JPH04262611A - Polarization method for piezoelectric component and its device - Google Patents

Abstract

PURPOSE:To take polarization for a specific part while preventing the production of crack or the chipping of a piezoelectric substrate by blowing out a hot air to the specific part and blowing a cold air so as to surround the hot air. CONSTITUTION:A controller 21 opens a stop valve 3 and supplies a compressed gas to a hot air nozzle 11 and a cold air nozzle 12 via flow regulating valves 4, 5. Moreover, the controller 21 supplies a current to a heater 13 to heat up air to a required temperature to heat the compressed gas fed to the hot nozzle 11. Thus, the hot air heated to a temperature to take polarization is blown out from the nozzle port 11a of the hot air nozzle 11 and a gas at a room temperature is blown to surround the hot air from the nozzle port 12a of the cold air nozzle 12. The gas is blown out to the capacitor part of a piezoelectric substrate 30 on the entire face of which polarization processing is applied and the polarization is taken to the surrounding including a point O on the extended line of the nozzle port 11a of the hot air nozzle 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for removing polarization in a specific part of a piezoelectric component whose entire surface is polarized.

0002

2. Description of the Related Art Conventionally, as shown in FIGS. 3 and 4, input and output side electrodes 31 and 32 and an intermediate electrode 3 are formed on the surface of a piezoelectric substrate 30.
A piezoelectric component is known in which a ground side electrode 34 is provided on the back surface. The input/output side electrodes 31 and 32 are the vibration electrodes 3
1a, 32a and terminal electrodes 31b, 32b, and the intermediate electrode 33 has two vibrating electrode parts 33a, 33b that are paired with the vibrating electrodes 31a, 32a, respectively, and a wide capacitive electrode 33.
It has c. Furthermore, the ground side electrode 34 has two vibrating electrodes 34a, 34b facing the vibrating electrodes 31a, 33a and 32a, 33b on the surface, respectively, and a capacitive electrode 33c.
and a terminal electrode 34c which also serves as a capacitor electrode and which faces the terminal electrode 34c. The piezoelectric substrate 30 is made of a ceramic substrate whose entire surface has been polarized in the thickness direction or in the planar direction. After forming each of the above electrodes, polarization is removed only in the vicinity of the capacitive electrode 33c, so that the equivalent circuit shown in FIG. 3 is obtained. As shown in FIG.
Resonator elements A and B are configured between 2a, 33b and 34b, and a coupling capacitor C is configured between capacitive electrode 33c and terminal electrode 34c.

[0003] The above-mentioned coupling capacitor C section requires only a capacitance, and vibration of this section will have an adverse effect on the characteristics. It is necessary to suppress vibration or eliminate polarization in the relevant part. Conventionally, in order to suppress vibrations in the capacitor part, a mass body such as solder is placed on the capacitor electrode 33c.
There is a method of damping vibrations, but in this case, there is a drawback that vibrations cannot be damped sufficiently unless the mass body is placed evenly on the capacitive electrode 33c.

0004

[Problems to be Solved by the Invention] On the other hand, as methods for eliminating polarization, there are two methods: performing polarization treatment without providing polarization electrodes in the portions of the piezoelectric substrate 30 where polarization is not desired;
Polarize the entire surface, then partially remove the polarization (
There is a method to do this. The former method has the advantage that there is no need to remove polarization later, but cracks, chips, and cracks are likely to occur due to stress differences in crystal strain on the boundary between the polarized and non-polarized regions, resulting in lower yields. The problem is that it's bad. In addition, as the latter method, a method is known in which a light beam or laser beam is applied to the main part and the polarization is taken out by heating, but this method requires an abnormally fast heating rate and the difference between the heated part and the non-heated part. Due to the large difference in thermal expansion of the materials,
Cracks and chips are likely to occur. Furthermore, since the light absorption rate differs depending on the color of the electrode material, it is difficult to control the heating temperature applied to the piezoelectric substrate 30, and furthermore, the electrodes are significantly oxidized during heating, so the entire device must be placed in an inert gas. However, there are problems such as the equipment being large-scale and expensive.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to remove polarization from a required portion while preventing cracks or chips from occurring in the piezoelectric substrate when partially polarizing a piezoelectric substrate that has been polarized over the entire surface. The object of the present invention is to provide a method for polarizing a piezoelectric component. Another object of the present invention is to provide an apparatus for removing polarization of a piezoelectric component that can remove polarization of necessary portions of a piezoelectric substrate and can be constructed at low cost.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a first invention provides a method for removing polarization of a specific portion of a piezoelectric substrate whose entire surface has been subjected to polarization treatment, in which a hot air nozzle is directed to the specific portion. It is characterized by removing the polarization of a specific region by blowing hot air and also blowing cold air from a cold air nozzle so as to surround the hot air.

[0007] Furthermore, the second invention provides an apparatus for removing polarization of a specific part of a piezoelectric substrate whose entire surface has been subjected to polarization treatment,
It has a double-structured nozzle device with a hot air nozzle in the center and cold air nozzles concentrically around it. Both nozzles are supplied with compressed gas from a compressed gas source, and the hot air nozzle is heated. The hot air blown from the hot air nozzle toward the specific area is surrounded by the cold air blown from the cold air nozzle.

[0008] By heating a polarized region above the Curie temperature, the polarization of that region can be removed. Since hot air can heat the piezoelectric substrate more slowly than conventional light beams or laser beams, it can suppress local thermal expansion and prevent the piezoelectric substrate from cracking, chipping, or cracking. However, the problem with blowing hot air is that it is not possible to intensively heat only a specific area, and the heat diffuses around the heated area, destroying polarization even in areas where polarization should remain. This problem is extremely serious when polarization is partially removed from extremely small components such as piezoelectric components. Therefore, in the present invention, the above problem is solved by blowing cold air from around the hot air as well as hot air. Since the cold air flows to surround the hot air, the effect of heat on areas other than those to be polarized can be reduced. After the hot air and cold air hit the piezoelectric substrate, these air currents flow along the piezoelectric substrate, but at this time, the hot air and cold air are mixed to form a relatively low-temperature air current, so the heat does not affect other parts. is not enough. Furthermore, since the heating temperature does not vary depending on the color of the electrode material, temperature control of the piezoelectric substrate is relatively easy. Note that in the present invention, removing polarization does not only mean completely eliminating polarization, but also includes reducing the degree of polarization.

[0009] In order to improve the accuracy of the area and shape of the polarized portion, it is desirable to match the shape of the hot air nozzle to the shape of the portion to be polarized. Moreover, if the nozzle shape is a double structure in which a cold air nozzle is provided concentrically around a hot air nozzle, the structure can be simplified and handling becomes easy. In this case, if a heater is provided inside the hot air nozzle and a heat insulating material is provided between the hot air nozzle and the cold air nozzle, the heat from the heater can be prevented from escaping, and the cold air may be heated unnecessarily. There is no. The high temperature gas blown from the hot air nozzle has
Inert gases can also be used. Thereby, oxidation of the electrodes during heating can be easily prevented without installing the entire device in an inert gas. In order to quickly raise the temperature of the area where polarization is to be removed, there are methods of blowing hot air first and then blowing cold air with the hot air, methods of adjusting the flow rate ratio of hot air and cold air, and methods of changing the hot air nozzle to a cold air nozzle. A method of extending the process further may also be adopted.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an apparatus for carrying out the polarization removal method according to the present invention. In the figure, 1 is a compressed gas source such as an air compressor or an inert gas cylinder, from which compressed gas is supplied to two flow rate regulating valves 4 and 5 via an on-off valve 3 provided in a pipe 2. The compressed gas that has passed through the flow rate regulating valves 4 and 5 is sent to the nozzle device 10 through pipes 6 and 7, respectively.

The nozzle device 10 has a double structure with a hot air nozzle 11 inside and a cold air nozzle 12 around it. The compressed gas that has passed through is sent to the inside of the cold air nozzle 12. A heating heater 13 is provided inside the hot air nozzle 11, and the compressed gas sent into the inside of the hot air nozzle 11 is heated to a predetermined temperature by the heater 13 and blown out from the nozzle port 11a. On the other hand, the compressed gas sent into the cold air nozzle 12 is blown out from the nozzle port 12a as it is. Note that a heat insulating material 14 is provided on the inner or outer wall of the hot air nozzle 11 to suppress the heat from the heater 13 from being transmitted to the cold air nozzle 12. In addition, hot air nozzle 1
The nozzle port 11a of No. 1 is the nozzle port 12a of the cold air nozzle 12.
Because it protrudes further forward, hot air flows through the center and cold air flows around it.

The heater 13 is Joule heated by the current supplied from the power source 20 via the controller 21, but the temperature of the hot air is detected by a temperature sensor 22 installed near the nozzle opening 11a in the hot air nozzle 11. Since the signal is sent to the controller 21, the hot air temperature can be precisely feedback controlled. Further, the controller 21 controls the on-off valve 3 and the flow rate adjustment valves 4 and 5,
The on-off valve 3 supplies and shuts off compressed gas, and the flow rate adjustment valves 4 and 5 adjust the amount of compressed gas supplied to the hot air nozzle 11 and the cold air nozzle 12.

The operation of the polarization removing device having the above structure will be explained. First, the controller 21 opens the on-off valve 3 and supplies the compressed gas to the hot air nozzle 11 through the flow rate adjustment valves 4 and 5.
and supplied to the cold air nozzle 12. Further, the controller 21 supplies current to the heater 13 to heat the compressed gas supplied to the hot air nozzle 11 to a required temperature. As a result, hot air heated to a temperature for removing polarization is blown out from the nozzle opening 11a of the hot air nozzle 11.
Room temperature gas is blown out from the nozzle opening 12a of the cold air nozzle 12 so as to surround the hot air. These gases are blown onto the capacitor portion of the piezoelectric substrate 30 provided at a predetermined distance h from the nozzle opening 11a. The entire surface of this piezoelectric substrate 30 has been subjected to polarization treatment in advance, and the polarization of the peripheral portion including point O, which is on an extension of the nozzle opening 11a of the hot air nozzle 11, is removed.

FIG. 2 is a temperature distribution diagram when only hot air is blown onto the piezoelectric substrate (indicated by a broken line) and when hot air and cold air are blown onto the piezoelectric substrate as in the present invention (indicated by a solid line). As can be seen from the figure, when only hot air is blown, the area D that is heated above the Curie temperature (approximately 320 to 360 degrees Celsius) expands, and there is a risk that polarization may be removed to areas where polarization should remain. be. In contrast, in the present invention, since the cold air flows to surround the hot air, the range d of the portion heated above the Curie temperature can be narrowed, and the thermal influence on areas other than those to be polarized can be reduced. Furthermore, since hot air can heat the piezoelectric substrate more slowly than light beams or laser beams, local thermal expansion can be suppressed, and the occurrence of cracks, cracks, etc. in the piezoelectric substrate can be prevented.

[0015] Note that if hot air and cold air are blown out at the same time,
The amount of heat from the hot air is taken away by the cold air, and the temperature rise of the heated portion of the piezoelectric substrate 30 tends to slow down. As a preventive measure, for example, a method can be considered in which first only hot air is blown out, the temperature of the heated part is raised to around the Curie temperature, and then cold air is also blown out. Further, although hot air and cold air are blown out at the same time, the flow rate of the hot air may be greater than the flow rate of the cold air. Furthermore, as shown in the figure, the nozzle opening 11a of the hot air nozzle 11 may be made to protrude further than the nozzle opening 12a of the cold air nozzle 12, and may be brought close to the heated portion. By using any one of these methods or a combination of these methods, it is possible to accelerate the temperature rise of the heated portion.

[0016] In order to prevent electrode oxidation during heating, an inert gas can be used as the gas blown onto the heated portion. In this case, an inert gas cylinder may be used as the compressed gas source 1. However, since inert gas is expensive, inert gas may be used only for the hot air that directly affects the oxidation of the electrode. If an inert gas is used as the gas to be blown onto the heated part in this way, there is no problem even if the surrounding atmospheric gas is air, and heating can be done without installing the entire device in an inert gas as in the case of conventional methods. oxidation of the electrode can be easily prevented.

Note that the direction in which the hot air and cold air are blown onto the piezoelectric substrate is not limited to the direction perpendicular to the piezoelectric substrate, but may be blown from an oblique direction. Particularly, when the capacitive electrode is formed at the end of the piezoelectric substrate, it is desirable to tilt the nozzle toward the end of the piezoelectric substrate, since this reduces the possibility that the hot air will affect other parts.

[0018]

[Effects of the Invention] As is clear from the above explanation, according to the present invention, since polarization is removed using hot air, it can be heated more slowly than conventional light beams or laser beams, and can prevent cracking of the piezoelectric substrate. The occurrence of chips, cracks, etc. can be prevented. Also,
Since cold air is blown from the surrounding area along with hot air, it is possible to prevent heat diffusion and intensively heat a specific area, and there is no risk of polarization being destroyed in areas where polarization should remain. Furthermore, if an inert gas is used as the high-temperature gas blown from the hot air nozzle, electrode oxidation during heating can be easily prevented without installing the entire device in an inert gas. Particularly, by providing a cold air nozzle concentrically around a hot air nozzle as in the device of the present invention, the nozzle device can be made smaller and simpler, making it easier to handle.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a polarization removing device according to the present invention.

FIG. 2 is a temperature distribution diagram when only hot air is blown onto the heated portion and when hot air and cold air are blown onto the heated portion.

FIG. 3 is a surface view of an example of a piezoelectric component.

FIG. 4 is a back view of an example of a piezoelectric component.

FIG. 5 is an equivalent circuit diagram of the piezoelectric component.

[Explanation of symbols]

1 compressed gas source 10
Nozzle device 11
Hot air nozzle 12 Cold air nozzle 13 Heater

Claims (2)

[Claims] 1. A method for removing polarization of a specific part of a piezoelectric substrate whose entire surface has been polarized, in which hot air is blown from a hot air nozzle onto the specific part, and at the same time, cold air is blown from a cold air nozzle so as to surround the hot air. A method for removing polarization of a piezoelectric component, characterized by removing polarization of a specific part by spraying the same. [Claim 2] A device for polarizing a specific part of a piezoelectric substrate whose entire surface has been subjected to polarization treatment, a double-structured nozzle device in which a hot air nozzle is provided in the center and cold air nozzles are provided concentrically around the hot air nozzle. Compressed gas is supplied from a compressed gas source to both nozzles, and a heating heater is provided in the hot air nozzle, and the hot air blown out from the hot air nozzle toward the specific area is surrounded by a cold air nozzle. A device for removing polarization of piezoelectric components, characterized in that cold air blown out from the device flows in a surrounding manner.