JP2020136999A - Crystal element, crystal device, and electronic apparatus - Google Patents

Abstract

To provide a crystal element that can reduce a difference in film thickness between excitation electrodes on both principal surfaces.SOLUTION: A crystal element 10 comprises: a crystal plate 12 in a substantially rectangular shape; excitation electrodes 14e, 14f; and protective films 143. The crystal plate 12 has, in plan view, two long sides 11a, 11b and two short sides 11c, 11d, two principal surfaces 13e, 13f surrounded by the two long sides 11a, 11b and the two short sides 11c, 11d and facing each other, and four side faces 13a, 13b, 13c, 13d sandwiched by the two principal surfaces 13e, 13f. The excitation electrodes 14e, 14f are located on the two principal surfaces 13e, 13f, respectively, and have outermost layers 142 formed of aluminum or aluminum alloy. The protective films 143 are located on the excitation electrodes 14e, 14f and prevent oxidation of the outermost layers 142.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a crystal element, a crystal device including a crystal element, and an electronic device including the crystal device. Examples of the crystal device include a crystal oscillator or a crystal oscillator.

The quartz element in the thickness sliding vibration mode has excitation electrodes formed of a metal film pattern formed on both main surfaces of an AT-cut quartz plate. The excitation electrode is mainly made of gold (Au).

The crystal device outputs a signal having a specific oscillation frequency by utilizing the piezoelectric effect and the inverse piezoelectric effect of the crystal element. A general crystal device has a structure in which a crystal element is housed in a package and the crystal element is hermetically sealed by a lid (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-139901

Since the conventional excitation electrode has a heavy gold density of 19.2 g / cm ³ , it is necessary to reduce the film thickness. This is because when the film thickness is increased, the mass of the excitation electrode increases and the oscillation frequency decreases. On the other hand, when the film thickness becomes thin, it becomes difficult to adjust the film thickness, so that a difference in film thickness tends to occur between the excitation electrodes on both main surfaces. As a result, a stress difference is generated between the excitation electrodes on both main surfaces due to the temperature change, and the crystal plate is distorted, which may adversely affect the electrical characteristics of the crystal element. In particular, in a crystal element having an oscillation frequency of 70 MHz or more, the thickness of the crystal plate is considerably thin, so that this problem is remarkable.

Therefore, an object of the present disclosure is to provide a quartz element capable of reducing the difference in film thickness between the excitation electrodes on both main surfaces.

The crystal element according to the present disclosure is a crystal element having an oscillation frequency of 70 MHz or more, and includes a substantially rectangular crystal plate, an excitation electrode, and a protective film. In a plan view, the crystal plate has two long sides and two short sides, two opposing main surfaces surrounded by the two long sides and the two short sides, and the two main surfaces. It has four sides, which are sandwiched between them. The excitation electrode is located on each of the two main surfaces and has an outermost layer made of aluminum or an aluminum alloy. The protective film is located on the excitation electrode and suppresses oxidation of the outermost layer.

The crystal device according to the present disclosure is provided with the crystal element according to the present disclosure, and the electronic device according to the present disclosure is provided with the crystal device according to the present disclosure.

According to the quartz element according to the present disclosure, since the excitation electrode having the outermost layer made of aluminum or an aluminum alloy is provided, the thickness of the excitation electrode on both main surfaces is higher than that of the excitation electrode having the outermost layer made of gold. The difference can be reduced, which ensures stable electrical characteristics. Moreover, by having the protective film on the excitation electrode, the oxidation of the outermost layer is suppressed, so that more stable electrical characteristics can be ensured.

1 [A] is a perspective view showing the crystal element of the first embodiment, FIG. 1 [B] is an enlarged sectional view taken along line Ib-Ib in FIG. 1 [A], and FIG. 1 [C] is Ic in FIG. 1 [A]. -Ic line enlarged sectional view. FIG. 2 [A] is a perspective view showing the crystal element of the second embodiment, and FIG. 2 [B] is an enlarged cross-sectional view taken along line IIb-IIb in FIG. 2 [A]. 3 [A] is a cross-sectional view showing the crystal element of the third embodiment, FIG. 3 [B] is a cross-sectional view showing the crystal element of the fourth embodiment, and FIG. 3 [C] is a cross-sectional view showing the crystal element of the fifth embodiment. Is. It is a top view which shows the modification of the crystal element of Embodiment 4. 5 [A] is a perspective view showing the crystal device of the sixth embodiment, and FIG. 5 [B] is a sectional view taken along line Vb-Vb in FIG. 5 [A]. FIG. 6A is a front view showing a first example of the electronic device of the seventh embodiment, and FIG. 6B is a front view showing a second example of the electronic device of the seventh embodiment.

Hereinafter, embodiments for carrying out the present disclosure (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings. In the present specification and the drawings, substantially the same components will be appropriately described by using the same reference numerals. The shapes drawn in the drawings are drawn for those skilled in the art to be easily understood, and therefore do not always match the actual dimensions and ratios. Further, the main surfaces 13e and 13f correspond to the "first main surface" and the "second main surface" in the claims, respectively.

<Embodiment 1>
As shown in FIGS. 1 [A], 1 [B], and 1 [C], the crystal element 10 of the first embodiment is a crystal element 10 having an oscillation frequency (fundamental wave) of 70 MHz or more. It includes a substantially rectangular crystal plate 12, excitation electrodes 14e and 14f, and a protective film 143. The crystal plate 12 has two long sides 11a. 11b, two short sides 11c, 11d, and two long sides 11a. Two opposing main surfaces 13e and 13f surrounded by 11b and two short sides 11c and 11d, and four side surfaces 13a sandwiched between the two main surfaces 13e and 13f. It has 13b, 13c, and 13d. The excitation electrodes 14e and 14f are located on the two main surfaces 13e and 13f, respectively, and have an outermost layer 142 made of aluminum or an aluminum alloy. The protective film 143 is located on the excitation electrodes 14e and 14f and suppresses the oxidation of the outermost layer 142. The crystal element 10 in FIG. 1 [B] is shown in a larger scale than the crystal element 10 in FIG. 1 [C].

The crystal element 10 may have the following configuration. The crystal element 10 further includes connection electrodes 14a and 14b electrically connected to the package, and extraction electrodes 14g and 14h connecting the connection electrodes 14a and 14b and the excitation electrodes 14e and 14f. The protective film 143 on the main surface 13f covers the extraction electrode 14h and does not cover the connection electrodes 14a and 14b. The two side surfaces 13a and 13b including the long sides 11a and 11b are the side surfaces that are substantially parallel to the slope portions 16a and 16b that are oblique in the thickness direction (Y'axis direction) of the crystal plate 12 and the thickness direction of the crystal plate 12. It has parts 17a and 17b. The slope portions 16a and 16b are m planes of the crystal plane, and the side surface portions 17a and 17b include planes perpendicular to the R plane of the crystal plane.

Next, the crystal element 10 will be described in more detail.

The crystal plate 12 is an AT-cut crystal plate. That is, in the crystal, the Cartesian coordinate system XYZ consisting of the X-axis (electric axis), the Y-axis (mechanical axis) and the Z-axis (optical axis) is 30 ° or more and 50 ° or less (for example, 35 °) around the X-axis. 15') When the orthogonal coordinate system XY'Z'is defined by rotating it, the wafer cut out parallel to the XZ'plane becomes the raw material of the crystal plate 12. The long sides 11a and 11b are parallel to the X axis, the short sides 11c and 11d are parallel to the Z'axis, and the thickness direction is parallel to the Y'axis. Taking the external dimensions of the crystal plate 12 as an example, the long sides 11a and 11b are 650 to 920 μm, the short sides 11c and 11d are 550 to 690 μm, and the thickness varies depending on the oscillation frequency. For example, when the oscillation frequency is 100 MHz or more, the thickness of the crystal plate 12 at the portion where the excitation electrodes 14e and 14f are located is 17 μm or less.

The pair of excitation electrodes 14e and 14f are substantially rectangular in a plan view, and are provided at substantially the center of both main surfaces 13e and 13f, respectively. On the main surface 13e, the extraction electrode 14g extends from the excitation electrode 14e along the long side 11a to the connection electrode 14a on the short side 11c. The connection electrode 14a extends from the main surface 13e through the side surface 13c to the opposite main surface 13f. On the main surface 13f, the extraction electrode 14h extends from the excitation electrode 14f to the connection electrode 14b on the short side 11c along the long side 11b. The connection electrode 14b extends from the main surface 13f through the side surface 13c to the opposite main surface 13e. That is, the connection electrode 14a conducts to the excitation electrode 14e via the extraction electrode 14g, and the connection electrode 14b conducts to the excitation electrode 14f via the extraction electrode 14h. The excitation electrodes 14e and 14f are not limited to a substantially rectangular shape, and may be, for example, a substantially circular shape or a substantially elliptical shape.

The excitation electrodes 14e and 14f form a laminate of, for example, a base layer 141 made of chromium (Cr) and an outermost layer 142 made of aluminum (Al) or an aluminum alloy. That is, the base layer 141 is located on the crystal plate 12, and the outermost layer 142 is located on the base layer 141. The base layer 141 mainly plays a role of obtaining an adhesive force with the crystal plate 12. The outermost layer 142 mainly serves to obtain electrical conduction. The connection electrodes 14a and 14b and the extraction electrodes 14g and 14h may also be a laminate of the base layer 141 and the outermost layer 142, similarly to the excitation electrodes 14e and 14f. The aluminum alloy contains aluminum as a main component (for example, contains 50 wt% or more), contains one or more selected from, for example, copper, manganese, silicon, magnesium and zinc, and has a density similar to that of aluminum. In addition, another layer may be provided between the base layer 141 and the outermost layer 142.

As a manufacturing process of the excitation electrodes 14e, 14f, etc., a method of forming a photoresist pattern on the quartz plate 12 after forming a film and etching, a method of forming a photoresist pattern on the quartz plate 12 and then forming a film and lifting off, or a method of lifting off. Examples thereof include a method of covering the crystal plate 12 with a metal mask to form a film. Sputtering or thin film deposition is used for film formation.

The protective film 143 is made of silicon dioxide (SiO ₂ ) in the first embodiment. However, the protective film 143 may be any material as long as it suppresses the oxidation of the outermost layer 142, and may be a metal such as gold. To form the protective film 143 on the quartz plate 12 after the excitation electrodes 14e and 14f are formed, a method of forming a photoresist pattern on the quartz plate 12 after film formation and etching is performed, and the photoresist pattern is formed on the quartz plate 12 and then etched. Examples thereof include a method of forming a film and lifting off, or a method of covering the crystal plate 12 with a metal mask to form a film. Sputtering or thin film deposition is used for film formation.

The extraction electrodes 14g and 14h may be covered with a protective film 143. The connection electrodes 14a and 14b on the side surface 13c and the main surface 13e may be covered with a protective film 143 as long as they are not locations to which a conductive adhesive or the like is attached. If the electrical characteristics are not affected, the entire crystal plate 12 after the excitation electrodes 14e and 14f are formed (excluding the connection electrodes 14a and 14b on the main surface 13f) may be covered with the protective film 143.

In the slope portions 16a and 16b and the side surface portions 17a and 17b, the mask (corrosion resistant film) on the main surface 13e and the mask (corrosion resistant film) on the main surface 13f are slightly displaced in the Z'axis direction during wet etching (outer shape processing step). Obtained by

The crystal element 10 can be manufactured as follows by using, for example, a photolithography technique and an etching technique.

First, a corrosion-resistant film is provided on the entire surface of the AT-cut crystal wafer, and a photoresist is provided on the film. Subsequently, a mask on which the pattern of the crystal plate 12 is drawn is placed on the photoresist to expose a part of the corrosion-resistant film by exposure and development, and in this state, wet etching is performed on the corrosion-resistant film. Then, the outer shape of the crystal plate 12 is formed by performing wet etching on the crystal wafer using the remaining corrosion-resistant film as a mask (outer shape processing step).

After that, the remaining corrosion-resistant film is removed from the crystal wafer, and metal films serving as excitation electrodes 14e, 14f and the like are provided on the entire surface of the crystal wafer. Subsequently, a photoresist mask composed of patterns such as the excitation electrodes 14e and 14f is formed on the metal film, and the unnecessary metal film is removed by etching to remove the unnecessary metal film by etching to obtain the excitation electrodes 14e and 14f composed of the base layer 141 and the outermost layer 142. Etc. (electrode forming step).

After that, unnecessary photoresist is removed, and a silicon dioxide film serving as a protective film 143 is provided on the entire surface of the crystal wafer. Subsequently, a photoresist mask composed of the pattern of the protective film 143 is formed on the silicon dioxide film, and unnecessary silicon dioxide is removed by etching to form the protective film 143 made of silicon dioxide (protective film forming step). ..

After that, a plurality of crystal elements 10 are formed on the crystal wafer by removing unnecessary photoresist. Finally, by individualizing the crystal wafer into individual crystal elements 10, a single crystal element 10 can be obtained (individualization step).

The operation of the crystal element 10 is as follows. An alternating voltage is applied to the crystal plate 12 via the excitation electrodes 14e and 14f. Then, the crystal plate 12 causes a thickness sliding vibration so that both main surfaces 13e and 13f are displaced from each other, and generates a specific oscillation frequency. In this way, the crystal element 10 operates so as to output a signal having a constant oscillation frequency by utilizing the piezoelectric effect and the inverse piezoelectric effect of the crystal plate 12. At this time, the thinner the crystal plate 12 between the excitation electrodes 14e and 14f, the higher the oscillation frequency.

Next, the action and effect of the crystal element 10 will be described.

According to the crystal element 10 of the first embodiment, the excitation electrodes 14e and 14f having the outermost layer 142 made of aluminum or an aluminum alloy are provided, so that the excitation electrodes 14 having the outermost layer made of gold (comparative example) are provided. , The difference in film thickness between the excitation electrodes 14e and 14f on both main surfaces 13e and 13f can be reduced, thereby ensuring stable electrical characteristics. Moreover, by having the protective film 143 on the excitation electrodes 14e and 14f, the oxidation of the outermost layer 142 is suppressed, so that more stable electrical characteristics can be ensured. The detailed reason is as follows.

Hereinafter, the outermost layer 142 in the first embodiment will be referred to as an Al film, and the outermost layer in the comparative example will be referred to as an Au film. The density of Au is 19.3 g / cm ³ , while the density of Al is 2.7 g / cm ³ . That is, the density of Al is about 1/7 of the density of Au. That is, when an Al film and an Au film having the same weight are formed, the film thickness of Al is about 7 times the film thickness of Au. Therefore, the film thickness of the Al film can be adjusted about 7 times easier than that of the Au film, so that the film thickness difference between the excitation electrodes 14e and 14f on both main surfaces 13e and 13f can be reduced. As a result, since the stress difference between the excitation electrodes 14e and 14f is small, the distortion of the crystal plate 12 can be avoided, so that the electrical characteristics of the crystal element 10 can be suppressed from being adversely affected. In particular, in the crystal element 10 having an oscillation frequency of 70 MHz or more, the thickness of the crystal plate 12 is considerably thin, so that this effect is remarkable.

Here, a numerical example of the film thickness of the Al film and the Au film will be described. The film thicknesses of the Al film and the Au film differ depending on the frequency band of the oscillation frequency of the crystal element 10. For example, when the frequency band is 38.4 MHz, the Al set film thickness is 1847.1 nm, the Al estimated film thickness is 1662.1 to 2040.0 nm, the Au set film thickness is 258.4 nm, and the Au estimated film thickness is 230. It is 0 to 285.0 nm. When the frequency band is 76.8 MHz, the Al set film thickness is 923.5 nm, the Al estimated film thickness is 830.0 to 1030.0 nm, the Au set film thickness is 129.2 nm, and the Au estimated film thickness is 110.0 to. It is 143.0 nm. The "set film thickness" is the set film thickness at the time of film formation, and the "estimated film thickness" is the actual estimated film thickness when the film is formed with the set film thickness.

Further, the surface of aluminum or an aluminum alloy is likely to be oxidized to aluminum oxide (Al ₂ O ₃ ). When the outermost layer 142 is oxidized, the mass of the outermost layer 142 increases, so that the oscillation frequency of the crystal element 10 during or after manufacturing fluctuates. Therefore, it is necessary to remove the aluminum oxide by dry etching, but this time there is a problem that the etching product adheres to the excitation electrodes 14e and 14f. Therefore, in the first embodiment, the oxidation of the outermost layer 142 is suppressed by covering the excitation electrodes 14e and 14f with the protective film 143, so that more stable electrical characteristics can be ensured.

Further, the conductive adhesive applied to the connection electrode 14b on the main surface 13f travels so as to crawl up on the extraction electrode 14h and reaches the excitation electrode 14f, so that the oscillation frequency may fluctuate. Therefore, in the first embodiment, by covering the lead-out electrode 14h on the main surface 13f with the protective film 143, the protective film 143 can prevent the conductive adhesive from creeping up. Therefore, in combination with the above-mentioned effects, further Stable electrical characteristics can be ensured.

In particular, when the protective film 143 is made of silicon dioxide, the difference in the coefficient of thermal expansion between the protective film 143 and the crystal plate 12 becomes the same composition (SiO ₂ ), so that the crystal plate 12 is distorted. And warpage can be suppressed.

Further, the two side surfaces 13a and 13b including the long sides 11a and 11b are substantially parallel to the slope portions 16a and 16b that are oblique in the thickness direction (Y'axis direction) of the crystal plate 12 and the thickness direction of the crystal plate 12. By having the side surface portions 17a and 17b, in other words, the slope portions 16a and 16b which are the m planes of the crystal plane and the side surface portions 17a and 17b including the planes perpendicular to the R plane of the crystal plane are provided. As a result, both end portions (both side surfaces 13a and 13b) are substantially thinned. Therefore, since the vibration displacement at both ends (both sides 13a and 13b) is greatly attenuated, the CI (crystal impedance) value can be reduced by the effect of confining the vibration energy. Due to this effect, it is not necessary to adopt a structure such as a so-called convex shape, bevel shape or mesa shape, so that the manufacturing process can be simplified. This effect is maximized when the thickness of the slope portions 16a and 16b and the thickness of the side surface portions 17a and 17b are equal in the thickness direction of the crystal plate 12 (Y'axis direction). At this time, as shown in FIG. 1 [B], the left and right sides are point-symmetrical with respect to the center of gravity of the crystal plate 12, so that the upper half and the lower half of the crystal plate 12 have the same vibration state. The vibration balance can be improved. In addition to this, according to the crystal element 10, since the sound velocity of the outermost layer 142 (Al) is close to the sound velocity of the crystal plate 12 (SiO ₂ ), the crystal plate 12 tends to vibrate, which is combined with the above effect. The CI value can be further reduced.

<Embodiment 2>
As shown in FIGS. 2 [A] and 2 [B], the crystal element 20 of the second embodiment differs from the first embodiment in the following points. That is, the crystal plate 21 is located between the vibrating portion 22 where the excitation electrodes 14e and 14f are located, the fixing portion 24 which is thicker than the vibrating portion 22, and the fixing portion 24 and the vibrating portion 22, and the vibrating portion from the fixing portion 24. It has a buffer portion 23 that becomes thinner toward 22. The main surface 13e of the fixed portion 24, the main surface 13e of the vibrating portion 22, and the main surface 13e of the buffer portion 23 are in the same plane. The main surface 13f of the fixed portion 24 is parallel to the main surface 13f of the vibrating portion 22, and the main surface 13f of the buffer portion 23 is inclined toward the main surface 13e side from the fixed portion 24 toward the vibrating portion 22.

The vibrating portion 22, the cushioning portion 23, and the fixing portion 24 are all substantially rectangular when viewed in a plan view. One main surface 13e is flush with the vibrating portion 22, the cushioning portion 23, and the fixing portion 24. The other main surface 13f is divided into three parts, the vibrating portion 22 and the fixing portion 24 are parallel to each other, and the cushioning portion 23 is slanted so as to be thicker from the vibrating portion 22 side to the fixing portion 24 side. The cross-sectional shape of the quartz plate 21 shown in FIG. 2 [B] is, for example, that the entire main surface 13e side is covered with a corrosion resistant film, only the fixed portion 24 on the main surface 13f side is covered with a corrosion resistant film, and wet etching is performed on the crystal. Obtained by

The thickness of the buffer portion 23 in the vertical direction (Y'axis direction) gradually increases from the vibrating portion 22 toward the fixed portion 24. Therefore, since the vibration generated in the vibrating portion 22 is gradually attenuated toward the fixed portion 24, the influence of the vibration reflected by the fixed portion 24 on the vibrating portion 22 is reduced. Therefore, according to the crystal element 20, the influence of the fixing portion 24 on the vibration of the vibrating portion 22 can be suppressed by the cross-sectional shape of the cushioning portion 23, so that the CI value can be reduced. Further, in the crystal element 20 having an oscillation frequency of 70 MHz or more, since the plate thickness of the vibrating portion 22 is considerably thin, it is necessary to pay attention to damage at the time of mounting. According to the crystal element 20, the handleability can be improved by mounting the crystal element 20 on the package by the thick fixing portion 24. Further, since the protective film 143 extends to the buffer portion 23 on the main surface 13f, the protective film 143 can prevent the conductive adhesive from creeping up, so that the electrical characteristics are more stable in combination with the above effects. Can be secured. Other configurations, actions and effects of the second embodiment are similar to those of the first embodiment.

<Embodiment 3>
As shown in FIG. 3 [A], the crystal element 30 of the third embodiment differs from the first embodiment in the following points. That is, the crystal plate 31 is located between the vibrating portion 32 in which the excitation electrodes 14e and 14f are located, the fixing portion 34 thicker than the vibrating portion 32, and the fixing portion 34 and the vibrating portion 32, and is located between the fixing portion 34 and the vibrating portion 34. It has a cushioning portion 33 that becomes thinner toward 32. The main surface 13e of the fixed portion 34 is parallel to the main surface 13e of the vibrating portion 32, and the main surface 13e of the buffer portion 33 is inclined toward the main surface 13f side from the fixed portion 34 toward the vibrating portion 32. .. The main surface 13f of the fixed portion 34 is parallel to the main surface 13f of the vibrating portion 32, and the main surface 13f of the buffer portion 33 is inclined toward the main surface 13e side from the fixed portion 34 toward the vibrating portion 32.

In other words, one of the main surfaces 13e is divided into three parts, which are parallel to the vibrating portion 32 and the fixing portion 34, and are slanted so as to be thicker from the vibrating portion 32 side to the fixing portion 34 side in the buffer portion 33. .. Similarly, the other main surface 13f is also divided into three parts, the vibrating portion 32 and the fixing portion 34 are parallel to each other, and the cushioning portion 33 is slanted so as to be thicker from the vibrating portion 32 side to the fixed portion 34 side. In such a cross-sectional shape of the crystal plate 31, for example, only the fixing portion 34 is covered with a corrosion resistant film on the main surface 13e side, and only the fixing portion 34 is covered with a corrosion resistant film on the main surface 13f side to perform wet etching on the crystal. Obtained by applying.

The thickness of the buffer portion 33 in the vertical direction (Y'axis direction) gradually increases from the vibrating portion 32 toward the fixed portion 34 on both the main surface 13e side and the main surface 13f side. Therefore, since the vibration generated in the vibrating portion 32 is gradually attenuated toward the fixed portion 34, the influence of the vibration reflected by the fixed portion 34 on the vibrating portion 32 is further reduced. Therefore, according to the crystal element 30, the influence of the fixing portion 34 on the vibration of the vibrating portion 32 can be further suppressed by the cross-sectional shape of the cushioning portion 33, so that the CI value can be further reduced. Further, in the crystal element 30 having an oscillation frequency of 70 MHz or more, since the plate thickness of the vibrating portion 32 is considerably thin, it is necessary to pay attention to damage at the time of mounting. According to the crystal element 30, the handleability can be improved by mounting the crystal element 30 on the package by the thick fixing portion 34. Further, since the protective film 143 extends to the buffer portion 33 on the main surface 13f, the protective film 143 can prevent the conductive adhesive from creeping up, so that the electrical characteristics are more stable in combination with the above effects. Can be secured. Other configurations, actions and effects of the third embodiment are similar to those of the first or second embodiment.

<Embodiment 4>
As shown in FIG. 3 [B], the crystal element 40 of the fourth embodiment is different from the first embodiment in the following points. That is, the crystal plate 41 has recessed portions 42e and 42f having a reduced thickness, and the excitation electrodes 14e and 14f are located in the recessed portions 42e and 42f.

In addition to the recessed portions 42e and 42f, the crystal plate 41 includes a reinforcing portion 43 located around the recessed portions 42e and 42f, a vibrating portion 44 in which the recessed portions 42e and 42f are formed, and a fixing portion fixed to the package. 45 and. The main surface 13e of the reinforcing portion 43 and the main surface 13e of the fixed portion 45 are flush with each other. The main surface 13e of the vibrating portion 44 and the main surface 13e of the reinforcing portion 43 and the fixing portion 45 are substantially parallel to each other. The other main surface 13f is the same as the main surface 13e. For the recessed portions 42e and 42f, for example, only the fixing portion 45 and the reinforcing portion 43 are covered with a mask (for example, a photoresist film or a corrosion resistant film) on the main surface 13e side, and the fixing portion 45 and the reinforcing portion 43 are formed on the main surface 13f side. It is obtained by covering only the crystal with a mask and performing dry etching or wet etching on the crystal. Then, the excitation electrodes 14e and 14f and the protective film 143 are formed at predetermined positions in the recessed portions 42e and 42f.

In addition, only one of the recessed portions 42e and 42f may be provided. Further, the main surface 13e of at least one of the part 43a, 43b, 43d of the reinforcing portion 43 and the part 45c of the fixing portion 45 shown by shading in FIG. 4 is the main surface 13e of the vibrating portion 44 (that is, the recessed portion 42e). It may be flush with the bottom surface). For example, the main surface 13e of a part 43d of the reinforcing portion 43 may be flush with the main surface 13e of the vibrating portion 44. The main surface 13e on both the part 43b of the reinforcing portion 43 and the part 45c of the fixing portion 45 may be made flush with the main surface 13e of the vibrating portion 44. The main surface 13f is the same as the main surface 13e.

According to the crystal element 40, by having the excitation electrodes 14e and 14f in the recesses 42e and 42f, the vibration energy can be confined in the recesses 42e and 42f, so that the CI value can be reduced. Further, in the crystal element 40 having an oscillation frequency of 70 MHz or more, since the plate thickness of the vibrating portion 44 is considerably thin, it is necessary to pay attention to damage at the time of mounting. According to the crystal element 40, the handleability can be improved by mounting the crystal element 40 on the package by the thick fixing portion 45. Other configurations, actions and effects of the fourth embodiment are similar to those of the first to third embodiments.

<Embodiment 5>
As shown in FIG. 3 [C], the crystal element 50 of the fifth embodiment differs from the first embodiment in the following points. That is, the crystal plate 51 has groove portions 52e and 52f surrounding the excitation electrodes 14e and 14f.

In addition to the groove portions 52e and 52f, the crystal plate 51 includes a vibrating portion 54 composed of a reinforcing portion 53 located around the groove portions 52e and 52f and a convex portion 56 surrounded by the groove portions 52e and 52f and the groove portions 52e and 52f. It has a fixing portion 55 fixed to the package. Then, the excitation electrodes 14e and 14f are located on the convex portion 56. Therefore, the groove portions 52e and 52f have a rectangular frame shape when the excitation electrodes 14e and 14f are rectangular, and a circular or elliptical frame shape when the excitation electrodes 14e and 14f are circular to elliptical in a plan view. ..

The grooves 52e and 52f can be obtained, for example, by forming the excitation electrodes 14e and 14f and the protective film 143, covering the portions other than the grooves 52e and 52f with a mask (for example, a photoresist film), and performing dry etching on the crystal. .. At this time, the groove portions 52e and 52f surrounding the excitation electrodes 14e and 14f are formed in a self-aligned manner. In addition, only one of the groove portions 52e and 52f may be used.

According to the crystal element 50, by having the excitation electrodes 14e and 14f on the convex portions 56 surrounded by the groove portions 52e and 52f, the vibration energy can be confined in the convex portions 56, so that the CI value can be reduced. Further, in the crystal element 50 having an oscillation frequency of 70 MHz or more, the plate thickness of the vibrating portion 54 is considerably thin, so that care must be taken for damage during mounting. According to the crystal element 50, the handleability can be improved by mounting the crystal element 50 on the package by the thick fixing portion 55. Other configurations, actions and effects of the fifth embodiment are similar to those of the first to fourth embodiments.

<Embodiment 6>
As shown in FIGS. 5A and 5B, the crystal device 60 of the sixth embodiment includes the crystal element 10 of the first embodiment, the substrate 61 on which the crystal element 10 is located, and the crystal element together with the substrate 61. A lid 62 for airtightly sealing the 10 is provided. The substrate 61, also called a package, is composed of a substrate 61a and a frame body 61b. The space surrounded by the upper surface of the substrate 61a, the inner surface of the frame 61b, and the lower surface of the lid 62 serves as the accommodating portion 63 of the crystal element 10. The crystal element 10 outputs a reference signal used in, for example, an electronic device.

In other words, the crystal device 60 includes a substrate 61a having a pair of electrode pads 61d on the upper surface and four external terminals 61c on the lower surface, a frame body 61b located along the outer peripheral edge of the upper surface of the substrate 61a, and a pair of electrode pads. A crystal element 10 mounted on the 61d via a conductive adhesive 61e, and a lid 62 for airtightly sealing the crystal element 10 together with the frame body 61b are provided.

The substrate 61a and the frame 61b are made of a ceramic material such as alumina ceramics or glass ceramics, and are integrally formed to form the substrate 61. The base body 61 and the lid 62 are substantially rectangular in plan view. The external terminal 61c, the electrode pad 61d, and the lid 62 are electrically connected to each other via a conductor formed inside or on the side surface of the substrate 61. More specifically, the external terminals 61c are located at the four corners of the lower surface of the substrate 61a. Two of them, the external terminals 61c, are electrically connected to the crystal element 10, and the remaining two external terminals 61c are electrically connected to the lid 62. The external terminal 61c is used for mounting on a printed wiring board of an electronic device or the like.

As described above, the crystal element 10 is on the crystal plate 12, the excitation electrode 14e formed on the upper surface of the crystal plate 12, the excitation electrode 14f formed on the lower surface of the crystal plate 12, and the excitation electrodes 14e and 14f. It has a protective film 143 and. Then, the crystal element 10 is bonded onto the electrode pad 61d via the conductive adhesive 61e, and plays a role of oscillating a reference signal of an electronic device or the like by stable mechanical vibration and a piezoelectric effect.

The electrode pads 61d are for mounting the crystal element 10 on the substrate 61, and a pair of electrode pads 61d are located adjacent to each other along one side of the substrate 61a. The pair of electrode pads 61d are connected to the connection electrodes 14a and 14b, respectively, so that one end of the crystal element 10 is a fixed end and the other end of the crystal element 10 is a free end separated from the upper surface of the substrate 61a. The crystal element 10 is fixed on the substrate 61a with a cantilever support structure. Further, by covering the lead-out electrode 14h with the protective film 143, the protective film 143 can prevent the conductive adhesive 61e from creeping up.

The conductive adhesive 61e contains, for example, a conductive powder as a conductive filler in a binder such as a silicone resin. The lid 62 is made of, for example, an alloy containing at least one of iron, nickel, and cobalt, and is joined to the frame 61b by seam welding or the like to be in a vacuum state or filled with nitrogen gas or the like. Is airtightly sealed.

According to the crystal device 60, stable electrical characteristics can be exhibited by providing the crystal element 10. The crystal device 60 is not limited to the crystal element 10 of the first embodiment, and may include a crystal element of another embodiment.

<Embodiment 7>
As shown in FIGS. 6A and 6B, the electronic devices 71 and 72 of the seventh embodiment each include a crystal device 60. The electronic device 71 illustrated in FIG. 6 [A] is a smartphone, and the electronic device 72 illustrated in FIG. 6 [B] is a personal computer.

The crystal device 60 configured as shown in FIG. 5 holds electronic devices 71 and 72 by fixing the bottom surface of the external terminal 61c to the printed circuit board by soldering, gold (Au) bumps, conductive adhesive, or the like. It is mounted on the surface of the constituent printed circuit board. The crystal device 60 is used as an oscillation source in various electronic devices such as smartphones, personal computers, watches, game machines, communication devices, and in-vehicle devices such as car navigation systems.

According to the electronic devices 71 and 72, by providing the crystal device 60, high-performance and highly reliable operation based on stable electrical characteristics can be realized.

<Others>
Although the present disclosure has been described above with reference to each of the above embodiments, the present disclosure is not limited thereto. Various changes that can be understood by those skilled in the art can be made to the structure and details of this disclosure. The present disclosure also includes a part or all of the configurations of the above embodiments, which are appropriately combined with each other. For example, the side surface of the crystal plate in the second to fifth embodiments may have the same structure as the side surface of the crystal plate in the first embodiment.

10, 20, 30, 40, 50 Crystal element 11a, 11b Long side 11c, 11d Short side 12, 21, 31, 41, 51 Crystal plate 13e, 13f Main surface 13a, 13b, 13c, 13d Side surface 14a, 14b Connection electrode 14e, 14f Excitation electrode 14g, 14h Extraction electrode 141 Base layer 142 Outer layer 143 Protective film 16a, 16b Slope 17a, 17b Side surface 22, 32, 44, 54 Vibration part 23, 33 Buffer part 24, 34, 45, 55 Fixed part 42e, 42f Recessed part 43, 53 Reinforcing part 52e, 52f Groove part 56 Convex part 60 Crystal device 61 Base 61a Board 61b Frame 61c External terminal 61d Electrode pad 61e Conductive adhesive 62 Lid 63 Containing part 71, 72 Electronics machine

Claims (11)

A crystal element with an oscillation frequency of 70 MHz or higher.
In a plan view, two long sides and two short sides, two opposing main surfaces surrounded by the two long sides and the two short sides, and four sandwiched between the two main surfaces. A substantially rectangular crystal plate with sides, and
Excitation electrodes located on the two main surfaces and having an outermost layer made of aluminum or an aluminum alloy, and
A protective film located on the excitation electrode and suppressing oxidation of the outermost layer,
Crystal element equipped with. The protective film is made of silicon dioxide,
The crystal element according to claim 1. Further provided with a connection electrode electrically connected to the package and a lead-out electrode connecting the connection electrode and the excitation electrode.
When the two main surfaces are the first main surface and the second main surface
The protective film on the second main surface covers the extraction electrode and does not cover the connection electrode.
The crystal element according to claim 1 or 2. The two side surfaces including the long side have a slope portion oblique in the thickness direction of the crystal plate and a side surface portion substantially parallel to the thickness direction of the crystal plate.
The crystal element according to any one of claims 1 to 3. The crystal plate is located between the vibrating portion where the exciting electrode is located, the fixing portion thicker than the vibrating portion, and the fixing portion and the vibrating portion, and becomes thinner from the fixed portion toward the vibrating portion. Has a buffer and
When the two main surfaces are the first main surface and the second main surface
The first main surface at the fixed portion, the first main surface at the vibrating portion, and the first main surface at the buffer portion are coplanar.
The second main surface at the fixed portion is parallel to the second main surface at the vibrating portion, and the second main surface at the buffering portion is the first as it goes from the fixed portion to the vibrating portion. Inclined to the main surface side,
The crystal element according to any one of claims 1 to 4. The crystal plate is located between the vibrating portion where the exciting electrode is located, the fixing portion thicker than the vibrating portion, and the fixing portion and the vibrating portion, and becomes thinner from the fixed portion toward the vibrating portion. Has a buffer and
When the two main surfaces are the first main surface and the second main surface
The first main surface at the fixed portion is parallel to the first main surface at the vibrating portion, and the first main surface at the buffering portion is the second as it goes from the fixed portion to the vibrating portion. Inclined to the main surface side,
The second main surface at the fixed portion is parallel to the second main surface at the vibrating portion, and the second main surface at the buffering portion is the first as it goes from the fixed portion to the vibrating portion. Inclined to the main surface side,
The crystal element according to any one of claims 1 to 4. The protective film extends to the buffer portion on the second main surface.
The crystal element according to claim 5 or 6. The quartz plate has a recessed portion that becomes thinner.
The excitation electrode is located in the recess.
The crystal element according to any one of claims 1 to 7. The quartz plate has a groove that surrounds the excitation electrode.
The crystal element according to any one of claims 1 to 8. The crystal element according to any one of claims 1 to 9,
The substrate on which the crystal element is located and
A lid that airtightly seals the crystal element together with the substrate,
Crystal device with. An electronic device comprising the crystal device according to claim 10.

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