JP3253333B2 - Method of adjusting characteristics of surface acoustic wave filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the characteristics of a small high-frequency surface acoustic wave filter used in a cellular phone, a transmission device and the like.
Regarding the adjustment method . More specifically, the present invention relates to a method for adjusting the characteristics of a surface acoustic wave filter in which the frequency characteristics or impedance characteristics can be changed by a bonding wire.

As typified by the recent miniaturization of portable telephones, the surface acoustic wave filters used in these devices are also required to be greatly miniaturized. Also, the high frequency band used is gradually increasing to 800 MHz or 1.8 GHz.

In order to obtain the performance of a surface acoustic wave filter,
In some cases, an inductance element is required outside the chip in addition to the design of the filter chip to improve frequency characteristics or impedance characteristics. 800MHz ~
As an inductance element in the 1.8 GHz band, a value of 1 nH to several tens of nH is often used, and it is an important practical problem how to realize these while achieving miniaturization.

[0004]

2. Description of the Related Art FIG. 4 is a view showing a conventional surface acoustic wave filter. This is provided with an input transducer or resonator 2 and an output transducer or resonator 3 in which a pair of comb-shaped electrodes are interdigitally combined on a substrate 1 formed of a piezoelectric crystal such as LiTaO ₃ or LiNbO _3. Have been. When an electric signal is input from the input transducer or the resonator 2, a surface acoustic wave 4 corresponding to the distance between the electrodes is generated and propagates on the surface of the substrate 1 to reach the output transducer or the resonator 3. Here, it is converted into an electric signal again.

[0005] In this case, by devising the design of the electrode pattern, an arbitrary filter characteristic can be obtained at the time of conversion from an electric signal to an acoustic signal or at the time of the reverse conversion. In such a surface acoustic wave device, since surface acoustic waves propagate on the surface of the substrate, the characteristics of the device are changed by being sensitive to the state of the surface, for example, adhesion of dust and moisture. For this reason, the surface acoustic wave device is housed in a package and sealed for use.

[0006]

In the above-mentioned conventional surface acoustic wave filter, the frequency impedance element is constituted by a chip coil, an air-core coil, a strip line, or the like outside the package. It was supposed to hinder miniaturization.

An object of the present invention is to realize a method of adjusting the characteristics of a surface acoustic wave filter miniaturized including a frequency impedance element.

[0008]

In the method of adjusting the characteristics of a surface acoustic wave filter according to the present invention, a surface acoustic wave resonator is used.
Multiple parallel and series arms are connected in a ladder
A surface acoustic wave filter having predetermined characteristics,
A bonding wire is connected in series with each of the plurality of parallel arms.
Surface acoustic wave filter
When adjusting the filter characteristics, provided on the surface acoustic wave filter chip or the package surface, the pad is independent of the co <br/> pendulum of the parallel arms, the electrode of the parallel arm resonator And by wire bonding to adjust the impedance characteristic or the frequency characteristic of the surface acoustic wave filter.

In addition, in the pair of wire bonding pads 14, the wires 15, 21 wire-bonded to the pads 14 are used to change the frequency characteristic or impedance characteristic of the surface acoustic wave filter. It is characterized by being used as an element. By employing this configuration, a downsized surface acoustic wave filter including the frequency impedance element can be obtained.

[0010]

1 (a) and 1 (b) are diagrams for explaining the principle of the present invention.
Circuit diagram). (A) In the case of the figure, the surface acoustic wave fill
The number of the chip 10 is one, and its input side and output side are
Improve impedance characteristics or frequency characteristics, respectively.
Inductance element L ₁, L_TwoIs provided. Ma
3B, three surface acoustic wave filter chips 1 are shown.
0_-1-10_-3Are provided in three stages, and contact
Subsequently, the surface acoustic wave filter chip 10_-Four, 10_-FiveProvided
The chip 10_-Four, 10_-FiveIn each
Inductors that improve impedance characteristics or frequency characteristics
Tance element L_Three, L_FourIs connected. In the present invention,
These inductance elements L₁~ L_FourThe surface acoustic wave
Filter chip or the package containing the filter chip.
It is provided in a part of the cage.

That is, as shown in FIG. 2 or FIG.
By providing a pair of wire bonding pads 14 and wire bonding the wires 15 or 21 between the pads 14, the lengths of the wires 15, 21 can be accurately determined, and the inductance having an accurate inductance value can be obtained. It can be an element. The impedance element or the frequency characteristic and the like are controlled by the inductance element, and a predetermined performance can be obtained.

[0012]

FIG. 2 shows a surface acoustic wave device in which the method of the present invention is carried out.
It is a figure which shows the 1st Example of a filter , (a) is a top view and (b) is a Z arrow view of (a) figure. In the figure, reference numeral 11 denotes a piezoelectric substrate such as LiTaO ₃ or LiNbO ₃ , on which an interdigital input transducer 12 and an output transducer 13 formed of a thin film metal are provided, and furthermore, a pad 14 is provided. _-1
-14 _-6 are provided.

One of the input transducers 12
Of the electrode 12a and the pad 14_-1Wire between
Fifteen_-1Is the pad portion of the other electrode 12b and the pad 14
_-FiveAnd 14_-6Between the wire 15_-Five, 15_-6Is each
Bonded. Output transducer 1
3 and the pad portion of one electrode 13a and the pad 14_-2With
Wire 15 between_-2Is the pad portion of the other electrode 13b
And pad 14_-3And 14 _-FourBetween the wire 15_-3, 15
_-FourAre respectively bonded. And each electrode
Wire 16_-1~ 16_-FourThrough a package (not shown)
Has been continued.

In the embodiment constructed as described above, the wires 15 _-1 to 15 _-6 are connected to the independent pads 14 _{-1 to} 14 _{-1.
-6, and} between the pad and the electrode pad, the length can be accurately set, and the inductance can be used as an accurate value of inductance. Therefore, since no inductance element is required outside the package, the size can be reduced. Note that not all the wires 15 _-1 to 15 _-6 are required, and the number thereof is adjusted to have a required inductance value.

FIG. 3 shows a surface acoustic wave in which the method of the present invention is performed.
FIG. 6 is a diagram illustrating a second example of the filter . In FIG. 1, reference numeral 10 denotes a surface elastic filter chip in which an input transducer 12 and an output transducer 13 are provided on a piezoelectric substrate 11 such as LiTaO ₃ or LiNbO _{3. The} filter chip 10 is housed in a package 20. . The package 20 is provided with a plurality of pads 14. A wire 21 used as an inductance element is bonded between the pads.
Note that the wire 21 may have a number that can obtain a required inductance value. The electrodes of the input / output transducers 12 and 13 and the package are connected by wires 22. The present embodiment configured as described above can achieve the same effects as the previous embodiment.

[0016]

According to the present invention, by forming an inductance element on a chip or in a package, it is possible to improve characteristics without increasing the size of a surface acoustic wave filter.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIGS. 2A and 2B are views showing a first embodiment of the present invention, wherein FIG. 2A is a plan view, and FIG.

FIG. 3 is a plan view showing a second embodiment of the present invention.

FIG. 4 is a perspective view showing a conventional surface acoustic wave filter.

[Explanation of symbols]

10, 10 _-1 to 10 _-5 Surface acoustic wave filter chip 11 Piezoelectric substrate 12 Input transducer 13 Output transducer 14, 14 _{-1 to} 14 _-6 Pad 15 _-1 to 15 _-6 , 16 _-1 ~ 16 _-4 , 21,22 ... wire 20 ... package

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Osamu Igata 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-59-6610 (JP, A) JP-A-60- 116216 (JP, A) JP-A-62-263710 (JP, A) JP-A-3-19415 (JP, A) JP-A-3-205907 (JP, A) JP-A-3-284008 (JP, A) Japanese Utility Model Application No. 3-77527 (JP, U) Japanese Utility Model Application No. Sho 60-66118 (JP, U) Japanese Utility Model Application No. 1-139621 (JP, U) Hiroaki Sato, Shigehisa Morishita "Pseudo SAW Resonator for VCO in UHF Band" A Note on the Revision of the Project ”97 IEEJ General Conference 97 P. 1-97 Shuji Urabe, Ryoji Habuka, Takashi Matsuura, "SAW Resonator-Type Piezoelectric Controlled Oscillator for PLL-FM Modulation" Transactions of the Institute of Electronics, Communication and Communication, 82/2 Vol. J65-B NO. 2 PP. 177-184

Claims (1)

(57) [Claims] A plurality of surface acoustic wave resonators;
Parallel arm and series arm are connected in a ladder form and have predetermined characteristics.
Surface acoustic wave filter, wherein each of the plurality of parallel arms
Inductors composed of bonding wires in series
When adjusting the characteristics of the surface acoustic wave filter that connects the reactance provided to the surface acoustic wave filter chip or the package surface, the pad is independent of the parallel arm resonators, the resonance of the parallel arm A method for adjusting the characteristics of a surface acoustic wave filter, wherein the impedance characteristics or the frequency characteristics of the surface acoustic wave filter are adjusted by wire-bonding the electrodes of the surface acoustic wave filter.