Monolithic quartz filter

Abstract

To provide a monolithic crystal filter capable of adjusting filter characteristics with high accuracy.SOLUTION: A monolithic crystal filter F consists of: 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. A marker M is formed on a virtual extension line L passing through the middle of an input electrode 21 and an output electrode 22. The marker M is formed independently outside a formation region for a common electrode formed on the other principal surface (an opposite surface) of the crystal diaphragm and between a formation region for an extension electrode and the formation region for the common electrode.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, business radios. 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 wide or narrow passband widths. Regarding these filter characteristics, reliability such as stability that is not affected by external factors is also required.

[0003] A monolithic crystal filter has a configuration in which input electrodes and output electrodes are formed in parallel at the central portion of one main surface of an AT-cut crystal vibrating plate, and on the other main surface, a common electrode facing the input electrodes and output electrodes is formed. By applying an alternating electric field to the input electrodes and output electrodes, it functions as a crystal filter.

[0004] As is well known, it is necessary to perform a plurality of types of filter characteristic adjustments on the electrodes of the monolithic crystal filter, such as adjusting the frequency balance and frequency band characteristics between the electrodes. For example, when performing the frequency balance between the electrodes with respect to the common electrode, it is done by adjusting the electrode film thickness (the film thickness of the metal thin film) in the common electrode regions corresponding to the input electrode and the output electrode on the back surface. When adjusting the frequency band characteristics, it is done by adjusting the electrode film thickness (the film thickness of the metal thin film) in the region corresponding to between the input electrode and the output electrode. Further, in the adjustment of the center frequency, it is done by adjusting the electrode film thickness over the entire surface of the common electrode.

[0005] However, in the actual manufacturing process, these filter characteristics are typically adjusted after the quartz diaphragm is mounted in the package (retainer). In practice, as mentioned above, the quartz diaphragm is held with the common electrode facing upwards in the package, and the above adjustments are made to the common electrode. However, for frequency balance and other aspects, it is necessary to accurately estimate the formation positions of the input and output electrodes, but the formation of the common electrode sometimes made it impossible to accurately estimate these positions. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 3436251 [Overview of the project] [Problems that the invention aims to solve]

[0007] In Patent Document 1, as shown in Section 0009, it is disclosed that various filter characteristics can be adjusted. However, as mentioned above, if the formation positions of the input and output electrodes cannot be properly estimated, the adjustment area relative to the common electrode may be misaligned, making it impossible to adjust the filter characteristics appropriately. As a result, the adjustment process can take a long time, and productivity can be significantly reduced. Furthermore, unnecessary adjustments may be made, resulting in defective products being manufactured that could otherwise be produced as good products with proper adjustment.

[0008] This invention has been made in view of the above problems, and aims to provide a monolithic quartz filter that can perform filter characteristic adjustment with high precision. [Means for solving the problem]

[0009] To achieve the above objective, the invention of claim 1 provides an input electrode and an output electrode formed on one main surface, and the input electrode and the output electrode formed on the other main surface Directly oppositeA 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 translucent quartz diaphragm having, Having an opening and holding the crystal diaphragm, two Connecting electrode and each Conductive bonding two Connecting electrode pads, One connecting electrode pad electrically connected to the common electrode and conductively joined to one connecting electrode pad, and the two connecting electrode pads and the one connecting electrode pad are separate, A monolithic quartz filter having a package having a grounding electrode pad to be grounded, wherein the quartz diaphragm is The aforementioned With one main surface facing the package, two Connecting electrode and the two The connecting electrode pads are electrically bonded, the common electrode is positioned on the opening side of the package, and one or more markers having positional information related to the formation positions of the input electrode and output electrode on one main surface are formed on the one main surface, and when viewed in plan, the markers are formed on the quartz diaphragm outside the common electrode.

[0010] According to this configuration, a translucent quartz diaphragm is used, and one or more markers related to the formation positions of the input and output electrodes on one main surface are formed on the one main surface. When viewed in plan, the markers are formed on the quartz diaphragm outside the common electrode formed on the other main surface, so the position of the markers can be seen from the other main surface where the common electrode is formed. Since the markers have positional information related to the formation positions of the input and output electrodes, the positions of the markers can be used to identify the positions of the input and output electrodes on the opposite surface that are hidden by the common electrode.

[0011] Therefore, the formation positions of the input and output electrodes can be identified on the common electrode when viewed in a planar view, and multiple filter characteristic adjustments related to the formation positions of the input and output electrodes can be performed on the common electrode side, thereby obtaining a monolithic quartz filter that can perform filter characteristic adjustments with high precision.

[0012] One or more markers related to the formation positions of the input electrode and the output electrode on the one main surface may be one, or may be two or more.

[0013] When forming one marker, the marker may be formed on the crystal vibrating plate outside the common electrode on the virtual intermediate line between the input electrode and the output electrode on the one main surface.

[0014] According to the above configuration, since it is a configuration formed outside the common electrode on the intermediate line between the input electrode and the output electrode, it is possible to adjust the filter characteristics for a desired adjustment region without inhibiting the vibration during driving of the monolithic crystal filter, and a high-precision monolithic crystal filter can be obtained.

Advantages of the Invention

[0015] According to the present invention, a monolithic crystal filter capable of adjusting filter characteristics with high precision can be obtained.

Brief Description of the Drawings

[0016] [Figure 1] It is a plan view of one main surface of the crystal vibrating plate formed with electrodes according to the present embodiment. [Figure 2] It is a plan view of the other main surface of the crystal vibrating plate formed with electrodes according to the present embodiment. [Figure 3] It is a plan view of the package according to the present embodiment. [Figure 4] It is a plan view of a state where the crystal vibrating plate is mounted on the package according to the present embodiment. [Figure 5] It is a cross-sectional view taken along line A-A of the state where the package of FIG. 4 is sealed with a lid. [Figure 6] It is a cross-sectional view taken along line B-B of the state where the package of FIG. 4 is sealed with a lid. [Figure 7] It is a plan view of one main surface of the crystal vibrating plate formed with electrodes showing another marker formation example.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0018] First Embodiment A first embodiment according to the present invention will be described with reference to FIGS. 1 to 6. FIG. 1 is a plan view of one main surface of a crystal vibrating plate with electrodes formed thereon according to this embodiment, and FIG. 2 is a plan view of the other main surface of the crystal vibrating plate with electrodes formed thereon. FIG. 3 is a plan view showing a package for housing and holding the crystal vibrating plate. FIG. 4 is a plan view showing a state where the crystal vibrating plate is housed and held in the package, FIG. 5 is a cross-sectional view taken along line A-A of FIG. 4 in a state where the package housing the crystal vibrating plate and conductively joined is hermetically sealed with a lid, and FIG. 6 is a cross-sectional view taken along line B-B of FIG. 4 in a state where the package is similarly hermetically sealed with a lid.

[0019] The monolithic crystal filter F is composed of a package 1 having a rectangular parallelepiped shape as a whole and having a recess with an open upper part, a crystal vibrating plate 2 which is a piezoelectric vibration element housed in the recess of the package 1, and a lid 3 joined to the opening of the package 1.

[0020] The package 1 is a ceramic package in which wirings are formed by metal films inside and outside, and is concave in cross-section, and has a dike portion (side wall) 10 around the concave portion and a circumferential metal seal portion 11 formed on the upper surface of the dike portion. The metal seal portion 11 is composed of a metallized layer made of tungsten or the like and a metal film layer formed on the metallized layer. The metal film layer is composed of, for example, a nickel plating layer in contact with the metallized layer and an extremely thin gold plating layer formed on the upper part of the nickel plating layer. A welding metal ring made of kovar or the like may also be attached.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 formation of an overcoat of the conductive bonding material can be omitted in the conductive bonding between the connecting electrode and the connecting electrode pad using the conductive bonding material described later.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 12c.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] Next, we will explain the method for adjusting the filter characteristics before hermetically sealing. Filter characteristics can be adjusted by increasing or decreasing the thickness of the electrode (metal thin film). For example, partial deposition can be used to increase the thickness, while ion milling can be used to decrease it. In actual manufacturing processes, adjustment is performed using either a method to increase or decrease the thickness.

[0039] This example demonstrates an adjustment method using ion milling to reduce the thickness of a metal thin film. When adjusting the frequency balance between electrodes for a common electrode 23 formed on the other main surface, the electrode 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 thickness is reduced by irradiating the common electrode region corresponding to the space between the input electrode and the output electrode with an ion beam.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Next, another embodiment using two markers will be described with reference to Figure 7. The example shown in Figure 7 has no extension electrodes or bridging capacitance, and an input electrode 21 and an output electrode 22 are formed on one main surface of the quartz diaphragm 2, and a common electrode 23 is formed on the other main surface. Marker M1 corresponding to the input electrode and marker M2 corresponding to the output electrode are formed, with marker M1 being formed in relation to the formation position of the input electrode and marker M2 being formed in relation to the formation position of the output electrode. In this example, markers M1 and M2 are formed directly above the midpoint of the short side direction of the input electrode and output electrode, respectively.

[0044] In this embodiment, the external size of the common electrode 23 is larger than the area where the input electrode and output electrode are arranged in parallel. Basically, when adjusting the filter characteristics of the common electrode from the other main surface, the exact positions of the input electrode and output electrode are unknown. However, with the marker configuration described above, the formation positions of the input electrode and output electrode can be accurately identified based on the positions of each marker. This allows for accurate adjustment of the filter characteristics, and enables the acquisition of highly accurate filter characteristics.

[0045] In this embodiment, markers M1 and M2 are small squares. By identifying the corners of the squares, positional information can be obtained more accurately, contributing to the acquisition of high-precision filter characteristics.

[0046] Furthermore, in the above example, marker M2 may be formed below the output electrode, and markers M1 and M2 may be formed at diagonal positions. Three or more markers may also be formed, however, the weight of the markers themselves may affect the vibration of the crystal diaphragm. Therefore, when forming multiple markers, it is preferable to form them at a distance from the excitation region formed by the input electrode, output electrode, and common electrode.

[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 translucent quartz 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, It has an opening and holds the crystal diaphragm, and comprises two connection electrode pads which are electrically joined to the two connection electrodes, and one connection electrode pad which is electrically joined to one connection electrode which is electrically connected to the common electrode, A package having the two connecting electrode pads and a grounding electrode pad that is separate from the one connecting electrode pad, A monolithic quartz filter having, The quartz diaphragm is configured such that one main surface faces the package, the two connecting electrodes and the two connecting electrode pads are electrically bonded, and the common electrode is positioned on the opening side of the package. A monolithic quartz filter characterized in that one or more markers having positional information related to the formation positions of the input electrode and output electrode on one of the main surfaces are formed on the one main surface, and when viewed in plan, the markers are formed on the quartz diaphragm outside the common electrode.

2. The monolithic quartz filter according to claim 1, characterized in that the marker is formed on a virtual median line between the input electrode and the output electrode of one of the main surfaces.

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