JP2009152717A - Piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric element capable of improving the resonance frequency shift of a piezoelectric element which may be generated due to the deterioration of conductivity between an electrode on the inside bottom of a package and an extraction electrode of a piezoelectric vibration piece. <P>SOLUTION: An epoxy group conductive adhesive 70 applied between the electrode 13 and the extraction electrode 31 is tightly stuck to the electrode 13 and the extraction electrode 31 independently of metal element species composing the electrode 13 and the extraction electrode 31 and is excellent in physical and chemical stability, so that conductivity between the electrode 13 and the extraction electrode 31 can be sufficiently secured and maintained. In addition, a silicon group adhesive 75 applied to a space between the electrode 13 and the extraction electrode 31, to which the epoxy group conductive adhesive 70 is not applied, is non-conductive, and thereby is not responsible for conductivity deterioration between the electrode 13 and the extraction electrode 31. Consequently, the resonance frequency shift of the piezoelectric element 1 which may be generated due to the conductivity deterioration can be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric element in which a piezoelectric vibrating piece connected by a plurality of types of adhesives is incorporated in a package.

  Conventionally, a piezoelectric element in which a piezoelectric vibrating piece connected by a plurality of types of adhesives is incorporated in a package is known (see, for example, Patent Document 1). The piezoelectric element includes a conductive adhesive that connects the lead electrode portion of the piezoelectric vibrating piece and the electrode portion on the inner bottom portion of the package. Here, the epoxy-based conductive adhesive or the polyimide-based adhesive as the conductive adhesive is provided on the lead electrode portion of the piezoelectric vibrating piece. In addition, the silicon-based conductive adhesive as the conductive adhesive is used between the epoxy-based conductive adhesive or polyimide-based adhesive provided on the lead electrode portion of the piezoelectric vibrating piece and the electrode portion on the inner bottom portion of the package. Is provided. Alternatively, the epoxy-based conductive adhesive or the polyimide-based adhesive is provided on the electrode portion on the inner bottom portion of the package. The silicon-based conductive adhesive is provided between the epoxy-based conductive adhesive or polyimide-based adhesive provided on the inner bottom electrode portion of the package and the lead electrode portion of the piezoelectric vibrating piece. Alternatively, the epoxy-based conductive adhesive or the polyimide-based adhesive is provided on the lead electrode portion of the piezoelectric vibrating piece and the electrode portion on the inner bottom portion of the package. Also, the silicon-based conductive adhesive is an epoxy-based conductive adhesive or polyimide-based adhesive provided on the lead electrode portion of the piezoelectric vibrating piece and an epoxy-based conductive agent provided on the inner bottom electrode portion of the package. It is provided between the adhesive or the polyimide adhesive.

JP 2003-198311 A (pages 4-6, FIGS. 1-6)

  However, in the conventional piezoelectric element, the lead electrode portion of the piezoelectric vibrating piece and the electrode portion on the inner bottom portion of the package are connected by an epoxy-based conductive adhesive or a polyimide-based adhesive and a silicon-based conductive adhesive. Yes. The adhesion of the silicon-based conductive adhesive to the adherend tends to be inferior to the adhesion of the epoxy-based conductive adhesive or the polyimide-based adhesive to the adherend. As a result, the silicon-based conductive adhesive and the lead electrode portion of the piezoelectric vibrating piece, the silicon-based conductive adhesive and the electrode portion at the inner bottom of the package, the silicon-based conductive adhesive, and the epoxy-based conductive adhesive or polyimide There is a possibility that sufficient adhesion between the adhesives cannot be secured. Therefore, the interface between the silicon-based conductive adhesive and the lead electrode portion of the piezoelectric vibrating piece, the interface between the silicon-based conductive adhesive and the electrode portion at the inner bottom of the package, the silicon-based conductive adhesive, and the epoxy-based There is a possibility that extremely slight peeling may occur at the interface with the conductive adhesive or the polyimide-based adhesive. This peeling deteriorates the electrical conductivity between the electrode part at the inner bottom of the package and the lead electrode part of the piezoelectric vibrating piece. Further, the physical and chemical stability of the silicon-based conductive adhesive tends to be inferior to the physical and chemical stability of the epoxy-based conductive adhesive or the polyimide-based adhesive. As a result, the electrical resistance value and capacitance value of the silicon-based conductive adhesive may change over time, and the conductivity of the silicon-based conductive adhesive itself may deteriorate. Therefore, there is a problem that the resonance frequency shift of the piezoelectric element is likely to occur with the above-described deterioration in conductivity.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A piezoelectric element according to this application example includes a package in which an electrode portion is formed on an inner bottom portion, and a piezoelectric vibrating piece that is disposed so as to face the inner bottom portion and has an extraction electrode portion formed at an end portion. An epoxy-based conductive adhesive or a polyimide-based conductive adhesive provided between the electrode unit and the lead-out electrode unit and connecting the electrode unit and the lead-out electrode unit, and the epoxy-based conductive bond A silicon-based adhesive that is provided between the electrode portion and the extraction electrode portion that is not provided with an agent or the polyimide-based conductive adhesive, and that connects the electrode portion and the extraction electrode portion. It is characterized by that.

  According to such a configuration, the electrode part and the lead electrode part are connected to the epoxy conductive adhesive or the polyimide conductive adhesive provided between the electrode part and the lead electrode part, and the epoxy conductive adhesive. It is connected by the silicon system adhesive provided between the electrode part in which the agent or the polyimide system conductive adhesive is not provided, and the extraction electrode part. Epoxy conductive adhesive or polyimide conductive adhesive adheres firmly to the electrode part and lead electrode part regardless of the metal element type constituting the electrode part and lead electrode part, and is physically and chemically Therefore, the electrical conductivity between the electrode part and the extraction electrode part is sufficiently ensured and maintained. Therefore, it is possible to improve the resonance frequency shift of the piezoelectric element that occurs as the conductivity deteriorates. Further, since the silicon-based adhesive has elasticity, it absorbs the inertial force acting on the piezoelectric vibrating piece in the direction opposite to the direction in which the impact force is applied with the impact force applied to the piezoelectric element. Therefore, it is possible to improve the impact resistance of the piezoelectric element.

  Application Example 2 In the piezoelectric element according to the application example described above, the epoxy conductive adhesive or the polyimide conductive adhesive is formed between the electrode portion and a lead electrode portion formed at one end of the piezoelectric vibrating piece. It is preferable that the silicon-based adhesive is provided so as to be closer to the center of the piezoelectric vibrating piece than the epoxy-based conductive adhesive or the polyimide-based conductive adhesive.

  According to such a configuration, the epoxy-based conductive adhesive or the polyimide-based conductive adhesive is provided between the electrode portion and the lead electrode portion formed at one end of the piezoelectric vibrating piece. The silicon adhesive is provided so as to be closer to the center of the piezoelectric vibrating piece than the epoxy conductive adhesive or the polyimide conductive adhesive. When an impact force is applied to the piezoelectric element, an inertial force accompanying the impact force acts on the piezoelectric vibrating piece. Due to this inertial force, the piezoelectric vibrating piece vibrates around a location where a silicon-based adhesive serving as a boundary between a location connected by an adhesive and a location not connected by an adhesive is provided. . Since the electrode part and the lead electrode part are connected to this fulcrum and an elastic silicon-based adhesive is provided, the above-described inertia force is efficiently absorbed. By efficiently absorbing the inertial force, the vibration of the piezoelectric vibrating piece is suppressed, and deterioration (cracking, chipping) of the piezoelectric vibrating piece due to the collision between the piezoelectric vibrating piece and the inner bottom portion of the package is suppressed. Therefore, it is possible to further improve the impact resistance of the piezoelectric element.

  Application Example 3 In the piezoelectric element according to the application example described above, the epoxy-based conductive adhesive or the polyimide-based conductive adhesive is formed between the electrode unit and the extraction electrode unit formed at one end of the piezoelectric vibrating piece. It is preferable that the silicon-based adhesive is provided between the epoxy-based conductive adhesive and the polyimide-based conductive adhesive.

  According to such a configuration, the epoxy-based conductive adhesive or the polyimide-based conductive adhesive is provided between the electrode portion and the lead electrode portion formed at one end of the piezoelectric vibrating piece. A silicon-based adhesive is provided so as to surround the epoxy-based conductive adhesive or the polyimide-based conductive adhesive circumferentially. Therefore, the epoxy-based conductive adhesive and the silicon-based adhesive, the polyimide-based conductive adhesive and the silicon-based adhesive have different thermal expansion coefficients, but even if the adhesive expands or contracts due to the temperature change of the piezoelectric element, Since the piezoelectric vibrating piece does not tilt, it does not contact the inner bottom portion of the package. Therefore, it is possible to provide a piezoelectric element with stable vibration.

  Application Example 4 In the piezoelectric element according to the application example, it is preferable that the silicon-based adhesive is a non-conductive adhesive.

  According to such a configuration, the silicon-based adhesive is a non-conductive adhesive. Compared to epoxy conductive adhesives or polyimide conductive adhesives, silicone adhesives have inferior adhesion to the metal that is the electrode part and lead electrode part, but silicon adhesives are non-conductive. For this reason, it is not involved in the deterioration of conductivity between the electrode portion and the extraction electrode portion. Therefore, it is possible to further improve the resonance frequency shift of the piezoelectric element that occurs as the conductivity deteriorates.

  Further, the non-conductive silicon-based adhesive does not contain conductive particles having elasticity that is inferior to that of the silicon resin constituting the non-conductive silicon-based adhesive. As a result, the non-conductive silicon adhesive has superior elasticity compared to the silicon conductive adhesive, so that the inertial force acting on the piezoelectric vibrating piece due to the impact force applied to the piezoelectric element is reduced. Absorb more efficiently. Therefore, it is possible to further improve the impact resistance of the piezoelectric element.

  Hereinafter, embodiments will be described with reference to the drawings. The drawings referred to in the following description are schematic views in which the vertical and horizontal scales of members or portions are different from actual ones for convenience of illustration.

(First embodiment)
FIG. 1 is a plan view showing the piezoelectric element of the first embodiment. 2 is a cross-sectional view taken along line AA in FIG. As shown in FIGS. 1 and 2, the piezoelectric element 1 includes a piezoelectric vibrating piece 30 in a space formed by a package 10 and a lid 50. As an example, the package 10 is formed by laminating aluminum oxide sintered substrates obtained by sintering ceramic green sheets. As an example, a pair of electrode portions 13 made of gold is provided on the inner bottom portion 11 of the package 10. The pair of electrode portions 13 are connected to the outside of the package 10 (not shown) and supply a driving voltage to the piezoelectric vibrating piece 30.

  An epoxy-based conductive adhesive 70 and a non-conductive silicon-based adhesive 75 are applied on the pair of electrode portions 13, and the epoxy-based conductive adhesive 70 and the non-conductive silicon-based adhesive 75 are connected to each other. The lead electrode portion 31 of the piezoelectric vibrating piece 30 is placed thereon. Then, the epoxy-based conductive adhesive 70 and the non-conductive silicon-based adhesive 75 are cured, and the electrode portion 13 on the inner bottom portion 11 of the package 10 and the lead electrode portion 31 of the piezoelectric vibrating piece 30 are connected. . For details of the connection between the electrode portion 13 of the inner bottom portion 11 of the package 10 and the lead electrode portion 31 of the piezoelectric vibrating piece 30 using the epoxy conductive adhesive 70 and the nonconductive silicon adhesive 75, It will be described later.

  The piezoelectric vibrating piece 30 is formed of quartz as an example, and includes a so-called tuning-fork type piezoelectric vibration including a base portion 34 on one end 32 side and a pair of vibrating arm portions 35 on the other end 33 side opposite to the one end 32. It is a piece. The lead electrode portion 31 described above is formed to transmit the drive voltage to the portion of the piezoelectric vibrating piece 30 that contacts the epoxy-based conductive adhesive 70 at one end 32, so that the piezoelectric vibrating piece 30 is connected to the piezoelectric vibrating piece 30. An excitation electrode (not shown) formed on the surface of 30 is electrically connected to the electrode portion 13 of the inner bottom portion 11 of the package 10 via the epoxy conductive adhesive 70. The extraction electrode part 31 is formed integrally with the excitation electrode and transmits a drive voltage to the excitation electrode. Therefore, the extraction electrode portion 31 is formed simultaneously with the excitation electrode of the piezoelectric vibrating piece 30 in the manufacturing process of the piezoelectric vibrating piece 30. As an example, the excitation electrode and extraction electrode portion 31 is formed of chromium in the lower layer and gold in the upper layer.

  The lid 50 is joined to the open end of the package 10 via a low melting glass brazing material 80. In addition, the lid 50 is formed of a light-transmitting material, for example, glass in order to perform frequency adjustment described later.

  Further, a through hole 15 is provided in the inner bottom portion 11 of the package 10, and the inner peripheral surface of the through hole 15 is covered with metal. Then, after fixing the piezoelectric vibrating piece 30 in the package 10, the through hole 15 is filled with a metal sealing material 85, so that the space formed by the package 10 and the lid 50 is airtight. Sealed. Thereafter, the laser beam is irradiated from the outside to the metal film (not shown) of the piezoelectric vibrating piece 30 through the transparent lid 50, and a part thereof is evaporated to adjust the frequency of the mass reduction method. .

  Here, as the metal sealing material 85, for example, an alloy of gold and tin is used, and for the metal formed on the inner peripheral surface of the through hole 15, the lower layer is nickel and the upper layer is gold, for example. The plating film is used.

  Next, details of the connection between the electrode portion 13 on the inner bottom portion 11 of the package 10 and the lead electrode portion 31 of the piezoelectric vibrating piece 30 using the epoxy-based conductive adhesive 70 and the non-conductive silicon-based adhesive 75 are described. A characteristic configuration of this embodiment will be described. The epoxy-based conductive adhesive 70 is provided between the electrode part 13 and the extraction electrode part 31. The epoxy conductive adhesive 70 is in close contact with the electrode portion 13 and the extraction electrode portion 31 regardless of the metal element type constituting the electrode portion 13 and the extraction electrode portion 31, and is physically and chemically bonded. Therefore, the electrical conductivity between the electrode portion 13 and the extraction electrode portion 31 is sufficiently ensured and maintained. Further, the silicon-based adhesive 75 is provided so as to be closer to the one end 32 of the piezoelectric vibrating piece 30 than the epoxy-based conductive adhesive 70. Since the silicon-based adhesive 75 has elasticity, it absorbs the inertial force acting on the piezoelectric vibrating piece 30 in the direction opposite to the direction in which the impact force is applied with the impact force applied to the piezoelectric element 1. The epoxy-based conductive adhesive 70 contains silver fine particles as conductive particles in an epoxy-based synthetic resin agent as an adhesive component that exhibits adhesive strength.

  Next, a connection process that is details of the connection between the electrode portion 13 of the inner bottom portion 11 of the package 10 and the extraction electrode portion 31 of the piezoelectric vibrating piece 30 will be described. FIG. 3 is a plan view showing the package. FIG. 4 is a schematic view showing a state in which the piezoelectric vibrating piece is placed on the package. As shown in FIG. 3, a certain amount of the epoxy-based conductive adhesive 70 is applied to the pair of electrode portions 13 formed on the inner bottom portion 11 of the package 10 using a dispenser. Next, a certain amount of silicon adhesive 75 is applied to the pair of electrode portions 13 formed on the inner bottom portion 11 using a dispenser so that the epoxy conductive adhesive 70 approaches the one end 17 of the package 10. To do. Next, as shown in FIG. 4, the piezoelectric vibrating piece 30 is opposed to the inner bottom portion 11 of the package 10, and the electrode portion 13 formed on the inner bottom portion 11 of the package 10 and one end 32 of the piezoelectric vibrating piece 30 are provided. The formed extraction electrode part 31 is made to oppose. Thereafter, a light load is applied to the piezoelectric vibrating piece 30 to heat the package 10 containing the piezoelectric vibrating piece 30, thereby curing the epoxy conductive adhesive 70 and the silicon adhesive 75, and pulling out the electrode portion 13. The electrode unit 31 is in close contact with and connected to the electrode unit 31 via the epoxy-based conductive adhesive 70 and the silicon-based adhesive 75. The manufacturing process other than the connection process is a manufacturing process using a known technique.

In the first embodiment described above, the following effects are obtained.
(1) The electrode part 13 and the extraction electrode part 31 are not provided with the epoxy conductive adhesive 70 provided between the electrode part 13 and the extraction electrode part 31 and the epoxy conductive adhesive 70. They are connected by a silicon adhesive 75 provided between the electrode part 13 and the extraction electrode part 31. The epoxy-based conductive adhesive 70 firmly adheres to the electrode part 13 and the extraction electrode part 31 regardless of the metal element type constituting the electrode part 13 and the extraction electrode part 31, and is physically and chemically stable. Therefore, the electrical conductivity between the electrode portion 13 and the extraction electrode portion 31 is sufficiently ensured and maintained. In addition, since the silicon-based adhesive 75 is non-conductive, it does not participate in the deterioration of the conductivity between the electrode part 13 and the extraction electrode part 31. Therefore, it is possible to improve the resonance frequency shift of the piezoelectric element 1 that occurs with the deterioration of conductivity. Further, since the non-conductive silicon-based adhesive 75 has elasticity superior to that of the silicon-based conductive adhesive as well as the epoxy-based conductive adhesive 70, the impact force is applied in accordance with the impact force applied to the piezoelectric element 1. The inertial force acting on the piezoelectric vibrating piece 30 is absorbed in the direction opposite to the direction in which is applied. Therefore, the impact resistance of the piezoelectric element 1 can be improved.

(Second Embodiment)
In the present embodiment, description of the same content as the above-described embodiment will be omitted, and different content will be described. FIG. 5 is a plan view showing the piezoelectric element according to the second embodiment. 6 is a cross-sectional view taken along line BB in FIG. As shown in FIGS. 5 and 6, in the piezoelectric element 2, the epoxy-based conductive adhesive 70 is provided between the electrode portion 13 and the extraction electrode portion 31. In the piezoelectric element 2, the silicon-based adhesive 75 is provided so as to be closer to the center 36 of the piezoelectric vibrating piece 30 than the epoxy-based conductive adhesive 70.

In the second embodiment described above, the following effects are obtained.
(2) An epoxy-based conductive adhesive 70 is provided between the electrode portion 13 and the extraction electrode portion 31. The silicon adhesive 75 is provided so as to be closer to the center 36 of the piezoelectric vibrating piece 30 than the epoxy conductive adhesive 70. When an impact force is applied to the piezoelectric element 2, an inertial force accompanying the impact force acts on the piezoelectric vibrating piece 30. Due to this inertial force, the piezoelectric vibrating piece 30 vibrates at a fulcrum 37 at a location where a silicon adhesive 75 serving as a boundary portion between a location connected by an adhesive and a location not connected by an adhesive is provided. It will be. Since the electrode part 13 and the extraction electrode part 31 are connected to the fulcrum 37 and the elastic silicon-based adhesive 75 is provided, the inertia force is efficiently absorbed. The vibration of the piezoelectric vibrating piece 30 is suppressed by efficiently absorbing the inertial force, and the piezoelectric vibrating piece 30 is deteriorated (cracked or chipped) due to the collision between the piezoelectric vibrating piece 30 and the inner bottom portion 11 of the package 10. It is suppressed. Therefore, the impact resistance of the piezoelectric element 2 can be further improved.

(Third embodiment)
In the present embodiment, description of the same content as the above-described embodiment will be omitted, and different content will be described. FIG. 7 is a plan view showing the piezoelectric element of the third embodiment. 8 is a cross-sectional view taken along line CC in FIG. As shown in FIGS. 7 and 8, in the piezoelectric element 3, an epoxy conductive adhesive 70 is disposed between the electrode portion 13 and the extraction electrode portion 31. In the piezoelectric element 3, a silicon adhesive 75 is provided so as to surround the epoxy conductive adhesive 70 in a circumferential shape.

In the above-described third embodiment, the following effects can be obtained.
(3) An epoxy-based conductive adhesive 70 is provided between the electrode portion 13 and the extraction electrode portion 31. A silicon adhesive 75 is provided so as to surround the epoxy conductive adhesive 70 in a circumferential shape. Accordingly, the adhesive is disposed between the electrode portion 13 and the extraction electrode portion 31 so as to have a symmetrical shape. Therefore, although the epoxy-based conductive adhesive 70 and the silicon-based adhesive 75 have different thermal expansion coefficients, the piezoelectric vibrating piece 30 does not tilt even if the adhesive expands or contracts due to a temperature change of the piezoelectric element 3. It does not contact the inner bottom portion 11 of the package 10. Therefore, the piezoelectric element 3 with stable vibration can be provided.

  In addition, the said embodiment is not limited to the above-mentioned content, In the range which does not deviate from the main point, it is possible to perform a various change other than the above-mentioned content. For example, the piezoelectric vibrating piece 30 may be formed of zinc oxide, lithium tantalate, lead zirconate titanate, lithium niobate, or the like.

  The piezoelectric vibrating piece 30 may be a rectangular piezoelectric vibrating piece or a circular piezoelectric vibrating piece.

  Moreover, it may replace with the epoxy-type conductive adhesive 70, and may use a polyimide-type conductive adhesive.

  One of the epoxy-based conductive adhesive 70 and the silicon-based adhesive 75 is applied before the piezoelectric vibrating piece 30 is placed on the pair of electrode portions 13, and after the piezoelectric vibrating piece 30 is installed. It may be cured. The other adhesive of the epoxy-based conductive adhesive 70 and the silicon-based adhesive 75 is a pair after the piezoelectric vibrating piece 30 is placed on the pair of electrode portions 13 (after curing of the one adhesive). The electrode portion 13 and the extraction electrode portion 31 may be applied so as to enter the gap, and then cured.

  The pair of electrode portions 13 may be formed of a gold alloy, silver, aluminum, or the like.

  In addition, the lower layer of the extraction electrode unit 31 may be formed of titanium, nickel, or the like, and the upper layer may be formed of gold alloy, silver, or the like. Furthermore, the extraction electrode part 31 may be formed of a single layer of aluminum or the like.

  Further, the sealing material 85 may be an alloy of gold and germanium.

The top view which shows the piezoelectric element of 1st Embodiment. AA sectional view taken on the line AA of FIG. The top view which shows a package. Schematic which shows the state by which the piezoelectric vibrating piece was mounted in the package. The top view which shows the piezoelectric element of 2nd Embodiment. BB sectional drawing of FIG. The top view which shows the piezoelectric element of 3rd Embodiment. CC sectional view taken on the line of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2, 3 ... Piezoelectric element, 10 ... Package, 11 ... Inner bottom part, 13 ... Electrode part, 30 ... Piezoelectric vibrating piece, 31 ... Extraction electrode part, 32 ... One end (end part), 36 ... Center, 70 ... Epoxy Conductive adhesive, 75 ... silicone adhesive.

Claims (4)

A package having an electrode part formed on the inner bottom; and
A piezoelectric vibrating reed disposed so as to face the inner bottom and having an extraction electrode portion formed at an end;
An epoxy-based conductive adhesive or a polyimide-based conductive adhesive that is provided between the electrode portion and the lead-out electrode portion and connects the electrode portion and the lead-out electrode portion;
Silicon-based adhesive that is provided between the electrode part and the extraction electrode part that is not provided with the epoxy-based conductive adhesive or the polyimide-based conductive adhesive and connects the electrode part and the extraction electrode part A piezoelectric element comprising an agent. The piezoelectric element according to claim 1.
The epoxy conductive adhesive or the polyimide conductive adhesive is provided between the electrode portion and a lead electrode portion formed at one end of the piezoelectric vibrating piece,
The piezoelectric element, wherein the silicon-based adhesive is provided closer to the center of the piezoelectric vibrating piece than the epoxy-based conductive adhesive or the polyimide-based conductive adhesive. The piezoelectric element according to claim 1.
The epoxy conductive adhesive or the polyimide conductive adhesive is provided between the electrode portion and a lead electrode portion formed at one end of the piezoelectric vibrating piece,
The piezoelectric element, wherein the silicon-based adhesive is provided so as to surround the epoxy-based conductive adhesive or the polyimide-based conductive adhesive in a circumferential shape. In the piezoelectric element according to any one of claims 1 to 3,
The piezoelectric element, wherein the silicon-based adhesive is a non-conductive adhesive.

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