Method of producing edge reflection type surface acoustic...

Details Method of producing edge reflection type surface acoustic... Method of producing edge reflection type surface acoustic...

2000-03-17

2003-10-28

Tugbang, A. Dexter (Department: 3729)

Metal working

Piezoelectric device making

C029S594000, C029S595000, C029S609100, C029S834000, C029S835000, C310S31300R, C310S320000, C310S366000, C333S150000, C333S187000, C333S193000, C333S195000, C333S196000

Reexamination Certificate

active

06637087

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing a surface acoustic wave device for use in a resonator, a bandpass filter, or other such apparatus, and more particularly, to a method of producing an edge reflection type surface acoustic wave device utilizing an SH type surface acoustic wave.
2. Description of the Related Art
In recent years, different types of edge reflection type surface acoustic wave devices for which no reflectors are required have been proposed.
FIG. 3
is a perspective view showing an edge reflection type surface acoustic wave resonator as an example of the above-described edge reflection type surface acoustic wave devices. In an edge reflection type surface acoustic wave resonator
1
, an interdigital transducer (hereinafter, referred to as IDT)
3
is formed on the upper side of a rectangular surface acoustic wave substrate
2
. The IDT
3
has a pair of interdigital electrodes
3
a
and
3
b
. The interdigital electrode
3
a
has plural electrode fingers
3
a
1
, and
3
a
2
. The interdigital electrode
3
b
has plural electrode fingers
3
b
1
and
3
b
2
. The electrode fingers
3
a
1
,
3
a
2
, and the electrode fingers
3
b
1
,
3
b
2
are arranged so as to be inserted between each other in an interdigitated manner. In the edge reflection type surface acoustic wave device
1
, the surface acoustic wave substrate
2
has a first edge
2
a
and a second edge
2
b
disposed opposite to each other. When an AC voltage is applied to the IDT
3
, the SH type surface acoustic wave is generated. The SH type surface acoustic wave is propagated in the direction passing through the first edge
2
a
and the second edge
2
b
, and is reflected by the edges
2
a
,
2
b.
Accordingly, it is unnecessary to provide reflectors on the opposite sides of the IDT
3
in the surface acoustic wave propagation direction, so that the surface acoustic wave device can be miniaturized.
Further, in Japanese Unexamined Patent Publication No. 7-50538, an example of the method of producing an edge reflection-type surface acoustic wave device is described. The above-described prior-art production method will be explained with reference to FIG.
4
.
First, a surface acoustic wave mother substrate
51
shown in
FIG. 4
is prepared. Plural IDTs
53
are formed on one side main surface
51
a
of the surface acoustic wave mother substrate
51
. The IDTs
53
correspond to the IDTs
3
of the edge reflection type surface acoustic wave resonators
1
, respectively. In the case of the edge reflection type surface acoustic wave resonator, it is necessary to form a reflection edge from which a surface acoustic wave is reflected with very high precision.
Thus, according to the above-described prior art method, the first and second reflection edges are provided by forming cut grooves on the surface acoustic wave mother substrate
51
from one side main surface
51
a thereof after the IDTs
53
are formed. More concretely, cut grooves each having a width T shown in
FIG. 4
are formed, for which a blade with a thickness T is used to form cut grooves
54
A and
54
B. In this case, the inner side walls of the grooves
54
A and
54
B which lie on the IDT
53
sides thereof constitute the first and second reflection edges, respectively. That is, in
FIG. 4
, the straight lines A
1
, A
2
, A
3
—and the straight lines B
1
, B
2
, B
3
—indicate the positions of the inner side walls on the IDT
53
sides of the above-described grooves
54
A and
54
B, that is, the positions of the first and second reflection edges, respectively.
As described in Japanese Unexamined Patent Publication No. 7-50538, it is necessary that the interval L, which is equal to the distance between lines B
1
and A
2
, of the cutting lines along which the above-described surface acoustic wave substrate
51
is cut is set at a larger value than the thickness T of the blade. That is, it is described that the cut grooves
54
A and
54
B can be easily formed by setting L>T.
Further, according to the above-described prior art method, the cut groove
54
A is formed along the cutting line A
1
shown in
FIG. 4
, and thereafter, the cut groove
54
B is formed along the cutting line B
1
. In this manner, the cutting is carried out along the cutting lines A
1
, B
1
, A
2
, B
2
, and A
3
in that order, respectively. In particular, when the cutting process for forming the first and second reflection edges on the surface acoustic wave substrate
51
is carried out, a cutting device is fed sequentially from one end of the surface acoustic wave substrate
51
to the other end thereof in the direction passing through the first and second reflection edges.
However, when the cutting device is fed in the direction passing through the first and second reflection edges to carry out the above-described cutting, a feeding-quantity C by which the cutting device is fed for the next cutting along the cutting line B
1
after the substrate
51
is cut along the cutting line A
1
, and a feeding-quantity D by which the cutting device is fed for cutting along the cutting line A
2
after the substrate
51
is cut along the cutting line Bt are considerably different from each other. Thus, the cutting device can not be fed sequentially at an equal pitch for cutting. That is, it is necessary to carry out the cutting while the feeding-pitch of the cutting device is changed.
In this case, unless the feeding-quantities C and D are accurately controlled, the distances between the first and second reflection edges of the respective edge reflecting type surface acoustic wave resonators become different, and thereby, dispersions in resonance characteristic occur. Accordingly, it has been necessary to use an expensive cutting device with which the feeding-pitch can be easily changed, and moreover, the feeding pitch can be accurately set. In addition, the change of the feeding-pitch is very difficult, and the productivity is low.
It is possible that the surface acoustic wave substrate
51
is formed so that the above-described feeding quantities C and D become equal- to each other. However, if the feeding quantities C and D are equal, the portion of the surface acoustic wave substrate which becomes eventually unnecessary, that is, the surface acoustic wave substrate portion sandwiched between the cutting line B
1
and the cutting line A
2
, is increased in size. Thus, the number of edge reflection type surface acoustic wave resonators which can be formed by use of the surface acoustic wave substrate
51
with a predetermined size is decreased and also, the productivity is reduced.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a method of producing an edge reflection type surface acoustic wave device, in which the process of forming reflection edges, carried out when individual edge reflection type surface acoustic wave devices are formed from a surface acoustic wave mother substrate, is improved, and many edge reflecting type surface acoustic wave devices can be efficiently produced with a high productivity.
According to one preferred embodiments of the present invention, the method of producing an edge reflection type surface acoustic wave device having first and second reflection edges opposed to each other preferably includes the steps of preparing a surface acoustic wave mother substrate having a plurality of IDTs formed on one surface side thereof, repeating the process of forming a cut groove on the surface acoustic wave mother substrate from one main surface side thereof whereby the first reflection edges of the respective surface acoustic wave devices are sequentially formed, and rep eating the process of forming a cut groove on the surface acoustic wave mother substrate from the one main surface side thereof whereby the second reflection edges of the respective surface acoustic wave devices are sequentially formed.
According to preferred embodiments of the present invention, since all of the distances between the first reflec

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