JP3991274B2 - Piezoelectric device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric device, and more particularly to a piezoelectric device suitable for vacuum-sealing a package that is required to be reduced in size and thickness.
[0002]
[Prior art]
Piezoelectric devices are used in various electronic devices. In recent years, piezoelectric devices are required to be further reduced in size and thickness as electronic devices become smaller and thinner. The piezoelectric resonator element mounted inside the piezoelectric device is kept in a vacuum inside the package that encloses the piezoelectric resonator element because the vibration is inhibited even in gas and the frequency shifts as the size of the piezoelectric resonator element increases. There is a need. For this reason, a hole for vacuum sealing is provided in the package base part or the package lid for mounting the piezoelectric vibrating piece inside. This hole is provided at any location facing the center of the package or the center of the lid, or the weight of the excitation electrode or tuning-fork type piezoelectric vibrating piece provided on the piezoelectric vibrating piece.
[0003]
And there exists the following technique as a method of sealing this hole. A circular recess having a depth of 40 μm and an opening surface of 350 μm in diameter is provided outside the hole, and a ball-shaped sealing material having a diameter of approximately 200 μm is placed in the recess. This sealing material is a technique of irradiating and melting the sealing material to close the hole.
[0004]
Moreover, the technique of patent document 1 is mentioned as another method. In this technique, a through hole is provided in a part of the lid, and solder as a sealing material is provided around the through hole. Then, after the package and the lid are fixed by welding, the package is placed in a vacuum container to create a vacuum inside the package. When the solder is melted by irradiating the sealing material with an electron beam or a laser in this vacuum state, the solder flows into the through hole and seals the inside of the hole. This technology shields between the lid and the piezoelectric vibrating piece so that the molten solder flux does not adhere to the quartz vibrating piece, or the electron beam is not directly applied to the quartz vibrating piece through the through hole. It is set as the structure which can also provide a board.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-193967 [0006]
[Problems to be solved by the invention]
However, when a ball is used as the sealing material, the depth of the recess is much shallower than the size of the sealing material, so that there is a problem that the sealing material does not fit well and moves. Moreover, since it is technically difficult to further reduce the ball-shaped sealing material, it is difficult to reduce the size and thickness of the piezoelectric device.
[0007]
Further, in the technique of Patent Document 1, if the position of the through hole provided in the lid is the central portion of the piezoelectric device, the through hole is not closed with a sealing material when the shield plate is not provided inside the package. There is a possibility that an electron beam or a laser for melting the solder as the sealing material is directly irradiated to the piezoelectric vibrating piece through the through hole. For this reason, there is a possibility of damaging the piezoelectric vibrating piece. When the piezoelectric vibrating piece is damaged, there arises a problem that the oscillation frequency of the piezoelectric vibrating piece changes. Even when only the solder is irradiated with an electron beam or the like, gas is generated when the solder is melted, and this gas may adhere to the piezoelectric vibrating piece and change the oscillation frequency. When the oscillation frequency changes, the oscillation frequency varies for each piezoelectric device, making it difficult to supply a highly accurate piezoelectric device. Further, in order to solve the above problems, when a shield plate is provided between the lid and the piezoelectric vibrating piece, there is a drawback that the package becomes thick because the shield plate is provided, and the package is not small and thin.
[0008]
Moreover, when providing a hole part in a package container, it is necessary to provide between the external terminals formed in the package lower surface. However, even if the package is downsized, the size of the external terminals cannot be reduced, the gap between the external terminals is narrowed, and the place where the hole is provided is restricted. In addition, when the hole is sealed with a conductive sealing material such as solder, there is a risk of short-circuiting if the hole is shifted from a predetermined mounting position of the package. For this reason, if a hole is provided in the package container, it is not suitable for downsizing.
[0009]
The present invention has been made to solve the above-described problems. Even if a hole for vacuum sealing is provided in the lid of the package, it is further reduced in size and thickness without being shifted in frequency to the oscillation frequency of the piezoelectric vibrating piece. It is an object of the present invention to provide a piezoelectric device that can be manufactured.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a piezoelectric device according to the present invention is a piezoelectric device in which a piezoelectric vibrating piece is mounted inside a package and the upper part of the package is sealed with a lid, and the lid is made of metal. In addition, a vacuum sealing hole is provided in the lid at a position facing the connection electrode formed in the piezoelectric vibrating piece. In this case, the hole portion can be configured by providing a concave portion for storing the sealing material and a through hole penetrating the lid body from the lower surface of the concave portion. The sealing material may be a thin plate pellet.
[0011]
Thereby, since the connection electrode of the piezoelectric vibrating piece is fixed to the package, it does not contribute to vibration when the piezoelectric vibrating piece oscillates. A hole is provided in the lid at a position opposite to the connection electrode, and when the thin plate-like pellet placed in the recess constituting the hole is irradiated with a laser, the pellet is melted to seal the hole. To do. At this time, since the hole is provided in the upper part of the connection electrode, even if gas is generated when the pellet is melted, only gas particles adhere to the connection electrode, and the oscillation frequency of the piezoelectric vibrating piece is reduced. Sealing can be performed without adverse effects. In addition, since the opening of the through hole is closed by the pellet, the piezoelectric vibrating piece, the connection electrode, and the package can be directly irradiated by the laser and sealed without being damaged. For this reason, damage to the laser and adhesion of gas do not adversely affect the oscillation frequency of the piezoelectric vibrating piece, so that it is possible to supply a highly accurate piezoelectric device in which the oscillation frequency of the piezoelectric vibrating piece does not shift.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a piezoelectric device according to the present invention will be described with reference to the accompanying drawings.
1 shows a piezoelectric device, FIG. 1 (a) is a plan view of the piezoelectric device, and FIG. 1 (b) is a side sectional view taken along line AA of FIG. 1 (a). FIG. 2 is an enlarged side sectional view of a hole formed in the lid of the package. The package 12 of the piezoelectric device 10 has a box-type structure in which a frame-shaped sealing ring 16 is laminated on a rectangular ceramic insulating substrate 14 and a lid 18 serving as a lid of the package 12 is provided on the sealing ring 16. is there. Kovar is used as the material of the sealing ring 16, and the surface of the Kovar is plated with nickel and gold.
[0013]
A cantilever-type piezoelectric vibrating piece 20 is mounted on the ceramic insulating substrate 14 inside the package 12. Excitation electrodes 22 are formed by sputtering, plating, or the like at the center of the upper and lower surfaces of the piezoelectric vibrating piece 20 (the excitation electrode on the lower surface is not shown). In addition, connection electrodes 24 are continuously provided on the upper and lower surfaces at both corners of one short side of the piezoelectric vibrating piece 20. The upper surface side excitation electrode 22 is connected to one connection electrode 24a, and the lower surface side excitation electrode 22 is connected to the other connection electrode 24b. Each electrode formed on the upper and lower surfaces of the piezoelectric vibrating piece 20 has a symmetrical shape between the upper surface and the lower surface.
[0014]
A pair of mount electrodes (not shown) for mounting the piezoelectric vibrating piece 20 is formed on the package 12 by thick film printing, plating, or the like corresponding to the connection electrode 24 of the piezoelectric vibrating piece 20. Then, the mount electrode and the connection electrode 24 are bonded to each other by the conductive adhesive 26 so that the mount electrode and the connection electrode 24 are mounted on the package 12.
[0015]
The lid 18 is formed of a metal having a nickel plating on the Kovar surface. The lid 18 is provided with a hole 28 in the upper portion facing the connection electrode 24a connected to the excitation electrode 22 provided on the upper surface of the piezoelectric vibrating piece 20 when the piezoelectric device 10 is formed. The hole 28 is provided to seal the inside of the package 12 with the pellet 30 shown in FIG. Further, the hole portion 28 formed in the lid 18 is pulled out from an excitation electrode (not shown) provided on the lower surface of the piezoelectric vibrating piece 20 and is connected to the upper portion facing the connection electrode 24b that wraps around the upper surface or the connection electrode 24a. However, it is preferable that the connection electrode 24a connected to the excitation electrode 22 formed on the upper surface of the piezoelectric vibrating piece 20 is formed on the upper portion.
[0016]
The hole portion 28 includes a recess 32 and a through hole 34. The recess 32 is provided facing the outside of the package 12 and stores the pellet 30 serving as a sealing material. The through hole 34 penetrates from the lower surface of the recess 32 to the inside of the package 12 and has an opening area smaller than that of the recess 32. The through hole 34 is provided at a position where the opening of the through hole 34 is reliably blocked by the pellet 30 when the pellet 30 is placed in the recess 32, for example, near the center of the recess 32.
[0017]
Further, the pellet 30 is made of a metal such as a gold-tin alloy or a gold-germanium alloy, and has a shape smaller than the concave portion 32 provided in the lid 18, that is, even if the pellet 30 is melted, the pellet 30 melts from the concave portion 32. It is formed in a size that does not flow out.
[0018]
Next, specific examples of the lid 18 and the pellet 30 will be described. In this embodiment, the lid 18 is made of a metal with nickel plating on the Kovar surface, and the thickness of the lid 18 is 70 μm. The concave portion 32 and the through hole 34 of the hole portion 28 provided in the lid 18 are formed by pressing, the concave portion 32 is a circular shape having a depth of 40 μm and a diameter of 200 μm, and the through hole 34 is a circular hole having a diameter of 100 μm. is there. The hole 28 is provided at a position facing the connection electrode 24 a connected to the excitation electrode 22 formed on the upper surface of the piezoelectric vibrating piece 20. The pellet 30 is a disk having a thickness of 30 μm and a diameter of 150 μm, and is formed by pressing.
[0019]
In the method of forming the piezoelectric device 10 configured as described above, a sealing ring 16 is first laminated on the ceramic insulating substrate 14, and a piezoelectric vibrating piece is formed using a conductive adhesive 26 on the mount electrode on the ceramic insulating substrate 14. 20 is implemented. Next, the lid 18 is fixed to the upper surface of the package 12 by seam welding. Specifically, roller electrodes having side surfaces formed in a tapered shape are brought into contact with the peripheral portions of both sides of the lid 18 that are joined to the upper surface of the package 12. When a high current is applied from the roller electrode to the lid 18, a portion with high electrical resistance such as between the lid 18 and the sealing ring 16 generates heat, and the temperature of the lid 18 rises. The current of the roller electrode is adjusted so that the temperature of the lid 18 rises to about 1450 ° C., which is the melting point of nickel plating. With this temperature rise, the nickel plating on the surface of the lid 18 is melted, and this serves as a sealing material to hermetically seal between the lid 18 and the sealing ring 16. The entire circumference of the lid 18 is fixed to the sealing ring 16 by moving the roller electrode along the peripheral edge of the lid 18 while rotating the roller electrode.
[0020]
Next, the package 12 is put into a vacuum container or the like to evacuate the container. At this time, since the hole portion 28 of the package 12 is opened, the inside of the container is evacuated and the inside of the package 12 is also evacuated. Next, the pellet 30 placed in the recess 32 provided in the lid 18 is irradiated with a laser to melt the pellet 30 and close the hole 28. At this time, since the through hole 34 of the hole 28 is provided at a position where the pellet 30 is blocked, for example, near the center of the recess 32, the piezoelectric vibrating reed 20 and the connection electrode 24 are not damaged by the laser. The position of the through hole 34 may be determined in consideration of the maximum error of the recess 32, the minimum error of the pellet 30 and the maximum error of the through hole 34. When gas is generated when the pellet 30 is melted, gas particles adhere to the connection electrode 24 under the hole 28. However, when the piezoelectric vibrating piece 20 of the piezoelectric device 10 oscillates, the vibration energy at the center of the piezoelectric vibrating piece 20 becomes the highest, the vibration energy attenuates toward the end, and the vibration energy at the end. Is the lowest. Further, since the connection electrode 24 portion of the piezoelectric vibrating piece 20 is fixed to the package 12, it does not contribute to oscillation vibration. That is, the position where the gas adheres is a portion that does not affect the oscillation of oscillation.
[0021]
According to such an embodiment, the hole portion 28 provided in the lid 18 is not near the center portion of the excitation electrode 22 where the oscillation frequency of the piezoelectric vibrating piece 20 is likely to cause a frequency shift, and does not contribute to oscillation vibration. It is provided on the upper part facing the connection electrode 24. For this reason, even if the gas is generated when the pellet 30 is melted and the gas adheres under the hole 28, the bottom of the hole 28 is the connection electrode 24 that does not contribute to the oscillation of the piezoelectric vibrating piece 20. The vibration of the resonator element 20 is not adversely affected. Moreover, since only the connection electrode 24 is formed in the lower part of the hole part 28, a short circuit with other electrodes does not occur. That is, the package 12 can be sealed without causing a frequency shift in the oscillation frequency of the piezoelectric vibrating piece 20 when the package 12 is sealed. Therefore, it is possible to supply the highly accurate piezoelectric device 10 with no variation in the oscillation frequency.
[0022]
In addition, when irradiating the laser to the pellet 30 that seals the hole portion 28, since the inside of the vacuum container is kept in a vacuum, the gas generated from the pellet 30 can be drawn out of the package 12. In addition, gas particles adhering to the connection electrode 24 can be reduced.
[0023]
Further, since the through-hole 34 constituting the hole 28 is provided at a position that is surely blocked by the pellet 30 placed in the recess 32, the laser is directly irradiated to the connection electrode 24 or the package 12. There is no. For this reason, the package 12 can be sealed without causing damage to the piezoelectric vibrating piece 20, the connection electrode 24, and the package 12 due to laser irradiation. Further, since the hole 28 is provided on the upper portion facing the connection electrode 24 that does not affect the oscillation of the piezoelectric vibrating piece 20, even if the connection electrode is irradiated with a laser, the oscillation is not affected. For this reason, it is not necessary to provide a shielding plate for preventing the piezoelectric vibrating reed 20, the connection electrode 24, and the package 12 from being directly irradiated to the laser, and the piezoelectric device 10 can be reduced in size and thickness. In addition, as a sealing material, a thin plate-like pellet 30 is used instead of a ball-shaped sealing material that does not fit into the recess 32. Since the thin plate-like pellets 30 and the recesses 32 are formed by pressing, the processing accuracy is good, and the pellets 30 can be reliably placed in the recesses 32. For this reason, the pellet 30 fits well when placed in the recess 32, and the laser is reliably irradiated without moving from the recess 32, and the piezoelectric vibrating reed 20, the connection electrode 24, and the package 12 are not damaged.
[0024]
Further, since the lid 18 is made of a metal with nickel plating on the Kovar surface, the thickness can be reduced as compared with a ceramic lid. The hole 28 provided in the lid 18 is formed by press working, but the metal lid 18 can have extremely high dimensional accuracy compared to the ceramic lid. Further, the pellets 30 placed in the holes 28 are also formed by pressing, so that the pellets 30 with extremely high accuracy can be supplied even if the size and thickness are reduced. Thereby, the dimension of the hole part 28 can be reduced in size, and also the package 12 can be reduced in size. Moreover, the recessed part 32 which comprises the hole part 28 should just be a magnitude | size which does not flow out when the pellet 30 is fuse | melted, and the diameter of the circular recessed part 32 may be large. Further, the concave portion 32 and the through hole 34 do not have to be circular and circular holes, respectively, and the concave portion 32 may have any shape as long as the pellet 30 is securely placed and does not flow out when melted. . In this case, it goes without saying that the shape of the pellet 30 is adjusted in accordance with the shape of the recess 32. As long as the opening of the through hole 34 is securely closed by the pellet 30 when the pellet 30 is placed in the recess 32, and the opening on the lower side of the lid 18 opens only above the connection electrode 24, any shape is possible. It may be a thing.
[0025]
Also, the hole portion 28 provided in the lid 18 is provided at a position facing the connection electrode 24 a connected to the excitation electrode 22 formed on the upper surface of the piezoelectric vibrating piece 20. That is, when the lid 18 is viewed from above, a hole 28 is formed at one corner of the lid 18. Therefore, the hole 28 can be used as a marker for recognizing the direction of the piezoelectric device 10 such as recognizing the mount portion side of the piezoelectric vibrating piece 20.
[0026]
Although the present embodiment has been described as seam welding in which the lid 18 is joined via the sealing ring 16, it can also be applied to direct seam welding in which the lid 18 is directly joined to the ceramic insulating substrate. And the sealing distortion which generate | occur | produces when performing seam welding and direct seam welding can be absorbed in a hole.
[0027]
The piezoelectric device 10 according to the present embodiment is a piezoelectric vibrator in which the piezoelectric vibrating piece 20 is mounted inside the package 12, but a semiconductor integrated circuit can be mounted inside the package 12 to form a piezoelectric oscillator. In the present embodiment, the piezoelectric device 10 using the piezoelectric vibrating piece 20 is used. However, the piezoelectric device 10 may be used as a tuning fork type piezoelectric vibrating piece or a lid of a piezoelectric device using a surface acoustic wave resonator.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a piezoelectric device according to an embodiment.
FIG. 2 is a cross-sectional view illustrating a hole portion of a lid according to the present embodiment.
[Explanation of symbols]
10 ......... Piezoelectric device, 12 ......... Package, 14 ......... Ceramic substrate, 16 ......... Sealing ring, 18 ......... Lid, 20 ......... Piezoelectric vibrating piece, 24 (24a, 24b) ... ... Connecting electrode, 28 ......... hole, 30 ......... pellet, 32 ......... concave, 34 ......... through hole.

Claims (3)

In a piezoelectric device in which a piezoelectric vibrating piece is mounted inside a package and the upper portion of the package is sealed with a lid, the lid is made of metal and faces a connection electrode formed on the piezoelectric vibrating piece. A piezoelectric device characterized in that a vacuum sealing hole is provided in the lid at a position. 2. The piezoelectric device according to claim 1, wherein the hole portion is provided with a concave portion for receiving a sealing material and a through hole penetrating the lid body from the lower surface of the concave portion. The piezoelectric device according to claim 2, wherein the sealing material is a thin plate-like pellet.

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