JPH11340709A - Circuit board and electronic device using the circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board and an electronic device using it capable of simultaneously reducing the parasitic capacitance of a concentrated constant element and miniaturizing a distributed constant element among circuit elements and lowering a price further. SOLUTION: In a first electric substrate 21 of a low dielectric constant where a first ground electrode 22 is formed on the almost entire surface of one main surface and a second ground electrode 23 is formed at a part of the other main surface and a second dielectric substrate 25 of a high dielectric constant where a third ground electrode 26 is formed at a part of one main surface and the distribution constant element 27 composed of a microstrip line and the concentrated constant element 28 are formed on the other main surface, one main surface of the second dielectric substrate 25 is piled up on the other main surface of the first dielectric substrate 21, the second ground electrode 23 and the third ground electrode 26 are electrically connected and this circuit board 20 is constituted. Thus, the reduction of the parasitic capacitance of the concentrated constant element, the miniaturization of the distributed constant element composed of the microstrip line, the improvement of the degree of freedom of circuit design, the miniaturization of the circuit board itself and price reduction further are simultaneously realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a circuit board and an electronic device using the same, and more particularly, to a circuit board used in a high frequency band and an electronic device using the same.

[0002]

2. Description of the Related Art In recent years, with the use of higher frequencies in communication equipment, there has been a demand for further miniaturization and lower cost of circuit boards used in high frequency bands such as RF stages.

FIG. 10 is a sectional view of a conventional circuit board. In FIG. 10, a circuit substrate 1 has a ground electrode 3 formed on the entire surface of one main surface of a dielectric substrate 2 and a distributed constant composed of a microstrip line having a high characteristic impedance as a circuit element on the other main surface of the dielectric substrate 2. An element 4, a distributed constant element 5 composed of a microstrip line having a low characteristic impedance, and a lumped constant element 6 are formed.
Here, the distributed constant element 4 is formed to have a narrow width in order to increase the characteristic impedance.
Are formed wide to reduce the characteristic impedance. The lumped constant element 6 is, for example, an inductance element formed by forming a narrow electrode in a meander shape, or a capacitance element formed by pairing comb-shaped electrodes.

FIG. 11 is a sectional view of another conventional circuit board. In FIG. 11, a circuit board 10 has a dielectric substrate 11 formed by sequentially stacking two dielectric layers 11a and 11b having a high dielectric constant and a dielectric layer 11c having a low dielectric constant. One ground electrode 12 is formed, the second ground electrode 13 is formed on almost the entire surface between the dielectric layers 11b and 11c, and the lumped constant elements 15 and 16 are formed on the other main surface of the dielectric substrate 11. The distributed constant element 17 is formed between the dielectric layers 11a and 11b. here,
The first ground electrode 12 and the second ground electrode 13 are connected by a through hole 14. In addition, the lumped constant elements 15 and 1
Reference numeral 6 denotes an inductance element or a capacitance element similar to the lumped constant element 6 in FIG. The distributed constant element 17 is an element composed of a triplate strip line. The lumped constant element 16 and the distributed constant element 17 are connected by a through hole 18.

As described above, one function is realized by forming a distributed constant element and a lumped constant element on one circuit board.

[0006]

In the circuit board 1 shown in FIG. 10, the size of the distributed constant elements 4 and 5 depends on the wavelength shortening rate of the circuit board 1. Since the wavelength reduction ratio of the circuit board 1 depends on the dielectric constant of the dielectric substrate 2, the size of the distributed constant elements 4 and 5 depends on the dielectric constant of the dielectric substrate 2. Therefore, in order to reduce the size of the distributed constant elements 4 and 5 in order to reduce the size of the circuit board 1, it is necessary to increase the dielectric constant of the dielectric substrate 2. Then, in this case, if the size of the distributed constant elements 4 and 5 is the same as before the dielectric constant of the dielectric substrate 2 is increased, the impedance of the distributed constant elements 4 and 5 is reduced. It is necessary to reduce the width of the track. However, especially with respect to the distributed constant element 4 in which the width of the line is originally narrowed in order to originally increase the characteristic impedance, if the line width is to be further narrowed, a line having a width narrower than a certain width is required. There is a problem that it is difficult to form a line having high dimensional accuracy. Further, depending on the situation, there is a problem that the target line width becomes narrower than the achievable line width, and the target characteristic impedance cannot be realized. further,
With respect to the lumped constant element 6, there is also a problem that by increasing the dielectric constant of the dielectric substrate 2, the parasitic capacitance between the lumped constant element 6 and the ground electrode 3 increases, and the characteristics of the element deteriorate.

In the circuit board 10 shown in FIG.
The lumped-constant elements 15 and 16 are formed on the low-dielectric-constant dielectric layer 11c, and the distributed-constant element 17 is formed on the high-dielectric-constant dielectric layer 11c.
It is formed in a triplate structure sandwiched between a and 11b. However, in this case, since the surface on which the distributed constant element and the lumped constant element are formed is different, it is necessary to provide the through hole 18 each time the two elements are connected, and there is a problem that the manufacturing cost is high and the price is high. There is also a problem that the parasitic capacitance component and the inductance component due to the through-hole 18 adversely affect the high-frequency characteristics of the circuit board, and the function as designed is not achieved. Furthermore, the tri-plate structure requires that the distributed constant element be formed using thick-film printing, which makes it difficult to achieve high dimensional accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to reduce the parasitic capacitance of the lumped constant element, downsize the distributed constant element, and reduce the cost at the same time. An electronic device using the same is provided.

[0009]

In order to achieve the above object, a circuit board according to the present invention has a first ground electrode formed on almost the entirety of one main surface and a second ground electrode formed on a part of the other main surface. A first dielectric substrate having a ground electrode formed thereon, and a second dielectric substrate having a third ground electrode formed on a part of one main surface and a circuit element formed on the other main surface.
The second ground electrode and the third ground electrode are formed by superposing one main surface of the second dielectric substrate on the other main surface of the first dielectric substrate. It is characterized by being electrically connected.

[0010] In the circuit board of the present invention, the first dielectric substrate is formed of a low dielectric constant dielectric, and the second dielectric substrate is formed of a high dielectric constant dielectric. And

Further, in the circuit board according to the present invention, the circuit element is formed so as to face one or both of the first ground electrode and the third ground electrode.

Further, in the circuit board according to the present invention, the circuit element is formed on an electrode formed on one main surface of the second dielectric substrate and on the other main surface of the second dielectric substrate. It is characterized by being formed by combining electrodes.

Further, an electronic device according to the present invention is characterized in that the electronic device is configured using the circuit board described above.

With this configuration, in the circuit board of the present invention, the reduction of the parasitic capacitance of the lumped constant element and the downsizing of the distributed constant element, and the downsizing of the circuit board itself and the cost reduction can be realized at the same time. can do.

Further, in the electronic device of the present invention, downsizing and cost reduction can be realized.

[0016]

FIG. 1 is a sectional view showing an embodiment of a circuit board according to the present invention. In FIG. 1, a first dielectric substrate 21 is made of a low dielectric constant ceramic having a relative dielectric constant of, for example, about 10, and a first ground electrode 22 is formed on substantially the entire main surface, while the other main surface is formed. Is formed with a second ground electrode 23, and the first ground electrode 22 and the second ground electrode 23 are connected by a through hole 24. The second dielectric substrate 25 is made of, for example, a high dielectric constant ceramic having a relative dielectric constant of about 100. A third ground electrode 26 is formed on one half of the main surface, and a third ground electrode 26 is formed on the other main surface. As circuit elements, a distributed constant element 27 and a lumped constant element 28 made of a microstrip line are formed. Then, the circuit board 20 is provided on the other main surface of the first dielectric substrate 21 with the second
The second ground electrode 23 of the first dielectric substrate 21 and the third ground electrode 26 of the second dielectric substrate 25 are connected by soldering or conducting. It is electrically connected with a paste or the like.

Here, on the other main surface of the first dielectric substrate 21, a portion facing the second dielectric substrate 25 is provided.
Except for the portion in contact with the third ground electrode 26, the second ground electrode 23 is hardly formed. On one main surface of the second dielectric substrate 25, the distributed constant element 27
The third ground electrode 26 is formed in a portion facing the lumped element 28, and the ground electrode 26 is not formed in a portion facing the lumped constant element 28.

As a result, the distributed constant element 27 formed on the other main surface of the second dielectric substrate 25 faces the third ground electrode 26 with a distance corresponding to the thickness of the second dielectric substrate 25. It is formed. The lumped element 28 formed on the other main surface of the second dielectric substrate 25 is separated by a distance corresponding to the thickness of both the second dielectric substrate 25 and the first dielectric substrate 21. It is formed to face the first ground electrode 22. In FIG. 1, the first dielectric substrate 2
Although it appears that there is a large gap between the first and second dielectric substrates 25, this is caused by emphasizing the thickness of each ground electrode, and in reality there is almost no gap.

FIG. 2 is a plan view showing one embodiment of the distributed constant element 27. In FIG. 2, the distributed constant element 27
Is an input side line 27a, one end of which is open and the other end of which is 1 / ground of ground.
Four-wavelength microstrip line resonators 27b, 27
c, 27d, 27e and an output side line 27f. Microstrip line resonators 27b, 27c, 2
7d and 27e are arranged side by side, and an input side line 27a and an output side line 27f are connected in the middle of the microstrip line resonators 27b and 27e at both ends thereof to form a comb line type filter.

FIG. 3 is a plan view of one embodiment of the lumped element 28. As shown in FIG. In FIG. 3, the lumped constant element 28 includes a comb-shaped electrode pair 28a, an input line 28b, and an output line 28.
c is a capacitive element made of c.

FIG. 4 is a plan view of another embodiment of the lumped element. In FIG. 4, the lumped constant element 29 is an inductance element including a narrow meandering line 29a, an input line 29b, and an output line 29c.

In FIGS. 2 to 4 described above,
The dielectric substrate 25 is omitted.

Returning to FIG. 1, in the circuit board 20 thus configured, the lumped constant element 28 is connected to the first ground via both the first dielectric substrate 21 and the second dielectric substrate 25. Since it is formed so as to face the electrode 22, the distance between the lumped element 28 and the first ground electrode 22 is equal to the total thickness of the first dielectric substrate 21 and the second dielectric substrate 25. . The effective dielectric constant of the dielectric between the lumped element 28 and the first ground electrode 22 is the first dielectric constant of the low dielectric constant.
Dielectric substrate 21 and high dielectric constant second dielectric substrate 25
Are superimposed, and therefore have a value between the two. For this reason, the parasitic capacitance formed between the lumped element 28 and the first ground electrode 22 is smaller than that formed on a circuit board made of only a dielectric having a high dielectric constant. As a result, it is possible to prevent the high frequency characteristics of the lumped element 28 from deteriorating.

That is, in the region where the lumped element 28 is formed, the parasitic capacitance with respect to the lumped element formed therein becomes small, and it can be seen that deterioration of the high frequency characteristics of the lumped element can be reduced.

On the other hand, the distributed constant element 27 composed of a microstrip line is formed so as to face the third ground electrode 26 with only the second dielectric substrate 25 interposed therebetween. The distance from the ground electrode 26 is the second
The thickness of the dielectric substrate 25. Since the dielectric material between them is only the high dielectric constant second dielectric substrate 25, the effective dielectric constant is the same as the dielectric constant of the second dielectric substrate 25. Therefore, the distributed constant element 27 and the second
The distributed capacitance (capacity between the electrode of the circuit element and the ground electrode per fixed area) formed between the ground electrode 26 and the ground electrode 26 is
It is much larger than the distributed capacitance (parasitic capacitance) formed between the lumped constant element 28 and the first ground electrode 22,
The wavelength shortening rate also increases.

An increase in the distributed capacitance of the distributed constant element 27 means that the characteristic impedance of the distributed constant line constituting the distributed constant element 27 is reduced. This means that when the same characteristic impedance is obtained, the line width can be reduced. Therefore, the size of the distributed constant element 27 can be reduced in addition to the increase in the wavelength shortening rate.

That is, in the long region where the distributed constant element 27 is formed, the wavelength shortening rate with respect to the distributed constant element formed therein becomes large, and it can be seen that the distributed constant element can be downsized.

Contrary to the above-described embodiment, when a distributed constant element having a high characteristic impedance is required, the distributed constant element is formed in the same region as the lumped constant element 28 so that the first
May be formed so as to face the ground electrode 22.

Further, when a lumped constant element such as a capacitor requiring a large capacitance is required between the lumped constant element and the ground electrode, the lumped constant element is formed in the same region as the distributed constant element 27, and the third constant element is formed. It may be formed so as to face the ground electrode 28.

As described above, by forming a circuit board by laminating a dielectric substrate having a high dielectric constant on a dielectric substrate having a low dielectric constant, a lumped element can be used with reduced parasitic capacitance. Deterioration of high frequency characteristics can be prevented. In the case of a distributed constant element composed of a microstrip line, the location where the distributed constant element is formed may be changed depending on the required characteristic impedance value, or the position of the third ground electrode facing the distributed constant element may be changed. Accordingly, the wavelength shortening rate of the line can be changed, and the line having the same width can be used with both high characteristic impedance and low characteristic impedance.
Furthermore, by forming a circuit element so as to extend over two regions, it can be designed to obtain optimum characteristics.

As a result, the degree of freedom in circuit design can be increased, and the size of the circuit board itself can be reduced. In addition, since it is possible to partially create an effective high or low effective permittivity part, the dielectric constant of the substrate is increased, so that the line width becomes too narrow to create a distributed constant line with a high characteristic impedance. Such a problem can be avoided.

FIG. 5 is a sectional view of another embodiment of the present invention. 5, the same or equivalent parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted.

In the circuit board 30 shown in FIG. 5, a lumped constant element 31 is provided as a circuit element instead of the lumped constant element 28 shown in FIG. Lumped element 31
Are formed by combining electrodes formed on one main surface and the other main surface of the second dielectric substrate 25.

FIG. 6 is a perspective view of one embodiment of the lumped element 31. As shown in FIG. In FIG. 6, the lumped element 31
Are a spiral line 31a and a linear line 31b,
A through hole 31c connecting the other end of the line 31a to one end of the line 31b, a through hole 31d leading the other end of the line 31b to the opposing surface of the dielectric substrate, an input side line 31e connected to one end of the line 31a, a through hole This is an inductance element composed of the output side line 31f connected to 31d. Here, the line 31a, the input side line 31e, and the output side line 31f are provided on the other main surface of the second dielectric substrate 25,
1b is formed on one main surface of the second dielectric substrate 25.

FIG. 7 is a perspective view of still another embodiment of the lumped element. In FIG. 7, the lumped element 32
Are a planar electrode 32a and a planar electrode 32b formed facing each other, and an input side line 32 connected to the planar electrode 32a.
c, an MIM structure (Metal Insulator M) comprising an output side line 32d connected to the planar electrode 32b.
etal (a structure in which two electrodes face each other via one insulating layer). Here, the planar electrode 32a and the input-side line 32c are formed on the other main surface of the second dielectric substrate 25, and the planar electrode 32b and the output-side electrode 32d are formed on one main surface of the second dielectric substrate 25. ing.

Note that in FIGS. 6 and 7,
The dielectric substrate 25 is omitted.

Returning to FIG. 5, the lumped element 3
1 is formed not only on the electrode formed on the other main surface of the second dielectric substrate 25 but also in combination with the electrode formed on one main surface of the second dielectric substrate 25. The same operation and effects as those of the circuit board 20 shown are exhibited,
The setting range of the capacitance value and the inductance value of the lumped constant element can be further widened.

In each of the above embodiments, each dielectric substrate is made of ceramic. However, the present invention is not necessarily limited to ceramic, and even if it is made of resin or semiconductor, similar effects can be obtained. is there.

Further, the first dielectric substrate is formed of a dielectric having a low dielectric constant, and the second dielectric substrate is formed of a dielectric having a high dielectric constant. However, the present invention is not limited to such a structure. Instead, each dielectric substrate may be made of a dielectric material having the same dielectric constant, or conversely, the first dielectric substrate may be made of a dielectric material having a high dielectric constant, and the second dielectric substrate may be made of a dielectric material having a low dielectric constant. It may be constituted by the above dielectric. In this case, it is almost impossible to use the difference of the wavelength shortening rate properly, but the same effect is obtained when the lines of the same width are selectively used for the high characteristic impedance and the low characteristic impedance and the parasitic capacitance of the lumped element is reduced. Is played.

In each of the above embodiments, through holes are used for connecting ground electrodes and circuit elements, but via holes may be used.

FIG. 8 shows an embodiment of an electronic device constructed using the circuit board 20 of the present invention. In FIG. 8, FIG.
The same reference numerals are given to the same or equivalent parts, and the description thereof is omitted.

In FIG. 8, an electronic device 40 is provided with a new electrode 4 on the other main surface of the second dielectric substrate 25 of the circuit board 20.
1, an IC 42 is mounted thereon, and a cover 43 that covers the entire other main surface of the first dielectric substrate 21 is provided. Here, FIG. 9 shows a block diagram of a circuit of the electronic device 40. 9, an input terminal 51 of an electronic device 40 is connected to a mixer 56 via a filter 52, an amplifier 53, and a filter 54 in this order. The local oscillator 55 is also connected to the mixer 56. And mixer 5
The output of 6 is connected to an output terminal 59 via a filter 57 and an amplifier 58. The electronic device 40 functions as a down converter by having such a configuration.
Each block such as a filter and an amplifier constituting the electronic device 40 is composed of lumped constant elements and distributed constant elements formed on the circuit board 20, and electronic components such as ICs mounted on the circuit board 20. Is what it is.

As described above, by forming the electronic device 40 using the circuit board 20 of the present invention, the size of the circuit elements formed on the circuit board 20 can be reduced, the high-frequency characteristics can be improved, and the design flexibility can be improved. The size and cost of the circuit board can be reduced. In addition, the electronic device 40 itself can be reduced in size and cost.

In the embodiment shown in FIG. 8, the electronic device 40 is constructed using the circuit board 20 shown in FIG. 1, but the electronic device is constructed using the circuit board 30 shown in FIG. The same operation and effect can be obtained.

The electronic device using the circuit board of the present invention is not limited to a downconverter, but may be an individual electronic device such as a filter, an amplifier, a mixer, an oscillator, or any other electronic device. It does not matter.

[0046]

According to the circuit board of the present invention, the first ground electrode is formed on almost the whole of one main surface, and the second ground electrode is formed on a part of the other main surface. A second dielectric substrate having a first dielectric substrate and a second dielectric substrate having a high dielectric constant and a third ground electrode formed on a part of one main surface and a circuit element formed on the other main surface; Is superimposed on the other main surface of the first dielectric substrate, and a second ground electrode and a third
By electrically connecting the ground electrodes of
Reduction of parasitic capacitance of lumped constant elements in circuit elements, miniaturization of distributed constant elements composed of microstrip lines, improvement of circuit design flexibility, miniaturization of circuit boards themselves,
The price can be reduced at the same time.

Further, according to the electronic device of the present invention, the size and the price can be reduced based on the size and the price of the circuit board.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a circuit board of the present invention.

FIG. 2 is a plan view showing one embodiment of a distributed constant element formed on the circuit board of FIG. 1;

FIG. 3 is a plan view showing one embodiment of a lumped constant element formed on the circuit board of FIG. 1;

FIG. 4 is a plan view showing another example of the lumped constant element formed on the circuit board of FIG. 1;

FIG. 5 is a sectional view showing another embodiment of the circuit board of the present invention.

FIG. 6 is a perspective view showing one embodiment of a lumped element formed on the circuit board of FIG. 5;

FIG. 7 is a perspective view showing another embodiment of the lumped element formed on the circuit board of FIG. 5;

FIG. 8 is a sectional view showing an embodiment of the electronic device of the present invention.

FIG. 9 is a block diagram of a circuit of the electronic device of FIG. 8;

FIG. 10 is a sectional view showing a conventional circuit board.

FIG. 11 is a sectional view showing another conventional circuit board.

[Explanation of symbols]

 20, 30 ... circuit board 21 ... first dielectric substrate 22 ... first ground electrode 23 ... second ground electrode 24 ... through hole 25 ... second dielectric substrate 26 ... third ground electrode 27 ... distribution Constant elements (circuit elements) 28, 29, 31, 32: Lumped constant elements (circuit elements) 40: Electronic devices

Claims (5)

[Claims] 1. A first dielectric substrate having a first ground electrode formed on substantially the entirety of one main surface and a second ground electrode formed on a part of the other main surface, and a part of the one main surface. A second dielectric substrate having a third ground electrode formed thereon and a circuit element formed on the other main surface, wherein one main surface of the second dielectric substrate is connected to the other of the first dielectric substrate. A circuit board, wherein the second ground electrode and the third ground electrode are electrically connected so as to overlap with a main surface. 2. The method according to claim 1, wherein said first dielectric substrate is made of a dielectric material having a low dielectric constant, and said second dielectric substrate is made of a dielectric material having a high dielectric constant. The described circuit board. 3. The circuit device according to claim 1, wherein the circuit element is formed so as to face one or both of the first ground electrode and the third ground electrode. Circuit board. 4. The circuit element is formed by combining an electrode formed on one main surface of the second dielectric substrate and an electrode formed on the other main surface of the second dielectric substrate. The circuit board according to any one of claims 1 to 3, wherein: 5. An electronic device comprising the circuit board according to any one of claims 1 to 4.