JPH0810957Y2 - Anti-reflection structure for internal circuits of high frequency electronic devices - Google Patents

Description

[Detailed description of the device]

[0001]

[Industrial application] The present invention prevents the reflection of radio waves in the internal circuits of electronic devices that perform transmission or reception in the high frequency band such as mobile communications such as mobile phones and car phones, satellite broadcasting and amateur radio. Regarding the structure.

[0002]

2. Description of the Related Art Mobile communication such as mobile phones and car phones,
Part of satellite broadcasting and amateur radio is 1 GHz to tens of GH
Radio waves in the high frequency band of about z are used as communication means, and a circuit for oscillating or amplifying the radio waves in the high frequency band is built in each device.
When these circuits form the transmitter, most of their outputs are directed to the antenna, while when these circuits form the receiver, most of their outputs are directed to the subsequent circuit of the receiver. It is configured. by the way,
It is known that electric waves are leaked to the surroundings other than passing through such a regular route, and particularly in a high frequency band called microwave, the electric waves easily propagate in the air,
For this reason, radio wave sources such as an oscillation circuit and / or an amplification circuit have been conventionally shielded by a metal shield box.

What is shown as FIG. 5 is an explanatory view showing this state, in which A is a substrate on which various circuits are arranged, and 1 is a radio wave generation source represented by an oscillation circuit and / or an amplification circuit. It is a metal shield box for exterior. FIG. 6 shows a state of the radio wave generation source which is covered by the metal shield box 1. In the figure, reference numeral 2 denotes a hybrid IC (hybrid IC) in which either the oscillation circuit or the amplification circuit is mounted, or the oscillation circuit and the amplification circuit are integrally mounted. The hybrid IC 2 is resin-molded 3 with an insulating resin, and is configured so that the parts do not come into contact with each other even when shock or vibration is applied by the insulating resin filled between the parts.

In such a structure, the radio wave in the high frequency band transmitted from a specific location on the hybrid IC 2 passes through a predetermined path on the circuit and is also radiated into the air as indicated by E in the figure. However, the metal shield box 1 for shielding the radio wave that covers the hybrid IC 2 prevents radio wave leakage to the outside of the metal shield box.

[0005]

As described above, although it is possible to prevent radio wave leakage to the outside of the metal shield box with this configuration, it has been found that there is a new problem. That is, the radio wave E emitted from the hybrid IC 2 is reflected by the inner surface of the metal shield box and returned to the hybrid IC 2, and this phenomenon causes circuit destruction and noise generation.
For example, when the hybrid IC 2 is a transmission circuit,
As shown in FIG. 7, a phenomenon in which an output of high power of 3 W to 5 W from the amplifier circuit is returned to the input side of the amplifier circuit, which causes destruction of the amplifier circuit, and radio waves emitted from the oscillator circuit in the air are metal shielded. After repeated reflections and radiation interference in Hakouchi,
When input to the amplifier circuit, an unnecessary wave that causes noise is generated around the original frequency (for example, 1 GHz) as shown in FIG. Although the above is mainly the case of the transmitter, the receiver has a small output but has a similar problem because the oscillator circuit is built therein. The present invention has been made in view of the current situation, and is intended to prevent circuit breakage and noise generation by suppressing the reflection phenomenon of radio waves inside a metal shield box for shielding radio waves.

[0006]

DISCLOSURE OF THE INVENTION The present invention, which has solved the above-mentioned problems, provides a resin insulating layer for covering a radio wave generation source such as an oscillation circuit and / or an amplification circuit, and a metal shield box for shielding the radio wave. Between the two, characterized in that the electromagnetic wave absorbing sheet provided with an adhesive layer on the back side, the adhesive layer on the back side is adhered to the resin insulating layer or metal shield box that covers the radio wave generation source. There is.

Of course, the present invention can be applied to a circuit configuration in which each component is normally arranged on a substrate, but it is particularly preferable to apply it to a resin-molded hybrid IC. In this case, an electromagnetic wave absorbing sheet is used. It is attached to the outer surface of the resin mold, and a part or the whole of the outer surface of the resin mold is covered with a radio wave absorbing sheet. The radio wave absorption sheet may be attached to the inner surface of the metal shield box.

The material for the electromagnetic wave absorbing sheet is, for example,
A material in which one or more selected from ferrite powder, carbon powder or metal powder is dispersed and blended in a synthetic resin binder or a rubber binder can be used.

[0009]

[Advantage] If such an antireflection structure is adopted, the radio waves transmitted from the oscillation circuit or the amplification circuit in the air will always pass through the inside of the radio wave absorption sheet interposed between the resin insulating layer and the metal shield box. As a result, it is converted into heat energy inside the radio wave absorption sheet and attenuated. Therefore, radio waves are less likely to be re-input to the input side of the amplifier circuit with high power, and radio waves are less likely to cause radiation interference in the metal shield box. Further, since the radio wave absorbing sheet has the adhesive layer on the back surface, it can be easily attached to a predetermined position, and the attaching work is extremely easy. Therefore, in the manufacturing stage of the electronic device, the electromagnetic wave absorption sheet may not be attached and may be attached according to the degree of the obstacle due to the reflected wave in the inspection process after the production. Further, since the radio wave absorbing sheet is attached by the adhesive layer, it can be removed and the pasting position of the radio wave absorbing sheet once pasted can be finely adjusted. Further, since it is a sheet shape, it is easy to follow the shape of the object to be attached, and since the adhesion with the object to be attached can be enhanced, an extremely excellent antireflection effect can be exhibited.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, details of the present invention will be described based on illustrated embodiments. FIG. 1 is a cross-sectional explanatory view showing an embodiment of the present invention, in which A is a substrate on which various circuits are arranged, 2 is a hybrid IC equipped with an oscillation circuit and / or an amplification circuit, and 3 is a hybrid IC 2. The resin mold 1 is a metal shield box. The present invention, in such a configuration,
Resin mold 3 as resin insulation layer and metal shield box 1
The outline is to interpose a radio wave absorbing sheet having a pressure sensitive adhesive layer on the back surface thereof, and in the example shown in the figure, the radio wave absorbing sheet 4 is attached to the outer surface of the resin mold 3. . As the radio wave absorbing sheet 4, known ones can be used. For example, one kind or two kinds or more selected from ferrite powder, carbon powder or metal powder is dispersed and blended in a synthetic resin binder or a rubber binder. Materials can be used. In particular, when the heat generation amount inside the radio wave absorption sheet 4 is not negligible when applied to a high output transmission circuit, it is preferable to use a synthetic resin having excellent heat resistance.

The radio wave absorbing sheet 4 can be attached only to the upper surface of the resin mold 3, or can be attached so as to cover the entire outer surface of the resin mold 3 as indicated by the chain line. The radio wave absorption sheet 4 is a hybrid IC.
It is also possible to selectively attach only to the portion on the upper part of the above 2, which is close to the main radio wave source.

Since the electromagnetic wave absorbing sheet 4 may be located between the resin mold 3 and the metal shield box 1, the electromagnetic wave absorbing sheet 4 is attached to the inner surface of the metal shield box 1 as shown in FIG. It is also possible to do so. Since the adhesive layer is provided on the back surface of the radio wave absorbing sheet 4, the adhesive layer can be easily attached to the outer surface of the resin mold 3 or the inner surface of the metal shield box 1, and the workability is excellent. Can be demonstrated. Further, since it is sheet-shaped, it can be attached along the shape of the object to be attached, so that an excellent antireflection effect can be exhibited. Further, since the radio wave absorbing sheet 4 is attached by the adhesive layer, it is possible to finely adjust the attaching position after attaching once.
The antireflection effect can be more perfect. Although the thickness of the radio wave absorbing sheet 4 is appropriately selected, the radio wave E not only passes in the thickness direction of the radio wave absorbing sheet 4, but also passes along the longitudinal direction of the radio wave absorbing sheet 4 as shown in FIG. It does not have to be thick, and the thickness d of the radio wave absorption sheet 4 is sufficient within the range of several mm. If the resin mold 3 is relatively thin, it is easy to cover the resin mold 3 along the outer shape thereof.

The present invention has a radio wave generation source such as an oscillation circuit and / or an amplification circuit, and the radio wave generation source is covered with a resin insulation layer, and the resin insulation layer is further covered with a metal shield box. Hybrid IC if it is
It is also applied to normal circuits other than, for example, as shown in FIG.
It is also adopted that the metal shield box 1 having the electromagnetic wave absorbing sheet 4 and the resin insulating layer 5 laminated on the inner surface is externally fitted to the normal circuit portion including the oscillation circuit and / or the amplification circuit on the substrate A.

According to the present invention having such a structure, since the radio waves transmitted from the oscillation circuit and the amplification circuit in the air always pass through the radio wave absorption sheet 4, these radio waves are converted into heat energy in the radio wave absorption sheet 4. Can be attenuated by
It is possible to prevent the reflected electric wave in the metal shield box from being re-input to the amplifier circuit or generating noise due to radiation interference.

[0015]

The present invention provides an adhesive layer on the back surface between a resin insulating layer that covers a radio wave generation source such as an oscillation circuit and / or an amplification circuit, and a radio wave shielding metal shield box that covers the resin insulation layer. Since the electromagnetic wave absorption sheet provided with the above is interposed by adhering the adhesive layer on the back surface to the resin insulating layer or the metal shield box that covers the radio wave generation source, it is of course possible to block the radio wave leakage by the metal shield box. Therefore, it is possible to pass the radio waves emitted in the air from the oscillation circuit or amplification circuit through the radio wave absorption sheet and attenuate them, which has been a problem in electronic devices for high frequency bands than before, circuit destruction due to output feedback. It is possible to prevent the generation of noise due to radiation interference.

Further, since the radio wave absorbing sheet has the adhesive layer on the back surface, it can be easily attached at a predetermined position, and the attaching work is extremely easy. Therefore, in the manufacturing stage of the electronic device, the electromagnetic wave absorption sheet may not be attached and may be attached according to the degree of the obstacle due to the reflected wave in the inspection process after the production. Further, since the radio wave absorbing sheet is attached by the adhesive layer, it can be removed and the pasting position of the radio wave absorbing sheet once pasted can be finely adjusted. Further, since it is a sheet shape, it is easy to follow the shape of the object to be attached, and since the adhesion with the object to be attached can be enhanced, an extremely excellent antireflection effect can be exhibited.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the state of radio waves passing through the inside of the radio wave absorption sheet.

FIG. 4 is an explanatory sectional view showing another embodiment of the present invention.

FIG. 5 is an explanatory view showing a state in which an oscillator circuit and / or an amplifier circuit is covered with a metal shield box on a substrate.

FIG. 6 is an explanatory cross-sectional view showing the structure inside a conventional metal shield box.

FIG. 7 is an explanatory diagram showing how the output of the amplifier circuit is fed back to the input side in the transmitter.

FIG. 8 is an explanatory diagram showing how unwanted waves are generated before and after the original radio wave.

[Explanation of symbols]

 A substrate 1 metal shield box 2 hybrid IC 3 resin mold 4 electromagnetic wave absorption sheet 5 resin insulation layer

Claims (2)

[Scope of utility model registration request] 1. Radio wave emission from an oscillator circuit and / or an amplifier circuit, etc.
A resin insulation layer that covers the live source and a radio wave shield that covers it
A metal adhesive box with an adhesive layer on the back
Cover the wave absorbing sheet with the adhesive layer on the back and the radio wave generation source.
By attaching it to the resin insulation layer or metal shield box
Reflection of internal circuit of electronic equipment for high frequency band
Prevention structure. 2. A radio wave absorber, ferrite powder, car
One or more selected from bon powder or metal powder
Dispersed in synthetic resin binder or rubber binder
2. The high frequency band electricity according to claim 1, which is made of the above material.
Anti-reflection structure of the internal circuit of the slave device.