JP3505691B2 - Electronic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electronic devices, and in particular
The present invention relates to an electronic device in which an active element such as a semiconductor element is mounted on a wiring board.

[0002]

2. Description of the Related Art Electronic devices such as digital electronic devices that utilize high frequencies tend to be miniaturized. In a digital electronic device having a high component mounting density on a wiring board, an LSI and an IC such as a central processing unit (CPU) or an image processor arithmetic logic unit (IPALU) are mounted on the wiring board. These LSIs and ICs are composed of a large number of semiconductor elements, and these semiconductor elements are generally called active elements because they receive an energy supply from the outside and perform an operation such as amplification or oscillation. And, such active elements often generate inductive noise. Due to this inductive noise, a high-frequency magnetic field is induced on the same surface as the element mounting surface of the wiring board and the opposite surface.

This induced high frequency magnetic field not only increases line coupling due to electromagnetic coupling in the wiring board, but also causes radiation noise. In this way, when radiation noise occurs, not only malfunctions occur inside the device, but also
This radiation noise is radiated to the outside through the external connection terminal. As a result, other devices may be adversely affected.
Such malfunctions and adverse effects on other devices are generally called electromagnetic interference.

Conventionally, the following measures have conventionally been taken against such electromagnetic interference.

A filter is connected to a circuit that generates inductive noise in an electronic device. Move problematic circuits (circuits that generate inductive noise) away from affected circuits. Shield. Perform grounding.

By taking the above-mentioned measures (1) to (3), the electromagnetic coupling, unnecessary radiation, and conduction noise that cause electromagnetic interference are suppressed.

[0007]

However, in order to efficiently deal with the above electromagnetic interference in a wiring board in which electronic components including active elements are mounted at a high density, conventional measures (noise suppressing method) are used. There are the following problems.

Expert knowledge and experience in noise suppression are required. It takes time to take measures. The filters used are expensive. There are often restrictions on the space for implementing filters. Difficulty is involved in the filter mounting work. Since a filter or the like is used, the number of steps required for assembling the electronic device is increased and the cost is increased.

In particular, in order to suppress the electromagnetic interference between the signal lines generated between the components in the same circuit and the mutual interference due to the unnecessary electromagnetic waves, it is necessary to take a countermeasure, but in the conventional suppressing method, it is necessary. Not enough. Further, in order to reduce the size and weight of the electronic device, it is necessary to eliminate the filter and its mounting space.

It is an object of the present invention to provide an electronic device which is small and lightweight and which can effectively suppress electromagnetic interference.

[0011]

According to the present invention, in an electronic device having a wiring board and an active element mounted on the wiring board and radiating inductive noise, the wiring board and the active element are provided. An electronic device is obtained in which an insulating soft magnetic material layer is formed between them. At this time, the insulating soft magnetic layer is also formed between the patterns on the wiring board. The insulating soft magnetic material layer has an organic binder and a soft magnetic powder dispersed in the organic binder, and the soft magnetic powder has at least one of a flat shape and a needle shape. It is desirable to have two shapes.

[0012]

By forming an insulating soft magnetic material layer between the wiring board and the active element and forming an insulating soft magnetic material layer between the patterns of the wiring board, increase in electromagnetic coupling due to unnecessary radiation is prevented. Suppressed by the soft magnetic layer.
This insulative soft magnetic layer is made by finely powdering soft magnetic metal, which is originally a conductive substance, and kneading with an insulating organic binder to disperse the soft magnetic powder in the organic binder. , Is an insulating layer. Then, by making the shape of the soft magnetic powder into at least one of a flat shape and a needle shape, shape magnetic anisotropy appears, and the complex magnetic permeability based on magnetic resonance increases in the high frequency region. This makes it possible to efficiently absorb and suppress unnecessary radiation components.

[0013]

EXAMPLES The present invention will be described below with reference to examples.

Referring to FIG. 1, in the illustrated electronic device, an LSI 2 is mounted on a wiring board 1. And LSI
Wiring conductors (patterns) 3 are wired on the back surface of the wiring board 1 located below the wiring board 2. LSI2 as shown
Is mounted on the wiring board 1 in a state of slightly floating from the wiring board 1, and between the wiring board 1 and the LSI 2,
An insulating soft magnetic layer A is printed on the wiring board 1. In this embodiment, the insulating soft magnetic material layer A is located directly below the LSI 2, and the area of the insulating soft magnetic material layer A is the same as the area of the LSI 2.

As described above, when the insulating soft magnetic material layer A is provided, the insulating soft magnetic material layer A focuses the magnetic flux in the high frequency electromagnetic field generated by the LSI 2. As a result, LSI2
The inductive coupling between the wiring board 1 and the wiring board 1 becomes weak, and the wiring board 3
It is possible to efficiently suppress the noise generated in the.

Another embodiment of the electronic device according to the present invention will be described with reference to FIG. In the illustrated electronic device, the LSIs 2 and 4 are mounted on the wiring board 1, and as shown in the drawing,
These LSIs 2 and 4 are wiring conductors (patterns) 5, 6,
And 7 are connected. An insulating soft magnetic material layer A is printed on the wiring board 1 between the wiring conductors 5 and 6 and between the wiring conductors 6 and 7.

As described above, when the insulating soft magnetic layer A is provided, the insulating soft magnetic layer A focuses the magnetic flux generated by the high frequency electromagnetic field generated from each wiring conductor. As a result, crosstalk between the wiring conductors is suppressed.

Here, the insulating soft magnetic material layer A will be described with reference to FIG. This insulating soft magnetic layer A
Contains the soft magnetic powder 8 and the organic binder 9. Specifically, as shown in the figure, the soft magnetic powder 8 is added to the organic binder 9.
Are evenly dispersed. Here, the shape of the soft magnetic powder 8 is flat or needle-like, or flat and needle-like. That is, the soft magnetic powder 8 has at least one of a flat shape and a needle shape.

As the soft magnetic powder 8, a powder having a high magnetic permeability is used. For example, iron aluminum silicon alloy powder (Sendust) or iron nickel alloy powder (Permalloy)
Is used. The aspect ratio of the soft magnetic powder 8 is preferably sufficiently large (about 5: 1 or more).

As the organic binder 9, for example, thermoplastic resin such as polyester resin, polyvinyl chloride resin, polyvinyl butyral resin, polyurethane resin, cellulose resin, nitrile-butadiene rubber, styrene-butadiene rubber, etc. Alternatively, a thermosetting resin such as a copolymer thereof, an epoxy resin, a phenol resin, an amide resin, or an imide resin may be used.

Here, an example of the above-mentioned electronic device will be specifically described.

In the board portion on which the active element is mounted and the board portion between the wiring conductors arranged in parallel with each other, a soft magnetic paste represented by the following <composition 1> is printed on the wiring board and dried. Cured As a result, the thickness is 0.
An insulating soft magnetic layer of 3 mm was formed on the wiring board. When this insulating soft magnetic layer was analyzed using a vibrating magnetometer and a scanning electron microscope, the easy axis of magnetization and the orientation of magnetic particles were in the in-plane direction of the sample.

<Composition 1> (1) Flat soft magnetic material differential powder ... 90 parts by weight Composition: Fe-Al-Si alloy average particle size: 10 μm Aspect ratio:> 5 (2) Organic binder polyurethane resin: 8 parts by weight Part curing material (isocyanate compound) 2 parts by weight (3) Solvent (compound of cyclohexanone and toluene)
40 parts by weight On the wiring board on which the insulating soft magnetic material layer was formed as described above, after mounting predetermined components, the circuit was operated. In this state, the electromagnetic field strength under the wiring board was measured with a spectrum analyzer to confirm the effect of suppressing electromagnetic interference.

For a wiring board on which an insulating soft magnetic material layer is not formed, the electromagnetic field strength under the wiring board was measured with a spectrum analyzer in a state where the circuit was operated after mounting predetermined components. .

The measurement results are shown in FIGS. 4 to 7. Here, the LSIs 2 and 4 are mounted as parts and
The results of measuring the electromagnetic field strength under the wiring board for the electronic device in which SIs 2 and 4 are connected by wiring conductors 5 to 7 are shown. FIG. 4 shows the back side (back side) of the LSI 12 mounting surface when using a wiring board on which the insulating soft magnetic material layer is not formed.
The frequency characteristic of the electromagnetic field strength in is shown. FIG. 5 shows an LSI 1 using a wiring board on which an insulating soft magnetic material layer is formed.
2 shows frequency characteristics of electromagnetic field strength on the back side (back side) of the mounting surface. FIG. 6 shows frequency characteristics of electromagnetic field strength on the back surface of the wiring board corresponding to the wiring conductor 7 when the wiring board on which the insulating soft magnetic material layer is not formed is used. FIG. 7 shows frequency characteristics of electromagnetic field intensity on the back surface of the wiring board corresponding to the wiring conductor 7 when the wiring board having the insulating soft magnetic layer is used.

As can be easily understood from FIGS. 5 to 7, when the wiring board on which the insulating soft magnetic material layer is formed is used, the electromagnetic field strength on the back surface of the wiring board on which the active element (LSI) is mounted is wide band. It turns out that is suppressed by. Further, it can be seen that crosstalk between adjacent wiring conductors is also reduced.

As described above, the electromagnetic interference can be effectively suppressed by providing the insulating soft magnetic material layer on the wiring substrate at a position where unnecessary radiation is a problem.

As can be easily understood from the above-mentioned embodiments, the insulating soft magnetic material layer can be made to have flexibility, and as a result, not only can it be deformed into a complicated shape, but also it can be impacted. However, it can respond well.

[0029]

As described above, according to the present invention, the insulating soft magnetic material is provided between the active element which becomes the noise source and the wiring board, and the insulating soft magnetic material is also provided between the wiring conductors if necessary. Since it is provided, it is possible to effectively suppress mutual interference due to electromagnetic induction and unnecessary electromagnetic waves, and further, it is possible to achieve size reduction and weight reduction because a filter or the like is unnecessary. As a result, it is possible to suppress electromagnetic interference in high frequency equipment such as mobile communication equipment.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an electronic device according to the present invention.

FIG. 2 is a plan view partially showing another embodiment of the electronic device according to the present invention.

FIG. 3 is a partial cross-sectional view of the insulating soft magnetic layer shown in FIGS. 1 and 2.

FIG. 4 is a diagram showing frequency characteristics of electromagnetic field intensity on the back side (back surface) of the active element mounting surface in an electronic device in which an insulating soft magnetic layer is not formed.

FIG. 5 is a diagram showing frequency characteristics of electromagnetic field intensity on the back side (back surface) of the active element mounting surface in an electronic device in which an insulating soft magnetic layer is formed.

FIG. 6 is a diagram showing frequency characteristics of electromagnetic field intensity on the back surface of a wiring board corresponding to a wiring conductor in an electronic device in which an insulating soft magnetic layer is not formed.

FIG. 7 is a diagram showing frequency characteristics of electromagnetic field intensity on a back surface of a wiring substrate corresponding to a wiring conductor in an electronic device in which an insulating soft magnetic layer is formed.

[Explanation of symbols]

A Insulating soft magnetic layer 1 wiring board 2,4 LSI (Active element) 3,5,6,7 wiring conductor

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-4-294567 (JP, A) JP-A-60-186040 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 23/00

Claims (3)

(57) [Claims] 1. An electronic device having a wiring board and an active element mounted on the wiring board and radiating inductive noise, in an area sandwiched between the wiring board and the active element .
An electronic device, wherein an insulating soft magnetic material layer is formed on the wiring board . 2. The electronic device according to claim 1 , wherein the insulating soft magnetic layer includes an organic binder and a soft magnetic powder dispersed in the organic binder. Electronic device to do. 3. The electronic device according to claim 2 , wherein the soft magnetic powder has at least one of a flat shape and a needle shape.