JPH10303565A - Multilayered circuit substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit substrate where no undesired stray capacity is formed between a high-impedance part in terms of a high frequency in a circuit element and a ground pattern, when a ground pattern is formed so that it is located between main surfaces. SOLUTION: In a circuit substrate, a window 16 is formed on a ground pattern 10a that is closest to a circuit element 13 on a main surface to reduce a stray, capacity so that the window 16 opposes a high-impedance part 15 in terms of a high frequency in the circuit element 13. Another ground pattern 11 is preferably formed so that it overlaps with the window 16, and a ground pattern 10a is electrically connected to the ground pattern 11 via a through hole 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer circuit board, and more particularly to a multilayer circuit board suitable for forming a high-frequency circuit for an electronic tuner or the like.

[0002]

2. Description of the Related Art FIG. 3 shows a tuner 2 having a circuit board 1 which is of interest to the present invention. In such a tuner 2, in order to reduce the size of a circuit module configured with the circuit board 1, circuit elements for configuring a high-frequency circuit, that is, a plurality of electronic components 3,
4, 5, 6, and 7 and the circuit patterns (not shown in FIG. 3) are arranged on each main surface of the circuit board 1, respectively.

The circuit board 1 is provided with a shield case 8
, So as to prevent interference with circuit elements outside of the tuner 2. However, as described above, when a plurality of electronic components 3, 4, 5, 6, 7 and the like for constituting a high-frequency circuit and circuit elements such as circuit patterns are arranged on each main surface of the circuit board 1. The electronic components 3 to 5 and the like arranged on one main surface and the electronic components 6 and 7 and the like arranged on the other main surface jump over the circuit board 1 and electromagnetically interfere with each other,
Interference between one another can occur undesirably.

As a measure against the above-mentioned problem, it is preferable to use a multilayer circuit board 9 as shown in FIG. FIG.
FIG. 3 shows a tuner 2a including a multilayer circuit board 9;
FIG. 4, in order to facilitate comparison with the configuration shown in FIG. 3 and to omit redundant description, elements corresponding to the elements shown in FIG. 3 are denoted by the same reference numerals.

In the multilayer circuit board 9 shown in FIG.
For example, two layers of ground patterns 10 and 11 are located between the main surfaces. According to this multilayer circuit board 9,
Since the ground patterns 10 and 11 can have a shielding effect, the electronic components 3 to 5 disposed on the upper main surface and the electronic components 6 and 7 disposed on the lower main surface interfere with each other. This can be advantageously prevented.

Incidentally, in addition to the above-mentioned ground patterns 10 and 11, signal lines and power supply lines may be arranged inside the multilayer circuit board 9.

[0007]

However, even if the structure shown in FIG. 4 is adopted, the following problem may be encountered. FIG. 5 is a plan view showing a part of the multilayer circuit board 9 shown in FIG. 4, and FIG. 6 is a sectional view taken along line VI-VI in FIG. FIGS. 5 and 6 show electronic components such as ICs arranged on the upper main surface of multilayer circuit board 9.
Circuit patterns 13 and 14 for soldering the terminals of the component 3 and the terminals of the coil 4 with solder 12 for electrical connection are shown. FIG. 6 also shows the ground patterns 10 and 11 described above.

As shown in FIG. 6, the circuit pattern 13 faces part of the ground pattern 10. As a result of such facing, more or less stray capacitance or stray capacitance results in this part. Also,
As is well shown in FIG. 5, the circuit pattern 13 has a relatively narrow portion, that is, a high-frequency high-impedance portion 15. As described above, the high-frequency high-impedance portion 15 is particularly susceptible to the stray capacitance.

For example, when a variable tuning circuit as shown in FIG. 7A is constructed using such a multilayer circuit board 9, if the above-mentioned stray capacitance exists, FIG.
As shown in the figure, the stray capacitance Cs is equivalent to connecting the stray capacitance Cs in parallel to the variable capacitance Cv including the capacitance due to the varactor diode or the like. Therefore, the following problem is caused.

The capacitance change ratio of the variable capacitance Cv becomes smaller,
In some cases, a frequency variable range required for the tuning circuit cannot be obtained. Even if the stray capacitance Cs occurs, it is necessary to reduce the inductance L in order to obtain the same resonance frequency. If the inductance L is reduced, the circuit impedance and Q are reduced, and the high frequency characteristics are maintained over a wide band. Becomes difficult.

As a method of reducing the stray capacitance Cs, it is conceivable to increase the distance between the circuit pattern 13 and the ground pattern 10 or to reduce the relative permittivity of the material existing in the distance in FIG. However, the former measure hinders the thinning of components such as tuners,
Neither of the latter measures is an effective measure because it causes a significant increase in cost.

An object of the present invention is to provide a multilayer circuit board which can solve the above-mentioned problems.

[0013]

According to the present invention, a circuit element for constituting a high-frequency circuit is arranged on each main surface, and a ground pattern for preventing interference between circuit elements on each main surface is provided. In order to solve the above-mentioned technical problem, the ground pattern is provided with a window at a portion opposed to a high-frequency high-impedance portion of the circuit element, which is located between the main surfaces and directed to the multilayer circuit board. It is characterized by forming.

In the present invention, when the ground pattern is formed so as to form a plurality of layers between the main surfaces, a window is provided in the ground pattern closest to the high-frequency high-impedance portion among the plurality of ground patterns. It is preferably formed. Further, as described above, when the ground pattern is formed so as to form a plurality of layers between the main surfaces, at least one layer of the ground pattern other than the above-described window-formed ground pattern has a portion overlapping the window. Is preferred.

Similarly, when the ground pattern is formed so as to form a plurality of layers between the main surfaces, the ground pattern in which the above-described window is formed is formed at the periphery of the window through at least one through hole. It is preferable to be electrically connected to at least one ground pattern other than the ground pattern.

[0016]

FIG. 1 is a plan view showing a part of a multilayer circuit board 9a according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line II-II in FIG. 1. FIGS. 1 and 2 correspond to FIGS. 5 and 6, respectively. In FIGS. 1 and 2, the elements corresponding to the elements shown in FIG. 5 or FIG. Reference numerals are assigned.

In this multilayer circuit board 9a, similarly to the multilayer circuit board 9 shown in FIGS. 5 and 6, circuit elements for forming a high-frequency circuit are arranged on each main surface.
1 and 2, as such circuit elements, electronic components, ie, IC components 3, coils 4, and circuit patterns 13 arranged on the upper main surface of the multilayer circuit board 9a are shown.
14 and the like, and an electronic component, that is, an IC component 6 arranged on the lower main surface of the multilayer circuit board 9a is illustrated. The terminals of the electronic components such as the IC component 3 and the coil 4 are soldered to the circuit patterns 13 and 14 and the like by the solder 12.

Also in this multilayer circuit board 9a,
Similar to the multilayer circuit board 9 described above, the two-layer ground pattern 1 for preventing interference between the circuit elements 3, 4, 13, 14 and the like on the upper main surface and the circuit elements 6 and the like on the lower main surface.
0a and 11 are located between these main surfaces. For example, the circuit pattern 13 includes a high-impedance portion 15 in high frequency. As a characteristic configuration of this embodiment, a window 16 is formed in the ground pattern 10a which is closest to the portion 15, that is, in which the stray capacitance which cannot be ignored with the portion 15 is most easily formed. In FIG. 1, the position of the window 16 is indicated by a broken line. This window 16 has a ground pattern 10a.
Are formed immediately below the high-impedance portion 15 in FIG.

As described above, by forming the window 16 in the ground pattern 10a, it is possible to extremely reduce the stray capacitance that may be formed between the high-impedance portion 15 in high frequency and the ground pattern 10a. it can. The ground pattern 11 which is a ground pattern other than the ground pattern 10a in which the window 16 is formed preferably has a portion 17 overlapping the window 16. The portion 17 of the ground pattern 11 that overlaps the window 16 functions to prevent interference between circuit elements on each main surface of the multilayer circuit board 9a, which may occur due to the formation of the window 16.

Since the above-described portion 17 faces the high-impedance portion 15 through the window 16, the formation of a stray capacitance between these portions 15 and 17 is avoided. Absent.
However, since the distance from the circuit pattern 13 having the portion 15 to the ground pattern 11 having the portion 17 is longer than the distance from the circuit pattern 13 to the ground pattern 10a, the stray capacitance that can be formed between the portions 15 and 17 is increased. Can be negligibly small.

Further, in this embodiment, the ground pattern 10 a in which the window 16 is formed is electrically connected to another ground pattern 11 via a through hole 18. The through hole 18 is located at the periphery of the window 16. As described above, by connecting the ground patterns 10a and 11 to each other through the through hole 18, the ground impedance can be reduced and the shielding effect can be enhanced.

It should be noted that the above-described through hole 18 is
In the peripheral part of the number 6, a plurality of pieces may be distributed at a plurality of places. As described above, the present invention has been described in relation to the illustrated embodiment. However, within the scope of the present invention,
Various modifications are possible. For example, the circuit design employed in the illustrated multilayer circuit board 9a is only a typical example that allows easier understanding of the present invention, and the present invention is applicable to other multilayer circuit boards having various circuit designs. Can also be applied.

In this regard, the illustrated multilayer circuit board 9a
Has two layers of ground patterns 10a and 11 formed therein, but such a ground pattern may be a single layer or three or more layers. Further, in addition to the ground pattern, signal lines, power supply lines, and the like may be arranged inside the multilayer circuit board.

[0024]

As described above, according to the present invention, circuit elements for forming a high-frequency circuit are arranged on each main surface, and interference between circuit elements on each main surface is prevented. In the multilayer circuit board in which the ground pattern is located between the main surfaces, since the ground pattern forms a window in a portion facing the high-frequency high-impedance portion of the circuit element, the high-frequency high-impedance portion The stray capacity that may be formed between the ground pattern and the ground pattern can be extremely reduced.

Therefore, when the present invention is applied to a tunable circuit as shown in FIG. 7, the variable range of the combined tuning capacitance including the varactor diode and the like becomes large,
The variable range of the resonance frequency is also expanded. Further, by reducing the combined capacitance value of the resonance circuit, the circuit impedance becomes appropriate, and high-frequency characteristics such as power gain and noise figure are improved.

In the present invention, when the ground pattern is formed so as to form a plurality of layers between the main surfaces, a window is formed in the ground pattern closest to the high-frequency high-impedance portion among the plurality of ground patterns. The formation can contribute more effectively to the reduction of the stray capacity as described above. Further, as described above, when the ground pattern is formed in a plurality of layers between the main surfaces, at least one layer of the ground pattern other than the above-described window-formed ground pattern has a portion overlapping the window. This allows the overlapping portions to function effectively to prevent interference between circuit elements on each major surface of the multilayer circuit board, which can occur due to the formation of windows.

Similarly, when the ground pattern is formed so as to form a plurality of layers between the main surfaces, the ground pattern in which the above-described window is formed is formed at the periphery of the window through at least one through hole. When electrically connected to at least one ground pattern other than the ground pattern, the ground impedance of each ground pattern can be reduced, and the shielding effect can be enhanced.

[Brief description of the drawings]

FIG. 1 shows a multilayer circuit board 9a according to an embodiment of the present invention.
It is a top view which shows a part of.

FIG. 2 is a cross-sectional view taken along line II-II of FIG.

FIG. 3 is a front view showing a tuner 2 including a conventional circuit board 1 of interest to the present invention, in which a front wall of a shield case 8 is removed.

FIG. 4 is a front view corresponding to FIG. 3, showing a tuner 2a including a conventional multilayer circuit board 9 of interest to the present invention.

5 is a plan view showing a part of the multilayer circuit board 9 shown in FIG. 4 and corresponding to FIG.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 5 and corresponding to FIG. 2;

FIGS. 7A and 7B are circuit diagrams showing a variable tuning circuit of interest to the present invention, wherein FIG. 7A shows a case where a stray capacitance is not formed, and FIG. 7B shows a case where a stray capacitance Cs is formed.

[Explanation of symbols]

 3-7 Electronic component (circuit element) 9a Multilayer circuit board 10a, 11 Ground pattern 13, 14 Circuit pattern (circuit element) 15 High impedance portion in high frequency 16 Window 17 Overlapping portion 18 Through hole

Claims (4)

[Claims] 1. A circuit element for forming a high-frequency circuit is arranged on each main surface, and a ground pattern for preventing interference between the circuit elements on each main surface is located between the main surfaces. The multilayer circuit board according to claim 1, wherein the ground pattern forms a window in a portion of the circuit element facing a high-frequency high-impedance portion of the circuit element. 2. The ground pattern is formed so as to form a plurality of layers between the main surfaces. Of the plurality of layers of the ground pattern, a first ground pattern closest to the high-frequency high-impedance portion is provided. The multilayer circuit board according to claim 1, wherein the window is formed. 3. The multilayer circuit board according to claim 2, wherein at least one layer of the ground pattern other than the first ground pattern has a portion overlapping the window. 4. The first ground pattern is electrically connected to at least one ground pattern other than the first ground pattern via at least one through hole in a peripheral portion of the window. ,
The multilayer circuit board according to claim 2.