the filter can be downsized as the operating frequency is higher, the cost merit over the prior art is increased.
[0060]
As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist thereof. Needless to say.
[0061]
For example, in the above-described embodiment, a microcomputer has been described as an example. However, the present invention can be applied to all LSI products for which low EMI characteristics are strongly required. It can be suitably applied to a power supply system of a circuit board.
[0062]
Further, according to the present invention, the attenuation effect can be improved and the loss can be improved by using an extremely thin dielectric in a high-frequency circuit (non-power supply system). This filter can also be applied as a component for noise suppression (power supply system, non-power supply system). Further, the present invention can be applied to a measure against a specific noise peak (high frequency) in combination with a conventional filter (chip bead or T-type filter).
[0063]
Further, in the present invention, the dielectric film is not limited to the aluminum oxide film, and may be a dielectric film such as an organic insulator, for example, as long as an extremely thin dielectric film is formed. .
[0064]
【The invention's effect】
The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.
[0065]
(1) A circuit having a lower impedance than the power supply path between the capacitor and the main power supply. One end of the circuit is connected to the power supply voltage and the reference voltage of the power supply path, and the other end is a pair of open circuits. By connecting the low-impedance circuit to the power supply path, it is possible to inject a current having an opposite phase to cancel the noise current from the stub wiring to the power supply path, thereby reducing the noise current and reducing the EMI. The effect can be obtained.
[0066]
(2) In particular, by combining a plurality of low impedance circuits in which the stub wiring length (1/4 wavelength) is combined with the basic operating frequency of the microcomputer and an operating frequency that is an integral multiple of the fundamental operating frequency, odd-numbered harmonics of the noise current can be reduced. Since even-order harmonics can be blocked, a sufficient EMI reduction effect can be obtained.
[0067]
(3) In particular, even in mobile devices and communication devices to which Bluetooth or the like is applied, noise current is prevented by using a low impedance circuit in which the stub wiring length (1/4 wavelength) is adjusted to the communication frequency of each device. A sufficient EMI reduction effect can be obtained.
[0068]
(4) In particular, even when a low impedance circuit is formed in a mounting substrate, it does not affect the size of the mounting substrate, and when it is formed as a mounting component, it can be adapted to various devices as individual components. It becomes.
[0069]
(5) Since power supply decoupling for a semiconductor device such as a microcomputer having high noise reduction effect at high frequencies without wasteful power consumption can be realized, a low noise and low power consumption system can be realized. .
[Brief description of the drawings]
FIG. 1 is a schematic circuit diagram showing a power supply system for a semiconductor device mounted on a mounting board in a system according to an embodiment of the present invention;
FIG. 2 is a conceptual diagram illustrating connection of a filter and noise cancellation by the connection in the system according to the embodiment of the present invention;
FIG. 3 is a pattern diagram showing a band pattern of a stub wiring in the filter in the system according to the embodiment of the present invention;
FIG. 4 is a pattern diagram showing a modification of the band pattern of the stub wiring in the filter in the system according to the embodiment of the present invention.
FIG. 5 is a pattern diagram showing another modification of the band pattern of the stub wiring in the filter in the system according to the embodiment of the present invention.
FIG. 6 is a pattern diagram showing a spiral pattern of a stub wiring in the filter in the system according to the embodiment of the present invention.
FIG. 7 is a pattern diagram showing a serpentine pattern of a stub wiring in the filter in the system according to the embodiment of the present invention.
FIG. 8 is a sectional view showing a mounting board in the system according to the embodiment of the present invention;
FIG. 9 is a layout diagram showing a signal wiring layer (surface layer) of the mounting board in the system according to the embodiment of the present invention;
FIG. 10 is a layout diagram showing a stub wiring layer of a mounting board in the system according to the embodiment of the present invention;
FIG. 11 is a layout diagram showing a reference voltage layer of the mounting board in the system according to the embodiment of the present invention;
FIG. 12 is a layout diagram showing a power supply voltage layer of a mounting board in the system according to the embodiment of the present invention;
FIG. 13 is a layout diagram showing a modification of the stub wiring layer of the mounting board in the system according to the embodiment of the present invention;
FIG. 14 is a perspective view showing a mounted component in the system according to the embodiment of the present invention.
FIG. 15 is a bottom view showing a mounted component in the system according to the embodiment of the present invention.
FIG. 16 is an explanatory diagram showing stub wiring of a mounted component in the system according to the embodiment of the present invention.
FIG. 17 is a perspective view showing another mounted component in the system according to the embodiment of the present invention;
FIG. 18 is a cross-sectional view showing another mounted component in the system according to the embodiment of the present invention.
FIG. 19 is an explanatory diagram showing stub wiring of another mounted component in the system according to the embodiment of the present invention.
FIG. 20 is an explanatory diagram showing characteristic evaluation by comparing dielectric thicknesses in the filter in the system according to one embodiment of the present invention.
FIG. 21 is an explanatory diagram showing pattern dependency evaluation in a filter in the system according to an embodiment of the present invention.
FIG. 22 is a pattern diagram showing a combination pattern of stub wiring in the filter in the system according to the embodiment of the present invention.
FIG. 23 is an explanatory diagram showing a combination evaluation of a plurality of stub wirings in the filter in the system according to the embodiment of the present invention.
FIG. 24 is an explanatory diagram showing a combination of a plurality of stub wirings in a filter in the system according to an embodiment of the present invention.
[Explanation of symbols]
1 LSI package
2 Basic power supply
3 Bypass capacitor
4,4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i Stub wiring
5,5a, 5b, 5c, 5d, 5e filter
6 chips
7 Module
8 Crystal oscillator
9 CPG
10 Input buffer
11 Output buffer
20 Mounting board
21 signal wiring layer
22, 26, 28 insulating layer
23 Stub wiring layer
24 Dielectric layer
25 Reference voltage layer
27 Power supply voltage layer
31a-31d pad
32a-32d wiring pattern
33a-33c Through hole
40 mounted components
41-44 terminals
50 mounted parts
51-54 lead

Claims (9)

A semiconductor device;
A capacitor connected between a power supply voltage of a power supply path for supplying power from a main power supply to the semiconductor device and a reference voltage,
One end is connected between the capacitor and the main power supply, one end is connected to a power supply voltage and a reference voltage of the power supply path, and the other end includes a pair of wires in an open state, and has a lower impedance than the power supply path. Circuit and
A system comprising: a mounting board on which the semiconductor device, the capacitor, and the circuit are mounted. The system according to claim 1,
The system according to claim 1, wherein each of the pair of wires is formed to have a length such that the operating frequency of the semiconductor device is １ ／ of a wavelength in a mounting substrate. The system according to claim 1,
The system according to claim 1, wherein each of the pair of wirings is formed to have a length that is 波長 of a wavelength in a mounting substrate that is an integral multiple of an operating frequency of the semiconductor device. The system according to claim 3,
The system is characterized in that the circuit is configured by combining a plurality of the pair of wires having a length such that the operating frequency of the semiconductor device is １ ／ wavelength of an integral multiple of the operating frequency. The system according to claim 4,
The system according to claim 1, wherein the pair of wires are formed in a strip shape, a spiral shape, or a serpentine shape. The system according to claim 1,
The system is characterized in that the circuit is formed by sandwiching a dielectric having a thickness of 10 μm to 0.2 μm between the pair of wirings, and is formed in the mounting substrate. The system according to claim 1,
The system is characterized in that the circuit is formed by sandwiching a dielectric having a thickness of 10 μm to 0.2 μm between the pair of wirings, and is formed as a component mounted on the mounting board. The system according to claim 1,
The wiring connected to the power supply voltage side of the circuit is a thin wire,
A system according to claim 1, wherein the wiring connected to the reference potential side is a plane. The system according to claim 2,
The system is characterized in that the circuit is formed by sandwiching a dielectric having a thickness of 10 μm to 0.2 μm between the pair of wirings, and is formed in the mounting substrate.

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