JPH09321398A - Printer wiring board and its characteristic measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to measure radiation noise without putting a printed wiring board under the same operating condition as when it is assembled in a real apparatus. SOLUTION: On the surface layer (signal layer) of a printed wiring board 1, electronic parts not shown in the Fig. are mounted, and pattern seats 4 (4a, 4b) and signal patterns for operating the electronic parts are provided. Besides, a power supply layer 2 and a grounding layer 3 are provided in the internal layer. To the pattern seats 4 a connector 6 is fitted. Into the connector 6, a connector provided at the tip of a coaxial cable is inserted, and a high-frequency signal is supplied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board having a power source pattern and an earth pattern.

[0002]

2. Description of the Related Art In general, there are various methods for measuring noise radiated by a printed wiring board, and radiation noise is measured using these methods, and effective noise countermeasures are taken based on the measurement results. As a method of measuring the radiation noise, for example, a small antenna is brought close to the printed wiring board, the antenna is moved along the printed wiring board, and the voltage induced in the antenna is processed by a computer to determine which part of the printed wiring board is large. There are a method of measuring whether or not radiation noise is being radiated, a method of placing a printed wiring board on an antenna array in which a plurality of small antennas are arranged on a plane, and measuring the radiation noise.

[0003]

In the conventional radiation noise measuring method described above, electric power is supplied to the printed wiring board so that electronic parts such as ICs and LSIs mounted on the printed wiring board can be mounted on the printed wiring board. The radiation noise could not be measured unless it was operated (actually operated) in the same state as when it was installed in an actual device. However, when the printed wiring board is operated, radiation noise is radiated from a plurality of places on the printed wiring board, and since these radiation noises are measured by the antenna, the source of the radiation noise can be specified.
It was not possible to identify the noise radiation source that actually serves as an antenna and radiates electromagnetic waves.

[0004]

Means for Solving the Problems The means for solving the above problems according to the present invention is to provide a pattern seat for supplying a high frequency signal from the outside to a power source pattern and an earth pattern.

According to the above-mentioned solution means, when a high frequency signal is supplied to the pattern seat, the electromagnetic wave is radiated due to the voltage fluctuation between the power source pattern and the ground pattern.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. In the present embodiment, a multilayer printed wiring board having a power supply layer and a ground layer as a printed wiring board will be described as an example of a four-layer printed wiring board. The elements common to the drawings are given the same reference numerals.

FIG. 1 is an enlarged side sectional view showing a printed wiring board according to an embodiment of the present invention, FIG. 2 is a schematic plan view of the printed wiring board of the embodiment, and FIG. 3 is a printed wiring board of the embodiment. FIG. 3 is an explanatory view of a supply state of the high frequency signal of FIG.

The printed wiring board 1 is A4 in this embodiment.
This is a four-layer printed wiring board of the size of a plate, on the surface layer (signal layer) of which electronic components (not shown) are mounted, and the pattern seat 4 (4
a, 4b) and signal patterns (not shown) for operating the electronic components are provided. The inner layer is provided with a power supply layer 2 and a ground layer 3. In the present embodiment, each of the layers 2 and 3 is a solid pattern of the copper foil on the entire surface, but not limited to the solid pattern, it may be a grid pattern or the like.

Power supply layer 2, pattern seat 4a, and ground layer 3
And the pattern seat 4b are respectively through holes 5 as shown in FIG.
Connected by In this embodiment, the pattern seats 4 are provided at nine places as shown in FIG. A connector 6 is attached to the pattern seat 4.

The connector 6 has a signal pin 6a and a ground shell 6b, and the signal pin 6a is connected to the pattern seat 4a by solder 7. In addition, the connector 6
Connector 8a provided at the tip of the coaxial cable 8 shown in FIG.
Is inserted and a high frequency signal is supplied.

Next, the relationship between the level of noise radiated when a high frequency signal is externally supplied to each pattern seat 4 of the printed wiring board 1 and the frequency will be described. 4 to 7 show radiation noise when a high-frequency signal is supplied to the pattern seat according to the embodiment, by a sweep generator, a tracking generator, or the like, in accordance with the VCCI (Voluntary Control Council for Interference by Information Processing Equipment) standard. It is a figure explaining the measured result.

In FIG. 4, the central pattern seat 4 (A
The measurement result at the point) is shown in FIG.
The measurement results at (any one of B1 to B4 points) are shown. In FIG. 6, at the pattern seat 4 (C1, any one of 2 points) on the central side of the long side of the printed wiring board 1. 7 shows the measurement result, and FIG. 7 shows the measurement result at the pattern seat 4 (D1, either one of the two points) on the center side of the short side of the printed wiring board 1. In each figure, the vertical axis indicates the level of radiation noise [dB
μ], and the horizontal axis represents frequencies from 30 to 1000 [MHz].

In each of the measurement result explanatory diagrams, it can be seen from the drawings that the frequency at which radiation noise is large is not fixed over the entire frequency range but is fixed at a specific frequency. For example, looking at the measurement results in Figure 4,
The first peak E is ¼ of one wavelength when one wavelength corresponds to the length of the long side of the printed wiring board 1.
It has a frequency equivalent to. The second peak F
Has a frequency corresponding to ¼ of one wavelength when one wavelength corresponds to the length of the short side of the printed wiring board 1.

The reason for this is that the radiation noise is radiated from the end of the printed wiring board 1 and the resonance frequency is determined by the outer dimensions of the printed wiring board 1. Details can be confirmed by the calculation shown in the following formula. Note that λ [m] indicates the wavelength of the signal propagating in the air, and Co indicates the speed of light (3 × 10
⁸ [m / s]) and fo [Hz] indicates the resonance frequency.

[0015]

[Equation 1]

Further, the resonance signal transmitted to the printed wiring board is inversely proportional to the square root of the dielectric constant ε of the printed wiring board, where λo is the wavelength [m].

[0017]

[Equation 2]

By applying the dielectric constant and the resonance frequency of the printed wiring board 1 to the equation (2), it can be confirmed that the resonance frequency is determined by the outer dimensions of the printed wiring board 1.

Here, the relationship between the level of radiation noise and the frequency when a lead wire having a length of about 1 [m], for example, an interface cord is connected from one corner (point B in FIG. 2) of the printed wiring board 1 is shown. explain. FIG. 8 is a diagram illustrating a result of measuring radiation noise when a high frequency signal is supplied to the pattern seat at point A of the printed wiring board according to the embodiment with a sweep generator, a tracking generator, or the like.

In the measurement result of FIG. 8, in comparison with the measurement result of FIG. 4, there is new radiation noise at the frequencies of peaks X, Y and Z. The peak X is a frequency ¼ of the resonance frequency (fo) when the lead wire is an antenna, the peak Y is a frequency 3/4 of the resonance frequency (fo), and the peak Z is the resonance frequency (f).
The frequency is 5/4 of o).

The reason for this is that the radiation noise is largely radiated when the length of the leader line corresponds to 1/4, 3/4, and 5/4 of one wavelength. It can be confirmed by the calculation shown in the formula. Co is the speed of light (3 × 10 ⁸ [m
/ S]), fo [Hz] indicates the resonance frequency, and L
[M] is the length of the leader line.

[0022]

(Equation 3)

The resonance frequency (fo) of the printed wiring board 1 to which the lead wire is connected can be obtained by applying the length of the lead wire to L in the equation (3). Then, by multiplying the obtained resonance frequency (fo) by 1/4, 3/4, or 5/4, radiation noise is
It can be confirmed that the radiation is large when it corresponds to the length of 4, 3/4, and 5/4.

In the present embodiment, by providing the pattern seat 4 which is formed on the surface layer of the printed wiring board 1 and is not connected to the signal pattern (not shown) for operating the electronic parts, the high frequency signal is supplied. Noise components radiated from the electronic components themselves and noise components radiated from the signal patterns without supplying the electric power to the printed wiring board 1 to operate the mounted electronic components (without operating the circuit). Separately, it is possible to know the radiation noise caused by the voltage fluctuation between the power supply layer 2 and the ground layer 3, and to identify the noise radiation source.

Further, in the present embodiment, the noise source generated by the voltage fluctuation between the two layers 2 and 3 can be specified without operating the circuit, so that an effective countermeasure against common mode noise can be taken.

In the present embodiment, the connector 6 is attached to the printed wiring board 1 in advance, and the connector 6
And the connector 8a of the coaxial cable 8 are connected,
The coaxial cable 8 may be directly soldered to the printed wiring board 1, for example.

In the present embodiment, the pattern seat 4 is shown in FIG.
However, the position is not limited to that shown in the figure. For example, if the pattern seat 4 is provided in the vicinity of an electronic component (for example, IC or LSI) of the printed wiring board 1, it is possible to identify the electronic component which is the noise source by confirming the spectrum change of the radiation noise. You can

In this case, first, the pattern seat 4 near the electronic component
A high-frequency signal is supplied to and the noise radiated by the voltage fluctuation between the layers 2 and 3 is measured. Next, the noise radiated when the printed wiring board 1 is actually operated is measured, and the measurement result at this time is compared with the measurement result when a high frequency signal is supplied to the pattern seat. Then, at a certain frequency of both measurement results, if a large radiation noise appears only in the measurement result when actually operated, it is possible to identify the electronic component that is the noise generation source.

Further, the pattern seats 4 may be provided more or less than 9 according to the purpose such as the size of the printed wiring board and the place where radiation noise is considered to occur.

By the way, in the present embodiment, an example in which the pattern seat 4 is provided on four layers of the printed wiring board among the multilayer printed wiring boards having the power supply layer and the ground layer as the printed wiring board has been described. Not limited to the multilayer printed wiring board, for example, a two-layer printed wiring board having a power supply pattern and an earth pattern on the front surface and electronic components such as LSI and IC mounted on the back surface, or a single-layer printed wiring board. Good.

[0031]

As described in detail above, the present invention provides
The same state as when the printed wiring board was installed in the actual device by measuring the electromagnetic waves generated by supplying the high frequency signal to the pattern seat by providing the pattern seat supplying the high frequency signal from the outside to the power supply pattern and the earth pattern. The radiated noise can be measured without operating the device.
As a result, the noise radiation source can be identified.

[Brief description of drawings]

FIG. 1 is an enlarged side sectional view showing a printed wiring board according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of the printed wiring board according to the embodiment.

FIG. 3 is an explanatory diagram of a high frequency signal supply state according to the embodiment.

FIG. 4 is an explanatory diagram of a radiation noise measurement result according to the embodiment.

FIG. 5 is an explanatory diagram of a radiation noise measurement result when a high frequency signal is supplied to the pattern seat of the embodiment.

FIG. 6 is an explanatory diagram of a radiation noise measurement result according to the embodiment.

FIG. 7 is an explanatory diagram of a radiation noise measurement result according to the embodiment.

FIG. 8 is an explanatory diagram of a radiation noise measurement result according to the embodiment.

[Explanation of symbols]

 1 Printed wiring board 2 Power supply layer 3 Earth layer 4a, 4b Pattern seat

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Takasagi 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (5)

[Claims] 1. A printed wiring board having a power source pattern for supplying electric power to a mounted electronic circuit and an earth pattern for grounding, wherein a pattern seat for supplying a high frequency signal from the outside to the power source pattern and the earth pattern is provided. A printed wiring board characterized by being provided. 2. The pattern seat is provided at a plurality of positions.
The printed wiring board as described. 3. The printed wiring board according to claim 1, wherein the pattern seat is provided near the electronic circuit. 4. The printed wiring board according to claim 1, wherein the power supply pattern and the ground pattern are solid patterns. 5. A printed wiring board characteristic measuring method for measuring characteristics of electromagnetic waves generated by supplying electric power to a printed wiring board having a power source pattern for supplying electric power to a mounted electronic circuit and an earth pattern for grounding. 2. A printed wiring board characteristic measuring method according to claim 1, wherein a pattern seat for signal supply is provided in the power source pattern and the ground pattern, and a characteristic of an electromagnetic wave generated by supplying a high frequency signal from the outside to the pattern seat is measured.