JP6137442B2 - Piezoelectric oscillator - Google Patents

Description

  The present invention relates to a surface-mounted piezoelectric oscillator in which a piezoelectric vibrator and other electronic components are mounted on a circuit board, and relates to a piezoelectric oscillator capable of changing a frequency by controlling a voltage.

  As an example of a piezoelectric oscillator used for optical transmission equipment, video equipment, etc., there is a crystal oscillator called a discrete type, for example. The crystal oscillator is formed by mounting a crystal resonator and other electronic components on a circuit board made of an insulating material such as ceramic. Due to the recent demand for miniaturization of various electronic devices, the discrete type crystal oscillator is also required to be miniaturized.

  In the discrete type crystal oscillator, for example, as shown in FIG. 9, in a region where the crystal resonator 2 is mounted on the circuit board 1 ′, a resonator terminal (hereinafter referred to as a resonator) corresponding to an external terminal of the crystal resonator. For short). In FIG. 9, four vibrator pads 12a, 12b, 12c, and 12d are arranged in an independent state in a plan view, and are conductively joined to four external terminals provided on the outer bottom surface of the crystal vibrator. It has become.

  A plate-like crystal vibrating piece is accommodated inside the crystal resonator, and excitation electrodes for driving the crystal vibrating piece are formed on the front and back of the crystal vibrating piece. This excitation electrode is electrically connected to two external terminals 12b and 12c for output among the four external terminals of the crystal resonator. Here, the two external terminals 12b and 12c are generally arranged diagonally with respect to the outer bottom surface of a substantially rectangular crystal resonator in plan view.

  In the conventional circuit board, as shown in FIG. 9, a pair of vibrator pads 12b and 12c are diagonally formed on the upper surface of the circuit board 1 'corresponding to the two external terminals for input / output of the crystal vibrator. Has been placed. Of the two input / output transducer pads, it is necessary to route the wiring DP1 'to the transducer pad 12c located far from the transducer input / output terminals 4a and 4b. However, if a conductor such as an electrode pattern exists below the wiring DP1 'with the substrate interposed therebetween, stray capacitance is generated. The generation of the stray capacitance leads to a decrease in negative resistance value and a decrease in frequency variable amount. In order to suppress such an increase in stray capacitance (parasitic capacitance), Patent Document 1 discloses a configuration in which a pair of external terminals electrically connected to an excitation electrode are arranged on one adjacent side with respect to a piezoelectric vibrator. ing.

  However, in Patent Document 1, although a pair of external terminals electrically connected to the excitation electrode can be disposed near the IC, the positional relationship between the pair of external terminals and the external terminal on the bottom surface of the oscillator is clarified. For example, the configuration of the oscillator shown in FIG. 9 of Patent Document 1 is different from the discrete type configuration, and a pair of external terminals connected to the excitation electrode overlap with the external terminals on the bottom surface of the oscillator in plan view. It has become. For example, when the pair of external terminals connected to the excitation electrode are in a positional relationship overlapping with the input power supply terminal of the external terminal on the bottom surface of the oscillator in a plan view, the problem is that it is easily affected by noise from the input power supply terminal. Exists.

  In addition, a conductive pattern having a reference potential (hereinafter abbreviated as a GND pattern) is formed on a mounting board of various electronic devices, but the following problems may occur when the piezoelectric oscillator is mounted on the mounting board. That is, when the piezoelectric oscillator is mounted on the mounting substrate, the GND pattern and the vibrator pad electrically connected to the excitation electrode of the piezoelectric vibrating piece may be in a positional relationship in plan view. is there. Further, since there is a substrate made of an insulating material between the vibrator pad and the GND pattern, stray capacitance is generated. Due to the generation of the stray capacitance, the initially set characteristics (frequency variable amount, etc.) change, and there arises a problem that desired characteristics cannot be obtained.

Patent No. 3843983

  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 suppresses the generation of stray capacitance and has stable characteristics.

In order to achieve the above object, the present invention provides a piezoelectric oscillator in which an oscillation circuit is configured by mounting a piezoelectric vibrator, a semiconductor integrated circuit element, and other electronic components on a circuit board.
The circuit board is a multilayer substrate made of an insulating material, and includes a reference potential conductor pattern at least on the lower surface of the lowermost substrate ,
A mounting pattern on which a piezoelectric vibrator, a semiconductor integrated circuit element, and other electronic components are mounted is formed on the upper surface of the substrate.
The mounting pattern includes four vibrator pads that are conductively bonded to the piezoelectric vibrator, and a pair of vibrator input / output terminals.
Of the four vibrator pads, a pair of adjacent vibrator pads is electrically connected to an excitation electrode formed on the piezoelectric vibrating piece and is adjacent to the pair of vibrator input / output terminals. Arranged
Of the four vibrator pads, at least the pair of vibrator pads overlaps the conductor pattern in plan view ,
The package of the piezoelectric vibrator has a mounting portion on which the piezoelectric vibrating piece is mounted inside the package, and has four external terminals on the outer bottom surface of the package,
Of the four external terminals, a pair of external terminals electrically connected to the excitation electrode is:
The area in plan view than two external terminals that are formed on the end portion of the pair of vias that penetrate the base material from the mounting portion to the outer bottom surface of the package and that are not electrically connected to the excitation electrode Is formed small,
The adjacent pair of vibrator pads has a shape corresponding to the pair of external terminals. Here, the “via” is a well-known via (Via) in which a conductor is filled in the through hole in order to electrically connect the front and back of the substrate.

  According to the above invention, of the four vibrator pads, the adjacent pair of vibrator pads is electrically connected to the excitation electrode formed on the piezoelectric vibrating piece and the pair of vibrator input / output terminals. Since they are arranged at adjacent positions, it is not necessary to route wiring to the transducer pad far from the transducer input / output terminal as in the prior art. As a result, the generation of stray capacitance due to the routing wiring can be suppressed. As a result, it is possible to suppress a decrease in the negative resistance value and prevent a decrease in the frequency variable amount.

  According to the above invention, the conductor pattern (GND pattern) of the reference potential is formed on at least the lowermost substrate lower surface of the circuit substrate. For example, when the GND pattern is formed only on the lower surface of the lowermost substrate, the distance in the circuit board thickness direction between the pair of vibrator pads electrically connected to the excitation electrode and the GND pattern is maximized. be able to. As a result, it is possible to suppress the amount of stray capacitance generated due to the overlapping of the pair of vibrator pads and the GND pattern in plan view.

  In the above configuration, the GND pattern may be formed not only on the lower surface of the lowermost layer of the circuit board but also on the intermediate layer of the circuit board. For example, the following effects can be obtained by disposing a part of an electronic component such as an IC mounted on the uppermost layer of the circuit board in a plan view. In other words, the heat generated from the IC etc. is conducted downward through the vias formed in the substrate, and the vias are connected to the intermediate layer and the GND pattern of the lowermost layer to disperse the heat to the intermediate layer. Can be made. As a result, the temperature of the entire circuit board can be easily made uniform, and the warpage of the circuit board due to thermal stress can be suppressed. In addition, since the GND pattern is also present in the intermediate layer of the circuit board, the area not covered with the GND pattern on the lower surface of the lowermost substrate can be covered with the GND pattern of the intermediate layer, thereby improving the electromagnetic shielding effect. Can be made.

  According to the above invention, since the pair of vibrator pads electrically connected to the excitation electrode overlaps at least the GND pattern provided on the lower surface of the lowermost substrate in plan view, various piezoelectric oscillators can be used. It is possible to prevent a change in the characteristics of the piezoelectric oscillator after being mounted on an external substrate such as an electronic device. This is because the pair of vibrator pads and the GND pattern on the bottom surface of the lowermost circuit board (the bottom surface of the circuit board) overlap in a plan view in the piezoelectric oscillator. In other words, even if the GND pattern is formed in a layer below the pair of vibrator pads, and is in a positional relationship that does not overlap in plan view, when the piezoelectric oscillator is mounted on the external substrate, the pair of vibrator pads and When the wiring pattern on the external substrate overlaps with the plan view, stray capacitance is generated.

  On the other hand, according to the configuration of the present invention, the pair of vibrator pads and the GND pattern on the bottom surface of the lowermost substrate already overlap in a plan view before mounting on the external substrate. It is possible to suppress an increase in stray capacitance due to overlapping of the vibrator pad and the wiring pattern of the external substrate in plan view. As a result, it is possible to prevent changes in the characteristics of the initially set piezoelectric oscillator accompanying an increase in stray capacitance.

  According to the above invention, the generation of stray capacitance can be further suppressed. This is because the pair of external terminals electrically connected to the excitation electrode is formed to have a relatively smaller area in plan view than the remaining two external terminals, and the pair of adjacent vibrator pads on the circuit board is also This is due to the shape corresponding to the pair of external terminals. Therefore, with the above configuration, the overlapping area in plan view of the pair of vibrator pads and the GND pattern can be made smaller than the overlapping area when the four vibrator pads are formed with the same area. . As a result, the generation of stray capacitance can be suppressed by reducing the overlapping area.

  Further, according to the above invention, in addition to the suppression of stray capacitance, it is possible to reduce the influence of the stub on the signal when the oscillation frequency is increased. For example, a pair of cylindrical vias are formed through the base material portion below the mounting portion of the package, and one end side of the via is exposed to the mounting portion side and the other end side is exposed to the outer bottom surface side of the package. A vibration piece mounting terminal that is conductively bonded to the piezoelectric vibration piece is formed on one end side of these vias, and an input / output external terminal is formed on the other end side of the via. Here, it is preferable that the resonator element mounting terminal and the input / output external terminal have a width dimension similar to the width dimension of the via. On the other hand, out of the four vibrator pads on the circuit board, the pair of vibrator pads that are conductively joined to the input / output external terminals has a shape corresponding to the shape of the input / output external terminals. With these configurations, the path of the electric signal in the circuit board thickness direction is substantially the same straight line in a cross-sectional view, and the influence of the stub on the signal can be reduced.

  In the above invention, the vias in plan view may have other shapes besides circular. In addition, the cross-sectional shape of the via may be a square shape or a trapezoidal shape.

  In order to achieve the above object, a notch extending in the depth direction of the package is formed at each corner of the outer surface of the package of the piezoelectric vibrator, and among the four external terminals of the piezoelectric vibrator, A pair of external terminals electrically connected to at least the excitation electrode may be formed on an end portion of the via on the package outer bottom surface side and extended to a notch portion close to the end portion. .

  According to the above invention, the bonding strength of the piezoelectric vibrator on the circuit board by solder or the like can be improved. This is because at least a pair of external terminals electrically connected to the excitation electrode are formed on the end portion of the via on the bottom surface side of the package and extended to a notch portion adjacent to the end portion, and adjacent to the circuit board. This is because the pair of vibrator pads to be formed has a shape corresponding to the pair of external terminals of the piezoelectric vibrator. That is, since the conductor extends to the notch portion between the pair of adjacent external terminals, when the piezoelectric vibrator is mounted on the circuit board with solder, the solder is likely to rise up to the notch portion. The joining strength of the pair of external terminals having a relatively small area can be compensated by the rising of the solder. Thereby, it is possible to suppress the uneven distribution of stress due to the bonding of the piezoelectric vibrator onto the circuit board.

  In the case where the four external terminals of the piezoelectric vibrator are formed with substantially the same area in plan view with respect to the above configuration, the piezoelectric vibrator may extend from each of the four external terminals to the notch at the corner adjacent to each terminal. Good. In this case, two external terminals that are not electrically connected to the excitation electrode may be set as a reference potential, and the two external terminals may be electrically connected to a metal lid joined to the upper surface of the package (container). . Thus, by electrically connecting the metal lid and the external terminal of the reference potential, it is possible to protect from noise outside the piezoelectric vibrator (electromagnetic shielding effect).

  As described above, according to the present invention, it is possible to provide a piezoelectric oscillator that suppresses the generation of stray capacitance and has stable characteristics.

The upper surface schematic diagram of the circuit board of the crystal oscillator which concerns on the 1st Embodiment of this invention Schematic sectional view taken along line AA in FIG. The upper surface schematic diagram of the intermediate | middle layer of the circuit board based on the 1st Embodiment of this invention The upper surface schematic diagram of the circuit board which shows the 1st Embodiment of this invention Schematic top view of a circuit board according to a second embodiment of the present invention Cross-sectional schematic diagram of a crystal resonator according to a second embodiment of the present invention Schematic diagram of the bottom surface of the crystal resonator according to the second embodiment of the present invention. Schematic diagram of the bottom surface of the crystal unit according to the third embodiment of the present invention. Schematic top view of a conventional crystal oscillator circuit board

  Embodiments of the present invention will be described below with reference to the drawings. In the embodiment of the present invention, a discrete type crystal oscillator will be described as an example of a piezoelectric oscillator. The oscillation frequency output from the crystal oscillator in this embodiment is 350 to 800 MHz in fundamental wave oscillation. The oscillation frequency is an example, and the present invention can be applied to frequencies other than the oscillation frequency.

-First embodiment-
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic top view of a circuit board used in the crystal oscillator according to the first embodiment of the present invention, and shows a state where a plurality of electronic components are not mounted. FIG. 2 is a schematic sectional view taken along line AA in FIG.

  In FIG. 1, a circuit board 1 is formed by laminating two ceramic green sheets of a lower layer 1a and an upper layer 1b (see FIG. 2), and is integrally formed by firing. In FIG. 1, the circuit board 1 has a substantially rectangular shape in plan view, and its outer dimensions are 7.0 mm × 5.0 mm. In addition, you may use glass epoxy resin as a base material of a circuit board other than a ceramic. A predetermined mounting pattern made of a metal conductor is formed on the upper surface 100 of the circuit board 1, and the crystal resonator 2, the integrated circuit element 3 (IC), and other electronic components (frequency adjusting member and voltage) are formed on the mounting pattern. An oscillation circuit is configured by mounting a coil, a capacitor, a resistor, a varicap diode, and the like constituting the control member. In this embodiment, gold (Au) is used for the mounting pattern. In FIG. 1, among the mounting patterns, vibrator pads (5a to 5d) on which the crystal vibrator is mounted and a pair of vibrator input / output terminals (4a, 4b) connected to the vibrator pad, Description of patterns other than the IC mounting pad (6) on which the IC is mounted is omitted. In FIG. 1, the crystal resonator 2 and the integrated circuit element 3 are represented by dotted lines, and the approximate position of the mounting pattern 4 in a region where other electronic components are mounted is also represented by dotted lines.

  In FIG. 1, four vibrator pads 5a, 5b, 5c, and 5d are formed in a region (indicated by a dotted line) on the upper surface 100 of the circuit board 1 where the crystal vibrator is mounted. These four vibrator pads are arranged on the circuit board in a rectangular shape in plan view so as to correspond to the four external terminals on the bottom surface of the crystal vibrator. The four vibrator pads 5a, 5b, 5c, and 5d are formed simultaneously with other mounting patterns on the circuit board upper surface 100, and are laminated in the order of tungsten, nickel plating, and gold plating from the circuit board side.

  Of the four vibrator pads 5a to 5d, the pair of vibrator pads 5a and 5b are arranged adjacent to one short side of a rectangle formed by using the vibrator pads 5a to 5d as four corners. Has been. The adjacent pair of vibrator pads 5a and 5b is connected to the pair of vibrator input / output terminals 4a and 4b via wirings DP1 and DP2, respectively. Here, the pair of resonator input / output terminals are part of a mounting pattern constituting an oscillation stage for exciting the crystal resonator, and a variable capacitance element (varicap) connected in series to the crystal resonator. One of the input / output terminals for the diode) (in this embodiment, the vibrator input / output terminal 4a is an output terminal and the vibrator input / output terminal 4b is an input terminal). In the present embodiment, coils are mounted on the vibrator input / output terminals 4a and 4b, and are connected in series to the varicap diode. The electronic component mounted on the vibrator input / output terminal may be not only a coil but also a capacitor, a varicap diode, or the like.

  According to the above configuration, the pair of adjacent vibrator pads 5a and 5b are electrically connected to the excitation electrode formed on the crystal vibrating piece and are adjacent to the pair of vibrator input / output terminals 4a and 4b. Therefore, it is not necessary to route the wiring to the transducer pad far from the transducer input / output terminals 4a and 4b as in the prior art. As a result, the generation of stray capacitance due to the routing wiring can be suppressed. As a result, it is possible to suppress a decrease in the negative resistance value and prevent a decrease in the frequency variable amount.

  As shown in FIG. 2, the circuit board 1 has a reference potential conductor pattern (hereinafter abbreviated as a GND pattern) GP1 formed on the lower surface (the bottom surface of the circuit board) of the lower layer 1a of the circuit board. A conductor pattern (GND pattern) GP2 having a reference potential is formed between the stacked layers (boundary between the upper layer 1b and the lower layer 1a). Both of the GND patterns GP1 and GP2 are a pair of vibrator pads 5a and 5b. In a plan view (see FIGS. 3 and 4). The GND patterns GP1 and GP2 are electromechanically connected via vias provided inside the circuit board. 3 to 4, for convenience of explanation, the transducer pattern, the mounting pattern, the GND pattern, and the like are indicated by dotted lines in order to clarify the positional relationship between the transducer pattern and the GND pattern in plan view.

  In the above configuration, the GND pattern is formed not only on the lower surface of the lowermost layer of the circuit board but also on the intermediate layer. The following effects can be obtained by forming the GND pattern GP2 of the intermediate layer at a position overlapping a part of an electronic component such as an IC mounted on the upper surface 100 of the circuit board 1 as shown in FIG. That is, heat generated from an IC or the like is conducted to the lower side of the circuit board through vias (not shown) formed in the board, and the GND patterns GP1 and GP2 connected to the vias are used for the inside of the circuit board and the bottom surface of the circuit board. Heat can be dispersed. As a result, the temperature of the entire circuit board can be easily made uniform, and warpage of the circuit board 1 due to thermal stress can be suppressed. In addition, since the GND pattern exists between the circuit board stacks, the area of the lower surface 110 of the lower layer 1a that is not covered with the GND pattern GP1 can be covered with the GND pattern GP2, thereby improving the electromagnetic shielding effect. Can do.

  3 to 4, the pair of vibrator pads 5a and 5b electrically connected to the excitation electrodes of the crystal vibrator overlap with the GND patterns GP1 and GP2 in a plan view. It is possible to prevent a change in the characteristics of the crystal oscillator after being mounted on the external substrate of the device. This is because the oscillator pads 5a and 5b and the GND pattern GP1 on the lower surface 1a of the circuit board are already overlapped in a plan view in the crystal oscillator.

  That is, even if the GND pattern is formed in a layer below the transducer pads 5a and 5b, if the positional relationship does not overlap in a plan view, the transducer pad 5a is mounted when the crystal oscillator is mounted on the external substrate. , 5b and the wiring pattern on the external substrate overlap each other in plan view, stray capacitance is generated.

  On the other hand, according to the configuration of the present invention, the vibrator pads 5a and 5b and the GND pattern GP1 in the lowermost layer already overlap with each other in plan view before mounting on the external substrate. And an increase in stray capacitance due to overlapping of the wiring pattern in plan view can be suppressed. As a result, it is possible to prevent a change in the characteristics of the initially set crystal oscillator accompanying an increase in stray capacitance.

  In the present embodiment, as shown in FIG. 2, the GND pattern is formed both on the lower surface of the lower layer 1a and between the stacked layers, but may be formed only on the lower surface of the lower layer 1a. In the present embodiment, the circuit board is composed of two layers, but the present invention is also applicable to a circuit board composed of two or more layers. In this case, a GND pattern that overlaps the vibrator pads 5a and 5b in a plan view may be formed not only on the lower surface of the lowermost substrate but also on the intermediate layer.

  When providing a GND pattern overlapping the vibrator pads 5a, 5b in plan view on the intermediate layer, by forming a part of a plurality of electronic components mounted on the uppermost layer of the circuit board in a plan view including an area, The shielding effect mentioned above can be improved. Note that the vibrator pad that overlaps the GND pattern in plan view is not limited to the vibrator pads 5a and 5b. For example, in addition to the pair of vibrator pads 5a and 5b, part of the remaining vibrator pads 5c and 5d that are not electrically connected to the excitation electrode may overlap the GND pattern in plan view.

  In the present embodiment, a thin insulating protective film that covers the surface of the GND pattern GP1 excluding the functional terminal 7f is formed on the lower surface of the lower layer 1a. The insulating protective film is made of an insulating resin material, and plays a role of protecting the surface of the GND pattern GP1 made of metal from the external environment. The present invention may be configured such that the insulating protective film does not exist on the lower surface of the lower layer 1a.

  As shown in FIG. 4, of the vibrator pads 5a to 5d, two vibrator pads 5c and 5d that are not electrically connected to the excitation electrode are used as reference potentials, and the vibrator pads 5c and 5d are Of the six functional terminals 7a to 7f (terminals that are conductively joined to the external substrate) provided on the lower surface 110 of the lower substrate 1a, the power terminal 7a is arranged so as to overlap with the power terminal 7a in plan view. Noise included in the input current can be reduced. In the present embodiment, the GND pattern GP1 on the lower surface of the lower layer 1a is connected to the grounding terminal 7f, and is formed in an alphabetic “L” shape in plan view.

-Second Embodiment-
The second embodiment of the present invention will be described focusing on the differences from the first embodiment with reference to FIGS. FIG. 5 is a schematic top view of a circuit board used in the crystal oscillator according to the second embodiment of the present invention. In FIG. 5, for convenience of explanation, only the four transducer pads 8a to 8d are shown by solid lines. The area where the crystal resonator is mounted and the GND pattern GP1 and the power supply terminal 7a formed on the lower surface of the lower layer 11a of the circuit board 11 are indicated by dotted lines, and the mounting pattern on which the IC and other electronic components are mounted. Description is omitted. The description of the same configuration as that of the first embodiment is omitted.

  In the present embodiment, the circuit board 12 is composed of two layers, a lower layer substrate 11a and an upper layer substrate 11b. The shape of the pair of transducer pads 8a and 8b, which are input / output terminals, is circular in plan view (see FIG. 5). The vibrator pads 8a and 8b are formed to have a smaller area in plan view than the other vibrator pads 8c and 8d, and are electrically connected to the vibrator input / output terminals 4a and 4b via the wirings DP3 and DP4. It is connected.

  The pair of vibrator pads 8a and 8b are input / output terminals that are electrically connected to the excitation electrodes of the crystal vibrating piece, and overlap with the GND pattern GP1 on the lower surface of the lower layer 11a of the circuit board 11 in plan view. It has become. Although not shown in FIG. 5, a GND pattern (GP2) is also formed between the lower layer 11a and the upper layer 11b of the circuit board 11, and the GND pattern is also connected to the vibrator pads 8a and 8b. It arrange | positions so that it may overlap with planar view.

  On the other hand, the vibrator pads 8c and 8d have the reference potential as in the first embodiment, and the vibrator pad 8c overlaps the power supply terminal 7a on the lower surface of the lowermost substrate 11a in a plan view. It has become a relationship. With such a positional relationship, noise included in the input current from the power supply terminal 7a can be reduced.

  Next, the crystal resonator 20 mounted on the above-described four vibrator pads 8a, 8b, 8c, and 8d will be described with reference to FIGS. The crystal resonator 20 has a substantially rectangular parallelepiped shape and has an internal structure shown in FIG. That is, a crystal vibrating piece 23 is accommodated in a package (container) 21 having a recess 26 in the upper portion, and the crystal vibrating piece is bonded to the upper surface of the package 21 through a sealing member. The structure is hermetically sealed. FIG. 6 is a schematic sectional view taken along line BB in FIG.

  In FIG. 6, the quartz crystal vibrating piece 23 is an AT-cut rectangular quartz crystal plate in plan view, and a pair of excitation electrodes (not shown) are formed to face each other on the front and back main surfaces of the quartz crystal plate. The excitation electrode is led out to one short side of the quartz crystal vibrating piece via an extraction electrode (not shown).

  The package 21 is a box-shaped container whose base material is an insulating material such as ceramic, and the mounting portion 25 is provided on the inner bottom surface 260 of the recess 26. A pair of vibrating piece mounting terminals 26a and 26b are formed on the mounting portion 25, and the quartz crystal vibrating piece 23 is placed on the vibrating piece mounting terminals 27a and 27b via a bonding member 24 such as a metal bump or a conductive adhesive. The one end side is cantilevered.

  A pair of vias V and V penetrating the base material portion from the mounting portion 25 to the outer bottom surface 280 of the package facing the mounting portion are formed immediately below the resonator element mounting terminals 27a and 27b. Here, the via V has a structure in which a metal is filled in a substantially cylindrical through-hole penetrating the base material between the inner bottom surface 260 and the outer bottom surface 280. The via shape is not limited to a cylindrical shape. For example, it may have a conical shape in sectional view.

  In FIG. 7, four external terminals 9a, 9b, 9c, 9d are formed in the vicinity of the corners of the outer bottom surface 280 of the package (container). Of these four external terminals in the present embodiment, a pair of external terminals 9a and 9b electrically connected to an excitation electrode formed on a crystal vibrating piece to be described later is more than the other external terminals 9c and 9d of the reference potential. Also, the area in plan view is small. The external terminals 9a and 9b are circular in plan view, and the other external terminals 9c and 9d are rectangular in plan view. That is, the pair of external terminals 9a and 9b serving as input / output terminals are formed in a different shape and smaller than the other external terminals 9c and 9d.

  Of the both ends of the via V, the aforementioned resonator element mounting terminals 27a and 27b are formed at the end on the inner bottom surface 260 side, and a pair of external terminals 9a and 9b are formed at the end on the outer bottom surface 280 side of the via. It is formed (see FIG. 6). The pair of external terminals 9a, 9b having a circular shape in plan view is formed with a size that is slightly larger than the diameter of the via V.

  In the present embodiment, the resonator element mounting terminal 27a (27b), the input / output external terminal 9a (9b), and the vibrator pad 8a (8b) of the circuit board overlap with each other in plan view and have substantially the same area. ing. The external terminals 9a and 9b are significantly smaller than the other external terminals 9c and 9d. Specifically, in this embodiment, the diameter of 9a (9b) is φ0.35 mm with respect to the short side dimension 0.7 mm of the square 9c (9d).

  According to the above invention, the generation of stray capacitance can be suppressed. This is because the pair of external terminals 9a and 9b electrically connected to the excitation electrodes is formed to have a relatively smaller area in plan view than the other external terminals 9c and 9d, and for the pair of vibrators on the circuit board. This is because the pads 8a and 8b have shapes corresponding to the external terminals 9a and 9b. Therefore, in the above configuration, the overlapping area in plan view of the vibrator pads 8a and 8b and the GND patterns GP1 and GP2 is set so that the input / output vibrator pad has the same area (square) as the other vibrator pads. It can be made smaller than when it is formed. Generation of stray capacitance can be suppressed by reducing the overlapping area.

  On the other hand, a pair of vias V are also formed in a portion of the inner bottom surface 260 of the recess that is separated from the mounting portion 25. The external terminals 9c and 9d are finally electrically connected to the metallic lid 22 via the vias and the wall conductors 29 and the like. Thus, by electrically connecting the metal lid and the external terminal of the reference potential, it is possible to protect from noise outside the crystal resonator.

  According to the second embodiment of the present invention, in addition to suppression of stray capacitance, it is possible to reduce the influence of the stub on the signal when the oscillation frequency is increased. This is because the resonator element mounting terminal and input / output external terminal of the crystal resonator having the above-described configuration and the oscillator pad of the circuit board overlap in plan view and have substantially the same shape and area. This is because the path of the signal in the thickness direction of the circuit board is substantially the same straight line in a sectional view, and the influence of the stub on the signal can be reduced.

-Third embodiment-
A third embodiment of the present invention will be described with a focus on differences from the second embodiment with reference to FIG. FIG. 8 is a schematic view of the bottom surface of the crystal resonator mounted on the circuit board according to the third embodiment of the present invention as viewed from above. The circuit board (not shown) in this embodiment is the same as that in the second embodiment except for the configuration related to the vibrator pads (8a and 8b in FIG. 5). In this embodiment, the input / output vibrator pads are circular in plan view, but wirings led out from the pair of input / output vibrator pads are formed in addition to the wirings DP3 and DP4 in FIG. (Not shown). This wiring has a shape corresponding to the shape of an input / output external terminal of the crystal resonator described later.

  In FIG. 8, the crystal resonator 30 has a substantially rectangular parallelepiped shape as in the second embodiment, and four external terminals 10 a, 10 b, 10 c, and 10 d are formed on the outer bottom surface 300 of the crystal resonator 30. In the present embodiment, notches (so-called castellations) C1, C2, C3, and C4 extending in the depth direction of the package are formed at each corner of the outer surface of the package 31. The external terminals 10a and 10b are electrically connected to the excitation electrodes of the quartz crystal vibrating piece, and are notched from the ends of the pair of vias (not shown) on the outer bottom side of the package via the lead-out portions L1 and L2. It extends to C1 and C2.

According to the above configuration, it is possible to improve the bonding strength of the crystal resonator 30 on the circuit board by solder or the like. This extends excited vibration electrode electrically connected to a pair of external terminals 10a, 10b are formed on the end of the package outside the bottom of the via, and to notches C1, C2 adjacent to the end This is because the pair of vibrator pads for input / output of the circuit board has a shape corresponding to the pair of external terminals 10a and 10b. That is, since the conductor extends to the notches C1 and C2 in the external terminal 10a (10b), when the crystal unit 30 is mounted on the circuit board with solder, the solder creeps up to the notches C1 and C2. It becomes easy to be done. The joining strength of the external terminals 10a and 10b having a relatively small area can be supplemented by the solder creeping and joining of the solder to the lead-out portion. Thereby, it is possible to suppress the uneven distribution of the stress due to the bonding of the crystal resonator on the circuit board. The above configuration is particularly effective when the area of the pair of external terminals for input / output of the crystal resonator is significantly smaller than the areas of the other two external terminals as in this embodiment.

  In the third embodiment described above, of the four notches, at least one notch may be formed so as to cover the entire vertical direction of each corner of the outer surface of the package. In other words, an external terminal having a reference potential that is not electrically connected to the excitation electrode is formed to extend to the upper surface of the package via the notch, and is electrically connected to the metal lid via the conductive sealing member. May be. Thus, by electrically connecting the metal lid and the external terminal of the reference potential, it is possible to protect from noise outside the crystal resonator.

  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, 11 Circuit board 1a, 11a Lower layer board 1b, 11b Upper layer board 2, 20, 30 Crystal oscillator 4a, 4b Oscillator input / output terminal 5, 8 Oscillator pad (circuit board) (5a-5d, 8a- 8d)
9, 10 External terminal (crystal oscillator) (9a-9d, 10a-10d)
GP1, GP2 Reference potential conductor pattern V Via

Claims (2)

In a piezoelectric oscillator in which an oscillation circuit is configured by mounting a piezoelectric vibrator, a semiconductor integrated circuit element, and other electronic components on a circuit board,
The circuit board is a multilayer substrate made of an insulating material, and includes a reference potential conductor pattern at least on the lower surface of the lowermost substrate ,
A mounting pattern on which a piezoelectric vibrator, a semiconductor integrated circuit element, and other electronic components are mounted is formed on the upper surface of the substrate.
The mounting pattern includes four vibrator pads that are conductively bonded to the piezoelectric vibrator, and a pair of vibrator input / output terminals.
Of the four vibrator pads, a pair of adjacent vibrator pads is electrically connected to an excitation electrode formed on the piezoelectric vibrating piece and is adjacent to the pair of vibrator input / output terminals. Arranged
Of the four vibrator pads, at least the pair of vibrator pads overlaps the conductor pattern in plan view ,
The package of the piezoelectric vibrator has a mounting portion on which the piezoelectric vibrating piece is mounted inside the package, and has four external terminals on the outer bottom surface of the package,
Of the four external terminals, a pair of external terminals electrically connected to the excitation electrode is:
The area in plan view than two external terminals that are formed on the end portion of the pair of vias that penetrate the base material from the mounting portion to the outer bottom surface of the package and that are not electrically connected to the excitation electrode Is formed small,
The piezoelectric oscillator, wherein the adjacent pair of vibrator pads has a shape corresponding to the pair of external terminals. Cutout portions extending in the depth direction of the package are formed at each corner of the outer surface of the piezoelectric vibrator package, and are electrically connected to at least the excitation electrode among the four external terminals of the piezoelectric vibrator. The pair of external terminals thus formed is formed on an end portion of the via on the outer bottom surface side of the package, and extends to a notch portion close to the end portion. Piezoelectric oscillator.

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