JP2017108365A - Piezoelectric vibrator and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibrator which comprises an excitation electrode containing silver as a main component, improves a frequency aging property and is made inexpensive.SOLUTION: A piezoelectric vibrator 10 comprises: a crystal piece 11; and an excitation electrode 13a consisting of a laminated film of adhesive layers 13aa provided on front and rear sides of the crystal piece 11, and a thin film 13ab provided on the adhesive layer 13aa, containing aluminum in 1 to 15 atomic wt.% and containing silver as a main component. The crystal piece 11 comprising the excitation electrode 13a is connected and fixed, at a position of a terminal electrode 13b, to a support pad 15b within a recess 15a of a container 15 by a conductive adhesive 19 and the container 15 is made airtight and sealed by a lid member 17.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric vibrator characterized by an excitation electrode and a method for manufacturing the same.

  As a typical example of a piezoelectric vibrator, an AT-cut quartz crystal vibrator is known. For example, in a surface-mount type AT-cut crystal resonator (SMD crystal resonator), a crystal piece having an excitation electrode and a terminal electrode on both main surfaces is electrically conductive at a position of the terminal electrode on a support pad in a ceramic package. The container is fixed with an adhesive, and the container is hermetically sealed. In the manufacturing process of this type of crystal unit, heat is applied to each member such as the electrode, crystal piece, and package. Depending on the type of adhesive used and the difference in the sealing method, each member is placed in a high temperature state of 250 ° C. to 450 ° C. in the thermosetting process and the hermetic sealing process of the adhesive.

As the electrode material, gold (Au) or silver (Ag) formed by vapor deposition or sputtering is used. In a crystal resonator provided with an Au electrode, high long-term frequency stability (aging characteristics) can be obtained, but there is a problem that the material cost is high. On the other hand, a quartz resonator including an Ag electrode is less expensive than an Au electrode, but has a problem that long-term frequency stability is inferior.
The change with time in the frequency of the crystal resonator including the Ag electrode is considered to be caused by aggregation of the Ag electrode due to heat in the hermetic sealing process. That is, it is known that gas adsorption from the package inner wall, adhesive, and sealing atmosphere, and mass change of the excitation electrode due to oxidation and / or sulfidation occur. It is presumed that the frequency fluctuation is caused by an increase in the amount of adsorption, surface oxidation and / or surface sulfidation.

  In order to suppress aggregation in the Ag thin film, it is known that addition of trace metals is effective. For example, in Patent Document 1, an Ag-based alloy containing bismuth (Bi) and / or antimony (Sb) in a total amount of 0.005 to 0.40% (meaning atomic weight%), In Patent Document 2, indium (In) is contained. An Ag—In alloy having a composition of 0.1 to 1.8 atomic weight%, the balance being Ag and inevitable impurities is disclosed.

Both are technologies aimed at suppressing light reflectance deterioration due to Ag aggregation, but the added metal (Bi, Sb, or In) is deposited on the thin film surface as a segregation layer, and the surface segregation layer As a result of exposure to oxygen in the atmosphere, a stable oxide film is formed, so that aggregation is suppressed and reflectance deterioration can be prevented.
Further, in Patent Document 3, an Ag alloy containing Ag as a main component and adding palladium (Pd) and copper (Cu), or an Ag alloy containing Ag as a main component and containing Pd and titanium (Ti) as an excitation electrode. The piezoelectric vibrator used is disclosed. This piezoelectric vibrator is said to have good aging characteristics.

JP 2004-139712 A JP 2014-19922 A JP 2001-44785 A

  However, in the manufacturing process of the crystal resonator, there is a step of adjusting the resonance frequency of the resonator by scraping the electrode film with an ion beam or a laser. When used as, the surface segregation layer formed as agglomeration suppression is scraped off during frequency adjustment, and the agglomeration suppression effect is greatly reduced, and there is a problem that frequency fluctuation due to a change with time is not reduced.

  In addition, in the case of Patent Document 3, since expensive palladium is used and it is a ternary alloy, it is not easy to manage the composition of the electrode film, whether it is a vapor deposition method or a sputtering method, There is a problem that the cost is about the same as that of the Au electrode vibrator.

  The present application has been made in view of the above points, and therefore the object of the present application is to provide a piezoelectric vibrator of an electrode material which is excellent in frequency aging characteristics and is inexpensive, and a manufacturing method suitable for the piezoelectric vibrator. It is in.

In order to achieve this object, according to the invention of the piezoelectric vibrator of this application, in the piezoelectric vibrator having the excitation electrode mainly composed of silver, the excitation electrode contains 1 to 15 atomic weight% of aluminum. It is characterized by that. Preferably, the excitation electrode contains 1 to 10 atomic% of aluminum. More preferably, the excitation electrode contains 5 to 10 atomic% of aluminum. In the following description, a film containing Al in the above range and containing Ag as a main component is also referred to as an “Ag—Al alloy film”.
In carrying out the present invention, the excitation electrode may be composed of only an Ag—Al alloy film, but an adhesion layer for improving the adhesion of the Ag—Al alloy film to the piezoelectric piece, and Ag -It is preferable to comprise a laminated film with an Al alloy film. Therefore, a piezoelectric vibrator of a preferred embodiment of the present invention includes a piezoelectric piece, an adhesion layer formed on the front and back surfaces of the piezoelectric piece, and an excitation electrode composed of an Ag-Al alloy film formed on the adhesion layer, This is a piezoelectric vibrator having a structure.

  In general piezoelectric vibrators, excitation electrodes and terminal electrodes connected to and formed integrally with the excitation electrodes are provided on the front and back surfaces of the piezoelectric piece. Therefore, in carrying out the present invention, typically, the extraction electrode is also composed of an Ag—Al alloy film, or a laminated film of an adhesion layer and an Ag—Al alloy film as in the above preferred example. To do. However, the present invention includes a case where the extraction electrode is formed of a thin film having a material or composition different from that of the Ag—Al alloy film.

On the other hand, according to the invention of the piezoelectric vibrator manufacturing method of the present application (hereinafter also referred to as the first invention of the manufacturing method), the excitation electrode (Ag- Al alloy film), preferably an excitation electrode (Ag-Al alloy film) containing 1 to 10 atomic% of aluminum and containing silver as a main component, more preferably 5 to 10 atomic% of aluminum and containing silver as a main ingredient. An excitation electrode (Ag—Al alloy film) to be formed is formed on the front and back surfaces of the piezoelectric piece by any suitable film formation method such as sputtering or vapor deposition, and then the structure is heat-treated at 250 to 450 ° C. It is characterized by giving.
According to this heat treatment, Al added to the Ag—Al alloy film can be segregated on the film surface. In addition, the surface segregated Al is oxidized by the heat treatment, or optionally after the heat treatment by exposure to the atmosphere or exposure to oxygen gas, thereby forming a stable oxide film (hereinafter referred to as a protective film). The surface can be coated. Moreover, you may perform the said heat processing after a frequency adjustment process. In this way, even if the protective film is reduced or eliminated by ion milling or laser milling during frequency adjustment, the protective film can be repaired.

  The manufacturing method for performing the above heat treatment is claimed from the following background. That is, after the Ag—Al alloy film of the present invention is formed on the piezoelectric piece by any suitable film forming method, the heat treatment in the manufacturing process of the piezoelectric vibrator, for example, an adhesive for fixing the piezoelectric piece to the package Since the heat treatment for curing and the heat treatment in the hermetic sealing process reach the Ag—Al alloy film, the formation and repair of the protective film are ensured during the manufacturing process. However, as in the invention of the manufacturing method, the protective film can be reliably formed or repaired by positively performing the treatment. Therefore, it may be preferable to use this manufacturing method.

  Here, the reason for setting the temperature in the case of performing the heat treatment to 250 to 450 ° C. is that there is a demerit such as requiring a long processing time because the effect of segregating aluminum on the electrode surface is small if this temperature is too low. If the temperature is too high, it may cause side effects on other members such as the electrode itself and the adhesive for fixing the crystal piece, and more heat treatment devices than necessary will be prepared, which is not preferable. It is. The atmosphere in which this heat treatment is performed can be arbitrarily selected according to the design of the piezoelectric vibrator. Unless otherwise limited, a nitrogen atmosphere is good.

In addition, according to the invention of the manufacturing method of the piezoelectric vibrator according to another aspect of the present application (hereinafter also referred to as the second invention of the manufacturing method), the excitation electrode (Ag-Al) containing silver as a main component and aluminum. An alloy film) on the front and back of the piezoelectric piece, a step of adjusting the frequency of the piezoelectric piece on which the excitation electrode is formed, and a step of sealing the piezoelectric piece on which the frequency adjustment is completed. In the method for manufacturing a piezoelectric vibrator, the above-described frequency adjustment is performed in consideration of a frequency shift amount generated in the above-described sealing process.
According to the second invention of this manufacturing method, the heat generated in the sealing process causes a protective film on the excitation electrode and / or repairs the excitation electrode. Even when the shift is performed before and after sealing, the frequency adjustment is performed so as to cancel the shift amount, so that a piezoelectric vibrator that oscillates at a desired frequency and has excellent frequency aging characteristics can be obtained. The frequency shift amount varies depending on the composition of the excitation electrode, particularly the amount of Al added, and the sealing conditions (for example, oxygen concentration in the sealing atmosphere, sealing temperature, etc.). Therefore, when carrying out the second invention, the frequency shift amount is grasped in advance, the set value of the frequency adjustment is determined according to the shift amount, and the frequency adjustment is performed.
In carrying out the second invention of the manufacturing method, the Ag-Al alloy film formed as the excitation electrode is an excitation electrode (Ag-Al alloy film) containing 5 to 10 atomic percent of aluminum and containing silver as a main component. It is good to do. This is because the Ag—Al alloy film having such a composition has higher reproducibility of the above-described frequency shift amount than the other cases (see FIG. 5), and therefore it is easy to improve the frequency adjustment accuracy of the crystal resonator.

  According to the piezoelectric vibrator and the manufacturing method thereof of this application, it is possible to provide a piezoelectric vibrator having an aging characteristic and an inexpensive electrode material.

(A), (B) is explanatory drawing of the piezoelectric vibrator 10 of embodiment. (A), (B) is a figure explaining the surface analysis result of the electrode for excitation of the piezoelectric vibrator of an Example and a comparative example. (A)-(D) is a figure explaining the surface state of the electrode for excitation of the piezoelectric vibrator of an Example and a comparative example. (A), (B) is a figure explaining the frequency aging characteristic of the piezoelectric vibrator of an Example and a comparative example. These are the figures explaining the relationship between the amount of Al addition in an Ag-Al alloy electrode film, and the amount of frequency shifts before and behind sealing. FIG. 6 is a diagram illustrating frequency aging characteristics of the piezoelectric vibrator of the example adjusted in consideration of the amount of frequency shift. These are the figures explaining the relationship between the amount of Al addition in an Ag-Al alloy electrode film, and the Al composition of the electrode surface.

  Hereinafter, embodiments of a piezoelectric vibrator and a manufacturing method thereof according to the present invention will be described with reference to the drawings. It should be noted that the drawings used for the description are merely schematically shown to the extent that the present invention can be understood. Moreover, in each figure used for description, about the same component, it attaches | subjects and shows the same number, The description may be abbreviate | omitted. In addition, the shape, dimensions, material, frequency, and the like described in the following description are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited only to the following embodiments.

1. Structure of Piezoelectric Vibrator First, the structure of an SMD type crystal vibrator as the piezoelectric vibrator 10 of the embodiment will be described. FIG. 1 is an explanatory diagram thereof, in particular, FIG. 1A is a plan view of the piezoelectric vibrator 10, and FIG. 1B is a diagram of the piezoelectric vibrator 10 cut along the line P-P in FIG. It is sectional drawing. In FIG. (A), illustration of the lid member 17 of the piezoelectric vibrator 10 is omitted.

The piezoelectric vibrator 10 according to the embodiment includes a crystal piece 11, an electrode 13 including an excitation electrode 13 a and a terminal electrode 13 b, a container 15, and a lid member 17.
The crystal piece 11 is an AT-cut crystal piece having a rectangular planar shape (including a substantially rectangular shape). Further, the excitation electrode 13a and the terminal electrode 13b of the electrode 13 are integrally formed, and are a laminated film of the adhesion layer 13aa and the Ag—Al alloy film (Ag-based alloy thin film) 13ab according to the present invention. In this case, the container 15 is a ceramic package having a recess 15a. The lid member 17 is a known member corresponding to the hermetic sealing method.

The crystal piece 11 provided with the electrode 13 is connected and fixed to the support pad 15b provided in the recess 15a of the container 15 by the conductive adhesive 19 at the position of the terminal electrode 13b. The container 15 includes an external connection terminal 15c on the bottom surface. The external connection terminal 15c and the support pad 15b are electrically connected by via wiring (not shown).
Here, the adhesion layer 13aa has sufficient adhesion between the crystal piece 11 and the Ag-Al alloy film 13ab, such as chromium (Cr), titanium (Ti), nickel (Ni), aluminum (Al). Any metal can be used as long as it can be obtained. Further, the thickness of the adhesion layer 13aa is not particularly limited, but sufficient adhesion can be obtained as long as it is in the range of 0.5 to 10 nm.
The adhesion layer 13aa and the Ag—Al alloy film 13ab can be formed by, for example, resistance heating method, electron beam evaporation method, or sputtering method.

  The surface of the excitation electrode 13a is trimmed by ion beam or laser to the crystal piece 11 with the electrode housed and fixed in the container 15 as described above and adjusted to a predetermined frequency, and then the lid member 17 is placed on the container 15 Then, the piezoelectric vibrator 10 can be obtained by hermetically sealing in any suitable atmosphere according to the design of the piezoelectric vibrator such as a nitrogen atmosphere. The surface segregation of Al added to the Ag—Al alloy film 13ab occurs at the time of thermosetting or hermetic sealing of the conductive adhesive.

2. Experimental result
2-1. Auger analysis Next, an electrode including an Ag-Al alloy film having an Al addition amount of 0.5 atomic% (hereinafter also referred to as at.%) As a piezoelectric vibrator of a comparative example according to the above procedure is provided. As the piezoelectric vibrator of the example, the Al addition amount is 8.0 at. Although two types of piezoelectric vibrators are manufactured, the results of composition analysis of the electrode surfaces of these vibrators using an Auger electron analyzer will be described. All the piezoelectric vibrators had a nominal frequency of 27 MHz.
Here, the electrode film was formed by sputtering, a 5 nm Cr film was used as the adhesion layer 13aa, and the Ag—Al alloy film 13ab had a thickness of 250 nm. In addition, Auger analysis was performed after the conductive adhesive was cured (that is, before frequency adjustment), after frequency adjustment, and after hermetic sealing. In this analysis, Ag, O (oxygen), Al and Si (silicon) due to the silicone-based conductive adhesive were mainly detected from the electrode surface.

FIG. 2 shows the results of this Auger analysis, in which the horizontal axis represents the process progress and the vertical axis represents the atomic weight ratio (percentage) in the analysis. (A) The figure shows the analysis result of the Al addition within the range of the present invention (Example), and (B) shows the analysis result of the Al addition outside the scope of the present invention (Comparative Example). The numerical values obtained during the Auger analysis are shown in Table 1 below.

  As can be seen from FIG. 2 and Table 1, the amount of Al added is 0.5 at. % (Comparative example), and 8.0 at. % (Example) In all cases, Al at an addition concentration or more was detected from the electrode surface, and it was found that Al was segregated on the electrode surface by the heat of curing the adhesive. In the state after frequency adjustment, the Al addition amount is 0.5 at. %, And 8.0 at. In any case, the ratio of Ag is larger than that before the frequency adjustment, and it can be seen that the surface segregation layer formed before the frequency adjustment is removed and Ag is exposed. On the other hand, the amount of Al added is 0.5 at. % And 8.0 at. %, A significant difference appears in the composition. Al and O are hardly detected before the hermetic sealing, and the Ag remains exposed, but after the hermetic sealing. Al and O are detected to the same extent as before adjustment, and Ag is hardly detected. From this result, it can be seen that Al dissolved in the film after frequency adjustment (during the sealing step) resegregated on the frequency adjustment surface. This resegregation of Al has an Al addition amount of 1.0 at. % Or more of the electrodes were confirmed. In this example, the protective layer was formed at the time of adhesive curing and hermetic sealing, but when an adhesive fixing method and a sealing method different from this example were adopted, the protective layer was used in these methods and methods. Is not formed, a protective layer is formed by providing a heat treatment step in a temperature range of 250 to 450 ° C. individually.

2-2. Film Surface Morphology Next, Ag-8.0 at. Of the present invention formed on a quartz substrate. The results of examining the surface state (morphology) of a% Al alloy film and a conventional pure Ag film at 300 ° C. for 30 minutes in a nitrogen atmosphere and then examining the surface state (morphology) of the both by an atomic force microscope (AFM) will be described. Here, pure Ag is also Ag-8.0 at. As with% Al, a film was formed by sputtering on a 5 nm Cr adhesion layer with a thickness of 250 nm.

FIG. 3 shows an observation image by AFM, and FIG. 3 (A) shows Ag-8.0 at. An AFM observation image immediately after the film formation of the% Al alloy film (Example), (B) shows Ag-8.0 at. An AFM observation image of a% Al alloy film after heat treatment at 300 ° C. for 30 minutes, (C) shows an AFM observation image immediately after the deposition of a pure Ag film (comparative example), and (D) shows an AFM observation image of the pure Ag film at 300 ° C. It is an AFM observation image after the heat processing for 1 minute.
As is clear from FIG. 3, in pure Ag, the surface unevenness is increased due to heat treatment and aggregation occurs, whereas Ag-8.0 at. It can be seen that in the% Al film, the size of the surface irregularities is not changed and aggregation is suppressed.

2-3. Frequency Aging Next, as an example, Ag-8.0 at. The frequency fluctuations (aging) when an AT-cut vibrator having a nominal frequency of 27 MHz was manufactured and annealed at 85 ° C. at a high temperature, each having a% Al electrode and a pure Ag electrode as a comparative example. The results of examining the characteristics will be described. A pure Ag electrode is also Ag-8 at. Similar to the% Al electrode, the adhesion layer was a 5 nm Cr film.
FIG. 4 shows these aging characteristics, with the horizontal axis representing the number of days and the vertical axis representing the frequency change rate (ppm) for each measurement relative to the frequency at the start of the test. (A) shows the characteristics of the piezoelectric vibrator of the example, and (B) shows the characteristics of the piezoelectric vibrator of the comparative example.
The crystal resonator of the example has a frequency fluctuation amount of less than −1 ppm when 21 days have elapsed (corresponding to aging for one year at room temperature), whereas the frequency of the crystal resonator of pure Ag electrode when 21 days have elapsed. The fluctuation amount is -3 ppm at the maximum, and it can be seen that the aging characteristics of the crystal resonator of the example (the crystal resonator using the Al-added Ag-based alloy of the present invention as an electrode) are very good.

この表２から分かるように、保護層の修復が起きなかったＡｌ添加量０．５ａｔ．％では２１日間エージング後の平均周波数変動量は純Ａｇと同じ−２ｐｐｍ程度であった。一方、保護層の修復が起きたＡｌ添加量１ａｔ．％以上では２１日間エージング後の平均周波数変動量が−１ｐｐｍ未満となった。ただし、Ａｌ添加量が１０ａｔ．％を越えると、良好なエージング特性は得られるものの、電極表面が白濁する。白濁の度合いは、Ａｌの添加量が増えるほどはっきりしてくる。この電極表面を走査型電子顕微鏡にて観察するとＡｌが粒状に析出している。電極表面にこのような粒が存在するような状態は信頼性上問題がある。したがって、Ａｌの添加量の上限としては、エージング特性が改善でき、かつ、Ａｌの粒状析出が生じない範囲が良く、１０原子％以下に限定される。以上から、Ａｌ添加濃度としては１．０ａｔ．％から１０ａｔ．％が好ましいといえる。 Further, the Al addition amount is 0 to 15 at. Table 2 shows the average frequency fluctuation amount (10 samples each) after aging an Ag-Al alloy electrode AT-cut vibrator (27 MHz) manufactured by changing between% and 21 days at 85 ° C.

As can be seen from Table 2, the amount of Al added was 0.5 at. %, The average frequency fluctuation amount after aging for 21 days was about −2 ppm, which is the same as that of pure Ag. On the other hand, the amount of Al added is 1 at. In the case of% or more, the average frequency fluctuation amount after aging for 21 days was less than −1 ppm. However, the Al addition amount is 10 at. If it exceeds 50%, good aging characteristics can be obtained, but the electrode surface becomes cloudy. The degree of white turbidity becomes clear as the amount of Al added increases. When this electrode surface is observed with a scanning electron microscope, Al is precipitated in a granular form. A state in which such grains are present on the electrode surface is problematic in terms of reliability. Accordingly, the upper limit of the amount of Al added is preferably in a range where the aging characteristics can be improved and no granular precipitation of Al occurs, and is limited to 10 atomic% or less. From the above, the Al addition concentration is 1.0 at. % To 10 at. % Is preferable.

3. Embodiment in which influence of sealing process is considered Sealing of the crystal unit is performed after frequency adjustment of the crystal unit. Since the process order is as described above, it is preferable to pay attention to the following points when adjusting the frequency of the crystal resonator using the Ag—Al alloy according to this application as an electrode.
The environment in the sealing device in the sealing step includes a trace amount of oxygen. For example, it is almost a nitrogen atmosphere but often contains a trace amount of oxygen. Also, the sealing temperature is often high (for example, a predetermined temperature between 100 and 300 ° C.). Therefore, when the surface of the Ag-Al alloy electrode is scraped by ion milling or laser milling with frequency adjustment and Al is exposed, the Al is oxidized by a small amount of oxygen present in the atmosphere of the sealing process. After sealing, the resonance frequency adjusted during the frequency adjustment process may shift to the minus side.

  FIG. 5 is a diagram for explaining the relationship between this frequency shift phenomenon and the amount of Al added to the Ag—Al alloy electrode. Specifically, each crystal resonator having a nominal frequency of 27 MHz and including an Ag—Al alloy electrode in which the Al addition amount is set to 7 levels from 0 to 8.3 atomic% is prepared. It is the figure which showed the relationship between the difference of the resonant frequency after the hermetic sealing of a vibrator | oscillator, and the resonant frequency at the time of frequency adjustment, and the addition amount of Al of an Ag-Al alloy electrode film. The horizontal axis represents the amount of Al added (atomic weight%), and the vertical axis represents the frequency shift amount (ppm) before and after sealing. Each level of the quartz crystal resonator includes a chromium film having a thickness of 5 nm as an adhesion layer, and an Ag—Al alloy electrode having a thickness of 250 nm on the adhesion layer. In addition, the number of crystal resonators manufactured at each level is 100.

As can be seen from FIG. 5, it can be seen that the frequency shift amount before and after sealing changes according to the amount of Al added. Specifically, when the amount of Al added is 1 to 4 atomic%, It turns out that it changes abruptly according to this, and it turns out that it will be in a saturated state at about 90 ppm when the addition amount of Al becomes more than 5 atomic weight% vicinity. Therefore, when performing the frequency adjustment of the crystal resonator using the Ag-Al alloy electrode, the frequency adjustment is performed with the frequency adjustment set value in consideration of the frequency shift amount generated in the sealing process (considering the frequency shift amount). I understand that is good.
Further, from FIG. 5, since the frequency shift amount is saturated when the additive amount of Al is 5 atomic% or more, the additive amount of Al is 5 in view of ease of frequency adjustment and characteristic stability of the crystal resonator. In view of the fact that the atomic weight% or more is good and the above-mentioned electrode becomes clouded, it is understood that the added amount of Al is preferably 5 to 10 atomic weight%.
Actually, when the frequency shift amount was calculated from the frequency before and after the sealing of each of the 100 crystal resonators having the frequency of 27.0 MHz having the Ag-Al alloy electrode in which the additive amount of Al was 6.0 atomic%, the frequency shift was calculated. The amount was in the range of 90 ± 3 ppm. Therefore, it can be seen from this example that the reproducibility of the frequency shift amount is improved by setting the addition amount of Al to 5 to 10 atomic%, and the set value at the time of frequency adjustment is the final target. It can be seen that it is better to set the value around 90 ppm higher than the frequency. Of course, this set value is an example and varies depending on the composition of the Ag—Al alloy film and the sealing conditions, and is determined by grasping the frequency shift amount in advance.

   In addition, as described above, the frequency fluctuation (aging) when 10 quartz crystal vibrators having a frequency of 27.0 MHz having an Ag—Al alloy electrode with an addition amount of Al of 6.0 atomic weight% are annealed at 85 ° C. The results of examining the characteristics are shown in FIG. The horizontal axis represents the number of days, and the vertical axis represents the frequency change rate (ppm) for each measurement with respect to the frequency at the start of the test. The average frequency fluctuation amount after 21 days was −0.74 ppm, and the variation of 10 samples was ± 0.13 ppm, indicating very good aging characteristics.

   FIG. 7 corresponds to the consideration data that the frequency shift amount fluctuates with the Al addition amount. Using an Auger analyzer, the relationship between the amount of Al added and the Al composition on the surface of the electrode film after sealing was investigated. The horizontal axis represents the amount of Al added (atomic weight%) in the Ag—Al alloy electrode film, and the vertical axis represents the Al composition ratio on the electrode surface after hermetic sealing. As can be seen from FIG. 7, the composition ratio of Al on the surface of the Ag-Al alloy electrode is such that the Al addition amount rises rapidly in the vicinity of 3 atomic weight% and then the Al addition amount ranges from 5 to 10 atomic weight%. Constant (35%). It can be seen that this tendency correlates with the tendency between the Al addition amount and the frequency shift amount shown in FIG. That is, it can be seen that the range of the Al addition amount at which the Al composition ratio on the electrode surface is saturated corresponds to the region where the frequency shift amount is also saturated. This also shows that when the frequency adjustment is taken into consideration, the addition amount of Al is preferably 5 to 10 atomic%.

4). In the above description, the embodiments of the piezoelectric vibrator and the manufacturing method thereof according to the present invention have been described. However, the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, an example in which the present invention is applied to an SMD type crystal resonator has been described. However, for example, for a resonator of a lead type using a metal cap and having a silver electrode. Even applicable. Of course, the present invention can also be applied to a crystal resonator in which the planar shape of the crystal piece is round (substantially round). Various modifications can be made without departing from the scope of the present invention. For example, the present invention is not limited to the AT-cut crystal unit, and the present invention is also applied to crystal units other than the AT-cut unit and resonators using other piezoelectric materials such as lithium tantalate and lithium niobate. it can.

10: Piezoelectric vibrator of embodiment 11: Piezoelectric piece (crystal piece)
13: Electrode 13a: Excitation electrode 13aa: Adhesion layer 13ab: Ag-Al alloy film of this invention 13b: Terminal electrode 15: Container 15a: Recess 15b: Support pad 15c: External mounting terminal 17: Lid member 19: Conductive adhesion Agent

Claims (13)

  A piezoelectric vibrator comprising an excitation electrode mainly composed of silver, wherein the excitation electrode contains 1 to 15 atomic% of aluminum.   A piezoelectric vibrator comprising an excitation electrode mainly composed of silver, wherein the excitation electrode contains 1 to 10 atomic weight% of aluminum.   A piezoelectric vibrator comprising an excitation electrode mainly composed of silver, wherein the excitation electrode contains 5 to 10 atomic weight% of aluminum.   A piezoelectric piece, an adhesion layer provided on the front and back surfaces of the piezoelectric piece, and an excitation electrode comprising a laminated film of a thin film containing 1 to 15 atomic percent of aluminum and containing silver as a main component, provided on the adhesion layer. A piezoelectric vibrating piece characterized by comprising.   A piezoelectric piece, an adhesion layer provided on the front and back surfaces of the piezoelectric piece, and an excitation electrode comprising a laminated film of a thin film mainly containing silver and containing 1 to 10 atomic% of aluminum provided on the adhesion layer. A piezoelectric vibrating piece characterized by comprising.   A piezoelectric piece, an adhesion layer provided on the front and back surfaces of the piezoelectric piece, and an excitation electrode comprising a thin film laminated on the adhesion layer and containing 5 to 10 atomic% of aluminum and containing silver as a main component. A piezoelectric vibrating piece characterized by comprising. In a method for manufacturing a piezoelectric vibrator including a step of forming an excitation electrode mainly containing silver and containing aluminum on a piezoelectric piece,
A method of manufacturing a piezoelectric vibrator, comprising: forming a thin film for the excitation electrode, and then subjecting the structure to a heat treatment at 250 to 450 ° C. In a method for manufacturing a piezoelectric vibrator including a step of forming an excitation electrode mainly containing silver in an amount of 1 to 15 atomic weight aluminum on a piezoelectric piece,
A method of manufacturing a piezoelectric vibrator, comprising: forming a thin film for the excitation electrode, and then subjecting the structure to a heat treatment at 250 to 450 ° C. In a method of manufacturing a piezoelectric vibrator including a step of forming an excitation electrode mainly containing silver in an amount of 1 to 10 atomic weight aluminum on a piezoelectric piece,
A method of manufacturing a piezoelectric vibrator, comprising: forming a thin film for the excitation electrode, and then subjecting the structure to a heat treatment at 250 to 450 ° C. In a method of manufacturing a piezoelectric vibrator including a step of forming an excitation electrode mainly containing silver in an amount of 5 to 10 atomic weight aluminum on a piezoelectric piece,
A method of manufacturing a piezoelectric vibrator, comprising: forming a thin film for the excitation electrode, and then subjecting the structure to a heat treatment at 250 to 450 ° C. In the manufacturing method of the piezoelectric vibrator according to any one of claims 7 to 10,
The heat treatment is performed after the step of removing a part of the excitation electrode surface of the piezoelectric vibrator and adjusting the frequency of the piezoelectric vibrator and before the step of hermetically sealing the piezoelectric vibrator. A method for manufacturing a piezoelectric vibrator characterized by the above.   A step of forming an excitation electrode containing aluminum and silver as a main component on the front and back of the piezoelectric piece; a step of adjusting the frequency of the piezoelectric piece on which the excitation electrode is formed; and a step of sealing the piezoelectric piece after the frequency adjustment. A method of manufacturing a piezoelectric vibrator, wherein the frequency adjustment is performed in consideration of a frequency shift amount generated in the sealing process. 13. The method for manufacturing a piezoelectric vibrator according to claim 12, wherein the excitation electrode contains 5 to 10 atomic% of aluminum.

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