JPH08204380A - Noise suppressing method for electric apparatus and noise suppressed electronic apparatus using this method - Google Patents

Abstract

PURPOSE: To provide a simply constituted low-cost noise suppressed electronic apparatus capable of preventing easily and efficiently electromagnetic troubles. CONSTITUTION: The title noise suppressed electronic apparatus has an interconnection board 3 mounting active electronic elements 1 which radiate inductive noises and mechanism parts 2, and electromagnetic interference suppressor 13 composed of a support and insulative soft magnetic body laid on the inner face of a case 4 which houses the entire board 3. The suppressor 13 converges the flux of a high frequency electromagnetic field produced by the elements 1 to make faint outwards radiating noises and the inductive coupling to other electronic parts mounted near to each other on the board 3, thereby high- accurately suppressing unwanted electromagnetic waves from being generated. This certainly prevents the mutual interference between parts in circuits on the board 3 and electromagnetic induction between power sources and signal lines, thus preventing electromagnetic troubles such as malfunctions at high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to noise in an electronic device for suppressing electromagnetic interference caused by interference of inductive noise (unwanted electromagnetic wave) radiated by an active element such as a semiconductor element mounted on a wiring board. The present invention relates to a suppression method and a noise suppression electronic device to which the suppression method is applied.

[0002]

2. Description of the Related Art In recent years, electronic devices (electronic devices) such as digital electronic devices that utilize high frequencies have been remarkably miniaturized. Particularly in a digital electronic device having a high component mounting density on a wiring board, LSIs and ICs such as a central processing unit (CPU) and an image processor arithmetic logic unit (IPALU) are mounted on the wiring board. Although LSIs and ICs are composed of a large number of semiconductor elements, the semiconductor elements are also called active elements because they are supplied with energy from the outside and have functions such as amplification and oscillation. Generally, an active element represented by a semiconductor element emits inductive noise which is an unnecessary electromagnetic wave.

When such inductive noise is radiated,
A high-frequency magnetic field is induced on the same surface as the element mounting surface of the wiring board or on the opposite surface thereof, and the induced high-frequency magnetic field increases line coupling, which is electromagnetic coupling, or causes radiation noise. In particular, when radiation noise occurs, not only does it malfunction within the device, but it is also radiated to the outside and adversely affects peripheral equipment. In particular, if the case enclosing the wiring board is an electronic device formed of a non-metallic material such as resin, the radiation noise to the outside will be diffused without being suppressed. Incidentally, such a phenomenon caused by unnecessary electromagnetic waves that causes malfunction or adversely affects other devices is called electromagnetic interference.

Conventionally, in an electronic device, as a measure against inductive noise that causes electromagnetic interference, if a resin case accompanying weight reduction is used, conductive paint is applied to the inside of the case or a conductive film is vapor-deposited. Take technical measures by taking measures, covering the noise generation site with a metal case, connecting a filter to the circuit that adversely affects it, keeping the problematic circuit away from the circuit that adversely affects it, strengthening grounding, etc. I am giving it. By taking such measures, electromagnetic coupling, unnecessary radiation, and conduction noise that cause electromagnetic interference are suppressed.

[0005]

However, in order to reduce the size and weight of the electronic device in order to efficiently take countermeasures against electromagnetic interference in an electronic device composed of a high-density mounted wiring board or the like, the following will be described. There are various problems.

First, apply conductive paint to the inside of the case,
Alternatively, in the case of conducting the conductor vapor deposition, not only the required number of man-hours and the required cost are increased, but also an auxiliary component such as an insulating sheet is required to be added as a measure for insulating the electronic component from the pattern.

Also, when performing other technical measures,
It requires expert knowledge and experience in noise countermeasures, takes too much time for countermeasures, expensive filters are used, there are often restrictions on the space for mounting filters, and filter mounting work is easy. However, there are various problems such as an increase in man-hours required for assembling the electronic device and an increase in cost. Especially in miniaturized and thin electronic devices, sufficient measures must be taken when shielding the case and suppressing mutual interference due to secondary radiation to the case internal circuit for the purpose of suppressing radiation noise to the outside. However, in order to reduce the size and thickness of the electronic device, it is indispensable to eliminate the filter and its mounting space. Therefore, the conventional technical measures cannot prevent the electromagnetic interference with high accuracy.

The present invention has been made to solve such a problem, and its technical problem is to apply a noise suppressing method in an electronic device which can prevent electromagnetic interference easily and accurately. An object of the present invention is to provide a low-priced noise suppression electronic device that is simply configured.

[0009]

According to the present invention, noise suppression in an electronic device including a mounting body portion on which an active element that radiates inductive noise is mounted, and a housing body that encloses and stores the entire mounting body portion. In the method, there is provided a noise suppression method in an electronic device, which suppresses inductive noise between the mounting body part and the housing body by an electromagnetic interference suppressor made of a support and an insulating soft magnetic material.

On the other hand, according to the present invention, in the noise suppressing electronic device including the mounting body part on which the active element for radiating inductive noise is mounted and the housing body for enclosing and housing the entire mounting body part, Also, it is possible to obtain the noise suppressing electronic device in which the electromagnetic interference suppressing body made of the insulating soft magnetic material is provided between the mounting body portion and the housing body.

Further, according to the present invention, in the above noise suppressing electronic device, the insulating soft magnetic material has an organic binder and a flat shape or a needle shape dispersed in the organic binder, or a mixture thereof. A noise suppression type electronic device including a soft magnetic powder having a shape is obtained.

Furthermore, according to the present invention, in any of the noise suppressing electronic devices described above, a noise suppressing electronic device in which the support is conductive or a noise suppressing electronic device in which the support is insulative. can get.

[0013]

In the present invention, the electromagnetic interference suppressor composed of the support and the insulating soft magnetic material used between the mounting body and the housing for the electronic device is the insulating soft magnetic material as the organic binder and the organic binder. The support is conductive or insulative, and is composed of a soft magnetic material powder dispersed in a flat shape, a needle shape, or a mixture thereof. When this electromagnetic interference suppressor is used in an electronic device, an increase in electromagnetic coupling due to reflection of unnecessary radiation is suppressed by the insulating soft magnetic material composed of the organic binder and the soft magnetic material powder. In the insulating soft magnetic material, the soft magnetic metal, which is originally a conductive substance, is finely powdered and kneaded and dispersed with an insulating organic binder to form an insulating layer. Magnetic anisotropy appears in the soft magnetic powder due to the above-mentioned shape, and the complex magnetic permeability based on magnetic resonance increases in the high-frequency region. Therefore, the insulating soft magnetic material efficiently absorbs and suppresses unnecessary radiation components. it can.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A noise suppressing method in an electronic device of the present invention and a noise suppressing electronic device to which the same is applied will be described in detail below with reference to the drawings.

First, a brief description will be given of an outline of a noise suppressing method in an electronic device of the present invention. In this noise suppressing method, a mounting body part in which an active element that radiates inductive noise is mounted and the mounting body part as a whole are An inductive noise is suppressed by an electromagnetic interference suppressor composed of a support and an insulating soft magnetic material between the package and a storage body.

FIG. 1 is a partial sectional view showing the basic structure of a noise suppressing electronic device to which the noise suppressing method in this electronic device is applied.

This noise suppression type electronic device comprises a wiring board 3 which is a mounting body portion on which an active element for radiating inductive noise is mounted, and a case 4 as a housing body which encloses and houses the entire wiring board 3. Includes wiring board 3 and case 4
An electromagnetic interference suppressor 13 composed of a support and an insulating soft magnetic material is provided inside the case 4 between and.
Further, here, the mechanical component 2 is mounted on the wiring board 3 together with the electronic component 1 as an active element, and the wiring board 3 is mounted in this state.
Is incorporated inside the case 4. The electromagnetic interference suppressor 13 has a thickness of 0.5 mm.

In this noise suppression type electronic device, the electromagnetic interference suppressor 13 focuses the magnetic flux of the high frequency electromagnetic field generated by the electronic component 1 to radiate noise to the outside and other components mounted close to the wiring board 3. The inductive coupling to electronic parts is made weak and the generation of inductive noise, which is an unnecessary electromagnetic wave, is highly accurately suppressed. As a result, in the noise suppression electronic device, the wiring board 3
Mutual interference between components inside the upper circuit and electromagnetic induction between the power supply and signal lines are properly suppressed to prevent electromagnetic interference such as malfunction.

FIG. 2 is a partial sectional view showing the basic structure of the electromagnetic interference suppressor 13. Electromagnetic interference suppressor 1
3 is composed of a conductive or insulating support 5 and an insulating soft magnetic layer 6. Further, the insulating soft magnetic layer 6 is
It is composed of an organic binder 8 and a soft magnetic powder 7 dispersed in the organic binder 8 in a flat shape, a needle shape, or a mixed shape thereof. Here, the soft magnetic powder 7 is uniformly dispersed in the organic binder 8 as shown.

Incidentally, when the support 5 is made conductive in the electromagnetic interference suppressor 13, the conductive support 5 is, for example, one of a conductive plate, a knitted conductive plate, and a conductive fiber woven plate. It is preferable to select and use, and in this case, it is desirable to use, as the case 4, a non-metallic molded case such as resin.

On the other hand, when the support 5 in the electromagnetic interference suppressor 13 is made to be insulative, the insulative support 5 is made of, for example, one of an insulator plate, a knitted insulator plate and a woven fabric plate of insulating fibers It is preferable to select and use, and in this case, it is desirable that the case 4 is made of metal, coated with a conductive coating, or has a conductive film deposited thereon.

The soft magnetic powder 7 may be made of a material having a high magnetic permeability, such as iron-aluminum-silicon alloy (Sendust) or iron-nickel alloy (Permalloy). It is desirable that the soft magnetic powder 7 has a sufficiently large aspect ratio (about 5: 1 or more).

Further, as the material of the organic binder 8, for example, polyester resin, polyvinyl chloride resin, polyvinyl butyral resin, polyurethane resin, cellulose resin, nitrile-butadiene rubber, styrene-butadiene rubber, etc. may be used. Examples include reversible resins and copolymers thereof, and thermosetting resins such as epoxy resins, phenol resins, amide resins, and imide resins.

FIG. 3 shows the electromagnetic interference suppressor 13 shown in FIG.
A characteristic evaluation system assuming an electromagnetic environment is shown in order to explain the characteristic effect regarding the above. The figure (a) relates to the evaluation system for measuring the transmission attenuation level [dB], and the figure (b) shows The present invention relates to an evaluation system for measuring the binding level [dB].

In each evaluation system, an electromagnetic field transmitting source 9 and an electromagnetic field intensity measuring device (reception element) 10 have a loop diameter of 2 mm or less, respectively, for transmitting a minute loop antenna 11 for electromagnetic field reception and for receiving an electromagnetic field. The one connected to the minute loop antenna 12 is used. Incidentally, a spectrum analyzer (not shown) was used to measure the transmission attenuation level and the coupling level.

Incidentally, here, four types of evaluation samples A, B, C and D obtained by forming the support 5 and the insulating soft magnetic material layer 6 of the electromagnetic interference suppressor 13 as different structures, and the electromagnetic interference suppressor 13 are described. Are two types of comparative samples α and β with different configurations
And prepared.

For the sample A for evaluation, the support 5 was made conductive and a 120-mesh copper net was used, and one side of the conductive support 5 was dried and cured so that the total thickness was 0. The average particle size is 10 μm so that it becomes 0.5 mm.
And the aspect ratio exceeds 5 and the composition is Fe-Al-Si
90 parts by weight of flat soft magnetic fine powder 7 represented by an alloy, 8 parts by weight of a polyurethane resin component as an organic binder 8 and 2 parts by weight of a curing agent (isocyanate compound) component,
The solvent (mixture of cyclohexanone and toluene) is 40
This is obtained by applying a soft magnetic paste composed of parts by weight by a doctor blade method and then curing it at a temperature of 85 ° C. for 24 hours to form an insulating soft magnetic layer. When the evaluation sample A obtained here was analyzed using a vibrating magnetometer and a scanning electron microscope, both the easy axis of magnetization and the orientation of the magnetic particles were in the in-plane direction of the sample.

The evaluation sample B was obtained in the same manner except that a copper plate having a thickness of 100 μm was used instead of the copper net used as the conductive support 5 as compared with the evaluation sample A. is there. For the evaluation sample C, the evaluation sample A
Compared with the above, a copper net used as the conductive support 5 was replaced by a polyethylene net of 120 mesh used as the insulating support 5 in the same manner. The evaluation sample D was obtained in the same manner as the evaluation sample A except that the polyethylene net used as the insulating support 5 in the evaluation sample C was replaced with a polyimide film having a thickness of 75 μm. It is a thing.

On the other hand, the thickness of the comparative sample α is 10
A copper plate of 0 μm is used, and for the sample β for comparison, a commercially available conductive paint is applied to one side of a polyimide film having a thickness of 75 μm so that the total thickness after drying and curing is 0.3 mm. It was obtained.

Therefore, the transmission attenuation level and the coupling level were measured for each of the evaluation samples A to D and the comparative samples α and β by the evaluation system shown in FIGS. 3 (a) and 3 (b).
The electromagnetic interference suppression effect has frequency dependence as shown in FIG. That is, FIG. 4A relates to the frequency f [GHz] -transmission attenuation level [dB] characteristic, and FIG. 4B relates to the frequency f [GHz] -coupling level [dB] characteristic.

However, the reference of the transmission attenuation level and the coupling level shown in FIGS. 4 (a) and 4 (b), respectively, is the electromagnetic field strength without the electromagnetic interference suppressor 13. When evaluating the evaluation samples C and D obtained by using the insulating support 5, the comparison sample β coated with the conductive paint was lined for the measurement. This is based on the assumption that the electromagnetic interference suppressor 13 is mounted on a resin case coated with conductive paint or conductively evaporated.

From FIGS. 4 (a) and 4 (b), although the transmission attenuation levels are significantly reduced in the comparative samples α and β,
Since the coupling level is increased, when this is used as an electromagnetic interference suppressor in an electronic device having the configuration shown in FIG. 1, the level of dielectric noise radiated to the outside can be suppressed, but secondary radiation is not generated. It is conceivable that mutual interference between parts will be a problem.

On the other hand, in the samples A to D for evaluation, the transmission attenuation level is sufficiently low and the coupling level is not increased, so that the electromagnetic interference suppressor 13 has the structure as shown in FIG. It can be seen that when used in a device, electromagnetic interference can be effectively suppressed without being affected by reflection due to unnecessary radiation.

[0034]

As described above, according to the method of suppressing noise in the electronic device of the present invention, the mounting body portion on which the active element that radiates inductive noise is mounted, and the mounting body portion is wrapped and stored. Inductive noise is suppressed between the housing and the support by the electromagnetic interference suppressor made of an insulating soft magnetic material. Therefore, radiation noise radiated from the mounting part to the outside, mounting part (wiring board) Mutual interference between components in the upper circuit and electromagnetic induction between the power supply and the signal line are simplified and appropriately suppressed, and electromagnetic interference such as malfunction can be prevented with high accuracy.

On the other hand, in the noise suppression type electronic device to which this noise suppression method is applied, the insulating soft magnetic material in the electromagnetic interference suppressor and the organic binder and the flat or needle-like shape dispersed in the organic binder, or It is composed of a mixture of soft magnetic powders, and the support of the electromagnetic interference suppressor is conductive or insulating, increasing the reflection of unwanted radiation caused by inserting a conductor. It is possible to secure a large transmission attenuation without causing the change. or,
Since the electromagnetic interference suppressor is a foil plate, the entire apparatus including parts for suppressing noise can be made smaller and lighter than before, and can be constructed at a low price. Furthermore, since the electromagnetic interference suppressor can easily be given flexibility by its constituent elements, it can be deformed into a complicated shape and can be used even under severe vibration conditions or shock conditions. Is extremely excellent. Therefore, the noise suppression type electronic device of the present invention is extremely useful because it can stably suppress electromagnetic interference even when used under severe environmental conditions represented by mobile communication equipment.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a basic configuration of a noise suppressing electronic device to which a noise suppressing method in an electronic device of the invention is applied.

FIG. 2 is a partial cross-sectional view showing the basic structure of an electromagnetic interference suppressor used in the noise suppression electronic device shown in FIG.

FIG. 3 shows a characteristic evaluation system assuming an electromagnetic environment in order to explain characteristic effects of an electromagnetic interference suppressor used in the noise suppression electronic device shown in FIG. 1, and (a) shows a transmission attenuation level [ The present invention relates to an evaluation system for measuring dB], and (b) relates to an evaluation system for measuring binding level [dB].

4 shows four types of evaluation samples obtained by forming a support and an insulating soft magnetic material layer in the electromagnetic interference suppressor used in the noise suppression electronic device shown in FIG. 1 with different configurations, and the electromagnetic interference suppressor. Shows the frequency dependence of the electromagnetic interference suppression effect, which is the result of measuring two types of comparative samples having different configurations with the evaluation systems shown in FIGS. 3 (a) and 3 (b), respectively. , (A) relates to frequency-transmission attenuation level characteristics, and (b) relates to frequency-coupling level characteristics.

[Explanation of symbols]

 1 Electronic Parts 2 Mechanical Parts 3 Wiring Board 4 Case 5 Support 6 Insulating Soft Magnetic Material Layer 7 Soft Magnetic Material Powder 8 Organic Binder 9 Electromagnetic Wave Source Oscillator 10 Electromagnetic Field Strength Measuring Device (Receiver) 11 Electromagnetic Field Micro loop antenna for transmission 12 Micro loop antenna for electromagnetic field reception 13 Electromagnetic interference suppressor

Claims (5)

[Claims] 1. A noise suppression method in an electronic device, comprising: a mounting body part on which an active element that radiates inductive noise is mounted; and a housing body that encloses and houses the entire mounting body part. A method for suppressing noise in an electronic device, characterized in that the inductive noise is suppressed by an electromagnetic interference suppressor composed of a support and an insulating soft magnetic material with respect to a housing. 2. A noise suppression type electronic device comprising a mounting body part on which an active element for radiating inductive noise is mounted, and a housing body enclosing and accommodating the entire mounting body part. An electromagnetic interference suppressing body comprising a body is provided between the mounting body portion and the housing body. 3. The noise suppressing electronic device according to claim 2, wherein the insulating soft magnetic material is an organic binder and a flat shape or a needle shape dispersed in the organic binder, or a shape in which these are mixed. 2. A noise-suppressing type electronic device, comprising: 4. The noise suppression electronic device according to claim 2, wherein the support is conductive. 5. The noise suppression electronic device according to claim 2, wherein the support is insulative.