JP2000188361A - High-frequency wiring board and mounting structure therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce variations in characteristic impedance with respect to a high-frequency signal, by electrically connecting first and second ground conductors with ground through conductors provided at a predetermined inter-conductor distance, on both sides of a through conductor through which ends of first and second line conductors are electrically connected. SOLUTION: A first ground conductor 24 and a second ground conductor 26 are formed of a microstrip line having a very thin dielectric thickness. The conductor 24 is formed on the upper surface of a first high-frequency transfer line formed on the upper surface of a dielectric substrate 22, and the conductor 26 is formed on the lower surface of a second high-frequency transfer line formed on the lower surface of the same substrate 22. As a result of this structure, an unwanted signal component of a high-order mode can be reduced. This reduces dielectric losses in a high-frequency band of 20 GHz or higher, and characteristic variations can be suppressed. Further, since a portion for connecting the first and second high-frequency transfer lines is formed into a coplanar line structure in which a ground through conductor 28 is provided at an inter-conductor distance of λ/4 or lower on both sides of a signal through conductor 27, phase deviations from a high-frequency signal current can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a substrate for a high-frequency circuit, a package for storing a high-frequency semiconductor element, a chip carrier for mounting a high-frequency semiconductor element, and mounted on an external electric circuit board by a surface mounting method. And a mounting structure thereof.

[0002]

2. Description of the Related Art In a high-frequency wiring board used for a high-frequency circuit board, a high-frequency semiconductor element storage package, a high-frequency semiconductor element mounting chip carrier, and the like, a high-frequency semiconductor element or the like mounted on the upper surface thereof is used. High-frequency transmission lines for transmitting high-frequency signals are formed on the upper and lower surfaces to electrically connect the components for high-frequency wiring of the external electric circuit board on which the high-frequency wiring board is mounted. A high-frequency input / output unit is formed by electrically connecting them with a through conductor. The high-frequency wiring board is mounted on the external electric circuit board, and the high-frequency transmission line on the lower surface is electrically connected to the connection line conductor of the external electric circuit board, so that the high-frequency wiring board is mounted and used. Will be done.

FIG. 3 is a perspective view showing an example of such a conventional high-frequency wiring board and its mounting structure. In FIG. 3, 1 is a high-frequency wiring board, 2 is a dielectric board, 3
Is a first line conductor formed on the upper surface of the dielectric substrate 2 for transmitting a high-frequency signal, 4 is a first same-plane ground conductor disposed on both sides of the first line conductor 3, and 5 is a dielectric. Body substrate 2
A second line conductor formed on the lower surface of the first line conductor 3 so as to face the first line conductor 3; 6 is a second same-plane ground conductor disposed on both sides of the second line conductor 5; Is a through conductor for electrically connecting the tips of the first line conductor 3 and the second line conductor 5 to each other; 8 is a first ground conductor 4 and a second ground conductor near the through conductor 7. 6 is a through conductor for grounding that is electrically connected to the grounding conductor 6. Thus, the first line conductor 3
And a first high-frequency transmission line having a coplanar line structure including the first coplanar grounding conductor 4 and a second high-frequency transmission line having a coplanar line structure including the second line conductor 5 and the second coplanar grounding conductor 6. The transmission line is electrically connected by the through conductor 7 and the grounding through conductor 8 to form a high frequency input / output unit. Note that a through-hole conductor or a via conductor is used for the through conductor 7 and the through conductor 8 for grounding.

Further, 9 is a circuit board on which an external electric circuit is formed, 10 is a substrate such as a multilayer wiring board made of a dielectric, 11 is a connection line conductor formed on the upper surface for transmitting a high-frequency signal, and 12 is a connection line conductor. Coplanar ground conductors arranged on both sides of the connection line conductor 11, and the same plane ground conductor 12 as the connection line conductor 11.
Thus, a high-frequency transmission line having a coplanar line structure is similarly formed.

Then, the high-frequency wiring board 1 is connected to the circuit board 9.
And the second line conductor 5 and the connecting line conductor 11 and the second same-plane ground conductor 6 and the same-plane ground conductor 12 are respectively connected by conductive connecting members such as solder bumps. Alternatively, the high-frequency wiring board 1 is mounted on the circuit board 9 by making electrical connection by a reflow process using a solder material.

In a conventional high frequency wiring board 1, as shown in FIG.
The structure in which the line conductor 3 is connected to the second line conductor 5 formed on the lower surface of the dielectric substrate 2 through the signal through conductor 7 is disclosed in, for example, JP-A-61-251059 and Japanese Patent No. 260550.
As disclosed in Japanese Unexamined Patent Application Publication No. 2 (1994) -2002, in order to adjust the inductance of the portion of the through conductor 7, the gap between the first line conductor 3 and the first ground conductor 4 and the second line conductor 5 and the second line conductor 5 are adjusted. A method of adjusting the gap with the same plane ground conductor 6 and optimizing the capacitance component between them is adopted.
In this case, on both sides near the through conductor 7, a grounding through conductor 8 for electrically connecting the first same-plane ground conductor 4 and the second same-plane ground conductor 6 is formed to form the line conductor 3. A coplanar line structure may be formed between the ground conductor 5 and the through conductor 7, or a plurality of ground through conductors 8 may be provided between the ground conductors 4 and 6 on the same plane to form a coaxial line structure with the through conductor 7. Had to be configured.

The reason why the coplanar line structure is selected as the high-frequency transmission line is to compensate for the discontinuity with the pattern width of the signal line on the high-frequency component side mounted on the high-frequency wiring board 1. For the purpose of improving the isolation between the signal lines, the connection between the coplanar line structures is preferable to the transmission line having the microstrip line structure.

[0008]

A surface-mount type transmission line in which the transmission line 3 on the upper surface and the transmission line 5 on the lower surface of such a dielectric substrate 2 are connected using through conductors 7 and 8 for signal and ground. The form of the high-frequency input / output unit has been limited to the application to high-frequency signals up to about 20 GHz until now, because it has caused the reflection of high-frequency signals in the input / output unit. On the other hand, in order to cope with the recent increase in speed and frequency of signal processing, it has been strongly required to configure a surface mount type high frequency input / output unit even in a high frequency band of 20 GHz or more.

However, in the conventional high-frequency wiring board 1 shown in FIG. 3, in order to cope with a high-frequency signal of 20 GHz or more, the dielectric board 2 is required to reduce the dielectric loss of the dielectric board 2 itself as much as possible. 2 had to be reduced in thickness, and as a result, the following problems were caused.

That is, in the case of a transmission line having a coplanar line structure, for example, when the thickness of the ceramic substrate as the dielectric substrate 2 is set as thin as 0.1 mm, the line of the line conductors 3 and 5 of the coplanar line structure is correspondingly set. The gap between the patterns of the line conductors 3 and 5 and the ground conductors 4 and 6 on the same plane becomes very narrow, and the gap between the second line conductor 5 and the second ground conductor 6 on the same plane is reduced during mounting. Even if a short circuit occurs, or even a slight change in the gap between the line conductors 3, 5 and the ground conductors 4, 6 at the same time during fabrication, the characteristic impedance greatly varies, so that the reflection loss of the high-frequency signal increases. There was a problem.

Further, in order to form a plurality of grounding through-conductors 8 in the vicinity of the through-conductors 7 or in a coaxial structure and to match the characteristic impedance of the through-conductors 7, the grounding through-conductors 8 must be provided. It is necessary to form the grounding conductor at a distance more than a predetermined distance from the through conductor 7, but the grounding through conductor 8 formed so far increases the path of the ground current for the current of the high-frequency signal. Therefore, there is also a problem that the phase shift of the ground current causes a loss in propagation of the high-frequency signal.

Further, the high-frequency wiring board 1 and the circuit board 9
4 are coplanar line structures, and as shown in the cross-sectional view of the connecting portion in FIG. 4, when an alignment error occurs during mounting, the second line conductor 5 and the connecting line A second ground conductor 6 near the line conductor 11
Further, since the ground conductors 12 on the same surface of the circuit board 9 are present, the distance between the line conductors 5 and 11 and the ground conductors 6 and 12 becomes extremely narrow, so that the high-frequency characteristics after mounting vary. In addition, there has been a problem that the line conductors 5 and 11 and the adjacent ground conductors 6 and 12 adjacent to the line conductors 5 and 11 are short-circuited due to a bridge or the like made of solder.

The present invention has been devised in view of the above-mentioned conventional problems, and has as its object to respond to a high-frequency signal of 20 GHz or more even if the thickness of the dielectric substrate becomes thinner. It has a transmission line with a small characteristic impedance variation for signals, a small phase shift of the ground current flowing through the ground through conductor adjacent to the signal through conductor, and good transmission characteristics. An object of the present invention is to provide a high frequency wiring board having a large alignment margin in mounting and a mounting structure thereof.

[0014]

In a high frequency wiring board according to the present invention, a first line conductor for transmitting a high frequency signal is formed on an upper surface of a dielectric substrate, and a first line conductor opposed to the first line conductor is formed on a lower surface. A first high-frequency transmission line on which one ground conductor is formed, a second line conductor for transmitting the high-frequency signal on a lower surface of the dielectric substrate, and an upper surface facing the second line conductor on the upper surface; A second ground conductor,
Of the first line conductor and the second line conductor are electrically connected to each other by a through conductor, and a quarter of the effective wavelength of the high frequency signal is provided on both sides of the through conductor. A high-frequency input / output unit formed by electrically connecting the first ground conductor and the second ground conductor with a ground through conductor disposed at a distance between conductors of 1 or less. Is what you do.

Further, in the mounting structure of the high-frequency wiring board of the present invention, the high-frequency wiring board having the above-described structure is formed by forming a connection line conductor for transmitting the high-frequency signal on an upper surface of a dielectric substrate, Mounted on an upper surface of a circuit board formed with a ground conductor facing the connection line conductor, and electrically connecting the second line conductor to the connection line conductor. .

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view similar to FIG. 3, showing an example of an embodiment of a high-frequency wiring board and its mounting structure according to the present invention. FIG. 2 is a sectional view of the connecting portion similar to FIG.

In these figures, 21 is a high-frequency wiring board, 22 is a dielectric substrate, 23 is a first line conductor formed on the upper surface of the dielectric substrate 22 for transmitting high-frequency signals, and 24 is The first ground conductor is formed on the lower surface of the dielectric substrate 22 so as to face the first line conductor 23. Reference numeral 25 denotes a second line conductor formed on the lower surface of the dielectric substrate 22 so that the tip thereof is opposed to the first line conductor 23. Reference numeral 26 denotes the dielectric substrate 22.
Is a second grounding conductor formed on the upper surface of the second conductor so as to face the second line conductor 25. 27 is the first line conductor 23
And a penetrating conductor for electrically connecting the tips of the second line conductor 25 to each other, and 28 are disposed on both sides of the penetrating conductor 27 at a distance between conductors equal to or less than a quarter of the wavelength of the high-frequency signal. Ground conductor 24
And a second ground conductor 26 for electrically connecting the second ground conductor 26 and the second ground conductor 26.

As described above, the first line conductor 23 and the first
A first high-frequency transmission line having a microstrip line structure including the ground conductor 24 of the first embodiment and a second high-frequency transmission line having a microstrip line structure also including the second line conductor 25 and the second ground conductor 26 are formed. , Signal through conductor 27
And a high-frequency input / output unit by forming a high-frequency input / output unit.

Reference numeral 29 denotes a circuit board on which an external electric circuit is formed, reference numeral 30 denotes a substrate such as a multilayer wiring board made of a dielectric, reference numeral 31 denotes a connection line conductor formed on an upper surface thereof for transmitting a high-frequency signal, Reference numeral 32 denotes a ground conductor formed on the lower surface of the substrate 30 so as to face the connection line conductor 31.

Reference numeral 33 denotes an upper surface grounding conductor formed on the upper surface of the substrate 30 and electrically connected to the first grounding conductor 24;
Is a board-side grounding through conductor that electrically connects the top ground conductor 33 and the ground conductor 32, and is necessary for improving the grounding state of the high-frequency wiring board 21 mounted on the circuit board 29. It is formed accordingly.

The high-frequency wiring board 21 of the present invention is mounted on the upper surface of the circuit board 29, the second line conductor 25 is connected to the connection line conductor 31, and the first ground conductor
The high-frequency wiring board 21 is mounted on the circuit board 29 by electrically connecting the 24 to the upper surface ground conductor 33 by a conductive connection member such as a solder bump or by a reflow process using a solder material.

According to the high-frequency wiring board 21 of the present invention, the line conductors 23 and 25 of the high-frequency transmission line formed on the upper and lower surfaces of the dielectric substrate 22 are electrically connected to each other through the through conductor 27. Regarding the high frequency input / output unit to be connected, in order to reduce the dielectric loss with respect to the transmission of the high frequency signal as much as possible and to suppress the variation in the characteristics due to the manufacturing variation, the thickness of each of the high frequency transmission lines is extremely thin, for example, 20 GHz.
0 and a thickness at a frequency greater than z relative dielectric constant epsilon _r is 9.
Line conductors 23 and 25 are formed on a 38 mm dielectric substrate 22, and the microstrip line structure is provided with ground conductors 24 and 26 on the surface opposite to the surface on which the line conductors 23 and 25 are formed. are doing.

The first and second ground conductors 24.
Reference numeral 26 denotes a larger area on the surface of the dielectric substrate 22 facing the first and second line conductors 23 and 25, respectively, at least facing the line conductors 23 and 25 in consideration of the transmission characteristics of high-frequency signals. It is formed.

Further, in order to eliminate the phase shift of the ground current with respect to the current of the high-frequency signal transmitted by the line conductors 23 and 25 having the microstrip line structure, the first high-frequency transmission line on the upper surface side of the dielectric substrate 22 is connected to the first high-frequency transmission line. The connection portion with the second high-frequency transmission line on the lower surface is provided on both sides of the through conductor 27 for signal with a conductor for grounding with a conductor distance of ４ (λ / 4) or less of the effective wavelength λ of the high-frequency signal. It has a coplanar line structure in which conductors 28 are provided.

As a result, according to the high-frequency wiring board 21 of the present invention, the first high-frequency transmission line formed on the upper surface of the dielectric substrate 22 is replaced with a very thin dielectric having the first ground conductor 24 on the lower surface. A second high-frequency transmission line formed on the lower surface of the dielectric substrate 22 is formed of a microstrip line having a very small dielectric thickness and having a second ground conductor 26 on the upper surface. As a result, unnecessary signal components in the higher-order mode can be reduced, so that dielectric loss can be reduced even in a high-frequency band of 20 GHz or more, and variation in characteristics can be suppressed. In addition, since the microstrip line structure without grounding on both sides of the line conductor is used, even if the line widths of the line conductors 23 and 25 are thinned due to manufacturing variations, there is no sudden change in characteristic impedance. A high-frequency transmission line can be supplied.

A connecting portion between the first high-frequency transmission line and the second high-frequency transmission line is provided with a through conductor for ground 28 on both sides of the through conductor 27 for signal with a conductor distance of λ / 4 or less. Because of the coplanar line structure provided, the grounding current is
Since the current flows through the path 28, the path of the ground current is shortened, so that it is possible to eliminate a phase shift with respect to the current of the high frequency signal transmitted through the microstrip line.

Further, according to the mounting structure of the high-frequency wiring board of the present invention, as shown in FIG.
In the connection portion between the line conductor and the circuit board 29, the line conductors connected to each other have a microstrip line structure, so that even if the connection position of the line conductor is slightly shifted, it is close to the ground like the conventional connection structure. Since there is no portion, a mounting structure having a large alignment margin in mounting on the circuit board 29 is obtained.

Thus, according to the mounting structure of the high-frequency wiring board of the present invention, the discontinuity with the pattern width of the signal line on the high-frequency component side mounted on the high-frequency wiring board 21 can be compensated, Improving isolation between lines can be solved simultaneously by reducing the thickness of the dielectric substrate 22. Further, in a high-frequency input / output section formed by connecting the first high-frequency transmission line and the second high-frequency transmission line, a ground through conductor 28 is disposed at a predetermined distance from the signal through conductor 27. With the provision, the isolation between the signal lines can be further improved.

It should be noted that the present invention is not limited to the above-described embodiments, and that various changes and improvements can be made without departing from the scope of the present invention. For example, in the example of the above-described embodiment, a case where one signal line is provided as a transmission line has been described. However, a case of a multi-port in which a plurality of transmission lines are provided may be used. At this time, in order to improve the isolation characteristics between adjacent line conductors, power supply lines, and adjacent line conductors on the circuit board on which the high-frequency wiring board is mounted, many through conductors and similar conductors are used. Is possible.

Further, a structure in which a connecting metal member such as a lead terminal or a ball is attached to the high-frequency transmission line may be employed.

[0032]

According to the high-frequency wiring board of the present invention, the high-frequency input / output section for electrically connecting the line conductors of the high-frequency transmission line formed on the upper and lower surfaces of the dielectric substrate via through conductors. For each, the high-frequency transmission line is configured as a microstrip line structure having a line conductor and a ground conductor formed on a surface facing the line conductor,
The connection between the first high-frequency transmission line on the upper surface of the dielectric substrate and the second high-frequency transmission line on the lower surface is connected to both sides of the signal through conductor by four minutes of the effective wavelength λ of the high-frequency signal. Of 1
The coplanar line structure in which the through conductors for grounding are arranged at the following distance between conductors reduces dielectric loss even in a high-frequency band of 20 GHz or more, suppresses characteristic variations, and reduces line conductors due to manufacturing variations. Of the characteristic impedance of the
The ground current flows through the ground through conductor near the signal through conductor, thereby shortening the path of the ground current. Therefore, it is possible to eliminate a phase shift with respect to the current of the high-frequency signal.

Further, according to the mounting structure of the high-frequency wiring board of the present invention, the line conductors to be connected have a microstrip line structure with each other. Since there is no portion close to a proper ground, the alignment margin for mounting the high-frequency wiring board on the circuit board can be increased, and the mounting can be performed without making the positioning unnecessarily strict.

As described above, according to the present invention, even if the thickness of the dielectric substrate is reduced in response to a high-frequency signal of 20 GHz or more, the transmission line having a small characteristic impedance variation with respect to the high-frequency signal is provided. Provided is a high-frequency wiring board having a small phase shift of a ground current flowing through a grounding through conductor adjacent to a through conductor and having good transmission characteristics, and having a large alignment margin when mounted on an external electric circuit board, and a mounting structure thereof. I was able to.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an embodiment of a high-frequency wiring board and a mounting structure thereof according to the present invention.

FIG. 2 is a sectional view of a connection portion of the mounting structure shown in FIG.

FIG. 3 is a perspective view showing an example of a conventional high-frequency wiring board and its mounting structure.

FIG. 4 is a sectional view of a connection portion of the mounting structure shown in FIG. 3;

[Explanation of symbols]

21: high frequency wiring board 22: dielectric board, 23: first line conductor, 24 ...
. A first ground conductor, 25 ... a second line conductor, 26 ...
Second ground conductor, 27: through conductor, 28: ground through conductor 29: circuit board 30: board, 31: connection line conductor, 32: ground conductor

Claims (2)

[Claims] A first line conductor for transmitting a high-frequency signal formed on an upper surface of a dielectric substrate, and a first ground conductor opposed to the first line conductor formed on a lower surface of the first substrate; A transmission line for transmitting the high-frequency signal to a lower surface of the dielectric substrate.
A second high-frequency transmission line formed by forming a second ground conductor facing the second line conductor on the upper surface of the first line conductor and the second line. The first ends of the conductors are electrically connected to each other by a through conductor, and the first through conductors for grounding are disposed on both sides of the through conductor at a distance between the conductors of 1/4 or less of the effective wavelength of the high-frequency signal. A high-frequency wiring board, comprising: a high-frequency input / output unit formed by electrically connecting a ground conductor and the second ground conductor. 2. The high-frequency wiring board according to claim 1, wherein a connection line conductor for transmitting the high-frequency signal is formed on an upper surface of a substrate made of a dielectric, and a ground surface facing the connection line conductor on a lower surface side. A mounting structure for a high-frequency wiring board, wherein the mounting is performed on an upper surface of a circuit board on which a conductor is formed, and the second line conductor is electrically connected to the connection line conductor.