JP6901250B2 - Piezoelectric parts - Google Patents

Description

The present disclosure relates to piezoelectric components that are preferably used as oscillators, for example.

Generally, the piezoelectric component used for the oscillator is a support substrate, a piezoelectric element mounted on the support substrate, and both ends of the piezoelectric element so that a minute distance is generated between the support substrate and the piezoelectric element. It is composed of a support portion for fixing the portion and a conductive bonding material, and a lid provided so as to cover the upper surface of the support substrate and the piezoelectric element. The piezoelectric element has a pair of excitation electrodes facing each other on the upper surface and the lower surface, and the excitation electrode and the pair of capacitive electrodes provided on the upper surface of the support substrate are electrically connected via a conductive bonding material. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 11-97965

Conventionally, there has been a problem that the oscillation frequency becomes unstable and fluctuates because the main vibration of the piezoelectric component (oscillator) is damped and weakened by firmly fixing the piezoelectric element.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a highly accurate piezoelectric component in which fluctuations in oscillation frequency are suppressed.

The piezoelectric component of the present disclosure is fixed by joining and fixing a support substrate, a long piezoelectric element arranged on the support substrate, and both ends of the piezoelectric element in the longitudinal direction to the upper surface of the support substrate. The conductive bonding material is bonded from the lower surface to the end surface of both ends of the piezoelectric element, and the first region located below the piezoelectric element and the other regions are joined. There is a difference in density from the second region of the above, and the conductive bonding material is characterized in that the density of the first region is lower than that of the second region .

According to the piezoelectric component of the present disclosure, damping of the main vibration is suppressed, fluctuation of the oscillation frequency is suppressed, and the oscillation frequency can be stabilized.

It is a schematic perspective view which shows an example of embodiment of a piezoelectric component. (A) is a partially omitted plan view of the piezoelectric component shown in FIG. 1, (b) is a cross-sectional view of the piezoelectric component shown in FIG. 1 cut along the line AA, and (c) is a bottom surface of the piezoelectric component shown in FIG. It is a figure. It is an enlarged sectional view of the main part which shows an example of embodiment of a piezoelectric part. It is an enlarged sectional view of the main part which shows the other example of embodiment of a piezoelectric part. It is an enlarged sectional view of the main part which shows the other example of embodiment of a piezoelectric part. It is an enlarged sectional view of the main part which shows another example of embodiment of a piezoelectric part.

Hereinafter, an example of the embodiment of the piezoelectric component will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

FIG. 1 is a schematic perspective view showing an example of an embodiment of a piezoelectric component. 2 (a) is a partially omitted plan view of the piezoelectric component shown in FIG. 1, FIG. 2 (b) is a cross-sectional view of the piezoelectric component shown in FIG. 1 cut along the line AA, and FIG. 2 (c) is. It is a bottom view of the piezoelectric component shown in FIG. Further, FIG. 3 is an enlarged cross-sectional view of a main part showing an example of an embodiment of the piezoelectric component.

The piezoelectric component 100 of the example shown in FIGS. 1 to 3 includes a support substrate 1, a long piezoelectric element 2 arranged on the support substrate 1, and a top surface of the support substrate 1 in the longitudinal direction of the piezoelectric element 2. A conductive joining material 4 is provided by joining and fixing both ends thereof, and the conductive joining material 4 is joined from the lower surface to the end face of both ends of the piezoelectric element 2 and is attached to the lower side of the piezoelectric element 2. There is a difference in density between the first region 41 located and the other second region 42.

The support substrate 1 is a substrate in which both ends of the elongated piezoelectric element 2 in the longitudinal direction are joined to and fixed to the upper surface. For example, it has a substrate body 11 made of a dielectric 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. There is. As the substrate main body 11, a ceramic material such as alumina or barium titanate, or a resin-based material such as glass epoxy can be used.

A pair of capacitive electrodes 12 (first capacitive electrode 121 and second capacitive electrode 122) are provided on the upper surface of the substrate main body 11 constituting the support substrate 1. The first capacitance electrode 121 and the second capacitance electrode 122 are electrically connected to the excitation electrode 21 of the piezoelectric element 2, electrically connected to the input / output terminal electrode 14, and also to the ground terminal electrode 13 described later. It is an electrode for forming a capacitance between the two.

The first capacitance electrode 121 is arranged on one end side (left side in the drawing) of the substrate main body 11 in the longitudinal direction and extends in the width direction (short direction) of the substrate main body 11 and the substrate main body 11. It has a region arranged extending from one end side in the longitudinal direction toward the central portion. Further, the second capacitance electrode 122 is arranged on the other end side (right side in the drawing) of the substrate main body 11 in the longitudinal direction and extends in the width direction (short direction) of the substrate main body 11 and a support substrate. It has a region arranged extending from the other end side in the longitudinal direction of 1 toward the central portion. The first capacitance electrode 121 and the second capacitance electrode 122 are arranged at intervals in the central portion of the upper surface of the substrate main body 11 in the longitudinal direction.

Further, the support substrate 1 is a ground terminal arranged on the lower surface of the substrate main body 11 between a pair of input / output terminal electrodes 14 electrically connected to the pair of capacitance electrodes 12 and a pair of input / output terminal electrodes 14. It has an electrode 13.

The pair of input / output terminal electrodes 14 are terminal electrodes that serve as inlets or outlets for electric signals, and are provided on the lower surface of the substrate main body 11 so as to extend in the width direction of the substrate main body 11. Further, the pair of input / output terminal electrodes 14 are electrically connected to the first capacitance electrode 121 or the second capacitance electrode 122 provided on the upper surface of the substrate main body 11, and when mounted on an external circuit board. It is electrically connected to an external circuit.

The ground terminal electrode 13 is arranged between a pair of input / output terminal electrodes 14 on the lower surface of the substrate main body 11, and is provided so as to extend in the width direction of the substrate main body 11. Further, the ground terminal electrode 13 forms a capacitance (load capacitance) so as to face the first capacitance electrode 121 and the second capacitance electrode 122 with the substrate main body 11 interposed therebetween. When mounted on an external circuit board, it is electrically connected to the ground potential.

As in this example, the first capacitance electrode 121, the second capacitance electrode 122, and the ground terminal electrode 13
When the two are opposed to each other via the substrate main body 11, the areas where the first capacitance electrode 121 and the ground terminal electrode 13 face each other and the area where the second capacitance electrode 122 and the ground terminal electrode 13 face each other are equal. By setting to, the capacitances obtained in the opposite regions become equal. When the first capacitance electrode 121 and the second capacitance electrode 122 and the ground terminal electrode 13 face each other via the substrate main body 11, the region where the first capacitance electrode 121 and the ground terminal electrode 13 face each other and the second capacitance Since the region where the electrode 122 and the ground terminal electrode 13 face each other can be increased, the capacitance can be increased. The capacitance obtained in each of the opposite regions is determined by the characteristics of the amplifier circuit element to which the piezoelectric component 100 is connected to form the oscillation circuit.

Further, on the side surface of the support substrate 1, a side electrode 15 for electrically connecting the first capacitance electrode 121 or the second capacitance electrode 122 and the input / output terminal electrode 14 is provided. Further, on the side surface of the support substrate 1, a side electrode 16 electrically connected to the ground terminal electrode 13 is also provided on the side surface of the support substrate 1 in relation to solder bonding (mountability) to an external circuit board. ing.

As materials for the first capacitance electrode 121, the second capacitance electrode 122, the ground terminal electrode 13, the input / output terminal electrode 14, and the side electrodes 15 and 16, metal powders such as gold, silver, copper, aluminum, and tungsten are contained in the resin. A dispersed conductive resin (conductive paste), a thick film conductor obtained by adding an additive such as glass to these metal powders and baking them can be used. If necessary, plating such as Ni / Au or Ni / Sn may be formed.

A rectangular parallelepiped piezoelectric element 2 is mounted on the support substrate 1 with both ends fixed in the longitudinal direction. Then, as shown in FIG. 2, a first support portion 31 and a second support portion 32 are provided on the support substrate 1 as needed, and both ends of the piezoelectric element 2 in the longitudinal direction are first. The piezoelectric element 2 is oscillatedly mounted so as to be supported by the support portion 31 and the second support portion 32 of the above.

The first support portion 31 and the second support portion 32 are protrusion-shaped portions formed by dispersing metal powders such as gold, silver, copper, aluminum, and tungsten in a resin. For example, it has a length (diameter) of 0.1 mm to 1.0 mm in the vertical and horizontal directions and a thickness of 10 μm to 100 μm, and is formed in a prismatic shape, a columnar shape, or the like. The first support portion 31 and the second support portion 32 may each have one configuration or a plurality of configurations as shown in FIG.

A conductive bonding material 4 is provided around the first support portion 31 and the second support portion 32, and both ends of the piezoelectric element 2 are the first support portion 31, the second support portion 32, and the second support portion 32. It is joined to the 1-capacity electrode 121 and the 2nd capacitance electrode 122, and is electrically connected.

The conductive bonding material 4 is bonded from the lower surface to the end surface of both end portions of the piezoelectric element 2. In the example shown in the figure, the conductive bonding material 4 is provided so as to crawl up the end surface of the piezoelectric element 2 and extend to the upper surface of the piezoelectric element 2. As such a conductive bonding material 4, for example, solder or a conductive adhesive can be used, and in the case of solder, for example, a lead-free material made of copper, tin, or silver can be used, and the conductive material 4 can be used. As an adhesive, an epoxy-based conductive resin or a silicone-based resin containing 75 to 95% by mass of conductive particles such as silver, copper, and nickel can be used.

In the examples shown in FIGS. 2 and 3, the first support portion 31 and the second support portion 32 are provided, but as shown in FIG. 4, the first support portion 31 and the second support portion 31 and the second support portion 32 are provided. The portions 32 may not be provided, and both ends of the piezoelectric element 2 may be fixed only with the conductive bonding material 4 so that the piezoelectric element 2 is mounted in a floating manner.

The piezoelectric element 2 includes a piezoelectric body 22 and a pair of excitation electrodes 21 provided so as to have regions (intersection regions) facing each other on one main surface (upper surface) and the other main surface (lower surface) of the piezoelectric body 22. It has.

The piezoelectric body 22 constituting the piezoelectric element 2 is formed in a long shape (rectangular parallelepiped shape) 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, for example. Is. The piezoelectric body 22 is formed by using piezoelectric ceramics based on, for example, lead titanate, lead zirconate titanate, lithium tantalate, lithium niobate, sodium niobate, potassium niobate, bismuth layered compound and the like. Can be done.

Further, the excitation electrode 21 provided on one main surface (upper surface) of the piezoelectric body 22 is provided so as to extend from one end portion in the longitudinal direction toward the other end portion side, and is provided on the other main surface (upper surface) of the piezoelectric body 22. The excitation electrode 21 provided on the lower surface) is provided so as to extend from the other end in the longitudinal direction toward one end, and each has a region facing each other. For the excitation electrode 21, for example, a metal such as gold, silver, copper, aluminum, chromium, or nickel can be used, and each of them is adhered to the surface of the piezoelectric body 22 to a thickness of, for example, 0.1 μm to 3 μm. Then, as shown in the figure, end face electrodes 23 are provided on both end faces of the piezoelectric element 2, and the excitation electrodes 21 on the upper surface are provided via the end face electrodes 23, the conductive bonding material 4, and the first support portion 31. Is electrically connected to the first capacitance electrode 121. Further, the excitation electrode 21 on the lower surface is electrically connected to the second capacitance electrode 122 via the conductive bonding material 4 and the second support portion 32.

When a voltage is applied between the pair of excitation electrodes 21, such a piezoelectric element 2 generates piezoelectric vibration of thickness longitudinal vibration or thickness sliding vibration at a specific frequency in a region (intersection region) where the excitation electrodes 21 face each other. It is designed to let you.

As shown in FIGS. 1 and 2B, the lid 5 may be provided on the support substrate 1 so as to cover the piezoelectric element 2. The lid 5 is bonded to the outer peripheral portion of the upper surface of the support substrate 1 with, for example, an epoxy-based or acrylic-based adhesive, preferably an epoxy-based adhesive from the viewpoint of reflow heat resistance. As a result, the function of protecting the piezoelectric element 2 housed in the internal space formed together with the support substrate 1 from external physical and chemical influences, water in the space formed together with the support substrate 1, etc. The piezoelectric component 100 has an airtight sealing function for preventing the intrusion of foreign matter. As the material of the lid 5, for example, a metal such as stainless steel, 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.

Further, as shown in FIG. 1, the side electrode 15 and the side electrode 16 may extend to the side surface of the lid body 5, which improves the mountability on the external circuit board.

As shown in FIG. 3, the conductive bonding material 4 has a density difference between the first region 41 located below the piezoelectric element 2 and the other second region 42. In other words, one of the first region 41 located below the piezoelectric element 2 and the other second region 42 is a sparse region and the other is a dense region.

The first region 41 and the second region 41 have different densities of the conductive bonding material 4 between the first region 41 located below the piezoelectric element 2 and the other second region 42. In addition to using two types of bonding materials having different resin densities at the time of curing in the region 42, there are examples such as making a difference in porosity.

For example, when differentiating the porosity, when the volume ratio of the void portion (void portion / (void portion + conductive resin portion)) to the entire region is taken as the void ratio, the porosity of the dense region is determined. The porosity of less than 5% and sparse areas is 5% or more. For this porosity, the area ratio is obtained from a scanning electron microscope (SEM) image of a cross section of the first region 41 of the conductive bonding material 4 and the other second region 42 cut at an arbitrary position. Can be calculated.

According to such a configuration, the conductive bonding material 4 is firmly fixed by the dense region, and the damping of the main vibration of the piezoelectric element 2 is suppressed by the sparse region of the conductive bonding material 4. Therefore, it is possible to obtain a highly accurate piezoelectric component that suppresses fluctuations in the oscillation frequency.

Here, the conductive bonding material 4 can be configured to have a lower density in the first region 41 than in the second region 42. Since the first region 41 close to the vibration region of the main vibration of the piezoelectric element 2 is a region having a high influence on the damping effect of the main vibration, the first region 41 has a lower density than the second region and is sparse. By setting the region, the damping of the main vibration of the piezoelectric element 2 by the conductive bonding material 4 can be suppressed, and the fluctuation of the oscillation frequency can be further suppressed.

Further, since the coefficient of thermal expansion of the conductive bonding material 4 due to the temperature change is larger than the coefficient of thermal expansion of the piezoelectric element 2, the stress applied to the bonding surface between the conductive bonding material 4 and the piezoelectric element 2 fluctuates, and the oscillation frequency. Also fluctuates. On the other hand, by making the first region 41, which is close to the vibration region of the main vibration of the piezoelectric element 2, a region having a lower density and a sparser region than the second region 42, the fluctuation of stress due to thermal expansion can be reduced. Fluctuations in oscillation frequency due to temperature changes can be suppressed.

Then, as shown in FIG. 5, when the first region 41 close to the vibration region of the main vibration of the piezoelectric element 2 is set to a region having a lower density and a sparse region than the second region 42, the first region 41 is used. In the above, the density of the portion 412 closer to the piezoelectric element 2 can be lower than that of the portion 411 on the side closer to the support substrate 1. Here, the boundary between the portion 411 on the side closer to the support substrate 1 and the portion 412 on the side closer to the piezoelectric element 2 is located at a position exactly half (t / 2) of the total thickness t of the first region 41. To do. In the first region 41, the portion 412 on the side closer to the piezoelectric element 2 has a lower density and is a sparse region, so that damping of the main vibration of the piezoelectric element 2 by the conductive bonding material 4 can be further suppressed. In addition, fluctuations in stress due to thermal expansion can be further suppressed.

Further, as shown in FIG. 6, when the first region 41 close to the vibration region of the main vibration of the piezoelectric element 2 is set to a region having a lower density and a sparse region than the second region 42, the first region 41 In the plan view, the density of the inner portion 414 may be lower than that of the outer peripheral portion 413 when viewed in a plan view.

The vibration energy of the piezoelectric element 2 is the largest near the center of the excitation electrode 21. Therefore, in the first region 41, the inner portion 414 has a lower density and is a sparse region than the outer peripheral portion 413 when viewed in a plan view, so that the main vibration of the piezoelectric element 2 due to the conductive bonding material 4 is caused. Damping can be further suppressed, and the loss of vibration energy can be suppressed.

Next, an example of a method for manufacturing the piezoelectric component 100 will be described.

First, a large number of boards for manufacturing the support substrate 1 are manufactured. For example, raw material powders such as lead titanate, lead zirconate titanate, and barium titanate are mixed with water and a dispersant using a ball mill, and then a binder, a plasticizer, and the like are added, and the powder is dried and sized. The raw material thus obtained is press-molded, bored if necessary, degreased at a predetermined temperature, fired at a peak temperature of, for example, 900 ° C. to 1600 ° C., and polished to a predetermined thickness. .. After that, for example, a conductive paste containing a metal powder such as silver or nickel and glass is printed and fired at a predetermined temperature to obtain a first capacitance electrode 121, a second capacitance electrode 122, a ground terminal electrode 13, and an input / output terminal electrode. 14 and the like are formed to obtain the support substrate 1.

On the obtained support substrate 1, a support portion made of a conductive paste is formed on the obtained support substrate 1 by screen printing or the like to a thickness of about 1 μm to 100 μm. Specifically, a bump-shaped first support portion 31 formed by dispersing, for example, metal powder in a resin and solidifying it is provided on the first capacitance electrode 121, and for example, a metal is provided on the second capacitance electrode 122. A bump-shaped second support portion 32 formed by dispersing the powder in the resin and solidifying it is provided.

Next, the piezoelectric body 22 constituting the piezoelectric element 2 is, for example, mixed with water and a dispersant using a ball mill, and then dried and sized by adding a binder, a plasticizer, and the like. The raw material thus obtained is press-molded and then fired to obtain a piezoelectric device. An electrode is formed on the end face of the obtained piezoelectric device, and a polarization treatment is performed by applying a voltage of, for example, 0.4 kV / mm to 6 kV / mm in the end face direction at a temperature of, for example, 25 ° C to 300 ° C.

The excitation electrode 21 formed on the upper and lower surfaces of the piezoelectric body 22 is obtained by coating the obtained piezoelectric body 22 with a metal film on the upper and lower surfaces of the piezoelectric body 22 by using a vacuum deposition method, a PVD method, a sputtering method, or the like. It can be formed by forming a photoresist film having a thickness of about 1 μm to 10 μm on each metal film by screen printing or the like, and then patterning by photoetching. The piezoelectric element 2 is manufactured by cutting the patterned piezoelectric body 22 to a predetermined size by dicing or the like.

Next, the piezoelectric element 2 is mounted and fixed on the first support portion 31 and the second support portion 32 of the support substrate 1 by using the conductive bonding material 4. When the conductive bonding material 4 is a conductive adhesive in which metal powder is dispersed in a resin, the conductive adhesive is applied on the first support portion 31 and the second support portion 32 by using a dispenser or the like. The piezoelectric element 2 may be placed on the first support portion 31 and the second support portion 32, and the resin of the conductive adhesive may be cured by heating or irradiation with ultraviolet rays.

Here, the conductive bonding material 4 is bonded from the lower surface to the end surface of both ends of the piezoelectric element 2, and is joined to the first region 41 located below the piezoelectric element 2 and the other second region 42. For example, in order to configure the structure in which the density of the first region 41 located below the piezoelectric element 2 is low and the density of the other second region 42 is high, first, air is used. The conductive bonding material 4 containing a large amount of kneaded air bubbles is applied to a portion below the piezoelectric element 2 (a portion located in the first region 41) using a dispenser or the like, and cured. Then, the piezoelectric element 2 may be mounted, and the defoamed conductive bonding material 4 may be applied to the other region (the portion to be the second region 42) using a dispenser or the like and cured.

Further, when the first region 41 is a region having a lower density than the second region 42 and is sparse, in the first region 41, it is closer to the piezoelectric element 2 than the portion 411 on the side closer to the support substrate 1. In order to make the side portion 412 have a lower density, first, the defoamed conductive bonding material 4 is printed and cured on the portion located in the first region 41 on the upper surface of the support substrate 1 by screen printing or the like. .. The conductive bonding material 4 containing a large amount of kneaded air bubbles is printed while introducing air from above. Then, the piezoelectric element 2 may be mounted, and the defoamed conductive bonding material 4 may be applied to the other region (the portion to be the second region 42) using a dispenser or the like and cured.

Further, when the first region 41 close to the vibration region of the main vibration of the piezoelectric element 2 is a region having a lower density than the second region 42 and is sparse, the first region 41 is viewed in a plan view. In order to configure the inner portion 414 to have a lower density than the outer peripheral portion 413, first, a mesh having a large number of meshes is used to remove the density from the portion located in the first region 41 on the upper surface of the support substrate 1 by screen printing or the like. The foamed conductive bonding material is printed and cured. The conductive bonding material 4 containing a large amount of air bubbles kneaded while introducing air from above is screen-printed using a mesh having a smaller number of meshes on the inner side than the outer peripheral portion. Then, the piezoelectric element 2 may be mounted, and the defoamed conductive bonding material 4 may be applied to the other region (the portion to be the second region 42) using a dispenser or the like and cured.

Then, if necessary, the opening peripheral surface of the lid 5 is joined to the peripheral edge of the upper surface of the support substrate 1 so as to cover the piezoelectric element 2. As the lid 5, a large number of collective lid sheets having a plurality of recesses are used, and a large number of collective lid sheets are placed on the substrate so that the recesses cover the piezoelectric element 2, and the lid 5 The convex portion of the collective lid sheet, which is the peripheral surface of the opening, is joined to the peripheral edge of the upper surface of the support substrate 1. For example, a thermosetting insulating adhesive is applied to the convex portion of the collective lid sheet which is the opening peripheral surface of the prepared lid body 5, and the lid body 5 is placed on the upper surface of the support substrate 1. After that, the insulating adhesive is heated to 100 to 150 ° C. to cure by heating the lid 5 or the support substrate 1, and the lid 5 is bonded to the upper surface of the support substrate 1.

Finally, after cutting along the boundary of each piezoelectric component (individual piece) by dicing or the like, a conductive paste is printed on the side surface of each piezoelectric component which has become an individual piece by screen printing or the like, and the temperature is 100 to 150 ° C. The piezoelectric component 100 can be obtained by forming the side electrodes 15 and 16 by raising the temperature to the surface and curing the mixture. After this, plating such as Ni or Au may be formed on the surfaces of the side electrodes 15 and 16.

By the above method, the piezoelectric component 100 of this example is manufactured. According to such a method, it is possible to manufacture a highly accurate piezoelectric component in which fluctuation of the oscillation frequency is suppressed.

1: Support substrate 11: Substrate body 12: Capacitive electrode 121: First capacitive electrode 122: Second capacitive electrode 13: Ground terminal electrode 14: Input / output terminal electrode 2: Piezoelectric element 21: Exciting electrode 22: Piezoelectric body 23: End face Electrode 31: First support portion 32: Second support portion 4: Conductive bonding material 41: First region 411: Part near the support substrate 412: Part near the piezoelectric element 413: Outer peripheral portion 414 : Inner part 42: Second region 5: Lid

Claims (4)

A support substrate, a long piezoelectric element arranged on the support substrate, and a conductive bonding material in which both ends of the piezoelectric element in the longitudinal direction are bonded and fixed to the upper surface of the support substrate. With
The conductive bonding material is bonded from the lower surface to the end surface of both ends of the piezoelectric element, and the density differs between the first region located below the piezoelectric element and the other second region. The conductive bonding material is a piezoelectric component characterized in that the density of the first region is lower than that of the second region. Before Kishirube conductive bonding material, wherein in the first region, the piezoelectric component according to claim 1, towards the side closer to the piezoelectric element than a side closer to the support substrate, wherein the density is low. Before Kishirube conductive bonding material, wherein in the first region, the piezoelectric component according to claim 1 or claim 2 towards the inner portion than the outer peripheral portion of the plan view is equal to or lower density. Claims 1 to 1, wherein the conductive bonding material is a bonding material in which the first region located below the piezoelectric element and the other second region are the same and have different porosities. The piezoelectric component according to any one of claims 3.

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