KR20040003615A - Surface acoustic wave filter - Google Patents

Abstract

PURPOSE: A surface acoustic filter is provided to reduce the size of a device by minimizing volume an area required for a signal electrode and a ground electrode. CONSTITUTION: A package(30) is provided with a plurality of connecting terminals(30a-30f). A piezoelectric substrate(40) is provided within the package(30). A plurality of input IDTs(InterDigital Transducers)(50,60) and output IDTs(70,80) are formed on the piezoelectric substrate(40) in a pattern and filter a signal inputted from an outside to output the filtered signal. A ground unit(90) is provided between the input IDTs(50,60) and the output IDTs(70,80) to eliminate noise of the filtered signal. The input IDTs(50,60), the output IDTs(70,80), and the ground unit(90) are connected to the connecting terminals(30a-30f) through a wire bonding in order to input/output a signal.

Description

Balanced surface acoustic wave filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balanced surface acoustic wave filter, and more particularly, to a balanced surface acoustic wave filter that can be easily miniaturized so as to meet the trend of miniaturization.

In general, surface acoustic waves represent a state of waves transmitted along the surface of the substrate and have a feature of rapidly attenuating in the depth direction. The SAW filter uses this feature as a frequency selective device.

That is, the surface acoustic wave element forms a metal electrode of a substrate having a large insulating property, and when the piezoelectric is applied, the surface of the substrate is temporarily warped. This action causes a physical wave. Surface acoustic wave Surface acoustic wave transmitted along the surface of the device is slower than electromagnetic waves, so it is used as a filter to temporarily delay an electric signal or pass only a specific frequency signal.

On the other hand, when the surface acoustic wave filter is connected to a MMIC (Monolithic Microwave Integrated Circuit) and a mixer (Mixer) requiring balanced input and output characteristics, a plurality of input interdigital transducers (IDTs) to have balanced input and output characteristics. And a balanced surface acoustic wave filter composed of an output IDT).

1 is a view illustrating a structure of a balanced surface acoustic wave filter according to a related art, and includes a package 10 in which a plurality of connection terminals 10a to 10f are formed so that an electronic component mounted therein may be electrically connected to the outside. ), A piezoelectric substrate 21 positioned inside the package 10, and a plurality of input IDTs 22 and 23 and output IDTs formed in a pattern on the piezoelectric substrate 21 to filter and output an external signal. And a ground portion 26 positioned between the input IDTs 22 and 23 and the output IDTs 24 and 25 to remove noise of the filtered signal. The input IDTs 22 and 23, the output IDTs 24 and 25, and the ground portion 26 are connected to the connection terminals 10a to 10f through wire bonding.

Here, the plurality of input IDTs 22 and 23 and the output IDTs 24 and 25 are signal electrodes 22a, 23a, 24a and 25a through which signals input from the outside are transmitted, and ground electrodes connected to an external ground ( A plurality of fingers 22c, 23c, 24c, 25c extending toward each other from 22b, 23b, 24b, 25b and the signal electrodes 22a, 23a, 24a, 25a and ground electrodes 22b, 23b, 24b, 25b. The signal electrodes 22a, 23a, 24a, and 25a, the ground electrodes 22b, 23b, 24b, and 25b and the connection terminals 10a to 10f are connected through wire bonding.

However, the balanced surface acoustic wave filter according to the related art has a signal thickness and a ground where the signal electrode and the ground electrode are connected to the connection terminal through wire bonding, and the other portions have the same thickness. In a plurality of input IDTs or output IDTs in which electrodes are adjacent to each other, the area required for the signal electrode and the ground electrode is increased, so that miniaturization is difficult.

The present invention has been made to solve the above-mentioned problems of the prior art, the object of which is to connect the adjacent signal electrodes or ground electrodes of a plurality of input IDT or output IDT and the connecting terminal formed in the package through wire bonding the signal electrode Or a balance that can be easily miniaturized by reducing the thickness of the signal electrode or the ground electrode except for the portion where the wire is connected to the ground electrode and placing the plurality of input IDTs or output IDTs so that the adjacent signal or ground electrodes cross each other. It is to provide a type surface acoustic wave filter.

1 is a view showing the structure of a balanced surface acoustic wave filter according to the prior art,

2 is a view showing a structure of a balanced surface acoustic wave filter according to the present invention;

3 is an enlarged view of A of FIG. 2.

<Explanation of symbols on main parts of the drawings>

30: Package 30a ~ 30f: Connection terminal

40: piezoelectric substrate 50, 60: input IDT

70, 80: output IDT90: ground part

According to a feature of the balanced surface acoustic wave filter according to the present invention for solving the above problems, the piezoelectric substrate is located in a package formed with a plurality of connection terminals; Balanced surface comprising a plurality of input IDT and output IDT consisting of a signal and a ground electrode disposed in parallel to face each other on one side of the piezoelectric substrate and a plurality of fingers formed between the signal and the ground electrode In the acoustic wave filter, recesses and grooves in which adjacent signal electrodes or ground electrodes of the plurality of input IDTs or output IDTs cross each other are formed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the balanced surface acoustic wave filter according to the present invention includes a package 30 in which a plurality of connection terminals 30a to 30f are formed, a piezoelectric substrate 40 located in the package 30, and And a plurality of input IDTs 50 and 60 and output IDTs 70 and 80 formed in a pattern on the piezoelectric substrate 40 to filter and output signals input from the outside, and the plurality of input IDTs 50 and 60. And a ground portion 90 positioned between the output IDTs 70 and 80 to remove noise of the filtered signal.

Here, the plurality of input IDTs 50 and 60, the output IDTs 70 and 80 and the ground unit 90 are connected to the connection terminals 30a to 30f through wire bonding to enable input and output of signals to the outside. .

Here, the plurality of input IDTs 50 and 60 and the output IDTs 70 and 80 are signal electrodes 51, 61, 71 and 81 through which signals are transmitted, and ground electrodes 52 and 62 connected to an external ground, respectively. 72, 82 and a plurality of fingers 53 extending from each other from the signal electrodes 51, 61, 71, 81 and the ground electrodes 52, 62, 72, 82 to filter signals input from the outside; 63, 73, and 83, and the connection terminals 30a to 30f, the signal electrodes 51, 61, 71, and 81, and the ground electrodes 52, 62, 72, and 82 are connected through wire bonding. .

In this case, the plurality of input IDTs 50 and 60 are formed to have a thin thickness except for a portion where the signal electrode 51 and the ground electrode 62 adjacent to each other are connected to the connection terminals 30a to 30f. The plurality of input IDTs 50 and 60 are disposed to intersect the adjacent signal electrode 51 and the ground electrode 62.

That is, as shown in FIG. 3, the plurality of input IDTs 50 and 60 have the signal electrodes 51 and the ground electrodes 62 adjacent to each other through the connection terminals 30a to 30f and wires, respectively. Concave portions 51a and 62a, which are connected portions, and groove portions 51b and 62b, which are thinner than the recess portions 51a and 62a, are portions which are not connected to the wire.

In addition, the adjacent signal electrode 51 and the ground electrode 62 cross each other so that the recessed portion 62a of the ground electrode 62 corresponds to the groove 51b of the adjacent signal electrode 51. In comparison, since the area required for the adjacent signal electrode 51 and the ground electrode 62 is reduced, the layout of the entire device can be reduced.

In this case, the thicknesses of the fingers 53 and 63 and the grooves 51b and 62b of the adjacent signal electrode 51 and the ground electrode 62 are 50 µm or more, which is the minimum thickness through which signals can be transmitted. The thickness of the fingers (53, 63) and the recesses (51a, 62a) is formed to be 150㎛ or more, the minimum thickness required when connecting to the connection terminal (30a ~ 30f) through wire bonding, When the recessed portion 62a of the ground electrode 62 corresponds to the groove portion 51b of the signal electrode 51, the balance type is spaced apart by a minimum distance of 10 μm or more to prevent mutual interference. The surface acoustic wave filter performs the filtering function at the same time and minimizes the area required by the recesses 51a and 62a and the grooves 51b and 62b where the adjacent signal electrodes 51 and the ground electrodes 62 may be intersected. It can be.

Meanwhile, the plurality of output IDTs 70 and 80 also form recesses and grooves in the ground electrode 72 and the signal electrode 81 which are adjacent to each other like the input IDTs 70 and 80, respectively. By intersecting the grooves so as to correspond, the area occupied by the adjacent ground electrode 72 and the signal electrode 81 can be minimized.

As a result, when the balanced surface acoustic wave filter according to the present invention forms a plurality of input IDTs and output IDTs, the balanced surface acoustic wave filter minimizes an area occupied by adjacent signal electrodes or ground electrodes, thereby enabling efficient use of a limited area.

In the balanced surface acoustic wave filter according to the present invention configured as described above, the balanced surface acoustic wave filter has a balanced input / output characteristic and includes a plurality of input IDTs and output IDTs capable of filtering a signal input from the outside. The signal electrodes or ground electrodes positioned adjacent to each other in the plurality of input IDTs or output IDTs are formed with recesses and grooves having different thicknesses from those required for wire bonding, and the signal electrodes or ground electrodes positioned adjacent to each other. Since the grooves correspond to the recesses so as to cross each other, the area required for the adjacent signal electrodes or the ground electrodes can be minimized to reduce the size of the entire device.

Claims (1)

A piezoelectric substrate positioned in a package in which a plurality of connection terminals are formed; A plurality of input interdigital transducers (hereinafter referred to as IDTs) comprising a signal and a ground electrode disposed in parallel to face each other on one side of the piezoelectric substrate and a plurality of fingers formed between the signal and the ground electrode. In the balanced surface acoustic wave filter comprising a) and an output IDT, Balanced surface acoustic wave filter, characterized in that the recessed portion and the groove portion of the adjacent signal electrode or the ground electrode of the plurality of input IDTs or output IDTs are formed to cross each other.