JP3279054B2 - Manufacturing method of thickness-sliding quartz crystal unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thickness-sliding quartz resonator, and more particularly to a method for forming electrodes on a very thin quartz plate.

[0002]

2. Description of the Related Art Recently, there is a strong need for high-speed processing of information processing apparatuses, and a high-speed operation of a DSP (Dig
Ital Signal Processor), and its clock source is a crystal oscillator.

[0003] The DSP has a duty of 50 with no jitter.
Requires a% clock. The best way to achieve this is to oscillate the frequency of the crystal oscillator at twice the clock.

In order to oscillate at a high frequency and to be simple, an oscillation circuit using a transistor or an inverting amplifier (these elements are individually or integrated and built in as a part of an LSI) as a main element is required to be a quartz crystal. The vibrator needs to be oscillated not by overtone but by fundamental (fundamental wave). In addition, there are restrictions on the temperature characteristics.

[0005] Therefore, these conditions are satisfied only by the AT.
Alternatively, it becomes a BT-cut ultrathin crystal oscillator. For example, a crystal oscillator having a thickness of 0.0167 mm with a 100 MHz _Z oscillation AT plate is obtained. These quartz oscillators are hereinafter represented by an AT plate.

[0006] Such an ultra-thin quartz crystal unit can be industrially produced by a polishing machine and a polishing technique, which have progressed rapidly in recent years, and a processing technique represented by an etching technique by photolithography.

[0007] Another need is an ultra-thin quartz mechanical filter that is incorporated into wireless devices. In order to use more radio waves and use more communication channels, increase the carrier frequency (for example, 800 MHz _Z band → 19G)
H _Z band) and narrowing of the channel spacing (e.g. 50KH _Z
→ 12.5 KHz _Z separation).

A key part for its practical use is a narrow band-pass quartz mechanical filter having a high center frequency. Center frequency, for example at 70MH _Z or more, AT-cut quartz crystal oscillation panel ultrathin is selected in consistency good fundamental oscillation of the circuit also in this case. The production of this ultra-thin quartz crystal mechanical filter is performed by the same technique as described above.

FIG. 5 shows an assembly view (a) of a conventional quartz oscillator and a side view (b) of a quartz plate. Electrode films 2 and 3 are formed on the front and back surfaces of a square AT quartz plate 1. The electrode films 2 and 3 are formed with opposing portions 2A and 3A which oppose each other on the front surface and the rear surface of the central portion of the quartz plate 1.
Lead portions 2B and 3B following A are formed up to both side portions.

A pair of lead terminals 5 and 6 are fixed through the holder 4 of the AT crystal plate 1.
The lead portions 2B and 3B of the electrode films 2 and 3 of the T quartz plate 1 are fixed by conductive bonding, respectively, and the electrodes are drawn out and the quartz plate 1 is supported.

The thickness of the quartz plate 1 is, for example, 100
0.0167mm in MH _Z vibrator, the thickness of the electrode films 2 and 3 are 500Å~3000Å (0.00005~0.0003m
m). The plane size of the quartz plate 1 is about 4 mm square.

The retainer 4 is round or oblong as viewed from the direction of the arrow, and is formed of ceramic or Kovar glass. Although not shown, a cap for covering the quartz plate 1 is generally resistance-welded or high-frequency-welded to the joint 4a of the retainer 4, and the inside of the cap is replaced with a vacuum or dry nitrogen gas (N ₂ ).

The plane shape of the quartz plate 1 is shown as a quadrangle, but various shapes such as a round shape, a shape having edges (thick portions) on four sides, and a shape having edges only on the lower side are provided. There is. Those having these edges are appropriately selected for the purpose of enhancing the vibration resistance and impact resistance against dropping of the crystal oscillator and the like, and omitting post-processing after photolithography.

Next, an example of the structure of a conventional quartz crystal mechanical filter will be described. FIG. 6 shows a top view (a), a back view (b) and a side sectional view (c) of a quartz crystal mechanical filter composed of a quartz plate having four edges and an electrode film. In the figure, an electrode film 12 is formed at the center on the surface of the quartz plate 11, and its lead portion 12 </ b> A is drawn out to the edge of the quartz plate 11.

A pair of divided electrode films 13 and 14 are formed on the back surface of the quartz plate 11 at a position facing the electrode film 12, and the lead portions 13 A and 14 A are connected to the quartz plate 1.
1 to the edge.

This structure constitutes a typical three-electrode energy confinement monolithic quartz mechanical filter.
In such a structure, the quartz plate 11 is formed by photolithography. The holder is an SMD type ceramic holder as shown in a top view (a), a side view (b), and another side view (c) of FIG. 7, in which a quartz plate 11 is housed. Hold and arrange electrode films 12-14
The connection with is made.

The lid 16 of the holder 15 is made of metal or ceramic, and hermetically seals the quartz plate 11 in the holder 15. Therefore, the inside of the retainer is replaced with a vacuum or dry nitrogen gas (N ₂ ) as in the case of the above-described quartz oscillator.

Reference numerals 17 to 19 denote metal pads, which are respectively connected to the electrode films 12 to 14 of the crystal plate 11 housed inside the holder.

Next, a manufacturing procedure of the crystal resonator having the structure shown in FIG. 5 or FIG. 6 will be described with reference to FIG.

The quartz plate is 1 or 11, the retainer is 4 or 15, and the lid is the cap or 1
6.

In forming the electrode film (S1), the metal electrode films 2, 3 or 12 to 14 are formed by vacuum deposition or sputtering.

The fixing of the cage (S2) is performed by bonding between the lead terminals 5 and 6 of the cage and the leads of the crystal plate 1, or by connecting the internal terminals of the pads 17 to 19 of the cage 15 and the leads of the crystal plate 11. Adhesion between the portions 12A to 14A is made, and application and curing of a conductive adhesive are performed.

In the frequency adjustment (S3), in the case of a quartz oscillator, the one shown in FIG. 5A before sealing with a cap is placed in a vacuum, and the electrode film 2A is oscillated or resonated while the quartz oscillator is oscillated or resonated. The metal is overlaid on the 3A portion, and the operating frequency is reduced to a desired frequency. For mechanical filter, a metal as the four frequencies of the counter 3 electrode layer 12 to 14, i.e. the logarithmic mode frequencies f _s and the oblique symmetrical mode frequencies f _a and one electrode frequency f ₁ and the other electrode the frequency f ₂ becomes a desired value Is adjusted.

In the case of a quartz oscillator, the characteristic inspection (S4) mainly inspects whether the frequency is within a desired deviation value, and whether the resonance resistance is below a desired value. In the case of a quartz mechanical filter, the above four frequencies f _s ,
Check frequency of f _a , f ₁ , f ₂ and characteristics as filter (center frequency, bandwidth, ripple, insertion loss, etc.)
Check.

Note that this characteristic inspection is omitted when it is confirmed that a significant change does not appear in those characteristics due to the storage of the cage in the next step.

In the case of the holder (S5), in the case of a quartz oscillator, the cap is sealed to the joint 4a of the holder 4. In the case of a mechanical filter, the lid 16 is sealed to the holder 15. In any case, the sealed interior is subjected to vacuum or dry nitrogen gas (N ₂ ) replacement.

The characteristic inspection (S6) includes a seal integrity check and the like in addition to the inspection performed in the characteristic inspection (S4).

[0028]

Conventional AT ultra-thin quartz crystal units or quartz mechanical filters are designed based on energy confinement theory. A representative document is “Analysis of Energy Confinement Type Piezoelectric Resonators, Onoe and Jonji, Journal of the Institute of Telecommunications, VOL48, 1574 (Showa 40)”.

Here, the thickness of the ultra-thin quartz plate is 0.04 m
If m and the outline size are about 4 mm, the ratio of the outline size to the thickness is 100 or more. Therefore, the design points are the size and thickness of the electrodes and the choice of metal for forming the electrodes.

Of these, the size of the electrode (the portion where the electrode films 2 and 3 face each other in FIG. 5, and the portion where the electrode films 12 to 14 face each other in FIG. 6) is required by an oscillation circuit in the case of a quartz oscillator. In the case of a quartz crystal mechanical filter, a larger value is desired from the viewpoint of low motional capacitance and low resonance resistance.

The size of the electrode is constrained by the following two requirements: (1) The dimension ratio of the contour to the electrode, which is not affected by the fixation on the contour on the quartz plate surface, is the degree of energy confinement. Is more than 6 is desired because there is enough.

(2) The thickness of the crystal under the electrode is sufficiently parallel and at least not concave.

The size of the electrode is determined by a trade-off with the above.

Next, the relationship between the thickness of the electrode and the metal will be described. First, the size of the facing portion of the electrode (the facing portion 2 in FIG. 5)
If the size of A, 3A) is 2a square, it is a vibrator plate having a sufficiently large plate surface according to the above-mentioned literature.
“Confinement” is a solution of the following equation (1).

[0035]

(Equation 1)

The frequency solution f is expressed by the following equation (2) where φ is 1
Exists between ０0.

[0037]

(Equation 2)

In the above equations (1) and (2), k _e and k _s are
It becomes the following formula.

[0039]

(Equation 3)

H: The thickness of the quartz oscillator plate f _s : The natural frequency of the quartz oscillator in the portion without the electrode f _e : The natural frequency of the quartz oscillator in the portion where the opposing portion is present Further, the natural frequencies f _s and f _e are Is determined by the following equation.

[0041]

(Equation 4)

Ρ: Density of the quartz plate, 2.65 g / cm ³ C ₆₆ ′: Elastic constant in the thickness direction of the quartz plate t: Thickness of one of the opposed electrodes ρ _e : Density of the opposed electrode Well-known energy closure The confining curve is obtained by calculating φ in the above equation (2) and a variate

[0043]

(Equation 5)

Λ: Ratio of elastic constants in the thickness direction and the contour direction Δ: Frequency return amount

Returning to the above equation (1), the upper solution is a symmetric mode (S _n ), and the lower solution is an oblique symmetric mode (a _n ). When the variable ξ is increased, the mode order n to be confined sequentially increases as shown below.

[0046]

(Equation 6)

Here, in the case of a crystal oscillator, the only mode to be confined is S ₀ , so the above-mentioned variable ξ is in the range of the following equation.

[0048]

(Equation 7)

However, if a quartz plate and an electrode symmetrical with respect to the center point can be formed, the obliquely symmetric mode a ₀ will not be excited, so that the variable ξ

[0050]

(Equation 8)

The S ₁ mode can be prevented from being confined.

In the above equation (11), the design condition becomes the following equation from the above equation (8).

[0053]

(Equation 9)

In this equation, λ is the angle AT plate selected from the temperature characteristics of the crystal, and the supporting direction is the Z ₀ ′ axis.

[0055]

Λ = 0.52, and H is 0.0167 mm in the case of 100 MHz _Z oscillation.
Assuming that a = 0.2 mm is selected from the above, the frequency return amount Δ is

[0056]

## EQU11 ## An electrode is formed under the restriction of Δ <0.0128 (13).

The standard of the frequency return amount is that the density of the electrode material is ρ
_Assuming that _e , it is determined as follows from the equations (9), (5), (6), and (7).

[0058]

(Equation 12)

When calculations are made for gold, silver, and aluminum as frequently used electrode materials, the following table shows the restrictions on the thickness t of the electrode film in relation to the respective densities ρ _e .

[0060]

[Table 1]

Here, another condition of the electrode is that the electric resistance is small, and among these metals, only aluminum satisfies it, and gold and silver cannot be used because of thin film resistance. The same applies to the case of a quartz crystal mechanical filter.

From the above, aluminum is selected as the electrode material of the ultra-thin quartz crystal resonator and quartz crystal mechanical filter.

However, in the manufacturing process shown in FIG. 8, aluminum is oxidized on the surface of the electrode between the formation of the electrode (S1) and the fixing of the retainer (S2), and becomes alumite.

Therefore, in the step of frequency adjustment (S3),
The frequency adjustment processing using the same or different metal becomes unstable, and the frequency-adjusted electrode surface has a structure in which the frequency adjustment metal adheres to the surface of the anodized film as shown in FIG. Become.

When aluminum is used as the electrode material,
With the thinning of the electrodes, a problem arises in that the resistance of the lead portion increases as compared with gold or silver electrode materials.

Under these circumstances, in the conventional method for manufacturing a quartz resonator and a quartz crystal mechanical filter using aluminum as an electrode film, electrical characteristics are deteriorated, and stability over time cannot be guaranteed.

When the electrode material is gold or silver, the surface of the electrode can be cleaned by chemical or plasma discharge immediately before the frequency adjustment (S3), as shown in FIG. 9 (b). , Frequency assimilation with metal can be obtained.

It is an object of the present invention to provide a method of manufacturing a thickness-sliding quartz crystal resonator which uses aluminum as an electrode material, has little aging, has excellent electrical characteristics, and can perform stable frequency adjustment.

[0069]

According to the present invention, in order to solve the above-mentioned problems, an aluminum electrode is formed by forming opposing portions on the front and back surfaces of an ultra-thin quartz plate, and overlying vapor deposition is performed on the opposing portions. In the method of manufacturing a thickness-sliding quartz crystal resonator to adjust the frequency of oscillation or resonance frequency by the thickness of the metal to be,
In the electrode formation, a conductive electrode is formed on the quartz plate surface except for at least the opposing portion, one end of the conductive electrode is connected to a lead terminal of a retainer, and the opposing portion of the quartz plate is formed in the electrode forming apparatus. An aluminum main electrode having a pattern up to a conductive electrode is formed, and the lead terminal is used as a connection terminal with a measuring instrument for frequency adjustment. After the main electrode is formed, the electrode is continuously exposed without exposing the main electrode to air. It is characterized in that metal deposition for frequency adjustment is performed in the forming apparatus.

[0070]

[0071]

[Action]

(First invention) An electrode is formed in a two-step process of a conduction electrode and a main electrode, and the conduction electrode is connected to a lead terminal of a retainer so as to be connected to a measuring instrument for frequency adjustment later. By forming the main electrode and forming the metal for frequency adjustment continuously in the same electrode forming apparatus, the aluminum electrode is prevented from being exposed to air and becoming anodized, and the frequency is reduced. An assimilation with the main electrode is obtained by overlaying metal deposition for adjustment.

[0072]

[0073]

FIG. 1 is a manufacturing process diagram showing one embodiment of the present invention.

In forming the conductive electrode (S11), a conductive electrode corresponding to only the lead portion of the electrode film or a lead portion of the lead portion which is connected to the lead terminal of the retainer is formed on an extremely thin quartz plate. That is, the opposing portions of the pair of electrodes opposing each other with the quartz plate interposed therebetween are not formed.

The fixing of the cage (S12) is performed in the step (S11).
The lead terminal of the cage is connected to the conductive electrode of the electrode film formed in the step. This process is performed in the same manner as the conventional cage fixing (S2).

As a result of the above processing, for example, in the case of a quartz oscillator, as shown in FIG. , 24 are formed, and the conductive electrodes 25 and 26 and the lead terminals 23 and 26 are formed.
24 and the crystal plate 21 is fixed to the holder 22.

Here, it is preferable that the conductive electrodes 25 and 26 have high conductivity and excellent surface cleanliness and electroless corrosion resistance.
For example, gold or silver treated as an electrode film is preferable.

The conductive electrodes 25 and 26 are wide and thick as long as they do not affect the oscillating operation. It is preferable that the conductive electrodes 25 and 26 extend to a portion near the facing portion of the electrode film in order to reduce resonance resistance and insertion loss. Become.

In the electrode formation (S13), electrodes (main electrodes) 27 and 28 having opposing portions in a predetermined pattern are formed on the front surface and the back surface of the central portion of the quartz plate 21. This main electrode 27,
Reference numeral 28 is made of aluminum, and has a surface configuration in which one end is overlapped with the conductive electrodes 25 and 26 at the center of the quartz plate 21 as shown in FIG. The method of forming the main electrodes 27 and 28 is performed by vacuum deposition, sputtering, or the like, as in the related art.

In the frequency adjustment (S14), the electrode formation (S1)
Subsequent to 3), the deposition is continuously performed in the same vacuum chamber, and metal deposition is performed on the surfaces of the main electrodes 27 and 28 without exposing the formed main electrodes 27 and 28 to air. At this time, the oscillation or resonance frequency measurement for adjusting the amount of metal over-deposition is obtained by using the lead electrodes 23 and 24 to connect to an external measuring instrument.

This electrode formation (S13) and frequency adjustment (S13)
14) Specifically, a large number of individual products are formed in the order of electrode formation and frequency adjustment, or a plurality of electrodes are formed at the same time, and then frequency adjustment is performed individually and sequentially.

Cage storage (S15) and characteristic inspection (S1)
6) In the same manner as in the prior art, the attachment of a cap or lid filled with vacuum or gas and the inspection of electrical characteristics such as frequency and resonance resistance are performed.

Therefore, according to the present embodiment, the formation and frequency adjustment of the main electrodes 27 and 28 made of aluminum are continuously performed in the same vacuum chamber, and the main electrodes are not exposed to air and the metal Since the vapor deposition is performed, the metal can be repeatedly vapor-deposited without causing anodization of aluminum, and the main electrode can be formed without aging and stable frequency adjustment can be performed.

The conductive electrodes 25 and 26 can be made of gold or silver, and their surfaces can be easily cleaned to ensure the assimilation at the time of forming the main electrode. Further, the resistance value of the lead portion can be reduced, and the resonance resistance and the insertion loss can be minimized.

FIG. 3 is a manufacturing process diagram showing another embodiment of the present invention.

The present embodiment is different from FIG. 1 in that after the formation of the conductive electrode (S21), the formation of the electrode (S22) and the frequency adjustment (S23) are continuously performed in the same chamber. After that, the retainer is fixed (S24) and the characteristics are inspected (S2).
5), the cage storage (S26) and the characteristic inspection (S27) are the same processing.

Since the frequency adjustment is performed before the holder is fixed, connection with the measuring instrument is performed by bringing a probe pin or the like into contact with the conductive electrode portion.

Also in the present embodiment, the electrode formation (S22) for forming the aluminum main electrode and the frequency adjustment (S23) for depositing a metal on the main electrode surface are continuously performed so that the main electrode surface is exposed to air. Exposure is eliminated, and the same operation and effect as in the above embodiment can be obtained.

Whether or not to expose to air between the formation of the conductive electrode (S21) and the formation of the electrode (S22) depends on the electrode forming apparatus (evaporator, sputtering, etc.). A cleaning process for conducting electrodes necessary for forming electrodes is performed.

FIG. 4 shows an example of electrode formation of the quartz crystal mechanical filter in the embodiment, and shows a top view (a), a back view (b) and a side sectional view (c) of the quartz crystal mechanical filter.

On the front and back surfaces of the quartz plate 31 having edges on four sides, the conductive electrodes 32, 3
3 and 34 are formed, and main electrodes 35, 36 and 37 are formed between the central portion of the quartz plate 31 and the conductive electrodes 32, 33 and 34, and constitute a three-electrode energy trapping monolithic quartz mechanical filter.

In such a quartz crystal mechanical filter as well, after the conductive electrodes 32, 33, and 34 are formed, the main electrodes 35, 36, and 37 are formed and the frequency is adjusted in the same chamber. Enables production that prevents production.

[0093]

As described above, according to the present invention, in forming an electrode using aluminum as an electrode material, a conductive electrode is formed on the surface of a quartz plate, and one end of the conductive electrode is connected to the lead terminal of the retainer. Or directly as the connection end with the measuring instrument,
Since the formation of the main electrode of aluminum having a pattern from the opposing portion of the quartz plate to the conductive electrode in the electrode forming apparatus and the subsequent metal deposition for frequency adjustment are continuously performed, the following effects are obtained.

(1) It is possible to prevent the aluminum electrode from being exposed to air and being converted to alumite, and to assimilate with the main electrode by overlapping vapor deposition of metal for frequency adjustment, thereby enabling stable frequency adjustment.

(2) Aging does not change due to assimilation of metal deposited on the main electrode.

(3) A metal having high conductivity and easy handling such as gold or silver can be used for the conductive electrode, and the resonance resistance and the insertion loss can be reduced to obtain excellent electrical characteristics.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram showing one embodiment of the present invention.

FIG. 2 is a crystal resonator structure of an embodiment.

FIG. 3 is a manufacturing process diagram showing another embodiment of the present invention.

FIG. 4 shows a quartz crystal mechanical filter structure according to the embodiment.

FIG. 5 shows a structure of a conventional crystal unit.

FIG. 6 shows a resonator structure of a conventional quartz crystal mechanical filter.

FIG. 7 is a holder for a quartz crystal mechanical filter.

FIG. 8 is a conventional manufacturing process diagram.

FIG. 9 is a cross-sectional view of an electrode film.

[Explanation of symbols]

 21, 31: Quartz plate 22: Cage 23, 24: Lead terminal 25, 26, 32, 33, 34: Conductive electrode 27, 28, 35, 36, 37: Main electrode

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masako Tanaka 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside Meidensha Co., Ltd. (56) References JP-A-1-221011 (JP, A) JP-A-58- 170210 (JP, A) JP-A-4-196610 (JP, A) JP-A-5-68124 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 3 / 00-3 / 04

Claims (1)

(57) [Claims] 1. A thickness for forming an aluminum electrode having opposing portions on the front and back surfaces of an ultra-thin quartz plate, and adjusting the frequency of oscillation or resonance frequency by the thickness of the metal deposited on the opposing portion. In the method of manufacturing a slip quartz crystal resonator, the electrode is formed by forming a conductive electrode on a quartz plate surface excluding at least the facing portion, connecting one end of the conductive electrode to a lead terminal of a retainer, Forming an aluminum main electrode having a pattern from the opposing portion of the quartz plate to the conducting electrode, using the lead terminal as a connection terminal with a frequency adjustment measuring instrument, and forming the main electrode with air after forming the main electrode. A method for producing a thickness-sliding quartz crystal resonator, wherein metal deposition for frequency adjustment is continuously performed in the electrode forming apparatus without exposure to a crystal.