JP2005303825A - Crystal filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric filter corresponding to miniaturization capable of obtaining desired attenuation characteristics and suppressing spurious and the like.
SOLUTION: A rectangular crystal vibrating plate 1 is made of an AT-cut crystal plate and has thin portions 11, 16 and a thick portion 12. The thin portions 11 and 16 are formed in a rectangular shape in plan view by digging both main surfaces of a thick flat plate in the thickness direction, and form a flat portion. On one main surface, the thick portion is provided on three sides along the outer periphery of the rectangular shape, and the flat portion 12b that does not form the thick portion so as to be flush with the aforementioned thin portion surface on the other side, It has become. Lead-out electrodes 13c and 14c are formed from the input electrode 13 and the output electrode 14 to the flat portion 12b described above. The leading end portions of these lead-out electrodes 13c and 14c are close to each other in a planar manner to form a bridging capacitance forming portion C.
[Selection] Figure 1

Description

  The present invention relates to a crystal filter used for communication equipment such as a mobile phone, electronic equipment, and the like, and more particularly to a configuration with improved attenuation characteristics.

  In recent years, mobile communication devices such as electronic devices such as portable information terminals have not only simple communication functions but also various additional functions incorporated therein and are becoming smaller. There is a demand for further miniaturization of the crystal filter used in this, and there is also a demand for ensuring the reliability of the crystal filter itself in terms of configuration and manufacturing in response to the miniaturization.

  Quartz filters have been devised to suppress various types of spurious due to the design of the electrodes formed on the quartz diaphragm, but as the miniaturization progresses, this electrode design becomes difficult and the frequency balance between the electrodes and Adjustment of the frequency band characteristic has to be performed in a limited narrow area.

  Further, when a crystal filter is used as an IF filter in a communication device, it is necessary to consider a guaranteed attenuation characteristic in the vicinity of an image frequency, which is disclosed in Japanese Patent Laid-Open No. 9-284092. This publication is composed of a piezoelectric substrate having a thin vibrating portion and a thick annular surrounding portion around the vibrating portion. The vibrating portion is formed with a split electrode and a back-side full surface electrode, and a bonding electrode derived from the split electrode. Is a predetermined interval, and a configuration in which a bridging capacitance is created between the input and output electrodes is disclosed. With this configuration, the attenuation pole can be matched with the negative side of the image frequency, and a high attenuation can be obtained.

  In the above configuration, a predetermined bridging capacity is obtained by bringing the bonding electrodes (leading electrodes) derived from the divided electrodes close to each other. With such a configuration, a short circuit between bonding electrodes, that is, between terminals is obtained. May cause a short circuit. Further, in the above-described conventional configuration, the piezoelectric substrate as a whole has a reverse concave configuration, and when the excitation electrode is formed in such a configuration, there is a problem that an equivalent series resistance value is deteriorated. That is, in general, for the formation of the concave shape, it is common to perform processing by etching using a photolithographic technique on a plate-like piezoelectric vibration plate whose surface is processed by parallel plane polishing. When only the surface is etched deeply, the etched surface tends to be rough. In addition, the polished surface is applied as it is to the plane portion of the other main surface where etching is not performed, but in this case as well, the surface is rough because it has a work-affected layer or a secondary crack layer with residual stress due to polishing. It was in a state. Since such a rough surface deteriorates the CI value, it is also commonly used to chemically remove the work-affected layer by etching the entire piezoelectric diaphragm in a flat plate stage. However, in this case as well, the front and back of the piezoelectric diaphragm are etched and thinned, which may adversely affect subsequent handling and processing.

  Japanese Patent Application Laid-Open No. 2004-48516 discloses another configuration example of a crystal filter in which a bridging capacitance is formed. In Japanese Patent Application Laid-Open No. 2004-48516, a split electrode and a common electrode that generate filter characteristics are formed on the front and back surfaces of a flat crystal plate, and lead electrodes extending from both electrodes are close to each other on the split electrode side. A bridging capacitance is formed on the quartz plate. The common electrode is formed at a position corresponding to the divided electrode. The common electrode is used in an adjustment region after being incorporated in a package, and partial vapor deposition is performed in which a metal vapor deposition material is partially attached to the common electrode.

  By the way, the partial vapor deposition may have an error of about 100 μm in a region where the metal vapor deposition material is attached depending on conditions. When the external size of the common electrode is large, even if the error occurs, the processing in the common electrode can be performed. However, when the size of the crystal filter is reduced as described above, and the external size of the common electrode is reduced accordingly, the crystal electrode is separated from the common electrode due to the error of the partial vapor deposition, and is not intended on the crystal plate. A metal film may be formed in the region. In such a case, if a lead-out electrode for forming bridging capacitance exists on the opposite surface of the quartz plate, the protruding metal film by partial vapor deposition may function as a new electrode, and unintended spurious may occur. It was.

JP-A-9-284092 JP 2004-48516 A

  The present invention has been made in view of the above points, and an object of the present invention is to provide a piezoelectric filter corresponding to miniaturization that can obtain desired attenuation characteristics and suppress spurious and the like. It is an object.

  In order to achieve the above object, according to the present invention, as shown in claim 1, a thin-walled portion, a piezoelectric diaphragm having a thick-walled portion formed in part or all of the outer periphery of the thin-walled portion, and one of the thin-walled portions An input electrode and an output electrode formed on the main surface of the thin film portion, a common electrode formed on the other main surface of the thin portion corresponding to the input electrode and the output electrode, and the input electrode, the output electrode, and the common electrode A piezoelectric filter comprising: each lead-out electrode drawn out to the end of each of the electrodes; and a bridging capacitance forming portion extending from each of the input electrode and the output electrode and extending in the vicinity of the end of the piezoelectric diaphragm. The thin-walled portion is configured to be thinned from both of the main surfaces, the input electrode, the output electrode, and the lead-out electrode are formed in the same plane, and the piezoelectric portion below the bridging capacitance forming portion of the lead-out electrode The diaphragm is thicker than the thin part. It is an.

  Since the input electrode, the output electrode, and the lead electrode are formed on the same plane on the surface of the bridging capacitance forming portion, each of the input electrode and the lead electrode, and each of the output electrode and the lead electrode when forming an electrode by vapor deposition or the like. The problem of electrode disconnection can be eliminated.

  In addition, the lower part of the bridging capacity forming portion has a thick structure. This thick structure is preferably thicker than the thin part and the same or slightly smaller than the thickness of the thick part on the common electrode side. A thick structure thicker than the thin-walled portion is effective in suppressing spurious due to formation of the lead electrode. For example, spurious may occur due to the adjustment metal material adhering to the opposite surface of the lead-out electrode and the bridging capacitance forming part, or foreign matter adhering, etc. The main vibration characteristics are not adversely affected.

  In addition, when partial vapor deposition for characteristic adjustment is performed on the common electrode, metal material may be formed in the lead electrode formation part on the opposite surface due to manufacturing errors, but there is a thick structure thicker than the thin part Thus, spurious attributed to the lead-out electrode can be suppressed.

  By the way, the conventional bridging capacitance forming portion is formed in a thin portion, but by forming this in a thick portion, the size of the quartz diaphragm can be reduced as compared with the conventional case. For example, when a large number of crystal diaphragms are obtained from a wafer by using a photolithography technique, the number of crystal plates that can be taken per wafer can be increased, and the productivity is improved. Of course, the upper surface of the thin structure is the same plane as the input and output electrode formation surfaces, and there is no problem of electrode breakage.

  Further, according to the present invention, as shown in claim 2, the piezoelectric diaphragm having a rectangular shape in a plan view in which a thick portion is formed in a part of or all of the thin portion and the outer periphery of the thin portion, and one of the thin portions. An input electrode and an output electrode formed on the main surface of the thin film portion, a common electrode formed on the other main surface of the thin portion corresponding to the input electrode and the output electrode, and the input electrode, the output electrode, and the common electrode Each of the lead-out electrodes to be drawn out to the end portion of the piezoelectric diaphragm, and a bridge capacitance forming portion extending from the input electrode and the output electrode in the vicinity of the end portion of one side of the piezoelectric diaphragm. In the filter, a thick portion on the input electrode and output electrode side is not formed on the side on the bridging capacitance forming portion side or on the side facing the bridging capacitance forming portion and the side facing the side, and the bridge A thick-walled structure is thicker than the thin-walled portion below the winding electrode forming portion. It is characterized.

  According to the above configuration, the thick part on the input electrode and output electrode side is not formed at least on the side of the bridging capacitance forming part side, thereby forming a flat part that is flush with the thin part. Therefore, fine patterning when forming the lead electrode and the bridging capacitance forming portion can be formed with high accuracy. That is, the surface tension functions in the boundary portion between the thin portion and the thick portion. For this reason, on the manufacturing side, the liquid resist film used for patterning tends to be thick in the vicinity of the boundary portion (that is, the corner portion) due to surface tension, and thin as the distance from the boundary portion increases. Such differences in thickness increase manufacturing variations during electrode formation, and it has been difficult to perform fine patterning with high accuracy. However, the above configuration eliminates adverse effects due to surface tension, and allows fine patterning with high accuracy. It can be carried out.

  According to the second aspect, since the thick portion is not formed on the input electrode forming side on the side of the bridging capacitance forming side, and is configured in the same plane as the thin portion, the adverse effects due to the surface tension as described above are eliminated. can do. In addition, by adopting a configuration in which the thick portion is not formed on the input / output electrode forming side with respect to the side facing the bridging capacitance forming side, it is possible to eliminate the adverse effects due to surface tension and obtain the intended electrode pattern. it can.

  In addition, by forming the same plane as the thin portion up to the outer peripheral end of the piezoelectric diaphragm, the chance of forming the electrode at the ridge of the piezoelectric diaphragm is reduced when the extraction electrode is led out. Problems such as cutting can be suppressed.

  Further, the present invention also discloses a configuration in consideration of characteristic adjustment as shown in claim 3. That is, a piezoelectric filter in which a piezoelectric diaphragm having a thin portion and a thick portion formed in a part or all of the outer periphery of the thin portion in a vertical direction is housed in a package. An input electrode and an output electrode formed on one main surface, a common electrode formed on the other main surface of the thin portion corresponding to the input electrode and the output electrode, and the input electrode, the output electrode, and the common electrode are piezoelectrically oscillated. Each lead-out electrode drawn out to the end of the plate, and a first bridge in which a narrow first lead-out electrode extends from the input electrode and the output electrode in the same plane and is brought close to each other in the vicinity of the end of the piezoelectric diaphragm A second bridging electrode in which a second lead-out electrode is led out from the capacitance forming portion and each of the input electrode and the output electrode to the surface of the thick portion, and each second lead-out electrode is brought close to the surface of the thick portion. A capacitance forming portion, and The piezoelectric diaphragm below the bridging capacitance forming portion is thicker than the thin portion, and is mounted on the package with the second bridging capacitance forming portion facing upward. The piezoelectric filter is characterized in that the characteristics can be adjusted with respect to the bridging capacitance portion.

  According to the third aspect, the second lead-out electrode is formed, and the piezoelectric diaphragm is mounted on the package by mounting the bridging capacitance forming portion adjacent to the lead-out electrode in the upward direction. After that, the characteristic adjustment can be performed on the second bridging capacitance forming portion. Therefore, highly accurate characteristics can be obtained. In addition, the second bridging capacitance part is pulled out to the common electrode side, and the common electrode and the second bridging capacitance forming part are mounted on the package facing upward, thereby adjusting the characteristics of both after the package is mounted. Can be executed.

  As described above, in the present invention, since the lead-out electrode and the bridging capacitance forming portion are formed on the same plane as the input electrode and the output electrode, reliable electrode formation can be performed. Further, since the lower portion of the bridging capacitance forming portion is thicker than the thin portion, spurious due to the formation of the lead electrode can be suppressed. Accordingly, it is an object of the present invention to provide a piezoelectric filter that can achieve a desired attenuation characteristic by forming a bridging capacitance and that can suppress spurious and the like and that can be reduced in size.

  A first embodiment of the present invention will be described with reference to FIGS. 1 and 2 by taking a surface mount type crystal filter as an example. FIG. 1 is a perspective view seen from one main surface of the quartz crystal diaphragm showing the present embodiment, and FIG. 2 is a perspective view seen from the other main surface.

The surface-mount type crystal filter has a rectangular parallelepiped shape as a whole, and has a ceramic package (not shown) having a recess with an open top, and a rectangular crystal diaphragm 2 that is a piezoelectric vibration element housed in the package, It consists of a metal lid (not shown) joined to the opening of the package.

  The rectangular crystal vibrating plate 1 is made of an AT-cut quartz plate and has thin portions 11 and 16 and a thick portion 12. The thin portions 11 and 16 are formed in a rectangular shape in plan view by digging both main surfaces of a thick flat plate in the thickness direction, and form a flat portion. As shown in FIG. 1, on one main surface, the thick part is provided on three sides along the outer periphery of the rectangular shape, and on the other side, the thick part is arranged so as to be flush with the surface of the thin part. The flat portion 12b is not formed. On the other hand, as shown in FIG. 2, in the other main surface, the thick part 12 is provided in four surroundings (four sides) along the rectangle, and the thin part 16 is formed in the center part.

Electrodes constituting a monolithic crystal filter are formed on both main surfaces of the crystal diaphragm 1. That is, as shown in FIG. 1, a rectangular input electrode 13 and an output electrode 14 are formed at a predetermined interval on the thin portion 11 of one main surface, and the other main surface is formed as shown in FIG. The thin portion 16 is formed with a rectangular common electrode 15 facing the input electrode and the output electrode.

The input electrode 13 and the output electrode 14 are led out to the end of the crystal diaphragm by lead electrodes 13a and 14a, respectively. These extraction electrodes 13a and 14a are extracted to connection electrodes 13b and 14b connected to electrode pads (not shown) formed in the ceramic package. The common electrode 15 is drawn out to the connection electrodes 15b and 15b via the lead electrodes 15a and 15a.

Lead-out electrodes 13c and 14c are formed from the input electrode 13 and the output electrode 14 to the flat portion 12b. The leading end portions of these lead-out electrodes 13c and 14c are close to each other in a planar manner to form a bridging capacitance forming portion C. The bridging capacitance forming portion C can adjust the value by changing the distance between the adjacent portions of the lead-out electrodes and the area of the electrodes facing each other.

The thickness direction lower portion of the bridging capacitance C is thicker than the thin portion 11. The thick structure 12a is preferably thicker than the thin part 11 and is the same as or slightly smaller than the thickness of the thick part 12 on the common electrode side. In the present embodiment, the thin portion 11, the thick structure 12a, and the thick portion 12 are thickened in this order. The thick structure 12a thicker than the thin-walled portion is effective in suppressing spurious due to the formation of the lead electrode.

In addition, although it is preferable from a viewpoint of spurious suppression that the part in which the lead-out electrodes 13c and 14c are formed is the above-described thick structure 12a, if the thick structure 12a is too close to the input electrode and the output electrode, the main vibration occurs. Since it may have an adverse effect, it is necessary to optimally adjust the design conditions depending on the operating frequency, the order of harmonics, and the like.

The thin-walled portion or the electrodes may be formed using a photolithography technique. That is, patterning for forming a thin portion is performed using a resist film, and the thin portion is formed using an etching technique. Thereafter, an electrode material, for example, a chromium film in contact with a quartz diaphragm and a gold film on the upper surface of the thin-walled portion are formed by vacuum deposition, followed by predetermined patterning with a resist film, and etching to form each electrode described above. Can be obtained. Since the connection electrodes 13b, 14b, and 15b are partly formed also in the thick portion, a vacuum using a metal mask having a predetermined pattern opening window is formed after the electrode formation by the photolithography technique described above. It can be formed by vapor deposition.

Although not shown, an electrode-formed crystal diaphragm is mounted on a ceramic package, bonded with a conductive bonding material, and then hermetically sealed with a lid. A filter can be obtained.

  A second embodiment of the present invention will be described with reference to FIGS. 3 and 4 by taking a surface-mount type crystal filter as an example. FIG. 3 shows the second embodiment, and is a plan view of the crystal diaphragm viewed from one main surface, and FIG. 4 is a plan view viewed from the other main surface.

  The rectangular crystal vibrating plate 2 is made of an AT-cut crystal plate and has thin portions 21 and 26 and a thick portion 22. The thin portion 21 is formed in a substantially rectangular shape in plan view by digging both main surfaces of a thick flat plate in the thickness direction, and forms a flat portion. As shown in FIG. 3, on one main surface, the thick portion 22 is provided on four sides along a rectangular outer periphery, but in the vicinity of a bridging capacitance forming portion C described later, a part of the thick portion Is not formed, and is a flat portion 22b that is flush with the surface of the thin portion described above. On the other hand, as shown in FIG. 4, in the other main surface, the thick part 22 is provided in four surroundings along the rectangle, and the thin part 26 is formed in the center part. In addition, the curvature surface 22c is formed in a part of rectangular four corner part which consists of a boundary part of a thin part and a thick part. The curvature surface is intended to improve the strength of the quartz diaphragm.

Electrodes constituting a monolithic crystal filter are formed on both main surfaces of the crystal diaphragm 2. That is, as shown in FIG. 3, a rectangular input electrode 23 and an output electrode 24 are formed at a predetermined interval on the thin portion 21 of one main surface, and as shown in FIG. A rectangular common electrode 25 facing the input electrode and the output electrode is formed on the thin portion 26 of the surface.

The extraction electrode side of the input electrode and the output electrode has a partial arc shape, and the common electrode 25 similarly has a partial arc shape on the extraction electrode side. The common electrode 25 has slits 25c and 25c formed at the center thereof, and has a configuration that substantially matches the shape of the input / output electrodes on the opposite surface. With such a configuration, spurious can be suppressed.

Extraction electrodes 23a and 24a are drawn from the input electrode 23 and output electrode 24, respectively, and extraction electrodes 25a and 25a are drawn from the common electrode in a direction perpendicular to the short side of the crystal diaphragm, and are perpendicular to the end of the thin portion. It is bent to 4 corners. These lead electrodes are formed symmetrically with respect to the AA line that bisects the input / output electrodes when viewed in a plane, and are configured to maintain a planar vibration balance. These lead electrodes 23a, 24a, and 25a are led to connection electrodes 23b, 24b, and 25b connected to electrode pads (not shown) formed in the ceramic package, respectively.

Lead-out electrodes 23c and 24c are formed from the input electrode 23 and the output electrode 24 to the flat portion 22b described above. The leading end portions of these lead-out electrodes 23c and 24c are close to each other in a planar manner to form a bridging capacitance forming portion C. The bridging capacitance forming portion C can adjust the value by changing the distance between the adjacent portions of the lead-out electrodes and the area of the electrodes facing each other.

Below the bridging capacitance C is a thicker structure 22 a than the thin-walled portion 21. The thick structure 22a is preferably thicker than the thin part 21 and is the same as or slightly smaller than the thickness of the thick part 22 on the common electrode side. Also in the present embodiment, the thin portion 21, the thick structure 22 a, and the thick portion 22 are thickened in this order. The thick structure 12a thicker than the thin-walled portion is effective in suppressing spurious due to the formation of the lead electrode. A balancer 27 made of a rod-like metal film is formed on the opposite side of the bridging capacitance forming portion with the input / output electrodes interposed therebetween. In the present embodiment, since the flat portion is formed only in the vicinity of the bridging capacitance forming portion and the thick portions are left on the four sides, the strength of the crystal diaphragm can be improved. The balancer 27 has a planar balance with the lead-out electrodes 23c and 24c.

  Note that the configuration shown in FIG. 5 may be adopted instead of the configuration shown in FIG. In FIG. 5, the thick portion 32 on the input electrode 33 and output electrode 34 sides is formed in four sides, but the width of the thick portion 32a in the vicinity of the bridging capacitance forming portion is reduced. As a result, patterning of the lead electrode constituting the bridging capacitance forming portion c is facilitated, and the strength of the crystal diaphragm 3 itself can be improved. The length of the balancer 27 is also reduced in accordance with the size of the bridging capacitance forming portion of the lead electrode.

  A third embodiment of the present invention will be described with reference to FIGS. 6 and 7 by taking a surface-mounted crystal filter as an example. FIG. 6 shows a third embodiment, and is a perspective view of the crystal diaphragm 4 viewed from one main surface, and FIG. 7 is a plan view viewed from the other main surface.

  The rectangular crystal vibrating plate 4 is made of an AT-cut quartz plate and has thin portions 41 and 46 and a thick portion 42. The thin portions 41 and 46 are formed in a rectangular shape in plan view by digging both major surfaces of a thick flat plate in the thickness direction, and form a flat portion. As shown in FIG. 6, on one main surface, the thick portion 42 is provided only on two opposite sides, and the other side has the same planar configuration as the thin portion, and forms a bridge capacity described later. The portion is also a flat portion 42b.

On the other hand, as shown in FIG. 7, in the other main surface, the thick part 42 is provided in four surroundings along the rectangle, and the thin part 46 is formed in the center part. In addition, a part of curvature surface is formed in the four corner parts of the boundary part of a thin part and a thick part. The curvature surface is intended to improve the strength of the quartz diaphragm.

Electrodes constituting a monolithic crystal filter are formed on both main surfaces of the crystal diaphragm 4. That is, as shown in FIG. 6, a rectangular input electrode 43 and an output electrode 44 are formed at a predetermined interval on the thin portion 41 of one main surface, and as shown in FIG. A rectangular common electrode 45 facing the input electrode and the output electrode is formed on the thin portion 46 of the surface.

Extraction electrodes 43a and 44a are extracted from the input electrode 43 and output electrode 44, respectively, and extraction electrodes 45a and 45a are extracted from the common electrode in a direction perpendicular to the short side of the crystal diaphragm. It is bent at a right angle at the end and pulled out to the four corners. Similar to the second embodiment, these extraction electrodes are formed symmetrically with respect to a line that bisects the input / output electrodes when viewed in plan, and are configured to maintain a planar vibration balance. These lead electrodes 43a, 44a, 45a are led to connection electrodes 43b, 44b, 45b connected to electrode pads (not shown) formed in the ceramic package, respectively.

Lead-out electrodes 43c and 44c are formed from the input electrode 43 and the output electrode 44 to the flat portion 22b described above. These lead-out electrodes 43c and 44c are close to each other in a plane and form a bridging capacitance forming portion C. The bridging capacitance forming portion C can adjust the value by changing the distance between the adjacent portions of the lead-out electrodes and the area of the electrodes facing each other.

Below the bridging capacitance C is a thicker structure 42 a than the thin-walled portion 41. The thick structure 42a is preferably thicker than the thin part 41 and is the same as or slightly smaller than the thickness of the thick part 42 on the common electrode side. Accordingly, the thin portion 41, the thick structure 42a, and the thick portion 42 are thickened in this order. The thick structure 42a thicker than the thin-walled portion is effective in suppressing spurious due to the formation of the lead electrode.

In the present embodiment, in addition to the effects of improving the damping characteristics, suppressing spurious, and downsizing, the thick part is provided only on two opposite sides on one main surface, so the thick part and the thin part The adverse effect of the surface tension acting on the surface is suppressed, fine patterning can be formed with high accuracy, and good characteristics can be obtained.

  A fourth embodiment of the present invention will be described with reference to FIGS. 8 and 9 by taking a surface mount type crystal filter as an example. FIG. 8 shows a fourth embodiment, and is a perspective view of the crystal diaphragm 5 viewed from one main surface, and FIG. 9 is a plan view viewed from the other main surface.

  The rectangular crystal vibrating plate 5 is made of an AT cut crystal plate and has thin portions 51 and 56 and a thick portion 52. The thin portions 51 and 56 are formed in a rectangular shape in plan view by digging both main surfaces of a thick flat plate in the thickness direction, and form a flat portion. As shown in FIG. 6, on one main surface, the thick portion 52 is provided only on two opposite sides, and the other side has the same planar configuration as the thin portion, and the bridge capacity formation described later is performed. The portions are also flat portions 52b and 52c.

Moreover, as shown in FIG. 7, also on the other main surface, the thick part 52 is provided only on two opposing sides, and the other side has the same plane configuration as the thin part. In addition, the thick part of the other main surface is formed in a direction orthogonal to the thick wall of the one main surface, and ensures the mechanical strength of the crystal diaphragm.

Electrodes constituting a monolithic crystal filter are formed on both main surfaces of the crystal diaphragm 5. That is, as shown in FIG. 8, a rectangular shaped input electrode 53 and an output electrode 54 are formed at a predetermined interval in the thin portion 51 of one main surface, and as shown in FIG. A rectangular common electrode 55 facing the input electrode and the output electrode is formed on the thin portion 56 of the surface.

Lead electrodes 53a and 54a are led out from the input electrode 53 and the output electrode 54, respectively, and lead electrodes 55a and 55a are led out from the common electrode in a direction perpendicular to the short side of the crystal diaphragm, and are perpendicular to the end of the thin portion. It is bent to 4 corners. Similar to the second embodiment, these extraction electrodes are formed symmetrically with respect to a line that bisects the input / output electrodes when viewed in plan, and are configured to maintain a planar vibration balance. These lead electrodes 53a, 54a, and 55a are led to connection electrodes 53b, 54b, and 55b connected to electrode pads (not shown) formed in the ceramic package, respectively.

Further, first lead-out electrodes 53c and 54c and second lead-out electrodes 53d and 54d are formed from the input electrode 53 and the output electrode 54 to the flat portions 52b and 52c, respectively. The tip portions of the first lead-out electrodes 53c and 54c are close to each other in a planar manner to form a bridging capacitance forming portion C1. In addition, the tip portions of the second lead-out electrodes 53d and 54d are close to each other in a planar manner to form a second bridging capacitance forming portion C2. These bridging capacitance forming portions can be adjusted in value by changing the distance between the adjacent portions of the lead-out electrodes and the area of the electrodes facing each other.

Below the bridging capacitance forming portions C <b> 1 and C <b> 2 is a thicker structure 52 a than the thin portion 51. This thick structure 52a is preferably thicker than the thin part 51 and is the same as or slightly smaller than the thickness of the thick part 52 on the common electrode side. Accordingly, the thin portion 51, the thick structure 52a, and the thick portion 52 become thicker in this order. The thick structure 52a thicker than the thin part is effective in suppressing spurious due to the formation of the lead electrode.

In the present embodiment, in addition to the effects of improving damping characteristics, suppressing spurious and miniaturization, the thick portions are provided only on the two opposing sides on both main surfaces, and these thick portions are orthogonal to each other. By arranging in such a manner, the adverse effect of the surface tension acting by the thick and thin portions can be suppressed, fine patterning can be accurately formed across both main surfaces, and good characteristics can be obtained. it can. Further, since the first and second bridging capacitance forming portions are formed on the target via the input electrode and the output electrode, a planar weight balance can be obtained.

  A fifth embodiment of the present invention will be described with reference to FIG. 10 by taking a surface mount type crystal filter as an example. FIG. 10 is a perspective view of the crystal diaphragm 6 viewed from one main surface.

  In the present embodiment, a configuration in which two bridging capacitance forming portions are provided is disclosed. The basic configuration is the same as that of the first embodiment, and has a flat portion 62b in which a thick portion is formed on three sides on one main surface and a thick portion is not formed. The rectangular crystal vibrating plate 6 is made of an AT cut crystal plate and has a thin portion 61 and a thick portion 62. The thin portion 61 is formed in a rectangular shape in plan view by digging both major surfaces of a thick flat plate in the thickness direction, and forms a flat portion.

Electrodes constituting a monolithic crystal filter are formed on both main surfaces of the crystal diaphragm 6. That is, as shown in FIG. 10, a rectangular input electrode 63 and an output electrode 64 are formed at a predetermined interval in the thin portion 61 of one main surface. Lead electrodes 63a and 64a are led out from the input electrode 63 and the output electrode 64 toward the connection electrodes 73b and 74b at the corners, respectively. The description of the other main surface is omitted, but the basic configuration is similar to that shown in FIG.

In addition, first lead-out electrodes 63c and 64c are formed from the input electrode 63 and the output electrode 64 to the flat portion 22b described above. These first lead-out electrodes 63c and 64c are close to each other in a plane and form a first bridging capacitance forming portion C1. The first bridging capacitance forming portion C1 can adjust the value by changing the distance between the adjacent portions of the first lead-out electrode and the area of the electrodes facing each other.

Below the first bridging capacitance forming portion C <b> 1 is a thicker structure 62 a than the thin-walled portion 61. The thick structure 62a is preferably thicker than the thin part 61 and is the same as or slightly smaller than the thickness of the thick part 62 on the common electrode side. Accordingly, the thin portion 61, the thick structure 62a, and the thick portion 62 become thicker in this order. The thick structure 62a thicker than the thin part is effective in suppressing spurious due to the formation of the lead electrode.

Further, the second lead-out electrodes 63d and 64d are formed to extend from the connection electrodes 73b and 74b to the surface of the thick portion, and are close to each other on the thick portion, and the second bridging capacitance forming portion C2 is formed. Forming.

In the present embodiment, since two bridging capacitance forming portions are provided, the characteristics can be adjusted more accurately. In addition, since any bridging capacitance forming portion is provided in a region different from the main vibration region composed of the input / output electrodes and the common electrode, there is no adverse effect on characteristics such as spurious due to the bridging capacitance forming portion.

  A sixth embodiment of the present invention will be described with reference to FIGS. 11, 12, and 13 by taking a surface mount type crystal filter as an example. FIG. 11 shows a fourth embodiment, and is a perspective view of the crystal diaphragm 7 viewed from one main surface, and FIG. 12 is a plan view viewed from the other main surface. FIG. 13 is a cross-sectional view showing a state in which the crystal diaphragm shown in the BB cross section of FIGS. 11 and 12 is mounted on a package.

  Also in the present embodiment, a configuration in which two bridging capacitance forming portions are provided is disclosed. The rectangular crystal vibrating plate 7 is made of an AT-cut quartz plate and has thin portions 71 and 76 and a thick portion 72. The thin portions 71 and 76 are formed in a rectangular shape in plan view by digging both main surfaces of a thick flat plate in the thickness direction, and form a flat portion. As shown in FIG. 11, on one main surface, the thick portion is provided on three sides along the outer periphery of the rectangular shape, and on the remaining one side, the thick portion is arranged so as to be flush with the surface of the thin portion. The flat portion 72b is not formed. On the other hand, as shown in FIG. 12, in the other main surface, the thick part 72 is provided in four surroundings (four sides) along the rectangle, and the thin part 76 is formed in the center part.

Electrodes constituting a monolithic crystal filter are formed on both main surfaces of the crystal diaphragm 7. That is, as shown in FIG. 11, a rectangular shaped input electrode 73 and output electrode 74 are formed at a predetermined interval in the thin portion 71 of one main surface, and as shown in FIG. A rectangular common electrode 75 facing the input electrode and the output electrode is formed on the thin portion 76 of the surface.

Lead electrodes 73a and 74a are led out from the input electrode 73 and output electrode 74, respectively, and lead electrodes 75a are led out from the common electrode toward the corners of the crystal diaphragm. The lead electrodes 73a, 74a, and 75a are led to connection electrodes 73b, 74b, and 75b connected to electrode pads 82 and 83 formed on the ceramic package, respectively.

In addition, first lead-out electrodes 73c and 74c are formed from the input electrode 73 and the output electrode 74 to the flat portion 22b described above. The tip portions of the first lead-out electrodes 73c and 74c are close to each other in a planar manner to form a first bridging capacitance forming portion C1. The first bridging capacitance forming portion C1 can adjust the value by changing the distance between the adjacent portions of the lead-out electrodes and the area of the electrodes facing each other.

Below the bridging capacitance forming portion C <b> 1 is a thicker structure 72 a than the thin-walled portion 71. This thick structure 72a is preferably thicker than the thin part 71 and is the same as or slightly smaller than the thickness of the thick part 72 on the common electrode side. In the present embodiment, the thin portion 71, the thick structure 72a, and the thick portion 72 are thickened in this order. The thick structure 72a thicker than the thin part is effective in suppressing spurious due to the formation of the lead electrode.

The connection electrodes 73b and 74b are formed so as to extend to the other main surface, and the second lead-out electrodes 73d and 74d are formed to extend from the other main surface portion to the surface of the thick portion of the other main surface. Has been. The tips of the second lead-out electrodes are close to each other on the thick portion to form a second bridging capacitance forming portion C2.

As shown in FIG. 13, the crystal diaphragm 7 is mounted on the ceramic package 8. The ceramic package 8 has a rectangular parallelepiped shape as a whole and is open at the top. A bank portion is provided on the outer periphery of the opening, a metallized layer 81 is formed on the top surface of the bank portion, and electrode pads 82 and 83 are formed on the bottom surface in the package. The crystal diaphragm 7 is mounted on the ceramic package 8. The crystal diaphragm 7 is mounted so that the other main surface faces upward, that is, the opening side of the ceramic package 8 as shown in FIG. As a result, the common electrode 75 and the second bridging capacitance forming portion C2 are arranged so as to face upward. The characteristics can be adjusted for the common electrode 75 and the second bridging capacitance forming portion C2. For example, the characteristics are adjusted by adding a metal material to the common electrode 75 and the second bridging capacitance forming portion C2 or removing the electrode. After the characteristic adjustment, the lid 9 made of a metal plate is hermetically sealed by seam bonding or the like by closing the opening of the ceramic package.

In the present embodiment, since two bridging capacitance forming portions are provided, the characteristics can be adjusted more accurately. In addition, since any bridging capacitance forming portion is provided in a region different from the main vibration region composed of the input / output electrodes and the common electrode, the main vibration is not adversely affected by characteristics such as spurious due to the bridging capacitance forming portion. In addition, since the second bridging capacitance forming portion is formed on the ceramic package opening side, it is possible to adjust the characteristics before hermetic sealing, and a more accurate piezoelectric filter can be obtained.

  The present invention is not limited to the exemplification of the above embodiment, and the embodiments can be combined with each other. In addition, although a surface mount type crystal filter using an AT cut crystal diaphragm is illustrated, other piezoelectric materials such as lithium niobate and piezoelectric ceramics may be used, and the present invention is not limited to the examples in the above embodiment. Absent.

  It can be applied to mass production of piezoelectric filters such as crystal filters.

The perspective view of the crystal filter by 1st Embodiment. The perspective view of the crystal filter by 1st Embodiment. The top view of the crystal filter by a 2nd embodiment. The top view of the crystal filter by a 2nd embodiment. The top view of the crystal filter which shows the other example of 2nd Embodiment. The perspective view of the crystal filter by 3rd Embodiment. The perspective view of the crystal filter by 3rd Embodiment. The perspective view of the crystal filter by 4th Embodiment. The perspective view of the crystal filter by 4th Embodiment. The perspective view of the crystal filter by 5th Embodiment. The perspective view of the crystal filter by 6th Embodiment. The perspective view of the crystal filter by 6th Embodiment. Sectional drawing of the crystal filter by 6th Embodiment.

Explanation of symbols

1, 2, 3, 4, 5, 6, 7 Quartz diaphragm 11, 16, 21, 26, 31, 41, 46, 51, 56, 61, 71, 76 Thin portion 12, 22, 32, 42, 52 , 62,72 Thick part
13, 23, 33, 43, 53, 63, 73 Input electrode 14, 24, 34, 44, 54, 64, 74 Output electrode 15, 25, 45, 55, 75 Common electrode 13c, 14c, 23c, 24c, 33c 34c, 43c, 44c, 53c, 54c63c, 63d, 64c, 64d, 73c, 73d, 74c, 74d Lead electrode
8 Ceramic package

Claims (3)

A piezoelectric diaphragm having a thin portion and a thick portion formed on a part or all of the outer periphery of the thin portion, an input electrode and an output electrode formed on one main surface of the thin portion, and an other main surface of the thin portion A common electrode formed corresponding to the input electrode and the output electrode, each extraction electrode for pulling out the input electrode, the output electrode, and the common electrode to an end of the piezoelectric diaphragm, and a lead electrode from each of the input electrode and the output electrode. A piezoelectric filter consisting of a bridging capacitance forming portion that extends and is brought close to the end portion of the piezoelectric diaphragm,
The thin-walled portion is configured to be thinned from both main surfaces, the input electrode, the output electrode, and the lead-out electrode are formed in the same plane, and the piezoelectric diaphragm below the bridging capacitance forming portion of the lead-out electrode is A piezoelectric filter having a thick structure thicker than the thin portion. A piezoelectric diaphragm having a rectangular shape in plan view in which a thick part is formed in a part or all of the thin part and the outer periphery of the thin part in the vertical direction, an input electrode and an output electrode formed on one main surface of the thin part, A common electrode formed on the other main surface of the thin portion corresponding to the input electrode and the output electrode, each extraction electrode for drawing the input electrode, the output electrode, and the common electrode to an end of the piezoelectric diaphragm, and the input electrode A piezoelectric filter comprising a narrowing lead electrode extending from each of the output electrodes to the vicinity of the end of one side of the piezoelectric diaphragm, and a bridging capacitance forming portion adjacent thereto,
In the side facing the bridging capacitance forming portion or the side facing the bridging capacitance forming portion and the side facing the side, the thick portion on the input electrode and output electrode side is not formed, and the bridging electrode forming portion A piezoelectric filter characterized by having a thick-walled structure below the thin-walled portion. A piezoelectric filter comprising a thin-film portion and a piezoelectric diaphragm having a thick-wall portion formed in a part or all of the thin-wall portion in the vertical direction of the outer periphery of the thin-wall portion.
The piezoelectric diaphragm includes an input electrode and an output electrode formed on one main surface of the thin portion, a common electrode formed on the other main surface of the thin portion corresponding to the input electrode and the output electrode, and the input Each lead electrode for drawing out the electrode, the output electrode, and the common electrode to the end of the piezoelectric diaphragm, and the first lead electrode having a narrow width extending from each of the input electrode and the output electrode on the same plane, and the end of the piezoelectric diaphragm A first bridging capacitance forming portion that is adjacent in the vicinity, a second lead-out electrode from each of the input electrode and the output electrode is drawn to the surface of the thick-wall portion, and each of the second lead-out electrodes is thick-walled. And having a second bridging capacitance forming portion brought close to the surface,
The piezoelectric diaphragm below the bridging capacitance forming portion of the lead-out electrode is thicker than the thin portion, and is mounted on the package with the second bridging capacitance forming portion facing upward. A piezoelectric filter characterized in that characteristics can be adjusted with respect to the second bridging capacitance section.

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