JP4359915B2 - Piezoelectric ceramic vibrator and piezoelectric resonator - Google Patents

Description

  The present invention relates to a piezoelectric ceramic vibrator and a piezoelectric resonator, and more particularly to a piezoelectric ceramic vibrator and a piezoelectric resonator formed by forming vibrating electrodes on both main surfaces of a piezoelectric ceramic plate.

  2. Description of the Related Art Conventionally, a piezoelectric ceramic plate used for a piezoelectric ceramic vibrator such as a piezoelectric resonator induces spontaneous polarization by being placed in a state of high temperature and high electric field during the production process, thereby expressing piezoelectricity. The piezoelectric ceramic vibrating body is formed with a vibrating electrode so as to face both main surfaces of the piezoelectric ceramic plate, and vibration is generated at a portion where the vibrating electrode faces.

  Conventionally, a vibrating electrode of a piezoelectric ceramic vibrating body has been formed into a film shape on a piezoelectric ceramic plate by a method such as vapor deposition (see Patent Document 1).

  The vibration electrode formed by vapor deposition is subjected to heat treatment (annealing) in order to strengthen the adhesion to the piezoelectric ceramic plate.

In addition, a piezoelectric resonator, which is a type of piezoelectric ceramic vibrating body, is integrated with a capacitive element having a capacitive component to constitute a piezoelectric resonator, whereby the overall size can be reduced. The integration of the piezoelectric resonator and the capacitive element has been performed by pasting together each of the piezoelectric resonator and the capacitive element, which is manufactured by soldering.
JP 2000-151343 A

  A piezoelectric ceramic plate is subjected to a polarization process in order to exhibit piezoelectricity, and a product such as a piezoelectric ceramic vibrator is manufactured through a process involving heating even after the polarization process. For example, a step of annealing in a state where the vibration electrode is formed on the piezoelectric ceramic plate in order to improve the fixing force of the vibration electrode on the piezoelectric ceramic plate, and a step of soldering to integrate the piezoelectric resonator and the capacitive element In addition, when an element formed by forming a vibrating electrode on a piezoelectric ceramic plate is housed in an external case, there is also a process of soldering in order to establish conduction between the electrode of the external case and the vibrating electrode of the element.

  By passing through such a process involving heating after the polarization treatment, the spontaneous polarization imparted to the piezoelectric ceramic plate is lost, and the piezoelectricity of the piezoelectric ceramic plate is lowered. In some cases, the piezoelectricity is not exhibited. Therefore, the heat treatment temperature after polarization is limited depending on the characteristics of the piezoelectric ceramic plate.

  Conventionally, the vibrating electrode has been formed by vapor deposition of Cr or Cu. When Cu is used as the vibration electrode, the resistance of the vibration electrode to the widely used Ag-based solder is good and the soldering state between the capacitive element and the piezoelectric resonator is good.

  Since the electrode formed by vapor deposition is weakly fixed to the piezoelectric ceramic, the fixing strength is increased by annealing at a high temperature as described above. On the other hand, Cu is oxidized when it is exposed to a temperature of about 170 ° C. or higher in air. Therefore, when annealing is performed at a temperature higher than the aforementioned temperature, conversely, an attempt is made to increase the fixing strength after forming a vibrating electrode by vapor deposition. It will come off. Therefore, when Cu is formed by vapor deposition and annealing is performed in the air, the annealing temperature is lowered to sacrifice the bonding strength, or the application is limited to applications where the bonding strength is not so required.

  Conventionally, when annealing treatment is performed at a high temperature in order to secure the bonding strength, Cr is vapor-deposited as a vibrating electrode. However, Cr has a poor resistance to solder and often causes solder erosion. It was.

  Accordingly, the present invention provides a piezoelectric ceramic vibrating body and a piezoelectric resonator capable of firmly fixing a vibrating electrode to the piezoelectric ceramic plate without causing the piezoelectric ceramic plate to be depolarized or oxidized by the heat treatment after polarization. It is intended.

The piezoelectric ceramic vibrator of the present invention is a piezoelectric ceramic vibrator formed by forming vibrating electrodes on both main surfaces of a piezoelectric ceramic plate, wherein the vibrating electrode is formed on the piezoelectric ceramic plate by electroless plating. It is formed of a base layer made of Cu and a vapor deposition film made of Ag provided on the base layer.

Piezoelectric ceramic vibrator of the present invention, the thickness of the underlayer is 0.2 to 0.4 [mu] m, the thickness of the deposited film is 0.8 to 1.6 [mu] m, the thickness of the vibrating electrode 1~2μm It is characterized by being.

  A piezoelectric resonance device according to the present invention includes the piezoelectric ceramic vibrator and a capacitive element.

In the piezoelectric ceramic vibrator of the present invention, since the base layer of the vibrating electrode is formed by electroless plating on the piezoelectric ceramic plate, the fixing strength between the vibrating electrode and the piezoelectric ceramic plate can be improved without performing high-temperature annealing. . That is, conventionally, in the case of forming the vibration electrodes by depositing a C u is the annealing at a high temperature was necessary in order to improve the adhesion strength between the vibration electrode and the piezoelectric ceramic plate, in the present invention, C Since the base layer was formed on the piezoelectric ceramic plate by electroless plating of u, the plating solution penetrates into the fine irregularities of the porcelain. The underlayer can be fixed with high fixing strength.

In the present invention, on an underlying layer formed by electroless plating, since the formation of the deposited film by depositing A g, it is possible to form a uniform arbitrary thickness vibration electrodes in a wide range. This makes it possible to suppress peeling due to internal stress while forming a complex contact surface at the interface between the vibrating electrode and the porcelain, and by using Ag for vapor deposition, it is suitable for bonding with widely used Ag-based solders. Is possible.

  In other words, the plating film formed by electroless plating is considered to have high internal stress in the surface direction. When the thickness is increased, the internal stress also increases, and even if it is in good contact with the porcelain surface, it is easy to peel off due to the stress. turn into. Therefore, in the present invention, the base layer is formed thinly by electroless plating, and Ag is deposited thereon to form a sufficient thickness.

  Further, in the present invention, by forming the base layer of the vibration electrode from Cu, the resistance of the vibration electrode to the widely used Ag-based solder is improved, and solder erosion can be prevented. Further, by forming the vapor deposition film from Ag, it is possible to suitably bond with a widely used Ag-based solder.

  Furthermore, in the present invention, by forming the thickness of the underlayer by electroless plating as thin as 0.2 to 0.4 μm, the peeling from the piezoelectric ceramic plate due to the internal stress of the underlayer is suppressed, and on the piezoelectric ceramic plate. Therefore, it is possible to obtain a vibrating electrode that is sufficiently fixed to the piezoelectric ceramic plate without forming an complicated and sufficiently contacted interface.

  In addition, by setting the thickness of the deposited film to 0.8 to 1.6, it is possible to achieve suitable adhesion with widely used Ag-based solder, and the vibration electrode itself is weighted to reduce piezoelectric vibration. Inhibiting sharpness can be prevented.

  Furthermore, by setting the thickness of the vibrating electrode to 1 to 2 μm, the vibrating electrode can have sufficient conductivity over the entire electrode surface, and the vibrating electrode itself becomes a weight and inhibits the sharpness of piezoelectric vibration. Can be prevented.

  Since the piezoelectric ceramic vibrator can firmly fix the vibrating electrode to the piezoelectric ceramic plate without annealing, and can obtain excellent vibration characteristics and improve the manufacturing yield, the piezoelectric resonator of the present invention can be obtained. However, excellent characteristics and a high production yield can be obtained.

  The piezoelectric ceramic vibrator of the present invention will be described in detail with reference to FIG. As shown in FIG. 1, the piezoelectric ceramic vibrator of the present invention is formed by forming vibrating electrodes 3 on both main surfaces of a piezoelectric ceramic plate 1, and the vibrating electrode 3 is electrolessly plated on the piezoelectric ceramic plate 1. The underlayer 3a formed by the above and the vapor deposition film 3b formed on the underlayer 3a.

  The vibration electrode 3 formed on the upper surface of the piezoelectric ceramic plate 1 extends from one side end of the piezoelectric ceramic plate 1 to the central portion, and the vibration electrode 3 formed on the lower surface of the piezoelectric ceramic plate 1 is connected to the piezoelectric ceramic plate 1. The other end of the piezoelectric ceramic plate 1 extends from the other end to the central portion, and overlaps at the central portion in the longitudinal direction of the piezoelectric ceramic plate 1. In this overlapping portion, the piezoelectric ceramic plate 1 vibrates.

The piezoelectric ceramic plate 1 is made of a piezoelectric ceramic material and is not particularly limited as long as it is a ceramic material having piezoelectricity. However, the piezoelectric ceramic plate 1 is made of a PbZrTiO ₃ (so-called PZT) -based material containing at least Pb, Zr, and Ti. It is desirable to become. The piezoelectric ceramic plate 1 is particularly preferably made of a PZT-based material containing Pb, Zr, Ti, La, Sr, and Sb. In addition, the code | symbol 1a in FIG.1 (c) shows the ceramic particle | grains of the piezoelectric ceramic board 1 typically.

  Such a piezoelectric ceramic plate 1 can be produced by forming a slurry containing a piezoelectric ceramic powder and an organic component into a sheet shape, and degreasing and firing a sheet cut into an arbitrary area. Moreover, the raw material containing a piezoelectric ceramic powder and an organic component is shape | molded in a block shape, This block-shaped molded object is baked, By cutting to arbitrary thickness, the flat piezoelectric ceramic board 1 can be produced. .

  In the case of a piezoelectric ceramic vibrating body using a mode such as thickness longitudinal vibration or thickness sliding vibration, the thickness of the ceramic ceramic ceramic 1 is made uniform through a process such as lapping because the ceramic thickness is an important factor governing the oscillation frequency. It is desirable to process.

The vibration electrode 3, as described above, which is composed of a base layer 3a and the deposited film 3b, since the resistance to solder because using C u becomes good as a base layer 3a, the solder The biting can be prevented, and thus a stable vibrating electrode can be formed.

  Moreover, in this invention, since the base layer 3a is formed by electroless plating, the heating of the piezoelectric ceramic plate 1 can be further reduced as compared with the case where the base is formed by vapor deposition. In addition, heating to the piezoelectric ceramic plate 1 can be suppressed as compared with the case of baking Ag, and a thin and uniform underlayer can be obtained.

  In the present invention, the thickness of the base layer 3a is preferably 0.2 to 0.4 μm. By controlling the thickness of the base layer 3a to 0.2 to 0.4 μm, the peeling due to the internal stress of the electroless plating is suppressed, and an annealed interface having a more complex and sufficient contact on the piezoelectric ceramic plate A vibration electrode that is sufficiently fixed can be formed without any treatment.

  The vapor deposition film 3b constituting the vibrating electrode 3 is further formed by vapor deposition on the base layer 3a formed by electroless plating. The vapor deposition film 3b formed by such vapor deposition is applied to the metal. Since it is vapor deposition of this, it can have high adhering compared with the case where it vapor-deposits directly to a ceramic.

  In the present invention, by forming the vapor deposition film 3b on the surface of the base layer 3a formed by electroless plating, it is possible to omit the annealing treatment for improving the adhesion after the vibration electrode is formed.

Deposited film 3b is intended A g or Ranaru, Ru can be suitably adhered to the solder Ag system is thereby widely used.

  Moreover, the thickness of the vapor deposition film 3b is desirably thicker than the thickness of the underlayer 3a because it resists the internal stress of the underlayer 3a formed by electroless plating, and is particularly 0.8 to 1.6 μm. It is desirable to be. By setting the thickness of the vapor deposition film 3b to 0.8 to 1.6 μm, it is possible to resist the internal stress of the base layer 3a formed by electroless plating. In particular, the thickness is desirably 1.0 to 1.6 μm.

  The thickness of the vibrating electrode 3 formed by forming the vapor deposition film 3b on the base layer 3a is preferably 1 to 2 μm. By setting the thickness of the vibrating electrode 3 to 1 to 2 μm, it is possible to prevent the occurrence of a part having a low conductivity in the vibrating electrode 3 and to inhibit the piezoelectric vibration of the porcelain by the weight of the vibrating electrode 3 itself. Can be suppressed. In particular, the thickness of the vibrating electrode 3 is desirably 1.3 to 2.0 μm for the reason that the electrode partially prevents a portion having low conductivity from being formed.

  The vibration electrode 3 is formed on the main surface facing the thickness direction of the flat piezoelectric ceramic plate 1, but if the amount of metal forming the vibration electrode 3 increases, the weight of the metal becomes a problem and the oscillation intensity decreases. Therefore, it is desirable that the amount of metal formed on the piezoelectric ceramic plate 1 as the vibrating electrode 3 is as small as possible and evenly formed.

In the piezoelectric ceramic vibrator configured as described above, since the base layer 3a is formed on the piezoelectric ceramic plate 1 by electroless plating, high-temperature annealing is not required, and the vibration electrode 3 and the piezoelectric ceramic plate 1 it is possible to improve the fixing strength, on an underlying layer formed by electroless plating, since the formation of the deposited film 3b by depositing a g, a good fixation on the piezoelectric ceramic plate 1 without performing an annealing treatment vibration The electrode 3 can be formed.

  FIG. 2 shows a piezoelectric resonance device (capacitor built-in type resonator) in which a capacitive element 35 is joined to a piezoelectric ceramic vibrator 31. The capacitive element 35 has capacitive electrodes 35b and 35c formed on the upper surface of a dielectric substrate 35a. The capacitor electrode 35d is formed on the lower surface. The vibrating electrode 3 formed on the upper surface of the piezoelectric ceramic plate 1 and the capacitive electrode 35c of the capacitive element 35 are connected by the end surface electrode 37a, and the vibrating electrode 3 formed on the lower surface of the piezoelectric ceramic plate 1 and the capacitive element 35 The capacitor electrodes 35b are connected by an end face electrode 37b.

  FIG. 3 shows a piezoelectric resonance device in which the built-in capacitor type oscillator of FIG. Although not shown, the end surface electrodes 37 a and 37 b and the capacitor electrode 37 d are drawn out to the outer surface of the storage container 37.

  In the piezoelectric resonance apparatus as shown in FIGS. 2 and 3, as described above, the adhesion strength of the vibrating electrode of the piezoelectric ceramic vibrating body can be improved without annealing, and it can be suitably bonded to the Ag-based solder. In addition, the manufacturing yield of the piezoelectric resonance device can be improved and good characteristics can be obtained.

Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , La ₂ O ₃ , SrCO ₃ , Sb ₂ O ₃ , Co ₂ O ₄ , MnCO ₃ raw material powders were mixed and mixed in air at 1000 ° C. for 3 to 5 hours. The calcined calcined powder was pulverized, and the pulverized powder was spray-dried to produce granules, thereby producing a piezoelectric ceramic powder.

  An organic binder is added to the piezoelectric ceramic powder, and this is press-molded to form a 30 mm square block shape. The binder is removed in air at 450 ° C. for 20 hours, and then in air at 1150 ° C. for 4 hours. Firing and sintering were performed.

  The sintered body was cut with a wire saw and lapped to form a 30 mm square plate with a thickness of 200 μm to produce a piezoelectric ceramic plate, and this piezoelectric ceramic plate was washed.

  A metal as shown in Table 1 was formed on the cleaned piezoelectric ceramic plate with a thickness t1 shown in Table 1 by a vacuum vapor deposition machine or by electroless plating to form an underlayer. The thickness of the underlayer was changed by changing the processing time, and the thickness t1 was obtained by X-ray microanalyzer (EPMA) surface analysis of the cross section.

  The piezoelectric ceramic plate on which the base layer was formed by electroless plating was ultrasonically washed in water, washed with isopropyl alcohol, and then dried in a dryer at 120 ° C. A deposited film made of Ag having a thickness shown in Table 1 was formed on the base layer of the piezoelectric ceramic plate by a vacuum deposition machine. Moreover, the vapor deposition film was formed by changing the amount of metal supplied to the vacuum vapor deposition machine, and the thickness t2 was obtained by EPMA plane analysis of the cross section.

  Further, the adhesion strength of the vibrating electrode was evaluated as shown in FIG. 4 before and after annealing treatment of the piezoelectric ceramic plate on which the vibrating electrode was formed at 260 ° C. for 90 minutes in air. In the evaluation, first, the adhesive tape 11 having a width of 15 mm is cut by about 10 cm and attached to the vibration electrode 3 formed on the 30 mm square piezoelectric ceramic plate 1, and one end of the tape 11 is wound around the rigid rod 13. The thread 11 was connected to the weight gauge 17 and the tape 11 was pulled up and peeled off together with the gauge 17 so that the tape 11 was perpendicular to the piezoelectric ceramic plate 1. The maximum weight indicated on the gauge 17 was read before all the tape 11 was peeled off. Five samples were evaluated, and the average value of the read values is shown in Table 1. Further, Table 1 shows whether the vibration electrode 3 and the piezoelectric ceramic plate 1 are separated when the tape 11 is pulled up, or whether the tape 11 and the vibration electrode 3 are separated.

Furthermore, as shown in FIG. 5, the copper wire 21 was soldered to five locations on the vibrating electrode 3, and the presence or absence of solder erosion of the vibrating electrode 3 was observed along with the work. In addition, it was judged that the porcelain exposed during the soldering process was eaten by solder. These results are shown in Table 1.

  From Table 1, it is possible to prevent solder erosion of the electrode by forming an Ag vapor deposition film after forming a Cu underlayer by electroless plating, and heat treatment (annealing) after forming the vibrating electrode It can be seen that the vibration electrode can be firmly fixed on the piezoelectric ceramic plate even if not.

  On the other hand, sample No. 1 was formed by depositing Cr or Cu to form an underlayer. In Nos. 1 and 2, it can be seen that the vibration electrode and the piezoelectric ceramic plate are not sufficiently fixed without annealing, and the vibration electrode is easily peeled off.

  Further, when the thickness of the base layer formed by electroless plating formed on the surface of the piezoelectric ceramic plate is thinner than 0.2 μm (Sample No. 3), Cu does not sufficiently play a role as the base layer and is stuck to the vibrating electrode. It can be seen that when the adhesive tape is peeled off, the whole or part of the vibrating electrode is easily peeled off together with the adhesive tape.

  Furthermore, when Cu of the underlayer by electroless plating is excessive and the thickness is thicker than 0.4 μm (sample No. 7), partial peeling is likely to occur on the vibrating electrode due to internal stress of electroless plating. I understand that.

The piezoelectric ceramic vibrating body of this invention is shown, (a) is sectional drawing, (b) is a top view, (c) is a cross-sectional schematic diagram which expands and shows a part of (a). It is explanatory drawing which shows the piezoelectric resonance apparatus which joined the capacitive element to the piezoelectric ceramic vibrating body. It is explanatory drawing which shows the piezoelectric resonance apparatus which accommodated the capacity | capacitance built-in type resonator which joined the capacitive element to the piezoelectric ceramic vibrating body in the storage container. It is explanatory drawing which shows the state which measures the adhering force of a piezoelectric ceramic board and a vibration electrode. It is explanatory drawing which shows the state which evaluates the solder erosion property of the vibration electrode of a piezoelectric ceramic board surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric ceramic board 3a ... Underlayer 3b ... Deposition layer 3 ... Vibrating electrode 31 ... Piezoelectric ceramic vibrating body 35 ... Capacitance element

Claims (5)

A piezoelectric ceramic vibrating body in which vibration electrodes are formed on both principal surfaces of a piezoelectric ceramic plate, wherein the vibration electrode includes a base layer made of Cu formed by electroless plating on the piezoelectric ceramic plate, A piezoelectric ceramic vibrator characterized by being formed from a vapor deposition film made of Ag provided in a formation. 2. The piezoelectric ceramic vibrator according to claim 1, wherein the foundation layer has a thickness of 0.2 to 0.4 μm. Piezoelectric ceramic vibrator according to claim 1 or 2 thickness of the deposited film characterized in that it is a 0.8～1.6Myuemu. Piezoelectric ceramic vibrator according to any one of claims 1 to 3 the thickness of the vibrating electrode is characterized by a 1 to 2 [mu] m. A piezoelectric ceramic vibrator according to any one of claims 1 to 4, a piezoelectric resonator, characterized in that it comprises a capacitive element.

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