JPH0774538A - Electronic circuit unit with planar antenna - Google Patents

Abstract

PURPOSE:To obtain an electronic circuit unit with planar antenna which is suitable to the use in a high frequency band by forming the dielectric layer between an antenna pattern and an earth layer by a specified thermoplastic resin foamed body. CONSTITUTION:In an electronic circuit with planar antenna composed by being provided with a circuit board 8 and a planar antenna part 1 and by electrically connecting an antenna pattern 3 and a circuit pattern 7 by a lead pin 4, the dielectric layer 2 between the antenna pattern 3 and an earth layer 5 is formed by a foamed body where base resin is thermoplastic resin whose melting point than 150 deg.C, foaming magnifications 2 to 5 times and the average bubble diameter of the surface of the foamed body is 5 to 50mum. By being excellent in a dielectric characteristic, the dielectric characteristic in a high frequency region, in particular, and reducing delay in signal propagation time by this constitution, an electronic circuit unit with planar antenna which is suitable to the use in a high frequency band can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved electronic circuit unit with a flat antenna, and more particularly to an electronic circuit unit suitable for use in a high frequency band.

[0002]

2. Description of the Related Art In a conventional planar antenna section 1 of an electronic circuit unit with a planar antenna, an antenna pattern 3 is formed on the surface of a dielectric layer 2 as shown in FIG. 1, and the dielectric layer 2 is penetrated from the antenna pattern 3. Then, a pair of lead pins protruding on the back surface of the dielectric layer 2 is provided. Lead pin 4
Are fixed to the antenna pattern 3 by soldering. A glass epoxy resin plate, a polytetrafluoroethylene resin plate, or the like is used for the dielectric layer 2, and a copper foil or the like whose surface is subjected to antirust treatment such as solder plating or nickel plating is used for the antenna pattern 3. .

[0003]

Since the material for mounting electronic parts is heated to the soldering temperature when mounting electronic parts, glass epoxy resin is often used in ordinary circuit boards, and mold boards are used. A resin having solder heat resistance such as a polyimide film or engineering plastic is used. On the other hand, in recent years, sophistication and expansion of information communication represented by satellite broadcasting and the like, and in the field of information processing equipment, delay of signal propagation time has become an important issue due to increase in storage capacity, which is required for substrates. As a characteristic, a material having a low dielectric constant and an excellent dielectric characteristic in a high frequency region is required. Further, along with the downsizing of electronic devices, downsizing of electronic components is also required.

Generally, the signal propagation delay time (τ) is proportional to the square root of the dielectric constant of a material and is represented by the following equation. [Τ ² = ε / c ² ] ε: dielectric constant, c: speed of light (= 3 × 10
⁸ [m / sec]) As can be seen from this, in order to reduce the signal propagation delay time, a low dielectric constant material must be selected.
Considering that it is necessary to use a plastic material with soldering heat resistance, 2.1 of polytetrafluoroethylene resin is the lowest among the materials conventionally used for the dielectric layer of the planar antenna, and further low dielectric constant It was impossible to give a rate characteristic. Therefore, one of the possible means for reducing the dielectric constant of the material is to use a resin foam as the material. However, since the existing existing resin foam has a large cell diameter, it is impossible to obtain a resin foam as a desired low dielectric constant material due to its large volume and low mechanical strength. .

[0005]

The present invention has been earnestly studied to develop an electronic circuit unit with a flat antenna having excellent dielectric characteristics, particularly in a high frequency band. As a result, the antenna pattern of the flat antenna and the circuit described above are obtained. This can be achieved by forming the dielectric layer between the ground layers of the substrate with a specific resin foam. That is, in the electronic circuit unit with a planar antenna of the present invention, an electronic component is mounted on one surface of an insulating plate, a circuit board having a ground layer on the other surface, and a dielectric layer having one surface in contact with the ground layer, A planar antenna having an antenna pattern on the other surface, wherein the antenna pattern and the circuit pattern are electrically connected by a lead pin, the electronic circuit unit with a planar antenna, between the antenna pattern and the ground layer The dielectric layer is made of a thermoplastic resin having a melting point of 150 ° C. or higher, a foaming ratio of 2 to 5 times, and a foam having an average cell diameter of a cut section of the foam of 5 μm or more and 50 μm or less. It is a feature.

In the present invention, the thermoplastic resin foam having a melting point of 150 ° C. or higher, which is used for the dielectric layer between the antenna pattern of the planar antenna and the ground layer of the circuit board, is, for example, polyethylene terephthalate (PET) or polybutylene. Saturated polyester resin such as terephthalate (PBT) and polyethylene naphthalate (PEN), polyphenylene sulfide resin (PPS), polyether ether ketone (PEEK), polypropylene resin (PP), polyetherimide resin (PEI), polycarbonate resin (PC) ), A polyamide-imide resin (PAI) or the like is used as a base resin, which is used in, for example, US Pat.
It is good to manufacture based on the manufacturing method of the fine resin foam disclosed by No. 473665. In this method for producing a fine resin foam, first, a pre-molded resin portion is placed in a high-pressure container, a gas serving as a bubble nucleus is injected into the container, and the gas is permeated into the resin for a certain period of time. After gas permeation for a certain period of time, the pressure is released to cause nucleation in the resin. Then, the gas-permeated resin is heated to foam, and further cooled to obtain a fine resin foam. As the base resin, PET, PBT, PPS, PC, P
Resins such as EEK are preferable because they are excellent in heat resistance, solder heat resistance, impact resistance and the like.

The resin foam forming the dielectric layer is
Foaming ratio 2 to 5 times and average cell diameter of cut section of foam is 5 μm
The reason for defining as 50 μm or less is that the expansion ratio exceeds 5 times, and the average cell diameter of the cut section of the foam exceeds 50 μm, the mechanical strength is lowered, and when used as a dielectric layer, deformation, Shrinkage or the like is likely to occur, and in some cases, the connection portion between the lead pin and the antenna pattern or the circuit pattern may be damaged. In addition, the surface condition of the foam also deteriorates, and the adhesion with the antenna pattern and the ground layer deteriorates. This is because the volume is large and the mounting area is large. Also,
If the expansion ratio is less than 2 times and the average cell diameter of the cut cross section of the foam is less than 5 μm, the target low dielectric constant of the dielectric layer cannot be achieved. A preferred range is one in which the expansion ratio is 3 to 4 times and the average cell diameter of the cut section of the foam is 20 μm or less.

[0008]

EXAMPLES Examples of the present invention will be shown below. Example 1 The expansion ratio was 3.1 times, and the average cell diameter of the cut section of the foam was 1.
4 μm PPS resin foam (compressive elastic modulus 1.4 × 10 ⁴
[Kg / cm ² ], relative permittivity is 1 MHz and 1 GHz
1.48) was used for the dielectric layer 2 to fabricate a planar antenna as shown in FIG. As shown in FIG. 2, this planar antenna is provided with a ground layer on one surface of an insulating plate 6 and a circuit pattern 7 on the other surface, and an electronic component 9 is provided on the circuit pattern.
An electronic circuit unit with a planar antenna was manufactured by incorporating the circuit board 8 on which was mounted on the ground layer 5 and covering the whole with a case 10. This electronic circuit unit with a flat antenna has good high frequency characteristics and delay of signal propagation time is 4.
It was as small as 06 × 10 ⁻⁹ [sec / m].

Example 2 The expansion ratio was 2.5 and the average cell diameter in the cut section of the foam was 2.
0 μm PET resin foam (compressive elastic modulus 1.1 × 10 ⁴
[Kg / cm ² ], relative permittivity is 1 MHz and 1 GHz
1.77) was used for the dielectric layer 2 to produce a planar antenna as shown in FIG. Using this planar antenna, an electronic circuit unit with a planar antenna was produced in the same manner as in Example 1. This electronic circuit unit with a flat antenna has good high-frequency characteristics and a signal propagation time delay of 4.43 × 10.
It was as small as ^-9 [sec / m].

Example 3 The expansion ratio was 2.5 and the average cell diameter of the cut section of the foam was 2.
0 μm PP resin foam (compression elastic modulus 5.1 × 10
³ [kg / cm ² ], relative permittivity 1MHz and 1GH
Using z of 1.49) as the dielectric layer 2, a planar antenna as shown in FIG. 1 was produced. Using this planar antenna, an electronic circuit unit with a planar antenna was produced in the same manner as in Example 1. The electronic circuit unit with a flat antenna has good high frequency characteristics and a signal propagation time delay of 4.06 × 1.
0 were those less ^-9 [sec / m].

Comparative Example 1 The expansion ratio is 6 times and the average cell diameter of the cut section of the foam is 100.
μm PP resin foam (compression elastic modulus 1.2 × 10 ³ [k
g / cm ² ], the relative permittivity is 1.20 for both 1 MHz and 1 GHz) was used for the dielectric layer 2 to fabricate a planar antenna as shown in FIG. Using this planar antenna, an electronic circuit unit with a planar antenna was produced in the same manner as in Example 1. This electronic circuit unit with a flat antenna has good high-frequency characteristics and a signal propagation time delay of 3.65 × 10.
^-9 [sec / m] is small, but the mounting area is large,
It was not suitable for practical use because of its low compression modulus.

Comparative Example 2 The expansion ratio was 7 times and the average cell diameter of the cut section of the foam was 150.
μm PPS resin foam (compression elastic modulus 1.3 × 10
³ [kg / cm ² ], relative permittivity 1MHz and 1GH
A planar antenna as shown in FIG. 1 was prepared by using 1.25) for both z and the dielectric layer 2. Using this planar antenna, an electronic circuit unit with a planar antenna was produced in the same manner as in Example 1. This electronic circuit unit with a flat antenna has good high-frequency characteristics and a signal propagation time delay of 3.72 × 1.
Although it was as small as 0 ^-9 [sec / m], it was not suitable for practical use because the mounting area was large and the compression modulus was low.

[0013]

As is apparent from the examples and the comparative examples as described above, in the electronic circuit unit with a planar antenna of the present invention, the base resin has a melting point of 150 ° C. or more in the dielectric layer between the antenna pattern of the planar antenna and the ground layer of the circuit board. With a thermoplastic resin of, the foaming ratio is 2 to 5 times, and the average cell diameter of the cut section of the foam is 5 μm to 50 μm, which is excellent in dielectric properties, especially in high frequency region. The signal propagation time delay is also small.

[Brief description of drawings]

FIG. 1 is a perspective view of a planar antenna unit.

FIG. 2 is a cross-sectional explanatory view of an electronic circuit unit with a planar antenna.

[Explanation of symbols]

 1 Planar Antenna Part 2 Dielectric Layer 3 Antenna Pattern 4 Lead Pin 5 Ground Layer 6 Insulation Plate 7 Circuit Pattern 8 Circuit Board 9 Electronic Component 10 Case

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Naoki Yoshida 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Kiyoshi Nakayama 2-6-1-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Kenzo Kobayashi 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (1)

[Claims] 1. A circuit board (8) having an electronic component (9) mounted on one surface of an insulating plate (6) and a ground layer (5) on the other surface, and one surface of the circuit board (8). 5) is provided with a dielectric layer (2) in contact with the plane pattern antenna part (1) having an antenna pattern (3) on the other surface, and the antenna pattern (3) and the circuit pattern (7) are connected to a lead pin (4). ), The dielectric layer (2) between the antenna pattern (3) and the ground layer (5) has a base resin with a melting point of 150 ° C. or higher. An electronic circuit unit with a planar antenna, which is made of a plastic resin and has a foaming ratio of 2 to 5 times and an average cell diameter of a cut section of the foam body of 5 μm or more and 50 μm or less.