JPH11195852A - Printed-wiring board unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed-wiring board unit which provides a filter characteristic equal to a characteristic in a state of single piezoelectrrc device such as a piezoelectric filter or the like before being mounted, even when the piezoelectric device is mounted on a printed-wiring board. SOLUTION: On a printed-wiring board 20 on which a piezoelectric device 1 is mounted, input/output wiring patterns 24, 25 which correspond respectively to input/output terminals are formed, isolation regions 22, 23 which surround the input/output patterns 24, 25 at least partly are formed, and grounding patterns 21 which are formed over a prescribed range on the printed-wiring board 20 are formed in such a way that the input/output wiring patterns 24, 25 are surrounded at least partly by separating the respective isolation regions 22, 23. In the grounding patterns 21, an insulating line 30 which cuts the grounding patterns 21 electrically into an input-side grounding pattern 32 and an output-side grounding pattern 31 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring structure of a printed wiring board on which a piezoelectric device such as a piezoelectric filter is mounted, and more particularly to a printed circuit having a wiring structure suitable for mounting a high-frequency filter such as a SAW filter on the printed wiring board. The present invention relates to a wiring board unit.

[0002]

2. Description of the Related Art In the field of communication equipment, the demand for higher frequency is increasing year by year, and higher frequency is also required for piezoelectric filters such as SAW filters and multimode filters. Conventionally, the frequency band is several tens of meters
The problem with the characteristics that did not occur when a filter of about Hz was mounted on a printed wiring board is the recent 800M filter.
SA corresponding to high frequency band such as 1.5 Hz and 1.5 GHz
The problem occurs when a piezoelectric device such as a W filter is mounted on a printed wiring board such as a wireless device, and it has been pointed out that a problem that desired filter characteristics cannot be obtained. The present inventor has carried out the following experiment in order to confirm this point, and reproduced the above-mentioned problem. That is, FIGS. 10 (a), (b) and
FIG. 11C is a front longitudinal sectional view, a plane transverse sectional view, and a bottom view showing the structure of a SAW device as an example of a conventional piezoelectric device. FIGS. 11A and 11B show printed wiring of the SAW device. FIG. 12 is a perspective view showing a procedure of mounting on a substrate and a state after mounting, FIG. 12 is a view showing filter characteristics of a mounted SAW device, and FIG. 13 is a view showing filter characteristics of a single SAW device not mounted. FIG. In the SAW device 1 shown in FIG. 10, a SAW device chip 3 is fixed to the inner bottom surface of a concave ceramic package 2 having an open top surface, and conductive pads 6 (6a, 6b, 6c) formed on steps 4, 5 are formed. ), 7 (7a, 7
b, 7c) and the electrodes 8 (8a, 8c) formed on the chip 3.
b, 8c) and 9 (9a, 9b, 9c) are connected by wire 10 in a one-to-one relationship. Each conductive pad 6 (6a, 6b, 6c), 7 (7a, 7b, 7c)
Is an output terminal group 12 (output terminal 12a, ground terminal 1) formed on the bottom surface (or side surface) of the package through a plurality of conductive patterns 11 wired inside and outside the package 2.
2b, 12c), input side terminal group 13 (input terminals 13a,
The ground terminals 13b, 13c) are electrically connected one to one. The upper surface of the package 2 is closed by the lid 15.

A SAW device 1 having such a configuration
11 is mounted on a printed circuit board (hereinafter referred to as a printed board) 20, a common ground pattern 21 made of a metal film is previously formed on the entire surface of the printed board 20 as shown in FIG. Is formed, and rectangular annular isolation regions (insulating regions exposing the substrate surface) 22 and 23 are formed only in portions corresponding to the output terminal 12a and the input terminal 13a on the bottom surface of the SAW device 1, respectively. An output wiring pattern 24 and an input wiring pattern 25 are separately formed inside each of the isolation regions 22 and 23. The entire pattern located outside the input / output wiring patterns 24 and 25 is used as the common ground pattern 21. In measuring the filter characteristics of the SAW device 1 mounted in this manner, as shown in FIG. 11B, the input wiring pattern 24 and the output wiring pattern 25 are connected to the input and output coaxial cables 30 and 31 respectively. The measurement was carried out by connecting to a measuring instrument via. FIG.
Is a graph showing characteristics of a SAW device mounted as shown in FIG. 2, and FIG. 13 is a graph showing characteristics of a single SAW device before mounting. Note that each graph shows a graph obtained by performing a calibration process in consideration of the influence of the coaxial cables 30 and 31. That is, when the input / output ground terminals 12b, 12c, 13b, and 13c of the SAW device 1 are connected by the common ground pattern 21 on the printed circuit board, respectively, the attenuation is smaller than the characteristic before mounting on the printed board 20 (FIG. 13). It has been found that the characteristics are degraded by 20 dB or more especially on the lower frequency side than the pass band.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and even when a piezoelectric device such as a piezoelectric filter is mounted on a printed circuit board, the device is still in a state of being alone before mounting. An object of the present invention is to provide a printed wiring board unit capable of obtaining filter characteristics equivalent to characteristics.

[0005]

In order to achieve the above object, the present invention is directed to an input terminal and an output terminal which are respectively arranged along two opposing sides of a package bottom surface, and the input terminal side A printed wiring board unit comprising: a piezoelectric device having a ground terminal disposed on the output terminal side; and a printed wiring board on which the piezoelectric device is mounted, wherein the input terminal is provided on the printed wiring board. And an input wiring pattern and an output wiring pattern respectively corresponding to the output terminal, an isolation region surrounding at least a part of each of the input and output wiring patterns, and at least an input and output wiring pattern separated by each isolation region. And a ground pattern formed over a predetermined area on the printed wiring board so as to surround a part thereof. In, the said earth pattern, the earth pattern, the input-side ground pattern,
It is characterized in that an insulating line for electrically dividing the output side ground pattern is formed. An input terminal and an output terminal formed on the bottom surface or the side surface of the package, and an input ground terminal and an output terminal formed on the bottom surface or the side surface of the package so as to be paired with the input terminal and the output terminal, respectively. A printed wiring board unit comprising: a piezoelectric device having a ground terminal; and a printed wiring board on which the piezoelectric device is mounted, wherein the printed wiring board has an input wiring pattern corresponding to an input terminal, and an output. An output wiring pattern corresponding to the terminal, an input-side ground pattern corresponding to the input-side ground terminal, and an output-side ground pattern corresponding to the output-side ground terminal are formed, and the two ground patterns are separated from each other. It is characterized by having. According to a third aspect of the present invention, there is provided a piezoelectric device having an input terminal and an output terminal, an input-side ground terminal and an output-side ground terminal which are respectively paired with the input terminal and the output terminal, and the piezoelectric device is mounted. A printed wiring board unit comprising a printed wiring board, wherein a ground potential generated by a signal current supplied from the input terminal and flowing to a ground terminal reduces an influence on an output signal output from the output terminal. Ground pattern on the printed wiring board
The input-side ground pattern and the output-side ground pattern are separated. The electronic device according to claim 4 is
A printed wiring board unit according to claim 1, 2, 3 or 4 is provided.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. [Basic principle of the present invention] Prior to the description of the embodiment,
The above-mentioned problem, that is, the cause of deterioration of characteristics when a piezoelectric device is mounted on a printed circuit board will be considered. Note that FIG. 10 to FIG. 13 are also referred to. As described above, the common ground pattern 21 in which the high-frequency piezoelectric filter 1 is connected to the ground pattern between the input and output.
If the cause of the remarkable decrease in the attenuation of the stop band when mounted on the printed wiring board 20 having the above is presumed, the following reasons may be considered. That is, the band-pass type S
Considering the AW filter, among the signals supplied to the input terminal 13a, the signal of the pass band frequency is transmitted to the output terminal 12a with almost no attenuation, whereas the signal of the stop band frequency is transmitted via the input side IDT. The energy flowing to the ground and transmitted to the output terminal 12a is reduced. On the other hand, as is well known, even a wide common ground pattern has a slight inductance component (function as a coil), and the reactance due to the inductance, that is, the current blocking component is proportional to the frequency (X = jω).
L, ω = 2πf, L inductance). That is, if there is an inductance due to the common ground pattern 21 in a current path through which a part of the signal supplied to the input terminal 13a flows,
At both ends, an electromotive force proportional to the inductance component and the flowing current and frequency is generated. If this electromotive force affects the output terminal 12a, it can be understood that the attenuation of the stop band will decrease. This phenomenon is represented by an equivalent circuit as shown in FIG. That is, conventionally, those earth pattern between the input and output terminals are connected is to that ground resistor R _G or and ground inductance L _G is inserted in common to the input IDT and the output IDT 8 Become. Accordingly, the output to the signal appearing at terminal electromotive force generated by these ground resistor R _G and ground inductance L _G is added, the attenuation of resulting stopband is presumed that reduction. Then, by taking measures to remove the connection between the ground patterns on the input terminal side and the output terminal side by experiments, the original characteristics of the piezoelectric device could be obtained. It is considered that this phenomenon can be shown by the equivalent circuit of FIG. That is, as a result of the grounding of the input end and the output end being separated, the input IDT and the output IDT are separated.
There is no common ground line, and the above-mentioned problem does not occur. It has been confirmed by experiments that the above effect is more remarkable in the continuous ground portion (common ground pattern 21) located immediately below the piezoelectric device or in the vicinity of the input end side and the output end side. That is, even if the input terminal side ground and the output terminal side ground are electrically connected to each other at a position distant from the input IDT or the output IDT by a required distance, the conventional problem may not occur. Therefore, the basic idea of the present invention is that the ground potential generated by the signal current supplied from the input terminal and flowing through the ground pattern does not affect the output signal or becomes small so that the input terminal side ground pattern and the output ground signal are not affected. The end-side ground pattern is separated.

[First Embodiment] Next, an example of the configuration of a printed wiring board unit developed based on the above-described principle of the present invention will be described. FIG. 1 is a diagram illustrating the configuration of a printed wiring board unit according to an embodiment of the present invention. The SAW filter 1 as a piezoelectric device has the same configuration as that of the conventional example described above. The same parts will be described with the same reference numerals. Also, for the printed wiring board 20, the same portions as those in FIG. 10 are denoted by the same reference numerals. The characteristic configuration of this embodiment is that the ground pattern 21 on the printed wiring board 20 is separated into an output-side ground pattern 31 and an input-side ground pattern 32 by dividing the narrow-band insulating line 30. It is in. The insulating line 30 is formed of both the wiring patterns 24 and 25 of the common ground pattern 21 shown in FIG.
This is a region where the upper surface of the substrate is exposed by linearly removing a portion located between them, and each of the ground patterns 31 and 32 is electrically isolated by an insulating line 30. When the SAW device 1 is mounted on the printed wiring board 20 having such a configuration, the output terminals 12a and the input terminals 13a on the device side are connected to the output wiring pattern 24 and the input wiring pattern 25, respectively, as indicated by dotted lines. Place so that they are connected. At this time, the output side ground terminal 12
b and 12c are connected to the output-side ground pattern 31, and the input-side ground terminals 13b and 13c are connected to the input-side ground pattern 32. When the characteristics of the SAW device were measured for the printed wiring board unit having such a configuration, as shown in FIG. 2, the filter characteristics were improved by about 10 dB as compared with the case of FIG. 12, and the attenuation characteristics on the low frequency side were improved. .

[Second Embodiment] FIG. 3 is a plan view showing the structure of a printed wiring board unit according to a second embodiment of the present invention. An experiment was performed. The piezoelectric device used in the experiment is a 1-3-order longitudinally coupled dual mode SAW filter, which is a filter in which two filters are cascaded, and thus has two ground terminals on each of the input and output sides. Therefore, insulating lines 40 and 41 as shown are added to separate the two ground terminals. These insulation lines 40 and 41
Is a slit-shaped insulating region led out from each of the isolation regions 22 and 23 toward the insulating line 30;
By providing the insulation lines 40 and 41, the current path between the earth terminals 12b and 12c on the output side of the SAW filter 1 placed at the position where the piezoelectric device is placed, and the ground current path between the input side earth terminals 13b and 13c. The energization path is configured to be an outer detour path that does not pass through the insulation lines 40 and 41, respectively. As described above, when the current path of the ground current was configured to be long and its influence was confirmed, the filter characteristics as shown in FIG. 4 could be confirmed. That is, it can be seen that the filter characteristics according to this embodiment are inferior to the first embodiment, but are significantly improved as compared with the conventional filter characteristics. [Third Embodiment] FIG. 5 is a plan view showing a ground pattern in a printed wiring board unit according to a third embodiment of the present invention, which is also a configuration for separating two ground terminals. In this embodiment, the U-shaped insulating lines 45 and 46 are formed on the ground patterns 31 and 32 corresponding to the device-side ground terminals 12b, 12c, 13b and 13c, respectively. The current path between the ground currents 12b and 12c and the current path between the input-side ground terminals 13b and 13c are configured to be outer detour paths that do not pass through the insulation lines 45 and 46, respectively. SA mounted on this printed wiring board
When the characteristics of the W device were measured, it was found that the filter characteristics according to this embodiment were inferior to those of the first embodiment, but were significantly improved as compared with the conventional filter characteristics. .

[Fourth Embodiment] FIG. 6 is a plan view of a printed wiring board used in a fourth embodiment of the present invention. In this embodiment, FIG. By removing the insulating line 30 to reproduce the common ground pattern 21 and extending the free ends of the U-shaped insulating lines 45 and 46 in FIG. The route is longer. That is, consideration is given to lengthening the path of the earth current between the output terminal 12b and the input terminal 13b and the path of the earth current between the output terminal 12c and the input terminal 13c. In this embodiment, the input and output ground patterns are not completely separated from each other, but the path of the ground current is distant, so that the same operation as in the case where the ground pattern is separated cannot be obtained at high frequencies. In consideration of this, an experiment was also performed on the configuration shown in FIG. In this case as well, although slightly inferior to the case of the first embodiment, a similar effect of improving characteristics could be confirmed.

[Other Modifications] In the above embodiments, the output wiring pattern 24 and the input wiring pattern 25 are completely surrounded by the ground pattern. However, this is only an example, and for example, FIG. Only part of the output wiring pattern 24 and the input wiring pattern 25 like the wiring shown in FIG.
You may comprise so that it may be surrounded (sandwiched) by the output side earth patterns 50 and 51, respectively. Then, when the piezoelectric device is mounted at the piezoelectric device mounting position indicated by the dotted line, the output terminal 12a and the input terminal 13a are connected corresponding to the output wiring pattern 24 and the input wiring pattern 25, respectively,
Ground terminals 12b, 12c and 13b, 13c located on both sides of the output terminal 12a and the input terminal 13a, respectively,
The output wiring pattern 24 and the input wiring pattern 25 are connected to ground patterns 50 and 51 disposed on both sides of the input wiring pattern 25 via insulating lines 55 and 56, respectively. In each of the embodiments described above, a piezoelectric device in which a 1-3 order dual mode SAW filter is cascade-connected in two stages has been described as an example. It is also applicable when mounting. In recent years, demands for miniaturization have increased the demand for a chip-on-board (COB) type in which a chip such as a SAW filter is directly mounted on a printed wiring board.
The present invention can be applied to COB. At this time, the connection between the chip component and the wiring pattern may be wire bonding or a so-called flip chip method, but any method is applicable. Needless to say. In each of the claims, the term “piezoelectric device” means not only a type in which a piezoelectric element is housed in a package, but also a piezoelectric device.
The concept includes a chip such as an AW filter. Further, the printed wiring board unit shown in each of the above embodiments is mounted on a communication device and other electronic devices,
Obviously, this contributes to improving the performance of each device.

[0011]

As described above, according to the present invention, even when a piezoelectric device such as a piezoelectric filter is mounted on a printed wiring board, a filter characteristic equivalent to that of the device alone before mounting is obtained. Printed circuit board unit can be provided. That is, according to the present invention, an input wiring pattern and an output wiring pattern corresponding to an input terminal and an output terminal, respectively, and an isolation surrounding at least a part of each of the input and output wiring patterns are provided on the printed wiring board. And a ground pattern formed over a predetermined range on the printed wiring board so as to surround at least a part of the input and output wiring patterns across each isolation region. Is formed with an insulating line for electrically dividing the ground pattern into an input-side ground pattern and an output-side ground pattern. In other words, the ground potential on the input end and the ground potential on the output end are such that the ground potential generated by the signal current supplied from the input terminal and flowing through the ground pattern has no effect on the output signal or is small. And separated. As described above, since the connection between the ground patterns on the input terminal side and the output terminal side was released, a reduction in the attenuation of the stop band was prevented, and the inherent characteristics of the piezoelectric device could be obtained. That is, as a result of the grounding of the input terminal side and the output terminal side being separated, there is no ground line common to the input IDT and the output IDT, and the above-mentioned problem does not occur. According to the invention of claim 2, an input wiring pattern corresponding to the input terminal, an output wiring pattern corresponding to the output terminal, an input-side ground pattern corresponding to the input-side ground terminal, and an output-side ground terminal are provided on the printed wiring board. And a corresponding output side ground pattern. According to the present invention, the connection between the input terminal side and the output terminal side ground patterns and the common ground which does not release the connection can be performed without limiting the shape and arrangement of the input / output wiring patterns and the input / output side ground patterns. Since the circuit for passing the ground current between the ground terminals on the pattern was used as a detour path, a reduction in the attenuation of the stop band was prevented, and the inherent characteristics of the piezoelectric device could be obtained. According to the third aspect of the present invention, a piezoelectric device having an input terminal and an output terminal, an input-side ground terminal and an output-side ground terminal that form a pair with the input terminal and the output terminal, respectively, and the piezoelectric device are mounted. A printed wiring board unit comprising a printed wiring board, wherein the ground potential generated by a signal current supplied from the input terminal and flowing to a ground terminal reduces an influence on an output signal output from the output terminal. Since the ground pattern on the printed wiring board is separated into an input-side ground pattern and an output-side ground pattern, not only the piezoelectric device containing the piezoelectric element but also the piezoelectric element is directly mounted on the wiring pattern on the printed wiring board. Type printed circuit board unit, and the same effect as in the other claims can be obtained. It can be exhibited. In claim 4, by mounting the printed wiring board unit described in each of the above claims on various electronic devices, it is possible to obtain effects corresponding to each claim.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a printed wiring board unit according to a first embodiment of the present invention.

FIG. 2 is a view showing filter characteristics of the embodiment of FIG. 1;

FIG. 3 is a configuration explanatory view of a printed wiring board unit according to a second embodiment of the present invention.

FIG. 4 is a view showing filter characteristics of the embodiment of FIG. 3;

FIG. 5 is a configuration explanatory view of a printed wiring board unit according to a third embodiment of the present invention.

FIG. 6 is a configuration explanatory view of a printed wiring board unit according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a main part configuration of a printed wiring board unit according to another embodiment of the present invention.

FIG. 8 is an equivalent circuit diagram of a conventional printed wiring board unit having a common ground pattern.

FIG. 9 is an equivalent circuit diagram of a printed wiring board unit having a ground pattern according to the present invention.

10 (a), (b) and (c) are front longitudinal sectional views showing the structure of a SAW device as an example of a conventional piezoelectric device.
Plane cross-sectional view and bottom view.

FIGS. 11A and 11B are perspective views showing a procedure for mounting this SAW device on a printed wiring board and a state after mounting.

FIG. 12 is a diagram showing filter characteristics of a SAW device mounted on a printed wiring board.

FIG. 13 is a diagram illustrating filter characteristics of a single SAW device that is not mounted.

[Explanation of symbols]

1. Piezoelectric device (SAW device), 2 ceramic package, 3 SAW device chip, 4, 5 steps, 66 (6a, 6b, 6c), 7 (7a, 7b, 7)
c) conduction pad, 8 (8a, 8b, 8c), 9 (9
a, 9b, 9c) electrodes, 10 wires, 11 conductive patterns, 12 output terminal groups, 12a output terminals, 12
b, 12c ground terminal, 13 input terminal group 13, 1
3a input terminal, 13b, 13c ground terminal, 20
Printed wiring board, 21 common ground pattern, 22,
23 isolation area, 24 output wiring pattern, 25 input wiring pattern, 30, 31 coaxial cable, 30 insulation line, 31 output side ground pattern,
32 Input side earth pattern, 40, 41 Insulation line, 45, 46 Insulation line.

Claims (4)

[Claims] An input terminal and an output terminal are respectively disposed along two opposing sides of a package bottom surface, and ground terminals are respectively disposed on the input terminal side and the output terminal side.
And a printed wiring board unit comprising a piezoelectric device having the same, and an input wiring pattern and an output wiring corresponding to the input terminal and the output terminal, respectively, on the printed wiring board. A pattern, an isolation region surrounding at least a part of each of the input and output wiring patterns, and a predetermined region on the printed wiring board surrounding at least a part of the input and output wiring patterns with each isolation region interposed therebetween. And a ground pattern formed over the range of: wherein the ground pattern is provided for electrically dividing the ground pattern into an input side ground pattern and an output side ground pattern. A printed wiring board unit, wherein an insulating line is formed. 2. An input terminal and an output terminal formed on a bottom surface or a side surface of a package, and an input-side ground terminal and an output-side ground terminal formed on a bottom surface or a side surface of the package so as to be paired with the input terminal and the output terminal, respectively. And a printed wiring board mounted with the piezoelectric device, comprising: a printed wiring board, wherein the printed wiring board has an input wiring pattern corresponding to an input terminal, and an output terminal. A corresponding output wiring pattern, an input-side ground pattern corresponding to the input-side ground terminal, and an output-side ground pattern corresponding to the output-side ground terminal are formed, and the two ground patterns are separated from each other. A printed wiring board unit characterized by the above-mentioned. 3. A piezoelectric device having an input terminal and an output terminal, an input-side ground terminal and an output-side ground terminal that form a pair with the input terminal and the output terminal, respectively, and printed wiring on which the piezoelectric device is mounted. A printed wiring board unit comprising: a printed wiring board unit configured to reduce an influence of a ground potential generated by a signal current supplied from the input terminal and flowing to a ground terminal on an output signal output from the output terminal. A printed wiring board unit wherein a ground pattern on a substrate is separated into an input-side ground pattern and an output-side ground pattern. 4. An electronic device comprising the printed wiring board unit according to claim 1.