JP2014146975A - Piezoelectric component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric component in which temperature changes cause little changes in the frequency.SOLUTION: A piezoelectric component includes: a support substrate 1; a piezoelectric element 2 mounted on the support substrate 1; and a cap 4 which is provided on the support substrate 1 so as to cover the piezoelectric element 2. The cap 4 is joined to the support substrate 1 through a joint material 5. A thickness of the joint material 5, which is formed along an inner wall of the cap 4 in a plane view, is increased in a corner 41 of the cap 4. The piezoelectric component, in which temperature changes cause little changes in the frequency, is obtained by the structure.

Description

  The present invention relates to a piezoelectric component that requires high reliability and highly accurate frequency characteristics.

  Conventionally, a support substrate, a piezoelectric element mounted on the support substrate, and a cap provided on the support substrate so as to cover the piezoelectric element, the cap being configured to be bonded to the support substrate via a bonding material. A piezoelectric component (resonator) is known (see Patent Document 1).

  Here, the cap is bonded onto the support substrate by a bonding material made of a thermosetting resin to seal the internal space. At this time, the bonding material is formed so that a part thereof crawls up the inner wall of the cap uniformly.

JP-A-8-111627

  In recent years, caps have become thinner to meet the demand for miniaturization. However, when the cap is thinned, when the cap expands or contracts due to heat, stress concentrates on the corner portion of the cap, and there is a possibility that deformation that twists at the corner portion of the cap may occur. Along with this torsional deformation, distortion occurs in the support substrate and the piezoelectric element, and the frequency of the piezoelectric component may fluctuate, which may reduce the accuracy of frequency tolerance.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric component in which the frequency variation is small even with a temperature change.

  The piezoelectric component of the present invention includes a support substrate, a piezoelectric element mounted on the support substrate, and a cap provided on the support substrate so as to cover the piezoelectric element, and the cap is interposed via a bonding material. The thickness of the bonding material in plan view along the inner wall of the cap is increased at the corner of the cap.

  In the piezoelectric component of the present invention, the shape of the bonding material along the inner wall of the cap is a fillet shape.

  In the piezoelectric component of the present invention, both the corner of the inner wall of the cap and the inner surface of the portion corresponding to the corner of the bonding material are rounded in plan view, and correspond to the corner of the bonding material. It is characterized in that the inner radius of the portion to be bent has a larger radius of curvature.

  Moreover, the piezoelectric component of the present invention is characterized in that the climbing height of the bonding material is higher in the part corresponding to the corner than in the other part.

  Moreover, the piezoelectric component of the present invention is characterized in that a corner portion of the inner wall of the cap is rounded in a plan view, and a radius of curvature of at least one of the corner portions is different.

  The piezoelectric component of the present invention is characterized in that the resin sealing material is formed on at least corners of the outer wall of the cap.

  Moreover, the piezoelectric component of the present invention is characterized in that the cap is made of metal.

  According to the present invention, torsional deformation can be suppressed because the thickness in plan view along the inner wall of the cap of the bonding material is increased at the corners of the cap. Therefore, since the distortion of the support substrate and the piezoelectric element is small and the frequency variation is small even with a temperature change, a piezoelectric component having a stable temperature characteristic of the frequency can be realized.

(A) is a schematic plan view with partial omission showing an example of an embodiment of a piezoelectric component of the present invention, and (b) is a schematic cross-sectional view cut along line AA shown in (a). It is a principal part enlarged plan view of an example of embodiment of the piezoelectric component of this invention. It is a principal part top view of the other example of embodiment of the piezoelectric component of this invention. (A) is a schematic sectional drawing of the other example of the piezoelectric component cut | disconnected by the CC line | wire shown in FIG. 3, (b) is a principal part expansion perspective view of the piezoelectric component shown to (a). (A) is a principal part top view of the other example of embodiment of the piezoelectric component of this invention, (b) is a principal part expansion perspective view of the piezoelectric component shown to (a). It is a principal part top view of an example of the conventional piezoelectric component as a comparative example.

  An example of an embodiment of a piezoelectric component of the present invention will be described in detail with reference to the drawings.

  FIG. 1 (a) is a partially omitted diagram showing an example of an embodiment of a piezoelectric component according to the present invention (cap top plate omitted), and is a schematic plan view (a cross-sectional view taken along line BB shown in FIG. 1 (b)). FIG. 1B is a schematic cross-sectional view taken along line AA shown in FIG.

  1 includes a support substrate 1, a piezoelectric element 2 mounted on the support substrate 1, and a cap 4 provided on the support substrate 1 so as to cover the piezoelectric element 2. 4 is bonded to the support substrate 1 via the bonding material 5, and the thickness in plan view along the inner wall of the cap 4 of the bonding material 5 is thick at the corner 41 of the cap 4.

  The support substrate 1 includes, for example, a support substrate body 11 formed as a rectangular flat plate having a length of 2.5 mm to 7.5 mm, a width of 1.0 mm to 3.0 mm, and a thickness of 0.1 mm to 1 mm. It is out. As the support substrate body 11, a ceramic material such as alumina and a resin material such as glass epoxy can be used.

  A pair of signal terminals 121 and 122 and a ground terminal 13 are provided on the lower surface of the support substrate body 11 constituting the support substrate 1. Further, wiring conductors 141 and 142 are provided on the upper surface of the support substrate body 11 so as to be electrically connected to the signal terminals 121 and 122. These are formed by printing and sintering a conductive paste containing metal powder such as gold, silver, copper, aluminum, tungsten, or the like. Moreover, what formed plating, such as Ni / Au and Ni / Sn, may be used as needed.

  On the support substrate 1, the piezoelectric element 2 is mounted so that both ends are fixed. Specifically, both ends of the piezoelectric element 2 are fixed on the support substrate 1 by the conductive bonding material 3 so as to vibrate.

  The piezoelectric body 21 constituting the piezoelectric element 2 is formed, for example, as a rectangular flat plate having a length of 1.0 mm to 4.0 mm, a width of 0.2 mm to 2 mm, and a thickness of 40 μm to 1 mm. The material is polarized in the thickness direction. The piezoelectric body 21 is made of, for example, piezoelectric ceramics based on lead titanate, lead zirconate titanate, sodium niobate, potassium niobate, a bismuth layered compound, etc., or a piezoelectric single unit such as lithium tantalate or lithium niobate. It can be formed using crystals.

  In addition, the piezoelectric element 2 includes electrodes (excitation electrodes 22 and 23) arranged so as to have regions facing each other on one main surface and the other main surface of the piezoelectric body 21. The excitation electrode 22 provided on the upper main surface of the piezoelectric body 21 is provided so as to extend from one end portion toward the other end portion, and is provided on the lower main surface of the piezoelectric body 21. The excitation electrode 23 is provided so as to extend from the other end toward the one end, and has regions facing each other. The excitation electrodes 22 and 23 can be made of metal such as gold, silver, copper, and aluminum, and are applied to the surface of the piezoelectric body 21 to a thickness of, for example, 0.1 μm to 3 μm. The excitation electrode 22 of the piezoelectric element 2 is electrically connected to the wiring conductor 141 via the conductive bonding material 3, and the excitation electrode 23 of the piezoelectric element 2 is connected to the wiring conductor 142 via the conductive bonding material 3. And are electrically connected.

  Here, the conductive bonding material 3 also has a function of ensuring a predetermined space (gap) between the upper surface of the support substrate 1 and the lower surface of the piezoelectric element 2. As such a conductive bonding material 3, for example, solder, a conductive adhesive, or the like is used. As long as the solder is used, a lead-free material such as copper, tin, or silver can be used. If it is an adhesive agent, the epoxy-type conductive resin or silicone-type resin containing 75-95 mass% of electroconductive particles, such as silver, copper, and nickel, can be used.

  In such a piezoelectric element 2, when a voltage is applied between the excitation electrode 22 and the excitation electrode 23 from both ends, thickness longitudinal vibration or thickness slip occurs at a specific frequency in a region where the excitation electrode 22 and the excitation electrode 23 face each other. The piezoelectric vibration is generated.

  A cap 4 is provided on the support substrate 1 so as to cover the piezoelectric element 2. The cap 4 has a thickness of, for example, 250 to 300 μm and is formed in, for example, a rectangular parallelepiped shape having an opening so as to correspond to the shape of the support substrate 1, and is bonded to the peripheral portion of the upper surface of the support substrate 1 with a bonding material 5. Has been. Thereby, the function of protecting the piezoelectric element 2 accommodated in the space formed with the support substrate 1 from the physical and chemical influences from the outside, water into the space formed with the support substrate 1, etc. It has a hermetic sealing function to prevent the entry of foreign matter.

  As a material of the cap 4, for example, a metal such as SUS, ceramics such as alumina, resin, glass, or the like can be used. Further, an insulating resin material such as an epoxy resin may contain an inorganic filler in a proportion of 25 to 80% by mass so as to reduce the difference in thermal expansion coefficient with the support substrate 1. In particular, the effect of the present invention described later works effectively when the metal is easily affected by external heat.

  Examples of the material of the bonding material 5 include an epoxy-based adhesive, an epoxy acrylate-based adhesive, and a silicone-based adhesive.

  As shown in FIG. 1A and FIG. 2, the thickness in plan view along the inner wall of the cap 4 of the bonding material 5 is thicker at the corner 41 (the corner 41 of the inner wall) of the cap 4.

Here, the thickness in plan view along the inner wall of the cap 4 of the bonding material 5 is thicker at the corner 41 of the cap 4 that the normal thickness of the bonding material 5 at the corner 41 of the cap 4 as shown in FIG. A structure with a thickness that is positively increased compared to the thickness.

  Specifically, as shown in FIG. 2, the thickness of the bonding material 5 corresponding to one surface of the inner wall of the cap 4 (thickness of the thinnest portion) is L1, and the adjacent caps 4 with the corner portion 31 in between. When the thickness in plan view (thickness of the thinnest portion) of the bonding material 5 corresponding to the other one surface of the inner wall is L2, the virtual extension line extending from the position of the inner wall of the cap 4 and the thickness of L1 and L2 A region surrounded by a virtual extension line extending from the thickness position is virtually formed inside the corner 41 of the cap 4. When the length of the diagonal line in this region is L3 and the distance from the corner 41 of the cap 4 to the inner wall of the bonding material 5 located on the extension of the diagonal line is L4, L4 is more than twice L3. It means the state that is.

  As shown in FIG. 6, if L4 is less than twice L3, the corner portion 41 of the cap 4 may be twisted and deformed. On the other hand, as in the present invention, the planar view thickness along the inner wall of the cap 4 of the bonding material 5 is thicker at the corner portion 41 of the cap 4 (the thickness is positively increased so that L4 is 2 of L3). (Twice or more), torsional deformation is suppressed and distortion of the support substrate 1 and the piezoelectric element 2 is reduced. Therefore, frequency fluctuations are suppressed even by temperature changes (frequency temperature characteristics become stable). In particular, as shown in FIG. 2, being 3 times or more is effective in terms of suppressing torsional deformation, and 5 times or less may be in terms of miniaturization of the piezoelectric component.

  Here, as shown in FIG.1 (b), it is preferable that the shape along the inner wall of the cap 4 of the joining material 5 is a fillet shape as a shape which suppresses torsional deformation. Note that the fillet shape means that the bottom of the support substrate 1 extends from the inner wall of the cap 4 to the upper surface of the support substrate 1 when viewed from the lower side. With such a shape, the bonding area can be increased, the bonding force can be increased, and peeling from the end of the bonding material 5 can be suppressed.

  Further, as shown in FIG. 3, the corner 41 of the inner wall of the cap 4 and the inner surface 51 of the portion corresponding to the corner of the bonding material 5 are both rounded in plan view and correspond to the corner of the bonding material 5. It is preferable that the radius of curvature is larger on the inner surface 51 of the portion to be performed.

  Although the destruction (crack progress) of the sealing surface is likely to occur from the corner portion 41 where stress is concentrated, both the corner portion 41 of the inner wall of the cap 4 and the inner surface 51 of the portion corresponding to the corner portion of the bonding material 5 are rounded in plan view. Since this fracture (crack progress) is suppressed, the inner surface 51 of the portion corresponding to the corner of the bonding material 5 has a larger radius of curvature, which has the effect of suppressing torsional deformation due to sufficient thickness. As it increases, the effect of suppressing breakage (crack progress) due to thermal stress also increases.

  Further, as shown in FIG. 4, the climbing height of the bonding material 5 is preferably higher in the portion corresponding to the corner portion 41 than in the other portion, and the portion corresponding to the corner portion 41 is higher than the other portion. By increasing the height, an effect of further suppressing torsional deformation can be obtained.

  Moreover, it is preferable that the corner portion 41 of the inner wall of the cap 4 is rounded in a plan view and at least one of the corner portions 41 has a different radius of curvature. Thereby, the effect of dispersing and reducing the resonance of the cap 4 and the support substrate 1 vibrating due to leakage from the piezoelectric component as an unnecessary mode or vibration from the outside is obtained.

Further, as shown in FIG. 5, the bonding material 5 may be formed on at least the corners 42 of the outer wall of the cap 4. For example, the bonding material 5 is formed upward from near the boundary between the cap 4 and the support substrate 1 so as to scoop up the outer wall of the cap 4 and also extends to the outer wall (lower side) of the support substrate 1. The structure in which the bonding material 5 is formed is mentioned. As a result, the effect of suppressing torsional deformation is further enhanced, and frequency fluctuations due to temperature changes are further suppressed (temperature characteristics of the frequency are further stabilized).

  The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention.

  Next, an example of a method for manufacturing a piezoelectric component according to the present embodiment will be described.

  First, a multi-piece substrate for producing the support substrate 1 is produced. For example, after the raw material powder is mixed with water and a dispersant using a ball mill, a binder, a solvent, a plasticizer, and the like are added to obtain a green sheet. The green sheet is subjected to hole processing as necessary, and then a conductive paste containing metal powder such as gold, silver, copper, aluminum, tungsten or the like is printed and laminated. This is fired at a peak temperature of, for example, 900 ° C. to 1600 ° C.

  Next, for example, after the raw material powder is mixed with water and a dispersant using a ball mill, the piezoelectric material 21 constituting the piezoelectric element 2 is added with a binder, a plasticizer, and the like, and dried and sized. The raw material thus obtained is press-molded and fired to obtain a piezoelectric ceramic. An electrode is formed on the end face of the obtained piezoelectric ceramic, and a polarization treatment is performed by applying a voltage of, for example, 0.4 kV / mm to 6 kV / mm in the thickness direction at a temperature of 25 ° C. to 300 ° C., for example.

  The excitation electrodes 22 and the excitation electrodes 23 formed on the upper and lower surfaces of the piezoelectric body 21 are coated with a metal film on the upper and lower surfaces of the piezoelectric body 21 by using a vacuum deposition method, a PVD method, a sputtering method, or the like. After forming a photoresist film having a thickness of about 1 μm to 10 μm on each metal film using screen printing or the like, it can be formed by patterning by photoetching. The piezoelectric element 2 is produced by cutting the patterned piezoelectric ceramic into a predetermined size by dicing or the like.

  Then, using the conductive bonding material 3, a large number of piezoelectric elements 2 are mounted on the substrate and fixed. When the conductive bonding material 3 is a conductive adhesive in which metal powder is dispersed in a resin, the conductive adhesive 3 is applied onto the wiring conductors 141 and 142 using a dispenser or the like, and the piezoelectric material is piezoelectric. The element 2 may be mounted and the conductive adhesive resin may be cured by heating or ultraviolet irradiation.

  Next, frequency adjustment is performed in a state where the piezoelectric element 2 is mounted on a multi-piece substrate. In the frequency adjustment, the excitation electrodes 22 and 23 formed on the surface of the piezoelectric element 2 are etched with an ion gun or the like, and matched with the IC by changing the length or thickness or changing the design value. The oscillation frequency is adjusted by connecting an oscillation frequency measurement terminal to the signal terminals 121 and 122 and the ground terminal 13 at the time of ion gun irradiation and measuring the oscillation frequency. When the oscillation frequency is reached, the ion gun is irradiated. Implement by stopping.

  Then, the opening peripheral surface of the cap 4 is joined to the peripheral portion of the upper surface of the support substrate 1 so as to cover the piezoelectric element 2. As the cap 4, a multi-cap assembly cap sheet having a plurality of recesses is used, and the multi-cap assembly sheet is placed on the substrate with the recess covering the piezoelectric element 2. The convex part of the collective cap sheet is joined to the peripheral edge part of the upper surface of the support substrate 1. For example, the bonding material 5 (thermosetting insulating adhesive) is applied to the convex portion of the collective cap sheet serving as the opening peripheral surface of the prepared cap 4, and the cap 4 is placed on the upper surface of the support substrate 1. After that, the cap 4 or the support substrate 1 is heated to raise the temperature of the bonding material 5 to 100 to 150 ° C. to be cured, and the cap 4 is bonded to the upper surface of the support substrate 1.

  In order to obtain a configuration in which the planar thickness along the inner wall of the cap 4 of the bonding material 5 is thick at the corner 41 of the cap 4, the printing range may be widened when the bonding material 5 is printed. Moreover, the shape of the bonding material 5 can be appropriately changed by selecting a temperature condition such as increasing the surface tension of the insulating adhesive (resin adhesive) softened at the time of curing. Furthermore, by appropriately changing the molding die of the cap 4, the shape of the corner portion 41 of the inner wall of the cap 4 can be rounded or the radius of curvature can be changed.

  Finally, it is cut by dicing or the like along the boundary of each piezoelectric component (piece).

  The piezoelectric component of the present invention is manufactured by the above method.

  According to the method as described above, it is possible to manufacture a piezoelectric component having a small frequency variation even with a temperature change with high productivity.

1: Support substrate 11: Support substrate body 121, 122: Signal terminal 13: Ground terminal 141, 142: Wiring conductor 2: Piezoelectric element 21: Piezoelectric body 22, 23: Excitation electrode 3: Conductive bonding material 4: Cap 41: Corner 42 of the inner wall: Corner 5 of the outer wall 5: Bonding material 51: Inner surface

Claims (7)

A support substrate, a piezoelectric element mounted on the support substrate, and a cap provided on the support substrate so as to cover the piezoelectric element;
The cap is bonded to a support substrate via a bonding material, and the thickness of the bonding material in plan view along the inner wall of the cap is increased at the corner of the cap.   The piezoelectric component according to claim 1, wherein a shape of the bonding material along an inner wall of the cap is a fillet shape.   The corner of the inner wall of the cap and the inner surface of the part corresponding to the corner of the bonding material are both rounded in plan view, and the inner surface of the part corresponding to the corner of the bonding material has a radius of curvature. The piezoelectric component according to claim 1, wherein the piezoelectric component is large.   The piezoelectric component according to any one of claims 1 to 3, wherein a climbing height of the bonding material is higher in a portion corresponding to the corner portion than in other portions.   The corner of the inner wall of the cap is rounded in plan view, and the radius of curvature of at least one of the corners is different. A piezoelectric component according to any one of the above.   The piezoelectric component according to any one of claims 1 to 5, wherein the bonding material is formed on at least corners of the outer wall of the cap.   The piezoelectric component according to claim 1, wherein the cap is made of metal.

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