JP6563792B2 - Piezoelectric parts - Google Patents

Description

  The present invention relates to a piezoelectric component used as an oscillator.

  A support substrate; a piezoelectric element having both ends fixed on the main surface of the support substrate; and a lid attached to an outer peripheral portion on the main surface of the support substrate so as to cover the piezoelectric element. 2. Description of the Related Art A piezoelectric oscillator having a configuration in which side electrodes electrically connected to piezoelectric elements are provided on the side surface of a body so as to extend in the thickness direction of a support substrate is known. This piezoelectric oscillator is used with a side electrode electrically connected to an external circuit board by, for example, solder (see, for example, Patent Document 1).

JP 2007-090003 A

  Since the piezoelectric oscillator as described above is also used as a vehicle-mounted component, high reliability of mechanical strength is required in an environment where a long-term thermal cycle in a wide temperature range is applied.

  However, in such an environment, the conventional piezoelectric oscillator has a boundary between the side electrode and the support substrate located at the end in the width direction of the side electrode connected to the external circuit board by solder, and the side electrode and the lid. There is a risk that stress is applied to the boundary with the body, peeling of the side electrodes may occur, and cracks may occur in the support substrate or the lid.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a piezoelectric component having high mechanical strength reliability even in an environment where a long-term thermal cycle in a wide temperature range is applied.

The piezoelectric component of the present invention includes a support substrate, a piezoelectric element mounted on the main surface of the support substrate, and a lid attached to an outer peripheral portion on the main surface of the support substrate so as to cover the piezoelectric element. wherein the from the side surface of the supporting substrate over the side surface of the lid side electrode is provided extending in the thickness direction of the supporting substrate, wherein with the width of the side electrode is changed along the thickness direction It is widest at the boundary between the support substrate and the lid .

  According to the present invention, even in an environment where a long-term thermal cycle in a wide temperature range is applied, the stress applied to the boundary between the side electrode and the support substrate and the boundary between the side electrode and the lid is dispersed, and the side electrode is peeled off. And the occurrence of cracks in the support substrate or the lid can be suppressed, and a piezoelectric component with high mechanical strength reliability can be obtained.

(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 schematic side view of an example of the piezoelectric component of this embodiment. It is a schematic side view of the other example of the piezoelectric component of this embodiment. It is a schematic side 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. FIG. 2 is a schematic side view of an example of the piezoelectric component of the present embodiment. In FIG. 1A, “partially omitted” means that the lid 5 is omitted.

  The piezoelectric component shown in FIG. 1 is attached to an outer peripheral portion on the main surface of the support substrate 1 so as to cover the support substrate 1, the piezoelectric element 2 mounted on the main surface of the support substrate 1, and the piezoelectric element 2. A side electrode 125 extending in the thickness direction of the support substrate 1 from the side surface of the support substrate 1 to the side surface of the cover body 5, and the width of the side electrode 125 changes along the thickness direction. ing.

  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 electrodes that are electrically connected to the vibration electrode 21 of the piezoelectric element 2 and form a capacitor with a ground electrode 123 described later. The first capacitor electrode 121 is arranged extending from one end side in the longitudinal direction of the support substrate 1 toward the center portion, and the second capacitor electrode 122 is centered from the other end portion in the longitudinal direction of the support substrate 1. It is arranged extending toward the part.

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

  Furthermore, the first capacitor electrode 121 or the second capacitor electrode 122 and the input / output electrode 124 are electrically connected to the side surface of the support substrate 1 from one main surface (upper surface in this example) to the other main surface (lower surface in this example). Side electrodes 125 are provided for connection.

  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 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, 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 materials for the first capacitor electrode 121, the second capacitor electrode 122, the ground electrode 123, and the side electrodes 125 and 126, a conductive resin in which a metal powder such as gold, silver, copper, aluminum, tungsten, or the like is dispersed in a resin ( Conductive paste), thick film conductors obtained by adding an additive such as glass to these metal powders, and the like can be used. If necessary, Ni / Au or Ni / Sn plating may be formed.

  On the main surface of the support substrate 1, the piezoelectric element 2 is mounted with both ends fixed. Specifically, a first support portion 31 and a second support portion 32 are provided on the support substrate 1, and both ends in the longitudinal direction of the piezoelectric element 2 are the first support portion 31 and the second support portion. The piezoelectric element 2 is mounted so as to be able to vibrate so as to be supported by the support portion 32.

  The first support portion 31 and the second support portion 32 are projecting portions formed by dispersing metal powder such as gold, silver, copper, aluminum, and tungsten 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 lower surface of both end portions of the piezoelectric element 2, the first support portion 31, The second support portion 32 is joined. In addition, since the 1st support part 31 and the 2nd support part 32 are formed with the material which has electroconductivity, the vibration electrode 21 of the piezoelectric element 2, the 1st capacity electrode 121, and the 2nd capacity electrode 122 are: Conducted. 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 is a long piezoelectric element including a piezoelectric body 22 and vibration electrodes 21 provided on both main surfaces (one main surface and the other main surface) of the piezoelectric body 22 so as to face each other. . The piezoelectric body 22 constituting the piezoelectric element 2 is formed, for example, 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. 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.

  In addition, the piezoelectric element 2 includes a vibrating electrode 21 disposed on the one main surface and the other main surface of the piezoelectric body 22 so as to have regions (intersection regions) facing each other. The vibration electrode 21 provided on one main surface (upper main surface) of the piezoelectric body 22 is provided so as to extend from one end portion in the longitudinal direction toward the other end portion, and the other main surface of the piezoelectric body 22. The vibration electrode 21 provided on the (lower main surface) is provided so as to extend from the other end in the longitudinal direction toward the one end, and has regions facing each other. For example, a metal such as gold, silver, copper, and aluminum can be used for the vibrating electrode 21, and each of the vibrating electrodes 21 is attached to the surface of the piezoelectric body 22 to a thickness of 0.1 μm to 3 μm, for example. As shown in the drawing, end face electrodes 23 are provided on both end faces of the piezoelectric element 2, and the vibration electrode 21 of the piezoelectric element 2 is connected to the first capacitance electrode via the end face electrode 23 and the conductive bonding material 4. The vibration electrode 21 of the piezoelectric element 2 is electrically connected to the second capacitance electrode 122 through the conductive bonding material 4.

  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 21 faces when a voltage is applied between the vibration electrodes 21. It is what has become.

  As shown in the figure, a lid 5 on the main surface of the support substrate 1 is provided so as to cover the piezoelectric element 2, and the lid 5 is attached to an outer peripheral portion on the main surface of the support substrate 1. ing. The lid 5 is bonded to the outer peripheral portion of the main surface (upper surface) of the support substrate 1 with, for example, an epoxy-based or acrylic-based adhesive or an epoxy-based adhesive from the viewpoint of reflow heat resistance. Thus, the function of protecting the piezoelectric element 2 accommodated in the internal space formed together with the support substrate 1 from the physical and chemical influences from the outside, water in the space formed together with the support substrate 1, etc. It has a hermetic sealing function to prevent the entry of foreign matter. 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.

  The side electrodes 125 and 126 are provided to extend in the thickness direction of the support substrate 1 from the side surface of the support substrate 1 to the side surface of the lid 5, and the widths of the side electrodes 125 and 126 change along the thickness direction. Yes.

  When the external circuit board and the side electrodes 125 and 126 are electrically and mechanically connected with solder, a stress is applied to peel off the side electrodes 125 and 126 from the external circuit board side. Here, the stress becomes large at the boundary between the side electrodes 125 and 126 and the support substrate 1 and the boundary between the side electrodes 125 and 126 and the lid 5. On the other hand, since the widths of the side electrodes 125 and 126 change along the thickness direction, at least one end of the side electrodes 125 and 126 in the width direction, in other words, the side surfaces extending in the thickness direction of the support substrate 1. At least one of the sides of the electrodes 125 and 126 does not have a shape extending in a straight line in the thickness direction (vertical direction) of the support substrate 1. Thereby, the stress generation position is not positioned on the straight line in the vertical direction, and the stress can be dispersed. Moreover, the stress per unit length can also be relieved. Therefore, even in an environment where a long-term thermal cycle in a wide temperature range is applied, it is possible to prevent the side electrodes 125 and 126 from being peeled off and cracks from being generated in the support substrate 1 or the lid 5. A piezoelectric component having high mechanical strength reliability can be obtained.

  Here, examples of the width of the side electrode 125 changing along the thickness direction include a shape in which the width gradually increases from one side to the other side in the thickness direction, and the width direction as viewed from the front. A shape in which both end portions are inclined at different angles, a shape having wide portions at both end portions in the thickness direction (so-called drum shape), and a shape in which at least one end portion in the width direction is curved And a shape in which at least one end portion in the width direction is wavy (a shape having curvilinear irregularities), a shape having the widest width in the center portion in the thickness direction, and the like. For example, the width at the narrowest part is set to 50 to 95% of the width at the widest part. Specifically, when the width of the widest portion of the side electrodes 125 and 126 is 1 mm, the difference in width between the widest portion and the narrowest portion is set to 50 to 500 μm.

  The width of the side electrodes 125 and 126 is preferably in the range of 0.2 mm to 1.2 mm, for example, as a range that is small and effective in reducing stress while preventing short circuits.

  Here, as shown in FIG. 2, it is preferable that at least one end of the side electrodes 125 and 126 in the width direction is curved. Further, as shown in FIG. 3, at least one end in the width direction of the side electrodes 125 and 126 may have a shape having curved irregularities. 2 and 3, both end portions in the width direction of the side electrodes 125 and 126 have a curved shape or a shape having curved irregularities. With such a configuration, the stress can be distributed in various directions, so that a piezoelectric component with higher mechanical strength reliability can be obtained.

  Here, as shown in FIG. 4, the widths of the side electrodes 125 and 126 may be widest at the boundary between the support substrate 1 and the lid 5. The bonding strength of the side electrodes 125 and 126 is likely to decrease at the bonding portion between the support substrate 1 and the lid 5, but the desired bonding strength is maintained by increasing the width of the side electrodes 125 and 126 at this portion. be able to.

  Next, a method for manufacturing an example of the piezoelectric component of the present 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 metal powder such as silver or nickel and glass is printed and fired at a predetermined temperature, and the first capacitor electrode 121, the second capacitor electrode 122, the ground electrode 123, and the side electrodes 125 and 126. Etc. are formed to obtain 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 vibrating electrodes 21 formed on the upper and lower surfaces of the piezoelectric body 22 are obtained by depositing metal films on the upper and lower surfaces of the piezoelectric body 22 by using a vacuum deposition method, a PVD method, a sputtering method, or the like. A photoresist film having a thickness of about 1 μm to 10 μm can be formed by forming a photoresist film on each metal film using screen printing or the like and then patterning it by photoetching. 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 on the first support portion 31 and the second support portion 32 of the support substrate 1 and fixed. Here, in the case where the conductive bonding material 4 is a conductive adhesive in which metal powder is dispersed in a resin, the conductive adhesive is used for the first support portion 31 and the second support portion using a dispenser or the like. The piezoelectric element 2 may be applied on the first support portion 31 and the second support portion 32, and the resin of the conductive adhesive may be cured by heating or ultraviolet irradiation.

  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 concave portions is used, and the multi-piece collective cover sheet is placed on the pick-up substrate so that the concave portions cover the piezoelectric elements 2. The convex portion of the collective lid sheet serving as the opening peripheral surface is joined to the peripheral portion of the upper surface of the support 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 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. Here, in order to obtain a configuration in which the widths of the side electrodes 125 and 126 are changed along the thickness direction, for example, the side electrode 125 is formed by screen printing using a plate making with a printing pattern having a predetermined shape. 126 may be formed. In addition, after that, plating of Ni, Au, or the like may be formed on the surface of the side electrodes 125, 126.

  The piezoelectric component of this example is manufactured by the above method. According to the above method, a piezoelectric component that suppresses stress generated at the boundary between the support substrate 1 and the lid 5 and the side electrodes 125 and 126 by soldering and exhibits high reliability can be obtained.

DESCRIPTION OF SYMBOLS 1 Support substrate 11 Dielectric material 121 1st capacity | capacitance electrode 122 2nd capacity | capacitance electrode 123 Ground electrode 124 Input / output electrodes 125 and 126 Side electrode 2 Piezoelectric element 21 Vibration electrode 22 Piezoelectric body 23 End surface electrode 31 1st support part 32 2nd Support part 4 Conductive bonding material 5 Lid

Claims (3)

A support substrate;
A piezoelectric element mounted on the main surface of the support substrate;
A lid attached to an outer peripheral portion on the main surface of the support substrate so as to cover the piezoelectric element, and a side electrode extends in a thickness direction of the support substrate from a side surface of the support substrate to a side surface of the lid body. The piezoelectric component is characterized in that the width of the side electrode changes along the thickness direction and is widest at the boundary between the support substrate and the lid .   2. The piezoelectric component according to claim 1, wherein at least one end in the width direction of the side electrode has a curved shape.   2. The piezoelectric component according to claim 1, wherein at least one end in the width direction of the side electrode has a shape having curved irregularities.