JP2017152969A - Piezoelectric component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high accuracy resonator which has high reliability for mechanical strength and a small oscillation frequency deviation.SOLUTION: A piezoelectric component 100 comprises: a supporting substrate 1 including a flat-plate dielectric substance 11, a pair of capacitor electrodes 12 provided to the dielectric substance 11, an input and output electrode 13, a ground electrode 14, and a side surface electrode 15; and a piezo electric element 2 that is mounted on the supporting substrate 1, and electrically connected to the pair of capacitor electrodes 12. The pair of capacitor electrodes 12, the input and output electrode 13, the ground electrode 14, and the side surface electrode 15 includes a conductive resin. The capacitor electrodes 12 include: a first region 121 extended to a width direction of the supporting substrate 1; and a second region 122 extended to a longitudinal direction toward a center part of the supporting substrate 1 from the first region 121. At least one of the second region 122 and the ground electrode 14 includes a metal film 17 in at least one part of the dielectric substance 11 and a conductive resin 16.SELECTED DRAWING: 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 generally includes a supporting substrate, a pair of supporting portions provided on the supporting substrate, and a piezoelectric element mounted on the pair of supporting portions and fixed at both ends with a conductive bonding material. It is comprised from the element and the cover body.

  On the upper surface of the support substrate, a pair of capacitive electrodes that are electrically connected to the piezoelectric element and form a capacitance with the ground electrode on the lower surface are provided. In addition, on the lower surface of the support substrate, a pair of input / output electrodes that are electrically connected to the pair of capacitance electrodes via the side electrodes are provided, and the ground is disposed between the pair of input / output electrodes. An electrode is provided. And the thing of the structure which consists of conductive resin is known as these electrodes (for example, refer patent document 1).

JP 2007-096429 A

  In such a resonator, since each electrode is made of a conductive resin, thermal stress generated between the piezoelectric element and the support substrate and between the piezoelectric component and the external circuit substrate, mechanical shock, etc. are applied to these electrodes. Therefore, the occurrence of cracks and the like in the support substrate can be suppressed, and the reliability with respect to mechanical strength is high.

  On the other hand, in recent years, there has been an increasing demand for resonators with high accuracy characteristics with small oscillation frequency deviation in addition to reliability with respect to mechanical strength.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a high-accuracy resonator having a small oscillation frequency deviation while having high reliability with respect to mechanical strength.

  The piezoelectric component of the present invention is provided on a flat dielectric, a pair of capacitive electrodes provided on one main surface of the dielectric, an input / output electrode and a ground electrode provided on the other main surface, and a pair of opposing side surfaces. A support substrate including a side electrode, and a piezoelectric element mounted on one main surface of the support substrate and electrically connected to a pair of capacitor electrodes provided on the one main surface. The electrode, the input / output electrode, the ground electrode, and the side electrode include a conductive resin. The capacitor electrode includes a first region extending in a width direction of the support substrate, and a central portion of the support substrate from the first region. A second region extending in a longitudinal direction toward the substrate, and at least one of the second region and the ground electrode is a metal in at least a part between the dielectric and the conductive resin. Characterized by having a membrane To.

  According to the piezoelectric component of the present invention, since the load capacity can be improved and variation in the load capacity can be suppressed, a highly accurate resonator with a small oscillation frequency deviation while having high reliability with respect to mechanical strength. Can be obtained.

It is a perspective view which shows the external appearance of the piezoelectric component of this embodiment. In the piezoelectric component shown in FIG. 1, (a) is a partially omitted schematic plan view, (b) is a cross-sectional view taken along line AA, and (c) is a bottom view. (A) is a schematic plan view which shows an example of the support substrate in the piezoelectric component shown in FIG. 2, (b) is sectional drawing which expands and shows the cross section of the principal part of (a). (A) is a schematic plan view which shows the other example of the support substrate in the piezoelectric component shown in FIG. 2, (b) is sectional drawing which expands and shows the cross section of the principal part of (a). It is sectional drawing which shows the principal part of the other example of the support substrate in the piezoelectric component shown in FIG.

  Hereinafter, an example of an embodiment of a piezoelectric component 100 of the present invention will be described in detail with reference to the accompanying drawings. 1 to 5, an orthogonal coordinate system xyz defined to be fixed to the piezoelectric component 100 is attached. In the following description, directions may be described with reference to this coordinate system. In the piezoelectric component 100, any direction may be a vertical direction or a horizontal direction, and the z-axis direction may be referred to as a vertical direction, a height direction, or a thickness direction. Further, when the piezoelectric component 100 is simply referred to as a plan view, it refers to viewing in the z-axis direction. In addition, this invention is not limited by embodiment shown below.

  The piezoelectric component 100 of the example shown in FIGS. 1 to 4 is provided with a vibrating substrate 22 so as to face the support substrate 1 and one main surface (upper surface in this example) and the other main surface (lower surface in this example). And a long piezoelectric element 2. A support portion 18 is provided on the support substrate 1, and both ends in the major axis direction of the piezoelectric element 2 are supported by the support portion 18 and bonded by the conductive bonding material 3. It is fixed on the support substrate 1.

  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.

  Two capacitive electrodes 12 are provided on the upper surface of the dielectric 11 constituting the support substrate 1. The capacitor electrode 12 is an electrode that is electrically connected to the vibration electrode 22 of the piezoelectric element 2 and forms a capacitor with the ground electrode 14 described later. The capacitive electrode 12 has a first region 121 extending in the width direction of the support substrate 1 (dielectric 11) and a second region 122 extending in the longitudinal direction from the first region 121 toward the center of the support substrate 1. ing. The first region 121 is a region that fixes the end of the piezoelectric element 2 and is electrically connected to the vibration electrode 22, and the second region 122 is a region that forms a capacitance with the ground electrode 14.

  The lower surface of the dielectric 11 has a ground electrode 14 at the center in the longitudinal direction. In the present embodiment, the ground electrode 14 faces the second region 122 of each of the two capacitive electrodes 12 with the dielectric 11 interposed therebetween. The ground electrode 14 and the second region 122 of the capacitor electrode 12 do not necessarily face each other. In order to form a larger capacity, it is preferable that a part of the ground electrode 14 and a part of the second region 122 of the capacity electrode 12 face each other as in this embodiment. Further, on the lower surface of the dielectric 11, in order to input and output signals, the ground electrode 14 is sandwiched, specifically, at positions facing the first regions 121 of the two capacitor electrodes 12 with the dielectric 11 sandwiched therebetween. Input / output electrodes 13 are provided. The ground electrode 14 and the input / output electrode 13 are joined to the electrode of the external circuit board with solder or a conductive adhesive.

When the second region 122 of the capacitive electrode 12 and the ground electrode 14 face each other through the dielectric 11 as in this example, the second region 122 and the ground electrode 14 of each of the two capacitive electrodes 12 face each other. By setting the areas of the portions to be equal to each other, the electrostatic capacities obtained in the respective opposing regions become equal.

  A side electrode 15 is provided on the side surface of the support substrate 1 to electrically connect the capacitor electrode 12 and the input / output electrode 13. Thereby, the vibration electrode 22 of the piezoelectric element 2 and the external circuit are electrically connected, and signal input / output is performed. In the present embodiment, the side electrodes 15 are provided on both side surfaces located in the width direction of the dielectric 11. In the figure, a side electrode 15 is also provided on a portion of the side surface of the support substrate 11 that is electrically connected to the ground electrode 14 in relation to solder bonding to an external circuit substrate.

  As in the prior art, the capacitive electrode 12, the input / output electrode 13, the ground electrode 14 and the side electrode 15 are made of a relatively flexible conductive resin 16, so that the piezoelectric element 2, the support substrate 1, and the piezoelectric component 100 are formed. Reliability of the mechanical strength of the connection between the circuit board and the external circuit board is increased. However, the second region 122 of the capacitor electrode 12 and the ground electrode 14 are portions that form a load capacitor with the dielectric 11 interposed therebetween. If this portion is made only of the conductive resin 16, the load capacity formed cannot be increased, and the load capacity may vary. This is presumably because the conductive resin 16 is obtained by dispersing conductive particles in an insulating resin, so that all the portions in contact with the dielectric 11 do not have conductivity. That is, the part of the bonding surface of the conductive resin 16 to the dielectric 11 that is in ohmic contact with the dielectric 11 is only the part where the conductive particles are present, and the part that functions as an electrode in the area of each electrode is It is because it becomes only a part.

  In the piezoelectric component 100 of the present embodiment, as in the example shown in FIGS. 3 to 5, the pair of capacitor electrodes 12, the input / output electrodes 13, the ground electrodes 14, and the side electrodes 15 include a conductive resin 16. At least one of the 12 second regions 122 and the ground electrode 14 has a metal film 17 on at least a part between the dielectric 11 and the conductive resin 16. In other words, the capacitive electrode 12, the input / output electrode 13, the ground electrode 14, and the side electrode 15 are mainly made of the conductive resin 16, and at least one of the second region 122 of the capacitive electrode 12 and the ground electrode 14 is the dielectric 11. It has a two-layer structure in which the upper metal film 17 and the upper conductive resin 16 overlap. With such a configuration, the load capacity can be improved by ensuring that the mechanical strength is ensured and the metal film 17 provided in the portion where the capacitance is formed is in ohmic contact with the dielectric 11. Since variation in load capacitance can be suppressed, the oscillation frequency deviation can be reduced, and the oscillation frequency can be increased in accuracy. In FIGS. 3A and 4A, the ground electrode 14 is indicated by a broken line, and the metal film 17 is indicated by a long broken line.

  The metal film 17 is mainly composed of metal. Specifically, it contains 95% by mass or more of metal. Examples of the metal of the metal film 17 include gold, silver, copper, nickel, aluminum, and tungsten. When the metal film 17 made of these metals is formed by vapor deposition, sputtering, or plating, the metal film 17 can be made of almost 100% metal. Alternatively, the metal film 17 may be formed of a thick film conductor that is baked by adding an additive such as glass to these metal powders. In this case, the amount of non-metallic components such as glass is less than 5% by mass.

  As the conductive resin 16, a resin in which conductive particles made of metal powder such as gold, silver, copper, nickel, aluminum, and tungsten are dispersed in an epoxy resin, a silicone resin, or the like can be used. Content of the electroconductive particle in the conductive resin 16 can be set to 75 mass%-95 mass%, for example.

  A plating film made of a metal such as Ni / Au or Ni / Sn may be formed on the surfaces of the input / output electrode 13, the ground electrode 14, and the side electrode 15 as necessary.

  If at least one of the second region 122 of the capacitive electrode 12 and the ground electrode 14 has the metal film 17, one of the pair of electrodes forming the load capacitance is ohmic-bonded, and thus the above effect is achieved. However, as in the example shown in FIG. 3, if both the second region 122 and the ground electrode 14 have the metal film 17, the region where the metal film 17 is in ohmic contact with the dielectric 11 increases. It is effective.

  The position of the metal film 17 may be set so that a larger capacity can be formed. In other words, the metal film 17 is preferably disposed in a portion near the ground electrode 14 in the second region 122 of the capacitor electrode 12 and a portion near the second region 122 in the ground electrode 14. More specifically, as shown in the example shown in FIG. 3, the metal film 17 is formed on the central portion side (tip side) in the longitudinal direction of the dielectric 11 in the second region 122 and the central portion in the width direction of the ground electrode 14. You may have. By adopting such a configuration, the metal film 17 in the second region 122 and the metal film 17 in the ground electrode 14 are arranged close to each other, so that the load capacity can be further improved, and the oscillation frequency deviation can be further reduced. The oscillation frequency can be further improved.

  Further, as in the example illustrated in FIG. 4, the second region 122 may have the metal film 17 from the center side to the first region 121. That is, the metal film 17 may be provided on almost the entire surface between the conductive resin 16 and the dielectric 11 in the second region 122 of the capacitor electrode 12. Since the portion of the second region 122 on the first region 121 side is separated from the ground electrode 14, the load capacitance formed between this portion and the ground electrode 14 is the tip side of the second region 122 and the ground electrode 14. Although it is small compared with the load capacity formed between the two, the load capacity can be further improved. For this reason, variation in load capacitance can be further suppressed, so that the oscillation frequency deviation can be reduced, and the oscillation frequency can be further improved in accuracy.

  Similarly, the metal film 17 of the ground electrode 14 may have the metal film 17 on almost the entire surface between the conductive resin 16 of the ground electrode 14 and the dielectric 11. Also in this case, the load capacity can be further improved. In the example shown in FIG. 4, the metal film 17 of the ground electrode 14 is provided so as to be spaced from the side surface of the dielectric 11. In other words, the end portion of the metal film of the ground electrode 14 is composed only of the conductive resin 16. As a result, stress relaxation at the end where the thermal stress applied to the ground electrode 14 is the largest is more effectively achieved.

  5, the metal film 17 may be thinner than the conductive resin 16 where the conductive resin 16 and the metal film 17 of the capacitor electrode 12 and the ground electrode 14 overlap. By adopting such a configuration, the thickness ratio of the flexible conductive resin 16 is increased in the portion where the conductive resin 16 and the metal film 17 of the capacitive electrode 12 and the ground electrode 14 overlap, so that a temperature change occurs. In such an environment, the stress generated in the capacitive electrode 12 and the ground electrode 14 due to the difference in thermal expansion can be reduced, and the variation in capacitance caused by the stress can be suppressed, so that the oscillation frequency can be further improved in accuracy. The thickness of the metal film 17 can be set to 0.0001 mm to 0.02 mm, for example. The thickness of the conductive resin 16 can be set to 0.005 mm to 0.03 mm at a portion overlapping with the metal film 17, and 0.005 mm to 0.05 mm at a portion not overlapping with the metal film 17. In addition, the input / output electrode 13 and the side electrode 15 which do not have the metal film 17 consist only of the conductive resin 16, and the thickness can be set to 0.005 mm to 0.2 mm.

As described above, the pair of support portions 18 are provided on the support substrate 1, and the piezoelectric element 2 is mounted on the support substrate 18 so as to vibrate. Specifically, the pair of support portions 18 support the end portions of the piezoelectric element 2 in the major axis direction, and the piezoelectric element 2 is mounted with a space between the support substrate 1. The support portion 18 has conductivity, for example, and is obtained by dispersing metal powder such as gold, silver, copper, nickel, aluminum, tungsten, or the like in a resin. Support part 18
Is bonded onto the first region 121 of the capacitor electrode 12. Moreover, the support part 18 is columnar bodies, such as prismatic shape and a column shape, for example, The dimension is 0.1 mm-1.0 mm in length (diameter) of a vertical and horizontal direction, and thickness (height), for example. Can be set to 10 μm to 100 μm.

  2B, the piezoelectric element 2 mounted on the support portion 18 is fixed on the support substrate 1 (capacitance electrode 12) by the conductive bonding material 3, and electrically It is connected. In addition, since the support portion 18 is formed of a conductive material, the vibration electrode 22 and the capacitive electrode 12 of the piezoelectric element 2 are electrically connected to each other even in the support portion 18, so that the support portion is insulative. The connection is lower resistance than in some cases. As the conductive bonding material 3, for example, solder, a conductive adhesive, or the like is used. If it is a solder, the lead-free material which consists of copper, tin, silver, etc. can be used, for example. In the case of a conductive adhesive, an epoxy or silicone resin containing 75 to 95% by mass of conductive particles such as silver, copper and nickel can be used.

  The piezoelectric element 2 includes, for example, as shown in FIG. 2B, a piezoelectric body 21, vibration electrodes 22 provided on both main surfaces (one main surface and the other main surface) of the piezoelectric body 21, a piezoelectric body, And an end face electrode 23 provided on the end face 21. The piezoelectric body 21 can be, for example, a long 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. The piezoelectric body 21 includes, for example, piezoelectric ceramics based on lead titanate, lead zirconate titanate, lithium tantalate, lithium niobate, sodium niobate, potassium niobate, bismuth layered compounds, and the like, and single crystal materials thereof. Can be used.

  In addition, the vibration electrode 22 is disposed on the one main surface and the other main surface of the piezoelectric body 21 so as to have regions (intersection regions) facing each other. The vibration electrode 22 provided on one main surface (upper surface) of the piezoelectric body 21 is provided so as to extend from one end portion in the longitudinal direction of the piezoelectric body 21 toward the other end portion. The vibration electrode 22 provided on the main surface (lower surface) is provided so as to extend from the other end in the longitudinal direction of the piezoelectric body 21 toward the one end, and has regions facing each other. . The vibration electrodes 22 are connected to end face electrodes 23 provided on both end faces of the piezoelectric body 21 in the longitudinal direction. The vibration electrode 22 of the piezoelectric element 2 is electrically connected to the capacitive electrode 12 through the end face electrode 23, the conductive bonding material 3 and the support portion 18. For example, gold, silver, copper, aluminum, chromium, nickel or the like can be used for the vibrating electrode 22 and the end face electrode 23, and each of them is deposited to a thickness of, for example, 0.0001 m to 0.003 m. The vibrating electrode 22 and the end face electrode 23 can be formed using, for example, a thin film forming method such as a vacuum deposition method, a PVD method, a sputtering method, or a thick film forming method in which a metal paste is applied and baked.

  Such a piezoelectric element 2 generates piezoelectric vibration of thickness longitudinal vibration or thickness shear vibration at a specific frequency in a region (crossing region) where the vibration electrode 22 is opposed when a voltage is applied between the vibration electrodes 22. It is what has become.

  As shown in FIGS. 1 and 2B, a lid 4 may be provided on the support substrate 1 so as to cover the piezoelectric element 2. The lid 4 is joined to the peripheral edge of the upper surface of the support substrate 1 with an adhesive or the like. Thereby, the function of protecting the piezoelectric element 2 accommodated in the internal space formed together with the support substrate 1 from the physical influence and chemical influence from the outside, the water in the space formed together with the support substrate 1, etc. It has a hermetic sealing function to prevent foreign material from entering. As the material of the lid 4, 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.

1: Support substrate 11: Dielectric 12: Capacitance electrode 121: First region 122: Second region 13: Input / output electrode 14: Ground electrode 15: Side electrode 16: Conductive resin 17: Metal film 18: Support part 2: Piezoelectric element 21: Piezoelectric body 22: Vibration electrode 23: End face electrode 3: Conductive bonding material 4: Cover body 100: Piezoelectric component

Claims (4)

A support substrate including a flat dielectric, a pair of capacitive electrodes provided on one main surface of the dielectric, an input / output electrode and a ground electrode provided on the other main surface, and side electrodes provided on a pair of opposing side surfaces When,
A piezoelectric element mounted on one main surface of the support substrate and electrically connected to a pair of capacitive electrodes provided on the one main surface;
The pair of capacitive electrodes, the input / output electrodes, the ground electrode, and the side electrodes include a conductive resin,
The capacitor electrode has a first region extending in the width direction of the dielectric, and a second region extending in the longitudinal direction from the first region toward the center of the dielectric,
At least one of the second region and the ground electrode has a metal film on at least a part between the dielectric and the conductive resin.   2. The piezoelectric component according to claim 1, wherein the metal film is provided on the central portion side of the second region and the central portion in the width direction of the ground electrode.   3. The piezoelectric component according to claim 1, wherein the second region includes the metal film from the central portion side to the first region. 4. The piezoelectric component according to claim 1, wherein the metal film is thinner than the conductive resin in a portion where the conductive resin and the metal film overlap each other.

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