JP2008252799A - Piezoelectric device - Google Patents

Abstract

There is provided a piezoelectric device in which the occurrence of problems due to unnecessary adhesion of a conductive adhesive is remarkably reduced, a conductive connection between a piezoelectric vibration element and an element connection electrode pad can be reliably ensured, and variation in individual characteristics is extremely small. thing.
A container body having a recess, an element connection electrode pad formed on the bottom surface of the recess, a piezoelectric vibration element provided with an excitation electrode and a container body connection electrode, a lid, A piezoelectric device in which a piezoelectric vibration element is mounted in a recess by mechanically and electrically connecting and fixing a container body connection electrode to an element connection electrode pad with a conductive adhesive. A piezoelectric device in which a ring body that annularly surrounds the center of the element connection side main surface of the element connection electrode pad is formed on the entire periphery of the edge portion of the element connection side main surface of the connection electrode pad.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric device such as a piezoelectric vibrator or a piezoelectric oscillator.

  Conventionally, piezoelectric vibrators in which various types of electrodes are formed on the surface of a piezoelectric base plate are mounted in a hermetic state inside a recess formed in a container body, integrated circuit elements incorporating this piezoelectric vibrator and oscillation circuit, etc. Is one of the electronic components, such as a piezoelectric oscillator or a piezoelectric filter that separates a specific frequency band, and an electronic device such as a portable communication device or an electronic computer. It is used a lot within.

  An example of a conventional piezoelectric device is shown in FIGS. 5 and 6 by taking a piezoelectric vibrator as one of the piezoelectric devices as an example. That is, the piezoelectric vibration element 101 used in the piezoelectric vibrator 100 which is one of the piezoelectric devices shown in FIGS. 5 and 6 is formed in the center of the front and back main surfaces of the piezoelectric element plate 102 having a rectangular shape in plan view and a flat plate shape. An excitation electrode 103 for exciting the piezoelectric element plate 102, an element connection electrode pad 105 formed in an insulating container body 104 that houses the piezoelectric vibration element 101 near one short side of the piezoelectric element plate 102, and A pair of container body connection electrodes 106, and an extraction electrode 107 that electrically connects the respective excitation electrodes 103 on the front and back main surfaces and the respective container body connection electrodes 106.

  The element connection electrode pad 105 is formed on the upper surface of the container body 104 in the vicinity of one short side surface of the inner bottom surface of the recess 108 formed in the container body 104. The element connection electrode pad 105 is formed of a conductive wiring (via hole or the like). ) To be electrically connected to the external connection electrode terminal 111 formed on the outer bottom surface of the container body 104.

  The piezoelectric vibration element 101 having various electrodes as described above formed thereon has a posture in which the main surface of the piezoelectric vibration element 101 is substantially parallel to the bottom surface in the recess 108, and the container body connection electrode 106 and the element mounting electrode. The pad 105 is disposed in the recess 108 so as to face the conductive layer 109 and is electrically fixed to the container body 104 by a conductive adhesive 109 applied between the container connecting electrode 106 and the element connecting electrode pad 105. Note that the piezoelectric adhesive element 101 is held in a desired posture inside the container body 104 by heating and solidifying the conductive adhesive 109.

  A container body 104 in which such a piezoelectric vibration element 101 is mounted in the recess 108 is covered with a metal lid 110 on the top surface of the side wall that surrounds the opening of the recess 108, and covering the opening of the recess 108. The piezoelectric vibrator 100 in which the inside of the recessed space 108 is hermetically sealed is formed by arranging and bonding the lid body 110 and the container body 104 (see, for example, Patent Document 1 or Patent Document 2).

  As a form (not shown) of a piezoelectric oscillator that is one of the piezoelectric devices, a support base having a height higher than the thickness of the integrated circuit element to be mounted is formed on the bottom surface of the concave portion of the container body. A piezoelectric oscillator in which an integrated circuit element including at least an oscillation circuit is mounted thereon and a piezoelectric vibration element is mounted on an element connection electrode pad formed on the upper surface of the support base and hermetically sealed is used (for example, Patent Document 3) And other various types of piezoelectric oscillators (see, for example, Patent Document 4 and Patent Document 5).

JP 2004-289470 A JP 2005-198227 A JP 2004-103627 A Japanese Patent Laid-Open No. 8-78955 JP 2005-159574 A

  Other than the prior art documents specified by the prior art document information, no prior art documents related to the present invention have been found by the time of filing of the present application.

  However, as piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators become smaller, the area of the element connection side main surface of each element connection electrode pad provided in the piezoelectric device must be reduced, and the element connection electrode Since a pair of pads are provided, the distance between adjacent element connection electrode pads must be reduced. In that case, when a sufficient amount of conductive adhesive necessary for connection fixation of the piezoelectric vibration element is applied on the electrode pad for element connection, the conductive adhesive flows out from the electrode pad for element connection onto the bottom surface in the recess. There is a risk of it. The discharged conductive adhesive adheres to the surface of the mounted piezoelectric vibration element, adversely affects the vibration characteristics of the piezoelectric vibration element, and other element connection electrodes formed close to each other for miniaturization. Since it contacts and short-circuits with a pad, there exists a possibility of producing a malfunction as a piezoelectric device.

  In addition, even when the amount of the conductive adhesive is the minimum amount that can be connected and fixed, when the piezoelectric vibration element is placed on the conductive adhesive, the weight of the piezoelectric vibration element or the placement of the piezoelectric vibration element There is a possibility that the conductive adhesive material flows out from the element connection electrode pad to the bottom surface in the recess due to the pressure.

  Furthermore, since the amount of the conductive adhesive flowing out from the element connection electrode pad cannot be controlled, when the amount of the conductive adhesive flowing out increases, the conductive adhesive for securely fixing the piezoelectric vibration element. The agent cannot be secured on the electrode pad for element connection, and the connection state between the piezoelectric vibration element and the electrode pad for element connection becomes incomplete due to impact at the time of dropping, and in the worst case, the piezoelectric vibration element may fall off . Also, due to the difference in the amount of conductive adhesive flowing out from the electrode pads for element connection, the height when the piezoelectric vibration element is mounted becomes uneven for each piezoelectric device, and the characteristics vary among individual piezoelectric devices. Will occur.

  Therefore, the object of the present invention is that even when the piezoelectric device is miniaturized, the piezoelectric vibration element can be connected and fixed with the conductive adhesive only on the electrode connecting electrode pad, and the conductive adhesive is unnecessary. Piezoelectric transducers can be reliably prevented from causing problems, and the conductive connection between the piezoelectric transducer and the element connection electrode pad can be reliably ensured. To provide a device.

  In the piezoelectric device according to the present invention, a container body in which a recess having an opening is formed on one main surface, a pair of element connection electrode pads formed on the inner bottom surface of the recess, and excitation on each of the front and back main surfaces A piezoelectric vibration element having a container body connection electrode extending from the excitation electrode to one edge of each of the front and back main surfaces, and covering the opening of the recess, It is composed of a lid that hermetically seals the space, and the piezoelectric element is mounted in the recess by mechanically and electrically connecting and fixing the container connection electrode to the element connection electrode pad with a conductive adhesive. A ring body that annularly surrounds the center of the element connection side main surface of the element connection electrode pad is formed around the entire periphery of the element connection side main surface of the element connection electrode pad. It is characterized by being.

  In the piezoelectric device described above, the material of the ring body is aluminum oxide.

  With the piezoelectric device of the present invention, miniaturization of the piezoelectric device has progressed, the area of the element connection side main surface of each element connection electrode pad is reduced, and the distance between other adjacent element connection electrode pads is reduced. Even when a sufficient amount of conductive adhesive necessary for connection and fixation of the piezoelectric vibration element is applied on the element connection electrode pad, the ring body provided on the element connection side main surface of the element connection electrode pad The conductive adhesive applied on the element connecting electrode pad can be prevented from flowing out from the element connecting electrode pad onto the bottom surface in the recess. Therefore, the conductive adhesive that has flowed out adheres to the surface of the mounted piezoelectric vibration element and adversely affects the vibration characteristics of the piezoelectric vibration element, or is formed in close proximity for miniaturization. There is no short circuit due to contact with the other element connection electrode pads, and there is no problem as a piezoelectric device.

  In addition, even when the amount of the conductive adhesive is the minimum amount that can be connected and fixed, when the piezoelectric vibration element is placed on the conductive adhesive, the weight of the piezoelectric vibration element or the placement of the piezoelectric vibration element With the pressure, it is possible to prevent the conductive adhesive from flowing out from the element connection electrode pad to the bottom surface in the recess.

  Furthermore, since the conductive adhesive does not flow out from the element connecting electrode pad, the amount of the conductive adhesive for securely fixing the piezoelectric vibration element can be secured on the element connecting electrode pad, Since the conductive connection between the piezoelectric vibration element and the element connection electrode pad is not incomplete due to impact or the like, and the amount of the conductive adhesive on the element connection electrode pad can be made constant, the piezoelectric vibration element The height when mounting can be made uniform for each individual piezoelectric device. Accordingly, since the piezoelectric vibration element does not come into contact with the lid body or the container body, it is possible to prevent the occurrence of variations in various characteristics among individual piezoelectric devices.

  Therefore, according to the present invention, the piezoelectric vibration element can be connected and fixed with the conductive adhesive only on the element connecting electrode pad, and the occurrence of trouble due to unnecessary adhesion of the conductive adhesive is remarkably reduced. The conductive connection between the element and the electrode pad for element connection can be ensured reliably, and the mounting height of the piezoelectric vibration element can be made uniform, thereby providing an effect of providing a piezoelectric device with extremely small variation in individual characteristics.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Note that, in each embodiment, the same components are denoted by the same reference numerals. In each figure, a part of the structure is not shown and a part of the dimensions is exaggerated for clarity. In particular, the thickness dimension in each structural portion is exaggerated.

(First embodiment)
FIG. 1 is an exploded perspective view showing an example of the piezoelectric device according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the piezoelectric device shown in FIG. 1 assembled and then cut along a virtual cutting line AA ′ shown in FIG. FIG. 3 is an enlarged partial cross-sectional view showing a structure in a two-dot chain line circle B shown in FIG. A piezoelectric vibrator 10 which is an example of the piezoelectric device illustrated in FIG. 1 is generally configured by a container body 11, a piezoelectric vibration element 12, and a lid body 13.

  A piezoelectric resonator element 11 mounted on the piezoelectric vibrator 10 shown in FIGS. 1 to 3 is cut out from an artificial crystalline lens at an AT cut angle and is subjected to external processing, thereby forming a piezoelectric base plate 12 having a rectangular shape in plan view and a flat plate shape. And an excitation electrode 13 for exciting the piezoelectric element plate 12 provided on the center part of the front and back main surfaces of the piezoelectric element plate 12. Further, in the vicinity of one short side of the piezoelectric base plate 12, an electrical connection is made with an element connection electrode pad 15 provided on the inner bottom surface of the recess 18 of the insulating container body 14 that houses the piezoelectric vibration element 11. A pair of container body connection electrodes 16 are provided, and the excitation electrodes 13 on the front and back main surfaces and the container body connection electrodes 16 are connected and connected by the extraction electrodes 17. .

  The container body 14 is made of a ceramic material such as glass-ceramic or alumina ceramic, and has a substantially rectangular parallelepiped outer shape that is rectangular in plan view. In addition, the container body 14 is provided with a recess 18 having an opening on one main surface thereof, near the one short side of the inner bottom surface of the recess 18, and along the short side of the piezoelectric vibration element 11. A pair of element connection electrode pads 15 for electrical connection with the provided container body connection electrodes 16 is provided. Furthermore, external connection electrode terminals 21 including those electrically connected to the element mounting electrode pads 15 are provided at the four corners of the other main surface of the container body 14. The element connection side main surface of the element connection electrode pad 15 is a quadrangle, and a metal having a relatively high conductivity is used as a material.

  On the element connection side main surface of the element connection electrode pad 15, the entire edge of the element connection side main surface of the element connection electrode pad 15 is formed on the element connection side main surface of the element connection electrode pad 15. A ring body 19 surrounding the center in an annular shape is provided. Here, the distance between the element connection side main surface of the element connection electrode pad 15 and the container body connection electrode 16 provided on the main surface facing the inner bottom surface of the recess 18 of the piezoelectric vibration element 11 is about 15 μm to 30 μm. The thickness of the ring body 19 is formed to be about 1/3 to 2/3 of the distance between the element connection side main surface of the element connection electrode pad 15 and the container body connection electrode 16. Yes. The ring body 19 is made of aluminum oxide. The ring body 19 is formed by screen printing or the like after the element connection electrode pad 15 is formed before the ceramic material of the container body 14 is laminated and fired.

  The piezoelectric vibration element 11 is mainly connected to the conductive adhesive 20 applied on the element connection side main surface of the element connection electrode pad 15 surrounded by the ring body 19 and opposed to the inner bottom surface of the recess 18 of the piezoelectric vibration element 11. The container body connection electrode 16 provided on the surface is joined, and the conductive adhesive 20 is heated and solidified, so that the main surface of the piezoelectric vibration element 11 is substantially parallel to the bottom surface in the recess 18. Mounted in. There is no possibility that the conductive adhesive 20 having fluidity before heating and solidifying flows out from the element connection electrode pad 15 onto the inner bottom surface of the recess 18 due to the action of the ring body 19. Therefore, the conductive adhesive 20 adheres to the surface of the mounted piezoelectric vibration element 11 and adversely affects the vibration characteristics of the piezoelectric vibration element 11, or is formed in close proximity for miniaturization. Therefore, there is no short circuit due to contact with the other element connection electrode pads 15, so that the piezoelectric vibrator 10 does not malfunction.

  Further, by providing the ring body 17, the conductive adhesive 20 between the container body connection electrode 16 of the piezoelectric vibration element 11, the element connection electrode pad 15, and the ring body 7 on the element connection side main surface thereof. The bonding area due to the above can be increased compared to the conventional case, and when an impact such as a drop is applied to the piezoelectric vibration element 11, the bonding state between the piezoelectric vibration element 11 and the conductive adhesive 20 is not deteriorated. It is possible to hold the piezoelectric vibration element 11 on the element connection electrode pad 15 in a state where the adhesion state is stable.

  In the container body 14 in which the piezoelectric vibration element 11 is mounted in the recess 18 in such a form, a metal made of 42 alloy, Kovar, phosphor bronze, or the like is formed on the top surface of the side wall that surrounds the opening of the container body 14. The lid 22 is arranged in a form covering the opening of the recessed space 18 and the inside of the recessed space 18 is hermetically sealed by joining the lid 22 and the container body 14 in a vacuum or in an inert gas. A piezoelectric vibrator 10 is configured.

(Second embodiment)
FIG. 4 is a cross-sectional view showing an example of a piezoelectric device according to the second embodiment of the present invention. That is, the piezoelectric oscillator 40 which is an example of the piezoelectric device shown in FIG. 4 is roughly composed of a substrate 42, a container body 41 composed of a first frame portion 43a and a second frame body 43b, and a piezoelectric vibration element 46. And an integrated circuit element 44 and a lid 45.

  The container body 41 is, for example, a rectangular substrate 42 made of a ceramic material such as glass-ceramic or alumina ceramic, and the same as the outer peripheral shape of the main surface of the substrate 42 bonded to both the front and back main surfaces of the substrate 42. It consists of a first frame body 43a and a second frame body 43b that have an outer peripheral shape and are made of the same ceramic material as that of the substrate. The container body 41 accommodates the piezoelectric vibration element 46 in a recess 49 surrounded by one main surface of the substrate 42 and the inner surface of the first frame 43a, and the other main surface of the substrate 42 and the second main surface. The integrated circuit element 44 is accommodated in the recess 50 surrounded by the inner surface of the frame 43b.

  The piezoelectric vibration element 46 accommodated in the concave portion 49 of the container body 41 is mainly composed of a piezoelectric element plate 52 that is cut out from the artificial crystalline lens at an AT cut angle and is shaped into a flat plate in a rectangular shape in plan view. An excitation electrode 53 for exciting the piezoelectric element plate 52 is provided on the central part of the front and back main surfaces of the piezoelectric element plate 52. Also, a pair of container body connection electrodes 54 for making electrical connection with the element connection electrode pad 47 in the vicinity of one short side of the piezoelectric element plate 52, excitation electrodes 53 on the front and back main surfaces, and each The piezoelectric vibration element 46 is configured by providing an extraction electrode 55 that is electrically connected to the container body connection electrode 54.

  Further, external connection terminals 56 are attached and formed at the four corners of the mounting side top surface of the second frame portion 43 b joined to the other main surface of the substrate 42. A flip chip type integrated circuit element 44 formed in a rectangular shape is connected to the substrate 42 via a conductive adhesive 57 on the other main surface of the substrate 42 surrounded by the second frame portion 43b. ing. Further, a connection portion between the integrated circuit element 44 and the substrate 42 is covered and protected with a resin 58.

  The integrated circuit element 44 has, for example, a temperature sensor element that detects an ambient temperature state and temperature compensation data that compensates for temperature characteristics of the piezoelectric vibration element 46 on its circuit formation surface. Based on this temperature compensation data, A temperature compensation circuit that corrects the vibration characteristics of the piezoelectric vibration element 46 according to temperature data from the temperature sensor element, an oscillation circuit that is connected to the temperature compensation circuit and generates a predetermined oscillation output signal, and the like are provided. The oscillation output signal generated by the oscillation circuit is output to the outside and then used as a reference signal such as a clock signal. Here, the element connection electrode pad 47 to which the piezoelectric vibration element 46 is connected and a predetermined terminal of the integrated circuit element 37 are connected by an internal wiring (not shown) provided in the substrate 42.

  An element connection electrode pad 47 is provided on one main surface of the substrate 42 surrounded by the first frame body 43a by joining the first frame body 43a. A piezoelectric vibration element 46 is mounted on 47 via a conductive adhesive 48. A pair of element connection electrode pads 47 is provided in the vicinity of one short side of the bottom surface of the recess 49 along the short side. The element connection side main surface of the element connection electrode pad 47 has a quadrangular shape, and a metal having a relatively high conductivity is used as a material.

  On the element connection side main surface of the element connection electrode pad 47, the entire edge of the element connection side main surface of the element connection electrode pad 47 is formed on the element connection side main surface of the element connection electrode pad 47. A ring body 51 surrounding the center in an annular shape is provided. Here, the distance between the element connection side main surface of the element connection electrode pad 47 and the container body connection electrode 54 provided on the main surface facing the inner bottom surface of the recess 49 of the piezoelectric vibration element 46 is about 15 μm to 30 μm. The thickness of the ring body 51 is formed to be about 1/3 to 2/3 of the distance between the element connection side main surface of the element connection electrode pad 47 and the container body connection electrode 54. Yes. The ring body 51 is made of aluminum oxide. The ring body 51 is formed by screen printing or the like simultaneously with the formation of the element connection electrode pads 47 before the ceramic material of the container body 41 is laminated and fired.

  The piezoelectric vibration element 46 is connected to the conductive adhesive 48 applied on the element connection side main surface of the element connection electrode pad 47 surrounded by the ring body 51 with the main surface facing the inner bottom surface of the recess 49 of the piezoelectric vibration element 46. The container body connection electrode 54 provided on the surface is joined, and the conductive adhesive 48 is heated and solidified to be mounted in the recess 49 in a desired posture. There is no possibility that the conductive adhesive 48 having fluidity before heating and solidifying flows out from the element connection electrode pad 47 onto the inner bottom surface of the recess 49 due to the action of the ring body 51. Therefore, the conductive adhesive 48 adheres to the surface of the mounted piezoelectric vibration element 46 and adversely affects the vibration characteristics of the piezoelectric vibration element 46, or is formed in close proximity for miniaturization. Therefore, the piezoelectric oscillator 40 does not cause a problem because it does not contact the other element connection electrode pads 47 and cause a short circuit.

  By providing the ring body 51 in this manner, the conductive adhesive between the container body connection electrode 54 of the piezoelectric vibration element 46, the element connection electrode pad 47, and the ring body 51 on the element connection side main surface is provided. The bonding area of the piezoelectric vibration element 46 can be made wider than before, and when a shock such as a drop is applied to the piezoelectric vibration element 46, the bonding state between the piezoelectric vibration element 46 and the conductive adhesive 48 is not deteriorated. Thus, the piezoelectric vibration element 46 can be held on the element connection electrode pad 47 in a state where the adhesion state is stable.

  In the container body 41 in which the piezoelectric vibration element 46 is mounted in the recess 49 and the integrated circuit element 44 is mounted in the recess 50 in such a form, the first frame body 43a surrounding the opening of the recess 49 of the container body 41. On the top surface, a metal lid 45 made of 42 alloy, Kovar, phosphor bronze, or the like is disposed so as to cover the opening of the recess 49, and the lid 45 and the container body 41 in vacuum or in an inert gas. And the piezoelectric oscillator 40 in which the inside of the concave portion 49 is hermetically sealed is configured.

  The present invention is not limited to each embodiment, and various changes and improvements can be made without departing from the scope of the present invention. In each of the above embodiments, a ring body having the same outer peripheral shape as the outer peripheral shape of the element connection side main surface of the element connection electrode pad is disclosed, but the shape of the ring body is not limited to the above embodiment. For example, a ring body having a circular or elliptical outer shape inscribed in the square outer periphery of the element connection side main surface of the element connection electrode pad may be used. Needless to say, this case is also included in the technical scope of the present invention. In addition, as for the material of the ring body, a material other than aluminum oxide may be used as long as the effect as described above is exhibited.

  Further, in each of the above embodiments, the container connecting electrode is formed only on one short side of the rectangular flat plate-shaped piezoelectric element plate as a fixed end, and the other short side is a free end that is not connected anywhere. Although a so-called cantilever type piezoelectric vibration element mounting form has been disclosed, a pair of excitation electrodes formed on the front and back main surfaces of the piezoelectric element plate are formed in the vicinity of two short sides facing each other. Even in the case where a so-called double-sided piezoelectric vibration element in a form where the container body connection electrode and the lead-out electrode are electrically connected to the container body connection electrode, the container of the double-sided piezoelectric vibration element is used. By providing the element connection electrode pad corresponding to the body connection electrode with the ring body according to the present invention, the effects of the present invention can be achieved.

It is the disassembled perspective view which showed an example of the piezoelectric device which concerns on 1st embodiment of this invention. FIG. 2 is a cross-sectional view when the piezoelectric device shown in FIG. 1 is assembled and then cut along a virtual cutting line AA ′ shown in FIG. 1. It is the fragmentary sectional view which expanded and showed the structure in the dashed-two dotted line circle B of FIG. It is sectional drawing which showed an example of the piezoelectric device which concerns on 2nd embodiment of this invention. It is sectional drawing which showed one Embodiment of the conventional piezoelectric device for the example of the piezoelectric vibrator which is one of the piezoelectric devices. It is the fragmentary sectional view which expanded and showed the structure in the dashed-two dotted line dotted line circle C of FIG.

Explanation of symbols

10 ... Piezoelectric vibrator (piezoelectric device)
DESCRIPTION OF SYMBOLS 11,46 ... Piezoelectric vibration element 12,52 ... Piezoelectric base plate 13,53 ... Excitation electrode 14,41 ... Container body 15,47 ... Electrode connection electrode pad 16,54- .... Container body connection electrodes 17, 55 ... Lead electrodes 18, 49, 50 ... Recess parts 19, 51 ... Ring bodies 20, 48, 57 ... Conductive adhesives 21, 56 ... External connection electrode terminals 22, 45 ... Lid 40 ... Piezoelectric oscillator (piezoelectric device)
42 ... Substrate 43a ... First frame 43b ... Second frame 44 ... Integrated circuit element 58 ... Resin

Claims (2)

A container body formed with a recess having an opening on one main surface;
A pair of element connecting electrode pads formed on the bottom surface of the recess;
Excitation electrodes are provided on each of the front and back main surfaces, and a piezoelectric resonator element provided with a container body connection electrode extending from the excitation electrode to one edge of each main surface;
A cover that covers the opening of the recess and hermetically seals the space in the recess;
A piezoelectric device in which a piezoelectric vibration element is mounted in the recess by mechanically and electrically connecting and fixing the container body connection electrode to the element connection electrode pad with a conductive adhesive,
A ring body that annularly surrounds the center of the element connection side main surface of the element connection electrode pad is formed on the entire circumference of the edge portion of the element connection side main surface of the element connection electrode pad. Piezoelectric device.   2. The piezoelectric device according to claim 1, wherein the ring body is made of aluminum oxide.

Images