JP2004153607A - Chip-shaped antenna element and antenna-mounted printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed antenna which secures a sufficient gain, is miniaturized and eliminates the need for mounting an antenna element on a printed wiring board. <P>SOLUTION: A via hole is formed in a resin substrate on which an antenna conductor is formed, and a high dielectric resin is embedded in the via hole for formation. Otherwise, a high dielectric resin layer is formed covering at least a portion of the antenna conductor. Furthermore, a partial area of the printed circuit board may be made to be at a high dielectric constant by these methods to form an antenna element integrally with the partial area. <P>COPYRIGHT: (C)2004,JPO

Description

図３は、高誘電樹脂の割合別に定在波比ＳＷＲを周波数に対してプロットしたものである。高誘電樹脂の割合が高くなるにつれピークが全体的に低周波側へとシフトしていることがわかる。図４は、共振周波数ｆ_０及び帯域中心周波数ｆｃｅｎｔｅｒを高誘電樹脂の割合に対してプロットしたものであり、図５は、帯域幅ＢＷと高誘電樹脂の割合の関係を示すものである。
【００３７】
本計算モデルにおいて、比誘電率６０の高誘電樹脂を孔埋めした場合、高誘電樹脂による共振周波数シフトの効果を線形近似すると、アンテナの共振周波数は高誘電樹脂量１％増加につき約１０ＭＨｚの低周波シフトとなる。
【００３８】
（第２の実施形態）
本実施形態は、高誘電樹脂を樹脂基板に埋め込む代わりに、アンテナ導体の表面を覆うように高誘電樹脂層を形成したものである。
【００３９】
図６に本実施形態のチップ状アンテナ素子２１を示す。樹脂基板２２上に蛇行状のアンテナ導体２３が形成されていることは、先の第１の実施形態のものと同様であり、それぞれの構成も先の第１の実施形態のものと同様である。
【００４０】
本実施形態のチップ状アンテナ素子２１では、樹脂基板２２にはベアホールは形成されておらず、高誘電樹脂も埋め込まれていない。その代わりに、アンテナ導体２３を覆って高誘電樹脂層２４が形成されている。
【００４１】
上記高誘電樹脂層２４は、先の第１の実施形態においてベアホールに埋め込まれる高誘電樹脂と同様のものを用いて形成することができ、これを塗布、あるいは印刷することにより簡単に形成することができる。
【００４２】
上記高誘電樹脂層２４は、アンテナ導体２３の全てを覆って形成することが好ましいが、必ずしもこれに限らず、アンテナ導体２３の一部を覆うように形成することも可能である。ただし、アンテナ導体２３を覆う面積が多いほど効果が高く、実効的な効果を実現するためには、アンテナ導体２３の５０％以上を覆うように形成することが好ましい。高誘電樹脂層２４の厚さは、任意に設定することができるが、１０〜１０００μｍ程度とすることが好ましい。下限である１０μｍを下回ると、十分な効果が得られない虞れがある。逆に上限である１０００μｍを越えて厚くなると、高誘電樹脂層２４が樹脂基板２２表面周辺の空間を占有することになり、小型化の妨げになる。
【００４３】
実際、本発明者らは、次のような実験を行って高誘電樹脂層２４の厚さに関する検討を行った。実験に用いたサンプルを図７（ａ）に示す。樹脂基板２２としては厚さ０．６ｍｍのＦＲ−４（ＭＣＬ−ＢＥ−６７Ｇ（Ｈ））基板を用いた。高誘電樹脂層２４の形成に用いたポッティング材は、イミド系樹脂（誘電率ε＝約９０）である。アンテナ導体２３のパターンの各寸法は図７（ｂ）に示す通りである。ここで、表２に示す通り、パターン幅Ｗの異なる複数のサンプルを作製した。
【００４４】
【表２】

各サンプルについて、高誘電樹脂層２４の厚さｄを０ｍｍ、０．２ｍｍ、０．６ｍｍ、１．０ｍｍと変え、それぞれについてピーク周波数（ＭＨｚ）及びセンター周波数（ＭＨｚ）を測定した。結果を表３及び図８（ａ），（ｂ）に示す。また、高誘電樹脂層２４の厚さｄがゼロ（ｄ＝０）における測定値を基準とした時の、高誘電樹脂層２４の厚さｄによる周波数変化を表４及び図９に示す。
【００４５】
【表３】

【表４】

これらの結果より、高誘電樹脂層２４が無い場合のサンプルＡ１−１（パターンサイズ８×１．９２５ｍｍ）と同等の周波数特性をサンプルＡ１−５（パターンサイズ８×１．１２５ｍｍ）のサイズで実現しようとする場合、誘電率ε＝約９０の高誘電樹脂層２４の厚さは１．０ｍｍ以上が必要であることがわかる。また、高誘電樹脂層２４の厚さによる周波数シフト量は、下記近似式で表され、各厚さでの周波数シフト量は表５に示す通りとなる。
【００４６】
Ｙ＝ａ１×Ｘ＋ａ２×Ｘ^２
ａ１＝−３６７．８５２
ａ２＝８０．６２３４３
｜ｒ｜＝０．９５９０６８７
【００４７】
【表５】

以上の構成を有するチップ状アンテナ素子２１は、先の図２（ｂ）に示す工程までは第１の実施形態と同様に行い、形成されたアンテナ導体を覆って高誘電樹脂層２４を塗布、あるいは印刷形成することにより作製することができる。あるいは、樹脂基板上に予め高誘電樹脂層を形成した後、この上に銅箔を貼り合わせ、これをパターニングしてアンテナ導体を形成するようにしてもよい。この場合には、アンテナ導体２３は高誘電樹脂層２４の表面に形成されることになるが、同様の効果を得ることができる。
【００４８】
本実施形態のチップ状アンテナ素子２１は、アンテナ導体２３を覆って高誘電樹脂層２４を形成しているので、波長短縮効果を得ることができ、それによりアンテナ素子を小型化することができる。また、高誘電樹脂層２４は、樹脂基板２２の表面に薄い層として形成されているので、樹脂基板２２表面周辺の空間をほとんど占有することがなく、この点からもアンテナ素子の小型化に有利である。
【００４９】
（第３の実施形態）
本実施形態は、プリント配線基板の一部領域を高誘電率化し、ここにアンテナ素子を一体的に形成したものである。
【００５０】
図１０に示すように、本実施形態のアンテナ実装プリント配線基板３１は、通常のプリント配線基板３２の一部領域にアンテナ導体３３を形成し、アンテナ素子を一体化したものである。アンテナ導体３３が形成される領域には、図１０（ｂ）に拡大して示すように、先の第１の実施形態と同様、アンテナ導体３３の周囲にベアホール３４が形成されている。そして、これらベアホール３４には高誘電樹脂３５が埋め込まれている。プリント配線基板３２の他の領域には、所定の配線パターン３６が形成されており、各種部品が実装される。
【００５１】
通常のプリント配線基板では、回路設計上の都合等により、あまり高誘電率を有する基板を用いることはできない。本実施形態では、ベアホール３４に高誘電樹脂３５を埋め込むことによりプリント配線基板３２を部分的に高誘電率化して、他の回路設計に影響を与えることなくアンテナ素子の一体形成を実現している。
【００５２】
以上の構成を有するアンテナ実装プリント配線基板では、他の回路と同じ基板上に小型アンテナを作り込むことができ、チップアンテナとして別途形成し、これを実装するといった作業が不要である。また、チップアンテナを実装するための専用のランドも不要である。
【００５３】
なお、プリント配線基板を部分的に高誘電率化する手法としては、前述のようにベアホールに高誘電樹脂を埋め込み形成する方法の他、図１１に示すように、先の第２の実施形態と同様、アンテナ導体３３を覆って高誘電樹脂層３７を形成する方法により行うようにしてもよい。
【００５４】
（第４の実施形態）
【００５５】
本実施形態は、プリントアンテナの他の例を示すものである。本実施形態のプリントアンテナは、先の第１の実施形態〜第３の実施形態のアンテナ導体として適用可能である。
【００５６】
プリントアンテナ４０は、図１２に示すように、断面の大きさが例えば３ｍｍ×８．８ｍｍの矩形状を呈する薄板状の基板をエッチングすることにより、放射電極としての複数の導体４１，４２，４３，４４，４５が基板の表面に露出形成されて構成される。具体的には、プリントアンテナ４０においては、基板上に、略コ字状の導体４１と矩形状の導体４２，４３，４４，４５とが形成される。また、プリントアンテナ４０は、放射電極としての複数の矩形状の導体４６，４７，４８，４９，５０，５１，５２が基板の下面に露出形成されて構成される。このうち、導体５１は、給電用の導体であり、導体５２は、接地用の導体として用いられる。
【００５７】
さらに、プリントアンテナ４０においては、内部に銅箔が施されて底面まで貫通した複数のスルーホール４１_１，４１_２，４２_１，４２_２，４３_１，４３_２，４４_１，４４_２，４５_１，４５_２が穿設される。具体的には、スルーホール４１_１，４２_１，４２_２，４４_１，４４_２が、互いに略等間隔に一列に穿設されるとともに、スルーホール４１_２，４３_１，４３_２，４５_１，４５_２が互いに略等間隔に一列に穿設され、スルーホール４１_１，４２_１，４２_２，４４_１，４４_２からなるスルーホール群と、スルーホール４１_２，４３_１，４３_２，４５_１，４５_２からなるスルーホール群とが、互いに平行に配列される。
【００５８】
そして、スルーホール４１_１は、基板の上面側に設けられた導体４１における一の端部を始点とするとともに、下面側に設けられた導体４７における一の端部を終点として穿設され、スルーホール４１_２は、導体１１における他の端部を始点とするとともに、下面側に設けられた導体４８における一の端部を終点として穿設される。また、スルーホール４２_１は、基板の上面側に設けられた導体４２における一の端部を始点とするとともに、導体４７における他の端部を終点として穿設され、スルーホール４２_２は、導体４２における他の端部を始点とするとともに、下面側に設けられた導体４９における一の端部を終点として穿設される。さらに、スルーホール４３_１は、基板の上面側に設けられた導体４３における一の端部を始点とするとともに、導体４８における他の端部を終点として穿設され、スルーホール４３_２は、導体４３における他の端部から下面側に設けられた導体５０における一の端部を終点として穿設される。さらにまた、スルーホール４４_１は、基板の上面側に設けられた導体４４における一の端部を始点とするとともに、導体４９における他の端部を終点として穿設され、スルーホール４４_２は、導体４４における他の端部から下面側に設けられた導体５１における一の端部を終点として穿設される。また、スルーホール４５_１は、基板の上面側に設けられた導体４５における一の端部を始点とするとともに、導体５０における他の端部を終点として穿設され、スルーホール４５_２は、導体４５における他の端部から下面側に設けられた導体５２における一の端部を終点として穿設される。
【００５９】
換言すれば、導体４１，４７がスルーホール４１_１を介して電気的に導通可能に接続され、導体４１，４８がスルーホール４１_２を介して電気的に導通可能に接続される。同様に、導体４２，４７がスルーホール４２_１を介して電気的に導通可能に接続され、導体４２，４９がスルーホール４２_２を介して電気的に導通可能に接続される。さらには、導体４３，４８がスルーホール４３_１を介して電気的に導通可能に接続され、導体４３，５０がスルーホール４３_２を介して電気的に導通可能に接続される。さらにまた、導体４４，４９がスルーホール４４_１を介して電気的に導通可能に接続され、導体４４，５１がスルーホール４４_２を介して電気的に導通可能に接続される。また、導体４５，５０がスルーホール４５_１を介して電気的に導通可能に接続され、導体４５，５２がスルーホール４５_２を介して電気的に導通可能に接続される。したがって、プリントアンテナ４０においては、導体４１，４２，４３，４４，４５，４７，４８，４９，５０，５１，５２が互いに電気的に導通可能に接続され、一連の導体として構成される。
【００６０】
より具体的には、プリントアンテナ４０は、複数のスルーホール４１_１，４１_２，４２_１，４２_２，４３_１，４３_２，４４_１，４４_２，４５_１，４５_２を介してミアンダ状に接続した複数の導体４１，４２，４３，４４，４５，４７，４８，４９，５０，５１，５２を、導体１１を中心にして略コ字状に屈曲させたような一連の導体パターンを形成して構成される。
【００６１】
このように、プリントアンテナ４０は、誘電率が低い基板を用いた場合には、通常であれば、周辺に存在するグラウンドの影響を考慮して長い導体パターンを形成し、これにともない大型化してしまうところ、３次元的な構造を呈する導体パターンを形成することにより、周辺に存在するグラウンドの影響に耐え得る値までインピーダンスを大きくすることができることから大幅な小型化を図ることができ、帯域幅も広帯域化することができる。
【００６２】
このようなプリントアンテナ４０は、導体４１，４６が基板の厚さ分だけ空間的に離隔されて配置されることにより、開放端を形成する。具体的には、プリントアンテナ４０は、導体４６がプリント基板にはんだ等を介して直接的に溶着される一方で、この導体４６と高さ方向に離隔されて導体４１が設けられる。これにより、プリントアンテナ４０においては、導体４１，４６の間に比較的大きなキャパシタンスが生じる。
【００６３】
ここで、プリントアンテナ４０においては、導体４１，４６によって形成される開放端に最大電圧を生じ、この開放端が、例えば接地用の電極といったように、各種モジュールの一部としてプリント基板上に実装される他の金属体の近傍に設けられた場合には浮遊容量が発生する。
【００６４】
しかしながら、プリントアンテナ４０は、導体４１，４６を空間的に離隔して積極的に大きなキャパシタンスを形成することにより、たとえ導体４６と金属体との間の距離にバラツキが生じた場合であっても、共振周波数の変動を無視できる程度に抑制することができる。したがって、プリントアンテナ４０は、周辺に存在するグラウンドの影響に対する耐性を非常に強くすることができ、むしろ近傍にグラウンドを配置し、このグラウンドを利用してマッチングをとることができる。
【００６５】
なお、プリントアンテナ４０は、導体４１，４６の間にキャパシタンスが生じることにより、これに起因してインピーダンスが低下するが、上述したように、３次元的な構造を呈する導体パターンを形成することにより、この問題を解消することができる。
【００６６】
【発明の効果】
以上の説明からも明らかなように、本発明のチップ状アンテナ素子によれば、いわゆるプリントアンテナにおいて、十分な利得を確保しながら小型化することが可能である。また、本発明のアンテナ実装プリント配線基板によれば、他の回路と同じ基板上にアンテナ素子を作り込むことができ、チップアンテナを実装する必要はない。
【図面の簡単な説明】
【図１】本発明を適用したチップ状アンテナ素子の一例を示すものであり、（ａ）は概略斜視図、（ｂ）は断面図である。
【図２】図１に示すチップ状アンテナ素子の製造プロセスを示す概略斜視図であり、（ａ）は両面銅貼り基板を示し、（ｂ）はアンテナ導体パターニング工程、（ｃ）はベアホール形成工程、（ｄ）は高誘電樹脂埋め込み工程を示す。
【図３】高誘電樹脂の割合別に定在波比ＳＷＲを周波数に対してプロットした特性図である。
【図４】共振周波数ｆ_０及び帯域中心周波数ｆｃｅｎｔｅｒを高誘電樹脂の割合に対してプロットした特性図である。
【図５】帯域幅ＢＷと高誘電樹脂の割合の関係を示す特性図である。
【図６】本発明を適用したチップ状アンテナ素子の他の例を示すものであり、（ａ）は概略斜視図、（ｂ）は断面図である。
【図７】実験に使用したサンプルの構成を示すものであり、（ａ）は斜視図、（ｂ）はアンテナ導体パターンの平面図である。
【図８】高誘電樹脂層の厚さによる特性の相違を示すものであり、（ａ）は各厚さにおけるパターン幅とピーク周波数の関係を示す特性図、（ｂ）は各厚さにおけるパターン幅とセンター周波数の関係を示す特性図である。
【図９】高誘電樹脂層の厚さによる周波数変化を示す特性図である。
【図１０】本発明を適用したアンテナ実装プリント配線基板の一例を示す概略斜視図である。
【図１１】本発明を適用したアンテナ実装プリント配線基板の他の例を示す概略斜視図である。
【図１２】プリントアンテナの一例を模式的に示す斜視図である。
【符号の説明】
１，２１ チップ状アンテナ素子
２，２２ 樹脂基板
３，２３，３３ アンテナ導体
４，３４ ベアホール
５，３５ 高誘電樹脂
２４，３７ 高誘電樹脂層
３２ プリント配線基板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a chip-shaped antenna element in which an antenna conductor is formed on a resin substrate, and further relates to an antenna-mounted printed wiring board in which an antenna conductor is formed directly on a part of a printed wiring board.
[0002]
[Prior art]
2. Description of the Related Art In recent years, various wireless technologies such as a mobile communication device such as a mobile phone and a wireless LAN (Local Area Network) based on the IEEE (Institute of Electronics and Electronics Engineers) 802.11 standard have been developed. Along with this, a technology relating to an antenna element for performing wireless communication has been developed.
[0003]
The antenna element is a member inevitably provided for performing wireless communication, and for example, an antenna element in which a radiation electrode, a surface electrode, and the like are formed on a columnar dielectric is known. This type of antenna element is generally used by being installed outside the communication device body. However, in the case of an antenna element that is used by being disposed outside, problems such as hindering miniaturization, requiring high mechanical strength, increasing the number of parts, and the like arise.
[0004]
Therefore, as an alternative antenna element, a chip-shaped antenna element that can be surface-mounted on a printed wiring board provided in a device main body has been proposed (for example, see Patent Documents 1 and 2).
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-221537
[0006]
[Patent Document 2]
JP-A-3-192804
[0007]
[Problems to be solved by the invention]
By the way, there are various types of chip-shaped antenna elements, and a typical one uses a high dielectric material such as ceramic for a base material. For example, Patent Document 1 mentioned above discloses a surface mount type in which a through hole is provided in parallel with the surface of a dielectric substrate, a radiation electrode is formed in the through hole, and a feed electrode is formed on a side surface of the dielectric substrate. An antenna is disclosed.
[0008]
However, chip antennas using high-dielectric materials such as ceramics have the disadvantage that the high-dielectric materials themselves are expensive and the processing is complicated, which leads to a reduction in productivity and an increase in manufacturing costs. Invite.
[0009]
For the purpose of solving such inconveniences, there has been proposed a printed antenna in which a printed wiring board having a copper foil on both sides is used as a base material and an antenna conductor is formed on the printed wiring board by using a photoetching technique. In this printed antenna, an inexpensive printed wiring board is used as a base material, and processing is easy, so that the manufacturing cost can be significantly reduced.
[0010]
However, in the printed antenna, since the dielectric constant of the base material of the printed wiring board, for example, the glass epoxy resin base material, is small, it is necessary to increase the length of the antenna conductor in order to secure the gain. Hindered. Therefore, improvement is desired.
[0011]
As a technique for increasing the dielectric constant of the base material, for example, there is a technique described in Patent Document 2. In the technique described in Patent Document 2, two types of dielectrics having different dielectric constants are used, and a dielectric having a high dielectric constant is disposed below the antenna conductor.
[0012]
However, it is difficult to apply the composite technology described in Patent Document 2 to a printed wiring board as it is, and it is difficult to insert a high dielectric material in a shape as described in each drawing of Patent Document 2 in a printed antenna. Is not realistic.
[0013]
The present invention has been proposed in order to solve such disadvantages of the prior art, and provides a chip-shaped antenna element which can be miniaturized while securing a sufficient gain in a so-called printed antenna. The purpose is to: Still another object of the present invention is to provide a completely novel antenna-mounted printed wiring board which does not require an antenna element to be mounted on a printed wiring board.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the chip-shaped antenna element of the present invention has an antenna conductor formed on a resin substrate, a bare hole is formed on the resin substrate, and a high dielectric resin is embedded in the bare hole. It is characterized by having. Alternatively, an antenna conductor is formed on a resin substrate, and at least a part of the antenna conductor is covered with a high dielectric resin.
[0015]
In the chip-shaped antenna element having each of the above configurations, since a high dielectric constant is ensured by the high dielectric resin, a sufficient gain can be obtained even if the length of the antenna conductor is shortened. Since the high dielectric resin is formed by filling the bare holes provided on the printed wiring board or by being applied to the surface of the printed wiring board, the high dielectric resin is easily compounded into the printed wiring board. Since it does not occupy the space around the printed wiring board, it does not hinder miniaturization.
[0016]
On the other hand, in the antenna-mounted printed wiring board of the present invention, a bare hole is formed in a partial region of the printed wiring board on which a wiring pattern is formed, and a high-dielectric resin is embedded in the bare hole. An antenna conductor is formed in an embedded region. Alternatively, an antenna conductor is formed in a partial area of a printed wiring board on which a wiring pattern is formed, and at least a part of the antenna conductor is covered with a high dielectric resin.
[0017]
In the antenna-mounted printed wiring board having each of the above configurations, similarly to the above-described chip-shaped antenna element, a high dielectric resin is easily compounded, and a sufficient gain can be obtained even if the length of the antenna conductor is shortened. Further, in the antenna-mounted printed wiring board of the present invention, the antenna conductor is formed on the printed wiring board, and it is not necessary to mount the antenna element on the printed wiring board.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a chip-shaped antenna element and an antenna-mounted printed wiring board to which the present invention is applied will be described with reference to the drawings.
[0019]
(1st Embodiment)
The present embodiment is an example of a printed antenna in which a resin substrate is used as a base material and an antenna conductor is formed on the surface thereof, in which a high dielectric resin is embedded in a bare hole formed in the resin substrate.
[0020]
FIG. 1 shows a chip antenna element of the present embodiment. This chip-shaped antenna element 1 is formed by patterning an antenna conductor 3 on a resin substrate 2 serving as a base material, and is a so-called printed antenna.
[0021]
As the resin substrate 2, any one can be used as long as it is generally used as a base material of a printed wiring board. Specifically, a paper phenol substrate (XXP, XPC, etc.), a paper polyester substrate (FR-2), a paper epoxy substrate (FR-3), a glass paper composite epoxy substrate (CEM-1), a glass nonwoven paper composite epoxy Substrate (CHE-3), glass cloth epoxy substrate (G-10), glass cloth epoxy substrate (FR-4), and the like can be given. The symbols in parentheses are the American Electrical Manufacturers Association (NEMA) symbols. Among these, a glass cloth epoxy substrate (FR-4) having little hygroscopicity and dimensional change and having self-extinguishing properties is most preferable.
[0022]
The antenna conductor 3 can be formed by patterning (etching) a copper foil laminated on the resin substrate 2 by a photolithography technique, and can be formed simultaneously with another electrode pattern or the like. As the type of the antenna conductor 3, any shape can be adopted. For example, a so-called inverted-F antenna in which the conductor is formed in an inverted F shape, a so-called helical antenna in which the conductor is formed in a coil shape, a meander-shaped antenna An antenna and the like can be given. Here, a meandering (comb-shaped) antenna pattern is formed as a meandering line.
[0023]
As described above, by forming the chip-shaped antenna element 1 using a printed wiring board having copper foils on both sides, the chip-shaped antenna element can be easily reduced in size and thickness, and the manufacturing cost can be reduced. Connect. However, since the dielectric constant of the resin substrate 2 as the base material is low, the length of the antenna conductor 3 has to be increased as it is, which hinders miniaturization. For example, the permittivity (1 MHz) of the paper phenol board (XXP) is 4.3, the permittivity (1 MHz) of the paper epoxy board (FR-3) is 4.1, and the permittivity of the glass cloth epoxy board (G-10). The ratio (1 MHz) is 4.8, and the dielectric constant (1 MHz) of the glass cloth epoxy substrate (FR-4) is about 4.5 to 4.8, which is insufficient as the dielectric constant of the chip-shaped antenna element.
[0024]
Thus, in the present embodiment, the shortage of the dielectric constant is compensated for by forming the bare hole 4 in the resin substrate 2 and filling the bare hole 4 with the high dielectric resin 5. Here, the bare hole 4 may be formed with the same size as that formed for interlayer connection or the like in a normal printed wiring board. Therefore, in the process of forming other bare holes and through holes, the bare holes 4 are formed. And through holes can be formed simultaneously. However, so-called through-hole plating is not performed on the bare hole 4. Although the bare hole 4 is a through hole here, the present invention is not limited to this, and the bare hole 4 does not have to penetrate the resin substrate 2.
[0025]
The bare hole 4 is formed only in a portion where the antenna conductor 3 is not formed so as to avoid the antenna conductor 3. This is due to manufacturing reasons or the like. In some cases, a bare hole 4 may be formed below the antenna conductor 3 and a high dielectric resin 5 may be embedded therein.
[0026]
The high dielectric resin 5 embedded in the bare hole 4 preferably has a dielectric constant higher than at least the dielectric constant of the resin substrate 2, and preferably uses a high dielectric resin material having a dielectric constant of about 20 to 40. Examples of such a high dielectric resin material include an imide resin and the like, and a resin material in which fine particles of a high dielectric constant material such as ceramics are dispersed can also be used as the high dielectric resin material.
[0027]
The formation density of the above-mentioned bare holes 4 is arbitrary and may be set to an extent that a sufficient dielectric constant can be ensured. However, if too many bare holes 4 are formed, the strength of the entire chip antenna element is reduced. There is. The optimum range depends on the dielectric constant of the high dielectric resin 5 to be embedded, but is, for example, 30 to 100 / cm.²It is preferable to set to about. It is conceivable that the resin substrate 2 itself is formed of a high dielectric resin material.
[0028]
The above is the configuration of the chip-shaped antenna element 1 of the present embodiment. In the chip-shaped antenna element 1 of the present embodiment, the high dielectric resin 5 is embedded near the antenna conductor 3, so that the wavelength shortening effect can be obtained. It is possible to reduce the size of the antenna element. Further, since the high dielectric resin 5 is embedded in the resin substrate 2 and does not occupy the space around the surface of the resin substrate 2, this is also advantageous in reducing the size of the antenna element.
[0029]
Next, a method for manufacturing the chip-shaped antenna element 1 will be described. In order to manufacture the chip-shaped antenna element 1, first, as shown in FIG. 2A, a double-sided copper-clad substrate having a copper foil 12 adhered to both sides of a resin substrate 11 is prepared, and as shown in FIG. The copper foil 12 is patterned as described above to form the comb-shaped antenna conductor 13. The patterning of the copper foil 12 may be performed by a normal photolithography technique together with other electrode patterns and the like. That is, a photoresist layer is formed on the copper foil 12, and the photoresist layer is exposed, developed and patterned to form a resist pattern. Then, the copper foil 12 is etched using the resist pattern as a mask. The etching is performed by, for example, wet etching.
[0030]
After patterning and forming the antenna conductor 13 as described above, a bare hole 14 is formed as shown in FIG. The bare hole 14 can be easily formed by, for example, machining using a drill.
[0031]
Next, as shown in FIG. 2D, the bare hole 14 is filled with a high dielectric resin 15 and the resin substrate 11 is cut into a chip size to complete a chip-shaped antenna element. The embedding of the high dielectric resin 15 may be performed by coating or printing.
[0032]
In the above process, after the antenna conductor 13 is formed in advance, the formation of the bare hole 14 and the embedding of the high dielectric resin 15 are performed. After embedding with the dielectric resin 15, the copper foil 12 may be adhered and the antenna conductor 13 and the like may be patterned. In this case, a bare hole 14 in which a high dielectric resin 15 is embedded also exists below the antenna conductor 13.
[0033]
The present inventors evaluated the frequency characteristics of a chip-shaped antenna element in which a hole was filled with a high dielectric resin in order to confirm the effect of resin embedding. The evaluation was performed on the influence of the high dielectric resin using electromagnetic field analysis software.
[0034]
In the experiment, a hole was made in the resin substrate (relative dielectric constant 4.49) of the chip-shaped antenna element having a meander line as shown in FIG. 1, and the hole was filled with a high dielectric resin having a relative dielectric constant of 60 for analysis. Was. The amount of the high dielectric resin is represented by the volume ratio to the chip-shaped antenna element body based on the following equation.
Ratio of high dielectric resin = (volume of high dielectric resin) / (volume of chip antenna element)
[0035]
As a calculation model, one having one row of holes filled with a high dielectric resin (1 line), two rows (2 lines), three rows (3 lines), and one having no holes (0 line) Were designed and the calculation results were compared. The calculation model is obtained by mounting a chip-shaped antenna element (size: 8 × 3 × 0.65 mm) on an evaluation substrate (size: 50 × 17 × 0.8 mm) of the back surface GND. Table 1 shows the bandwidth BW, band center frequency fcenter, and resonance frequency f of each sample.₀, The voltage standing wave ratio VSWR, and the ratio (%) of the high dielectric resin.
[0036]
[Table 1]

FIG. 3 is a graph in which the standing wave ratio SWR is plotted with respect to the frequency according to the ratio of the high dielectric resin. It can be seen that as the ratio of the high dielectric resin increases, the peak shifts to the lower frequency side as a whole. FIG. 4 shows the resonance frequency f₀And the center frequency fcenter of the band is plotted with respect to the ratio of the high dielectric resin, and FIG. 5 shows the relationship between the bandwidth BW and the ratio of the high dielectric resin.
[0037]
In this calculation model, when a hole is filled with a high dielectric resin having a relative dielectric constant of 60, the resonance frequency shift effect of the high dielectric resin is linearly approximated. It becomes a frequency shift.
[0038]
(Second embodiment)
In this embodiment, instead of embedding a high dielectric resin in a resin substrate, a high dielectric resin layer is formed so as to cover the surface of the antenna conductor.
[0039]
FIG. 6 shows a chip antenna element 21 of the present embodiment. The formation of the meandering antenna conductor 23 on the resin substrate 22 is the same as that of the first embodiment, and the configuration of each is also the same as that of the first embodiment. .
[0040]
In the chip-shaped antenna element 21 of the present embodiment, no bare hole is formed in the resin substrate 22 and no high dielectric resin is embedded. Instead, a high dielectric resin layer 24 is formed to cover the antenna conductor 23.
[0041]
The high-dielectric resin layer 24 can be formed using the same high-dielectric resin embedded in the bare hole in the first embodiment, and can be easily formed by coating or printing. Can be.
[0042]
The high dielectric resin layer 24 is preferably formed so as to cover the entire antenna conductor 23, but is not limited to this, and may be formed so as to cover a part of the antenna conductor 23. However, the effect is higher as the area covering the antenna conductor 23 is larger, and in order to realize an effective effect, the antenna conductor 23 is preferably formed so as to cover 50% or more of the antenna conductor 23. The thickness of the high dielectric resin layer 24 can be arbitrarily set, but is preferably about 10 to 1000 μm. If the thickness is below the lower limit of 10 μm, a sufficient effect may not be obtained. Conversely, if the thickness exceeds the upper limit of 1000 μm, the high dielectric resin layer 24 occupies the space around the surface of the resin substrate 22 and hinders miniaturization.
[0043]
In fact, the present inventors have conducted the following experiment to study the thickness of the high dielectric resin layer 24. The sample used in the experiment is shown in FIG. As the resin substrate 22, an FR-4 (MCL-BE-67G (H)) substrate having a thickness of 0.6 mm was used. The potting material used for forming the high dielectric resin layer 24 is an imide resin (dielectric constant ε = about 90). Each dimension of the pattern of the antenna conductor 23 is as shown in FIG. Here, as shown in Table 2, a plurality of samples having different pattern widths W were produced.
[0044]
[Table 2]

For each sample, the thickness d of the high dielectric resin layer 24 was changed to 0 mm, 0.2 mm, 0.6 mm, and 1.0 mm, and the peak frequency (MHz) and the center frequency (MHz) were measured for each. The results are shown in Table 3 and FIGS. 8 (a) and 8 (b). In addition, Table 4 and FIG. 9 show frequency changes depending on the thickness d of the high dielectric resin layer 24 when the thickness d of the high dielectric resin layer 24 is zero (d = 0) as a reference.
[0045]
[Table 3]

[Table 4]

From these results, the frequency characteristics equivalent to that of sample A1-1 (pattern size 8 × 1.925 mm) without the high dielectric resin layer 24 were realized with the size of sample A1-5 (pattern size 8 × 1.125 mm). In this case, it is understood that the thickness of the high dielectric resin layer 24 having the dielectric constant ε = about 90 needs to be 1.0 mm or more. The amount of frequency shift depending on the thickness of the high dielectric resin layer 24 is represented by the following approximate expression, and the amount of frequency shift at each thickness is as shown in Table 5.
[0046]
Y = a1 × X + a2 × X²
a1 = −367.8852
a2 = 80.24343
| R | = 0.9590687
[0047]
[Table 5]

The chip-shaped antenna element 21 having the above configuration is performed in the same manner as in the first embodiment up to the step shown in FIG. 2B, and a high dielectric resin layer 24 is applied so as to cover the formed antenna conductor. Alternatively, it can be produced by printing. Alternatively, an antenna conductor may be formed by forming a high dielectric resin layer on a resin substrate in advance and then bonding a copper foil thereon and patterning the copper foil. In this case, the antenna conductor 23 is formed on the surface of the high dielectric resin layer 24, but the same effect can be obtained.
[0048]
In the chip-shaped antenna element 21 of the present embodiment, since the high dielectric resin layer 24 is formed so as to cover the antenna conductor 23, an effect of shortening the wavelength can be obtained, and the antenna element can be downsized. Further, since the high dielectric resin layer 24 is formed as a thin layer on the surface of the resin substrate 22, it hardly occupies the space around the surface of the resin substrate 22, which is advantageous for miniaturization of the antenna element. It is.
[0049]
(Third embodiment)
In this embodiment, a part of the printed wiring board has a high dielectric constant, and an antenna element is formed integrally therewith.
[0050]
As shown in FIG. 10, an antenna-mounted printed wiring board 31 of the present embodiment has an antenna conductor 33 formed in a partial area of a normal printed wiring board 32 and integrated with an antenna element. In a region where the antenna conductor 33 is formed, a bare hole 34 is formed around the antenna conductor 33 as shown in FIG. In these bare holes 34, a high dielectric resin 35 is embedded. In another area of the printed wiring board 32, a predetermined wiring pattern 36 is formed, and various components are mounted.
[0051]
In a general printed wiring board, a board having a very high dielectric constant cannot be used due to circuit design convenience and the like. In the present embodiment, the printed wiring board 32 is partially made to have a high dielectric constant by embedding the high dielectric resin 35 in the bare hole 34, thereby realizing the integral formation of the antenna element without affecting other circuit designs. .
[0052]
In the antenna-mounted printed wiring board having the above configuration, a small antenna can be formed on the same substrate as other circuits, and there is no need to separately form a chip antenna and mount it. Also, a dedicated land for mounting the chip antenna is not required.
[0053]
As a technique for partially increasing the dielectric constant of the printed wiring board, in addition to the method of embedding a high dielectric resin in the bare hole as described above, as shown in FIG. Similarly, it may be performed by a method of forming the high dielectric resin layer 37 covering the antenna conductor 33.
[0054]
(Fourth embodiment)
[0055]
This embodiment shows another example of the printed antenna. The printed antenna of this embodiment is applicable as the antenna conductor of the first to third embodiments.
[0056]
As shown in FIG. 12, a plurality of conductors 41, 42, and 43 as radiating electrodes are formed by etching a thin plate-shaped substrate having a rectangular cross section of, for example, 3 mm × 8.8 mm. , 44, 45 are formed by being exposed on the surface of the substrate. Specifically, in the printed antenna 40, a substantially U-shaped conductor 41 and rectangular conductors 42, 43, 44, and 45 are formed on a substrate. In addition, the printed antenna 40 is configured such that a plurality of rectangular conductors 46, 47, 48, 49, 50, 51, and 52 as radiation electrodes are formed on the lower surface of the substrate so as to be exposed. Among them, the conductor 51 is a power supply conductor, and the conductor 52 is used as a grounding conductor.
[0057]
Further, in the printed antenna 40, a plurality of through holes 41 which are provided with copper foil inside and penetrate to the bottom surface are provided.₁, 41₂, 42₁, 42₂, 43₁, 43₂, 44₁, 44₂, 45₁, 45₂Is drilled. Specifically, the through hole 41₁, 42₁, 42₂, 44₁, 44₂Are formed in a line at substantially equal intervals from each other, and₂, 43₁, 43₂, 45₁, 45₂Are formed in a line at substantially equal intervals from each other, and through holes 41 are formed.₁, 42₁, 42₂, 44₁, 44₂Through-hole group consisting of₂, 43₁, 43₂, 45₁, 45₂Are arranged in parallel with each other.
[0058]
And the through hole 41₁Are formed with one end of the conductor 41 provided on the upper surface side of the substrate as a starting point and one end of the conductor 47 provided on the lower surface side as an end point.₂Is formed with the other end of the conductor 11 as a starting point and one end of the conductor 48 provided on the lower surface side as an end point. Also, the through hole 42₁Are formed with one end of the conductor 42 provided on the upper surface side of the substrate as a starting point and the other end of the conductor 47 as an end point.₂Is formed with the other end of the conductor 42 as a starting point and the one end of the conductor 49 provided on the lower surface side as an end point. Furthermore, through holes 43₁Is formed with one end of the conductor 43 provided on the upper surface side of the substrate as a start point and the other end of the conductor 48 as an end point,₂Is drilled with one end of the conductor 50 provided on the lower surface side from the other end of the conductor 43 as an end point. Furthermore, the through hole 44₁Are formed with one end of the conductor 44 provided on the upper surface side of the substrate as a start point and the other end of the conductor 49 as an end point,₂Is drilled with one end of the conductor 51 provided on the lower surface side from the other end of the conductor 44 as an end point. Also, through-hole 45₁Are formed with one end of the conductor 45 provided on the upper surface side of the substrate as a starting point and the other end of the conductor 50 as an end point.₂Is drilled with one end of the conductor 52 provided on the lower surface side from the other end of the conductor 45 as an end point.
[0059]
In other words, the conductors 41 and 47 are formed in the through holes 41.₁And the conductors 41 and 48 are connected through the through hole 41₂Are electrically connected to each other. Similarly, the conductors 42 and 47 are₁And the conductors 42 and 49 are connected through the through holes 42₂Are electrically connected to each other. Further, the conductors 43 and 48 are₁The conductors 43 and 50 are electrically connected to each other through the₂Are electrically connected to each other. Furthermore, the conductors 44 and 49 are formed through the through holes 44.₁And the conductors 44 and 51 are electrically connected to each other through the through hole 44.₂Are electrically connected to each other. Also, the conductors 45 and 50 are₁Are electrically connected to each other through the conductors 45 and 52, and the conductors 45 and 52 are₂Are electrically connected to each other. Therefore, in the printed antenna 40, the conductors 41, 42, 43, 44, 45, 47, 48, 49, 50, 51, and 52 are electrically connected to each other and configured as a series of conductors.
[0060]
More specifically, the printed antenna 40 has a plurality of through holes 41.₁, 41₂, 42₁, 42₂, 43₁, 43₂, 44₁, 44₂, 45₁, 45₂A plurality of conductors 41, 42, 43, 44, 45, 47, 48, 49, 50, 51, 52, which are connected in a meandering manner via the conductor 11, are bent in a substantially U-shape around the conductor 11. It is formed by forming a series of conductor patterns.
[0061]
As described above, when a substrate having a low dielectric constant is used, the printed antenna 40 normally forms a long conductor pattern in consideration of the influence of the ground present in the vicinity, and is enlarged accordingly. However, by forming a conductor pattern having a three-dimensional structure, the impedance can be increased to a value that can withstand the influence of the ground present in the periphery, so that the size can be significantly reduced, and the bandwidth can be reduced. Can also be widened.
[0062]
Such a printed antenna 40 forms an open end when the conductors 41 and 46 are spatially separated by the thickness of the substrate. Specifically, in the printed antenna 40, the conductor 46 is directly welded to the printed circuit board via solder or the like, and the conductor 41 is provided apart from the conductor 46 in the height direction. As a result, in the printed antenna 40, a relatively large capacitance is generated between the conductors 41 and 46.
[0063]
Here, in the printed antenna 40, a maximum voltage is generated at an open end formed by the conductors 41 and 46, and the open end is mounted on a printed circuit board as a part of various modules, such as an electrode for grounding. If it is provided in the vicinity of another metal body to be formed, a stray capacitance is generated.
[0064]
However, the printed antenna 40 positively forms a large capacitance by spatially separating the conductors 41 and 46, so that even if the distance between the conductor 46 and the metal body varies, the printed antenna 40 may vary. In addition, the variation of the resonance frequency can be suppressed to a negligible level. Therefore, the printed antenna 40 can make the resistance to the influence of the ground present in the periphery very strong. Rather, it is possible to arrange the ground nearby and use this ground to perform matching.
[0065]
In the printed antenna 40, the impedance is reduced due to the capacitance generated between the conductors 41 and 46. However, as described above, the printed antenna 40 is formed by forming the conductor pattern having a three-dimensional structure. This problem can be solved.
[0066]
【The invention's effect】
As is clear from the above description, according to the chip antenna element of the present invention, it is possible to reduce the size of a so-called printed antenna while securing a sufficient gain. Moreover, according to the antenna-mounted printed wiring board of the present invention, the antenna element can be built on the same substrate as other circuits, and it is not necessary to mount a chip antenna.
[Brief description of the drawings]
FIG. 1 shows an example of a chip antenna element to which the present invention is applied, wherein (a) is a schematic perspective view and (b) is a cross-sectional view.
2A and 2B are schematic perspective views showing a manufacturing process of the chip-shaped antenna element shown in FIG. 1, wherein FIG. 2A shows a double-sided copper-clad substrate, FIG. 2B shows an antenna conductor patterning step, and FIG. , (D) show a high dielectric resin embedding step.
FIG. 3 is a characteristic diagram in which a standing wave ratio SWR is plotted with respect to frequency according to a ratio of a high dielectric resin.
FIG. 4 shows a resonance frequency f₀FIG. 4 is a characteristic diagram in which a band center frequency fcenter and a ratio of a high dielectric resin are plotted.
FIG. 5 is a characteristic diagram showing a relationship between a bandwidth BW and a ratio of a high dielectric resin.
6A and 6B show another example of a chip antenna element to which the present invention is applied, wherein FIG. 6A is a schematic perspective view, and FIG. 6B is a cross-sectional view.
FIGS. 7A and 7B show a configuration of a sample used in an experiment, wherein FIG. 7A is a perspective view and FIG. 7B is a plan view of an antenna conductor pattern.
FIGS. 8A and 8B show differences in characteristics depending on the thickness of a high dielectric resin layer, wherein FIG. 8A is a characteristic diagram showing a relationship between a pattern width and a peak frequency at each thickness, and FIG. FIG. 4 is a characteristic diagram illustrating a relationship between a width and a center frequency.
FIG. 9 is a characteristic diagram showing a frequency change according to a thickness of a high dielectric resin layer.
FIG. 10 is a schematic perspective view showing an example of an antenna-mounted printed wiring board to which the present invention has been applied.
FIG. 11 is a schematic perspective view showing another example of an antenna-mounted printed wiring board to which the present invention is applied.
FIG. 12 is a perspective view schematically showing an example of a printed antenna.
[Explanation of symbols]
1,21 chip antenna element
2,22 resin substrate
3,23,33 Antenna conductor
4,34 Bear hole
5,35 High dielectric resin
24,37 High dielectric resin layer
32 Printed wiring board

Claims (12)

An antenna conductor is formed on a resin substrate,
A chip antenna element, wherein a bare hole is formed in the resin substrate, and a high dielectric resin is embedded in the bare hole. The chip-shaped antenna element according to claim 1, wherein the bare hole is formed so as to avoid the antenna conductor. The chip-shaped antenna element according to claim 1, wherein the resin substrate is made of a glass cloth epoxy substrate. An antenna conductor is formed on a resin substrate, and at least a part of the antenna conductor is covered with a high dielectric resin. The chip-shaped antenna element according to claim 4, wherein the whole of the antenna conductor is covered with a high dielectric resin. The chip-shaped antenna element according to claim 4, wherein the resin substrate is made of a glass cloth epoxy substrate. A bare hole is formed in a part of the printed wiring board on which the wiring pattern is formed, and a high dielectric resin is embedded in the bare hole,
An antenna-mounted printed wiring board, wherein an antenna conductor is formed in a region where the high dielectric resin is embedded. The antenna printed circuit board according to claim 7, wherein the bare hole is formed so as to avoid the antenna conductor. The printed circuit board according to claim 7, wherein the printed circuit board is made of a glass cloth epoxy substrate. An antenna-mounted printed wiring board, wherein an antenna conductor is formed in a partial area of the printed wiring board on which a wiring pattern is formed, and at least a part of the antenna conductor is covered with a high dielectric resin. 11. The printed circuit board according to claim 10, wherein the entire antenna conductor is covered with a high dielectric resin. 11. The printed circuit board according to claim 10, wherein the printed circuit board is a glass cloth epoxy board as a base material.

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