JPS60244100A - Unnecessary radiation preventing method of electronic equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for preventing unnecessary radiation in electronic equipment that can effectively prevent noise radiated to the outside.

(Background technology) The problem of radiated noise has been raised as an important issue in today's electronic equipment, and legal regulations are strict.
Countermeasures against this problem have become an important issue. As a countermeasure for this,
Conventionally, various ideas have been made, such as using metal cases with shielding properties or conductive plastic cases as exterior materials for electronic devices.

However, in high-frequency power switches, microwave ovens (ventilation openings, door openings, etc.), video disc devices, etc., where electronic equipment cannot be completely hermetically shielded, there is a problem that noise is radiated to the outside from the gaps. The reality is that this issue has not been completely resolved. Furthermore, the radiated noise radio waves generated from various electronic components (oscillators, etc.) cause a resonance phenomenon within the shield case due to the dimensions of the shield case and the internal component configuration, and become large electromagnetic energy, causing the shield case to This also adversely affected other circuit elements within the device, causing various problems such as instability of the operating frequency.

(Object of the Invention) The present invention has been made to solve the above-mentioned drawbacks of the prior art, and relates to an electronic device covered with an outer case made of metal, conductive plastic, or the like. The purpose is to prevent noise radiated from the voids in these outer cases and to remove high energy caused by resonance phenomena occurring inside the outer case.

(Summary of the Invention) This invention provides a method for combining ferrite and metal magnetic material in a weight ratio of 3.
A composite magnetic material made by dispersing materials mixed in a ratio of 7:3 to an organic polymer material of 60% by weight or more is installed at the position of maximum magnetic field in the external shielding case of electronic equipment, thereby eliminating the need for electronic equipment. It is characterized by effectively preventing radiation.

The ferrite used in this invention is 1, for example, Ni.
Examples include -Zn ferrite and Mn-Zn ferrite, and examples of metal magnetic materials include carbonyl iron. As the organic polymer material, for example, com or plastic resin is used.

It should be noted that the materials exemplified above do not limit the present invention, and various materials suitable for achieving the object of the present invention can be used.

(Structure and operation of the invention) Generally, in cases surrounded by metal etc.

There is a resonance mode determined by the length, width, and height of the casing. This resonance mode occurs both vertically and horizontally of the housing.

Let the height dimensions be a, b, and c, respectively.

(where m, n, and q are mode numbers in the vertical (X-axis), horizontal (y-axis), and height (two-axis) directions, respectively).

For example, 71.4 x 71.4. X 32.3 rM
An example of the resonance mode of the metal casing of I is shown in FIG. This example is for excitation in TE mode.

Regarding unnecessary radiated electromagnetic waves in a shield case having a gap, not all of the frequency components included in the unnecessary radiated electromagnetic waves (noise) are radiated to the outside according to the intensity of each frequency component of the noise. That is.

It is determined by the dimensions of the shielded outer case of the electronic device and the various electronic components inside. There is a resonance mode unique to the electronic device, and noise at a frequency corresponding to the resonance frequency is particularly strongly radiated to the outside.

As a method of preventing this radiation, it has been considered to attach a radio wave absorbing member to the entire inner surface of the shield outer case. It has been confirmed that this method significantly reduces the noise radiated to the outside. However, this method has problems in terms of practicality (as the cost is significantly high). Furthermore, until now (5), the frequency band from 30 MHz to I GHz, such as wireless radio waves (approximately I GHz), video disc devices (approximately I GHz), etc., has been a problem, but recently the frequency band of 12 GHz has been considered.
With the practical application of broadcasting satellites in the 12 GHz band, radiation noise in the 12 GHz band has also become a problem, and in the future it will be more likely that
Radiation noise at 18 GHz has become a problem. Until now, no suitable material having such broadband characteristics in the microwave region has been found.

Possible materials for achieving the above purpose include carbon-based dielectric loss materials and magnetic loss materials represented by ferrite. However, since the magnetic field is maximum and the electric field is minimum on the shielding surface of the case, the use of magnetic loss materials is limited. Furthermore, in order to use a thin magnetic loss material without sacrificing the internal effective space of the outer case, it is effective to attach it to the surface of the shield case.

In view of the above, this invention uses the magnetic loss material as a magnetic loss material and attaches the prevention member.

Focusing on the unique resonance mode created by each electronic device inside the shielded exterior case, check the maximum magnetic field position for each y-axis, y-axis, and y-axis, mainly using that resonance mode.

The prevention member is attached to the case portion corresponding to the maximum position of these magnetic fields to eliminate the resonance mode, thereby preventing noise radiated to the outside.

Ferrite is a typical magnetic loss material. Examples of its characteristics are shown in FIGS. 2 and 3. Figure 2 is M
Fig. 3 is a diagram showing the characteristics of a composite magnetic material containing 80% by weight of n-Zn ferrite and having a resin matrix;
(contains 85% by weight of i-Zn ferrite and contains resin) IJ
FIG. 3 is a diagram showing the characteristics of a smooth composite magnetic material. Here, μ′, μ″ are the complex magnetic permeability μ(−μ′+jμ″, where j
ε′ and ε″ are the real and imaginary parts of the complex dielectric constant ε(−ε′+jε″). Among these, μ'' indicates magnetic loss. As is clear from FIGS. 2 and 3, there is a large loss up to 4 GHz, but the loss rapidly decreases above 4 GHz.

On the other hand, Fig. 4 shows carbonyl iron 8, which is a metal powder magnetic material.
0% by weight and has a resin matrix, but in this case, the loss is very large, but I
The loss is stable from GHz to over 10 GHz.

In this invention, both of the above features are taken into account to ensure a large loss from IGHz to 10 GHz or higher.

A mixture of ferrite and metal magnetic material. The mixing ratio of the two is selected mainly depending on which frequency of noise is the largest, but in order to have good loss characteristics, it is effective to mix the two at a weight ratio of about 3=7 to 7:3.

The composite ratio of the above-mentioned mixed material and the organic polymer material (1) is more effective as the amount of magnetic material increases, but it is impossible to mix more than 95% by weight due to moldability problems. Therefore, a composite ratio of 60% by weight or more is desirable so that magnetic loss can be effectively utilized.

FIG. 5 shows a composite magnetic material (Ni-Z
The characteristics of a mixed material made by mixing 35% by weight of n-ferrite and 55% by weight of carbonyl iron with 10% by weight of resin are shown.

It can be seen from this figure that there is a constant loss from 1 to 10 GHz or higher. The composite magnetic material of this example was
Figure 6 shows the state of electromagnetic waves when it is attached to a part of the inner wall (the position of maximum magnetic field) of the same metal casing used to obtain the data in the figure. Comparing this figure with FIG. 1, it can be seen that according to this embodiment, the mode is greatly attenuated, making it possible to effectively prevent unnecessary radiation.

(Effects of the Invention) According to the present invention, it is possible to effectively prevent noise radiated from a gap in an external case of an electronic device, and to remove high energy based on a resonance phenomenon occurring inside the case. Moreover, since it is only necessary to attach the noise radiation prevention member to the position of the maximum magnetic field of the case, and there is no need to provide the noise radiation prevention member on the entire inner surface of the case, unnecessary radiation can be prevented at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a resonance mode of a metal casing. Figure 2 shows the loss characteristics of a material made by mixing Mn-Zn ferrite with resin, Figure 3 shows the loss characteristics of a material made by mixing Ni-Zn ferrite with resin, and Figure 4 shows the loss characteristics of a material made by mixing Ni-Zn ferrite with resin.
Figure 5 shows the loss characteristics of a material made by mixing carbonyl iron with resin, Figure 5 shows the characteristics of a composite magnetic material according to an embodiment of the present invention, and Figure 6 shows (9) Figure 1. Part of the inner surface of the metal casing used in (maximum magnetic field position)
FIG. 3 is a diagram showing the state of electromagnetic waves when a composite magnetic material according to an embodiment of the present invention is provided in the device. Patent applicant TDC Co., Ltd. Patent application agent Patent attorney Megumi Yamamoto - (10)

Claims (4)

[Claims] (1) A composite magnetic material made by dispersing 60% by weight or more of a material obtained by mixing ferrite and a metal magnetic material at a weight ratio of 3 to 7 in an organic polymer material is used as an external shield case for electronic equipment. A method for preventing unnecessary radiation from electronic equipment, characterized by preventing unnecessary radiation from the electronic equipment by installing the electronic equipment at a position where the magnetic field is maximum. (2) The ferrite is MP'e204 (M is Ni,
Co. The method for preventing unnecessary radiation according to claim 1, characterized in that the spinel ferrite is a spinel ferrite having a chemical formula of (one or a combination of two or more elements such as Fe, Mn + Zn, Cd, Mg, Li, etc.) . (3) The method for preventing unnecessary radiation according to claim 1 or 2, wherein the metal magnetic material is carbonyl iron. (4) Claims 1 to 3, characterized in that the organic polymer material is rubber or plastic resin.
The unnecessary radiation prevention method described in any one of the following paragraphs.