JP4758123B2 - Piezoelectric device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a piezoelectric device such as a piezoelectric vibrator or a piezoelectric oscillator used in an electronic device such as a portable communication device or an electronic computer, and a manufacturing method thereof.

  Conventionally, piezoelectric vibration elements in which electrodes are formed on both main surfaces of a piezoelectric element plate are mounted in an airtight package. For example, a piezoelectric vibrator, a piezoelectric oscillator in which a piezoelectric vibrator and an oscillation circuit are mounted in the same package, Alternatively, piezoelectric devices such as a piezoelectric filter that separates a specific frequency band are frequently used in electronic devices such as portable communication devices and electronic computers. In recent years, piezoelectric devices having a shape corresponding to surface mounting have been developed, and along with downsizing and thinning of electronic devices, piezoelectric devices mounted in electronic devices are also being downsized and thinned.

  As an example of such a conventional piezoelectric device, FIG. 5 shows a crystal resonator using quartz as a piezoelectric material. A pair of element connection electrode pads are provided on the bottom surface of the cavity 21 of the container body 21. On this element connection electrode pad, there is mounted a crystal resonator element 22 having a pair of excitation electrodes electrically connected via a conductive adhesive on the front and back main surfaces. A conductor pattern layer 23 is formed on the top of the side wall of the surrounding container body 21.

  By covering the conductor pattern layer 23 with a metal lid 24 and bonding the conductor pattern layer 23 and the lid 24 by thermocompression bonding or the like, the mounting space (cavity space) of the crystal resonator element 22 is removed. This is a hermetically sealed crystal unit. (For example, see Patent Document 1 below.)

  The lid 24 is manufactured by adopting a conventionally known metal processing method and molding a metal such as 42 alloy into a predetermined shape. A nickel (Ni) layer is formed on the upper surface of the lid 24, and a gold (Au) layer is further formed on the upper surface of the nickel (Ni) layer. Sn) layer is formed.

  When such a crystal resonator is applied with a variable voltage from the outside between the excitation electrodes of the crystal resonator element 22 via an input / output terminal provided on the lower surface of the container body 21 and an external terminal 25 such as a ground terminal, the crystal oscillator Thickness shear vibration is caused at a predetermined frequency corresponding to the characteristics of the element 22, and a reference signal having a predetermined frequency is oscillated and output by an external oscillation circuit based on the resonance frequency. Such a reference signal is used as a clock signal in an electronic device such as a portable communication device.

The following documents are disclosed about the piezoelectric device including the above-described crystal resonator and the like.
JP 2001-274649 A JP 2004-236183 A

  In addition, the applicant did not come to discover prior art documents related to the present invention by the time of the filing of the application other than the prior art documents specified by the prior art document information described above.

  However, in the conventional piezoelectric device, the sealing material formed on the lid constituting the package is melted by thermocompression bonding or the like, and wets and spreads on the metal layer formed on the surface inside the package of the lid body. In some cases, gas is generated from the encapsulating material that spreads wet during high-temperature heating. Oscillation frequency and frequency temperature characteristics of the piezoelectric device fluctuate when this gas component adheres to the piezoelectric vibration element mounted inside the package or adversely affects the excitation electrode formed on the piezoelectric vibration element. There was a drawback that could end up.

  In addition, as the size and thickness of the piezoelectric device progresses, the space between the sealing material and the piezoelectric vibration element wetted and spread on the metal layer on the inner surface of the package of the lid body is remarkably narrowed. There is a possibility that the stray capacitance is generated between the elements and the oscillation frequency fluctuates.

  The present invention has been devised in view of the above drawbacks, and an object of the present invention is to provide a piezoelectric device in which unnecessary fluctuations that occur in the oscillation frequency and frequency temperature characteristics are remarkably small.

The present invention has been made in view of the above problems, and the piezoelectric vibrating element, a rectangular container body provided with a cavity capable of mounting the piezoelectric vibrating element, Ri consists 42 alloy, Kovar or phosphor bronze, flat And a lid body having a rectangular main surface, and a sealing material made of a gold-tin alloy is provided on the outer peripheral edge of one main surface of the lid body, and a piezoelectric vibration element is provided in the cavity portion. Is mounted on the top of the side wall of the container body so as to cover the opening of the cavity and so that the sealing material faces the top of the side wall. In a piezoelectric device in which a layer is fixed, a metal layer is provided only between the outer surface of the lid body between the one main surface of the lid body and the sealing material, and the sealing material is provided. cage, sealing material, so as not to contact the cover, provided only on the metal layer Cage, the metal layer is made of nickel and gold, a piezoelectric device, which is a structure obtained by stacking the lid side nickel, in the order of gold.

In addition, a piezoelectric vibration element is mounted in the cavity portion of the rectangular container body, and a sealing material made of a gold-tin alloy at the outer peripheral edge portion of one main surface of the rectangular lid body made of 42 alloy, Kovar or phosphor bronze The lid is disposed so as to cover the opening of the cavity and the sealing material faces the top of the side wall of the container body, and the sealing material and the conductor pattern layer provided on the top of the side wall in the method for manufacturing a piezoelectric device comprising a be secured, to prepare a metal substrate of a flat plate having a formation region of the plurality of the lid, on one main surface of the metal substrate, nickel and gold, the metal A metal layer is formed by plating in the order of nickel and gold from the substrate side, and the metal layer formed at locations other than the outer peripheral edge in each lid formation region of the metal substrate is removed by etching. a step a of, the sealing material, Outside on only the metal layer left in the peripheral edge, and deposited so as not to be in contact with the metal substrate, the cover forming area periphery by dicing a metal substrate and the metal layer in each of the lid forming region of the genus substrate And the step formed by dividing the lid body into individual lid bodies, and mounting the piezoelectric vibration element inside the cavity of the container body, and then opening the lid body formed by the above-mentioned process A and the above-mentioned process B into the opening of the cavity portion. And a step C of placing the sealing material on the top of the side wall of the container body so that the sealing material faces the top of the side wall of the container body, and joining the sealing material and the conductor pattern layer. This is a method for manufacturing a piezoelectric device.

  According to the piezoelectric device and the method of manufacturing the same of the present invention, the metal formed on the surface of the lid body rather than the metal forming the lid body only on the outer peripheral edge of the lid body on the sealing surface side with the container body. Since the sealing material with good wettability with the layer is formed, the sealing material prevents the sealing material from spreading on the exposed portion of the metal inside the lid body inside the package. A very small amount of gas generated from the surface can be obtained. In addition, since the sealing material can be prevented from getting wet and spread on the exposed parts of the lid body inside the package, the space between the lid and the excitation electrode of the piezoelectric vibration element can be secured as designed, and unnecessary floating There is no capacity.

  Therefore, according to the present invention, it is possible to provide a piezoelectric device in which unnecessary fluctuations such as oscillation frequency and frequency temperature characteristics are extremely small.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an exploded perspective view illustrating a crystal resonator as an example of the piezoelectric device according to the present invention, which is an example of a crystal resonator that is one of the piezoelectric devices, from an obliquely upper side of the lid. 2A is a side cross-sectional view showing a case where the crystal unit shown in FIG. 1 is assembled, and FIG. 2B is an enlarged view of the dotted circle A portion shown in FIG. It is sectional drawing. 3A is a perspective view illustrating one form of the lid described in FIG. 1 and FIG. 2 from the container body joining surface side, and FIG. 3B is a perspective view of the lid illustrated in FIG. 1 and FIG. It is the perspective view which illustrated another form from the container body joint surface side. In each figure, a part of the structure is not shown for the sake of clarity. Each dimension is also partially exaggerated, and the thickness dimension component in each figure is particularly exaggerated. Furthermore, the same reference numerals in the drawings indicate the same objects.

  That is, the crystal resonator shown in FIGS. 1 and 2 is generally configured by a container body 1, a crystal vibration element 2 as a piezoelectric vibration element, and a lid body 3. The container body 1 is formed, for example, by laminating a plurality of insulating layers made of a ceramic material such as alumina ceramics and glass-ceramics, and on the upper surface thereof, a cavity portion 4 that opens in a rectangular shape in the central region is formed. An annular conductor pattern layer 6 surrounding the opening of the cavity portion 4 is formed on the top of the side wall portion forming the cavity portion 4, and an input terminal, an output terminal and a ground terminal are provided on the outer lower surface of the container body 1. A plurality of external connection terminal electrodes 7 are provided.

  A pair of element mounting pads 5 provided on the bottom surface in the cavity portion 4 of the container body 1 are electrically connected via an excitation electrode of the crystal resonator element 2 described later on the upper surface side and a conductive adhesive 8. Input / output terminals (input terminal, output terminal) on the outer bottom surface of the container body 1 via the conductor pattern layer 6 formed on the container body 1 on the lower surface side and via conductors formed inside the structure of the container body. Is electrically connected.

  On the other hand, the conductor pattern layer 6 is electrically connected to a lid 3 described later on the upper surface side via a sealing material 10, and the container body 1 on the lower surface side via a via conductor or the like inside the structure of the container body 1. It is electrically connected to a ground terminal which is one of the external connection terminal electrodes 7 on the outer lower surface.

  The quartz resonator element 2 is formed by attaching and forming a pair of excitation electrodes on both main surfaces of a flat plate crystal piece cut from a lump of artificial crystalline lens with a predetermined crystal axis and polished. Is applied to the crystal piece via a pair of excitation electrodes, excitation vibration occurs at a predetermined frequency. Such a quartz-crystal vibrating element 2 is electrically and mechanically connected via the conductive adhesive 8 to the excitation electrodes attached to both main surfaces thereof and the corresponding mounting pads 5 on the upper surface of the container body. Is mounted on the bottom surface of the cavity portion 4 of the container body 1.

  The conductive adhesive 8 is formed by adding and mixing a predetermined amount of conductive particles made of Ag or the like into a resin material made of silicon resin or polyimide resin.

  Furthermore, a lid 3 is attached to the periphery of the opening of the cavity 4 of the container body 1. As the lid 3, 42 alloy, Kovar, phosphor bronze, or the like may be used, and a metal layer 9 of Ni or Au is formed on the outer peripheral edge of the container body joint side surface of the lid 3. A sealing material 10 such as gold tin (Au—Sn) is applied on the upper surface. When the sealing material 10 formed on the outer peripheral edge of the lid 3 and the conductor pattern layer 6 of the container 1 are in close contact with each other in an annular shape, the lid 3 is attached on the top of the side wall of the container 1. The cavity part 4 is hermetically sealed.

  The metal layer 9 made of Ni, Au or the like formed on the outer peripheral edge of the surface of the lid 3 on the container body bonding side is formed by plating and sealed with gold tin (Au-Sn) or the like. The wettability with the material 10 is better than 42 alloy and Kovar, which are metals constituting the lid body. Therefore, when the lid 3 and the container body 1 are hermetically sealed, the sealing material 10 wets and spreads only in the portion where the metal layer 9 is formed, and the metal film 9 on the container body joining side surface of the lid 3 is formed. Since the encapsulant 10 does not spread over the part where it is not formed, the amount of gas generated from the surface of the encapsulant 10 during high-temperature heating can be extremely reduced, and the oscillation frequency and frequency caused by this gas Variations in temperature characteristics can be prevented. Further, since the sealing material 10 does not wet and spread on the container-joining side surface of the lid 3 at the position where the excitation electrode of the crystal resonator element 2 faces, the excitation electrode of the crystal resonator element 2 and the sealing material 10 Since no stray capacitance is generated between them, it is possible to suppress fluctuations in the oscillation frequency.

  The lid 3 is for accommodating the quartz vibrating element 2 in the cavity 4 surrounded by the container body 1 and hermetically sealing the container 3, and the container body 1 through the conductor pattern layer 6 described above. The external connection terminal electrode 7 on the outer lower surface is connected to the ground terminal. Therefore, when the crystal resonator is used, if the external terminal electrode 7 is used for connection to an electronic circuit network such as an external motherboard, the lid 3 is held at the ground potential, and the crystal resonator element 2 is held by the lid 3. By the shielding effect, it is well protected from unnecessary external electrical effects such as noise.

  In addition, as a form of the metal layer 9 formed on the container body bonding side surface of the lid 3, a metal is formed only on the outer peripheral edge portion of the container body bonding side surface as shown in FIG. In addition to the form in which the layer 9 is formed, as shown in FIG. 3 (b), the metal layer 9 formed on the entire surface of the lid 3 on the container body bonding side has a belt-like part inside the outer peripheral edge. It is in a form removed in an annular shape.

Next, a method for manufacturing a piezoelectric device according to the present invention will be described with reference to FIG.
Here, FIGS. 4A to 4E are perspective process diagrams for explaining the manufacturing method of the present invention by exemplifying a crystal resonator.

(Process A)
First, as shown in FIGS. 4A and 4C, a metal substrate 11 having a plurality of lid forming regions is prepared (FIG. 4A), and one main substrate 11 of the metal substrate 11 is prepared. A metal layer 9 is formed on the surface by plating (FIG. 4B), and the metal layer 9 formed in a portion other than the outer peripheral edge of each lid forming region is removed by etching (FIG. 4). 4 (c)). First, the metal substrate 11 is made of 42 alloy, Kovar, phosphor bronze, or the like, and the metal layer 9 is formed by stacking nickel (Ni) and gold (Au) in this order. The metal layer 9 other than the outer peripheral edge is removed by applying an etching resist to the outer peripheral edge of each lid forming region of the metal substrate 11 and performing an etching process. Next, the etching resist is removed, and the metal layer 9 is formed only at the outer peripheral edge of each lid forming region.

(Process B)
Next, in FIG.4 (d), the sealing material 10 which is brazing materials, such as gold tin (Au-Sn), is adhered on the metal layer 9 left in the cover body formation area of the metal substrate 11, By cutting along each cutting line B on the outer periphery in each lid forming region of the metal substrate 11, each lid forming region is separated from the surrounding marginal region. The metal substrate 11 is cut by dicing using a dicer or the like, and the metal substrate 11 is divided into individual lid forming regions through the cutting process. Thereby, the some cover body 3 is obtained simultaneously.

(Process C)
As shown in FIG. 4 (e), the crystal resonator element 2 is accommodated in the cavity portion 4 of the container body 1. A crystal resonator element 2 is accommodated inside the container body 1. For example, when the container body 1 is formed of a ceramic material, a conductive paste serving as a wiring conductor is printed in a predetermined pattern on the surface of a ceramic green sheet obtained by adding and mixing an appropriate organic solvent to the ceramic material powder. The quartz vibrating element 2 is mounted on the cavity portion 4 of the container body 1 obtained by coating, forming a plurality of sheets, press-molding them, and firing them at a high temperature. At this time, the excitation electrode of the crystal resonator element 2 and the element mounting pad 5 provided in the cavity portion 4 of the container body 1 are electrically and mechanically connected via the conductive adhesive 8. And the cover body 3 created by the said process is mounted on the conductor pattern layer 6 of the side wall part top part of the container body 1, the sealing material 10 formed in the cover body 3, and the conductor pattern layer formed in the container body 1 6, the lid 3 is attached on the top of the side wall of the container 1 and the cavity 4 is hermetically sealed. A crystal resonator is assembled through these steps.

  In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention. For example, in the above-described embodiment, the description has been given of the crystal resonator. However, a crystal oscillator in which an integrated circuit element including a crystal resonator element and an oscillation circuit electrically connected to the container is mounted on the container body may be used. Absent.

  Further, in the above embodiment, the quartz resonator including the quartz resonator element using quartz as the piezoelectric material is illustrated, but the piezoelectric resonator element using lithium tantalate, lithium niobate or piezoelectric ceramic as the piezoelectric material is also mounted. A piezoelectric device may be used. Further, in the above-described embodiment, the description has been given by taking as an example a crystal resonator using a crystal resonator as the piezoelectric resonator, but instead of this, other piezoelectric resonators such as a surface acoustic wave (SAW) filter are used as the piezoelectric resonator. The present invention is also applicable when using an element.

FIG. 1 is an exploded perspective view illustrating a crystal resonator as an example of the piezoelectric device according to the present invention, which is an example of a crystal resonator that is one of the piezoelectric devices, from an obliquely upper side of the lid. 2A is a side cross-sectional view showing a case where the crystal unit shown in FIG. 1 is assembled, and FIG. 2B is an enlarged view of the dotted circle A portion shown in FIG. It is sectional drawing. 3A is a perspective view illustrating one form of the lid described in FIG. 1 and FIG. 2 from the container body joining surface side, and FIG. 3B is a perspective view of the lid illustrated in FIG. 1 and FIG. It is the perspective view which illustrated another form from the container body joint surface side. 4A to 4E are perspective process diagrams for explaining the manufacturing method of the present invention by exemplifying a manufacturing method of a crystal resonator. It is side surface sectional drawing of the conventional crystal oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Container body 2 ... Quartz crystal vibration element (piezoelectric vibration element)
DESCRIPTION OF SYMBOLS 3 ... Lid body 4 ... Cavity part 5 ... Element mounting pad 6 ... Conductor pattern layer 7 ... Terminal electrode for external connection 8 ... Conductive adhesive material 9 ... Metal layer 10 ... Sealant 11 ... Metal substrate

Claims (2)

A piezoelectric vibration element;
A rectangular container having a cavity portion on which the piezoelectric vibration element can be mounted;
42 alloy, Ri consists Kovar or phosphor bronze, the main surface with a flat plate is provided with a rectangular lid,
The outer peripheral edge of one main surface of the lid is provided with a sealing material made of a gold-tin alloy,
The lid is disposed on the top of the side wall of the container body on which the piezoelectric vibration element is mounted in the cavity so that the opening of the cavity is covered and the sealing material faces the top of the side wall. And
In the piezoelectric device in which the sealing material and the conductor pattern layer provided on the top of the side wall are fixed,
A metal layer is provided between one main surface of the lid and the sealing material, and only on the outer peripheral edge of the lid where the sealing material is provided.
The sealing material is provided only on the metal layer so as not to contact the lid,
2. The piezoelectric device according to claim 1, wherein the metal layer is made of nickel and gold and is laminated in the order of nickel and gold from the lid side. A piezoelectric vibration element is mounted in the cavity of the rectangular container body,
Forming a sealing material made of a gold-tin alloy on the outer peripheral edge of one main surface of a rectangular lid made of 42 alloy, Kovar or phosphor bronze,
The lid is disposed so as to cover the opening of the cavity and the sealing material faces the top of the side wall of the container,
In the method for manufacturing a piezoelectric device comprising fixing the sealing material and the conductor pattern layer provided on the top of the side wall,
Prepare the metal substrate of a flat plate having a formation region of the plurality of movable cover, on one main surface of the metal substrate, nickel and gold are laminated from the metal substrate side nickel, in the order of gold Forming a metal layer by plating, and removing the metal layer formed at a location other than the outer peripheral edge in each lid forming region of the metal substrate by etching,
The sealing material is deposited only on the metal layer left on the outer peripheral edge in each lid forming region of the metal substrate so as not to contact the metal substrate, and the metal substrate and the metal substrate Cutting the metal layer along the outer periphery of each lid forming region by dicing and dividing it into individual lids; and
After mounting the piezoelectric vibration element inside the cavity of the container body, the lid formed by the process A and the process B covers the opening of the cavity part, and the sealing material is used for the container body. A method of manufacturing a piezoelectric device comprising: a step C of placing the sealing member and the conductor pattern layer on the top of the side wall of the container body so as to face the top of the side wall.

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