JP6026883B2 - Piezoelectric parts - Google Patents

Description

  The present invention relates to a piezoelectric component capable of obtaining highly reliable and highly accurate frequency characteristics.

  A piezoelectric component such as a resonator is composed of a piezoelectric element and a capacitor substrate (see, for example, Patent Document 1). Here, a general resonator is made of a material whose dielectric constant increases as the temperature rises, such as lead zirconate titanate, in order to increase the capacitance formed by the capacitance substrate.

  On the other hand, in order to produce a highly accurate piezoelectric component (resonator) having an oscillation frequency, it is conceivable to use a piezoelectric element having a flat oscillation frequency temperature characteristic and a capacitance substrate having a flat capacitance temperature characteristic.

JP 2000-286665 A

  Here, examples of the piezoelectric body constituting the piezoelectric element having a flat temperature characteristic of the oscillation frequency include a lithium tantalate single crystal. Examples of the dielectric substance constituting the capacitive substrate having a flat capacity temperature characteristic include titanic acid. Examples include a composition system in which calcium oxide and strontium carbonate are added to magnesium. However, since such a dielectric has a low dielectric constant, it is necessary to have a laminated structure in order to ensure its capacity, and there is a problem that the productivity is low and the productivity is poor. Further, when the capacitor substrate has a laminated structure, there is a problem that the withstand voltage is lowered.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric component that suppresses high cost and has a sufficient withstand voltage and good temperature characteristics.

The piezoelectric component according to the present invention includes a capacitor substrate having an electrode provided on a main surface of a dielectric, and a piezoelectric element mounted on the main surface of the capacitor substrate and provided with an electrode facing the surface of the piezoelectric body. Prepared ,
The piezoelectric element have a characteristic that the oscillation frequency decreases as the temperature rises, the have a characteristic that the capacitance value decreases capacitance substrate as the temperature rises, the dielectric, with contains barium titanate as a main component In addition, Mg and Yb are included as additive components for shifting the phase transition point of the main component to the low temperature side, and a part of Ba is replaced with Y and a part of Ti is replaced with Mn. In addition, 1 to 10 mol of Mg is included with respect to 100 mol of the sum of Ba and Y, and 6 to 10 mol of Yb is included with respect to 100 mol of the sum of Ti and Mn .

  According to the present invention, since the capacitance substrate has a characteristic that the capacitance value decreases as the temperature increases, the piezoelectric element itself has a property that the oscillation frequency decreases as the temperature increases, but the capacitance value of the capacitance substrate decreases. Since it acts so that the oscillation frequency of the piezoelectric element increases, the temperature characteristic of the oscillation frequency as a piezoelectric component approaches to flat. In other words, since it is possible to secure a desired capacity without a capacitor substrate having a laminated structure, it is possible to suppress high cost, and to realize a piezoelectric part with sufficient withstand voltage and good temperature characteristics due to a long distance between electrodes. it can.

(A) is an external appearance perspective view which shows an example of embodiment of the piezoelectric component of this invention, (b) is an external appearance perspective view of the state which removed the cover of the piezoelectric component shown to (a). It is sectional drawing cut | disconnected by the AA line shown in FIG.

  An example of an embodiment of a piezoelectric component of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is an external perspective view showing an example of an embodiment of a piezoelectric component according to the present invention, and FIG. 1B is an external perspective view in a state in which the lid of the piezoelectric component shown in FIG. FIG. FIG. 2 is a cross-sectional view taken along line AA shown in FIG.

  The piezoelectric component of the example shown in FIG. 1 includes a capacitor substrate 1 in which an electrode 12 is provided on the main surface of a dielectric 11, and an electrode 22 that is mounted on the main surface of the capacitor substrate 1 and faces the surface of the piezoelectric body 21. (Piezoelectric element 2 provided with (vibrating electrodes 221 and 222)), the piezoelectric element 2 has a characteristic that the oscillation frequency decreases as the temperature rises, and the capacitance substrate 1 has a characteristic that the capacitance value decreases as the temperature increases. doing.

  The capacitor substrate 1 includes a dielectric 11 formed as a rectangular flat plate having a length of 2.5 mm to 7.5 mm, a width of 1.0 mm to 3.0 mm, and a thickness of 0.1 mm to 1 mm, for example. Yes.

  An electrode 12 is provided on the main surface of the dielectric 11 constituting the capacitive substrate 1. This electrode 12 is an electrode for forming a capacitance. Specifically, the electrode 12 extends from one main surface (upper surface in this example) to the other main surface (lower surface in this example) through a side surface. 12 (first capacitor electrode 121) and electrode 12 (second capacitor electrode 122) are provided. The first capacitor electrode 121 is arranged extending from one end side in the longitudinal direction of the dielectric 11 toward the center, and the second capacitor electrode 122 is centered from the other end in the longitudinal direction of the dielectric 11. It is arranged extending toward the part. The first capacitor electrode 121 is electrically connected to a signal terminal 124 provided on the other main surface of the dielectric 11, and the second capacitor electrode is a signal terminal provided on the other main surface of the dielectric 11. 125 is electrically connected.

Then, the electrode facing the electrode 12 (first capacitance electrode 121) and the electrode 12 (second capacitance electrode 122) across the dielectric 11 on the other main surface (lower surface in this example) of the dielectric 11 1
2 (ground electrode 123) is provided.

  When the first capacitor electrode 121 and the second capacitor electrode 122 and the ground electrode 123 are opposed to each other through the dielectric 11 as in the present example, the region where the first capacitor electrode 121 and the ground electrode 123 are opposed to each other and the second By setting the areas of the regions where the capacitive electrode 122 and the ground electrode 123 are opposed to each other, the capacitances obtained in the opposed regions are equalized. When the first capacitor electrode 121 and the second capacitor electrode 122 and the ground electrode 123 are opposed to each other through the dielectric 11, the region where the first capacitor electrode 121 and the ground electrode 123 are opposed and the second capacitor electrode 122. Since the region where the ground electrode 123 and the ground electrode 123 face can be increased, the capacitance can be increased. Note that the capacitance obtained in each of the opposing regions is determined by the characteristics of the amplifier circuit element that is connected to the piezoelectric component and constitutes the oscillation circuit.

  In the figure, the ground electrode 123 is formed so as to reach the side surface of the dielectric 11 and extend in the thickness direction.

  As the material of the first capacitor electrode 121, the second capacitor electrode 122, the ground electrode 123, and the signal terminals 124 and 125, a conductive resin obtained by dispersing metal powder such as gold, silver, copper, aluminum, tungsten or the like in the resin. Alternatively, a thick film conductor or the like obtained by adding an additive such as glass to the metal powder and baking it can be used. If necessary, Ni / Au or Ni / Sn plating may be formed.

  A piezoelectric element 2 is mounted on the capacitor substrate 1. Specifically, both ends of the piezoelectric element 2 are fixed on the capacitive substrate 1 by the conductive bonding material 3 so as to vibrate.

  The piezoelectric element 2 includes a piezoelectric body 21 and electrodes (vibration electrodes 22 and 23) provided on both main surfaces of the piezoelectric body 21. The piezoelectric element 2 itself has a characteristic that the oscillation frequency decreases as the temperature increases.

  The piezoelectric body 21 constituting the piezoelectric element 2 is formed on a rectangular flat plate having a length of 1.0 mm to 4.0 mm, a width of 0.2 mm to 2 mm, and a thickness of 40 μm to 1 mm, for example. The piezoelectric body 21 can be formed using, for example, piezoelectric ceramics based on lead titanate, lead zirconate titanate, sodium niobate, potassium niobate, a bismuth layered compound, or the like.

  In addition, the piezoelectric element 2 includes electrodes 22 (vibrating electrodes 221 and 222) arranged so as to have regions facing each other on one main surface and the other main surface of the piezoelectric body 21. The vibration electrode 221 provided on the upper main surface of the piezoelectric body 21 is provided so as to extend from one end portion in the longitudinal direction toward the other end portion, and on the lower main surface of the piezoelectric body 21. The provided vibration electrode 222 is provided so as to extend from the other end portion in the longitudinal direction toward the one end portion side, and has regions facing each other. The vibrating electrodes 221 and 222 may be made of metal such as gold, silver, copper, and aluminum, and are attached to the surface of the piezoelectric body 21 to a thickness of, for example, 0.1 μm to 3 μm. The vibration electrode 221 of the piezoelectric element 2 is electrically connected to the first capacitor electrode 121 through the conductive bonding material 3, and the vibration electrode 222 of the piezoelectric element 2 is connected to the first capacitance electrode 121 through the conductive bonding material 3. It is electrically connected to the two-capacitance electrode 122.

The conductive bonding material 3 also has a function of ensuring a predetermined space (gap) between the upper surface of the capacitive substrate 1 and the lower surface of the piezoelectric element 2. As such a conductive bonding material 3, for example, solder, a conductive adhesive, or the like is used. As long as the solder is used, a lead-free material such as copper, tin, or silver can be used. If it is an adhesive, conductive particles such as silver, copper, and nickel are 75 to 75
An epoxy-based conductive resin or a silicone-based resin containing 95% by mass can be used.

  In such a piezoelectric element 2, when a voltage is applied between the vibration electrode 221 and the vibration electrode 222 from both ends, a thickness longitudinal vibration or thickness slip occurs at a specific frequency in a region where the vibration electrode 221 and the vibration electrode 222 face each other. The piezoelectric vibration is generated.

  A lid 4 is provided on the capacitor substrate 1 so as to cover the piezoelectric element 2. The lid 4 is bonded to the peripheral edge of the upper surface of the capacitor substrate 1 with an adhesive or the like, thereby causing the piezoelectric element 2 housed in the space formed together with the capacitor substrate 1 to physically influence from the outside. And a function of protecting from chemical influences, and a hermetic sealing function for preventing entry of foreign matters such as water into the space formed together with the capacitor substrate 1. In addition, as a material of the cover body 4, metal, such as SUS, ceramics, such as an alumina, resin, glass, etc. can be used, for example. In addition, an insulating resin material such as an epoxy resin may contain an inorganic filler in a proportion of 25 to 80% by mass so as to reduce the difference in thermal expansion coefficient from the capacitive substrate 1.

  Then, the capacitor substrate 1 in which the electrode 12 is provided on the main surface of the dielectric 11, and the electrodes 22 (vibrating electrodes 221 and 222) mounted on the main surface of the capacitor substrate 1 and facing the surface of the piezoelectric body 21. The capacitance substrate 1 has a characteristic that the capacitance value decreases as the temperature rises (the dielectric 11 has a capacitance value that decreases as the temperature rises).

  Since the capacitance substrate 1 has a characteristic that the capacitance value decreases as the temperature increases, the piezoelectric element 2 itself has a property that the oscillation frequency decreases as the temperature increases. However, when the capacitance value of the capacitance substrate 1 decreases, the piezoelectric element 2. Therefore, the temperature characteristic of the oscillation frequency approaches flat. That is, as the dielectric 11 used for the capacitance substrate 1 having the characteristic that the capacitance value decreases as the temperature rises, a material having a higher dielectric constant than the dielectric that has a flat temperature characteristic of the capacitance value can be used. A desired capacity can be ensured without the capacitor substrate 1 having a laminated structure. Therefore, the high cost can be suppressed, and the distance between the electrodes is long, so that a piezoelectric component having sufficient withstand voltage and good temperature characteristics can be realized.

  Here, as the dielectric 11 used for the capacitance substrate 1 to decrease the capacitance value as the temperature rises, a material having a high dielectric constant and acting so that the capacitance value of the capacitance substrate 1 decreases as the temperature rises, for example, Materials such as barium titanate, lead titanate + lanthanum, and the like, are included as main components, and it is preferable that an additive component for shifting the phase transition point of the main components to a low temperature side is included. .

  As a result, since the capacitance substrate 1 whose capacitance value continues to decrease as the temperature rises is formed, the temperature characteristics of the oscillation frequency on the low temperature side can be accurately adjusted.

  The main component is preferably barium titanate. This is because the temperature characteristic of the oscillation frequency can be made nearly flat by utilizing the characteristic that the capacitance value decreases as the temperature increases at the phase transition point of barium titanate near 0 ° C.

  Further, examples of the additive component include a configuration in which at least one of alkaline earth metal elements and at least one of rare earth elements are used.

According to these combinations, the effect of suppressing the grain growth of the additive component and the effect of moving the phase transition point to the low temperature side can be combined to suppress the dielectric constant on the high temperature side. Thereby, since the capacitance substrate 1 whose capacitance value decreases as the temperature rises can be obtained, the temperature characteristics of the oscillation frequency can be made closer to flat.

  Furthermore, it is preferable that at least one of the alkaline earth metal elements is Mg and at least one of the rare earth elements is Yb. Yb has a small ion radius among rare earths, and has an effect of suppressing grain growth. Mg has a great effect of moving the phase transition point to the low temperature side among the depressor effect and alkaline earth metals. Therefore, it is preferable to add Yb to suppress grain growth and to move the phase transition point to a lower temperature side by adding Mg, rather than adding Mg alone. Can be made more flat.

In particular, part of Ba in barium titanate (BaTiO ₃ ) is substituted with Y and part of Ti is substituted with Mn, and 1 to 10 mol of Mg is contained with respect to 100 mol of Ba and Y. Therefore, it is preferable that 6 to 10 mol of Yb is contained with respect to 100 mol of the sum of Ti and Mn. As a result, a capacitance substrate composition can be obtained in which the capacitance value decreases as the temperature increases, and the temperature characteristics of the oscillation frequency are flat. become.

  It is effective that the phase transition point of the dielectric 11 is −40 ° C. or lower and the Curie point of the dielectric 11 is 130 ° C. or higher.

  The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

  Next, a method for manufacturing the piezoelectric component according to the present embodiment will be described.

  First, a multi-piece substrate for producing the capacitor substrate 1 is produced. For example, after the raw material powder is mixed with water and a dispersant using a ball mill, a binder, a solvent, a plasticizer, and the like are added to obtain a green sheet. This is fired at a peak temperature of, for example, 900 ° C. to 1600 ° C. A conductive paste containing metal powder such as gold, silver, copper, aluminum, or tungsten is printed and baked on the substrate. In addition, as raw material powder, for example, 99 mol of barium carbonate, 98 mol of titanium oxide, 1 mol of yttrium oxide, and 2 mol of manganese oxide are prepared. Mix the total formulation weight, solvent and media in a 1: 2: 15 ratio. The mixed raw materials are calcined at a peak of 800 to 1100 ° C. 1-10 mol of magnesium carbonate and 6-10 mol of ytterbium oxide are added to this. The total weight after addition, solvent, and media are pulverized at a ratio of 1: 2: 15. A binder, a plasticizer, and the like are added to the raw material thus obtained, and after press molding, firing is performed at a peak temperature of 1100 to 1400 ° C. to obtain a dielectric ceramic.

  Next, the piezoelectric body 21 constituting the piezoelectric element 2 is prepared by, for example, mixing raw material powders such as lead titanate and lead zirconate titanate together with water and a dispersant using a ball mill, and then adding a binder, a plasticizer, and the like. Dry, size. The raw material thus obtained is press-molded and fired to obtain a piezoelectric ceramic. An electrode is formed on the end face of the obtained piezoelectric ceramic, and a polarization treatment is performed by applying a voltage of, for example, 0.4 kV / mm to 6 kV / mm in the thickness direction at a temperature of 25 ° C. to 300 ° C., for example.

  The vibrating electrode 221 and the vibrating electrode 222 formed on the upper and lower surfaces of the piezoelectric body 21 are formed by coating the obtained piezoelectric ceramic with a metal film on the upper and lower surfaces of the piezoelectric body 21 using a vacuum deposition method, a PVD method, a sputtering method, or the like. After forming a photoresist film having a thickness of about 1 μm to 10 μm on each metal film using screen printing or the like, it can be formed by patterning by photoetching. The piezoelectric element 2 is produced by cutting the patterned piezoelectric ceramic into a predetermined size by dicing or the like.

  Then, using the conductive bonding material 3, a large number of piezoelectric elements 2 are mounted on the substrate and fixed. When the conductive bonding material 3 is a conductive adhesive in which metal powder is dispersed in a resin, this conductive adhesive is applied onto the first capacitor electrode 121 and the second capacitor electrode 122 using a dispenser or the like. Then, the piezoelectric element 2 may be placed and the conductive adhesive resin may be cured by heating or ultraviolet irradiation.

  Then, the opening peripheral surface of the lid 4 is joined to the peripheral portion of the upper surface of the capacitor substrate 1 so as to cover the piezoelectric element 2. As the lid 4, a multi-piece collective cover sheet having a plurality of concave portions is used, and the multi-piece collective cover sheet is placed on the substrate so that the concave portions cover the piezoelectric elements 2. The convex portion of the collective lid sheet serving as the peripheral surface is joined to the peripheral portion of the upper surface of the capacitor substrate 1. For example, a thermosetting insulating adhesive is applied to the convex portion of the collective lid sheet that is the peripheral edge surface of the prepared lid body 4, and the lid body 4 is placed on the upper surface of the capacitor substrate 1. Thereafter, the lid 4 or the capacitor substrate 1 is heated to cure the insulating adhesive by raising the temperature to 100 to 150 ° C., and the lid 4 is bonded to the upper surface of the capacitor substrate 1.

  Finally, it is cut by dicing or the like along the boundary of each piezoelectric component (piece).

  The piezoelectric component of the present invention is manufactured by the above method.

1: capacitive substrate 11: dielectric 12: electrode 121: first capacitive electrode 122: second capacitive electrode 123: ground electrode 124, 125: signal terminal 2: piezoelectric element 21: piezoelectric body 22: electrode 221, 222: vibrating electrode 3: Conductive bonding material 4: Lid

Claims (1)

Comprising a capacitor substrate comprising electrodes provided on the major surface of the dielectric, it is mounted on the main surface of said capacitive substrate, and a piezoelectric element electrode opposed to the surface of the piezoelectric element is provided,
The piezoelectric element have a characteristic that the oscillation frequency decreases as the temperature rises, has a characteristic that the capacitance substrate capacitance decreases as the temperature rises,
The dielectric contains barium titanate as a main component, and contains Mg and Yb as additive components for shifting the phase transition point of the main component to a low temperature side,
A part of Ba is substituted with Y and a part of Ti is substituted with Mn, and 1 to 10 mol of Mg is contained with respect to 100 mol of Ba and Y. On the other hand, 6 to 10 mol of Yb is contained .

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