JP2019220795A - Piezoelectric generator - Google Patents

Abstract

To provide a piezoelectric vibration generator with high reliability by corresponding to a low cost and a miniaturization.SOLUTION: A piezoelectric generator comprises: a rectangular parallelepiped shape base 2 made of an insulation material and having a housing part in which one opening part and a middle step are formed; a rectangular shape piezoelectric oscillation element 3 arranged in an inner bottom surface of the hosing part of the base 2 and forming an excitation electrode; a rectangular integrated circuit element 4 arranged in the middle part of the housing part of the base 2 and having a main surface area larger than the piezoelectric oscillation element 3; and a lid 5 hermetically sealing the opening part of the base 2. On the inner bottom surface of the housing part of the base 2, both end parts of the piezoelectric oscillation element 3 are bonded, and in a situation that the integration circuit element 4 covers the piezoelectric oscillation element 3, both end parts of the integration circuit element 4 are bonded in the middle step of the housing part of the base 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface mount type piezoelectric oscillator.

  As a piezoelectric oscillator, for example, a surface mount type crystal oscillator has a piezoelectric vibrating element made of crystal or the like and an integrated circuit element mounted in a storage portion provided on a base (package) made of an insulating material, and is covered with a lid. It has a structure in which the storage section is hermetically sealed. A plurality of external connection terminals are formed on an outer bottom surface of the base. Such a piezoelectric oscillator is mounted on an external circuit board by being electrically and mechanically bonded to a mounting pad on the external circuit board by a conductive bonding material such as solder at an external connection terminal.

  Among such piezoelectric oscillators, as disclosed in Patent Documents 1 to 3, a so-called single package structure in which a piezoelectric vibrating element and an integrated circuit element are housed in one housing and hermetically sealed. By arranging the piezoelectric vibrating element on the inner bottom surface side of the storage part and arranging the integrated circuit element on the opening side of the storage part, after performing the quality inspection etc. after the characteristic inspection step etc. of the mounted piezoelectric vibration element There has been proposed a device capable of mounting an integrated circuit element, thereby reducing production costs and improving yield, such as improving yield.

JP 2000-77944 A JP 2001-217650 A JP 2001-306644 A

  However, in the above-described piezoelectric oscillator, no consideration is given to the fact that the characteristics are adversely affected by the change in the parasitic capacitance due to the change in the gap size between the piezoelectric vibrating element and the integrated circuit element and the temperature difference between them. Not. At present, such a problem is becoming more significant as the size of the piezoelectric oscillator is reduced.

The present invention has been made in view of the above circumstances, and has as its object to provide a highly reliable piezoelectric oscillator having more stable electrical characteristics while responding to cost reduction and miniaturization of the piezoelectric oscillator. It is.

In order to achieve the above object, the present invention provides a base having a rectangular parallelepiped shape having an opening formed of an insulating material and one storage part having a middle step formed therein, and forming an excitation electrode disposed on an inner bottom surface of the storage part of the base. Rectangular piezoelectric vibrating element, a rectangular integrated circuit element that is arranged in the middle portion of the housing of the base and has a larger main surface area than the piezoelectric vibrating element, and hermetically seals the opening of the base. A lid, wherein both ends of the piezoelectric vibrating element are joined on an inner bottom surface of the base accommodating section, and the integrated circuit element covers the piezoelectric vibrating element, and the accommodating section of the base is provided. Characterized in that both ends of the integrated circuit element are joined on the middle stage.

  According to the above invention, the piezoelectric vibrating element and the integrated circuit element are housed in one housing portion of the base and have a single package structure hermetically sealed by a lid. It can be structured.

  In addition, the piezoelectric vibrating element is arranged on the inner bottom surface of the storage section of the base, and the integrated circuit element is arranged in the middle section located on the opening side of the storage section. For this reason, with only the piezoelectric vibrating element mounted on the base, after performing a characteristic inspection process on only the piezoelectric vibrating element, a non-defective product is determined, and only those that are satisfied are mounted on the integrated circuit element. As a result, the piezoelectric oscillator can be completed. Therefore, productivity can be increased, such as reduction in manufacturing cost and improvement in yield.

  In addition, both ends of the rectangular piezoelectric vibrating element are joined on the inner bottom surface of the storage part of the base, and both ends of the rectangular integrated circuit element are joined on the middle part of the storage part of the base. Therefore, even if an external impact is applied after mounting, the piezoelectric vibrating element and the integrated circuit element do not tilt, and the mutual positional relationship is maintained while maintaining a certain gap size. As a result, not only does the excitation electrode formed on the piezoelectric vibration element and the integrated circuit element not come into contact, but also the parasitic capacitance generated between the excitation electrode formed on the piezoelectric vibration element and the integrated circuit element is initially designed. It does not change with respect to the value, and it is possible to obtain a configuration in which the electrical characteristics are stable without fluctuation of the oscillation frequency.

  In addition, with the integrated circuit element covering the piezoelectric vibrating element, a rectangular integrated circuit element having a main surface area larger than that of the piezoelectric vibrating element is arranged in a middle portion located on the opening side of the storage section. Therefore, the arrangement relationship between the piezoelectric vibration element and the integrated circuit element is maintained while the piezoelectric vibration element and the integrated circuit element maintain a certain gap size in a state where the piezoelectric vibration element is completely covered. That is, the heat of the integrated circuit element is evenly transmitted to the piezoelectric vibrating element, and a temperature difference between the integrated circuit element and the piezoelectric vibrating element is less likely to occur, so that the electrical characteristics of the piezoelectric oscillator are not adversely affected. In particular, when a piezoelectric oscillator is used as a so-called TCXO having a temperature compensation function in an integrated circuit element, the temperature difference between the temperature sensor built in the integrated circuit element and the piezoelectric vibrating element becomes small, and correction accompanying the frequency temperature characteristic is performed. There is no influence of displacement and the like, and higher performance and stable electrical characteristics can be obtained.

  In the above configuration, a wiring pattern for a piezoelectric vibration element connected to the piezoelectric vibration element may be formed in a region of the middle section where the integrated circuit element is not mounted. A terminal for a piezoelectric vibrating element whose part exposes a part of the side wall of the base may be formed. In this case, it is not only possible to easily carry out a characteristic inspection process of only the piezoelectric vibrating element by using the wiring pattern for the piezoelectric vibrating element or the terminal for the piezoelectric vibrating element, but also to perform the piezoelectric vibration even after the integrated circuit element is mounted. Since the element wiring pattern and the piezoelectric vibrating element terminal can be used, characteristic measurement and adjustment can be easily performed as a piezoelectric oscillator combining a piezoelectric vibrating element and an integrated circuit element.

  As described above, it is possible to provide a highly reliable piezoelectric oscillator with more stable electric characteristics while supporting cost reduction and miniaturization of the piezoelectric oscillator.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a crystal oscillator according to an embodiment of the present invention. FIG. 2 is a plan view showing a state where only the crystal resonator of FIG. 1 is mounted. FIG. 3 is a plan view before the lid of FIG. 2 is put on.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As an embodiment of the piezoelectric oscillator of the present invention described below, a surface-mounted crystal oscillator (hereinafter, referred to as a crystal oscillator) incorporating an IC (integrated circuit element) having an oscillation circuit will be described as an example.

  The crystal oscillator 1 is a substantially rectangular parallelepiped package having a substantially rectangular shape in plan view and a concave shape in cross section. The crystal oscillator 1 includes a base 2, a crystal vibrating element (piezoelectric vibrating element) 3, an IC 4, and a lid 5 as main components. Hereinafter, the outline of each member constituting the crystal oscillator 1 will be described in detail.

  The base 2 is composed of a laminate of a substrate part and a frame part, which are made of an insulating material such as ceramic and has a substantially rectangular shape in plan view having long sides and short sides, and is formed by a laminate of at least three layers of an upper layer, an intermediate layer, and a lower layer. It is a rectangular parallelepiped container having a storage section 2a in which two openings 2b and a middle section 21b are formed.

  In the present embodiment, the base 2 includes a flat (substantially rectangular in plan view) substrate portion 20 serving as a base lower layer, and an outer peripheral edge 210 extending upward along an outer peripheral portion 200 of one main surface 201 of the substrate portion 20. A first frame portion 21 having an inner peripheral edge 211 formed in a substantially rectangular shape in plan view and serving as a base middle layer, and an outer peripheral edge 220 and an inner peripheral edge 221 extending upward along the outer peripheral portion 200 of the first frame portion 21 are formed in plan view. A second frame portion 22 (frame portion) which is formed in a substantially rectangular shape and serves as an upper layer of the base has a three-layer structure including a main constituent member (concave shape in cross section).

  Then, by combining the inner bottom surface of one main surface 201 of the substrate portion 20, the inner space inside the inner peripheral edge of the first frame portion 21, and the inner space inside the inner peripheral edge of the second frame portion, The storage section 2a of the base is configured.

  Inside the base 2, the lower surface (the inner bottom surface side of the storage portion 2 a) includes an inner bottom surface formed by one main surface 201 of the substrate portion 20 and the first frame portion 21. One storage portion 21a is formed, and an upper portion of the first storage portion 21a (on the side of the opening 2b of the storage portion 2a) is formed by a middle step 21b and a second frame portion 22 projecting upward from the bottom surface of the first storage portion. A second storage section 22a configured to store an IC 4 described later is formed.

  As shown in FIG. 1 and FIG. 2, one end of the upper surface of the substrate portion 20 (the inner bottom surface of the first storage portion 21 a), which is the lower layer of the base 2, Are formed side by side, and a pillow wiring pattern H22 that is mechanically connected to the crystal vibrating element 3 described later is formed at the other end. The pair of first wiring patterns H21 are, for example, via wiring wiring patterns H23 formed above cutouts 21c and 21d formed at one end of the outer peripheral edge of the first frame 21. It extends to the upper surface of the middle stage 21b and is connected to a part of a second wiring pattern H24 for mounting an IC 4 described later.

The pair of routing wiring patterns H23 also has a function of a terminal that is electrically connected to the later-described quartz-crystal vibrating element 3, and a contact probe of the quartz-crystal vibrating element characteristic device is brought into contact therewith. By doing so, it is possible to measure the characteristics of the crystal vibrating element 3 alone, which will be described later. Further, a plurality of external connection terminals H20 for connecting to an external circuit board are formed on the lower surface of the substrate portion 20 which is a lower layer of the base 2.

  On the upper surface of the first frame portion 21 (the bottom surface of the second storage portion 22a), which is the middle layer of the base 2, as shown in FIGS. 21b is formed, and a plurality of second wiring patterns H24 that are electrically and mechanically connected to an IC 4 described later are formed on the upper surface thereof. The plurality of second wiring patterns H24 are conductive vias (not shown) that penetrate and connect the first frame portion 21 and the substrate portion 20 and the routing formed on a part of the outer peripheral edge of the substrate portion 20 of the first frame portion 21. It is connected to a plurality of external connection terminals formed on the lower surface of the substrate unit 20 described later via a wiring pattern or the like.

  As shown in FIGS. 1 and 2, a sealing portion 222 for joining a lid 5 described later is formed on the upper surface of the second frame portion 22 which is the upper layer of the base 2. In this embodiment, the sealing portion 222 is formed by metallization, and the sealing portion 222 and the lid 5 described later are joined by a joining material such as a brazing metal.

  Each of the substrate portion 20, the first frame portion 21, and the second frame portion 22 configured as described above is, for example, a ceramic green sheet (alumina), and each outer peripheral edge has a substantially same rectangular shape in plan view. Is formed. These three sheets are integrally formed by firing in a laminated state, and constitute a substantially rectangular parallelepiped base 2 having a substantially rectangular shape in plan view and a concave shape in cross section. The external connection terminals (not shown), the first wiring pattern H21, the pillow wiring pattern H22, the wiring wiring pattern H23, the second wiring pattern H24, and the sealing portion 222 are each made of tungsten or molybdenum. In this configuration, a nickel plating layer and a gold plating layer are formed on the upper surface of the metallization layer.

  Each of these sheets (the sheet of the substrate portion, the sheet of the first frame portion, and the sheet of the second frame portion) is divided not only into a single layer but also into a plurality of layers according to the form of extension of the internal wiring between laminations. May be formed. More specifically, one or more sheets corresponding to another frame may be added between the first frame 21 and the second frame 22 to form a base composed of a laminate of four or more layers. .

  The crystal vibrating element 3 mounted on the inner bottom surface of the first storage portion 21a is, for example, a rectangular AT-cut crystal vibrating plate, and a pair of excitation electrodes and extraction electrodes are formed on the front and back surfaces, respectively. Among these, the pair of extraction electrodes extend only to one end of the crystal resonator element 3. These electrodes are, for example, at least two or more laminated thin films including a chromium or nickel base electrode layer and a silver or gold electrode layer. These electrodes can be formed by a thin film forming means such as a vacuum evaporation method or a sputtering method.

  Bonding of the quartz vibrating element 3 and the base 2 on the inner bottom surface of the first housing portion 21a is, for example, a paste of silicone-based conductive resin containing metal fine pieces such as silver filler (conductive bonding material). ) S is used. That is, as shown in FIGS. 1 and 2, the upper surface of the wiring pattern H21 formed on the inner bottom surface of the first storage portion 21a of the base 2 and the upper surface of a part of the wiring pattern H22 for the pillow are bonded to the conductive resin. The agent S is applied. Then, the conductive resin adhesive S is interposed between the pair of extraction electrodes extended to one end in the long side direction of the quartz crystal vibrating element 3 and the first wiring pattern H21 on the inner bottom surface, and is cured. They are electrically and mechanically joined to each other. In addition, the conductive resin adhesive S is interposed between the region where the central electrode is not formed at the other end in the long side direction of the quartz vibrating element 3 and the pillow wiring pattern H22 on the inner bottom surface, and is cured. By doing so, they are mechanically joined to each other.

  As described above, both ends of the quartz vibrating element 3 in the long side direction are held and joined while providing a gap from the inner bottom surface of the first storage portion 21 a of the base 2. In the present embodiment, a configuration in which bonding is performed using a silicone-based conductive resin adhesive is described as an example. However, as the conductive bonding material, other conductive resin adhesives, metal bumps, bump materials such as metal plated bumps, brazing materials, etc. A material may be used.

  The IC 4 mounted on the middle stage 21b of the base 2 is a one-chip rectangular integrated circuit element having a built-in inverter amplifier (oscillation amplifier) such as a C-MOS, and constitutes an oscillation circuit together with the crystal resonator element 3 described later. I do. Further, the area of the main surface of the IC 4 is selected to be larger than the area of the main surface of the crystal resonator element 3. A plurality of pads are formed on the bottom side of the IC 4. The IC 4 connects the plurality of pads of the IC 2 and the plurality of second wiring patterns H24 formed on the middle stage 21b of the base 2 with, for example, FCB via a metal bump C such as gold at both ends in the long side direction of the IC 2. Are electromechanically bonded. At this time, the crystal resonator element 3 is covered with the IC 2 having a large main surface area. In the present embodiment, the configuration in which the metal bumps are joined by metal bumps C is used as an example, but metal wire bumps may be used. Note that the present invention is not limited to this embodiment, and both ends of the IC 2 in the short side direction may be electromechanically bonded depending on the arrangement of the middle stage of the base 2.

  The IC 4 used in the present embodiment is not limited to a so-called SPXO IC having only an oscillation circuit section for amplifying the frequency signal of the crystal resonator element 3, but a so-called VCXO IC having a frequency adjusting circuit as an additional function. It may be a so-called TCXO IC provided with a temperature compensation function and the like as an additional function. Further, an IC in which these are combined may be used. The IC 4 may be a bipolar transistor other than the CMOS, a bi-CMOS, or the like.

  The lid 5 that hermetically seals the base 2 has a configuration in which, for example, a metal brazing material (sealing material) is formed on a core material made of Kovar or the like. The joining material made of the brazing metal is joined to the sealing portion 222 of the base 2. The outer shape of the metal lid 5 in a plan view is substantially the same as or slightly smaller than the outer shape of the ceramic base.

  The sealing portion 222 of the base 2 in which the IC 4 and the crystal resonator element 3 are stored in the storage portion 2a is covered with a metal lid 5, and the joining material of the metal lid 5 and the sealing portion 222 of the base are sealed. The surface-mounted crystal oscillator 1 is completed by melt-hardening and performing hermetic sealing.

  The surface-mounted crystal oscillator 1 configured as described above is joined to a wiring pattern of a circuit board (not shown) using a joining material such as solder.

  According to the above-described embodiment, a single package structure in which the crystal resonator element 3 and the IC 4 are housed in one housing portion 2 a of the base 2 and hermetically sealed by the lid 5 has a simple, compact and advantageous surface for reducing the height. The mounting type crystal oscillator 1 can be obtained.

  Further, the quartz vibrating element 3 is arranged on the inner bottom surface side of the storage section 2a of the base, and the IC 4 is arranged on the middle section 21b located on the opening 2b side of the storage section 2a. For this reason, in a state where only the crystal resonator element 3 is mounted on the base 2, after performing a characteristic inspection process or the like of only the crystal resonator element 2, a non-defective product is determined, and only those which are satisfied are selected. Is mounted so that the crystal oscillator 1 can be completed. Therefore, productivity can be increased, such as reduction in manufacturing cost and improvement in yield.

  Further, both ends of the rectangular crystal vibrating element 3 in the long side direction are joined on the inner bottom surface of the base storage section 2a, and both ends of the rectangular IC 4 in the long side direction are connected to the middle section 21b of the storage section 2a. Since the parts are joined, the crystal resonator element 2 and the IC 4 do not tilt even if an external impact or the like is applied after mounting, and the mutual positional relationship is maintained while maintaining a certain gap size. As a result, not only is there no short circuit between the excitation electrode formed on the crystal resonator element 2 and the functional surface of the IC 4, but also the parasitic capacitance generated between the excitation electrode formed on the crystal resonator element 2 and the IC 4 is initially reduced. The configuration does not change with respect to the design value, and a configuration in which the electrical characteristics are stable and the oscillation frequency does not change can be obtained.

  In addition, since the IC 4 covers the quartz-crystal vibrating element 3, the rectangular IC 4 whose main surface area is larger than that of the quartz-crystal vibrating element 3 is arranged in the middle section 21 b located on the opening side of the storage section 2 a. In the state where the crystal vibrating element 2 is completely covered and the crystal vibrating element 2 and the IC 4 maintain a certain gap size, the mutual positional relationship is maintained. In other words, the heat of the IC 4 is evenly transmitted to the crystal vibrating element 2 and a temperature difference between the ICs 4 is hardly generated, so that the electrical characteristics of the crystal oscillator 1 are not adversely affected. In particular, when the crystal oscillator 1 is used as a so-called TCXO having a temperature compensation function in the IC 4, the temperature difference between the temperature sensor incorporated in the IC 4 and the crystal resonator element 2 becomes small, and the correction deviation due to the frequency-temperature characteristic, etc. And the stable and high-performance electrical characteristics can be obtained.

  In addition, the pair of wiring patterns for wiring H23 are electrically connected to the excitation electrodes of the quartz vibrating element 3 and are provided with notches 21c and 21d formed on one end side of the outer peripheral edge of the first frame portion 21. It functions as a terminal for a crystal vibrating element formed on the upper part and exposed on the outer surface of the base 2. For this reason, using the terminals for the crystal vibrating element, it is not only easy to carry out the characteristic inspection step of only the crystal vibrating element 3 and the like, but also the wiring pattern H23 and the crystal vibrating element Since the terminal 3 can be used, characteristic measurement and adjustment can be easily performed as the crystal oscillator 1 in which the crystal resonator element 3 and the IC 4 are combined.

  As described above, it is possible to provide a highly reliable crystal oscillator with more stable electrical characteristics while responding to cost reduction and size reduction of the crystal oscillator.

In the above-described embodiment, the AT-cut quartz vibrating plate is used as the piezoelectric vibrating element. However, the present invention is not limited to this, and a quartz vibrating plate of another vibration mode may be used. In addition, although quartz is used as a material for the piezoelectric vibrating element, the material is not limited thereto, and a piezoelectric single crystal material such as piezoelectric ceramics or LiNbO ₃ may be used. That is, any piezoelectric vibration element can be applied.

  Further, in the present embodiment, the sealing with the metal brazing material is taken as an example, but the present invention is not limited to this, and it is also possible to use seam sealing, beam sealing (for example, laser beam, electron beam), glass sealing, or the like. Can be applied.

  The present invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in every aspect, and should not be interpreted in a limited manner. The scope of the present invention is defined by the appended claims, and is not limited by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  Applicable to mass production of piezoelectric oscillators.

1 crystal oscillator 2 base 3 crystal vibrating element 4 IC
5 Lid C Metal bump S Conductive resin adhesive

Claims (1)

A rectangular parallelepiped base having an opening made of an insulating material and having a single storage section in which a middle step is formed; a rectangular piezoelectric vibrating element disposed on an inner bottom surface of the storage section of the base and formed with an excitation electrode; A rectangular integrated circuit element which is disposed in the middle part of the storage part and has a larger area of the main surface than the piezoelectric vibration element, a lid for hermetically sealing the opening of the base,
In a state where both ends of the piezoelectric vibrating element are joined on the inner bottom surface of the housing of the base and the integrated circuit element covers the piezoelectric vibrating element, the integrated circuit is mounted on the middle stage of the housing of the base. A piezoelectric oscillator, wherein both ends of an element are joined.

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