JP6538408B2 - Piezoelectric device - Google Patents

Description

  The present invention relates to a piezoelectric device having a structure in which a piezoelectric chip having a vibrating portion and a frame portion surrounding the vibrating portion is sandwiched between a lid portion and a base portion.

  An AT-cut quartz oscillator is known as a representative of piezoelectric devices. However, with the progress of miniaturization of AT-cut quartz oscillators, production of quartz oscillators becomes difficult with a mechanical processing method, and a structure has been proposed to avoid this.

  For example, Patent Document 1 proposes a piezoelectric device having a structure in which a piezoelectric chip (referred to as a quartz frame in the literature) integrally formed with a vibrating portion and a frame portion surrounding it is sandwiched between a lid portion and a base portion. ing. Specifically, the piezoelectric device includes, between the vibrating portion and the frame portion, a penetrating portion that cuts off both of the vibrating portion and the frame portion, and a connecting portion that connects a part of the vibrating portion and the frame portion. Furthermore, excitation electrodes are provided on the front and back of the vibrating portion. Furthermore, a first lead-out electrode is provided on the first main surface of each of the connection portion and the frame portion, and a second lead-out electrode is provided on the second main surface of each of the connection portion and the frame portion. These first and second lead-out electrodes are connected to corresponding excitation electrodes. The first lead-out electrode is provided on substantially the entire first main surface of the frame portion, and the second lead-out electrode is provided on substantially the entire second main surface of the frame portion.

  On the other hand, the region of each of the lid portion and the base portion in contact with the frame portion is provided with a metal film capable of eutectic bonding with the first lead electrode or the second lead electrode. Then, the first lead electrode or the second lead electrode and the metal film are joined by eutectic bonding to join the lid portion to one surface of the piezoelectric chip and the base portion to the other surface of the piezoelectric chip. ing.

JP 2012-195918 A

  However, in the case of the conventional piezoelectric device described above, since the first lead electrode and the second lead electrode are provided to face the front and back of the frame portion of the piezoelectric chip, capacitance caused by the lead electrode is generated. As a result, the parallel capacitance of the crystal unit is increased. For this reason, since the so-called capacity ratio of the crystal unit becomes large, depending on the application of the crystal unit, the variable amount of frequency is insufficient.

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a piezoelectric device in which the parallel capacitance is difficult to increase.

  In order to achieve this object, the piezoelectric device of the present invention comprises a piezoelectric chip, a lid portion and a base portion. The piezoelectric chip includes a vibrating portion, a frame portion surrounding the vibrating portion, a connecting portion connecting the vibrating portion and the frame portion, and a first excitation electrode provided on a first main surface of the vibrating portion. A second excitation electrode provided on the second main surface of the vibrating portion, and a first lead-out electrode provided on the first main surface of each of the connecting portion and the frame portion and connected to the first excitation electrode; And a second lead-out electrode provided on the second main surface of each of the connecting part and the frame part and connected to the second excitation electrode. Further, the lid portion is joined to the piezoelectric chip on one of the first and second main surfaces of the frame portion. Further, the base portion is bonded to the piezoelectric chip on the main surface of the first and second main surfaces of the frame opposite to the side to which the lid portion is bonded. The portion of the first lead electrode on the frame is provided on the inner peripheral side or the outer peripheral side of the first main surface of the frame, and the portion on the frame of the second lead electrode is provided. A portion is provided on a side of the second main surface of the frame portion not facing the first lead electrode.

  Here, with the inner peripheral side or the outer peripheral side, typically, the vibrating portion side is the inner peripheral side bordering on the center of the width of the frame portion, and the opposite side is the outer peripheral side. It is preferable to border the center of the width of the frame because the widths of the first and second lead electrodes can be made equal and the bonding width of the eutectic bonding can be made equal. However, the boundary between the inner circumferential side and the outer circumferential side may be unevenly distributed intentionally on the vibrating portion side or the opposite side from the center of the frame portion.

  When the first and second lead-out electrodes are provided so as not to oppose each other on the inner peripheral side or the outer peripheral side of the frame, it is preferable to distribute the first and second lead electrodes substantially all around the frame. However, in some cases, this uneven distribution rate can be changed in consideration of the reduction rate of the target capacitance. However, for the purpose of the present invention, the first and second lead electrodes are not opposed to each other at a ratio of preferably 50% or more, more preferably 70% or more with respect to the length or area of the entire circumference of the frame. It is good to make it unevenly distributed.

  Also, the connecting part may be one or two or more. However, in the case of one location, there is an advantage that the interaction between the frame and the vibrating part (for example, the effect of acoustic leak or stress) can be reduced easily. In addition, when making a connection part into one place, the parts provided in the 1st main surface of this connection part, and the 2nd main surface of each of the 1st lead-out electrode and the 2nd lead-out electrode do not face each other good. This is to avoid an increase in capacitance at the connection portion. For example, the first lead electrode may be provided in a half area of the first main surface in the width direction of the connection portion, and the second lead electrode may be provided on the second main surface of the connection portion not facing the first lead electrode.

  Further, for bonding between the piezoelectric chip and the lid portion and bonding between the piezoelectric chip and the base portion, any method such as a method using low melting point glass, a method using eutectic bonding, a method using an adhesive can be used. . In the case of the method using eutectic bonding, there are merits such as less influence of the outgassing as compared with the case of using a low melting point glass or an adhesive and that the first and second lead electrodes can be used as one of the bonding members. When eutectic bonding is used, the first and second lead electrodes are provided along the entire circumference of the main surface of the frame, and the base corresponds to the second lead electrode or the first lead electrode in contact with the first lead electrode. The region is provided with a first metal film to be eutectically bonded to the lead electrode, and the lid portion is eutectic to the lead electrode in a region corresponding to the first lead electrode or the second lead electrode in contact with the lid portion. A second metal film to be bonded is provided. In this case, eutectic bonding can be easily performed, which is useful for reducing the number of manufacturing steps and costs of the piezoelectric device.

  Further, in the practice of the present invention, the frame portion of the piezoelectric chip has a rectangular shape in a plan view, and the first and second lead-out electrodes are widened so as to extend across the entire width of the frame portion at four corners of the frame portion. It is preferable to use one that has a wide portion. In this case, the first and second metal films provided on the lid portion and the base portion also widen in that portion. This increases the bonding area at the four corners of the piezoelectric device. In the piezoelectric device, junction breakdown is likely to occur from the four corners, but by increasing the junction area of the four corners as described above, the incidence of junction breakdown from the four corners can be reduced.

  Further, in the practice of the present invention, the base portion has a first mounting terminal and a second mounting terminal on the surface opposite to the piezoelectric chip, and connects the first lead electrode and the first mounting terminal. It is preferable to include a first via wiring and a second via wiring connecting the second lead electrode and the second mounting terminal. In the case where the bonding between the piezoelectric chip and the lid portion and the bonding between the piezoelectric chip and the base portion are performed by eutectic bonding, it becomes difficult to lead the wiring to the outside of the piezoelectric device, but the above first and second via wiring structures Adopting it makes it easy.

  According to this aspect of the invention, since the area of the connecting portion or the frame portion where the first and second lead-out electrodes face each other can be narrowed, unnecessary capacitance can be reduced.

(A), (B) is a perspective view for demonstrating especially the piezoelectric chip 10 of the piezoelectric device of 1st Example, (A) is a figure by the side of the 1st principal surface of piezoelectric chip 10, (B ) Is a diagram of the second main surface side of the piezoelectric chip 10. FIG. 1 is a perspective view for explaining the entire piezoelectric device 100 of the first embodiment, and is a diagram showing the piezoelectric chip 10, a base portion 30, and a lid portion 50 in a disassembled state. These are the figure which showed the upper surface, the side, and the bottom face collectively, in order to demonstrate the external appearance of the piezoelectric device 100 of 1st Example. (A), (B) is a perspective view for demonstrating especially the piezoelectric chip 200 of the piezoelectric device of 2nd Example, (A) is a figure of the 1st main surface side of the piezoelectric chip 200, (B) ) Is a diagram of the second main surface side of the piezoelectric chip 200. FIG. [FIG. 6] is a figure explaining the example of a manufacturing method of the piezoelectric device 100 of 1st Example, and is explanatory drawing of the piezoelectric wafer 10W which had many piezoelectric chips 10 especially. [FIG. 6] is a figure explaining the example of a manufacturing method of the piezoelectric device 100 of 1st Example, It is explanatory drawing of base wafer 30W which had many base parts 30 especially. [FIG. 6] is a figure explaining the example of a manufacturing method of the piezoelectric device 100 of 1st Example, It is explanatory drawing of the lid wafer 50W which had many lid parts 50 especially.

  Hereinafter, embodiments of the piezoelectric device of the present invention will be described with reference to the drawings. The drawings used for the description are only schematically shown to the extent that the present invention can be understood. Moreover, in each figure used for description, it attaches | subjects and shows the same number about the same component, and the description may be abbreviate | omitted. In addition, the shapes, dimensions, materials, and the like described in the following embodiments are only preferable examples within the scope of the present invention. Accordingly, the present invention is not limited to the following examples.

(First embodiment)
FIGS. 1A and 1B are perspective views for explaining a piezoelectric chip 10 provided in the piezoelectric device of the first embodiment, and in particular, FIG. 1A is a view on the first main surface S1, and FIG. It is a figure of 2 main surface S2 side.

  The piezoelectric chip 10 is provided on the vibrating portion 12, the frame portion 14 surrounding the vibrating portion 12, the connecting portion 16 connecting the vibrating portion 12 and the frame portion 14, and the first main surface S1 of the vibrating portion 12. The first excitation electrode 18a, the second excitation electrode 18b (FIG. 1B) provided on the second main surface S2 (FIG. 1B) of the vibrating portion, and the connecting portion 16 and the frame portion 14 respectively. On the first lead electrode 20a provided on the first main surface S1 of the first embodiment and connected to the first excitation electrode 18a, and on the second main surface S2 (FIG. 1B) of the connecting portion 16 and the frame portion. And a second lead-out electrode 20b (FIG. 1 (B)) provided and connected to the second excitation electrode 18b.

  The first lead electrode 20 a is configured of a first portion 20 aa provided on the connecting portion 16 and a second portion 20 ab provided on the frame portion 14. The second lead-out electrode 20 b (FIG. 1B) includes a first portion 20 ba provided on the connection portion 16 and a second portion 20 bb provided on the frame portion 14. Further, the connecting portion 16 is one place, and the piezoelectric chip 10 is a penetrating portion 22 which cuts off the vibrating portion 12 and the frame portion 14 in a portion other than the connecting portion 16 between the vibrating portion 12 and the frame portion 14. Is provided. Furthermore, the piezoelectric chip 10 is provided with castellations 24 in a part of the frame portion 14, specifically, in the inside portion of one corner of the frame portion 14 in this example. The castellation 24 is for connecting the first lead electrode 20a to the first via wiring (details will be described later) of the base portion (details will be described later).

  The vibrating portion 12 has a so-called table top structure including a central portion 12a and a peripheral portion 12b thinner than the central portion 12a. Furthermore, the vibrating portion 12 has a rectangular planar shape. Further, the planar shape of the frame portion 14 is also rectangular. Accordingly, the planar shape of the entire piezoelectric chip 10 in the case of this embodiment is square.

  Further, in the piezoelectric chip 10, the second portion 20ab of the first lead electrode 20a is provided on the inner peripheral side (the vibrating portion 10 side) of the first main surface S1 of the frame portion 14, and the second lead The second portion 20bb (FIG. 1B) of the electrode 20b is the side of the second main surface S2 (FIG. 1B) of the frame 14 not facing the first lead electrode 20a, that is, in this example It is provided on the outer peripheral side of the frame portion 14. Moreover, each of the first extraction electrode 20a and the second extraction electrode 20b is provided on the entire periphery of the frame portion 14, that is, in the case of this example, on the frame portion 14 in a square ring shape in plan view. It is In this case, since the first lead electrode 20a and the second lead electrode 20b are provided in different regions with respect to the central portion in the width direction of the frame portion 14, the width of each of the lead electrodes 20a and 20b is , Half the width W of the frame portion 14 (W / 2).

  The first portion 20aa provided on the connection portion 14 of the first lead electrode 20a is provided in a half area of the first main surface S1 of the connection portion 14 in the width direction, and the first portion 20aa of the second lead electrode 20b is provided. The first portion 20ba (FIG. 1B) provided on the connecting portion 14 is provided in a region not facing the first portion 20aa of the first extraction electrode, that is, in a half region in the width direction of the connecting portion is there.

The piezoelectric chip 10 itself is constituted by an AT-cut crystal plate. The excitation electrode and the extraction electrode are composed of a laminated film having chromium or nickel as a base and gold formed thereon.
According to the piezoelectric chip 10 described above, the area of the connecting portion 14 and the frame portion 16 in which the first and second lead-out electrodes 20a and 20b face each other can be substantially zero. The capacitance can be reduced compared to the conventional one.

Next, with reference to FIG. 2, the structure of the base 30, the structure of the lid 50, and the joint structure of the base 30, the lid 50, and the piezoelectric chip 10 described above will be described.
The base portion 30 of the first embodiment has the same and substantially the same dimensions as the piezoelectric chip 10, that is, the planar shape is square and substantially the same. Then, in a region of the surface of the base portion 30 to be joined to the piezoelectric chip 10, in a region corresponding to the second portion 20bb (FIG. 1B) of the second lead electrode 20b, eutectic with the second lead electrode 20b It comprises a first metal film 32 to be bonded.
Further, mounting terminals 34a to 34d for connecting the piezoelectric device to an external wiring board (not shown) or the like are provided on the surface of the base 30 opposite to the surface to which the piezoelectric chip 10 is bonded.

  Further, in the portion of the base portion 30 corresponding to the castellation 24 of the piezoelectric chip 10, the first via wiring 36a for connecting the first lead electrode 20a of the piezoelectric chip to the mounting terminal 34a (the first mounting terminal 34a) It is equipped. In addition, a second via wiring 36b is provided in a suitable area other than the area where the first via wiring 36a is provided in the base portion 30, in this example, at a corner diagonally to the position of the first via wiring 36a. There is. The second via wiring 36 b is for connecting the second lead electrode 20 b of the piezoelectric chip to the mounting terminal 34 b (second mounting terminal 34 b). The first and second via wirings 36a and 36b have a structure in which a through hole is provided in the base 30, and a suitable conductive material is filled in the through hole. In this example, four mounting terminals 34a to 34d are provided. The mounting terminals 34c and 34d can be used, for example, as a ground terminal or as terminals for increasing the mounting strength. However, only the first and second mounting terminals 34a and 34b may be provided.

  In addition, the lid portion 50 in the embodiment has the same and substantially the same dimensions as the piezoelectric chip 10, that is, the planar shape is substantially the same as the square shape. Then, in a region corresponding to the portion provided on the frame portion 14 of the first lead electrode 20a, that is, the second portion 20ab)) on the surface to be bonded to the piezoelectric chip 10, the first lead electrode 20a A second metal film 52 is crystallized.

As in the case of the piezoelectric chip 10, the base portion 30 and the lid portion 50 are constituted by an AT cut plate of quartz. Further, as a material of the first metal film 32 and the second metal film 52, known materials such as a gold silicon alloy, a gold germanium alloy, a gold tin alloy and the like are used.
In the configuration described with reference to FIG. 2, the piezoelectric chip 10 and the base 30 are formed by eutectic bonding of the second portion 20bb of the second lead wire 20b (FIG. 1B) and the first metal film 32. The piezoelectric chip 10 and the lid 50 are joined by eutectic metal joining of the second portion 20 ab of the first lead-out wiring 20 a and the second metal film 52. The internal space of the piezoelectric device configured by joining the piezoelectric chip 10, the base portion 30, and the lid portion 50 is a vacuum or a nitrogen atmosphere or an inert gas atmosphere.

  FIG. 3 is a view showing the appearance of the piezoelectric device 100 according to the first embodiment described above, and is a view showing the top, side and bottom together. The figure shows a state in which the piezoelectric chip 10, the base portion 30 and the lid portion 50 are stacked, and four mounting terminals 34a to 34d are provided on the bottom surface of the base portion.

Second Embodiment
Next, the piezoelectric device of the second embodiment will be described. FIG. 4 is an explanatory view thereof, and is a perspective view focusing on the piezoelectric chip 200 provided in the piezoelectric device of the second embodiment. Similarly to FIG. 1, the piezoelectric chip 200 is shown in a state (FIG. A) when viewed from the one principal surface side and in a state (FIG. B) when viewed from the other principal surface side.

The difference between the piezoelectric chip 200 of the second embodiment and the piezoelectric chip 10 of the first embodiment is the shape of the portion provided on the frame of the first and second lead electrodes. That is, the piezoelectric chip 200 of the second embodiment has the widening portion 206 which is widened so that each of the first extraction electrode 202 and the second extraction electrode 204 is spread over the entire width of the frame 14 at the four corners of the frame 14. It is characterized by Although not shown, the first metal film and the second metal film provided to the base portion and the lid portion also have a widened portion obtained by widening the portion corresponding to the widened portion 206. The other configuration is the same as that of the first embodiment.
According to the structure of the second embodiment, the bonding area between the piezoelectric chip and the base and the bonding area between the piezoelectric chip and the lid at the corners of the piezoelectric device are at least twice as large as those in the first embodiment. Thus, the joint strength at the corners can be made stronger than in the first embodiment.

(Description of manufacturing method)
Next, in order to deepen the understanding of the present invention, an example of a method of manufacturing the piezoelectric device 100 will be briefly described with reference to FIGS.
As shown in FIG. 5, an AT-cut quartz wafer is prepared, and the quartz wafer is processed by a known photolithographic technique, wet etching technique, film forming technique, etc. to form the piezoelectric chips 10 of the first embodiment in a matrix The piezoelectric wafer 10W formed on is manufactured. At this time, the frequency adjustment of the vibration unit is also performed. In addition, the broken line shown by "L" in FIG. 5 is a location divided | segmented by dicing later (the same in FIG. 6, FIG. 7).
The base wafer 30W and the lid wafer 50W are formed respectively by the same method as the method of manufacturing the piezoelectric wafer 10W (FIG. 6, FIG. 7).

  Next, the piezoelectric wafer 10W, the base wafer 30W and the lid wafer 50W are stacked in a predetermined positional relationship, and then, in a state where they are placed in a predetermined atmosphere, they are pressurized and heated at a predetermined pressure and temperature. In this process, eutectic bonding occurs to bond the wafers. Next, the bonded wafer is diced along dicing lines to separate the piezoelectric devices from the wafer.

    Although the embodiment of the piezoelectric device of the present invention has been described above, the present invention is not limited to the above-described embodiment. For example, in the above-mentioned example, although a vibration part was made into the thing of a table top structure, of course, you may be a structure other than this. Although the vibrating portion has a square shape in plan view, the shape of the vibrating portion may be another structure. Moreover, although quartz was used as a piezoelectric material, it is not restricted to this.

10: Piezoelectric chip of the embodiment 10W: Piezoelectric wafer 12: Vibrating part 12a: Center part of vibrating part 12b: Peripheral part of vibrating part 14: Frame part 16: Connecting part 18a: First excitation electrode, 18b: Second Excitation electrode 20a: first extraction electrode, 20b: second extraction electrode 20aa: first portion of first extraction electrode (portion on connection portion)
20ab: Second portion of first extraction electrode (portion on frame)
20ba: The first part of the second extraction electrode (the part located on the connecting part)
20bb: second part of second extraction electrode (part on frame)
22: penetrating portion 24: castellation 30: base portion, 30 W: base wafer 32: first metal film 34a: first mounting terminal, 34b: second mounting terminal, 34c, 34d: mounting terminal 36a: first via wiring, 36b: second via wiring 50: lid portion, 50W: lid wafer 52: second metal film S1: first main surface, S2: second main surface L: dicing line 100: piezoelectric device of the first embodiment 200: Piezoelectric Chip of Piezoelectric Device of Second Embodiment 202: First Lead Wiring of Second Embodiment,
204: Second lead-out wire of the second embodiment 206: Widening section

Claims (2)

A vibrating portion; a frame portion surrounding the vibrating portion; a connecting portion connecting the vibrating portion to the frame; a first excitation electrode provided on a first main surface of the vibrating portion; A second excitation electrode provided on the main surface of 2, a first lead-out electrode provided on the first main surface of each of the connection portion and the frame portion and connected to the first excitation electrode, the connection portion, and A piezoelectric chip comprising a second lead-out electrode provided on a second main surface of each of the frame parts and connected to the second excitation electrode, the main surface of any one of the main surfaces of the frame parts A piezoelectric device comprising: a lid portion joined to a piezoelectric chip; and a base portion joined to the piezoelectric chip on a main surface of the frame opposite to the side to which the lid portion is joined.
A portion of the first lead electrode on the frame portion is provided on an inner peripheral side or an outer peripheral side of the first main surface of the frame portion,
A portion of the second lead electrode on the frame portion is provided on a side of the second main surface of the frame portion not facing the first lead electrode,
The base portion includes, in a region corresponding to the second lead-out electrode or the first lead-out electrode in contact therewith, a first metal film which is eutectically bonded to the lead-out electrode,
The lid portion includes, in a region corresponding to the first lead electrode or the second lead electrode in contact with the lid portion, a second metal film which is eutectic-bonded to the lead electrode,
The piezoelectric device according to claim 1, wherein the frame portion has a rectangular shape in plan view, and the first and second lead-out electrodes are widened at four corners of the frame portion so as to extend over the entire width of the frame portion. In the piezoelectric device according to claim 1 ,
The base portion has a first mounting terminal and a second mounting terminal on the surface opposite to the piezoelectric chip,
And,
Providing a first via wiring connecting the first lead-out electrode and the first mounting terminal, and a second via wiring connecting the second lead-out electrode and the second mounting terminal; Feature Piezoelectric device.