Monolithic quartz filter

Abstract

To provide a monolithic crystal filter capable of stabilizing adjustment of filter characteristics by a bridge capacitance.SOLUTION: A monolithic crystal filter F comprises: a package 1 that is in a rectangular parallelepiped shape as a whole, having a recessed part whose upper part is opened; a crystal diaphragm 2 housed in the recessed part of the package 1; and a lid 3 that is joined with the opening of the package 1. The crystal diaphragm 2 formed with an input electrode 21 and an output electrode 22 on one principal surface and formed with a common electrode 23 and a bridge capacitance C on the other principal surface, is conductively joined with the package. A ground electrode pad 12d is formed below the bridge capacitance C.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a monolithic crystal filter used in wireless communication devices and the like.

Background Art

[0002] In recent years, wireless communication devices include, for example, professional wireless devices. Depending on their applications and specifications, monolithic crystal filters with various filter characteristics are required. For example, there are requirements such as miniaturization, suppression of spurious signals, relatively steep guaranteed attenuation characteristics, and the width of the passband being wide or narrow. Regarding these filter characteristics, reliability such as stability that is not affected by external factors is also required.

[0003] In crystal filters, various measures have been taken to improve filter characteristics such as suppressing various spurious signals by electrode design (forming a metal thin film) on the crystal diaphragm. However, as miniaturization progresses, this electrode design becomes difficult, and it has become necessary to adjust the frequency balance and frequency band characteristics between each electrode in a limited and narrow area.

[0004] For example, the adjustment area (the gap area where the crystal substrate is exposed) between the input electrode and the output electrode of a monolithic crystal filter may become narrow, causing a decrease in the guaranteed attenuation amount.

[0005] In order to solve such problems, the applicant has proposed to form a bridging capacitance part by bringing the wiring patterns connected to each divided electrode close to each other in another area on the crystal diaphragm, thereby expanding the width of the above adjustment and solving the problems of short - circuit between electrodes and decrease in guaranteed attenuation amount. See Patent Document 1.

[0006] In this proposal, the input and output electrodes on the back surface of the quartz diaphragm are led to the surface, and the electrodes are positioned close together on the surface. The bridging capacitance can be adjusted by changing this proximity distance. As shown in Figure 3 of Patent Document 1, when the proximity distance t between the electrodes is increased, the bridging capacitance increases, the attenuation bandwidth narrows, and the attenuation pole of the guaranteed attenuation changes in the positive direction (to the right). Conversely, when the proximity distance t between the electrodes is increased, and the bridging capacitance decreases, the attenuation bandwidth widens, and the attenuation pole of the guaranteed attenuation changes in the negative direction (to the left). Through such adjustment, an attenuation pole can be created and swept to a predetermined position, thereby minimizing the attenuation at the so-called image frequency. The width of the attenuation bandwidth is determined by the required specifications. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 3436251 [Overview of the project] [Problems that the invention aims to solve]

[0008] In Patent Document 1, a bridging capacitance is formed on the outer circumference of the quartz diaphragm, and the characteristics of the monolithic quartz filter are adjusted as described above. However, the bridging capacitance formation region can deviate from the set capacitance value due to the influence of external electromagnetic noise and potential fluctuations, which can become a factor in the characteristic adjustment. Specifically, while the formation of bridging capacitance allows for the adjustment of filter characteristics to desired values, such as minimizing the attenuation pole as described in Patent Document 1, the adjusted filter characteristics (passband characteristics, guaranteed attenuation characteristics, frequency characteristics, etc.) can deviate due to the influence of external electromagnetic noise and potential fluctuations.

[0009] As is well known, various characteristic adjustments are made to monolithic quartz filters. For example, frequency balancing between electrodes with respect to a common electrode is done by adjusting the electrode thickness (thickness of the thin metal film) in the common electrode region corresponding to the input and output electrodes on the back surface. Similarly, frequency band characteristics are adjusted by adjusting the electrode thickness (thickness of the thin metal film) in the region corresponding to the area between the input and output electrodes. Furthermore, the center frequency is adjusted by adjusting the electrode thickness across the entire surface of the common electrode.

[0010] Regarding the adjustment of electrode film thickness (thickness of the metal thin film), to increase the film thickness, for example, metal material is added by partial deposition. To decrease the film thickness, for example, ion milling is used to reduce the electrode film thickness (thickness of the metal thin film). Generally, adjustments are made by either adding or decreasing the film thickness. Then, perform characteristic adjustments.

[0011] Such partial deposition and ion milling adjustments involve using a metal mask with an opening in the region to be adjusted, and performing a film thickness adjustment on the metal thin film exposed through the opening. However, this process sometimes causes the film thickness of the metal thin film in the aforementioned bridging capacitance formation region to also fluctuate (adjust). In particular, ion milling adjusts the film by irradiating the metal thin film with an argon ion beam and removing metal atoms, but the argon ion beam itself can spread, causing the metal thin film to be removed from areas other than the desired region. In the configuration described in Patent Document 1, the metal thin film in the bridging capacitance region was sometimes removed, degrading the filter characteristics.

[0012] This invention has been made in view of the above problems, and aims to provide a monolithic quartz filter that can stabilize the adjustment of filter characteristics due to bridging capacitance. [Means for solving the problem]

[0013] The monolithic quartz filter according to the present invention has input electrodes and output electrodes formed on one main surface, and the input electrodes and output electrodes formed on the other main surface Directly opposite A common electrode is formed, and it is electrically connected independently of the input electrode and the output electrode. two Connecting electrode And, one connecting electrode electrically connected to the common electrode. A quartz diaphragm having the quartz diaphragm, and a holder for the quartz diaphragm, two Connecting electrode and each Conductive bonding two Connecting electrode pads, The one connecting electrode pad, which is electrically connected to the common electrode, is conductively joined to the one connecting electrode pad, and the crystal diaphragm is not joined to the one connecting electrode pad, and A monolithic quartz filter having a package having a grounding electrode pad that is grounded, wherein the input electrode and One extension electrode is drawn out from one electrically connected connecting electrode to the outer peripheral region of the quartz diaphragm, The output electrode One extension electrode is drawn out from one of the connecting electrodes, which is electrically connected to the quartz diaphragm, to the outer peripheral region of the quartz diaphragm. By bringing them close together in the outer peripheral region, a bridge capacity is formed, and below the bridge capacity The ground electrode pad is positioned across a gap from the quartz diaphragm, and the gap is 0.01 mm to 0.08 mm. This is its defining characteristic.

[0014] In this configuration, a ground electrode pad is formed on the package, and the ground electrode pad is positioned directly below the bridging capacitance formed on the quartz diaphragm. With this configuration, even if external electromagnetic noise or potential fluctuations occur in the bridging capacitance region, the ground electrode pad located below the bridging capacitance region allows for the intended adjustment during characteristic adjustment by the bridging capacitance, and a monolithic quartz filter that can stabilize the adjusted filter characteristics can be obtained.

[0015] Furthermore, the quartz diaphragm may be rectangular in plan view, and the bridging capacitance may be formed at the corners of the quartz diaphragm.

[0016] According to the above configuration, the region where the bridging capacitance is formed is located at the corner of the rectangular quartz diaphragm. Since the input electrode, output electrode, and common electrode are formed in the central part of the quartz diaphragm, the bridging capacitance can be located at a distance from each of these electrodes, thereby significantly reducing the influence of adjustment work on each electrode.

[0017] Regarding this point, a more detailed explanation will be given. The monolithic crystal filter uses thickness-shear vibration by an AT-cut crystal diaphragm, and in order for this thickness-shear vibration mode not to be affected by the outer periphery of the crystal diaphragm, excitation electrodes are formed in the central part of the crystal diaphragm. That is, electrode groups of input electrodes, output electrodes, and common electrodes are formed in the central part of the crystal diaphragm. Thereby, the energy confinement effect of the thickness-shear vibration mode is exerted, and it becomes easier to obtain an operation in a single vibration mode.

[0018] And in the formation of each of these electrodes, that is, the formation of a metal thin film, and in the adjustment of various filter characteristics by adjusting the film thickness for these input electrodes, output electrodes, and common electrodes, it is performed on the central region of the crystal diaphragm on which each electrode is formed. Since the position for forming the bridging capacitance according to the present invention is at the corner of the crystal diaphragm, it is separated from the formation regions of the input electrode, output electrode, and common electrode that are the objects of filter characteristic adjustment, and even if adjustment work is performed on these input electrodes, output electrodes, and common electrodes, it is not affected by that.

[0019] For example, when frequency adjustment is performed on each electrode by ion milling, since the position for forming the bridging capacitance is formed at the corner of the crystal diaphragm, even if the argon ion beam itself spreads, the chance for the argon ion beam to reach the bridging capacitance is extremely reduced, and there is no longer any such thing as shaving the metal thin film of the bridging capacitance. And in combination with the effect of suppressing the influence of external electromagnetic noise and the like, a monolithic crystal filter with stable characteristics can be obtained.

Effect of the Invention

[0020] According to the present invention, a monolithic crystal filter in which the adjustment of filter characteristics by the bridging capacitance is stabilized can be obtained.

Brief Explanation of the Drawings

[0021] [Figure 1] It is a plan view of one main surface of the crystal diaphragm on which electrodes are formed according to the present embodiment. [Figure 2]This is a plan view of the other main surface of the electrode-formed quartz diaphragm according to this embodiment. [Figure 3] This is a plan view of the package according to this embodiment. [Figure 4] This is a plan view of the package according to this embodiment with a quartz diaphragm mounted on it. [Figure 5] Figure 4 shows a cross-sectional view of the package sealed with the lid. [Figure 6] Figure 4 is a cross-sectional view of the BB package sealed with the lid. [Modes for carrying out the invention]

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0023] First Embodiment A first embodiment of the present invention will be described with reference to Figures 1 to 6. Figure 1 is a plan view of one main surface of an electrode-formed quartz diaphragm showing this embodiment, and Figure 2 is a plan view of the other main surface of the electrode-formed quartz diaphragm. Figure 3 is a plan view showing a package that houses and holds the quartz diaphragm. Figure 4 is a plan view showing the quartz diaphragm housed and held in the package, Figure 5 is a cross-sectional view AA of Figure 4 showing the package housed and electrically bonded with the quartz diaphragm hermetically sealed with a lid, and Figure 6 is a cross-sectional view BB of Figure 4 showing the package hermetically sealed with a lid.

[0024] The monolithic quartz filter F has an overall rectangular parallelepiped shape and consists of a package 1 having a recess with an open top, a quartz diaphragm 2 which is a piezoelectric vibrating element housed in the recess of the package 1, and a lid 3 which is joined to the opening of the package 1.

[0025] Package 1 is a ceramic package with metal film wiring formed on the inside and outside, and is concave in cross-section, having a ridge (side wall) 10 around the concave shape and a circumferential metal seal portion 11 formed on the upper surface of the ridge. The metal seal portion 11 consists of a metallized layer made of tungsten or the like and a metal film layer formed on the metallized layer. The metal film layer consists of, for example, a nickel plating layer in contact with the metallized layer and an extremely thin gold plating layer formed on top of the nickel plating layer. A metal ring for welding, such as Kovar, may also be attached.

[0026] Inside the package 1, connection electrode pads 12a, 12b, and 12c are formed at the four corners, and a ground electrode pad 12d is also formed. Each of these connection electrode pads and ground electrode pad is led out via conductive electrodes to the opposite side of the electrode pad formation surface, i.e., the external connection surface on the back of the package which makes electrical connections to the outside, and is electrically connected to the external connection terminals. Specifically, connection electrode pad 12a is electrically connected to external connection terminal 13a via conductive electrode 12a1, connection electrode pad 12b is electrically connected to external connection terminal 13b via conductive electrode 12b1, connection electrode pad 12c is electrically connected to external connection terminal 13c via conductive electrode 12c1, and ground electrode pad 12d is electrically connected to external connection terminal 13d via conductive electrode 12d1.

[0027] Furthermore, castellations 13a1, 13b1, 13c1, and 13d1 extending in the thickness direction are formed at the corners of the ceramic package, and castellations 13e1 and 13f1 are also formed on the side walls. Each of the castellations 13a1, 13b1, 13c1, and 13d1 is electrically connected to the external connection terminals 13a, 13b, 13c, and 13d, respectively. Although not shown in the diagram, castellations 13e1 and 13f1 are connected to external connection terminals 13e and 13f formed on the back surface of the package, respectively.

[0028] These external connection terminals and castellations are constructed, for example, by applying nickel plating, gold plating, etc., to the top of a tungsten metallization layer.

[0029] The quartz diaphragm 2 is made of an AT-cut quartz plate and has a rectangular shape with a short side and a long side when viewed in plan. Electrodes constituting a monolithic quartz filter are formed on the front and back surfaces of the quartz diaphragm 2. Specifically, on one main surface, a rectangular input electrode 21 and a rectangular output electrode 22 are formed in parallel with a predetermined distance apart when viewed in plan, and on the other main surface, a common electrode 23 corresponding to the input electrode 21 and the output electrode 22 is formed. The common electrode 23 is also rectangular when viewed in plan and has an external size corresponding to the area formed in parallel by the input electrode 21 and the output electrode 22.

[0030] From the input electrode 21 and the output electrode 22, lead electrodes 21a and 22a extend in directions away from each other (long side direction), respectively. After reaching the ends (short side ends) of the crystal diaphragm 2, these lead electrodes 21a and 22a extend to the diagonally opposite corners, forming connecting electrodes 21b and 22b at these corners.

[0031] An extension electrode 21c is formed on the opposite side (the other main surface) of the region where the connecting electrode 21b is formed. The extension electrode 21c extends along the short side and extends to the vicinity of the other end of this short side. Similarly, an extension electrode 22c is formed on the opposite side (the other main surface) of the region where the connecting electrode 22b is formed. The extension electrode 22c extends along the long side and extends to the vicinity of the other end of this long side. Furthermore, a portion of the connecting electrode and a portion of the extension electrode overlap at each corner. Although not shown in the figures, the connecting electrode 21b and extension electrode 21c of the input electrode 21, and the connecting electrode 22b and extension electrode 22c of the input electrode 22 may be electrically connected by side electrodes (metal thin films) formed on the side surface of the crystal diaphragm in the overlapping region. In this case, the application of the conductive bonding material can be omitted in the conductive bonding between the connecting electrode and the connecting electrode pad, which will be described later.

[0032] With the above configuration, as shown in the upper right of Figure 2, the extension electrodes 21c and 22c are positioned close together at the corner of the quartz diaphragm, and the end faces of extension electrodes 21c and 22c are positioned opposite each other with a gap t. This gap between the extension electrodes forms a bridging capacitance C. It is preferable that the end faces of the opposing extension electrodes 21c and 22c are positioned at a constant distance from each other. This facilitates the design of capacitance formation.

[0033] Furthermore, as shown in Figure 1, a marker M is formed on a virtual extension line L that passes midway between the input electrode 21 and the output electrode 22. This positional relationship allows the formation positions of the input electrode 21 and the output electrode 22 to be determined relative to the formation position of the marker M.

[0034] Marker M is, for example, circular in shape and is formed independently between the extension electrode formation region and the other main surface (opposite surface) of the quartz diaphragm, outside the common electrode formation region. Since the quartz diaphragm is transparent, the marker can be seen from the other main surface as well, functioning as a positioning starting point during manufacturing and proving useful for identifying the adjustment region during characteristic adjustment, as described later.

[0035] Each of the aforementioned electrodes, namely the input / output electrodes, common electrode, lead electrode, connecting electrode, extension electrode, and marker, is made of a thin metal film. For example, a configuration is adopted in which chromium (Cr) is used as the underlayer in contact with the quartz diaphragm, and gold (Au) or silver (Ag) is formed on top of the underlayer. Other metal materials may be used for these thin metal films; for example, a single-layer aluminum (Al) metal material may be used.

[0036] The dimensions of the electrodes and markers formed on the above-mentioned quartz diaphragm are exemplified below. The quartz diaphragm has a long side dimension of 1.55 mm and a short side dimension of 1.35 mm, and its thickness is determined by the frequency as an AT-cut quartz plate is used. The input electrode and output electrode have a long side dimension of 0.3 mm, a short side dimension of 0.19 mm, and a thickness of approximately 600 angstroms. The common electrode corresponding to the input electrode and output electrode has a long side dimension of 0.66 mm, a short side dimension of 0.3 mm, and a thickness of approximately 1200 to 1500 angstroms. The marker is circular with a diameter of 0.1 mm and a thickness of approximately 600 angstroms. Note that the film thickness of the above electrodes (metal thin films) is the film thickness before filter characteristic adjustment. As will be described later, the common electrode is adjusted by reducing its film thickness by ion milling, so the film thickness after filter characteristic adjustment will be less than the above film thickness.

[0037] Figure 4 shows the crystal diaphragm 1 mounted flat on the package 1. The crystal diaphragm 2, on which the electrodes described above are formed, is mounted on the ceramic package such that one main surface on which the input and output electrodes are formed faces the electrode pads 12a, 12b, 12c, and 12d of the package, and is electrically and mechanically connected with a conductive bonding material S. Specifically, as shown in Figures 5 and 6, each connecting electrode and each connecting electrode pad are conductively bonded via the conductive bonding material S. The conductive bonding material S is, for example, a resin bonding material with a paste-like conductive filler added, and the bonding material hardens due to thermoplasticity, conductively bonding the crystal diaphragm 2 to the package 1.

[0038] As a result, as shown in Figure 4, the common electrode 23 is located on the opening side of the package, the extended electrode 22c extends along the long side of the upper end of the quartz diaphragm, and the extended electrode 21c extends along the short side of the right end of the quartz diaphragm, and the device is supported and fixed in this state. The conductive bonding material S is supplied to the connecting electrodes 21b, 22b, 23b and above them, which require conductive connection, as shown in Figures 1 and 4, and the connecting electrode 21b, the extended electrode 21c and the connecting electrode pad 12c, the connecting electrode 22b, the extended electrode 22c and the connecting electrode pad 12a, and the connecting electrode 23b and the connecting electrode pad 12b are electrically joined independently.

[0039] Figure 5 shows a cross-sectional view AA of Figure 4, in which the conductive bonding material S conductively bonds the connecting electrode 23b and the connecting electrode pad 12b, and also conductively bonds the connecting electrode 22b, the extension electrode 22c, and the connecting electrode pad 12a.

[0040] Figure 6 shows a cross-sectional view of BB in Figure 4, where the conductive bonding material S conductively bonds the connecting electrode 21b, the extension electrode 21c, and the connecting electrode pad 12c. In the region of bridging capacitance C, the ground electrode pad is located directly below it, separated from the quartz diaphragm by a gap G. Here, the gap G is set to 0.01 mm to 0.08 mm. A shorter gap G is preferable for improving characteristics such as suppressing the influence of external noise, but since this is the free end portion, there is a possibility that the quartz diaphragm may be damaged if it comes into contact with the ground electrode pad due to external shocks, etc. Therefore, the above-mentioned gap G distance is preferable. More preferably, the gap G is in the range of 0.02 mm to 0.06 mm, which further improves the stability of the filter characteristics against external noise and potential fluctuations, as well as improving shock resistance.

[0041] Alternatively, the extension electrodes may be formed on the input electrode and output electrode formation sides, and a bridging capacitance may be formed on one of the main surfaces. With this configuration, the distance between the bridging capacitance formation region and the ground electrode pad can be brought closer, further improving the stability of the filter characteristics.

[0042] As shown in Figures 5 and 6, the crystal diaphragm housing space is kept airtight by hermetically sealing package 1 with lid 3. This housing space may be filled with an inert gas or may be in a vacuum atmosphere.

[0043] Next, we will explain the method for adjusting the filter characteristics before hermetically sealing. In this example, we show an example of adjustment by reducing the thickness of the metal thin film using ion milling. When adjusting the frequency balance between electrodes for a common electrode 23 formed on the other main surface, the electrode film thickness is reduced by irradiating the corresponding common electrode regions of the input electrode 21 and output electrode 22 on one main surface (opposite surface) with an ion beam. Similarly, when adjusting the frequency band characteristics, the electrode film thickness is reduced by irradiating the common electrode region corresponding to the input electrode and output electrode with an ion beam.

[0044] It is desirable that the positions of the input electrode 21 and output electrode 22 formed on one main surface of the quartz diaphragm be directly opposite the common electrode 23 formed on the other main surface. However, during film formation using methods such as vacuum deposition or sputtering with a mask, a shift in the front and back surfaces may occur. In this case, the estimation of the corresponding positions of the input electrode 21 and output electrode 23 on the common electrode 23 may be inaccurate. This is because the common electrode 23 covers the input electrode 21 and output electrode 22 formed on its opposite surface, causing the estimated positions of the input electrode 21 and output electrode 22 to be inaccurate.

[0045] In this invention, a marker M is formed on the same surface as the input electrode 21 and the output electrode 22. These input electrodes, output electrodes, and marker are formed using a mask means having openings for their formation. As a result, the formation positions of the input electrodes and output electrodes are determined with respect to the formation position of the marker M, and there is no misalignment in their relative positions. The marker is formed in a manner that makes it visible on one of the main surfaces by passing through the transparent quartz diaphragm. Using this visible marker M as a reference, the adjustment area for the common electrode 23 can be identified. In this embodiment, since the marker M is located midway between the input electrode 21 and the output electrode 22, the positions of the input electrode 21 and the output electrode 22 can be identified using it as a reference.

[0046] Furthermore, the center frequency is adjusted by increasing or decreasing the film thickness across the entire surface of the common electrode 23. The adjustment area is narrowed (limited) using a partial aperture mask with an opening in a metal plate. In Figure 4, the area shown by the dashed line represents the partial aperture mask PW, which is used, for example, to reduce the film thickness across the entire surface of the common electrode where the center frequency is to be adjusted. Although not shown in the figure, adjustment to the input electrode area or the output electrode area of ​​the common electrode is performed by setting a partial aperture mask with an opening only in that area and then performing ion milling.

[0047] Furthermore, the bridging capacitance C may be adjusted locally. For example, the bridging capacitance can be adjusted by partially removing electrodes near each extension electrode using a laser or ion milling, or by adding electrodes (adding a thin metal film) by localized partial vacuum deposition, thereby changing the gap t or the electrode size.

[0048] Incidentally, when reducing the proximity distance or increasing the size of the extraction electrode in the proximity region, electrode addition by partial deposition or the like is necessary. In this case, to facilitate electrode addition and stabilize film formation, an extremely thin metal film may be formed in advance in the region where the electrode is to be added. This allows for adjustment of the bridging capacitance. The metal film should be made of chromium, for example, and its thickness should be several angstroms to several tens of angstroms, so that its resistance is high enough that it does not have the ability to conduct electricity between the two extension electrodes. Furthermore, the intermediate portion of each extension electrode that is in close proximity to each other may not have a metal film formed on it.

[0049] After completing the necessary adjustments described above, the electrode (metal film) is stabilized with an annealing treatment, and then hermetically sealed with lid 3. Lid 3 is made of a metal plate with a base material of a flat plate-shaped metal such as Kovar, and its surface is nickel-plated. Lid 3 is mounted on the metal seal portion 11, and in this state, the lid and the metal seal portion are melted and hermetically sealed by seam welding, laser beam welding, or brazing.

[0050] Although the above explanation uses a 2-pole monolithic quartz filter as an example, the same principles can be applied to 3-pole or 4-pole quartz filters.

[0051] The embodiments disclosed herein are illustrative in all respects and are not intended to be restrictive. Therefore, the technical scope of the present invention is not construed solely by the embodiments described above, but is defined by the claims. This includes all modifications within the meaning and scope of the equivalents of the claims. [Explanation of Symbols]

[0052] 1 package 10 Embankment 11 Metal seal part 2 Crystal diaphragm 3 Lid 12a, 12b, 12c connecting electrode pads 12d Ground electrode pad 13a, 13b, 136c, 13d, 13e, 13f Castelation C Bridging capacity

Claims

1. A crystal diaphragm having input electrodes and output electrodes formed on one main surface, a common electrode directly opposite the input electrodes and output electrodes formed on the other main surface, two connecting electrodes electrically connected independently to the input electrodes and output electrodes, and one connecting electrode electrically connected to the common electrode, The crystal diaphragm is held by two connection electrode pads which are electrically joined to the two connection electrodes, and one connection electrode pad which is electrically joined to the one connection electrode which is electrically connected to the common electrode, A package having a ground electrode pad that is not bonded to the quartz diaphragm and is grounded, A monolithic quartz filter having, A monolithic quartz filter characterized by forming a bridging capacitance by bringing in close proximity in the outer peripheral region one extension electrode drawn out from one of the connecting electrodes electrically connected to the input electrode to the outer peripheral region of the quartz diaphragm, and one extension electrode drawn out from one of the connecting electrodes electrically connected to the output electrode to the outer peripheral region of the quartz diaphragm, the ground electrode pad located below the bridging capacitance with a gap between it and the quartz diaphragm, the gap being 0.01 mm to 0.08 mm.

2. The monolithic quartz filter according to claim 1, characterized in that the quartz diaphragm is rectangular in plan view, and the bridging capacitance is formed at the corners of the quartz diaphragm.

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