Etching a substrate: processes – Gas phase etching of substrate – Application of energy to the gaseous etchant or to the...
Reexamination Certificate
2000-05-13
2002-10-01
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Gas phase etching of substrate
Application of energy to the gaseous etchant or to the...
C216S059000, C216S041000, C216S013000, C216S045000, C216S091000, C204S001001, C204S001001, C204S001001, C204S001001, C156S345240, C156S345390
Reexamination Certificate
active
06458285
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for controlling the frequency of piezoelectric components. More specifically, the present invention relates to a method and an apparatus for controlling the frequency of piezoelectric components such as piezoelectric ceramic resonators, filters, discriminators, or traps, by removing portions of the electrodes disposed on a piezoelectric substrate, or by adding a frequency control substance on the electrodes.
2. Description of the Related Art
Recently, with piezoelectric components such as filters, there has been a growing need for frequencies having very high precision. Conventionally, the frequency has been controlled by the steps of forming electrodes having frequencies that are somewhat higher than the target or desired frequency on both sides of a piezoelectric substrate, and applying frequency control ink on the electrodes by screen printing or by spray coating to increase the mass thereof. However, in the method described above, concentration of the frequency is too low to improve precision because the quantities of ink applied may vary widely. In addition, in the case of screen printing, the conventional method has another disadvantage in that it may cause cracking of the piezoelectric substrate because this method is based upon contact operation and therefore, the object is subjected to a load.
Accordingly, the applicant of the present invention has proposed a method for carrying out a non-contact frequency control with very high precision (Japanese Unexamined Patent Publication No. 3-289807). According to this method, the marking of a predetermined pattern is carried out by the steps of dividing the pattern to be marked into regions defining a matrix, charging ink particles by applying voltages proportional to the positional information obtained from each region, and directing charged particles of ink to the object to be marked by deflecting them in the electrostatic field. Therefore, a predetermined amount of ink can be applied to a piezoelectric resonator without variations in mass thereof, and thus, frequency control can be carried out with high precision.
When manufacturing piezoelectric components, in order to achieve the economies of mass production, a number of elements are formed first as mother substrates in a first step, and then the mother substrates are cut into individual elements. However, these elements may have differing frequencies even within one mother substrate due to a variety of factors. In such a case, even if the electrically controlled marking method is used as an alternative to screen printing, or other such method, it is difficult to reduce variations of frequencies among individual elements within the mother substrate, though it is possible to reduce variations of frequencies among mother substrates. It is also possible to change the amount of ink to be applied to the elements within a mother substrate on an individual basis according to frequencies thereof, however, it requires longer time because ink must be applied on the element one by one.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a frequency control apparatus for piezoelectric components which controls variations in frequency among individual elements quickly and achieves the economies of mass production, when a plurality of elements are formed within or on a piezoelectric substrate.
The frequency control apparatus for piezoelectric components in accordance with a preferred embodiment of the present invention preferably includes a pattern board disposed on a piezoelectric substrate having a plurality of electrodes disposed thereon and provided with an aperture pattern for selectively exposing the electrodes, a shielding board disposed on the pattern board and provided with a window for selectively exposing aperture patterns on the pattern board, and an electrode removal device arranged to remove portions of the electrodes disposed on the piezoelectric substrate exposed through the aperture pattern on the pattern board and though the window on the shielding board.
In accordance with this preferred embodiment of the present invention, since the electrodes disposed on the piezoelectric substrate are exposed selectively through the aperture pattern on the pattern board and the aperture patterns are exposed selectively through the window on the shielding board, frequency is controlled by selectively exposing electrodes which require frequency control through the aperture pattern according to variations in frequency of respective elements including electrodes from the target frequency, and removing portions of those exposed electrodes.
In addition, in accordance with the present preferred embodiment of the present invention, frequencies of a plurality of electrodes are controlled simultaneously very efficiently by a group of electrodes exposed simultaneously through the window on the shielding board. By repeating frequency control procedures after changing the aperture pattern to be exposed through the window on the shielding board, very precise frequency control is achieved for a plurality of electrodes exposed through the window on the shielding board, and thus, frequencies of individual elements are controlled with high precision.
The frequency control apparatus for piezoelectric components in accordance with another preferred embodiment of the present invention includes a pattern board disposed on a piezoelectric substrate having a plurality of electrodes disposed on the surface thereof and provided with an aperture pattern for selectively exposing the electrodes, a shielding board disposed on the pattern board and provided with a window for selectively exposing an aperture pattern on the pattern board, and frequency control substance coating device arranged to apply a frequency control substance on the electrodes located on the piezoelectric substrate and exposed through the aperture pattern on the pattern board and though the window on the shielding board.
In accordance with the present preferred embodiment of the present invention, since the electrodes provided on the piezoelectric substrate are exposed selectively through the aperture pattern on the pattern board, and the aperture patterns are exposed selectively through the window on the shielding board, frequency may be controlled by selectively exposing electrodes which require frequency control through the aperture pattern according to variations from the target frequency of respective elements which include electrodes, and applying a frequency control substance only on those exposed electrodes.
In addition, in accordance with this preferred embodiment of the present invention, frequencies of a plurality of electrodes may be controlled simultaneously with efficiency by a group of electrodes exposed simultaneously through the window on the shielding board. By repeating frequency control procedures after changing the aperture pattern to be exposed through the window on the shielding board, very accurate frequency control is achieved for a plurality of electrodes exposed through the window on the shielding board. As a result, frequencies of individual elements are controlled with very high precision.
The frequency control apparatus for piezoelectric components in accordance another preferred embodiment of the present invention preferably includes a pattern board disposed on a plurality of piezoelectric substrates having electrodes provided on the surface thereof and provided with an aperture pattern for selectively exposing the electrodes located on a plurality of piezoelectric substrates, a shielding board disposed on the pattern board and provided with a window for selectively exposing aperture pattern on the pattern board, and an electrode removing device arranged to remove portions of the electrodes provided on the piezoelectric substrate and exposed through the aperture pattern on the pattern board and through the window on the shieldin
Iyama Kiyoshi
Kitano Hiroki
Tatsumi Tetsuo
Gulakowski Randy
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Winter Gentle E.
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