JP2017098887A - Piezoelectric component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric component in which generation of ripples in a main vibration band is suppressed.
A piezoelectric component according to the present invention includes a support substrate 1 and a piezoelectric element 2 provided with a first excitation electrode 211 and a second excitation electrode 212 which are fixed to the support substrate 1 and have opposing regions facing each other. And at least one of the first excitation electrode 211 and the second excitation electrode 212 has a portion having a different thickness. Thereby, it is possible to realize a piezoelectric component in which the occurrence of ripples in the main vibration band is suppressed.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric component that is suitably used as, for example, a resonator.

  A piezoelectric component as a resonator is generally composed of a support substrate, a piezoelectric element, a pair of support portions on which the piezoelectric element is mounted, a conductive bonding material, and a lid. The piezoelectric element has excitation electrodes of uniform thickness formed on the respective main surfaces so as to have opposing regions facing each other (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2006-67496

  In such a piezoelectric component, a ripple caused by unnecessary vibration may occur in the band (between the resonance frequency and the anti-resonance frequency), which causes a decrease in the accuracy of the oscillation frequency.

  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 the occurrence of ripples in the main vibration band.

  The piezoelectric component of the present invention includes a support substrate and a piezoelectric element that is fixed on the support substrate and includes a first excitation electrode and a second excitation electrode that have opposing regions facing each other, and the first piezoelectric element is provided. At least one of the second excitation electrode and the second excitation electrode has a portion having a different thickness.

  According to the piezoelectric component of the present invention, since the harmonic of the vibration mode existing in the low frequency region, that is, the resonance frequency of the unnecessary vibration can be changed, the ripple out of the band of the thickness vibration (main vibration) used for oscillation And the occurrence of ripples in the main vibration band can be suppressed.

(A) is a partially omitted schematic plan view of an example of the piezoelectric component of this embodiment, (b) is a cross-sectional view of the piezoelectric component shown in (a) cut along line AA, and (c) is (a). It is a bottom view of the piezoelectric component shown. It is a principal part expanded sectional view of the other example of the piezoelectric component of this embodiment. It is a principal part expanded sectional view of the other example of the piezoelectric component of this embodiment. It is a principal part expanded sectional view of the other example of the piezoelectric component of this embodiment. It is a principal part expanded sectional view of the other example of the piezoelectric component of this embodiment. It is a principal part expanded sectional view of the other example of the piezoelectric component of this embodiment.

  Hereinafter, an example of the piezoelectric component of the present embodiment will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  1A is a partially omitted schematic plan view of an example of the piezoelectric component of the present embodiment, FIG. 1B is a cross-sectional view of the piezoelectric component shown in FIG. FIG. 2C is a bottom view of the piezoelectric component shown in FIG. In FIG. 1A, “partially omitted” means that the lid 5 is omitted. The piezoelectric component shown in FIG. 1 includes a support substrate 1 and a piezoelectric element 2 provided with a first excitation electrode 211 and a second excitation electrode 212 that are fixed to the support substrate 1 and have opposing regions facing each other. In addition, at least one of the first excitation electrode 211 and the second excitation electrode 212 has a portion having a different thickness.

  The support 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. As the dielectric 11, a ceramic material such as alumina or barium titanate, and a resin-based material such as glass epoxy can be used.

  A first capacitor electrode 121 and a second capacitor electrode 122 are provided on one main surface (upper surface in this example) of the dielectric 11 constituting the support substrate 1. The first capacitor electrode 121 and the second capacitor electrode 122 are electrically connected to the excitation electrode 21 (the first excitation electrode 211 and the second excitation electrode 212) of the piezoelectric element 2, and a ground electrode 123 described later. And an electrode for forming a capacitance between them. The first capacitor electrode 121 is disposed so as to extend from one end side in the major axis direction of the support substrate 1 toward the center portion, and the second capacitor electrode 122 is disposed on the other end side in the major axis direction of the support substrate 1. It extends from the center toward the center.

  The other main surface (the lower surface in this example) of the support substrate 1 is connected to the ground electrode 123 across the first capacitor electrode 121 and the second capacitor electrode 122 with the dielectric 11 in between, and the signal input / output Input / output electrodes 124 are provided.

  Further, a side electrode 125 that electrically connects the first capacitor electrode 121 or the second capacitor electrode 122 and the input / output electrode is provided on the side surface of the support substrate 1 from one main surface to the other main surface.

  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 this example, the first capacitor electrode 121 and the ground electrode 123 are opposed to each other in the region By setting the area of the region where the two-capacitance electrode 122 and the ground electrode 123 are opposed to each other, the capacitance obtained in each of the opposed regions becomes equal. 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 opposed 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, a side electrode 126 is also provided on a side surface of the support substrate 1 that is electrically connected to the ground electrode 123 due to solder bonding to an external circuit board.

  As the material of the first capacitor electrode 121, the second capacitor electrode 122, the ground electrode 123, the input / output electrode 124, and the side 125, 126 surface electrode, metal powder such as gold, silver, copper, aluminum, tungsten, etc. is dispersed in the resin. It is possible to use a conductive resin (conductive paste), a thick film conductor that is baked by adding an additive such as glass to the metal powder, and the like. If necessary, Ni / Au or Ni / Sn plating may be formed.

  On the support substrate 1, the 1st support part 31 and the 2nd support part 32 are provided, and the piezoelectric element 2 is mounted on these so that a vibration is possible. Specifically, the first support portion 31 and the second support portion 32 are connected to the other main surface of the piezoelectric element 2, and the first support portion 31 and the second support portion 32 are the long axes of the piezoelectric element 2. The piezoelectric element 2 is mounted so as to vibrate so as to support both ends in the direction. The first support portion 31 and the second support portion 32 have conductivity, for example, and are columnar bodies in which metal powder such as gold, silver, copper, aluminum, tungsten, and the like is dispersed in a resin. . For example, the length (diameter) in the vertical and horizontal directions is 0.1 mm to 1.0 mm, the thickness is 10 μm to 100 μm, and the columnar shape or the columnar shape is formed.

  In FIG. 1, the conductive bonding material 4 is provided on the first support portion 31 and the second support portion 32, and at least the other main surface of the both ends of the piezoelectric element 2 and the first support portion. 31 and the second support portion 32 are joined and fixed. In addition, since the 1st support part 31 and the 2nd support part 32 are formed with the material which has electroconductivity, the excitation electrode 21 (the 1st excitation electrode 211, the 2nd excitation electrode 212) of the piezoelectric element 2 The first capacitor electrode 121 and the second capacitor electrode 122 are electrically connected. As such a conductive bonding material 4, for example, solder, a conductive adhesive, or the like is used, and if it is a solder, for example, a lead-free material such as copper, tin, or silver can be used. If it is an adhesive agent, the epoxy-type conductive resin or silicone-type resin containing 75-95 mass% of electroconductive particles, such as silver, copper, and nickel, can be used.

  The piezoelectric element 2 fixed to the support substrate 1 is provided so as to have a piezoelectric body 22 and regions (opposing regions) facing each other on both main surfaces (one main surface and the other main surface) of the piezoelectric body 22. Excitation electrode 21 (first excitation electrode 211, second excitation electrode 212) is provided.

  The piezoelectric body 22 constituting the piezoelectric element 2 has, for example, a rectangular shape or a long shape having a major axis direction 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. It can be a flat plate. The piezoelectric body 22 is formed using, for example, piezoelectric ceramics based on lead titanate, lead zirconate titanate, lithium tantalate, lithium niobate, sodium niobate, potassium niobate, a bismuth layered compound, or the like. Can do.

  The first excitation electrode 211 provided on one main surface (upper main surface) of the piezoelectric body 22 extends from one end portion in the major axis direction of the piezoelectric body 22 toward the other end portion. It is provided as follows. The second excitation electrode 212 provided on the other main surface (lower main surface) of the piezoelectric body 22 is directed from the other end portion in the major axis direction of the piezoelectric body 22 toward the one end portion. It is provided to extend. The first excitation electrode 211 and the second excitation electrode 212 are arranged at the center between both end portions (one end portion and the other end portion) of the piezoelectric body 22. Each of the excitation electrodes 212 has opposing regions facing each other. For this excitation electrode 21 (first excitation electrode 211, second excitation electrode 212), for example, a metal such as gold, silver, copper, aluminum, chromium, nickel or the like can be used. For example, it is deposited to a thickness of 0.1 μm to 3 μm. As shown in the figure, end face electrodes 23 are provided on both end faces of the piezoelectric body 22, and the second end of the piezoelectric element 2 is interposed via the end face electrode 23, the conductive bonding material 4 and the first support portion 31. The first excitation electrode 211 is electrically connected to the first capacitance electrode 121, and the second excitation electrode 212 of the piezoelectric element 2 is connected to the second capacitance via the conductive bonding material 4 and the second support portion 32. The electrode 122 is electrically connected.

  In such a piezoelectric element 2, when a voltage is applied between the first excitation electrode 211 and the second excitation electrode 212, the opposing region where the first excitation electrode 211 and the second excitation electrode 212 face each other. The piezoelectric vibration of thickness longitudinal vibration or thickness shear vibration is generated at a specific frequency.

  As shown in FIG. 1B, a lid 5 may be provided on the support substrate 1 so as to cover the piezoelectric element 2. The lid 5 is bonded to the peripheral edge portion of the upper surface of the support substrate 1 with an adhesive or the like, whereby the piezoelectric element 2 accommodated in the internal space formed together with the support substrate 1 is physically supplied from the outside. It has a function of protecting from influences and chemical influences, and a hermetic sealing function for preventing entry of foreign matters such as water into the space formed together with the support substrate 1. In addition, as a material of the cover body 5, for example, a metal such as stainless steel, a ceramic such as alumina, a resin, glass, or the like can be used. Further, 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 with the support substrate 1.

  As shown in FIG. 1B, the piezoelectric element 2 has a portion having a different thickness in at least one of the first excitation electrode 211 and the second excitation electrode 212. In FIG. 1B, the first excitation electrode 211 has a thick portion 211b on one end side and the other end side, and a thick portion 211b on one end side. A thin portion 211a is provided between the other end portion and a thick portion 211b, and these are along the major axis direction of the piezoelectric element 2 (the length direction of the first excitation electrode 211). It is provided alternately.

  By adopting such a configuration, it is possible to fluctuate the harmonics of the vibration mode existing in the low frequency region, that is, the resonance frequency of unnecessary vibrations, and therefore ripple outside the band of the thickness vibration (main vibration) used for oscillation. Can be shifted. For example, the ripple is shifted to the high frequency side by providing a portion 211a that is thinner than the other region, or the ripple is shifted to the low frequency side by providing a portion 211b that is thicker than the other region. Can do. Therefore, ripples in the main vibration band can be suppressed.

  When the thickness of the thick part 211b in the first excitation electrode 211 is, for example, 1 μm to 2 μm, the thin part 211a is, for example, 0.2 μm to 0.8 μm. In this case, the thick part The ratio of the thickness of the thin part 211a to the thickness of 211b is about 10 to 80%.

  Here, as shown in FIG. 2, at least one of the first excitation electrode 211 and the second excitation electrode 212 is on one end side of the piezoelectric body 22 or on the other end side of the piezoelectric body 22. The thick portion 211b may be provided, and the thin portion 211a may be provided on the central portion side of the piezoelectric body 22. In the example shown in FIG. 2, specifically, the first excitation electrode 211 provided on one main surface of the piezoelectric body 22 has a thick portion 211b on one end side, and the other end A thin portion 211a is provided on the side of the portion. Further, among the thin portions 211a provided in the central portion of the piezoelectric body 22, the thinnest portion 211a 'is provided on the other end side. The thinnest part 211a ′ is set to have a thickness of at least 0.2 μm, and the thin part 211a is set to a thickness of 0.6 to 0.8 μm, for example.

  With such a configuration, the reflected wave reflected by the end face of the piezoelectric element 2 can be damped, and leakage vibration from the facing region where the first excitation electrode 211 and the second excitation electrode 212 face each other is further suppressed. The ripple in the main vibration band can be further suppressed. Note that such an effect is sufficient if the first excitation electrode 211 has a thick portion 211b on one end side, and can also be obtained by the form shown in FIG.

  Moreover, as shown in FIG. 3, the thick part 211b and the thin part 211a are not partitioned by a clear boundary such as a step shape, and gradually become thicker from the thick part 211b. The form which transfers to 211a may be sufficient. Although not shown, the thickness may gradually change between the thin part 211a and the thinnest part 211a '.

  Further, as shown in FIG. 4, in at least one of the first excitation electrode 211 and the second excitation electrode 212, a thick portion may be in a region other than the region facing the other excitation electrode. In other words, in at least one of the first excitation electrode 211 and the second excitation electrode 212, even if a portion thicker than the thickness of the region facing the other excitation electrode is in a region not facing the other excitation electrode. Good. Here, in the form shown in FIG. 4, the thick portion 211 b of the first excitation electrode 211 is in a region other than the region facing the second excitation electrode 212, and the second excitation electrode 211 A portion 211b having a large thickness is provided over almost the entire region that does not face the excitation electrode 212, and a portion 211a having a thin thickness is provided over almost the entire region of the first excitation electrode 211 that faces the second excitation electrode 212. Yes. In addition, the thick portion 212b of the second excitation electrode 212 is in a region other than the region facing the first excitation electrode 211, and the region of the second excitation electrode 212 is not opposed to the first excitation electrode 211. A thick portion 212b is provided over almost the entire region, and a thin portion 212a is provided over almost the entire region of the second excitation electrode 212 facing the first excitation electrode 211.

  By setting it as such a structure, the amplitude of the thickness vibration (main vibration) utilized for an oscillation can be reduced by reducing the mass load of an opposing area | region.

  In the example shown in FIG. 4, in both the first excitation electrode 211 and the second excitation electrode 212, a configuration in which a thick part is in a region other than a region facing the other excitation electrode is shown. However, the present invention is not limited to this configuration, and any one of the excitation electrodes may be configured such that a thick portion is in a region other than the region facing the other excitation electrode. Further, the thinnest part may be provided in the thin part.

  Further, as shown in FIG. 5, in at least one of the first excitation electrode 211 and the second excitation electrode 212, the central portion of the facing region facing the other excitation electrode may be the thinnest. Here, the form shown in FIG. 5 has a thick portion 211b over almost the entire region of the first excitation electrode 211 that does not face the second excitation electrode 212, and the second excitation electrode 211 has a second thickness. A thin portion 211a is provided over almost the entire opposing region facing the excitation electrode 212. In particular, the thinnest portion 211a 'is provided at the center of the opposing region of the first excitation electrode 211 facing the second excitation electrode 212. It is what you have. The thinnest part 211a ′ is set to have a thickness of at least 0.2 μm, and the thin part 211a around it is set to a thickness of 0.6 to 0.8 μm, for example.

  According to this configuration, it is possible to reduce the mass load at the central portion of the opposing region that most affects vibration, to improve the amplitude of thickness vibration (main vibration) used for oscillation, and to improve the stability of oscillation.

  As described above, the configuration shown in FIG. 5 is such that only the first excitation electrode 211 has the thinnest central portion of the region facing the other excitation electrode (second excitation electrode 212). As shown in FIG. 4, the central portion of the region facing the other excitation electrode in both the first excitation electrode 211 and the second excitation electrode 212 may be the thinnest.

  In such a case, as shown in FIG. 6, the thickness of the central portion of the region facing the other excitation electrode may be different between the first excitation electrode 211 and the second excitation electrode 212.

Here, the form shown in FIG. 6 has a thick portion 211 b over almost the entire region of the first excitation electrode 211 that does not face the second excitation electrode 212, and the first excitation electrode 21.
1 has a thin portion 211a over almost the entire area of the opposing region facing the second excitation electrode 212, and most particularly at the center of the opposing region of the first excitation electrode 211 facing the second excitation electrode 212. It has a thin part 211a ′. Further, the first excitation electrode 212 has a thick portion 212b over almost the entire region of the second excitation electrode 212 that does not face the first excitation electrode 211, and the second excitation electrode 212 faces the first excitation electrode 211. In the second excitation electrode 212, the thinnest part 212a 'is provided at the center of the opposing region of the second excitation electrode 212 facing the first excitation electrode 211. The thickness of the thinnest part 211a ′ in the first excitation electrode 211 is different from the thickness of the thinnest part 212a ′ in the second excitation electrode 212.

  In the form as shown in FIG. 6, the thickness of the thinnest portion of the first excitation electrode 211 and the second excitation electrode 212 is different, so that the thickness vibration (main vibration) used for oscillation by reducing the mass load is reduced. ) Can be improved, and the resonance frequency of unwanted vibration can be dispersed.

  Next, a method for manufacturing the piezoelectric component of this embodiment will be described.

  First, a multi-piece substrate for producing the support substrate 1 is produced. For example, after mixing raw material powders such as lead titanate, lead zirconate titanate, and barium titanate together with water and a dispersant using a ball mill, a binder, a plasticizer, and the like are added, followed by drying and sizing. The raw material thus obtained is press-molded and, if necessary, subjected to hole processing, degreased at a predetermined temperature, fired at a peak temperature of, for example, 900 ° C. to 1600 ° C., and polished to a predetermined thickness . Thereafter, for example, a conductive paste containing a metal powder such as silver or nickel and glass is printed and fired at a predetermined temperature to form the first capacitor electrode 121, the second capacitor electrode 122, and the like, thereby obtaining the support substrate 1. .

  A support portion made of a conductive paste is formed on the obtained support substrate 1 with a thickness of about 1 μm to 100 μm using screen printing or the like. Specifically, for example, a bump-shaped first support portion 31 formed by dispersing and solidifying metal powder in a resin, for example, is provided on the first capacitor electrode 121, and, for example, a metal is formed on the second capacitor electrode 122. A bump-like second support portion 32 is provided in which powder is dispersed in a resin and solidified.

  Next, the piezoelectric ceramic (piezoelectric body 22) constituting the piezoelectric element 2 is, for example, mixed with raw material powder together with water and a dispersant using a ball mill, and then added with a binder, a plasticizer, and the like, and dried and sized. 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 end face direction at a temperature of 25 ° C. to 300 ° C., for example.

  The excitation electrodes 21 formed on the upper and lower surfaces of the piezoelectric body 22 are obtained by depositing a metal film on the upper and lower surfaces of the piezoelectric body using the vacuum deposition method, the PVD method, the sputtering method, etc. Can be formed by patterning by photoetching after forming a photoresist film of about 1 μm to 10 μm on each metal film by screen printing or the like. Here, in order to make the thickness of the excitation electrode 21 different, resist printing may be partially performed and the thickness of the excitation electrode 21 may be reduced by etching.

  The piezoelectric element 2 is manufactured by cutting the patterned piezoelectric body 22 into a predetermined size by dicing or the like.

Then, using the conductive bonding material 4, the piezoelectric element 2 is mounted and fixed on the first support portion 31 and the second support portion 32 of the support substrate 1. Here, in the case where the conductive bonding material 4 is a conductive adhesive in which metal powder is dispersed in a resin, this conductive adhesive is first used by using a dispenser or the like.
The piezoelectric element 2 is placed on the first support portion 31 and the second support portion 32, and is electrically bonded by heating or ultraviolet irradiation. The resin of the agent may be cured.

  Then, the opening peripheral surface of the lid 5 is joined to the peripheral portion of the upper surface of the support substrate 1 so as to cover the piezoelectric element 2. As the lid 5, a multi-piece collective cover sheet having a plurality of recesses is used, and the collective cover sheet is placed on the pick-up substrate so that the concave portions cover the piezoelectric elements. The convex part of the collective cover sheet used as a peripheral surface is joined to the peripheral part of the upper surface of a support substrate. 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 5, and the lid body 5 is placed on the upper surface of the support substrate 1. Thereafter, the lid 5 or the support substrate 1 is heated to cure the insulating adhesive by raising the temperature to 100 to 150 ° C., and the lid 5 is bonded to the upper surface of the support substrate 1.

  Finally, after cutting by dicing or the like along the boundary of each piezoelectric component (piece), a conductive paste is printed on the side surface of the piezoelectric component that has become a piece using screen printing or the like, and the temperature is 100 to 150 ° C. A piezoelectric component can be obtained by increasing the temperature and curing.

  The piezoelectric component of this example is manufactured by the above method. According to such a method, it is possible to manufacture a high-accuracy resonator that suppresses ripples in the main vibration band that causes a decrease in the accuracy of the oscillation frequency with high productivity.

1: support substrate 121: first terminal electrode 122: second terminal electrode 121: first capacitor electrode 122: second capacitor electrode 123: ground electrode 124: input / output electrode 125, 126: side electrode 2: piezoelectric element 21: excitation Electrode 211: First excitation electrode 212: Second excitation electrode 211a, 212a: Thin part 211a'212a ': Thinnest part 211b, 212b: Thick part 22: Piezoelectric body 23: End face electrode 31: First 1 support portion 32: second support portion 4: conductive bonding material 5: lid

Claims (5)

  A support substrate; and a piezoelectric element provided with a first excitation electrode and a second excitation electrode fixed on the support substrate and having opposing regions facing each other, wherein the first excitation electrode and the second excitation electrode are provided. A piezoelectric component having a portion having a different thickness in at least one of the excitation electrodes. In the piezoelectric element, the first excitation electrode is provided on one main surface of the piezoelectric body from one end portion toward the other end portion, and one side from the other end portion to the other main surface of the piezoelectric body. The second excitation electrode is provided toward the end of the piezoelectric element, and the first excitation electrode and the second excitation electrode are opposed to each other at a central portion between both ends of the piezoelectric body. Has an opposing area,
At least one of the first excitation electrode and the second excitation electrode has a thick portion on one end side of the piezoelectric body or on the other end side of the piezoelectric body, and the center The piezoelectric component according to claim 1, wherein the piezoelectric component has a thin portion on the side of the portion.   3. The piezoelectric component according to claim 2, wherein in at least one of the first excitation electrode and the second excitation electrode, the thick portion is in a region other than the facing region.   The center part of the said opposing area | region is the thinnest in at least one of the said 1st excitation electrode and the said 2nd excitation electrode, The Claim 1 thru | or 3 characterized by the above-mentioned. Piezoelectric parts. 5. The piezoelectric component according to claim 4, wherein a thickness of a central portion of the facing region is different between the first excitation electrode and the second excitation electrode.