JP6350248B2 - Piezoelectric oscillator - Google Patents

Description

  The present invention relates to a piezoelectric oscillator in which a piezoelectric vibrator is conductively bonded to an upper part of a flat circuit board on which electronic components are mounted.

  A surface-mounted structure is widely used as a piezoelectric oscillator used in various electronic devices. For example, by joining a flat circuit board on which an integrated circuit element (IC) including an oscillation circuit, a temperature compensation circuit, and the like is mounted on the lower part of a piezoelectric vibrator in which a piezoelectric element is hermetically sealed in a package, A surface-mount type piezoelectric oscillator can be obtained without preparing a dedicated package for enclosing a piezoelectric element or an integrated circuit element. A piezoelectric oscillator having such a configuration is disclosed in Patent Document 1, for example.

  In the piezoelectric oscillator disclosed in Patent Document 1, a bonding material (13) made of solder or conductive adhesive is used for bonding the package (1) and the circuit board (6). In this piezoelectric oscillator, the external terminal (10) on the lower surface of the circuit board (6) is soldered to a wiring on an external board (external wiring board) such as a mother board. Heat generated from various electronic components mounted on the external substrate is also conducted to the piezoelectric oscillator mounted on the substrate. Specifically, heat generated from the external board is conducted from the external terminal (10) to the semiconductor integrated component (7) on the upper surface of the circuit board via the wiring conductor (9) and the like. The heat generated from the external substrate is also conducted from the external terminal (10) to the piezoelectric vibrator (5) via the bonding material (13) and the like.

  In the configuration of the piezoelectric oscillator in Patent Document 1, the heat conduction path of heat generated from the external substrate or the integrated circuit element to the piezoelectric vibrator is the bonding material 13 mainly made of solder. For this reason, it takes time until heat is conducted from the circuit board to the piezoelectric vibrator and the entire piezoelectric oscillator is in a thermal equilibrium state. Thus, for example, in the case of a temperature compensated piezoelectric oscillator (TCXO) having an integrated circuit element incorporating a temperature sensor and a temperature compensation circuit, the follow-up property (temperature follow-up property) with respect to the temperature change is not good, so that the change in the ambient temperature It is difficult to improve the so-called frequency drift characteristic, which represents the fluctuation of the frequency with respect to. That is, there is a problem that high-precision temperature compensation becomes difficult. Also, in the case of a piezoelectric oscillator (SPXO) using an integrated circuit element that does not incorporate a temperature sensor or a temperature compensation circuit, it is difficult to improve the so-called start-up characteristic, the time from when the power is turned on until the oscillation frequency is stabilized. End up.

JP 2007-067779

  The present invention has been made in view of this point, and an object of the present invention is to provide a piezoelectric oscillator that does not require a dedicated design and realizes highly accurate temperature compensation or good starting characteristics.

  In order to achieve the above object, the present invention provides a piezoelectric vibrator having a plurality of external electrodes including an electrode electrically connected to the piezoelectric element on the outer bottom surface of an insulating container in which the piezoelectric element is accommodated, and a flat plate And having a plurality of pads for mounting an integrated circuit element in the central portion of the one main surface, and a plurality of bonding electrodes corresponding to the external electrodes of the piezoelectric vibrator on the outer peripheral portion of the one main surface A piezoelectric oscillator integrally bonded via a conductive bonding material, wherein the plurality of bonding electrodes are for piezoelectric vibrators electrically connected to a part of the plurality of pads. A bonding electrode is included, and the external electrode of the piezoelectric vibrator and the bonding electrode of the insulating substrate are bonded via a conductive bonding material so as to cover the integrated circuit element bonded to the plurality of pads. In a state where the lower surface of the external electrode And the upper surface of the serial integrated circuit devices are in contact.

  According to the above invention, it is possible to realize high-precision temperature compensation or an improvement in the start-up characteristic of the piezoelectric oscillator. This is because the external electrode of the piezoelectric vibrator and the bonding electrode of the insulating substrate are bonded via a conductive bonding material, and the lower surface of the external electrode of the piezoelectric vibrator is in contact with the upper surface of the integrated circuit element. by. The heat conducted from the external substrate to the insulating substrate of the piezoelectric oscillator is conducted to the piezoelectric vibrator through the conductive bonding material. Furthermore, the heat conducted to the insulating substrate is also conducted to the piezoelectric vibrator via the external electrode that is in contact with the upper surface of the insulating substrate via the integrated circuit element. That is, since the heat conduction path to the piezoelectric vibrator is increased as compared with the conventional case, the piezoelectric oscillator can be shifted to a state of thermal equilibrium more quickly. Thereby, temperature followability improves and it is possible to realize highly accurate temperature compensation or improved start-up characteristics.

  In order to achieve the above object, a plurality of external connection terminals for connection to the outside are formed on the outer peripheral portion of the other main surface of the insulating substrate, and the electrical connection with the bonding electrode for the piezoelectric vibrator A plurality of pads including pads that are not connected to each other, and the plurality of external connection terminals are electrically connected via any one of connecting means of vias, through holes, or side electrodes provided on the insulating substrate. Even if a part of the plurality of junction electrodes is not electrically connected to the connection means and partially overlaps with an external connection terminal facing each of the plurality of junction electrodes in plan view. Good.

  According to the above invention, some of the plurality of bonding electrodes are electrically connected to the connecting means for connecting the pads (functional terminal pads) that are not electrically connected to the bonding electrodes for the piezoelectric vibrator and the external connection terminals. Therefore, the plurality of external connection terminals, which are function terminals, and the piezoelectric vibrator can be kept at different potentials. In addition, since some of the plurality of bonding electrodes partially overlap with the external connection terminals facing each of the bonding electrodes in plan view, the bonding electrodes and the external connection terminals facing each other across the insulating substrate The stray capacitance generated between the two can be reduced.

  In order to achieve the above object, the conductive bonding material may be a conductive adhesive having thixotropy.

  According to the above invention, since the conductive bonding material has thixotropy (so-called thixotropy), the conductive bonding material can be retained in the gap between the piezoelectric vibrator and the insulating substrate. In addition, it becomes easy to maintain the thickness (height) of the conductive bonding material to be equal to or greater than the thickness (height) of the integrated circuit element before the bonding between the piezoelectric vibrator and the insulating substrate. By doing in this way, the desired diameter of the columnar conductive bonding material can be ensured in a state after being weighted from above with respect to the piezoelectric vibrator located above the insulating substrate. That is, local diameter reduction of the conductive bonding material can be suppressed. As a result, the bonding strength between the piezoelectric vibrator and the insulating substrate can be improved. In addition, it is possible to prevent a short circuit due to the outflow of the bonding material to a plurality of pads or the like for mounting the integrated circuit element positioned inside the bonding electrode.

  As described above, according to the present invention, it is possible to provide a piezoelectric oscillator that does not require a dedicated design and realizes highly accurate temperature compensation or good start-up characteristics.

1 is a schematic cross-sectional view of a crystal oscillator according to an embodiment of the present invention. Schematic top view of an insulating substrate of a crystal oscillator according to an embodiment of the present invention Schematic top view of an insulating substrate of a crystal oscillator according to an embodiment of the present invention The upper surface schematic diagram of the insulated substrate of the crystal oscillator which concerns on the modification of embodiment of this invention

  Embodiments of the present invention will be described below with reference to FIGS. In the embodiment of the present invention, a temperature compensated crystal oscillator (so-called TCXO) will be described as an example of a piezoelectric oscillator. FIG. 1 is a schematic sectional view of a crystal oscillator according to an embodiment of the present invention. As shown in FIG. 1, a crystal oscillator 1 has a structure in which a crystal resonator 2 is integrally bonded to a top of a flat insulating substrate 3 on which an integrated circuit element (IC) 4 is mounted via a conductive bonding material 9. It has become. The crystal resonator 2 is disposed on the insulating substrate 3 so as to completely cover the upper surface of the integrated circuit element 4.

  Hereinafter, main members constituting the crystal oscillator will be described. First, the crystal resonator will be described, and then the insulating substrate and the like bonded to the crystal resonator will be described. In FIG. 1, a crystal resonator 2 is a surface-mount type piezoelectric resonator. The crystal resonator 2 has a substantially rectangular parallelepiped shape, and the outer dimensions in plan view are 2.05 mm on the long side and 1.65 mm on the short side. The crystal resonator 2 includes a crystal element 5, an insulating container 20 provided with a recess 8 for accommodating the crystal element 5, a metal ring R attached to the upper surface of a bank portion surrounding the recess 8, and a recess 8. The lid 21 which is joined to the upper surface of the metal ring R so as to cover the main part is a main member.

  The container 20 is a box-shaped body integrally formed by firing in a state where two ceramic green sheets 20a and 20b are laminated. Specifically, the container 20 is a laminate in which a frame-like upper layer sheet 20b having an open central portion is laminated on the upper surface of the lower layer sheet 20a. A recess 8 is formed by the lower layer 20a and the upper layer 20b, and the recess 8 is substantially rectangular in plan view. The upper layer sheet 20b corresponds to the bank portion described above.

  The outer bottom surface of the container 20 is a flat surface having a rectangular shape in plan view, and external electrodes 7 for connecting the crystal resonator to the outside are formed near the four corners of the outer bottom surface. That is, a total of four external electrodes 7a, 7b, 7c, and 7d are formed near the four corners of the outer bottom surface of the container 20, and only 7b and 7d are shown in FIG. The external electrodes 7b and 7d are electrically connected to excitation electrodes on the front and back sides of the crystal element 5 described later. The remaining two external electrodes 7 a and 7 c are non-connected electrodes that are not electrically connected to the crystal element 5. The four external electrodes 7a, 7b, 7c, and 7d are substantially rectangular in plan view. Of the four external electrodes, for example, a notch or the like may be provided in one corner of one external electrode as a mark for identifying the direction when the crystal resonator is mounted. In the embodiment of the present invention, the shape of the external electrode in plan view is substantially rectangular, but it may be other than rectangular.

  The inner bottom surface 801 of the concave portion 8 of the container 20 has a rectangular shape in plan view, and a pair of crystal element mounting pads 6a, 6b (in FIG. 1, the crystal element mounting pad 6b is shown) on one short side of the inner bottom surface 801. Is omitted) in parallel with the one short side. From the quartz element mounting pad 6a, wiring 6a1 is drawn out from between the lamination of the lower layer sheet 20a and the upper layer sheet 20b via the outer surface of the lower layer sheet 20a to the outer bottom surface of the lower layer sheet 20a. The end of the wiring 6a1 is connected to an external electrode 7a formed on the outer bottom surface of the container 20. Thereby, the excitation electrode (not shown) formed on one main surface of the crystal element 5 is electrically connected to the external electrode 7a via the crystal element mounting pad 6a and the wiring 6a1.

  Similarly, from the quartz element mounting pad 6b, the wiring 6b1 wraps around from the inner bottom surface 801 of the recess 8 to the outer bottom surface of the lower layer sheet 20a through the lamination between the lower layer sheet 20a and the upper layer sheet 20b and the outer surface of the lower layer sheet 20a. Has been pulled out. The end of the wiring 6b1 is connected to an external electrode 7b formed on the outer bottom surface of the container 20. Thereby, the excitation electrode (not shown) formed on the other main surface of the crystal element 5 is electrically connected to the external electrode 7b through the crystal element mounting pad 6b and the wiring 6b1.

  The external electrodes 7a and 7c that are not electrically connected to the crystal element 5 are finally connected to the lid 21 via vias (not shown) and metal rings R provided in the vertical direction inside the bank portion of the container 20. And electrically connected. Either or both of the external electrodes 7a and 7c are used as grounding electrodes, and the crystal oscillator 1 is conductively bonded to the land of the reference potential (ground) of the external substrate through the conductive bonding material 9, the insulating substrate 3, etc. An electromagnetic shielding effect can be obtained.

  On the other short side of the inner bottom surface 801, a substantially rectangular pillow member made of a conductive material in a plan view is formed (not shown). The pillow member is arranged so that its long side is substantially parallel to the short side of the inner bottom surface 801 of the container, and is positioned below the free end of the crystal element in a state where the crystal element 5 is cantilevered to the container 20. It is supposed to be. The pillow member is formed by a printing process of tungsten, and a nickel plating layer and a gold plating layer are sequentially laminated on the surface thereof.

  A metal ring R made of Kovar is attached to the upper surface of the bank portion of the container 20. The metal ring 6 is joined to a metal lid 21 described later by a seam welding method.

  In FIG. 1, a quartz crystal element 5 is a piezoelectric element in which various electrodes (not shown) are formed on each of the front and back main surfaces of an AT-cut quartz crystal vibrating piece that is a plate-like piezoelectric body. Specifically, the various electrodes are an excitation electrode for driving the crystal vibrating piece, an extraction electrode drawn from the excitation electrode to one end side of the quartz crystal vibrating piece, and a terminal portion of the extraction electrode, which is joined to the outside. It is the adhesive electrode used. These electrodes are formed on each of the front and back main surfaces of the crystal element and are paired on the front and back.

  The pair of adhesive electrodes are conductively bonded to the pair of crystal element mounting pads 6a and 6b of the container 20 on a one-to-one basis through the conductive adhesive S. That is, one end side of the plate-like crystal element 5 is cantilevered with the crystal element mounting pads 6 (6a, 6b) via the conductive adhesive S. The crystal element 5 is cantilevered on the crystal element mounting pad 6 so that a slight gap is generated between the free end side and the above-described pillow member in a steady state.

  In the present embodiment, as the conductive adhesive S, a silicone-based conductive resin bonding material containing a silver filler, a resin binder, an organic solvent, or the like is used. The conductive adhesive is not limited to a silicone-based conductive resin bonding material, and an epoxy-based conductive resin bonding material may be used in addition to the silicone-based adhesive. Moreover, you may use metal bumps other than a conductive adhesive.

In FIG. 1, the lid 21 is a flat plate having a substantially rectangular shape in plan view. The lid 21 is made of Kovar as a base material, and the surface of the base material is plated with nickel.
This completes the description of the crystal unit 1. Next, the insulating substrate 3 will be described.

  In FIG. 1, an insulating substrate 3 is a single-layer circuit board made of a ceramic material such as alumina. In FIG. 1, the insulating substrate 3 has a substantially rectangular shape in plan view, its outer dimensions are 2.10 mm × 1.71 mm, and its thickness is 0.1 to 0.15 mm. In addition to the ceramic material, a glass epoxy resin may be used as the base material of the insulating substrate. On one main surface (the upper surface in FIG. 1) of the front and back main surfaces of the insulating substrate 3, a plurality of pads for mounting bonding electrodes and integrated circuit elements are formed. On the other hand, on the other main surface (the lower surface in FIG. 1) of the insulating substrate 3, a plurality of external connection terminals that are conductively bonded to the lands (terminals) of the external substrate through solder or the like are formed. In addition, by making the base material of the container 20 and the insulated substrate 3 into the same material, the influence of the stress resulting from the difference in a thermal expansion coefficient of a container and an insulated substrate can be suppressed.

  FIG. 2 is a schematic view seen from the upper surface (one main surface 301) of the insulating substrate 3. FIG. A plurality of pads 11 (11a, 11b, 11c, 11d, 11e, and 11f) on which an integrated circuit element having a rectangular shape in a plan view is mounted are arranged in a rectangular shape in a plan view in the central portion of the one principal surface 301 of the insulating substrate 3. ing. These six pads correspond to the six functional terminals of an integrated circuit element (IC) in which an oscillation circuit, a temperature compensation circuit, a temperature sensor, etc. are integrated on a single chip. 2 represents the approximate position where the integrated circuit element (4) is mounted on six pads. These six pads are formed simultaneously with the lead pattern, bonding electrode, and the like on the upper surface 301 of the insulating substrate 3, and are laminated in the order of tungsten metallization, nickel plating, and gold plating from the substrate side.

  Of the six pads, pads 11b and 11e are pads for crystal resonators connected to the crystal resonators. The pad 11 d is a pad that is electrically connected to a ground connection terminal among the plurality of external connection terminals of the crystal oscillator 1.

  Four bonding electrodes 10a, 10b, 10c, and 10d corresponding to the external electrodes of the crystal resonator are disposed on the outer peripheral portion of the one main surface 301 of the insulating substrate 3 in a state of being separated from each other. The joining electrodes 10a and 10b are arranged in alignment with the short side of the main surface 301 of the insulating substrate 3 having a rectangular shape in plan view. Similarly, the bonding electrodes 10c and 10d are also arranged in alignment with the short side of the one main surface 301 of the insulating substrate 3 in substantially parallel. When these four bonding electrodes are connected with a straight line, the four bonding electrodes are formed on one main surface 301 so as to be rectangular in plan view.

  As shown in FIG. 2, the arrangement direction of the four bonding electrodes and the arrangement direction of the six pads are substantially parallel. Specifically, the arrangement direction in the short side direction of the one main surface 301 of the insulating substrate 3 of the four bonding electrodes 10a to 10d and the short side direction of the one main surface 301 of the insulating substrate 3 in the six pads 11a to 11e. The arrangement direction is substantially parallel. That is, the longitudinal direction of the six pads having a rectangular shape in plan view and the short side direction of the insulating substrate 3 are substantially parallel to each other.

  By adopting such an arrangement, the crystal resonator bonding electrodes 10b and 10d and the crystal resonator pad 11b, as compared with the insulating substrate having a configuration in which only the six pads in FIG. 11e can be relatively shortened. In other words, the length of the drawing patterns 12 and 13 described later can be shortened. Thereby, the conduction of heat conducted from the external substrate to the integrated circuit element 4 through the insulating substrate 3 to the bonding electrode can be accelerated. As a result, the crystal oscillator can be shifted to a thermal equilibrium state more quickly.

  The bonding electrode may be circumferentially covered with an insulating film such as alumina so that only the central portion of the upper surface of the bonding electrode is exposed. By forming such an insulating film on the bonding electrode, it is possible to improve the effect of preventing the conductive bonding material from flowing out to the pad or the like.

  The bonding electrode 10b is a bonding electrode for a crystal resonator drawn out from the pad 11b by the drawing pattern 12, and the bonding electrode 10d is a bonding electrode for a crystal resonator drawn out from the pad 11e by the drawing pattern 13. That is, the four bonding electrodes include bonding electrodes for crystal resonators drawn from some of the six pads.

  As shown in FIG. 2, the pad 11a is led out through the lead-out pattern 11a1 to a position near the periphery on one long side of the insulating substrate 3 and close to the bonding electrode 10a. A via V1 penetrating the substrate 3 in the thickness direction is formed. The pad 11c is led out through the lead pattern 11c1 to a position near the periphery of the long side of the insulating substrate 3 and close to the bonding electrode 10d, and the terminal portion penetrates the insulating substrate 3 in the thickness direction. A via V4 is formed.

  The pad 11f is led out through the lead pattern 11f1 to the position near the periphery on the other long side of the insulating substrate 3 and outside the pad 11c (side where the 10b is arranged).

  On the other hand, the pad 11d is connected to the bonding electrode 10c via a lead pattern 11d1 passing through the vicinity of the peripheral edge on the other long side of the insulating substrate 3. A via V3 penetrating the insulating substrate 3 in the thickness direction is formed in the middle of the lead pattern 11d1 connecting the pad 11d and the bonding electrode 10c. In FIG. 1, only the via V1 and the via V4 are illustrated. The above-described via is a member in which a metal (for example, copper) having a good thermal conductivity is filled in a through hole penetrating the front and back of the insulating substrate.

  The other main surface 302 of the insulating substrate 3 has a substantially rectangular shape in plan view, and four external connection terminals 14a for electrically bonding the crystal oscillator 1 to the lands of the external substrate via solder or the like in the vicinity of the four corners. 14b, 14c and 14d (only 14b and 14d are shown in FIG. 1) are formed. The four vias V1, V2, V3, and V4 described above are electrically connected to the external connection terminals 14a, 14b, 14c, and 14d on a one-to-one basis. In addition to the via, a through hole in which a conductor is attached to an inner wall surface of a through hole drilled in an insulating substrate may be used.

  In this way, the four external connection terminals and a part of the pad for mounting the integrated circuit element are electrically connected through the via filled with the metal having a good thermal conductivity, thereby insulating from the external substrate. The heat conducted to the lower surface side of the substrate can be efficiently conducted to the integrated circuit element on the upper surface of the insulating substrate in a short distance. The heat conducted to the integrated circuit element is detected by a temperature sensor inside the integrated circuit element, and the outside of the crystal resonator that is in contact with the upper surface of the integrated circuit element other than the heat conduction path through the conductive bonding material 9. Conducted to the electrode. At this time, heat generated from the integrated circuit element is also conducted to the external electrode of the crystal unit in contact with the upper surface of the integrated circuit element. One of the four external connection terminals (14c) is a terminal for ground connection, and an electromagnetic shielding effect is obtained by conductively bonding the ground external electrode of the crystal resonator to the terminal. Can do.

  In addition, by electrically connecting the four external connection terminals and a part of the pads for mounting the integrated circuit elements via the vias, a plurality of insulating substrates are individually formed from a collective substrate integrally formed in a matrix form. It is possible to prevent the generation of metal scrap when dividing into the insulating substrates. Note that the above-described insulating film such as alumina is coated on the upper surface of the end portion of the via in a circumferential shape so that the central portion is opened, thereby further enhancing the effect of preventing the generation of the metal scraps. In this case, the electrical connection between one main surface and the other main surface of the insulating substrate having a substantially rectangular shape in a plan view is made by a quarter-round castellation (details will be described later) at the four corners of the insulating substrate. The case where it performs by providing is demonstrated.

  In order to form the castellation having the above-described shape, a through-hole having a full circle shape extends across the four adjacent insulating substrates in plan view with respect to the intersection of the vertical and horizontal boundary lines of the four adjacent insulating substrates in the collective substrate state. So as to drill. Then, after a conductor (metal) is deposited on the inner wall surface of the drilled through-hole, the collective substrate is divided by dicing, breaking, or the like using the vertical and horizontal boundary lines as a reference. As a result, a quarter-round castellation is formed at the four corners of the individual insulating substrate in plan view. And at the time of the division, there is a possibility that a part of the conductor in the portion where the conductor is deposited (the portion that becomes castellation after the division) is peeled off. On the other hand, by using a via without forming the castellation itself on an insulating substrate, the possibility of partly peeling the conductor can be eliminated.

  Of the four external connection terminals 14a to 14d, the external connection terminal 14b is provided with a protruding portion 7b1 that protrudes in the long side direction of the other main surface 302 of the substantially rectangular insulating substrate in plan view. That is, the projection 7b1 and the external connection terminal 14b form an alphabetic “L” shape in plan view. The protrusion 7b1 is used as an index for identifying the directionality of the external connection terminals 14a to 14d, which are four function terminals. This protrusion 7b1 is connected to 11f which is a pad for power supply. Unlike the other three terminals 14a, 14c, and 14d, the via V2 is arranged in the region of the protruding portion 7b1 in plan view. With such an arrangement, it is possible to secure a larger distance between the bonding electrode 10b and the via V2 on the one main surface 301. Thereby, the short circuit between the conductive bonding material 9 applied to the bonding electrode 10b and the via V2 can be further prevented.

  The integrated circuit element 4 is placed on the upper surface side of the insulating substrate 3 so that the circuit surface side faces the one main surface 301. At this time, bumps G made of gold are flip-chip mounted on each of the six functional terminals provided on the circuit surface side of the integrated circuit element 4 in advance. The integrated circuit element 4 is placed on the six pads so that the bump G mounted on each of the six functional terminals of the integrated circuit element 4 and the six pads on the one principal surface 301 of the insulating substrate have a one-to-one correspondence. While being positioned and placed, an ultrasonic wave is applied from the upper surface side of the integrated circuit element 4 and pressure is applied while heating. Thus, the six bumps G previously bonded to the integrated circuit element 4 and the six pads are ultrasonically bonded (Flip Chip Bonding). Note that the silicon substrate which is the upper surface (inactive surface) of the integrated circuit element 4 is thinned by back grinding to become a flat surface.

  A conductive bonding material 9 is disposed on the upper surfaces of the four bonding electrodes 10a, 10b, 10c, and 10d of the insulating substrate 3. The conductive bonding material 9 is an adhesive having thixotropic properties. The conductive bonding material 9 contains more silver filler than the conductive adhesive S, and has a higher thermal conductivity than the conductive adhesive S in a state after curing.

  Since the conductive bonding material 9 has thixotropic properties, the conductive bonding material can be retained in the gap between the crystal resonator 2 and the insulating substrate 3. In addition, the thickness (height) of the conductive bonding material can be easily maintained to be equal to or greater than the thickness (height) of the integrated circuit element 4 before the crystal resonator 2 and the insulating substrate 3 are bonded. By doing in this way, the desired diameter of the columnar conductive bonding material can be ensured in a state after the crystal resonator 2 is weighted from above. That is, local diameter reduction of the conductive bonding material can be suppressed. As a result, the bonding strength between the crystal unit 2 and the insulating substrate 3 can be improved. In addition, it is possible to prevent a short circuit due to the outflow of the bonding material to the six pads for mounting the integrated circuit element positioned on the inner side of the bonding electrode, the drawing pattern, or the like.

  In the state after curing, the conductive bonding material 9 has a side surface shape in which a central portion in the height direction is recessed in a curved shape as shown in FIG. That is, the width gradually decreases in a curved shape from each of the bonding interface between the conductive bonding material and the external electrode and the bonding interface between the conductive bonding material and the bonding electrode toward the central portion in the height direction of the bonding material. It has a side shape. With such a shape, it is possible to suppress stress concentration at the bonding interface, so that the bonding reliability can be improved.

  The integrated circuit element 4 covers the integrated circuit element on the insulating substrate 3 conductively bonded to one main surface 301, and the upper surface of the four conductive bonding materials 9 applied in a columnar shape and the four external parts of the crystal resonator. The crystal resonator 2 is positioned and placed so that the electrode partially overlaps the planar view. In this state, as shown in FIG. 3, a part of each of the four external electrodes 7a, 7b, 7c, 7d of the crystal resonator 2 and the upper surface 400 of the integrated circuit element 4 are partially overlapped in plan view. It is in a state.

  Then, the crystal resonator is pressurized from the upper side to the lower side of the crystal resonator 2 in the state where the above-described positioning is performed (at the same time, the conductive bonding material is also cured in an environment of a predetermined temperature). ). Thereby, as shown in FIG. 3, the conductive bonding material 9 is bonded in each region near the outside of the lower surface 70 of the four external electrodes of the crystal resonator 2. At the same time, the regions near the inside of the lower surface 70 of the four external electrodes of the crystal unit 2 are in contact with the vicinity of the corners of the upper surface 400 of the integrated circuit element 4. At this time, in the outer bottom surface of the crystal unit 2 (the bottom surface of the container 20), the insulating base portion inside the four external electrodes is not in contact with the top surface 400 of the integrated circuit element 4 due to the thickness of the external electrodes. It is in a state. The total area in plan view of the region (15) where the four external electrodes 7a to 7d of the crystal resonator are in contact with the upper surface (near the corner) of the integrated circuit element 4 is four conductive bonding materials. 9 is smaller than the sum of areas in plan view of contact areas between the external electrodes 7a to 7d. As a result, it is possible to shift the crystal oscillator to a state of thermal equilibrium more quickly while suppressing capacitive coupling due to superimposition of the external electrode of the crystal resonator and the circuit surface of the integrated circuit element in plan view.

  The base material of the integrated circuit element 4 is silicon, and its thermal conductivity is lower than silver (a filler component contained in the conductive bonding material), but higher than alumina. Therefore, the integrated circuit element 4 has a higher thermal conductivity than the base material of the crystal resonator container 20 and the base material of the insulating substrate 3.

  According to the above configuration, it is possible to realize high-accuracy temperature compensation or an improvement in starting characteristics of the crystal oscillator. This is because the external electrodes 7a to 7d of the crystal resonator and the bonding electrodes 10a to 10d of the insulating substrate are bonded via the conductive bonding material 9, and the lower surface 70 of the external electrode of the crystal resonator and the integrated circuit element. This is because the upper surface 400 is in contact. The heat conducted from the external substrate to the insulating substrate 3 is conducted to the crystal unit 2 through the conductive bonding material 9. Further, the heat conducted to the insulating substrate 3 is also conducted to the quartz crystal resonator 2 via the integrated circuit element 4 and the external electrodes 7a to 7d contacting the upper surface 400 thereof. That is, since the heat conduction path to the crystal resonator is increased as compared with the conventional case, the crystal oscillator can be shifted to a thermally balanced state more quickly. Thereby, temperature followability improves and it is possible to realize highly accurate temperature compensation or improved start-up characteristics.

  As a modification of the embodiment of the present invention, for example, as shown in FIG. 4, a part of the plurality of pads 11 a to 11 f on one main surface 303 of the insulating substrate 30 and the outside of the other main surface (lower surface) of the insulating substrate 30. Electrical connection with the connection terminal is performed via the inner wall surface of a portion (castellation) in which the ridges of the four corners of the insulating substrate 30 are cut out into a quarter columnar shape in the thickness direction of the substrate. Also good.

  In FIG. 4, four external connection terminals are formed on the other main surface of the insulating substrate 30 as in the above-described embodiment of the present invention (not shown). A lead pattern 11a2 is drawn from the pad 11a and is connected to one external connection terminal on the other main surface of the insulating substrate 30 via a castellation C1. Similarly, a lead pattern 11c2 is drawn from the pad 11c and connected to another external connection terminal on the other main surface of the insulating substrate 30 via a castellation C4. A lead pattern 11f2 is drawn from the pad 11f and connected to one of the remaining two external connection terminals on the other main surface of the insulating substrate 30 via the castellation C2. A lead pattern 11d2 is drawn from the pad 11d and connected to one external connection terminal remaining on the other main surface of the insulating substrate 30 via a castellation C3. The pad 11d is also connected to the bonding electrode 10c which is a terminal for ground connection at the same time.

  As shown in FIG. 4, the castellation is formed on the outer surface of the corner portion of the insulating substrate 30, so that when the crystal oscillator is reflow-mounted on the external substrate via the solder, the solder crawls up on the metal portion of the castellation. Therefore, the bonding strength to the external substrate can be improved. Even when the crystal oscillator is miniaturized, it is easy to visually recognize the solder joint state by forming the solder creeping. Such a configuration is particularly suitable for applications that require higher bonding reliability such as in-vehicle use.

  In the embodiment of the present invention described above, a temperature-compensated crystal oscillator is given as an example of a piezoelectric oscillator, but the present invention is also applicable to a piezoelectric oscillator using an integrated circuit element that does not incorporate a temperature sensor or a temperature compensation circuit. Is possible.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not restricted 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.

  It can be applied to mass production of piezoelectric oscillators.

DESCRIPTION OF SYMBOLS 1 Crystal oscillator 2 Crystal oscillator 3 Insulating substrate 4 Integrated circuit element 5 Crystal element 7a, 7b, 7c, 7d External electrode 9 Conductive joining material 10a, 10b, 10c, 10d Junction electrode 11a, 11b, 11c, 11d, 11e, 11f Integrated circuit element mounting pads V1, V2, V3, V4 Vias 14a, 14b, 14c, 14d External connection terminals 20 Container 21 Lid

Claims (3)

A piezoelectric vibrator having a plurality of external electrodes including an electrode electrically connected to the piezoelectric element on an outer bottom surface of an insulating container containing the piezoelectric element;
A flat plate having a plurality of pads for mounting an integrated circuit element at a central portion of one main surface, and a plurality of joints corresponding to external electrodes of the piezoelectric vibrator on an outer peripheral portion of the one main surface. An insulating substrate having electrodes,
A piezoelectric oscillator integrally bonded through a conductive bonding material,
The plurality of bonding electrodes include a bonding electrode for a piezoelectric vibrator electrically connected to a part of the plurality of pads,
In a state where the external electrode of the piezoelectric vibrator and the bonding electrode of the insulating substrate are bonded via a conductive bonding material so as to cover the integrated circuit element bonded to the plurality of pads.
A piezoelectric device, wherein a lower surface of the external electrode and an upper surface of the integrated circuit element are in contact with each other. A plurality of external connection terminals for connecting to the outside are formed on the outer peripheral portion of the other main surface of the insulating substrate,
A plurality of pads including pads that are not electrically connected to the bonding electrodes for the piezoelectric vibrator, and the plurality of external connection terminals are either vias, through holes, or side electrodes provided on an insulating substrate. Electrically connected via one connection means,
A part of the plurality of bonding electrodes is not electrically connected to the connection means, and partially overlaps with an external connection terminal facing each of the plurality of bonding electrodes in a plan view. The piezoelectric oscillator according to claim 1.   The piezoelectric oscillator according to claim 1 or 2, wherein the conductive bonding material is a conductive adhesive having thixotropic properties.

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