JP2007103995A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device, wherein the operation stability of an electronic element mounted inside is enhanced by shielding external electromagnetic noise. <P>SOLUTION: The piezoelectric device disclosed herein is formed in such a way that a piezoelectric resonator element is mounted in an internal space of a rectangular package, a rectangular lid for covering the internal space of the package is arranged on a top of side walls of the package, the lid and a conductor layer provided to the top of the side walls are fixed. A ground terminal formed on the side face of the package is connected to the lid through the side face of the package and the conductor layer, and the occupied forming area of the ground terminal formed on the side face of the package amounts to 30 to 50% of the side face area of the package. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators used in electronic devices such as portable communication devices and electronic computers.

  Conventionally, a piezoelectric vibration element in which electrodes are formed on both main surfaces of a piezoelectric element plate is mounted inside a package. For example, a piezoelectric vibrator or an oscillation circuit that connects the piezoelectric vibration element to the piezoelectric vibration element and excites the element is the same. Piezoelectric oscillators mounted in the package or piezoelectric devices such as a piezoelectric filter for separating a specific frequency band are widely 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 with the miniaturization of electronic equipment, these piezoelectric devices are also being miniaturized.

  As an example of such a conventional piezoelectric device, FIG. 5 shows a cross-sectional view of a quartz crystal resonator 50 using quartz as a piezoelectric material. A pair of element connection electrode pads 53 are provided on the bottom surface of the recessed space 52 formed in the container body 51. On this element connecting electrode pad 53, a crystal resonator element 55 having a pair of excitation electrodes electrically connected via a conductive adhesive 54 on the front and back main surfaces is mounted. A seal ring 56 is attached to the top surface of the side wall portion of the container body 51 surrounding 55. A metal lid 57 is placed on the seal ring 56, and the seal ring 56 and the lid 57 are melt-bonded by seam welding or the like, whereby the space for mounting the crystal resonator element 55 (recessed space 52) is hermetically sealed. It is a stopped crystal unit. (For example, refer to Patent Document 1 below.)

  In such a crystal resonator, the excitation electrode of the crystal resonator element 55 mounted inside the container body 51 through the input / output terminals provided on the mounting side main surface of the container body 51 and the electrode terminal 58 such as a ground terminal. When an external excitation voltage is applied between them, vibration is generated in a predetermined vibration mode and frequency according to the form of the crystal resonator element 55 and the like, and the external oscillation circuit determines a predetermined frequency based on the frequency. A frequency reference signal is oscillated and output. 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.

  In a conventional piezoelectric device, by using a so-called hat-shaped metallic lid, it was possible to shield the entire internal space surrounded by the lid from electromagnetic noise. And in a miniaturized piezoelectric device using a flat-type lid, there is a risk that the electromagnetic noise shielding property in the side surface direction is inferior to that of the conventional one. Therefore, there is a drawback in that it is easily affected by external electromagnetic noise and adversely affects the stability of the oscillation frequency.

  Also, if the stability of the oscillation frequency is disturbed, the piezoelectric device is used as a reference signal source for data transfer in electronic equipment, so that data transfer is not successful and bit errors occur inside and outside the electronic equipment. There was a drawback.

  The present invention has been devised in view of the above drawbacks, and its object is to provide a piezoelectric device with improved stability of oscillation frequency by shielding external electromagnetic noise from entering the interior. is there.

  In order to solve the above-described problems, the present invention is configured such that at least a piezoelectric vibration element is mounted in a concave internal space formed in a container body having a rectangular main surface shape, and a side wall portion surrounding the internal space is provided. A metal lid that covers the opening of the internal space is disposed on the top surface of the internal space opening side, and the piezoelectric body is formed by fixing this lid and a conductor layer provided on the top surface of the internal space opening side. In the device, a ground terminal among various electrode terminals formed on the bottom surface and the side surface of the container body is electrically connected to the lid through the side surface and the conductor layer of the container body, and the container body The piezoelectric device is characterized in that the formation exclusive area of the ground terminal formed on the side surface is 30% to 50% with respect to the side surface area of the container body.

  Further, an integrated circuit element is accommodated in the internal space of the container body, and at least two of the electrode terminals formed on the side surface are dual-purpose terminals serving as the monitor electrode terminal and the ground terminal of the piezoelectric vibration element. It is also the above-mentioned piezoelectric device characterized by this.

  According to the piezoelectric device of the present invention, the ground terminal among the electrode terminals formed on the side surface of the container body is made of a metal lid through the conductor layer formed on the side surface of the container body and the top surface of the side wall of the container body. The lid that is electrically connected to the ground terminal is electrically stabilized at the ground potential, and is generated at the interval between the lid and the excitation electrode of the piezoelectric vibration element. Since the stray capacitance is stable and the stability of the oscillation frequency is not disturbed, it is possible to reliably transfer data inside and outside the electronic device equipped with the piezoelectric device. This also makes it possible to prevent the oscillation characteristics of the piezoelectric vibration element from fluctuating.

  Moreover, according to the piezoelectric device of the present invention, the formation exclusive area of the ground terminal formed on the side surface of the container body is 30% to 50% of the side surface area of the container body. Therefore, it is possible to prevent external electromagnetic noise from being superimposed on the piezoelectric vibration element.

  Furthermore, in the piezoelectric device of the present invention, the integrated circuit element is accommodated in the container body, and the electrode terminal for monitoring and the ground terminal of the piezoelectric vibration element formed on the side surface can be used as one electrode terminal. Therefore, the number of electrode terminals formed on the side surface of the device can be reduced, and the piezoelectric device can be miniaturized.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an external exploded perspective view illustrating a piezoelectric device according to an embodiment of the present invention using a vibrator using quartz as a piezoelectric material (hereinafter referred to as a quartz vibrator) as an example. FIG. 2 is a cross-sectional view after assembling the crystal unit shown in FIG. 1, and the crystal unit shown in these figures is a container body having a rectangular main surface in which a crystal resonator element 5 is housed. 1 is hermetically sealed by a lid 2.

  The container body 1 is made of a ceramic material such as glass-ceramic or alumina ceramic, and the lid body 2 is made of a metal such as 42 alloy, Kovar, or phosphor bronze. A concave internal space 8 that opens to one main surface is formed on one main surface of the container body 1, and the conductor layer 3 is formed on the opening-side top surface of the side wall that surrounds the internal space 8. Is formed. The conductor layer 3 has a metallized layer made of tungsten (W), molybdenum (Mo), or the like, and a nickel (Ni) layer is formed on the upper surface of the metallized layer, and on the upper surface of the nickel (Ni) layer. , A gold (Au) layer is formed. The lid 2 is placed and fixed on the upper surface of the conductor layer 3 so as to cover the opening of the internal space 8.

  The container body 1 will be described more specifically. The container body 1 is for accommodating the crystal resonator element 5 in the internal space 8 and hermetically sealed by the lid body 4, and the excitation electrode of the crystal resonator element 5 and the electricity are provided on the inner bottom surface of the internal space 8 of the container body 1. A pair of element connection electrode pads 9 are connected to each other, and external connection electrode terminals 7 such as an input terminal, an output terminal, and a ground terminal are formed on the outer lower surface of the container body 1. These terminals and the like are electrically connected to each other through a wiring conductor on the surface of the container body and a conductive wiring such as a via hole embedded in the container body.

  When the container body 1 is made of a ceramic material such as glass-ceramic, for example, a conductor serving as a wiring conductor on the surface of a ceramic green sheet obtained by adding and mixing a suitable organic solvent to the ceramic material powder. The paste is applied by well-known screen printing or the like, and a plurality of the pastes are laminated, press-molded, and then fired at a high temperature.

  As described above, the conductor layer 3 is formed on the opening side top surface of the side wall portion surrounding the internal space 8 of the container body 1, and the structure thereof is a metallization made of tungsten (W), molybdenum (Mo), or the like. A layer is formed, and the thickness is 10 μm to 20 μm. A nickel (Ni) layer is formed on the upper surface of the metallized layer, and the thickness is 8 μm to 20 μm. Further, a gold (Au) layer is formed on the upper surface of the nickel (Ni) layer, and the thickness thereof is 0.3 μm to 1.0 μm.

  Moreover, the electrode body including what is electrically connected with the electrode terminal 7 for external connection provided in the lower surface of the container body 1 is formed in the side surface of the container body 1, Out of the electrode terminals The ground terminal 10 electrically connected to the ground electrode of the connection electrode terminal 7 is electrically connected to the ground terminal 10 by being electrically connected through the lid 2 and the outer surface of the container body 1 and the conductor layer 3 described later. Since the lid 3 connected to the capacitor is electrically stable at the ground potential, and the stray capacitance generated at the interval between the lid 2 and the excitation electrode of the crystal resonator element 5 is also stabilized, the oscillation frequency is stable. Since it is not disturbed, it is possible to reliably perform data transfer inside and outside an electronic device in which a crystal resonator is mounted as an electronic component. This also makes it possible to prevent the oscillation characteristics of the crystal resonator element 5 from fluctuating.

  The lid 2 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 2, and a gold tin (Au—Sn) layer, which is a sealing material 4, is formed at least on the upper surface of the nickel (Ni) layer at a location facing the conductor layer 3. It is formed. The thickness of the gold tin (Au—Sn) layer is 10 μm to 40 μm. For example, the component ratio is 80% gold and 20% tin. Moreover, such a sealing material 4 can relieve unevenness on the surface of the conductor layer 3 and prevent a decrease in hermeticity.

  The crystal vibrating element 5 is mounted and fixed on the element connection electrode pad 9 formed on the inner bottom surface of the internal space 8 of the container body 1 using the conductive adhesive 6, and then the lid 2 is placed on the conductor layer 3. Is arranged so as to cover the opening of the internal space 8 and the container layer 1 and the lid 2 are hermetically sealed by heating and melting the conductor layer 3 and the sealing material 4 by a seam welding method or the like. The child is assembled.

  On the other hand, the crystal resonator element 5 accommodated in the container body 1 is provided with a pair of excitation electrodes on both main surfaces of a crystal piece cut at a predetermined angle from the crystal axis of the artificial lens and cut and polished on the outer shape. When a fluctuation voltage from the outside is applied to the crystal piece via a pair of excitation electrodes, vibration occurs in a predetermined vibration mode and frequency. The quartz resonator element 5 is formed by electrically connecting and fixing a pair of excitation electrodes to element connection electrode pads 9 corresponding to the respective excitation electrodes on the inner bottom surface of the internal space 8 through the conductive adhesive 6. 8, whereby electrical connection and mechanical connection between the crystal resonator element 5 and the container body 1 are made simultaneously.

  Here, if the lid 2 is connected to the external terminals 7 for the ground terminals arranged on the lower surface and the side surface of the container body via the conductor layer 3 of the container body 1, the lid can be used when the crystal unit is used. Since the electromagnetic noise shielding function by the lid body 2 and the ground terminal 10 is acted by the body 2 being grounded, it is possible to better protect the crystal resonator element 5 from an unnecessary electrical action from the outside. it can. The formation area of the ground terminal 10 is formed within a range of 30% to 50% of the side surface area of the container body 1. That is, if it is less than 30%, the required electromagnetic noise shielding effect cannot be obtained, and if the ground terminal 10 is formed with an area occupied by more than 50%, other electrode terminals cannot be formed or The ground terminal 10 and other electrode terminals are too close to each other, which may cause problems such as a short circuit between the terminals.

  Further, as shown in FIGS. 3 and 4, a crystal oscillator can be formed by mounting an integrated circuit element 11 and an electronic component element 12 in addition to the crystal resonator element 5 on the container body. The integrated circuit element 11 is electrically and mechanically connected to the container body by a flip chip method. In the integrated circuit element 11, an oscillation circuit that generates an oscillation output is provided based on the crystal resonator element 5. The oscillation output generated by this oscillation circuit is output to the outside and then used as a reference signal such as a clock signal. Further, the integrated circuit element 11 may be connected by a conventionally known wire bonding method.

  The electronic component element 12 is a variable capacitance diode, a chip component, or the like, and adjusts the oscillation frequency. This variable capacitance diode plays the role of adjusting the oscillation frequency by applying an external control voltage, and the inductor element has a role of expanding the frequency adjustment range when connected in series with the crystal vibrating element 5. It is conceivable to add a resistance element or the like.

  In addition, in order to measure the oscillation characteristics of the crystal resonator element 5, the monitor electrode terminal 13 may be formed on the side surface of the container body 1. However, the monitor electrode terminal 13 and the ground terminal 10 described above are combined. In addition, it is possible to increase the electromagnetic noise shielding performance as a piezoelectric device by increasing the formation area of the monitor electrode terminal 13.

  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, individual container bodies are used. However, there is no problem even if a multi-piece substrate is used, and there is an advantage that productivity is further improved.

  In the above-described embodiment, quartz is used as the piezoelectric material constituting the piezoelectric vibration element. However, in addition to quartz, lithium tantalate, lithium niobate, or piezoelectric ceramic is used as long as it has a piezoelectric effect. You can use it.

  Furthermore, in the above-described embodiment, the crystal resonator or the crystal oscillator using the crystal resonator element as the piezoelectric resonator element has been described as an example. However, instead of this, as the piezoelectric resonator element, a surface acoustic wave (SAW) filter or the like can be used. The present invention can also be applied when using other piezoelectric vibration elements.

FIG. 1 is an external exploded perspective view of a piezoelectric device according to an embodiment of the present invention, taking a crystal resonator as an example. FIG. 2 is a cross-sectional view when the crystal unit shown in FIG. 1 is assembled. FIG. 3 is an external exploded perspective view showing a piezoelectric oscillator as an example of a piezoelectric device according to another embodiment of the present invention. 4 is a cross-sectional view when the crystal oscillator shown in FIG. 3 is assembled. FIG. 5 is a cross-sectional view showing a conventional piezoelectric device using a piezoelectric vibrator as an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Container body 2 ... Cover body 3 ... Conductive layer 4 ... Sealing material 5 ... Quartz vibration element 6 ... Conductive adhesive 7 ... Terminal electrode 8 for external connection ... Internal space 9 ... Element connection electrode pad 10 ... Ground terminal 11 ... Integrated circuit element 12 ... Electronic component element 13 ... Monitor electrode terminal

Claims (2)

At least a piezoelectric vibration element is mounted in a concave internal space formed in a container body having a rectangular main surface shape, and an opening portion of the internal space is formed on an inner space opening side top surface of a side wall portion surrounding the internal space. In a piezoelectric device in which a cover body in a covering form is arranged and the cover body and a conductor layer provided on the top surface on the inner space opening side are fixed,
A ground terminal of various electrode terminals formed on the bottom surface and the side surface of the container body is electrically connected to the lid body through the side surface of the container body and the conductor layer, and the side surface of the container body The piezoelectric device is characterized in that the formation exclusive area of the ground electrode terminal formed in is 30% to 50% with respect to the side surface area of the container body.   An integrated circuit element is accommodated in the internal space of the container body, and at least two of the electrode terminals formed on the side surface are a monitoring electrode terminal of the piezoelectric vibration element and a ground terminal. The piezoelectric device according to claim 1, wherein the piezoelectric device is a dual-purpose terminal.

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