JP2008113285A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device capable of ensuring an excellent crystal impedance (CI) characteristic and shock resistance and executing stable production by allowing a conductive adhesive to creep up on an extracting electrode extracted to an end surface of a piezoelectric vibration element. <P>SOLUTION: The piezoelectric device is provided with piezoelectric vibration element mounting pads 14 and bank parts 15 projecting toward an opening of recessed space 11 on a bottom surface between short sides in the recessed space 11 and a side wall surface in long sides continuing the short sides, wherein the height dimension of the bank part 15 is lower than a side wall of a container 20, and is within the range higher than the arrangement position of a principal plane of an opening side of the mounted piezoelectric vibration element 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric device such as a piezoelectric vibrator or a piezoelectric oscillator, which is one of electronic components used in an electronic device such as a portable communication device or an electronic computer.

  Conventionally, in electronic devices such as portable communication devices, piezoelectric devices are used as one of various electronic components mounted in the electronic devices. Piezoelectric devices include piezoelectric vibrators, piezoelectric oscillators and piezoelectric filters that are integrated by combining piezoelectric vibrators and oscillation circuits, such as reference signals and clock signals for electronic devices or electronic components mounted on electronic devices. It is used as a filter for extracting only a desired new synthesized component from the generation source or various frequency components and attenuating other unnecessary components.

  As an example of such a conventional piezoelectric device, there is a piezoelectric vibrator (quartz crystal vibrator) that uses quartz as a piezoelectric material that is a main material of a piezoelectric vibration element mounted inside a component. That is, a pair of element mounting pads are provided on the bottom surface in the recessed space formed in the container body. On this piezoelectric vibration element mounting pad, a piezoelectric vibration element made of a quartz material having a pair of excitation electrodes electrically connected via a conductive adhesive on the front and back main surfaces is mounted. A seal ring is attached to the entire top surface of the opening side top surface of the side wall of the container body that surrounds the recessed space containing the element. A flat metal lid is placed on the seal ring, and the seal ring and the edge of the lid are welded to each other by seam welding or the like, whereby the piezoelectric vibration element mounting space (recessed space) is hermetically sealed. It is a vibrator. (For example, see Patent Document 1 below.)

  In such a piezoelectric vibrator, between the excitation electrodes of the crystal resonator element mounted inside the container body via the external connection electrode terminals such as the input / output terminals and the ground terminal provided on the mounting side main surface of the container body When an alternating voltage is applied from the outside, vibration occurs in a predetermined vibration mode and frequency according to the form of the crystal resonator element, etc., and the external oscillation circuit has a predetermined frequency based on the frequency. A 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.

  In addition, as a piezoelectric device other than the above-described piezoelectric vibrator, an integrated circuit including a piezoelectric vibration element and an oscillation circuit electrically connected to the piezoelectric vibration element in the concave space in the container as described above. There are a piezoelectric oscillator in which an element is mounted together, a piezoelectric filter in which a piezoelectric vibration element mounted inside functions as a filter, and the like.

The following prior arts are disclosed for the piezoelectric device including the piezoelectric vibrator and the like as described above.
JP 2002-111435 A (page 5-6, FIG. 2) JP-A-9-33228 JP 2001-185986 A

  The applicant did not find any prior art documents related to the present invention by the time of filing of the application other than the prior art documents specified by the specified prior art document information.

  However, in the conventional piezoelectric device, as described above, a plate-like piezoelectric vibration element mounting pad is provided on the bottom surface of the recessed space formed in the container body on which the piezoelectric vibration element is mounted, and the piezoelectric vibration element mounting pad is provided on the piezoelectric vibration element mounting pad. In order to mount the piezoelectric vibration element, a conductive adhesive is applied, and the piezoelectric vibration element is mounted on the conductive adhesive. However, the piezoelectric vibration element of the lead electrode formed on the short edge of the piezoelectric vibration element and electrically connected to the excitation electrode due to variations in the mounting position of the piezoelectric vibration element and the application amount of the conductive adhesive There existed a subject that a conductive adhesive did not adhere to the part formed in the side surface. In a form in which the conductive adhesive does not adhere to the extraction electrode formed on the side surface portion of the piezoelectric vibration element, the contact area between the conductive adhesive and the extraction electrode is reduced, and the conduction resistance is increased or the conduction failure is caused. There was a problem that the crystal impedance (CI) characteristics deteriorated. In particular, in the high frequency band where the fundamental vibration frequency of the piezoelectric vibration element is 100 MHz or more, the deterioration of the crystal impedance (CI) characteristic due to the conductive adhesive not rising on the extraction electrode becomes significant.

  Further, in the form in which the conductive adhesive does not adhere to the lead electrode formed on the side surface portion of the piezoelectric vibration element, the conductive adhesive and the lead electrode are bonded to the lead electrode on the main surface of the piezoelectric vibration element. Since it becomes a substantially two-dimensional adhesion form with the agent, when an external force is applied from an unspecified direction due to dropping or the like, there is a possibility that it is not possible to have equal impact resistance with respect to the external force in all directions.

  The present invention has been devised in view of the above-described problems, and its purpose is to obtain a good crystal impedance (CI) characteristic and resistance to the conductive electrode from the lead-out electrode drawn out on the end face of the piezoelectric vibration element. An object of the present invention is to provide a piezoelectric device that can ensure impact resistance and can perform stable production.

The present invention, which has been made to solve the above-mentioned problems, is provided at least along the short side in the vicinity of one short side of the inner bottom surface of the recessed space formed in the container body having a substantially rectangular main surface shape. A pair of piezoelectric vibration element mounting pads is formed. The piezoelectric vibration element mounting pad has a piezoelectric vibration element mounted thereon, and a rectangular lid that covers the opening of the container body at the top of the side wall of the container body In the piezoelectric device in which the lid and the sealing conductor pattern provided on the top of the side wall are fixed and the piezoelectric vibration element in the recessed space is hermetically sealed.
A bank portion protruding toward the opening of the recess space is provided on the bottom surface between the piezoelectric vibration element mounting pad and the short side in the recess space and the side wall surface on the long side continuous with the short side. The piezoelectric device is characterized.

  Further, the height of the bank described in the preceding paragraph is such that the height of the bank is lower than the side wall of the container body and higher than the arrangement position of the opening-side main surface of the mounted piezoelectric vibration element. The piezoelectric device according to the preceding paragraph, characterized by having a size.

  The embankment described in paragraph (0011), wherein the planar shape viewed from the opening side of the recess space of the embankment is formed in an L-shape. It is also a piezoelectric device.

  With the piezoelectric device of the present invention, as described above, the piezoelectric vibration element mounting pad is formed on the bottom surface of the recess space in the container body, and the bank portion is formed between the piezoelectric vibration element mounting pad and the side wall surface of the container body. When the conductive adhesive is applied to the piezoelectric vibration element mounting pad and the piezoelectric vibration element is mounted on the conductive adhesive, the conductive adhesive protrudes from the piezoelectric vibration element mounting pad and is on the bottom surface in the recess space. It is possible to prevent the conductive adhesive from wrapping around and sticking to the lead electrode portion formed on the side surface of the piezoelectric vibration element by damming the spread to the bank by the bank and further crushing the conductive adhesive on the surface of the bank. Become. Due to this action, the contact area between the lead electrode and the conductive adhesive is increased, so that it is possible to suppress increase in conduction resistance and to significantly reduce the occurrence of conduction failure, and to secure stable crystal impedance (CI) characteristics. It becomes possible.

  Further, in the form in which the conductive adhesive is attached to the extraction electrode formed on the side surface portion of the piezoelectric vibration element, the bonding form between the conductive adhesive and the extraction electrode is the extraction electrode and the piezoelectric vibration on the main surface of the piezoelectric vibration element. Since the lead electrode formed on the side surface perpendicular to the element main surface and the conductive adhesive are almost three-dimensionally bonded, even when an external force is applied from an unspecified direction due to dropping, etc. It is possible to have good impact resistance against external force in the direction of.

  Furthermore, the height dimension of the bank portion is lower than the side wall of the container body and is a height dimension within a range higher than the arrangement position of the opening-side main surface of the mounted piezoelectric vibration element. Since the conductive adhesive can be attached not only to the lead electrode portion formed on the side surface but also to the lead electrode portion formed on the upper main surface of the piezoelectric vibration element facing the opening when mounted, The contact area with the conductive adhesive can be increased. Therefore, it is possible to secure highly stable crystal impedance (CI) characteristics with less occurrence of conduction failure.

  Furthermore, the planar shape of the bank as viewed from the direction of the opening of the concave space is formed in an L shape, so that the conductive property can reach the tip of the corner where the lead electrode of the mounted piezoelectric vibration element is formed. Since the adhesive can be attached, the contact area with the conductive adhesive can be further increased. Therefore, it becomes possible to eliminate conduction failure and to secure stable crystal impedance (CI) characteristics.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an exploded perspective view showing an embodiment of a piezoelectric device according to the present invention, taking as an example a quartz crystal resonator using quartz as a piezoelectric material, which is one of piezoelectric devices. FIG. 2 is a schematic cross-sectional view when the crystal resonator shown in FIG. 1 is assembled and then cut along a virtual cutting line AA ′ shown in FIG. FIG. 3 is a plan view showing the container body 10 shown in FIG. 1 from the opening side of the recessed space 11, (a) is a plan view before mounting a crystal resonator element, and (b) is a piezoelectric resonator element. It is the top view which showed the form after the crystal vibration element was mounted in the mounting electrode pad. For the sake of explanation, the upper side of the sheet on which the drawing is described is described as the upper side of the crystal unit.
In each figure, the same reference numerals indicate the same parts, and a part of the structure is not shown for clarity. Further, the illustrated dimensions are partially exaggerated.
The crystal resonators shown in these drawings generally have a structure in which a crystal resonator element 20 is accommodated inside a container body 10 having a rectangular main surface shape, and a crystal resonator element accommodation space is hermetically sealed by a lid 30. .

  Here, the container body 10 is formed by laminating a plurality of insulating layers made of a ceramic material such as alumina ceramics or glass-ceramic, for example. An annular sealing conductor pattern 12 is formed on the opening side top surface of the side wall portion surrounding the opening portion of the recess space 11, and the concave sealing space 11 opening in the shape is formed on the mounting side main surface. Are provided with a plurality of external connection electrode terminals 13 including an input terminal, an output terminal and a ground terminal.

  The container body 10 is for accommodating a plate-shaped crystal resonator element 20 made of quartz, which is one of piezoelectric materials, in a recessed space 11 having an opening on the upper main surface thereof. In the vicinity of one short side of the bottom surface in the electrode 11, a lead electrode 22 drawn out from the excitation electrode 21 formed on both the front and back main surfaces of the crystal resonator element 20 is electrically connected along the short side. A pair of piezoelectric vibration element mounting pads 14 to be attached is formed. In addition, a recess space is formed on the bottom surface between the piezoelectric vibration element mounting pad 14 and a short side in the recess space 11 and a side wall surface on a long side continuous with the short side, in parallel with the side of the piezoelectric vibration element mounting pad 14. A bank portion 15 for covering the lead electrode 22 formed on the front main surface of the crystal resonator element 20 with the conductive adhesive 40 in a form protruding toward the opening portion 11 is formed. The pair of piezoelectric vibration element mounting pads 14 are electrically connected to the extraction electrode 22 extracted from the excitation electrode 21 of the crystal vibration element 20 through the conductive adhesive 40 on the upper surface side exposed in the concave space 11. The lower surface side in contact with the surface of the container body 10 is electrically connected to the input / output terminals (input terminals / output terminals) of the external connection electrode terminals 13 via the wiring conductors and via-hole conductors inside the container body 10. The

  In addition, the bank portion 15 formed on the bottom surface in the concave space 11 of the container body 10 is formed by laminating two or more base layers made of tungsten (W), molybdenum (Mo), etc., for example, on the surface of the base layer. A nickel (Ni) layer and a gold (Au) layer are sequentially deposited between the side wall portion of the container body 10 and the piezoelectric vibration element mounting pad 14 so that the planar shape forms an L shape. By forming the bank portion 15 having such a configuration, when the conductive adhesive 40 is applied to the piezoelectric vibration element mounting pad 14 and the crystal vibration element 20 is mounted on the conductive adhesive 40, the conductive adhesive is used. 40 is protruded from the piezoelectric vibration element mounting pad 14 and spreads on the bottom surface of the recess space 11 by the bank 15, and the surface of the bank 15 is scooped up by the conductive adhesive 40, so that It becomes possible for the conductive adhesive 40 to wrap around and adhere to the formed lead electrode 22 portion. Due to this action, the contact area between the extraction electrode 22 and the conductive adhesive 40 is increased, so that the occurrence of poor conduction can be remarkably reduced, and stable crystal impedance (CI) characteristics can be ensured. .

  Further, in the form in which the conductive adhesive 40 is attached to the lead electrode 22 formed on the side surface portion of the crystal resonator element 20, the adhesive form between the conductive adhesive 40 and the lead electrode 22 is on the main surface of the crystal resonator element 20. Since the lead electrode 22 and the lead electrode 22 formed on the side surface perpendicular to the main surface of the crystal resonator element 20 and the conductive adhesive 40 are in a substantially three-dimensional bonding form, they are unspecified by dropping or the like. Even when an external force is applied from the direction, it is possible to have good impact resistance against the external force in all directions.

  Furthermore, since the height dimension of the bank portion 15 is lower than the side wall of the container body 10 and within a range higher than the front main surface of the mounted crystal resonator element 20, the drawer pulled out to the side surface of the crystal resonator element 20. Since the conductive adhesive 40 adheres not only to the electrode 22 but also to the lead electrode 22 on the upper surface of the crystal resonator element 20, the contact area with the conductive adhesive 40 can be further increased. Therefore, it is possible to remarkably reduce the increase in conduction resistance and the occurrence of conduction failure and ensure stable crystal impedance (CI) characteristics.

  Further, the sealing conductor pattern 12 formed on the top surface of the opening side of the recess space 11 in the side wall portion of the container body 10 is made of nickel (Ni) on the surface of a base layer made of tungsten (W), molybdenum (Mo), or the like. ) Layer and gold (Au) are formed in a thickness of 10 μm to 25 μm by sequentially depositing the recess space 11 in an annular shape, and the inner periphery side of the sealing conductor pattern 12 is The outer peripheral side edge is exposed to the outer peripheral surface of the container body 10 on the inner wall surface of the recessed space 11. The sealing conductor pattern 12 is obtained by joining a lid body 30 to be described later to the upper surface of the container body 10 via a sealing member 31 formed on the lid body 30, and the sealing conductor pattern 12. As described above, the sealing is performed by sequentially depositing a nickel (Ni) layer and a gold (Au) layer on the surface of a base layer made of tungsten (W) or molybdenum (Mo). It is possible to improve the wettability of the sealing member 31 with respect to the stopping conductor pattern 12 and improve the airtight reliability and productivity of the piezoelectric vibrator.

  Further, inside the container body 10, there is a via conductor (not shown) in which one end is led to the opening side top surface of the side wall portion of the container body 10 and the other end is led to the mounting surface of the container body 10. The lid body 30 is bonded to the sealing conductor pattern 12 via the sealing member 31 on the sealing conductor pattern 12 that is buried and is deposited on the opening side top surface of the side wall portion of the container body 10. It is electrically connected to the ground terminal in the external connection electrode terminal 13 formed on the mounting side main surface of the container body 10 via the via conductor. In this way, the lid 30 made of a metal material is electrically connected to the external connection electrode terminal 13 so that the lid 30 becomes a ground potential when the piezoelectric vibrator is used. Due to the electromagnetic shielding action of the body 30, the quartz resonator element 20 can be well protected by an unnecessary electrical action from the outside. When the piezoelectric vibrator is mounted on an external wiring board such as a motherboard, the external connection electrode terminal 13 on the main surface of the container 10 mounting side including such a ground terminal is connected to the wiring of the external wiring board and solder or metal bumps. It functions as an electrode terminal for electrical connection through a bonding material having electrical conductivity.

  When the container body 10 is made of alumina ceramic, the external connection electrode terminal 13 and the piezoelectric vibration element are formed on the surface of a ceramic green sheet obtained by applying and mixing an appropriate organic solvent or the like to a predetermined ceramic material powder. Produced by applying a conductive paste to be the mounting pad 14, the sealing conductor pattern 12, the bank portion 15, and the like by screen printing or the like, laminating a plurality of them, press-molding, and then baking at a high temperature. Is done.

  On the other hand, the crystal resonator element 20 accommodated in the concave space 11 of the container body 10 is a substantially flat plate-shaped crystal element plate having a rectangular main surface shape, which is cut from the artificial crystal lens at a predetermined cut angle and subjected to external processing. A pair of excitation electrodes 21 and extraction electrodes 22 drawn separately from each excitation electrode 21 to one short side end portion are formed on both the front and back main surfaces of the quartz base plate. Thus, when an alternating voltage from the outside is applied from the extraction electrode 22 to the quartz base plate via the excitation electrode 21, such a quartz crystal vibrating element 20 is configured to vibrate in a predetermined vibration mode and frequency. Electrically connects the lead-out electrode 22 drawn out from the excitation electrode 21 attached to both main surfaces thereof and the corresponding piezoelectric vibration element mounting pad 14 on the bottom face in the concave space 11 through the conductive adhesive 40. And machine Mounted in the recess space 11 in the bottom surface of the container body 10 by connecting. When the fundamental resonance frequency of the crystal resonator element 20 is set to a high frequency band of 100 MHz or more, the thickness of the crystal base plate is uniformly processed to the target thickness dimension over the entire surface by mechanical polishing such as polishing. By doing so, it is possible to oscillate stably, but the adhesive strength with the conductive adhesive 40 decreases. Like the crystal resonator according to the present embodiment, the height dimension of the bank portion 15 formed on the inner bottom surface of the recessed space 11 of the container body 10 is lower than the side wall of the container body 10 and is mounted. By setting the height dimension within a range higher than the arrangement position of the opening side main surface, not only the portion of the extraction electrode 22 formed on the side surface of the crystal vibration element 20 but also the extraction electrode 22 on the upper surface of the crystal vibration element 20 In addition, since the conductive adhesive 40 adheres, it is possible to eliminate poor conduction and secure stable crystal impedance (CI) characteristics.

  The conductive adhesive 40 contains conductive powder in a resin material made of silicone resin, polyimide resin, or the like. Examples of the conductive powder include aluminum (Al), molybdenum (Mo), tungsten (W ), Platinum (Pt), palladium (Pd), silver (Ag), titanium (Ti), nickel (Ni), nickel iron (NiFe), or combinations thereof are used.

  The lid 30 disposed on the container body 10 is manufactured by adopting a conventionally known processing method and shaping a metal such as 42 alloy into a predetermined shape. A nickel (Ni) layer is formed on the surface of the lid 30, and a gold tin (Au—Sn) layer, which is a sealing member 31, is provided at least on the upper surface of the Ni layer at a location facing the sealing conductor pattern 12. 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 member 31 can relieve unevenness on the surface of the sealing conductor pattern 12 and prevent a decrease in hermeticity. Such a lid 30 is disposed on the sealing conductor pattern 12 formed on the top of the side wall that surrounds the recessed space 11 in which the crystal resonator element 20 is mounted so as to cover the opening of the recessed space 11. The sealing member 31 and the sealing conductor pattern 12 are melt-bonded to hermetically seal the inside of the recessed space 11 to constitute a crystal resonator.

  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, a description has been given of a crystal resonator having a relatively simple structure as an example in a piezoelectric device. However, the present invention is not limited to this embodiment, and other than the above-described crystal resonator. As another piezoelectric device, a piezoelectric (crystal) vibration element and an integrated circuit element including an oscillation circuit electrically connected to the piezoelectric vibration element are mounted together in the recessed space in the container as described above. The present invention may be applied to a piezoelectric oscillator having the above-described form or a piezoelectric filter in which a piezoelectric vibration element mounted inside functions as a filter. In the above-described embodiment, the quartz resonator element using quartz as the piezoelectric material constituting the piezoelectric resonator element has been described. However, as other piezoelectric materials, lithium niobate, lithium tantalate, or piezoelectric ceramics is used as the piezoelectric material. The piezoelectric vibration element used as the above may be used.

  Moreover, although the bank portion 15 formed on the bottom surface 11 in the recessed space 11 of the container body 10 is formed by laminating a metal layer as described above, it may be formed by applying a resin material. good.

FIG. 1 is an exploded perspective view showing an embodiment of a piezoelectric device according to the present invention, taking as an example a crystal resonator which is one of the piezoelectric devices. FIG. 2 is a schematic cross-sectional view of the crystal unit when the crystal unit illustrated in FIG. 1 is assembled and then the crystal unit is cut along the virtual cutting line A-A ′ illustrated in FIG. 1. FIG. 3 is a plan view showing the container body used in the crystal resonator shown in FIG. 1 from the recessed space opening side, and (a) is a diagram showing a form before the crystal resonator element is mounted, (B) is the figure after the piezoelectric vibration element was mounted in the piezoelectric vibration element mounting electrode pad.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Container body 11 ... Recessed space 12 ... Conductive pattern for sealing 13 ... Electrode terminal for external connection
14 ... Piezoelectric vibration element mounting pad 15 ... Ryge part 20 ... Piezoelectric vibration element (crystal vibration element)
DESCRIPTION OF SYMBOLS 21 ... Excitation electrode 22 ... Lead-out electrode 30 ... Cover body 31 ... Sealing member 40 ... Conductive adhesive agent

Claims (3)

In the vicinity of one short side of the bottom surface inside the recessed space formed in the container body having a substantially rectangular main surface outer shape, at least a pair of piezoelectric vibration element mounting pads are formed along the short side, A piezoelectric vibration element is mounted on the mounting pad, and a rectangular lid that covers the opening of the container body is disposed at the top of the side wall of the container body, and provided on the lid body and the top of the side wall. In the piezoelectric device that fixes the sealing conductor pattern and hermetically seals the piezoelectric vibration element in the recessed space,
A bank portion protruding toward the opening of the recess space is provided on the bottom surface between the element mounting pad and the short side in the recess space and the side wall surface on the long side continuous with the short side. A piezoelectric device characterized by comprising:   2. The bank portion according to claim 1, wherein a height dimension of the bank portion is lower than a side wall of the container body and within a range higher than an arrangement position of an opening side main surface of the mounted piezoelectric vibration element. The piezoelectric device according to claim 1, wherein the piezoelectric device has a height dimension.   2. The piezoelectric device according to claim 1, wherein the planar shape of the bank portion viewed from the opening side of the concave space of the bank portion is formed in an L shape.

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