JPH11177372A - Chip type piezoelectric parts and oscillation circuit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate adjustment of a capacitance incorporated in a chip type piezoelectric parts. SOLUTION: An electrode pattern consisting of oscillation electrodes 6a and 6b and terminal electrodes 7a and 7b connected to these electrodes is formed on both sides of a piezoelectric element plate 1 and sealing plates 2a and 2b at least one side of which is composed of a derivative ceramics are adhered on both sides of this piezoelectric element plate in a lamination state. Three mounting electrodes are provided almost in a parallel belt so that they circulating a stacked matter of the piezoelectric element plate and the sealing plates 2a and 2b and mounting electrodes on both sides are connected to the terminal electrodes 7a and 7b formed on the piezoelectric element plates and constructs leading electrodes 3a and 3b and the mounting electrode in the center constructs a grounded electrode 4. The grounded electrode 4 is isolated by a cut part 5 on the sealing plates 2a and 2b of the dielectric ceramics. By selecting a length (d) of the cut part 5, a value of a capacitance formed between the leading electrodes 3a and 3b and the grounded electrode 4 is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-type piezoelectric component, and more particularly to a chip-type piezoelectric component with a built-in capacitor suitable for use in an oscillation circuit for generating a clock signal of a microcomputer or the like. Further, the present invention relates to an oscillation circuit using a chip-type piezoelectric component having a built-in capacitance.

[0002]

2. Description of the Related Art In chip-type piezoelectric components such as a piezoelectric resonator and a piezoelectric filter, both main surfaces of a piezoelectric element plate on which vibration electrodes are formed are sealed to protect the piezoelectric element plate or suppress unnecessary vibration. The plate is adhered, and external electrodes for mounting are formed on the outer periphery of the sealing plate. Such a chip-type piezoelectric component can be reduced in size as compared with a piezoelectric component of a type in which a piezoelectric element is sealed in a container, thereby reducing a mounting space.

An example in which such a chip-type piezoelectric component is configured as a built-in capacitor type and can be miniaturized when used in a Colpitts-type oscillation circuit is disclosed in Japanese Patent Laid-Open Publication No. Hei 3-240311. Is disclosed. This piezoelectric component with a built-in capacitor has a sealing plate formed of dielectric ceramics and electrically connected to an electrode pattern of a piezoelectric element plate. The two lead-out electrodes formed on the sealing plate are electrically connected to each other. A ground electrode is arranged in parallel with these electrodes. The equivalent circuit of this piezoelectric component is as shown by Q in FIG. 2, and a capacitance C1 formed by a sealing plate made of a dielectric ceramic between the extraction electrodes at both ends of the piezoelectric component Q and the ground electrode. , C2 are obtained. Therefore, by using these capacitances C1 and C2 as capacitors between both terminals of the piezoelectric component Q and the ground and connecting an inverting amplifier (inverter) A between the two terminals, a Colpitts type oscillation circuit can be realized. Be composed. Note that a feedback resistor R may be connected between both terminals. Therefore, the two capacitors required for the Colpitts type oscillation circuit can be obtained as the capacitances C1 and C2 formed by the sealing plate of the piezoelectric component Q. An oscillation circuit can be configured without using a capacitor. Therefore, the mounting space of the oscillation circuit can be significantly reduced, in combination with the fact that the piezoelectric component itself is chip-type and compact.

By the way, the value of the additional capacitance of the Colpitts oscillation circuit, that is, the capacitor between both terminals of the piezoelectric component and the ground, must be adjusted depending on the application for impedance matching. However, in the above-described conventional example in which the additional capacitance of the Colpitts-type oscillation circuit is obtained as the capacitance generated by the dielectric material of the sealing plate, the relative dielectric constant of the dielectric material has a small temperature dependency, Good compatibility between the dielectric material and the electrode forming material,
And other conditions must be satisfied. Therefore, since a dielectric material having an arbitrary dielectric constant cannot be used, it is extremely difficult to select a dielectric material so that the capacitance has a desired value. For this reason, Japanese Unexamined Patent Application Publication No.
No. 81, the distance between the ground electrode and the lead electrode is adjusted by forming an uneven portion on the edge in the width direction of the ground electrode or the lead electrode of the chip type piezoelectric component. Adjusting the capacitance has been proposed.

[0005]

However, even if the method of providing the concave and convex portions to adjust the capacitance as described above is employed, the adjustment range of the capacitance value is not sufficient, and furthermore, the electric capacity is not sufficiently adjusted. The reliability of the dynamic connection was not satisfactory. That is, in order to cope with the miniaturization of electronic devices and the increase in mounting density, miniaturization of piezoelectric components is required, and the width of the lead electrode and the ground electrode of the chip type piezoelectric component is reduced due to this request. And Japanese Patent Laid-Open No. 6-224.
In the piezoelectric component disclosed in Japanese Patent No. 681, since the capacitance value is adjusted by forming uneven portions on these narrow electrodes, the adjustable range of the capacitance value is limited. Therefore, at present, the adjustment range of the capacitance value is narrow.

Further, it is conceivable that the uneven portion of the electrode is formed by first forming an electrode having a constant width and then trimming the electrode. In such a case, it is necessary to adjust the capacitance value. Therefore, if the width of the electrode is extremely reduced by trimming, the electrode may be cut. Therefore, the adjustment range of the capacitance value is narrow, and it is necessary to pay close attention to the adjustment of the capacitance value, and the yield of the product is reduced. The present invention has been made in view of the problems of the conventional example, and a first object of the present invention is to provide a chip-type piezoelectric component which has a wide adjustment range of a capacitance value, is easy to manufacture, and has a high yield. It is to provide.
A second object of the present invention is to provide a small-sized,
An object of the present invention is to provide an oscillation circuit provided with a piezoelectric component, in which matching can be easily adjusted.

[0007]

In order to achieve the first object, in a chip-type piezoelectric component of the present invention, an electrode pattern comprising a vibration electrode and a terminal electrode connected to the vibration electrode is provided on both sides. The formed piezoelectric element plate, and the first and second sealing plates that are in close contact with the piezoelectric element plate from both sides in a stacked state, such that a space is formed on the vibration electrode of the piezoelectric element plate. A first and a second sealing in which a concave portion is provided at a position on the first and second sealing plates facing the vibration electrode, and at least the first sealing plate is made of dielectric ceramics; Plate, and three mounting electrodes provided in a strip shape substantially in parallel so as to go around a laminate of the piezoelectric element plate and the first and second sealing plates, and the mounting electrodes on both sides are piezoelectric elements. Connected to two terminal electrodes formed on the plate, and the first and second lead-out electrodes And the center mounting electrode forms a ground electrode, and at least one of the first lead electrode, the second lead electrode, and the ground electrode is separated by a cut portion on at least the first sealing plate. Have been
And a capacitance value formed by at least the first sealing plate between the first extraction electrode and the ground electrode and between the second extraction electrode and the ground electrode.
It is characterized in that it can be adjusted depending on the size of the cutting portion.

In the chip-type piezoelectric component of the present invention, the cut portion may be provided only on the ground electrode, or may be provided only on the first or second extraction electrode. Further, the cut portion may be provided on all of the ground electrode and the first and second extraction electrodes. In the chip-type piezoelectric component of the present invention,
The second sealing plate is made of dielectric ceramics, an inorganic material, or an epoxy resin. Further, the second
In order to achieve the above object, an oscillation circuit according to the present invention provides a chip-type piezoelectric component having the above-described configuration, and an inverting amplifier in which an input terminal and an output terminal are connected to first and second lead electrodes of the piezoelectric component. And is characterized by having.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a piezoelectric component according to the present invention will be described with reference to FIG. FIG. 1A is a perspective view of the piezoelectric component of the present invention, and FIG. 1B is an explanatory view with a part removed for explaining the arrangement of internal electrodes of the piezoelectric component. 1
Is a piezoelectric element plate. On both surfaces of the element plate 1, main electrodes or vibrating electrodes 6a and 6b are disposed at the center thereof, and terminal electrodes 7a and 6b extending from these vibrating electrodes 6a and 6b are provided at both ends. 7b is arranged. As described above, sealing plates 2a and 2b made of a dielectric material are laminated on both surfaces of the piezoelectric element plate 1 having the electrodes arranged on both surfaces. Although not shown, a recess is provided at a position of the sealing plates 2a, 2b on the piezoelectric element plate 1 which faces the vibration electrodes 6a, 6b, whereby a space is formed on the vibration electrode. ing. Lead electrodes 3a, 3b electrically connected to the terminal electrodes 7a, 7b are provided in a circling state at both ends of the laminated body composed of the piezoelectric element plate 1 and the sealing plates 2a, 2b. Further, a lead electrode 3 is provided around the center of the laminate.
A ground electrode 4 is provided substantially in parallel with a and 3b, and the ground electrode 4 is cut by a cutting portion 5 on at least one of the sealing plates 2a and 2b. Extraction electrodes 3a, 3
Each of the b and the ground electrode 4 has a band-like shape and a substantially constant width.

[0010] The piezoelectric component of the present invention having such a structure is manufactured as follows. (1) On both surfaces of the piezoelectric element plate 1, electrode patterns of the vibrating electrodes 6a and 6b and the terminal electrodes 7a and 7b are formed, and the sealing plate 2
a and 2b are provided with depressions or recesses at portions facing the vibration electrodes 6a and 6b, and the extraction electrodes 3a and 3b are provided.
b, and an electrode pattern of the ground electrode 4 (4a and 4b) separated by the cutting portion 5 is formed. (2) Thereafter, the piezoelectric element plate 1 and the sealing plates 2a and 2b are laminated and bonded. (3) Terminal electrodes 7a and 7b of piezoelectric element plate 1 and sealing plate 2
a, 2b are electrically connected to the extraction electrodes 3a, 3b, and the extraction electrodes provided on the two sealing plates 2a, 2b, and the ground electrodes are electrically connected. Note that the cut portion 5 may not be provided on the ground electrode 4 but may be provided on one or both of the extraction electrodes 3a and 3b. Also,
The cut portion may be provided on the ground electrode 4 and one of the extraction electrodes 3a and 3b, or may be provided on all three electrodes. The number, position, and size of the cut portions are appropriately set according to the required capacitance value.

In the above step (1), the piezoelectric element plate 1 is selected from piezoelectric materials such as lead titanate ceramics and lithium niobate single crystal according to the intended specifications such as frequency. The electrode pattern on the piezoelectric element 1 is
It is formed by depositing or sputtering silver or the like, printing a resist ink, and then etching. At least one of the sealing plates 2a and 2b needs to be made of dielectric ceramics in order to form capacitance. As the dielectric ceramics, strontium titanate, barium titanate, lead titanate-based material, or the like is used. preferable. When one sealing plate is made of dielectric ceramic, the other sealing plate can be made of an inorganic material or an epoxy resin. As the inorganic material, alumina, cordierite or the like is preferable, and when an epoxy resin is used, it is necessary to use it in consideration that heat resistance is not relatively high. Whether to form both of the sealing plates or one of the sealing plates with dielectric ceramics is determined in consideration of the relative dielectric constant of the dielectric ceramics and the required capacitance value.

The electrode patterns on the sealing plates 2a and 2b, that is, the lead electrodes 3a and 3b and the ground electrode 4 are formed by baking silver paste or the like, applying a conductive adhesive, electroless plating, sputtering or vapor deposition. It can be formed by an appropriate method such as formation. However, conductive adhesives generally have poor solder wettability, and when only electroless plating is used, the electrode is liable to deteriorate. Therefore, after forming the electrode, a film of tin or the like is formed by electrolytic plating or the like. It is desirable to form on top. The electrolytic plating can also be performed after the external electrodes, ie, the lead electrodes 3a, 3b, and the internal electrodes, ie, the terminal electrodes 7a, 7b, are electrically connected. Cutting part 5 which is an electrode non-forming part
Can be formed by determining the electrode pattern in advance, but after forming the electrode, measuring the value of the generated capacitance, and trimming the electrode by trimming such as a mechanical method or laser processing. By adjusting the length d of the forming portion, a desired capacitance can be obtained. The method using the trimming is extremely effective when the printing accuracy is not so high.

When only one of the sealing plates 2a and 2b is formed of dielectric ceramics, a lead electrode and a ground electrode may be provided only on one of the sealing plates.
In this case, the mounting surface of the piezoelectric component is on the side of the sealing plate made of dielectric ceramics. Further, the cut portion 5 may be formed at any portion on the sealing plate. However, when the electrode pattern is formed by a printing technique, it is preferable to form the cut portion at the center portion in consideration of printing deviation. When the cut portion 5 is on the mounting surface side, it is preferable to dispose the cut portion 5 at the center in order to secure mounting strength.

The piezoelectric element plate 1 in the above step (2)
It is preferable to use an epoxy-based or polyimide-based adhesive from the viewpoints of sealing properties and heat resistance for bonding between the sealing plates 2a and 2b. However, when the piezoelectric element plate 1 is formed of a material having sufficient heat resistance, an inorganic adhesive material such as glass can be used. The electrical connection after the lamination and bonding of the piezoelectric element plate 1 and the sealing plates 2a and 2b in the step (3) is performed by forming a conductor. The formation of such a conductor can be realized by a method such as screen printing, dipping, vapor deposition, or sputtering. In order to increase the reliability such as the strength of the conductor, it is preferable to form a metal film on the conductor by electrolytic plating or the like.

In the chip type piezoelectric component according to the present invention, the above steps (1) to (3) can be performed after the piezoelectric element plate and the sealing plate are processed into a predetermined shape for one element. A plurality of piezoelectric element wafers and sealing plates are prepared, and the above steps (1) and (2) are executed. The dicing machine is used to cut out one element, and then the above step (3) is executed. By doing so, it can be assembled. In the case of mass production of piezoelectric components, if the latter method is adopted, the number of steps such as lamination can be greatly reduced, so that the production cost of the element can be greatly reduced.

The following Examples 1 to 3 are preferred examples for producing the chip type piezoelectric component of the present invention. Example 1 A lead titanate-based piezoelectric material was 40 mm x 30 mm x 15 mm
After firing into a block shape and baking, it is sliced into a flat plate shape. Then, after polishing to a thickness of 0.22 mm with a lapping machine, silver electrodes are deposited on the front surfaces of both surfaces of the flat plate, polarized, and an electrode pattern for 50 elements is resist-printed on both surfaces, and the electrode patterns are removed by etching. Then, the resist is removed by washing. The size of one element is 3.2mm x 2.5m
m. In order to form one of a pair of sealing plates for 50 elements, a dielectric material having a relative dielectric constant of 530 mixed with an organic binder and granulated using strontium titanate-based ceramics was used. The piezoelectric element is press-formed and fired so that a concave portion having a depth of 0.15 mm is formed in a portion facing the vibration electrode. Further, the surface on the side provided with the concave portion is polished to a thickness of 0.5 mm in order to enhance the adhesion to the piezoelectric element plate. On the surface on which the concave portion is not provided, mounting electrodes having a width of 0.6 mm (that is, lead electrodes and ground electrodes) are printed in a band shape using a paste containing a silver-palladium alloy at intervals of 0.8 mm. ,
After baking, a cut portion having a length corresponding to a target capacitance value is provided in a central portion of only a central electrode serving as a ground electrode. The other sealing plate is formed by using alumina in the same manner so as to have a concave portion, and a mounting electrode is similarly formed. However, neither electrode is provided with a cut portion. Then, the piezoelectric element plate is adhered with an epoxy adhesive so as to be sandwiched between the two sealing plates, and this is divided into individual elements by using a dicing machine. Next, the corresponding ones of the electrodes on the two sealing plates (lead electrodes and ground electrodes) are electrically connected by applying a conductive paste to the laminate by printing using a brush. .
At the same time, the terminal electrode on the piezoelectric element plate and the lead electrode on the sealing plate are connected by a conductive paste. Then, barrel plating is performed to deposit a solder layer on the conductive paste and the silver-palladium electrode. Thus, 50 chip-type piezoelectric components as shown in FIG. 1 can be manufactured.

Example 2 In the same manner as in Example 1, a piezoelectric element plate and a sealing plate on which electrodes were formed were manufactured and bonded to form a laminate, which was divided into one element, and electrode connection was made for each element. Do. However, a cut portion is provided at the center of the sealing portion for all mounting electrodes formed on the sealing plate made of dielectric ceramics. Example 3 In the same manner as in Example 1, a piezoelectric element plate and a sealing plate on which electrodes were formed were manufactured and bonded to form a laminate, divided into one element, and electrode connection was performed for each element. However, when forming electrodes on the sealing plate made of dielectric ceramics,
After cutting the piezoelectric element plate and the sealing plate into a laminated body without providing a cut portion in any of the three electrodes, only the center of the center electrode serving as the ground electrode is ground using abrasive grains. By doing so, a cutting portion is provided.

Table 1 below shows that, for each of the above-described Examples 1 to 3, 50 piezoelectric components were actually manufactured, and the capacitance value between the two extraction electrodes and the ground electrode (for each element) was shown. FIG. 4 shows the results of measuring the capacitance values (additional capacitance values) and calculating the average of the capacitance values for each of Examples 1 to 3.
However, in each of Examples 1 to 3, the length d of the cut portion of the ground electrode was set to 0.5 mm, 1.0 mm, and 1.5 m.
m and 2.0 mm. Further, for comparison, the capacitance value when no cut portion is formed in the electrode, that is, when the length of the cut portion is 0 mm, is also measured and shown.

[Table 1]Table 1  Capacitance (pF)Length d (mm) of cut section Example 1 Example 2 Example 3 0 4.6 4.6 4.6 0.5 4.4 4.2 4.5 1.0 4.0 4.0 3.8 3.9 1.5 3.3 3.2 3.3 2.0 2.0 2.7 2.5 2.8 As is clear from Table 1, the longer the length d of the cut portion, the greater the length.
Since the capacitance value becomes smaller, if you adjust the length of the cutting part,
It is clear that the desired capacitance value can be obtained.

Table 2 below shows the results of producing a piezoelectric component based on the technical idea of the conventional example and measuring the capacitance value. In this example, the electrode was manufactured in the same manner as in Example 1 of the present invention described above, but among the electrodes formed on the sealing plate made of a dielectric material, as schematically shown in FIG. The width of the central electrode was symmetrically reduced. The width w of the reduced ground electrode is set to 0.1 mm, 0.1.
The electrode width was set to 2 mm, 0.3 mm, 0.4 mm, and 0.5 mm. However, for the electrode width of 0.1 mm, the capacitance was not measured because the wire was broken halfway.

[Table 2]Table 2 Electrode width w (mm) Capacitance (pF) 0.5 4.6 0.4 4.3 0.3 4.0 0.2 3.8

Comparing Tables 1 and 2, in Examples 1 to 3 of the present invention, the capacitance value changes in the range of 2.5 pF to 4.6 pF by changing the length of the cut portion. On the other hand, when the electrode width is changed as in the conventional example, it can be seen that the capacitance value can be changed only in the range of 3.8 pF to 4.6 pF. Furthermore,
Experiments have also revealed that in the conventional example, there is a problem of reliability degradation such as disconnection occurring when the electrode width is reduced. As described above, according to the chip-type piezoelectric component of the present invention, by providing a cut portion on the mounting electrode and adjusting the length of the cut portion, the adjustment width of the capacitance can be reduced as compared with the conventional example. It can be greatly expanded, and the yield of piezoelectric components can be improved to improve reliability.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a chip-type piezoelectric component of the present invention, and an explanatory diagram for explaining the arrangement of vibration electrodes and terminal electrodes in the component.

FIG. 2 is a block diagram of a Colpitts oscillation circuit using a chip-type piezoelectric component with a built-in capacitor.

FIG. 3 is a schematic perspective view of a conventional chip-type piezoelectric component manufactured for comparison with the chip-type piezoelectric component of the present invention.

Claims (5)

[Claims] 1. A chip-type piezoelectric component, comprising: a piezoelectric element plate having an electrode pattern formed of a vibrating electrode and a terminal electrode connected to the vibrating electrode formed on both sides; First and second sealing plates, wherein recesses are formed at positions on the first and second sealing plates facing the vibration electrodes so as to form spaces on the vibration electrodes of the piezoelectric element plate. And a laminate of the first and second sealing plates, wherein at least the first sealing plate is made of dielectric ceramic, and a piezoelectric element plate and the first and second sealing plates. Three mounting electrodes provided in a strip shape substantially in parallel so as to go around the body, and the mounting electrodes on both sides are connected to two terminal electrodes formed on the piezoelectric element plate to form first and second mounting electrodes. A lead electrode is formed, a center mounting electrode forms a ground electrode, and At least one of the first extraction electrode, the second extraction electrode, and the ground electrode includes a mounting electrode that is separated by a cut portion on at least the first sealing plate, and includes a first extraction electrode and a ground electrode. And that the capacitance value formed by at least the first sealing plate between the second extraction electrode and the ground electrode can be adjusted depending on the size of the cut portion. Characterized chip type piezoelectric parts. 2. The chip-type piezoelectric component according to claim 1, wherein the cut portion is formed only in the ground electrode. 3. The chip-type piezoelectric component according to claim 1, wherein the second sealing plate is made of a dielectric ceramic. 4. The chip-type piezoelectric component according to claim 1, wherein the second sealing plate is made of an inorganic material or an epoxy resin. 5. An oscillation circuit using a piezoelectric component, wherein the chip-type piezoelectric component according to claim 1 and the first and second lead electrodes of the chip-type piezoelectric component have input terminals and output terminals. An oscillation circuit comprising an inverting amplifier connected to the oscillation circuit.