JP2002118423A - Piezoelectric device and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Problem] A surface mount type piezoelectric element capable of efficiently and accurately adjusting a frequency without affecting an IC element mounted in the same package and capable of responding to miniaturization and thinning. Make the device relatively inexpensive. A piezoelectric device in which a tuning-fork type quartz vibrating piece (5) and an IC chip (6) are vacuum-sealed in a package (4) in which a metal lid (3) is joined to an upper end of a base (1) via a seal ring (2). Are the first layers 7 to 4 of the ceramic material thin plate.
It has a substantially rectangular box-like structure in which the layers 10 are laminated, and a small-diameter circular through hole 20 is provided at an intermediate position between the weights 19 at the tips of the two vibrating arms 18 of the crystal vibrating piece. It is formed so as to partially include it. The weight portion of the crystal vibrating piece has a thick film portion 25 in which a weight material such as Au is attached more thickly in a region corresponding to the through hole. Based on the frequency measured by driving the IC chip and oscillating the crystal resonator element,
The thick film portion is irradiated with laser light through the through hole, and the weight material is trimmed to finely adjust the frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric device used for various electronic devices, for example, and hermetically sealing a piezoelectric vibrating reed and a semiconductor IC element such as an IC (semiconductor integrated circuit) chip in a package.

[0002]

2. Description of the Related Art Conventionally, piezoelectric devices such as piezoelectric vibrators have been used in various information and communication devices, OA devices, and electronic devices such as consumer devices. Particularly in recent years, in the field of small information devices such as mobile computers and IC cards, and communication devices such as mobile phones, the size and performance of devices have been remarkably reduced, and correspondingly, the size and thickness of piezoelectric devices have been reduced. Demands have arisen for the development of piezoelectric devices such as oscillators and real-time clock modules in which a piezoelectric vibrator and an IC chip are sealed in the same package, as well as surface-mounted devices suitable for mounting the device on a circuit board. I have.

The frequency of a piezoelectric vibrator hermetically sealed in a package is adjusted, for example, through a transparent ceramic window provided in an enclosing case as described in Japanese Patent Application Laid-Open No. Sho 57-106211, or a surface mount type. A method is generally known in which a weight portion provided at the tip of a piezoelectric vibrating reed is irradiated with laser light from the outside through a transparent glass thin plate lid for sealing the package, and the weight material is trimmed.

Japanese Unexamined Patent Publication No. 57-53123 discloses that one of two upper and lower box-shaped containers, each of which has a quartz-crystal vibrating piece sandwiched therebetween and hermetically sealed, is provided directly above a frequency adjusting portion of the vibrating piece. Is described, and a frequency adjustment is performed by attaching a weight material from the outside by vapor deposition or the like through the through hole.

More recently, for example, as described in Japanese Patent Application Laid-Open No. 11-321948 by the present applicant, a tuning fork type is formed by using an opening provided in a base or a metal lid (lid) constituting a package. A small, thin, and inexpensive surface-mount type piezoelectric vibrator has been proposed which can irradiate the tip of the vibrating arm of a piezoelectric vibrating piece with a laser beam or an electron beam and trim the weight material to adjust the frequency.

[0006]

However, the above-mentioned conventional piezoelectric device has the following problems.
First, the provision of a transparent window portion in a package in an airtight manner as described in JP-A-57-106211,
This is very troublesome, leading to a decrease in productivity and a rise in price. In particular, when miniaturizing a piezoelectric device, it is technically difficult.

Further, since the transparent lid for sealing the surface mount type package is formed of a high-quality glass material such as borosilicate glass so that the weight portion can be trimmed with high precision, The cost of the material itself and the cost of cutting it into a desired minute rectangular shape with high precision are high, and this makes the piezoelectric vibrator expensive. Furthermore, as the size of the package decreases, the high heat generated when the glass lid is bonded to the base with the sealing glass acts on the piezoelectric vibrating reeds and the IC chip to have an undesirable effect. There is a risk that the laser light irradiated through the IC chip may hit the IC chip and affect its operation.

Further, in order to adjust the frequency by attaching a weight material from the through hole provided in the package, it is necessary to increase the size of the through hole by a certain degree or more. However, it is difficult to provide a through hole having a size large enough for vapor deposition of a weight material in a small package that responds to recent demands for miniaturization. Furthermore, the high heat acting during the deposition of the weight material may adversely affect the IC chip in the package, and may significantly reduce the operational reliability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to adjust the resonance frequency with higher precision and to cope with miniaturization and thinning. An object of the present invention is to provide a surface mount type piezoelectric device to be obtained at relatively low cost.

It is another object of the present invention to provide a piezoelectric device which can be hermetically sealed without affecting an IC element mounted in the same package, and can perform frequency adjustment with higher precision and efficiency. An object of the present invention is to provide a device manufacturing method.

[0011]

According to the present invention, in order to achieve the above object, a package having a base and a lid joined to the base, a package mounted on the base and sealed in the package. Tuning fork type piezoelectric vibrating reed and IC
A through hole at an intermediate position of a weight portion provided at each of the distal ends of the two vibrating arms of the piezoelectric vibrating piece, and partially connecting the weight portions within a range of the opening. And the through-hole is hermetically closed.

By providing the weight portion and the through-hole in this manner, before joining the lid and before closing the through-hole and sealing the package, for example, a laser beam or an electron beam can be externally applied through the through-hole. By irradiating, the weight portions of both vibrating arms can be trimmed uniformly and with good balance, whereby the resonance frequency of the piezoelectric vibrating reed can be adjusted with high precision.

In one embodiment, each weight portion has a thicker weight material attached to a region corresponding to the through hole, and by trimming this region, even a minute through hole can be more efficiently used. Thus, the frequency can be adjusted in a short time.

The through-hole can be formed, for example, in a circular shape, and correspondingly, the area of each weight can be formed in a substantially semicircular shape. In this case, trimming of the weight portion can be efficiently performed in a semicircular shape along the inner peripheral edge of the through hole.

In one embodiment, since the lid is made of metal and is seam-welded to the base, when the lid is joined to the base, high heat is generated as in the case of joining a glass lid. Since it does not act on the vibrator and the IC element, the performance of the piezoelectric vibrating reed and especially the IC element is stabilized.

If the base has a laminated structure of thin plates made of an insulating material such as a ceramic material, it is easy to assemble a box-shaped package for accommodating the piezoelectric vibrating reed and the IC element and to form a through hole in the base. It is preferable because it can be performed.

In one embodiment, the piezoelectric vibrating reed is a quartz vibrating reed.

According to another aspect of the present invention, a step of mounting an IC element on a base constituting a package of a piezoelectric device, a step of mounting a tuning-fork type piezoelectric vibrating piece on the base, Adjusting the frequency, bonding a metal lid to the base, performing a second frequency adjustment on the piezoelectric vibrating reed using a through hole formed in the base, and closing the through hole in an airtight manner. And sealing the package.

The metal lid can be joined to the base by, for example, seam welding. In all processes including the process of joining the lid to the base, high heat as in the case of joining a glass lid can be applied to the IC element and the base. Since it does not act on the piezoelectric vibrating reed, it is possible to obtain a high-performance and highly reliable piezoelectric device in which the performance of the IC element is particularly stable and the resonance frequency of the piezoelectric vibrating reed is adjusted with high precision.

Further, according to the present invention, the second frequency adjustment is performed by utilizing the frequency measured by driving the IC element to oscillate the piezoelectric vibrating reed, thereby achieving more accurate piezoelectric vibrating reed. Can be adjusted, and a more reliable piezoelectric device can be manufactured.

The first and second frequency adjustments can be performed by trimming the weight material attached to the tip of each vibrating arm of the piezoelectric vibrating reed. The trimming of the weight material can be performed by irradiating the tip of each vibrating reed with, for example, an energy beam such as a laser beam or an electron beam to melt and remove the weight material.

In one embodiment, the frequency of the piezoelectric vibrating reed can be efficiently adjusted by irradiating the energy beam along the inner peripheral edge of the circular through hole, for example.

In another embodiment, the piezoelectric device can be sealed in a vacuum by closing the through hole hermetically in a vacuum atmosphere.

[0024]

1A to 1C show a preferred embodiment of a piezoelectric device to which the present invention is applied. This piezoelectric device has a package 4 consisting of a base 1 and a metal lid 3 joined to a top end thereof via a seal ring 2. In the package 4, a tuning-fork type crystal vibrating piece 5 mounted on the base 1 and an IC chip 6 are sealed in a vacuum. The lid 3 is exposed to high heat as in the case of joining a glass lid with sealing glass by, for example, seam welding.
, And is joined in a short time.

The base 1 has a substantially rectangular box-like structure in which first to fourth layers 7 to 10 of thin plates made of a plurality of ceramic materials are laminated. In the space of the package 4 defined by the openings 11 and 12 formed in the second layer 8 and the third layer 9 of the base 1, an IC chip 6 is placed on the lowermost first layer 7 with a conductive adhesive. Fixed. Each input / output electrode pad 13 formed on the upper surface of the IC chip 6 is electrically connected to a wiring pattern (not shown) on the upper surface of the second layer 8 exposed through the opening 12 in the third layer 9 by a bonding wire 14. It is connected to the. This wiring pattern is generally W,
It is formed by screen-printing a metal wiring material such as Mo on the surface of a ceramic thin plate and plating Ni and Au thereon.

In the quartz-crystal vibrating reed 5, each of the extraction electrodes 15 provided on the base end portion is formed on the upper surface of the third layer 9 in the base 1.
The electrode pads 17 on the pair of connection electrodes 16 are fixedly supported by a conductive adhesive in a cantilever manner and are electrically connected.
The opening 12 in the third layer 9 covers the lower area of both vibrating arms 18 so that the tip of the vibrating arm 18 of the crystal vibrating reed 5 does not come into contact with the inner surface of the package 4 even if the tip of the vibrating arm 18 swings up and down due to impact such as dropping. It is formed large to include. The uppermost fourth layer 10 is
The vibrating arm 1 of the quartz vibrating reed 5 has a substantially rectangular frame shape extending along the outer periphery of the third layer 9, and is similarly affected by a drop or the like.
8 has a sufficient height so that it does not come into contact with the lower surface of the lid 3 even when the tip of the lid 8 swings up and down.

The base 1 has two vibrating arms 1 of a quartz vibrating piece 5.
A small-diameter circular through-hole 20 is formed at a position corresponding to the weight portion 19 formed at the tip of the 8. More specifically,
1C, the center of the through hole 20 is located in the middle of the weight portion 19, and both of the weight portions are partially included within the opening, that is, the inner peripheral edge of the through hole 20 is The vibrating arm 18 is formed so as not to exceed the outer side thereof. In this embodiment, the through-hole 20 is formed in the first layer 7 and the second layer 8 of the base 1, and the through-hole opening of the bottom-side first layer 7 is closed in a final step as described later. A step 22 is provided for mounting a metal ball 21 of Au-Sn or the like to be welded at the time of mounting.

As shown in FIG. 2, the quartz-crystal vibrating piece 5 is provided with a flat electrode 23 connected to each of the extraction electrodes 15 at the base end on the surface of a quartz-crystal element piece having a tuning-fork shape as in the prior art.
A side electrode 24 is formed, and a weight 19 made of an electrode film is provided at the tip of each vibrating arm 18. At each weight portion, a thick film portion 25 formed thicker than other portions by applying a weight material such as Au to the electrode film by vacuum deposition or the like at a position corresponding to the through hole 20 of the base 1. It is provided in. The thick film portion is formed in a size substantially corresponding to the circular opening of the through hole 20, preferably in a substantially semicircular shape slightly larger than the circular opening. Therefore, when the through hole 20 is viewed from the bottom surface of the base 1, the thick film portions 25 of both weight portions can be seen therein.

The steps of manufacturing the piezoelectric device of this embodiment will be described. First, place the IC chip 6 in the base 1
The electrode pads 13 on the upper surface of the IC chip are fixed to the wiring patterns on the upper surface of the second layer 8 by wire bonding with a conductive adhesive fixed to the bottom surfaces of the cavities defined by the openings 12 and 13 in the second and third layers. To make an electrical connection. Next, the crystal vibrating reed 5 is placed in the base 1, the respective extraction electrodes 15 are respectively cantilevered to the corresponding electrode pads 17 with a conductive adhesive, and the thick film portions 25 of the respective vibrating arms 18 are aligned with the through holes 20. And fix it as shown.

In this state, by trimming each weight of the quartz-crystal vibrating piece 5, a first frequency adjustment for coarse adjustment to adjust its resonance frequency within a predetermined range is performed. This trimming is performed by using a means for irradiating an energy beam such as a laser beam or an electron beam, and the thick film portion 25 of each weight portion 18 is formed by the high heat of the energy beam.
The weight material in the other region is partially melted and removed to reduce the weight of the weight portion, and the oscillation frequency of the crystal resonator piece set in advance is adjusted to a desired high value.

Next, the metal lid 3 is hermetically joined to the seal ring 2 provided at the upper end of the base 1 by seam welding.
In seam welding, the temperature is lower than when using sealing glass, and the high heat acts only locally on the joint,
In addition, since the time is as short as several seconds, the IC chip 6
There is no risk of affecting the operation of.

Here, the IC chip is supplied with power and driven from a power supply terminal provided on the outer surface of the package 4 to oscillate the crystal resonator element 5, and its resonance frequency is measured from the output terminal on the outer surface of the package 4. Then, based on this measurement,
A second frequency adjustment for finely adjusting the resonance frequency of the crystal unit 5 to a predetermined frequency value is performed.

The second frequency adjustment is performed using the through hole 20 from the bottom surface side of the package 4. As shown in FIG.
The laser beam 27 is radiated from the laser beam irradiating means 26 disposed above the package 4 to the thick film portion 25 of each weight portion through the through hole 20 to trim the weight material. As a result, the weight materials of both vibrating arms are uniformly processed in a well-balanced manner, and the frequency can be adjusted efficiently and in a short time even in a minute through hole. Further, the risk that the removed weight material is scattered around and reattached to the IC chip 6 is reduced. Also, this trimming can be performed using an energy beam that generates a high temperature, such as an electron beam, in addition to the laser beam, as in the first frequency adjustment.

Preferably, the laser beam 27 is irradiated along the inner peripheral edge of the through hole 20. FIG. 4 shows a laser mark 28 of the thick film portion 25 thus trimmed.
In this way, the laser beam is alternately applied to the weight material of the thick film portion 25 of both vibrating arms, and the laser beam is processed into a semicircular shape so that the weight portions of both vibrating arms are processed more uniformly and in a well-balanced manner. It is preferable to perform frequency adjustment more efficiently.

Finally, the package 4 is sealed in a vacuum by closing the through hole 20 with a filler in a vacuum atmosphere. As the filler, for example, a metal ball 21 formed of a high-melting-point Pb-Sn solder-based material such as Au-Sn solder or 9: 1 solder is used. 22 and welded by a batch-type vacuum sealing device, a laser device, an electron beam device, or the like. Thereby, the piezoelectric device of the present invention is completed.

Each of the first and second frequency adjustments can be performed in a vacuum. In particular, by performing the second frequency adjustment in a vacuum, it is possible to finely adjust the resonance frequency of the crystal unit to a desired value with higher accuracy.

In the above embodiment, in the first frequency adjustment, the region other than the thick film portion 25 of the weight portion 18 of the crystal resonator element 5 is trimmed. However, in another embodiment, the thick film portion on the upper surface side is trimmed. Only 25 can be trimmed by irradiating it with laser light or the like. In this case, the possibility that the laser beam hits the IC chip 6 is lower, and therefore, the possibility that the operation of the IC chip is affected is lower. Further, the second frequency adjustment is preferably performed by trimming the thick film portion 25 on the lower surface directly visible from the through hole 20. This can be easily performed by adjusting the focal position of the laser light to be irradiated.

The present invention can be similarly applied to various piezoelectric materials other than quartz, such as lithium tantalate and lithium niobate. Further, it is apparent to those skilled in the art that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications and changes. For example, since it is relatively easy to adjust the focal position of the laser beam as described above, the pressure film portion 2 of the weight portion 18 is adjusted.
5 may be provided only on one of the upper surface and the lower surface of the vibrating arm.
In this case, the amount of Au generally used as the weight material can be reduced, which is advantageous in reducing the manufacturing cost.

[0039]

According to the piezoelectric device of the present invention, as described above, the weight portions of the two vibrating arms of the piezoelectric vibrating reed are uniformly balanced by utilizing the through holes provided on the bottom surface side of the base. Trimming is possible, so the resonance frequency of the piezoelectric vibrating reed can be adjusted with high precision,
It can respond to the demand for thinning.

Further, according to the method for manufacturing a piezoelectric device of the present invention, it is possible to perform frequency adjustment with higher precision and efficiency without affecting the IC elements mounted in the same package. Thus, a surface-mount type piezoelectric device having high reliability can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1A is a plan view of a piezoelectric device according to the present invention, and FIG.
The figure is a longitudinal sectional view, and the figure C is a bottom view.

FIG. 2 is a plan view of a tuning-fork type quartz vibrating reed used in the piezoelectric device of FIG.

FIG. 3 is a schematic perspective view showing a state in which a second frequency adjustment is performed on the piezoelectric device of FIG. 1;

FIG. 4 is a partially enlarged view showing a weight portion at the tip of a vibrating arm of the crystal vibrating piece.

[Explanation of symbols]

 Reference Signs List 1 base 2 seal ring 3 lid 4 package 5 crystal vibrating piece 6 IC chip 7 first layer 8 second layer 9 third layer 10 fourth layer 11, 12 opening 13 electrode pad 14 bonding wire 15 extraction electrode 16 connection electrode 17 electrode Pad 18 Vibrating arm 19 Weight part 20 Through hole 21 Metal ball 22 Step 23 Flat electrode 24 Side electrode 25 Thick film part 26 Laser light irradiation means 27 Laser light 28 Laser mark

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 41/09 H03H 3/04 B 41/18 9/02 A 41/22 H01L 41/08 C H03H 3 / 04 41/18 101A 9/02 41/22 Z

Claims (16)

[Claims] A package having a base and a lid joined to the base; a tuning-fork type piezoelectric vibrating reed and an IC element mounted on the base and sealed in the package; A through hole is formed at an intermediate position between weight portions provided at the tips of the two vibrating arms of the piezoelectric vibrating reed so as to partially include the weight portions within a range of the opening, and A piezoelectric device, wherein a through hole is hermetically closed. 2. The piezoelectric device according to claim 1, wherein a weight material is attached to each of the weight portions in a region corresponding to the through hole. 3. The piezoelectric device according to claim 2, wherein the through-hole has a circular shape, and the area of each of the weights corresponding to the through-hole has a substantially semicircular shape. 4. The cover according to claim 1, wherein said lid is made of metal and is seam-welded to said base.
The piezoelectric device according to any one of the above. 5. The piezoelectric device according to claim 1, wherein the base has a laminated structure of thin plates made of an insulating material. 6. The piezoelectric device according to claim 5, wherein the thin plate is made of a ceramic material. 7. The piezoelectric device according to claim 1, wherein the piezoelectric vibrating reed is a quartz vibrating reed. 8. A step of mounting an IC element on a base constituting a package of the piezoelectric device, a step of mounting a tuning-fork type piezoelectric vibrating piece on the base, and a step of performing a first frequency adjustment on the piezoelectric vibrating piece. A step of joining a metal lid to the base; a step of performing a second frequency adjustment on the piezoelectric vibrating reed using a through-hole formed in the base; Sealing the package. 9. Using a frequency measured by driving the IC element to oscillate the piezoelectric vibrating reed,
9. The method according to claim 8, wherein the second frequency adjustment is performed.
3. The method for manufacturing a piezoelectric device according to claim 1. 10. The method according to claim 8, wherein the first and second frequency adjustments are performed by trimming a weight material attached to a tip of each vibrating arm of the piezoelectric vibrating reed. 3. The method for manufacturing a piezoelectric device according to claim 1. 11. The method for manufacturing a piezoelectric device according to claim 10, wherein the trimming is performed by irradiating an energy beam to a weight material at the tip of each of the vibrating bars and melting and removing the energy beam. 12. The method according to claim 11, wherein the energy beam is a laser beam or an electron beam. 13. The method according to claim 11, wherein the energy beam is applied along an inner peripheral edge of the through hole. 14. The method according to claim 13, wherein the through hole has a circular shape. 15. The method for manufacturing a piezoelectric device according to claim 8, wherein the through hole is hermetically closed in a vacuum atmosphere. 16. The method according to claim 8, wherein the lid is joined to the base by seam welding.