JP2006229283A - Piezoelectric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device of such a structure as a package and a lid are sealed with no risk of environmental pollution, a frequency can be regulated precisely and an CI value can be prevented from increasing. <P>SOLUTION: The piezoelectric device comprises a base substrate 31, a piezoelectric oscillating piece 32, and a glass lid 48. In the base substrate or a package including the base substrate, a metal film containing gold is formed at a joint to the lid, and a lid side metal film for bonding is formed on the bonding face of the lid excepting a position 49 corresponding to a metal film for a frequency regulation provided to the piezoelectric oscillating piece after bonding. The metal film of the base substrate or a package including the base substrate and the lid side metal film of the lid are bonded and sealed by melting a sealing metal of gold and a tin alloy. Furthermore, the base substrate 31 or the package is formed with a sealing through hole 43 being sealed by a filler. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improvement in a piezoelectric device in which a piezoelectric vibrating piece is accommodated in a package.

Piezoelectric devices such as piezoelectric vibrators and piezoelectric oscillators in small information devices such as HDDs (hard disk drives), mobile computers, IC cards, and mobile communication devices such as mobile phones, car phones, and paging systems Is widely used.
A conventional piezoelectric device is configured, for example, as shown in FIG. (See Patent Document 1).
In the figure, a piezoelectric device 1 has a structure in which a piezoelectric vibrating piece 3 is accommodated in a package 2 and the package 2 is hermetically sealed with a metal lid 4.

In such a structure, when the frequency is measured after the piezoelectric vibrating reed 3 is accommodated in the package 2 and hermetically sealed, there is often a slight deviation from the desired frequency.
In this case, even after the lid 4 is hermetically sealed, for example, if the electrode formed on the piezoelectric vibrating piece 3 is irradiated with laser light from the outside and part of the electrode is evaporated, The mass of the vibrating arm of the piezoelectric vibrating piece can be reduced and finely adjusted to increase the frequency.
However, as shown in FIG. 5, if the lid 4 is made of metal, the laser beam irradiated from the outside cannot be guided into the package 2, and thus the lid is preferably formed of glass.

JP 2003-188678 A

Here, in joining a plate made of a glass material to a ceramic package or the like, the joining material is a low melting point of 320 degrees (“Centigrade”, and all the temperature indications used in the following are Celsius). A melting point glass is used.
However, this type of low-melting glass contains lead, and the use of a lead-containing sealing material is undesirable because it leads to environmental pollution.
Therefore, low-melting glass not containing lead is used. However, the melting point of such a glass is 400 ° C. or higher, which is a relatively high temperature, which may deteriorate the characteristics of the piezoelectric vibrating piece itself. In addition, lead-free low-melting glass having a relatively low melting point has been studied, but it is expensive and unsuitable.

  Therefore, a metal film is formed on the glass lid, and a metal sealing material (brazing material) is used. As the metal brazing material, there is solder. Lead-free solder that does not contain lead in particular is an alloy of tin, silver, copper, etc., which is as low as about 200 to 220 degrees, and may not withstand the reflow process when mounting a piezoelectric device. When the gas is generated later and the gas component adheres to the piezoelectric vibrating piece, the CI value increases.

  The present invention has been made to solve the above-described problems, and has a structure in which the package and the lid are sealed without fear of environmental pollution, and the frequency can be precisely adjusted to prevent an increase in CI value. An object is to provide a piezoelectric device.

  According to the first aspect of the present invention, the glass substrate is hermetically bonded to the base substrate, the piezoelectric vibrating piece fixed to the base substrate, and the base substrate or a package including the base substrate. A metal film containing gold is formed at a joint portion with the lid body, and the joint surface of the lid body is joined to the base body or a package including the base base body. A lid-side metal film for bonding is formed so as to exclude a position corresponding to a metal film for frequency adjustment provided on the piezoelectric vibrating piece later, and the metal film of the base substrate or a package including the base substrate And the lid-side metal film of the lid is bonded and sealed by melting a metal for sealing using a gold-tin alloy, and the base substrate or package further includes a sealing through-hole. And the Through hole for locking by a piezoelectric device is sealed Anafu by the filling material, it is achieved.

According to the configuration of the first aspect of the invention, the lid is made of glass, and the position of the lid corresponding to the frequency adjusting metal film provided on the piezoelectric vibrating piece after bonding is removed, so that the lid side metal film for bonding After sealing with the lid, the laser is radiated from the outside to evaporate part of the metal film such as the electrode of the piezoelectric vibrating piece in the package. Can do.
In addition, since a gold-tin alloy is used to join the glass lid, it can withstand the heat during reflow during mounting of the piezoelectric device, and adversely affects the piezoelectric vibrating piece when the lid is sealed. This is also prevented at the same time.
Further, since the package has a sealing through hole, the gas in the package can be discharged from the through hole when the lid is sealed, and then the hole can be sealed.
Thus, it is possible to provide a piezoelectric device having a structure in which the package and the lid can be sealed without fear of environmental pollution, and the frequency can be precisely adjusted to prevent the CI value from increasing.

According to a second aspect of the present invention, in the configuration of the first aspect, the sealing metal is precoated on the joint surface of the lid.
According to the configuration of the second invention, since the sealing metal is pre-coated on the lid body side, for example, the ring-shaped sealing metal is aligned between the package and the lid during sealing. Troublesome work can be avoided.

According to a third invention, in the configuration of the first or second invention, the sealing metal or the lid-side metal film and the sealing metal are bonded to the base body or the package of the lid. It is characterized in that it is provided in a limited area.
According to the configuration of the third invention, the use of the lid-side metal film and the sealing metal can be made to the minimum amount, and unnecessary flow of unjoined metal and waste of expensive materials including gold can be avoided. Can be prevented.

1 and 2 show one embodiment of the piezoelectric device of the present invention, FIG. 1 is a schematic plan view thereof, FIG. 2 is a schematic cut end view taken along line AA of FIG. 1, and FIG. It is a schematic plan view of the state which removed the body.
In these drawings, the piezoelectric device 30 shows an example in which a piezoelectric vibrator is configured. The piezoelectric device 30 has a structure in which a piezoelectric vibrating piece 32 is accommodated in a package 40 and hermetically sealed by a lid 48. is there.
Specifically, the package 40 of the piezoelectric device 30 contains a piezoelectric vibrating piece in an airtight manner. For example, a plurality of substrates formed by molding an aluminum oxide ceramic green sheet as an insulating material are stacked. After that, it is formed by sintering. That is, the package 40 includes a first substrate 41 to be the base substrate 31, a second substrate 42 stacked on the first substrate 41, and a third stack further stacked on the second substrate 42. Substrate 47.

The first substrate 41 of the package 40 constitutes the bottom surface of the package, and an end portion of the second substrate 42 stacked thereon, for example, in the vicinity of the left end in FIGS. Electrode portions 33 are formed at each end. On the electrode portions 33, 33, the portion of the extraction electrode at the base portion of the piezoelectric vibrating piece 32 is mounted and joined via the conductive adhesives 34, 34. The electrode portions 33 and 33 are connected to mounting terminals, which are external electrodes (not shown) of the package 40, using conductive through holes (not shown).
In FIG. 2, a concave portion 42a is formed by removing the material in a concave shape below the tip of the piezoelectric vibrating piece 32 of the second substrate 42, and the tip of the piezoelectric vibrating piece 32 is caused by vibration from the outside. Even if it is swung in the vertical direction, the front end portion thereof is prevented from colliding with the inner bottom portion of the package 40 and being damaged.

  The first substrate 41 and the second substrate 42 have a through hole 43 formed approximately in the vicinity of the center thereof. In this embodiment, the through hole has a first hole 44 formed in the first substrate 41 and a second hole 45 formed in the second substrate 42 and having a smaller diameter than the first hole 44. The first hole 44 and the second hole 45 communicate with each other. The through hole 43 is a stepped hole as shown in the figure, and a conductive pattern (metal covering portion) (not shown) is formed in the step portion, and the hole is sealed by filling the metal filler 46. Has been.

  The piezoelectric vibrating piece 32 shown in FIG. 3 is made of, for example, quartz, and piezoelectric materials such as lithium tantalate and lithium niobate can be used in addition to quartz. As shown in FIG. 1, the piezoelectric vibrating piece 32 includes a base portion 35 fixed to the package 40 side, and a pair of vibrations extending in parallel to be divided into two forks toward the right in the drawing with the base portion 35 as a base end. This is a so-called tuning-fork type vibration piece including arms 36 and 37. The piezoelectric vibrating piece is not limited to this, and may be an AT-cut vibrating piece obtained by cutting a quartz wafer into a rectangle.

A lead electrode is formed on the base portion 35 of the piezoelectric vibrating piece 32 and is electrically connected to the package 40 side electrode portions 33 and 33. The vibrating arms 36 and 37 preferably extend along the direction in which the arms extend. Long grooves can be formed on the front and back in the same form to form excitation electrodes, which are driving electrodes, and can be connected to the extraction electrodes.
Further, for example, near the tips of the vibrating arms 36 and 37 of the piezoelectric vibrating piece 32, metal cover portions 36a and 37a for frequency adjustment are formed. The frequency-adjusting metal cover portions 36a and 37a are made of the same metal as an excitation electrode (not shown), which is a drive electrode formed on the piezoelectric vibrating piece 32, and can be formed in the same process. Alternatively, part of the excitation electrode of the piezoelectric vibrating piece 32 may be used for the metal cover portions 36a and 37a for frequency adjustment.

The lid 48 is made of glass, and can be cut out from a plate-like material made of, for example, borosilicate glass. The lid 48 is provided with a lid-side metal film and a sealing metal made of a gold-tin alloy on the joint surface.
Here, as shown in FIG. 1, a sealing metal is formed in a region excluding the light passage portion 49 of the lid 48. The light passing portion 49 of the lid body 48 is formed on the metal coating portions 36a and 37a for frequency adjustment provided on the piezoelectric vibrating piece 32 after the lid body 48 is joined to the package 40, as shown in FIG. It is a region that transmits laser light from the outside at a corresponding position. Here, depending on the material, the lid-side metal film may not be formed to avoid the light passage portion 49, but the light amount of the laser light for frequency adjustment is remarkably reduced or a large amount of light is reflected. Thus, when the amount of light necessary for frequency adjustment cannot be ensured, the lid-side metal film is also formed in a region avoiding the light passage portion 49 as in the case of the sealing metal.

Next, the lid side metal film and the sealing metal will be described.
FIG. 4 is an enlarged partial cross-sectional view showing a joint portion between the package 40 and the lid 48.
In the figure, a metal film 54 is formed on the bonding surface 40 a which is the upper end of the package 40. The metal film 54 is formed, for example, by coating a nickel (Ni) layer 52 on a tungsten (W) layer 51 which is a base for ceramics, and coating a gold (Au) layer 53 thereon. In addition, each metal layer shown in the figure is shown thicker than the actual thickness for convenience of understanding.

  On the other hand, a lid-side metal film 65 is formed on the bonding surface 48 a that is one surface of the lid 48. The lid-side metal film 65 has, for example, a chromium (Cr) layer 61 formed on the glass surface, preferably a nickel (Ni) layer 62 formed on the surface, and a gold (Au) layer 63 formed on the surface. It is a thing. The nickel layer 62 is provided to prevent chromium from diffusing from the chromium layer 61 to the gold layer 63.

Each layer constituting the lid-side metal film 65 for the lid 48 can be formed by vapor-depositing or sputtering a metal corresponding to each layer on a glass plate. Preferably, a sealing metal 64 is precoated on the surface side of the lid-side metal layer 65. The sealing metal 64 is made of a gold-tin alloy (AuSn). The gold-tin alloy constituting the sealing metal 64 can be bonded by punching an alloy plate prepared in advance into the shape of the lid 48 and heating and melting it.
Alternatively, gold and tin may be sequentially formed on the surface side of the lid-side metal film 65 by vapor deposition or sputtering, and heated and melted to form an alloy.

The present embodiment is configured as described above. The manufacturing process thereof will be briefly described. First, as a previous process, the package 40 and the lid 48 are separately formed.
The package 40 performs the bonding process of the piezoelectric vibrating piece 32 in a state where the through hole 43 is not blocked.
That is, the conductive adhesives 34 and 34 are applied on the electrode portions 33 and 33 exposed on the inner surface of the package 40, and the piezoelectric vibrating piece 32 is mounted thereon, dried, and cured, thereby the piezoelectric vibrating piece 32. Is fixed in the package 40.
Next, for example, the package 40 is placed in a vacuum chamber, and a sealing process is performed. In this case, the metal film 54 described in FIG. 4 is formed on the package 40, the lid 48 is formed with the lid-side metal film 65, and the sealing metal 64 is pre-coated. The lid 48 can be bonded and sealed to the package 40 simply by placing the lid 48 on the substrate 40 and performing predetermined heating.

In this case, since the sealing metal 64 is a gold-tin alloy, the sealing metal 64 can be melted at about 280 degrees and is not high enough to adversely affect the piezoelectric vibrating piece 32. Also, when the piezoelectric device 30 is mounted. It is possible to seal without using a high temperature that flows out in the reflow step.
During this heating, the conductive adhesive bonded to the piezoelectric vibrating piece 32 and the moisture inside the package 40 are generated as gas, and the generated gas is released to the outside from the through hole 43 (degassing). Thereafter, for example, a spherical AuGe alloy is disposed on the inner step portion of the through hole 43 and melted by a laser beam or the like to form a filled metal (metal filler) 46, and the through hole 43 can be sealed.

Finally, as shown in FIG. 2, when the laser beam LB is irradiated from the outside, the laser beam LB is transmitted through the glass lid 48 and the laser beam LB is frequency-adjusted metal coating portions 36a and 37a (FIG. 3). ), The frequency is adjusted by the mass reduction method.
Thus, the piezoelectric device 30 is completed.

  As described above, in this embodiment, the lid 48 is made of glass, and the positions corresponding to the frequency-adjusting metal cover portions 36a and 37a provided on the piezoelectric vibrating piece 32 after being joined to the package 40 are excluded. Since the lid-side metal film 65 is formed, after sealing with the lid 48, the laser beam LB is irradiated from the outside to evaporate the metal coating portions 36a and 37a of the piezoelectric vibrating piece 32 in the package 40. Thus, the frequency can be adjusted by the mass reduction method.

Further, since the sealing metal 64 made of a gold-tin alloy is used for the bonding of the glass lid 48, the glass lid 48 can withstand heat during reflow when the piezoelectric device 30 is mounted. An adverse effect on the piezoelectric vibrating piece 32 at the time of sealing is also prevented.
Further, since the package 40 includes the sealing through-hole 43, the gas in the package 40 can be discharged from the through-hole 43 when the lid 48 is sealed, and then the hole can be sealed. . For this reason, the CI value does not increase due to the gas component adhering to the piezoelectric vibrating piece 32.
Thus, it is possible to provide a piezoelectric device having a structure in which the package and the lid can be sealed without fear of environmental pollution, and the frequency can be precisely adjusted to prevent the CI value from increasing.

Of the metal layers constituting the lid-side metal film 65, the chromium layer 61 can transmit the laser beam LB without being formed avoiding the light passage portion 49.
Further, the sealing metal 64 may be precoated on the surface of the metal film 54 on the package 40 side.
Further, the sealing metal 64 can be formed on the lid 48 side or the package 40 side only in a region corresponding to the bonding surface 40a in FIG. As a result, it is possible to prevent AuSn from flowing out unnecessarily at the time of sealing and causing waste of expensive materials.

The present invention is not limited to the above-described embodiment. Each configuration of the embodiment may be omitted as appropriate and combined with other configurations not shown.
In addition, the present invention can be applied to all piezoelectric devices regardless of the names of piezoelectric vibrators, piezoelectric oscillators, etc., as long as they are covered with a package and accommodate a piezoelectric vibrating piece inside. .

The schematic plan view which shows embodiment of the piezoelectric device of this invention. FIG. 2 is a schematic cut end view taken along line AA in FIG. 1. The schematic plan view except the cover of the piezoelectric device of FIG. The expanded sectional view of the junction part of the cover body and package of the piezoelectric device of FIG. FIG. 6 is a schematic cross-sectional view showing an example of a conventional piezoelectric device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 ... Piezoelectric device, 31 ... Base base | substrate, 32 ... Piezoelectric vibrating piece, 33 ... Electrode part, 36, 37 ... Vibrating arm, 40 ... Package, 43 ... Through-hole 48 ... Lid, 54 ... Metal film, 64 ... Metal for sealing, 65 ... Metal film on the lid side

Claims (4)

A piezoelectric device comprising: a base substrate; a piezoelectric vibrating piece fixed to the base substrate; and a glass lid body airtightly bonded to the base substrate or a package including the base substrate.
In the base substrate or a package including the base substrate, a metal film including gold is formed at a joint portion with the lid,
On the bonding surface of the lid, a lid-side metal film for bonding is formed so as to exclude a position corresponding to the frequency-adjusting metal film provided on the piezoelectric vibrating piece after bonding,
The base substrate or the metal film of the package including the base substrate and the lid-side metal film of the lid are bonded and sealed by melting a metal for sealing with a gold-tin alloy,
Furthermore, the base substrate or the package includes a through hole for sealing, and the through hole for sealing is hole-sealed with a filler.   The piezoelectric device according to claim 1, wherein the sealing metal is precoated on a joint surface of the lid.   2. The sealing metal or the lid-side metal film and the sealing metal are provided in a region limited to a bonding surface of the base substrate or package of the lid. 3. The piezoelectric device according to any one of 2 above.   4. The base substrate or package includes a through hole for sealing, and the through hole for sealing is filled with a metal material and sealed. A piezoelectric device according to claim 1.

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