JP2020120345A - Piezoelectric vibration device and manufacturing method thereof - Google Patents

Abstract

To provide a simple shield structure of high shield effect, in piezoelectric vibration device of sandwich structure.SOLUTION: A crystal-controlled oscillator 101 is configured by joining a first encapsulation component 3, a second piezoelectric diaphragm 2 and a second encapsulation component 4. The piezoelectric diaphragm 2 and the second encapsulation component 4 have a joining pattern formed by laminating an Au film on a base film, and are joined by Au-Au diffusion junction of Au films in the joining patterns of the piezoelectric diaphragm 2 and the second encapsulation component 4. A second excitation electrode 222 of the piezoelectric diaphragm 2 is formed by laminating the Au film on the base film, so that a lamination structure same as that of the joining pattern is obtained. On the inner surface side of the second encapsulation component, a first excitation electrode 221 and the second excitation electrode 222 are not electrically bonded, and a shield electrode 44 connected to a fixed potential is formed. The shield electrode 44 includes at least the same base film as the joining pattern, and Au is not exposed on the surface thereof.SELECTED DRAWING: Figure 8

Description

The present invention relates to a piezoelectric vibration device and a method for manufacturing the same.

2. Description of the Related Art In recent years, operating frequencies of various electronic devices have been increased, and downsizing of packages (in particular, height reduction) has been advanced. Therefore, along with higher frequencies and smaller packages, piezoelectric vibrating devices (eg, crystal oscillators, crystal oscillators, etc.) are also required to respond to higher frequencies and smaller packages.

In this type of piezoelectric vibrating device, its housing is formed of a substantially rectangular parallelepiped package. This package includes a first sealing member and a second sealing member made of, for example, glass or crystal, and a piezoelectric vibrating plate made of, for example, crystal and having excitation electrodes formed on both main surfaces thereof. The second sealing member and the second sealing member are laminated and bonded to each other via the piezoelectric vibration plate. The vibrating portion (excitation electrode) of the piezoelectric vibrating plate disposed inside the package (internal space) is hermetically sealed. Hereinafter, such a laminated form of the piezoelectric vibration device is referred to as a sandwich structure.

Further, in the piezoelectric vibrating device, when the excitation electrode inside the package or the internal wiring is capacitively coupled with other wiring or electrodes outside the package, it is affected by the potential change, and the frequency and other characteristics change. In the piezoelectric vibration device having the sandwich structure, since the package is thin, when the piezoelectric vibration device is mounted on the circuit board, capacitive coupling between the excitation electrode and the wiring formed on the circuit board may occur. .. For this reason, if no shield measures are taken, the frequency characteristics of the piezoelectric vibration device may change before and after mounting on the circuit board.

For example, Patent Document 1 discloses a shield measure in a piezoelectric vibration device having a sandwich structure. In the piezoelectric vibrating device in Patent Document 1, in each of the piezoelectric vibrating plate, the first sealing member, and the second sealing member, a bonding pattern is formed on a bonding surface with another member. And the first sealing member and the piezoelectric vibrating plate and the second sealing member are joined by these joining patterns. That is, the bonding pattern is formed by stacking an Au film on a base film (for example, a Ti film), and each member is bonded by Au-Au diffusion bonding of Au films included in the bonding pattern.

The piezoelectric vibrating device in Patent Document 1 is configured to form a shield electrode having the same film structure as the bonding pattern on the package inner surface of the second sealing member that is the base side member. That is, this shield electrode can be formed in the same step as the bonding pattern, and a piezoelectric vibration device provided with a shield measure can be obtained without increasing the number of steps.

International Publication No. 2018/092776

In the piezoelectric vibrating device disclosed in Patent Document 1, the shield electrode has the same film structure as the bonding pattern, and therefore the uppermost layer thereof is the Au film. Further, in this piezoelectric vibrating device, the excitation electrode formed on the vibrating portion of the piezoelectric vibrating plate is also formed in the same step as the bonding pattern, and has the same film structure as the bonding pattern. Therefore, the uppermost layer of the excitation electrode is also the Au film.

However, when the uppermost layers of the excitation electrode and the shield electrode are both Au films, there is a possibility that the excitation electrode may be fixed to the shield electrode by Au-Au diffusion bonding between these Au films. Since the inside of the package of the piezoelectric vibrating device is kept airtight at a high degree of vacuum, the surface of the Au film is in an active state, and the vibrating portion of the piezoelectric vibrating device is largely displaced by a shock such as dropping, and the exciting electrode becomes the shield electrode. Upon contact, such sticking can easily occur.

In addition, as a measure against the above-mentioned problem, Patent Document 1 describes that an opening is provided in a part of the shield electrode (a region in which there is a possibility of contact with the excitation electrode). However, such a measure cannot be said to be the best method because the area of the shield electrode is reduced by the opening and the shield effect is reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a piezoelectric vibration device having a sandwich structure, which is simple and has a high shielding effect.

In order to solve the above-mentioned problems, a piezoelectric vibration device of the present invention has a first excitation electrode formed on one principal surface of a substrate and a second excitation electrode paired with the first excitation electrode on the other principal surface of the substrate. A piezoelectric vibrating plate having electrodes formed thereon, a first sealing member that covers the first excitation electrode of the piezoelectric vibrating plate, and a second sealing member that covers the second excitation electrode of the piezoelectric vibrating plate are provided. The first sealing member and the piezoelectric vibrating plate are joined together, the second sealing member and the piezoelectric vibrating plate are joined together, and the first exciting electrode and the second exciting electrode are included. In a piezoelectric vibrating device having an internal space formed by hermetically sealing a vibrating portion of a piezoelectric vibrating plate, the piezoelectric vibrating plate and the second sealing member have a bonding pattern formed by laminating an Au film on a base film. And is bonded by Au-Au diffusion bonding between Au films of the bonding patterns of the piezoelectric diaphragm and the second sealing member, respectively. The excitation electrode is formed by stacking an Au film on a base film so as to have the same stacked structure as the bonding pattern, and the second sealing member is provided on the inner surface side of the inner space with the first electrode. The first excitation electrode and the second excitation electrode are not electrically bonded to each other, and a shield electrode connected to a fixed potential is formed, and the shield electrode includes at least the same underlying film as the bonding pattern, Moreover, it is characterized in that Au is not exposed on the surface thereof.

According to the above configuration, the shield electrode formed on the inner surface of the second sealing member prevents capacitive coupling between the excitation electrode and the terminal or wiring of the mounting board, thereby suppressing frequency fluctuation before and after mounting on the board. You can In addition, the shield electrode can be formed by utilizing the step of forming the bonding pattern. Further, since Au is not exposed on the surface of the shield electrode, Au-Au coupling between the shield electrode and the excitation electrode can be surely prevented and the shield electrode can easily have a large area. Can be obtained.

In the piezoelectric vibrating device, the shield electrode may include the base film and not the Au film.

According to the above configuration, when forming the shield electrode by using the step of forming the bonding pattern, the Au film is removed by etching in the formation region of the shield electrode layer and only the base film is left to be the shield electrode. You can As a result, the shield electrode can be formed without increasing the number of manufacturing steps, that is, without increasing the cost. The base film here includes a concept of a metal film whose surface is oxidized (for example, a Ti film whose surface is oxidized Ti).

Further, in the piezoelectric vibrating device, the shield electrode may be formed so as to overlap with the entire first exciting electrode and the second exciting electrode in a plan view.

According to the above configuration, it is possible to completely prevent capacitive coupling between the excitation electrode and the terminal or wiring of the mounting substrate, and it is possible to obtain a more effective shield electrode.

In order to solve the above problems, a method for manufacturing a piezoelectric vibration device of the present invention is a method for manufacturing a piezoelectric vibration device described above, wherein the bonding pattern and the shield electrode in the second sealing member are It is characterized in that it is formed in a process including the following steps (1) to (3).
(1) The base film is formed on the entire surface of the second sealing member.
(2) The Au film is formed on the entire surface of the base film.
(3) The Au film is left in the bonding pattern formation region, and the Au film is removed by etching in the shield electrode formation region.

The piezoelectric vibrating device and the method for manufacturing the same according to the present invention, in the formed shield electrode formed by using the step of forming the bonding pattern, do not expose Au on the surface of the shield electrode, thereby Au-Au coupling the shield electrode and the excitation electrode. It is possible to reliably prevent the occurrence of the above, and it is possible to obtain a highly effective shield electrode.

It is a schematic block diagram which showed typically each structure of the crystal oscillator which concerns on this Embodiment. It is a schematic plan view of the 1st sealing member of a crystal oscillator. It is a schematic back view of the 1st sealing member of a crystal oscillator. It is a schematic plan view of a crystal diaphragm of a crystal oscillator. It is a schematic back view of the crystal diaphragm of the crystal oscillator. It is a schematic plan view of the 2nd sealing member of a crystal oscillator. It is a schematic rear view of the 2nd sealing member of a crystal oscillator. It is a schematic cross section which shows the example at the time of applying the shield structure of this invention to a crystal oscillator.

[Basic structure of piezoelectric vibration device]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The piezoelectric vibrating device according to the present embodiment is characterized by the shield structure. First, a basic structure other than the shield structure will be described.

FIG. 1 is a schematic configuration diagram schematically showing the configuration of a crystal oscillator 101. The crystal oscillator 101 shown in FIG. 1 has an IC chip 5 mounted on the upper surface of a crystal oscillator. The IC chip 5 as an electronic component element is a one-chip integrated circuit element that constitutes an oscillation circuit together with a crystal oscillator. The piezoelectric vibrating device of the present invention is a concept including both a crystal oscillator and a crystal oscillator.

As shown in FIG. 1, the crystal oscillator 101 according to the present embodiment is provided with a crystal diaphragm (piezoelectric diaphragm) 2, a first sealing member 3, and a second sealing member 4. In the crystal oscillator 101, the crystal diaphragm 2 and the first sealing member 3 are joined together, and the crystal diaphragm 2 and the second sealing member 4 are joined together to form a package 12 having a sandwich structure. The first sealing member 3 is bonded to the crystal diaphragm 2 so as to cover the first excitation electrode 221 (see FIG. 4) formed on the one main surface 211 of the crystal diaphragm 2. The second sealing member 4 is bonded to the crystal diaphragm 2 so as to cover the second excitation electrode 222 (see FIG. 5) formed on the other main surface 212 of the crystal diaphragm 2.

In the crystal oscillator 101, the first sealing member 3 and the second sealing member 4 are bonded to both main surfaces (the one main surface 211 and the other main surface 212) of the crystal diaphragm 2 so that the inside of the package 12 is sealed. The space 13 is formed, and the vibrating portion 22 (see FIGS. 4 and 5) including the first excitation electrode 221 and the second excitation electrode 222 is hermetically sealed in the internal space 13. The crystal oscillator 101 according to the present embodiment has a package size of, for example, 1.0×0.8 mm, and is intended to be downsized and have a low profile.

Next, each structure of the above-mentioned crystal oscillator 101 will be described with reference to FIGS. Here, for each of the quartz crystal diaphragm 2, the first sealing member 3, and the second sealing member 4, the configuration of a single member will be described.

The crystal vibrating plate 2 is a piezoelectric substrate made of crystal, and as shown in FIGS. 4 and 5, both main surfaces 211 and 212 thereof are formed as flat smooth surfaces (mirror surface processing). In this embodiment, an AT-cut crystal plate that performs thickness shear vibration is used as the crystal vibration plate 2. In the crystal diaphragm 2 shown in FIGS. 4 and 5, both main surfaces 211 and 212 of the crystal diaphragm 2 are XZ' planes. In this XZ' plane, the lateral direction (short side direction) of the crystal diaphragm 2 is the X axis direction, and the longitudinal direction (long side direction) of the crystal diaphragm 2 is the Z'axis direction. The AT cut is 35° around the X-axis with respect to the Z-axis among the three crystal axes of the artificial quartz: the electrical axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). This is a processing method of cutting out at an angle inclined by 15'. In the AT-cut quartz plate, the X axis coincides with the crystal axis of quartz. The Y′ axis and the Z′ axis correspond to the axes inclined by 35° 15′ from the Y axis and the Z axis of the crystal axis of quartz, respectively. The Y'-axis direction and the Z'-axis direction correspond to the cutting directions when cutting the AT-cut quartz crystal plate.

A pair of excitation electrodes (first excitation electrode 221 and second excitation electrode 222) are formed on both main surfaces 211 and 212 of the crystal diaphragm 2. The crystal diaphragm 2 includes a vibrating portion 22 formed in a substantially rectangular shape, an outer frame portion 23 surrounding the outer periphery of the vibrating portion 22, and a connecting portion 24 connecting the vibrating portion 22 and the outer frame portion 23. Thus, the vibrating portion 22, the connecting portion 24, and the outer frame portion 23 are integrally provided. In the present embodiment, the connecting portion 24 is provided only at one place between the vibrating portion 22 and the outer frame portion 23, and the place where the connecting portion 24 is not provided becomes the space (gap) 22b. There is. The vibrating portion 22 and the connecting portion 24 are formed thinner than the outer frame portion 23. Due to the difference in thickness between the outer frame portion 23 and the connecting portion 24, the natural frequency of piezoelectric vibration of the outer frame portion 23 and the connecting portion 24 is different. This makes it difficult for the outer frame portion 23 to resonate with the piezoelectric vibration of the connecting portion 24.

The connecting portion 24 extends (projects) from the one corner portion 22a of the vibrating portion 22 located in the +X direction and the −Z′ direction to the outer frame portion 23 in the −Z′ direction. As described above, the connecting portion 24 is provided at the corner portion 22a of the outer peripheral end portion of the vibrating portion 22 where the displacement of the piezoelectric vibration is relatively small. Section, it is possible to suppress leakage of piezoelectric vibration to the outer frame section 23 via the connecting section 24, and it is possible to more efficiently vibrate the vibrating section 22.

The first excitation electrode 221 is provided on the one main surface side of the vibrating portion 22, and the second excitation electrode 222 is provided on the other main surface side of the vibrating portion 22. Extraction electrodes (first extraction electrode 223 and second extraction electrode 224) are connected to the first excitation electrode 221 and the second excitation electrode 222. The first extraction electrode 223 is extracted from the first excitation electrode 221, and is connected to the connection joint pattern 131 formed on the outer frame portion 23 via the connection portion 24. The second extraction electrode 224 is extracted from the second excitation electrode 222, and is connected to the connection joint pattern 115c formed on the outer frame portion 23 via the connection portion 24. The first excitation electrode 221 and the first extraction electrode 223 are formed by laminating a base PVD film formed by physical vapor deposition on the one main surface 211 and physical vapor growth on the base PVD film. And an electrode PVD film. The second excitation electrode 222 and the second extraction electrode 224 are formed by laminating the underlying PVD film formed on the other main surface 212 by physical vapor deposition and the physical vapor deposition on the underlying PVD film. And an electrode PVD film.

On both main surfaces 211 and 212 of the crystal diaphragm 2, vibration-side sealing portions for joining the crystal diaphragm 2 to the first sealing member 3 and the second sealing member 4 are provided, respectively. The vibrating-side sealing portion includes a vibrating-side first bonding pattern 251 formed on the one main surface 211 of the crystal diaphragm 2 and a vibrating-side second bonding pattern 252 formed on the other main surface 212. The vibration-side first bonding pattern 251 and the vibration-side second bonding pattern 252 are provided on the outer frame portion 23 described above, and are formed in an annular shape in a plan view. The first excitation electrode 221 and the second excitation electrode 222 are not electrically connected to the vibration-side first bonding pattern 251 and the vibration-side second bonding pattern 252.

The vibration-side first bonding pattern 251 includes an underlying PVD film formed by physical vapor deposition on the one main surface 211 and an electrode PVD film formed by physical vapor deposition on the underlying PVD film. Consists of. The vibration-side second bonding pattern 252 includes an underlying PVD film formed on the other main surface 212 by physical vapor deposition and an electrode PVD film formed on the underlying PVD film by physical vapor deposition. Consists of. That is, the vibrating-side first bonding pattern 251 and the vibrating-side second bonding pattern 252 have the same configuration, and are formed by stacking a plurality of layers on both the main surfaces 211 and 212, and from the bottom layer side thereof, Ti( A titanium layer and an Au (gold) layer are formed by vapor deposition. Further, the first excitation electrode 221 and the vibration side first bonding pattern 251 formed on the one main surface 211 of the crystal diaphragm 2 have the same thickness, and the first excitation electrode 221 and the vibration side first bonding pattern 251 are formed. The surface of is made of the same metal. Similarly, the second excitation electrode 222 and the vibration-side second bonding pattern 252 formed on the other main surface 212 of the crystal diaphragm 2 have the same thickness, and the second excitation electrode 222 and the vibration-side second bonding pattern 252 are formed. And the surface are made of the same metal. The vibration-side first bonding pattern 251 and the vibration-side second bonding pattern 252 are non-Sn patterns.

Here, since the first excitation electrode 221, the first extraction electrode 223, and the vibration-side first bonding pattern 251 have the same configuration, they can be collectively formed by the same process. Similarly, by making the second excitation electrode 222, the second extraction electrode 224, and the vibration-side second bonding pattern 252 have the same structure, they can be collectively formed by the same process. Specifically, by forming a base PVD film or an electrode PVD film by a PVD method such as vacuum deposition, sputtering, ion plating, MBE, or laser ablation (for example, a film forming method for patterning in processing such as photolithography). By collectively forming the film, the number of manufacturing steps can be reduced to contribute to cost reduction.

As shown in FIGS. 4 and 5, the quartz crystal diaphragm 2 has five through holes (first to fifth through holes 111 to 115) penetrating between the one main surface 211 and the other main surface 212. Has been formed. The first to fourth through holes 111 to 114 are the outer frame portion 23 of the crystal diaphragm 2 and are provided in the four corner (corner) regions of the crystal diaphragm 2. The fifth through hole 115 is the outer frame portion 23 of the crystal diaphragm 2, and is located on one side of the vibrating portion 22 of the crystal diaphragm 2 in the Z′-axis direction (−Z′ direction side in FIGS. 4 and 5). It is provided.

The first through hole 111 is connected to the sixth through hole 116 of the first sealing member 3 and the twelfth through hole 122 of the second sealing member 4. The second through hole 112 is connected to the seventh through hole 117 of the first sealing member 3 and the thirteenth through hole 123 of the second sealing member 4. The third through hole 113 is connected to the eighth through hole 118 of the first sealing member 3 and the fourteenth through hole 124 of the second sealing member 4. The fourth through hole 114 is connected to the ninth through hole 119 of the first sealing member 3 and the fifteenth through hole 125 of the second sealing member 4. The fifth through hole 115 is connected to the second extraction electrode 224 extracted from the second excitation electrode 222 and the tenth through hole 120 of the first sealing member 3 via the wiring pattern 33.

The first to fifth through holes 111 to 115 have through electrodes 111a to 115a for achieving electrical continuity of electrodes formed on the one main surface 211 and the other main surface 212, respectively. 115 are formed along the inner wall surface of each. Then, the central portion of each of the first to fifth through holes 111 to 115 becomes hollow penetrating portions 111b to 115b penetrating between the one main surface 211 and the other main surface 212. Connection joint patterns 111c to 115c are formed on the outer peripheries of the first to fifth through holes 111 to 115, respectively. The connection joint patterns 111c to 115c are provided on both main surfaces 211 and 212 of the crystal diaphragm 2.

The connection bonding patterns 111c to 115c have the same configuration as the vibration-side first bonding pattern 251, the vibration-side second bonding pattern 252, and the same process as the vibration-side first bonding pattern 251 and the vibration-side second bonding pattern 252. Can be formed with. Specifically, the bonding patterns 111c to 115c for connection are formed on the both principal surfaces 211 and 212 of the quartz crystal diaphragm 2 by physical vapor deposition, and a physical PVD film on the underlying PVD film. The electrode PVD film is formed by vapor phase growth and laminated.

The connection bonding patterns 111c to 114c formed on the one main surface 211 and the other main surface 212 of the crystal diaphragm 2 are provided in the four corners (corners) of the crystal diaphragm 2 and are located on the vibration side first. The bonding pattern 251 and the vibration-side second bonding pattern 252 are provided at a predetermined interval. The connection bonding pattern 115c formed on the other main surface 212 of the crystal diaphragm 2 extends along the X-axis direction in the outer frame portion 23 of the crystal diaphragm 2 and is extracted from the second excitation electrode 222. It is formed integrally with the second extraction electrode 224.

Further, on the one main surface 211 of the quartz crystal diaphragm 2, a connection bonding pattern 131 integrally formed with the first extraction electrode 223 extracted from the first excitation electrode 221 is provided. The connection bonding pattern 131 is the outer frame portion 23 of the crystal diaphragm 2, and is provided on the −Z′ direction side of the vibration portion 22 of the crystal diaphragm 2. Further, on the one main surface 211 of the crystal diaphragm 2, the connection bonding pattern 132 is provided at a position opposite to the connection bonding pattern 131 in the Z′-axis direction with the vibrating portion 22 of the crystal diaphragm 2 interposed therebetween. Has been. That is, the connecting joint patterns 131 and 132 are provided on both sides of the vibrating portion 22 in the Z′-axis direction. The connecting joint pattern 132 extends along the X-axis direction in the outer frame portion 23 of the crystal diaphragm 2.

Further, on the one main surface 211 of the crystal diaphragm 2, connection patterns 133 and 134 are provided on the outer frame portion 23 of the crystal diaphragm 2 on both sides of the vibration portion 22 in the X-axis direction. .. The connection joint patterns 133 and 134 are provided in the long side vicinity region along the long side of the crystal diaphragm 2, and extend along the Z′-axis direction. The connecting joint pattern 133 is provided between the connecting joint pattern 111c and the connecting joint pattern 113c formed on the one main surface 211 of the crystal diaphragm 2. The connecting joint pattern 134 is provided between the connecting joint pattern 112c and the connecting joint pattern 114c.

On the other main surface 212 of the crystal diaphragm 2, a connecting joint pattern 135 is provided at a position opposite to the connecting joint pattern 115c in the Z'-axis direction with the vibrating portion 22 of the crystal diaphragm 2 interposed therebetween. There is. That is, the connecting joint patterns 115c and 135 are provided on both sides of the vibrating portion 22 in the Z′-axis direction. In addition, on the other main surface 212 of the crystal diaphragm 2, connection joint patterns 136 and 137 are provided on the outer frame portion 23 of the crystal diaphragm 2 on both sides of the vibration portion 22 in the X-axis direction. .. The connection bonding patterns 136 and 137 are provided in the long side vicinity region along the long side of the crystal diaphragm 2 and extend along the Z′-axis direction. The connecting joint pattern 136 is provided between the connecting joint pattern 111c and the connecting joint pattern 113c formed on the other main surface 212 of the crystal diaphragm 2. The connecting joint pattern 137 is provided between the connecting joint pattern 112c and the connecting joint pattern 114c.

In the crystal oscillator 101, the first to fourth through holes 111 to 114 and the connection bonding patterns 111c to 114c, 133, 134, 136, 137 are more than the vibration side first bonding pattern 251 and the vibration side second bonding pattern 252. It is provided on the outer peripheral side. The fifth through hole 115 and the connecting joint patterns 115c, 131, 132, 135 are provided on the inner peripheral side of the vibrating-side first joint pattern 251 and the vibrating-side second joint pattern 252. The connection joint patterns 111c to 115c and 131 to 137 are not electrically connected to the vibration side first joint pattern 251 and the vibration side second joint pattern 252.

A material having a bending rigidity (second moment of area×Young's modulus) of 1000 [N·mm 2] or less is used for the first sealing member 3. Specifically, as shown in FIGS. 2 and 3, the first sealing member 3 is a rectangular parallelepiped substrate formed from one crystal wafer, and the other main surface 312 ( The surface bonded to the crystal diaphragm 2 is formed as a flat smooth surface (mirror surface processing).

On the other main surface 312 of the first sealing member 3, a sealing-side first bonding pattern 321 is formed as a sealing-side first sealing portion for bonding to the crystal diaphragm 2. The sealing-side first bonding pattern 321 is formed in a ring shape in a plan view.

The sealing-side first bonding pattern 321 is formed by laminating the underlying PVD film formed by physical vapor deposition on the first sealing member 3 and the physical vapor deposition on the underlying PVD film. An electrode PVD film. In the present embodiment, Ti is used for the underlying PVD film and Au is used for the electrode PVD film. Moreover, the sealing-side first bonding pattern 321 is a non-Sn pattern.

As shown in FIGS. 2 and 3, on one main surface 311 of the first sealing member 3 (the surface on which the IC chip 5 is mounted), six electrodes including mounting pads for mounting the IC chip 5 which is an oscillation circuit element are provided. A pattern 37 is formed. In FIG. 2, the mounting area of the IC chip 5 is virtually shown by a broken line. The six electrode patterns 37 are individually connected to the sixth to eleventh through holes 116 to 121, respectively.

The first sealing member 3 has six through holes (sixth to eleventh through holes 116 to 121) penetrating between the one main surface 311 and the other main surface 312. The sixth to ninth through holes 116 to 119 are provided in the four corner (corner) regions of the first sealing member 3. The tenth and eleventh through holes 120 and 121 are provided on both sides in the A2 direction of FIG.

The sixth through hole 116 is connected to the first through hole 111 of the crystal diaphragm 2. The seventh through hole 117 is connected to the second through hole 112 of the crystal diaphragm 2. The eighth through hole 118 is connected to the third through hole 113 of the crystal diaphragm 2. The ninth through hole 119 is connected to the fourth through hole 114 of the crystal diaphragm 2. The tenth through hole 120 is connected to the fifth through hole 115 of the crystal diaphragm 2 via the wiring pattern 33. The eleventh through hole 121 is connected to the first extraction electrode 223 extracted from the first excitation electrode 221.

The sixth to eleventh through holes 116 to 121 have through electrodes 116 a to 121 a for achieving electrical continuity of electrodes formed on the one main surface 311 and the other main surface 312, and the sixth to eleventh through holes 116 to 121. 121 is formed along the inner wall surface of each. Then, the central portion of each of the sixth to eleventh through holes 116 to 121 is a hollow through portion 116b to 121b which penetrates between the one main surface 311 and the other main surface 312. Connection joint patterns 116c to 121c are formed on the outer peripheries of the sixth to eleventh through holes 116 to 121, respectively. The connection joint patterns 116c to 121c are provided on the other main surface 312 of the first sealing member 3.

The connection bonding patterns 116c to 121c and the wiring pattern 33 have the same configuration as the sealing-side first bonding pattern 321, and can be formed in the same process as the sealing-side first bonding pattern 321. Specifically, the connection bonding patterns 116c to 121c and the wiring pattern 33 are a base PVD film formed by physical vapor deposition on the other main surface 312 of the first sealing member 3, and the base PVD film. The electrode PVD film is formed on the electrode PVD film by physical vapor deposition.

The connection joint patterns 116c to 119c of the sixth to ninth through holes 116 to 119 are provided in the regions of the four corners (corners) of the other main surface 312 of the first sealing member 3, and are the sealing side first. The one bonding pattern 321 is provided with a predetermined space. The connecting joint pattern 120c of the tenth through hole 120 extends along the arrow A1 direction of FIG. 3 and is formed integrally with the wiring pattern 33. Further, on the other main surface 312 of the first sealing member 3, a connection joint pattern 138 is provided at a position on the opposite side in the arrow A2 direction with the wiring pattern 33 sandwiched between the connection joint pattern 120c. .. That is, the connecting joint pattern 120c is connected to one end side of the wiring pattern 33 in the arrow A2 direction, and the connecting joint pattern 138 is connected to the other end side. The A1 direction and the A2 direction in FIG. 3 correspond to the X axis direction and the Z′ axis direction in FIG. 4, respectively.

Further, on the other main surface 312 of the first sealing member 3, connection bonding patterns 139 and 140 are provided in a region near the long side along the long side of the first sealing member 3. The connection joint patterns 139 and 140 extend along the arrow A2 direction in FIG. The connection joint pattern 139 is provided between the connection joint pattern 116c and the connection joint pattern 118c formed on the other main surface 312 of the first sealing member 3. The connecting joint pattern 140 is provided between the connecting joint pattern 117c and the connecting joint pattern 119c.

In the crystal oscillator 101, the sixth to ninth through holes 116 to 119 and the connection bonding patterns 116c to 119c, 139, 140 are provided on the outer peripheral side of the sealing-side first bonding pattern 321. The tenth and eleventh through holes 120, 121 and the connecting joint patterns 120c, 121c, 138 are provided on the inner peripheral side of the sealing-side first joint pattern 321. The connection joint patterns 116c to 121c and 138 to 140 are not electrically connected to the sealing-side first joint pattern 321 except for the connection joint pattern 117c. Also, the wiring pattern 33 is not electrically connected to the sealing-side first bonding pattern 321.

A material having a bending rigidity (second moment of area×Young's modulus) of 1000 [N·mm 2] or less is used for the second sealing member 4. Specifically, as shown in FIGS. 6 and 7, the second sealing member 4 is a rectangular parallelepiped substrate formed from one crystal wafer, and one main surface 411 (of the second sealing member 4). The surface bonded to the crystal diaphragm 2 is formed as a flat smooth surface (mirror surface processing).

A sealing-side second bonding pattern 421 is formed on one main surface 411 of the second sealing member 4 as a sealing-side second sealing portion for bonding to the crystal diaphragm 2. The second sealing-side bonding pattern 421 is formed in an annular shape in plan view.

The sealing-side second bonding pattern 421 is formed by laminating the underlying PVD film formed by physical vapor deposition on the second sealing member 4 and by physical vapor deposition on the underlying PVD film. An electrode PVD film. In the present embodiment, Ti is used for the underlying PVD film and Au is used for the electrode PVD film. The second sealing-side bonding pattern 421 is a non-Sn pattern.

On the other main surface 412 of the second sealing member 4 (the outer main surface that does not face the crystal diaphragm 2), four external electrode terminals (first to fourth external electrode terminals 433) electrically connected to the outside are provided. ~436) are provided. The first to fourth external electrode terminals 433 to 436 are located at the four corners (corners) of the second sealing member 4, respectively. These external electrode terminals (first to fourth external electrode terminals 433 to 436) are formed by physical vapor deposition on the other main surface 412, and a physical PVD film is formed on the underlying PVD film. And a laminated PVD film.

As shown in FIGS. 6 and 7, the second sealing member 4 has four through holes (twelfth to fifteenth through holes 122 to 125) penetrating between the one main surface 411 and the other main surface 412. Has been formed. The twelfth to fifteenth through holes 122 to 125 are provided in regions of four corners (corners) of the second sealing member 4. The twelfth through hole 122 is connected to the first external electrode terminal 433 and the first through hole 111 of the crystal diaphragm 2. The thirteenth through hole 123 is connected to the second external electrode terminal 434 and the second through hole 112 of the crystal diaphragm 2. The fourteenth through hole 124 is connected to the third external electrode terminal 435 and the third through hole 113 of the crystal diaphragm 2. The fifteenth through hole 125 is connected to the fourth external electrode terminal 436 and the fourth through hole 114 of the crystal diaphragm 2.

The twelfth to fifteenth through holes 122 to 125 have through electrodes 122a to 125a for conducting the electrodes formed on the one main surface 411 and the other main surface 412, respectively. It is formed along the inner wall surface of each 125. Then, the central portion of each of the twelfth to fifteenth through holes 122 to 125 becomes hollow through portions 122b to 125b penetrating between the one main surface 411 and the other main surface 412. Connection joint patterns 122c to 125c are formed on the outer peripheries of the twelfth to fifteenth through holes 122 to 125, respectively. The connection joint patterns 122c to 125c are provided on the one main surface 411 of the second sealing member 4.

The connection bonding patterns 122c to 125c have the same configuration as the sealing-side second bonding pattern 421 and can be formed in the same process as the sealing-side second bonding pattern 421. Specifically, the bonding patterns 122c to 125c for connection are formed on the one principal surface 411 of the second sealing member 4 by physical vapor phase growth, and on the underlying PVD film. The electrode PVD film is formed by vapor phase growth and laminated.

The joint patterns 122c to 125c for connection of the twelfth to fifteenth through holes 122 to 125 are provided in the regions of the four corners (corners) of the one main surface 411 of the second sealing member 4, and are the sealing side first. The two-bonding pattern 421 is provided at a predetermined interval. Further, on the one main surface 411 of the second sealing member 4, connection bonding patterns 141, 142 are provided in a region near the long side along the long side of the second sealing member 4. The connecting joint patterns 141 and 142 extend along the arrow B2 direction in FIG. The connection joint pattern 141 is provided between the connection joint pattern 122c and the connection joint pattern 124c formed on the one main surface 411 of the second sealing member 4. The connecting joint pattern 142 is provided between the connecting joint pattern 123c and the connecting joint pattern 125c.

Further, the one main surface 411 of the second sealing member 4 is provided with connection bonding patterns 143 and 144 extending in the direction of arrow B1 in FIG. The connection joint patterns 143 and 144 are provided in the regions on both ends in the direction of arrow B2 in FIG. The connection joint pattern 143 is provided between the connection joint pattern 122c and the connection joint pattern 123c formed on the one main surface 411 of the second sealing member 4. The connecting joint pattern 144 is provided between the connecting joint pattern 124c and the connecting joint pattern 125c. The B1 direction and the B2 direction in FIG. 6 correspond to the X axis direction and the Z′ axis direction in FIG. 4, respectively.

In the crystal oscillator 101, the twelfth to fifteenth through holes 122 to 125 and the connecting joint patterns 122c to 125c, 141 and 142 are provided on the outer peripheral side of the sealing side second joint pattern 421. The connection joint patterns 143, 144 are provided on the inner peripheral side of the sealing-side second joint pattern 421. The connection joint patterns 122c to 125c and 141 to 144 are not electrically connected to the sealing-side second joint pattern 421 except for the connection joint pattern 123c.

In the crystal oscillator 101 including the crystal diaphragm 2, the first sealing member 3, and the second sealing member 4, the crystal diaphragm 2 and the first sealing member 3 are the vibrating side first bonding pattern 251 and the sealing side. Diffusion bonding is performed in a state where the first bonding patterns 321 are overlapped with each other, and the crystal diaphragm 2 and the second sealing member 4 are in a state where the vibration-side second bonding pattern 252 and the sealing-side second bonding pattern 421 are stacked. The package 12 having a sandwich structure is manufactured by diffusion bonding. As a result, the internal space 13 of the package 12, that is, the accommodating space of the vibrating portion 22 is hermetically sealed without separately using a bonding-only material such as an adhesive.

Then, as shown in FIG. 1, the vibration-side first bonding pattern 251 and the sealing-side first bonding pattern 321 themselves become the bonding material 15a generated after the diffusion bonding, and the vibration-side second bonding pattern 252 and the sealing-side bonding material 15a. The two-bonding pattern 421 itself becomes the bonding material 15b generated after the diffusion bonding.

At this time, the above-described connecting joint patterns are also diffusion-joined in a state of being overlapped with each other. Specifically, the connection bonding patterns 111c to 114c at the four corners of the crystal diaphragm 2 and the connection bonding patterns 116c to 119c at the four corners of the first sealing member 3 are diffusion bonded. The bonding patterns 133 and 134 for connection in the vicinity of the long side of the crystal diaphragm 2 and the bonding patterns 139 and 140 for connection in the vicinity of the long side of the first sealing member 3 are diffusion bonded. The connection bonding pattern 115c of the crystal diaphragm 2 and the connection bonding pattern 138 of the first sealing member 3 are diffusion bonded. The connection bonding pattern 131 of the crystal diaphragm 2 and the connection bonding pattern 121c of the first sealing member 3 are diffusion bonded. The connection bonding pattern 132 of the crystal diaphragm 2 and the connection bonding pattern 120c of the first sealing member 3 are diffusion bonded. The bonding material, which is generated after the diffusion bonding of the bonding pattern for connection itself, has a function of electrically connecting the through electrodes of the through holes and a function of hermetically sealing the bonding portion.

Similarly, the bonding patterns 111c to 114c for connection at the four corners of the crystal diaphragm 2 and the bonding patterns 122c to 125c for connection at the four corners of the second sealing member 4 are diffusion bonded. The bonding patterns 136, 137 for connection in the vicinity of the long sides of the crystal diaphragm 2 and the bonding patterns 141, 142 for connection in the vicinity of the long sides of the second sealing member 4 are diffusion bonded. The connection bonding pattern 115c of the crystal diaphragm 2 and the connection bonding pattern 144 of the second sealing member 4 are diffusion bonded. The connection bonding pattern 135 of the crystal diaphragm 2 and the connection bonding pattern 143 of the second sealing member 4 are diffusion bonded.

[Piezoelectric vibration device shield structure]
Next, the shield structure which is a feature of the present invention will be described. The shield structure in the present invention is composed of a plurality of types of shield electrodes. FIG. 8 is a schematic cross-sectional view showing an example in which the shield structure of the present invention is applied to the crystal oscillator 101.

As shown in FIG. 8, the shield structure according to the present embodiment is composed of the shield electrode 44 formed on the one main surface 411 of the second sealing member 4. The shield electrode 44 is formed inside the second sealing-side bonding pattern 421, that is, in the crystal oscillator 101, is formed on the inner surface side of the internal space 13 of the package 12. At this time, the shield electrode 44 is formed on substantially the entire inner surface of the sealing-side second bonding pattern 421 and is electrically connected to the sealing-side second bonding pattern 421. It is electrically separated from 144.

The shield electrode 44 needs to be applied with a fixed potential which does not fluctuate during the operation of the crystal oscillator 101, in order to prevent the influence of potential fluctuations of the terminals and wirings. It is preferable to use a GND (ground) potential as such a fixed potential. Therefore, the sealing-side second bonding pattern 421 is electrically connected to the connecting bonding pattern 123c, and the shield electrode 44 has a GND potential via the sealing-side second bonding pattern 421 and the connecting bonding pattern 123c. To be given.

The shield electrode 44 according to the present embodiment is formed in the same process as the sealing-side second bonding pattern 421, which has the advantage that a shield structure can be obtained without increasing the manufacturing process of the crystal oscillator 101. Have. That is, the sealing-side second bonding pattern 421 is formed by sequentially forming a base PVD film and an electrode PVD film on the entire one main surface 411 of the second sealing member 4, and patterning these by etching. It The shield electrode 44 can be formed in the same process as the sealing-side second bonding pattern 421 by devising the etching mask at this time. That is, in the step of etching the electrode PVD film, the electrode PVD film is left in the region where the second sealing pattern 421 on the sealing side is formed, and the electrode PVD film is removed by etching in the region where the shield electrode 44 is formed.

In addition, the sealing-side second bonding pattern 421 has a laminated structure of the underlying PVD film and the electrode PVD film as described above, and the uppermost electrode PVD film is the Au film. On the other hand, in the shield electrode 44, the electrode PVD film is removed by etching, and the underlying PVD film is left unetched. Therefore, the shield electrode 44 has a structure in which Au is not exposed on the surface thereof. In the shield electrode 44, after the electrode PVD film is removed by etching, a metal oxide film may be formed on the surface of the underlying PVD film. For example, when the underlying PVD film is a Ti film, the Ti oxide film can be easily formed on the surface by exposing the Ti film to air. When the underlying PVD film is a Ti film and a Ti oxide film is formed on the surface of the TiV film, Ti oxide is less likely to adhere to Au than Ti and has the advantage of risk reduction. That is, when the second excitation electrode 222 comes into contact with the shield electrode 44 due to vibration, since the surface of the shield electrode 44 is a Ti oxide film, the fixation between the second excitation electrode 222 and the shield electrode 44 can be more reliably prevented. .. Further, since it is difficult to manufacture a wafer without being exposed to oxygen, the manufacturing equipment can be simplified by forming the surface of the shield electrode 44 with a Ti oxide film.

As described above, by not exposing Au to the surface of the shield electrode 44, even if the vibrating portion 22 of the crystal diaphragm 2 is largely displaced due to an impact such as a drop and the second excitation electrode 222 comes into contact with the shield electrode 44. , Au—Au diffusion bonding can prevent the second excitation electrode 222 from being fixed to the shield electrode 44.

Since the shield electrode 44 can prevent sticking to the second excitation electrode 222 by not exposing Au to the surface thereof, the shield electrode 44 is superposed on the entire first excitation electrode 221 and the second excitation electrode 222 in a plan view. Can be formed. As a result, the shield electrode 44 can completely prevent capacitive coupling between the excitation electrode and the terminal or wiring of the mounting board, and a higher shield effect can be obtained.

Further, the shape of the shield electrode in the above description is merely an example, and the present invention is not limited to this. Hereinafter, some modified examples of the shield electrode will be described.

The shield electrode 44 described above has a structure in which Au is not exposed on the surface by etching away the electrode PVD film with the Au film. However, the present invention is not limited to this, and instead of etching away the electrode PVD film, another metal oxide film (insulating film) or the like is laminated on the electrode PVD film, and Au is not exposed on the surface. It may be configured. Even with such a configuration, when the second excitation electrode 222 contacts the shield electrode 44, it is possible to prevent the second excitation electrode 222 from being fixed to the shield electrode 44 by Au-Au diffusion bonding.

In the crystal oscillator 101 described above, the wiring pattern 33 is formed on the other main surface 312 of the first sealing member 3, and the wiring pattern 33 is formed in the same process as the sealing-side first bonding pattern 321. Therefore, the outermost layer thereof is an electrode PVD film which is an Au film. In the configuration example (layout) shown in FIGS. 3 and 4, the wiring pattern 33 does not overlap the first excitation electrode 221 in plan view, and the wiring pattern 33 and the first excitation electrode 221 are Au-Au diffusion bonded. Does not cause sticking. However, when the layout is such that at least a part of the wiring pattern 33 overlaps with the first excitation electrode 221, the electrode PVD film in the wiring pattern 33 is removed by etching, and Au is not exposed on the surface. It may be configured.

Although crystal is used for the first sealing member 3 and the second sealing member 4 in the above embodiment, the present invention is not limited to this, and glass may be used. Further, although the AT-cut quartz plate is used as the piezoelectric vibrating plate, it is not limited to this and quartz other than AT-cut quartz may be used. The piezoelectric diaphragm may be made of any other material as long as it is a piezoelectric material, such as lithium niobate or lithium tantalate.

By configuring the first sealing member 3 and the second sealing member 4 with quartz, the crystal diaphragm 2, the first sealing member 3, and the second sealing member 4 have the same coefficient of thermal expansion, Since the deformation of the package 12 due to the difference in thermal expansion between the crystal diaphragm 2, the first sealing member 3, and the second sealing member 4 can be suppressed, the internal space where the vibrating portion 22 of the crystal diaphragm 2 is hermetically sealed. The airtightness of 13 can be improved. Further, the distortion due to the deformation of the package 12 is transmitted to the first excitation electrode 221 and the second excitation electrode 222 via the connecting portion 24 and may cause a frequency variation. By configuring the sealing member 3 and the second sealing member 4 with crystal, it is possible to suppress such frequency fluctuation.

The embodiment disclosed this time is an example in all respects, and is not a basis for a limited interpretation. Therefore, the technical scope of the present invention should not be construed only by the above-described embodiments, but should be defined based on the claims. For example, not only the crystal oscillator but also the crystal oscillator can be applied. Also, the meaning equivalent to the scope of the claims and all modifications within the scope are included.

101 Crystal oscillator (Piezoelectric vibration device)
2 Crystal diaphragm (piezoelectric diaphragm)
3 1st sealing member 4 2nd sealing member 5 IC chip 12 package 13 internal space 111-125 1st-15th through-hole 22 vibrating part 23 outer frame part 24 connecting part 221 1st excitation electrode 222 2nd excitation electrode 37 Electrode Patterns 433 to 436 First to Fourth External Electrode Terminals 44 Shield Electrode (Shield Electrode)

Claims (4)

A piezoelectric vibrating plate having a first excitation electrode formed on one main surface of a substrate and a second excitation electrode paired with the first excitation electrode formed on the other main surface of the substrate;
A first sealing member that covers the first excitation electrode of the piezoelectric vibrating plate;
A second sealing member that covers the second excitation electrode of the piezoelectric vibrating plate,
The first sealing member and the piezoelectric vibrating plate are joined together, the second sealing member and the piezoelectric vibrating plate are joined together, and the piezoelectric vibration includes the first excitation electrode and the second excitation electrode. In a piezoelectric vibrating device in which an internal space is formed by hermetically sealing the vibrating part of a plate,
The piezoelectric vibrating plate and the second sealing member have a bonding pattern in which an Au film is laminated on a base film, and the piezoelectric vibrating plate and the second sealing member are bonded to each other. The Au films of the pattern are joined by Au-Au diffusion joining,
The second excitation electrode of the piezoelectric vibrating plate is formed by laminating an Au film on a base film so as to have the same laminated structure as the bonding pattern,
A shield electrode that is not electrically connected to the first excitation electrode and the second excitation electrode and is connected to a fixed potential is formed on the inner surface side of the internal space of the second sealing member. Cage,
The piezoelectric vibrating device, wherein the shield electrode includes at least the same underlying film as the bonding pattern, and Au is not exposed on the surface thereof. The piezoelectric vibration device according to claim 1, wherein
The piezoelectric vibrating device, wherein the shield electrode includes the base film and does not include the Au film. The piezoelectric vibration device according to claim 1 or 2, wherein
The piezoelectric vibration device, wherein the shield electrode is formed so as to overlap the entire first excitation electrode and the second excitation electrode in a plan view. A method of manufacturing a piezoelectric vibration device according to claim 1, wherein
A method of manufacturing a piezoelectric vibrating device, characterized in that the bonding pattern and the shield electrode in the second sealing member are formed in a process including the following steps (1) to (3).
(1) The base film is formed on the entire surface of the second sealing member.
(2) The Au film is formed on the entire surface of the base film.
(3) The Au film is left in the bonding pattern formation region, and the Au film is removed by etching in the shield electrode formation region.

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