JPS5821965B2 - Method for forming side electrodes of tuning fork type piezoelectric vibrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming side electrodes of an ultra-small tuning fork type piezoelectric vibrator formed by corrosion removal processing.

An object of the present invention is to easily form side electrodes on a tuning fork type piezoelectric vibrator formed by corrosion removal processing, and to obtain a higher performance tuning fork type piezoelectric vibrator at a low cost.

BACKGROUND ART In recent years, as crystal oscillation type electronic wristwatches have become widespread, crystal resonators used as time standards are required to be further downsized, higher in performance, and lower in price.

For this reason, instead of the conventional machined crystal resonator,
A corrosion-free crystal resonator has been put into practical use, and its widespread use is expected.

However, although this crystal resonator is superior in terms of size and cost reduction compared to conventional mechanically processed resonators, it is insufficient in terms of performance.

It is inferior in terms of performance, especially in terms of high CI value,
This is a major impediment to the widespread use of ultra-compact resonators that require corrosion removal processing.

The reason for the high CI value is that the crystal resonator formed by conventional corrosion removal processing does not have electrodes on the side surface that is the corrosion processing surface.

FIG. 1 shows an example of a conventional quartz crystal resonator which does not have side electrodes and has been subjected to corrosion removal processing.

FIG. 1A shows a plan view of the crystal resonator, and its M-M'
Representative examples of processing steps in cross section are shown in FIGS. 1B-F.

In FIG. 1A, 1 is a crystal oscillator, 2 and 3 are two electrodes provided on the surface of the crystal oscillator, and electrodes 2 and 3 are provided on the back surface of the crystal oscillator, respectively. In-phase electrodes 4 and 5 are provided in a mirror image relationship with the surface electrodes with respect to the plane of the crystal resonator.

The general corrosion removal processing process for the crystal resonator shown in FIGS. A step of forming an electrode-shaped photoresist 8 on the conductive thin film 6 shown in FIG. A step of forming electrodes 2.3, 4.5 by etching the conductive thin film 6 using the photoresist 8 shown in FIG. 1E as a corrosion-resistant film, FIG. 1F. and removing the photoresist.

As mentioned above, the conventional corrosion-removed crystal oscillators do not have electrodes on the side surfaces, which are the corroded surfaces, and electrodes are formed only on the front and back surfaces, so when an electric field is applied, the lines of electric force are localized. However, it has the disadvantage that efficient excitation cannot be performed, resulting in a high CI value.

For this reason, attempts have been made to form side electrodes on a crystal resonator by a corrosion removal process, and FIG. 2 shows an example of a crystal resonator having side electrodes formed by a conventional corrosion removal process.

FIG. 2A is a plan view of a conventional crystal resonator having side electrodes, where 9 is the crystal resonator, 10.11 is the two electrodes provided on the surface of the crystal resonator, and 12.13 is the side surface. It is an electrode.

Further, FIG. 2B shows a diagram in which the negative pattern of the electrode is formed of photoresist, and 14 is the photoresist.

FIG. 2 C-G is an explanatory diagram showing an example of the conventional corrosion removal processing process on the o-o' cross section of the crystal resonator, and FIG. FIG. 3 is an explanatory diagram showing an example of a conventional corrosion removal process in FIG.

2C and 2H show a step of forming a photoresist 14 having a negative pattern of an electrode shown in FIG. 2B on a two-layer conductive thin film 16, 17 having the external shape of a vibrator formed on a crystal thin plate 15; In the second diagram, I is a process of removing corrosion from a crystal thin plate into the external shape of a vibrator using the conductive thin film as a corrosion-resistant film, and in Figure 2 E and J, sputtering is performed from the surface.
By forming a conductive thin film 18 that is the same as the conductive thin film 16 and a conductive thin film 19 that is the same as the other conductive thin film 17, and then sputtering from the back side, a conductive thin film 20 that is the same as the conductive thin film 16 and a conductive thin film 19 that is the same as the other conductive thin film 17 are formed. FIG. 2F is a step of forming a conductive thin film 21 that is the same as another conductive thin film 17.

K is a step in which the photoresist is removed by a lift-off method, and G and L in FIG. 2 are steps in which each layer of the conductive thin film is removed by etching.

The crystal resonator having side electrodes produced by the conventional manufacturing method described above has the following drawbacks.

(1) In order to reliably peel off the photoresist and remove the conductive thin film formed on the photoresist by the lift-off method, it is necessary to thicken the photoresist, which reduces the pattern accuracy of the photoresist.

Therefore, it is an ultra-small oscillator. This makes it difficult to form fine electrode shapes.

(2) The photoresist formed on the orifice of the tuning fork is likely to peel off or change shape during the corrosion removal process of the crystal thin plate, and therefore short-circuits between the electrodes at the orifice are likely to occur.

(3) The photoresist formed on the orifice of the tuning fork obstructs the circulation of the corrosive liquid during etching removal of the crystal thin plate, and the shape of the orifice of the tuning fork deteriorates.

Next, FIG. 3 shows another embodiment of a crystal resonator having side electrodes formed by conventional corrosion removal processing.

FIG. 3A is a plan view of the crystal resonator in this example, and FIG. 3B is a cross-sectional view taken along the Q-Q' cross section. There are two electrodes formed on the back surface of the crystal resonator.
．． Electrodes 25 and 26, which are electrically in phase with 24, are formed in a mirror image relationship with the front and back electrodes with respect to the plane of the crystal resonator.

27°28.29.30 are side electrodes formed in this example.

In this example, after the corrosion removal process of the external shape of the vibrator and the corrosion process of the front and back electrodes, as shown in FIG. 3C,
A side electrode is formed by sputtering by closely contacting the crystal resonator with a mask 31° 32 having a hole shape that allows a conductive thin film to be formed by sputtering only on the side surface of the tuning fork arm and the connecting portion between the side surface and the front and back electrodes. It is.

The third diagram is a sectional view taken along the line R-R'.

The crystal resonator shown in this example has the following drawbacks.

(1) The dimensional accuracy of the mask must be at least less than the width of the outer electrode of the crystal resonator, but generally the dimensional accuracy of the mask is ±15 degrees of thick plate, so the dimensional accuracy should be improved. To achieve this, the thickness of the mask must be made thinner.

However, if the thickness of the mask is made thinner, it becomes easier to break and workability becomes worse, so the thickness of the mask is 100 mm.
The limit is considered to be around μm.

Therefore, it is difficult to apply it to minute electrode shapes provided in ultra-small vibrators.

(2) It takes time and effort to align the mask and the crystal resonator and to fix the mask and the crystal resonator evenly and closely together.

Further, if the precision of alignment between the mask and the crystal resonator is poor, or if the crystal resonator and the mask are not in close contact due to warping of the mask, intervening dust, etc., a short circuit between the electrodes will occur.

Furthermore, if the mask and the crystal resonator are not fixed evenly and some parts are strongly fixed, the crystal resonator will crack and the mask will be damaged.

As mentioned above, it is even more difficult to apply the conventional quartz crystal resonator having side electrodes processed by corrosion removal processing due to miniaturization of the crystal resonator.

The present invention enables the side electrodes of an ultra-small tuning fork type piezoelectric vibrator to be easily formed by corrosion removal processing, and provides a piezoelectric vibrator with better performance at a low cost. As shown in the figure.

FIG. 4A shows the state of the crystal resonator shown in FIG. 1 after the front and back electrodes are formed, and FIG.
Figure 4B shows a state in which Cr is used as the first conductive thin film and Au is sputtered as the second conductive thin film.
As an example, Cr33 is first sputtered from the surface as a first conductive thin film, and then Au34 is sputtered as a second conductive thin film.

At this time, Cr33 and Au34 are formed not only on the front surface but also on a part of the side surface and the back surface.

Next, sputter Cr35 from the back side, then Au
Sputterlink a6.

At this time, cr 35 and Au 36 are formed not only on the back surface but also on the side surfaces and a part of the front surface.

Therefore, as shown in this figure, one layer each of Cr and Au is newly formed on the front and back surfaces of the crystal resonator, and two layers each of Cr and Au are formed on the side surfaces and the connecting portions between the side surfaces and the front and back surfaces. be done.

Next, the outer Au 36 is removed by corrosion processing using the inner Cr 35 as a corrosion resistant film, and the Cr 35 that appeared on the outer surface by this corrosion processing is then removed by corrosion processing using the inner Au 34 as a corrosion resistant film. As shown in Figure 4C, a single layer of Cr and Au films formed by sputtering remain on the side surfaces and the connections between the side surfaces and the front and back surfaces, and the electrodes shown in Figure 4A are left on the other front and back surfaces. Hail!

In this way, the side electrode 3T is formed as shown in the fourth diagram, but since the two electrodes will short-circuit through the side electrode if left as is, the conductive thin film 38 at the other end will be removed by laser beam irradiation, etc. do.

As described above, the present invention has the following advantages.

(1) Corrosion removal processing of the vibrator external shape and formation of front and back electrodes are performed in the same process as conventional piezoelectric vibrators using corrosion removal processing without side electrodes, so the accuracy of the vibrator external shape and electrode shape is It can be easily applied to ultra-small piezoelectric vibrators.

(2) During sputtering, there is no need to align the mask and the piezoelectric vibrator and to fix the piezoelectric vibrator to a jig, which simplifies the work.

Furthermore, according to the technical premise of the present invention, the formation of a conductive thin film on one side and a part of the opposite plane by sputtering is possible by selecting the sputtering conditions, the method of installing the piezoelectric vibrator during sputtering, etc. This is easily achieved.

Next, an application example of the present invention is shown in FIG.

In FIG. 5A, a photoresist 39 is formed near the crotch portion of the crystal resonator illustrated in FIG. 1A.

When a conductive thin film is sputtered, the conductive thin film is not formed only in the vicinity of the groove where the photoresist is formed.

Therefore, similarly to FIGS. 4B and 4C, at least two types of conductive thin films are sputtered from the front and back surfaces of the crystal resonator shown in FIG. 5A, and each layer of the conductive thin films is removed by etching. Further, when the photoresist is removed, two double-sided electrodes 40 and 41 connected to the front and back electrodes are formed, as shown in FIG. 5B.

As described above, the present invention allows side electrodes to be simply formed on a crystal resonator that has been subjected to corrosion removal processing, but the present invention is not limited to crystal resonators. It can be applied to any tuning fork type piezoelectric vibrator whose external shape is formed by; and the electrode structure is not limited to this example.

The present invention can easily achieve performance comparable to relatively large piezoelectric vibrators produced by conventional machining, without sacrificing the characteristics of ultra-miniaturization and low cost of piezoelectric vibrators produced by corrosion removal processing. The effect is very strong in that it can be used.

[Brief explanation of the drawing]

Figure 1 is an example of a conventional quartz crystal resonator that does not have side electrodes and has been processed to eliminate corrosion. Figure 2 is an example of a conventional corrosion-removed crystal resonator with side electrodes. FIG. 3 shows another example of a conventional corrosion-removed crystal resonator with side electrodes. FIG. 4 shows an embodiment of the present invention. FIG. 5 shows an example of application of the present invention. 111380. Crystal oscillator,
2, 3...Curved surface electrode, 4゜5...Back surface electrode,
6... Conductive thin film, 7... Crystal thin plate,
8...Photoresist, 9...Crystal resonator, 10.11...Surface electrode, 12,13.
... Side electrode, 14 ... Photoresist, 15 ... Crystal thin plate, 16.17.18.19
, 20.21... Conductive thin film, 22...
・Crystal resonator, 23.24...Surface electrode, 25
．． 26... Back electrode, 27, 28° 29.30
...Side electrode, 31.32...Mask, 33.34, 35.36...Conductive thin film, 3
7... Side electrode, 38... Also conductive thin film, 39... Photoresist, 40, 41
・・・・・・Side electrode.

Claims (1)

[Claims] 1. In a method for forming side electrodes of a tuning fork type piezoelectric vibrator, in which a conductive thin film is formed on the surface and midwinter plane of a piezoelectric thin plate that has been subjected to corrosion removal processing to give the external shape of the tuning fork type piezoelectric vibrator,
A first step of forming electrodes on the front and back surfaces using the conductive thin film, sputtering at least a first conductive thin film and a second conductive thin film on the surface of the thin plate on which the electrodes are formed, both on the front and back surfaces. A second step of sputtering to form at least two conductive thin films each on the front and midwinter planes of the thin plate and at least four layers on the side surfaces, followed by forming the two conductive thin films formed on the outside on the inside. A method for forming side electrodes of a tuning fork type piezoelectric vibrator, comprising a third step of removing the conductive thin film as a corrosion-resistant film by corrosion processing.