JP2008078313A - Housing for electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a housing for electronic component exhibiting good electromagnetic shielding performance and capable of preventing corrosion due to contact of different kinds of metal. <P>SOLUTION: Since a base mount 12 and a cover 13 are bonded by a shield adhesive layer 15 composed of a material produced by adding and dispersing filler having high permittivity to an adhesive material such as a polymer material exhibiting adhesion, the base mount 12 and the cover 13 can be insulated in DC and connected (short-circuited) in high frequency. Consequently, a contact potential generated through contact of different kinds of metal does not cause a DC current to flow between the base mount 12 and the cover 13, thus eliminating the risk of galvanic corrosion. Since the impedance between the base mount 12 and the cover 13 is low for an electromagnetic wave, the electromagnetic wave can be released as a noise current to a GND circuit 23 and an electronic component 21 can be shielded electromagnetically from the outside of the housing 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a housing that houses an electronic component that requires an electromagnetic shield.

Conventionally, in an electronic device equipped with an electronic component, the electronic device is damaged by an external electromagnetic wave, or the electromagnetic wave generated from the electronic component leaks outside the electronic device and affects other electronic devices. , Prevention of electromagnetic interference is a problem.
Therefore, an electromagnetic shield that prevents transmission of electromagnetic waves is performed by covering the electronic component with a conductive material such as a metal cover in the casing of the electronic component. Furthermore, the effect of electromagnetic shielding is also enhanced by grounding the metal cover.
As such a housing structure, for example, Patent Document 1 discloses a structure in which a metal cover is brought into contact with a grounded metal plate and fixed with screws.
JP 2004-95929 A

However, in the case structure configured as described above, when the metal cover, the metal plate, and the screw portion are formed of different metal materials, there are places where different metals come into contact with each other.
When the housing of electronic components is placed in the engine room of a vehicle, etc., moisture exists in the environment around the housing, so a contact potential is generated at the part where the dissimilar metal contacts, and a direct current flows. May cause galvanic corrosion.
When galvanic corrosion occurs, a metal with a low potential elutes in the vicinity of the contact part of dissimilar metals, and electromagnetic waves leak from a slight gap generated by this, so there is a problem that good electromagnetic shielding properties cannot be maintained. there were. Further, there is a possibility that sealing failure such as moisture may occur, and there is a problem that reliability is lowered.

  Therefore, an object of the present invention is to realize an electronic component housing case that can prevent corrosion due to contact of different metals and has good electromagnetic shielding properties.

  In the present invention, in order to achieve the above object, according to the first aspect of the present invention, a base on which an electronic component is placed, a cover that covers the electronic component, and at least one of the base and the cover are grounded. An electronic component housing housing configured to shield electromagnetic waves, wherein the base and the cover insulate the base and the cover from each other in a direct current and at a high frequency. Adopting a technical means that it is bonded and fixed via an adhesive layer having a dielectric constant connectable to.

According to the first aspect of the present invention, in the housing that accommodates the electronic component, the base and the cover are insulated in a direct current and connected in a high frequency manner by the adhesive layer that adheres and fixes the base and the cover. can do.
As a result, a direct current flows due to a contact potential generated by contact between different metals between the base and the cover, and there is no possibility that galvanic corrosion will occur.
In addition, since the impedance between the base and the cover is low with respect to electromagnetic waves that are high-frequency components, the electromagnetic waves can be released as noise current to the grounding means. Accordingly, since the electronic component can be electromagnetically shielded from the outside of the electronic component housing case, the electromagnetic wave generated from the electronic component leaks to the outside of the electronic component housing case and from the outside of the electronic component housing case. The influence of electromagnetic waves on electronic components can be prevented.
That is, galvanic corrosion due to contact of different metals can be prevented, and an electronic component housing case having good electromagnetic shielding properties can be realized.

  According to a second aspect of the present invention, in the electronic component housing electronic component according to the first aspect, the adhesive layer is formed by dispersing a filler made of a dielectric material in a resin material. Adopt means.

  According to the invention described in claim 2, since the adhesive layer is formed by dispersing the filler made of the dielectric material in the resin material, the degree of freedom in selecting the dielectric material and the mixing ratio with the resin material is high. An adhesive layer having desired characteristics can be easily formed.

  According to a third aspect of the present invention, there is employed a technical means that in the electronic component housing case according to the first or second aspect, the filler is made of an aluminum titanate material.

  According to the invention described in claim 3, since the filler is formed of a ferroelectric aluminum titanate material having a high dielectric constant, an adhesive layer having a high dielectric constant can be formed. Characteristics can be improved.

  According to a fourth aspect of the present invention, in the electronic component housing case according to any one of the first to third aspects, the electronic component includes the base, the cover, and the adhesive layer. The technical means of being kept airtight and being cut off from the outside air is adopted.

  According to the invention described in claim 4, since the electronic component is held in an airtight state by the base, the cover, and the adhesive layer and is shielded from the outside air, the electronic component has good electromagnetic shielding characteristics, and the electronic component Intrusion of water and foreign matter into the housing for housing can be prevented, and electronic components can be more effectively protected.

  According to a fifth aspect of the present invention, in the electronic component housing case according to any one of the first to fourth aspects, the base is a heat dissipation means thermally connected to the electronic component. The technical means of being formed is adopted.

  According to the fifth aspect of the present invention, since the base is formed as a heat radiating means thermally connected to the electronic component, the heat generated by the electronic component disposed on the base is generated by the electronic component housing case. Can be dissipated outside. Further, it is not necessary to newly provide a heat radiating member, and the electronic component housing can be downsized.

  According to a sixth aspect of the present invention, in the electronic component housing case according to any one of the first to fifth aspects, the adhesive layer is disposed between the base and the cover at a predetermined interval. The technical means that the spacer for forming in is provided.

  According to the invention described in claim 6, since the spacer for forming the adhesive layer at a predetermined interval is provided between the base and the cover, the adhesive layer can be kept at a constant thickness. Therefore, it is possible to prevent the base and the cover from being electrically connected by contact.

  An electronic component housing case according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing the structure of an electronic component housing. 1A is a plan view of the electronic component housing case as viewed from the cover side, and FIG. 1B is a cross-sectional view taken along the line XX in FIG. FIG. 2 is an explanatory diagram illustrating a modification example of the bonding structure between the base and the cover.

As shown in FIGS. 1A and 1B, a housing 11 for housing an electronic component 21 includes a metal base 12 on which a substrate 22 on which the electronic component 21 is mounted is disposed, and a substrate 22. And a shield cover layer 15 that is interposed between the adhesive surfaces of the base 12 and the cover 13 and bonds the two together. That is, in the housing 11, the board 22 on which the electronic component 21 is mounted is accommodated in a space formed by the base 12 and the cover 13.
For example, the housing 11 is mounted in an engine room of a vehicle.

In the present embodiment, the base 12 is formed as a heat radiating member by a plate member made of a material having high thermal conductivity, for example, an alloy containing aluminum as a main component, and heat generated by the electronic component 21 is dissipated to the outside. Can be made. Moreover, it is not necessary to newly provide a heat radiating member, and the housing 11 can be reduced in size.
The base 12 can also be formed in a shape in which heat radiating fins protrude from the heat radiating surface. Thereby, the area of a heat radiating surface can be increased and heat dissipation efficiency can be improved.

On the upper surface 12a of the base 12, a substrate 22 on which an electronic component 21 such as a power transistor forming a high frequency circuit is mounted, a GND circuit 23 connected to an external wiring and grounded at a terminal (not shown), Is fixed by bonding.
The substrate 22 is bonded and fixed in an electrically insulated state by an adhesive layer 14 made of an insulating resin adhesive. The GND circuit 23 is provided adjacent to the substrate 22 and electrically connected by a wiring 25, and is bonded and fixed to the upper surface 12a of the base 12 by a shield adhesive layer 16 described later.
Outside the substrate 22 and the GND circuit 23, a spacer 24 is formed to form a shield adhesive layer 15 described later at a predetermined interval when the cover 13 is attached to the base 12.
It should be noted that at least the GND circuit 23 may be bonded and fixed to the upper surface 12 a of the base 12, and the substrate 22 is not necessarily arranged on the base 12.

  The cover 13 is formed of a metal material having electromagnetic shielding properties, for example, stainless steel into a box shape having an open end portion 13a at one end. An adhesive portion 13b, which is formed by bending outward at a substantially right angle in order to adhere and fix to the upper surface 12a of the base 12, extends over the entire circumference of the open end portion 13a. Is formed.

The shield adhesive layers 15 and 16 are made of a material obtained by adding and dispersing a filler having a high dielectric constant to an adhesive material such as a polymer material having an adhesive force.
As the adhesive material, for example, an epoxy resin or an acrylic resin can be used. Various adhesive materials such as thermoplastic resins such as polybutyl acrylate resins, thermosetting resins such as phenol resins, and UV curable resins can be used.
In order to increase the dielectric constant of the shield adhesive layers 15 and 16, it is desirable to use a resin having a high dielectric constant, and an example of such a resin is polyvinylidene fluoride.
Furthermore, an inorganic adhesive material such as alumina cement or a glass material can also be used.

The filler is formed into a spherical shape, a plate shape, a chop shape, or the like by a material having a high dielectric constant.
As the filler material, both a ferroelectric and a paraelectric can be used, and in particular, a material having a relative dielectric constant exceeding 20 can be suitably used. As the ferroelectric, a barium titanate-based material having a relative dielectric constant exceeding 1000 can be used, and it can be suitably used for a circuit whose frequency is not high. As the paraelectric material, for example, aluminum oxide, forsterite, barium magnesium niobate, barium titanate titanate, or the like can be used, which can be suitably used for a circuit having a high frequency.

The filler is added to the adhesive material at a ratio that can exhibit a sufficient adhesive force and good electromagnetic shielding properties.
In this embodiment, the shield adhesive layers 15 and 16 are made of an epoxy resin as an adhesive material and spherical barium titanate having an average particle diameter of about 100 μm as a filler, and titanic acid with respect to 100 parts by weight of the epoxy resin. It is made of a material to which barium is added at a ratio of 20 to 80 parts by weight.
Thereby, for example, the shield adhesive layers 15 and 16 having a high dielectric constant with a relative dielectric constant of 100 or more can be formed, and the electromagnetic shielding effect can be improved.
As described above, since the shield adhesive layers 15 and 16 are formed by dispersing the filler made of the dielectric material in the adhesive material, the degree of freedom in selecting the dielectric material and the mixing ratio with the adhesive material is high. The shield adhesive layers 15 and 16 having characteristics can be easily formed.

The shield adhesive layer 15 is formed by applying an adhesive formed by mixing a filler to the adhesive material described above to the bonding position of the base 12 or the bonding portion 13b of the cover 13 and attaching the cover 13 to the base 12. Later, it is formed by curing.
Here, the height of the spacer 24 is set such that the shield adhesive layer 15 has a predetermined thickness, for example, 500 μm, when the cover 13 is mounted on the base 12. Thereby, since the shield adhesive layer 15 can be maintained at a constant thickness, it is possible to prevent the base 12 and the adhesive portion 13b of the cover 13 from being electrically connected by contact.
Further, the shield adhesive layer 15 is formed to have a width of about 2 mm in order to avoid the formation of shrinkage cavities and unbonded portions due to shrinkage of the adhesive material.
In this way, the shield adhesive layer 15 is interposed between the upper surface 12a cover 13 of the base 12 and the adhesive portion 13b of the cover 13, and adheres over the entire circumference of the opening end portion 13a of the cover 13, so that the substrate 22 is exposed to the outside air. It is shut off and hermetically sealed.

  With the above-described configuration, in the housing 11, the GND circuit 23 and the base 12 are bonded by the shield adhesive layer 16, and the base 12 and the cover 13 are bonded by the shield adhesive layer 15. The housing 11 formed by the cover 13 and the base 12 is connected to the GND circuit 23 via the shield adhesive layers 15 and 16. Since the shield adhesive layers 15 and 16 have a high dielectric constant, they are insulated in a direct current, and have a low impedance for a high frequency signal and are connected (short-circuited) in a high frequency. That is, a so-called AC coupling state is formed.

Thus, the AC coupling formed by the shield adhesive layers 15 and 16 provides a direct current insulation between the base 12 and the cover 13 and between the cover 13 and the GND circuit 23.
Thus, a direct current flows between the base 12 and the cover 13 due to the contact potential generated by the contact between different metals, and there is no possibility that galvanic corrosion will occur.

Moreover, since the impedance between the base 12 and the cover 13 and between the cover 13 and the GND circuit 23 is low with respect to the electromagnetic wave that is a high-frequency component, the electromagnetic wave is released to the GND circuit 23 as a noise current. be able to.
Therefore, for example, the electronic component 21 can be electromagnetically shielded from the outside of the housing 11 against electromagnetic waves in a high frequency band such as several hundreds of MHz, so that leakage of the electromagnetic waves generated from the electronic components 21 to the outside of the housing 11 and The influence of the electromagnetic wave from the outside of the housing 11 on the electronic component 21 can be prevented.
Here, an attenuation effect of several tens dB can be obtained in a frequency band of 100 kHz to 1 GHz by selecting the dielectric constant, shape, addition ratio, and the like of the filler according to the application.
That is, the galvanic corrosion due to the contact of different metals can be prevented, and the electronic component housing case 11 having good electromagnetic shielding properties can be realized.
Furthermore, since the electronic component 21 is held in an airtight state by the base 12, the cover 13, and the shield adhesive layer 15 and is blocked from the outside air, it is possible to prevent water and foreign matter from entering the housing 11. The electronic component 21 can be protected.

(Example of change)
The structure for adhering the cover 13 to the base 12 is not limited to the structure shown in FIG. 1. For example, as shown in FIG. 2A, the side surface 12 b of the base 12 and the open end of the cover 13 are used. A configuration in which the inner side surface 13c in the vicinity of the portion 13a is bonded and fixed by the shield bonding layer 15 may be used. If this configuration is used, it is not necessary to form a space for adhering the cover 13 to the upper surface 12a of the base 12, so that the housing 11 can be reduced in size.
Further, as shown in FIG. 2B, a groove 12c is formed on the upper surface 12a of the base 12 so as to surround the substrate 22 and the GND circuit 23, and the opening end of the cover 13 is inserted into the groove 12c. A configuration in which the shield adhesive layer 15 is bonded and fixed can be employed. When this configuration is used, the shield adhesive layer 15 is filled in the groove 12c and does not move in the surface direction of the upper surface 12a. There is no risk of contamination.
Further, as shown in FIG. 2C, a configuration in which a cover fixing member 17 for fixing the cover is erected on the upper surface 12a of the base 12 adjacent to the groove 12c may be used.
The cover fixing member 17 is a member having a plate-like portion in which a protruding portion 17a for fixing the cover 13 is formed outward, and is provided at a position in contact with the inner side surface 13c of the cover. The cover 13 has a locking portion 13d formed in a shape that can be locked to the protruding portion 17a at a position corresponding to the protruding portion 17a. Moreover, when the cover 13 is attached to the base 12, the open end 13a is inserted into the groove 12c.
By covering the cover 13 from the outside of the cover fixing member 17 and fitting the protrusion 17a to the locking portion 13d, the cover 13 is fixed in a state where the opening end portion 13a of the cover 13 is inserted into the groove portion 12c. The At this time, the shield adhesive layer 15 is filled and formed inside the groove 12c. When this configuration is used, the cover 13 is mechanically attached to the base 12, so that the reliability is high and a strong adhesive force is not required for the shield adhesive layer 15, so that the degree of freedom of material selection is increased. Can do.

As the shield adhesive layer 15, a double-sided pressure-sensitive adhesive tape in which a filler is dispersed can also be used. If this structure is used, the base 12 and the cover 13 can be adhere | attached by the simple operation | work which only sticks the said double-sided adhesive tape to the adhesive surface of the base 12 and the cover 13. FIG.
Further, the shield adhesive layer 15 may be bonded by sandwiching a pre-cured layer between the base 12 and the cover 13.

In the present embodiment, the configuration using the GND circuit 23 as a means for grounding the casing 11 is shown, but the base 12 or the cover 13 may be grounded.
Further, the base 12 and the cover 13 can be formed of a metal material other than the exemplified materials, for example, an alloy containing copper as a main component.

[Effects of best mode]
(1) According to the electronic component housing case according to the present invention, the base 12 and the cover 13 are provided by the shield adhesive layer 15 that bonds and fixes the base 12 and the cover 13 in the housing 11 that houses the electronic components. And can be connected (short-circuited) in a high frequency manner.
Thus, a direct current flows between the base 12 and the cover 13 due to the contact potential generated by the contact between different metals, and there is no possibility that galvanic corrosion will occur.
Further, since the impedance between the base 12 and the cover 13 becomes low with respect to the electromagnetic wave that is a high-frequency component, the electromagnetic wave can be released to the GND circuit 23 as a noise current. Accordingly, since the electronic component 21 can be electromagnetically shielded from the outside of the housing 11, leakage of electromagnetic waves generated from the electronic component 21 to the outside of the housing 11 and electromagnetic waves from the outside of the housing 11 to the electronic component 21. The effect can be prevented.
That is, the galvanic corrosion due to the contact of different metals can be prevented, and the electronic component housing case 11 having good electromagnetic shielding properties can be realized.

(2) Since the shield adhesive layers 15 and 16 are formed by dispersing a filler made of a dielectric material in a resin material, the degree of freedom in selecting the dielectric material and the mixing ratio with the resin material is high, so that desired characteristics are obtained. Can be easily formed.

(3) Since the ferroelectric aluminum titanate-based material having a high dielectric constant can be used as the filler, the shield adhesive layers 15 and 16 having a high dielectric constant can be formed, thereby improving the electromagnetic shielding characteristics. be able to.

(4) The electronic component 21 is held in an airtight state by the base 12, the cover 13, and the shield adhesive layer 15 and is shielded from the outside air. Intrusion of water and foreign matter can be prevented, and the electronic component 21 can be protected more effectively.

(5) Since the base 12 is formed as a heat radiating means thermally connected to the electronic component 21, heat generated by the electronic component disposed on the base 12 can be dissipated outside the housing 11. Moreover, it is not necessary to newly provide a heat radiating member, and the housing 11 can be reduced in size.

(6) Since the spacer 24 for forming the shield adhesive layer 15 at a predetermined interval is provided between the base 12 and the cover 13, the adhesive layer can be kept at a constant thickness. It is possible to prevent the base 12 and the cover 13 from being electrically connected by contact.

[Correspondence between each claim and embodiment]
The shield adhesive layers 15 and 16 correspond to the adhesive layer described in claim 1, and the GND circuit 23 corresponds to the grounding means.

It is explanatory drawing which shows the structure of the housing | casing for electronic component accommodation. 1A is a plan view of the electronic component housing case as viewed from the cover side, and FIG. 1B is a cross-sectional view taken along the line XX in FIG. It is explanatory drawing which shows the example of a change of the adhesion structure of a base and a cover.

Explanation of symbols

11 Housing 12 Base 13 Cover 15, 16 Shield Adhesive Layer (Adhesive Layer)
21 Electronic components
23 GND circuit (grounding means)
24 Spacer

Claims (6)

A base on which electronic components are placed;
A cover covering the electronic component;
A grounding means for grounding at least one of the base and the cover; and an electronic component housing case configured to shield electromagnetic waves,
The base and the cover are galvanically insulated from the base and the cover in a direct current manner, and are bonded and fixed via an adhesive layer having a dielectric constant that can be connected at a high frequency. Component housing.   The electronic component housing case according to claim 1, wherein the adhesive layer is formed by dispersing a filler made of a dielectric material in a resin material.   3. The electronic component housing case according to claim 2, wherein the filler is formed of an aluminum titanate-based material.   4. The electronic component according to claim 1, wherein the electronic component is held in an airtight state by the base, the cover, and the adhesive layer, and is blocked from outside air. Electronic component housing.   5. The electronic component housing case according to claim 1, wherein the base is formed as a heat radiating means thermally connected to the electronic component.   6. The electron according to claim 1, wherein a spacer for forming the adhesive layer at a predetermined interval is provided between the base and the cover. Component housing.

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